Electrode

Organic chemistry

Anode

Engineering

Faraday efficiency

Physical chemistry

Composite material

Inorganic chemistry

Chemistry

Materials science

Phosphate

Solvent

Trimethyl phosphate

Graphite

Electrolyte

Flammable liquid

Chemical engineering

Nature Energy

Non-flammable electrolytes could intrinsically eliminate fire hazards and improve battery safety, but their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces. Here, we report an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent. At a high Li salt-to-solvent molar ratio (~1:2), the phosphate solvent molecules are mostly coordinated with the Li+ cations, and the undesired reactivity of the solvent molecules toward the graphite anode can be effectively suppressed. High cycling Coulombic efficiency (99.7%), good cycle life and safe operation of commercial 18650 Li-ion cells with these electrolytes are demonstrated. In addition, these non-flammable electrolytes show reduced reactivity toward Li-metal electrodes. Non-dendritic Li-metal plating and stripping in Li–Cu half-cells are demonstrated with high Coulombic efficiency (&gt;99%) and good stability. Non-flammable electrolytes such as phosphates offer safety advantages for batteries, but they are prone to decomposition when coupled with graphite anodes. Here, the authors report a phosphate with a high salt-to-solvent ratio that displays high stability as well as compatibility with graphite in a commercial 18650-type cell.

Non-flammable electrolytes with high salt-to-solvent ratios for Li-ion and Li-metal batteries