Electrolyte, electrochemical device and vehicle
By introducing sulfate and fluorocarboxylate compounds of specific structures into the electrolyte, the problem of unstable interface between the electrolyte and the ternary positive electrode material is solved, and the stability and performance of the battery are improved under high temperature and high pressure.
Patent Information
- Application Number
- CN202410216864.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-27
- Publication Date
- 2025-08-29
AI Technical Summary
The interface between traditional carbonate electrolytes and other positive electrode materials under high temperature and high pressure is unstable, and side reactions are prone to occur, resulting in poor battery high-temperature circulation and storage performance.
The electrolyte containing sulfate ester compounds and fluorocarboxylate compounds of a specific structure is used. The sulfate ester compounds have lower LUMO energy level and high electron affinity. F atoms are introduced into fluorocarboxylate compounds to improve the oxidation resistance of the electrolyte, form a stable SEI film and improve interface stability.
Improve the interface stability of lithium-ion batteries under high temperature and high pressure, reduce side reactions, and improve the battery's high-temperature circulation and storage performance.
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Figure CN120565798A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of secondary batteries, and in particular to an electrolyte, an electrochemical device, and a vehicle. Background Art
[0002] With the rapid development of pure electric vehicles and hybrid electric vehicles, people's requirements for the range, service life and safety of electric vehicles are constantly increasing. High-nickel ternary positive electrode materials with high specific capacity, lithium-rich manganese-based positive electrode materials and high-specific capacity silicon-based negative electrode materials have become important directions for the development of positive and negative electrode materials for high-energy-density batteries.
[0003] In traditional carbonate electrolytes, the interface between positive electrode materials such as ternary positive electrode materials and the electrolyte is unstable under high temperature and high pressure, and side reactions are prone to occur, resulting in high-temperature cycling and storage performance that cannot meet design requirements.
[0004] Therefore, there is an urgent need to develop an electrolyte that has good interface stability with positive electrode materials such as ternary positive electrode materials under high temperature and high pressure, with fewer side reactions, thereby improving the high-temperature cycle and storage performance of the battery. Summary of the Invention
[0005] The present application aims to solve one of the technical problems in the related art at least to a certain extent.
[0006] In view of this, one object of the present application is to provide an electrolyte containing a sulfate compound and a fluorocarboxylate compound of a specific structure, wherein the sulfate compound itself has a stable structure, a lower LUMO energy level and a higher electron affinity, and can be reduced before the solvent to form a stable SEI film, while the fluorocarboxylate compound introduces F atoms with a strong electron-withdrawing effect, which can improve the oxidation resistance of the electrolyte, thereby enabling it to have good interface stability with positive electrode materials such as ternary positive electrode materials under high temperature and high pressure, with few side reactions, and when used in lithium-ion batteries, etc., it can improve the high-temperature cycle and storage performance of the battery.
[0007] Another object of the present application is to provide an electrochemical device.
[0008] Yet another object of the present application is to provide a vehicle.
[0009] To achieve the above-mentioned object, the first aspect of the present application provides an electrolyte, comprising an electrolyte, a solvent and an additive; the additive comprises a sulfate ester compound, and the sulfate ester compound comprises at least one of the compound represented by Formula I or the compound represented by Formula II;
[0010]
[0011] The solvent includes a fluorocarboxylate compound, and the fluorocarboxylate compound has a structure shown in Formula III:
[0012]
[0013] Among them, at least one of R1, R2, R3, R4, R5, and R6 is F, and the rest are alkyl or H.
[0014] In some embodiments, the fluorocarboxylate compound includes at least one of compounds T1-T4:
[0015]
[0016] In some embodiments, the mass content of the sulfate ester compound in the electrolyte is 0.1-2%.
[0017] In some embodiments, the fluorocarboxylate compound is present in the electrolyte in an amount of 0.1-30% by weight, including but not limited to 0.1-1 wt %, or greater than 20 wt % and less than 30 wt %.
[0018] In some embodiments, the electrolyte includes at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium dioxalatoborate (LiBOB), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalatoborate (LiODFB), lithium bis(trifluoromethanesulfonyl imide) (LiN(SO2CF3)2, abbreviated as LiTFSI), lithium bis(fluorosulfonyl imide) (LiN(SO2F)2, abbreviated as LIFSI), and lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl imide (LiHFDF).
