One-Step Integrated Surface Modification To Build a Stable Interface on High-Voltage Cathode for Lithium-Ion Batteries.

Abstract

As one of the most promising cathode materials for next-generation energy storage applications, spinel LiNi0.5Mn1.5O4 (LNMO) has been highlighted due to many advantages. However, it is still hindered by poor electrochemical stability derived from the bulk/interface structure degradation and side reactions under high working voltage. In this work, fast ion conductor Li3V2(PO4)3 (LVPO) is adopted to modify the surface of spinel LNMO by a one-step facile method to harvest the maximum benefit of interface properties. It is found that 1 wt % LVPO-LNMO exhibits the most excellent cycling performances, retaining great capacity retention of 87.8% after 500 cycles at room temperature and 82.4% for 150 cycles at 55 °C. Moreover, the rate performance is also significantly improved (90.4 mAh g-1 under 20C). It is revealed that the LVPO-involved layer could effectively suppress the surface side reactions under high working voltage, which mainly contributes to an improved interface with desirable structural stability and excellent kinetics behavior without sacrificing the surface electrochemical activity in an electrochemical environment. Thus, the dissolution of transition-metal ions is effectively mitigated, avoiding further structure degradation of the bulk material. Especially, it is also established that the vanadium (V) ions in LVPO could be to a certain extent migrated into the surface lattice of LNMO to generate a V-involved transition layer (Li-Ni-Mn-V-O surface solid solution), which greatly co-contributes to the enhanced electrochemical performances owing to the prominently depressed charge-transfer resistance.