A high-entropy mixed ionic and electronic conductor for accelerating the cathode dynamics in all solid-state lithium...

Both electron and ion transports determine the dynamics of the cathode in all solid-state lithium metal batteries (ASSLMBs). Traditional composite strategies combining solid electrolytes and electronic conductors cause complex solid-state interfaces that hinder carrier migration. We present a high-entropy mixed ionic and electronic conductor (HE-O-MIEC), Li_1/6-x(LaPrNdSrBa)_1/6CoO_3-δ, based on oxidation-resistant electronic conductors. HE-O-MIEC exhibits an electronic conductivity of 1150 siemens per centimeter and a Li⁺ conductivity of 2.3 × 10^-4 siemens per centimeter at room temperature. The enhanced Li⁺ conductivity is attributed to the large configurational entropy, promoting multicomponent solubility and increased Li⁺ concentration. HE-O-MIEC exhibits electrochemical and thermodynamic compatibility with LiCoO₂ and stabilizes ion/electron transport in the ASSLMB using the Li_6.4La₃Zr_1.4Ta_0.6O₁₂ electrolyte. Without organic electrolyte or additional pressure, the ASSLMB achieves 115-milliampere·hours per gram initial discharge capacity at 30°C and retains 83% capacity after 500 cycles. Homogeneous electron and ion transport in the HE-O-MIEC demonstrates potential to improve active material utilization and address interfacial challenges in ceramic-based ASSLMBs.