CN-122025813-A - Electrolyte additive, preparation method and application thereof

CN122025813ACN 122025813 ACN122025813 ACN 122025813ACN-122025813-A

Abstract

The invention relates to the technical field of battery materials, in particular to an electrolyte additive, a preparation method and application thereof. The electrolyte additive comprises vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone and thiophosphoric acid silane additive. The phosphorothioate silane additive is prepared by reacting hexamethyldisilazane with monoammonium phosphate, condensing with sulfonyl chloride intermediate containing R group at low temperature, and compounding with the rest components according to a specific mass ratio. The electrolyte additive can form a high-conductivity lithium protective film rich in LiF and LiSxOy at an electrode interface, so that the ion transmission capacity and stability of the interface are remarkably improved, meanwhile, the P-O-Si structure can capture trace water, inhibit HF generation and effectively control the acidity and chromaticity change of the electrolyte. The additive is particularly suitable for a quick-charge lithium ion battery, and ensures the long-acting stability of electrolyte while prolonging the cycle life, high-temperature storage performance and multiplying power characteristics.

Inventors

DU ZHIWEI
WANG HAONAN
HU LONGKE
JIN LINGZHI
TANG WEN

Assignees

孝感楚能新能源创新科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260226

Claims (10)

1. An electrolyte additive comprising vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone and a thiophosphoric silane additive comprising a compound having the structure shown in the following formula: ; wherein R is selected from one of C1-C6 alkyl, nitrile group and benzene ring.
2. The electrolyte additive according to claim 1, wherein R is a nitrile group in the structure of the thiophosphoric silane-based additive.
3. The electrolyte additive according to claim 1, wherein the thiophosphoric silane-based additive comprises at least one of additive a, additive B, or additive C having a structure represented by the following formula: Additive A: ; Additive B: ; Additive C: 。
4. The electrolyte additive according to claim 1, wherein the mass ratio of the vinylene carbonate, the fluoroethylene carbonate, the 1, 3-propane sultone and the thiophosphoric acid silane additive is (3-5): 0.5-2): 0.1-0.8): 0.1-3.
5. A method for preparing the electrolyte additive according to any one of claims 1 to 4, comprising the steps of: s1, reacting hexamethyldisilazane with ammonium dihydrogen phosphate in an inert atmosphere to generate an intermediate I; S2, reacting an alcohol or phenol compound containing a target R group with chlorosulfonic acid under a low temperature condition to generate an intermediate II; s3, dropwise adding the intermediate II into the solution of the intermediate I under the condition of inert atmosphere and low temperature for reaction, and obtaining the phosphorothioate silane additive through post-treatment; And S4, mixing vinylene carbonate, fluoroethylene carbonate, 1, 3-propane sultone and thiophosphoric acid silane additives according to a preset proportion to obtain the electrolyte additive.
6. The preparation method according to claim 5, wherein in the step S1, the molar ratio of hexamethyldisilazane to ammonium dihydrogen phosphate is 1 (2-4), the reaction temperature is 90-150 ℃, and the reaction time is 3-8 hours; and/or in the step S2, the alcohol or phenol compound containing the target R group is n-butanol, ethanedinitrile or phenol, and the molar ratio of the alcohol or phenol compound containing the target R group to chlorosulfonic acid is 1 (0.8-1.3); And/or in the step S3, the molar ratio of the intermediate II to the intermediate I is (0.8-1.2): 1, the low temperature is an ice bath condition, and the reaction time is 3-6 hours.
7. The lithium ion battery electrolyte is characterized by comprising, by mass, 11-15% of lithium salt, 80-85% of an organic solvent and 2-9% of an electrolyte additive, wherein the electrolyte additive is the electrolyte additive according to any one of claims 1-6.
8. The lithium ion battery electrolyte of claim 7, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis-fluorosulfonyl imide, lithium difluoro-oxalato-borate.
9. The lithium ion battery electrolyte of claim 7, wherein the organic solvent comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, ethyl acetate.
10. A lithium ion battery, characterized by comprising the lithium ion battery electrolyte as claimed in any one of claims 7 to 9.

