Fabrication of honeycomb-structured composite material of Pr2O3, Co3O4, and graphene on nickel foam for high-stability supercapacitors

The Pr2O3/Co3O4/rGO/NF electrode has been prepared by hydrothermal method and annealing process, with high specific capacitance and excellent cycle stability.

Organophosphorus Hybrid Solid Electrolyte Interphase Layer Based on LixPO4 Enables Uniform Lithium Deposition for High‐Performance Lithium Metal Batteries

Lithium metal is a promising anode candidate for the next‐generation rechargeable battery system because of its highest specific capacity and lowest potential. However, low Coulombic efficiency (CE) and the formation of Li dendrites during the cycling process seriously hinder its practical application. Here, an organophosphorus hybrid flexible solid electrolyte interphase (SEI) layer is proposed based on a surface chelation strategy using phytic acid (PA) as Li metal surface treatment chemicals. Different from the traditional SEI layer, the polynuclear complex between PA and Li+ serves as a “connecter” in this SEI layer, which not only ensures its mechanical flexibility but also improves its lithiophilic property and ionic conductivity. With these advantages, the Li || Cu cells exhibit a high CE of 99.0% over 500 cycles at a current density of 0.5 mA cm−2. Li || Li symmetrical cells can also maintain a stable Li plating/stripping process over 2500 h at a high current density of 10.0 mA cm−2. Besides, all Li metal batteries (Li || S, Li || NCM, Li || LFP et al.) based on this strategy exhibit long cycling life and high capacity retention. This surface chelation strategy is believed to offer a new avenue to fabricate a stable and efficient SEI layer for practical application of Li metal batteries.

Specific Ion Solvation and Pairing Effects in Glycerol Carbonate

Identifying the driving forces behind the solvation of inorganic salts by nonaqueous solvents is an important step in the development of green solvents. Here we focus on one promising solvent: glycerol carbonate (GC). Using ab initio molecular dynamics simulations, we build upon our previous work by detailing glycerol carbonate's interactions with a series of anions, a lithium ion, and the LiF ion pair. Through these investigations, we highlight the changes in solvation behavior as the anion size increases, the competition of binding shown by lithium for the oxygens of GC, and the behavior of the LiF ion pair in a GC solution. These results indicate the importance of the cation's identity in ion-pairing structure and dynamics and lend insight into the key factors behind the specific ion effects seen in GC.

Utilization of Cellulose to Its Full Potential: A Review on Cellulose Dissolution, Regeneration, and Applications

As the most abundant natural polymer, cellulose is a prime candidate for the preparation of both sustainable and economically viable polymeric products hitherto predominantly produced from oil-based synthetic polymers. However, the utilization of cellulose to its full potential is constrained by its recalcitrance to chemical processing. Both fundamental and applied aspects of cellulose dissolution remain active areas of research and include mechanistic studies on solvent-cellulose interactions, the development of novel solvents and/or solvent systems, the optimization of dissolution conditions, and the preparation of various cellulose-based materials. In this review, we build on existing knowledge on cellulose dissolution, including the structural characteristics of the polymer that are important for dissolution (molecular weight, crystallinity, and effect of hydrophobic interactions), and evaluate widely used non-derivatizing solvents (sodium hydroxide (NaOH)-based systems, N,N-dimethylacetamide (DMAc)/lithium chloride (LiCl), N-methylmorpholine-N-oxide (NMMO), and ionic liquids). We also cover the subsequent regeneration of cellulose solutions from these solvents into various architectures (fibers, films, membranes, beads, aerogels, and hydrogels) and review uses of these materials in specific applications, such as biomedical, sorption, and energy uses.

MOF-derived porous carbon inlaid with MnO2 nanoparticles as stable aqueous Zn-ion battery cathodes

Cathodes derived from metal-organic framework materials offer unique advantages in terms of improved structural reversibility and electron conduction efficiency. Nevertheless, the capacity contribution of cathodes based on the carbon framework system has not been clearly discussed or is controversial in aqueous batteries. In this essay, we have uncovered the capacity contribution arising from the adsorption of anions/cations onto the carbon surface by examining the bonds of the carbon and the details of unsteady voltage in the CV/GITT during the discharge. Benefiting from the synergistic contribution of the double-layer capacitance and pseudocapacitance, Zn/C-MnO₂ exhibits excellent long-cycling stability and fast kinetics. To the best of our knowledge, this is the first report on the ion adsorption-based double layer effect in aqueous zinc ion batteries. Such a capacity contribution mechanism, and a renewed knowledge of the discharge mechanism, will contribute to the development of high-performance aqueous zinc ion batteries.

