Detailed explanation: Advantages and flaws of the 21700 battery cell
21700 battery development
Looking back on the development path of 21700, it can be summarized with the word "rapid". At the investor meeting on January 4 this year, Tesla announced the mass production of a new 21700 battery jointly developed with Panasonic. Tesla said that this battery will be produced at the Gigafactory super battery factory and emphasized that this is currently available. The battery with the highest energy density and the lowest cost among mass-produced batteries. Tesla CEO Musk said that the power density of the 21700 battery is currently the highest in the world, and the price will be more approachable.
At the 2017 North American International Auto Show, Samsung SDI also tit-for-tat displayed its new battery 21700, which claims to have "the same specifications". Samsung SDI claims that the energy density of the new battery is twice that of the battery in production at the time, and the battery pack composed of the new battery can charge the battery capacity of 370 miles (600 kilometers) in 20 minutes.
So far, the news of Samsung SDI has not mass-produced 21700.
Advantages of 21700 battery
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 the 250Wh / kg of its original 18650 battery system. From the test data of Panasonic's power lithium battery cells, the volume energy density of its 21700 battery is much higher than that of the 18650 battery cell. The increase in energy density of individual cells is much higher than the 20% increase after grouping.
Battery system cost decreased by about 9%
According to the battery price information disclosed by Tesla, the lithium battery big data is expected to sell the 21700 power lithium battery system for 170 US dollars / KWh, compared with the 18650 price of 185 US dollars / KWh, the price drop can reach about 8.1%. The cost of the 18650 system is about US $ 171 / KWh. After switching to 21700, the system cost can be reduced by about 9% to US $ 155 / KWh.
After the unit capacity is increased, the number of parts required for PACK is reduced by the same proportion, which leads to a decrease in PACK costs. After switching from the 18650 model to the 21700 model, the battery cell capacity can reach 3 ~ 4.8Ah, a substantial increase of 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 Series and parallel battery packs, on the new Models 3, after using 21700, the number of battery cells 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 by the same proportion. Tesla's Pack cost accounts for about 24% of the total system cost. It is expected that the battery pack cost reduction will be considerable.
Samsung mentioned that after switching to the new 21700 battery, the system can reduce the components and weight by 10% compared to the current battery, thereby further reducing the weight of the battery pack, and the energy density of the vehicle will be partially improved.
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