Double-Salts Super Concentrated Carbonate Electrolyte Boosting Electrochemical Performance of Ni-Rich LiNi0.90Co0.05Mn0.05O2 Lithium Metal Batteries

Current lithium-ion batteries cannot meet the requirement of higher energy density with further large-scale application of electrical vehicles. Lithium metal batteries combined with Ni-rich layered oxides cathode are expected as the one of promising solutions, while the poor electrode and electrolyte interface impedes the commercial development of lithium metal batteries. A new double-salts super concentrated (DSSC) carbonate electrolyte is proposed to improve the electrochemical performance of LiNi0.90Co0.05Mn0.05O2 (NCM9055)||Li metal battery which exhibits stable cycling performance with the capacity retention of 93.04% and reversible capacity of 173.8 mAh g-1 after 100 cycles at 1 C, while cells with conventional 1 m diluted electrolyte remains only 60.55% and capacity of 114.2 mAh g-1. The double salts synergistic effect in super concentrated electrolyte promotes the formation for more balanced stable cathode electrolyte interface (CEI) inorganic compounds of CFx, LiNOx, SOF2, Li2SO4, and less LiF by X-ray photoelectron spectroscopy (XPS) test, and the uniform 2-3 nm rock-salt phase protection layer on the cathode surface by transmission electron microscope (TEM) characterization, improving the cycling performance of the Ni-rich NCM9055 layered oxide cathode. The DSSC electrolyte also can relief the Li dendrite growth on Li metal anode, as well as exhibit better flame retardance, promoting the application of more safety Ni-rich NCM9055||Li metal batteries.

Investigations on Tunnel-Structure MnO2 for Utilization as a High-Voltage and Long-Life Cathode Material in Aqueous Ammonium-Ion and Hybrid-Ion Batteries

Recently, nonmetal NH4 + ions have attracted extensive attention for use as charge carries in the field of energy storage due to their abundant resources, environmental friendliness, and low cost. However, the development of aqueous ammonium-ion batteries (AAIBs) is constrained by the absence of high-voltage and long-life materials. Herein, different tunnel-structure MnO2 materials (α-, β-, and γ-MnO2) are utilized as cathodes for AAIBs and hybrid-ion batteries and compared, and α-MnO2 is demonstrated to exhibit the most remarkable electrochemical performance. The α-MnO2 cathode material delivers the highest discharge capacity of 219 mAh g-1 at a current density of 0.1 A g-1 and the best cyclability with a capacity retention of 95.4% after 10 000 cycles at 1.0 A g-1. Moreover, aqueous ammonium-ion and hybrid-ion (ammonium/sodium ions) full batteries are successfully constructed using α-MnO2 cathodes. This work provides a novel direction for the development of aqueous energy storage for practical applications.

Research on the facile regeneration of degraded cathode materials from spent LiNi0.5Co0.2Mn0.3O2 lithium-ion batteries

Rational reusing the waste materials in spent batteries play a key role in the sustainable development for the future lithium-ion batteries. In this work, we propose an effective and facile solid-state-calcination strategy for the recycling and regeneration of the cathode materials in spent LiNi0.5Co0.2Mn0.3O2 (NCM523) ternary lithium-ion batteries. By systemic physicochemical characterizations, the stoichiometry, phase purity and elemental composition of the regenerated material were deeply investigated. The electrochemical tests confirm that the material characteristics and performances got recovered after the regeneration process. The optimal material was proved to exhibit the excellent capacity with a discharge capacity of 147.9 mAh g-1 at 1 C and an outstanding capacity retention of 86% after 500 cycles at 1 C, which were comparable to those of commercial NCM materials.

Bio-Inspired Electrodes with Rational Spatiotemporal Management for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are currently the predominant energy storage power source. However, the urgent issues of enhancing electrochemical performance, prolonging lifetime, preventing thermal runaway-caused fires, and intelligent application are obstacles to their applications. Herein, bio-inspired electrodes owning spatiotemporal management of self-healing, fast ion transport, fire-extinguishing, thermoresponsive switching, recycling, and flexibility are overviewed comprehensively, showing great promising potentials in practical application due to the significantly enhanced durability and thermal safety of LIBs. Taking advantage of the self-healing core-shell structures, binders, capsules, or liquid metal alloys, these electrodes can maintain the mechanical integrity during the lithiation-delithiation cycling. After the incorporation of fire-extinguishing binders, current collectors, or capsules, flame retardants can be released spatiotemporally during thermal runaway to ensure safety. Thermoresponsive switching electrodes are also constructed though adding thermally responsive components, which can rapidly switch LIB off under abnormal conditions and resume their functions quickly when normal operating conditions return. Finally, the challenges of bio-inspired electrode designs are presented to optimize the spatiotemporal management of LIBs. It is anticipated that the proposed electrodes with spatiotemporal management will not only promote industrial application, but also strengthen the fundamental research of bionics in energy storage.

Enhancing Li-Ion Battery Anodes: Synthesis, Characterization, and Electrochemical Performance of Crystalline C60 Nanorods with Controlled Morphology and Phase Transition

Recently, C60 has emerged as a promising anode material for Li-ion batteries, attracting significant interest due to its excellent lithium storage capacity. The electrochemical performance of C60 as an anode is largely dependent on its internal crystal structure, which is significantly influenced by the synthesis method and corresponding conditions. However, there have been few reports on how the synthesis process affects the crystal structure and Li+ storage capacity of C60. This study used the liquid-liquid interface precipitation method and a low-temperature annealing process to fabricate one-dimensional C60 nanorods (NRs). We thoroughly investigated synthesis conditions, including the growth time, drying temperature, annealing time, and annealing atmosphere. The results demonstrate that these synthesis conditions directly impact the morphology, phase transition, and electrochemical efficiency of pure C60 NRs. Remarkably, the hexagonal close-packed structural C60 NRs-6012h, in a metastable form, exhibits a reversible Li+ storage capacity as an anode material in Li-ion batteries. Furthermore, the face-centered cubic C60 NRs-603001h electrode shows significantly enhanced rate performance and long-cycle stability. A discharge-specific capacity of 603 mAh g-1 was maintained after 2000 cycles at a current density of 2 A g-1. This study elucidates the effect of synthesis conditions on C60 crystals, offering an effective strategy for preparing high-performance C60 anode materials.

Selective Lattice Doping Enables a Low-Cost, High-Capacity and Long-Lasting Potassium Layered Oxide Cathode for Potassium and Sodium Storage

Layered transition metal oxides are highly promising host materials for K ions, owing to their high theoretical capacities and appropriate operational potentials. To address the intrinsic issues of KxMnO2 cathodes and optimize their electrochemical properties, a novel P3-type oxide doped with carefully chosen cost-effective, electrochemically active and multi-functional elements is proposed, namely K0.57Cu0.1Fe0.1Mn0.8O2. Compared to the pristine K0.56MnO2, its reversible specific is increased from 104 to 135 mAh g-1. In addition, the Cu and Fe co-doping triples the capacity under high current densities, and contributes to long-term stability over 500 cycles with a capacity retention of 68 %. Such endeavor holds the potential to make potassium-ion batteries particularly competitive for application in sustainable, low-cost, and large-scale energy storage devices. In addition, the cathode is also extended for sodium storage. Facilitated by the interlayer K ions that protect the layered structure from collapsing and expand the diffusion pathway for sodium ions, the cathode shows a high reversible capacity of 144 mAh g-1, fast kinetics and a long lifespan over 1000 cycles. The findings offer a novel pathway for the development of high-performance and cost-effective sodium-ion batteries.

