Enhancing the Electrochemical Performance of Ni-Rich LiNi0.88Co0.09Al0.03O2 Cathodes through Tungsten-Doping for Lithium-Ion Batteries

The tungsten-doped (0.5 and 1.0 mol%) LiNi_0.88Co_0.09Al_0.03O₂ (NCA) cathode materials are manufactured to systematically examine the stabilizing effect of W-doping. The 1.0 mol% W-doped LiNi_0.88Co_0.09Al_0.03O₂ (W1.0-NCA) cathodes deliver 173.5 mAh g⁻¹ even after 100 cycles at 1 C, which is 95.2% of the initial capacity. While the capacity retention of NCA cathodes cycled in identical conditions is 86.3%. The optimal performances of the W1.0-NCA could be ascribed to the suppression of impendence increase and the decrease in anisotropic volume change, as well as preventing the collapse of structures during cycling. These findings demonstrate that the W-doping considerably enhances the electrochemical performance of NCA, which has potential applications in the development of Ni-rich layered cathode materials that can display high capacity with superior cycling stability.

Ionic Liquid-Impregnated ZIF-8/Polypropylene Solid-like Electrolyte for Dendrite-free Lithium-Metal Batteries

Metal-organic framework (MOF)-based solid-like electrolytes have attracted more prospective due to the combined merits of solid-state electrolytes and liquid electrolytes. However, most MOF-based solid-like electrolytes using organic liquid electrolytes cannot fundamentally solve the safety issues of lithium-metal batteries, and the ionic conductivity and mechanical strength of the electrolytes should be further enhanced. Herein, the ionic liquid-impregnated polypropylene (PP) porous membrane with integrally distributed ZIF-8 nanoparticles is designed. The solid-like electrolyte possesses an increased ionic conductivity of 2.09 × 10^-4 S cm^-1 at 25 °C, lithium-ion transference number (0.45), mechanical strength, electrochemical window, and excellent nanowetted interfaces. Furthermore, the Li symmetrical cell shows excellent Li plating/stripping properties for 550 h at 0.1 mA cm^-2 and 0.1 mA h cm^-2. The LiFePO₄/Li full battery with the solid-like electrolyte demonstrates an excellent rate capability and cycling stability with the initial discharge capacity of 157.9 mA h g^-1 and a capacity retention ratio of 91.23% after 450 cycles at 0.2 C. The work offers a new avenue toward MOF-based solid-like electrolytes for high-safety lithium-metal batteries.

Investigating the Impact of the Washing Steps of Layered Double Hydroxides (LDH) on the Electrochemical Performance

The washing of layered double hydroxides (LDH) material is mostly purposed to discard the unreacted products after the reaction has been completed. However, this study demonstrated that the washing stage can also be targeted to optimise the electrochemical performance of LDH by using an appropriate solvent. Solvents, namely, ethanol, acetone, and an ethanol–acetone solution (2:1) were used for the washing of LDH and the impacts thereof on the structural, physical, chemical, morphological, and electrochemical properties were investigated. Using Williamson–Hall analysis, we observed modifications on the crystalline domain. The specific surface area and pore parameters for all the samples were also differently affected. The Fourier transform infrared (FTIR) measurements displayed evident changes in the basic sites. The electrochemical performances of samples were analysed. The sample washed with the ethanol–acetone solution exhibited a specific capacitance of 1807.26 Fg⁻¹ at 10 mVs⁻¹, which is higher than that of other samples as well as low internal resistance compared to its counterpart. This demonstrates that the use of an appropriate solvent during the washing stage of LDH affects the electrochemical properties.

Self-Enhancing Gel Polymer Electrolyte by In Situ Construction for Enabling Safe Lithium Metal Battery

Lithium metal battery (LMB) possessing a high theoretical capacity is a promising candidate of advanced energy storage devices. However, its safety and stability are challenged by lithium dendrites and the leakage of liquid electrolyte. Here, a self-enhancing gel polymer electrolyte (GPE) is created by in situ polymerizing 1,3-dioxolane (DOL) in the nanofibrous skeleton for enabling safe LMB. The nanofiber membrane possesses a better affinity with poly-DOL (PDOL) than commercial separator for constructing homogeneous GPE with enhanced ion conductivity. Furthermore, polydopamine is introduced on nanofiber membrane to form hydrogen bonding with PDOL and bis((trifluoromethyl)sulfonyl)imide anion, dramatically improving the mechanical strength, ionic conductivity, and transference number of GPE. Besides, molecular dynamic simulation is used to reveal the intrinsic factors of high ionic conductivity and reinforcing effect in the meantime. Consequently, the LiFePO4 //Li batteries using self-enhancing GPE show extraordinary cyclic stability over 800 cycles under high current density of 2 C, with a capacity decay of 0.021% per cycle, effectively suppressing the growth of lithium dendrites. This ingenious strategy is expected to manufacture advanced performance and high safety LMBs and compatible with the current battery production.

