Additive composition, electrolyte, and battery

Abstract

The present application provides an additive composition, an electrolyte, and a battery. The additive composition comprises a first additive and a second additive; the first additive comprises a compound having a structural formula of formula 1; and the second additive comprises trimethylolpropane phosphite. The additive composition provided by the present application, when applied to an electrolyte, can enable batteries to exhibit excellent normal-temperature and high-temperature cycle performance, rate performance, and safety performance.

Description

An additive composition, an electrolyte, and a battery

[0001] This application claims priority to Chinese Patent Application No. 202410961803.7, filed on July 18, 2024, entitled “An Additive Composition, Electrolyte and Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to an additive composition, and more particularly to an additive composition, an electrolyte, and a battery, belonging to the field of secondary battery technology. Background Technology

[0003] With the rapid development of markets such as pure electric vehicles, smart homes, power tools, and intelligent transportation, consumers are constantly increasing their demands for battery performance. Rechargeable batteries, due to their advantages such as high energy density, long cycle life, and low self-discharge, are widely used in consumer electronics and energy storage and power batteries.

[0004] Currently, electrolyte additives are often added to the electrolyte to improve battery performance. However, current electrolyte additives still have problems in practical applications, such as causing high impedance, poor cycle performance at room temperature and high temperature, and gas generation during battery operation, thereby degrading the battery's cycle performance, rate performance, and safety performance.

[0005] Therefore, there is an urgent need to develop an additive composition that can improve the room temperature and high temperature cycle performance, rate performance, and safety performance of batteries. Summary of the Invention

[0006] This application provides an additive composition that, when applied to an electrolyte, can improve the battery's room temperature and high temperature cycle performance, rate performance, and safety performance.

[0007] This application provides an electrolyte that enables the battery to exhibit excellent room temperature and high temperature cycling performance, rate performance, and safety performance.

[0008] This application provides a battery that has excellent room temperature and high temperature cycling performance, rate performance, and safety performance.

[0009] This application provides an additive composition, wherein the additive composition comprises a first additive and a second additive; the first additive comprises a compound having the structural formula of Formula 1:

[0010] Where n is 0 or 1, A is selected from methylene or O, X is selected from sulfonyl or carbonyl, and R1 and R2 are each independently selected from H, One of them, and R1 and R2 are not both selected from H, and at least one sulfur atom is contained in X, R1 and R2;

[0011] The second additive includes trimethylolpropane phosphite.

[0012] The additive composition as described above, wherein the first additive comprises a compound having the structural formula of Formula 2:

[0013] X, R1, and R2 contain one or two sulfur atoms.

[0014] The additive composition as described above, wherein the first additive comprises at least one compound having a structural formula of formula 3-6:

[0015] The additive composition as described above, wherein the mass ratio of the first additive to the second additive is (0.25-20):1.

[0016] The additive composition as described above, wherein the additive composition further comprises a third additive, the third additive comprising vinyl sulfate.

[0017] The additive composition as described above, wherein the mass ratio of the first additive to the third additive is (0.25-20):1.

[0018] This application provides an electrolyte comprising the additive composition described above.

[0019] In the electrolyte as described above, the first additive has a mass percentage content of 0.5-2% in the electrolyte;

[0020] And / or, the second additive has a mass percentage content of 0.1%-1% in the electrolyte;

[0021] And / or, the electrolyte includes a third additive, the third additive being present in the electrolyte at a mass percentage of 0.1%-1%.

[0022] The electrolyte as described above further includes a negative electrode film-forming additive, which includes at least one of vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate; each of the negative electrode film-forming additives has a mass percentage of 0.5-1% in the electrolyte.

[0023] The electrolyte as described above further includes triphenyl phosphite; the mass percentage of triphenyl phosphite in the electrolyte is 0.01-0.5%.

