Electrolyte additive, electrolyte, and battery

Abstract

This application belongs to the field of battery technology, and provides an electrolyte additive, as well as an electrolyte and a battery. The electrolyte additive includes: a first additive, which comprises a compound of formula I; and a second additive, which comprises a compound of formula II, wherein A1 and A2 are each independently selected from C x H 2x O y Given x = 0 or 1, y = 0 or 1, this electrolyte additive, when applied to batteries, can improve the battery's cycle and storage performance under high temperature and high pressure conditions.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to electrolyte additives, electrolytes, and batteries. Background Technology

[0002] Currently, improving the energy density of commercial lithium-ion batteries is mainly limited by the performance of the cathode material. Using cathode materials with higher operating voltages or larger theoretical specific capacities is a key method to effectively improve the energy density of lithium-ion batteries.

[0003] Among them, lithium nickel manganese oxide (LiNi) with spinel structure 0.5 Mn 1.5 Lithium hexafluorophosphate (LiPF6) has attracted widespread attention due to its high operating voltage and low cost. However, while increasing the operating voltage to improve energy density, it also makes conventional carbonate electrolytes more susceptible to oxidation on the electrode surface. Furthermore, traditional LiPF6 electrolytes suffer from poor thermal stability; under high temperatures, they undergo complex autocatalytic decomposition reactions, generating hydrofluoric acid (HF), a byproduct that damages the solid electrolyte interphase (SEI) film on the negative electrode surface and the crystal structure of the electrode material. This leads to a sharp increase in impedance and rapid capacity decay during high-temperature cycling and storage, severely impairing the battery's cycle life and safety performance.

[0004] To address the above problems, there is an urgent need to develop an electrolyte with high temperature and high pressure resistance. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art, to at least some extent.

[0006] In a first aspect, this application provides an electrolyte additive. According to an embodiment of this application, the electrolyte additive comprises: a first additive, the first additive comprising a compound of formula I; and a second additive, the second additive comprising a compound of formula II.

[0007]

[0008] Among them, A1 and A2 are independently selected from C. x H 2x O y x = 0 or 1, y = 0 or 1.

[0009] In the embodiments of this application, the first additive enhances the high-temperature and high-pressure performance of the battery by forming an interfacial film of carbonate materials rich in benzene ring groups on the electrode surface. However, the boron-containing oxygen compounds formed by the decomposition of the first additive when subjected to electron attack have strong reducing properties and are easily consumed and reduced in large quantities on the negative electrode surface to participate in the film formation process. Therefore, if there is too much of the first additive, the SEI film formed during the first charge and discharge process is too thick, and the lithium conductivity of carbonate compounds containing benzene ring groups is poor, resulting in increased battery impedance and capacity loss. If there is too little, an effective CEI film cannot be formed on the positive electrode surface, resulting in poor cycle and storage performance of the battery under high temperature and high pressure. The second additive has a higher reduction potential and can preferentially form sulfur-containing compounds with good lithium conductivity on the negative electrode surface during the first cycle of the battery, compared with the first additive. When the second additive is subjected to electron attack, SO will preferentially break down to generate sulfonyl radicals. These radicals can form anions through proton transfer to attack EC (ethylene carbonate) and trigger EC decomposition, thereby polymerizing on the negative electrode surface to form an SEI film and reducing the consumption of the first additive at the negative electrode, allowing the first additive to participate more in the formation of the CEI film. Therefore, the combined use of the two can effectively improve the cycle and storage performance of lithium-ion batteries under high temperature and high pressure conditions.

[0010] According to embodiments of this application, the electrolyte additive further includes at least one of the following additional technical features:

[0011] According to an embodiment of this application, the mass ratio of the first additive to the second additive is (1-30):1. Therefore, by keeping the mass ratio of the first additive and the second additive within the above range, they can work together more effectively, enhancing the high-temperature and high-pressure performance of the lithium-ion battery while reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving the battery's capacity retention. According to an embodiment of this application, the mass ratio of the first additive to the second additive is (1-10):1.

