Toward Alleviating Voltage Decay by Sodium Substitution in Lithium-Rich Manganese-Based Oxide Cathodes

Lithium-rich manganese-based oxides (LMROs), as one of the most promising high-capacity cathodes, suffer from serious capacity fading and discharge voltage decay during repeated cycles. Here we have successfully enhanced cycle stability and rate capability of LMRO cathode material through introducing a certain amount of Na into LMRO microspheres. In particular, the discharge voltage decay per cycle significantly decreases from 4.40 to 1.60 mV. These enhancements may be attributed to the Na in Li layers, which can promote the kinetics of lithium ion diffusion and facilitate the electronic and ionic conductivity. More remarkably, Na dopant can effectively suppress the transformation from layered to spinel structure by serving as the fixed pillars in Li layers to inhibit the formation of three adjacent vacancies and Mn migration. In addition, full-cell investigations further show the Na-doped LMRO materials have great commercial value. Therefore, our findings may boost understanding in designing high-capacity and good stability cathode materials for LIBs.