An electrolyte additive composition, an electrolyte, and a battery

Abstract

This application provides an electrolyte additive composition, an electrolyte, and a battery, relating to the field of lithium-ion battery technology. The electrolyte additive composition includes lithium salt additives and functional additives. The functional additives have the following structural formula: applying functional additives with specific structural formulas as electrolyte additives in batteries can effectively improve the high-temperature cycle performance and high-temperature storage performance of batteries under high voltage.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and more specifically, to an electrolyte additive composition, an electrolyte, and a battery. Background Technology

[0002] With the development of portable electronic devices, electric vehicles, and hybrid vehicles, consumers have increasingly higher requirements for battery energy density, power density, and cycle life. Increasing the operating voltage is one method to improve the energy density of lithium-ion batteries. However, under high voltage, especially during cycling or storage at high temperatures, the content of water and HF (hydrofluoric acid) in the electrolyte increases, leading to increased electrolyte acidity. HF and H2O can damage the SEI (solid electrolyte interphase) and CEI (positive electrode electrolyte interphase) films formed on the electrode surfaces, resulting in decreased cycle performance. Furthermore, HF in an acidic environment can corrode electrode materials, exacerbating internal side reactions and reducing capacity retention and shortening cycle life during cycling or storage. Summary of the Invention

[0003] The main objective of this application is to provide an electrolyte additive composition, an electrolyte, and a battery to solve the problem of increased electrolyte acidity and deterioration of electrochemical performance in high-voltage battery systems under high-temperature conditions in related technologies.

[0004] To achieve the above objectives, according to a first aspect of this application, an electrolyte additive composition is provided, comprising a lithium salt additive and a functional additive, the functional additive having the structural formula shown in Formula 1:

[0005]

[0006] Furthermore, the mass ratio of lithium salt additive to functional additive is (0.5-1):(0.3-1);

[0007] Preferably, the lithium salt additive includes at least one of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(oxalato)borate, and lithium difluorobis(oxalato)phosphate.

[0008] Furthermore, the electrolyte additive composition also includes carbonate additives; the mass ratio of carbonate additives to functional additives is (0.2-1):(0.3-1);

[0009] Preferably, the carbonate additives include vinylene carbonate and / or fluoroethylene carbonate;

[0010] Furthermore, the electrolyte additive composition also includes sulfur-containing additives; the mass ratio of sulfur-containing additives to functional additives is (0.5-2):(0.3-1);

[0011] Preferably, the sulfur-containing additive includes at least one of propylene sulfite, 1,3-propane sultone, and ethylene sulfite.

[0012] According to a second aspect of the present application, there is provided an electrolyte, which includes a lithium salt, an organic solvent, and the electrolyte additive composition provided in the first aspect.

[0013] Further, the mass fraction of the lithium salt in the electrolyte is 9.5% to 15%; and / or,

[0014] the mass fraction of the organic solvent in the electrolyte is 80% to 90%; and / or,

[0015] the mass fraction of the electrolyte additive composition in the electrolyte is 0.5% to 5%.

[0016] Further, the mass fraction of the functional additive in the electrolyte is 0.3% to 1%; and / or,

[0017] the mass fraction of the lithium salt additive in the electrolyte is 0.5% to 1%; and / or,

[0018] the mass fraction of the carbonate additive in the electrolyte is 0.2 to 1%; and / or,

[0019] the mass fraction of the sulfur-containing additive in the electrolyte is 0.5% to 2%.

[0020] Further, the organic solvent includes at least two of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;

[0021] Preferably, the organic solvent includes ethylene carbonate and ethyl methyl carbonate;

[0022] More preferably, the organic solvent further includes at least one of dimethyl carbonate and diethyl carbonate.

[0023] According to a third aspect of the present application, there is provided a battery, which includes the electrolyte provided in the second aspect.

[0024] Further, the battery further includes a negative electrode sheet containing a negative electrode active material; and / or,

[0025] the battery further includes a positive electrode sheet containing a positive electrode active material;

[0026] Preferably, the negative electrode active material includes a carbon-based negative electrode material; the positive electrode active material includes a nickel cobalt manganese ternary material, and the chemical formula of the nickel cobalt manganese ternary material is Li(Ni x Co y Mn z )O2, where 0.5 ≤ x < 0.8, 0 < y ≤ 0.3, 0 < z ≤ 0.3 and x + y + z = 1.

