Abstract Lithium-rich manganese-based (LRM) cathode materials have attracted considerable attention for next-generation lithium-ion batteries owing to their superior energy density. However, their cycling stability in conventional electrolytes is severely challenged by the high operating voltage (4.8 V vs. Li/Li+), particularly under fast-charging and low-temperature conditions. To overcome this mismatch, we construct a steric hindrance-guided electrolyte design strategy to tune the solvation structure. By systematically increasing the steric hindrance of carboxylic ester solvents, ethyl trimethyl acetate is ultimately identified to effectively weaken the Li+-solvent interactions. The resulting anion-involved structure enhances Li+ transport kinetics while inducing a stable cathode-electrolyte interphase. With this steric hindrance-induced low-temperature electrolyte, the LRM cathode delivers exceptional fast-charging durability (1500 cycles at 3C, RT) and an extended low-temperature cycle life (1000 cycles at −20 °C, 0.33C). This work validates molecular-level steric hindrance tuning as an effective strategy to unlock the extreme-condition performance of high-energy-density LRM cathodes.