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CN-116799303-B - Additive, preparation method thereof, electrolyte and secondary battery

CN116799303BCN 116799303 BCN116799303 BCN 116799303BCN-116799303-B

Abstract

The application relates to the field of secondary batteries, and discloses an additive, a preparation method, electrolyte and a secondary battery. The electrolyte additive comprises a compound with a structure shown in a formula A, wherein R 1 ～R 4 is independently selected from any one of -CH 3 ,-C 2 H 5 ,-CH 2 CF 3 ,-CHC 2 F 6 ,-Ph,-C(CH 3 ) 3 ,-Si(CH 3 ) 3 , R 5 and R 6 are independently selected from any one of C1-C20 alkylene or-R 7 -O-R 8 -, R 7 is selected from phenyl or C1-C20 alkyl, and R 8 is selected from C1-C20 alkyl. The additive can reduce the deposition of Mn of the negative electrode, reduce impedance and assist in forming a stable interfacial film on the surface of the negative electrode. The additive contains P-O bond, trivalent P is easy to oxidize, so that oxygen generated from an anode interface is consumed, free radicals generated by P-O bond fracture are diffused to the anode surface to form CEI film, dissolution of anode interface Mn can be inhibited, initial internal resistance of the battery and internal resistance increase in a storage process are reduced, and high-temperature storage and cycle performance of the battery are improved.

Inventors

  • XU CAN
  • LV GUOXIAN
  • QIAO FEIYAN
  • CHU CHUNBO

Assignees

  • 欣旺达动力科技股份有限公司

Dates

Publication Date
20260508
Application Date
20230626

Claims (9)

  1. 1. An additive comprising a compound having the structure of formula a: Wherein R 1 ～R 4 is independently selected from any one of -CH 3 ,-C 2 H 5 ,-CH 2 CF 3 ,-CHC 2 F 6 ,-Ph,-C(CH 3 ) 3 ,-Si(CH 3 ) 3 ; R 5 and R 6 are respectively and independently selected from any one of C1-C20 alkylene or-R 7 -O-R 8 -, wherein R 7 is selected from phenyl or C1-C20 alkyl, and R 8 is selected from C1-C20 alkyl.
  2. 2. The additive of claim 1, wherein R 1 ～R 4 is selected from any one of -CH 3 ,-C 2 H 5 ,-CH 2 CF 3 ,-CHC 2 F 6 ,-Ph,-C(CH 3 ) 3 and-Si (CH 3 ) 3 ; R 5 and R 6 are respectively and independently selected from any one of C1-C5 alkylene or-R 7 -O-R 8 -, wherein R 7 is selected from phenyl or C1-C5 alkyl, and R 8 is selected from C1-C5 alkyl.
  3. 3. An additive according to claim 1, wherein-R 7 -O-R 8 -comprises any one of the following substituents: 、 、 。
  4. 4. The additive of claim 1, wherein the structural compound of formula a comprises at least one of the following compounds: 。
  5. 5. the method for preparing the additive according to claim 1, comprising: Reacting a structural compound shown in a formula II with formic acid to generate an intermediate product II-1; the intermediate product II-1 reacts with hydrochloric acid to generate an intermediate product II-2; The intermediate product II-2 reacts with phosphorus trichloride to generate an intermediate product II-3, or the intermediate product II-2 reacts with Cl-R 7 -OH to generate an intermediate product II-4; The intermediate product II-3 reacts with X-OH to generate a structural compound shown in a formula A in the claim 1, or the intermediate product II-4 reacts with phosphorus trichloride to generate an intermediate product II-5, and the intermediate product II-5 reacts with X-OH to generate the structural compound shown in the formula A in the claim 1; wherein X is at least one of R 1 ～R 4 ; II II-1 II-2 II-3 II-4 II-5 wherein n is an integer of 1 to 20.
  6. 6. An electrolyte is characterized by comprising lithium salt, an organic solvent and the additive according to any one of claims 1-5, wherein the mass of the additive accounts for 0.1% -5% of the total mass of the electrolyte.
  7. 7. The electrolyte according to claim 6, wherein the mass of the additive is 0.5% -2% of the total mass of the electrolyte.
  8. 8. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and the electrolyte of claim 6 or 7.
  9. 9. The secondary battery of claim 8, wherein the positive electrode sheet comprises a positive electrode active material comprising a chemical formula Li a Ni x Co y Mn z M e O 2 , wherein 0.9 ∈a ∈1.1,0 ∈e ∈0.1,0.3 ∈x <1.0,0< y <0.4,0.1< z <0.4, x+y+z=1.0, and m comprises at least one of Al, zr, sr, ti, B, mg, sn, W, Y, ba, nb, mo, ta, si, la, er, nd, gd, ce.

