Electrolyte, lithium ion battery and power system

Abstract

This application discloses an electrolyte, a lithium-ion battery, and an electrical system. The electrolyte includes a first additive and a second additive. The first additive includes 4-fluorophenyl acetate, and the second additive contains a sulfonic acid group. The mass ratio of the first additive to the second additive is (1-1.4):1.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an electrolyte, a lithium-ion battery, and an electrical system. Background Technology

[0002] The DC internal resistance (DCR) of a battery cell is a crucial performance parameter, measuring the resistance within the battery when a direct current flows through it. Lower resistance generally indicates higher energy efficiency, meaning the battery can deliver more electrical energy with less internal heat loss. Among various battery types, lithium-ion batteries (Li-ion batteries) are the preferred choice for energy storage due to their high energy density, long lifespan, and stable discharge characteristics. However, with technological advancements, consumer and industrial applications are demanding increasingly higher battery performance, particularly in energy storage, leading to a growing need for low-resistance batteries. Therefore, researching ways to further reduce cell DCR has become particularly important.

[0003] For energy storage products, a lower cell discharge ratio (DCR) is better. First, a higher DCR means more energy is converted into heat rather than electricity during battery discharge, reducing battery efficiency. Similarly, some energy is lost as heat during charging, thus lowering energy utilization during both charging and discharging. Second, a higher DCR during discharge leads to greater heat generation, potentially causing a significant increase in battery temperature. Increased temperature accelerates the degradation of battery materials, potentially leading to further performance degradation. Finally, due to internal heat accumulation, batteries with high DCR may face the risk of thermal runaway under extreme conditions, potentially causing battery damage or even safety incidents such as fires or explosions.

[0004] Therefore, reducing the DCR of battery cells is an urgent problem to be solved. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to provide an electrolyte, a lithium-ion battery, and an electrical device. The electrolyte of this application can form a fast ion conductor on the negative electrode surface, thereby reducing the battery's drain-ceiling coefficient (DCR) and improving the battery's power performance.

[0006] In one aspect of this application, an electrolyte is provided. According to an embodiment of this application, the electrolyte comprises: a first additive and a second additive, the first additive comprising 4-fluorophenyl acetate, the second additive containing a sulfonic acid group, and the mass ratio of the first additive to the second additive being (1-1.4):1.

[0007] According to the electrolyte of the present application, a first additive comprising 4-fluorophenyl acetate (4-FPA) and a second additive containing sulfonic acid groups are compounded, and the first additive and the second additive are mixed at a mass ratio of (1-1.4):1. The two can exert a good synergistic effect. The first additive has sufficient molecular groups to not only improve the wettability of the electrolyte, but also attract the second additive to form a uniform and stable SEI film containing fast ion conductors on the surface of the negative electrode active material, thereby reducing the DCR of the battery and improving the power performance of the battery.

[0008] In addition, the electrolyte according to the above embodiments of this application may also have the following additional technical features:

[0009] In some embodiments of this application, the mass ratio of the first additive to the second additive is (1.1-1.3):1.

[0010] In some embodiments of this application, the second additive includes at least one of methylene methane disulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, and 1,4-butenesulfonate lactone.

[0011] In some embodiments of this application, the mass percentage 'a' of the first additive is 0.1%-2.8% based on the total mass of the electrolyte.

[0012] In some embodiments of this application, the mass percentage b of the second additive is 0.1%-2% based on the total mass of the electrolyte.

[0013] In some embodiments of this application, the electrolyte further includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0014] In some embodiments of this application, the electrolyte further includes a solvent, which includes at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, and dimethyl carbonate.

[0015] In a second aspect, this application proposes a lithium-ion battery. According to an embodiment of this application, the lithium-ion battery includes:

[0016] A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active layer, the negative active layer being disposed on the surface of the negative current collector;

[0017] A separator membrane is disposed on one side of the negative electrode sheet;

[0018] A positive electrode sheet, disposed on the side of the separator opposite to the negative electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer, the positive active layer being disposed on the surface of the positive current collector; and

[0019] The electrolyte described in the first aspect of this application.

[0020] Therefore, the lithium-ion battery possesses all the advantages of the electrolyte, which will not be elaborated further here.

[0021] In some embodiments of this application, the negative electrode active layer comprises graphite, and in the graphite Raman spectrum, I D / I G =c, where c is 0.04-0.07, and I D I represents the intensity of peak D in the graphite Raman spectrum. G This represents the intensity of the G peak in the graphite Raman spectrum. This intensity can suppress side reactions, thereby reducing the cell's DCR.

