Lithium ion battery electrolyte and lithium ion battery containing same
By using a synergistic design of carboxylic acid ester solvent and negative electrode binder in lithium-ion batteries and optimizing the electrolyte formulation, the problems of fast charging and cycle performance of batteries under low temperature conditions were solved, achieving high lithium-ion flux and low impedance.
Patent Information
- Application Number
- CN202511742555.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-25
- Publication Date
- 2026-02-17
AI Technical Summary
Existing lithium-ion batteries suffer from poor electrolyte stability at low temperatures, leading to a decline in battery cycle performance and fast-charging capability. Furthermore, traditional binders have poor interfacial compatibility with the electrolyte, making it difficult to simultaneously improve the bottlenecks in electron conduction and lithium-ion transport.
An electrolyte formulation containing carboxylic acid ester solvent, linear carbonate solvent, cyclic carbonate solvent, lithium salt and additives is adopted. Through the synergistic effect of carboxylic acid ester solvent and negative electrode binder, the interfacial compatibility and ion transport network are optimized, thereby improving the battery's fast charging capability and stability in low-temperature environments.
It achieves high lithium-ion flux and low impedance in batteries at low temperatures, improves the battery's fast-charging performance and cycle stability, reduces the risk of electrolyte solidification at low temperatures, and enhances the electron transfer efficiency at the negative electrode interface.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium ion battery materials, and particularly relates to a lithium ion battery electrolyte and a lithium ion battery containing the electrolyte. BACKGROUND
[0002] In the prior art, the commonly used binder for the negative electrode material of a lithium ion battery includes polyvinylidene fluoride and butadiene-styrene rubber, etc. Although the water-based SBR binder is environmentally friendly, the adhesion of the binder to non-polar electrode material graphite is insufficient, and the electrode is prone to cracking after drying, resulting in high electronic contact resistance between the negative electrode active material, the conductive agent and the current collector. In addition, the interface compatibility between the binder and the electrolyte is poor, and a high impedance SEI layer is easily formed, further hindering the ion transfer and deintercalation process. The traditional carbonate electrolyte has high viscosity at low temperature, and the ion migration rate is slow. Lithium dendrites are easily caused due to lithium transfer lag during fast charging. The use of electrolyte solvent alone has limited effect on the improvement of fast charging performance, and it is difficult to form an interface synergy with the negative electrode material.
[0003] In addition, the binder and the electrolyte additive are usually optimized independently, and there is a lack of "negative electrode binder-electrolyte additive" synergistic design. For example, although the binder can be improved alone to improve electronic conduction, it cannot solve the bottleneck of lithium ion transport in the electrolyte. Although the addition of ester electrolyte additives alone can improve lithium ion migration, it is difficult to reduce the electronic resistance of the negative electrode interface, resulting in difficulty in synchronously improving the fast charging capacity of the lithium battery and the efficiency of the negative electrode electron transfer. Through the interface contact interaction between the carboxylic acid ester solvent and the propylene-based binder negative electrode, the low viscosity of the carboxylic acid ester accelerates the penetration of the electrolyte into the negative electrode, and the high swelling of propylene makes the electrolyte more enter the interstitial gap of the binder molecular chain, forming a continuous ion transport network to avoid lithium ion deficiency polarization. At the same time, the interface formed by the decomposition of the carboxylic acid ester solvent relieves the cracking of the SEI layer, enhances the interface repair ability, and enhances the cycle stability of the battery.
[0004] Under low temperature environment, the electrolyte is prone to solidification and viscosity change, thereby causing the fast charging performance of the battery to decay and the performance of the battery cell to decrease under low temperature environment. SUMMARY
[0005] The purpose of the present application is to provide a lithium ion battery electrolyte and a lithium ion battery containing the electrolyte, so as to solve the technical problems of poor electrolyte stability, battery cycle performance and fast charging capacity decay under low temperature environment in the prior art.
[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is to provide a lithium ion battery electrolyte, characterized in that it comprises a carboxylic acid ester solvent, a linear carbonate solvent, a cyclic carbonate solvent, a lithium salt and an additive. The structural formula of the carboxylic acid ester solvent is:
[0007] Wherein, 0≤n≤3, n=0 is methyl propionate, n=1 is methyl butyrate, n=2 is methyl valerate, and n=3 is methyl hexanoate.
[0008] In one of the embodiments, The linear carbonate solvent is one of dimethyl carbonate, ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate.
