Blocking oxidation of α-hydrogens enables non-fluorinated solvents to achieve high-potential stability in lithium batteries

Developing next-generation batteries that are high-energy, low-cost and eco-friendly is crucial for industrial applications. Lithium-rich manganese-based oxide positive electrodes offer substantial specific energy, enabled by their high specific capacity at high charging potential (>4.6 V versus Li/Li⁺). However, stable operation at such high potentials remains challenging, as most electrolytes rely on environmentally unfriendly fluorinated solvents. Here we identified α-oxidation of the carbonyl group as the main oxidation mechanism of carboxylate esters. By removing all the reactive α-hydrogens of methyl acetate, we demonstrate that methyl trimethylacetate is a non-fluorinated, high-potential-stable solvent. This solvent exhibits outstanding oxidative stability up to 5.6 V versus Li/Li⁺, and electrochemical cells using methyl-trimethylacetate-based electrolytes maintain stable cycling at 4.6/4.7 V, outperforming many fluorinated systems. An industrial-scale 7.2-Ah pouch cell reached a maximum specific energy of 652.4 Wh kg⁻¹ with 94.5% capacity retention after 28 cycles at 0.1 C/0.2 C. This work provides a simple molecular design strategy that addresses specific energy, cost and sustainability in next-generation high-voltage lithium batteries. (Figure presented.)