One-Stone-for-Two-Birds Strategy for VSe2 to Enable High Capacity and Long-Life Zinc Storage

Based on a specific zinc storage mechanism and excellent electronic conductivity, transition metal dichalcogenides, represented by vanadium diselenide, are widely used in aqueous zinc-ion battery (AZIB) energy storage systems. However, most vanadium diselenide cathode materials are presently limited by low specific capacity and poor cycling life. Herein, a simple hydrothermal process has been proposed for obtaining a vanadium diselenide cathode for an AZIB. The interaction of defects and crystal planes enhances zinc storage capacity and reduces the migration energy barrier. Moreover, abundant lamellar structure greatly increases reaction sites and alleviates volume expansion during the electrochemical process. Thus, the as-obtained vanadium diselenide AZIB exhibits an excellent reversible specific capacity of 377 mAh g-1 at 1 A g-1, and ultralong cycle stability of 291 mAh g-1 after 3200 cycles, with a nearly negligible capacity loss. This one-stone-for-two-birds strategy would be expected to be applied to large-scale synthesis of a high-performance zinc-ion battery cathode in the future.

Optimizing Performance in Supercapacitors through Surface Decoration of Bismuth Nanosheets

Bismuth (Bi) exhibits a high theoretical capacity, excellent electrical conductivity properties, and remarkable interlayer spacing, making it an ideal electrode material for supercapacitors. However, during the charge and discharge processes, Bi is prone to volume expansion and pulverization, resulting in a decline in the capacitance. Deposition of a nonmetal on its surface is considered an effective way to modulate its morphology and electronic structure. Herein, we employed the chemical vapor deposition technique to fabricate Se-decorated Bi nanosheets on a nickel foam (NF) substrate. Various characterizations indicated that the deposition of Se on Bi nanosheets regulated their surface morphology and chemical state, while sustaining their pristine phase structure. Electrochemical tests demonstrated that Se-decorated Bi nanosheets exhibited a 51.1% improvement in capacity compared with pristine Bi nanosheets (1313 F/g compared to 869 F/g at a current density of 5 A/g). The energy density of the active material in an assembled asymmetric supercapacitor could reach 151.2 Wh/kg at a power density of 800 W/kg. These findings suggest that Se decoration is a promising strategy to enhance the capacity of the Bi nanosheets.

Anion-Cation Competition Chemistry for Comprehensive High-Performance Prussian Blue Analogs Cathodes

The extensively studied Prussian blue analogs (PBAs) in various batteries are limited by their low discharge capacity, or subpar rate etc., which are solely reliant on the cation (de)intercalation mechanism. In contrast to the currently predominant focus on cations, we report the overlooked anion-cation competition chemistry (Cl-, K+, Zn2+) stimulated by high-voltage scanning. With our designed anion-cation combinations, the KFeMnHCF cathode battery delivers comprehensively superior discharge performance, including voltage plateau >2.0 V (vs. Zn/Zn2+), capacity >150 mAh g-1, rate capability with capacity maintenance above 96 % from 0.6 to 5 A g-1, and cyclic stability exceeding 3000 cycles. We further verify that such comprehensive improvement of electrochemical performance utilizing anion-cation competition chemistry is universal for different types of PBAs. Our work would pave a new and efficient road towards the next-generation high-performance PBAs cathode batteries.

Tuning A-Site Cation Deficiency in Pr0.5La0.5BaCo2O5+ δ Perovskite to Realize Large-Scale Hydrogen Evolution at 2000 mA cm-2

Industrial-level hydrogen production from the water electrolysis requires reducing the overpotential (η) as much as possible at high current density, which is closely related to intrinsic activity of the electrocatalysts. Herein, A-site cation deficiency engineering is proposed to screen high-performance catalysts, demonstrating effective Pr0.5- xLa0.5BaCo2O5+ δ (P0.5- xLBC) perovskites toward alkaline hydrogen evolution reaction (HER). Among all perovskite compositions, Pr0.4La0.5BaCo2O5+ δ (P0.4LBC) exhibits superior HER performance along with unique operating stability at large current densities (J = 500-2000 mA cm-2 geo). The overpotential of ≈636 mV is achieved in P0.4LBC at 2000 mA cm-2 geo, which outperforms commercial Pt/C benchmark (≈974 mV). Furthermore, the Tafel slope of P0.4LBC (34.1 mV dec-1) is close to that of Pt/C (35.6 mV dec-1), reflecting fast HER kinetics on the P0.4LBC catalyst. Combined with experimental and theoretical results, such catalytic activity may benefit from enhanced electrical conductivity, enlarged Co-O covalency, and decreased desorption energy of H* species. This results highlight effective A-site cation-deficient strategy for promoting electrochemical properties of perovskites, highlighting potential water electrolysis at ampere-level current density.

Metal-Organic Framework-Based Materials for Advanced Sodium Storage: Development and Anticipation

As a pioneering battery technology, even though sodium-ion batteries (SIBs) are safe, non-flammable, and capable of exhibiting better temperature endurance performance than lithium-ion batteries (LIBs), because of lower energy density and larger ionic size, they are not amicable for large-scale applications. Generally, the electrochemical storage performance of a secondary battery can be improved by monitoring the composition and morphology of electrode materials. Because more is the intricacy of a nanostructured composite electrode material, more electrochemical storage applications would be expected. Despite the conventional methods suitable for practical production, the synthesis of metal-organic frameworks (MOFs) would offer enormous opportunities for next-generation battery applications by delicately systematizing the structure and composition at the molecular level to store sodium ions with larger sizes compared with lithium ions. Here, the review comprehensively discusses the progress of nanostructured MOFs and their derivatives applied as negative and positive electrode materials for effective sodium storage in SIBs. The commercialization goal has prompted the development of MOFs and their derivatives as electrode materials, before which the synthesis and mechanism for MOF-based SIB electrodes with improved sodium storage performance are systematically discussed. Finally, the existing challenges, possible perspectives, and future opportunities will be anticipated.

The Utilization of Metal-Organic Frameworks and Their Derivatives Composite in Supercapacitor Electrodes

Up to now, the mainstream adoption of renewable energy has brought about substantial transformations in the electricity and energy sector. This shift has garnered considerable attention within the scientific community. Supercapacitors, known for their exceptional performance metrics like good charge/discharge capability, strong power density, as well as extended cycle longevity, have gained widespread traction across various sectors, including transportation and aviation. Metal-organic frameworks (MOFs) with unique traits including adaptable structure, highly customizable synthetic methods, and high specific surface area, have emerged as strong candidates for electrode materials. For enhancing the performance, MOFs are commonly compounded with other conducting materials to increase capacitance. This paper provides a detailed analysis of various common preparation strategies and characteristics of MOFs. It summarizes the recent application of MOFs and their derivatives as supercapacitor electrodes alongside other carbon materials, metal compounds, and conductive polymers. Additionally, the challenges encountered by MOFs in the realm of supercapacitor applications are thoroughly discussed. Compared to previous reviews, the content of this paper is more comprehensive, offering readers a deeper understanding of the diverse applications of MOFs. Furthermore, it provides valuable suggestions and guidance for future progress and development in the field of MOFs.

Facilely Fabricating F-Doped Fe3N Nanoellipsoids Grown on 3D N-Doped Porous Carbon Framework as a Preeminent Negative Material

Transition metal nitride negative electrode materials with a high capacity and electronic conduction are still troubled by the large volume change in the discharging procedure and the low lithium ion diffusion rate. Synthesizing the composite material of F-doped Fe3N and an N-doped porous carbon framework will overcome the foregoing troubles and effectuate a preeminent electrochemical performance. In this study, we created a simple route to obtain the composite of F-doped Fe3N nanoellipsoids and a 3D N-doped porous carbon framework under non-ammonia atmosphere conditions. Integrating the F-doped Fe3N nanoellipsoids with an N-doped porous carbon framework can immensely repress the problem of volume expansion but also substantially elevate the lithium ion diffusion rate. When utilized as a negative electrode for lithium-ion batteries, this composite bespeaks a stellar operational life and rate capability, releasing a tempting capacity of 574 mAh g-1 after 550 cycles at 1.0 A g-1. The results of this study will profoundly promote the evolution and application of transition metal nitrides in batteries.