[0019] In some embodiments, the electrolyte has a mass content of 12-15% in the electrolyte solution.
[0020] In some embodiments, the solvent further comprises a carbonate compound.
[0021] In some embodiments, the additive further includes an auxiliary agent, and the auxiliary agent includes at least one of lithium difluorophosphate, triphenyl phosphate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate, vinylene carbonate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and fluoroethylene carbonate.
[0022] In some embodiments, the carbonate compound has a mass content of 40-85% in the electrolyte.
[0023] In some embodiments, the mass content of the auxiliary agent in the electrolyte is 0.1-5%.
[0024] In a second aspect of the present application, an electrochemical device is provided, comprising the electrolyte described in the present application.
[0025] In some embodiments, the electrochemical device further comprises a negative electrode, and the active material of the negative electrode comprises at least one of a silicon-based material and a carbon material.
[0026] In some embodiments, the electrochemical device further comprises a positive electrode, and the active material of the positive electrode comprises a ternary positive electrode material.
[0027] In a third aspect of the present application, a vehicle is proposed, comprising the electrolyte described in the present application or the electrochemical device described in the present application.
[0028] The electrolyte of the present application can at least bring the following beneficial effects:
[0029] Because it contains sulfate compounds and fluorocarboxylate compounds with specific structures, it can have good interface stability with cathode materials such as ternary cathode materials under high temperature and high pressure, with few side reactions. When used in lithium-ion batteries, it can improve the high-temperature cycle and storage performance of the battery. Specifically:
[0030] The sulfate ester compounds of the structure shown in Formula I or Formula II of the present application have a lower LUMO energy level and a higher electron affinity. They can decompose (be reduced) before the solvent, forming an effective and stable SEI film at the negative electrode whose main products are sulfur-containing organic compounds such as Li2SO3 and CH3CH(OSO2Li), thereby improving ionic conductivity and reducing film formation impedance. Furthermore, the introduction of double bonds or carbonyl groups will reduce the chemical hardness, and molecules with lower hardness will be more stable in their reduced form, forming a denser and more stable SEI film, which is beneficial to improving the stability of the battery cell under high temperature and high pressure and improving high-temperature storage performance. In addition, the sulfate ester compounds of the structure shown in Formula I or Formula II of the present application themselves have a stable structure and are not easy to decompose, which makes the electrolyte itself more stable and facilitates transportation and storage.
[0031] The fluorinated carboxylate compound of the structure shown in Formula III of the present application introduces F atoms, which replace H atoms or alkanes. The F atoms have a strong electron-withdrawing effect, which reduces the energy of their highest occupied orbitals and improves the oxidation resistance of the solvent, thereby improving the oxidation resistance of the electrolyte and improving the stability of the electrolyte under high temperature and high pressure, thereby achieving the cycle and high-temperature performance stability of high-nickel ternary positive electrode materials.
[0032] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:
[0034] Figure 1 2 is a comparison chart of the high temperature storage performance test results of Example 1 and Comparative Example 1.
[0035] Figure 2 2 is a comparison chart of the high temperature cycle performance test results of Example 1 and Comparative Example 1. DETAILED DESCRIPTION
[0036] The embodiments of the present application are described in detail below. The embodiments are exemplary and intended to be used to explain the present application, but should not be understood as limiting the present application.
[0037] Throughout this application, the disclosure of numerical ranges includes disclosure of all values within the entire range and further subdivided ranges, including endpoints and subranges given within those ranges.
[0038] In the application, the raw materials, equipment, etc. involved, unless otherwise specified, are all raw materials and equipment that can be produced through commercial channels or known methods; the methods involved, unless otherwise specified, are all conventional methods.
[0039] The electrolyte of the embodiment of the present application includes an electrolyte, a solvent, and an additive. The additive includes a sulfate compound, and the sulfate compound includes at least one of the compound represented by Formula I or the compound represented by Formula II;
[0040]
[0041] The solvent includes a fluorocarboxylate compound having a structure shown in Formula III:
[0042]
[0043] Among them, at least one of R1, R2, R3, R4, R5, and R6 is F, and the rest are alkyl or H.
