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Abstract High‐voltage lithium metal batteries with nickel‐rich oxide cathodes (LiNi_0.8Co_0.1Mn_0.1O₂, NCM811) represent one of the most promising approaches to achieve high energy density up to 500 Wh kg⁻¹. However, severe interfacial side reactions occur at both NCM811 cathode and lithium anode at ultrahigh voltages (>4.6 V). To address these issues, various electrolytes have been developed, but they still suffer from electrolyte decomposition, leading to moderate voltages and insufficient cycling. Herein, we introduce (3,3,3‐trifluoropropyl)trimethoxy silane (TTMS) as an asymmetrically fluorinated single solvent, which incorporates both strongly solvating (─OCH₃) and weakly solvating (─CF₃) groups. The designed 2.1 mol L⁻¹(M) LiFSI/TTMS electrolyte achieves excellent compatibility with both NCM811 cathode and Li metal anode due to its unique anion‐dominating solvation structures and inorganic‐rich interphase formation. Consequently, it enables stable cycling in the Li||NCM811 battery at an ultrahigh voltage of 4.8 V, with 84.5% capacity retention after 300 cycles. Even under more aggressive conditions, including high temperature (60 °C) and anode‐less configuration (N/P ratio = 1.76), the Li||NCM811 battery exhibits remarkable capacity retention (>80%) over 300 cycles. This work underscores the effectiveness of electrolyte engineering for developing ultrahigh‐voltage and long‐cycling battery systems. 

Abstract Solid‐state batteries (SSBs) are competitive contenders for energy storage due to their inherent safety and high energy. However, the lack of an appropriate anode has hindered their development. Graphite and lithium metal are widely used anode materials, but graphite suffers from a low capacity, whereas lithium metal presents severe dendrite and reactivity challenges. Herein, the promising performance of micro‐sized alloys is demonstrated as high‐capacity and long‐cycling anodes for SSBs. Using antimony as a model anode, its full theoretical capacity (660 mAh g⁻¹), high‐rate capability (3 A g⁻¹), and long cycling life (1000–2000 cycles) is achieved at room temperature. Comparative studies further reveal an overlooked “micro‐size effect”, where micro‐sized alloys establish more efficient electron/ion conduction pathways, significantly exceeding their nano‐sized counterparts. This micro‐size effect challenges the conventional belief that nano‐sized alloys always outperform micro‐sized ones. Based on this discovery, similarly high performance of other micro‐alloys (lead and bismuth) in SSBs is further demonstrated. Given the additional benefits of easy synthesis, low cost, high tap density, and high stability, micro‐sized alloys hold great promise as excellent anode candidates for SSBs.