Preparation and Electrochemical Performance of Three-Dimensional Vertically Aligned Graphene by Unidirectional Freezing Method

Three-dimensional vertically aligned graphene (3DVAG) was prepared by a unidirectional freezing method, and its electrochemical performances were evaluated as electrode materials for zinc−ion hybrid supercapacitors (ZHSCs). The prepared 3DVAG has a vertically ordered channel structure with a diameter of about 20−30 μm and a length stretching about hundreds of microns. Compared with the random structure of reduced graphene oxide (3DrGO), the vertical structure of 3DVAG in a three−electrode system showed higher specific capacitance, faster ion diffusion, and better rate performance. The specific capacitance of 3DVAG reached 66.6 F·g⁻¹ and the rate performance reached 92.2%. The constructed 3DVAG zinc−ion hybrid supercapacitor also showed excellent electrochemical performance. It showed good capacitance retention up to 94.6% after 3000 cycles at the current density of 2 A·g⁻¹.

Surface Atomic Decoration of a Manganite to a Modulable Oxygen Evolution Reaction

Aiming at the fundamental understanding of oxygen evolution reaction (OER) in epitaxial perovskite transition metal oxide (TMO) thin films, we evaluate the surface decoration conditions, including lattice orientation and surface morphology, of La_2/3Sr_1/3MnO₃ (LSMO) related to its modulable OER performance. The LSMOs with orientations of (001), (110), and, (111) exhibit different OER activities owing to the discrepant surface density of Mn. Furthermore, tuning of the surface atomic terrace width of LSMO shows a more efficient path to modulate the OER performance by introducing a high-valence Mn state owing to the surface dangling bonds of LSMO. As the electrochemical process is dominated by the interface of the TMO surface and electrolyte, our investigation can approach the fundamental understanding of a perovskite-type TMO surface state and its OER performance while highlighting the role of the nonbulk electron state in a promising TMO electrocatalyst in abundant electrochemical processes.

Ti3Si0.75Al0.25C2 Nanosheets as Promising Anode Material for Li-Ion Batteries

Herein we report that novel two-dimensional (2D) Ti₃Si_0.75Al_0.25C₂ (TSAC) nanosheets, obtained by sonically exfoliating their bulk counterpart in alcohol, performs promising electrochemical activities in a reversible lithiation and delithiation procedure. The as-exfoliated 2D TSAC nanosheets show significantly enhanced lithium-ion uptake capability in comparison with their bulk counterpart, with a high capacity of ≈350 mAh g^-1 at 200 mA g^-1, high cycling stability and excellent rate performance (150 mAh g^-1 after 200 cycles at 8000 mA g^-1). The enhanced electrochemical performance of TSAC nanosheets is mainly a result of their fast Li-ion transport, large surface area and small charge transfer resistance. The discovery in this work highlights the uniqueness of a family of 2D layered MAX materials, such as Ti₃GeC₂, Ti₃SnC₂ and Ti₂SC, which will likely be the promising choices as anode materials for lithium-ion batteries (LIBs).

Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO₆octahedra by the addition of edge-sharing NbO₆octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb₂O₅·15WO₃nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb₂O₅·15WO₃nanowires do exhibit more advantages over h-WO₃nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g^-1, at 10C, 1C = 100 mA g^-1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H⁺ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO₃. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.