[0009] In one of the embodiments, The cyclic carbonate solvent is vinyl carbonate or propylene carbonate.
[0010] In one of the embodiments, The lithium salt is a phosphorus-containing lithium salt, a boron-containing lithium salt or a lithium lithium salt.
[0011] In one of the embodiments, The additive is one or more of a film-forming additive, an overcharge-preventing additive, a flame-retardant additive, a conductive additive or a wetting additive.
[0012] In one of the embodiments, The film-forming additive is one of vinylene carbonate, fluorinated vinylene carbonate, lithium difluorobis(oxalato)borate, tris(trimethylsilyl)phosphate or 1,3-propane sultone, the overcharge-preventing additive is cyclohexylbenzene or biphenyl, the flame-retardant additive is trimethyl phosphate or triethyl phosphate, and the conductive high-voltage stabilizing additive is one of dimethoxyethane, butanedinitrile, hexanedinitrile or octanedinitrile.
[0013] In one of the embodiments, According to the mass percentage, the carboxylic acid ester solvent accounts for 20-50 %, the linear carbonate solvent accounts for 8.5-50 %, the cyclic carbonate solvent accounts for 5-35 %, the lithium salt accounts for 5-15 %, and the additive accounts for 0.1-5 %.
[0014] In one of the embodiments, The content of the carboxylic acid ester solvent and the linear carbonate solvent needs to meet: 0.4≤carboxylic acid ester solvent / linear carbonate solvent≤5, and the content of the carboxylic acid ester solvent and the cyclic carbonate solvent needs to meet: 0.6≤carboxylic acid ester solvent / cyclic carbonate solvent≤10.
[0015] The application also provides a lithium ion battery for a low-temperature environment, comprising a negative electrode material, a lithium ion battery electrolyte of any one of the above embodiments, a positive electrode sheet, a negative electrode sheet and a separator. The negative electrode material comprises, according to the mass percentage, 2-8 % of a negative electrode binder acrylate polymer, 1-2 % of conductive carbon and 90-97 % of graphite.
[0016] In one of the embodiments, The acrylate polymer is one of acrylate, methacrylate, acrylamide, acrylonitrile, sulfurized polyacrylonitrile or alcohol grafted acrylate; The content of the carboxylate solvent and the negative electrode binder needs to meet: 0.04 ≤ negative electrode binder / carboxylate solvent ≤ 0.4; The thickness of the separator is 5-10 μm, and the thickness of the negative electrode sheet and the positive electrode sheet is 50-300 μm.
[0017] The present application provides a kind of lithium ion battery electrolyte and the lithium ion battery containing the electrolyte, by acrylate modification binder and ester group solvent formula improve battery fast charging and low temperature performance, develop a kind of "binder-electrolyte additive" synergistic system, through the interface interaction of both, simultaneously optimize lithium ion transport and electron transfer, break through the bottleneck of prior art, realize the dual effect of lithium battery fast charging ability promotion and negative electrode electron transfer efficiency enhancement;Compared with prior art, the present application has the following beneficial effects: 1、The carboxylate solvent added in the present application is a straight-chain carboxylate and does not contain halogen functional groups. Through the polar group of its own molecular structure, the intermolecular force is weaker than that of traditional carbonate solvents, so it has low viscosity characteristics, effectively reduces the internal ion migration resistance of the electrolyte, reduces the activation energy of ion movement, makes the lithium ion more easily separate from the solvation sheath in the solvent, and provides a basis for high ion flux in fast charging scenarios. 2、The carboxylate solvent added in the present application has a low melting point, which reduces the overall freezing point of the electrolyte, avoids the freezing of the electrolyte at low temperatures, and keeps the viscosity of the electrolyte from increasing at low temperatures, making it more suitable for fast charging in low temperature environments. 3、The ester group of the carboxylate solvent has unique electrochemical activity. The oxygen atom in its molecule contains a lone pair of electrons, has weak nucleophilicity, and can preferentially undergo moderate reduction decomposition at the negative electrode interface before other solvents, participating in the construction of the solid electrolyte interface layer. 4、The polarity and molecular size of the carboxylate solvent are moderate, and it has good compatibility with the acrylate polymer in the negative electrode binder, avoiding performance degradation due to poor interaction between the solvent and the material, reducing damage to the graphite layer structure, and inhibiting graphite peeling.
