The bottleneck of power lithium battery development has been overcome, and the energy is super high

by:CTECHi     2021-09-17
The lithium-sulfur battery, which has the characteristics of high energy density, large capacity, environmental protection, and low cost, is known as the development direction of the next generation of power lithium battery system after the lithium ion battery. Recently, Li Mingtao's research group at the School of Chemical Engineering of Xi'an Jiaotong University has broken through the bottleneck problem that affects the use of lithium-sulfur batteries. It has designed and developed a two-dimensional structure of graphene protective layer cathode material, and obtained a lithium-sulfur battery with a long cycle life. The detailed principle is that the two-dimensional intercalation structure of g-C3N4/graphene sandwich is like a multi-layer anti-shark net built between the positive and negative electrodes of the battery, which can not only block polysulfides from the positive and negative electrodes through the dual use of physics and chemistry. Shuttle between, but also accelerate the diffusion of lithium ions, thereby greatly improving the cycle life of the battery. In my country, the development of lithium-sulfur batteries is relatively late, still in the laboratory research and development stage, and the actual use is very small. The dissolution of lithium polysulfide, an intermediate product in the charge and discharge process of lithium-sulfur batteries, causes the shuttle effect, which has always been regarded as a key factor limiting its practical use. Dr. Qinghai Li, who was the vice president of Mengshi Technology, once said that the dissolution and shuttle of polysulfides is the most important and difficult problem for lithium-sulfur batteries, and related improvement work is still in its infancy, but he is optimistic about lithium-sulfur batteries as a kind of High energy density secondary batteries have great development prospects. Compared with the current mainstream ternary NCM lithium-ion battery, the theoretical specific energy of a battery with a sulfur positive electrode is as high as 2600Wh/kg, which is more than ten times that of the currently widely used lithium-ion battery. In addition, sulfur has the advantages of abundant element reserves and low cost. Once used on a large scale, it will greatly help the price of electric vehicles powered by lithium-ion batteries fall. In 2016, the National Development and Reform Commission proposed in the 'Energy Technology Revolution and Innovation Action Plan (2016-2030)' to break through the lithium-sulfur battery technology with an energy density of 300Wh/kg. As a comparison, the power lithium batteries that have been used in batches, according to the 'Action Method for Promoting the Development of the Automotive Power Lithium Battery Industry' published in 2017, and the 'Mid and Long-term Development Plan for the Automobile IndustryAbove kg, it will reach 500Wh/kg by 2025. The theoretical energy density of lithium-sulfur batteries exceeds 500Wh/kg, so it is regarded as the development direction of the next-generation power lithium battery system after lithium-ion batteries. In order to deal with the practical use of lithium-sulfur batteries, including the team of Academician Qian Yitai of the University of Science and Technology of my country, the team of Wang Haihui of South China University of Technology, the Advanced Energy Storage Materials and Technology Research Group of Qingdao Institute of Energy, Chinese Academy of Sciences, the team of Nanfeng Zheng, a chemist from Xiamen University in my country, and Shanghai Transportation The university Wang Jiulin's research team made relevant breakthroughs. In October 2018, the team of Academician Qian Yitai of the University of Science and Technology of my country and the team of Professor Wang Gongming found that the position of the p band center of the valence electron of the anion in the cobalt-based compound relative to the Fermi level affects the electron transfer at the interface of the Li-S battery An important factor in the kinetic nature of the reaction. Researchers found that the cobalt-based compound sulfur-carrying material with the smallest positive pole polarization and the best rate performance, even at 40.0C, still has a capacity of 417.3mAhg-1, which corresponds to the current highest power density of 137.3kWkg -1. The research results were published in the international outstanding energy materials journal 'Joule'. Lithium-sulfur battery is a battery system that uses sulfur as the battery anode and metal lithium as the battery anode. In dealing with the safety problem of the easy formation of dendrites in the metal Li anode, the Wang Jiulin research team of Shanghai Jiaotong University prepared a new type of lithium. Sulfur battery electrolyte solution (the saturated electrolyte is obtained by dissolving lithium bisfluorosulfonimide in triethyl phosphate and high flash point fluoroether). Compared with high-concentration electrolyte, the new electrolyte has low cost and low viscosity Moreover, the protection of the metal Li electrode is strengthened, and the dendrite of the Li electrode can be effectively removed, thereby removing possible safety hazards, and at the same time, the safety and electrochemical performance are improved at a high temperature of 60 degrees or more. In addition to scientific research, battery companies also use lithium-sulfur batteries as one of their technical reserves in actively demanding technological breakthroughs. Among listed companies, China Nuclear Titanium Dioxide, Tibet Urban Investment, Jinlu Group, Guoxuan Hi-Tech, and Mengshi Technology have all used lithium-sulfur batteries. The sulfur battery project has been deployed. Although there are still some problems in the process of achieving the ideal energy density of lithium-sulfur batteries, there are some areas of use that have high requirements on the lightness of the battery, such as drones, submarines, and power packs carried by soldiers. Since weight is more important than price or life, lithium-sulfur batteries have begun to be used in practice. The newly developed lithium-sulfur battery by Oxis Energy, a British start-up company, can store nearly twice as much energy per kilogram as the lithium-ion batteries currently used in electric vehicles. However, they do not continue for a long time and will fail after about 100 charge-discharge cycles. Oxis's small experimental plant aims to produce 10,000 to 20,000 batteries per year. It is said that these batteries will be packaged in a thin bag the size of a mobile phone.
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