Improved interfacial chemistry and enhanced high voltage-resistance capability of an in situ polymerized electrolyte for LiNi0.8Co0.15Al0.05O2–Li batteries

Abstract

Ni-rich layered oxide LiNi_0.8Co_0.15Al_0.05O₂ (NCA) is one of the most promising cathode candidates for high-energy-density lithium batteries. However, the extensive application of NCA is hindered due to the notorious electrode/electrolyte interfacial issues. To address the above bottleneck, a new gel polymer electrolyte is prepared with maleic anhydride/hexafluorobutyl methacrylate/methyl methacrylate at a ratio of 1 : 1 : 1 via in situ polymerization. A high electrochemical stability window of 5.5 V vs. Li⁺/Li and ionic conductivity of 1.1 × 10⁻³ S cm⁻² are achieved, which suggest the superior high-voltage stability and fast ion migration dynamics of poly(maleic anhydride–hexafluorobutyl methacrylate–methyl methacrylate) (PMHM) electrolyte that are contributed by C–F and ester/acid anhydride groups in the polymer chain. As a result, the NCA/PMHM/Li battery delivers stable cycling performance with a capacity retention of 91.8% after 200 cycles at 0.5C, and a high capacity retention of 77.7% after 500 cycles at 1C. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) results reveal the stability of interfacial chemistry and the integrity of cathode structure. This work indicates that the in situ polymerized hexafluorobutyl methacrylate-based electrolyte is imperative to address the interfacial issues and boost the development of high-energy lithium metal batteries with a Ni-rich cathode.