WO2023050766A1 - 一种电解液体系及其应用 - Google Patents

一种电解液体系及其应用 Download PDF

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Publication number
WO2023050766A1
WO2023050766A1 PCT/CN2022/086196 CN2022086196W WO2023050766A1 WO 2023050766 A1 WO2023050766 A1 WO 2023050766A1 CN 2022086196 W CN2022086196 W CN 2022086196W WO 2023050766 A1 WO2023050766 A1 WO 2023050766A1
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Prior art keywords
electrolyte
electrolyte system
solution according
lithium
vinylene carbonate
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PCT/CN2022/086196
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English (en)
French (fr)
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支岩辉
田林
杨红新
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蜂巢能源科技股份有限公司
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Priority to EP22874166.6A priority Critical patent/EP4300653A1/en
Publication of WO2023050766A1 publication Critical patent/WO2023050766A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0438—Processes of manufacture in general by electrochemical processing
    • H01M4/044—Activating, forming or electrochemical attack of the supporting material
    • H01M4/0445—Forming after manufacture of the electrode, e.g. first charge, cycling
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present disclosure relates to the field of lithium-ion batteries, for example, to an electrolyte system and its application.
  • the density of carboxylate is significantly lower than that of carbonate. Adding a large amount of carboxylate to the electrolyte solvent can effectively reduce the overall density of the electrolyte; but the addition of a large amount of carboxylate will obviously affect the cycle performance of the cell, especially at high temperature. cycle performance, so a large amount of negative electrode additives is needed to improve the protection of the cell interface and improve the cycle performance of the cell; however, the addition of a large amount of negative electrode additives also increases the DC internal resistance of the cell, resulting in a decrease in the power performance and low temperature performance of the cell. deteriorating.
  • the disclosure provides an electrolyte system and its application.
  • the disclosure combines the low-density electrolyte with the secondary liquid injection technology, and adds a large amount of negative electrode film-forming additives during the secondary liquid injection process to improve the protection of the negative electrode interface. , reduce the side reaction of carboxylate on the surface of the negative electrode, improve the cycle performance of the cell, and at the same time, the secondary injection technology also ensures the low impedance of the cell, thereby ensuring the power performance and low temperature performance of the cell; low-density electrolysis
  • the application of liquid also significantly reduces the quality of the electrolyte under the same volume of electrolyte and improves the energy density of the battery cell.
  • the present disclosure provides an electrolyte system
  • the electrolyte system includes A electrolyte system and B electrolyte system
  • the A electrolyte system includes a first solvent, a lithium salt and a first functional additive
  • the B electrolyte system includes a second solvent and a second functional additive
  • the mass ratio of the carboxylate in the first solvent is ⁇ 40%, for example: 40%, 42%, 45%, 50%, 55%, 60% % or 80%, etc.
  • the mass ratio of carboxylate in the second solvent is >50%, for example: 55%, 60%, 65%, 70% or 80%, etc.
  • the first functional additive includes Vinyl ester and vinyl sulfate
  • the second functional additive includes fluorobenzene and vinylene carbonate
  • the A electrolyte system is the electrolyte used for primary injection
  • the B electrolyte system is used for secondary injection
  • step (1) can be performed first and then step (2), or step (2) can be performed first and then step 1).
  • Both the A electrolyte system and the B electrolyte system in this disclosure are independently prepared, and the electrolyte system is used in a battery, and the liquid is injected through the secondary injection technology, and 40 % or more carboxylate, greatly reducing the density of the electrolyte, reducing the quality of the electrolyte under the relative use volume, using the secondary injection technology,
  • a proper amount of vinylene carbonate is added to the electrolyte system to stabilize it on the surface of the negative electrode.
  • film by adjusting the amount of addition, the content of inorganic components in the SEI film is increased to ensure low impedance and good low-temperature performance of the battery cell; during the second liquid injection process, a high content of vinylene carbonate is added to repair the cycle and high temperature.
