Salt precipitation at temperatures far above the freezing point of solvents is primarily responsible for performance decay of rechargeable batteries at low temperature, yet is still challenged by a lack of in‐depth understanding of the design principle and ultimate solutions. Here, this is resolved via tuning the entropy of solvation in a strong‐solvation (SS) and weak‐solvation (WS) solvent mixture, in which a solvation structure can spontaneously transform at low temperature to avoid salt precipitation, endowing the electrolyte with a temperature‐adaptive feature. The results affirm that such temperature‐adaptive electrolyte ensures encouraging low‐temperature performance in a hard carbon||Na2/3Ni1/4Cu1/12Mn2/3O2 full cell with 90.6% capacity retention over 400 cycles at −40 °C. The generality of the concept is further expanded to construct a series of SS–WS electrolytes as potential candidates for rechargeable low‐temperature sodium‐ion batteries. The work shed lights on the importance of entropy tuning and affords a rational viewpoint on designing low‐temperature electrolytes.