Design of a Dual-Electrolyte Battery System Based on a High-Energy NCM811-Si/C Full Battery Electrode-Compatible Electrolyte

Rechargeable lithium-ion batteries using high-capacity anodes and high-voltage cathodes can deliver the highest possible energy densities among all electrochemical devices. However, there is no single electrolyte with a wide and stable electrochemical window that can accommodate both a high-voltage cathode and a low-voltage anode so far. Here, we propose that a strategy of using a hybrid electrolyte should be applied to realize the full potential of a Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811)-silicon/carbon (Si/C) full cell by simultaneously achieving optimal redox chemistry at both the NCM811 cathode and the Si/C anode. The hybrid-electrolyte design spatially separates the cathodic electrolytes from anodic electrolytes by a Nafion-based separator. The ionic liquid electrolyte (LiTFSI-Pyr₁₃TFSI) on the cathode side can stand high work potentials and form a stable cathodic electrolyte intermediate (CEI) on NCM811. Meanwhile, a stable solid electrolyte intermediate (SEI) and high cycling stability can also be achieved on the anode side, enabled by a localized high concentration of ether-based electrolytes (LiTFSI-DME/HFE). The decoupled NCM811-Si/C full cell exhibits excellent long-term cycling performance with ultrahigh capacity retention for over 1000 cycles, thanks to the synergy of the cathode-side and anode-side electrolytes. This hybrid-electrolyte strategy has been proven to be applicable for other high-performance battery systems such as dual-ion batteries (DIB).

Self-assembled cationic organic nanosheets: role of positional isomers in a guanidinium-core for efficient lithium-ion conduction

The growing energy demand with the widespread use of smart portable electronics, as well as an exponential increase in demand for smart batteries for electric vehicles, entails the development of efficient portable batteries with high energy density and safe power storage systems. Li-ion batteries arguably have superior energy density to all other traditional batteries. Developing mechanically robust solid-state electrolytes (SSEs) for lithium-ion conduction for an efficient portable energy storage unit is vital to empower this technology and overcome the safety constraints of liquid electrolytes. Herein, we report the formation of self-assembled organic nanosheets (SONs) utilizing positional isomers of small organic molecules (AM-2 and AM-3) for use as SSEs for lithium-ion conduction. Solvent-assisted exfoliation of the bulk powder yielded SONs having near-atomic thickness (∼4.5 nm) with lateral dimensions in the micrometer range. In contrast, self-assembly in the DMF/water solvent system produced a distinct flower-like morphology. Thermodynamic parameters, crystallinity, elemental composition, and nature of H-bonding for two positional isomers are established through various spectroscopic and microscopic studies. The efficiency of the lithium-ion conducting properties is correlated with factors like nanostructure morphology, ionic scaffold, and locus of the functional group responsible for forming the directional channel through H-bonding in the positional isomer. Amongst the three different morphologies studied, SONs display higher ion conductivity. In between the cationic and zwitterionic forms of the monomer, integration of the cationic scaffold in the SON framework led to higher conductivity. Amongst the two positional isomers, the meta-substituted carboxyl group forms a more rigid directional channel through H-bonding to favor ionic mobility and accounts for the highest ion conductivity of 3.42 × 10^-4 S cm^-1 with a lithium-ion transference number of 0.49 at room temperature. Presumably, this is the first demonstration that signifies the importance of the cationic scaffold, positional isomers, and nanostructure morphologies in improving ionic conductivity. The ion-conducting properties of such SONs having a guanidinium-core may have significance for other interdisciplinary energy-related applications.

Ionic Liquid-Mediated Mass Transport Channels for Ultrahigh Rate Lithium-Ion Batteries

Excellent mass transport capability is indispensable to building a high-power lithium-ion battery (LIB) system. Nanomaterials with enhanced electrochemical properties have been used for next-generation high-performance LIBs. However, due to the high surface free energy, nanomaterials tend to form agglomeration. The resulting insufficient mass transport channels limit the high rate performance of nanomaterials. Here, we increase the electrolyte accessibility of nanomaterials through a facile ionic liquid (IL) mediation method. The fluidity and affinity enable the IL to infiltrate into the interstitials of nanomaterial aggregations under capillary force, enhancing the electrochemically active contact area and ensuring rapid mass transport. As a proof of concept, IL-mediated LiFePO₄ electrodes delivered extraordinary rate performance (112 and 95 mAh g^-1 at 200 and 300 C, respectively). In terms of simplicity, the IL mediation can be used as a general strategy to achieve an ultrahigh rate for LIBs.

Multifunctional High-Efficiency Additive with Synergistic Anion and Cation Coordination for High-Performance LiNi0.8Co0.1Mn0.1O2 Lithium Metal Batteries

Safety and high energy density have long restricted the large-scale practical application of lithium metal batteries because of the unbridled growth of lithium dendrites and the rapid deteriorating cycle performance of the LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode. Herein, an additive of RbNO₃ with multiple functions is proposed for dendrite-free NCM811 lithium metal batteries. Benefiting from the electrostatic shielding effect formed by Rb⁺ during the Li⁺ deposition process and the solvation effect of NO₃^- to regulate lithium deposition, a high Coulombic efficiency of 95.02% (compared with the low Coulombic efficiency of 89.37% in the blank electrolyte) is acquired in Li//Cu cells, and the uniform growth of the lithium metal deposition with a large strawberry-like morphology is achieved. Moreover, when a cathode of NCM811 matches with a lithium metal anode, an extraordinary capacity retention of 93.67% after 200 cycles with a high Coulombic efficiency of 99.7% in the electrolyte with the RbNO₃ system (a capacity retention of 80.1% with a Coulombic efficiency of 98.0% for the blank electrolyte) is achieved at 1C. This work provides guidance for the development of high-efficiency additives with dual synergistic regulation effects of anions and cations for lithium metal batteries in the future.

