As the global energy landscape transitions toward cleaner and more sustainable sources, the demand for efficient energy storage systems has become increasingly pressing. Lithium-ion batteries (LIBs) are among the most commercially successful electrochemical energy storage technologies due to their high energy density, long cycle life, and relatively low environmental impact, and are widely deployed in consumer electronics, electric vehicles, and grid-scale energy storage systems. As a core component of LIBs, cathode materials largely determine the energy density, cycling stability, and safety of the battery. This review systematically examines the developmental history and recent research progress of five representative LIB cathode materials, including lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, high-nickel ternary materials, and lithium-rich manganese-based materials, addressing the incomplete and outdated perspectives in existing literature. The crystal structures, key scientific challenges, and recent modification strategies, such as surface coating, bulk doping, structural design, and interface engineering, are comprehensively discussed. By integrating multiscale approaches, including in situ characterization techniques and machine-learning-assisted analysis, this review connects historical developments with emerging research frontiers and provides guidance for the rational design of next-generation high-performance, safe, and cost-effective LIB cathode materials.

Owing to their intrinsic safety and low cost, aqueous zinc-ion batteries (AZIBs) have emerged as promising large-scale energy storage devices. Hydrogel electrolytes have been extensively studied because of their superior electrochemical performance their ability to endow AZIBs with excellent flexibility. However, traditional hydrogel electrolytes typically suffer from a narrow electrochemical stability potential window (ESPW) and poor cycling stability, primarily due to their high water content. In recent years, lean-water hydrogel electrolytes (L-WHEs) have been developed to address these issues. By confining free water molecules and regulating ion transport within the hydrogel network, L-WHEs can efficiently suppress side reactions, widen the ESPW, and enhance interfacial stability. This review systematically discusses the fundamental principles of L-WHEs, current strategies for developing practical L-WHEs, and recent research progress. Finally, future prospect and challenges in the development of high-performance L-WHEs are outlined.

With the growing global energy demand and the pressing need for a clean energy transition, supercapacitors (SCs) have demonstrated significant application potential in electric vehicles, wearable electronics, and renewable energy storage systems owing to their rapid charge–discharge capability, exceptional power density, and prolonged cycle life. The improvement of their overall performance fundamentally depends on the synergistic design of electrode materials and electrolyte systems, as well as the precise regulation of the electrode-electrolyte interface. This review focuses on the key components of supercapacitors, systematically reviewing the design strategies of high-performance electrode materials, outlining recent advances in novel electrolyte systems, and comprehensively discussing the critical roles of interfacial reinforcement and optimization in enhancing device energy density, power performance, and cycling stability. Furthermore, interfacial engineering strategies and innovations in device architecture are proposed to address interfacial degradation in flexible SCs under mechanical stress. Finally, key future research directions are highlighted, including the development of high-voltage and wide-temperature-range electrolyte systems and the integrated advancement of multiscale in situ characterization techniques and theoretical modeling. This review aims to provide theoretical guidance and innovative strategies for material design, contributing toward the realization of next-generation supercapacitors with enhanced energy density and reliability.

Recycling spent lithium-ion batteries (LIBs) is crucial for environmental protection and sustainability. Currently, the main methods for recycling spent LIBs include element extraction and material regeneration. Materials upcycling is a complementary strategy aimed at transforming existing materials into next-generation high-performance materials. This review summarizes recent advancements in upcycling cathode materials from spent LIBs into high-performance cathode. We begin by outlining the development of cathode materials and exploiting how material upcycling can meet the needs of future battery technologies. Next, we introduce the concept and historical evolution of cathode material upcycling and provide a detailed summary of strategies such as doping, coating, and the transformation between different cathode materials. Finally, we discuss the challenges of cathode upcycling and offer guidance for future research directions.

Sodium-ion batteries (SIBs) have been commercialized in 2023 and are expected to capture a substantial market share in the future. However, the material systems in SIBs are very similar to those in lithium-ion batteries (LIBs), which necessitate consideration of recycling in terms of safety issues, environmental concerns, and economic values. In this study, we present the first evaluations of the disassembly of spent commercialized SIBs and the leaching and regeneration of their cathode material (NaNi_1/3Fe_1/3Mn_1/3O₂). We find that pretreatment of SIBs recycling offers advantages, particularly in separating the cathode and removing impurities from the material surface. The primary challenge in recycling is that failed cathode materials are difficult to dissolve in traditional inorganic acids, with an extraction rate of only 57.4% even when a reducing agent is added. Fortunately, there is a possibility for the failed NaNi_1/3Fe_1/3Mn_1/3O₂ regeneration. By replenishing sodium and repairing the structure through thermal treatment, the capacity can be restored to 109.4 mAh g⁻¹, with potential practical applications. Economic analysis indicates that the recycling of spent SIBs through cathode material regeneration results in a profit of ＄3.76 kg⁻¹ battery, even surpassing the ＄2.64 kg⁻¹ battery profit from LIB recycling. We hope that this research will provide a foundation for SIB recycling.