Porous Carbon Interlayer Derived from Traditional Korean Paper for Li-S Batteries

A carbonized interlayer effectively helps to improve the electrochemical performance of lithium-sulfur (Li-S) batteries. In this study, a simple and inexpensive carbon intermediate layer was fabricated using a traditional Korean paper called "hanji". This carbon interlayer has a fibrous porous structure, with a specific surface area of 91.82 m2 g-1 and a BJH adsorption average pore diameter of 26.63 nm. The prepared carbon interlayer was utilized as an intermediary layer in Li-S batteries to decrease the charge-transfer resistance and capture dissolved lithium polysulfides. The porous fiber-shaped carbon interlayer suppressed the migration of polysulfides produced during the electrochemical process. The carbon interlayer facilitates the adsorption of soluble lithium polysulfides, allowing for their re-utilization in subsequent cycles. Additionally, the carbon interlayer significantly reduces the polarization of the cell. This simple strategy results in a significant improvement in cycle performance. Consequently, the discharge capacity at 0.5 C after 150 cycles was confirmed to have improved by more than twofold, reaching 230 mAh g-1 for cells without the interlayer and 583 mAh g-1 for cells with the interlayer. This study demonstrates a simple method for improving the capacity of Li-S batteries by integrating a functional carbon interlayer.

Electrochemical Performance and Microstructure Evolution of a Quasi-Solid-State Lithium Battery Prepared by Spark Plasma Sintering

Solid-state lithium batteries are promising next-generation energy storage systems for electric vehicles due to their high energy density and high safety and require achieving and maintaining intimate solid-solid interfaces for lithium-ion and electron transport. However, the solid-solid interfaces may evolve over cycling, disrupting the ion and electron diffusion pathways and leading to rapid performance degradation. The development of solid-state lithium batteries has been hindered by the lack of fundamental understanding of the interfacial microstructure change over cycling and its relation to electrochemical properties. Herein, we prepared a quasi-solid-state lithium battery, 30%LiFePO4-55%Li1.5Al0.5Ge1.5(PO4)3-15%C| Li1.5Al0.5Ge1.5(PO4)3|Li, by spark plasma sintering, and employed it as a model system to reveal the microstructure evolution at the solid-solid interfaces with electrochemical performance of the batteries. The electrochemical assessment showed that the quasi-solid-state lithium battery exhibited a discharge specific capacity of about 150 mAh g-1 in the first 80 cycles and then experienced severe capacity attenuation afterward, accompanied by a gradual internal resistance increase. Scanning electron microscopy observation showed that more cracks were formed inside the solid-state electrolyte and at the solid-solid interfaces as the battery cycled from 10 to 67 and 157 cycles. Detailed microstructure and phase analysis by high-resolution transmission electron microscopy and selected area electron diffraction discovered that the crack formation and performance decay were mainly caused by (1) the volume change of the LiFePO4 composite cathode during cycling, (2) the grain expansion of the Li1.5Al0.5Ge1.5(PO4)3 solid-state electrolyte at its interface with lithium anode, and (3) the formation of a solid electrolyte interphase layer, comprising Li2CO3, LiF, and LiTFSI, at the cathode-solid-state electrolyte interface. These microstructure changes built up over repeated battery cycling, ultimately causing the structure collapse and battery failure. The microstructure evolution information is expected to guide the design of better structures and interfaces for solid-state lithium batteries.

MOF-Derived Bimetallic Selenide CoNiSe2 Nanododecahedrons Encapsulated in Porous Carbon Matrix as Advanced Anodes for Lithium-Ion Batteries

Transition metal selenides have received considerable attention as promising candidates for lithium-ion battery (LIB) anode materials due to their high theoretical capacity and safety characteristics. However, their commercial viability is hampered by insufficient conductivity and volumetric fluctuations during cycling. To address these issues, we have utilized bimetallic metal-organic frameworks to fabricate CoNiSe2/C nanodecahedral composites with a high specific surface area, abundant pore structures, and a surface-coated layer of the carbon-based matrix. The optimized material, CoNiSe2/C-700, exhibited impressive Li+ storage performance with an initial discharge specific capacity of 2125.5 mA h g-1 at 0.1 A g-1 and a Coulombic efficiency of 98% over cycles. Even after 1000 cycles at 1.0 A g-1, a reversible discharge specific capacity of 549.9 mA h g-1 was achieved. The research highlights the synergistic effect of bimetallic selenides, well-defined nanodecahedral structures, stable carbon networks, and the formation of smaller particles during initial cycling, all of which contribute to improved electronic performance, reduced volume change, increased Li+ storage active sites, and shorter Li+ diffusion paths. In addition, the pseudocapacitance behavior contributes significantly to the high energy storage of Li+. These features facilitate rapid charge transfer and help maintain a stable solid-electrolyte interphase layer, which ultimately leads to an excellent electrochemical performance. This work provides a viable approach for fabricating bimetallic selenides as anode materials for high-performance LIBs through architectural engineering and compositional tailoring.

Effect of Graphene on the Performance of Silicon-Carbon Composite Anode Materials for Lithium-Ion Batteries

(Si/graphite)@C and (Si/graphite/graphene)@C were synthesized by coating asphalt-cracked carbon on the surface of a Si-based precursor by spray drying, followed by heat treatment at 1000 °C under vacuum for 2h. The impact of graphene on the performance of silicon-carbon composite-based anode materials for lithium-ion batteries (LIBs) was investigated. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) images of (Si/graphite/graphene)@C showed that the nano-Si and graphene particles were dispersed on the surface of graphite, and thermogravimetric analysis (TGA) curves indicated that the content of silicon in the (Si/graphite/graphene)@C was 18.91%. More bituminous cracking carbon formed on the surface of the (Si/graphite/graphene)@C due to the large specific surface area of graphene. (Si/Graphite/Graphene)@C delivered first discharge and charge capacities of 860.4 and 782.1 mAh/g, respectively, initial coulombic efficiency (ICE) of 90.9%, and capacity retention of 74.5% after 200 cycles. The addition of graphene effectively improved the cycling performance of the Si-based anode materials, which can be attributed to the reduction of electrochemical polarization due to the good structural stability and high conductivity of graphene.

Rational Design of Ion-Conductive Layer on Si Anode Enables Superior-Stable Lithium-Ion Batteries

Silicon (Si) is considered a promising commercial material for the next-generation of high-energy density lithium-ion battery (LIB) due to its high theoretical capacity. However, the severe volume changes and the poor conductivity hinder the practical application of Si anode. Herein, a novel core-shell heterostructure, Si as the core and V3 O4 @C as the shell (Si@V3 O4 @C), is proposed by a facile solvothermal reaction. Theoretical simulations have shown that the in-situ-formed V3 O4 layer facilitates the rapid Li+ diffusion and lowers the energy barrier of Li transport from the carbon shell to the inner core. The 3D network structure constructed by amorphous carbon can effectively improve electronic conductivity and structural stability. Benefiting from the rationally designed structure, the optimized Si@V3 O4 @C electrode exhibits an excellent cycling stability of 1061.1 mAh g-1 at 0.5 A g-1 over 700 cycles (capacity retention of 70.0%) with an average Coulombic efficiency of 99.3%. In addition, the Si@V3 O4 @C||LiFePO4 full cell shows a superior capacity retention of 78.7% after 130 cycles at 0.5 C. This study opens a novel way for designing high-performance silicon anode for advanced LIBs.

Highly Stable Organic Molecular Porous Solid Electrolyte with One-Dimensional Ion Migration Channel for Solid-State Lithium-Oxygen Battery

Solid-state lithium-oxygen (Li-O2 ) batteries have been widely recognized as one of the candidates for the next-generation of energy storage batteries. However, the development of solid-state Li-O2 batteries has been hindered by the lack of solid-state electrolyte (SSE) with high ionic conductivity at room temperature, high Li+ transference number, and the high stability to air. Herein, the organic molecular porous solid cucurbit[7]uril (CB[7]) with one-dimensional (1D) ion migration channels is developed as the SSE for solid-state Li-O2 batteries. Taking advantage of the 1D ion migration channel for Li+ conduction, CB[7] SSE achieves high ionic conductivity (2.45 × 10-4 S cm-1 at 25 °C). Moreover, the noncovalent interactions facilitated the immobilization of anions, realizing a high Li+ transference number (tLi + = 0.81) and Li+ uniform distribution. The CB[7] SSE also shows a wide electrochemical stability window of 0-4.65 V and high thermal stability and chemical stability, as well as realizes stable Li+ plating/stripping (more than 1000 h at 0.3 mA cm-2 ). As a result, the CB[7] SSE endows solid-state Li-O2 batteries with superior rate capability and long-term discharge/charge stability (up to 500 h). This design strategy of CB[7] SSE paves the way for stable and efficient solid-state Li-O2 batteries toward practical applications.

