[搜狐汽车E电园]When it comes to buying an electric car, most consumers may think of policies such as "preferential", "unlimited line", "unlimited number" and other policies the first time. But if you really want to buy an electric car, and you want to drive comfortably with rest assured, it is not enough to just know the preferential policies. As the core component of electric vehicles, the battery has always been regarded as an important landmark technology for the development of electric vehicles, and it is also a bottleneck restricting the development of electric vehicles. Its performance directly determines the length of the electric vehicle's cruising range, and various electric vehicle spontaneous combustion events It also makes consumers have lingering fears. Therefore, before buying an electric car, you must understand its "heart". Starting from this issue, "E-Diantong" will carry out a series of popularization of basic knowledge about new energy vehicles, hoping to provide help for consumers to buy new energy vehicles in the future.
As electric carsAccumulatorThere are many types, and most of them have been eliminated by the market, so we first have a general understanding of the basic characteristics of these batteries through a table, and then explain the common types of batteries on the market.
Lead-acid batteries are currently widely used batteries. The main advantages are stable voltage and low price; the disadvantages are low specific energy (that is, the electric energy stored per kilogram of batteries), short service life and frequent routine maintenance. Old-fashioned batteries generally have a lifespan of about 2 years, and it is necessary to regularly check the height of the electrolyte and add distilled water. However, with the development of technology, the life of lead-acid batteries has become longer and maintenance is easier. The same is true for lead-acid batteries, which are bulky due to their low energy density. In addition, since its component is sulfuric acid electrolyte, it will pollute the environment relatively seriously after being discarded. And its biggest shortcoming is that the continuous driving ability is relatively low, so it can't meet people's daily needs when applied to pure electric vehicles. From the current point of view, lead-acid batteries are mostly used in low-speed electric vehicles, especially scooters and electric bicycles in the old age.
Lithium iron phosphate battery is a kind of lithium ion battery. Its characteristic is that it does not contain noble metal elements such as cobalt. The raw materials used are phosphorus and iron. These elements are not only rich in resources, but also relatively inexpensive. The safety of lithium iron phosphate batteries is second to none in lithium batteries. It decomposes at 700℃~800℃, but it will not be as violent as the chemical reaction of ternary lithium materials, nor will it release oxygen molecules. It has a good safety. In addition, high charging and discharging efficiency and no pollution to the environment are also its advantages. However, it also has its own shortcomings. Due to the low energy density of the battery, its volume is relatively large; the battery capacity is small, which makes its continued driving ability relatively low; after it is scrapped, its recyclable value is very low; Moreover, due to its poor low-temperature performance, studies have shown that a battery with a capacity of 3500mAh, if it is operated in an environment of -10°C, after less than 100 charge and discharge cycles, the power will decay sharply to 500mAh, which is basically scrapped.
The energy density of the ternary lithium battery used in the Tesla MODEL S is higher than that of the lithium iron phosphate battery, which means that the ternary lithium battery of the same weight has a longer range than the lithium iron phosphate battery. However, when the temperature of the ternary lithium battery itself is 250-350°C, its internal chemical components begin to decompose, so higher requirements are placed on the battery management system, and the cost of the battery is also relatively high. To put it simply, ternary lithium materials are more likely to catch fire than lithium iron phosphate materials. However, as consumers have higher and higher requirements for driving mileage, car companies have attracted more and more attention in recent years. They adopt certain technical and design measures to avoid its defects as much as possible.
Japanese manufacturers choose lithium manganese oxide batteries because their overall performance is relatively balanced, and the technology is not as radical as ternary lithium batteries. Because no precious metal cobalt is required, the cost is much lower and there is no patent restriction. This sounds like Japanese The electrification of economically applicable strategies continues. Lithium manganate is a positive electrode material with low cost, safety and low temperature performance, but its material itself is not very stable and easily decomposes to produce gas, so it is mostly used in combination with other materials to reduce the cost of battery cells, but its cycle life Faster attenuation, prone to bulging, poor high-temperature performance, and relatively short life. It is mainly used for large and medium-sized batteries and power batteries. Its nominal voltage is 3.7V. Although its energy density is not as good as the ternary lithium battery, other comprehensive performance is quite outstanding.
The high cost and safety of lithium batteries are the main reasons why Toyota mainly uses nickel-metal hydride batteries in vehicles. Ni-MH batteries gradually developed after the 1990s. For example, many hybrid vehicles represented by Toyota Prius use such batteries as energy storage components. Its main advantage is that it can adapt to high current discharge, which is more suitable for occasions that require greater power output. Its energy density is larger, which increases the mileage. Ni-MH batteries discharge electricity relatively smoothly and generate less heat. Its main disadvantage is the "memory effect", that is, the capacity of the battery will attenuate during the cycle of charging and discharging, and overcharging or discharging may aggravate the capacity loss of the battery. Therefore, for manufacturers, the NiMH battery control system will actively avoid excessive charging and discharging in settings, such as artificially controlling the battery charging and discharging interval within a certain percentage of the total capacity to reduce the rate of capacity decay.
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