Description

Additive, preparation method thereof, electrolyte and secondary battery Technical Field The application relates to the field of secondary batteries, in particular to an additive, a preparation method thereof, electrolyte and a secondary battery. Background With the rapid development of electric vehicles, the energy density, cycle life and safety requirements of lithium ion batteries are continuously improved. However, in the traditional electrolyte system, the ternary positive electrode material can undergo severe structural change and interface side reaction at high pressure and high temperature, which brings great challenges to practical application, in particular to the cycle life and safety of the high-nickel ternary material. Among these, the development of adapted electrolyte additives is one of the most cost-effective methods for improving the electrochemical performance of lithium ion batteries. Therefore, the design of a film forming additive for improving the positive electrode interface film is very important for further improving the comprehensive performance of the high-power system battery. In addition, the SEI film formed on the graphite cathode for the first time plays an important role on the battery performance, and the formed SEI film has too high impedance to exacerbate the polarization of the battery, so that lithium is easily separated out from the surface of the cathode, and the reversible capacity of the battery is greatly reduced. Therefore, it is necessary to develop a novel positive and negative electrode film forming additive and electrolyte containing the additive, and a passivation film with small and stable impedance can be formed at the interface of the positive electrode and the negative electrode, so that the positive electrode can be protected, the problems of capacity loss and storage gas expansion caused by excessive side reaction between the positive electrode and the electrolyte can be inhibited, the negative electrode can be protected, a low-impedance SEI film can be formed, lithium ions can rapidly pass through, polarization is reduced, and a lithium precipitation window is improved. Disclosure of Invention In view of the above, an object of the present application is to provide an additive capable of reducing the initial internal resistance of a battery and the increase of internal resistance during storage, and improving the capacity retention rate of high temperature cycle and high temperature storage. In order to achieve the above object, as a first aspect of the present application, there is provided an electrolyte additive comprising a structural compound represented by formula a: Wherein R 1～R4 is independently selected from any one of -CH3,-C2H5,-CH2CF3,-CHC2F6,-Ph,-C(CH3)3,-Si(CH3)3; R 5 and R 6 are respectively and independently selected from any one of C1-C20 alkylene or-R 7-O-R8 -, wherein R 7 is selected from phenyl or C1-C20 alkyl, and R 8 is selected from C1-C20 alkyl. Further, the R 1～R4 is selected from any one of -CH3,-C2H5,-CH2CF3,-CHC2F6,-Ph,-C(CH3)3 and-Si (CH 3)3; r 5 and R 6 are respectively and independently selected from any one of C1-C10 alkylene or-R 7-O-R8 -, wherein R 7 is selected from phenyl or C1-C5 alkyl, and R 8 is selected from C1-C5 alkyl. Further, the-R 7-O-R8 -includes any one of the following substituents: 、、。 Further, the structural compound shown in the formula A comprises at least one of the following compounds: As a second aspect of the present application, there is provided a method for preparing the additive, comprising: Reacting a structural compound shown in a formula II with formic acid to generate an intermediate product II-1; the intermediate product II-1 reacts with hydrochloric acid to generate an intermediate product II-2; The intermediate product II-2 reacts with phosphorus trichloride to generate an intermediate product II-3, or the intermediate product II-2 reacts with Cl-R 7 -OH to generate an intermediate product II-4; The intermediate product II-3 reacts with X-OH (X is at least one of R 1～R4) to generate a structural compound shown in a formula A, or the intermediate product II-4 reacts with phosphorus trichloride to generate an intermediate product II-5, and the intermediate product II-5 reacts with X-OH (X is at least one of R 1～R4) to generate a structural compound shown in a formula A; wherein n is an integer of 1 to 20. As a third aspect of the present application, there is provided an electrolyte comprising an electrolyte lithium salt, an organic solvent and an electrolyte additive according to the present application. Further, the mass of the electrolyte additive accounts for 0.1% -5% of the total mass of the electrolyte. Further, the mass of the additive accounts for 0.5% -2% of the total mass of the electrolyte. As a fourth aspect of the present application, there is provided a secondary battery containing the electrolyte according to the present application. Compared with the prior art, the inventi