Porous Carbon Foam with Carbon Nanotubes as Cathode for Li-CO2 Batteries

With the extensive use of fossil fuels, the ever-increasing greenhouse gas of mainly carbon dioxide emissions will result in global climate change. It is of utmost importance to reduce carbon dioxide emissions and its utilization. Li-CO2 batteries can convert carbon dioxide into electrochemical energy. However, developing efficient catalysts for the decomposition of Li2 CO3 as the discharge product represents a challenge in Li-CO2 batteries. Herein, we demonstrate a carbon foam composite with growing carbon nanotube by using cobalt as the catalyst, showing the ability to enhance the decomposition rate of Li2 CO3 , and thus improve the electrochemical performance of Li-CO2 batteries. Benefiting from its abundant pore structure and catalytic sites, the as-assembled Li-CO2 battery exhibits a desirable overpotential of 1.67 V after 50 cycles. Moreover, the overpotentials are 1.05 and 2.38 V at current densities of 0.02 and 0.20 mA cm-2 , respectively. These results provide a new avenue for the development of efficient catalysts for Li-CO2 batteries.

Ni-rich lithium nickel manganese cobalt oxide cathode materials: A review on the synthesis methods and their electrochemical performances

The demand for lithium-ion batteries (LIBs) has skyrocketed due to the fast-growing global electric vehicle (EV) market. The Ni-rich cathode materials are considered the most relevant next-generation positive-electrode materials for LIBs as they offer low cost and high energy density materials. However, by increasing Ni content in the cathode materials, the materials suffer from poor cycle ability, rate capability and thermal stability. Therefore, this review article focuses on recent advances in the controlled synthesis of lithium nickel manganese cobalt oxide (NMC). This work highlights the advantages and challenges associated with each synthesis method that has been used to produce Ni-rich materials. The crystallography and morphology obtained are discussed, as the performance of LIBs is highly dependent on these properties. To address the drawbacks of Ni-rich cathode materials, certain modifications such as ion doping, and surface coating have been pursued. The correlation between the synthesized and modified NMC materials with their electrochemical performances is summarized. Several gaps, challenges and guidelines are elucidated here in order to provide insights for facilitating research in high-performance cathode for lithium-ion batteries. Factors that govern the formation of nickel-rich layered cathode such as pH, reaction and calcination temperatures have been outlined and discussed.

Preparation and Electrochemical Performance of Na2-xLixFePO4F/C Composite Cathode Materials with Different Lithium/Sodium Ratios

With their advantages of abundant raw material reserves, safety, and low toxicity and cost, sodium-ion batteries (SIBs) have gained increasing attention in recent years. Thanks to a high theoretical specific capacity (124 mAh g-1), a high operating voltage (about 3.2 V), and a very stable three-dimensional layered structure, sodium ferric fluorophosphate (Na2FePO4F, NFPF) has emerged as a strong candidate to be used as a cathode material for SIBs. However, applications are currently limited due to the low electronic conductivity and slow ion diffusion rate of NFPF, which result in a low actual specific capacity and a high rate performance. In this study, the authors used a high-temperature solid-phase technique to produce Na2-xLixFePO4F/C (0 ≤ x ≤ 2) and evaluated the impact on electrode performance of materials with different Na+ and Li+ contents (values of x). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were also used to analyze the material's crystal structure and nanostructure. The results show that the material had the best room-temperature performance when x = 0.5. At a charge-discharge rate of 0.1 C, the first discharge-specific capacity of the resulting Na1.5Li0.5FePO4F/C cathode material was 122.9 mAh g-1 (the theoretical capacity was 124 mAh g-1), and after 100 cycles, it remained at 118 mAh g-1, representing a capacity retention rate of 96.2% and a Coulomb efficiency of 98%. The findings of this study demonstrate that combining lithium and sodium ions improves the electrochemical performance of electrode materials.

Exploring the Potential of Carbonized Nano-Si within G@C@Si Anodes for Lithium-Ion Rechargeable Batteries

This study presents the synthesis, characterization, and electrochemical performance evaluation of carbon@silicon (C@Si) and graphite@carbon@silicon (G@C@Si) nanocomposites as potential anode materials for lithium-ion batteries (LIBs). Employing a combination of mechanical milling and carbonization using citric acid, we developed nanocomposites exhibiting unique core-shell structures, as confirmed by detailed SEM and TEM analysis. The G@C@Si nanocomposite displayed superior electrochemical performance, delivering an initial discharge capacity of 1724 mAh g-1 and a high initial Coulombic efficiency of 87.37%. The nanocomposite demonstrated remarkable cycling durability with a discharge capacity of 1248 mAh g-1 over 200 cycles and an average Coulombic efficiency of 99.1% and high-capacity retention of about 83%. Notably, a high capacity of 1325 mAh g-1 was observed at a high 3C rate, and the electrode showed excellent resilience by rapidly recovering to a discharge capacity of 1637 mAh g-1 when the C rate was reduced back to 0.5C. Electrochemical impedance spectra revealed a reduced charge transfer resistance of approximately 43 Ω in the G@C@Si nanocomposite as compared to that of C@Si (∼56 Ω) and nano-Si (105 Ω), indicating enhanced lithium-ion diffusion due to the integration of graphite. Postcycle electrode analysis revealed excellent structural integrity, with minimized volume changes in both C@Si and G@C@Si. XPS studies revealed a thinner SEI layer formation in the G@C@Si electrode compared to C@Si. The C@Si core-shell formation through the citric acid treatment of nano-Si and integration of graphite by mechanical milling significantly boosts the electrochemical performance of the G@C@Si nanocomposite. These findings suggest that the G@C@Si nanocomposite offers immense potential for utilization in high-capacity and high-efficiency LIBs.

Dual Strategies with Anion/Cation Co-Doping and Lithium Carbonate Coating to Enhance the Electrochemical Performance of Lithium-Rich Layered Oxides

Lithium-rich layered oxides (LLOs, Li1.2 Mn0.54 Ni0.13 Co0.13 O2 ) are widely used as cathode materials for lithium-ion batteries due to its high specific capacity, high operating voltage and low cost. However, the LLOs are faced with rapid decay of charge/discharge capacity and voltage, as well as interface side reactions, which limit its electrochemical performance. Herein, the dual strategies of sulfite/sodium ion co-doping and lithium carbonate coating were used to improve it. It founds that modified LLOs achieve 88.74 % initial coulomb efficiency, 295.3 mAh g-1 first turn discharge capacity, in addition to 216.9 mAh g-1 at 1 C, and 87.23 % capacity retention after 100 cycles. Mechanism research indicated that the excellent electrochemical performance benefits from the doping of both Na+ and SO3 2- , and it could significantly reduce the migration energy barrier of Li+ and promote Li+ migration. Meanwhile, anion and cation are co-doped greatly reduces the band gap of LLOs and increase its electrical conductivity, and its binding effect on Li+ is weakened, making it easier for Li+ to shuttle through the material. In addition, the lithium carbonate coating significantly inhibits the occurrence of interfacial side reactions of LLOs. This work provides a theoretical basis and practical guidance for the further development of LLOs with higher electrochemical performance.