  • the ruptured SEI film during storage reduces the side reaction of a large amount of carboxylate on the surface of the negative electrode and improves the high temperature performance and cycle performance of the battery.
  • the electrolyte system A is an electrolyte for one-time injection.
  • the B electrolyte system is an electrolyte used for secondary liquid injection.
  • the first solvent includes any one or a combination of at least two of ethylene carbonate, ethyl methyl carbonate, ethyl propionate or propyl propionate.
  • the lithium salt includes lithium hexafluorophosphate.
  • the first functional additive includes vinylene carbonate and vinyl sulfate.
  • the mass concentration of the lithium salt in the electrolyte system A is 15-18%, for example: 15%, 15.5%, 16%, 17% or 18%.
  • the mass concentration of vinylene carbonate in the electrolyte system A is 1.5-2.5%, for example: 1.5%, 1.8%, 2%, 2.2% or 2.5%.
  • the mass concentration of vinyl sulfate in the electrolyte system A is 0.5-2%, for example: 0.5%, 1%, 1.2%, 1.5% or 2%.
  • the second solvent includes any one or a combination of at least two of dimethyl carbonate, ethyl acetate or methyl propionate.
  • the second functional additive includes fluorobenzene and vinylene carbonate.
  • the mass concentration of fluorobenzene in the B electrolyte system is 3-5%, for example: 3%, 3.5%, 4%, 4.5% or 5%.
  • the mass concentration of vinylene carbonate in the B electrolyte system is 5-20%, for example: 5%, 8%, 10%, 15% or 20%.
  • the present disclosure provides a lithium-ion battery, the lithium-ion battery includes the above electrolyte system.
  • the lithium ion battery includes a positive electrode.
  • the positive electrode has a single surface density > 20 mg/cm 2 , for example: 22 mg/cm 2 , 24 mg/cm 2 , 26 mg/cm 2 , 30 mg/cm 2 or 35 mg/cm 2 .
  • the compacted density of the positive electrode is >2.55g/cm 3 , for example: 2.58g/cm 3 , 2.6g/cm 3 , 2.7g/cm 3 , 2.75g/cm 3 or 2.8g/cm 3 cm 3 etc.
  • the lithium ion battery further includes a separator.
  • the diaphragm is a ceramic diaphragm.
  • This embodiment provides an electrolyte system, the electrolyte system is composed of A electrolyte system and B electrolyte system; wherein the A electrolyte system is composed of an organic solvent, electrolyte lithium salt and functional additives; the organic solvent is composed of carbonic acid Vinyl, ethyl methyl carbonate, ethyl propionate and propyl propionate, the mass ratio of ethylene carbonate, ethyl methyl carbonate, ethyl propionate and propyl propionate is 2:2:2:4; electrolyte
  • the lithium salt is lithium hexafluorophosphate, with a mass concentration of 18%;
  • the functional additive is composed of the following components in parts by weight: vinylene carbonate with a mass concentration of 2%, vinyl sulfate with a mass concentration of 1.5%;
  • the B electrolyte system consists of an organic solvent and a functional additive Composition; Wherein organic solvent is made up of dimethyl carbonate and eth
  • This embodiment provides an electrolyte system, the electrolyte system is composed of A electrolyte system and B electrolyte system; wherein the A electrolyte system is composed of an organic solvent, electrolyte lithium salt and functional additives; the organic solvent is composed of carbonic acid Vinyl, ethyl methyl carbonate, ethyl propionate and propyl propionate, the mass ratio of ethylene carbonate, ethyl methyl carbonate, ethyl propionate and propyl propionate is 2:2:2:4; electrolyte The lithium salt is lithium hexafluorophosphate with a mass concentration of 16%; the functional additive is composed of the following components in parts by weight: vinylene carbonate mass concentration 1.5%, vinyl sulfate mass concentration 1.2%; B electrolyte system consists of organic solvent and functional additive Composition; Wherein organic solvent is made up of dimethyl carbonate and ethyl acetate, the ratio of dimethyl carbonate and ethyl
  • Example 1 The only difference between this example and Example 1 is that the amount of vinylene carbonate in the A electrolyte system is 1.2 parts by mass, and other conditions and parameters are exactly the same as those of Example 1.