[0022] In some embodiments of this application, the mass percentage of the first additive is 'a' based on the total mass of the electrolyte, and the mass percentage of the second additive is 'b' based on the total mass of the electrolyte, where a, b, and c satisfy 0.006 ≤ 100(a+b)c ≤ 0.336. This can further reduce the battery's DCR.

[0023] In a third aspect, this application proposes an electricity consumption system. According to an embodiment of this application, the electricity consumption system includes:

[0024] Electrical equipment, and

[0025] An energy storage device that supplies power to the electrical equipment, the energy storage device comprising at least one lithium-ion battery as described in the second aspect of this application.

[0026] Therefore, the power system possesses all the advantages of the lithium-ion battery, which will not be elaborated further here.

[0027] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Detailed Implementation

[0028] The embodiments of this application are described in detail below. The following embodiments are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0029] In one aspect of this application, an electrolyte is provided. According to an embodiment of this application, the electrolyte comprises: a first additive and a second additive, the first additive comprising 4-fluorophenyl acetate, the second additive containing a sulfonic acid group, and the mass ratio of the first additive to the second additive being (1-1.4):1.

[0030] Therefore, the electrolyte in this embodiment of the application is formulated by compounding a first additive including 4-fluorophenyl acetate (4-FPA) and a second additive containing sulfonic acid groups. 4-fluorophenyl acetate has ester groups, which have a certain polarity. They can form hydrogen bonds or dipole interactions with solvent molecules in the electrolyte through oxygen atoms. Furthermore, the highly electronegative fluorine atoms in 4-fluorophenyl acetate can enhance the overall polarity of the molecule, thereby enhancing the interaction with polar electrode materials. That is, 4-fluorophenyl acetate has both electrolyte-loving ester groups and electrode-loving fluorophenyl groups. The synergistic effect of these two functional groups can reduce the surface tension between the electrolyte and the electrode material, reduce the contact angle, and improve the wettability of the electrolyte. Furthermore, the sulfonic acid groups on the second additive containing sulfonic acid groups have a strong electron-withdrawing effect. The π electrons of the benzene ring on 4-fluorophenyl acetate can donate electrons to the attached atoms or groups through a conjugation effect. 4-fluorophenyl acetate can attract the second additive containing sulfonic acid groups to accumulate on the electrode material surface. This second additive can form a film at a certain potential, thereby forming an SEI film (solid electrolyte interface film) containing sulfonate as a fast ion conductor on the surface of the negative electrode material. However, the inventors found that if the mass ratio of the first additive to the second additive is higher than 1.4:1, that is, if the amount of the first additive is too large, its physical adsorption on the negative electrode surface will hinder the reduction process of the second additive, which is not conducive to the formation of an SEI film containing fast ion conductors on the negative electrode surface. If the mass ratio of the first additive to the second additive is less than 1:1, that is, if the content of the first additive is insufficient, its ability to induce the second additive to form a film on the negative electrode surface is low, thus making it difficult to form a uniform and stable SEI film. Therefore, this application controls the first additive and the second additive to be mixed at a mass ratio of (1-1.4):1, so that the two play a good synergistic role. The first additive has enough molecular groups to not only improve the wettability of the electrolyte, but also attract the second additive to form a uniform and stable SEI film containing fast ion conductors on the surface of the negative electrode active material, thereby reducing the DCR of the battery and improving the power performance of the battery.

[0031] According to some specific embodiments of this application, the mass ratio of the first additive and the second additive is (1.1-1.3):1. Therefore, by controlling the mixing of the first additive and the second additive in this ratio, they can further exert a good synergistic effect, thereby forming a more uniform and stable SEI film containing fast ion conductors on the surface of the negative electrode active material, reducing the battery's DCR and improving the battery's power performance.

[0032] According to further specific embodiments of this application, the second additive includes at least one of methylene methane disulfonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, 1,4-butanesulfonate lactone, and 1,4-butenesulfonate lactone. Thus, all the above-mentioned second additives have sulfonic acid groups, which have a strong electron-withdrawing effect. The π electrons of the benzene ring on 4-fluorophenyl acetate can provide electrons to the connected atoms or groups through a conjugation effect. 4-fluorophenyl acetate can attract the second additive containing sulfonic acid groups to accumulate on the surface of the electrode material. This second additive can form a film at a certain potential, thereby forming a SEI film (solid electrolyte interface film) containing sulfonate as a fast ion conductor on the surface of the negative electrode material, reducing the battery's DCR and improving the battery's power performance.

