Review on synthesis methods to obtain LiMn2O4-based cathode materials for Li-ion batteries

Lithium manganese spinel (LiMn2O4) is considered a promising cathode material for lithium-ion batteries (LIBs). Its structure, morphology, and electrochemical performances are strongly connected to the precursors, synthesis route, and heat treatment; hence, by optimizing the synthesis procedure, improved materials can be obtained. Recently investigated routes focus on the synthesis of enhanced LiMn2O4 spinel, with uniform morphology, high crystallinity, which can deliver large discharge capacity at high rates for a longer period of time. Also, the synthesis procedure must be easily applicable on industrial scale, not just for pilot and laboratory investigations. In the current study, main synthesis procedures (solid-state reactions, sol-gel, hydrothermal reactions, combustion method plus several newly employed methods) used for obtaining lithium manganese oxide, along with its electrochemical effectiveness, are described. Among the considered synthesis methods, some of the best electrochemical performances are recorded for lithium manganese oxide obtained by sol-gel process and hydrothermal method. Even though solid-state reaction method is a simple and has few stages, particle crystallinity and size are more difficult to control, while sol-gel and hydrothermal method provides more evenly sized particles. Also, the latter two syntheses do not need very high calcination temperatures like in the samples obtained by solid-state reactions method. Lithium manganese spinel with uniform spherical and octahedral particles delivered the highest initial discharge capacities and has the ability to retain most of the capacity during the charge-discharge cycles.