With the rapid development of new energy vehicles in recent years, lithium batteries have also become popular. Power batteries have always been an important field of new energy vehicles. Whoever masters power batteries will master new energy vehicles. Among the power batteries, the most eye-catching is undoubtedly the lithium-ion battery.
The energy density of lithium-ion batteries is very high, and its capacity is 1.5 to 2 times that of nickel-hydrogen batteries of the same weight, and it has a very low self-discharge rate. In addition, lithium-ion batteries have almost no "memory effect" and do not contain toxic substances. These advantages of lithium-ion batteries make it widely used in the field of new energy vehicles.
Nowadays, the more widely used cylindrical lithium-ion batteries are 18650 batteries and 21700 batteries.
18650 battery:
18650 batteries originally referred to nickel-metal hydride batteries and lithium-ion batteries. As nickel-metal hydride batteries are now less used, they now refer to lithium-ion batteries. 18650 is the originator of lithium-ion batteries-a standard lithium-ion battery model set by SONY in Japan in order to save costs, where 18 means a diameter of 18mm, 65 means a length of 65mm, and 0 means a cylindrical battery. Common 18650 batteries include ternary lithium-ion batteries and lithium iron phosphate batteries.
Speaking of 18650 batteries, Tesla has to be mentioned. When Tesla is developing electric car batteries, it has tested many types of batteries, but in the end it focused on 18650 batteries and used 18650 batteries as new energy electric car batteries. Technical route. It can be said that the reason why Tesla is able to have performance that is not inferior to traditional fuel vehicles, in addition to electric motor technology, also benefits from Tesla's advanced battery technology. So why did Tesla choose the 18650 battery as its source of power?
advantage
Process maturity and high consistency
Before entering the field of new energy vehicles, 18650 batteries have been widely used in electronic products. They are the earliest, most mature and most stable lithium-ion batteries. After years of experience, Japanese manufacturers have accumulated 18650 batteries in consumer products. Advanced technology is extremely well applied in the field of vehicle batteries. Panasonic is one of the world's largest battery technology and scale companies. Compared with other manufacturers, it has the fewest product defects and larger scale, and it is also easy to select batteries with good consistency.
In contrast, other batteries, such as laminated lithium-ion batteries, are far from mature enough. Many products cannot even be unified in size and size, and the production technology of battery manufacturers cannot meet the conditions. In general, the consistency of the battery does not reach the level of the 18650 battery. If the consistency of the battery fails to meet the requirements, the management of a large number of battery strings and battery packs formed in parallel will not allow the performance of each battery to be better played, and 18650 batteries can solve this problem well.
High safety performance
The 18650 lithium battery has high safety performance, non-explosive, non-combustible; non-toxic, non-polluting, and has passed RoHS trademark certification; and has good high temperature resistance, and the discharge efficiency is 100% at 65 degrees.
The 18650 battery is generally packaged in a steel shell. In extreme situations such as a car collision, it can reduce the occurrence of safety accidents as much as possible, and the safety is higher. In addition, the size of each battery cell of the 18650 is small, and the energy of each cell can be controlled in a smaller range. Compared with the use of large-size battery cells, even if a unit of the battery pack fails, it can be reduced The impact of the failure.
High energy density
The capacity of 18650 lithium battery is generally between 1200mah and 3600mah, while the general battery capacity is only about 800mah. If combined into a 18650 lithium battery pack, the 18650 lithium battery pack can exceed 5000mah. Its capacity is 1.5 to 2 times that of a nickel-hydrogen battery of the same weight, and it has a very low self-discharge rate. The energy density of the 18650 battery cell can currently reach the level of 250Wh/kg, which meets the requirements of Tesla's high cruising range.
Low cost and high cost performance
The 18650 lithium battery has a long service life, and the cycle life can reach more than 500 times in normal use, which is more than twice that of ordinary batteries. The 18650 product has a high degree of technological maturity. The structural design, manufacturing technology, and manufacturing equipment, as well as the derived 18650 module technology are all mature, all of which reduce its operating and maintenance costs.