[0027] By applying the technical solution of this application to the electrolyte additive composition of this application in a battery, on the one hand, the electrolyte additive has good reactivity, which can effectively promote the formation of CEI film and SEI film, separate the electrolyte from the electrode, reduce the occurrence of side reactions of the electrolyte, and improve the cycle performance of the battery; on the other hand, the functional additive contains N with lone pair electrons in its structural formula, which can effectively eliminate HF and H2O in the electrolyte, inhibit the rise of electrolyte acidity, and improve the stability of the electrolyte. In addition, the functional additive has strong oxidation stability, making it less prone to decomposition under high voltage, enhancing the high voltage resistance of the electrolyte, thereby effectively improving the high temperature cycle performance and high temperature storage performance of the battery under high voltage, and extending the cycle life of the battery. Detailed Implementation

[0028] As described in the background section of this application, existing high-voltage battery systems suffer from increased electrolyte acidity and deteriorated electrochemical performance under high-temperature conditions. To address these issues, a first aspect of this application provides an electrolyte additive composition comprising a lithium salt additive and a functional additive, the functional additive having the structural formula shown in Formula 1:

[0029]

[0030] First, the functional additive's structure contains C=C bonds, allowing it to participate in the formation of CEI and SEI films on the positive and negative electrode surfaces. The formation of stable CEI and SEI films effectively separates the electrolyte from the electrodes, reducing side reactions in the electrolyte. Second, the functional additive's structure contains a benzene ring and fluorine atoms (F) on the benzene ring. The high electronegativity of the fluorine atom and the strong CF bond enhance the oxidative stability of the molecule, making the functional additive less prone to decomposition under high voltage, thus enhancing the electrolyte's high-voltage resistance. Furthermore, the functional additive's structure contains nitrogen-containing groups, such as carbon-nitrogen bonds and dimethylamino groups. Dimethylamino refers to a nitrogen atom (N) linked to two methyl groups (CH3) via a single bond. These nitrogen-containing groups have a certain degree of basicity and can react with acidic substances in the electrolyte, such as HF, reducing the electrolyte's acidity and improving its stability. This, in turn, improves the battery's performance under high voltage at room temperature, high temperature, and high-temperature storage.

[0031] Lithium salt additives and functional additives can jointly participate in the formation of SEI and CEI films. Under the combined action of functional additives and lithium salt additives, the stability and compactness of the films can be promoted. In addition, lithium salt additives also have high oxidation stability and can participate in electrochemical reactions. They can maintain the stability of the electrolyte under high voltage and reduce electrolyte decomposition. Under the synergistic effect of lithium salt additives and functional additives, the stability of the electrolyte under high voltage conditions can be significantly improved.

[0032] In summary, by introducing functional additives with specific structural formulas, the combined effect of functional additives and lithium salt additives can effectively suppress the rise in electrolyte acidity, reduce side reactions, protect electrode materials, and significantly improve the cycle performance and storage performance of high-voltage battery systems under high-temperature conditions by enhancing the reactivity, oxidation stability, and chemical stability of the additives. This leads to the achievement of long-term stable and efficient operation of the battery system.

[0033] In some embodiments, the mass ratio of lithium salt additive to functional additive is (0.5–1):(0.3–1), for example, a range consisting of 0.5:1, 0.8:1, 1:1, 0.8:0.5, 0.8:0.3, 0.5:0.3, or any combination thereof. By limiting the mass ratio of lithium salt additive to functional additive, electrolyte stability can be further improved, SEI / CEI film formation can be optimized, the performance of high-voltage battery systems at high temperatures can be improved, and battery cycle life can be extended.

[0034] This application does not limit the specific type of lithium salt additive, and it can be a conventional lithium salt additive in the art. For example, in some preferred embodiments, the lithium salt additive includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), and lithium difluorobis(oxalato)phosphate (LiODFP).

[0035] In some embodiments, the electrolyte additive composition further includes carbonate additives; the mass ratio of carbonate additives to functional additives is (0.2 to 1):(0.3 to 1), for example, a range of 0.2:1, 0.5:1, 0.8:1, 1:1, 1:0.8, 1:0.5, 1:0.3 or any two of these.