Atomic Welded Dual-Wall Hollow Nanospheres for Three-in-One Hybrid Storage Mechanism of Alkali Metal Ion Batteries

The rational design of hierarchical hollow nanomaterials is of critical significance in energy storage materials. Herein, dual-wall hollow nanospheres (DWHNS) Sn/MoS₂@C are constructed by in situ confined growth and interface engineering. The inner hollow spheres of Sn/MoS₂ are formed by atomic soldering MoS₂ nanosheets with liquid Sn at high temperature. The formation mechanism of the hierarchical structure is explored by the morphology evolutions at different temperatures. The DWHNS Sn/MoS₂@C manifest abundant inner space and high specific surface area, which provides more support sites for Li⁺/Na⁺/K⁺ storage and alleviates the volume effect of tin-based electrode materials to a certain extent. The composite material manifests an outstanding specific capacity and satisfactory reversibility of lithium ion batteries (∼931 mAh g^-1 at 1 A g^-1 after 500 cycles), sodium ion batteries (∼432 mAh g^-1 at 1 A g^-1 after 400 cycles), and potassium ion batteries (∼226 mAh g^-1 at 1 A g^-1 after 300 cycles). Additionally, the morphology evolution and mechanism analysis of DWHNS Sn/MoS₂@C in alkali metal ion batteries are verified by ex situ measurement, which confirms the three-in-one hybrid storage mechanism, i.e., intercalation reaction of carbon shells, conversion reaction of MoS₂, and alloying reaction of tin.

The Role of Alkali Cation Intercalates on the Electrochemical Characteristics of Nb2 CTX MXene for Energy Storage

The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li⁺ -, Na⁺ -, and K⁺ -based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb₂ CT_x electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li₂ SO₄ , Na₂ SO₄ , and K₂ SO₄ electrolytes with d-spacing. Additionally, our results showed that the Nb₂ CT_x electrode exhibited higher electrochemical performance in the presence of Li₂ SO₄ than in that of Na₂ SO₄ and K₂ SO₄ . This is partly because the smaller-sized Li⁺ transports quickly and intercalates between the layers of Nb₂ CT_x easily. Poor ion transport in the Na₂ SO₄ electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li⁺ >Na⁺ >K⁺ . Our experimental studies provide direct evidence for the intercalation mechanism of Li⁺ , Na⁺ , and K⁺ on the 2D layered Nb₂ CT_x electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes.

Electrodeposition of Zinc onto Au(111) and Au(100) from the Ionic Liquid [MPPip][TFSI]

The improvement of rechargeable zinc/air batteries was a hot topic in recent years. Predominantly, the influence of water and additives on the structure of the Zn deposit and the possible dendrite formation were studied. However, the effect of the surface structure of the underlying substrate was not focused on in detail, yet. We now show the differences in electrochemical deposition of Zn onto Au(111) and Au(100) from the ionic liquid N‐methyl‐N‐propylpiperidinium bis(trifluoromethanesulfonyl)imide. The fundamental processes were initially characterized via cyclic voltammetry and in situ scanning tunnelling microscopy. Bulk deposits were then examined using Auger electron spectroscopy and scanning electron microscopy. Different structures of Zn deposits are observed during the initial stages of electrocrystallisation on both electrodes, which reveals the strong influence of the crystallographic orientation on the metal deposition of zinc on gold.

Grafting and Depositing Lithium Polysulfides on Cathodes for Cycling Stability of Lithium-Sulfur Batteries

Based on dissolution/deposition chemistry, together with multielectron redox reactions, lithium-sulfur (Li-S) batteries have been demonstrated as a promising energy storage system. However, the diffusion of soluble lithium polysulfide intermediates (LiPSs) to bulk electrolyte results in the fast capacity fade of a Li-S cell. How to confine the LiPSs within the cathode while retaining high reversible capacity remains a huge challenge. In this work, N-bromophthalimide, an organic molecule with an aromatic heterocyclic ring and a reactive halogen bond, is introduced as an electrolyte additive to conquer the excessive dissolution and diffusion of LiPSs by in situ formation of an organopolysulfide deposition layer. This electrochemically active layer not only maintains the internal sulfur conversion but also prevents LiPSs from diffusing into the electrolyte bulk, thereby improving the cycling and rate performance of Li-S batteries. This study provides a feasible strategy for regulating the reaction region and path for high-performance Li-S batteries.

