Pulse High Temperature Sintering to Prepare Single-Crystal High Nickel Oxide Cathodes with Enhanced Electrochemical Performance

Abstract

For the currently most dominant cathode of Li(NixCoyMnz)O2(NCM, x + y + z = 1) in lithium-ion batteries, higher nickel content brings higher energy density but is accompanied by heavier interfacial reactions with electrolyte and worse safety performance. Single crystal cathode materials have the advantages of fewer grain boundaries, higher density, and greatly suppressed microcracks during cycling, these benefits in turn suppress interfacial side reactions, as well as the improve volumetric energy density and safety performance. Here, a strategy of pulse high-temperature sintering (PHTS) is reported to prepare single-crystal Li(Ni0.9Co0.05Mn0.05)O2 (SC-NCM90), in which an extra PHTS at 1040 °C for 1 min is added in the traditional calcination process at 750 °C, yielding well defined octahedral particles with an initial capacity of 209 mAh g−1. Compared with the counterpart NCM90 secondary spheres, the tap density of SC-NCM90 increases by 1/3 to 2.76 g cm−3 and the microcracks are successfully suppressed, improving both the cycling performance and thermal stability. The calcination time and temperature are optimized, showing that overlong time or overhigh temperature of the PHTS treatment would result in particles with better defined octahedral shape but heavier Li/Ni intermixing and capacity loss.