[0024] The electrolyte as described above, wherein the electrolyte further comprises an electrolyte salt and an organic solvent, the molar concentration of the electrolyte salt in the electrolyte is 0.8 mol / L - 2 mol / L; the electrolyte salt is a lithium salt or a sodium salt, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate and lithium bis(trifluoromethanesulfonyl)imide; the sodium salt includes at least one of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide.

[0025] And / or, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

[0026] The present application also provides a battery comprising the electrolyte as described above.

[0027] The battery as described above, wherein the battery comprises a positive electrode plate and a negative electrode plate, and the positive active material in the positive electrode plate is Li a Ni b Co c M1 d M2 e O f R g , wherein 1 ≤ a ≤ 1.2, 0.6 < b < 1, 0 < c < 1, 0 < d < 1, 0 ≤ e ≤ 0.2, b + c + d + e = 1, 1 ≤ f ≤ 2, 0 ≤ g ≤ 1, f + g = 2; M1 includes Mn and / or Al, M2 includes at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb; R includes at least one of N, F, S, Cl;

[0028] Or, the positive active material in the positive electrode plate is at least one of three-dimensional tunnel type Na 0.44 MnO2, P2 layered type NaMO2, NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, Na3V2(PO4)2F3, Na2Fe(CN)6, Na2MnFe(CN)6; wherein, M is at least one of Ni, Mn, Fe;

[0029] The negative active material in the negative electrode plate includes at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials and lithium-containing metal composite oxide materials.

[0030] The additive composition provided in this application limits the selection of the first additive and the second additive in the electrolyte. The first additive and the second additive work together to generate a CEI film and an SEI film with strong lithium conductivity and uniform density on the positive and negative electrode surfaces. The second additive can improve the ion transport efficiency of the CEI film and reduce the acidity of the electrolyte, thereby improving the battery's room temperature and high temperature cycle performance, rate performance and safety performance.

[0031] This application provides an electrolyte comprising the above-mentioned additive composition, which can improve the room temperature and high temperature cycle performance, rate performance and safety performance of the battery.

[0032] The battery described in this application is prepared based on the electrolyte as described above. The battery exhibits excellent room temperature and high temperature cycling performance, rate performance, and safety performance at high temperatures. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] This application provides an additive composition comprising a first additive and a second additive; the first additive comprises a compound having the structural formula of Formula 1:

[0035] Where n is 0 or 1, A is selected from methylene or O, X is selected from sulfonyl or carbonyl, and R1 and R2 are each independently selected from H, One of them, and R1 and R2 are not simultaneously selected from H, and X, R1 and R2 contain at least one sulfur atom; the second additive includes trimethylolpropane phosphite.

[0036] In the compounds of this application having the structure shown in Formula 1, n is 0 or 1, meaning that the compound of Formula 1 can be a five-membered ring or a six-membered ring. Specifically, R2 in the structural formula of Formula 1 is a substituent for the methylene or methine group in the five-membered or six-membered ring, that is, it can substitute for the hydrogen atom in the methylene or methine group. For example, the compound of Formula 1 can be... In this application, A is methylene (which may be substituted by R2) or O, and X is selected from sulfonyl or carbonyl. In this application, R1 and R2 are each independently selected from H, One of them, Any methylene group in the five-membered ring can be converted into a methine group, becoming a substituent. For example, the compound of formula 1 can be... In this application, R1 and R2 are not both selected from H; that is, when R1 is H, R2 cannot be H, or when R2 is H, R1 cannot be H. X, R1, and R2 in this application contain at least one sulfur atom.