[0012] According to embodiments of this application, the second additive comprises at least one of the following substances:

[0013]

[0014] Therefore, the aforementioned types of second additives can preferentially form sulfur-containing compounds with good lithium conductivity on the negative electrode surface, optimizing the interfacial film composition and effectively reducing the impedance of the SEI film. They can also effectively reduce the consumption of the first additive at the negative electrode, reduce irreversible capacity loss during the first cycle, and improve capacity retention. Specifically, the increased number of O atoms in the structure of compound 2-1 effectively slows down the decomposition process of the second additive, resulting in a more complete SEI film. Furthermore, it makes it more likely to form interfacial film compositions such as ROSO3Li, ROSO2Li, and Li2SO3, reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving battery capacity retention.

[0015] In a second aspect, this application provides an electrolyte. According to an embodiment of this application, the electrolyte includes the electrolyte additives described in the first aspect. Thus, adding this electrolyte to a secondary battery can form a stable carbonate-based interface film on the electrode surface, enhancing the battery's high-temperature and high-pressure performance, while simultaneously reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving the battery's capacity retention rate.

[0016] According to embodiments of this application, the electrolyte further includes at least one of the following additional technical features:

[0017] According to an embodiment of this application, the first additive accounts for 1-5% of the total mass of the electrolyte. Thus, within the aforementioned mass percentage range, the first additive can form a carbonate-based interfacial film containing benzene rings on the electrode surface, improving the battery's storage and cycle performance under high temperature and high pressure conditions while reducing negative impacts on battery capacity.

[0018] According to an embodiment of this application, the second additive accounts for 0.1-2% of the total mass of the electrolyte. Thus, within the aforementioned mass percentage range, the second additive can form a sulfur-containing compound with good lithium conductivity on the negative electrode surface, reduce the formation of benzene ring-containing carbonate compounds, optimize the interface film composition, thereby effectively reducing the impedance of the SEI film, reducing irreversible capacity loss during the first cycle of the battery, and improving capacity retention.

[0019] According to embodiments of this application, the electrolyte further includes a lithium salt and a solvent. This enables the transport of lithium ions within the battery.

[0020] In a third aspect of this application, the present invention provides a lithium-ion battery. According to an embodiment of this application, the battery includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, as well as the electrolyte described in the second aspect. Therefore, the battery exhibits excellent storage and cycle performance under high temperature and high pressure conditions.

[0021] According to an embodiment of the present application, the lithium-ion battery further includes at least one of the following additional technical features:

[0022] According to an embodiment of the present application, the positive electrode includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector; the positive electrode material layer includes a positive electrode active material, the positive electrode active material includes lithium nickel manganate, and the chemical formula of the lithium nickel manganate is LiNi x Mn 2-x O4, where 0 < x ≤ 0.5. Thus, the battery has excellent storage and cycling performance under high temperature and high pressure conditions.

[0023] According to an embodiment of the present application, the negative electrode includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector; the negative electrode material layer includes at least one of a silicon-based material and a carbon-based material. Thus, the battery has excellent storage and cycling performance under high temperature and high pressure conditions.

[0024] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. Detailed Description of the Embodiment

[0025] The embodiments of the present application will be described in detail below, which are intended to explain the present application and should not be construed as a limitation to the present application.

[0026] Referring to "embodiment" herein means that the specific features, structures, or characteristics described in combination with the embodiment can be included in at least one embodiment of the present application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0027] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each individually disclosed point or single numerical value itself can be used as a lower limit or an upper limit to be combined with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0029] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this application but do not exclude other contents.

[0030] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0031] Lithium-ion batteries possess a series of advantages such as high energy density and long cycle life, making them a widely used high-quality power source in consumer electronics products such as mobile phones and laptops. Simultaneously, with the booming development of electric vehicles, the demand for lithium-ion batteries as their power batteries has also increased significantly. As technology advances, there is a need for lithium-ion batteries with even higher energy density to better meet people's growing demand for longer driving ranges.

[0032] A key approach to improving the energy density of lithium-ion batteries is to increase battery voltage; voltages of 4.5V and higher have become a focus and hot topic in the development of high-energy-density lithium-ion batteries. Currently, high-voltage lithium-ion batteries face significant challenges in high-temperature cycling and storage. To further improve battery performance at high voltages, the development of novel, highly efficient functional electrolyte additives has become crucial.

[0033] In view of this, the first aspect of this application provides an electrolyte additive. According to an embodiment of this application, the electrolyte additive includes: a first additive, the first additive comprising a compound of formula I, and a second additive, the second additive comprising a compound of formula II.

