Mixed hydroxide materials with a large specific charge capacity (417 C g−1) and charge retention capacity (86%) even after 5000 galvanostatic charge–discharge processes at 25 A g−1, promising as electrode materials of energy storage devices such as hybrid batteries, are realized by isomorphic substitution of Ni(II) by Mn(II) ions in the turbostratic alpha‐nickel hydroxide lattice, generating for the first time double hydroxide salt types (Ni‐95 and Ni‐75) instead of layered double hydroxide type materials, significantly enhancing the electrochemical properties and stability of nickel hydroxide nanoparticles (Ni‐100). The presence of Mn(II) ions in the alpha‐Ni(OH)2 structure is confirmed by flame atomic absorption spectrometry (FAAS), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffractometry (XRD) of the mixed nickel–manganese hydroxide materials.