Description

Electrolyte additive, preparation method and application thereof Technical Field The invention relates to the technical field of battery materials, in particular to an electrolyte additive, a preparation method and application thereof. Background With the rapid development of global energy structure transformation and electric automobile industry, the performance of the lithium ion battery is directly related to the endurance mileage, the safety reliability and the service life of the vehicle as a core power source. Among the numerous positive electrode materials, lithium iron phosphate (LFP) has become one of the widely used material systems in the new energy automobile field due to its excellent thermal stability, cycle life and cost advantages. LFP batteries present significant advantages especially in passenger cars and energy storage scenarios where safety requirements are extremely high. However, in contrast to its excellent safety performance, the mass energy density and the volume energy density of the LFP battery are both lower than those of the high-nickel ternary system, so that the whole vehicle is subject to a bottleneck in driving mileage improvement, and the driving anxiety becomes one of the key factors for restricting the further expansion of the market. In order to relieve endurance anxiety, the industry starts with improving energy supplementing efficiency and promotes the development of quick charging technology. The fast charge not only requires the battery to support high-rate charge and discharge, but also provides more severe stability and interface regulation and control requirements for an electrolyte system. The electrolyte is used as a medium for transmitting lithium ions between the anode and the cathode, and the composition of the electrolyte directly influences the high-rate performance, the cycle life and the storage stability of the battery. In practical applications, various functional additives are often introduced to optimize the electrode/electrolyte interface, form a stable solid electrolyte interface film (SEI film), inhibit side reactions, enhance ionic conductivity, and enhance thermal and chemical stability of the electrolyte itself. Currently, additives commonly used in the market to enhance quick-fill properties mainly include sulfate-containing compounds such as vinyl sulfate (DTD) and Methylene Methane Disulfonate (MMDS). The additive can participate in interfacial film formation in the battery cycle process, and improve lithium ion migration kinetics. However, the polarity of the sulfur-oxygen-carbon bond in the molecular structure is strong, and the sulfur-oxygen-carbon bond is easy to generate hydrolysis reaction with trace moisture remained in the electrolyte, so that the additive is decomposed and deactivated, acidic substances are continuously released, and the acidity of the electrolyte is gradually increased. After long-term storage, the electrolyte often changes from an initial clear transparent to brown-yellow, which is not only an appearance problem, but also means that the electrolyte system has undergone irreversible chemical changes. The increase of acidity accelerates corrosion to electrode active materials, damages the integrity of SEI films, increases internal resistance of batteries, reduces capacity retention rate and cycle life, and can cause performance attenuation and even potential safety hazards of batteries when serious. In addition, the stability of the existing additive under the conditions of high temperature and high multiplying power is also obviously insufficient. The battery has obvious local heating in the fast charge process, and if the decomposition product of the additive can not form a compact interfacial film with excellent lithium conducting performance, the problems of nonuniform lithium deposition, dendrite growth and the like can be aggravated, and the safety and long-acting cycle of the battery are affected. Therefore, developing a novel additive which can adapt to a fast charge system and maintain long-term chemical stability and interface compatibility of electrolyte becomes an important research direction for improving the comprehensive performance of the LFP battery. Disclosure of Invention Under the background, the invention aims to provide an electrolyte additive, a preparation method and application thereof, and various active elements such as silicon, phosphorus, sulfur and the like are introduced into a molecular design to enable the electrolyte additive to play multiple functions in a battery, so that the electrolyte additive not only can participate in constructing an inorganic interface film with high ion conductivity and high mechanical stability and promote lithium ion migration efficiency, but also can effectively inhibit the acidity rise and chromaticity change of the electrolyte through a capture mechanism of moisture and fluoride ions and enhance the chemical stability of the system in the storage and