[0018] 5、The ester group of the carboxylate solvent forms a hydrogen bond interaction with the acrylate polymer on the surface of the negative electrode binder, which can improve the interfacial compatibility of the negative electrode binder with the electrolyte and reduce the swelling of the binder. DETAILED DESCRIPTION
[0019] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear and explicit, the present application is further described in detail. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.
[0020] Example 1 In this embodiment, the carboxylic acid ester solvent is selected as methyl propionate, the content of methyl propionate is 20 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 724 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 589 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 485 cls.
[0021] Example 2 The difference between this embodiment and Example 1 is that the content of methyl propionate is 25 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 729 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 594 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 492 cls.
[0022] Example 3 The difference between this embodiment and Example 1 is that the content of methyl propionate is 30 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 737 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 596 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 511 cls.
[0023] Example 4 The difference between this embodiment and Example 1 is that the content of methyl propionate is 35 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 733 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 599 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 513 cls.
[0024] Example 5 The difference between this embodiment and Example 1 is that the content of methyl propionate is 40 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 746 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 604 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 519 cls.
[0025] Example 6 The difference between this embodiment and Example 1 is that the content of methyl propionate is 45 %, the performance of the battery cell is tested, the cycle life when the capacity decays to 80 % at 25 ℃ is 748 cls, the cycle life when the capacity decays to 80 % at 0 ℃ is 608 cls, and the cycle life when the capacity decays to 80 % at -10 ℃ is 515 cls.
[0026] Example 7 The difference between this embodiment and embodiment 1 is that the content of methyl propionate is 50%, and the performance of the battery cell is tested. The cycle life when the capacity decays to 80% at 25°C is 740 cls, the cycle life when the capacity decays to 80% at 0°C is 601 cls, and the cycle life when the capacity decays to 80% at -10°C is 509 cls.
[0027] By comparing the effects of different contents of carboxylic acid ester solvents on the performance of battery cells through embodiments 1-7, within the additive amount defined in this application, the cycle performance and rate performance of the battery at low temperature are obviously improved. Therefore, the carboxylic acid ester solvent can optimize the electrolyte example migration dynamics, provide high lithium ion flux + low impedance, and improve the fast charging capacity and battery stability.
[0028] Embodiment 8 In this embodiment, the acrylic ester polymer is selected from acrylic acid, the content of acrylic acid is 3%, the content of methyl propionate is 45%, and the negative electrode binder / carboxylic acid ester solvent=0.06. The performance of the battery cell is tested, the expansion rate after 20 days of storage at 60°C is 16%, the cycle life when the capacity decays to 80% at 25°C is 701 cls, and the cycle life when the capacity decays to 80% at -10°C is 483 cls.
[0029] Embodiment 9 The difference between this embodiment and embodiment 8 is that the content of acrylic acid is 6%, the content of methyl propionate is 45%, and the negative electrode binder / carboxylic acid ester solvent=0.13. The performance of the battery cell is tested, the expansion rate after 20 days of storage at 60°C is 7%, the cycle life when the capacity decays to 80% at 25°C is 742 cls, and the cycle life when the capacity decays to 80% at -10°C is 511 cls.
[0030] Embodiment 10 The difference between this embodiment and embodiment 8 is that the content of acrylic acid is 3%, the content of methyl propionate is 35%, and the negative electrode binder / carboxylic acid ester solvent=0.086. The performance of the battery cell is tested, the expansion rate after 20 days of storage at 60°C is 15%, the cycle life when the capacity decays to 80% at 25°C is 742 cls, and the cycle life when the capacity decays to 80% at -10°C is 511 cls.
[0031] Embodiment 11 The difference between this embodiment and embodiment 8 is that the content of acrylic acid is 6%, the content of methyl propionate is 35%, the negative electrode binder / carboxylate solvent = 0.17, and the performance of the battery cell is tested. The expansion rate is 5% after 20 days of storage at 60°C, the cycle life is 728 cls when the capacity decays to 80% at 25°C, and the cycle life is 509 cls when the capacity decays to 80% at -10°C.
[0032] Example 12 The difference between this embodiment and embodiment 8 is that the content of acrylic acid is 3%, the content of methyl propionate is 25%, the negative electrode binder / carboxylate solvent = 0.12, and the performance of the battery cell is tested. The expansion rate is 12% after 20 days of storage at 60°C, the cycle life is 679 cls when the capacity decays to 80% at 25°C, and the cycle life is 466 cls when the capacity decays to 80% at -10°C.
