Gradient Ion Doping for High Performance Nickel-Rich Cathode Materials in Lithium-Ion Batteries

Abstract

Lithium-ion batteries are the primary candidate for use in electrified transportation, grid energy storage, and aerospace applications. Structurally layered nickel-rich cathode materials such as LiNi\(_{1-x-y}\)Co\(_{x}\)Mn\(_{y}\)O\(_{2}\) with 1-x-y \(\geq\) 0.8 (NCM) especially show promise due to its high specific capacity and low cost. However, nickel-rich NCM batteries face issues of poor long-term cyclability and thermal runaway, which leads to worse long-term performance and potential fire hazards, respectively. Doping ions into the cathode materials has been shown to improve electrochemical performance, but controlling doping concentration and distribution is challenging using traditional coprecipitation methods. This project explores the effects of doping dysprosium (Dy) into both nitrate- and acetate-based NCM811 cathodes on electrochemical performance, as well as the creation of a concentration gradient via a high temperature aerosol pyrolysis synthesis method. The results show that Dy-doped NCM811 batteries have improved overall electrochemical performance, with superior capacity retention and rate capability. Thermochemical stability and thus improved fire safety was demonstrated via an increased onset temperature for O\(_{2}\) evolution and reduced gas release. Additionally, as high temperature spray pyrolysis is a low-cost, scalable, and environmentally-benign synthesis method, these results demonstrate its potential for commercialization.