ZIF-based heterojunction filler boosting Li-ion transport of composite solid-state electrolytes

Composite solid electrolytes (CSEs) are regarded as one of the most promising candidates for solid state battery. However, their low ionic conductivity and ion transference number frustrate the application in solid state batteries due to the low mobile Li⁺. Herein, we construct a bimetallic zeolitic imidazolate frameworks coupled amorphous titanium oxide (TiO₂@Zn/Co-ZIF) heterojunction nanoparticle as filler to form composite solid-state electrolyte (PVZT). The amorphous TiO₂ layer on filler can effectively facilitate the dissociation of salt by Lewis acid-base interaction with Li salt anion. The Zn/Co-ZIF not only provides extra selective ion pathway for Li⁺ transport, but also sieves anion by limited pore sizes. The synergistic effect contributes to the high room temperature ionic conductivity (8.8×10⁻⁴ S cm⁻¹) and ion transference number (0.47) of PVZT. The symmetrical battery using PVZT exhibits steady Li⁺ deposition/stripping more than 1100 h at charge/discharge of 0.1 mA cm⁻². The LiNi_0.8Co_0.1Mn_0.1O₂/Li full battery using PVZT retains 75.0% of capacity after 1200 cycles at 2C. This work provides valuable insights into the functional filler design highly efficient ion transport CSEs.