[0044] It should be noted that in the embodiments of the present application, the compound represented by Formula I is spiro disulfate, which can be referred to as spiro DTD; the compound represented by Formula II is disulfate, which can be referred to as di-DTD.
[0045] As an optional example, at least one of R1, R2, R3, R4, R5, and R6 is F, and the rest are C. 1-6 Alkyl or H.
[0046] It should be noted that, in the embodiments of this application, the prefix "C u-v" indicates that the following group has from u to v carbon atoms. For example, "C 1-6 "Alkyl" means an alkyl group having 1 to 6 carbon atoms.
[0047] As a non-limiting example, the number of carbon atoms in the alkyl group in R1, R2, R3, R4, R5, and R6 includes, but is not limited to, 1, 2, 3, 4, 5, or 6.
[0048] In some embodiments, the fluorocarboxylate compounds include but are not limited to at least one of compounds T1-T4, etc.:
[0049]
[0050] It should be noted that the compound T1 is a fluorocarboxylate, the compound T2 is ethyl trifluoroacetate, the compound T3 is ethyl difluoroacetate (abbreviated as EFA), and the compound T4 is difluoroethyl acetate (abbreviated as DFEA).
[0051] In some embodiments, the mass content of the sulfate ester compound in the electrolyte is 0.1-2%, including but not limited to 0.1%, 0.3%, 0.5%, 0.75%, 1.0%, 1.25%, 1.5%, 1.75%, or 2%. If the mass content of the sulfate ester compound in the electrolyte is less than 0.1%, storage performance deteriorates; if it is greater than 2%, impedance deteriorates significantly.
[0052] Compared with conventional chain carbonate solvents, in the embodiments of the present application, fluorinated carboxylate compounds introduce F atoms. Due to the strong electron-withdrawing effect of fluorine, the energy of its highest occupied orbital is reduced, the oxidation resistance of the solvent is improved, and it is more suitable for ternary systems.
[0053] In some embodiments, the mass content of the fluorocarboxylate compound in the electrolyte is 0.1-30%, including but not limited to 0.1%, 1%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5%, 20%, 22.5%, 25%, 27.5%, or 30%. When the mass content of the fluorocarboxylate compound in the electrolyte is within the above range, stable long-term cycling at high temperatures can be achieved; when the mass content is below 0.1%, high-temperature cycling performance deteriorates; and when the mass content is above 30%, impedance deteriorates.
[0054] As an optional example, the mass content of the fluorocarboxylate compound in the electrolyte is 0.1-1%, including but not limited to 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%.
[0055] As another optional example, the mass content of the fluorocarboxylate compound in the electrolyte is greater than 20% and less than 30%, including but not limited to 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28% or 29%. In the embodiments of the present application, when the mass content of the fluorocarboxylate compound in the electrolyte is greater than 20% and less than 30%, the advantages of the fluorocarboxylate compound are obvious, the overall kinetic performance of the electrolyte is improved, the DCR is reduced, and at the same time, due to the formation of a LiF-rich SEI film, the high-temperature cycle performance of the battery cell is significantly improved; when the mass content of the fluorocarboxylate compound in the electrolyte is less than 20%, the DCR performance cannot be well improved.
[0056] It should be noted that the electrolyte of the embodiment of the present application can be used not only in lithium-ion batteries, but also in secondary batteries such as sodium-ion batteries.
[0057] In some embodiments, when the electrolyte is used in a lithium-ion battery, the electrolyte includes but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium dioxalatoborate (LiBOB), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorooxalatoborate (LiODFB), lithium bis(trifluoromethanesulfonyl imide) (LiN(SO2CF3)2, abbreviated as LiTFSI), lithium bis(fluorosulfonyl imide) (LiN(SO2F)2, abbreviated as LIFSI), 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl imide (LiHFDF), etc.