[0036] During the initial charging process of lithium-ion batteries, carbonate additives preferentially decompose on the electrode surface, participating in the formation of the SEI and CEI films, reducing internal side reactions, and thus controlling gas generation and expansion during high-temperature storage or cycling. Simultaneously, carbonate solvents possess high thermal stability, maintaining the physicochemical properties of the electrolyte at high temperatures. Adding carbonate solvents enhances the overall thermal stability of the electrolyte and reduces the likelihood of electrolyte decomposition at high temperatures. Therefore, by introducing carbonate additives, and through the combined action of lithium salt additives, functional additives, and carbonate additives, the composition of the electrolyte is optimized, thereby further improving the battery's high-temperature storage performance, extending battery life, and enhancing battery safety and reliability.

[0037] By limiting the mass ratio of carbonate additives to functional additives to (0.2-1):(0.3-1), the physicochemical properties of the entire electrolyte, including viscosity, conductivity, and chemical stability, can be optimized, thereby improving the overall performance of the battery.

[0038] This application does not limit the specific type of carbonate additive, and it can be any conventional carbonate additive in the art. For example, in some embodiments, the carbonate additive includes vinylene carbonate and / or fluoroethylene carbonate.

[0039] In some embodiments, the electrolyte additive composition further includes a sulfur-containing additive; the mass ratio of the sulfur-containing additive to the functional additive is (0.5-2):(0.3-1).

[0040] During battery cycling, sulfur-containing additives can promote the formation of more stable and dense SEI and CEI films on the electrode surface. These two films effectively isolate the electrode materials from the electrolyte, reducing side reactions and thus improving the battery's cycle efficiency and lifespan. Simultaneously, sulfur-containing additives enhance the electrolyte's oxidation resistance, enabling the battery to maintain stable cycle performance even at high voltages. This helps reduce the rate of performance degradation under high-temperature storage conditions, decreases internal gas generation, reduces battery expansion, and improves capacity retention after prolonged high-temperature storage. Furthermore, sulfur compounds possess high thermal stability, enhancing the thermal stability of the electrolyte system. This allows the battery to maintain good electrochemical performance even at high temperatures, reducing electrolyte decomposition and inhibiting the formation of harmful substances (such as moisture and hydrofluoric acid).

[0041] The mass ratio of sulfur-containing additives to functional additives is (0.5–2):(0.3–1), for example, it can be a range of 0.5:1, 0.8:1, 1:1, 2:1, 2:0.5, 2:0.3, or any combination thereof. By limiting the mass ratio of sulfur-containing additives to functional additives within the above range, the formation of the SEI / CEI film inside the battery can be optimized through synergistic effects, which can further improve the cycle performance and storage performance of the battery under high-temperature conditions.

[0042] This application does not limit the specific type of sulfur-containing additive, and it can be a conventional sulfur-containing additive in the art. For example, in some embodiments, the sulfur-containing additive includes at least one of propylene sulfite (PS), 1,3-propanesulfonate lactone (PST), and ethylene sulfate (DTD).

[0043] A second aspect of this application provides an electrolyte comprising a lithium salt, an organic solvent, and the electrolyte additive composition provided in the first aspect.

[0044] Because the electrolyte additive composition includes the above-mentioned additives, it not only improves the battery's cycle performance under high-temperature conditions, but also helps to reduce the rate of performance degradation under high-temperature storage conditions, reduces gas generation inside the battery, reduces battery expansion, and improves the battery's capacity retention rate after long-term high-temperature storage.

[0045] Lithium salts are the main source of conductive ions in the electrolyte. In some embodiments, the mass fraction of lithium salts in the electrolyte is 9.5% to 15%. By limiting the amount of lithium salt added within the above range, it is possible to ensure that the electrolyte has sufficient conductivity, guaranteeing efficient ion transport during battery charging and discharging, while also ensuring that sufficient lithium salt participates in the formation of the SEI / CEI film.

[0046] The lithium salt has a mass fraction of 9.5% to 15% in the electrolyte, for example, a range of 9.5%, 10%, 11%, 12%, 13%, 14%, 15%, or any combination thereof.

[0047] In some embodiments, the electrolyte additive composition has a mass fraction of 0.5% to 5% in the electrolyte. By limiting the amount of electrolyte additive composition added to the above range, it is ensured that the electrolyte additive composition can exert its effective function in the electrolyte to the maximum extent.

[0048] The electrolyte additive composition has a mass fraction of 0.5% to 5% in the electrolyte, for example, a range of 0.5%, 1%, 2%, 3%, 4%, 5%, or any two of these.

