Oxygen reduction reaction (ORR) is an important cathodic reaction, but its slow reaction kinetics seriously hinders the application of clean energy devices such as fuel cells and metal-air batteries. Although platinum (Pt)-based catalysts possess excellent ORR activity, their high cost, scarce reserves, poor stability and tolerance make it difficult to commercialize current clean energy technologies. To address the above problems, it is urgent to develop new types of efficient and low-cost ORR catalysts. As an emerging carbon-based material, nanodiamond (ND) exhibits broad application prospects in ORR catalysis due to its advantages such as low cost, controllable functional group modification, high surface energy (>1000 mJ·m^-2), and unique π and σ bond configurations. This paper reviews the latest research progress of ND catalysts. Firstly, preparation methods such as detonation, chemical vapor deposition, pulsed laser ablation, and high-pressure high-temperature are introduced. Subsequently, modification strategies including heteroatom doping, surface functionalization, material composite, and morphology regulation are summarized, and their formation mechanism of active centers and regulation rules of reaction paths are analyzed, covering influence of different modification strategies on catalytic performance and comparison of relevant performance data. Finally, the challenges faced by current ND catalysts in catalytic mechanism, synthesis process, characterization technology, and design methods are analyzed to suggest the future development directions for the research and development of new carbon-based ORR catalysts.

Synergistic innovation of solar energy collection and storage technology provides an important direction for constructing a new type of self-supply system, in which photo-assisted charging supercapacitor has become a research hotspot due to their unique photo-induced charge storage mechanism and fast charging/discharging characteristics with high power density and fast charging/discharging characteristics, which provides an efficient, environmentally friendly, and sustainable new strategy for energy harvesting and storage in wearable electronic devices and other related products. In this work, ZnFe₂O₄ was synthesized by hydrothermal method and employed as the supercapacitor photoanode, while reduced graphene oxide hydrogel (rGH), prepared using an improved Hummers method followed by hydrothermal treatment, served as the cathode, and Zn(CF₃SO₃)₂ aqueous solution was used as the electrolyte to construct an aqueous photo-assisted charging supercapacitor. The results from the synthesized products, including phase composition, microscopic morphology, chemical structure, light absorption properties, and photoelectrochemical performance of the supercapacitor, show that under the photoelectrical synergistic charging conditions (a current density of 0.2 A·g^-1 and a light intensity of 95 mW·cm^-2), specific capacity of supercapacitor reaches 148 F·g^-1, 17% higher than that under only electric charging conditions. The capacity retention rates of the device are 80% and 90% after 10000 cycles under only electric charging and photoelectric synergistic charging, respectively. Based on all above results, the constructed aqueous photo-assisted charging supercapacitor exhibits high specific capacity and excellent cycling stability, demonstrating promising potential for applications in wearable electronics and related fields.

With the growing demand for efficient and environmental-friendly energy storage systems, zinc-air batteries have emerged as highly promising energy storage devices due to their high energy density, low cost, and environmental friendliness. The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which suffer from sluggish kinetics, are critical factors limiting battery performance. Therefore, the development of high-performance and low-cost bifunctional oxygen electrocatalysts is of great significance. In this work, Fe single atoms/clusters anchored graphene hybrid catalysts (Fe-N/Gra) were prepared via a ball-milling assisted pyrolysis method. A series of Fe-N/Gra catalysts were obtained by adjusting the mass ratio of the metal phthalocyanine precursor to graphene, and their bifunctional oxygen electrocatalytic performances were systematically investigated. The results demonstrate that the loading amount of different metal phthalocyanine precursors exerts a significant influence on the catalytic performance of the catalysts. When the loading amount of iron phthalocyanine was 0.02 g, the resulting Fe-N/Gra-0.02 catalyst exhibited the optimal bifunctional catalytic activity for ORR and OER. The ORR half-wave potential reached as high as 0.911 V, and the OER overpotential was 610 mV at a current density of 10 mA·cm^-2. The rechargeable zinc-air batteries assembled with this catalyst as the air electrode achieved a maximum power density of 315 mW·cm^-2 and could sustain stable discharge for 210 h at 10 mA·cm^-2. The excellent bifunctional oxygen catalytic activity of Fe-N/Gra-0.02 is mainly attributed to the atomically dispersed Fe-N_x active sites and the high electrical conductivity of graphene support. In addition, the agglomeration of active sites in the catalysts with excessive loading amounts is detrimental to the manifestation of their high-efficiency catalytic activity. This work provides an experimental basis for the controllable preparation of high-performance non-noble metal bifunctional oxygen catalysts and their practical applications in rechargeable zinc-air batteries.

With the rapid development of the Internet of Things, smart healthcare, and wearable electronics, there is an increasingly urgent demand for high-performance flexible energy storage devices. Supercapacitors (SCs) have emerged as promising candidates due to their high power density and long cycle life. However, conventional electrode materials often suffer from limited specific capacitance, insufficient mechanical flexibility, and poor long-term cycling stability under flexible conditions, which severely restricts their practical application. To address these challenges, this study aims to develop a novel electrode material that combines high electrochemical performance with excellent mechanical flexibility. By constructing a ternary composite of sulfur-doped graphene oxide (SGO) with two conductive polymers, polyaniline (PANI) and polypyrrole (PPy), a highly conductive hierarchical porous network is formed through the interweaving of mixed nano-sized PANI and PPy. The incorporation of sulfur atoms into SGO effectively enlarges the interlayer spacing of graphene, significantly mitigating the restacking of graphene sheets and thereby exposing more active surfaces. Electrochemical tests demonstrate that the as-prepared SGO/PANI/PPy ternary composite electrode exhibits outstanding performance, delivering a high specific capacitance of 561.8 F·g^-1. At a power density of 250.62 W·kg^-1, the device achieves an energy density of 19.51 Wh·kg^-1. Moreover, the electrode retains 98.12% of its initial capacitance after 10000 consecutive charge-discharge cycles. This work confirms the great potential of the ternary composite as an electrode for flexible supercapacitors and provides new insights into addressing the performance limitations of flexible energy storage devices through multi-component synergy and structural design.

