Preparation of high performance MnO2 cathode for lithium primary battery through uniform particle size and crystal modulation

Abstract

Commercial electrolytic manganese dioxide (EMD) is a widely applicable cathode material in lithium primary batteries (LPBs). Nevertheless, the EMD is limited by several key issues in practical use, which are mainly low electronic conductivity and slow diffusion kinetics. A particle size and crystal type modulation strategy were used to improve the electronic conductivity and ion diffusion kinetics of EMD for the first time. EMD treated with sand milling has a smaller and narrower particle size distribution, which improves reaction kinetics. As analyzed by Rietveld structure refinement, the heat treatment at different temperatures resulted in different degrees of phase transition from γ-MnO₂ to β-MnO₂ in EMD. The β-MnO₂ improved the electrical conductivity of EMD, and the crystal structure defects caused by mixing γ-MnO₂ with β-MnO₂ provided more electrochemical reaction sites. Electrochemical tests demonstrated that the heat-treated EMD after sand milling (SEMD-T) exhibited enhanced electrochemical properties. In particular, the specific capacity of SEMD-380 is 245.7 mAh g⁻¹ at 0.1 C, which reached 79.8 % of theoretical specific capacity. The maximum energy density of SEMD-380 at 5 C (332.50 Wh kg⁻¹) exceeds that of EMD by a factor of three. These findings offer effective guidance for designing high performance electrodes in the future.