Synthesis of ZnFe2O4 Nanospheres with Tunable Morphology for Lithium Storage

ZnFe2O4 (ZFO) nanospheres with complex structures have been synthesized by a one-step simple solvothermal method using two different types of precursors-metal chlorides and nitrates -and were fully characterized by XRD, SEM, XPS, and EDS. The ZFO nanospheres synthesized from chloride salts (ZFO_C) were loose with a size range of 100-200 nm, while the ZFO nanospheres synthesized from nitrate salts (ZFO_N) were dense with a size range of 300-500 nm but consisted of smaller nanoplates. The different morphologies may be caused by the different hydrolysis rates and different stabilizing effects of chloride and nitrate ions interacting with the facets of forming nanoparticles. Electrochemical tests of nitrate-based ZFO nanospheres as anode materials for lithium-ion batteries demonstrated their higher cyclic stability. The ZFO_C and ZFO_N samples have initial specific discharge/charge capacities of 1354/1020 and 1357/954 mAh∙g-1, respectively, with coulombic efficiencies of 75% and 71%. By the 100th cycle, ZFO_N has a capacity of 276 mAh∙g-1, and for ZFO_C, only 210 mAh∙g-1 remains after 100 cycles.

Recent Advances on F-Doped Layered Transition Metal Oxides for Sodium Ion Batteries

With the development of social economy, using lithium-ion batteries in energy storage in industries such as large-scale electrochemical energy storage systems will cause lithium resources to no longer meet demand. As such, sodium ion batteries have become one of the effective alternatives to LIBs. Many attempts have been carried out by researchers to achieve this, among which F-doping is widely used to enhance the electrochemical performance of SIBs. In this paper, we reviewed several types of transition metal oxide cathode materials, and found their electrochemical properties were significantly improved by F-doping. Moreover, the modification mechanism of F-doping has also been summed up. Therefore, the application and commercialization of SIBs in the future is summarized in the ending of the review.

Na+ Preintercalated MoO3 Microrods for Aqueous Zinc/Sodium Batteries with Enhanced Performance

Layered molybdenum trioxide (MoO3) is being investigated as a cathode material with high theoretical capacity and holds promise for aqueous secondary batteries. Unfortunately, the severe structural degradation of MoO3 and insufficient intrinsic properties hinder its practical application. Herein, a Na+ preintercalation strategy is reported as an effective method to construct cathodes with high performance for aqueous zinc/sodium batteries (AZSBs). Compared with pristine MoO3, the Na+ preintercalated Na0.25MoO3 cathode delivers a reversible capacity of 251.1 mAh g-1 at 1 A g-1, achieves a capacity retention of 79.2% after 500 cycles, and exhibits a high rate capability (121.5 mAh g-1 at 20 A g-1), which is superior to that in most of the previous reports. Through the experimental measurements and density functional theory (DFT) calculations, the preintercalation method could shorten the forbidden band gap and modulate the electronic structure and hence effectively inhibit the structural collapse of MoO3 microrods, induce reversible Na+ insertion, and enhance the discharge potential. This work is of significance for further research on molybdenum-based compounds as cathode materials for aqueous secondary batteries.

Improved Electrochemical Performance in an Exfoliated Tetracyanonickelate-Based Metal-Organic Framework

Tetracyanonickelate (TCN)-based metal-organic frameworks (MOFs) show great potential in electrochemical applications such as supercapacitors due to their layered morphology and tunable structure. This study reports on improved electrochemical performance of exfoliated manganese tetracyanonickelate (Mn-TCN) nanosheets produced by the heat-assisted liquid-phase exfoliation (LPE) technique. The structural change was confirmed by the Raman frequency shift of the C≡N band from 2177 to 2182 cm-1 and increased band gap from 3.15 to 4.33 eV in the exfoliated phase. Statistical distribution obtained from atomic force microscopy (AFM) shows that 50% of the nanosheets are single-to-four-layered and have an average lateral size of ∼240 nm2 and thickness of ∼1.2-4.8 nm. High-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) patterns suggest that the material maintains its crystallinity after exfoliation. It exhibits an almost 6-fold improvement in specific capacitance (from 13.0 to 72.5 F g-1) measured at a scan rate of 5 mV s-1 in 1 M KOH solution. Galvanostatic charge-discharge (GCD) measurement shows a capacity enhancement from ∼18 F g-1 in the bulk phase to ∼45 F g-1 in the exfoliated phase at a current density of 1 A g-1. Bulk crystals exhibit an increasing trend of capacitance retention by ∼125% over 1000 charge-discharge cycles attributed to electrochemical exfoliation. Electrochemical impedance spectroscopy (EIS) demonstrates a 5-fold reduction in the total equivalent series resistance (ESR) from 4864 Ω (bulk) to 1089 Ω (exfoliated). The enhanced storage capacity in the exfoliated phase results from the combined effect of the electrochemical double-layer charge storage mechanism at the nanosheet-electrolyte interface and the Faradic process characteristic of the pseudocapacitive charge storage behavior.

P-N heterojunction NiO/ZnO nanowire based electrode for asymmetric supercapacitor applications

Nickel-based oxides are selected for their inexpensive cost, well-defined redox activity, and flexibility in adjusting nanostructures via optimization of the synthesis process. This communique explores the field of energy storage for hydrothermally synthesized NiO/ZnO nanowires by analysing their capacitive behaviour. The p-type NiO was successfully built onto the well-ordered mesoporous n-type ZnO matrix, resulting in the formation of p-n heterojunction artefacts with porous nanowire architectures. NiO/ZnO nanowire-based electrodes exhibited much higher electrochemical characteristics than bare NiO nanowires. The heterojunction at the interface between the NiO and ZnO nanoparticles, their specific surface area, as well as their combined synergetic influence, are accountable for the high specific capacitance (Cs) of 1135 Fg-1at a scan rate of 5 mV s-1. NiO/ZnO nanowires show an 18% dip in initial capacitance even after 6000 cycles, indicating excellent capacitance retention and low resistance validated by electrochemical impedance spectroscopy. In addition, the specific capacitance, energy and power density of the solid state asymmetric capacitor that was manufactured by employing NiO/ZnO as the positive electrode and activated carbon as the negative electrode were found to be 87 Fg-1, 23 Whkg-1and 614 Wkg-1, respectively. The novel electrode based on NiO/ZnO demonstrates excellent electrochemical characteristics all of which point to its promising application in supercapacitor devices.

Solution Combustion Synthesis of High-Performance Nano-LiFePO4/C Cathode Material from Cost-Effective Mixed Fuels

Solution combustion synthesis (SCS) is considered as an efficient and energy-saving method for preparing LiFePO4/C composite material with the nanostructure (Nano-LiFePO4/C). In this study, Nano-LiFePO4/C cathode material was prepared using SCS using a cost-effective combination of urea and sorbitol as mixed fuels. The effect of mixed fuels on combustion behavior and microstructure as well as on electrochemical performance was studied using XRD, BET, SEM, TEM, and electrochemical characterization methods. Multiple characterization results indicated that the maximum temperature (Tm) and particle size were influenced by the usage of urea and sorbitol. The sample derived under optimum conditions exhibits a mesoporous nanostructure with a large surface specific area and attractive electrochemical performance with a discharge capacity of 153.5 mAh/g at 0.1 C, which shows strong potential for commercial applications in the future.

The Influence of Titanium Dioxide Nanosheet on Water Permeability of Silicone Rubber after Nitrogen Dioxide Aging Treatment

In this study, the aging process of a surface-functional titanium dioxide nanosheet (f-TNS) composited room-temperature-vulcanized silicone rubber (RTV) composite coating was simulated in a NO2 generation device, and then the electrochemical impedance spectroscopy (EIS) of the aged composite coating was tested in a 3.5% NaCl solution. The water permeation process was analyzed by the changes in the impedance modulus, porosity, and breakpoint frequency of the composite coating. The experimental results show that the water permeability of aged RTV decreases first and then increases with the increase in the composite proportion of f-TNS. When the composite proportion of TNS was 0.3 wt.%, the composite sample had the minimum water permeability and the best resistance to NO2 corrosion. The effect of TNS on the NO2 aging resistance of RTV composites and its mechanism were studied by SEM, FT-IR, and XPS. The impedance modulus and porosity of the aged 0.3% f-TNS/RTV, respectively, were 1.82 × 107 Ω cm2 and 0.91 × 10-4%, which increased by 2.23 times and decreased by 0.37 times, respectively, compared with the values of aged pure RTV sample. In addition, the breakpoint frequency of the aged 0.3% f-TNS/RTV also significantly reduced to 11.3 Hz, whereas it was 35 Hz in aged pure RTV.

