Knowledge Analysis of Electric Vehicle Power Battery

As we all know, the traditional fuel vehicle has three parts, namely, engine, gearbox and chassis. These core components determine the performance and quality of the car. Coincidentally, today's pure electric vehicles also have so-called three parts, namely, power battery, electric drive system, electronic control system,

Among them, the power battery is undoubtedly the most concerned part of consumers. After all, the quality, safety, performance and reliability of power batteries are directly related to the use experience of pure electric vehicles. Especially this year, the spontaneous combustion events of electric vehicles frequently occur, which makes the power battery become the focus of discussion on spontaneous combustion events.

Of course, in recent years, the market share and user acceptance of pure electric vehicles are indeed getting higher and higher, but at present, most consumers still know little about power batteries. So, today, let's talk about those things about power batteries and learn about their classification and their respective characteristics.

● Structural composition of power battery (storage battery)

At present, almost all pure electric vehicles on the market use batteries as power batteries. We might as well analyze the structure of batteries. The power battery is composed of multiple cells, CSC information acquisition system, battery management control unit (BMU), battery high-voltage power distribution unit, cooling system, etc.

Battery cell is the smallest unit of storage battery, which consists of positive electrode, negative electrode and organic electrolyte. The battery module consists of several battery cells connected in parallel. By connecting several battery cells in series to form a battery cell, and then connecting several battery cells in series, an assembly of a power battery can be formed.

At present, the load capacity of power batteries on the market is mainly provided by ternary lithium batteries and lithium iron phosphate batteries. Here we will focus on these two types of power batteries.

● What is a ternary lithium battery?

Ternary lithium battery, also known as ternary polymer battery, is a lithium-ion battery with nickel, cobalt and manganese or nickel, cobalt and aluminum as cathode materials.

According to the latest loading data of power battery, 20 19,1-1,the cumulative loading capacity of ternary battery accounts for 68. 1% of the whole vehicle, with the highest market share.

The reason why ternary lithium batteries are favored by many car companies is mainly because of their high energy density. The greater the energy density, the more power stored in the power battery per unit volume or weight.

Generally speaking, the higher the energy density of the battery, the higher the endurance of the pure electric vehicle. Therefore, the endurance advantage of ternary lithium batteries is very attractive to new energy vehicle companies that strive to pursue long cruising range.

At the same time, ternary lithium batteries also have certain advantages in low temperature resistance. Under the same low temperature conditions, ternary lithium batteries have less power attenuation than other types of batteries in winter, and are more suitable for use in northern areas in cold winter.

The disadvantages of ternary lithium battery are poor stability, easy thermal runaway when the temperature reaches 250-350℃, and high risk of spontaneous combustion during fast charging. Therefore, ternary lithium batteries have strict requirements for heat dissipation performance, which also has higher technical requirements for BMS battery management system.

● What is a lithium iron phosphate battery?

Lithium iron phosphate battery is a lithium ion battery with lithium ferrous phosphate as cathode material, and its biggest advantage is high safety. At present, lithium iron phosphate battery has the best thermal stability, and the thermal runaway temperature is generally above 500 degrees, so the risk of battery spontaneous combustion is very low.

Secondly, the cycle life of lithium iron phosphate battery is also relatively long, and it will begin to decay after the number of charge and discharge cycles exceeds 3500, which is equivalent to 10 year. In addition, the price of lithium iron phosphate battery also has certain advantages.

However, the energy density of lithium iron phosphate battery is not as high as that of ternary lithium battery. At present, the average energy density of the former is 130- 140Wh/kg, and the average energy density of ternary lithium battery is 160Wh/kg, so it is difficult to compare with ternary lithium battery in battery life, which is why few pure electric vehicles use lithium iron phosphate batteries.

However, with the decline of new energy subsidies, or even the total cancellation of subsidies, lithium iron phosphate batteries will rise again with their price advantages, and the cumulative loading capacity of lithium iron phosphate batteries will account for 29.5% of the total vehicle volume in 20 19.

● What is a hydrogen fuel cell?

Compared with storage battery, hydrogen fuel cell with small volume is a real "zero emission" clean energy. They directly convert the chemical energy of hydrogen and oxygen into power generation devices.

The basic principle is the reverse reaction of electrolytic water, which provides hydrogen and oxygen to cathode and anode respectively. Hydrogen diffuses outward through the cathode and reacts with the electrolyte, releasing electrons to reach the anode through external load, only generating water and heat.

It can be said that the advantages of hydrogen fuel cells are not only reflected in the high energy conversion efficiency of the cells, but also pollution-free and noise-free. In the long run, hydrogen fuel cell will be a key development direction of power battery industry in the future.

For example, Hyundai Motor recently announced a "2025 Strategy". In addition to expanding the sales of pure electric vehicles, hydrogen-fueled electric vehicles are also in its sales planning. In addition, well-known car companies such as Toyota and Honda are also actively promoting the development of hydrogen fuel cell technology.

However, at present, many problems of hydrogen-fueled electric vehicles have not been effectively solved. The main reason is that hydrogen storage is inconvenient and the current construction cost is too high.

● Summary:

At present, these power batteries have their own advantages and disadvantages. At this stage, the cruising range is still the most critical performance index of the battery when the charging experience is not pleasant enough.

Therefore, ternary lithium batteries will also be the mainstream application in the pure electric vehicle market. Finally, for those consumers who have bought pure electric vehicles, do you know what kind of power battery their electric vehicles use?