Nickel-doped Sb₄O₅Cl₂ enables bifunctional electrochemical systems for efficient energy storage and saline water treatment

Aqueous chloride-ion batteries (CIBs) have emerged as promising dual-functional electrochemical systems, offering simultaneous energy storage and desalination capabilities along with inherent environmental and economic benefits. Although Sb₄O₅Cl₂-based anodes operate at favorable low potentials that help mitigate electrode dissolution, their practical application is hindered by limited cycling stability and suboptimal charge efficiency. In this work, we propose a nickel doping strategy that simultaneously enhances the structural stability and chloride-ion storage capacity of Sb₄O₅Cl₂ in aqueous electrochemical systems. The optimized sample exhibits outstanding chloride storage performances, delivering a specific capacity of 74.19 mAh g⁻¹ at 0.3 A g⁻¹ against an Ag counter electrode, while retaining 85% of its capacity after 200 cycles. When integrated into a hybrid desalination system utilizing a Prussian blue electrode, it delivers an impressive initial desalination capacity of 107.42 mg g⁻¹ at 1.2 V, maintaining 62.6% capacity retention after 30 cycles. This work proposes a defect chemistry strategy for developing stable, multifunctional electrodes with both energy storage and water purification functionalities, offering a promising material solution for sustainable and integrated resource management.