[0058] In the embodiments of the present application, when the electrolyte is used in a lithium-ion battery and the electrolyte is a lithium salt, the fluorocarboxylate compound can help form a LiF-rich SEI film (that is, the fluorocarboxylate compound participates in film formation to form a LiF-rich SEI film), and the bulk LiF crystal material has excellent physical properties, such as high mechanical strength, low solubility, a wide band gap (effectively preventing electron tunneling) and a high voltage window (up to 6.4 V vs. Li / Li+).
[0059] In some embodiments, the mass content of the electrolyte in the electrolyte is 12-15%, including but not limited to 12%, 13%, 14% or 15%.
[0060] In some embodiments, the solvent further includes but is not limited to carbonate compounds and the like.
[0061] As a non-limiting example, the carbonate compound includes but is not limited to at least one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), and the like.
[0062] In the embodiments of the present application, carbonate compounds are compared to ether solvents, and the stability and pressure resistance of carbonate compounds are better, wherein, cyclic carbonates (for example, EC, PC, etc.) have extremely high dielectric constants, but the viscosity is too large, and chain carbonates (for example, EMC, DEC, DMC, etc.) have low viscosity, but the dielectric constant is also low. And excellent solvent systems need to have both high dielectric constants and low viscosity to ensure high electrical conductivity. Therefore, in the embodiments of the present application, preferably cyclic esters and chain esters are used in combination to ensure high lithium salt dissociation ability and migration ability.
[0063] In some embodiments, the mass content of the carbonate compound in the electrolyte is 70-99.9%, including but not limited to 40%, 50%, 60%, 70%, 80% or 85%.
[0064] In some embodiments, in addition to fluorocarboxylate compounds and carbonate compounds, the solvent may also include other solvents, including but not limited to at least one of ether compounds and nitrile compounds. Ether compounds include but are not limited to tetrahydrofuran, 2-methyltetrahydrofuran, dimethoxymethane, 1,2-dimethoxyethane, and the like, while nitrile compounds include but are not limited to acetonitrile. When the solvent contains these other solvents, the weight content of the other solvent in the electrolyte does not exceed 20%, for example, 5%, 10%, 15%, etc.
[0065] In some embodiments, the additive further includes an auxiliary agent, including but not limited to at least one of lithium difluorophosphate (LiOP2F2), triphenyl phosphate (TPP), lithium difluorooxalatoborate (LiODFB), lithium difluorooxalatophosphate (LiODFP), vinylene carbonate (VC), tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB), fluoroethylene carbonate (FEC), etc.
[0066] In the embodiments of the present application, the role of adding an auxiliary agent to the electrolyte is to help construct a thin and stable CEI film and reduce the direct current internal resistance (DCR).
[0067] In some embodiments, the mass content of the additive in the electrolyte is 0.1-5%, including but not limited to 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, etc.
[0068] As an optional example, the auxiliary agent is tris(trimethylsilyl) phosphate, and its content in the electrolyte is 0.1-1%, for example 0.5%. The auxiliary agent has a mass content in the electrolyte within the above range and can play the role of removing acid and inhibiting water.
[0069] The electrolyte of the present application can at least bring the following beneficial effects:
[0070] Because it contains sulfate compounds and fluorocarboxylate compounds with specific structures, it can have good interface stability with cathode materials such as ternary cathode materials under high temperature and high pressure, with few side reactions. When used in lithium-ion batteries, it can improve the high-temperature cycle and storage performance of the battery. Specifically:
[0071] The sulfate ester compounds of the structure shown in Formula I or Formula II of the present application have a lower LUMO energy level and a higher electron affinity. They can decompose (be reduced) before the solvent, forming an effective and stable SEI film at the negative electrode whose main products are sulfur-containing organic compounds such as Li2SO3 and CH3CH(OSO2Li), thereby improving ionic conductivity and reducing film formation impedance. Furthermore, the introduction of double bonds or carbonyl groups will reduce the chemical hardness, and molecules with lower hardness will be more stable in their reduced form, forming a denser and more stable SEI film, which is beneficial to improving the stability of the battery cell under high temperature and high pressure and improving high-temperature storage performance. In addition, the sulfate ester compounds of the structure shown in Formula I or Formula II of the present application are structurally stable and not easy to decompose, which makes the electrolyte itself more stable and is beneficial to electrolyte transportation and storage.
