As long as people who have a certain understanding of new energy vehicles today know that the biggest barrier to electric vehicle technology development currently lies in the difficulty of making breakthroughs in battery technology... Due to the high manufacturing cost of batteries, most of the electric vehicles' mileage cannot be greatly improved at a limited cost, making their application range greatly limited. Compared with traditional fuel vehicles, their competitiveness is also greatly reduced. Do not make great efforts to subsidize new energy vehicles. Therefore, the importance of batteries for new energy vehicles is almost equivalent to the importance of engines and gearboxes for traditional fuel vehicles. This time, we will be as easy as possible to understand the current car battery. What are we concerned about when discussing the batteries of new energy vehicles? If you are in a restricted first-tier city, I think you will consider purchasing a new energy vehicle or even a pure electric vehicle. Because the cost per kilometer of an electric vehicle is generally about one-tenth that of an equivalent petrol vehicle, power consumption will not be your primary consideration. And most electric vehicles have a powerful acceleration capability, and they do not need to run fast in urban commuting, so power and torque are not the most important. However, most people buy cars in addition to daily commuting, and sometimes they have to run some long-distance journeys. At this time, the mileage of a single charge becomes a very important constraint. If you want to have a cruising range that is long enough, you must give priority to batteries that have as large a capacity as possible. However, the batteries themselves are bulky, and the space for batteries on the vehicles is limited. So for the car battery, the most important performance parameter is undoubtedly the energy density. In addition, the power, voltage, efficiency, service life, etc. that can withstand the charge and discharge are also very important considerations. Energy density can be measured in two ways: one is volume energy density (Wh/L), and the other is mass energy density (Wh/kg). In addition, because the battery used by an electric vehicle is often a battery pack or a battery pack that is composed of a plurality of cells in series and in parallel, and is managed centrally through a battery management system (BMS), the conversion efficiency is divided. Therefore, the energy density of the single cells and the energy density of the entire battery system will be separately discussed. In order to meet the needs of the general arrangement, most depots will choose to purchase the supplier's batteries and design and package their own battery systems. How many kinds of batteries? I believe many people have heard of Tesla's lithium batteries, or BYD's iron batteries. In fact, they are just one of these new energy vehicle batteries. Battery classification can be said to be various, from a structural point of view, the batteries used in new energy vehicles, can be divided into three basic: Prismatic battery (Prismatic), soft pack battery (Pouch) and cylindrical battery (Cylindrical). However, if the composition of the materials is divided, the classification of the batteries is more complicated. Generally, the classification of the batteries is based on positive and negative materials, including lead-acid batteries, nickel-hydrogen batteries, lithium batteries, and even zinc-air batteries and super capacitors. And other less mainstream batteries. Among them, the lead-acid battery is actually a lot of batteries that are used in traditional automobiles. Because the cost is relatively low, it will be applied to some low-speed electric vehicles, but it is outdated. At present, the most common are nickel-metal hydride batteries and lithium batteries. Nickel-metal hydride batteries are nickel metal hydride batteries, a square and cylindrical, because the anode uses nickel hydride, the anode uses hydrogen storage alloy, and the name of potassium hydroxide electrolyte. It is generally used in conventional hybrid vehicles. The nickel-hydrogen battery is currently used by Toyota's Camry Twin Engines and Corolla/Ralink Twin Engines. The lithium battery is now the mainstream of new energy vehicles. In fact, it should be called a lithium-ion battery. The material used for the positive electrode is not pure lithium but a compound of lithium, which has a great influence on the energy density of the cell. The anode materials are mostly carbon materials that can be intercalated with lithium ions. Currently, most of them are graphite, and silicon carbide materials may be used in the future. The electrolyte uses organics. It can also be divided into square and cylindrical packages. The difference in structure and raw material composition of the battery core has a relatively large influence on the energy density of the battery core. The main force of new energy vehicles - lithium