[0037] The first additive has oxidation and reduction potentials that are higher than those of the electrolyte solvent. Therefore, during battery pre-charging, it is preferentially oxidized at the positive electrode and reduced at the negative electrode, leading to the formation of a CEI film at the positive electrode and an SEI film at the negative electrode. This reduces gas production during charging and discharging, and as a low-impedance additive, it lowers battery impedance and improves fast-charging cycle performance. However, because the main component of the first additive in the positive electrode film is lithium carbonate, a high lithium carbonate content makes it susceptible to corrosion by HF, resulting in a thicker CEI film and thus a decrease in battery performance. Moreover, under high-temperature cycling and storage conditions, electrolyte salts (such as lithium hexafluorophosphate) are prone to hydrolysis to generate hydrofluoric acid, which damages the CEI and SEI solid electrolyte films, causing electrolyte decomposition on the positive and negative electrode surfaces, thereby reducing battery performance and increasing gas production. The second additive is trimethylolpropane phosphite. Compared to phosphate ester additives, it has a lower LUMO energy level and is more easily oxidized. While participating in the positive electrode film formation, it also modifies the positive electrode surface, making the positive electrode closer to the original positive electrode. On the other hand, the three-dimensional framework structure of the second additive can form cavity channels during film formation, increasing the porosity of the CEI film and thus improving ion transport efficiency and cell performance. When the second additive is used in combination with the first additive, the resulting phosphorus- and sulfur-containing CEI film is denser and has superior performance. Simultaneously, the second additive, utilizing its electron-deficient compound characteristics, preferentially reacts with water and hydrogen fluoride in the electrolyte, reducing the electrolyte acidity and preventing HF corrosion of the lithium carbonate component in the CEI film, thereby reducing the risk of increased impedance and decreasing gas generation. This improves the battery's room temperature and high temperature cycle performance, rate performance, and safety performance.

[0038] In one specific embodiment, the first additive comprises a compound having the structural formula of Formula 2:

[0039] X, R1, and R2 contain one or two sulfur atoms.

[0040] When the first additive includes a compound having the structure of Formula 2, the first additive can further synergize with the second additive to improve the stability and lithium conduction performance of the SEI film and CEI film to a greater extent, thereby reducing the battery impedance. At the same time, it can avoid contact between the electrolyte and the positive and negative electrodes to a greater extent, suppress the gas generation problem of the battery, and thus make the battery's room temperature and high temperature cycle performance, rate performance and safety performance better.

[0041] In one specific embodiment, the first additive comprises at least one compound having a structural formula of formulas 3-6:

[0042] When the above-mentioned compounds are selected as the first additive, they can work synergistically with the second additive to generate SEI and CEI films with higher lithium conductivity and better stability, thereby reducing battery impedance and reducing battery gas generation problems. Furthermore, the second additive can better perform its function, resulting in better room temperature and high temperature cycle performance, rate performance and safety performance of the battery.

[0043] In one specific embodiment, the mass ratio of the first additive to the second additive is (0.25-20):1, for example, the mass ratio of the first additive to the second additive is 0.25:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 or 20:1, etc. When the mass ratio of the first additive and the second additive is within the above range, the first additive and the second additive have a further synergistic effect, which makes the performance of the SEI film and CEI film better, and can further improve the porosity of the CEI film, reduce the electrochemical impedance, accelerate the lithium ion transport rate, and further reduce the acidity of the electrolyte, effectively inhibit the corrosion of the positive electrode by HF and prevent the decomposition of the electrolyte solvent, thereby reducing the generation of gas. As a result, the battery has higher room temperature and high temperature cycle performance, rate performance and safety performance.

[0044] In one specific embodiment, the additive composition further includes a third additive, which comprises vinyl sulfate. When vinyl sulfate is selected as the third additive, it can be used in combination with the first and second additives. During the formation process, the third additive reacts with the electrolyte to generate a substance similar to the first additive. Simultaneously, the third additive has a lower LUMO energy level than the first additive, so it is preferentially reduced at the negative electrode before the first additive. The compound formed after the third additive undergoes ring opening promotes the reduction of the first additive at the negative electrode, accelerating the film formation of the first additive and reducing the lithium carbonate content in the SEI film. Simultaneously, the lithium carbonate is reacted with Li₂SO₄ and its over-lithium products (lithium oxide and amorphous Li₂). x S and Li xThe O) sandwiched in the middle restricts the decomposition by HF in the electrolyte and the thickening of the SEI film, thereby avoiding damage to the SEI film. This results in a higher and denser SEI film with higher conductivity, which in turn improves the battery's room temperature and high temperature cycling performance, rate performance, and safety performance. Furthermore, the third additive can work synergistically with the first and second additives to construct a denser and more uniform CEI film, thereby further improving the battery's room temperature and high temperature cycling performance, rate performance, and safety performance.