  • Example 1 The only difference between this example and Example 1 is that the amount of vinylene carbonate in the A electrolyte system is 3 parts by mass, and other conditions and parameters are exactly the same as those of Example 1.
  • Example 1 The only difference between this example and Example 1 is that the amount of vinylene carbonate in the B electrolyte system is 3 parts by mass, and other conditions and parameters are exactly the same as those of Example 1.
  • Example 1 The only difference between this example and Example 1 is that the amount of vinylene carbonate in the B electrolyte system is 25 parts by mass, and other conditions and parameters are exactly the same as those of Example 1.
  • Example 1 The only difference between this comparative example and Example 1 is that only the A electrolyte system is used, and other conditions and parameters are exactly the same as those of Example 1.
  • Example 1 The only difference between this comparative example and Example 1 is that only B electrolyte system is used, and other conditions and parameters are exactly the same as those of Example 1.
  • the electrolytic solution that embodiment 1-6 and comparative example 1-2 obtains is made into battery, and described battery comprises positive electrode sheet, separator, negative electrode sheet and lithium ion battery electrolyte of the present embodiment;
  • the active material layer on the current collector the active material in the active material layer is LiFePO 4 , the surface density of the positive electrode is 22 mg/cm 2 , and the compacted density is 2.60 g/cm 3 .
  • the lithium ion battery is assembled according to the prior art, and after Obtained after activation.
  • the cell after the first liquid injection, the cell is soaked at 45°C for 12 hours, and then pre-charged after 24 hours of normal temperature soaking; after the pre-charge, the second liquid injection is performed, and after the second liquid injection, it is aged at 45°C for 24 hours, and after aging at room temperature for 24 hours, subsequent formation, Divide capacity.
  • the cycle performance test was carried out on the obtained lithium-ion batteries, and each battery was cycled 1000 times, and the battery capacity retention rate before and after the cycle was calculated.
  • the test conditions are as follows, high temperature test: 1.0C rate discharge, 1.0C rate charge, voltage range 2.5 ⁇ 3.65V, temperature 45 ⁇ 5°C; normal temperature DC internal resistance test charge to 50% SOC, 4C discharge 10s, voltage range 2.5 ⁇ 3.65V, temperature 25 ⁇ 5°C; low temperature performance test: fully charge at 25 ⁇ 5°C, adjust the load to 50% SOC, discharge at 4C for 10S at -20°C, voltage range 2.5 ⁇ 3.65V.
  • the test results are shown in Table 1:
  • Example 1 From the comparison of Example 1 and Example Examples 3-4, it can be obtained that in the A electrolyte system, the content of vinylene carbonate will affect the performance of the prepared electrolyte, and the concentration of vinylene carbonate in the A electrolyte system will be controlled At 1.5-2.5%, the performance of the prepared electrolyte is excellent. If the concentration of vinylene carbonate in the A electrolyte system is too high, the initial DC internal resistance of the battery will be high, and the low-temperature performance and power performance of the battery will be affected. Deterioration, if the concentration of vinylene carbonate in the A electrolyte system is too low, the film-forming effect will be poor during the pre-charging process of the battery, which will affect the cycle performance of the battery.
  • Example 1 From the comparison of Example 1 and Example Examples 5-6, it can be obtained that in the B electrolyte system, the content of vinylene carbonate will affect the performance of the prepared electrolyte, and the concentration of vinylene carbonate in the B electrolyte system will be controlled At 5-20%, the performance of the prepared electrolyte is excellent. If the concentration of vinylene carbonate in the B electrolyte system is too high, it will obviously increase the cost of the electrolyte but will not significantly improve the performance of the battery. If B The concentration of vinylene carbonate in the electrolyte system is too low, and there is no excess film-forming additive to repair the damaged SEI film during the electrolyte circulation process, which will cause the degradation of the high-temperature cycle performance of the battery.
