Potentiostatic Reconstruction of Nickel‐Cobalt Hydroxysulfate with Self‐Optimized Structure for Enhancing Energy Storage

• Published in: Advanced energy materials 2022-11, Vol.12 (41), p.n/a
• Main Authors: Yang, Wang, Zhang, Chengxiao, Du, Shaoxiong, Jiang, Bo, Wang, Chaonan, Bai, Hengxuan, Li, Zhengxuan, Huang, Guoyong, Li, Yongfeng
• Format: Article
• Language: English
• Subjects: Charge transfer; Cobalt sulfide; electrochemical activations; Electrochemical analysis; Energy storage; Modulation; Nickel; Reconstruction; reconstructions; supercapacitors; Transition metal compounds; transition metal hydroxysulfates; transition metal sulfides
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202202286

Transition metal chalcogenides (TMCs) are widely used as energy storage materials, however, most studies have neglected the reconstruction process that occurs during the operation. Thus, the intrinsic energy storage mechanism of TMCs and the identification and modulation of the reconstruction process are not adequately investigated. Herein, a proactive modulation strategy for reconstruction kinetics under nonoperating conditions is proposed, and a potentiostatic reconstruction method is developed. The effects of three electrochemical techniques of potentiostatic, cyclic voltammetry, and galvanostatic on reconstruction products are also revealed. Notably, under potentiostatic reconstruction, the needle‐like nickel‐cobalt sulfide precursor is transformed into columnar, polycrystalline, defect‐rich nickel‐cobalt hydroxysulfate (NCHS‐E), and the process is analyzed in detail by in situ and ex situ characterization. NCHS‐E exhibits an excellent electrochemical performance with a specific capacity of 5040 mC cm−2 at 1 mA cm−2 and capacity retention of 67.1% at 50 mA cm−2. Kinetic analysis and theoretical calculations show that NCHS‐E has fast charge transfer ability and low deprotonation energy, indicating a favorable energy storage pathway. This work proves the important potential of reconstruction kinetic modulation to optimize the structure and properties of the products and provides new insights into the mechanism of reconstruction occurrence. A potentiostatic reconstruction strategy is proposed using the modulation of reconstruction kinetics and is compared in detail with cyclic voltammetry and galvanostatic methods. The mechanism of potentiostatic reconstruction is analyzed in depth, and the reconstructed product is nickel‐cobalt hydroxysulfate with a large number of grain boundaries and defects, which exhibits excellent electrochemical properties, and its energy storage kinetics is investigated.