[0034]

[0035] Among them, A1 and A2 are independently selected from C. x H 2x O y x = 0 or 1, y = 0 or 1.

[0036] According to embodiments of this application, the combined effect of the first and second additives improves the cycle and storage performance of lithium-ion batteries under high temperature and high pressure conditions. Specifically, the first additive effectively forms an interface film of carbonate materials rich in benzene ring groups on the electrode surface. This type of interface film has good chemical stability, which not only enhances the stability at the electrode-electrolyte interface but also improves the compatibility between the electrolyte and the high-voltage positive electrode material, thereby improving the high temperature and high pressure performance of the lithium-ion battery. However, when the first additive is used alone, the boron-containing oxygen compounds formed by the decomposition of the first additive under electron attack have strong reducing properties and are easily consumed and reduced in large quantities on the negative electrode surface to participate in the film formation process. Therefore, if there is too much of the first additive, the solid electrolyte interphase (SEI) film formed during the first charge and discharge process is too thick, and the lithium conductivity of carbonate compounds containing benzene ring groups is poor, resulting in increased battery impedance and capacity loss. At this time, the second additive plays a key role. Due to its high reduction potential, the battery preferentially forms sulfur-containing compounds with excellent lithium conductivity on the negative electrode surface during the first charge, reducing the formation of carbonate compounds containing benzene rings, optimizing the interfacial film composition, thereby effectively reducing the impedance of SEI, reducing irreversible capacity loss during the first cycle, improving the battery's capacity retention rate, and reducing the consumption of the first additive at the negative electrode, allowing the first additive to participate more in the formation of the CEI film.

[0037] In some embodiments of this application, the mass ratio of the first additive to the second additive is (1-30):1. For example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 10:1, 20:1, 30:1, or any range of the above values. Therefore, by keeping the mass ratio of the first additive and the second additive within the above range, they can work together more effectively, enhancing the high-temperature and high-pressure performance of the lithium-ion battery while reducing the formation of benzene-ring-containing carbonate compounds, optimizing the interface film composition, reducing SEI film impedance, reducing irreversible capacity loss in the first cycle, and improving the battery's capacity retention. According to an embodiment of this application, the mass ratio of the first additive to the second additive is (1-10):1.

[0038] In some embodiments of this application, the second additive includes at least one of the following substances:

[0039]

[0040] Therefore, the aforementioned types of second additives can preferentially form sulfur-containing compounds with good lithium conductivity on the negative electrode surface, optimizing the interfacial film composition and effectively reducing the impedance of the SEI film. They can also effectively reduce the consumption of the first additive at the negative electrode, reduce irreversible capacity loss during the first cycle, and improve capacity retention. Specifically, the increased number of O atoms in the structure of compound 2-1 effectively slows down the decomposition process of the second additive, resulting in a more complete SEI film. Furthermore, it makes it more likely to form interfacial film compositions such as ROSO3Li, ROSO2Li, and Li2SO3, reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving battery capacity retention.

[0041] In a second aspect, this application proposes an electrolyte. According to embodiments of this application, the electrolyte includes the electrolyte additives described in the first aspect. Thus, adding this electrolyte to a secondary battery can form a sulfur-containing compound with good lithium conductivity on the negative electrode surface, regulate the formation of benzene-ring-containing carbonate compounds at the negative electrode, thereby forming a stable carbonate interface film on the electrode surface, enhancing the battery's high-temperature and high-pressure performance, while reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving the battery's capacity retention rate.

[0042] In some embodiments of this application, the mass percentage of the first additive is 1-5% based on the total mass of the electrolyte. For example, it can be 1%, 2%, 3%, 4%, 5%, or any range of the above values. Thus, within the above mass percentage range, the first additive can form a carbonate-based interface film on the electrode surface, improving the battery's storage and cycle performance under high temperature and high pressure conditions while avoiding the formation of an excessively thick SEI film and excessive increase in impedance during the first charge-discharge process, thereby reducing the negative impact on battery capacity.

