Electrodeposition‐Potential Tuning Rejuvenates the Concurrent Preparation from α‐Co(OH)2 with Larger Interlayer‐Spacings to β‐Co(OH)2

Abstract Electrodeposition is a popular method for preparing α‐Co(OH) 2 as an electrode material for electrochemical energy storage. However, the preparation of technically important β‐Co(OH) 2 through electrodeposition remains lacking thus far. Herein, we successfully prepared Co(OH) 2 in two phases, α‐ and β‐Co(OH) 2 , by simply adjusting the electrodeposition potentials, as evidenced by a package of microcopy and spectroscopy analysis. Benefited from a delicate embedding and sectioning technique that may inhibit the loss of interlayer water in microscopy analysis, we find the presence of Co tetrahedron in the interlayer of α‐Co(OH) 2 results in a large interlayer spacing of 7.2 Å for the crystal plane (003) compared to β‐Co(OH) 2 , as well as a higher chemical valence of cobalt in electrodeposited β‐Co(OH) 2 . The large interlayer spacing creates wider ion channels and more active storage sites for effective energy storage. Consequently, the α‐Co(OH) 2 electrode exhibits more competitive electrochemical performance compared to its β counterpart.