Thick‐electrode design is a promising strategy for achieving high‐energy‐density lithium‐ion batteries. In this work, an electrochemical–mechanical coupled model is developed for bilayer cathodes consisting of two distinct active materials. Using a bilayer LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC)/LiFePO 4 (LFP) cathode as a representative system, the effects of material arrangement on Li‐ion transport, rate capability, and stress evolution are systematically investigated. The model is validated against experimental polarization data. Results show that the configuration with the NMC layer adjacent to the separator exhibits significantly improved rate capability under high C‐rate conditions. Optimization of the sublayer thickness ratio involves a trade‐off between maximizing theoretical capacity and maintaining high‐rate performance. Owing to the distinct lithiation‐induced volume expansion behaviors of NMC and LFP, pronounced stress gradients and severe local stress concentration develop near the bilayer interface, imposing stringent requirements on interfacial adhesion during cycling. Furthermore, when the LFP sublayer occupies a sufficiently large thickness fraction, a saddle‐shaped distribution of Li‐ion concentration and von Mises stress emerges within the LFP layer near the current collector. These findings provide quantitative design guidelines for bilayer cathodes with balanced electrochemical performance and mechanical durability.
The recent commercialization of next‐generation blade batteries, as exemplified by BYD’s second‐generation systems, has reaffirmed the relevance of LiFePO 4 ‐based cathodes for high‐safety lithium‐ion batteries, yet their limited energy density remains a key bottleneck. Partial substitution of Fe with Mn to form LiMn x Fe 1− x PO 4 is considered an effective strategy to enhance energy density, but is hindered by Jahn–Teller distortion of Mn (III). Although Fe/Mn solid‐solution engineering has been widely explored, considerable inconsistency persists regarding the optimal Fe/Mn ratio, with conflicting reports of 4:6, 5:5, and 6:4. Here, nanocrystalline LiMn x Fe 1– x PO 4 solid solutions are synthesized by a microwave‐assisted hydrothermal route, and their composition‐dependent electrochemical behavior and phase transition mechanisms are elucidated. A non‐monotonic dependence on Fe/Mn ratio is identified, with the equimolar composition (Fe/Mn = 1:1) delivering the optimal balance of energy density, polarization, and cycling stability. A transition from biphasic to solid‐solution‐like behavior is revealed by in situ X‐ray diffraction at this composition, enabling improved structural stability and reaction kinetics. These results provide a systematic composition‐dependent understanding of how Fe/Mn stoichiometry regulates reaction kinetics and apparent phase‐transition behavior in nanocrystalline LiMn x Fe 1− x PO 4 /C, offering guidance for the rational design of high‐energy‐density olivine cathodes.
The rapidly growing deployment of electric vehicles and energy storage systems is generating increasing quantities of spent LiFePO 4 (LFP) batteries and creating an urgent need for environmentally sound and economically viable recycling. Compared with Ni‐ and Co‐rich cathodes, spent LFP has a lower intrinsic resource value, which reduces the profitability of conventional pyrometallurgical and hydrometallurgical routes and limits their suitability for closed‐loop utilization. This review summarizes recent advances in the high‐value recycling and regeneration of spent LFP batteries, with an emphasis on retirement trends, degradation mechanisms, recycling challenges, and advanced regeneration strategies. Conventional pyrometallurgical and hydrometallurgical recovery routes are first compared in terms of efficiency, cost, environmental burden, and scalability. Recent progress in direct regeneration is then discussed, including lithium replenishment, lattice repair, carbon‐coating reconstruction, hydrothermal treatment, and molten‐salt‐assisted regeneration. Upgraded regeneration strategies, including defect modulation, doping, surface engineering, micro/nanoscale structural optimization, cross‐system conversion, and transformation into multifunctional materials, are also highlighted. Finally, key barriers associated with feedstock heterogeneity, impurity control, process economics, environmental sustainability, and industrial standardization are identified. This review provides systematic insights into green, scalable, and value‐added recycling pathways for spent LFP batteries.
Sodium metal batteries, with their high theoretical specific capacity and energy density, are ideal candidates for long‐duration applications. As progress in Na metal batteries continues, the demands on the anode have become increasingly stringent. However, the high reactivity of Na metal poses a significant safety challenge that limits the application of Na metal batteries. During battery cycling, Na ions continuously nucleate, deposit, and eventually form Na dendrites on the anode side. Therefore, understanding the formation mechanism of Na dendrites and the measures to prevent them plays a direct role in the further application of Na metal batteries. This review aims to enhance the understanding of the relationship between the fundamental principles of Na metal anode failure and improved design. The review focuses on the analysis and summary of the latest Na metal anodes based on commonly used carbon‐based and metal‐based matrix materials, and on optimizing the anode against dendrite formation mechanisms. Additionally, it provides a perspective on the development of Na metal anodes. A deep understanding of anode optimization engineering will pave the way for the development of practical, safe, and durable high‐performance Na metal batteries.
