Thermal response interface passivator composition, electrolyte and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a thermal response interface passivator composition, an electrolyte and a lithium ion battery. The thermal response interface passivator composition comprises a silane component and a chalcogenide component, the silane component is selected from any one or more of 3-mercaptopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane or gamma-methacryloyloxypropyltrimethoxysilane, and the silane component is selected from any one or more of 3-mercaptopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane and gamma-methacryloyloxypropyltrimethoxysilane; the sulfur component is selected from diisopropyl xanthate disulfide and / or diphenyl disulfide. The thermal response interface passivator composition provided by the invention does not influence the electrochemical performance of a battery under the conventional operation condition of the battery, and can spontaneously polymerize on the surface of a negative electrode at the high temperature of 100-120 DEG C to form a stable and compact passivation layer, namely, an effective thermal barrier is formed before a diaphragm is broken, so that electron leakage and electrolyte decomposition are effectively blocked, and the service life of the battery is prolonged. And the thermal safety of the battery is obviously improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more particularly to a thermally responsive interface passivator composition, an electrolyte, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, energy storage, and consumer electronics due to their high energy density and long cycle life. However, with the continuous improvement of energy density, battery safety issues have become increasingly prominent. In particular, under extreme thermal, electrical, and mechanical conditions, battery cells are prone to triggering a chain reaction of exothermic reactions within the battery, leading to thermal runaway and ultimately causing fires or even explosions. Current electrolytes are mostly based on carbonate systems, which have low flash points and poor thermal stability, making them a significant contributing factor to thermal runaway chain reactions.

[0003] Existing thermal safety protection technologies for lithium-ion batteries mainly rely on high-flash-point solvents, flame-retardant additives, or gelled electrolytes. Among these, thermally responsive additives have attracted significant attention due to their combined environmental sensing and interface regulation functions. These materials can inhibit thermal runaway chain reactions by spontaneously polymerizing or forming films at high temperatures, thereby blocking electrode side reactions. However, traditional thermally responsive additives have several drawbacks: First, the response temperature is too high. The polymerization reaction temperatures of typical silanes, benzoxazoles, and phosphorus-containing self-polymerizing additives are generally higher than 150°C, while the melting and rupture temperature of commercial polyolefin separators is only about 120°C, resulting in a thermal response that lags behind separator failure. Second, the film-forming quality is poor. Some additives suffer from uneven interfacial polymerization due to insufficient electrolyte dispersion, forming a loosely structured passivation layer that cannot effectively block electron conduction. Third, the system has poor compatibility. Highly reactive additives are prone to side reactions with lithium salts or electrode surfaces, leading to electrochemical performance degradation at room temperature.

[0004] Therefore, it is desirable to provide a new thermally responsive additive and electrolyte. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a thermally responsive interface passivator composition, an electrolyte, and a lithium-ion battery. The thermally responsive interface passivator composition provided by this invention does not affect the electrochemical performance of the battery under normal operating conditions. However, at high temperatures of 100-120°C, it can spontaneously polymerize on the surface of the negative electrode to form a stable and dense passivation layer, thus forming an effective thermal barrier before the separator ruptures. This effectively blocks electron leakage and electrolyte decomposition, significantly improving the thermal safety of the battery.

[0006] In a first aspect, the present invention provides a thermally responsive interface passivating agent composition, the thermally responsive interface passivating agent composition comprising a silane component and a sulfide component; The silane component is selected from any one or more of 3-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane; The sulfur-based components are selected from diisopropyl xanthate disulfide and / or diphenyl disulfide.

[0007] The thermally responsive interface passivating agent composition provided by this invention comprises silane components and sulfide components, combining the condensation film-forming ability of silane molecules with the low-temperature free radical induction characteristics of sulfide compounds. When applied to the electrolyte, it does not affect the electrochemical performance of the battery under normal operating conditions. However, at high temperatures of 100-120°C, the two components work synergistically to spontaneously polymerize on the negative electrode surface through a "free radical-induced silane condensation" polymerization mechanism, forming a stable and dense passivation layer. This achieves rapid interface passivation at low response temperatures, thereby inhibiting electrolyte decomposition and HF generation, preventing battery thermal runaway. Compared with traditional additives, the response temperature is significantly lower (30-50°C earlier), far below the membrane melting threshold, overcoming the problems of high response temperature, slow film-forming rate, and insufficient interface stability of existing thermally responsive additives.

[0008] The silane components exist in a dispersed state at room temperature, without affecting lithium-ion migration or electrode interface stability. When the battery temperature rises to 100-120℃, the -SS- bonds in the sulfide components undergo thermal decomposition, generating sulfur free radicals. These free radicals can induce silane molecules to undergo de-alcoholization condensation reactions, forming Si-O-Si and Si-OM (M is a metal element on the negative electrode surface) bonds. This results in a dense passivation layer on the negative electrode surface. This passivation layer forms spontaneously in the early stages of heating and can form an effective thermal barrier before the separator ruptures, blocking electron leakage and electrolyte decomposition, thereby significantly improving battery thermal safety while maintaining excellent electrochemical performance at room temperature.