[0043] In some embodiments of this application, the mass percentage of the second additive is 0.1-2% based on the total mass of the electrolyte. For example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, or any range of the above values. Therefore, within the above mass percentage range, the second additive can form a sulfur-containing compound with good lithium conductivity on the negative electrode surface, reduce the formation of benzene ring-containing carbonate compounds, optimize the interfacial film composition, thereby effectively reducing the impedance of the SEI film, reducing irreversible capacity loss during the first cycle of the battery, and improving capacity retention.

[0044] In some embodiments of this application, the electrolyte further includes a lithium salt and a solvent. This enables the transport of lithium ions within the battery.

[0045] In some embodiments of this application, the lithium salt includes, but is not limited to, at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium difluorooxalate-phosphate, lithium tetrafluorooxalate-phosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0046] In some embodiments of this application, the solvent includes, but is not limited to, at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, phenyl acetate, 1,4-butylsulfonyl lactone, 3,3,3-trifluoropropylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl trifluoroethyl carbonate, (2,2,2)-trifluoroethyl carbonate, 2,2-difluoroethyl acetate, 2,2-difluoroethyl propionate, and 2,2-difluoroethyl methyl carbonate.

[0047] In a third aspect of this application, the present invention provides a lithium-ion battery. According to an embodiment of this application, the battery includes a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes, as well as the electrolyte described in the second aspect. Therefore, the battery exhibits excellent storage and cycle performance under high temperature and high pressure conditions.

[0048] [positive electrode]

[0049] In some embodiments of this application, the positive electrode includes a positive current collector, which may be a metal foil, a foamed metal, or a composite current collector. For example, as a metal foil, silver-surfaced aluminum or stainless steel, stainless steel, copper, aluminum, nickel, carbon electrodes, carbon, or titanium may be used. The composite current collector may include a polymer material substrate and a metal layer. The foamed metal may be foamed nickel, foamed copper, foamed aluminum, foamed alloy, etc. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0050] In some embodiments of this application, the positive electrode further includes a positive electrode material layer disposed on at least one surface of the positive electrode current collector, the positive electrode material layer comprising a positive electrode active material, the positive electrode active material comprising lithium nickel manganese oxide; the molecular formula of the lithium nickel manganese oxide is LiNi. x Mn 2-x O4, 0 < x ≤ 0.5.

[0051] In some embodiments of this application, the positive electrode material 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.

[0052] In some embodiments of this application, the positive electrode material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0053] In some embodiments of this application, the positive electrode can be prepared by dispersing the above-mentioned components for preparing the positive electrode, such as positive electrode active material, conductive agent, and binder, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then obtaining the positive electrode after drying, cold pressing, and other processes.

[0054] [negative electrode]

[0055] In some embodiments of this application, the negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material.

[0056] 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.).

[0057] In some embodiments of this application, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of silicon-based materials and carbon-based materials, specifically, it may be selected from at least one of the following materials: natural graphite, artificial graphite, soft carbon, hard carbon, mesophase carbon microspheres, nano-carbon, elemental silicon, silicon oxides, silicon-carbon composites, silicon alloys, and tin-carbon composites.

[0058] In some embodiments of this application, the negative electrode material layer may optionally include an adhesive. The adhesive 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).

[0059] In some embodiments of this application, the negative electrode material 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.

[0060] In some embodiments of this application, the negative electrode material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0061] In some embodiments of this application, the negative electrode can be prepared by dispersing the above-mentioned components for preparing the negative electrode, such as 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 obtaining the negative electrode after drying, cold pressing and other processes.

[0062] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0063] In some embodiments of this application, the material of the separator may include at least one of glass fiber, non-woven fabric, polyolefin membrane, aromatic polyamide membrane, polytetrafluoroethylene membrane, and polyethersulfone membrane.

[0064] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0065] Example 1

[0066] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1ppm, oxygen content <1ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and lithium hexafluorophosphate (LiPF6) is added in small, repeated additions until the concentration in the electrolyte is 1M. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 1%, 2%, 3%, 4%, and 5% by mass, and the second additive accounting for 1% by mass.

[0067]

[0068] The above components are mixed to obtain the electrolyte.

[0069] Example 2

[0070] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the second additives accounting for 0.1%, 0.5%, 1.5%, and 2% by mass, respectively, and the first additive accounting for 3% by mass.

[0071] The above components are mixed to obtain the electrolyte.