The rapid growth of electric vehicles and portable electronic devices has substantially increased the demand for recycling end‐of‐life batteries. Although traditional pyrometallurgical and hydrometallurgical recycling technologies are industrially established, their broader application is constrained by high energy consumption, long processing times, and severe secondary pollution. Recently, electrochemical strategies have emerged as cleaner and more selective alternatives. By utilizing electrons as the primary reagent, these methods can provide controllable reaction selectivity and environmental compatibility under relatively mild conditions. This review summarizes recent advances in electrochemical strategies for the closed‐loop regeneration and upcycling of spent batteries, covering electrochemical leaching, selective electrodeposition, direct cathode/anode regeneration, and functional upcycling. Particular attention is given to transforming degraded battery components into regenerated electrodes, electrocatalysts, water treatment, electromagnetic absorption materials, flexible biosensors, and next‐generation energy storage materials. We further discuss key challenges and future directions such as mitigating manual risks through battery passports and AI‐driven robots. This review aims to provide theoretical guidance and a forward‐looking perspective for developing the next generation of low‐carbon battery recycling technologies.
Ion exchange membranes (IEMs) are pivotal components in electrochemical energy technologies such as fuel cells, water electrolyzers, and redox flow batteries. This review systematically analyses recent advances and structure‐performance relationships in IEMs, categorized into cation exchange membranes (CEMs) and anion exchange membranes (AEMs). For CEMs, strategies like inorganic hybridization and microporous polymer design effectively enhance proton conductivity while mitigating fuel crossover and swelling. For AEMs, approaches including ether‐free polymer backbones, side‐chain engineering, and cross‐linked networks improve hydroxide ion conductivity and chemical stability in alkaline environments. The discussion highlights how tailored material design—from perfluorinated and hydrocarbon‐based polymers to emerging covalent organic frameworks—governs device efficiency, durability, and scalability. Finally, future research directions are outlined to overcome existing challenges and accelerate the development of next‐generation IEMs for sustainable energy conversion and storage.
Rechargeable sodium‐based seawater batteries (SWBs) that store energy in the form of metallic Na at the anode require cathodes laden with bifunctional electrocatalysts that can efficiently perform the otherwise kinetically sluggish oxygen evolution (OER) and reduction reactions (ORR). Here, we report the systematic evaluation of NiFe layered double hydroxides (NiFe‐LDHs) as suitable bifunctional electrocatalysts for use in rechargeable SWBs. NiFe‐LDHs with various Ni/Fe ratios were synthesized using a hydrothermal approach to ensure spherical particle morphologies comprising of flowerlike nanosheets pattern on the surface with high surface area of ~63 m 2 /g. The electrocatalytic activities and operational stabilities of these synthesized catalysts were evaluated using linear sweep voltammetry and chronopotentiometry in both simulated seawater and natural seawater. The LDH catalysts evaluated in our study showed comparable catalytic behavior in simulated seawater, whereas in natural seawater, performances drastically varied. Additionally, the best performing catalyst was tested in a dual compartment Na seawater cell, demonstrating successful sequential OER and ORR operation in natural seawater. Overall, this study highlights the potential of NiFe‐LDH bifunctional electrocatalysts for rechargeable Na‐based seawater batteries and elucidates the feasibility and design parameters of such catalysts for effective OER and ORR activity in conditions employing natural seawater in SWBs.
Stable electrode materials with reversible ion insertion/extraction are central to developing sodium‐ and potassium‐ion batteries as lithium‐ion alternatives. Here, we investigated the impact of different monovalent insertion ions on the performance and reliability of the same electrode. We chose Berlin Green (BG, Fe III [Fe III (CN) 6 ]), a Prussian Blue analog (PBA), due to its rigid structure, ability to accommodate different ion sizes, and two different redox‐active Fe atoms. We conducted electrochemical tests, intermittent scanning electron microscopy (SEM), and operando substrate curvature experiments on BG as we changed the counter electrode and electrolyte. With this novel experimental strategy, we report for the first time sequential insertion/extraction of all three ions in/from the same single BG electrode, eliminating electrode variations and ensuring direct comparability of ion insertion, degradation, and stress. While Li + and Na + follow comparable pathways, K + leads to distinct electrochemical and mechanical responses, underscoring ion‐specific interactions within the host framework. We demonstrate that BG enables highly reversible insertion/extraction with a high tolerance to ionic size variation and great surface stability, despite volume changes and phase transitions. These results position BG as a model system for understanding alkali ion insertion and as a versatile and sustainable electrode material for future energy storage systems.
