Reasons for the decrease in lithium battery capacity.LR726 battery

　　Lithium batteries have been widely used since they entered the market. The reason is that lithium batteries have the characteristics of large capacity, small size, and no pollution to the environment. However, in low-temperature environments, the use of lithium battery packs has problems such as low capacity, severe attenuation, and poor cycling function.

　　According to reports, 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 is between -20~+55 ℃. However, in the fields of aerospace, military industry, etc., batteries are required to operate normally at temperatures of -40 ℃ or lower. Therefore, improving the low-temperature properties of lithium battery packs is of great significance.

　　In terms of its influencing factors and reasons, it is actually its electrolyte. The electrolyte has a significant impact on the low-temperature function of lithium battery packs, and the composition and physicochemical function of the electrolyte have a significant impact on the low-temperature function of the battery. The problem faced by the cycling of batteries at low temperatures is that the viscosity of the electrolyte increases, the ion conduction speed slows down, and the electron migration speed of the external circuit does not match, resulting in severe polarization of the battery and a sharp decrease in charge discharge capacity.

　　Especially when charging at low temperatures, lithium ions can easily form lithium dendrites on the surface of the negative electrode, leading to ground failure of the battery. The low-temperature function of electrolytes is closely related to the conductivity of the electrolyte itself. Electrolytes with high conductivity transport ions quickly and can exert more capacity at low temperatures. The more lithium salts in the electrolyte dissociate, the more they are relocated, and the higher the conductivity. The higher the conductivity and the faster the ion conduction rate, the smaller the polarization received, and the better the functional performance of the battery at low temperatures. Therefore, a high conductivity is a necessary condition for achieving good low-temperature function of lithium-ion batteries.

　　The conductivity of the electrolyte is related to its composition, and reducing the viscosity of the solvent is one of the ways to improve the conductivity of the electrolyte. The good fluidity of the solvent at low temperatures ensures ion transport, and the solid electrolyte membrane formed by the electrolyte at the negative electrode at low temperatures is also a key factor affecting lithium ion conduction, and RSEI is the main impedance of lithium battery packs in low-temperature environments.

　　Lithium battery manufacturers analyze that electrolyte is one of the low-temperature characteristics that affects their lithium battery packs. But if you only need to use batteries locally, you can't do without using lithium battery packs locally. So at low temperatures, we can only use low-temperature cells for low-temperature lithium battery packs, which can operate at -40 degrees Celsius. However, if the temperature is lower than this, our skills need to be further improved. However, everything is carried out with the progress of technology, and the future is promising.

　　There are many production processes for lithium battery positive electrode materials, and there is a risk of introducing metal foreign objects at every step of the manufacturing process. This puts higher requirements on the equipment automation level and on-site quality management level of the material supplier. However, due to cost constraints, the automation level of the data supplier's equipment is low, there are many interruptions in the manufacturing process, and uncontrollable hazards are added. Therefore, in order to ensure the stability of battery functions and avoid self discharge, battery manufacturers must promote data suppliers to avoid the introduction of metal foreign objects from five aspects: human, machine, material, law, and environment.

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