How do you restrain the expansion of lithium titanate battery?

At present, there are three main solutions to inhibit gas expansion in lithium titanate batteries. The first is the processing modification of LTO negative electrode materials, including improved preparation methods and surface modification. Secondly, develop electrolytes that match the negative electrode of LTO, including additives and solvent systems; thirdly, improve battery technology.

(1) Improve the purity of raw materials and avoid the introduction of impurities in the manufacturing process. Impurity particles not only catalyze the separation of electrolytes to produce gas, but also greatly reduce the performance, cycle life and safety of lithium batteries. Therefore, it is necessary to minimize the introduction of impurities in batteries.

(2) The surface of lithium titanate is covered with carbon Nan particles. The apparent reason of negative pole LTO forming gas is that SEI film is formed slowly and less, which leads to the phenomenon of bloating. It was found that the presence of an insulating layer between the lithium titanate and the electrolyte interface (e.g., nano-carbon cladding on the lithium titanate surface (LTO/C), coupled with the formation of a solid electrolyte interface (SEI) film on the cladding, reduced the contact area between the LTO material and the electrolyte and prevented gas generation.

On the other hand, carbon itself can produce SEI film to make up for the deficiency of LTO, and enhance the electrical conductivity of LTO materials. The above research results are of great significance for solving the gas generation behavior of lithium titanate batteries and promoting the design, large-scale application and development of high-energy lithium titanate power batteries.

(3) improve the electrolyte function. For the development of new electrolytes, many patents favor the use of additives to facilitate the formation of a dense SEI film on the surface of LTO to inhibit the occurrence of interface side reactions between LTO and electrolytes. Some electrolytic additives, such as fluorinated carbonates and phosphates, contribute to the formation of a stable SEI film on the positive electrode surface, reducing the dissolution of metal ions on the positive electrode surface and thus reducing gas generation.

Film-forming additives can restrain gas production, film forming additive added with boric acid lithium salt, butyl nitrile or adiponitrile 2, the structure of the R - CO - CH = N2 compounds (R or alkyl phenyl of C1 ~ C8), cyclic phosphate ester and phenyl derivatives, phenyl acetylene derivatives, LiF additives, the formation of the SEI film forming additive are conducive to LTO surface membrane, to some extent inhibited the bilge gas.

(4) Positive electrode surface coating. Covering the positive electrode with stable compounds such as alumina can effectively inhibit the dissolution of metal ions. However, the complex coating can inhibit lithium ion delamination and affect the electrochemical properties of the material.

(5) Improve the battery production process. When battery is produced, we should control the environmental humidity, operation process water introduction. From the reason why the gas is produced, it can be seen that the water in the air reacts with the positive material to form lithium carbonate and accelerate the electrolyte decomposition to produce carbon dioxide. In addition, the lithium titanate material itself has a strong water absorption (which needs to be operated in a dry chamber). After the negative electrode absorbs water, it reacts with the PF5 generated by the reversible decomposition of the electrolyte to produce H2, so strict water control is essential.

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