Simplified crystal grain boundary engineering of solid electrolyte-infused LiNi0.5Mn1.5O4 cathodes for high cycling stability lithium-ion batteries

Grain boundary has been a key challenge for crystal structure stability of cathode material during cycle process, especially for LiNi0.5Mn1.5O4 (LNMO) for its high working voltage. In previous reports, crystal grain boundary engineering has been proposed as a potential method to improve the stability of grain boundary, but the complex operation and high cost limitted its practical application. Herein, based on previous reports, we proposed a simplified crystal grain boundary engineering under guidance of corrosion simulation test. This method can targeted protect grain boundary by infusing solid-state-electrolyte assisted with molten salt. Meanwhile, part of F- ions from solid-state-electrolyte was doped into the bulk of LNMO during anneal process, which can expand the lattice parameter. The modified samples exhibit superior electrochemical property, especially under harsh environment, such as, at 55 degrees C the modified sample (LNMO-CG-3%) delivers a discharge capacity of 133 mA h/g under 2C, much larger than that of LNMO (89.5 mA h/g). Furthermore, the action mechanism of crystal grain boundary engineering on improving cycling stability is investigated from aspects of crystal structure stability and charge-discharge reaction process. This paper provides new insights for surface modification, if engineering, it may be a big step forward for the commercialization of LNMO as cathode material in LIBs.