Unlocking oxygen vacancy-rich high-entropy oxides in upgrading composite solid electrolyte

Recently, high-entropy materials are attracting enormous attention in battery applications, encompassing both electrode materials and solid electrolytes, due to the pliability and diversification in material composition and electronic structure. Theoretically, the rapid ion transport and the abundance of surface defects in high-entropy materials suggest a potential for enhancing the performance of composite solid-state electrolytes (CPEs). Herein, using a high-entropy oxide (HEO) filler to assess its potential contributions to CPEs is proposed. The distinctive structural distortions in HEO significantly improve the ionic conductivity (5 × 10⁻⁴ S·cm⁻¹ at 60 °C) and Li-ion transference number (0.57) of CPEs. Furthermore, the enhanced Li-ion transport capability extends the critical current density from 0.6 to 1.5 mA·cm⁻² in Li/Li symmetric cells. In addition, all-solid-state batteries incorporating the HEO-modified CPEs exhibit superior rate performance and cycling stability. The work will enrich the application of HEOs in CPEs and provide fundamental understanding.