A double-layer covered architecture with spinel phase induced by LiPP for Co-free Li-rich cathode with high-rate performance and long lifespan

Co-free Li-rich Mn-based layered oxides are promising candidates for next-generation lithium-ion batteries(LIBs)due to their high specific capacity,high voltage,low cost.However,their commercialization is hindered by limited cycle life and poor rate performance.Herein,an in-situ simple and low-cost strategy with a nanoscale double-layer architecture of lithium polyphosphate(LiPP)and spinel phase covered on top of the bulk layered phase,is developed for Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2)(LMNO)using Li^(+)-conductor LiPP(denoted as LMNO@S-LiPP).With such a double-layer covered architecture,the half-cell of LMNO@S-LiPP delivers an extremely high capacity of 202.5 mAh·g^(−1)at 1 A·g^(−1)and retains 85.3%of the initial capacity after 300 cycles,so far,the best highrate electrochemical performance of all the previously reported LMNOs.The energy density of the full-cell assembled with commercial graphite reaches 620.9 Wh·kg^(−1)(based on total weight of active materials in cathode and anode).Mechanism studies indicate that the superior electrochemical performance of LMNO@S-LiPP is originated from such a nanoscale double-layer covered architecture,which accelerates Li-ion diffusion,restrains oxygen release,inhibits interfacial side reactions,suppresses structural degradation during cycling.Moreover,this strategy is applicable for other high-energy-density cathodes,such as LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2),Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_(2),LiCoO_(2).Hence,this work presents a simple,cost-effective,scalable strategy for the development of high-performance cathode materials.