Room-Temperature Synthesis of LiMn2O4by Electrochemical Ion Exchange in an Aqueous Medium

An exclusive room-temperature synthesis process is developed for producing cubic spinel LiMn2O4 (CLMO), a low-cost, environmentally friendly, and fast-charging cathode material for Li-ion batteries. CLMO is synthesized using an electrochemical ion-exchange (ECIE) process in an aqueous electrolyte, starting from Mn3O4 nanocrystallites that are obtained based on facile solution reduction chemistry. In the ECIE process, Mn2+ from the Mn3O4 tetrahedral site is exchanged by Li+ from the electrolyte by applying a cyclic voltammetry (CV) routine. The ECIE mechanism is clearly revealed by the combination of CV profile evolution and in situ/operando synchrotron X-ray diffraction and X-ray absorption spectroscopy analyses. The resulting CLMO electrode presents a typical battery behavior with promising high-rate characteristics, showing, for instance, 62% of the full capacity at a charging–discharging (C–D) rate of 8C in an aqueous electrolyte together with a capacity retention of 80% over 500 cycles with a C–D current density of 1 A g–1. The electrochemical ion-exchange process may offer the opportunity to prepare other high-performance electrode materials for Li-ion battery applications.