  • Example 1 From the comparison of Example 1 and Comparative Example 1-2, it can be obtained that the present disclosure combines the low-density electrolyte with the secondary liquid injection technology, and adds a large amount of negative electrode film-forming additives during the secondary liquid injection process to improve the negative electrode interface. protection, reduce the side reaction of carboxylate on the surface of the negative electrode, and improve the cycle performance of the battery cell.
  • the secondary liquid injection technology also ensures the low impedance of the battery cell, thereby ensuring the power performance and low temperature performance of the battery cell;
  • the application of density electrolyte also significantly reduces the quality of the electrolyte under the same volume of electrolyte and improves the energy density of the cell.

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Abstract

本公开提供一种电解液体系及其应用，本公开将低密度电解液同二次注液技术相结合，在二次注液过程中添加大量的负极成膜添加剂，来提升对负极界面的保护，减少羧酸酯在负极表面的副反应，提升电芯的循环性能。

Description

一种电解液体系及其应用 技术领域
本公开涉及锂离子电池领域，例如涉及一种电解液体系及其应用。
背景技术
随电动车市场的快速发展，电动汽车续航里程不断增加，单体电芯能量密度不断提升。为提升单体电芯能量密度一方面采用克容量和压实较高的正极材料，另一方面是提升壳体盖板的轻量化设计。随能量密度的提升，电芯注液量不断下降，以满足能量密度的要求，但随着注液系数的降低，电芯循环性能不断下降，因此，急需开发低密度电解液，来满足电芯对高能量密度的需求。
羧酸酯的密度明显小于碳酸酯，在电解液溶剂中加入大量的羧酸酯，可有效降低电解液的整体密度；但大量羧酸酯的加入会明显影响电芯的循环性能，尤其是高温循环性能，故又需大量的负极添加剂来提升对电芯界面的保护，改善电芯循环性能；但大量负极添加剂的加入又造成电芯直流内阻的增加，造成电芯功率性能和低温性能的劣化。
发明内容
本公开提供一种电解液体系及其应用，本公开将低密度电解液同二次注液技术相结合，在二次注液过程中添加大量的负极成膜添加剂，来提升对负极界面的保护，减少羧酸酯在负极表面的副反应，提升电芯的循环性能，同时，二次注液技术，也保证了电芯的低阻抗，进而保证电芯的功率性能和低温性能；低密度电解液的应用，也明显降低了相同体积电解液下的电解液质量，提升了电芯的能量密度。
