Lithium manganese oxide (LMO) is a state-of-the-art cathode material for lithium-ion batteries. LMO works well at ambient temperature; however, it undergoes rapid capacity-fading during cycling at elevated temperatures (~55 ^oC) due to the manganese-dissolution. The last two decades have witnessed a number of strategies reported in the literature (including patents) to mitigate this problem and allow the LMO for large-scale applications. Unfortunately, most of the proposed strategies are either time-consuming or involve extensive use of materials that add to the cost of the final product, and/or require the use of less environmentally-friendly chemicals including very harsh acids that must be handled with utmost caution. There is need therefore to explore the use of simpler, fast, less expensive and ‘greener’ synthesis strategy.

In our work, microwave-assisted solid-state reaction has been used to dope LMO with very low amount of nickel (i.e., LiNi_0.2Mn_1.8O_4, herein abbreviated as LMNO) for lithium-ion battery from Mn₃O₄ prepared from electrolytic manganese oxide (EMD, g-MnO₂). To establish the impact of microwave irradiation on the electrochemical cycling performance at elevated temperature (60 ^oC), the Mn³⁺ concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, ⁶LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). In this presentation, we will show that microwave-treated sample (LMNO_mic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn³⁺ content, promoting structural and cycle stability at elevated temperature. Importantly, at elevated temperature (60 ^oC), the LMNO_mic gave an improved cycling stability (> 80% capacity retention and ca. 90 % coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi_0.2Mn_1.8O₄ at elevated temperature and lithium-ion diffusion kinetics have been clearly demonstrated.