[0009] As a preferred embodiment of the present invention, the mass ratio of the silane component to the sulfur component is 1:(0.5-2), for example, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc.

[0010] As a preferred embodiment of the present invention, the silane component is selected from γ-aminopropyltriethoxysilane.

[0011] When the silane component is selected from γ-aminopropyltriethoxysilane, it exists in a dispersed state at room temperature, which does not affect lithium-ion migration and electrode interface stability. However, when the battery temperature rises to 100-120℃, on the one hand, the -SS- bonds in the sulfur-based components undergo thermal decomposition to generate sulfur free radicals, which induce silane molecules to undergo de-alcoholization condensation reactions to form Si-O-Si and Si-OM (M is the metal element on the negative electrode surface) bonds. On the other hand, sulfur free radicals can crosslink with the amino groups in the γ-aminopropyltriethoxysilane molecules, thereby forming a dense and stable organic-inorganic composite passivation layer in situ on the negative electrode surface, which more effectively blocks electron leakage and electrolyte decomposition, and further improves the thermal safety of the battery.

[0012] As a preferred embodiment of the present invention, the sulfur-based component is selected from diisopropyl disulfide xanthate.

[0013] In a second aspect, the present invention provides an electrolyte comprising the thermally responsive interface passivating agent composition described in the first aspect.

[0014] The electrolyte provided by this invention includes the thermally responsive interface passivator composition described in the first aspect. Under normal battery operating conditions, it does not affect the electrochemical performance of the battery. However, at a high temperature of 100-120°C, the thermally responsive interface passivator composition can spontaneously polymerize on the surface of the negative electrode to form a stable and dense passivation layer, forming an effective thermal barrier before the separator ruptures. This effectively blocks electron leakage and electrolyte decomposition, significantly improving the thermal safety of the battery.

[0015] As a preferred embodiment of the present invention, the content of the thermal response interface passivating agent composition is 1-4%, for example, 1%, 2%, 3%, 4%, etc., based on the total mass of the electrolyte as 100%.

[0016] As a preferred embodiment of the present invention, the content of the thermally responsive interface passivating agent composition is 2.5-4% based on the total mass of the electrolyte being 100%.

[0017] As a preferred embodiment of the present invention, the electrolyte further includes lithium salt, additives, and carbonate organic solvents.

[0018] As a preferred embodiment of the present invention, the carbonate organic solvent is selected from any one or more of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, or diethyl carbonate.

[0019] As a preferred embodiment of the present invention, the carbonate organic solvent is selected from a combination of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate.

[0020] As a preferred embodiment of the present invention, the mass ratio of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate is 5:8:3.

[0021] As a preferred embodiment of the present invention, the content of the carbonate organic solvent is 77-84% based on the total mass of the electrolyte as 100%, for example, 77%, 80%, 82%, 84%, etc.

[0022] As a preferred embodiment of the present invention, the additive is selected from any one or more of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, ethylene sulfate, or lithium difluorooxalate borate.

[0023] As a preferred embodiment of the present invention, the content of the additive is 2-5%, for example, 2%, 3%, 4%, 5%, etc., based on the total mass of the electrolyte as 100%.

[0024] As a preferred embodiment of the present invention, the lithium salt is selected from lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0025] As a preferred embodiment of the present invention, the lithium salt content is 9-16% based on the total mass of the electrolyte as 100%, for example, 9%, 10%, 12%, 14%, 16%, etc.

[0026] Thirdly, the present invention provides a lithium-ion battery comprising the thermally responsive interface passivating agent composition described in the first aspect or the electrolyte described in the second aspect.

[0027] The lithium-ion battery provided by this invention exhibits no significant thermal runaway at 120°C, with a significantly reduced internal temperature rise and a significantly improved safety threshold.

[0028] As a preferred embodiment of the present invention, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator.

[0029] As a preferred embodiment of the present invention, the positive electrode is a lithium iron phosphate positive electrode.

[0030] As a preferred embodiment of the present invention, the negative electrode is a graphite negative electrode.

[0031] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: 1. In the thermally responsive interface passivating agent composition provided by this invention, the sulfur-based component containing -SS- bonds can induce the silane condensation reaction to occur earlier, reducing the passivation layer formation temperature from approximately 150°C in traditional thermally responsive additive systems to 100-120°C, effectively covering the safety window before the separator ruptures. Moreover, the sulfur radical-induced condensation reaction rate is high, enabling the formation of a dense passivation layer in situ on the negative electrode surface in a short time, rapidly cutting off the side reaction chain path, thereby significantly improving the battery's safety performance.

