Enhancing Electrochemical Performances of Rechargeable Lithium-Ion Batteries via Cathode Interfacial Engineering

Lithium-ion batteries (LIBs) have transformed modern electronics and rapidly advancing electric vehicles (EVs) due to their high energy and power densities, cycle-life, and acceptable safety. However, the comprehensive commercialization of EVs necessitates the invention of LIBs with much enhanced and stable electrochemical performances, including higher energy/power density, cycle-life, and operational safety, but at a lower cost. Herein, we report a simple method for improving the high-voltage (up to 4.5 V) charge capability of LIBs by applying a Li⁺-ion-conducting artificial cathode-electrolyte interface (Li⁺-ACEI) on the state-of-the-art cathode, LiCoO₂ (LCO). A superionic ceramic single Li⁺ ion conductor, lithium aluminum germanium phosphate (Li_1.5Al_0.5Ge_1.5(PO₄)₃, LAGP), has been used as a novel Li⁺-ACEI. The application of Li⁺-ACEI on LCO involves a scalable and straightforward wet chemical process (sol-gel method). Cycling performance, including high voltage charge, of bare and LAGP-coated cathodes has been determined against the most energy-dense anode (lithium, Li metal) and state-of-the-art carbonate-based organic liquid electrolyte (OLE). The application of an LAGP-based Li⁺-ACEI on LCO displays many improvements: (i) reduced charge-transfer and interfacial resistance; (ii) higher discharge capacity (167.5 vs 155 mAh/g) at 0.2C; (iii) higher Coulombic efficiency (98.9 vs 97.8%) over 100 cycles; and (iv) higher rate capability (143 vs 80.1 mAh/g) at 4C. Structural and morphological characterizations have substantiated the improved electrochemical behavior of bare and Li⁺-ACEI LCO cathodes against the Li anode.