Aqueous zinc-ion batteries hold considerable promise for grid-scale energy storage, capitalizing on their intrinsic safety and low cost. However, the practical deployment of these batteries is severely hampered by the uncontrollable growth of zinc dendrites on the anode during repeated plating/stripping cycles. As the substrate for zinc deposition, the interfacial properties of the current collector have a decisive impact on the zinc deposition behavior. Herein, a facile high-temperature annealing strategy to modulate the microstructure of a commercial copper current collector is reported. This reconstruction profoundly influences the zinc deposition mechanism and electrochemical performance. The results demonstrate that annealing treatment induces significant crystallographic reconstruction of the copper current collector, resulting in a preferred orientation dominated by the Cu(111) crystal plane and effectively reducing the dislocation density and surface defects. Theoretical calculations reveal that the Cu(111) facet provides both a low diffusion barrier for zinc adatoms and the lowest interfacial energy with the Zn(002) plane. This synergistic thermodynamic and kinetic regulation promotes uniform and epitaxial zinc deposition, effectively suppressing dendrite formation and guiding the preferential growth of a (002)-textured zinc layer. Consequently, the modified current collector achieves exceptional plating/stripping reversibility, supporting a prolonged cycle life of over 4000 cycles with an average Coulombic efficiency of 99.9%. When applied to the aqueous zinc-iodine full battery with a zinc-free anode, it maintains a capacity retention rate of over 82% after 700 cycles at a current density of 3 A·g⁻¹. This work provides fundamental insights and a practical strategy for the design of high-performance current collectors through crystallographic and interfacial engineering.

This study presents a new kind of sealing glass based on P₂O₅-Al₂O₃-B₂O₃-R₂O-NaF system, which exhibits a high coefficient of thermal expansion (CTE) suitable for sealing power lithium batteries. The effects of Al₂O₃/P₂O₅ molar ratio on the structure, thermal properties, sealing performance and chemical stability of the sealing glass were characterized. The results show that as the Al₂O₃/P₂O₅ molar ratio increases from 0.35 to 0.76, the number of P-O-P bridge oxygen bonds within the glass structure gradually decreases, and the content of [AlO₄] tetrahedra initially increases and then decreases, leading to an initial increase in the compactness of the phosphate glass network structure, followed by a decrease. Correspondingly, the CTE of the glass firstly decreases from 164.5×10^-7 ℃^-1 to 160.0×10^-7 ℃^-1, and then gradually increases to 175.9×10^-7 ℃^-1, while the sealing temperature initially rises to 588 ℃ and subsequently falls to 549 ℃. The acid resistance of the glass also follows this trend, initially improving and then deteriorating. The phosphate sealing glass prepared in this study displays proper balance among high CTE, low sealing temperature and excellent chemical stability, providing theoretical and technical support for the development of a low-temperature sealing process for the electrodes of power lithium batteries.

Silicon, due to its exceptionally high theoretical capacity, is widely regarded as an ideal candidate for the anode material in next-generation high-energy-density lithium-ion batteries. However, its practical application is limited by several critical issues, including significant volume expansion during repeated cycling, poor intrinsic conductivity, and instability at the electrode-electrolyte interface. Mechanical ball milling, a solid-state processing technique, offers significant advantages in the performance enhancement of silicon-based anode materials due to its adjustable structure, simplicity in operation, and scalability. This method enables precise control over particle size, morphology, and structural characteristics, providing an efficient and flexible strategy for improving material performance without the need for overly complex or stringent processing conditions. This review summarizes the recent progress in the application of mechanical ball milling for the performance optimization of silicon-based anode materials. Representative advancements include the controlled preparation of nanosilicon, rational design of silicon- carbon composite materials, construction of silicon-metal and metal silicide composite systems, and the implementation of in situ coating strategies. Overall, these studies clearly demonstrate that mechanical ball milling plays a key role in enhancing the structural stability and electrochemical performance of silicon-based anodes. Furthermore, this paper discusses the main challenges currently faced in this field, such as poor uniformity of composite materials, complexity of controlling energy input during milling, and limited understanding of the interface reaction mechanisms. Finally, emerging directions in the field are highlighted, including smart ball milling, interface engineering, and data-driven optimization, which are expected to provide valuable insights for the practical application and commercial promotion of high-performance silicon-based anode materials in high-energy-density lithium-ion batteries.

Sodium-ion batteries are widely considered a promising alternative to lithium-ion batteries owing to their low cost and the abundance of sodium resources. Advances in development and application of all-solid-state sodium-ion batteries (ASSBs) critically depend on the availability of solid electrolytes that combine high ionic conductivity with wide electrochemical stability window. Among various solid electrolytes, chloride solid electrolytes have attracted considerable attention in recent years due to their high ionic conductivity, high oxidation potential and favorable deformability. This review provides a comprehensive overview of development of sodium chloride solid electrolytes, emphasizing interplay of chemical composition, crystal structure and ionic conductivity, and further examining how modification approaches, including cation/anion doping, amorphization and heterostructure engineering, govern their ionic transport behavior. In addition, this review also evaluates the electrochemical stability of sodium chloride solid electrolytes, and their chemical and electrochemical compatibility with common cathode materials, which are crucial for enabling practical cell configurations. The interfacial degradation mechanisms that arise at the interface with sodium metal anode are also analyzed, and recent advances in chloride-based ASSBs are concisely reviewed. Finally, key challenges that hinder practical deployment of chloride-based ASSBs are highlighted, and prospective research directions are proposed, which are expected to provide valuable insights to guide future application of chloride solid electrolytes in energy conversion and storage technologies.