[0072] The fluorinated carboxylate compound of the structure shown in Formula III of the present application introduces F atoms, which replace H atoms or alkanes. The F atoms have a strong electron-withdrawing effect, which reduces the energy of their highest occupied orbitals and improves the oxidation resistance of the solvent, thereby improving the oxidation resistance of the electrolyte, thereby improving the stability of the electrolyte under high temperature and high pressure, thereby achieving the cycle and high-temperature performance stability of high-nickel ternary positive electrode materials, etc., and enabling the commercial application of ternary positive electrode material systems (especially high-nickel ternary positive electrode material systems).
[0073] The preparation method of the electrolyte in the embodiment of the present application is not limited and can be any method for preparing the electrolyte in the art.
[0074] As an optional example, a method for preparing an electrolyte includes the following steps: mixing a solvent and an electrolyte, then adding an additive and mixing again to obtain an electrolyte.
[0075] The electrochemical device according to the embodiment of the present application includes the electrolyte according to the embodiment of the present application.
[0076] In some embodiments, the electrochemical device includes but is not limited to secondary batteries such as lithium-ion batteries and sodium-ion batteries, capacitors, etc. The secondary battery is not limited to button batteries, soft-pack batteries, etc.
[0077] In some embodiments, the electrochemical device further comprises a negative electrode. The specific selection of the active material of the negative electrode (ie, negative electrode active material) is not limited and can be any negative electrode active material in the art that can be used as a secondary battery such as a lithium ion battery.
[0078] As an optional example, the active material of the negative electrode includes at least one of a silicon-based material and a carbon material.
[0079] As a non-limiting example, silicon-based compounds include but are not limited to elemental silicon, SiO x (x includes but is not limited to 1 or 2, etc.), at least one of silicon carbide, silicon-carbon composite materials (SiNPs-amorphous carbon, SiNPs-graphite, etc.), etc.
[0080] As a non-limiting example, the carbon material includes but is not limited to at least one of graphite, hard carbon, soft carbon, mesocarbon microbeads, graphene, and the like.
[0081] In some embodiments, the negative electrode includes a negative electrode material, which includes at least one of the above-mentioned negative electrode active material, negative electrode conductive agent, negative electrode binder, and negative electrode thickener. It should be noted that there is no particular limitation on the specific selection of the negative electrode conductive agent and negative electrode binder in the embodiments of the present application. As non-limiting examples, the negative electrode conductive agent includes but is not limited to at least one of carbon nanotubes, conductive carbon black, conductive graphite, vapor-grown carbon fiber, and graphene; the negative electrode binder includes but is not limited to at least one of styrene-butadiene rubber (SBR) or polyacrylic acid (PAA); and the negative electrode thickener includes but is not limited to at least one of carboxymethyl cellulose and lithium carboxymethyl cellulose.
[0082] In some embodiments, the negative electrode further comprises a negative electrode current collector, which may be selected to comprise copper or any other suitable conductive metal foil (such as solid or mesh or covered foil) known to those skilled in the art, a metal grid or screen, or a porous metal. In some variations, the surface of the negative electrode current collector may comprise a metal foil that has been surface treated (e.g., carbon coated and / or etched).
[0083] In some embodiments, the electrochemical device further comprises a positive electrode, and the active material of the positive electrode (ie, positive electrode active material) comprises a ternary positive electrode material.
[0084] Ternary positive electrode materials usually refer to layered nickel cobalt manganese oxide (NCM) or nickel cobalt aluminum oxide (NCA), which have high weight energy density, good cycle stability and safety performance.
[0085] As a preferred example, the active material of the positive electrode is a high nickel ternary positive electrode material, including but not limited to LiNi 0.8 Co 0.1 Mn 0.102(NCM811), LiNi 0.6 Co 0.2 Mn 0.2 At least one of O2 (NCM622), etc.
[0086] In some embodiments, the positive electrode includes a positive electrode material, which includes at least one of the above-mentioned positive electrode active material, positive electrode conductive agent, positive electrode binder, etc. It should be noted that the present application does not particularly limit the specific selection of positive electrode conductive agent and positive electrode binder, etc. As non-limiting examples, positive electrode conductive agents include but are not limited to one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotubes; positive electrode binders include but are not limited to one or more of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose and polyacrylic acid.