Ultralong-Life Cathode for Aqueous Zinc-Organic Batteries via Pouring 9,10-Phenanthraquinone into Active Carbon

Organic carbonyl electrode materials have shown a great potential in various rechargeable batteries but limited by the problems of poor cycling and rate performance owing to their high solubility in aqueous electrolytes and low conductivity. To address these problems, the 9,10-phenanthraquinone (PQ)@active carbon (AC) composite fabricated by melting PQ molecules into porous AC is considered as a superstable cathode material for aqueous zinc batteries. The introduction of AC improves the structural stability and restrains the PQ dissolution in an aqueous electrolyte. As a result, the PQ@AC composite electrode delivers a reversible discharge capacity of 150.0 mA h g^-1 at a current density of 0.1 A g^-1, and it also features an unprecedented cycling performance of 36 000 cycles with a capacity retention of 96.3% at 5 A g^-1. Moreover, the Zn²⁺ and H⁺ in an aqueous electrolyte are verified to co-insert into the PQ@AC composite electrode using various ex situ characterizations and electrochemical test. This strategy provides a new avenue for organic carbonyl compounds with quinone substructures to improve their electrochemical performance of other batteries.

Joint Enhancement in the Electrochemical Reversibility and Cycle Lives for Copper Sulfide for Sodium- and Potassium-Ion Storage via Selenium Substitution

Transition metal sulfides have received considerable interest as the anodes for sodium-ion (SIBs) and potassium-ion batteries (PIBs) owing to their high theoretical capacity and suitable working potential. However, they suffer from poor electrochemical reversibility and limited cycle lives. Herein, we design and synthesize a Se-substituted CuS material, which demonstrates superior electrochemical properties for both potassium and sodium storage because of the enhanced electronic conductivity, lowered diffusion barrier, and shortened diffusion pathway. The anode delivers a specific capacity of 374 mA h g^-1 at a current density of 5 A g^-1 in SIBs and 341 mA h g^-1 at 2 A g^-1 in PIBs and nearly 100% capacity retention over 2000 cycles (SIBs) and 600 cycles (PIBs), respectively. Moreover, a combined measurement including X-ray diffraction, Raman, and transmission electron microscopy reveals an interesting discharge product of Na₂S_0.8Se_0.2, which could accelerate the conversion reaction and enhance the electrochemical reversibility.

The Synergetic Effect Induced High Electrochemical Performance of CuO/Cu2O/Cu Nanocomposites as Lithium-Ion Battery Anodes

Due to the high theoretical capability, copper-based oxides were widely investigated. A facile water bath method was used to synthesis CuO nanowires and CuO/Cu₂O/Cu nanocomposites. Owing to the synergetic effect, the CuO/Cu₂O/Cu nanocomposites exhibit superior electrochemical performance compared to the CuO nanowires. The initial discharge and charge capacities are 2,660.4 mAh/g and 2,107.8 mAh/g, and the reversible capacity is 1,265.7 mAh/g after 200 cycles at 200 mA/g. Moreover, the reversible capacity is 1,180 mAh/g at 800 mA/g and 1,750 mAh/g when back to 100 mA/g, indicating the excellent rate capability. The CuO/Cu₂O/Cu nanocomposites also exhibit relatively high electric conductivity and lithium-ion diffusion coefficient, especially after cycling. For the energy storage mechanism, the capacitive controlled mechanism is predominance at the high scan rates, which is consistent with the excellent rate capability. The outstanding electrochemical performance of the CuO/Cu₂O/Cu nanocomposites indicates the potential application of copper-based oxides nanomaterials in future lithium-ion batteries.

3D Printing for Solid-State Energy Storage

Ever-growing demand to develop satisfactory electrochemical devices has driven cutting-edge research in designing and manufacturing reliable solid-state electrochemical energy storage devices (EESDs). 3D printing, a precise and programmable layer-by-layer manufacturing technology, has drawn substantial attention to build advanced solid-state EESDs and unveil intrinsic charge storage mechanisms. It provides brand-new opportunities as well as some challenges in the field of solid-state energy storage. This review focuses on the topic of 3D printing for solid-state energy storage, which bridges the gap between advanced manufacturing and future EESDs. It starts from a brief introduction followed by an emphasis on 3D printing principles, where basic features of 3D printing and key issues for solid-state energy storage are both reviewed. Recent advances in 3D printed solid-state EESDs including solid-state batteries and solid-state supercapacitors are then summarized. Conclusions and perspectives are also provided regarding the further development of 3D printed solid-state EESDs. It can be expected that advanced 3D printing will significantly promote future evolution of solid-state EESDs.

