As the country has higher and higher requirements for the driving range of new energy vehicles, the system energy density of power lithium-ion batteries, and energy consumption, the lightweight of power lithium-ion batteries has become a topic of concern. The lightweight of ion batteries and the improvement of the group efficiency of power lithium ion batteries are imminent.
Battery pack efficiency comparison
Regarding the irregular battery box, the cylindrical battery can make full use of the space, which is more advantageous than the square and soft case. By reducing the cell spacing and the light weight of the module, the efficiency of the module assembly can be greatly improved.
The single energy density of the soft-packed cell has a higher improvement space than the cylindrical and square, but it has higher requirements for the module design, and the safety is not easy to control.
The square cell is more suitable for a regular box. The larger cell volume is beneficial to increase the energy density of the cell. The efficiency of subsequent modules is limited and depends on the improvement of the energy density of the single cell.
It is understood that at present, the grouping efficiency of cylindrical batteries in the industry is about 87%, and the grouping efficiency of the system is about 65%; the grouping efficiency of soft-packed batteries is about 85%, and the grouping efficiency of the system is about 60%. ; The grouping efficiency of the square cells is about 89%, and the grouping efficiency of the system is about 70%.
If calculated according to the current system group efficiency, the energy density of 260Wh/kg for the new lithium-ion battery system proposed in the “Action Measures for Promoting the Development of the Automotive Power Lithium-ion Battery Industry” must be met. To reach 400Wh/kg, the energy density of the soft-packed cell should reach 433Wh/kg, and the energy density of the square cell should reach 371Wh/kg. Obviously, it is difficult for the energy density of single cells to reach this level in 2020, so it becomes very necessary and urgent to further improve the group efficiency of power lithium-ion batteries.
At the “‘Ingenuity for the future’ new energy industry summit and seminar on the development direction of power lithium-ion batteries under the new situation in 2018,” Huating (Hefei) Power Technology Co., Ltd. President Assistant Xie Ruiwen said that to improve the efficiency of power lithium-ion battery packs You can start with two aspects: module optimization and lightweight design.
Module optimization design
Module optimization can start from multiple aspects. Regarding the cylinder, the industry has newly developed 21700 batteries. Compared with 18650, after the diameter of the batteries increases, the battery holder plate and current collector holes become larger, the corresponding weight is reduced, the number of batteries in the battery system is reduced, and the welding is at the same time The number of accessories is also reduced accordingly.
Improving space utilization is also an important way to optimize modules. The power lithium-ion battery PACK company can improve the design of modules and thermal management systems to reduce the cell spacing, thereby improving the utilization of the space in the battery box.
There is another way to deal with it, which is to use new materials. For example, the busbar in the power lithium-ion battery system (the bus in the parallel circuit, usually made of copper plates) is replaced by copper with aluminum, and the module fixing parts are replaced by sheet metal materials with high-strength steel and aluminum, which can also reduce power Weight of Li-ion battery.
Lightweight shell design
Compared with other parts of new energy vehicles, the power lithium-ion battery housing has particularly stringent requirements for collision avoidance, waterproofing, fireproofing, and dustproofing. In addition to guaranteeing and accommodating the battery, the power lithium-ion battery case also effectively isolates the operator, passengers and the battery from contact. Therefore, the power lithium-ion battery case has a higher degree of protection. Therefore, it is difficult to reduce the weight of the power lithium-ion battery casing. It is necessary to ensure the safety of the power lithium-ion battery and the passengers, but also to achieve light weight.
According to calculations, if the power lithium-ion battery sheet metal shell is replaced with an all-aluminum shell, the weight can be reduced by about 30%. In addition, carbon fiber materials are also regarded as more potential shell materials. Carbon fiber material has low density, light weight, tensile strength above 3400MPa, corrosion resistance and high temperature resistance, and has great advantages in absorbing impact. It is a good material for realizing lightweight cars. However, due to technical difficulties and other reasons, the price of carbon fiber battery boxes is higher than that of ordinary materials, and it will take time to become popular. With the continuous maturity of carbon fiber processing technology and the rapid development of new energy vehicles, the demand for carbon fiber battery boxes will further increase.
From the current point of view, there are not too many ways to improve the energy density of the power lithium-ion battery system. It is nothing more than improving the energy density of the monomer, the optimization of the module, and the lightweight of the housing. In short, when the power lithium-ion battery has a certain amount of charge, try to improve its group efficiency.