Boosting interfacial Li+ transport with a MOF-based ionic conductor for solid-state batteries

Abstract

Concerning the large interfacial resistance of materials within solid-stated batteries (SSBs) caused by the unstable solid contact, an assistant ionic conductor is introduced to improve the interfacial Li+ transport of SSBs. The assistant ionic conductor is achieved by impregnating an ionic liquid (Li-IL) into a porous metal-organic framework (MOF) host. When integrated with LLZO solid-state electrolyte (SSE), the solidified Li-IL guest can make direct contact with the LLZO particles through the open channels in MOF host, which changes the original unstable solid-solid contact into “nanowetted” interfaces to boost Li+ transport. Benefited from the unique nanowetted interfaces, the hybrid SSE demonstrates a high ionic conductivity of 1.0 × 10−4 S cm−1 with a wide electrochemical window of 5.2 V, and also exhibits excellent compatibility with Li metal anode. Furthermore, the LLZO based LiCoO4 and LiFePO4 SSBs with the ionic conductor additive to favor the interfacial Li+ transport achieve high capacity retention of 97% after 150 cycles with reasonable rate capability. The good electrochemical performance is attributed to the effective Li+ transport networks established inside the SSBs by the ionic conductor through the nanowetted interfacial mechanism, which is proved to be a promising approach to the safe and high-power energy storage.