Renovating the electrode-electrolyte interphase for layered lithium- & manganese-rich oxides

Layered lithium- & manganese-rich oxides (LMR), with their high capacity and cost-effective advantage, are considered as a potent alternative of the next-generation cathode material for lithium-ion batteries. The behaviors of the electrode-electrolyte interphase (EEI) are crucial to the electrochemical properties of LMR as a cathode material operating at wide voltage regions (from 2 to 4.8 ​V). Nonetheless, the understanding of EEI for LMR materials and the related renovation techniques are somewhat lacking. Herein, we gain insight into the EEI change mechanism for LMR materials during long electrochemical cycles and demonstrate a renovating method to mitigate its deterioration. As for the pristine electrode based on LMR materials, the increasing amount of PO_xF_y ^z− and metal fluorides lead to unpleasant degradation for both the EEI and the active material particle, causing evident performance decay. Whereas, the lithium phosphate, if employed in the electrode, effectively enhances the lithium ions transfer, impedes the decomposition of electrolyte salt, and leads to a more stable EEI, thus promoting the electrochemical performances of LMR materials. All results indicate that the EEI should be one of the critical components for comprehensively understanding the LMR material, and the success renovation by the lithium phosphate offers a new orientation for those intrinsic drawbacks of LMR material.