Li metal is the ultimate anode choice due to its highest theoretical capacity and lowest electrode potential, but it is far from practical applications with its poor cycle lifetime. Recent research progresses show that materials designs of interphase and host structures for Li metal are two effective ways addressing the key issues of Li metal anodes. Despite the exciting improvement on Li metal cycling capability, problems still exist with these methodologies, such as the deficient long-time cycling stability of interphase materials and the accelerated Li corrosion for high surface area three-dimensional composite Li anodes. As a result, Coulombic efficiency of Li metal is still not sufficient for full-cell cycling. In the near future, an interphase protected three-dimensional composite Li metal anode, combined with high performance novel electrolytes might be the ultimate solution. Besides, nanoscale characterization technologies are also vital for guiding future Li metal anode designs.

Electrochemical energy storage systems such as fuel cells and metal–air batteries can be used as clean power sources for electric vehicles. In these systems, one necessary reaction at the cathode is the catalysis of oxygen reduction reaction (ORR), which is the rate-determining factor affecting overall system performance. Therefore, to increase the rate of ORR for enhanced system performances, efficient electrocatalysts are essential. And although ORR electrocatalysts have been intensively explored and developed, significant breakthroughs have yet been achieved in terms of catalytic activity, stability, cost and associated electrochemical system performance. Based on this, this review will comprehensively present the recent progresses of ORR electrocatalysts, including precious metal catalysts, non-precious metal catalysts, single-atom catalysts and metal-free catalysts. In addition, major technical challenges are analyzed and possible future research directions to overcome these challenges are proposed to facilitate further research and development toward practical application.

Single-atom catalysis is a powerful and attractive technique with exceptional performance, drastic cost reduction and notable catalytic activity and selectivity. In single-atom catalysis, supported single-atom catalysts contain isolated individual atoms dispersed on, and/or coordinated with, surface atoms of appropriate supports, which not only maximize the atomic efficiency of metals, but also provide an alternative strategy to tune the activity and selectivity of catalytic reactions. This review will highlight the attributes of single-atom catalysis and summarize the most recent advancements in single-atom catalysts with a focus on the design of highly active and stable single atoms. In addition, new research directions and future trends will also be discussed.

With the rapid popularization and development of lithium-ion batteries, associated safety issues caused by the use of flammable organic electrolytes have drawn increasing attention. To address this, solid-state electrolytes have become the focus of research for both scientific and industrial communities due to high safety and energy density. Despite these promising prospects, however, solid-state electrolytes face several formidable obstacles that hinder commercialization, including insufficient lithium-ion conduction and surge transfer impedance at the interface between solid-state electrolytes and electrodes. Based on this, this review will provide an introduction into typical lithium-ion conductors involving inorganic, organic and inorganic–organic hybrid electrolytes as well as the mechanisms of lithium-ion conduction and corresponding factors affecting performance. Furthermore, this review will comprehensively discuss emerging and advanced characterization techniques and propose underlying strategies to enhance ionic conduction along with future development trends.

Compared with commercial Li-ion cathode materials (LiCoO₂, LiFePO₄, NMC111, etc.), Li-rich Mn-based cathode materials (LMR-NMCs) possess higher capacities of more than 250 mAh g⁻¹ and have attracted great interest from researchers as promising candidates for long-endurance electric vehicles. However, unsolved problems need to be addressed before commercialization with one being voltage decay during cycling. Here, researchers have proposed that the mechanisms of voltage decay in Li-rich Mn-based cathode materials involve factors such as surface phase transformation, anion redox and oxygen release and have found evidence of transition metal-migration, microstructural defects caused by LMR and other phenomena using advanced characterization techniques. As a result, many studies have been conducted to resolve voltage decay in LMR-NMCs for practical application. Based on this, this article will systematically review the progress in the study of voltage decay mechanisms in LMR materials and provide suggestions for further research.