[0049] Organic solvents are a major component of the electrolyte, responsible for transporting lithium ions. In some embodiments, the organic solvent accounts for 80% to 90% of the electrolyte by mass. By limiting the amount of organic solvent added within this range, sufficient fluidity can be provided to ensure rapid lithium ion transport between electrodes, thereby maintaining the high conductivity of the battery. Secondly, a suitable solvent ratio is beneficial for the formation of a stable and dense interfacial film, promoting the formation of the SEI / CEI film and reducing side reactions. In addition, it helps ensure that the electrolyte has suitable viscosity, conductivity, and chemical stability, maintaining stable lithium ion transport even under high temperature conditions, thus improving the high-temperature cycle performance and high-temperature storage performance of lithium-ion batteries.

[0050] The organic solvent has a mass fraction of 80% to 90% in the electrolyte, for example, a range of 80%, 82%, 84%, 86%, 88%, 90%, or any combination thereof.

[0051] The synergistic effect of lithium salt, electrolyte additive composition and organic solvent can optimize the viscosity and conductivity of the electrolyte, maintain its good stability, and thus improve the cycle performance and storage performance of the battery under high temperature conditions.

[0052] This application does not limit the proportion of each additive in the electrolyte, as long as the above requirements are met. For example, in some embodiments, the mass fraction of the functional additive in the electrolyte is 0.3% to 1%. By limiting the amount of functional additives added, their effects of improving high-temperature cycling performance and high-temperature storage performance can be achieved, while avoiding changes in electrolyte viscosity or increased costs, which helps to optimize electrolyte formulation and improve lithium-ion battery performance.

[0053] In some embodiments, the functional additive has a mass fraction of 0.3% to 1% in the electrolyte, for example, a range of 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination thereof. By limiting the amount of functional additive added, its effect can be maximized, effectively improving the battery's cycle performance and storage performance under high voltage and high temperature, thereby optimizing the electrolyte formulation and enhancing the battery's electrochemical performance.

[0054] In some embodiments, the lithium salt additive is present in the electrolyte at a mass fraction of 0.5% to 1%, for example, a range consisting of 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination thereof. The lithium salt additive can participate in electrochemical reactions, and by limiting the amount of lithium salt additive added, in addition to maintaining the high-temperature cycle performance and high-temperature storage performance of the battery, the energy density of the battery can also be improved.

[0055] In some embodiments, the carbonate additive is present in the electrolyte at a mass fraction of 0.2% to 1%, for example, a range of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination thereof. By limiting the amount of carbonate additive added, a uniform and dense SEI film can be formed, maximizing its multiple functions.

[0056] In some embodiments, the sulfur-containing additive is present in the electrolyte at a mass fraction of 0.5% to 3%, for example, a range consisting of 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, or any combination thereof. By limiting the amount of sulfur-containing additive added, both the effectiveness of the additive and cost can be considered.

[0057] This application does not limit the specific type of organic solvent; it can be any organic solvent conventional in the art. In some embodiments, the organic solvent includes at least two of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). This combines the advantages of carbonate solvents and improves the overall performance of the battery.

[0058] In some embodiments, the organic solvent includes ethylene carbonate and ethyl methyl carbonate; further, the organic solvent also includes at least one of dimethyl carbonate and diethyl carbonate. By finely adjusting the volume ratio of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, the cycle performance, high and low temperature adaptability, safety, and electrolyte stability of high-voltage lithium-ion batteries can be significantly improved, thereby enhancing the overall performance and lifespan of the battery.

[0059] This application does not limit the specific preparation method of the electrolyte, as long as it contains the above-mentioned components. For example, a specific preparation method of the electrolyte includes the following steps: under a protective atmosphere, adding an electrolyte additive composition to an organic solvent, then adding a lithium salt, and stirring and mixing at a first temperature to obtain the electrolyte; wherein, the protective atmosphere can be argon, and the first temperature can be 5-15°C.

[0060] A third aspect of this application provides a battery comprising the electrolyte provided in the second aspect.

[0061] Due to the inclusion of the aforementioned electrolyte, this battery exhibits excellent high-temperature cycling and storage performance. Specifically, it demonstrates reduced gas production and HF content during charge-discharge cycles under high voltage and high temperature conditions, high capacity retention after long-term cycling, and low capacity loss and volume expansion during high-temperature storage.

[0062] In some embodiments, the battery further includes a negative electrode sheet containing a negative electrode active material and a positive electrode sheet containing a positive electrode active material.

[0063] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer formed of negative electrode active material disposed on the surface of the negative electrode current collector.

