Important Progress on the Negative Pole of Lithium Battery

Lithium-ion batteries have not significantly increased their specific capacity since they were used on a large scale in the 1990s, so they are increasingly unable to meet the requirements of smartphones for long standby times, electric vehicles for longer runs, and power storage requirements for grid peaking.

The fundamental reason for this dilemma is that the electrode material capacity of lithium batteries is difficult to break through. For example, commercial negative electrode materials can only use low-specific capacity carbon-based materials with a theoretical capacity of 372 mAh/g. Although studies have shown that elements such as Si, Ge, and Sn have a high specific capacity as negative poles, they are limited by the rapid decay of capacity after multiple uses and are difficult to apply in practice. In recent years, SnO2 negative electrode materials have received great attention for their superior cyclic properties. Their theoretical capacity(783 mAh/g) has reached twice the negative electrode of graphite.

However, the existing SnO2 and the elemental negative electrode materials can not overcome the bottleneck of volumetric expansion during the electrochemical process of lithium ion batteries, and the cyclic stability is difficult to meet the application needs. Therefore, how to develop a new high cyclic stability/high capacity SnO2 lithium electrode material is of great significance.

Recently, the New Energy Materials and Devices Section of the School of Chemistry and Molecular Engineering of Peking University jointly studied with the Institute of Silicate, Chinese Academy of Sciences, the University of Pennsylvania, and Beijing Institute of Technology, and invented a black tin dioxide nanometer material based on original preparation technology. As a lithium negative electrode, the material has a reversible capacity of 1340 mAh/g, which is much better than the theoretical capacity limit of SnO2(783 mAh/g). After the material was combined with graphene, it also showed excellent cyclic stability and ploidy performance. After circulating 100 laps at a current density of 0.2 A/g, the capacity did not decay, maintaining a capacity of 950 mAh/g; Maintain a capacity of 700 mAh/g in the large current of 2A / G.

Through in-depth and detailed research, the researchers realized that the unique new black tin dioxide material is different from the existing tin dioxide, has the characteristics of excellent electron conductivity and rich oxygen vacancies, and induces an isotropic reduction reaction of Nano active materials. Thus, a highly thermodynamic and highly stable Sn and Li2O uniformly dispersed microscopic composite Nanostructures were formed, which finally solved the scientific problem of metal Sn agglomeration during the cycle process. The researchers were surprised to find that this special microscopic composite nanostructure can ensure that metal tin is completely reversible oxidized to tin dioxide in the electrochemical reaction of energy storage. This phenomenon and mechanism have not been reported in the literature. Based on the new storage mechanism, the theoretical capacity of tin dioxide negative electrode materials has been increased from the original 783 mAh/g to 1494 mAh/g of the new mechanism. The black tin dioxide invented by the researchers provides a new idea for the design and synthesis of other new types of electronegative materials, and it also has the industrial application value of high-capacity lithium electronegative materials.

"ArbustandCondutiveTinOxideNanostortureutur" was published on April 21, 2017 as the author of the Chinese Chemical Lithium-IonBatteriesPossible, and the first graduate student of the <ORGANIZATION::0>, Xujijian Huangfuqiang on April 21, 2017(DOI: 10.1002 / maad.00136), and the Peking University Academy of Sciences. The project is supported by the National key basic research and development plan, the National Natural Science Foundation Committee, the Shanghai Municipal Science and Technology Committee and the main research projects of the Chinese Academy of Sciences.

The page contains the contents of the machine translation.