The 18650 battery, which is currently widely used, has a history of development for many years. Although the technology is relatively mature compared to other types of batteries, it still faces problems such as high heat production, complex grouping, and inability to achieve fast charging. In this context, 21700 cylindrical ternary batteries came into being.
On January 4, 2017, Tesla announced the start of mass production of the new 21700 battery jointly developed by Tesla and Panasonic, and emphasized that this is the battery with the highest energy density and the lowest cost among the batteries currently available for mass production.
21700 battery:
The battery 21700 is a cylindrical battery model, specifically: 21-refers to the cylindrical battery with an outer diameter of 21mm; 700-refers to the cylindrical battery with a height of 70.0mm.
This is a new model developed to meet the requirements of electric vehicles for longer driving mileage and to improve the effective utilization of vehicle battery space. Compared with the common 18650 cylindrical lithium battery, the capacity of 21700 can be more than 35% higher than that of the same material.
The new 21700 has four significant advantages:
(1) The battery cell capacity is increased by 35%. Take the 21700 battery produced by Tesla as an example. After switching from the 18650 model to the 21700 model, the battery cell capacity can reach 3 to 4.8 Ah, a significant increase of 35%.
(2) The energy density of the battery system is increased by about 20%. According to the data disclosed by Tesla, the energy density of the 18650 battery system used in the early days was about 250Wh/kg. Later, the energy density of the 21700 battery system produced by it was about 300Wh/kg. The volumetric energy density of the 21700 battery was higher than the original 18650. Nearly 20%.
(3) The cost of the system is expected to drop by about 9%. From the analysis of battery price information disclosed by Tesla, the power lithium battery system of the 21700 battery is priced at $170/Wh, and the price of the 18650 battery system is $185/Wh. After using 21700 batteries on Model 3, the cost of the battery system alone can be reduced by about 9%.
(4) The weight of the system is expected to drop by about 10%. The overall volume of 21700 is greater than 18650. As the monomer capacity increases, the energy density of the monomer is higher, so the number of battery monomers required under the same energy can be reduced by about 1/3, which will reduce the difficulty of system management and reduce the number of batteries. The number of metal structural parts and electrical accessories used in the bag further reduces the weight of the battery. After Samsung SDI switched to a new set of 21700 batteries, it was found that the weight of the system was reduced by 10% compared to the current battery.
Maintaining the high reliability and stable performance of the 18650 battery, the performance of the 21700 battery is greatly improved compared to the 18650 in all aspects. In addition, compared with other battery models, the 21700 is similar to the more mature 18650 battery in terms of battery raw material selection, production process and technical process. Therefore, most of the production lines of 18650 and 21700 are compatible, and some companies have a safer way to make a fuss on the production line and move the production line closer to the compatibility of 21700 and 18650.
The pursuit of high specific energy for power batteries has become an irreversible trend, and many battery companies have begun to turn their attention to the layout of 21700 batteries. The production lines of some companies are imported from abroad, but the assembly is done by themselves, so you can invest less cost to realize the conversion from 18650 to 21700.
At present, domestic manufacturers represent Lishen Battery, BAK Battery, Yiwei Lithium Energy, Mengshi Technology and other companies. In addition, Tianchen New Energy, Tianpeng Power, Chuangming New Energy, Smart Energy, Zhihang New Energy, Hengdian Dongci, Haistar, Anhui Taineng and other battery companies have also deployed 21700 batteries.
Lishen battery
In 2015, Hua Ting Power began to supply JAC with cylindrical 18650 ternary batteries on a large scale. On July 20, 2017, it was announced that its 21700 production line was officially put into production. This is the first domestic production line customized for 21700 products.
According to reports, Tianjin Lishen’s subsidiary, Suzhou Lishen 21700, has a daily shipment of more than 400,000 batteries and a monthly output of more than 10 million batteries. With the continuous improvement of production capacity and through rate, the monthly output of 20-25 million pieces per month can be achieved by the end of the year, and the annual output is expected to be 160 million pieces.