[0045] In one specific embodiment, the mass ratio of the first additive to the third additive is (0.25-20):1, for example, the mass ratio of the first additive to the third additive is 0.25:1, 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1, etc. When the mass ratio of the first additive to the third additive is within the above range, the first additive, the second additive, and the third additive exert a further synergistic effect, resulting in better stability and lithium conductivity of the SEI film and CEI film. Furthermore, the third additive can significantly promote the film formation rate of the first additive on the negative electrode surface, while further reducing the lithium carbonate content in the SEI film, thereby further improving the stability of the SEI film. This leads to higher room temperature and high temperature cycle performance, rate performance, and safety performance of the battery.

[0046] This application provides an electrolyte comprising the above-mentioned additive composition, which enables the battery to exhibit excellent room temperature and high temperature cycle performance, rate performance, and safety performance.

[0047] In one specific embodiment, the mass percentage of the first additive in the electrolyte is 0.5-2%, for example, the mass percentage of the first additive in the electrolyte is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%, etc. When the mass percentage of the first additive is within the above range, the first additive, the second additive, and the third additive further synergistically enhance the lithium conductivity and stability of the SEI and CEI films of the battery, thereby reducing the battery impedance and mitigating gas generation issues, thus improving the battery's room temperature and high temperature cycle performance, rate performance, and safety performance.

[0048] In one specific embodiment, the second additive has a mass percentage content of 0.1%-1% in the electrolyte, for example, the mass percentage content of the second additive in the electrolyte is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc. When the mass percentage content of the second additive is within the above range, the first additive, the second additive, and the third additive further synergistically generate SEI and CEI films with higher stability and lithium conductivity, and can further improve the porosity of the CEI film and enhance the ion transport efficiency of the CEI film, thereby further improving the battery's room temperature and high temperature cycle performance and rate performance. At the same time, it can further reduce the acidity of the electrolyte, thereby further suppressing the battery's gas generation problem and improving the battery's safety performance.

[0049] In one specific embodiment, the electrolyte includes a third additive, the third additive having a mass percentage of 0.1%-1% in the electrolyte, for example, a mass percentage of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. When the mass percentage of the third additive is within the above range, the first, second, and third additives further synergistically enhance the stability and lithium conductivity of the SEI and CEI films. Furthermore, the third additive can further accelerate the film formation rate of the first additive and significantly improve the stability of the SEI film, thereby resulting in superior room temperature and high temperature cycle performance, rate performance, and safety performance of the battery.

[0050] In one specific embodiment, the electrolyte further includes a negative electrode film-forming additive, which includes at least one selected from vinylene carbonate, fluoroethylene carbonate, and ethylene ethylene carbonate. The mass percentage of each negative electrode film-forming additive in the electrolyte is 0.5-1%, meaning that the mass percentage of each additive in the electrolyte is 0.5-1%, for example, the mass percentage of vinylene carbonate in the electrolyte is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%, etc. When the above-mentioned compounds are selected as negative electrode film-forming additives and their mass percentage is controlled within the above range, the addition of the negative electrode film-forming additives can participate in the construction of the SEI film, improve the uniformity of SEI film formation, thereby further protecting the negative electrode and reducing gas generation problems caused by the reaction between the electrolyte and the negative electrode, thus further improving the battery's room temperature and high temperature cycle performance and safety performance.

[0051] In one specific embodiment, the electrolyte further includes triphenyl phosphite, which has a mass percentage content of 0.01-0.5% in the electrolyte, for example, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%. When the mass percentage content of triphenyl phosphite is within the above range, the storage stability of the electrolyte can be improved, which helps the electrolyte maintain its properties during storage and transportation, and reduces deterioration caused by changes in the external environment.