[0032] 2. The electrolyte provided by the present invention includes a thermally responsive interface passivating agent composition, which does not affect the electrochemical performance of the battery under normal battery operating conditions. However, at a high temperature of 100-120°C, the thermally responsive interface passivating agent composition can spontaneously polymerize on the surface of the negative electrode to form a stable and dense passivation layer, that is, to form an effective thermal barrier before the separator ruptures, thereby effectively blocking electron leakage and electrolyte decomposition, and significantly improving the thermal safety of the battery. Detailed Implementation

[0033] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0035] In the following embodiments, unless otherwise specified, all raw materials used are commercially available products. The sources of some of these raw materials are as follows: Ethylene carbonate: CAS No. 96-49-1, Beijing Bailingwei Technology Co., Ltd.; Ethyl methyl carbonate: CAS No. 623-53-0, Beijing Bailingwei Technology Co., Ltd.; Dimethyl carbonate: CAS No. 616-38-6, Beijing Bailingwei Technology Co., Ltd.; Fluorinated vinyl carbonate: CAS No. 114435-02-8, Beijing Bailingwei Technology Co., Ltd.; Vinylene carbonate: CAS No. 872-36-6, Duoduo Chemical Reagent Platform Company; Lithium difluorophosphate: CAS No. 24389-25-1, owned by Duoduo Chemical Reagent Platform Company; Lithium hexafluorophosphate: CAS No. 21324-40-3, owned by Duoduo Chemical Reagent Platform Company; γ-aminopropyltriethoxysilane: CAS No. 919-30-2, Shanghai Adamas Reagent Co., Ltd.; Diisopropyl disulfide xanthate: CAS No. 105-65-7, Aladdin Reagent (Shanghai) Co., Ltd.

[0036] Example 1 This embodiment provides an electrolyte comprising a composition of lithium salt, additives, carbonate organic solvents, and thermally responsive interface passivating agent. The carbonate organic solvent is a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, with a mass ratio of 5:8:3. The carbonate organic solvent accounts for 80% of the total mass of the electrolyte. The lithium salt is lithium hexafluorophosphate, and it accounts for 13.5% of the total mass of the electrolyte. The additive is a mixture of vinylene carbonate, lithium difluorophosphate, and fluoroethylene carbonate, with a mass ratio of 3:0.5:0.5, and the additive accounts for 4% of the total mass of the electrolyte. The thermally responsive interface passivator composition is a mixture of γ-aminopropyltriethoxysilane and diisopropyl xanthate disulfide, with a mass ratio of 1:1.5. The thermally responsive interface passivator composition accounts for 2.5% of the total mass of the electrolyte.

[0037] The electrolyte was prepared in an argon-protected glove box (with water and oxygen contents both less than 0.1 ppm). Lithium salt was added to a carbonate organic solvent, followed by an additive and a thermally responsive interface passivating agent composition, and the mixture was stirred at room temperature for 10 h.

[0038] Example 2 This embodiment provides an electrolyte with the same composition as in Example 1. The difference is that in this embodiment, the content of carbonate organic solvent is 78.5% and the content of thermally responsive interface passivating agent composition is 4%.

[0039] Example 3 This embodiment provides an electrolyte with the same composition as in Example 1. The difference is that in this embodiment, the content of carbonate organic solvent is 81.5% and the content of thermally responsive interface passivating agent composition is 1%.

[0040] Example 4 This embodiment provides an electrolyte with the same composition as in Example 1. The difference is that in this embodiment, the mass ratio of γ-aminopropyltriethoxysilane to diisopropyl xanthate disulfide is 1:0.5.

[0041] Example 5 This embodiment provides an electrolyte with the same composition as in Example 1. The difference is that the thermal response interface passivator composition in this embodiment is a mixture of 3-mercaptopropyltrimethoxysilane and diphenyl disulfide, and the mass ratio of the two is 1:2.

[0042] Comparative Example 1 This comparative example provides an electrolyte with the same composition as Example 1. The difference from Example 1 is that the content of carbonate organic solvent in this comparative example is 77.5%, and the content of thermally responsive interface passivating agent composition is 5%.

[0043] Comparative Example 2 This comparative example provides an electrolyte with the same composition as Example 1. The difference from Example 1 is that the content of carbonate organic solvent in this comparative example is 82%, and the content of thermally responsive interface passivating agent composition is 0.5%.

[0044] Comparative Example 3 This comparative example provides an electrolyte with the same composition as Example 1. The difference from Example 1 is that no thermally responsive interface passivating agent composition is added in this comparative example, and the content of carbonate organic solvent is 82.5%.