Hard carbon is a promising anode material for sodium-ion batteries due to its low cost, wide source and long lifespan. However, its lower initial Coulombic efficiency (ICE) and poor capacity limit its practical applications. At present, heteroatom doping is an effective strategy to modulate the amorphous carbon microcrystalline structure and improve the sodium storage performance of carbon materials. The synergistic effect generated by combined heteroatom doping is more conducive to enhancing the electrochemical reactivity of carbon materials than single heteroatom doping. In this study, carbon spheres were synthesized by hydrothermal reaction, with waste residue extracted from potato starch processing waste liquid as precursor, based on which boron and nitrogen co-doped biomass carbon spheres were prepared by ball milling and pyrolysis using urea and sodium tetraborate as doping sources. Subsequently, the effects of B and N co-doping on the microstructure and sodium storage properties of carbon materials were investigated. The results indicated that B and N co-doping increased disorder and enlarged layer spacing of carbon materials, while forming suitable C=O bonds that were conducive to stabilizing solid electrolyte interphase film generation. The as-prepared electrode exhibited a reversible capacity of 284.3 mAh·g^-1 at a current density of 50 mA·g^-1 with an ICE of 77.0%. After 500 cycles at 2 A·g^-1, its capacity decayed to 122.5 mAh·g^-1, with 56.1% capacity retention. Therefore, boron and nitrogen co-doped biomass carbon sphere anode material is a promising one for sodium-ion batteries with superior sodium storage properties.

NiMn-layered double hydroxide (NiMn-LDH) is a promising cathode material for hybrid supercapacitors (HSCs) due to its inherent environmental sustainability, exceptionally high theoretical specific capacitance, and robust cycling stability. However, its widespread practical application faces significant limitations due to its poor electronic conductivity, which results in low specific capacitance and rate capability. Particularly at mg·cm^-2 magnitude loading, the specific capacitance at high current densities of 50 A·g^-1 or above is much lower than 1500 F·g^-1, a performance threshold critically insufficient for the energy-power balance required in commercial HSC devices. To address this limitation, this work innovatively developed a novel NiMn_x-LDH@Ni₉₅Cu₅ electrode via a simple two-step electrodeposition strategy. Ni₉₅Cu₅ dendritric foams with hierarchical porous structure were prepared by hydrogen bubble template method, and NiMn-LDH was anchored to the Ni₉₅Cu₅ substrate by electrochemical deposition. By adjusting the Mn/Ni stoichiometric ratio in NiMn-LDH which was electrodeposited on the surface of Ni₉₅Cu₅ dendritic foam through variations of the metal ion ratios in electrodeposition solution, its influence on the composition, elemental valence state, crystal structure, morphology, energy band configuration, and electrochemical behavior of NiMn-LDH was investigated. As the Mn content in NiMn-LDH increases, the size of NiMn-LDH nanosheets decreases. The optimized NiMn_0.6-LDH@Ni₉₅Cu₅ electrode exhibits superior crystallinity, minimized charge-transfer resistance, the narrowest band gap, and synergistically exceptional electrochemical performance, delivering outstanding specific capacitances of 2365 F·g^-1 at a current density of 1 A·g^-1 and 1803 F·g^-1 at an ultrahigh current density of 50 A·g^-1, even under high mass loadings (>2 mg·cm^-2). Furthermore, it demonstrates remarkable cycling stability and retains 88.8% of its initial capacity after 3000 cycles at 20 A·g^-1. Collectively, this study confirms that the composition, crystallinity and energy band structure of LDH can be synergistically optimized by precisely tuning the bimetallic ratio, thus solving the problem of specific capacitance and multiplicity performance degradation of high-loading electrodes, and provides a new idea for the design of next-generation high-performance HSC electrodes.

LiNi_xCo_yMn_1-x-yO₂ (NCM, x≥0.8), a promising cathode material for lithium-ion batteries, possesses high energy density and excellent discharge performance. However, it also appears drawbacks such as severe cation disorder, poor cycling performance and insecurity at high temperatures and high cut-off voltages. In this study, a high-entropy (HE) doping modification strategy was introduced into a high-nickel and low-cobalt LiNi_0.86Co_0.04Mn_0.1O₂ cathode material, and a high-nickel single-crystal layered ternary cathode material was synthesized by a high-temperature solid-state reaction method. The results show that at 0.1C (1C=180 mA·g^-1) and 25 ℃, the battery equipped with modified material has a reversible discharge capacity of 197 mAh·g^-1 and exhibits excellent discharge performance at high temperatures and high cut-off voltages. At 0.5C, 55 ℃ and 4.3 V, the discharge capacity reaches 281 mAh·g^-1, while at 0.5C, 25 ℃ and 4.5 V, the discharge capacity is as high as 194 mAh·g^-1. This material has a good layered structure with a uniform arrangement of nanoscale primary particles at microscale and a smaller total impedance. This work significantly improves cycling performance and safety of high-nickel ternary cathode materials at high temperatures and high cut-off voltages, providing a good modification method for the cobalt-free, high-nickel and practical application of ternary materials.

Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP), one of the NASICON-type solid-state electrolytes, possesses a high ionic conductivity, excellent chemical stability, and high shear modulus (40-60 GPa). However, the tetravalent titanium ion in LATP is particularly prone to undergo reduction reaction with lithium metal during cycling, leading to the structure degradation and electron introduction in LATP electrolyte. In order to maintain the chemical and electrochemical stability of LATP, this work modified the surface of LATP solid electrolyte with a Prussian blue (PB) interfacial layer to optimize the contact between electrolyte and anode. Using PB with abundant open-frame lithium ion diffusion channels as the mixed conductive modification layer has several advantages. (1) Intrinsic conductivity of PB layer is enhanced after lithiation, accelerating homogenized transmission of electrons from the interfacial layer to the negative electrode. (2) Lithiation process is accompanied by enhancing lithium affinity of PB intermediate layer, which enables the interface contact between LATP and lithium metal to be closer during the electrochemical process. (3) Lithiated PB still maintains a three-dimensional skeleton structure, which is conducive to the homogenization effect of lithium ion flux at interface, thereby promoting stabilization of lithium deposition/stripping process. (4) The PB with metal-organic framework (MOF) structure is conducive to ensuring the mechanical stability of interface during cycling and reducing volume change of lithium negative electrode. (5) The PB structure does not collapse after lithiation, not easy to cause phase separation and additional phase boundaries or phase gaps, which is conducive to the integration of lithium ion flow and electron flow. (6) More uniquely, redox potential of PB is higher than those of lithium metal and LATP on both sides of the PB interface, conducive to the formation of an electron transport barrier between Li and LATP, and prevents the reduction and degradation of LATP. The improved solid-state battery has good cycling stability and kinetic performance. At a current density of 0.025 mA·cm^-2, the PB-modified Li/Li symmetric solid-state cell can achieve a stable cycle of 800 h. After 160 cycles at a current density of 0.025 mA·cm^-2, the capacity of PB-modified Li/LiFePO₄ solid-state battery is still close to 200 mAh·g^-1. The modified Li/FeF₃ solid-state battery can be operated at 0.025 mA·cm^-2 with the preservation of a high Coulombic efficiency, indicating that the PB modification has good tolerance to the volume change generated during electrochemical cycling.