Carbonaceous Hosts for Sulfur Cathode in Alkali-Metal/S (Alkali Metal = Lithium, Sodium, Potassium) Batteries

Alkali-metal/sulfur batteries hold great promise for offering relatively high energy density compared to conventional lithium-ion batteries. By providing viable sulfur composites that can be effectively used, carbonaceous hosts as a key component play critical roles in overcoming the preliminary challenges associated with the insulating sulfur and its relatively soluble polysulfides. Herein, a comprehensive overview and recent progress on carbonaceous hosts for advanced next-generation alkali-metal/sulfur batteries are presented. In order to encapsulate the highly active sulfur mass and fully limit polysulfide dissolution, strategies for tailoring the design and synthesis of carbonaceous hosts are summarized in this work. The sticking points that remain for sulfur cathodes in current alkali-metal/sulfur systems and the future remedies that can be provided by carbonaceous hosts are also indicated, which can lead to long cycling lifetimes and highly reversible capacities under repeated sulfur reduction reactions in alkali-metal/sulfur during cycling.

Boosting the Electrochemical Performance of Li1.2Ni0.13Co0.13Mn0.54O2 by Rough Coating with the Superionic Conductor Li7La3Zr2O12

Li-rich Mn-based layered compounds have progressed as promising cathode materials for lithium-ion batteries (LIBs) due to their relatively low cost, considerable energy storage capacity, and high operating voltage. However, they suffer critical drawbacks, such as capacity decay and inferior rate performance, which restrain their real applications. We carried out surface modification via rough coating of superionic conductor Li₇La₃Zr₂O₁₂ (LLZO) on the Li-rich Mn-based layered cathode. The cathode with a LLZO coating exhibits significantly improved electrochemical performance, which mainly benefits from the enhanced Li-ion diffusion and reduced side reactions at electrode/electrolyte interfaces via effective coating of LLZO layer. This work provides a facile and efficient way to design Li-rich Mn-based cathodes for high-energy and stable LIBs.

Polyethylene Oxide as a Multifunctional Binder for High-Performance Ternary Layered Cathodes

Nickel cobalt manganese ternary cathode materials are some of the most promising cathode materials in lithium-ion batteries, due to their high specific capacity, low cost, etc. However, they do have a few disadvantages, such as an unstable cycle performance and a poor rate performance. In this work, polyethylene oxide (PEO) with high ionic conductance and flexibility was utilized as a multifunctional binder to improve the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials. Scanning electron microscopy showed that the addition of PEO can greatly improve the adhesion of the electrode components and simultaneously enhance the integrity of the electrode. Thus, the PEO-based electrode (20 wt% PEO in PEO/PVDF) shows a high electronic conductivity of 19.8 S/cm, which is around 15,000 times that of the pristine PVDF-based electrode. Moreover, the PEO-based electrode exhibits better cycling stability and rate performance, i.e., the capacity increases from 131.1 mAh/g to 147.3 mAh/g at 2 C with 20 wt% PEO addition. Electrochemical impedance measurements further indicate that the addition of the PEO binder can reduce the electrode resistance and protect the LiNi_0.6Co_0.2Mn_0.2O₂ cathode materials from the liquid electrolyte attack. This work offers a simple yet effective method to improve the cycling performance of the ternary cathode materials by adding an appropriate amount of PEO as a binder in the electrode fabrication process.

Exploring the Effect of a MnO2 Coating on the Electrochemical Performance of a Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material

The effect of electrochemically active MnO2 as a coating material on the electrochemical properties of a Li1.2Mn0.54Ni0.13Co0.13O2 (LTMO) cathode material is explored in this article. The structural analysis indicated that the layered structure of the LTMO was unchanged after the modification with MnO2. The morphology inspection demonstrated that the rod-like LTMO particles were encapsulated by a compact coating layer. The MnO2 layer was able to hinder the electrolyte solution from corroding the LTMO particles and optimized the formation of a solid electrolyte interface (SEI). Meanwhile, lithium ions were reversibly inserted into and extracted from MnO2, which afforded an additional capacity. Compared with the bare LTMO, the MnO2-coated sample exhibited enhanced electrochemical performance. After the MnO2 coating, the first discharge capacity rose from 224.2 to 239.1 mAh/g, and the initial irreversible capacity loss declined from 78.2 to 46.0 mAh/g. Meanwhile, the cyclic retention climbed up to 88.2% after 100 cycles at 0.5 C, which was more competitive than that of the bare LTMO with a value of 71.1%. When discharging at a high current density of 2 C, the capacity increased from 100.5 to 136.9 mAh/g after the modification. These investigations may be conducive to the practical application of LTMO in prospective automotive Li-ion batteries.