[0064] In the specific preparation of the negative electrode sheet, the negative electrode active material, the first conductive agent, and the first binder can be dispersed in an appropriate amount of solvent and thoroughly stirred to form a uniform negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector, and after drying, rolling, and slitting, the negative electrode sheet is obtained. In one specific embodiment, the negative electrode active layer comprises, by mass percentage, 70%–99% graphite negative electrode material, 0.5%–15% conductive agent, and 0.5%–15% binder.

[0065] The negative electrode current collector can be made of at least one of copper foil, nickel foam, and copper foam; the first conductive agent can be selected from at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and graphene; the first binder can be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyvinyl alcohol, and sodium polyacrylate.

[0066] The present application does not limit the specific type of the negative electrode active material in the negative electrode sheet, which can be the negative electrode active materials commonly used in current batteries. In some embodiments, the negative electrode active material includes carbon-based negative electrode materials, such as at least one of graphite, hard carbon, soft carbon, and mesocarbon microbeads.

[0067] The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer formed by a positive electrode active material disposed on the surface of the positive electrode current collector.

[0068] When specifically preparing the positive electrode sheet, the positive electrode active material, a second conductive agent, and a second binder can be dispersed in an appropriate amount of solvent, and sufficiently stirred and mixed to form a uniform positive electrode paste; the positive electrode paste is uniformly coated on the positive electrode current collector, and after drying, rolling, and slitting, the positive electrode sheet is obtained. In a specific embodiment, the positive electrode active layer includes 70% - 99% of the positive electrode active material, 0.5% - 15% of the conductive agent, and 0.5% - 15% of the binder by mass percentage.

[0069] Among them, the material of the positive electrode current collector can be at least one of aluminum foil and nickel foil; the second conductive agent can be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber; the second binder can be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polyethylene, polypropylene, polyvinyl alcohol, and sodium polyacrylate.

[0070] The present application does not limit the specific type of the positive electrode active material in the positive electrode sheet, which can be the positive electrode active materials commonly used in current batteries, such as at least one composite oxide of lithium and at least one metal of cobalt, nickel, manganese, and their combinations. Specifically, the positive electrode active material can be a nickel-cobalt-manganese ternary material, and the chemical formula of the nickel-cobalt-manganese ternary material is Li(Ni x Co y Mn z )O2, where 0.5 ≤ x < 0.8, 0 < y ≤ 0.3, 0 < z ≤ 0.3 and x + y + z = 1.

[0071] The battery further includes a separator. The present application does not limit the specific selection of the separator material, which can be the separator materials commonly used in current batteries, such as polypropylene separator, polyethylene separator, polypropylene / polyethylene double-layer composite separator, polypropylene / polyethylene / polypropylene (PP / PE / PP) three-layer composite separator, etc.

[0072] When preparing the battery, the positive electrode sheet, the separator, and the negative electrode sheet are wound or laminated to obtain an electrode core, the electrode core is encapsulated into a pre-stamped aluminum plastic film, after the encapsulated battery is dried to remove moisture, an electrolyte is injected into the dried battery, and the battery is completed after aging, formation, and secondary sealing.

[0073] The present application will be further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0074] Example 1

[0075] The electrolyte in this embodiment is composed of an organic solvent, a lithium salt, and additives; the additives include fluoroethylene carbonate (FEC), lithium difluorophosphate (LiPO2F2), 1,3-propanesulfonic acid lactone, and a functional additive as shown in Formula 1, with CAS number 138716-60-6.

[0076] The electrolyte contains 0.5% fluoroethylene carbonate, 0.5% lithium difluorophosphate, 1,3-propanesulfonic acid lactone, and 0.3% functional additives.

[0077]

[0078] The lithium salt is lithium hexafluorophosphate, with a concentration of 1.0 mol / L in the electrolyte and a mass fraction of 12.5%. The organic solvent has a mass fraction of 85.2% in the electrolyte and consists of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 30%, the volume fraction of diethyl carbonate is 20%, and the volume fraction of methyl ethyl carbonate is 50%.

[0079] The preparation method of the electrolyte in this embodiment includes: under an argon atmosphere, adding the formulated amounts of vinylene carbonate, lithium difluorophosphate, 1,3-propanesulfonic acid lactone, and functional additives to an organic solvent according to the above mass fractions, followed by adding lithium hexafluorophosphate, and stirring and mixing at 10°C to obtain the electrolyte.