Metal–air seawater batteries have emerged as promising energy‐storage systems owing to their high theoretical energy density, intrinsic safety, economic viability, and compatibility with natural seawater or seawater‐derived electrolytes. However, sluggish oxygen electrocatalysis and poor cathode durability in chloride‐rich seawater cause large polarization, low energy efficiency, and limited stability. Coupling solar energy with these batteries offers an effective strategy to accelerate cathode reactions through photoelectric and photothermal effects. In view of the rapid progress in this emerging field, this Review summarizes recent advances in solar‐coupled metal–air seawater batteries, focusing on device configurations, working principles, photoelectrode materials, and representative battery systems. Inorganic, organic, and composite semiconductor photoelectrodes are discussed in terms of light harvesting, charge separation, oxygen electrocatalysis, and seawater compatibility. Recent advances in solar‐coupled Na–air, Zn–air, and value‐added seawater batteries are further highlighted. Finally, key challenges related to photoelectrode stability, interfacial microenvironments in seawater, performance evaluation, and device integration are outlined to guide the development of efficient and durable solar‐coupled metal–air seawater batteries.
SnSe is a promising lithium‐ion battery anode owing to its layered structure and high theoretical capacity, yet suffers from severe volume expansion and structural degradation. Herein, polyacrylonitrile‐derived nitrogen‐doped carbon‐coated SnSe/C composites were synthesized via ball milling and calcination, with the Se/SnS 2 molar ratio tuned to optimize the structure. Characterization confirms uniform SnSe dispersion within the carbon matrix and a stable core–shell architecture. Electrochemically, the composite achieves an initial Coulombic efficiency of 80.8% at 0.1 A g −1 , delivers discharge capacities from 974.9 to 451.8 mAh g −1 over 0.1–5 A g −1 (excellent rate capability), and retains 777.9 mAh g −1 after 500 cycles at 1 A g −1 (94.0% retention), demonstrating outstanding long‐term cycling stability. Kinetic analysis reveals that the N‐doped carbon layer substantially enhances Li + diffusion and pseudocapacitive contribution. This work offers a facile and scalable route to high‐performance Sn‐based anodes.
Aqueous zinc‐ion batteries (AZIBs) have attracted increasing attention due to their advantages of low cost and high safety, as well as their high bulk energy density. Nevertheless, serious corrosion and dendritic growth of zinc anode during cycling, as well as anode–electrolyte side reactions primarily restrict the large‐scale applications of AZIBs. To address these issues, herein, an artificial CoWO 4 protective layer was coated on the surface of zinc metal anode via the blade method. Results showed that this hydrophobic coating layer could effectively inhibit the direct contact of Zn metal anode with electrolyte, suppressing its corrosion and side reactions during Zn deposition and stripping. Benefiting from this advantage, the CoWO 4 @Zn anode could steadily cycle for 200 cycles with a high average Coulombic efficiency in the half‐cell test at a current density of 0.5 mA cm −2 . The symmetrical battery with CoWO 4 @Zn electrode could cycle for 2700 h with a low overpotential at 0.25 and 0.05 mAh cm −2 . In addition, when assembled with Mn‐ and V‐based cathodes, the cell with CoWO 4 @Zn anode exhibited better cycling stability than bare Zn anode. Thus, this strategy brings new opportunities for the future development of rechargeable AZIBs.
Rechargeable sodium‐metal batteries are attractive for large‐scale energy storage due to the high abundance and low cost of sodium. However, their development is hindered by the limited availability of electrolytes that simultaneously provide high ionic conductivity, high Na metal compatibility, and suppressed anion mobility. Here, we report a chemically simple gel polymer electrolyte (GPE) based on a commercially available hydroxyl‐terminated fluoropolymer, in which a borate‐mediated network is generated in situ using sodium borohydride as a low‐cost crosslinking agent. The resulting GPE exhibits excellent Na + ionic conductivity up to 1.6 × 10 −3 S cm −1 at 30 °C and near single‐ion conduction (Na + ion transference number up to ~0.84). Galvanostatic cycling of a symmetric Na||Na cell using glass fiber‐supported GPE exhibits stable performance over 750 cycles, demonstrating excellent GPE compatibility with Na metal. A coin cell assembled from an Na anode and a Na 3 V 2 (PO 4 ) 3 /C cathode with this GPE exhibits an exceptional cycling performance with over 2000 charge–discharge cycles within the voltage range from 1 to 2 V.