Flexible All-Solid-State Asymmetric Supercapacitors Based on PPy-Decorated SrFeO3-δ Perovskites on Carbon Cloth

The defective structure and high oxygen vacancy concentration of SrFeO3-δ perovskite enable fast ion-electron transport, but its low conductivity still hinders the high electrochemical performance. Herein, to enhance the conductivity of SrFeO3-δ-based electrodes, polypyrrole-modified SrFeO3-δ perovskite on carbon cloth (PPy@SFO@CC) has been successfully fabricated by electrodeposition of polypyrrole (PPy) on the surface of SFO@CC. The optimal PPy700@SFO@CC electrode exhibits a specific capacitance of 421 F g-1 at 1 A g-1. It was found that the outside PPy layer not only accelerates the electron transport and ion diffusion but also creates more oxygen vacancies in SrFeO3-δ, enhancing the charge storage performance significantly. Moreover, the NiCo2O4@CC//PPy700@SFO@CC device maintains a specific capacitance of 63.6% after 3000 cycles, which is ascribed to the weak adhesion forces between the active materials and carbon cloth. Finally, the all-solid-state flexible supercapacitor NiCo2O4@CC//PPy700@SFO@CC is constructed with PVA-KOH as the solid electrolyte, delivering an energy density of 16.9 W h kg-1 at a power density of 984 W kg-1. The flexible supercapacitor retains 69% of its specific capacitance after 1000 bending and folding times, demonstrating a certain degree of foldability. The present study opens new avenues for perovskite oxide-based flexible all-solid-state supercapacitors.

Electrochemical Investigation of Calcium Substituted Monoclinic Li3 V2 (PO4 )3 Negative Electrode Materials for Sodium- and Potassium-Ion Batteries

Herein, the electrochemical properties and reaction mechanism of Li3-2 x Cax V2 (PO4 )3 /C (x = 0, 0.5, 1, and 1.5) as negative electrode materials for sodium-ion/potassium-ion batteries (SIBs/PIBs) are investigated. All samples undergo a mixed contribution of diffusion-controlled and pseudocapacitive-type processes in SIBs and PIBs via Trasatti Differentiation Method, while the latter increases with Ca content increase. Among them, Li3 V2 (PO4 )3 /C exhibits the highest reversible capacity in SIBs and PIBs, while Ca1.5 V2 (PO4 )3 /C shows the best rate performance with a capacity retention of 46% at 20 C in SIBs and 47% at 10 C in PIBs. This study demonstrates that the specific capacity of this type of material in SIBs and PIBs does not increase with the Ca-content as previously observed in lithium-ion system, but the stability and performance at a high C-rate can be improved by replacing Li+ with Ca2+ . This indicates that the insertion of different monovalent cations (Na+ /K+ ) can strongly influence the redox reaction and structure evolution of the host materials, due to the larger ion size of Na+ and K+ and their different kinetic properties with respect to Li+ . Furthermore, the working mechanism of both LVP/C and Ca1.5 V2 (PO4 )3 /C in SIBs are elucidated via in operando synchrotron diffraction and in operando X-ray absorption spectroscopy.

Trapping Halogen Anions in Cationic Viologen Porous Organic Polymers for Highly Cycling-Stable Cathode Materials

Halogens, especially Br2 and I2 , as cathode materials for lithium-ion batteries exhibit high energy density with low cost, but poor cycling performance due to their high solubility in electrolyte solution. Herein, viologen-based cationic porous organic polymers (TpVXs, X = Cl, Br, or I) with abundant pores and ionic redox-active moieties are designed to immobilize halogen anions stoichiometrically. TpVBr and TpVI electrodes exhibit high initial specific capacity (116 and 132 mAh g-1 at 0.2 C) and high average discharge voltage (≈3.0 V) without any host materials. Notably, benefiting from the porous and ionic structure, TpVBr and TpVI present excellent long-term cycling stability (86% and 98% capacity retention after 600 cycles at 0.5 C), which are far superior to those of the state-of-the-art halogen electrodes. In addition, the charge storage mechanism is investigated by in situ Raman and ex situ X-ray photoelectron spectroscopy.

Enhancing the Initial Coulombic Efficiency of Sodium-Ion Batteries via Highly Active Na2 S as Presodiation Additive

Recently, sodium-ion batteries (SIBs) have received considerable attention for large-scale energy storage applications. However, the low initial Coulombic efficiency of traditional SIBs severely impedes their further development. Here, a highly active Na2 S-based composite is employed as a self-sacrificial additive for sodium compensation in SIBs. The in situ synthesized Na2 S is wrapped in a carbon matrix with nanoscale particle size and good electrical conductivity, which helps it to achieve a significantly enhanced electrochemical activity as compare to commercial Na2 S. As a highly efficient presodiation additive, the proposed Na2 S/C composite can reach an initial charge capacity of 407 mAh g-1 . When 10 wt.% Na2 S/C additive is dispersed in the Na3 V2 (PO4 )3 cathode, and combined with a hard carbon anode, the full cell achieves 24.3% higher first discharge capacity, which corresponds to a 18.3% increase in the energy density from 117.2 to 138.6 Wh kg-1 . Meanwhile, it is found that the Na2 S additive does not generate additional gas during the initial charging process, and under an appropriate content, its reaction product has no adverse impact on the cycling stability and rate performance of SIBs. Overall, this work establishes Na2 S as a highly effective additive for the construction of advanced high-energy-density SIBs.

Operando Spatial Pressure Mapping Analysis for Prototype Lithium Metal Pouch Cells Under Practical Conditions

Monitoring and diagnosing the battery status in real-time are of utmost importance for clarifying failure mechanism, improving battery performance, and ensuring safety, particularly under fast charging conditions. Recently, advanced operando techniques have been developed to observe changes in the microstructures of lithium deposits using laboratory-scale cell designs, focusing on understanding the nature of Li metal electrodes. However, the macroscopic spatial inhomogeneity of lithium electroplating/stripping in the prototype pressurized pouch cells has not been measured in real-time under practical conditions. Herein, a new noninvasive operando technique, spatial pressure mapping analysis, is introduced to macroscopically and quantitatively measure spatial pressure changes in a pressurized pouch cell during cycling. Moreover, dynamic spatial changes in the macroscopic morphology of the lithium metal electrode are theoretically visualized by combining operando pressure mapping data with mechanical analyses of cell components. Additionally, under fast charging conditions, the direct correlation between abrupt capacity fading and sudden increases in spatial pressure distribution inhomogeneity is demonstrated through comparative analysis of pouch cells under various external pressures, electrolyte species, and electrolyte weight to cell capacity (e/c) ratios. This operando technique provides insights for assessing the current battery status and understanding the complex origin of cell degradation behavior in pressurized pouch cells.

Design and Performance of a New Zn0.5Mg0.5FeMnO4 Porous Spinel as Anode Material for Li-Ion Batteries

Due to the low capacity, low working potential, and lithium coating at fast charging rates of graphite material as an anode for Li-ion batteries (LIBs), it is necessary to develop novel anode materials for LIBs with higher capacity, excellent electrochemical stability, and good safety. Among different transition-metal oxides, AB2O4 spinel oxides are promising anode materials for LIBs due to their high theoretical capacities, environmental friendliness, high abundance, and low cost. In this work, a novel, porous Zn0.5Mg0.5FeMnO4 spinel oxide was successfully prepared via the sol-gel method and then studied as an anode material for Li-ion batteries (LIBs). Its crystal structure, morphology, and electrochemical properties were, respectively, analyzed through X-ray diffraction, high-resolution scanning electron microscopy, and cyclic voltammetry/galvanostatic discharge/charge measurements. From the X-ray diffraction, Zn0.5Mg0.5FeMnO4 spinel oxide was found to crystallize in the cubic structure with Fd3¯m symmetry. However, the Zn0.5Mg0.5FeMnO4 spinel oxide exhibited a porous morphology formed by interconnected 3D nanoparticles. The porous Zn0.5Mg0.5FeMnO4 anode showed good cycling stability in its capacity during the initial 40 cycles with a retention capacity of 484.1 mAh g-1 after 40 cycles at a current density of 150 mA g-1, followed by a gradual decrease in the range of 40-80 cycles, which led to reaching a specific capacity close to 300.0 mAh g-1 after 80 cycles. The electrochemical reactions of the lithiation/delithiation processes and the lithium-ion storage mechanism are discussed and extracted from the cyclic voltammetry curves.

