How Synthetic Quench Rate and Composition Affect the Performance of Lithium Nickel Manganese Oxide Cathode Materials

Abstract

A survey of layered lithium-rich nickel manganese oxides cathodes, (formula Li[NixLi(1/3–2x/3)Mn(2/3−x/3)]O2), was conducted. We varied the nickel content from 0.1 to x = 0.25, and the post-calcination quench rate was controlled by employing three different methods: direct metal contact, water immersion, and liquid nitrogen immersion. Both composition and quench methodology impacted materials properties and electrochemical function. We observed that there is a synthetic limit for LLRNMO cathodes that occurs in the range of 0.17 > x > 0.10 below which quenching proved to be critically important in determining phase content and electrochemical behavior. Galvanostatic testing revealed the specific discharge capacities of the LLRNMO cathodes increased over the course of cycling, while the XRD characterization after cycling revealed reduced transition metal ordering. We found that the layered lithium-rich nickel manganese oxide materials made with water quenching performed the best with initial C/20 capacities increasing from around 200 mAh g−1 to over 250 mAh g−1 after 28 cycles while retaining C/2 capacities in excess of 200 mAh g−1.