Multianion Synergism Boosts High-Performance All-Solid-State Lithium Batteries

As candidates for next-generation energy storage, all-solid-state lithium batteries (ASSLBs) are highly dependent on advanced solid electrolytes (SEs). For further application of SEs to ASSLBs, it is necessary to focus on addressing the poor compatibility of SEs with electrodes in addition to improving the ionic conductivity. Herein, we report Li₃YCl_6-2<i>x</i>Br_<i>x</i>I_<i>x</i> (0 ≤ <i>x</i> ≤ 1) SEs, which possesses a high ionic conductivity of 1.98 mS cm^-1 and a low activation energy of 0.257 eV, as well as good compatibility with both Li₄Ti₅O₁₂ (LTO) cathode and Li-In alloy anode. The construction of anionic mixed states not only reduces the constriction of the anionic framework on Li⁺ migration for improving the ionic conductivity but also softens the anionic lattice to reduce the activation energy. More importantly, introducing I^- enhances the Li interface stability by generating LiI self-limited passivated interfacial layer in situ. As a result, ASSLB exhibits high-rate capability up to 10C and excellent reversibility, with stable cycling of more than 2000 cycles at 1C and a capacity retention of 93.7% after 1000 cycles at 2C. This study also highlights the significant impact of local structural distortions in SE systems, suggesting that developing hybrid anion-based SEs is a cost-effective method to enhance the overall performance of halide SEs.