Super-reversible CuCl cathode enabled by Cu2+-coordinated alginate and carbon composite film for chloride ion battery

Research on clean energy materials represents a necessary response to the urgent global needs for sustainable development and environmental impact mitigation. Chloride-ion batteries (CIBs) with metal chlorides as cathodes have been widely noticed due to their high theoretical gravimetric energy density. However, the significant volume changes during charging and discharging, the poor electrical conductivity and the dissolution of metal chlorides limit the application of metal chloride electrodes. Herein, a Cu 2+ -coordinated sodium alginate (SA)/carbon (C) layer can be formed on the surface of cuprous chloride (CuCl) particles by treating the ball-milled composite of CuCl, SA, and carbon material with water first and then with ethanol. After water treatment, the trace quantity of basic cupric chloride (Cu 2 (OH) 3 Cl) that is formed on the surface of CuCl particles facilitates the in-situ cross-linking with SA. Benefiting from the cross-linking of Cu²⁺ with SA and the chemical and hydrogen bonding between SA and graphene oxide (GO), the CuCl/SA-H₂O/GO cathode delivers a maximum initial discharge capacity of 248 mAh g⁻¹ (92 % of the theoretical capacity) at 100 mA g⁻¹ and retained a reversible capacity of 58 mAh g⁻¹ after 50 cycles.