BAK battery
BAK Battery has demonstrated 18650-3. 0Ah high-energy core this year, and its 18650 battery cell energy density has reached the international leading level. BAK 18650-3. 0Ah high-energy core products adopt advanced fully automatic production lines and have been mass-produced in BAK Industrial Park in Zhongmou, Zhengzhou, with a production capacity of 6.5GWh and a daily output of 2 million pieces. They have been put into market application.
According to Luo Zhaojun, chief engineer of BAK Battery, BAK Battery’s 21700 cells have completed multiple offline internal tests, and 4.8Ah21700 cylindrical batteries have begun small batch samples. It is expected that mass shipments will be realized in the fourth quarter of 2018. It is planned to launch 5.0Ah products by the end of the year.
Yiwei Lithium Energy
On June 28, 2017, Yiwei Lithium Energy "Hubei Jinquan Second District Commissioning Ceremony and Third District Launching Ceremony" was held in Hubei Jinquan. Yiwei's lithium-energy cylindrical ternary battery production line was officially completed and put into production, which marked that my country's cylindrical ternary battery officially entered the 21700 era. Regarding the future development plan of the 21700 battery, He Wei, director of the Lithium Energy Technology Department of Yiwei, said that Yiwei Lithium plans to increase the energy density of the 21700 battery to 260Wh/kg in the next three years, and it is expected to come out in 2019.
Lion Technology
After the first 18650 production line was successfully completed in the Zhaoan production base, Mengshi Technology invested in R&D to develop the 21700 cylindrical battery cell. On August 16, 2017, the construction of the 21700 battery production line with a 2GW capacity of Mengshi Technology began, and it is expected to reach full production in the first half of 2019.
Tianchen New Energy
The company's 18650 batteries are mainly used in two areas of "one high and one low". "High" refers to high-end passenger cars similar to Tesla; "low" refers to mini-cars and logistics vehicles with a value of less than 100,000 yuan. It is reported that its 21700 battery has been in trial production and is expected to be officially put into production in 2018, with a single battery capacity of 4.5Ah.
Tianpeng Energy
The company's total production capacity is expected to reach about 6GWh in 2018. The equipment configured in the No. 2 production base is compatible with the production of Model 21700 products, which can switch between Model 18650 and Model 21700, and the energy density of the product can reach 200-240Wh/Kg.
Chuangming New Energy
One of the earliest three-yuan 18650 battery manufacturers in China to install vehicles in batches. The power battery has many cooperative car companies with superior qualifications. According to previous reports, the company has already started the research and development of 21700 products in the early stage, and its 21700 production line is in the testing phase.
Smart energy
Sanyuan 18650 lithium battery has a production capacity of more than 3GWh. In 2017, the focus will be on the layout of 21700 batteries. Six new automated production lines of 21700-5Ah will be built, and the total planned scale of 21700 will reach 7GW. At present, it has formed a supporting cooperative relationship with mainstream domestic new energy smart car companies, and continues to expand strategic customers, emerging Internet car companies, etc.
Zhihang New Energy
The existing 18650 battery cell production line has been upgraded, and 21700 lithium batteries have been developed and relevant production conditions are available. The 21700 lithium batteries will be launched in due course according to the actual situation of the market.
Hengdian Toci
Since 2016, it has been involved in the power battery industry. The power batteries produced are mainly 18650 type. It is planned to start the layout of 21700 batteries in the second quarter of 2018.
Seastar
The overall production capacity has reached 2.6GWh, and the products involve three routes: cylindrical, square and soft. The company plans to invest in the construction of two power battery production lines in 2018, including a 21700-type power battery production line. It is estimated that by 2019, Haistar's total production capacity will reach 4GWh.
Anhui Taineng
In 2017, it announced an investment of 5 billion yuan to plan construction and production of 21700 power batteries.
Mainstream battery companies such as Lishen Battery and Yiwei Lithium Energy stated that they will not be too aggressive in increasing the energy density of 21700 batteries, but they are also developing new products to increase specific energy.
Industry expert Su Jinran pointed out that whether the 21700 battery can be marketed quickly to achieve industrial production depends on whether the battery company has enough experience in R&D technology, manufacturing process and terminal applications, rather than saying that it can be done as long as the last 21700 production line of. It remains to be seen how the 18650 battery and 21700 battery will develop in the future.
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