Lithium Lanthanum Titanium Oxides: A Fast Ionic Conductive Coating for Lithium-Ion Battery Cathodes

This work introduces Li–La–Ti–O (LLTO), which is a fast lithium-ion conductor, as an effective coating material for cathode materials used in rechargeable lithium-ion batteries. This fast Li-ion conductor is characterized by first-principles calculations showing low activation barrier for lithium diffusion at various different lithium concentrations. The morphology and the microstructure of the pristine electrode and coated electrode materials are characterized systematically, and we show clear evidence of the presence of the coating after electrochemical cycling. The coated electrodes show significantly improved rate capabilities and cycling performance, compared to the pristine electrodes. The possible reasons for such enhancements are explored experimentally using potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS). Because of the high lithium conductivity in the LLTO coating material, the chemical Li+ diffusion coefficient is one magnitude of order higher in the coated samples than that in the uncoated samples. In addition, the impedances of both interfacial charge transfer and Li+ transportation in the solid-electrolyte-interphase (SEI) layer are reduced up to 50% in the coated samples. Our findings provide significant insights into the role of coating regarding the improvements of electrochemical properties, as well as the potential use of solid electrolyte as an effective coating material.