"Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries"

Zhiao Yu: Hansen Wang , Xian Kong , William Huang, Yuchi Tsao, David G. Mackanic , Kecheng Wang, Xinchang Wang, Wenxiao Huang, Snehashis Choudhury, Yu Zheng, Chibueze V. Amanchukwu, Samantha T. Hung, Yuting Ma, Eder G. Lomeli, Jian Qin , Yi Cui  and Zhenan Bao ; Nature Energy, 06/22/20.

Additional Authors: Hansen Wang , Xian Kong , William Huang, Yuchi Tsao, David G. Mackanic , Kecheng Wang, Xinchang Wang, Wenxiao Huang, Snehashis Choudhury, Yu Zheng, Chibueze V. Amanchukwu, Samantha T. Hung, Yuting Ma, Eder G. Lomeli, Jian Qin , Yi Cui  and Zhenan Bao 

Abstract:

Electrolyte engineering is critical for developing Li metal batteries. While recent works improved Li metal cyclability, a methodology for rational electrolyte design remains lacking. Herein, we propose a design strategy for electrolytes that enable anode-free Li metal batteries with single-solvent single-salt formations at standard concentrations. Rational incorporation of –CF2– units yields fluorinated 1,4-dimethoxylbutane as the electrolyte solvent. Paired with 1 M lithium bis(fluorosulfonyl)imide, this electrolyte possesses unique Li–F binding and high anion/solvent ratio in the solvation sheath, leading to excellent compatibility with both Li metal anodes (Coulombic efficiency ~ 99.52% and fast activation within five cycles) and high-voltage cathodes (~6 V stability). Fifty-μm-thick Li|NMC batteries retain 90% capacity after 420 cycles with an average Coulombic efficiency of 99.98%. Industrial anode-free pouch cells achieve ~325 Wh kg−1 single-cell energy density and 80% capacity retention after 100 cycles. Our design concept for electrolytes provides a promising path to high-energy, long-cycling Li metal batteries.