Physics

Electrode

Organic chemistry

Ethylene oxide

Propylene carbonate

Anode

Endocrinology

Engineering

Physical chemistry

Copolymer

Power (physics)

Inorganic chemistry

Ethylene carbonate

Chemistry

Materials science

Phosphate

Solvent

Trimethyl phosphate

Lithium (medication)

Graphite

Cathode

Battery (electricity)

Quantum mechanics

Electrolyte

Chemical engineering

Polymer

Medicine

Nature Energy

The traditional electrolyte for lithium-ion batteries is a combination of 1 M LiPF6 with a cyclic carbonate-based solvent (for example, ethylene carbonate). The lack of a suitable alternative solvent has hindered further exploration of new functional electrolytes. Here we design and synthesize a fluorinated cyclic phosphate solvent, 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphospholane 2-oxide (TFEP), for use in lithium-ion batteries. Our design rationale is that this solvent molecule has a fused chemical structure of cyclic carbonates that can form a stable solid electrolyte interphase and organic phosphates that can trap hydrogen radicals and prevent combustion. An electrolyte formula composed of 0.95 M LiN(SO2F)2 in TFEP/2,2,2-trifluoroethyl methyl carbonate shows excellent non-flammability with zero self-extinguishing time and enables the highly stable operation of graphite anodes (~0.1 V versus lithium) and high-voltage LiNi0.5Mn1.5O4 cathodes (~4.7 V versus lithium), and thereby outperforms traditional electrolytes. This work opens up new frontiers in electrolyte developments towards safe lithium-ion batteries with higher energy densities. Non-flammable high-performance electrolytes are in high demand for rechargeable batteries. Here the authors design cyclic phosphate-based electrolytes to enable stable operations of graphite anodes and high-voltage cathodes for lithium-ion batteries.

A cyclic phosphate-based battery electrolyte for high voltage and safe operation