Guest anionic intercalation of cobalt‑nickel layered double hydroxide induces α-phase Ni(OH)2 generation to enhance its capacitive properties

The low specific capacity of capacitor electrode materials has been the main problem restricting their development. Compared with β-phase CoNi LDH, α-phase CoNi LDH has high specific capacity and cycling stability, and has broad application prospects, but there are fewer related studies. In this paper, the preparation of α-phase CoNi LDH is realized by introducing Cl − and WO₄ 2− intercalation into CoNi LDH, and the mechanism of the intercalation ions on the enhancement of the electrochemical properties of the LDH is deeply investigated. Different charge densities and ionic radii of the intercalation anions affect the valence states of the cations in the main LDH layer as well as the spacing of the LDH layers, and phase structure. Cl − possesses a smaller ionic radius and lower charge density than WO 4 2− , and changed the electronic as well as the phase structure of LDH by bonding with doped Co atoms, which induces the formation of interlayer water molecule chains, facilitating electron transfer and structural stabilization. Remarkably, the specific capacity of CoNi-Cl LDH/NF (Cl − inserted CoNi LDH) electrode at 1 A g −1 (2828.74 F g −1 ) is 4 times that of CoNi LDH/NF and 1.9 times that of CoNi-W LDH/NF (WO 4 2− inserted CoNi LDH) respectively, and remained 88.7 % constant after 5000 cycles at 10 A g −1 . This study provided a new idea for the use of anionic intercalated LDH to modulate the phase structure to enhance the electrochemical performance of electrode materials.