Compared to Li-ion batteries, Na-ion batteries hold significant advantages and market value for achieving low-cost and large-scale energy storage, thanks to the utilization of cheap and abundant Na resources. However, the use of highly flammable liquid electrolytes with leaky risk raises safety concerns for conventional Na-ion batteries under abuse conditions such as mechanical damage, short-circuiting, and thermal runaway. Limited electrochemical stability of liquid electrolytes also hinders further enhancement of the performance of Na-ion batteries for practical use. This study reports a facile way for the preparation of high-performance gel polymer electrolyte (GPE) by thermal-driven radical in-situ polymerization of dipentaerythritol penta-/hexa-acrylat (DPEPA). This GPE exhibits an ionic conductivity of 1.97 mS·cm^-1, a Na⁺ transference number of 0.66, and a broad electrochemical stability window. The DPEPA displays a lower lowest unoccupied molecular orbit (LUMO) energy level than that of ethylene carbonate (EC) and diethyl carbonate (DEC) solvents, allowing for its preferential decomposition alongside NaPF₆ on the anode surface. This leads to a stable organic-inorganic composite film of solid-state electrolyte interphase, inhibiting the decomposition of electrolyte solvents on the anode surface. The quasi-solid-state Na-ion battery employing Na(Ni _1/3Fe_1/3Mn _1/3)O₂ (NFM) cathode and hard carbon (HC) anode in this GPE exhibits a high capacity retention rate of 92% after 300 stable cycles at a current density of 120 mA·g^-1, while achieving the specific capacities of 99-120 mAh·g^-1 within a wide temperature range of 20-80 ℃. In-situ X-ray diffractometer analysis reveals the highly reversible structural evolution of the NFM cathode during Na storage and the “adsorption-pore-filling” mechanism of Na⁺ storage in the HC anode. All data in this research demonstrates that introducing polymers with low LUMO energy levels proves an effective approach to enhance the electrochemical stability of solid-state Na-ion batteries while improving cell safety.

Garnet-type solid electrolytes (LLZTO) have attracted tremendous attention in the past few years, owing to their high ionic conductivity and wide electrochemical stability window. However, the poor wettability with lithium metal and severe lithium dendrite formation during cycling greatly hindered their application in large-scale devices. In this study, a composite anode (LAF) was prepared by melting Li metal and AlF₃, which eventually formed fluorides (LiF, AlF₃) and Li-Al alloys. Elemental distribution analysis revealed that a fluoride layer was formed at LLZTO|LAF interface upon contact with LLZTO. Compared to metallic lithium, the composite anode formed a significantly smaller interface contact angle with LLZTO, notably improving the interfacial wettability. As a result, the modified LAF3|LLZTO interface (a mass ratio of Li to AlF3 is 3 : 1) exhibits an ultralow interfacial resistance of 3.9 Ω/cm², which is much lower than that of the lithium anode with LLZTO (138.6 Ω/cm²). Meanwhile, the critical current density of the composite anode with LLZTO increases from 0.2 mA/cm² to 0.8 mA/cm². LAF|LLZTO|LAF symmetric cells demonstrate stable plating/stripping for 3500 h under a current density of 0.2 mA/cm², illustrating the good stability of lithium-ion plating/stripping process. LiFePO₄|LLZTO|LAF quasi-solid-state battery delivers a high discharge capacity of 151.1 mAh/g at 0.1C rate (1C=170 mA/g) and retains 96.5% of its initial capacity after 240 cycles at 1C rate. The LAF composite anode demonstrated in this study effectively decreases the interfacial resistance between LLZTO and anode, and stabilizes lithium-ion plating/stripping process, offering a promising approach for designing high-performance LLZTO-based lithium metal batteries.

Sodium-ion batteries (SIBs) have emerged as a significant alternative to lithium-ion batteries, offering a cost-effective and safe solution with promising potential in energy storage. Among these, P2-type Ni/Mn based oxides possess the advantages of high theoretical capacity and wide operating voltage. However, the P2-O2 phase transition under high voltage and Jahn-Teller aberration significantly impact the cycling reversibility and structural stability. To address the above issues, here, P2-type Na_0.8Ni_0.33Mn_0.67-xAl_xO₂ materials with different doping contents of Al using a high-temperature solid-phase method were prepared, and employed as cathodes for sodium-ion batteries. It was observed that Al doping resulted in strengthening of their metal-oxygen bonds (M-O bonds) and expansion of the distance of Na layer, thereby facilitating Na⁺ diffusion and enhancing structural stability. The electrochemical properties demonstrated that Al doping could impede the high-voltage phase transition, stimulate the electrochemical activity of Mn, and diminish the charge transfer resistance, leading to enhanced electrochemical properties of the materials. Among these P2-type Na_0.8Ni_0.33Mn_0.67-xAl_xO₂ materials, Na_0.8Ni_0.33Mn_0.62Al_0.05O₂ cathode displayed the optimal cycling performance with a capacity retention of 87.3% after 200 cycles at 0.1C (1C=200 mA·g^-1) in the range of 2.0-4.2 V, and the superior rate performance with a discharge specific capacity of 100.9 mAh·g^-1 at 2C in the range of 2.0-4.2 V.