Phase Engineering of Nonstoichiometric Cu2-xSe as Anode for Aqueous Zn-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are receiving widespread attention due to their abundant resources, low material cost, and high safety. However, the susceptibility of Zn metal anodes to corrosion and hydrogen evolution limits their further practical applications. Replacing Zn metal with intercalation-type anode material and constructing rocking-chair-type batteries could be an effective way to significantly prolong the cycle life of AZIBs. Herein, we present copper selenide with different crystal phase structures through a facile redox reaction as an anode for AZIBs. By comparing and analyzing different copper selenide phases, it is found that the cubic Cu2-xSe shows superior structural stability and highly reversible Zn2+ storage. Theoretical calculation results further demonstrate that the cubic Cu2-xSe possesses an increased electrical conductivity, higher Zn2+ adsorption energy, and reduced diffusion barrier, thereby promoting the storage reversibility and (de)intercalation kinetics of the Zn2+ ion. Thus, the Cu2-xSe anode delivers a long-term service life of over 15 000 cycles and impressive cumulative capacity. Furthermore, the full-cells assembled with the MnO2/CNT cathode operate stably for over 1500 cycles at 6 mA cm-2 at a negative/positive (N/P) capacity ratio of ∼1.53. This work provides a more ideal Zn-metal-free anode, which helps to push the practical applications of AZIBs.

Graphdiyne and its Composites for Lithium-Ion and Hydrogen Storage

Graphynes (GYs) are a novel type of carbon allotrope composed of sp and sp2 hybridized carbon atoms, boasting both a planar conjugated structure akin to graphene and a pore-like configuration in three-dimensional space. Graphdiyne (GDY), the first successfully synthesized member of GYs family, has gained much interest due to its fascinating electrochemical properties including a greater theoretical capacity, high charge mobility and advanced electronic transport properties, making it a promising material for energy storage applications for lithium-ion and hydrogen storage. Various methods, including heteroatom substitution, embedding, strain, and nanomorphology control, have been employed to further enhance the energy storage performance of GDY. Despite the potential of GDY in energy storage applications, there are still challenges to overcome in scaling up mass production. This review summarizes recent progress in the synthesis and application of GDY in lithium-ion and hydrogen storage, highlighting the obstacles faced in large-scale commercial application of GDY-based energy storage devices. Suggestions on possible solutions to overcome these hurdles have also been provided. Overall, the unique properties of GDY make it a promising material for energy storage applications in lithium-ion and hydrogen storage devices. The findings presented here will inspire further development of energy storage devices utilizing GDY.

Effect of Laser-Textured Cu Foil with Deep Ablation on Si Anode Performance in Li-Ion Batteries

Si is a highly promising anode material due to its superior theoretical capacity of up to 3579 mAh/g. However, it is worth noting that Si anodes experience significant volume expansion (>300%) during charging and discharging. Due to the weak adhesion between the anode coating and the smooth Cu foil current collector, the volume-expanded Si anode easily peels off, thus damaging anode cycling performance. In the present study, a femtosecond laser with a wavelength of 515 nm is used to texture Cu foils with a hierarchical microstructure and nanostructure. The peeling and cracking phenomenon in the Si anode are successfully reduced, demonstrating that volume expansion is effectively mitigated, which is attributed to the high specific surface area of the nanostructure and the protection of the deep-ablated microgrooves. Moreover, the hierarchical structure reduces interfacial resistance to promote electron transfer. The Si anode achieves improved cycling stability and rate capability, and the influence of structural features on the aforementioned performance is studied. The Si anode on the 20 μm-thick Cu current collector with a groove density of 75% and a depth of 15 μm exhibits a capacity of 1182 mAh/g after 300 cycles at 1 C and shows a high-rate capacity of 684 mAh/g at 3 C.

Oxygen-doped NiCoP derived from Ni-MOFs for high performance asymmetric supercapacitor

Oxygen doping strategy is one of the most effective methods to improve the electrochemical properties of nickel-cobalt phosphide (NiCoP)-based capacitors by adjusting its inherent electronic structure. In this paper, O-doped NiCoP microspheres derived from porous nanostructured nickel metal-organic frameworks (Ni-MOFs) were constructed through solvothermal method followed by phosphorization treatment. The O-doping concentration has a siginificant influence on the rate performance and cycle stability. The optimized O-doped NiCoP electrode material shows a specific capacitance of 632.4 F-g-1at 1 A-g-1and a high retention rate of 56.9% at 20 A g-1. The corresponding NiCoP-based asymmetric supercapacitor exhibits a high energy density of 30.1 Wh kg-1when the power density is 800.9 W kg-1, and can still maintain 82.1% of the initial capacity after 10 000 cycles at 5 A g-1.

Cobalt Oxide Arrays Anchored to Copper Foam as Efficient Binder-free Anode for Lithium Ion Batteries

The development of lithium-ion batteries with simplified assembling steps and fast charge capability is crucial for current battery applications. In this study, we propose a simple in-situ strategy for the construction of high-dispersive cobalt oxide (CoO) nanoneedle arrays, which grow vertically on a copper foam substrate. It is demonstrated that this nanoneedle CoO electrodes provide abundant electrochemical surface area. The resulting CoO arrays directly act as binder-free anodes in lithium-ion batteries with the copper foam functioning as the current collector. The highly-dispersed feature of the nanoneedle arrays enhances the effectiveness of active materials, leading to outstanding rate capability and superior long-term cycling stability. These impressive electrochemical properties are attributed to the highly-dispersed self-standing nanoarrays, the advantages of binder-free constituent, and the high exposed surface area of the copper foam substrate compared to copper foil, which enrich active surface area and facilitate charge transfer. The proposed approach to prepare binder-free lithium-ion battery anodes streamlines the electrode fabrication steps and holds significant promise for the future development of the battery industry.

Construction of Porous Carbon Nanosheet/Cu2S Composites with Enhanced Potassium Storage

Porous C nanosheet/Cu2S composites were prepared using a simple self-template method and vulcanization process. The Cu2S nanoparticles with an average diameter of 140 nm are uniformly distributed on porous carbon nanosheets. When used as the anode of a potassium-ion battery, porous C nanosheet/Cu2S composites exhibit good rate performance and cycle performance (363 mAh g-1 at 0.1 A g-1 after 100 cycles; 120 mAh g-1 at 5 A g-1 after 1000 cycles). The excellent electrochemical performance of porous C nanosheet/Cu2S composites can be ascribed to their unique structure, which can restrain the volume change of Cu2S during the charge/discharge processes, increase the contact area between the electrode and the electrolyte, and improve the electron/ionic conductivity of the electrode material.

Electrochemical Performances of Nickel-Rich Single-Crystal LiNi0.83 Co0.12 Mn0.05 O2 Cathode Material for Lithium-Ion Batteries Synthesized by Tuning Li+ /Ni2+ Mixing

Single-crystal nickel-rich materials are promising alternatives to polycrystalline cathodes owing to their excellent structure stability and cycle performance while the cathode material usually appears high cation mixing, which may have a negative effect on its electrochemical performance. The study presents the structural evolution of single-crystal LiNi0.83 Co0.12 Mn0.05 O2 in the temperature-composition space using temperature-resolved in situ XRD and the cation mixing is tuned to improve electrochemical performances. The as-synthesized single-crystal sample shows high initial discharge specific capacity (195.5 mAh g-1 at 1 C), and excellent capacity retention (80.1 % after 400 cycles at 1 C), taking account of lower structure disorder (Ni2+ occupying Li sites is 1.56 %) and integrated grains with an average of 2-3 μm. In addition, the single-crystal material also displays a superior rate capability of 159.1 mAh g-1 at the rate of 5 C. This excellent performance is attributed to the rapid Li+ transportation within the crystal structure with fewer Ni2+ cations in Li layer as well as intactly single grains. In sum, the regulation of Li+ /Ni2+ mixing provides a feasible strategy for boosting single-crystal nickel-rich cathode material.

