In Situ X‐Ray Absorption Near‐Edge Structure Evidence for Quadrivalent Nickel in Nickel Battery Electrodes

Abstract

The oxidation state of nickel in a nickel oxide battery has been examined using x‐ray absorption spectroscopy. Chemically synthesized β‐NiOOH and were used as reference standards for the Ni(III) and Ni(IV) oxidation states of nickel, respectively. The shift of the Ni K‐edge absorption in both a completely charged nickel oxide electrode (NOE) and a 1000% overcharged nickel oxide electrode corresponds to a Ni oxidation state of +3.5. This oxidation state clearly indicates the presence of in the charged electrodes.