[0080] Example 2

[0081] The difference from Example 1 is that the functional additive has a mass fraction of 0.5% in the electrolyte, and the total mass fraction is reduced to 100% with an organic solvent, while the contents of other components are the same as in Example 1.

[0082] Example 3

[0083] The difference from Example 1 is that the functional additive has a mass fraction of 1% in the electrolyte, and the total mass fraction is reduced to 100% by using an organic solvent, while the contents of other components are the same as in Example 1.

[0084] Example 4

[0085] The difference from Example 1 is that the functional additive has a mass fraction of 2% in the electrolyte, and the total mass fraction is reduced to 100% with an organic solvent, while the contents of other components are the same as in Example 1.

[0086] Example 5

[0087] The difference from Example 1 is that the mass fraction of lithium difluorophosphate in the electrolyte is 0.8%, and the total mass fraction is reduced to 100% by organic solvent, while the contents of other components are the same as in Example 1.

[0088] Example 6

[0089] The difference from Example 1 is that the mass fraction of lithium difluorophosphate in the electrolyte is 1%, and the total mass fraction is reduced to 100% by organic solvent, while the contents of other components are the same as in Example 1.

[0090] Example 7

[0091] The difference from Example 1 is that the mass fraction of lithium difluorophosphate in the electrolyte is 2%, and the total mass fraction is reduced to 100% by organic solvent, while the contents of other components are the same as in Example 1.

[0092] Example 8

[0093] The difference from Example 1 is that the mass fraction of fluoroethylene carbonate in the electrolyte is 0.2%, and the total mass fraction is increased to 100% by using an organic solvent, while the contents of other components are the same as in Example 1.

[0094] Example 9

[0095] The difference from Example 1 is that the mass fraction of fluoroethylene carbonate in the electrolyte is 1%, and the total mass fraction is reduced to 100% by organic solvent, while the contents of other components are the same as in Example 1.

[0096] Example 10

[0097] The difference from Example 1 is that the mass fraction of fluoroethylene carbonate in the electrolyte is 2%, and the total mass fraction is reduced to 100% by organic solvent, while the contents of other components are the same as in Example 1.

[0098] Example 11

[0099] The difference from Example 1 is that the mass fraction of 1,3-propanesulfonic acid lactone in the electrolyte is 0.5%, and the total mass fraction is increased to 100% by using an organic solvent, while the contents of other components are the same as in Example 1.

[0100] Example 12

[0101] The difference from Example 1 is that the mass fraction of 1,3-propanesulfonic acid lactone in the electrolyte is 2%, and the total mass fraction is reduced to 100% by using an organic solvent. The contents of other components are the same as in Example 1.

[0102] Example 13

[0103] The difference from Example 1 is that the mass fraction of 1,3-propanesulfonic acid lactone in the electrolyte is 3%, and the total mass fraction is reduced to 100% by using an organic solvent. The contents of other components are the same as in Example 1.

[0104] Example 14

[0105] The difference from Example 1 is that fluoroethylene carbonate is not added, and the total mass fraction is increased to 100% using an organic solvent, while the contents of other components are the same as in Example 1.

[0106] Example 15

[0107] The difference from Example 1 is that 1,3-propanesulfonic acid lactone is not added, and the total mass fraction is increased to 100% with an organic solvent, while the contents of other components are the same as in Example 1.

[0108] Example 16

[0109] The difference from Example 1 is that the organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent being 100%, the volume fraction of ethylene carbonate is 40%, the volume fraction of diethyl carbonate is 10%, and the volume fraction of methyl ethyl carbonate is 50%.

[0110] Example 17

[0111] The difference from Example 1 is that the organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent being 100%, the volume fraction of ethylene carbonate is 10%, the volume fraction of diethyl carbonate is 70%, and the volume fraction of methyl ethyl carbonate is 20%.

[0112] Comparative Example 1

[0113] The difference from Example 1 is that no functional additives are added, and the total mass fraction is increased to 100% using organic solvents, while the contents of other components are the same as in Example 1.

[0114] Comparative Example 2

[0115] The difference from Example 1 is that lithium difluorophosphate is not added, and the total mass fraction is increased to 100% using an organic solvent, while the contents of other components are the same as in Example 1.