[0033] Example 13 The difference between this embodiment and embodiment 8 is that the content of acrylic acid is 3%, the content of methyl propionate is 25%, the negative electrode binder / carboxylate solvent = 0.24, and the performance of the battery cell is tested. The expansion rate is 6% after 20 days of storage at 60°C, the cycle life is 711 cls when the capacity decays to 80% at 25°C, and the cycle life is 486 cls when the capacity decays to 80% at -10°C.
[0034] By comparing the performance of the battery cell with different contents of negative electrode binder polymer in examples 8-13, the cycle performance changes with the change of the ratio of carboxylate / negative electrode binder. Because of the coordination ability of the negative electrode binder with the surface hydroxyl group of graphite / silicon, the interface peeling of the negative electrode binder occurs due to the expansion of the electrode in fast charging cycle, which causes the stability problem. With the change of the content of the negative electrode binder, the battery expansion rate and fast charging cycle also change obviously.
[0035] Example 14 In this embodiment, the content of the additive is 4% (specifically, fluoroethylene carbonate accounts for 2%, and difluoroboric acid lithium dioxalate accounts for 2%), the content of lithium salt is 12.5%, the cyclic carbonate solvent is selected as ethylene carbonate, the content of ethylene carbonate is 10%, the content of methyl propionate is 45%, and the carboxylate solvent / cyclic carbonate solvent = 4.5. The performance of the battery cell is tested. The cycle life is 528 cls when the 3C charging and discharging capacity decays to 80% at 25°C, and the cycle life is 452 cls when the 2C charging and discharging capacity decays to 80% at 25°C.
[0036] Example 15 The content of ethylene carbonate in this example is 30%, the content of methyl propionate is 45%, the carboxylic acid ester solvent / cyclic carbonate solvent = 1.5, and the performance of the battery cell is tested. The cycle life when the 3C charge-discharge capacity decays to 80% at 25°C is 538 cls, and the cycle life when the 2C charge-discharge capacity decays to 80% at 25°C is 466 cls.
[0037] Example 16 The content of ethylene carbonate in this example is 10%, the content of methyl propionate is 35%, the carboxylic acid ester solvent / cyclic carbonate solvent = 3.5, and the performance of the battery cell is tested. The cycle life when the 3C charge-discharge capacity decays to 80% at 25°C is 506 cls, and the cycle life when the 2C charge-discharge capacity decays to 80% at 25°C is 433 cls.
[0038] Example 17 The content of ethylene carbonate in this example is 30%, the content of methyl propionate is 35%, the carboxylic acid ester solvent / cyclic carbonate solvent = 1.16, and the performance of the battery cell is tested. The cycle life when the 3C charge-discharge capacity decays to 80% at 25°C is 518 cls, and the cycle life when the 2C charge-discharge capacity decays to 80% at 25°C is 442 cls.
[0039] Example 18 The content of ethylene carbonate in this example is 10%, the content of methyl propionate is 25%, the carboxylic acid ester solvent / cyclic carbonate solvent = 2.5, and the performance of the battery cell is tested. The cycle life when the 3C charge-discharge capacity decays to 80% at 25°C is 497 cls, and the cycle life when the 2C charge-discharge capacity decays to 80% at 25°C is 429 cls.
[0040] Example 19 The content of ethylene carbonate in this example is 30%, the content of methyl propionate is 25%, the carboxylic acid ester solvent / cyclic carbonate solvent = 0.83, and the performance of the battery cell is tested. The cycle life when the 3C charge-discharge capacity decays to 80% at 25°C is 503 cls, and the cycle life when the 2C charge-discharge capacity decays to 80% at 25°C is 417 cls.
[0041] By implementing examples 14-19, the different content ratio of cyclic carbonate solvent and carboxylic acid ester solvent is compared to the performance of the battery. With the change of the ratio of carboxylic acid ester solvent / cyclic carbonate solvent, the fast charging cycle performance changes, because the cyclic carbonate destroys the lithium ion and anion pair by strong polarity, forming free moving lithium ions. Low content of cyclic carbonate solvent will significantly reduce the ionic conductivity, increase the charging time and improve the internal resistance, and the SEI stability decreases, reducing the cycle performance.
[0042] The specific types of carboxylic acid ester solvent, linear carbonate solvent, cyclic carbonate solvent, lithium salt and additive can be arbitrarily replaced as needed, and the performance of the electrolyte is not affected. Other combinations are not listed here.
