Ion gradient and vacancy energy enhancement: Reduced voltage attenuation and oxygen evolution of Lithium-rich manganese-based oxides

Abstract

Li-rich Mn-based oxides (LRMOs) are promising high energy–density cathodes, but the low initial Coulombic efficiency (ICE), voltage attenuation and oxygen evolution hinder the commercialization of LRMOs. Here, we incorporate acid radical ion into materials’ lattices to construct a LRMO with gradient ion concentration and layer-spinel mosaic structure via a practical and controllable strategy of chemical de-lithium route. The experimental and theoretical analyses demonstrate that the phosphate radical (PO43−) enter the lattice to enhance the vacancy energy of the material, which can improve the structural stability, inhibit oxygen evolution and voltage decay. As results, the best modified LRMO (PTS-20) exhibits suppressed voltage decay (∼27.16 mV at 1 C after 200 cycles) and higher initial discharge specific capacity of 283.5 mAh g−1 at 0.05 C with high ICE of 95.4%. In-situ differential electrochemical mass spectrometry (DEMS) further demonstrate that PTS-20 has less oxygen evolution. Furthermore, full cells assembled with graphite behave excellent electrochemical performances at 1 C. This work provides an effective strategy to fabricate LRMO cathodes with promising practical electrochemical performances.