Locally Concentrated Ionic Liquid Electrolytes Enabling Low-Temperature Lithium Metal Batteries

Lithium metal is a promising anode material for next-generation high-energy-density batteries but suffers from low stripping/plating Coulombic efficiency and dendritic growth particularly at sub-zero temperatures. Herein, a poorly-flammable, locally concentrated ionic liquid electrolyte with a wide liquidus range extending well below 0 & DEG;C is proposed for low-temperature lithium metal batteries. Its all-anion Li+ solvation and phase-nano-segregation solution structure are sustained at low temperatures, which, together with a solid electrolyte interphase rich in inorganic compounds, enable dendrite-free operation of lithium metal anodes at -20 & DEG;C and 0.5 mA cm(-2), with a Coulombic efficiency of 98.9 %. As a result, lithium metal batteries coupling thin lithium metal anodes (4 mAh cm(-2)) and high-loading LiNi0.8Co0.15Al0.05O2 cathodes (10 mg cm(-2)) retain 70 % of the initial capacity after 100 cycles at -20 & DEG;C. These results, as a proof of concept, demonstrate the applicability of locally concentrated ionic liquid electrolytes for low-temperature lithium metal batteries.

Automated summary

A new electrolyte for low-temperature lithium metal batteries is proposed, which shows good performance in sub-zero conditions. By using this electrolyte, dendrite-free operation of lithium metal anodes at -20℃ and 0.5 mA cm(-2) with a Coulombic efficiency of 98.9% is achieved.