Insights into the Enhanced Structural and Thermal Stabilities of Nb-Substituted Lithium-Rich Layered Oxide Cathodes

Lithium-rich manganese-based layered oxides (LLOs) are considered to be the most promising cathode materials for next-generation lithium-ion batteries (LIBs) for their higher reversible capacity, higher operating voltage, and lower cost compared with those of other commercially available cathode materials. However, irreversible lattice oxygen release and associated severe structural degradation that exacerbate under high temperature and deep delithiation hinder the large-scale application of LLOs. Herein, we propose a strategy to stabilize the layered lattice framework and improve the thermal stability of cobalt-free Li_1.2Mn_0.53Ni_0.27O₂ by doping with 4d transition metal niobium (Nb). Detailed atomic-scale imaging, in situ characterization, and DFT simulations confirm that the induced strong Nb-O bonds stabilize the oxygen lattice framework and restrains the fracture of TM-O bonds, thereby inhibiting the release of lattice oxygen and the continuous migration of TM ions to the lithium layer during the cycle. Furthermore, Nb doping also promotes the surface rearrangement to form a Ni-enrichment layered/rocksalt heterogeneous interface to enhance surface structural stability. As a result, the Nb-doped material delivers a capacity of 181.7 mAh g^-1 with retention of 85.5% after 200 cycles at 1C, extraordinary thermal stability with a capacity retention of 80.7% after 200 cycles at 50 °C, and superior rate capability.

Rational Design of Effective Binders for LiFePO4 Cathodes

Polymer binders are critical auxiliary additives to Li-ion batteries that provide adhesion and cohesion for electrodes to maintain conductive networks upon charge/discharge processes. Therefore, polymer binders become interconnected electrode structures affecting electrochemical performances, especially in LiFePO4 cathodes with one-dimensional Li+ channels. In this paper, recent improvements in the polymer binders used in the LiFePO4 cathodes of Li-ion batteries are reviewed in terms of structural design, synthetic methods, and working mechanisms. The polymer binders were classified into three types depending on their effects on the performances of LiFePO4 cathodes. The first consisted of PVDF and related composites, and the second relied on waterborne and conductive binders. Profound insights into the ability of binder structures to enhance cathode performance were discovered. Overcoming the bottleneck shortage originating from olivine structure LiFePO4 using efficient polymer structures is discussed. We forecast design principles for the polymer binders used in the high-performance LiFePO4 cathodes of Li-ion batteries. Finally, perspectives on the application of future binder designs for electrodes with poor conductivity are presented to provide possible design directions for chemical structures.

Self-Assembled Triple (H+/O2-/e-) Conducting Nanocomposite of Ba-Co-Ce-Y-O into an Electrolyte for Semiconductor Ionic Fuel Cells

Triple (H⁺/O^2-/e^-) conducting oxides (TCOs) have been extensively investigated as the most promising cathode materials for solid oxide fuel cells (SOFCs) because of their excellent catalytic activity for oxygen reduction reaction (ORR) and fast proton transport. However, here we report a stable twin-perovskite nanocomposite Ba-Co-Ce-Y-O (BCCY) with triple conducting properties as a conducting accelerator in semiconductor ionic fuel cells (SIFCs) electrolytes. Self-assembled BCCY nanocomposite is prepared through a complexing sol-gel process. The composite consists of a cubic perovskite (Pm-3m) phase of BaCo_0.9Ce_0.01Y_0.09O_3-δ and a rhombohedral perovskite (R-3c) phase of BaCe_0.78Y_0.22O_3-δ. A new semiconducting-ionic conducting composite electrolyte is prepared for SIFCs by the combination of BCCY and CeO₂ (BCCY-CeO₂). The fuel cell with the prepared electrolyte (400 μm in thickness) can deliver a remarkable peak power density of 1140 mW·cm^-2 with a high open circuit voltage (OCV) of 1.15 V at 550 °C. The interface band energy alignment is employed to explain the suppression of electronic conduction in the electrolyte. The hybrid H⁺/O^2- ions transport along the surfaces or grain boundaries is identified as a new way of ion conduction. The comprehensive analysis of the electrochemical properties indicates that BCCY can be applied in electrolyte, and has shown tremendous potential to improve ionic conductivity and electrochemical performance.

