Lithium-rich layered oxide cathodes with high specific energy have become one of the most popular cathode materials for high-performance lithium-ion batteries. However, spinel phase formation due to the migration of transition metals and the release of lattice oxygen leads to the degradation of electrochemical performance. Here, we develop a synthesis approach for Li-rich layered oxide cathodes by a two-step heat-treatment process, which includes precursor calcination and pellet sintering. Compared with the sample prepared by the traditional one-step calcination, the oxide particles prepared by the two-step heat treatment show increased grain size from 217 to 425 nm. The Li-rich layered oxide cathodes with larger crystal grains indicate a mitigated formation of spinel phase and reduced voltage decay, which result in improved specific capacity, cycle stability, and rate capability. In addition, the thermal stability of the oxides is also improved. The improved electrochemical performance is because of the large single grains having a reduced contact area with a liquid electrolyte and the stable crystal lattice during cycling. Our strategy not only provides a simple and effective way to enhance the stability of the Li-rich layered oxide cathodes but also extends to the preparation of oxide powders with large grains.

Solid-state batteries using ceramic solid electrolytes promise to deliver enhanced energy density and intrinsic safety. However, the challenge of integrating solid electrolytes with electrode materials limits the electrochemical performance. Herein, we report a solvent-free ceramic-based lithium-metal battery with good cycling stability at a wide temperature range from 45 to 100 °C, enabled by an inorganic ternary salt of low eutectic point. By using a garnet electrolyte with molten salts at the electrolyte|cathode interface, the Li||LiFePO4 cells perform a long cycling with capacity retention of 81.4% after 1000 cycles at 1 C. High-voltage LiFe0.4Mn0.6PO4 cathodes also deliver good electrochemical performance. Specifically, commercial electrode pieces with high area capacities can be adopted directly in the quasi-solid-state lithium-metal batteries. These stable performances are ascribable to the low melting point, high ionic conductivity and good thermal/electrochemical stability of the ternary salt system. Our findings provide an effective method on fabrication of solid-state batteries for practical applications.

Nowadays solid‐state lithium metal batteries (SSLMBs) catch researchers’ attention and are considered as the most promising energy storage devices for their high energy density and safety. However, compared to lithium‐ion batteries (LIBs), the low ionic conductivity in solid‐state electrolytes (SSEs) and poor interface contact between SSEs and electrodes counteract some advantages of SSEs. As a result, SSLMBs show high energy density but low critical current density and slow charging speed. Herein, the recent progress and proposed strategies for fast‐charging SSLMBs are reviewed. In the second part of this review, various strategies for improving SSE performance in fast‐charging batteries are comprehensively highlighted. In the third part, various rational structure design schemes benefitting fast‐charging batteries are discussed. Finally, the development of fast‐charging SSLMBs is concluded and prospected. It is believed that the combination of fast‐charging times and SSLMBs is rather competitive for next‐generation, high energy density, high safety, and high charging rate energy storage devices.

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