SMM Network News: in the energy storage and power of the two main application areas of lithium-ion batteries are in the early stage of development, safety has undoubtedly become the most important problem to be solved.
Power and energy storage fire accidents sound safety alarm
According to the China Association of Automobile Industries, from January to April 2019, China's new energy vehicles produced 367600 vehicles and sold 360000 vehicles, up 58.47 percent and 59.79 percent respectively over the same period last year. Among them, the production and sales of pure electric vehicles were 286000 and 278000 respectively, an increase of 66.1 per cent and 65.2 per cent respectively over the same period last year. While the production and sales of new energy vehicles represented by pure electric vehicles have soared, more and more new energy vehicles have caught fire and exploded in the newspapers. Among them, there is no lack of Tesla, Weilai, BYD, Mercedes-Benz, BAIC new energy and other well-known electric vehicle brands. Although the board responsible for the electric vehicle fire accident can not be hit alone on the power battery, the safety of the power battery is receiving more and more attention.
Another application of battery electrochemical energy storage field, in recent years also ushered in a large-scale development. In 2018, the installed capacity of electrochemical energy storage in China has exceeded "GW", and the large-scale benefit of electrochemical energy storage will be realized in the next 2 to 3 years. However, a number of fire accidents at energy storage power stations in South Korea in 2018 have sounded the alarm for the developing electrochemical energy storage in China. According to Yu Zhenhua, executive vice chairman of Zhongguancun Energy Storage Industry Technology Union, due to the frequent occurrence of previous safety accidents, many domestic electrochemical energy storage projects have made slow progress, and some projects have even suspended fire safety rectification. Similarly, the cause of fire safety accidents in energy storage power stations is not all from batteries, but batteries are undoubtedly one of the important drivers of fire accidents.
Starting from the material, solving the short board of battery safety
Whether it is the battery, or the new energy vehicle or the energy storage industry, people in the industry believe that the safety problems in the field of battery applications are not just the problems of the cell itself, but also include the design of the cell chemical system. Consistency in the production process, cell life cycle management, to supporting BMS design and implementation, cell, battery package connection structure design, and even including the application of fire safety measures and so on a series of problems. In a word, security is a systematic project, and any link in the application may become the deficiency of system security.
At the level of chemical system design of the cell, Chen Liwei, a professor at Shanghai Jiaotong University, has revealed that his team is working on a highly safe ternary positive additive material that enables ternary soft package batteries after acupuncture tests. It can still discharge normally, which ensures the safety of the battery. Similar material doping experiments are also being carried out in the laboratories of a number of scientific institutions and enterprises, in order to find materials that can ensure the high safety of batteries, so that high energy density batteries can also have high safety.
German Nano, a domestic manufacturer of positive materials, has said that the company's nano-lithium iron phosphate material combined with carbon nanotube electro-hydraulic conductivity, so that the performance of the material, especially safety, has been greatly improved, and has achieved batch supply. A study by American company Celgard, which is engaged in diaphragm research and development and production, shows that adding ceramic coating to the negative electrode can inhibit the heat transmission inside the negative electrode, thereby reducing the generation of heat out of control and effectively ensuring the safety of the battery. In the aspect of electrolyte manufacturing, adding flame retardants to existing electrolytes or developing more safe electrolyte materials can also reduce the risk of cell safety accidents.
New battery design, power generation battery safety
The battery system with new materials can also become an effective way to improve the safety of batteries.
At the "Energy Storage International Summit and Exhibition 2019," which ended a few days ago, Amway Energy, a unit of Chaowei Group, displayed the recently put into production of sodium-nickel battery products. It is understood that the battery is mainly composed of solid nickel, sodium chloride particles and ceramic tubes, the reaction temperature is 260 to 300 degrees Celsius, there is no flammable and explosive material in the whole process. Even if the ceramic tube breaks, the monomer sodium formed by the reaction will be the first to bind to the molten sodium tetrachloroaluminate and will not come into contact with air. Therefore, the safety of the battery is excellent. Compared with lithium-ion batteries, the low cost and high performance of this sodium-nickel battery makes it more suitable for large-scale energy storage.
Similar to Amway's sodium-nickel battery, Liaoning Xingkong sodium battery also showed off the latest sodium battery products at the exhibition. According to the person in charge of the Star Sodium booth, the battery's positive and negative electrode materials, diaphragm and electrolyte are self-developed high-safety materials. After the production of the soft coating process, the battery will not lose control at 90 degrees Celsius. After the puncture, extrusion and high-altitude falling tests of the standard lithium-ion battery, the battery will not catch fire and explode.
In recent years, sodium ion battery is gradually coming into people's field of vision with high safety and low cost, and solid state battery is also one of the most effective and vocal ways to solve the safety problem of lithium ion battery. In July 2018, the 08116337-CO-36Ah solid soft package ternary material power lithium-ion battery developed and produced by Jiawei passed the compulsory inspection of the National Motor vehicle quality Supervision and Inspection Center. Its supporting vehicles also appeared in the 313th batch of "Road Motor vehicle Manufacturing Enterprises and products notice" in October of that year.
Power generation of the system to reduce the hidden danger of safety accidents
The industry has always stressed that "safety is a systematic project", which refers not only to battery systems, but also to integrated systems such as new energy vehicles and energy storage power stations. In recent years, the research and development and application of solving security problems from the system level is not uncommon.
Whether in the new energy vehicle battery box, or in the energy storage box, cabinet, the battery is usually in a relatively closed space, which will have a negative impact on the heat dissipation of the battery, once the heat accumulates, it is likely to be a safety risk due to local overheating. At the above exhibition, Shandong Boyi New Energy demonstrated a new battery package thermal management technology for battery module heat dissipation. The core of the technology is superconducting thermal material, which quickly exports the heat inside the battery module, so as to ensure that the whole module maintains a low temperature.
Tesla Model 3 also adopted a different safety design, the battery box removed the roof, in the event of a fire inside the box, because there is no pressure, thereby reducing the damage caused by the explosion. In addition, the line welded joints are all facing the ground, in case of flammable gas injection, you can also ensure that it is not sprayed to both sides and above.
Once there is a fire, timely fire fighting is also very necessary, which requires battery applications, especially in the field of energy storage, there should be corresponding flame retardant and fire protection measures. According to Xiaokang, a senior scientist at the Chinese Academy of Electrical Sciences, his team is working on flame retardant materials for energy storage PACK boxes to ensure that other boxes nearby will not be endangered in the event of a fire.
Yantai is a new energy independently developed "lithium-ion battery thermal out-of-control model" and automatic fire extinguishing technology, through the installation of a number of sensors in and around the box to judge the battery box thermal out of control situation, in the early stage of thermal out of control alarm, to prevent trouble. It is worth noting that even the early flammable gas leakage, the system can also be detected and alarm, effectively ensuring the safety of the battery system.
Although the safety problem has sounded the alarm for the development of new energy vehicles and energy storage industry, it is better to prevent micro-du gradually than to stop moving forward. With the continuous improvement and introduction of related safety problem solving technologies and methods, The safety risk of battery applications will also be reduced.