Enhancement of room-temperature performance in solid-state batteries by succinonitrile-based composite solid...

A critical barrier to commercializing solid-state batteries lies in the inadequate performance of existing solid electrolytes, particularly their poor conductivity at room temperature and unsatisfactory long-term stability. In this context, a self-healing composite solid electrolyte based on succinonitrile (SCN) reinforced with lithium lanthanum titanate (LLTO) is introduced. Leveraging the increased interfacial lithium-ion (Li⁺) transport channels in composite systems, the resultant LLTO-enhanced SCN electrolyte demonstrates remarkable ionic conductivity of 2.5 mS cm^-1 at room temperature. The insight into the transport mechanism of Li⁺ was provided using density functional theory. In addition to its superior conductivity, the electrolyte also exhibits excellent anodic stability, with an electrochemical oxidation potential reaching 5.1 V. Furthermore, LLTO effectively mitigates the inherent instability of SCN-based electrolytes while circumventing undesired side reactions. The self-healing properties enable autonomous repair of defects in the electrolyte, thereby enhancing battery safety characteristics. Consequently, symmetric Li cells demonstrated stable cycling for 1800 h at 0.1 mA cm^-2. Notably, the Li||LiFePO₄ cell retains 100 mAh g^-1 of capacity at 1.0C after 1100 cycles at room temperature. The pouch cell further underscores the long-cycle durability and safety characteristics, with over 80 % capacity retention following 530 cycles. The investigation indicates that the LLTO-enhanced SCN electrolyte holds strong potential for the commercial application of solid-state lithium metal batteries under ambient conditions.