Recently, Yongbing Tang, a researcher at the Functional Thin Film Materials Research Center of the Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and members of his team, along with Chenghua Sun, the Lightfoot Professor at the University of St. Andrews, UK, Huiming Cheng, a professor at Swinburne University of Technology, Australia, and a researcher at Tsinghua University, Berkeley, Shenzhen, have successfully developed a new cathode material for lithium-ion batteries with dual anionic and cationic electrochemical activity. . This work is an important reference for the research of new energy storage devices and related materials based on multiple electrochemical reaction activity centers. The related research results of oxalate cathode for lithium-ion batteries with combined cation and polyanion redox ("Oxalate lithium-ion battery cathode materials with cation and polyanion redox activity") have been published online in Nature Communications ( (Nature Communications, 2019, DOI): 10.1038 / s41467-019-11077-0).
With the rapid growth of key industries such as portable electronics, electric passenger tools, and energy storage, lithium-ion batteries have been forced to have higher performance specifications. However, just like the barrel effect, the drawback of lithium-ion battery performance lies in the cathode. Therefore, the design and development of cathode materials is the focus of current research. Conventional lithium-ion battery cathode materials mainly include oxides and polyanions. Among them, oxide cathodes such as lithium cobaltate have two pairs of redox pairs of transition metals and oxygen anions, and thus have high capacity. However, the electrochemical reaction of the oxygen anion is unstable and tends to produce gas and cause collapse of the cathode structure, which leads to battery failure and serious safety accidents. Polyanionic positive electrodes (e.g., lithium iron phosphate) significantly improve the structural stability of the material due to the polyanion as the structural framework, but the polyanion as an inactive component reduces the total energy density. Therefore, if new cathode materials can be developed, the advantages of both reaction mechanisms can be effectively combined, and high safety and high energy density are expected to be achieved.
Based on the above considerations, Yongbing Tang and his team members Wenjiao Yao, Xiaolong Zhou et al. successfully developed new Li2Fe(C2O4)2 polyanionic cathode materials in a UNI team and found the first polyanionic cathode material with two electrochemical activities of iron ions and oxalate moieties. The reversibility of the Fe2 + / Fe3 + change has been verified by Mössbauer spectroscopy and in situ synchrotron near- and extended absorption side fine structures; in situ Raman spectroscopy and carbon-oxygen synchrotron radiation near-side absorption side structure verification gives the reversible change of the oxalate anion group; further theoretical calculations give the electrochemical reaction mechanism of the new cathode material. A novel polyanionic cathode material with dual electrochemical activity of anion and cation is discovered, which is an important guideline for the research and development of secondary battery cathode materials based on multiple electrochemical activity centers.
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