Preparation of TiSi2 Powders with Enhanced Lithium-Ion Storage via Chemical Oven Self-Propagating High-Temperature Synthesis

Although silicon has highest specific capacity as anode for lithium-ion battery (LIB), its large volume change during the charge/discharge process becomes a great inevitable hindrance before commercialization. Metal silicides may be an alternative choice because they have the ability to accommodate the volume change by dispersing Si in the metal matrix as well as very good electrical conductivity. Herein we report on the suitability of lithium-ion uptake in C54 TiSi₂ prepared by the "chemical oven" self-propagating high-temperature synthesis from the element reactants, which was known as an inactive metal silicide in lithium-ion storage previously. After being wrapped by graphene, the agglomeration of TiSi₂ particles has been efficiently prevented, resulting in an enhanced lithium-ion storage performance when using as an anode for LIB. The as-received TiSi₂/RGO hybrid exhibits considerable activities in the reversible lithiation and delithiation process, showing a high reversible capacity of 358 mAh/g at a current density of 50 mA/g. Specially, both TiSi₂ and TiSi₂/RGO electrodes show a remarkable enhanced electrochemical performance along with the cycle number, indicating the promising potential in lithium-ion storage of this silicide. Ex-situ XRD during charge/discharge process reveals alloying reaction may contribute to the capacity of TiSi₂. This work suggests that TiSi₂ and other inactive transition metal silicides are potential promising anode materials for Li-ion battery and capacitor.

Stabilizing P2-Type Ni-Mn Oxides as High-Voltage Cathodes by a Doping-Integrated Coating Strategy Based on Zinc for Sodium-Ion Batteries

The key to development of high-voltage P2-type Na_0.66Ni_0.33Mn_0.67O₂ is the modification methods that can effectively improve its electrochemical reversibility. Herein, a doping-integrated coating strategy based on zinc element is proposed to modify P2-type Na_0.66Ni_0.33Mn_0.67O₂, which can be achieved by a facile one-step solid-state reaction. The formation mechanism of Na_0.66Ni_0.26Zn_0.07Mn_0.67O₂@0.06ZnO (NNZM@0.06ZnO) is investigated, revealing that the spinel and P3 intermediate phases appear prior to the formation of the P2 phase. Ni²⁺ can be preferentially incorporated into the P2 structure in competition with Zn²⁺ at high temperature, resulting in a uniform enrichment of ZnO on the surface. A small amount of Zn²⁺ doping significantly suppresses the Na⁺/vacancy ordering effect and improves the structural reversibility. Furthermore, the electrolyte decomposition is effectively reduced because of the presence of the ZnO coating layer, leading to the formation of a thin cathode electrolyte interphase film that is favorable to fast Na⁺ diffusion. In virtue of the Zn²⁺ doping and in situ formed ZnO coating, NNZM@0.06ZnO exhibits excellent cycling stability with a capacity retention of 83.7% after 100 cycles at 100 mA g^-1 and rate performance with a discharge capacity of 56.4 mAh g^-1 at 2000 mA g^-1, which significantly outperforms the uncoated Na_0.66Ni_0.26Zn_0.07Mn_0.67O₂ and the Na_0.66Ni_0.26Zn_0.07Mn_0.67O₂/0.06ZnO with the coating layer introduced by mechanical milling. This work provides a new strategy to design high-performance cathode materials for sodium-ion batteries.

MIL-53 Metal-Organic Framework as a Flexible Cathode for Lithium-Oxygen Batteries

Li-air batteries possess higher specific energies than the current Li-ion batteries. Major drawbacks of the air cathode include the sluggish kinetics of the oxygen reduction (OER), high overpotentials and pore clogging during discharge processes. Metal-Organic Frameworks (MOFs) appear as promising materials because of their high surface areas, tailorable pore sizes and catalytic centers. In this work, we propose to use, for the first time, aluminum terephthalate (well known as MIL-53) as a flexible air cathode for Li-O₂ batteries. This compound was synthetized through hydrothermal and microwave-assisted routes, leading to different particle sizes with different aspect ratios. The electrochemical properties of both materials seem to be equivalent. Several behaviors are observed depending on the initial value of the first discharge capacity. When the first discharge capacity is higher, no OER occurs, leading to a fast decrease in the capacity during cycling. The nature and the morphology of the discharge products are investigated using ex situ analysis (XRD, SEM and XPS). For both MIL-53 materials, lithium peroxide Li₂O₂ is found as the main discharge product. A morphological evolution of the Li₂O₂ particles occurs upon cycling (stacked thin plates, toroids or pseudo-spheres).