[0116] Comparative Example 3

[0117] The difference from Example 1 is that the functional additive is replaced with an additive as shown in Formula 2:

[0118]

[0119] Comparative Example 4

[0120] The difference from Example 1 is that the functional additive is replaced with an additive as shown in Formula 3:

[0121]

[0122] Comparative Example 5

[0123] The difference from Example 1 is that the functional additive is replaced with an additive as shown in Formula 4:

[0124]

[0125] Comparative Example 6

[0126] The difference from Example 1 is that the functional additive is replaced with an additive as shown in Formula 5:

[0127]

[0128] Test case

[0129] The electrolytes of the examples and comparative examples were applied to lithium-ion batteries, and the performance of the lithium-ion batteries was tested. The specific preparation method of the lithium-ion battery includes: mixing graphite, acetylene black, carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 94:1:2:3 to form a negative electrode slurry; coating the negative electrode slurry onto a copper foil current collector, vacuum drying, and obtaining a negative electrode sheet;

[0130] The cathode material Li(Ni) 0.5 Co 0.2 Mn 0.3 O2, acetylene black, and polyvinylidene fluoride are mixed in a mass ratio of 94:3:3 to form a positive electrode slurry; the positive electrode slurry is coated onto an aluminum foil current collector, vacuum dried, and a positive electrode sheet is obtained.

[0131] A battery cell is obtained by winding or stacking a positive electrode sheet, a Celgard 2400 separator, and a negative electrode sheet. The battery cell is then packaged into a pre-stamped aluminum-plastic film. After the packaged battery is dried, the electrolytes from the examples and comparative examples are injected into the dried battery. After aging, formation, and secondary sealing, a lithium-ion battery is obtained.

[0132] Electrochemical tests were conducted using a Xinwei charge-discharge test cabinet, and the HF content of the electrolyte was determined using the ice-water titration method.

[0133] (1) Room temperature cycling performance test:

[0134] At 25°C, the lithium-ion battery was charged at a constant current of 1.0C (nominal capacity) to a voltage of 4.4V, then charged at a constant voltage of 4.4V until the current ≤0.05C. After resting for 10 minutes, it was discharged at a constant current of 1C to a cutoff voltage of 2.8V. This constitutes one charge-discharge cycle. The lithium-ion battery was subjected to 1000 charge-discharge cycles under the above conditions.

[0135] The capacity retention rate (%) of a lithium-ion battery after 1000 cycles = (discharge capacity of the 1000th cycle / initial discharge capacity) × 100%.

[0136] (2) High-temperature cycling performance test

[0137] At 45°C, the lithium-ion battery is charged at a constant current of 1.0C (nominal capacity) to a voltage of 4.4V, then charged at a constant voltage of 4.4V until the current is ≤0.05C. After resting for 10 minutes, it is discharged at a constant current of 1C to a cutoff voltage of 2.8V. This constitutes one charge-discharge cycle. The lithium-ion battery is subjected to 1000 charge-discharge cycles under the above conditions.

[0138] The capacity retention rate (%) of a lithium-ion battery after 1000 cycles = (discharge capacity of the 1000th cycle / initial discharge capacity) × 100%.

[0139] (3) Electrolyte HF content test:

[0140] The electrolyte was stored at 45°C, and the HF content at 0d and 15d was tested by ice-water titration, and recorded as HF-0d and HF-15d, respectively.

[0141] (4) High-temperature storage performance test of lithium-ion batteries:

[0142] At 25℃, the lithium-ion battery was charged at a constant current of 1C to a voltage of 4.4V, and then charged at a constant voltage of 4.4V to a current of 0.05C. The volume of the lithium-ion battery was measured as V0, and the initial capacity was measured as C0. After that, the lithium-ion battery was placed in a constant temperature chamber at 60℃ and stored for 90 days. The volume of the lithium-ion battery was measured and recorded as V1, the capacity was kept as C1, and the capacity was restored to C2.

[0143] The volume expansion rate (%) of a lithium-ion battery after storage at 60°C for 90 days is calculated as (V1-V0) / V0×100%.

[0144] Capacity retention rate (%) of lithium-ion batteries after 90 days of storage at 60°C = (C1 / C0) × 100%.

[0145] The capacity recovery rate (%) of a lithium-ion battery after 90 days of storage at 60°C is calculated as (C2 / C0) × 100%.