[0052] In one specific embodiment, the electrolyte further includes a lithium salt, which includes at least one selected from lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, and lithium bis(trifluoromethanesulfonyl)imide. The molar concentration of the lithium salt in the electrolyte is 0.8 mol / L to 2 mol / L, for example, the molar concentration of the lithium salt in the electrolyte is 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2 mol / L. When the above-mentioned compounds are selected as the lithium salt and their molar concentration is controlled, the lithium salt can be fully dissolved in the solvent and release lithium ions, so that the lithium ions and the solvent form a solvated structure, which is conducive to the rapid migration of lithium ions. Preferably, the lithium salt can be lithium bis(fluorosulfonyl)imide. Lithium bis(fluorosulfonyl)imide helps reduce the generation of hydrogen fluoride in the electrolyte.

[0053] In one specific embodiment, the electrolyte further includes a sodium salt, which includes at least one selected from sodium hexafluorophosphate and sodium difluorosulfonamide. The molar concentration of the sodium salt in the electrolyte is 0.8 mol / L to 2 mol / L, for example, the molar concentration of the sodium salt in the electrolyte is 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2 mol / L. When the above-mentioned compounds are selected as the sodium salt and its molar concentration is controlled, the sodium salt can be fully dissolved in the solvent and release sodium ions, allowing the sodium ions to form a solvated structure with the solvent, which is beneficial for the rapid migration of sodium ions.

[0054] In a specific embodiment, the electrolyte further includes an organic solvent, and the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate. When the above-mentioned organic solvent is selected, as an important carrier for ion transport, the electrolyte salt, the first additive, the second additive, the third additive, the negative electrode film-forming additive, and the stabilizing additive can be fully dissolved, obtaining an electrolyte with high stability and high conductivity. At the same time, the viscosity of the electrolyte is appropriate, so that the electrolyte salt, the first additive, the second additive, the third additive, and the negative electrode film-forming additive can better play their roles, making the battery exhibit higher room-temperature and high-temperature cycling performance and safety performance.

[0055] The present application also provides a battery including the electrolyte as described above. Based on the electrolyte provided by the present application, the battery provided by the present application exhibits excellent room-temperature and high-temperature cycling performance and safety performance.

[0056] In a specific embodiment, the battery of the present application includes a positive electrode plate, and the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on the surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. Among them, the positive electrode current collector is generally aluminum foil. As an example, when the battery is a lithium-ion battery, the positive electrode active material is Li a Ni b Co c M1 d M2 e O f R g , where 1≤a≤1.2, 0.6<b<1, 0<c<1, 0<d<1, 0≤e≤0.2, b + c + d + e = 1, 1≤f≤2, 0≤g≤1, f + g = 2; M1 includes Mn and / or Al, M2 includes at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and R includes at least one of N, F, S, Cl. When the above-mentioned positive electrode active material is selected, the specific capacity of the positive electrode active material can be improved, thereby reducing the cost of the positive electrode active material in the battery.

[0057] As another example, when the battery is a sodium-ion battery, the positive electrode active material includes, but is not limited to, three-dimensional tunnel-type Na 0.44 MnO2, P2-layered NaMO2, NaFePO4, Na4Fe3(PO4)2P2O¬7, Na3V2(PO4)3, Na3V2(PO4)2F3, Na2Fe(CN)6, Na2MnFe(CN)6; where M is at least one of Ni, Mn, Fe.

[0058] In one specific embodiment, in addition to the electrolyte and positive electrode provided in this application, it also includes a negative electrode and a separator, specifically:

[0059] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The negative active material layer includes a negative active material, a conductive agent, and a binder. The negative current collector is generally copper foil, and the negative active material is selected from one or more of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials, and lithium-containing metal composite oxide materials.

[0060] The conductive agents and binders used in both the positive and negative electrode active material layers can be conventional materials in this field.