Electrospun Fe3O4-Sn@Carbon Nanofibers Composite as Efficient Anode Material for Li-Ion Batteries

Nanoscale Fe₃O₄-Sn@CNFs was prepared by loading Fe₃O₄ and Sn nanoparticles onto CNFs synthesized via electrostatic spinning and subsequent thermal treatment by solvothermal reaction, and were used as anode materials for lithium-ion batteries. The prepared anode delivers an excellent reversible specific capacity of 1120 mAh·g^-1 at a current density of 100 mA·g^-1 at the 50th cycle. The recovery rate of the specific capacity (99%) proves the better cycle stability. Fe₃O₄ nanoparticles are uniformly dispersed on the surface of nanofibers with high density, effectively increasing the electrochemical reaction sites, and improving the electrochemical performance of the active material. The rate and cycling performance of the fabricated electrodes were significantly improved because of Sn and Fe₃O₄ loading on CNFs with high electrical conductivity and elasticity.

Electrochemistry, ion adsorption and dynamics in the double layer: a study of NaCl(aq) on graphite

Graphite and related sp² carbons are ubiquitous electrode materials with particular promise for use in e.g., energy storage and desalination devices, but very little is known about the properties of the carbon–electrolyte double layer at technologically relevant concentrations. Here, the (electrified) graphite–NaCl(aq) interface was examined using constant chemical potential molecular dynamics (CμMD) simulations; this approach avoids ion depletion (due to surface adsorption) and maintains a constant concentration, electroneutral bulk solution beyond the surface. Specific Na⁺ adsorption at the graphite basal surface causes charging of the interface in the absence of an applied potential. At moderate bulk concentrations, this leads to accumulation of counter-ions in a diffuse layer to balance the effective surface charge, consistent with established models of the electrical double layer. Beyond ∼0.6 M, however, a combination of over-screening and ion crowding in the double layer results in alternating compact layers of charge density perpendicular to the interface. The transition to this regime is marked by an increasing double layer size and anomalous negative shifts to the potential of zero charge with incremental changes to the bulk concentration. Our observations are supported by changes to the position of the differential capacitance minimum measured by electrochemical impedance spectroscopy, and are explained in terms of the screening behaviour and asymmetric ion adsorption. Furthermore, a striking level of agreement between the differential capacitance from solution evaluated in simulations and measured in experiments allows us to critically assess electrochemical capacitance measurements which have previously been considered to report simply on the density of states of the graphite material at the potential of zero charge. Our work shows that the solution side of the double layer provides the more dominant contribution to the overall measured capacitance. Finally, ion crowding at the highest concentrations (beyond ∼5 M) leads to the formation of liquid-like NaCl clusters confined to highly non-ideal regions of the double layer, where ion diffusion is up to five times slower than in the bulk. The implications of changes to the speciation of ions on reactive events in the double layer are discussed.

CμMD reveals multi-layer electrolyte screening in the double layer beyond 0.6 M, which affects ion activities, speciation and mobility; asymmetric charge screening explains concentration dependent changes to electrochemical properties.

Synthesis of Nickel Fumarate and Its Electrochemical Properties for Li-Ion Batteries

Metal–organic frameworks (MOFs) have found a potential application in various domains such as gas storage/separation, drug delivery, catalysis, etc. Recently, they have found considerable attention for energy storage applications such as Li- and Na-ion batteries. However, the development of MOFs is plagued by their limited energy density that arises from high molecular weight and low volumetric density. The choice of ligand plays a crucial role in determining the performance of the MOFs. Here, we report a nickel-based one-dimensional metal-organic framework, NiC4H2O4, built from bidentate fumarate ligands for anode application in Li-ion batteries. The material was obtained by a simple chimie douce precipitation method using nickel acetate and fumaric acid. Moreover, a composite material of the MOF with reduced graphene oxide (rGO) was prepared to enhance the lithium storage performance as the rGO can enhance the electronic conductivity. Electrochemical lithium storage in the framework and the effect of rGO on the performance have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and EIS studies. The pristine nickel formate encounters serious capacity fading while the rGO composite offers good cycling stability with high reversible capacities of over 800 mAh g−1.

Revealing the Multi-Electron Reaction Mechanism of Na3 V2 O2 (PO4 )2 F Towards Improved Lithium Storage

Na₃ V₂ O₂ (PO₄ )₂ F (NVOPF) as an attractive electrode material has received much attention based on the one-electron reaction of V⁴⁺ /V⁵⁺ . However, the electrochemical reactions involving lower vanadium valences were not investigated till now. Herein, a composite of graphene decorated nanosheet-assembled NVOPF microflowers (NVOPF/G) was synthesized and the multi-electron reaction of NVOPF/G was conducted by controlling the operation voltage windows. The reaction mechanism, structural changes, and vanadium valences during the insertion/extraction of Li ions (from 2 to 6) were elucidated clearly by in-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy. Theoretical computations also revealed the Li-ion locations in the structure of NaV₂ O₂ (PO₄ )₂ F. Due to the additional redox couple of V³⁺ /V⁴⁺ , NVOPF/G displayed a much higher initial capacity of 183.3 mAh g^-1 in the wider voltage window of 1.0-4.8 V than that of 2.5-4.8 V (129.3 mAh g^-1 ). Moreover, excellent Li-storage performance of NVOPF/G at a lower voltage (≤2.5 V) with the active reaction of V²⁺ /V³⁺ /V⁴⁺ was obtained for the first time, demonstrating the high potential of NVOPF/G as an anode material for Li ion storage.

