Interfacial engineering of LiCoO2/Li10GeP2S12 with electron-ion mixed conductor Li7.5La3Zr1.5Co0.5O12 for high stable all-solid-state batteries

The space charge layer and interfacial side reactions between cathode and solid electrolyte seriously limit the electrochemical performances of sulfide electrolyte-based all-solid-state lithium batteries (ASSLIBs). In addition, the periodic strain of the cathode material during the charging-discharging process causes the cathode particles cracking and detachment from the electrolyte. Surface coating is an effective approach to improve electrochemical performances, and the coating material should have high ion and electron conductivity to ensure ion and electron conduction. Ionic-electronic mixed conductor Li7.5La3Zr1.5Co0.5O12 (LLZCO) is chosen as the coating material, and coated on the surface of LiCoO2 (LCO) by co-precipitation method. The pristine and coated LCO are assembled into LCO|Li10GeP2S12|InLi ASSLIBs. The buffering layer can reduce the space charge layer and maintain the stability of the cathode particles. The initial discharge specific capacity of the coated sample is 121.0 mAh g−1 (1.9–3.6 V, 0.2C, RT), with a capacity retention rate of 96.0 % after 100 cycles.