[0061] The separator is a separator known in the art that can be used in batteries and is stable to the electrolyte used. It may include one or more of polyolefins, aromatic polyamides, polytetrafluoroethylene, and polyethersulfone, and may be configured as needed.

[0062] The present application will be further described in detail below through specific embodiments.

[0063] Example 1

[0064] The electrolyte provided in this embodiment includes: lithium salt including lithium hexafluorophosphate, the molar concentration of lithium hexafluorophosphate being 1 mol / L; organic solvent including ethylene carbonate, methyl ethyl carbonate, and dimethyl carbonate, the mass ratio of ethylene carbonate and methyl ethyl carbonate being 3:5:2; the first additive being a compound having the structural formula 3, the mass percentage of the first additive being 0.5%; the second additive being trimethylolpropane phosphite, the mass percentage of the second additive being 1%, with any remaining amount being supplemented by organic solvent.

[0065] The electrolyte preparation method of this embodiment includes: preparing the electrolyte in a glove box, the glove box being filled with argon gas of 99.999% purity, the moisture content in the glove box being controlled at ≤0.1ppm, the temperature being controlled at room temperature, thoroughly mixing ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate, then mixing lithium salt into the mixed solvent, mixing evenly, then adding the first additive and the second additive and mixing thoroughly, finally obtaining the electrolyte.

[0066] The electrolyte formulations provided in Examples 2-55 and Comparative Examples 1-3 are basically the same as those in Example 1, and the specific parameters are shown in Table 1.

[0067] Table 1

[0068] Test case

[0069] Examples 1 to 49, Examples 51 to 54, Comparative Examples 1 to 3

[0070] Lithium-ion batteries were prepared by combining the electrolytes of the examples and comparative examples with positive electrode sheets, negative electrode sheets, and separators. Specifically, the positive electrode active material NCM811, binder polyvinylidene fluoride (PVDF), conductive agent carbon black (SP), and conductive agent carbon nanotubes (CNT) were mixed evenly in a weight ratio of NCM811:SP:CNT:PVDF = 97.3:1:0.5:1.2. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil with a coating amount of 35 g / m². 2 After drying at 85℃, the material is cold-pressed, trimmed, cut into sheets, and slit. After slitting, it is dried at 85℃ under vacuum for 4 hours. The tabs are then welded to obtain the positive electrode sheet. The total thickness of the positive electrode sheet is 113μm, and the compaction density of the positive electrode active material layer is 3.4mg / cm³. 3 .

[0071] The negative electrode active material graphite, conductive agent carbon black, thickener sodium carboxymethyl cellulose (CMC-Na), and binder styrene-butadiene rubber were mixed in a weight ratio of 95:1.5:1:2.5, and deionized water was added. The mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto the negative electrode current collector copper foil with a coating amount of 20 g / m². 2 After drying at 85℃, the material is cold-pressed, trimmed, cut into sheets, and slit. After slitting, it is dried at 85℃ under vacuum for 4 hours. The tabs are then welded to obtain the negative electrode sheet. The total thickness of the negative electrode sheet is 164μm, and the compaction density of the negative electrode active material layer is 1.5mg / cm³. 3 .

[0072] The prepared positive electrode, negative electrode, and separator were stacked in sequence. An 8μm thick polyethylene separator was used. The separator was placed between the positive and negative electrodes, and after winding, the cell was encapsulated in an aluminum-plastic film and dried to produce a lithium-ion battery with a thickness of 4.7mm, a width of 55mm, and a length of 60mm. The battery was then vacuum-baked at 75℃ for 10 hours and injected with the previously prepared electrolyte. After standing for 24 hours, the battery was placed at 45℃ under a pressure of 3kg and charged to 4.0V at 0.1C (160mA). It was then left to stand for 2 days (to fully activate the battery) to obtain the lithium-ion battery.

