What are the benefits of increasing the battery size from 18650 to 21700?

The 21700 battery fire began with the full use of the 21700 ternary lithium battery in the Tesla Model3, opening a new stage of cylindrical battery capacity improvement. The energy density of the 21700 battery system of the Tesla Model 3 is about 300Wh/kg, which is more than 20% higher than the 18650 battery used in the original Models. The single capacity is increased by 35%, and the system cost is reduced by about 9%. In summary, the scale increase from 18650 to 21700 has the following benefits: 1) When the energy density is appropriately increased, conventional materials can be used, which has stable performance and high cost performance; 2) The multi-pole mechanism can be appropriately designed to reduce Internal resistance; 3) Under the same energy density, graphite with fast charging characteristics can be selected to improve fast charging performance; 4) Appropriately increase the diameter and height to obtain a more effective volume. 5) The single cell capacity is increased, the proportion of auxiliary components is reduced, and the packaging cost is reduced. At present, there are only a few companies in the world that can process 21,700 batteries in batches. In addition to the mass production of the 21700 battery jointly developed by Panasonic and Tesla, Samsung SDI has also demonstrated related 21700 products before, but it is reported that this product has not yet been mass produced. There are 21,700 domestic manufacturers. According to the data, the 21,700 manufacturers are BAK, Diansheng, Yiwei Lithium Energy, Tianpeng Power, Far East Foster, and Manshi Xinneng. The 32131 battery announced by Guoxuan Hi-Tech plans to build a 32131 cylindrical battery processing line in Lujiang, Hefei. There is a strong correlation between unit volume capacity and cycle life, multiplier and safety: for every 10% increase in capacity, the cycle life is reduced by about 20%. For every 10% increase in capacity, the charge-discharge rate is reduced by 30-40%. For every 10% increase in capacity, the temperature rise will increase by about 20%, which is a geometric increase. The higher the energy density, the greater the safety risk. Based on the defects of the 18650 battery, the new energy density required by the policy has increased the cost of materials A. The supply chain of new materials such as NCA and silicon carbon is not mature yet, the cost is high, and the supply is unstable; B. The manufacturing process of new materials is correct High environmental requirements, high investment in fixed assets, high energy consumption; low battery capacity, high technical requirements, and high packaging costs; C. Single cells can adapt to the structure of positive monaural and negative bipolar ears at most, which has a significant impact on energy density ; D. The proportion of high-curvature parts is large, which has a great impact on the cycle life; E. When high energy density and high power charging are required at the same time, the design space reaches the limit. Larger diameter cylindrical lithium batteries will become an inevitable trend. 21 is a better choice than 18, and the 32131 series is also a future direction. However, based on the current technology level and other types of competition, it is difficult to present it in a short time. Explosive rise. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.