The cathode materials comprising an alkali metal ion are considered promising for high‐energy rechargeable batteries. In room‐temperature sodium‐sulfur batteries (RT‐Na/S), the sodium metal anode is used in excess, posing safety challenges; the elemental sulfur cathode is susceptible to polysulfide dissolution, leading to cell failure. These issues can simultaneously be addressed by incorporating sodium ions into the cathode matrix. Unfortunately, most sodium‐containing sulfur cathodes are either chemically unstable or prone to disintegration, limiting their use under ambient conditions. In this contribution, we report the development of an air‐stable sodium‐containing metal sulfide (NaCu 3 S 2 (NCS)) and demonstrate it as a potential cathode for sodium‐metal‐free RT‐Na/S batteries. In a half‐cell configuration, the cathode demonstrates a remarkably high cycling stability of over 1300 cycles with a capacity fade of around 0.31 mAh g −1 per cycle. Further, a full RT‐Na/S cell is fabricated with the NCS cathode and a hard‐carbon anode. The full cell delivers a high discharge capacity of about 460 mAh g −1 and functions reversibly for over 500 cycles. The postmortem analysis of the cathode unravels that the as‐developed cathode undergoes conversion reactions. We believe these findings are critical and may pave the way for the development of a safe, high‐energy RT‐Na/S battery.
Enhancing the energy density of supercapacitors (SCs) is essential for advancing their capabilities, broadening their range of applications, and making them more competitive with other energy storage technologies like batteries. Although aqueous SCs are emerging as a desirable technology, their energy density is severely restricted by the low thermodynamic stability window of aqueous electrolytes. Achieving a high‐energy supercapacitor that leverages the benefits of an aqueous electrolyte is both highly desirable and challenging. In this study, we address this challenge by utilizing a water‐in‐salt 17 m NaClO 4 (WiS) electrolyte that allows an operational window of 2.87 V, coupled with engineered potassium‐incorporated manganese dioxide (K‐MnO 2 ) electrode. Our research demonstrates that the insertion of potassium ions (K + ) into manganese dioxide (MnO 2 ) significantly enhances its pseudocapacitive behavior via the Mn 3+ /Mn 4+ redox mechanism. This enhancement, facilitated by the wide potential range provided by the electrolyte, results in a high areal capacitance of 1051 mF/cm 2 (294.3 F/g). Furthermore, the asymmetric supercapacitor, featuring an activated carbon negative electrode and K‐MnO 2 positive electrode, operates at 2.3 V, achieving an energy density of 59.5 Wh/kg. This study underscores the critical role of well‐defined electrochemical interfaces in enhancing the energy density of SCs. It also offers a powerful approach to utilizing WiS electrolytes, enabling wide‐window operation of electrodes in aqueous SCs to achieve battery‐like energy densities.
Designing and optimizing electrolyte compositions beyond carbonate/NaPF 6 is vital to advancing commercial sodium‐ion batteries, as electrode–electrolyte interface instability gravely affects the battery cycling stability and rate performance. Sulfones are known as high‐voltage solvents/additives in commercial lithium‐ion batteries. Here, sulfolane has been used as a cosolvent with a baseline electrolyte containing 1 M NaPF 6 in EC:PC (v/v, 1:1) in SIBs to improve performance and safety metrics. The electrolyte’s oxidative stability increases with the addition of SL, which has two S═O bonds, thereby forming a robust sulfur‐rich cathode‐electrolyte interface layer. The battery metrics of the commercial oxide cathode, O3‐NaNi 0.33 Fe 0.33 Mn 0.33 O 2 , were optimized with 15 vol% sulfolane co‐solvent at high temperature (60 °C) and voltage (4.2 V) to improve rate capability and capacity retention. The optimized electrolyte retains ∼90% of its specific capacity compared to the baseline electrolyte (78%). To understand interfacial chemistry, the influence of the cosolvent on electrolyte solvation structure on the cathode interface layer was mapped. The thermostability and non‐flammability of sulfolane further enhance the safety of commercial SIBs.
