Lithium battery fast charging technology -Lithium - Ion Battery Equipment

Why lithium batteries are not suitable for fast charging -Lithium - Ion Battery Equipment

The fast charging problem of lithium-ion batteries needs to be analyzed from two levels. From the cell level, the rate performance of lithium-ion batteries is restricted by the intrinsic transmission characteristics of the material matching system such as positive electrode/negative electrode/electrolyte on the one hand, and on the other hand. In terms of pole piece technology and cell structure design, the rate performance is also greatly affected.

However, in terms of the most intrinsic carrier conduction and transport behavior, lithium batteries are not suitable for the development of fast charging technology. The intrinsic carrier conduction and transport behavior of lithium-ion battery systems depends on several important factors, including the conductance and lithium ion diffusion coefficients of the cathode and anode materials, as well as the conductivity of the electrolyte. Based on the embedded reaction mechanism, the diffusion coefficients of lithium ions in cathode materials and graphite anode materials are generally several orders of magnitude lower than the rate constants of heterogeneous redox reactions in aqueous secondary batteries. Also, the ionic conductivity of the organic electrolyte is two orders of magnitude lower than that of the aqueous secondary battery electrolyte. There is a layer of SEI film on the negative electrode surface of lithium ion battery, in fact, the rate performance of lithium ion battery is largely controlled by the diffusion of lithium ions in the SEI film. Since the polarization of the powder electrode in the electrolyte is much more serious than that of the water system, lithium is easily precipitated on the surface of the negative electrode under high rate or low temperature conditions, which brings serious safety hazards.(Lithium - Ion Battery Equipment)

In addition, under high-rate charging conditions, the lattice of the positive electrode material is easily damaged, and the graphite sheet of the negative electrode may also be damaged. These factors will accelerate the capacity decay, thus seriously affecting the service life of the power lithium battery. Therefore, the essential characteristics of the embedded reaction determine that lithium-ion batteries are not suitable for high-current fast charging. The research results of Lithium battery engineers have confirmed that the cycle life of a single lithium-ion battery in the long-term high-current fast charge and fast discharge mode will be greatly reduced, resulting in the destruction of the positive and negative electrode material structure, the phenomenon of lithium deposition in the negative electrode, and in the The performance of lithium-ion batteries deteriorates significantly in the later period of use.

As for the lithium-ion battery pack (PACK), the situation will be more complicated. During the charging process, the charging voltage and charging current of different single lithium-ion batteries are not consistent, which will inevitably cause the charging time of the lithium-ion battery to exceed that of the single lithium-ion battery. Battery. This means that while a single Li-ion battery can be charged to half its capacity in 30 minutes using conventional charging techniques, the charging time of a Li-ion battery pack (PACK) will certainly exceed the single charging time to a certain extent. It means that the advantages of fast charging technology are not very obvious.



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