本公开在一实施例中提供一种电解液体系，所述电解液体系包括A电解液体系和B电解液体系，所述A电解液体系包括第一溶剂、锂盐和第一功能添加剂，所述B电解液体系包括第二溶剂和第二功能添加剂，所述第一溶剂中羧酸酯的质量占比≥40％，例如：40％、42％、45％、50％、55％、60％或80％等，所述第二溶剂中羧酸酯的质量占比>50％，例如：55％、60％、65％、70％或80％等，所述第一功能添加剂包括碳酸亚乙烯酯和硫酸乙烯酯，所述第二功能添加剂包括氟苯和碳酸亚乙烯酯,所述A电解液体系为用于一次注液的电解液，所述B电解液体系为用于二次注液的电解液，所述一次注液的电解液和二次注液的电解液的体积比为(8～9):1，例如：8:1、8.2:1、8.5:1、8.8:1或9:1等。
本公开对制备方法中的步骤(1)和步骤(2)的操作顺序不作具体限制，例如可以是先进行步骤(1)再进行步骤(2)，也可以是先进行步骤(2)再进行步骤(1)。
本公开所述A电解液体系和B电解液体系均独立地制得，将所述电解液体系体系用于电池，通过二次注液技术进行注液，本公开所述电解液体系中加入40％以上羧酸酯，大大降低电解液的密度，降低相对使用体积下电解液的质量，采用二次注液技术，A电解液体系中加入适量的碳酸亚乙烯酯，使其在负极表面稳定成膜，通过对添加量的调控，提升SEI膜无机组分含量，保证电芯的低阻抗和良好的低温性能；二次注液过程中，加入高含量的碳酸亚乙烯酯，以修补循环及高温存储过程中破裂的SEI膜，减少大量羧酸酯在负极表面发生副反应，提升电芯的高温性能和循环性能。
在一实施例中，所述A电解液体系为用于一次注液的电解液。
在一实施例中，所述B电解液体系为用于二次注液的电解液。
在一实施例中，所述第一溶剂包括碳酸乙烯酯、碳酸甲乙酯、丙酸乙酯或丙酸丙酯中的任意一种或至少两种的组合。
在一实施例中，所述锂盐包括六氟磷酸锂。
在一实施例中，所述第一功能添加剂包括碳酸亚乙烯酯和硫酸乙烯酯。
在一实施例中，所述A电解液体系中锂盐的质量浓度为15～18％，例如：15％、15.5％、16％、17％或18％等。
在一实施例中，所述A电解液体系中碳酸亚乙烯酯的质量浓度为1.5～2.5％，例如：1.5％、1.8％、2％、2.2％或2.5％等。
在一实施例中，所述A电解液体系中硫酸乙烯酯的质量浓度为0.5～2％，例如：0.5％、1％、1.2％、1.5％或2％等。
在一实施例中，所述第二溶剂包括碳酸二甲酯、乙酸乙酯或丙酸甲酯中的任意一种或至少两种的组合。
在一实施例中，所述第二功能添加剂包括氟苯和碳酸亚乙烯酯。
在一实施例中，所述B电解液体系中氟苯的质量浓度为3～5％，例如：3％、3.5％、4％、4.5％或5％等。
在一实施例中，所述B电解液体系中碳酸亚乙烯酯的质量浓度为5～20％，例如：5％、8％、10％、15％或20％等。
本公开在一实施例中提供一种锂离子电池，所述的锂离子电池包含上述电解液体系。
在一实施例中地，所述锂离子电池包括正极。
在一实施例中地，所述正极的单面面密度＞20mg/cm 2，例如：22mg/cm 2、24mg/cm 2、26mg/cm 2、30mg/cm 2或35mg/cm 2等。
在一实施例中地，所述正极的压实密度＞2.55g/cm 3，例如：2.58g/cm 3、2.6g/cm 3、2.7g/cm 3、2.75g/cm 3或2.8g/cm 3等。
在一实施例中地，所述锂离子电池还包括隔膜。
在一实施例中地，所述隔膜为陶瓷隔膜。
具体实施方式
实施例1
