Ionic liquid interlayer enable room-temperature, high-voltage, high-specific-capacity solid-state lithium-metal batteries

Li7La3Zr2O12 (LLZO)-based solid-state lithium-metal batteries (SLBs) are strong candidates for next generation high specific capacity and high safety energy storage devices. Unfortunately, poor interfacial contact between the cathode and the solid-state electrolyte (SSE) severely limits the practical application of SLBs. Here, a pyrrole-based (1-Butyl-1-methyl pyrrolidinium Bis (trifluoromethanesulfonyl) imide) ionic liquid (BMP-IL) electrolyte interlayer is used to address this issue. The IL interlayer provides a fast Li+ transport channel at the SSE and cathode interface. As a result, SLBs exhibit excellent electrochemical performance at 25 °C. Further, the IL interlayer strategy combines with a high-voltage cathode to achieve higher energy density, and the batteries perform discharge specific capacities as high as 147 mA h g−1. At the same time, the SLBs also exhibit more pronounced capacity degradation, which is attributed to the interfacial side reactions at high voltages. This work demonstrates the robust feasibility of the IL interlayer strategy and provides insights into the degradation mechanisms at the interface when matched with a high-voltage cathode. It offers valuable insights into the practical applications of SLBs and lays the foundation for subsequent research on high-voltage SLBs.