Lignocellulosic Biomass-Derived Carbon Electrodes for Flexible Supercapacitors: An Overview

With the increasing demand for high-performance electronic devices in smart textiles, various types of flexible/wearable electronic device (i.e., supercapacitors, batteries, fuel cells, etc.) have emerged regularly. As one of the most promising wearable devices, flexible supercapacitors from a variety of electrode materials have been developed. In particular, carbon materials from lignocellulosic biomass precursor have the characteristics of low cost, natural abundance, high specific surface area, excellent electrochemical stability, etc. Moreover, their chemical structures usually contain a large number of heteroatomic groups, which greatly contribute to the capacitive performance of the corresponding flexible supercapacitors. This review summarizes the working mechanism, configuration of flexible electrodes, conversion of lignocellulosic biomass-derived carbon electrodes, and their corresponding electrochemical properties in flexible/wearable supercapacitors. Technology challenges and future research trends will also be provided.

Direct epitaxial growth of nickel phosphide nanosheets on nickel foam as self-support electrode for efficient non-enzymatic glucose sensing

Design and develop of cost-effective non-enzymatic electrode materials is of great importance for next generation of glucose sensors. In this work, we report a high-performance self-supporting electrode fabricated via direct epitaxial growth of nickel phosphide on Ni foam (Ni₂P/NF) for nonenzymatic glucose sensors in alkaline solution. Under the optimal conditions, the uniform Ni₂P nanosheets could be obtained with an average thickness of 80 nm, which provides sufficient active sites for glucose molecules. As a consequence, the Ni₂P/NF electrode displays superior electrochemistry performances with a high sensitivity of 6375.1μA mM^-1cm^-2, a quick response about 1 s, a low detection limit of 0.14μM (S/N = 3), and good selectivity and specificity. Benefit from the strong interaction between Ni₂P and NF, the Ni₂P/NF electrode is also highly stable for long-term applications. Furthermore, the Ni₂P/NF electrode is capable of analyzing glucose in human blood serum with satisfactory results, indicating that the Ni₂P/NF is a potential candidate for glucose sensing in real life.

One-Pot Hydrothermal-Derived NiS2 -CoMo2 S4 with Vertically Aligned Nanorods as a Binder-Free Electrode for Coin-Cell-Type Hybrid Supercapacitor

Transition bimetallic sulfides are exploited as high-capacity electrode materials in energy storage devices owing to their abundant electroactive sites and relatively high electrical conductivity compared with metal oxides. Here, an in situ conversion of metal ions into NiS₂ -CoMo₂ S₄ vertically aligned nanorod arrays on nickel foam (NS-CMS NRAs@NF) using a one-step hydrothermal technique to address the "dead-mass" limitation and multi-step preparation methods is reported. An in situ-converted NS-CMS NRAs obtained for 12 h of reaction time (NS-CMS NRAs-12 h@NF) delivers a superior areal capacity of 780 μAh cm^-2 to the other NS-CMS electrodes synthesized for 6 h (543.1 μAh cm^-2 ) and 18 h (636.7 μAh cm^-2 ) at 7 mA cm^-2 . A coin-cell-type hybrid supercapacitor (HSC) is also fabricated to unveil the practical adaptability of NS-CMS NRAs-12 h@NF electrode. Utilizing its structural and active material intriguing features, assembled coin-cell-type HSC achieves a high areal capacitance of 246.2 mF cm^-2 (5 mA cm^-2 ) along with maximum areal energy density (147 μWh cm^-2 ) and power density (21.3 mW cm^-2 ), respectively. Furthermore, the capability of coin-cell-type HSC in real-time applications is also inspected. This work promotes in situ deposition strategy to fabricate metal sulfide-based nanostructures for high-performance electrochemical capacitors.