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 Co 2+ /Co 3+ and Fe 2+ /Fe 3+ during charge/discharge and the improved electronic conductivity by hybridizing with CNTs. It is interesting that the invertible insertion/extraction of interlayer H 2 O 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.