Why does the capacity of lithium batteries become low in winter
- Categories:Industry news
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- Time of issue:2022-05-12 15:51
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(Summary description)Since entering the market, lithium ion battery has been widely used because of its advantages such as long life, large specific capacity and no memory effect. The low temperature use of lithium ion battery has some problems, such as low capacity, serious attenuation, poor cycle rate performance, obvious lithium evolution and imbalanced lithium removal. However, with the continuous expansion of the application field, the low temperature performance of lithium-ion batteries brought more and more obvious constraints.
Why does the capacity of lithium batteries become low in winter
(Summary description)Since entering the market, lithium ion battery has been widely used because of its advantages such as long life, large specific capacity and no memory effect. The low temperature use of lithium ion battery has some problems, such as low capacity, serious attenuation, poor cycle rate performance, obvious lithium evolution and imbalanced lithium removal. However, with the continuous expansion of the application field, the low temperature performance of lithium-ion batteries brought more and more obvious constraints.
- Categories:Industry news
- Author:
- Origin:
- Time of issue:2022-05-12 15:51
- Views:
Since entering the market, lithium ion battery has been widely used because of its advantages such as long life, large specific capacity and no memory effect. The low temperature use of lithium ion battery has some problems, such as low capacity, serious attenuation, poor cycle rate performance, obvious lithium evolution and imbalanced lithium removal. However, with the continuous expansion of the application field, the low temperature performance of lithium-ion batteries brought more and more obvious constraints.
It has been reported that the discharge capacity of lithium-ion batteries at -20℃ is only about 31.5% of that at room temperature. The operating temperature of traditional lithium-ion batteries ranges from -20 ℃ to +55℃. However, in aerospace, military, electric vehicles and other fields, batteries are required to work at -40℃. Therefore, it is of great significance to improve the low temperature properties of lithium ion batteries.
Factors restricting low temperature performance of lithium ion batteries
Under low temperature environment, the electrolyte viscosity is large, and even partially solidifies, which leads to the decrease of the conductivity of lithium-ion batteries.
At low temperature, the compatibility between the electrolyte and the negative electrode and the diaphragm becomes worse.
In the low temperature environment, the negative electrode of lithium ion battery precipitates lithium seriously, and the precipitated metal lithium reacts with the electrolyte, and the product deposition leads to the increase of solid electrolyte interface (SEI) thickness.
In low temperature environment, the diffusion system of Li-ion battery inside the active material decreases, and the charge transfer impedance (Rct) increases significantly.
Discussion on the decisive factors affecting the low temperature performance of lithium ion battery
Expert opinion 1: The electrolyte has a great impact on the low temperature performance of lithium-ion batteries, and the composition and physical and chemical properties of the electrolyte have an important impact on the low temperature performance of batteries. Battery low temperature circulation facing the problem is: electrolyte viscosity will become larger, ion conduction velocity becomes slower, resulting in the external circuit electron migration speed mismatch, so the battery serious polarization, charge and discharge capacity sharply reduced. Especially when charging at low temperature, lithium ions are easy to form lithium dendrites on the surface of the negative electrode, leading to battery failure.
The low temperature performance of the electrolyte is closely related to the size of the conductivity of the electrolyte itself. The transmission of the large conductivity electrolyte is fast, and the low temperature can play more capacity. The more lithium dissociates from the electrolyte, the more the number of migrations and the higher the conductivity. The higher the conductivity, the faster the ion conduction rate, the smaller the polarization, and the better the performance of the battery at low temperature. Therefore, high conductivity is a necessary condition to achieve good low temperature performance of lithium ion battery.
The conductivity of electrolyte is related to the composition of electrolyte. Reducing the viscosity of solvent is one of the ways to improve the conductivity of electrolyte. The good fluidity of solvent at low temperature is the guarantee of ion transport, and the solid electrolyte film formed by electrolyte at the negative electrode at low temperature is also the key to affect lithium ion conduction, and RSEI is the main impedance of lithium ion battery at low temperature.
Panelist 2: The main factor limiting the low temperature performance of lithium-ion batteries is the sharply increased Li+ diffusion impedance at low temperature, not the SEI film.
Low temperature characteristics of cathode materials for lithium ion batteries
Low temperature characteristics of layered cathode materials
The layered structure is the earliest commercial cathode material for lithium ion batteries, which not only has the incomparable multiplier performance of the one-dimensional lithium ion diffusion channel, but also has the structural stability of the three-dimensional channel. The representative substances are LiCoO2, Li(Co1-XNix)O2 and Li(Ni,Co,Mn)O2.
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