Boosting cyclability performance of the LiNi0.8Co0.15Al0.05O2 cathode by a polyacrylonitrile-induced conductive carbon surface coating

Abstract

Although the high energy density of Ni-rich LiNi0.8Co0.15Al0.05O2 (NCA) cathode holds great promise in Li-ion batteries, the moisture sensitivity and undesired dissolution of Ni2+ in electrolytes that causes rapid capacity fading restrict their further commercial applications. Surface coating is an efficient method to address the problems above. Herein, surface modification of the NCA cathode by using a cheap and highly conductive polyacrylonitrile-induced carbon coating is investigated, and molecular dynamics simulation results suggest that the carbon layer should be as thin as possible. In this way, NCA coated with a highly conductive carbon layer of 5 nm in thickness with enhanced cyclability and integral electrochemical performance is made. The coated carbon film also served as a protective layer by shielding the host NCA cathode materials from direct contact with the electrolyte, thus resulting in enhanced electron transfer. During the charge-discharge repeated cycles 100 times, the carbon-coated NCA cathode exhibits an improved capacity retention (98.4%) at a rate of 1 C over pristine NCA (93.1%). The uniform surface coating strategy might serve as an industrial scalable approach to coat a continuous carbon layer on other electrode materials at a relatively low cost.