The research team of Li Mingtao from the School of Chemical Engineering of Xi’an Jiaotong University has made a breakthrough in the application of lithium-sulfur batteries by designing and developing a cathode material with a two-dimensional graphene protective layer. This cathode material has a long cycle life.

2d intercalation G-C3N4/graphene sandwich forms a multilayer shark net between the positive and negative electrodes of the battery. It can not only block the movement of polysulfides between the positive and negative electrodes through physical and chemical uses, but also accelerate the diffusion of lithium ions, thereby greatly increasing the cycle life of the battery.

In my country, the development of lithium-sulfur batteries is relatively late, and it is still in the laboratory research and development stage, with few practical applications. The shuttle effect caused by the dissolution of the intermediate product lithium sulfide during the charging and discharging process of lithium sulphur batteries is considered to be a key factor limiting its practical application.

The former vice president of Qinghai Dr. Li Technician Technology once said that the polysulfide dissolved space shuttle is the most important and difficult lithium-sulfur battery problem, and related improvement work is still in the initial stage, but he is optimistic that lithium-sulfur batteries can be used as secondary batteries. With high energy density, it has broad development prospects.

Compared with the current mainstream ternary NCM, the theoretical specific energy of the sulfur cathode battery is as high as 2600Wh/kg, which is more than ten times that of the currently widely used lithium battery. In addition, sulfur reserves are abundant and inexpensive, which may help reduce the price of electric vehicles powered by lithium batteries.

In 2016, the National Development and Reform Commission proposed a breakthrough in lithium-sulfur battery technology with an energy density of 300Wh/kg in the “Energy Technology Revolution and Innovation Action Plan (2016-2030)”.

In contrast, according to the Action Measures to Promote the Development of the Automotive Power Industry and the Medium and Long-term Development Plan for the Automotive Industry released in 2017, the single-machine ratio can reach more than 300Wh/kg by 2020, and the single-machine ratio can reach 500Wh by 2025. /kg above. The theoretical energy density of lithium-sulfur batteries is greater than 500Wh/kg, so it is considered to be the development direction of the next generation of power lithium battery systems after lithium batteries.

In order to solve the practical problems in the application of lithium-sulfur batteries, including the Qian Hanlin team of the University of Science and Technology of China, the Wang Haihui team of South China University of Technology, the Qingdao Energy and Energy Storage Materials Advanced Technology Research Team of the Chinese Academy of Sciences, our Xiamen University Chemical Nan Fengzheng team and Shanghai Jiaotong University Wang’s research team has made breakthrough progress.

In October 2018, Professor Wang, Yitaiqian and various University of Science and Technology of China (University of Science and Technology) found that the dynamic performance of the p-band center position of valence electrons relative to the Fermi level is an important factor in li-S batteries Interface electron transfer reaction. The researchers found that the cobalt-based sulfur-carrying material with the smallest positive polarization and the best rate performance has a capacity of 417.3 Mahg-1 even at 40.0°C, which corresponds to the current highest power density of 137.3 kwkg-1. The research results were published in “Joule”, an international journal of excellent energy materials.

Lithium-sulfur battery is a metal lithium battery positive battery system with sulfur as the positive electrode. To solve the safety problem of Li dendrites produced in the metal positive electrode on Shanghai Jiaotong University, Wang’s team prepared a new type of lithium battery electrolyte solution (using double Lithium fluorosulfonimide is dissolved in triethyl phosphate and high flash point fluoroether to obtain saturated electrolyte). Compared with the high-concentration electrolyte, the new electrolyte has low cost and low viscosity, enhances the protection of the metal Li electrode, can effectively remove the dendrites of the Li electrode, and eliminates potential safety hazards. At the same time, safety and electrochemical performance are improved under high temperature conditions above 60°C.

In addition to scientific research, battery companies also use lithium-sulfur batteries as one of their technical reserves, actively demanding technological breakthroughs. Among these listed companies, China Nuclear Titanium Dioxide, Tibet Urban Investment, Jinlu Group, Guoxun High-tech, Dream Vision Technology and other companies have deployed lithium-sulfur battery projects.

Although lithium-sulfur batteries have some problems in the process of achieving the ideal energy density, there are higher requirements for the thinness of some battery applications, such as unmanned aerial vehicles (UAV), submarines, and soldier carrying bags. For power supplies for other purposes, since weight is more important than price or life, lithium-sulfur batteries have begun to be put into practical use. The new lithium-sulfur battery developed by the British start-up company Oxis Energy can store almost twice the energy per kilogram of lithium batteries currently used in electric vehicles. However, they cannot last long and will fail after about 100 charge-discharge cycles. The goal of Oxis’s small pilot plant is to produce 10,000 to 20,000 batteries per year. It is said that the battery is packed in a thin bag the size of a mobile phone. Why do we need to promote the regeneration and recycling of power lithium batteries as soon as possible? Although my country’s lithium resources rank fourth in the world, due to the poor grade of lithium ore, the difficulty of purification, and the high cost, a large amount of lithium ore is imported every year, and the degree of foreign dependence exceeds 85%. In addition, Chinese demand has also driven the price of battery-grade lithium carbonate soaring. In recent years, the price has risen nearly three times, which has greatly increased the procurement costs of Chinese lithium battery manufacturers. On the one hand, the elimination of power lithium batteries is a precious “urban mine”. The metal content is much higher than that of ore, lithium, cobalt, nickel and other precious metals. Recycling and recycling can improve resource utilization efficiency, reduce imports, and reduce external Depend on and protect the security of the national resource strategy. Zhang Tianren said that, on the other hand, from the perspective of preventing pollution and protecting the environment, if discarded lithium batteries are not properly disposed of, they will also cause great harm to the ecological environment.

In order to better promote the recovery and reuse of lithium batteries for new energy vehicles, protect the ecological environment, and ensure the safety of national strategic resources, there are three important issues: the imperfect recycling system, the immature regeneration technology, and the weak incentive mechanism. Several aspects have put forward suggestions to promote the healthy and sustainable development of my country’s new energy automobile industry.

Speeding up the development of standards and unifying management standards are the basis for carrying out related work. He suggested that relevant departments speed up the formulation of management standards, technical standards and evaluation standards for the recycling and reuse of used batteries. Encourage regions with industrial advantages to formulate new energy lithium battery supervision, recovery, and recycling plans and implementation measures, and through preliminary pilots, explore national implementation measures that are more in line with industry realities and are more operable.