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

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.