[0146] (5) High-temperature storage experiment:

[0147] The battery was subjected to 5 charge-discharge cycles at 1C at room temperature, followed by full charge at 1C. The 1C capacity Q0 and battery volume V0 were recorded. The fully charged battery was stored at 60℃ for 90 days, and the battery volume V1 and 1C discharge capacity Q1 were recorded. Then, the battery was charged and discharged at 1C at room temperature for 5 weeks, and the 1C discharge capacity Q2 was recorded. Experimental data such as high-temperature storage capacity retention rate, capacity recovery rate, and volume change rate were calculated, and the results are shown in the table below. The calculation formulas used are as follows: Capacity retention rate (%) = Q1 / Q0 × 100%; Capacity recovery rate (%) = Q2 / Q0 × 100%; Volume change rate (%) = (V1 - V0) / V0 × 100%.

[0148] The test results are shown in Table 1.

[0149] Table 1

[0150]

[0151] As shown in Table 1, the electrolyte in the embodiment has a low HF content and excellent stability during storage. Applying the electrolyte additive composition of this application to the battery can significantly improve the battery's cycle performance and enhance the electrolyte's high voltage resistance, thereby effectively improving the battery's high-temperature cycle performance and high-temperature storage performance under high voltage and extending the battery's cycle life.

[0152] A comparison of Example 1 and Comparative Examples 3-6 shows that additives containing only a single functional group cannot achieve the same effect on battery cycle performance as those in Formula 1. Therefore, the functional additives of this application with the structure shown in Formula 1 do not rely on the independent action of a single functional group, but rather the entire structure produces a multifaceted synergistic effect in the electrolyte. This synergistic effect is key to improving battery performance and stability.

[0153] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An electrolyte additive composition, characterized in that, The electrolyte additive composition includes lithium salt additives and functional additives, and the structural formula of the functional additives is shown in Formula 1: Formula 1.

2. The electrolyte additive composition according to claim 1, characterized in that, The mass ratio of the lithium salt additive to the functional additive is (0.5~1):(0.3~1). The lithium salt additive includes at least one of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(oxalato)borate, and lithium difluorobis(oxalato)phosphate.

3. The electrolyte additive composition according to claim 1, characterized in that, The electrolyte additive composition further includes carbonate additives; the mass ratio of the carbonate additives to the functional additives is (0.2~1):(0.3~1). The carbonate additives include vinylene carbonate and / or fluoroethylene carbonate.

4. The electrolyte additive composition according to any one of claims 1 to 3, characterized in that, The electrolyte additive composition further includes a sulfur-containing additive; the mass ratio of the sulfur-containing additive to the functional additive is (0.5~2):(0.3~1). The sulfur-containing additives include at least one of propylene sulfite, 1,3-propanesulfonate lactone, and ethylene sulfate.

5. An electrolyte, characterized in that, The electrolyte comprises lithium salt, organic solvent, and electrolyte additive composition according to any one of claims 1 to 4.

6. The electrolyte according to claim 5, characterized in that, The lithium salt has a mass fraction of 9.5% to 15% in the electrolyte; and / or, The organic solvent in the electrolyte has a mass fraction of 80% to 90%; and / or, The electrolyte additive composition has a mass fraction of 0.5% to 5% in the electrolyte.

7. The electrolyte according to claim 5 or 6, characterized in that, The functional additive has a mass fraction of 0.3% to 1% in the electrolyte; and / or, The lithium salt additive has a mass fraction of 0.5% to 1% in the electrolyte; and / or, The mass fraction of carbonate additives in the electrolyte is 0.2% to 1%; and / or, The sulfur-containing additive has a mass fraction of 0.5% to 2% in the electrolyte.

8. The electrolyte according to claim 5 or 6, characterized in that, The organic solvent includes at least two of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

9. The electrolyte according to claim 5 or 6, characterized in that, The organic solvents include ethylene carbonate and methyl ethyl carbonate.

10. The electrolyte according to claim 9, characterized in that, The organic solvent also includes at least one of dimethyl carbonate and diethyl carbonate.

11. A battery, characterized in that, The battery comprises the electrolyte according to any one of claims 5 to 10.

12. The battery according to claim 11, characterized in that, The battery further includes a negative electrode sheet containing a negative electrode active material; and / or, The battery also includes a positive electrode sheet containing a positive electrode active material; The negative electrode active material includes a carbon-based negative electrode material; the positive electrode active material includes a nickel cobalt manganese ternary material, and the chemical formula of the nickel cobalt manganese ternary material is Li(Ni x Co y Mn z )O2, where 0.5 ≤ x < 0.8, 0 < y ≤ 0.3, 0 < z ≤ 0.3 and x + y + z = 1.

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