CN-122025822-A - Electrolyte additive for lithium secondary battery and nonaqueous electrolyte

CN122025822ACN 122025822 ACN122025822 ACN 122025822ACN-122025822-A

Abstract

The invention provides an electrolyte additive for a lithium secondary battery and a nonaqueous electrolyte, and relates to the technical field of lithium batteries. The additive is at least one selected from compounds with the following chemical structural general formula: . The additive of the invention forms a high-stability and high-conductivity interfacial film containing sulfur and nitrogen by utilizing polar groups and heterocyclic structures, solves the problems of high pressure impedance and gas production, and improves the performances of circulation and wide temperature range. The introduced alkali metal cations regulate and control solvation structures, promote desolvation, improve low-temperature/rate performance, inhibit lithium dendrites by utilizing electrostatic shielding effect and enhance safety. The additive has the advantages of environmental protection and low cost.

Inventors

WANG YINGMEI
HE KUANG
QIN KAI
YANG TIANXIANG
SHAO HONGMING
JIN YIZHONG
WANG JIANBIN
YIN XINYU

Assignees

浙江永太新能源材料有限公司
浙江永太科技股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (9)

1. An electrolyte additive for a lithium secondary battery, characterized in that the additive is selected from at least one of compounds having the following chemical structural formula: ; Wherein R is a cation selected from any one of H, li, na, K, rb, cs, X is a substituent at position 6 selected from halogen, C1-C5 alkyl optionally substituted with one or more substituents, C1-C5 alkoxy optionally substituted with one or more substituents, aryl or heteroaryl optionally substituted with one or more substituents; The substituents are selected from the group consisting of halogen, cyano, alkyl, alkoxy, alkenyl, and alkynyl.
2. The electrolyte additive for lithium secondary batteries according to claim 1, wherein R is selected from H, li, K, rb or Cs, and/or, X is selected from fluorine atom, trifluoromethyl, cyano, methyl, ethyl, n-propyl, isopropyl, methoxy or phenyl, and/or, The electrolyte additive for lithium secondary batteries is selected from at least one of the following compounds: Lithium salt of 6-methyl-1, 2, 3-oxathiazine-4 (3H) -one-2, 2-dioxide, sodium salt of 6-methyl-1, 2, 3-oxathiazine-4 (3H) -one-2, 2-dioxide, potassium salt of 6-methyl-1, 2, 3-oxathiazine-4 (3H) -one-2, 2-dioxide, rubidium salt of 6-methyl-1, 2, 3-oxathiazine-4 (3H) -one-2, 2-dioxide, cesium salt of 6-methyl-1, 2, 3-oxathiazine-4 (3H) -one-2, 2-dioxide, and compounds wherein in the chemical structural formula, the cation R is potassium ion and the substituent X in the 6-position is ethyl, trifluoromethyl, methoxy, cyano, fluorine atom or phenyl.
3. The electrolyte additive for a lithium secondary battery according to claim 2, wherein the electrolyte additive for a lithium secondary battery is selected from at least one of the following compounds: 。
4. A nonaqueous electrolyte for a lithium secondary battery, comprising a nonaqueous organic solvent, a conductive lithium salt electrolyte, and the electrolyte additive for a lithium secondary battery according to any one of claims 1 to 3.
5. The nonaqueous electrolyte solution for lithium secondary batteries according to claim 4, wherein the mass percentage of the nonaqueous organic solvent is 45-95%, the mass percentage of the conductive lithium salt electrolyte is 5-30%, the mass percentage of the electrolyte additive for lithium secondary batteries is 0.01-2%, and/or the nonaqueous electrolyte solution for lithium secondary batteries further comprises fluoroethylene carbonate, wherein the mass ratio of the electrolyte additive for lithium secondary batteries to fluoroethylene carbonate is 1 (1-10), calculated by taking the total mass percentage of the nonaqueous electrolyte solution for lithium secondary batteries as 100%.
6. A lithium secondary battery comprising a positive electrode sheet, a negative electrode sheet, and a separator, and the nonaqueous electrolyte for a lithium secondary battery according to any one of claims 4 to 5.
7. The lithium secondary battery of claim 6, wherein the positive electrode sheet comprises a positive electrode active material selected from at least one of LiM z N 1-z PO 4 、Li 1+x Ni y Mn 2-x-y O 4 and Li 1+a Ni b Co c M` 1-a-b-c O 2 ; Wherein M and N are respectively one of Fe, mn, co or Ni, M' is at least one of Mg, al, ca, sc, ti, V, cr, mn, fe, zn, ga, Y, zr, nb, mo, sn and Ba, and z is more than or equal to 0 and less than or equal to 1, x is more than or equal to 0 and less than or equal to 0.05, y is more than or equal to 0 and less than or equal to 0.5, a is more than or equal to 0 and less than or equal to b, c is more than or equal to 1 and 0 and less than or equal to a+b+c is less than or equal to 1, and/or, The negative electrode plate comprises a negative electrode active material, wherein the negative electrode active material is at least one selected from natural graphite, artificial graphite, mesophase carbon microspheres, elemental silicon, silicon oxygen compound SiO X , silicon carbon composite materials, lithium titanate, lithium metal and lithium alloy, wherein 0<X is less than or equal to 2, and/or, The surface of the negative electrode plate is provided with a solid electrolyte interface film, and the solid electrolyte interface film contains at least one inorganic component of Li 2 SO 3 、Li 2 S and Li 3 N.
8. A lithium metal battery, comprising a positive electrode, a metal lithium negative electrode and an electrolyte, wherein the electrolyte comprises the electrolyte additive for a lithium secondary battery according to claim 1, and the cation R in the electrolyte additive for a lithium secondary battery is selected from Rb or Cs.
9. An electrical device comprising the lithium secondary battery according to claim 6 or the lithium metal battery according to claim 8.