Laser-Ablated Red Phosphorus on Carbon Nanotube Film for Accelerating Polysulfide Conversion toward High-Performance and Flexible Lithium-Sulfur Batteries

The use of a conducting interlayer between separator and cathode is one of the most promising methods to trap lithium polysulfides (LiPSs) for enhancing the performance of lithium-sulfur (Li-S) batteries. Red phosphorus nanoparticles (RP_EN )-coated carbon nanotube (CNT) film (RP_EN @CF) is reported herein as a novel interlayer for Li-S batteries, which shows strong chemisorption of LiPSs, good flexibility, and excellent electric conductivity. A pulsed laser ablation method is engaged for the ultrafast production of RP_EN of uniform morphology, which are deposited on the CNT film by a direct spinning method. The RP_EN @CF interlayer provides pathways for effective Li⁺ and electron transfer and strong chemical interaction with LiPSs. The S/RP_EN @CF electrode shows a superior specific capacity of 782.3 mAh g^-1 (3 C-rate) and good cycling performances (769.5 mAh g^-1 after 500 cycles at 1 C-rate). Density functional theory calculations reveal that the morphology and dispersibility of RP_EN are crucial in enhancing Li⁺ and electron transfer kinetics and effective trap of LiPSs. This work demonstrates the possibility of using the RP_EN @CF interlayer for the enhanced electrochemical performances of Li-S batteries and other flexible energy storage devices.

Lignin biopolymer: the material of choice for advanced lithium-based batteries

Lignin, an aromatic polymer, offers interesting electroactive redox properties and abundant active functional groups. Due to its quinone functionality, it fulfils the requirement of erratic electrical energy storage by only providing adequate charge density. Research on the use of lignin as a renewable material in energy storage applications has been published in the form of reviews and scientific articles. Lignin has been used as a binder, polymer electrolyte and an electrode material, i.e. organic composite electrodes/hybrid lignin-polymer combination in different battery systems depending on the principal charge of quinone and hydroquinone. Furthermore, lignin-derived carbons have gained much popularity. The aim of this review is to depict the meticulous follow-ups of the vital challenges and progress linked to lignin usage in different lithium-based conventional and next-generation batteries as a valuable, ecological and low-cost material. The key factor of this new finding is to open a new path towards sustainable and renewable future lithium-based batteries for practical/industrial applications.

Electrocatalytic performance of NiNH2BDC MOF based composites with rGO for methanol oxidation reaction

Present work comprehensively investigated the electrochemical response of Nickel-2 Aminoterephthalic acid Metal-Organic Framework (NiNH2BDC) and its reduced graphitic carbon (rGO) based hybrids for methanol (CH3OH) oxidation reaction (MOR) in an alkaline environment. In a thorough analysis of a solvothermally synthesized Metal-Organic Frameworks (MOFs) and its reduced graphitic carbon-based hybrids, functional groups detection was performed by FTIR, the morphological study by SEM, crystal structure analysis via XRD, and elemental analysis through XPS while electrochemical testing was accomplished by Chronoamperometry (CA), Cyclic Voltametric method (CV), Electrochemically Active Surface Area (EASA), Tafel slope (b), Electron Impedance Spectroscopy (EIS), Mass Activity, and roughness factor. Among all the fabricated composites, NiNH2BDC MOF/5 wt% rGO hybrid by possessing an auspicious current density (j) of 267.7 mA/cm2 at 0.699 V (vs Hg/HgO), a Tafel slope value of 60.8 mV dec-1, EASA value of 15.7 cm2, and by exhibiting resistance of 13.26 Ω in a 3 M CH3OH/1 M NaOH solution displays grander electrocatalytic activity as compared to state-of-the-art platinum-based electrocatalysts.

Core-shell NiSe/Ni(OH)2with NiSe nanorods and Ni(OH)2nanosheets as battery-type electrode for hybrid supercapacitors

Novel core-shell nanostructure electrodes benefit from the excellent properties of their constituent materials, as well as the synergy between them. However, it is challenging to fabricate such structures efficiently. In this study, NiSe nanorods were fabricated using Ni foam as the conductive substrate and reactant via a one-step hydrothermal process, and Ni(OH)₂nanosheets were coated on the surface of the nanorods via one-step electrodeposition. The effect of the structure and morphology on the properties of the material was explored using scanning electron microscopy, x-ray diffraction, and electrochemical technology. The obtained core-shell NiSe/Ni(OH)₂exhibited an areal capacity of 1.89 mAh cm^-2at a current density of 5 mA cm^-2. The assembled NiSe/Ni(OH)₂//AC hybrid supercapacitor exhibited excellent energy and power densities, indicating that NiSe/Ni(OH)₂has great potential for use as a battery-type electrode in energy storage systems.

