With the increasing demand for energy density and power density of lithium-ion batteries in new energy storage and electric vehicles, cobalt-free spinel LiNi0.5Mn1.5O4 (LNMO) has emerged as a core candidate material for next-generation high-voltage cathodes due to its high operating voltage of 4.7V, high theoretical energy density of 650 Wh kg−1, low cost, and environmental friendliness. However, traditional electrolytes are prone to oxidative decomposition under complex conditions of high voltage, fast charging, and wide temperature range, leading to obstructed ion transport, deteriorated electrode interface stability, and flammability risks. Although existing weakly solvating electrolytes can form solvation structures rich in contact ion pairs (CIP) and aggregates (AGG), optimizing the cathode/electrolyte interface (CEI), they generally suffer from issues such as low salt solubility and poor oxidation resistance. The research team led by Professor Wang Pengfei from Xi'an Jiaotong University proposed a salt-in-salt mediated strong-weak synergistic strategy to construct a fluorinated weakly solvating electrolyte, LMDFT. By introducing dual salts of Mg(TFSI)₂ and LiDFOB, Mg²⁺'s moderate Lewis acidity was utilized to promote LiDFOB dissociation, enrich anion-rich CIP/AGG solvation structures, and accelerate Li⁺ desolvation, forming a thin and dense inorganic cathode electrolyte interface layer. This electrolyte enables the LNMO//Li half-cell to achieve excellent fast-charging and cycling stability performance within the temperature range of -30 to 70°C, with a capacity retention rate of 89.2% after 1200 cycles at 5C and 88.9% after 400 cycles at 0.5C for pouch cells. Moreover, the electrolyte is non-flammable and exhibits broad compatibility with high-nickel NCM811, NCM92, and olivine-type LiFePO₄ cathodes.