Aqueous Chloride-Ion Battery within a Neutral Electrolyte Based on a CoFe-Cl Layered Double Hydroxide Anode

Aqueous chloride-ion batteries (ACIBs) with environmental friendliness and high safety hold great potential to fulfill the green energy demand for ocean desalination. Herein, for the first time, a composite consisting of Cl^--intercalated CoFe layered double hydroxides (CoFe-Cl-LDH) cross-linked with CNTs (CoFe-Cl-LDH/CNT) is synthesized and demonstrated to be a novel high-performance anode for ACIBs in a neutral NaCl aqueous solution. While exhibiting a high initial capacity of ∼190 mAh g^-1 at 200 mA g^-1, CoFe-Cl-LDH/CNT is capable of delivering a reversible capacity of ∼125 mAh g^-1 after 200 cycles. At a high current density of 400 mA g^-1, it still holds a capacity of ∼120 mAh g^-1. The excellent Cl^- storage performance can be contributed to the unique topochemical transformation feature that reverses intercalation/deintercalation of Cl^- along with valence changes of Co²⁺/Co³⁺ and Fe²⁺/Fe³⁺ during charge/discharge and the improved electronic conductivity by hybridizing with CNTs. It is interesting that the invertible insertion/extraction of interlayer H₂O was discovered, which could be beneficial to the capacity after cycles to a certain extent. The Cl^--intercalated LDH material declared in this work shows its feasibility on Cl^- capture/release in aqueous anion-type batteries and provides a new opportunity for future development of ACIBs or aqueous desalination technology.