Enhanced Electrochemical Performance of Ni‐Rich Layered Cathode Materials by using LiPF6 as a Cathode Additive

Abstract

AbstractResidual Li compounds are inevitably present in the form of Li2O, LiOH, and Li2CO3 on the surface of layered cathode materials, which not only causes slurry gelation in the cathode‐coating process but also degrades liquid electrolyte in the batteries. Owing to their strong alkaline nature, the residual Li compounds can react with acidic LiPF6 to form Li3PO4 and LiF, two of the main components of robust solid electrolyte interphases. By demonstrating LiNi0.80Co0.10Mn0.10O2 (NCM811) as an example in this work, we simply dissolved a small amount of LiPF6 into the cathode‐coating slurry, finding that as the amount of LiPF6 is controlled in the 0.5–1.0 wt % range versus the mass of NCM811, the LiPF6 additive not only improves the cycling stability but also enhances rate capability of the Li/NCM811 cells. The former is because the strongly alkaline residual Li compounds react with acidic LiPF6 to form stable Li3PO4 and LiF. The latter is attributed to a reduction in the surface layer resistance on the cathode, as suggested by the results of surface chemistry and impedance analyses.