本实施例提供了一种电解液体系，所述电解液体系由A电解液体系和B电解液体系组成；其中A电解液体系，由有机溶剂、电解质锂盐和功能添加剂组成；有机溶剂由碳酸乙烯酯，碳酸甲乙酯，丙酸乙酯和丙酸丙酯组成，碳酸乙烯酯，碳酸甲乙酯，丙酸乙酯和丙酸丙酯的质量比为2：2：2：4；电解质锂盐为六氟磷酸锂，质量浓度18％；功能添加剂由以下重量份数的组分组成：碳酸亚乙烯酯质量浓度2％、硫酸乙烯酯质量浓度1.5％；B电解液体系，由有机溶剂和功能添加剂组成；其中有机溶剂由碳酸二甲酯和乙酸乙酯组成，碳酸二甲酯和乙酸乙酯的比例为1:1；功能添加剂由浸润添加剂氟苯质量浓度5％和成膜添加剂 碳酸亚乙烯酯质量浓度15％组成，在注液过程中，A电解液体系和B电解液体系的体积比为8.2:1。
实施例2
本实施例提供了一种电解液体系，所述电解液体系由A电解液体系和B电解液体系组成；其中A电解液体系，由有机溶剂、电解质锂盐和功能添加剂组成；有机溶剂由碳酸乙烯酯，碳酸甲乙酯，丙酸乙酯和丙酸丙酯组成，碳酸乙烯酯，碳酸甲乙酯，丙酸乙酯和丙酸丙酯的质量比为2：2：2：4；电解质锂盐为六氟磷酸锂，质量浓度16％；功能添加剂由以下重量份数的组分组成：碳酸亚乙烯酯质量浓度1.5％、硫酸乙烯酯质量浓度1.2％；B电解液体系，由有机溶剂和功能添加剂组成；其中有机溶剂由碳酸二甲酯和乙酸乙酯组成，碳酸二甲酯和乙酸乙酯的比例为1:1；功能添加剂由浸润添加剂氟苯质量浓度4％和成膜添加剂碳酸亚乙烯酯质量浓度16％组成，在注液过程中，A电解液体系和B电解液体系的体积比为8.5:1。
实施例3
本实施例与实施例1区别仅在于，A电解液体系中碳酸亚乙烯酯为1.2质量份，其他条件与参数与实施例1完全相同。
实施例4
本实施例与实施例1区别仅在于，A电解液体系中碳酸亚乙烯酯为3质量份，其他条件与参数与实施例1完全相同。
实施例5
本实施例与实施例1区别仅在于，B电解液体系中碳酸亚乙烯酯为3质量份，其他条件与参数与实施例1完全相同。
实施例6
本实施例与实施例1区别仅在于，B电解液体系中碳酸亚乙烯酯为25质量份，其他条件与参数与实施例1完全相同。
对比例1
本对比例与实施例1区别仅在于，仅使用A电解液体系，其他条件与参数与实施例1完全相同。
对比例2
本对比例与实施例1区别仅在于，仅使用B电解液体系，其他条件与参数与实施例1完全相同。
性能测试：
将实施例1-6和对比例1-2得到的电解液，制成电池，所述电池包括正极片、隔膜、负极片和本实施例的锂离子电池电解液；正极片包括集流体和设置在集流体上的活性物质层，活性物质层中的活性物质为LiFePO 4，正极面密度22mg/cm 2，压实密度2.60g/cm 3，所述锂离子电池按照现有技术进行组装，经活化后得到。其中，一次注液后，电芯45℃浸润12h，常温浸润24h后进行预充；预充后进行二次注液，二次注液后45℃老化24h，常温老化24h后，进行后续化成、分容。
对得到的锂离子电池进行循环性能测试，将各电池分别循环1000次，计算循环前后的电池容量保持率。测试条件如下，高温测试：1.0C倍率放电，1.0C倍率充电，电压范围2.5～3.65V，温度45±5℃；常温直流内阻测试调荷至50％SOC，4C放电10s，电压范围2.5～3.65V，温度25±5℃；低温性能测试：25±5℃下充满电，调荷至50％SOC，-20℃条件下，4C放电10S，电压范围2.5～3.65V。 测试结果如表1所示：
表1
Figure PCTCN2022086196-appb-000001
由表1可以看出，由实施例1-6可得，通过使用该电解液及注液方法，可有效降低电解液注液量同时保证电芯的高温循环性能。
