Analysis and outlook of the safety of lithium-ion batteries

　　According to statistics, in the current electrochemical energy storage market, lithium iron phosphate batteries account for nearly 90% of the mainstream technology route, and is also one of the fastest commercialization process.

　　In the rapid development of the lithium battery industry, from time to time exposed to the relevant accidents, has also caused concern. SES Power has more than 20 years of experience in the research and development of lithium-ion batteries, and has completed many large projects, and has a deep understanding of the safety and future development of lithium-ion batteries, the following we will briefly analyze and discuss this aspect The topic of.

　　A: "lithium battery" energy storage safety concerns still exist

　　Bluetooth headset, electronic cigarettes, cell phones, laptops, delivery robots, two-wheeled electric vehicles, passenger cars, energy storage power plants ...... This is only part of the list of products that apply lithium-ion batteries, but it is enough to outline the modern lifestyle, from which we can also see the weight of lithium batteries in people's lives.

　　Today, on the user side, energy storage 'lithium battery' is a trend. Compared with lead-acid and nickel-hydrogen batteries, lithium batteries are environmentally compatible, less polluting, more cost-effective and have outstanding advantages. This is also an important reason why lithium batteries can be rapidly popularized.

　　Along with the rapid promotion of lithium batteries, some safety hazards have gradually surfaced, especially in the application of larger capacity lithium batteries such as electric vehicles and energy storage power plants.

　　Among them, the biggest impact on the industry when the Beijing energy storage power plant fire and explosion accident, Tesla's energy storage project in Australia's fire.

　　In terms of safety alone, lithium iron phosphate technology in the industry's reputation is quite high. In the field of electrochemical energy storage, lithium iron phosphate is the first choice for large-scale domestic energy storage power plants at this stage.

　　"The olivine structure of lithium iron phosphate is difficult to precipitate oxygen, iron ion oxidation ability is not strong, the P-O bond in the crystal is solid, at 200 to 400 degrees Celsius basically does not decompose, so its thermal stability and structural stability is currently the highest of all cathode materials. In the field of lithium-ion battery energy storage, lithium iron phosphate is a more reliable technology path. sES Power do all the energy storage projects are using lithium iron phosphate "SES Power engineers said that the mainstream lithium battery technology route, lithium iron phosphate safety and stability of high, long cycle life, environmental pollution, high cost advantages are more obvious.

　　B: energy storage safety is a system engineering

　　However, even in the industry is known for the high stability of lithium iron phosphate batteries, internal short-circuit failure can occur, thus causing a fire accident, lithium battery safety we can still rest assured?

　　SESPower believes that, from a professional point of view, the battery quality and body safety is fundamental to the safe operation of energy storage systems. There are many reasons for short circuit inside the battery, for example, the lithium battery itself may have some small defects in the manufacturing process, which will form a short circuit; in the process of use, there is a crash, overcharge or over discharge, which may also lead to a short circuit.

　　SES Power engineers said: "The stability of the material system does not mean that the absolute safety of the battery, lithium iron phosphate nanoscale particles are small, the use of carbon coating process, the binder adhesion of its nanoparticles is poor, so in the battery preparation and charging and discharging cycle, there is the possibility of nanoparticles detached from the internal micro-short circuit caused by the battery; in addition, the battery thermal runaway In addition, when the battery thermal runaway, organic electrolyte combustion also causes certain safety risks. Traditional lithium iron phosphate batteries are liquid electrolyte batteries, battery breakage, the reaction between water and electrolyte will generate highly toxic hydrogen fluoride, after combustion will also emit sulfur dioxide, carbon dioxide, carbon monoxide, etc., the danger of these toxic gases may be more troublesome than the fire, the explosion itself."

　　In addition to strict control of the safety performance of lithium batteries, we should also pay sufficient attention to the layout, operation and maintenance, fire and safety management of the energy storage system, timely processing of the BMS feedback on battery performance monitoring and abnormal status, timely and effective firefighting measures, flammable and explosive gas diffusion prevention after fire, etc., can prevent accidents and prevent serious consequences of accidents.

　　Therefore, we should be rational about the safety of lithium batteries. Even fuel cars have the risk of fire and explosion, electrochemical energy storage as a technology based on the principle of chemical reaction, it is difficult to achieve absolute safety, but this does not necessarily affect the safe use of people. The key is to reduce its unstable and uncontrollable safety risks to a low enough level to control the impact of accidents within an acceptable range for people.

　　C: "Solid state +" or open a new direction of "lithium battery" safety development

　　How to minimize the inherent safety risks of the technology and improve the overall safety level of the lithium battery system? Behind the pain points of the industry, there are often huge business opportunities.

　　SES Power understands that in order to solve the safety problems of traditional lithium iron phosphate batteries, lithium-ion battery companies have done a lot of technical exploration. Among them, some companies have made a major breakthrough in the technical attempt to gradually replace the liquid electrolyte with solid electrolyte.

　　In our opinion, safety is the premise of the development of the lithium battery industry, but also the lifeline. Under the premise of keeping this lifeline, the goal of power lithium battery is to do high energy density; energy storage lithium battery is to achieve long cycle life to achieve cost reduction. Considering these two points, the most promising future technical route in the field of electrochemical energy storage should be solid state technology grafted lithium iron phosphate technology, that is, solid state lithium iron phosphate batteries.

　　In addition to the battery technology itself, lithium battery energy storage system optimization and technology upgrades, is also an important aspect of ensuring safety, in this area, there is still more room for improvement.

　　"Many people think that the battery is the most critical in the energy storage system, but in our opinion, using a good battery is equally critical. On the basis of an objective and rational understanding of the existing mainstream lithium battery technology route, it is more important to do a good job of system testing and control." SES Power engineers said, "large-scale energy storage batteries are often multiple cells in series or parallel together, a cell problem, will inevitably affect other adjacent cells, thus causing accidents. SES Power advocates full-cell testing, but because of the high cost of cell-by-cell testing, the industry is not uniform views on this. "

　　Because the cost control ability of each energy storage enterprise is different, coupled with the current testing and safety standard system in the field of large-scale lithium-ion battery storage is still not sound, the safety of some energy storage battery systems is still difficult to accurately assess how.