Tailoring structural stability of LiMn2O4 via molybdenum doping and lithium excess engineering for aqueous lithium-ion batteries

Aqueous lithium-ion batteries possess inherent safety advantages. Lithium manganese oxide (LiMn2O4), a widely studied cathode material, suffers from cycling instability due to Jahn-Teller distortion and manganese dissolution. In this study, a Mo-doped lithium manganese oxide with a slight lithium excess, Li1.02Mo0.02Mn1.98O4, was prepared. Doping with molybdenum and introducing excess lithium increases the lattice spacing of the Li1.02Mo0.02Mn1.98O4 material, thereby accelerating the Li+ diffusion coefficient. Li1.02Mo0.02Mn1.98O4 demonstrates excellent rate capability and cycling stability in a half-cell, achieving capacity retention of 93 % after 500 cycles at 1 C. Moreover, it exhibits remarkable stability in an aqueous electrolyte. In a full-cell setup using NaTi2(PO4)3 as the anode, the material delivers stable cycling performance for over 500 cycles. A 5 Ah pouch cell was fabricated, achieving a discharge capacity of 3.8 Ah at 1 C and retaining a capacity of 2.52 Ah after 200 cycles, confirming the material's robustness in larger-format cells.