[0043] Example 20 A lithium ion battery electrolyte, including 45 % of methyl propionate, 10 % of dimethyl carbonate, 30 % of ethylene carbonate, 10 % of phosphorus-containing lithium salt and 5 % of additives (2 % of vinylene carbonate, 2 % of cyclohexylbenzene, and 1 % of dimethoxyethane).
[0044] Example 21 A lithium ion battery electrolyte, including 45 % of methyl propionate, 10 % of dimethyl carbonate, 30 % of ethylene carbonate, 5 % of phosphorus-containing lithium salt and 0.5 % of additives (0.2 % of tris(trimethylsilyl) phosphate, 0.2 % of trimethyl phosphate, and 0.1 % of adiponitrile).
[0045] Example 22 A lithium ion battery for low temperature environment, including 6 % of acrylic acid, 1 % of conductive carbon, 93 % of graphite, the lithium ion battery electrolyte prepared in example 20, 150 μm thick positive electrode sheet, 150 μm thick negative electrode sheet and 8 μm thick separator.
[0046] Example 23 The difference between this example and example 22 is that the negative electrode material ratio is: 3 % of acrylic acid, 2 % of conductive carbon, and 95 % of graphite. The rest of the operation is the same.
[0047] The above only describes the preferred embodiments of the present application and does not limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A lithium-ion battery electrolyte, characterized in that, The carboxylic ester solvent, linear carbonate solvent, cyclic carbonate solvent, lithium salt and additive; The structural formula of the carboxylic ester solvent is: 0≤n≤3.
2. The electrolyte for lithium ion batteries according to claim 1, wherein The linear carbonate solvent is one of dimethyl carbonate, methyl ethyl carbonate, dimethyl carbonate or diethyl carbonate.
3. The electrolyte for lithium ion battery according to claim 1, wherein The cyclic carbonate solvent is ethylene carbonate or propylene carbonate.
4. The electrolyte for lithium ion batteries according to claim 1, characterized in that, The lithium salt is a phosphorus-containing lithium salt, a boron-containing lithium salt or a lithium lithium salt of sulfonimide.
5. The electrolyte for lithium ion battery according to claim 1, wherein The additive is one or more of a film-forming additive, an overcharge-preventing additive, a flame-retardant additive, a conductive additive or a wetting additive.
6. The electrolyte for lithium ion batteries according to claim 5, characterized in that, The film-forming additive is one of vinylene carbonate, fluorinated vinylene carbonate, lithium difluorobis(oxalato)borate, tris(trimethylsilyl)phosphate or 1,3-propane sultone, the overcharge-preventing additive is cyclohexylbenzene or biphenyl, the flame-retardant additive is trimethyl phosphate or triethyl phosphate, and the conductive high-voltage stabilizing additive is one of dimethoxyethane, butanedinitrile, hexanedinitrile or octanedinitrile.
7. The electrolyte for lithium ion battery according to claim 1, wherein The carboxylic ester solvent accounts for 20-50 %, the linear carbonate solvent accounts for 8.5-50 %, the cyclic carbonate solvent accounts for 5-35 %, the lithium salt accounts for 5-15 % and the additive accounts for 0.1-5 % by mass percentage.
8. The electrolyte for lithium ion batteries according to claim 7, characterized in that, The content of the carboxylic ester solvent and the linear carbonate solvent needs to satisfy 0.4≤carboxylic ester solvent / linear carbonate solvent≤5, and the content of the carboxylic ester solvent and the cyclic carbonate solvent needs to satisfy 0.6≤carboxylic ester solvent / cyclic carbonate solvent≤10.
9. A lithium ion battery for use in a cryogenic environment, characterized in that, The negative electrode material, the lithium ion battery electrolyte according to any one of claims 1-8, the positive electrode sheet, the negative electrode sheet and the separator are included. The negative electrode material includes 2-8 % of a negative electrode binder acrylate polymer, 1-2 % of conductive carbon and 90-97 % of graphite by mass percentage.
10. The lithium-ion battery for cryogenic environment according to claim 9, wherein, The acrylate polymer is one of acrylic acid, methacrylic acid, acrylamide, acrylonitrile, vulcanized polyacrylonitrile or alcohol grafted acrylic acid; The content of the carboxylic ester solvent and the negative electrode binder needs to satisfy 0.04≤negative electrode binder / carboxylic ester solvent≤0.
4. The thickness of the separator is 5-10 μm, and the thickness of the negative electrode sheet and the positive electrode sheet is both 50-300 μm.