To improve the energy density of lithium (Li) batteries and solve the problems of conventional single-salt electrolytes such as poor thermal stability, low conductivity, and Li dendrites, developing new blended-salts electrolytes has become an important research direction of Li battery electrolytes. Blended-salts can change the ion conductivity, Li ion solubility, viscosity, and other properties of the solution, and can improve the electrochemical performance of the battery by affecting the interface of electrode and electrolyte as well as the surface and interface of electrode materials. This paper collects the latest research literature at home and abroad, and reviews the research progress of blended-salts electrolytes for Li batteries, including different research directions such as Li ion batteries, Li metal batteries, Li sulfur batteries, and solid state batteries. The advantages and disadvantages of commonly used single-salts are summarized, the effects and mechanism explanations of hybrid electrolytes on different surface interfaces of batteries are elaborated, and the applications of blended-salts in different battery systems are analyzed. At last, the existing problems of blended-salts electrolytes and interface reactions are discussed, and the development direction and application of characterization of novel blended-salts and interface reactions are given. The current research studies of blended-salts are mostly limited to performance improvement and its mechanism needs to be further investigated. The existing explanation usually unfolds from single-salts, and the mechanism of synergistic effect of blended-salts is an important research direction in the future.