Transition metal vanadates, as an advantageous anode material for lithium-ion batteries, currently have bottlenecks such as unsatisfied conductivity and cycle stability caused by drastic volume changes during charging and discharging. In this study, NiCo₂V₂O₈@TiO₂@NC material with a multi-level composite core-shell structure was prepared using a step-by-step coating strategy to improve this defect. Initially, yolk-shell structured NiCo₂V₂O₈ nanospheres were synthesized as the precursor through hydrothermal synthesis and ion exchange methods. Subsequently, a robust TiO₂ layer and a nitrogen-doped carbon (NC) network structure were coated on the surface, resulting in formation of a hierarchical mesoporous nanostructure. The specific yolk-shell nanosphere structure provides abundant channels for Li⁺ transport in NiCo₂V₂O₈, a promising electrochemical active material. Further coating with a TiO₂ layer not only enhances the stability and durability of the material, but also offers additional electrochemical active sites. Moreover, introduction of the nitrogen-doped carbon network structure not only improves conductivity of the ordered multi-level core-shell NiCo₂V₂O₈@TiO₂@NC material but also facilitates rapid electron transport, further optimizing its electrochemical performance. When lithium-ion battery anode materials were prepared under optimal conditions, the obtained cell exhibited an initial specific capacity of 1422.0 mAh∙g^-1, which remained 1011.9 mAh∙g^-1 after 500 cycles, corresponding to a specific capacity retention rate of 71.2%. This material demonstrates high specific capacity, good rate performance, and excellent cycle stability, displaying promising prospective for a wide range of applications in energy storage devices.

To solve the problems of large volume expansion, poor cycling stability, low electrical conductivity and high energy consumption of silicon-anode materials, a porous silicon-carbon anode material (P-Si@G@C) was prepared by a non-solvent low-temperature method with nano-silicon as active substance, graphite as conductive carrier, asphalt as carbon precursor, and potassium chloride as pore-forming agent. Structure and performance of P-Si@G@C anode were systematically studied by comparing with a series of silicon-carbon anodes. The results showed that insertion of silica nanoparticles in graphite matrix (Si@G) could improve the electrical conductivity of the whole material which is beneficial for electron transport, and the graphite matrix could alleviate the volume expansion of silica nanoparticles. Then the porous carbon shell coated on the surface of Si@G greatly reduced the volume expansion of nano-silicon, and improved the diffusion rate of lithium ion and electron transport rate. Compared with Si@G and unperforated Si@G@C anodes, the P-Si@G@C anode presented the best electrical performance with initial Coulombic efficiency of 85.8%. At the current density of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 A·g^-1, the specific capacities of P-Si@G@C anode were 1403.6, 1291.7, 1206.1, 1093.6, 868.4, and 609.5 mAh·g^-1, respectively. Its recovery rate of specific capacity reached 98.3%, displaying excellent rate performance. The specific capacity still remained 770.7 mAh·g^-1 after 200 cycles at 1.0 A·g^-1, showing good long-cycle stability.

Bentonite is an abundant, cheap and readily available natural clay mineral, with montmorillonite (MMT) as its main mineral composition. MMT possesses excellent ion exchange, adsorption and ion transport properties due to its unique two-dimensional layered nanostructure, abundant pore structure, and high specific surface area. Moreover, it also possesses excellent thermal, chemical and mechanical stabilities. In recent years, MMT has attracted extensive attention in the field of electrochemical energy storage owing to the above excellent characteristics, especially the inherent fast ion (Li⁺, Na⁺, Zn²⁺, etc.) transport properties. Thus, the bentonite-based functional materials have been widely applied to the key components (i.e., electrodes, polymer electrolytes, and separators) of electrochemical energy storage devices and show good application prospects. In this review, the structure and physicochemical properties of bentonite are firstly introduced, and then the research progress of bentonite-based functional materials in the field of electrochemical energy storage, mainly including metal anodes, lithium-sulfur battery cathodes, solid/gel polymer electrolytes, and polymer separators, is comprehensively summarized. On the basis of these facts, the ion transport promotion mechanism of bentonite-based functional materials during the process of electrochemical energy storage is elaborated. Finally, the current problems and challenges faced by application of bentonite-based materials in electrochemical energy storage devices are pondered, and the possible future research directions are prospected. This review provides useful guidance for the design and development of bentonite-based electrochemical energy storage functional materials.

Sodium-ion batteries are economical and environmentally sustainable energy storage batteries. Among them, β-NaMnO₂, a promising sodium-ion cathode material, is a manganese-based oxide with a corrugated laminar structure, which has attracted significant attention due to its structural robustness and relatively high specific capacity. However, it has short cycle life and poor rate capability. To address these issues, Ti atoms, known for enhancing structural stability, and Cu atoms, which facilitate desodiation, were doped into β-NaMnO₂ by first-principles calculation and crystal orbital Hamilton population (COHP) analysis. β-NaMn_0.8Ti_0.1Cu_0.1O₂ exhibits a notable increase in reversible specific capacity and remarkable rate properties. Operating at a current density of 0.2C (1C = 219 mA·g^-1) and within a voltage range of 1.8-4.0 V, the modified material delivers an initial discharge capacity of 132 mAh·g^-1. After charge/discharge testing at current densities of 0.2C, 0.5C, 1C, 3C, and 0.2C, the material still maintains a capacity of 110 mAh·g^-1. The doping of Ti atoms slows down the changes in the crystal structure, resulting in only minimal variation in the lattice constant c/a during the desodiation process. Mn and Cu engage in reversible redox reactions at voltages below 3.0 V and around 3.5 V, respectively. The extended plateau observed in the discharge curve below 3.0 V signifies that Mn significantly contributes to the overall battery capacity. This study provides insights into modifying β-NaMnO₂ as a cathode material, offering experimental evidence and theoretical guidance for enhancing battery performance in Na-ion batteries.

