Conventional carbonate solvents with low HOMO levels are theoretically compatible with the low-cost, high-voltage chemistry of Zn/graphite batteries. However, the nucleophilic attack of the anion on carbonates induces an oxidative breakdown at high potentials. Here, we restore the inherent anodic stability of carbonate electrolytes by designing a micro-heterogeneous anion solvation network. Based on the addition of a strongly electron-donating solvent, trimethyl phosphate (TMP), the oxidation-vulnerable anion-carbonate affinities are decoupled because of the preferential sequestration of anions into solvating TMP domains around the metal cations. The hybridized electrolytes elevate the electrochemical window of carbonate electrolytes by 0.45 V and enable the operation of Zn/graphite dual-ion cells at 2.80 V with a long cycle life (92 % capacity retention after 1000 cycles). By inheriting the non-flammability from TMP and the high ion-transport kinetics from the carbonate systems, this facile strategy provides cells with the additional benefits of fire retardancy and high-power capability.
Keywords: anion solvation; carbonate electrolytes; high power density; micro-heterogeneous distribution; oxidation stability.
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