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21700 battery: can the gale of model change blow?

turnover time :2020-06-18 10:19:04
1. The cylindrical battery reform is approaching - the trend of large-scale appears
1.1. 18650 meets the needs of the stage and takes on the historical mission of the primary application stage of power lithium battery 
At the beginning of the development of power lithium battery, Tesla's success in adopting 18650 greatly guided the application of 18650 batteries in the field of electric vehicles. 18650 batteries have highly mature technology and high degree of automation. As a standardized product, the good rate and consistency are guaranteed (the good rate of foreign three star enterprises is more than 98%, and the domestic market is generally more than 90%), and the cost is low (the unit price of 2ah is 5 ~At present, China's mainstream power lithium batteries are mainly 18650 cylinders. For example, foster, bicker power, Zhihang new energy, delonair, Tianpeng power, Yiwei lithium energy and other companies adopt the cylinder 18650 product technology route. However, the 18650 is limited by the volume limit, which is generally between 2.2-3.6ah. Under the current requirements for the continuous improvement of power battery energy pack energy, the space for monomer capacity improvement is limited, and the promotion progress in the future will also slow down.
1.2. Model upgrade: "thickening and lengthening" is the trend
There are two ways to improve the energy density of power lithium battery: one is to improve the mechanism and performance of lithium battery material system, which requires high requirements for material development and matching, and the progress is slow. The second is the production control of model and process.
The target of power lithium battery energy density will force product model transformation and promotion. The current subsidy standard for new energy vehicles before 2020 is positively related to the energy density of power lithium batteries. Therefore, in the case of no great breakthrough in the battery material system, it is an inevitable trend to appropriately increase the "diameter and length" of batteries to obtain higher effective capacity from the product model design. 18650 has initially completed the historical mission of the primary application stage of power lithium batteries In the future, "larger size" lithium battery models will emerge.
In the long term, according to the national guidelines on the energy density of power lithium batteries, China has clearly proposed that the energy density of power battery unit should exceed 300wh / kg in 2020, and the energy density of power battery system should reach 260wh / kg; the energy density of power battery system should reach 350wh / kg in 2025. Taking the 18650 battery of bicker company as an example, the energy density of ternary lithium battery is 215wh / kg, which needs to be increased by 39.5% to reach the target of single battery in 2020. In the general direction, state subsidies promote enterprises' endogenous power to improve battery energy density, and product model improvement is much faster than that of materials (NCA, 811). 21700 batteries that increase energy density by increasing volume will undoubtedly become the focus of enterprises. The continuous improvement of power lithium battery energy density is bound to continue to promote the change of Li ion battery model.
2. "Thickened and lengthened" 21700 battery rolled 18650 in terms of performance and cost
2.1. Battery energy density increased by more than 20% 
The energy density of 21700 battery is better than 18650 battery. According to the information disclosed by Tesla, under the existing conditions, the energy density of its 21700 battery system is about 300wh / kg, which is about 20% higher than that of its original 18650 battery system (250wh / kg). At the same time, according to the test data of Panasonic's power lithium battery, the volume energy density of its 21700 battery is much higher than that of 18650 battery. The increase of energy density of single cell is much higher than that of group by 20%. 
2.2. The cost of battery system will be reduced by about 9%
The cost of 21700 decreased by about 9%. According to the battery price information disclosed by Tesla, it is estimated that the price of 21700 power lithium battery system is $170 / wh, which is about 8.1% lower than that of 18650, which is 185 US dollars / wh. The cost of 18650 system is about 171 US dollars / wh. After using 21700, the system cost can be reduced by about 9%, reaching 155 US dollars / wh. 
With the increase of monomer capacity, the number of accessories required for pack decreases in the same proportion, which leads to the decrease of pack cost. After switching from 18650 model to 21700 model, the capacity of single battery can reach 3 ~ 4.8ah, which is greatly increased by 35%. The number of batteries required under the same energy can be reduced by about 1 / 3. Tesla models electric vehicles use 7104 18650 batteries in series and parallel to form a battery pack. It is expected that the number of battery cells in the new Model3 will be greatly reduced. While reducing the difficulty of system management, the number of metal structure parts and conductive connectors used in the battery pack will be reduced in the same proportion. Tesla's pack cost accounts for about 24% of the total system cost. It is estimated that the cost of battery pack will decrease significantly.
The contribution of lightweight. Samsung mentioned that after switching to the new 21700 battery, the system can reduce the components and weight by 10% compared with the current battery. As a result, the weight of the battery pack will be further reduced, and the energy density of the whole vehicle will be partially improved.
2.3. Why 21700?
21700 is not superior to other models in absolute performance, but the result of comprehensive balance of physical and economic properties. The increase of the physical size of the cylindrical cell not only improves the energy density, but also negatively affects the performance such as cycle life and rate. It is estimated that every 10% increase in capacity will reduce the cycle life by about 20%; the charge discharge rate will be reduced by 30 ~ 40%; at the same time, the temperature rise of the cell will be about 20%. If the size continues to increase, the security risk will be increased.
In terms of economy, the cylinder cell is improved in 18650 mature process, and the cost is controlled on the premise of ensuring the yield and consistency. If the size is too large, the safety and adaptability will be reduced, leading to the larger cylinder 26500, 32650 and other reasons can not occupy the mainstream market on a large scale.
The general production change cost of production line is low. First of all, from the perspective of domestic lithium battery manufacturers, it is now in a large scale

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