Lithium (Li) metal is the ultimate anode choice for next generation high energy density batteries. However, the high nucleation energy barrier and nonuniform electric field distribution, as well as huge volume expansion, lead to the uncontrollable growth of Li dendrites and poor utilization of Li metal, which hinders its practical application. Herein, titanium dioxide/cuprous oxide (TiO₂/Cu₂O) heterostructure is constructed on the rimous skeleton of Cu mesh, and the heterostructure decorated rimous Cu mesh (H-CM) can act as both current collector and host for dendrite-free Li metal anode. The TiO₂/Cu₂O heterostructure realizes selective Li nucleation by nano TiO₂ and then induces fast and uniform Li conduction with the aid of heterostructure interface and nano Cu₂O contributing to dendrite-free Li deposition. While the internal and external space of rimous skeletons in H-CM is used to accommodate the deposited Li and buffer its volume change. Therefore, the cycling reversibility of the derived Li metal anode in H-CM is improved to a high Coulombic efficiency of 98.8% for more than 350 cycles at a current density of 1 mA·cm⁻², and 1,000 h (equals to 500 cycles) stable repeated Li plating/stripping can be operated in a symmetric cell. Furthermore, full cells with limited Li anode and high loading LiFePO₄ cathode present excellent cycling and rate performances.

The ever-growing pursuit of high energy density batteries has triggered extensive efforts toward developing alkali metal (Li, Na, and K) battery (AMB) technologies owing to high theoretical capacities and low redox potentials of metallic anodes. Typically, for new battery systems, the electrolyte design is critical for realizing the battery electrochemistry of AMBs. Conventional electrolytes in alkali ion batteries are generally unsuitable for sustaining the stability owing to the hyper-reactivity and dendritic growth of alkali metals. In this review, we begin with the fundamentals of AMB electrolytes. Recent advancements in concentrated and fluorinated electrolytes, as well as functional electrolyte additives for boosting the stability of Li metal batteries, are summarized and discussed with a special focus on structure–composition–performance relationships. We then delve into the electrolyte formulations for Na- and K metal batteries, including those in which Na/K do not adhere to the Li-inherited paradigms. Finally, the challenges and the future research needs in advanced electrolytes for AMB are highlighted. This comprehensive review sheds light on the principles for the rational design of promising electrolytes and offers new inspirations for developing stable AMBs with high performance.

Nickel-rich LiNi_1−x−yCo_xMn_yO₂ (NCM, 1−x−y ≥ 0.6) is known as a promising cathode material for lithium-ion batteries since its superiority of high voltage and large capacity. However, polycrystalline Ni-rich NCMs suffer from poor cycle stability, limiting its further application. Herein, single crystal and polycrystalline LiNi_0.84Co_0.07Mn_0.09O₂ cathode materials are compared to figure out the relation of the morphology and the electrochemical storage performance. According to the Li⁺ diffusion coefficient, the lower capacity of single crystal samples is mainly ascribed to the limited Li⁺ diffusion in the large bulk. In situ XRD illustrates that the polycrystalline and single crystal NCMs show a virtually identical manner and magnitude in lattice contraction and expansion during cycling. Also, the electrochemically active surface area (ECSA) measurement is employed in lithium-ion battery study for the first time, and these two cathodes show huge discrepancy in the ECSA after the initial cycle. These results suggest that the single crystal sample exhibits reduced cracking, surface side reaction, and Ni/Li mixing but suffers the lower Li⁺ diffusion kinetics. This work offers a view of how the morphology of Ni-rich NCM effects the electrochemical performance, which is instructive for developing a promising strategy to achieve good rate performance and excellent cycling stability.

Air-stable layered structured cathodes with high voltage and good cycling stability are highly desired for the practical application of Na-ion batteries. Herein, we report a P2-Na_2/3Ni_2/3Te_1/3O₂ cathode that is stable in ambient air with an average operating voltage of ~3.8 V, demonstrating excellent cycling stability with a capacity retention of more than 92.7% after 500 cycles at 20 mA g⁻¹ and good rate capability with 91.9% capacity utilization at 500 mA g⁻¹ with respect to capacity at 5 mA g⁻¹ between 2.0 and 4.0 V. When the upper cutoff voltage is increased to 4.4 V, P2-Na_2/3Ni_2/3Te_1/3O₂ delivers a reversible capacity of 71.9 mAh g⁻¹ and retains 91.8% of the capacity after 100 cycles at 20 mA g⁻¹. The charge compensation during charge/discharge is mainly due to the redox couple of Ni²⁺/Ni³⁺ in the host with a small amount of contribution from oxygen. The stable structure of the material without phase transformation and with small volume change during charge-discharge allows it to give excellent cycle performance especially when the upper cutoff voltage is not higher than 4.2 V.

Porous Si can be synthesized from diverse silica (SiO₂) via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries. However, concerns regarding the influence of residual silicon oxide (SiO_x) component on resulted Si anode after reduction are still lacked. In this work, we intentionally fabricate a cauliflower-like silicon/silicon oxide (CF-Si/SiO_x) particles from highly porous SiO₂ spheres through insufficient magnesiothermic reduction, where residual SiO_x component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase. Moreover, the hierarchically structured CF-Si/SiO_x exhibits uniformly-dispersed channels, which can improve ion transport and accommodate large volume expansion, simultaneously. As a result, the CF-Si/SiO_x-700 anode shows excellent electrochemical performance with a specific capacity of ~1,400 mA·h·g^-1 and a capacity retention of 98% after 100 cycles at the current of 0.2 A·g^-1.