[0073] Example 50

[0074] Except for adjusting the electrolyte formulation according to Table 1, replacing the electrolyte salt LiPF6 with NaPF6, and replacing the positive electrode active material with Na4Fe3(PO4)2P2O7 in the preparation of the positive electrode sheet, the rest is the same as in Example 47, and a sodium-ion battery is prepared.

[0075] Example 55

[0076] In addition to replacing the positive electrode active material with LiNi during the preparation of the positive electrode sheet... 0.88 Co 0.06 Mn 0.03 Fe 0.03 Except for O2, the rest is the same as in Example 48, and a lithium-ion battery is prepared.

[0077] The following battery performance tests were performed on the batteries using the electrolytes from the examples and comparative examples, and the test methods are as follows:

[0078] At an ambient temperature of 25℃, the battery was left to stand for 4 hours, and then subjected to 600 charge-discharge cycles at a current of 0.5C. The test voltage window was 2.75-4.25V. The discharge capacity of the first cycle was recorded as C1, and the discharge capacity of the 600th cycle was recorded as C2. 600 Record the capacity retention rate η1 = C after 600 cycles at 25°C. 600 / C1×100%, see Table 2.

[0079] The battery was left to stand for 4 hours at an ambient temperature of 45℃, and then subjected to 600 charge-discharge cycles at a current of 0.5C. The test voltage window was 2.75-4.25V. The discharge capacity of the first cycle was recorded as Q1, and the discharge capacity of the 600th cycle was recorded as Q. 600 Record the capacity retention rate η2 = Q after 600 cycles at 45℃. 600 / Q1×100%, see Table 2.

[0080] The formation gas production ΔV was measured using the water displacement method. The specific test procedure is as follows: In a constant temperature environment of 25℃, the battery was suspended from a balance by a thin thread and completely immersed in a container of water. The balance reading at this time was recorded as m1. Then, the battery was placed in an explosion-proof oven at 45℃, and a pressure of 29.4N was applied. After charging to 4.0V at 0.1C (160mA), the battery was left to stand at 45℃ for 2 days (to fully activate the battery). The battery was then suspended from a thin thread and completely immersed in a container of water again, and the balance reading was recorded as m2.

[0081] The gas production rate ΔV = (m2 - m1) / ρ, where ρ is the density of liquid water. See Table 2.

[0082] After storing the battery at 60℃ for 30 days, it was discharged at 1C constant current to the cutoff voltage of 2.5V, allowed to stand for 5 minutes, and then charged at 1C constant current and constant voltage to the upper limit voltage of 4.25V, with a cutoff current of 0.05C. It was then discharged at 1C constant current for 30 minutes. The battery, adjusted to 50% SOC, was then allowed to stand at 25℃ for 5 minutes and discharged at 2C constant current for 30 seconds. The discharge current during 2C discharge was I. 2C Record the initial voltage V0 and the voltage V1 after 30 seconds of discharge. The formula for calculating the DC internal resistance of discharge at 50% SOC is as follows: DCR(mΩ)=(V0-V1) / I 2C ×100%.

[0083] Place the battery in a 25℃ environment and discharge it at a constant current of 1C to the cutoff voltage of 2.5V. Let it stand for 5 minutes, then charge it at a constant current and constant voltage of 1.6C to the upper limit voltage of 4.25V. The cutoff current is 0.05C. Then charge and discharge it at a constant current of 1.6C / 1C for 600 cycles. Record the discharge capacity of the first cycle as C3 and the discharge capacity of the 600th cycle as C4. η3=C4 / C3×100%, see Table 2.