[0087] In some embodiments, the positive electrode further comprises a positive electrode current collector, which may be selected to comprise aluminum or any other suitable conductive metal foil (such as solid or mesh or covered foil) known to those skilled in the art, a metal grid or screen, or a porous metal. In some variations, the surface of the positive electrode current collector may comprise a metal foil that has been surface treated (e.g., carbon coated and / or etched).
[0088] In some embodiments, the electrochemical device further comprises a separator. Specifically, the separator includes, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polytetrafluoroethylene-based polyolefin (PO) separators, polyester films (e.g., polyethylene terephthalate (PET) films), cellulose films, polyimide films (PI), polyamide films (PA), spandex or aramid films, woven films, nonwoven films (non-woven fabrics), microporous membranes, composite membranes, separator paper, rolled membranes, or spun membranes.
[0089] It should be noted that in the embodiments of the present application, there is no limitation on the specific technical parameters such as the thickness of the positive electrode, negative electrode, and separator, as long as the purpose of the present application can be achieved.
[0090] The preparation method of the electrochemical device in the embodiment of the present application is not limited and can be any method known to those skilled in the art.
[0091] The vehicle of the embodiments of the present application may be any vehicle containing the electrolyte of the embodiments of the present application or any of the electrochemical devices of the embodiments of the present application, including but not limited to automobiles, motorcycles, power-assisted bicycles, bicycles, power tools, etc.
[0092] The electrochemical device and vehicle according to the embodiments of the present application both have at least the beneficial effects of the electrolyte according to the embodiments of the present application.
[0093] Certain features of the present technology are further illustrated in the following non-limiting examples.
[0094] Example 1
[0095] (Electrolyte)
[0096] The electrolyte of this embodiment includes an electrolyte, a solvent, and an additive. The electrolyte is LiPF6, and the mass content of the electrolyte in the electrolyte is 14%. The solvent is a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and difluoroethyl acetate (the aforementioned compound T4, referred to as DFEA) in a mass ratio of 30:55:15. The additives are composed of fluoroethylene carbonate (FEC), spiro disulfate (also represented by the aforementioned formula I, referred to as spiro DTD), and lithium difluorophosphate (LiOP2F2). The mass contents of fluoroethylene carbonate, spiro disulfate, and lithium difluorophosphate in the electrolyte are 3%, 1%, and 0.5%, respectively.
[0097] (Method for preparing electrolyte)
[0098] The method for preparing the electrolyte of this embodiment comprises the following steps:
[0099] (1) mixing the solvent and electrolyte in the formulated amount and stirring them uniformly to obtain a primary mixed electrolyte;
[0100] (2) Add additives to the pre-mixed electrolyte and stir evenly to obtain the electrolyte of this embodiment.
[0101] (Electrochemical device and method for manufacturing the same)
[0102] The electrochemical device in this example is a SiOx / NCM811 silicon anode battery. Its preparation method is as follows: the anode is a composite material of SiOx (x=1) and artificial graphite, with a silicon content of 10wt% and a gram capacity of 450mAh / h. The positive electrode is an NCM811 ternary material, and a 10Ah soft-pack battery is prepared.
[0103] The electrolytes, electrolyte preparation methods, electrochemical devices, and preparation methods thereof of Examples 2-17 and Comparative Examples 1-5 are substantially the same as those of Example 1, except that the solvents and additives in the electrolytes are different, as specifically shown in Table 1.
[0104] The electrolytes of the embodiments and comparative examples were subjected to 4C 10s HPPC test at 25°C, high temperature storage test at 60°C and 4C cycle test at 45°C. The test voltage range was 2.5V-4.25V. The test results are shown in Table 1 and Figure 1-2 shown.
[0105] Table 1 Electrolyte composition and performance test results of each embodiment and comparative example
[0106]
[0107]
[0108]
[0109] Note: The proportions of each substance in the solvent column in Table 1 are all mass ratios, and EA is ethyl acetate.
