18650 lithium battery.Analysis of the advantages and disadvantages of 4 battery technologies

　　The development of electric vehicles is inseparable from battery innovation. Many articles have mentioned the current problems faced by electric vehicles such as battery life and inconvenience of charging.

　　The development of electric vehicles is inseparable from battery innovation. Many articles have mentioned the current problems faced by electric vehicles such as battery life and inconvenience of charging. While we're complaining, is electric vehicle battery technology really stalling? In fact, this is not the case. Major manufacturers are also constantly innovating the battery quality and capacity of electric vehicles. There are currently several types of batteries on the market: lead-acid batteries, lithium iron manganese phosphate batteries, lithium iron phosphate batteries, lithium cobalt oxide batteries and ternary polymer lithium batteries, etc., and the endurance of electric vehicles has also been improved, so , what is the specific situation of current battery technology? Lead-acid battery: Your most common battery Lead-acid battery Lead-acid battery is the most common battery in daily life. Its main advantages are stable voltage and cheap price, but it also has low specific energy, short service life and frequent daily maintenance. question.

　　In China, lead-acid batteries are widely used in domestic low-speed electric vehicles. In addition to the advantages mentioned above, the price of this battery is also lower than other batteries. Lead-acid batteries are available in 2V, 4V, 6V, 8V, 12V and 24V series, with capacities from 200mAh to 3000mAh. So now let’s calculate the discharge time of the lead-acid battery. Here is a formula that can be used for rough calculation: rated capacity × discharge capacity rate × [1 + temperature coefficient × (ambient temperature - 25)] / discharge current = discharge time. Although lead-acid batteries are cheap, their battery life is relatively low.

　　Therefore, it is not very suitable for electric vehicles to be powered entirely by this kind of battery. Lithium iron manganese phosphate battery: BYD's battery technology Lithium iron manganese phosphate battery Recently, BYD Chairman Wang Chuanfu said that BYD's latest lithium iron manganese phosphate battery has broken through the energy density limit of traditional lithium iron phosphate batteries and reached the level of ternary materials. level, and is better than ordinary lithium iron phosphate in terms of cost control, and has been used in BYD electric vehicles, and the battery life has been greatly improved.

　　This kind of battery is used in the BYD Qin electric car. This battery is an improved version of the lithium iron phosphate route, called lithium iron manganese phosphate, which adds manganese element to the material. The energy density of this kind of battery has reached the density of ternary materials. In terms of battery life, it is more durable than the current lithium iron phosphate battery. Since there is currently no exact price information, we will not compare it for the time being.

　　Lithium iron phosphate battery: Another option for electric vehicle batteries, lithium iron phosphate battery is a lithium-ion secondary battery, mainly used as a power battery, and its discharge efficiency is high, and the charge and discharge efficiency can be reduced under multiple discharge conditions. Reaching more than 90%, while lead-acid batteries are about 80%. Among batteries, lithium iron phosphate batteries are also safer than other batteries. The theoretical life span can reach 7 to 8 years, and the actual service life is about 3 to 5 years. The performance-to-price ratio is theoretically more than 4 times that of lead-acid batteries. . Let’s talk about its shortcomings. The price of lithium iron phosphate batteries is higher than other types of batteries. Moreover, the battery capacity is small, the mileage is short, and it basically cannot be recycled and reused after being scrapped, so it has no recyclable value. In summary, the application of lithium iron phosphate batteries in electric vehicles will increase the overall cost, and the batteries cannot be recycled, which will cause waste and consumption of resources. Lithium cobalt oxide battery: Tesla's exclusive battery lithium cobalt oxide battery. The battery of Tesla's electric vehicle uses the NCA series (nickel cobalt aluminum system) 18650 lithium cobalt oxide battery provided by Panasonic. The capacity of a single battery is 3100 mAh. . Tesla has adopted a battery pack strategy. The battery unit of the 85kWh MODELS uses a total of 8,142 18650 lithium batteries. Engineers first evenly distribute these batteries into bricks and slices one by one and finally form a complete battery pack. The battery pack is located on the floor of the vehicle body.

　　Lithium cobalt oxide batteries have stable structure, high capacity ratio, and outstanding comprehensive performance. However, they have poor safety and very high cost. They are mainly used for small and medium-sized batteries with a nominal voltage of 3.7V. When Tesla combines such batteries, safety becomes an issue that needs great attention. Tesla engineers distribute the safety device in the battery pack to each 18650 lithium cobalt oxide battery, and each 18650 Lithium cobalt oxide batteries are equipped with fuses at both ends. When the battery overheats or the current is too high, the fuse will be cut off to prevent abnormal conditions (overheating or excessive current) in one battery from affecting the entire battery pack. So, from this point of view, although lithium cobalt oxide batteries have their own flaws, the safety of Tesla engineers' packaging can basically be ignored. Obviously, such a solution is still very suitable for the development of pure electric vehicles.

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