In order to achieve super fast charging, the battery, the most important carrier in the charging process, also needs to be adjusted. The fast charging of the battery mainly depends on the charging and discharge magnification of the battery. There are three main reasons for affecting the charging magnification: electrode material, charging power of charging pile and power battery temperature. For battery enterprises, the charging power of charging piles is an objective factor, and electrode materials and temperature control are where battery factories can make changes.
In the power battery link, the fast charging ability of the battery depends on multiple capabilities such as the fast lithium embedding ability of the negative electrode, the conductivity of the electrolyte, and the thermal management ability of the battery system.
When fast charging, lithium ions need to be accelerated and instantly embedded into the negative electrode. This challenges the ability of negative electrodes to quickly receive lithium ions. If the negative electrode does not have high-speed lithium embedding capacity, lithium precipitation or even lithium dendrite will occur, which will lead to irreversible attenuation of battery capacity and shorten service life. In addition, electrolyte also requires high conductivity and requires high temperature resistance, flame retardant and anti-overcharge. On the other hand, high-power fast charging will bring a significant increase in heat, and the thermal management of high-voltage battery packs is crucial.
Generally speaking, in the safe design of the battery pack, thermal diffusion protection can be carried out by applying thermal insulation materials with higher thermal insulation performance, such as ceramic insulation pads and mica boards. However, in addition to passive thermal protection, active thermal protection solutions are also crucial. At the Shanghai Auto Show, various power battery enterprises also “showed their skills” around material innovation and whole package heat management.
Previously, the ultra-fast charging technology in the Ningde era has covered electronic networks, fast ion rings, isotropic graphite, superconducting electrolytes, high pore diaphragms, multi-gradient electrodes, multipolar ears, anode potential monitoring, etc.
Anotropic technology allows lithium ions to be embedded in a graphite channel 360 degrees to significantly improve the charging speed. Anode potential monitoring can adjust the charging current in real time, so that the battery can maximize its charging capacity within the safe range without lithium analysis side reactions, and achieve a balance between extreme charging speed and safety. The ternary Kirin battery adopts a high nickel cathode + silicon-based negative electrode system, with an energy density of up to 255Wh/kg, supporting 5-minute fast hot start and 10min charging 80%. However, during the charging and discharge process, the volume expansion of silicon can be as high as 400%, and the active material is easy to detach from the polar plate, causing a rapid attenuation of capacity and forming an unstable SEI membrane. Therefore, the conductive materials in the Ningde era adopt single-walled carbon nanotubes with a diameter of 1.5~2 nanotubes, which are more binding on silicon anodes and have a fuller conductive network. Even if the silicon anode particles expand in volume and begin to appear cracks, they can still maintain a good connection through single-walled carbon nanotubes. In addition, the electrolyte of Kirin battery adopts LiFSI and uses FEC additives to form lithium fluoride at the negative electrode. The ion radius is small, which can repair cracks in time. In terms of thermal management, Kirin Battery integrates the liquid cooling system and thermal insulation pad into a multi-functional elastic sandwich between the cells. Compared with the traditional liquid-cooled plate scheme laid above the cell, the heat transfer area has been quadrupled. Thanks to the larger cooling area, the temperature control efficiency of the cell has been increased by 50%. The vertical cooling plate creates a horizontal relative isolation space. There is an expansion compensation sheet + adiabatic aerogel between the longitudinal cells, which effectively insulates the heat to achieve “zero thermal runaway”.
Post time: Jun-26-2023