Description

Electrolyte additive for lithium secondary battery and nonaqueous electrolyte Technical Field The invention relates to the technical field of lithium batteries, in particular to an electrolyte additive for a lithium secondary battery and a nonaqueous electrolyte. Background Secondary batteries are widely used as important carriers for modern energy storage in the fields of new energy automobiles, portable electronic equipment, energy storage systems and the like. Among them, lithium secondary batteries have taken up important market positions due to their high energy density, long cycle life, and the like. The electrolyte is used as a bridge for connecting the anode and the cathode in the secondary battery, plays a key role in ion transmission, and the composition and the property of the electrolyte more directly determine the cycle stability, the service life, the safety and the electrochemical performance of the battery in a wide temperature range. In order to improve the performance of the battery, a small amount of additive is generally added into the electrolyte, and a stable Solid Electrolyte Interface (SEI) film is formed by chemical or electrochemical reaction on the surface of the electrode, so that the electrode material is protected, and the continuous decomposition of the electrolyte is inhibited. Currently, film forming additives commonly used in commercial electrolytes mainly include Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), and the like. These additives can improve the cycle performance of the battery to some extent. For example, VC is often used to form a protective film on the surface of the negative electrode, and FEC is often used in high-voltage or silicon-based negative electrode systems to improve the stability of the interface. However, with the increasing energy density of batteries and the increasingly severe application scenarios, these conventional additives increasingly exhibit their limitations. Specifically, under high voltage (e.g., greater than 4.2V) conditions, VC tends to undergo excessive oxidative decomposition and polymerization, resulting in a significant increase in internal impedance of the battery, which in turn causes rapid decay of capacity later in the battery cycle. FEC has good film forming performance, but has poor thermal stability and poor compatibility with widely used lithium hexafluorophosphate (LiPF 6) salt, and is easy to undergo defluorination reaction to generate Hydrogen Fluoride (HF), so that not only electrode materials are corroded, but also electrochemical performance of a battery under a high-temperature environment is seriously deteriorated. In addition, the synthesis process of the traditional fluorine-containing additive is often complex, harmful fluoride can be released in the waste treatment process, a certain environmental risk exists, and the sulfur-containing additives such as 1, 3-Propane Sultone (PS) and the like have good film forming effect, but part of the compounds have proven cancerogenic risks, and health and safety hazards exist in the production and use processes. In summary, when the existing electrolyte additive is used for dealing with complex working conditions such as high voltage and high temperature, the film forming stability, impedance control and chemical compatibility are difficult to be considered, and part of the additive has the hidden trouble of environmental protection and safety. Therefore, a novel electrolyte additive which can be kept stable under high voltage, has good compatibility with common lithium salt, is environment-friendly and has low cost is sought, so that the defects of the prior art are overcome, and the problem to be solved in the technical field of the current secondary battery is urgent. In view of this, the present invention has been made. Disclosure of Invention The invention aims to provide an electrolyte additive and a nonaqueous electrolyte for a lithium secondary battery, wherein the additive remarkably improves the high-voltage cycling stability, wide-temperature area/rate performance and safety of the battery and is environment-friendly and low in cost by forming a sulfur-nitrogen-containing high-stability interface film and introducing a cation to regulate and control solvation and electrostatic shielding effect. In order to achieve the above object of the present invention, the following technical solutions are specifically adopted: In a first aspect, the present invention provides an electrolyte additive for a lithium secondary battery, the additive being selected from at least one of compounds having the following chemical structural formula: ; Wherein R is a cation selected from any one of H, li, na, K, rb, cs, X is a substituent at position 6 selected from halogen, C1-C5 alkyl optionally substituted with one or more substituents, C1-C5 alkoxy optionally substituted with one or more substituents, aryl or heteroaryl optionally substituted w