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, and 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 Li1.2Mn0.6Ni0.2O2 (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 high-rate 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, and suppresses structural degradation during cycling. Moreover, this strategy is applicable for other high-energy-density cathodes, such as LiNi0.8Co0.1Mn0.1O2, Li1.2Ni0.13Co0.13Mn0.54O2, and LiCoO2. Hence, this work presents a simple, cost-effective, and scalable strategy for the development of high-performance cathode materials.