[0110] According to Table 1:
[0111] Comparing the test data of Examples 1-17 and Comparative Examples 1, 4 and 5, it can be seen that the introduction of the sulfate compound having the structure of Formula I or Formula II and the fluorocarboxylate compound having the structure of Formula III in the embodiments of the present application can simultaneously improve the high temperature storage performance and cycle performance of the electrochemical device. This is because: on the one hand, the fluorocarboxylate compound having the structure of Formula III can help form a LiF-rich SEI film, and the bulk LiF crystal material has excellent physical properties, such as high mechanical strength, low solubility, wide band gap (effectively preventing electron tunneling) and high voltage window (up to 6.4 V vs. Li / Li+); on the other hand, the sulfate compound having the structure of Formula I or Formula II preferentially forms a film at the negative electrode, helps to build a stable SEI, while improving the stability of the electrolyte, and facilitates transportation and storage.
[0112] Comparison of the test data of Example 1 and Comparative Example 2 shows that the introduction of DFEA in Example 1 improves the high-temperature storage performance and cycle performance of the electrochemical device due to the oxidation resistance of the fluorinated solvent.
[0113] Comparison of the test data of Example 1 and Comparative Example 3 shows that Example 1 introduces spiro DTD, which can decompose before the solvent, promotes the formation of a stable SEI film, and significantly improves the cycle performance of the electrochemical device.
[0114] Figure 1 The figure is a comparison chart of the high temperature storage performance test results of Example 1 and Comparative Example 1. Figure 1 It can be seen that the electrolyte of Example 1 of the present application can effectively improve high-temperature performance and increase the high-temperature storage capacity recovery rate.
[0115] Figure 2 The figure is a comparison chart of the high temperature cycle performance test results of Example 1 and Comparative Example 1. Figure 2 It can be seen that the electrolyte of Example 1 of the present application can significantly improve the cycle performance of the battery.
[0116] In this application, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.
[0117] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.
Claims
1. An electrolyte, characterized in that: It includes an electrolyte, a solvent and an additive; the additive includes a sulfate compound, and the sulfate compound includes at least one of the compound represented by formula I or the compound represented by formula II; The solvent includes a fluorocarboxylate compound, and the fluorocarboxylate compound has a structure shown in Formula III: Among them, at least one of R1, R2, R3, R4, R5, and R6 is F, and the rest are alkyl or H.
2. The electrolyte according to claim 1, characterized in that The fluorocarboxylate compound includes at least one of compounds T1-T4:
3. The electrolyte according to claim 1, characterized in that The mass content of the sulfate ester compound in the electrolyte is 0.1-2%; And / or, the mass content of the fluorinated carboxylate compound in the electrolyte is 0.1-30%.
4. The electrolyte according to claim 3, characterized in that The mass content of the fluorocarboxylate compound in the electrolyte is 0.1-1%; or The mass content of the fluorocarboxylate compound in the electrolyte is greater than 20% and less than 30%.
5. The electrolyte according to claim 1, characterized in that The electrolyte includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium dioxalatoborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorooxalatoborate, lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), and lithium 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl imide; And / or, the mass content of the electrolyte in the electrolyte is 12-15%.
6. The electrolyte according to claim 1, characterized in that The solvent also includes a carbonate compound; And / or, the additive further includes an auxiliary agent, and the auxiliary agent includes at least one of lithium difluorophosphate, triphenyl phosphate, lithium difluorooxalatoborate, lithium difluorooxalatophosphate, vinylene carbonate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and fluoroethylene carbonate.
7. The electrolyte according to claim 6, characterized in that The mass content of the carbonate compound in the electrolyte is 40-85%; And / or, the mass content of the auxiliary agent in the electrolyte is 0.1-5%.
8. An electrochemical device, characterized in that Comprising the electrolyte according to any one of claims 1 to 7.
9. The electrochemical device according to claim 8, characterized in that Also included is a negative electrode, wherein the active material of the negative electrode includes at least one of a silicon-based material and a carbon material; And / or, it also includes a positive electrode, and the active material of the positive electrode includes a ternary positive electrode material.
10. A vehicle, characterized in that: Comprising the electrolyte according to any one of claims 1 to 7 or the electrochemical device according to claim 8 or 9.