Hierarchical Porous Graphene Bubbles as Host Materials for Advanced Lithium Sulfur Battery Cathode

The serious shuttle effect, low conductivity, and large volume expansion have been regarded as persistent obstacles for lithium sulfur (Li-S) batteries in its practical application. Carbon materials, such as graphene, are considered as promising cathode hosts to alleviate those critical defects and be possibly coupled with other reinforcement methods to further improve the battery performance. However, the open structure of graphene and the weak interaction with sulfur species restrict its further development for hosting sulfur. Herein, a rational geometrical design of hierarchical porous graphene-like bubbles (PGBs) as a cathode host of the Li-S system was prepared by employing magnesium oxide (MgO) nanoparticles as templates for carbonization, potassium hydroxide (KOH) as activation agent, and car tal pitch as a carbon source. The synthesized PGBs owns a very thin carbon layer around 5 nm that can be comparable to graphite nanosheets. Its high content of mesoporous and interconnected curved structure can effectively entrap sulfur species and impose restrictions on their diffusion and shuttle effect, leading to a much stable electrochemical performance. The reversible capacity of PGBs@S 0.3 C still can be maintained at 831 mAh g⁻¹ after 100 cycles and 512 mAh g⁻¹ after 500 cycles.

Aluminum and lithium sulfur batteries: a review of recent progress and future directions

Advanced materials with various micro-/nanostructures have attracted plenty of attention for decades in energy storage devices such as rechargeable batteries (ion- or sulfur based batteries) and supercapacitors. To improve the electrochemical performance of batteries, it is uttermost important to develop advanced electrode materials. Moreover, the cathode material is also important that it restricts the efficiency and practical application of aluminum-ion batteries. Among the potential cathode materials, sulfur has become an important candidate material for aluminum-ion batteries cause of its considerable specific capacity. Two-dimensional materials are currently potential candidates as electrodes from lab-scale experiments to possible pragmatic theoretical studies. In this review, the fundamental principles, historical progress, latest developments, and major problems in Li-S and Al-S batteries are reviewed. Finally, future directions in terms of the experimental and theoretical applications have prospected.

Organophosphorus decorated lithium borate and phosphate salts with extended π-conjugated backbone

Several new bifunctional salts, Li[B(DPN)₂], Li[B(DPN)(ox)] and Li[P(DPN)₃], have been prepared from the phosphorus(v)-containing chelating ligand 2,3-dihydroxynaphthalene-1,4-(tetraethyl)bis(phosphonate) (H₂-DPN). The new lithium salts were characterized by a variety of spectroscopic techniques. Both H₂-DPN and Li[B(DPN)₂] have been structurally characterized by X-ray crystallographic methods. These salts are related to materials being examined for use in electrolyte solutions for lithium-ion battery (LIB) applications.

High energy density and extremely stable supercapacitors based on carbon aerogels with 100% capacitance retention up to 65,000 cycles

In terms of ideal future energy storage systems, besides the always-pursued energy/power characteristics, long-term stability is crucial for their practical application. Here, we report a facile and sustainable strategy for the scalable fabrication of carbon aerogels with three-dimensional interconnected nanofiber networks and rationally designed hierarchical porous structures, which are based on the carbonization of bacterial cellulose assisted by the soft template of Zn-1,3,5-benzenetricarboxylic acid. As binder-free electrodes, they deliver a fundamentally enhanced specific capacitance of 352 F ⋅ g^-1 at 1 A ⋅ g^-1 in a wide potential window (1.2 V, 6 M KOH) in comparison with those of bacterial cellulose-derived carbons (178 F ⋅ g^-1) and most activated carbons (usually lower than 250 F ⋅ g^-1). The as-assembled supercapacitors exhibit an ultrahigh capacitance of 297 F ⋅ g^-1 at 1 A ⋅ g^-1, remarkable energy density (14.83 Wh ⋅ kg^-1 at 0.60 kW ⋅ kg^-1), and extremely high stability, with 100% capacitance retention for up to 65,000 cycles at 6 A ⋅ g^-1, representing their superior energy storage performance when compared with that of state-of-the-art supercapacitors of commercial activated carbons and biomass-derived analogs.