Supercapacitors, distinguished by their unique advantages, including high power performance, stable cycling behavior, and excellent safety, emerge as highly promising energy storage devices in the fields of new energy vehicles and mobile electronic applications. However, the issue of relatively low energy density continues to constrain their practical applications. To enhance electrochemical activity, CoS nanosheets were deposited onto ZnCo₂O₄-ZnO microspheres coated with carbon (ZCO-ZO@C@CoS) using a facile solvothermal method, calcination treatment, and electrochemical deposition reaction. Carbon layer not only promoted electron transport to enhance electrical conductivity, but also improved the stability of the structure. The open network space formed between CoS nanosheets facilitated rapid ion transport. Additionally, CoS nanosheets possessed abundant electroactive sites, enabling rapid reversible redox reactions. The co-effect of nanowires of the core-shell structure, the carbon layer, and the outer nanosheets effectively enhanced the overall electrochemical performance. Consequently, ZCO-ZO@C@CoS exhibited a specific capacitance of 1944 F·g^-1 (972.0 C·g^-1) at 1.5 A·g^-1, with an initial capacity retention of 75% after 10000 cycles at high current density of 20 A·g^-1. The asymmetric supercapacitor device, comprising ZCO-ZO@C@CoS (positive electrode) and activated carbon (negative electrode), also demonstrated excellent specific capacitance, high-rate performance, and exceptional cycling stability, indicating significant potential for practical applications.

Rechargeable zinc-ion batteries (ZIBs) have captured significant attention as promising solutions for large-scale energy storage. They offer advantages such as low cost, inherent safety, high specific energy, and eco-friendliness. Though numerous breakthroughs have been achieved in the development of cathodes, anodes and electrolytes, ZIBs are still far behind for practical application due to the lack of advanced materials. In the realm of ZIBs, two-dimensional (2D) MXenes have emerged as a fascinating candidate, leveraging their exceptional properties such as high richness, customizability, and unique physiochemical attributes. This review aims to provide a concise overview of advancements in MXene application for ZIBs, encompassing multiple synthesis routes, properties, morphological and structural characteristics, as well as various chemistries employed. Furthermore, detailed elucidation is provided on the recent progress in MXene-based cathodes, anodes, and electrolytes/separators for ZIBs, indicating the great potential of MXenes for achieving high-performance ZIBs. Strategies to enhance the performance of MXene-based ZIBs are also highlighted, including ion-intercalation adjustment, surface modification, heteroatoms doping, and layer spacing widening. Lastly, the review discusses the current challenges and future prospects for MXene-based ZIBs, paving the way for further research and development in this exciting field.

Selenium (Se) is considered as a new generation energy storage material of lithium-selenium (Li-Se) battery due to its high volume specific capacity (3253 mAh·cm^-3) and high electronic conductivity (1×10^-5 S·m^-1). To address the problems of volume expansion, fast capacity decay, and low utilization of active materials during its charging-discharging process, a ZIF-L derived nitrogen-doped nanosheets/selenium (Se@NC/CC) flexible self-supported composite electrode is designed in this study for lithium-selenium battery by growing two-dimensional zinc-based metallic organic framework (ZIF-L) on carbon cloth (CC). The rich microporous structure in the nitrogen-doped carbon nanosheets can effectively alleviate the volume expansion during the reaction process, and the doping of heteroatoms N helps to adsorb Li₂Se and reduce the loss of active substances. In particular, it is found that there is strong chemical bonding between Se and C in the Se@NC/CC electrode, which also helps to reduce the loss of active materials and improve the performance. Electrochemical results show that the initial discharge specific capacity of the Se@NC/CC electrode is 574 mAh·g^-1 at a current density of 0.5C (1.0C=675 mAh·g^-1), demonstrating a high initial discharge specific capacity. At a current density of 2.0C, the initial discharge specific capacity is 453.3 mAh·g^-1, which maintains at 406.2 mAh·g^-1 after cycling for 500 cycles and it also displays excellent rate performance compared to literature. Such a flexible self-supported selenium cathode designed in this study provides a new research route on the design of selenium host materials for advanced alkali metal-selenium batteries.

With rapid development of lithium ion batteries (LIB) and sodium ion batteries (SIB), hard carbon (HC) as new anode material has earned much attention. Besides its rich precursor sources and low cost, HC has higher Li⁺ storage capacity and better rate performance than graphite for LIB. Furthermore, it is also recognized as the most commercially potential anode material for SIB. However, low initial Coulombic efficiency is a common issue for HC. In addition, it is believed that the specific capacity can be further improved with the clarification of the Li/Na ion storage mechanism. In recent years, many researches on electrochemical mechanism have been conducted with some model assumptions proposed for better understanding the mechanism. This review introduced the structures and preparation approaches of HC as well as its application in LIB and SIB. The advantages, especially in fast charging, coating and other subdivision were discussed, and the different modification strategies such as pore structure design, doping, optimizing interface between electrode and electrolyte were summarized, aiming at the increase of capacity and the improvement of Coulombic efficiency of batteries.

