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Fluorine-free water-in-ionomer electrolytes for sustainable lithium-ion batteries.

  • Author(s): He, Xin
  • Yan, Bo
  • Zhang, Xin
  • Liu, Zigeng
  • Bresser, Dominic
  • Wang, Jun
  • Wang, Rui
  • Cao, Xia
  • Su, Yixi
  • Jia, Hao
  • Grey, Clare P
  • Frielinghaus, Henrich
  • Truhlar, Donald G
  • Winter, Martin
  • Li, Jie
  • Paillard, Elie
  • et al.
Abstract

The continuously increasing number and size of lithium-based batteries developed for large-scale applications raise serious environmental concerns. Herein, we address the issues related to electrolyte toxicity and safety by proposing a "water-in-ionomer" type of electrolyte which replaces organic solvents by water and expensive and toxic fluorinated lithium salts by a non-fluorinated, inexpensive and non-toxic superabsorbing ionomer, lithium polyacrylate. Interestingly, the electrochemical stability window of this electrolyte is extended greatly, even for high water contents. Particularly, the gel with 50 wt% ionomer exhibits an electrochemical stability window of 2.6 V vs. platinum and a conductivity of 6.5 mS cm-1 at 20 °C. Structural investigations suggest that the electrolytes locally self-organize and most likely switch local structures with the change of water content, leading to a 50% gel with good conductivity and elastic properties. A LiTi2(PO4)3/LiMn2O4 lithium-ion cell incorporating this electrolyte provided an average discharge voltage > 1.5 V and a specific energy of 77 Wh kg-1, while for an alternative cell chemistry, i.e., TiO2/LiMn2O4, a further enhanced average output voltage of 2.1 V and an initial specific energy of 124.2 Wh kg-1 are achieved.

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