Recently, the Institute of Crystal Materials has made new progress in interface structure optimization and energy storage devices. The relevant research results are titled "Water Invoking Interface Corrosion: An Energy Density Booster for Ni//Zn Battery" and published online in Advanced Energy Materials ( District 1, Chinese Academy of Sciences, IF=25.245). 2020 PhD student He Weidong is the first author, Professor Xiaopeng Hao and Professor Yongzhong Wu are the co-corresponding authors, and Shandong University is the first author and corresponding author.
Aqueous zinc-based batteries are expected to become important substitutes for lithium-ion batteries due to their low production cost, high voltage platform, high power density, safety and environmental friendliness. However, the limited surface chemical activity limits the utilization of the material, resulting in insensitive edge states and low capacity of the cathode material. Inspired by the phenomenon of metal corrosion, the team proposed a method of using water to induce interfacial corrosion of bimetallic sulfides to regulate their surface chemical valence through in-situ reconstruction. Thanks to the surface enrichment effect of low-valent metal ions, a NiCo-OH layer with high electrochemical reaction activity and stable structure is reconstructed on the surface of metal sulfide. The electrochemical performance is best when the corrosion layer is about 40 nm thick; and Summarized the reconstruction mechanism of water-corrosion effect, and the internal relationship between corrosion degree and electrochemical capacity.
Due to the improvement of material utilization rate, the electrodes of the reconstructed interface show high specific capacity (390 mAh g-1, 2.45 mAh cm-2); the assembled Ni//Zn battery exhibits long cycle life and high Area energy density (4.29 mWh cm-2) and power energy density (52.50 mW cm-2). This water-induced interfacial corrosion method provides an effective path for preparing transition metal sulfide and phosphide electrode materials with a highly reactive interface.
In the previous research, the research group improved the stability and electrochemical activity of electrode materials through the optimization of the interface structure. A built-in electric field is introduced at the interface of MnS-MoS2 heterojunction to improve its ion transport capacity and conductivity, and phase engineering design is used to guide MnS and MoS2 to undergo phase change during lithium ion storage, so as to increase the lithium storage capacity of the anode material ability. This heterojunction design not only solves the problem of low ion transmission rate and electrical conductivity, but also slows down the volume expansion of the negative electrode material during charge and discharge. In addition, a bimetallic oxynitride material with oxygen vacancies modified at the interface of the oxynitride layer was designed and synthesized to effectively introduce oxygen vacancies, adjust the electronic structure and metal valence of the interface layer, and thereby improve the conductivity and chemical properties of the electrode material. Relevant research results were completed by special funded postdoctoral fellow Wang Shouzhi and doctoral student Chen Fuzhou and published in Advanced Functional Materials (2020, 30(27), 2000350 and 2021, 2007132, District 1, Chinese Academy of Sciences, IF=16.836).
This series of research work was funded by the National Natural Science Foundation of China, the Natural Science Foundation of Shandong Province and the State Key Laboratory of Crystal Materials of Shandong University. (Author: Faye Wong)
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