MXenes with two-dimensional layered structure are widely used in the field of potassium ion supercapacitors because of their excellent electrical properties and adjustable surface functional groups, but their limited dual-capacitor storage capacity severely retards the application of MXenes materials in electrode materials. In this work, the strategy of “Lewis acid molten salt pre-etching + liquid phase etching + in situ hydrothermal recombination” was used to prepare the Ti₃C₂-based heterojunction with Ti₃C₂ as matrix and MnO₂ coated surface to improve the storage of potassium ions in electrode materials. The connection mode, electrical properties and the change of potassium adsorption law at Ti₃C₂-based heterojunction interfaces were studied by using the first principles calculation method based on density functional theory. The results show that the maximum adsorption capacity of potassium ions in the constructed Ti₃C₂-based heterojunction is about 3 times that of Ti₃C₂. The presence of Ti-O-H-O connecting channel increases the number of free electrons in MnO₂, causing Ti₃C₂-based heterojunction exhibiting excellent electrical properties. The electrochemical test results of the three-electrode system show that, at a current density of 1 A·g^-1, Ti₃C₂-based heterojunction can provide 431 F·g^-1 specific capacitance which is much higher than 128 F·g^-1 of bare Ti₃C₂. At a voltage sweep rate of 100 mV·s^-1, the contribution of pseudocapacitance is up to 89%. In addition, the Ti₃C₂-based heterojunction exhibits lower electrochemical impedance, which improves the potassium ion transport rate and electron transfer rate. Therefore, this study demonstrates that the electrochemical performance of Ti₃C₂ matrix can be improved by constructing Ti₃C₂-based heterojunction, and the corresponding energy storage mechanism can provide a theoretical basis for the design of other MXenes-based electrode materials.

In comparison to Li-ion batteries, Na-ion batteries offer the benefits of low cost, good low-temperature performance, and safety, attracting great attention in the cost- and reliability-sensitive applications. With high capacity and low cost, Prussian blue-like materials (PBAs) stand as promising cathode materials for Na-ion batteries. However, the presence of crystalline water within their structure induces fast performance decay of the battery, serving as a critical bottleneck limiting their application. This work reports a facile thermal treatment strategy to effectively remove crystalline water from PBAs cathode materials, improving capacity retention from 73% to 88% after 340 cycles. The in-situ analysis uncovers that the initial loss of Coulombic efficiency of PBAs cathode is a result of its irreversible transformation from a trigonal form to cubic phase during the charging and discharging process. This issue can be addressed by introducing of Na₂C₂O₄ to compensate the irreversible Na loss in the cathode. On this basis, a high-performance quasi-solid-state Na-ion battery is built by pairing a low-water-content PBAs cathode with Na₂C₂O₄ additive and a hard carbon (HC) anode within a poly(ethylene glycol) diacrylate (PEGDA)-based quasi-solid-state electrolyte with high ionic conductivity and electrochemical stability. This battery exhibits the specific capacities ranging from 58 to 105 mAh·g^-1 at current densities from 20 to 500 mA·g^-1, capable of sustaining stable cycling for over 200 cycles. This study underscores the significant improvement in stability and capacity of PBAs cathode materials by the efficient removal of crystalline water in them.

As an anode for lithium-ion batteries, silicon material has the advantage of high energy density. However, the volume effect during charge-discharge cycles causes instability in the active coating's surfaces and diffusion stress induced by internal polarization, leading to inevitable structural degradation and capacity fading. Inspired by functionally gradient materials, this study proposed a five-layer composite gradient silicon electrode. Experiments and multi-scale electro-chemo-mechanical coupled model demonstrate that the designed symmetric and linear gradient silicon electrodes effectively mitigate mechanochemical coupled degradation, showing superior cycling and rate performance compared to traditional uniform electrode. Specifically, the symmetric gradient electrode retains a specific capacity of 2065 mAh·g^-1 after 100 cycles at 0.2C (1C=2.65 mA·cm^-2) rate, with a capacity retention rate of 81%, while that of uniform electrode is 51%. The linear gradient electrode exhibits an average discharge capacity 1.5 times that of the uniform electrode at 1C rate. Moreover, both types of gradient electrodes demonstrate smaller impedance variations before and after cycling compared to the uniform electrode. These composite gradient electrodes are implemented through an innovative multi-layer coating process, and improved structural stability and electrochemical performance without material modifications, providing a reference for designing and fabricating high-performance silicon electrodes.

Metal phosphides have been studied as prospective anode materials for sodium-ion batteries (SIBs) due to their higher specific capacity compared to other anode materials. However, rapid capacity decay and limited cycle life caused by volume expansion and low electrical conductivity of phosphides in SIBs remain still unsolved. To address these issues, GeP₃ was first prepared by high-energy ball milling, and then Ketjen black (KB) was introduced to synthesize composite GeP₃/KB anode materials under controlled milling speed and time by a secondary ball milling process. During the ball milling process, GeP₃ and KB form strong chemical bonds, resulting in a closely bonded composite. Consequently, the GeP₃/KB anodes was demonstrated excellent sodium storage performance, achieving a high reversible capacity of 933.41 mAh·g^-1 at a current density of 0.05 A·g^-1 for a special formula of GeP₃/KB-600-40 sample prepared at ball milling speed of 600 r/min for 40 h. Even at a high current density of 2 A·g^-1 over 200 cycles, the capacity remains 314.52 mAh·g^-1 with a retention rate of 66.6%. In conclusion, this work successfully prepares GeP₃/KB anode-carbon composite for electrodes by high-energy ball milling, which can restrict electrode volume expansion, enhance capacity, and improve cycle stability of SIBs.

Compared with traditional lithium-ion batteries, sodium-ion batteries are an ideal alternative due to their cost advantages and sustainable resource supply. At present, the cathode materials for sodium-ion batteries mainly include transition metal oxides, polyanionic compounds and Prussian blue analogues. However, irreversible phase conversion, Jahn-Teller effect and interface instability of cathode materials seriously affect the cycling stability of sodium-ion batteries. In this paper, the research progress and industrialization process of strategies for improving cyclic stability of cathode materials for sodium-ion batteries are systematically introduced. Firstly, the structure as well as advantages and disadvantages of cathode materials is analyzed in detail, and the structural stability, cost and cycling performance are compared. Secondly, the latest research progress of structure optimization and chemical element doping strategies in improving the cycling stability of cathode materials is elaborated in detail, and the interaction between structural stability, electronic conductivity, ion intercalation/deintercalation of cathode materials and electrochemical performance is revealed. Then, the development process and industrialization progress of sodium-ion batteries are summarized. Finally, the significant problems that still need to be addressed for cathode materials and systems for sodium-ion batteries are sorted out and their future developments are prospected, aiming to propel the steady and healthy development of sodium-ion battery industry.

