Surface Magnesium Substitution at Spinel Lithium Manganate 8a Tetrahedral Sites for Suppressed Manganese Dissolution and Enhanced Cycle Stability

Surface degradation induced by the dissolution of manganese is a major failure mechanism that has hampered the large-scale adoption of spinel LiMn2O4 cathode material for decades. Although modifications based on restraining manganese disproportionation reactions have received much attention, many of these methods may sacrifice batteries' specific capacity and rate capability. Here, we present a strategy that surface-populated magnesium ion substitution at 8a tetrahedral sites in LiMn2O4 could significantly suppress spinel surface evolution and Mn dissolution during cycling. With a total trace amount of magnesium surface doping (0.3 wt %) introduced by ALD coating and annealing, the LiMn2O4 cathode shows a capacity retention of 98.6% after 250 cycles. This study reveals the role of atomic doping site selection and the significance of the electrode materials' surface stability at the charged state.