18650 battery lithium ion 2200mah

　　Is a breakthrough in 18650 battery lithium ion 2200mah technology still far away?

　　It was these three fathers of lithium batteries who led the automobile industry to open the door to new energy electric vehicles. What lithium batteries have brought to the automotive industry is a leapfrog change from fossil fuels to clean energy. From lithium cobalt oxide batteries, lithium manganate batteries, to lithium iron phosphate batteries, ternary lithium batteries, and the latest cutting-edge all-solid-state batteries, the seemingly distant Nobel light has illuminated the power battery industry.

　　The long journey of lithium batteries

　　Throughout the history of 18650 battery lithium ion 2200mah development, three scientists were indispensable for the debut of lithium batteries in the automotive field. The first thing to mention is British scientist Whittingham, who used titanium sulfide as the positive electrode material and metallic lithium as the negative electrode material to create the world's first new lithium-ion battery.

　　Subsequently, American scientist Goodenough and others discovered that manganese spinel is an excellent cathode material with low price, stability and excellent conductivity and lithium conductivity. This material has become the lithium ion that is widely used in production and life. Battery cathode material. After Whittingham invented the rechargeable 18650 battery lithium ion 2200mah, after repeated experimental calculations, Goodenough discovered a material more suitable for the cathode of lithium electronic batteries than the previous titanium sulfide - lithium cobalt oxide with a layered structure.

　　Based on Goodenough's research, Japanese scientist Akira Yoshino discovered more suitable lithium-containing compound anode materials and established the basic framework of modern lithium batteries. The lithium-ion battery designed by Akira Yoshino uses carbon-based materials as the anode and lithium cobalt oxide as the cathode, completely removing metallic lithium in the battery and using lithium-containing compounds to improve safety. In 1991, the lithium-ion battery jointly invented by the two was introduced to the market by Sony, marking the large-scale use of lithium-ion batteries. Depending on the cathode material, this lithium-ion battery is called a "lithium cobalt oxide battery."

　　As the originator of lithium batteries, lithium cobalt oxide batteries are not widely used as power batteries in electric vehicles. It was first used in Tesla Roadster, but due to its low cycle life and safety, it turns out that it is not suitable as a power battery. In order to make up for this shortcoming, Tesla uses what is known as the world's most advanced battery management system to ensure the stability of the battery, but it still cannot get rid of safety issues, especially under severe impact. Stability and cost issues hinder the popularization of lithium cobalt oxide batteries, making them can only be used in daily 3C products.

　　Subsequently, new energy electric vehicles also experienced the era of lithium manganate batteries. This battery was proposed by Japan's AESC and was first used in the Nissan Leaf. It has low price, medium energy density, and average safety performance, making it gradually used by new replaced by technology.

　　The advent of lithium iron phosphate batteries has truly changed the current status of power battery production and use. Compared with the unstable layered structure of lithium cobalt oxide, the space skeleton structure of lithium iron phosphate batteries is more stable, and lithium ions can also move quickly in the channels of the skeleton. At the same time, cheaper raw material prices also make the manufacturing cost of lithium iron phosphate lower.

　　Although lithium iron phosphate batteries are still popular today, it is an indisputable fact that their energy density is low. Therefore, although it has high safety, its low energy density will cause its installed battery to be heavy, and it is currently more used in the field of new energy buses.

　　But since 2016, ternary lithium batteries have begun to enter people's field of vision. Ternary lithium batteries refer to lithium batteries in which the anode material uses three materials, nickel, cobalt and manganese, mixed in a certain proportion. It is divided into different models according to the different material ratios, and therefore has more research and development directions.

　　In terms of energy density, ternary lithium batteries are significantly better than lithium iron phosphate batteries. And because the research is still in the initial stage, there may be more improvements in energy density and even technological breakthroughs. Therefore, ternary lithium batteries have become the choice of more manufacturers. At present, mainstream power battery manufacturers Samsung, LG Chem, CATL, etc. all regard it as one of their main directions of attack.

　　As far as the current domestic market is concerned, although ternary lithium batteries emerged relatively late, as the latest and most popular power battery option, the installed capacity is still growing. Statistics show that from January to August 2019, the domestic installed capacity of power batteries was approximately 38.4GWh, a year-on-year increase of 66%. Among them, the installed capacity of ternary lithium batteries in the first eight months was about 25GWh, a year-on-year increase of 85%; the installed capacity of lithium iron phosphate batteries in new energy buses and special vehicles is relatively large, and is gradually recovering.