[0033] According to some specific embodiments of this application, the mass percentage 'a' of the first additive is 0.1%-2.8% based on the total mass of the electrolyte. The inventors have discovered that by adding the aforementioned amount of the first additive to the electrolyte, not only can the surface tension between the electrolyte and the electrode material be significantly reduced, the contact angle decreased, and the electrolyte wettability improved, but this amount of the first additive can also fully attract the second additive to form a uniform and stable SEI film containing fast ion conductors on the surface of the negative electrode active material, thereby reducing the battery's DCR.

[0034] According to some specific embodiments of this application, the mass percentage b of the second additive is 0.1%-2% based on the total mass of the electrolyte. The inventors have discovered that by adding the above-mentioned amount of the second additive to the electrolyte, on the one hand, a stable and dense SEI film containing sulfonate fast ion conductors can be formed. This SEI film allows lithium ions to rapidly embed into the negative electrode near the interface film, significantly reducing the battery's DCR; on the other hand, it can improve the toughness of the SEI film, making it less prone to cracking during battery charging and discharging, thus improving the battery's cycle performance.

[0035] According to some specific embodiments of this application, the electrolyte further includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0036] According to some specific embodiments of this application, the electrolyte further includes a solvent, which includes at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, methyl ethyl carbonate, and dimethyl carbonate.

[0037] In a second aspect, this application proposes a lithium-ion battery. According to an embodiment of this application, the lithium-ion battery includes:

[0038] A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active layer, the negative active layer being disposed on the surface of the negative current collector;

[0039] A separator membrane is disposed on one side of the negative electrode sheet;

[0040] A positive electrode sheet, disposed on the side of the separator opposite to the negative electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer, the positive active layer being disposed on the surface of the positive current collector; and

[0041] The electrolyte as described above.

[0042] During battery charging and discharging, active lithium ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator, placed between the positive and negative electrode plates, primarily prevents short circuits between the two electrodes while allowing ions to pass through.

[0043] The positive electrode includes a positive current collector and a positive active layer disposed on the surface of the positive current collector. The positive active layer includes a positive active material, which may be a known positive active material for batteries. Examples of positive active materials include lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, etc.

[0044] In some embodiments of this application, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0045] In some embodiments of this application, the positive electrode active layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0046] In some embodiments of this application, the positive electrode active layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0047] In some embodiments of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet (e.g., positive active material, conductive agent, binder) in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0048] The negative electrode sheet includes a negative current collector and a negative active layer disposed on the surface of the negative current collector, the negative active layer including a negative active material.

[0049] In some embodiments of this application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0050] In some embodiments of this application, the negative electrode active layer comprises graphite, and in the graphite Raman spectrum, I D / I G =c, where c is 0.04-0.07:1, and I D I represents the intensity of peak D in the graphite Raman spectrum. G This represents the intensity of the G peak in the Raman spectrum of graphite. Specifically, in the Raman spectroscopy analysis of graphite, I... D / I G It can be used to evaluate the structure and properties of materials. Among them, I... D The G peak can be used as an indicator to assess the defect level of graphite materials. The presence and intensity of the G peak are related to the crystal structure of the material and are a marker of the integrity of the graphite material's crystal structure. D / I G The higher the peak ratio, the higher the degree of graphite defects. These defects easily catalyze the decomposition reaction of the electrolyte (such as electrolyte solvent decomposition), leading to a decrease in cell performance. This is mainly manifested in the repeated damage and repair of the SEI film, resulting in a thicker film and an increase in battery DCR. However, the inventors of this application unexpectedly discovered that using I... D / I GWhen the peak ratio is between 0.04 and 0.07 for graphite, the first and second additives can suppress this side reaction. The main mechanism is that the amorphous carbon at the defects of the graphite anode material has a high specific surface area and activity. The highly electronegative fluorine atoms in the first additive can enhance the overall molecular polarity, thereby strengthening the interaction with the polar electrode material, especially with the amorphous carbon. At the same time, the first additive can induce the second additive to target and form a film at the graphite defects, forming a high-quality SEI film in the initial stage of cell formation, thus avoiding the increase in DCR caused by repeated solvent decomposition and film formation at the defects.

