Deuterated Aprotic Electrolytes Enable Rechargeable Lithium Batteries With High (Electro)Chemical and Thermal Stability

ABSTRACT Electrolytes with exceptional (electro)chemical and thermal stability are essential prerequisites for high‐energy‐density rechargeable lithium batteries. Conventional aprotic ether and ester solvents contain polarizable C─H bonds that trigger parasitic proton transfer reactions on the high‐voltage cathode surface, driving exothermic electrolyte decomposition and impairing battery cycling stability and safety. Here, we show that deuterium substitution at polarizable C–H moieties introduces kinetic and thermodynamic isotope effects to retard proton transfer and lower solvent oxidation Gibbs free energy. Consequently, the deuterated electrolytes exhibit improved anodic stability and mitigated decomposition during high‐voltage charge–discharge of layered oxide cathodes, forming a compact and robust cathode–electrolyte interphase with suppressed CO 2 release. The deuterated solvents also have lower combustion enthalpies than their protiated analogs, which translates to substantially reduced heat generation as confirmed by calorimetric measurements. Using deuterated tetrahydrofuran and dimethyl carbonate as model solvents, we validate that such electrolytes enable reversible cathode electrochemistry, as well as markedly improved cycling performance and thermal safety of Li||LiNi 0.8 Co 0.1 Mn 0.1 O 2 batteries. This subatomic modification strategy offers a rational electrolyte design framework toward high‐performance batteries.