Electrochemical activation of Ni-based layered double hydroxides via host layer oxidation-induced conductivity enhancement

Compared with lithium-ion secondary batteries using flammable organic solvents, classical storage batteries using aqueous solutions have the advantage of low fire hazard, but they have a short cycle life because most of them use dissolution and precipitation reactions of electrode active materials. Therefore, we focused on layered double hydroxides (LDHs) as aqueous active materials that undergo intercalation-type reactions. LDHs are hydroxides containing anions between layers, and it has been reported that LDHs can be used as active materials in batteries because their anions can enter and leave the crystal; however, the detailed mechanism has not been elucidated. In this study, we focused on the conductivity of LDHs during redox and the valence change of metal elements in the crystal during the redox process to elucidate the mechanism by which LDHs develop charge‒discharge capacity.