Designing phosphazene-derivative electrolyte matrices to enable high-voltage lithium metal batteries for extreme working conditions

The current high-energy lithium metal batteries are limited by their safety and lifespan owing to the lack of suitable electrolyte solutions. Here we report a synergy of fluorinated co-solvent and gelation treatment by a butenoxycyclotriphosphazene (BCPN) monomer, which facilitates the use of ether-based electrolyte solutions for high-energy lithium metal batteries. We show that the safety risks of fire and electrolyte leakage are eliminated by the fluorinated co-solvent and fireproof polymeric matrices. The compatibility with high-energy cathodes is realized by a well-tailored Li + solvation sheath, along with BCPN-derived protective surface films developed on the cathodes. Our Li | |LiNi 0.8 Co 0.1 Mn 0.1 O 2 cells reach high-capacity retention, superior low-temperature performance, good cyclability under high pressure and steady power supply under abusive conditions. Our electrolyte design concept provides a promising path for high energetic, durable and safe rechargeable Li batteries. Intensive efforts are under way to develop Li metal batteries with ether electrolytes, but their performance fails to meet practical requirements. Here the authors develop an ether-based electrolyte for Li metal batteries that substantially improves battery cyclability, especially at low temperatures.