Towards Higher Electric Conductivity and Wider Phase Stability Range via Nanostructured Glass-Ceramics Processing

This review article presents recent studies on nanostructured glass-ceramic materials with substantially improved electrical (ionic or electronic) conductivity or with an extended temperature stability range of highly conducting high-temperature crystalline phases. Such materials were synthesized by the thermal nanocrystallization of selected electrically conducting oxide glasses. Various nanostructured systems have been described, including glass-ceramics based on ion conductive glasses (silver iodate and bismuth oxide ones) and electronic conductive glasses (vanadate-phosphate and olivine-like ones). Most systems under consideration have been studied with the practical aim of using them as electrode or solid electrolyte materials for rechargeable Li-ion, Na-ion, all-solid batteries, or solid oxide fuel cells. It has been shown that the conductivity enhancement of glass-ceramics is closely correlated with their dual microstructure, consisting of nanocrystallites (5-100 nm) confined in the glassy matrix. The disordered interfacial regions in those materials form "easy conduction" paths. It has also been shown that the glassy matrices may be a suitable environment for phases, which in bulk form are stable at high temperatures, and may exist when confined in nanograins embedded in the glassy matrix even at room temperature. Many complementary experimental techniques probing the electrical conductivity, long- and short-range structure, microstructure at the nanometer scale, or thermal transitions have been used to characterize the glass-ceramic systems under consideration. Their results have helped to explain the correlations between the microstructure and the properties of these systems.

Emerging trends in anion storage materials for the capacitive and hybrid energy storage and beyond

Electrochemical capacitors charge and discharge more rapidly than batteries over longer cycles, but their practical applications remain limited due to their significantly lower energy densities. Pseudocapacitors and hybrid capacitors have been developed to extend Ragone plots to higher energy density values, but they are also limited by the insufficient breadth of options for electrode materials, which require materials that store alkali metal cations such as Li⁺ and Na⁺. Herein, we report a comprehensive and systematic review of emerging anion storage materials for performance- and functionality-oriented applications in electrochemical and battery-capacitor hybrid devices. The operating principles and types of dual-ion and whole-anion storage in electrochemical and hybrid capacitors are addressed along with the classification, thermodynamic and kinetic aspects, and associated interfaces of anion storage materials in various aqueous and non-aqueous electrolytes. The charge storage mechanism, structure-property correlation, and electrochemical features of anion storage materials are comprehensively discussed. The recent progress in emerging anion storage materials is also discussed, focusing on high-performance applications, such as dual-ion- and whole-anion-storing electrochemical capacitors in a symmetric or hybrid manner, and functional applications including micro- and flexible capacitors, desalination, and salinity cells. Finally, we present our perspective on the current impediments and future directions in this field.

Polysaccharides for sustainable energy storage - A review

The increasing amount of electric vehicles on our streets as well as the need to store surplus energy from renewable sources such as wind, solar and tidal parks, has brought small and large scale batteries into the focus of academic and industrial research. While there has been huge progress in performance and cost reduction in the past years, batteries and their components still face several environmental issues including safety, toxicity, recycling and sustainability. In this review, we address these challenges by showcasing the potential of polysaccharide-based compounds and materials used in batteries. This particularly involves their use as electrode binders, separators and gel/solid polymer electrolytes. The review contains a historical section on the different battery technologies, considerations about safety on batteries and requirements of polysaccharide components to be used in different types of battery technologies. The last sections cover opportunities for polysaccharides as well as obstacles that prevent their wider use in battery industry.

Trifunctional Electrolyte Additive Hexadecyltrioctylammonium Iodide for Lithium-Sulfur Batteries with Extended Cycle Life

Lithium-sulfur (Li-S) battery with a very high theoretical energy density (∼2500 Wh kg^-1) is a very promising alternative to the commercial lithium-ion battery as the next-generation energy storage device. However, the Li-S battery suffers from shuttle effect and Li dendrites growth due to the solubility of polysulfides in the electrolyte system and the inhomogeneous deposition of Li, resulting in short cycling life span, which is the major obstacle in its practical application. Herein, we report an additive, hexadecyltrioctylammonium iodide (HTOA-I), in the conventional electrolyte system, which shows trifunctional effect on extending Li-S battery cycle life. It can not only help us to form a protective solid-electrolyte interface (SEI) on the surface of Li anode so as to reduce the contact of polysulfides with Li but also hinder the shuttling of polysulfides to the Li anode due to the strong combination of large-sized HTOA⁺ with polysulfide anions (S_n^2-), which retard the migration of S_n^2- and cause homogeneous Li deposition owing to the large size and stronger trend of HTOA⁺ to be absorbed on Li anode as well. A new method of phosphorescence analysis for direct observation of polysulfides shuttling has been put forward for the first time, which can be further developed in future studies. The cell with the HTOA-I-added electrolyte system shows high cycling stability, retaining 83.4% of the initial capacity after 200 cycles at 1 A g^-1 and achieving 689 mAh g^-1 even after 1000 cycles. This cost-effective and facile approach will not increase the complexity of the battery manufacturing process. Compared to other electrolyte additives, the additive in our work, HTOA-I, has better positive effects on extending cycle life. This trifunctional electrolyte additive will inspire the design of other new additives and further promote the development of Li-S batteries.

