Battery company inhibits three solutions to lithium titanate negative expansion

Battery company inhibits three solutions to lithium titanate negative expansion

Lithium titanate (Li4TI5O12 commonly known as LTO) space group belongs to FD3M, spinel structure, due to its own three-dimensional lithium ion diffusion channel, has advantages such as excellent power characteristics and high and low temperature performance. At the same time, the lithium titanate crystal structure can maintain a high degree of stability volume in a lithium ion deinterlaxation of less than 1%, which is a basic negative electrode material to make a basic material..

More importantly, the safety hazard of the battery is eliminated, called the safest lithium ion battery negative electrode material. The physical structure of lithium titanate is suitable as a lithium ion battery negative electrode material, then what is its electrochemical characteristics? Compared with the carbon negative electrode material, the lithium titanate potential is high, which is 1.55VVSLI + / li, the theoretical capacity of 175mAh / g, the open circuit voltage 2.

4V, the energy density and the voltage platform are lower.. The lithium titanate ion battery has the advantages of high safety, which can be charged with a long time, and the length of cycle life is long.

. Although the study of lithium titanate ion battery swelling has never stopped, including carbon cladding modification, hybridization, nanochem, but its flatulence is still completely solved, hindering the marketing promotion of lithium titanate ion batteries. I.

The lithium-based ion battery flatulence mechanism is considered to be a serious cause of lithium titanate / NCM battery. Liquid reaction. During the charge and discharge process, the electrolyte always contacts the surface of Li4Ti5O12, resulting in continuous reduction of the electrolyte on the surface of Li4Ti5O12 material, which may be the root cause of Li4Ti5o12 battery flatulence.

. An important component of the gas is H2, CO2, CO, CH4, C2H6, C2H4, C3H8, etc..

When the lithium titanate is separately immersed in the electrolyte, only CO2 occurs, and after the NCM material is prepared into a battery, the gas that occurs into H2, CO2, CO, and a small amount of gaseous hydrocarbons, and after being generated, only at circulation When the charge is charged, H2 will occur, and the gas in the gas, the content of H2 exceeds 50%.. This indicates that H2 and CO gas will appear during charge and discharge.

. LiPF6 exists in the electrolyte: PF5 is a very strong acid, which is easy to cause decomposition of carbonate, and the amount of PF5 increases with temperature..

PF5 contributes to electrolyte decomposition, CO2, CO and CXHY gases. According to relevant studies, the trace water from the electrolyte is derived from the trace water in the electrolyte, but the water content in the general electrolyte is about 20 × 10-6, and the production of H2 is very low..

Shanghai Jiaotong University Wu Kai’s experiment was used as a battery for graphite / NCM111. The conclusion concluded that the source of H2 is the decomposition of carbonate under high voltage..

Second, the lithium titanate ion battery flatulence inhibits the solution of lithium titanate lithium-ion battery flatulence, three, first, LTO negative electrode material processing modification, including improved preparation method and surface modification, etc., the second, development and Electrolytic solutions matching the LTO negative, including additives, solvent systems; third, improve battery process technology. (1) Improve the purity of raw materials and prevent the introduction of impurities during the manufacturing process.

Impurity particles will not only catalyze the graded gases of electrolytes, but also greatly reduce the performance, cycle life and safety of lithium-ion batteries, so they must reduce the introduction of impurities in batteries as much as possible.. (2) Lithium titanate surface cover nanocarbon particles.

The apparent reason for the negative electrode LTO forming gas is that the SEI film is slow, fewer, resulting in a phenomenon that the phenomenon is accompanied by its life.. The study found that the isolation layer is established between the lithium titanate and the electrolyte interface (such as constructing nanocarbon coating in a lithium titanate surface (LTO / C), a solid electrolyte interface (SEI) film formed on the coating layer.

Aspect, reduce the contact area of ​​LTO material and electrolyte, preventing the occurrence of gas. On the other hand, the carbon itself can show the lack of LTO, while also enhance the conductivity of LTO material..

The above research results have important significance to solve the production of lithium titanate ion batteries, the design and scale application and development of high energy titanate-based lithium battery and development have promoted. (3) Improve electrolyte functionality. Regarding the development of the new electrolyte, many patents are tended to use the additive to facilitate the formation of a dense SEI film on the surface of the LTO to suppress the occurrence of the LTO and the electrolyte interface.

. Some electrolyte additives, such as fluorinated carbonates and phosphates, facilitate the formation of a stable SEI film on the surface of the positive electrode, reducing the dissolution of the surface metal ions of the positive electrode, thereby reducing the occurrence of gas..

The film forming additive can also inhibit the amount of gas production, the film formable additive added is a lithium borate salt, butadiamonlonitrile or hexonitrile, R-CH = N2 structure (wherein R is C1 to C8 alkyl or phenyl) ), Cyclic phosphate, phenyl derivative, phenylecetylene derivative, LIF additive, etc.. (4) Positive surface coating.

Covered stable compounds on the surface of the positive electrode, such as alumina, or the like, can effectively inhibit metal ions. However, it is too complex cladding to inhibit lithium ion deinterlating, affecting electrochemical properties of materials..

(5) Improve battery production process. When the battery is produced, the environmental humidity is controlled, and the operation process water is introduced..

From the cause of the gas, it is understood that the water in the air and the positive electrode material reactively form lithium carbonate and accelerate electrolyte decomposition, and produce carbon dioxide.. Further, the lithium titanate material itself has a very strong water absorption (to operate in a dry room), and the negative electrode sheet absorbs moisture and the PF5 reaction that occurs in reversibility of the electrolyte in reversibility, so strict moisture control is essential.

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