由实施例1和实施例实施例3-4对比可得，A电解液体系中，碳酸亚乙烯酯的含量会影响制得电解液的性能，将A电解液体系中碳酸亚乙烯酯的浓度控制在1.5～2.5％，制得电解液的性能较优异，若A电解液体系中的碳酸亚乙烯酯的浓度过高，电芯初始直流内阻较高，电芯的低温性能和功率性能将被劣化，若A电解液体系中的碳酸亚乙烯酯的浓度过低，电芯预充过程中成膜效果较差，影响电芯循环性能。
由实施例1和实施例实施例5-6对比可得，B电解液体系中，碳酸亚乙烯酯的含量会影响制得电解液的性能，将B电解液体系中碳酸亚乙烯酯的浓度控制在5～20％，制得电解液的性能较优异，若B电解液体系中的碳酸亚乙烯酯的浓度过高，会明显造成电解液成本的增加但对电芯性能无明显提升，若B电解液体系中的碳酸亚乙烯酯的浓度过低，电解液循环过程中没有多余的成膜添加剂来修补破损的SEI膜，会造成电芯高温循环性能的劣化。
由实施例1和对比例1-2对比可得，本公开将低密度电解液同二次注液技术相结合，在二次注液过程中添加大量的负极成膜添加剂，来提升对负极界面的保护，减少羧酸酯在负极表面的副反应，提升电芯的循环性能，同时，二次注液技术，也保证了电芯的低阻抗，进而保证电芯的功率性能和低温性能；低密度电解液的应用，也明显降低了相同体积电解液下的电解液质量，提升了电芯的能量密度。

Claims (14)

  1. 一种电解液体系，所述电解液体系包括A电解液体系和B电解液体系，所述A电解液体系包括第一溶剂、锂盐和第一功能添加剂，所述B电解液体系包括第二溶剂和第二功能添加剂，所述第一溶剂中羧酸酯的质量占比≥40％，所述第二溶剂中羧酸酯的质量占比>50％，所述第一功能添加剂包括碳酸亚乙烯酯和硫酸乙烯酯，所述第二功能添加剂包括氟苯和碳酸亚乙烯酯，所述A电解液体系为用于一次注液的电解液，所述B电解液体系为用于二次注液的电解液，所述一次注液的电解液和二次注液的电解液的体积比为(8～9):1。
  2. 如权利要求1所述的电解液，其中，所述第一溶剂包括碳酸乙烯酯、碳酸甲乙酯、丙酸乙酯或丙酸丙酯中的任意一种或至少两种的组合。
  3. 如权利要求1或2所述的电解液，其中，所述锂盐包括六氟磷酸锂；
  4. 如权利要求1-3任一项所述的电解液，其中，所述第一功能添加剂包括碳酸亚乙烯酯和硫酸乙烯酯。
  5. 如权利要求1-4任一项所述的电解液，其中，所述A电解液体系中锂盐的质量浓度为15～18％；
  6. 如权利要求1-5任一项所述的电解液，其中，所述A电解液体系中碳酸亚乙烯酯的质量浓度为1.5～2.5％；
  7. 如权利要求1-6任一项所述的电解液，其中，所述A电解液体系中硫酸乙烯酯的质量浓度为0.5～2％。
  8. 如权利要求1-7任一项所述的电解液，其中，所述第二溶剂包括碳酸二甲酯、乙酸乙酯或丙酸甲酯中的任意一种或至少两种的组合。
  9. 如权利要求1-8任一项所述的电解液，其中，所述第二功能添加剂包括氟苯和碳酸亚乙烯酯。
  10. 如权利要求1-9任一项所述的电解液，其中，所述B电解液体系中氟苯的质量浓度为3～5％；
  11. 如权利要求1-10任一项所述的电解液，其中，所述B电解液体系中碳酸亚乙烯酯的质量浓度为5～20％。
  12. 一种锂离子电池，所述锂离子电池采用如权利要求1-11任一项所述的电解液体系。
  13. 如权利要求12所述的锂离子电池，其中，所述锂离子电池包括正极，所述正极的单面面密度＞20mg/cm 2，所述正极的压实密度＞2.55g/cm 3。
  14. 如权利要求12或13所述的锂离子电池，其中，所述锂离子电池还包括隔膜，所述隔膜为陶瓷隔膜。
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