This article proposes a lithium‐ion battery capacity degradation trajectory prediction framework using the voltage, current, and capacity curves extracted from a single cycle during the ultra‐early stage of the battery testing process. This framework is composed of three phases: image construction, knot prediction, and trajectory prediction. First, the voltage, current, and capacity curves are converted to images. Then, a convolutional neural network (CNN) model composed of three AlexNet blocks is employed to predict multiple knots on the trajectory. Finally, piecewise cubic Hermite interpolating polynomial (PCHIP) interpolation is implemented to construct the trajectory based on the predicted knots. The effectiveness of the proposed framework is demonstrated using the Severson dataset with 124 battery cells. For the 29 cells in the test set, the average trajectory prediction error is 46.7 cycles in terms of mean absolute error (MAE), 51.3 cycles in terms of root mean square error (RMSE), and 7.6% in terms of mean absolute percentage error (MAPE), respectively.
To clarify the rate‐dependent electro‐thermo‐mechanical response and spatially nonuniform surface stress behavior of commercial prismatic lithium‐ion batteries during cycling, this study investigates the rate‐dependent electro‐thermo‐mechanical behavior and spatial stress heterogeneity of a commercial 12 Ah prismatic lithium‐ion battery during cycling. Utilizing a multipoint monitoring platform, surface stress, temperature, and voltage were synchronously recorded under 0.5 C charge and 1/2 C discharge conditions. The results reveal that surface stress fluctuates periodically and escalates with continued cycling, with the 2 C high‐rate discharge significantly amplifying voltage polarization, stress fluctuation intensity, and thermal responses compared to the 1 C discharge. Furthermore, seven‐point surface measurements demonstrate distinct spatial heterogeneity; regions C3 and C7 act as mechanically sensitive stress concentrators, whereas region C6 exhibits stable, localized stress‐relief behavior. Thermally, while the temperature field remains relatively uniform at 1 C, the 2 C discharge doubles local temperature fluctuations (from approximately ±2 to ±4 °C at C1) primarily due to enhanced ohmic heating and heat accumulation. Ultimately, these findings underscore the necessity of using spatially resolved monitoring, rather than relying solely on global average metrics, to accurately evaluate local battery responses, providing a crucial experimental foundation for optimizing sensor layouts, designing cycling strategies, and conducting mechanical safety assessments.
Rechargeable magnesium batteries (RMBs) are promising next‐generation energy storage systems due to high volumetric capacity of Mg anode, dendrite‐free deposition, and high natural abundance. However, their development is largely restricted by sluggish Mg 2+ diffusion, strong electrostatic interactions within host lattices, and severe interfacial desolvation barriers. Sulfide‐based cathodes, featuring soft anion frameworks and enhanced ionic mobility, have emerged as attractive candidates, yet they suffer from limited conductivity, structural instability, and a voltage‐kinetics trade‐off. This review comprehensively summarizes recent progress in defect engineering strategies for sulfide cathodes in RMBs. The fundamental mechanism of Mg 2+ migration is discussed, followed by a systematic classification of defect types and their roles in regulating diffusion pathways, electronic structure, redox activity, and interfacial behavior. Synthetic approaches for controlled defect construction and their electrochemical implications are critically evaluated. Finally, key challenges including quantitative defect characterization, interfacial instability, structural degradation, and limited practical validation are identified, and future design strategies for high‐performance defect‐engineered sulfide cathodes are proposed.
Supercapacitors, especially micro‐supercapacitors for on‐chip integration in flexible/wearable electronics, are efficient storage devices for intermittent renewable energy sources, bridging the gap between batteries and conventional capacitors by offering high power density, rapid charge–discharge rates, and long cycle life. However, achieving superior electrochemical performance at the molecular scale remains a challenge. Here, we report the synthesis of four unprecedented zinc complexes ( 1 –4 ) incorporating sulfur‐ and selenium‐functionalized abnormal N ‐heterocyclic carbene ligands, highlighting the unexplored potential of molecular coordination complexes as active materials for micro‐supercapacitors ( 1–3 ). All complexes were characterized by single‐crystal X‐ray diffraction, UV–vis, IR, and Raman spectroscopy, XPS, and thermogravimetric analysis, confirming their distinct structural and electronic properties. Electrochemical studies reveal that complexes 1–3 exhibit significant pseudocapacitive behavior with good charge storage capability and cycling stability. Complex 2 delivered the highest areal capacitance of 8.149 mF cm −2 , followed by complexes 3 and 1 , respectively. The micro‐supercapacitor device based on complex 3 achieved the highest capacitance retention (108.78%) after 1050 cycles, indicating a highly reversible electrochemical process. This work demonstrates the synthesis, characterization, and stable pseudocapacitive performance of S/Se‐functionalized carbene–Zn complexes for energy storage applications.
