Wet milling synthesis of NH4CoPO4·H2O platelets: Formation reaction, growth mechanism, and conversion into high-voltage LiCoPO4 cathode for Li-ion batteries

Abstract

A ball milling process not only affords particle size reduction by grinding but also particle synthesis induced by mechanical actions at ambient temperature. However, in traditional mechanical synthesis, it is difficult to control the particle morphology, including the size and shape, because of collision with the balls. This study shows that platelet-like NH4CoPO4·H2O particles are synthesized via wet planetary ball milling and converted into a high-voltage LiCoPO4 cathode for Li-ion battery. The NH4CoPO4·H2O platelets formed by the dissolution–precipitation reaction are repeatedly ground, dissolved into a solution, and recrystallized to afford crystal growth during the milling treatment. The converted LiCoPO4 cathodes retain the precursor morphologies, exhibiting high discharge capacities for flake particles and better cyclabilities for large platelet particles. The mechanical-assisted particle synthesis in solution is a simple method for the large-scale production of morphology-controlled nanomaterials.