[0051] In some embodiments of this application, the mass percentage of the first additive is 'a' based on the total mass of the electrolyte, and the mass percentage of the second additive is 'b' based on the total mass of the electrolyte. a, b, and c satisfy 0.006 ≤ 100(a+b)c ≤ 0.336. The inventors have found that when the relationship between a, b, and c satisfies 0.006 ≤ 100(a+b)c ≤ 0.336, on the one hand, a uniform and stable film can be formed at the defects in the graphite, thus reducing solvent decomposition into a film after cycling; on the other hand, a smaller degree of graphite defect does not lead to increased graphite expansion during lithium-ion insertion and extraction, thereby reducing the probability of SEI film rupture and thus lowering the battery's DCR value.

[0052] In some embodiments of this application, the negative electrode active material may further include at least one of the following materials: soft carbon, hard carbon, silicon-based materials, tin-based materials, etc. Silicon-based materials may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide compounds, and tin alloys.

[0053] In some embodiments of this application, the negative electrode active layer may optionally include a binder. The binder may include at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0054] In some embodiments of this application, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0055] In some embodiments of this application, the negative electrode active layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0056] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet (e.g., negative electrode active material, conductive agent, binder and any other components) in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0057] This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected. In some embodiments of this application, the material of the separator membrane may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0058] The lithium-ion battery of this application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, battery cells may be assembled into a battery module, and the number of battery cells contained in a battery module may be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, and the number of battery modules contained in a battery pack may be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0059] In a third aspect, this application proposes an electrical system. According to an embodiment of this application, the electrical system includes electrical equipment and an energy storage device, the energy storage device providing power to the electrical equipment, and the energy storage device including at least one of the aforementioned lithium-ion batteries.

[0060] The electrical devices used in this application embodiment can include, but are not limited to, portable electronic devices such as mobile phones, tablets, laptops, desktop computers, smart bracelets, smartwatches, e-readers, and game consoles. They can also be vehicles such as cars, trucks, sedans, vans, freight cars, bullet trains, high-speed trains, and electric vehicles. Furthermore, they can be various household appliances. Further, the energy storage device in this application can be an energy storage battery cabinet.

[0061] It should be noted that the features and advantages described above for lithium-ion batteries also apply to this power system, and will not be repeated here.

[0062] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0063] Example 1

[0064] 1) Preparation of the positive electrode sheet:

[0065] Lithium iron phosphate (LiFePO4), conductive carbon black (SP), and polyvinylidene fluoride (PVDF) binder are dispersed in N-methylpyrrolidone (NMP) solvent and mixed evenly to obtain a positive electrode slurry. The mass ratio of LiFePO4, PVDF, and conductive carbon black is 90:3:7. The positive electrode slurry is coated onto aluminum foil for the positive electrode current collector. After drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0066] 2) Preparation of the negative electrode sheet:

[0067] Artificial graphite (anode active material), conductive carbon (SP), thickener (CMC), and binder (SBR) were dispersed in deionized water at a mass ratio of 80:1:1:18 and mixed evenly to obtain a negative electrode slurry. The negative electrode slurry was coated onto a copper foil current collector, and after drying, cold pressing, slitting, and cutting, a negative electrode sheet was obtained. The ID / IG peak ratio of the artificial graphite is shown in Table 1.

[0068] 3) Preparation of electrolyte:

[0069] In an argon-atmospheric glove box with a moisture content ≤1ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed at a mass ratio of 1:2:1. Then, dried lithium hexafluorophosphate, the electrolyte salt, was dissolved in the solvent and stirred until completely dissolved and homogeneous. The first additive, 4-fluorophenyl acetate, and the second additive, methylene methane disulfonate, were added and mixed thoroughly to obtain the electrolyte. The lithium salt concentration was 1 mol / L, the mass concentration of 4-fluorophenyl acetate in the electrolyte was 0.1%, and the mass concentration of methylene methane disulfonate in the electrolyte was 0.1%.

[0070] 4.) Preparation of the separating membrane:

[0071] A 16-micron polypropylene film was selected as the separator.

[0072] 5) Battery assembly:

[0073] The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator in the middle to separate the positive and negative electrode sheets. After winding, a bare cell is obtained. After welding the tabs, the cell is assembled into the outer packaging. After injecting the prepared electrolyte, the cell is packaged, left to stand, formed, shaped, and tested for capacity, and finally a soft-pack lithium-ion battery is prepared.

[0074] The specific differences between Examples 2-7 and Comparative Examples 1-3 and Example 1 are shown in Table 1.