FeF₃∙0.33H₂O possesses the characteristics of high theoretical capacity and high voltage, but its electrochemical cycling performance is unsatisfactory due to its poor conductivity and serious volume change during redox reaction, resulting in limited application. In this study, by using the strategies of dopamine self-assembly coating, carbonization, HCl etching and HF fluorination, the yolk-shell structured composite FeF₃∙0.33H₂O@carbon nanoboxes (FeF₃∙0.33H₂O@CNBs) composed of N-doped graphene shell and nanocube FeF₃∙0.33H₂O core was synthesized. Its particle size is about 250 nm and thickness of carbon shell is 30-40 nm. FeF₃∙0.33H₂O@CNBs displays an initial charge-discharge capacity of 208 mAh·g^-1 at a current density of 0.2C(1C=237 mA·g^-1). After 50 cycles, the capacity remains 173 mAh·g^-1, and the capacity attenuation rate per cycle is only 0.3%. In comparison, the initial capacity of bare FeF₃∙0.33H₂O is 112 mAh·g^-1, and after 50 cycles, only 95 mAh·g^-1 reserves, indicating superior cycle performance of FeF₃·0.33H₂O@CNBs. Furthermore, charging and discharging results at 0.1C-1C show that the rate performance is also significantly better than bare FeF₃∙0.33H₂O. It’s due to that N-doped graphene shell prepared by this strategy provides good electron/ion transport performance. At the same time, the carbon shell can not only buffer and inhibit the volume change of the core FeF₃∙0.33H₂O, but also shorten the ion migration distance and improve the Li⁺ migration rate on the electrolyte storage and retention performance of the electrolyte. As a result, the electrochemical performances are better than those of previous literature.

Silicon sludge, the photovoltaic cutting silicon waste, has become one of the expected raw materials for the key silicon carbon anode materials used in high energy density batteries above 300 Wh·kg^-1 due to its low cost, two-dimensional lamellar structure and ultrahigh specific capacity (4200 mAh·g^-1). However, silicon sludge requires systematic modification because of its challenges such as complex composition, large particle size, poor electrical conductivity, low stability and poor electrochemical performance. This paper systematically reviews the application status and research progress of silicon sludge in lithium-ion batteries. Firstly, the important effects of metal and non-metal impurities on battery performance are summarized, in which metal impurities are normally removed by magnetic separation and acid pickling, and non-metallic impurities are removed by liquid-liquid extraction and heat treatment. Secondly, detailed elucidation about the initial performance and modification methods of the silicon sludge is provided. Concretely, silicon sludge can be nano-sized to reduce expansion by grinding, etching, electrothermal shock, and alloy dealloying, enhance electrical conductivity through doping the intrinsic silicon and doping the carbon layer on the silicon surface, improve stability through the construction of inert layer, conductive layer and functional group, and obtain mechanical support and protection through silicon-carbon composite. Finally, the challenges, development directions and future prospects of silicon-based anode based on silicon sludge are put forward, aiming to provide a reference for converting silicon sludge into treasure and promote the rapid development of high energy density lithium-ion batteries.

The development of low-cost and long-lifespan sodium-ion battery (SIB) cathode materials is crucial for large-scale energy storage. Iron-based phosphate cathode materials have attracted significant attention in recent years for their high theoretical capacity, excellent structural stability and rich resources. Here, a series of Na₄Fe_xP₄O_12+x/C (x=2.6-3.3) electrode materials are prepared using Sol-Gel technique and thermal treatment process. Effect of the phase structure on electrochemical performance of Na₄Fe_xP₄O_12+x/C electrode materials is investigated. It is found that three phases, including Na₂FeP₂O₇ (NFPO), Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) and NaFePO₄ (NFP), mainly exist in the Na₄Fe_xP₄O_12+x/C system. Among Na₄Fe_xP₄O_12+x/C electrode materials, Na₄Fe_3.1P₄O_15.1/C electrode material with the highest content of NFPP phase possesses rapid electronic and sodium-ion conduction characteristics, thereby exhibiting the optimal electrochemical performance. As a result, the SIB equipped with Na₄Fe_3.1P₄O_15.1/C electrode material shows high reversible capacity, with a discharge specific capacity of 102.8 mAh·g^-1 at a current density of 0.1C (1C=129 mAh·g^-1), as well as capacity retention of 88.7% after 700 cycles. Furthermore, the as-assembled battery exhibits excellent rate performance with a discharge specific capacity of 61.5 mAh·g^-1 at a current density of 5C.

The research of sodium-ion batteries (SIBs) is of great significance for development of new energy and energy storage methods. As cathode material, P2-type layered oxide material Na_2/3Ni_1/3Mn_2/3O₂ has attracted wide attention due to its excellent capacity and high working voltage. However, it suffers from undesired P2-O2 phase transition, which leads to a drastic change in volume and rapid capacity decay. Here, a P2-Na_0.67Ni_0.18Cu_0.10Mg_0.05Mn_0.67O₂ (NCMM-10-05) cathode was synthesized through solid-state method with synergetic substitution of Cu and Mg. The results indicated that the incorporation of Cu and Mg suppressed irreversible P2-O2 phase transition when charging to high voltage and initialized OP4 phase formation, which improved reversible stability of structure. Thus the as-obtained material exhibited excellent electrochemical performance, which delivered an initial discharge capacity of 113 mAh·g^-1 in the voltage range of 2.00-4.35 V (vs. Na⁺/Na), a reversible capacity of 64.1 mAh·g^-1 at 8C (1C=100 mA·g^-1), and a capacity retention of 88.9% after 200 cycles at 1C. The effect of Cu and Mg synergetic substitution on the structure and electrochemical properties of P2-type layered oxides was explored, and the specific roles played by Cu and Mg in the structural evolution were further investigated by in situ X-ray diffraction (XRD) analysis and density functional theory (DFT) calculations. This work provides a new insight into the rational design of highly stable cathode materials with rapid Na⁺ transport capability for SIBs.