Rational Design of Lithium Sulphonamide Polymeric Cation Exchange Membranes for LiOH Production by Electro‐Electrodialysis

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Abstract
The use of electro‐electrodialysis (EED) for the conversion of lithium salts obtained from either hard‐rock minerals or brines into high‐value battery‐grade lithium hydroxide is gaining traction as an alternative green technology. Current cation exchange membranes employed in Li‐salt EED possess low selectivity towards Li + and are dominated by polyfluoroalkyl polymer‐based membranes, which pose significant environmental concerns. Hence, there is a need for the development of inexpensive membranes for Li‐salt EED applications with a lower content of environmentally hazardous fluorinated compounds. In this work, novel self‐standing Li‐selective and low‐fluorine content membranes have been developed based on inexpensive methacrylic monomers, including a lithium sulfonyl‐1‐(trifluoromethylsulfonyl)imide monomer. The membranes were prepared via fast UV‐photopolymerisation. Rational design of the membranes with different co‐monomer compositions and crosslinking degrees enabled the tailoring of the membrane properties including water uptake, mechanical strength, and electrochemical performance. The membranes showed a high Li‐ion conductivity of up to 6.2 mS cm −1 and comparable EED performance to that of the Nafion117 membrane as benchmark, i.e., relatively low energy consumption of 13.9 kWh kg −1 LiOH and high molar flux of up to 3.9 mmol h −1 , with a Li + /Na + molar fluxes ratio of 0.98.
Funding Information
  • H2020 Marie Skłodowska-Curie Actions (Grant 101129945)
  • Ministerio de Ciencia, Innovación y Universidades (Grant PID2023‐153050OB‐I00)
  • Eusko Jaurlaritza (Grant GV‐IT1525‐22)

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