Synergetic LaPO4 and Al2O3 hybrid coating strengthens the interfacial stability of LiCoO2 at 4.6 V

Abstract

To date, LiCoO2 (LCO), as one of the dominating cathodes for lithium-ion batteries, still can't satisfy the growing demand for higher energy density required by consumer electronic devices. Raising the charge cut-off voltage is an effective strategy for promoting the discharge capacity and thus energy density of LCO batteries. However, the accelerated cycle fading caused by unstable lattice structure and LCO/electrolyte interface at high voltage (≥4.5 V) restricts its practical application. To conquer the challenge, a hybrid coating layer of LaPO4 and Al2O3 is rationally designed and constructed on LCO surface for ≥4.6 V high voltage operation. The hybrid coating layer can effectively suppress the side reactions between LCO and electrolyte, and mitigate the oxygen release and cobalt ion dissolution from the bulk structure of LCO. In addition, the LaPO4 with good lithium-ion conductivity is conducive for the timely transportation of lithium ions during cycling. During cycling at charge cut-off 4.6 V, the LaPO4 and Al2O3 hybrid coated LCO cathode achieves an enhanced capacity retention of 87.0% (vs. 3.8% for Bare LCO) after 200 cycles.