Single Crystal Li1+x[Ni0.6Mn0.4]1−xO2 Made by All-Dry Synthesis

Abstract

Cobalt-free, single crystal layered-oxide positive electrode materials like Li1+x[Ni0.6Mn0.4]1−xO2 (NM64) have received recent interest because of their low cost, high-voltage stability, and good cycle life. In this work, single crystal NM64 is successfully produced with a simple all-dry synthesis process that requires no water, no intermediate chemicals, and produces little waste. The all-dry synthesized NM64 has ≤ 4% nickel in the lithium layer based on Rietveld refinement of powder XRD patterns, has a median particle size of 2–5 μm based on SEM and particle size analysis, and has excellent high-voltage stability at C/5 up to 4.4 V vs Li+/Li compared to a commercial material. Additionally, tungsten coating is shown to decrease the median particle size and improve the cycling stability in half cells from 91% retained capacity after 100 cycles to 93% retained capacity when 0.3% tungsten is added. It is believed that this incredibly simple process could be adopted relatively easily into current commercial positive electrode manufacturing facilities to reduce the complexity, cost, and time of manufacture.