[0045] Comparative Example 4 This comparative example provides an electrolyte with the same composition as in Example 1. The difference from Example 1 is that the thermally responsive interface passivator composition is replaced with γ-aminopropyltriethoxysilane in this comparative example.

[0046] Comparative Example 5 This comparative example provides an electrolyte with the same composition as in Example 1. The difference from Example 1 is that the thermally responsive interface passivator composition is replaced with diisopropyl disulfide xanthate in this comparative example.

[0047] Application examples The electrolytes provided in the examples and comparative examples were used to assemble batteries.

[0048] 314 Ah dry cell batteries purchased from EVE Energy were selected and injected with the electrolytes provided in the examples and comparative examples, respectively. The cells were formed and tested by charging and discharging at a rate of 0.1 C to obtain cells with stable electrochemical performance.

[0049] Performance testing The battery cells assembled according to the method described in the application example will be subjected to performance testing.

[0050] (1) High temperature cycle capacity retention test: In accordance with the requirements of national standard GB / T 36276-2023, a battery charge and discharge test system was used to perform 100 charge and discharge cycles at room temperature with a constant power of 1 P in the voltage range of 2.5 V-3.65 V, and the discharge capacity of each cycle was recorded. High-temperature cycling capacity retention % = (Discharge capacity of the 100th high-temperature cycle / Discharge capacity of the 1st high-temperature cycle) × 100%; (2) High temperature energy efficiency test: In accordance with the requirements of national standard GB / T 36276-2023, the same test system as the high temperature cycle capacity retention test was used. In the voltage range of 2.5 V-3.65 V, one charge-discharge cycle was performed at a rate of 1 P, and the charge-discharge energy was recorded respectively. High-temperature energy efficiency % = (Total discharge energy / Total charge energy) × 100%; (3) Needle penetration safety test: According to GB / T 31485-2015 standard, under the full charge state of the battery cell, a steel needle with a diameter of 6 mm is inserted along the thickness direction of the battery cell under the monitoring of thermocouple, and the battery cell is observed to see if it catches fire, explodes or expands significantly.

[0051] The test results are shown in Table 1: Table 1

[0052] As shown in Table 1, the electrolyte system prepared using the thermally responsive interface passivator composition provided by this invention is superior to the comparative examples in terms of high-temperature cycling performance, energy efficiency, and safety performance. The high-temperature cycling capacity retention rate and energy efficiency of the cells in the examples reach over 99% and over 95.95%, respectively, which are significantly higher than those of the systems without the thermally responsive interface passivator composition of this invention (Comparative Examples 3-5).

[0053] In the needle penetration test, the cells in the example samples all showed no valve opening and no smoke, while the comparative samples all showed valve opening and smoke. This indicates that the thermally responsive interface passivator composition provided by the present invention can rapidly form a stable passivation layer under heating conditions, forming an effective thermal barrier before the separator ruptures, thereby effectively suppressing interfacial side reactions and thermal runaway, and improving the thermal stability and intrinsic safety of lithium-ion batteries.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0055] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thermally responsive interface passivating agent composition, characterized in that, The thermally responsive interface passivating agent composition includes silane components and sulfur-based components; The silane component is selected from any one or more of 3-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane; The sulfur-based components are selected from diisopropyl xanthate disulfide and / or diphenyl disulfide.

2. The thermally responsive interface passivating agent composition according to claim 1, characterized in that, The mass ratio of the silane component to the sulfide component is 1:(0.5-2).

3. The thermally responsive interface passivating agent composition according to claim 1 or 2, characterized in that, The silane component is selected from γ-aminopropyltriethoxysilane; And / or, the sulfur-based component is selected from diisopropyl disulfide xanthate.

4. An electrolyte, characterized in that, The electrolyte comprises the thermally responsive interface passivating agent composition according to any one of claims 1-3.

5. The electrolyte according to claim 4, characterized in that, Based on the total mass of the electrolyte (100%), the content of the thermally responsive interface passivating agent composition is 1-4%, preferably 2.5-4%.

6. The electrolyte according to claim 4 or 5, characterized in that, The electrolyte also includes lithium salts, additives, and carbonate organic solvents.

7. The electrolyte according to claim 6, characterized in that, The carbonate organic solvent is selected from any one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate. And / or, based on the total mass of the electrolyte, the content of the carbonate organic solvent is 77-84%.

8. The electrolyte according to claim 6 or 7, characterized in that, The additive is selected from any one or more of vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, ethylene sulfate, or lithium difluorooxalate borate. And / or, based on the total mass of the electrolyte, the content of the additive is 2-5%.

9. The electrolyte according to any one of claims 6-8, characterized in that, The lithium salt is selected from lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide; And / or, based on the total mass of the electrolyte, the lithium salt content is 9-16%.

10. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the thermally responsive interface passivator composition according to any one of claims 1-3 or the electrolyte according to any one of claims 4-9.

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