Flexible Antifreeze Zn-Ion Hybrid Supercapacitor Based on Gel Electrolyte with Graphene Electrodes

Zn-ion energy storage devices employing hydrogel electrolytes are considered as promising candidates for flexible and wearable electronics applications. This is because of their safe nature, low cost, and good mechanical characteristics. However, conventional hydrogel electrolytes face limitation at subzero temperatures. Herein, we report an antifreezing, safe, and nontoxic gel electrolyte based on the poly(vinyl alcohol) (PVA)/Zn/ethylene glycol system. The optimal gel electrolyte membrane exhibits a high ionic conductivity (15.03 mS cm^-1 at room temperature) and promising antifreezing performance (9.05 mS cm^-1 at -20 °C and 3.53 mS cm^-1 at -40 °C). Moreover, the antifreezing gel electrolyte can suppress the growth of Zn dendrites to display a uniform Zn plating/stripping behavior. Also, a flexible antifreezing Zn-ion hybrid supercapacitor fabricated with the optimum antifreezing gel electrolyte membrane exhibits excellent electrochemical properties. The supercapacitor possesses a high specific capacity of 247.7 F g^-1 at room temperature under a high working voltage of 2 V. It also displays an outstanding cyclic stability at room temperature. Moreover, the supercapacitor shows an extraordinary electrochemical behavior and cyclic stability over up to 30 000 cycles at -20 °C under a current load of 5 A g^-1, demonstrating its outstanding low-temperature electrochemical performance. Besides, the antifreezing supercapacitor device also offers high flexibility under different deformation conditions. Therefore, it is believed that this work provides a simplistic method of realizing the application of flexible antifreezing Zn-ion energy storage devices in a subzero-temperature environment.

Fe-cation Doping in NiSe2 as an Effective Method of Electronic Structure Modulation towards High-Performance Lithium-Sulfur Batteries

The commercialization of Li-S batteries is hindered by the shuttling of lithium polysulfides (LiPSs), the sluggish sulfur redox kinetics as well as the low sulfur utilization during charge/discharge processes. Herein, a free-standing cathode material was developed, based on Fe-doped NiSe₂ nanosheets grown on activated carbon cloth substrates (Fe-NiSe₂ /ACC) for high-performance Li-S batteries. Fe-doping in NiSe₂ plays a key role in the electronic structure modulation of NiSe₂ , enabling improved charge transfer with the adsorbed LiPSs molecules, stronger interactions with the active sulfur species and higher electrical conductivity. Effective promotion of the sulfur redox kinetics and enhanced sulfur utilization were achieved under high areal sulfur loadings. The stronger interactions with LiPSs together with the unique 3D structure of Fe-NiSe₂ /ACC also induced the transformation of Li₂ S₂ /Li₂ S growth from conventional 2D films to 3D particles, significantly eliminating the barriers of solid nucleation and growth during the phase transition of liquid LiPSs to solid Li₂ S₂ /Li₂ S. With a high sulfur loading of 9.9 mg cm^-2 , the Fe-NiSe₂ /ACC cathode enabled a high area capacity of 9.14 mAh cm^-2 with a low average decay of 0.11 % per cycle over 200 cycles at 0.1 C.

Supercapacitor electrode materials: addressing challenges in mechanism and charge storage

In recent years, rapid technological advances have required the development of energy-related devices. In this regard, Supercapacitors (SCs) have been reported to be one of the most potential candidates to meet the demands of human’s sustainable development owing to their unique properties such as outstanding cycling life, safe operation, low processing cost, and high power density compared to the batteries. This review describes the concise aspects of SCs including charge-storage mechanisms and scientific principles design of SCs as well as energy-related performance. In addition, the most important performance parameters of SCs, such as the operating potential window, electrolyte, and full cell voltage, are reviewed. Researches on electrode materials are crucial to SCs because they play a pivotal role in the performance of SCs. This review outlines recent research progress of carbon-based materials, transition metal oxides, sulfides, hydroxides, MXenes, and metal nitrides. Finally, we give a brief outline of SCs’ strategic direction for future growth.

Quantum Simulations of Hydrogen Bonding Effects in Glycerol Carbonate Electrolyte Solutions

The need for environmentally friendly nonaqueous solvents in electrochemistry and other fields has motivated recent research into the molecular-level solvation structure, thermodynamics, and dynamics of candidate organic liquids. In this paper, we present the results of quantum density functional theory simulations of glycerol carbonate (GC), a molecule that has been proposed as a solvent for green industrial chemistry, nonaqueous alternatives for biocatalytic reactions, and liquid media in energy storage devices. We investigate the structure and dynamics of both the pure GC liquid and electrolyte solutions containing KF and KCl ion pairs. These simulations reveal the importance of hydrogen bonding that controls the structural and dynamic behavior of the pure liquid and ion association in the electrolyte solutions. The results illustrate the difficulties associated with classical modeling of complex organic solvents. The simulations lead to a better understanding of the underlying mechanisms behind the previously observed peculiar ion-specific behavior in GC electrolyte solutions.