　　Is thermal runaway difficult to avoid?

　　But with the rise of electric vehicles and the rapid development of the power battery industry, its problems are emerging faster.

　　The problem of spontaneous combustion bears the brunt of the problem, and thermal runaway has become the most troublesome problem for electric vehicle companies, especially power battery manufacturers. Studies have shown that thermal runaway is one of the main causes of spontaneous combustion in electric vehicles. At the "3rd International Battery Safety Symposium (2019IBSW)", Ouyang Minggao, academician of the Chinese Academy of Sciences and professor of Tsinghua University, said that among the three main causes of thermal runaway, oxygen release from the positive electrode, lithium deposition from the negative electrode, and separator collapse are the three main reasons. .

　　Theoretically speaking, in addition to operational problems such as mechanical collision and overcharging, when the positive electrode and negative electrode are combined, the negative electrode is oxidized, and the positive electrode releases oxygen and reacts violently with the negative electrode to generate heat, which may also lead to thermal runaway. As the performance of the separator continues to increase, the nickel content of the cathode ternary material continues to increase, and the oxygen release temperature continues to decrease, the thermal stability of the cathode material will also decrease.

　　In addition, Ouyang Minggao said that the most important factor affecting the safety of the entire life cycle is lithium precipitation. If there is no lithium precipitation attenuation, the battery safety will not become worse. The same is the case of lithium precipitation. The results caused by the amount of lithium precipitation are obviously different. More lithium precipitation will release a larger amount of heat. The precipitated lithium will directly react violently with the electrolyte, causing a large amount of temperature rise, which will directly induce thermal runaway.

　　An engineer engaged in 18650 battery lithium ion 2200mah research said in an interview with a Beijing News reporter on October 10 that if lithium ions cannot be completely embedded in the cathode material during the precipitation process, some lithium will be deposited on the surface of the cathode material, forming sharp peaks. If the structure further develops, it is easy to pierce the separator, causing an internal short circuit in the battery, and then thermal runaway causing combustion and explosion.

　　Goodenough said in an interview in February 2017 that for lithium-ion batteries in electric vehicles, the problem lies in the flammable electrolyte it uses. In addition to flammability, when metallic lithium and salts are precipitated, After dendrites are formed, it is easy to pierce the separator, causing an internal short circuit and causing combustion; at the same time, the operating voltage of lithium-ion batteries to maintain a long life is very limited.

　　Goodenough believes that the safety issues of lithium-ion batteries are still relatively obvious, and problems such as overcharging can easily cause safety problems in lithium-ion batteries. In addition, managing the battery is also a major expense when using an electric vehicle.

　　The era of all-solid-state batteries is coming

　　Akira Yoshino believes that there will be more progress in the application of lithium batteries in electric vehicles in the future. If lithium batteries are used in new uses and new fields, technological improvements must be made, but there are still many unknown things about lithium batteries.

　　Goodenough’s ongoing all-solid-state battery research is an exploration of unknown things about lithium batteries.

　　All-solid-state batteries replace the original liquid organic electrolyte with a new solid-state electrolyte. Solid electrolytes can not only ensure the original electricity storage performance, but also prevent the occurrence of dendrite problems, and are safer and cheaper. The safety issues currently plaguing lithium batteries will be improved or solved with the emergence of all-solid-state batteries.

　　In terms of solid-state electrolyte selection, Portuguese physicist Braga provided him with a glass with good lithium ion conductivity. Goodenough immediately introduced this glass into the development of all-solid-state batteries.

　　At present, the research and development of all-solid-state batteries has begun to take shape, and relevant results have been displayed in many authoritative publications. The future of lithium-ion batteries and even power batteries is being changed by this 97-year-old scientist.

　　On the foreign side, Japan's New Energy Industrial Technology Comprehensive Development Agency led an investment of 10 billion yen, with 23 Japanese automobile, battery and material companies including Toyota, Honda, Nissan, and Panasonic, as well as 15 academic institutions including Kyoto University and Japan's RIKEN They will jointly participate in research and plan to fully master all-solid-state battery related technologies by 2022.

　　As the future development direction of power batteries, solid-state batteries have achieved a certain degree of technological breakthrough, but the current production and preparation maturity needs to be strengthened. Large-scale and automated production lines need further research and development, and there is still a certain distance before industrial commercialization. distance.

　　Some insiders believe that the current industrial layout has just begun. It is expected that small-scale mass production will be realized after 2020, and large-scale application will take longer.

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