In-situ construction of hierarchical cathode electrolyte interphase for high performance LiNi0.8Co0.1Mn0.1O2/Li metal battery

High energy density LiNi0.8Co0.1Mn0.1O2 (NCM811)/Li metal batteries exhibit poor cycling due to the inferior structure stability of NCM811. Herein, a hierarchical cathode electrolyte interphase (CEI) with highly dense, resistive and protective properties is in-situ growth on NCM811 by decomposition reaction of lithium difluoro(oxalato)borate (LiDFOB). The hierarchical CEI presents special two-layered structure, where the inner layer is rich in LiF and outer layer mainly contains organic components such as LixBOyFz. The highly resistive inner layer can effectively prevent the NCM811 from further reacting with electrolyte and reduce the accumulation of organic products in outer layer during long cycling. Additionally, the LiDFOB can also induce the uniform deposition of Li ion, increase the Li plating/striping coulombic efficiency and inhibit the growth of Li dendrites. The NCM811/Li battery using LiDFOB presents a greatly improved rate and cycling performance. For instance, the NCM811/Li metal batteries using LiDFOB and LiPF6 based electrolyte delivers a specific capacity of 127.5 and 80.5 mAh g-1 at 10C, respectively and their capacity retentions are 69.8% and 17.1% after 400 cycles. The LiDFOB is a promising lithium salt for advanced high energy density NCM811/Li metal battery.