Methylcellulose/Polymethyl Methacrylate/Al₂O₃ Composite Polymer Matrix towards Ni-Rich Cathode/Lithium Metal Battery

Gel polymer electrolyte (GPE) has attracted extensive interest due to superior interfacial compatibility, excellent plasticity, and improved electrochemical stability. Polymer matrix is of great importance to the performance of lithium metal battery, especially for Ni-rich cathode system with high working potential. Herein, a rigid-flexible composite polymer matrix comprising methylcellulose (MC), polymethyl methacrylate (PMMA), and Al₂O₃ is prepared. After saturated with the liquid electrolyte of 1 M LiDFOB in EC/DMC (1:1, v:v), the obtained GPE exhibits a high ionic conductivity of 0.20 × 10⁻³ S cm⁻¹ and a wide electrochemical stable window up to 5.6 V. The synergistic effect of inorganic fillers and the ester groups on polymer matrix are conducive to the uniform deposition of Li-ion and advantageous to the formation of smooth and robust interfacial passivation layer. After assembled with Ni-rich cathode LiNi_0.8Co_0.15Al_0.05O₂ (NCA), a capacity of 158.1 mAh g⁻¹ is maintained after 200 cycles at 0.1 C, while a high value of 133.1 mAh g⁻¹ is delivered at 2 C. These results indicate that the as-prepared MC-PMMA-Al₂O₃ GPE (abbreviated as MPAA) is favorable for the interfacial compatibility of lithium metal batteries and shows superior electrochemical stability at high working voltage.