Improved Electrochemical Performance of Li-Rich Cathode Materials via Spinel Li2MoO4 Coating

Li-rich manganese-based cathode materials (LRMs) are considered one of the most promising cathode materials for the next generation of lithium-ion batteries (LIBs) because of their high energy density. However, there are problems such as a capacity decay, poor rate performance, and continuous voltage drop, which seriously limit their large-scale commercial applications. In this work, Li1.2Mn0.54Co0.13Ni0.13O2 coated with Li2MoO4 with a unique spinel structure was prepared with the wet chemistry method and the subsequent calcination process. The Li2MoO4 coating layer with a spinel structure could provide a 3D Li+ transport channel, which is beneficial for improving rate performance, while protecting LRMs from electrolyte corrosion, suppressing interface side reactions, and improving cycling stability. The capacity retention rate of LRMs coated with 3 wt% Li2MoO4 increased from 69.25% to 81.85% after 100 cycles at 1 C, and the voltage attenuation decreased from 7.06 to 4.98 mV per cycle. The lower Rct also exhibited an improved rate performance. The results indicate that the Li2MoO4 coating effectively improves the cyclic stability and electrochemical performance of LRMs.

Recent advances in MXene-based nanocomposites for supercapacitors

MXene materials have become a competitive candidate for electrochemical energy storage due to their unique two-dimensional layered structure, high density, metal-like conductivity, fast ion intercalation, tunable surface terminal groups, and good mechanical flexibilities, showing unique application advantages in the field of supercapacitors. With widely research of MXene in energy storage applications, plenty of studies in synthesis strategies of MXene, including etching, intercalation and exfoliation processes, and its charge storage mechanism in supercapacitors have been conducted. However, the restacking of two-dimensional MXene nanosheets severely affects their electrochemical performance. To prevent the stacking of MXene, MXene-based nanocomposite electrode materials have been developed with remarkable electrochemical performance by incorporating conventional active capacitive materials, including metal oxides/sulfides and conductive polymers, with MXene. This review summarizes the etching strategies of MXenes and selection of intercalants, also discusses the charge storage mechanism of MXenes in aqueous and nonaqueous electrolytes. It mainly expounds the preparation strategies and applications of MXene-based nanocomposites in supercapacitors, including MXene/metal oxide, MXene/metal sulfide, MXene/conducting polymer, and MXene/carbon-based composites. Additionally, the advantages of combining MXene with other active materials in supercapacitor applications, which support its promising prospects, are discussed. Finally, the critical challenges faced by MXene-based nanocomposites in long-term research are mentioned.

Electrochemistry of Titanium Carbide MXenes in Supercapacitor

Novel electrode materials are always explored to achieve better performance of supercapacitors. Titanium carbide MXenes, Ti3 C2 Tx , are one of the very promising candidates for electrode materials in supercapacitors due to their unique structural and ion storage properties as 2D materials. Their large specific surface area, adjustable functionalized surface terminals, high electrical conductivities, hydrophilicity, and high Faradaic capacitance, also known widely but confusingly as pseudocapacitance, are highly desirable for making high-performance electrodes with increased dis-/charging rates and capacities. Herein, some selective electrochemical considerations of Ti3 C2 Tx MXenes for uses in supercapacitors are critically reviewed and assessed, aiming at a better fundamental understanding of the electrochemical basics and processes in Ti3 C2 Tx MXene-based electrode materials for supercapacitor applications.

Synthesis and Properties of Carbon Microspheres from Waste Office Paper

As a kind of biomass resource, waste office paper can be used as a carbon precursor to prepare carbon materials. In this work, carbon microspheres with regular shape, uniform particle size and high carbon content were successfully prepared from waste office paper via a hydrothermal synthesis method with sulfuric acid as the catalyst. The effects of reaction temperature and sulfuric acid dosage on the morphology of the carbon microspheres were studied. The formation mechanism of the carbon microspheres was investigated by analyzing the structure and composition of the products. The results show that the hydrolysis of cellulose in waste paper under hydrothermal conditions was the key for the formation of carbon microspheres. The temperature of hydrothermal reaction and the use of sulfuric acid can affect the morphology of carbon microspheres. The carbon microspheres synthesized at 210 °C with 10 mL sulfuric acid have the best surface morphology, with uniform particle size and higher dispersion. Cyclic voltammetry and electrochemical impedance spectroscopy show that the carbon microspheres have good capacitance performance and can be used in capacitors. This study provides a low-cost precursor for carbon microspheres as well as a new method for the recycle of waste paper.

Thermal Expansion Neutralization Enhancing the Cycling Stability of Ni-Rich LiNi0.6Co0.2Mn0.2O2 Cathode Material

As promising cathode candidates with advantageous capacity and price superiority for lithium-ion batteries, Ni-rich materials are severely impeded in the practical application due to their poor microstructural stability induced by the intrinsic Li⁺/Ni²⁺ cation mixing and mechanical stress accumulation upon cycling. In this work, a synergetic approach is demonstrated to improve the microstructural and thermal stabilities of Ni-rich LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode material through taking advantage of the thermal expansion offset effect of the LiZr₂(PO₄)₃ (LZPO) modification layer. The optimized NCM622@LZPO cathode exhibits a significantly enhanced cyclability with a capacity retention of 67.7% after 500 cycles at 0.2 C and delivers a specific capacity of 115 mAh g^-1 with a capacity retention of 64.2% after 300 cycles under 55 °C. Exploiting the chemical environment analysis of the Ni element detected by the synchrotron radiation technique, it is found that the mixing degree of Li⁺/Ni²⁺ cations in the bulk Ni-rich material can be effectively depressed through interfacial Zr⁴⁺ doping during the preparation of the LZPO-modified material. Additionally, time- and temperature-dependent powder diffraction spectra were collected to monitor the structure evolutions of pristine NCM622 and NCM622@LZPO cathodes in the initial cycles and under various temperatures, revealing the contribution of negative thermal expansion LZPO coating in promoting microstructural stability of the bulk NCM622 cathode. The introduction of NTE functional compounds might provide a universal strategy to address the stress accumulation and volume expansion issues of various cathode materials for advanced secondary-ion batteries.

Low temperature-synthesized MgAl2 O4 :Eu3+ nanophosphors and their structural validations using density functional theory: photoluminescence, photocatalytic, and electrochemical properties for multifunctional applications

A low temperature-assisted and oxalyl dihydrazide fuel-induced combustion synthesized series of uncalcined MgAl2 O4 :Eu3+ nanophosphors showed an average crystallite size of ~20 nm, and bandgap energy (Eg ) of 4.50-5.15 eV, and were validated using density functional theory and found to match closely with the experimental values. The photoluminescence characteristic emission peaks of Eu3+ ions were recorded between 480 and 680 nm. The nanophosphors excited at 392 nm showed f-f transitions assigned as 5 D0 →7 FJ (J = 0, 1, 2, and 3). The optimized MgAl2 O4 phosphors had Commission Internationale de l'Eclairage coordinates in the red region, a correlated colour temperature of 2060 K, and a colour purity of 98.83%. The estimated luminescence quantum efficiency ( η ) was observed to be ~63% using Judd-Ofelt analysis. Electrochemical and photocatalytic performance were explored and indicated its multifunctional applications. Therefore, MgAl2 O4 :Eu3+ nanophosphors could be used for the fabrication of light-emitting diodes, industrial dye degradation, and as electrodes for supercapacitor applications.