batteries At one time, lithium batteries were mostly composed of binary compounds such as lithium manganate, lithium phosphate, and lithium cobaltate. Now the mainstream has developed to use ternary lithium compounds, also known as ternary lithium batteries. Sanyo, Panasonic, Sony, LG, Samsung and other mainstream cell manufacturers in the world have already launched their own ternary lithium batteries. Current mainstream ternary lithium batteries include lithium iron phosphate (LFP), nickel cobalt manganese (NCM), and nickel cobalt aluminum (NCA) types. Among the iron batteries advertised by BYD, lithium iron phosphate (LFP) batteries are included. Although its safety is relatively high and its price is low, the energy density is the lowest among three-cell lithium batteries, and is only about 135 Wh/kg. Mostly used in passenger cars, basically no future development. At present, the major hotspots of major manufacturers are on nickel-cobalt-manganese (NCM) and nickel-cobalt-aluminum (NCA). BYD E6 uses a lithium iron phosphate battery (LFP) Nickel-cobal-manganese (NCM) lithium batteries have become the preferred choice for most conventional automotive manufacturers due to their high stability and relatively low cost. According to the ratio between the three elements, nickel-cobalt-manganese (NCM) lithium batteries can be divided into 111/523/622/811 and other types. The higher the content of nickel, the higher the specific capacity of the cell, the greater the energy density, and the corresponding decrease in the proportion of expensive cobalt, driving down the cost of the cell, which is also an important reason for the development trend of high nickel cells. . Obviously, 811 is the highest proportion of nickel, energy density can reach levels above 200Wh/kg, the current major manufacturers are competing to adopt, but the proportion of nickel has been difficult to significantly increase. Chevrolet BoltEV battery pack with nickel-cobalt-manganese (NCM) lithium cells The Panasonic cylindrical cell used by Tesla is nickel-cobalt-aluminum (NCA), which is the same type of cell used in notebook computers. The nickel-cobalt-aluminum (NCA) lithium battery has a higher energy density than the nickel-cobalt-manganese (NCM), but the stability and cost are currently not as good as those of the nickel-cobalt-manganese (NCM). Models used a cylindrical 18650 cell, which is also the most heard of Tesla people, energy density is about 250Wh/kg. Tesla's current model MODEL3 has been transitioned to a cylindrical 2170 core with an energy density of 300 Wh/kg. The application of silicon-carbon anodes is also an important means of increasing energy density, and Tesla is currently the first automotive manufacturer to successfully apply silicon-carbon anode materials. TeslaModelS dismantled battery pack with nickel-cobalt-aluminum (NCA) lithium cells Battery Pack Vehicle battery packs have a large capacity and a high driving voltage, so they formally consist of a large number of battery packs that are connected together in series and in parallel. The requirements of different cell shapes, capacities, working environments, etc., and the layout space, chassis height, and cooling conditions that the entire vehicle leaves for the battery pack will have an important influence on the final package type of the battery pack. Therefore, the same type of batteries will have different shapes to meet the layout requirements put forward by automobile manufacturers. A123's explosion of power battery box In general, the batteries in a battery pack are divided into a plurality of modules. Each battery cell in the module has a cooling sheet at intervals, and the pins are generally connected by soldering. The entire mold is then replaced with an insulating sponge and a frame. Group packaging, and finally according to the actual layout of the vehicle to install different modules, plus an external protective shell package, it will probably form a complete vehicle battery pack. Of course, there will be a special battery management system inside the battery pack. By means of a built-in temperature Sensor, voltage detection circuit, etc., the operation of the battery pack will be regulated according to temperature, voltage, etc. to ensure the safety of the battery pack and prolong its service life. Driving official summary: It can be foreseen that, whether it is a single cell or a battery pack, the energy density is constantly increasing, and the cost of the battery is also rapidly declining. Therefore, the future cruising range of new electric vehicles will continue to increase, and prices will continue to decline until powerful and real pressure is exerted on the fuel vehicles. Optoelectronic Information Series Photoelectric information series laboratory related equipment Optoelectronic Information Product,Optical Bench Experiments Physics,Optical Devices Physics,Optical Physics Properties Yuheng Optics Co., Ltd.(Changchun) , https://www.yuhengcoder.com