[0075] Table 1

[0076]

[0077]

[0078] The DCR of the lithium-ion batteries prepared in Examples 1-7 and Comparative Examples 1-3 were tested respectively, and the specific test methods are as follows:

[0079] The battery obtained in the above embodiments was placed at 25°C and discharged at a constant current of 0.5C to a voltage of 2.5V. It was then allowed to stand for 5 minutes, followed by constant current charging at 0.5C to a voltage of 3.65V, and constant voltage charging to a current of 0.025C. After standing for 5 minutes, it was discharged at a constant current of 0.1C to 2.5V, and the discharge capacity at this point was recorded as C1. It was then charged at a constant current of 0.5C to 3.65V, constant voltage to a current of 0.025C, allowed to stand for 5 minutes, and discharged at a constant current of 0.1C for 5 hours, and the voltage at this point was recorded as V1. Next, it was discharged at a constant current of 1C for 1 second, and the voltage at this point was recorded as V2. The DCR of the battery at 50% SOC is: (V1 V2) / I, where I = 1C. The characterization results are shown in Table 2.

[0080] Table 2

[0081]

[0082]

[0083] As can be seen from Table 1, the mass ratio of the first additive and the second additive in the electrolyte of the batteries in Examples 1-7 is (1-1.4):1; the mass ratio of the first additive and the second additive in the electrolyte of the battery in Comparative Example 1 is 2:1; the mass ratio of the first additive and the second additive in the electrolyte of the battery in Comparative Example 2 is 0.5:1; the mass ratio of the first additive and the second additive in the electrolyte of the battery in Comparative Example 3 is 2:1. As can be seen from Table 2, compared with Comparative Examples 1-3, the DCR of the batteries in Examples 1-7 is significantly smaller, indicating that controlling the mass ratio of the first additive and the second additive in the electrolyte to (1-1.4):1 can reduce the DCR of the battery.

[0084] Furthermore, in Examples 1-5, the graphite I D / I G The peak ratio was 0.04-0.07, and 100(a+b)c was 0.006-0.336, while the graphite in Example 6 had a peak ratio of 1. D / I G The peak ratio is 0.08, and 100(a+b)c is 0.384; the graphite in Example 7 has an I... D / I GThe peak ratio is 0.05, and 100(a+b)c is 0.005. According to the data in Table 2, the DCR of the lithium batteries in Examples 1-5 is significantly lower than that in Examples 6-7, indicating that using I... D / I G Graphite with a peak ratio of 0.04-0.07 and 100(a+b)c satisfying 0.006-0.336 can further reduce the DCR of the battery.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0086] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An electrolyte, characterized in that, include: The first additive and the second additive, wherein the first additive comprises 4-fluorophenyl acetate and the second additive is methylene methane disulfonate, and the mass ratio of the first additive and the second additive is (1-1.4):1; Based on the total mass of the electrolyte, the mass percentage 'a' of the first additive is 0.1%-2.8%.

2. The electrolyte according to claim 1, characterized in that, The mass ratio of the first additive to the second additive is (1.1-1.3):

1.

3. The electrolyte according to claim 1, characterized in that, Based on the total mass of the electrolyte, the mass percentage b of the second additive is 0.1%-2%.

4. The electrolyte according to claim 1, characterized in that, It also includes lithium salts, including at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

5. The electrolyte according to claim 1 or 4, characterized in that, It also includes solvents, said solvents comprising at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, and dimethyl carbonate.

6. A lithium-ion battery, characterized in that, include: A negative electrode sheet, the negative electrode sheet comprising a negative current collector and a negative active layer, the negative active layer being disposed on the surface of the negative current collector; A separator membrane is disposed on one side of the negative electrode sheet; A positive electrode sheet, disposed on the side of the separator opposite to the negative electrode sheet, the positive electrode sheet including a positive current collector and a positive active layer, the positive active layer being disposed on the surface of the positive current collector; and The electrolyte according to any one of claims 1-5.

7. The lithium-ion battery according to claim 6, characterized in that, The negative electrode active layer comprises graphite, and in the graphite Raman spectrum, I D / I G =c, where c is 0.04-0.07, and I D I represents the intensity of peak D in the graphite Raman spectrum. G This represents the intensity of the G peak in the graphite Raman spectrum.

8. The lithium-ion battery according to claim 7, characterized in that, Based on the total mass of the electrolyte, the mass percentage of the first additive is a. Based on the total mass of the electrolyte, the mass percentage of the second additive is b. a, b, and c satisfy 0.006 ≤ 100(a+b)c ≤ 0.

336.

9. An electrical system, characterized in that, include: Electrical equipment, and An energy storage device that supplies power to the electrical equipment, the energy storage device comprising at least one lithium-ion battery as described in any one of claims 6-8.

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