[0084] Table 2

[0085] As shown in Table 2, the compound with Formula 1 and trimethylolpropane phosphite synergistically participate in the construction of the SEI and CEI films, generating highly conductive and uniformly dense CEI and SEI films, thereby improving the battery's room temperature and high temperature cycle performance, rate performance, and safety performance. Furthermore, the addition of vinyl sulfate to the electrolyte further enhances the synergistic effect between the compound with Formula 1, trimethylolpropane phosphite, and vinyl sulfate, resulting in even higher lithium conductivity and stability of the CEI and SEI films, thus further improving the battery's room temperature and high temperature cycle performance, rate performance, and safety performance. In addition, the addition of negative electrode film-forming additives and stabilizing additives can further improve the lithium conductivity and stability of the SEI film, thereby further enhancing the battery's room temperature and high temperature cycle performance, rate performance, and safety performance.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

An additive composition characterized in that, The additive composition includes a first additive and a second additive; the first additive includes a compound having a structural formula of Formula 1: wherein n is 0 or 1, A is selected from methylene or O, X is selected from sulfonyl or carbonyl, R1, R2are each independently selected from H, one of X, R1 and R2 contains one or two sulfur atoms; the second additive comprises trimethylolpropane phosphite. The additive composition according to claim 1, characterized in that The first additive includes a compound having the structural formula of Formula 2: one of X, R1 and R2 contains one or two sulfur atoms. The additive composition according to claim 2, characterized in that The first additive includes at least one of the compounds having the structural formula of Formula 3-Formula 6: The additive composition according to claim 3, characterized in that the mass ratio of the first additive to the second additive is (0.25-20):

1. The additive composition according to claim 4, characterized in that the additive composition further comprises a third additive, the third additive comprising vinyl sulfonate. The additive composition according to claim 5, characterized in that the mass ratio of the first additive to the third additive is (0.25-20):

1. An electrolyte, characterized in that the electrolyte comprises the additive composition of any one of claims 1-6. The electrolyte according to claim 7, characterized in that the first additive has a mass percentage content of 0.5%-2% in the electrolyte; and / or, the second additive has a mass percentage content of 0.1%-1% in the electrolyte; and / or, the electrolyte further comprises a third additive, the third additive having a mass percentage content of 0.1%-1% in the electrolyte. The electrolyte according to claim 8, characterized in that the electrolyte further comprises a negative electrode film-forming additive, the negative electrode film-forming additive comprising at least one of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate; each of the negative electrode film-forming additives has a mass percentage content of 0.5%-1% in the electrolyte. The electrolyte according to claim 9, characterized in that the electrolyte further comprises triphenyl phosphite; the triphenyl phosphite has a mass percentage content of 0.01%-0.5% in the electrolyte. The electrolyte according to claim 10, characterized in that the electrolyte further comprises an electrolyte salt and an organic solvent, the electrolyte salt has a molar concentration of 0.8 mol / L-2 mol / L in the electrolyte; the electrolyte salt comprises a lithium salt or a sodium salt, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium tetrafluoroborate and lithium bis-trifluoromethanesulfonimide, the sodium salt comprises at least one of sodium hexafluorophosphate and sodium bisfluorosulfonylimide; and / or, the organic solvent comprises at least one of vinyl carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate. A battery characterized by the battery comprises the electrolyte of any one of claims 7-11. The battery according to claim 12, wherein The battery includes a positive electrode sheet and a negative electrode sheet, and the positive electrode active material in the positive electrode sheet is Li a Ni b Co c M1 d M2 e O f R g , wherein 1≤a≤1.2, 0.6<b<1, 0<c<1, 0<d<1, 0≤e≤0.2, b+c+d+e=1, 1≤f≤2, 0≤g≤1, f+g=2; M1 includes Mn and / or Al, M2 includes at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and R includes at least one of N, F, S, and Cl. or, the positive electrode active material in the positive electrode plate is a three-dimensional tunnel type Na 0.44 at least one of MnO2, P2 layered type NaMO2, NaFePO4, Na4Fe3(PO4)2P2O7, Na3V2(PO4)3, Na3V2(PO4)2F3, Na2Fe(CN)6, Na2MnFe(CN)6; wherein M is at least one of Ni, Mn, Fe; the negative electrode active material in the negative electrode tab comprises at least one of graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-based negative electrode material and lithium-containing metal composite oxide material.

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