[0072] Example 3

[0073] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1ppm, oxygen content <1ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-2, with the first additive accounting for 3% and the second additive accounting for 1% by mass.

[0074]

[0075] The above components are mixed to obtain the electrolyte.

[0076] Example 4

[0077] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1ppm, oxygen content <1ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is a compound shown in Formula I, and the second additive is compounds 2-3, with the first additive accounting for 3% by mass and the second additive accounting for 1% by mass.

[0078]

[0079] The above components are mixed to obtain the electrolyte.

[0080] Example 5

[0081] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 1% of the mass and the second additive accounting for 0.1% of the mass.

[0082] The above components are mixed to obtain the electrolyte.

[0083] Example 6

[0084] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 5% and the second additive accounting for 2% by mass.

[0085] The above components are mixed to obtain the electrolyte.

[0086] Example 7

[0087] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 0.1% and the second additive accounting for 0.1% and 1% of their respective mass percentages.

[0088] The above components are mixed to obtain the electrolyte.

[0089] Example 8

[0090] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 6% of the mass and the second additive accounting for 0.1% and 1% of the mass, respectively.

[0091] The above components are mixed to obtain the electrolyte.

[0092] Example 9

[0093] This embodiment provides an electrolyte, which, by mass percentage, is composed as follows: In a glove box filled with high-purity argon (moisture content <1 ppm, oxygen content <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a mass ratio of 3:7, and LiPF6 is added in small amounts several times to achieve a concentration of 1 M in the electrolyte. After the LiPF6 is completely dissolved, a first additive and a second additive are added; wherein the first additive is the compound shown in Formula I, and the second additive is compound 2-1, with the first additive accounting for 3% and the second additive accounting for 4% and 0.01% of the mass, respectively.

[0094] The above components are mixed to obtain the electrolyte.

[0095] Example 10

[0096] This embodiment provides a lithium-ion battery, and the specific preparation method is shown below:

[0097] 1. Preparation of electrolyte: The electrolyte provided in the above embodiment is used.

[0098] 2. Preparation of the positive electrode: LiNi 0.5 Mn 1.5 O4 cathode material (LNMO), conductive agent SuperP (conductive carbon black), conductive agent CNT (carbon nanotubes), and binder PVDF (polyvinylidene fluoride) were mixed evenly at a mass ratio of 94:2.5:1.5:2 and vacuum stirred until uniform flowability was achieved. This slurry was then evenly coated onto an aluminum foil current collector and subsequently dried at 85°C, rolled, trimmed, cut into sheets, slit, and vacuum dried at 85°C for 12 hours. After welding the tabs, a surface density of 30 mg / cm³ was obtained. 2 The positive electrode sheet.

[0099] 3. Preparation of the negative electrode sheet: Graphite negative electrode material, conductive agent Super P (conductive carbon black), thickener CMC (sodium carboxymethyl cellulose), and binder SBR (styrene-butadiene rubber latex) are thoroughly mixed in a mass ratio of 94.5:2:1.5:2 to form a uniform slurry. After coating both sides of copper foil, it is dried at 85℃, then rolled, trimmed, cut, and slit. Finally, it is dried under vacuum at 85℃ for 12 hours, and the electrode tabs are welded to obtain a sheet with an areal density of 11.7 mg / cm³. 2 The negative electrode sheet.

[0100] 4. Preparation of diaphragm: Using a 9μm thick porous polyethylene polymer film as the substrate, a 2μm adhesive coating is applied to both sides of the substrate.

[0101] 5. Assemble lithium-ion batteries:

[0102] The positive electrode, separator, and negative electrode are sequentially stacked and then wound to form a bare cell with a theoretical capacity of 1600mAh. The bare cell is placed in an outer packaging aluminum foil and vacuum baked at 85°C for 48 hours before being injected with the electrolyte. After vacuum sealing, settling, formation, aging, and capacity testing, the lithium-ion battery manufacturing process is complete.

[0103] Among them, the battery samples prepared using the electrolyte provided in Example 1 are named 1#, 2#, 3#, 4# and 5# in sequence.

[0104] The battery samples prepared using the electrolyte provided in Example 2 were named 6#, 7#, 8# and 9#, respectively.

[0105] The battery sample prepared using the electrolyte provided in Example 3 is named 10#.

[0106] The battery sample prepared using the electrolyte provided in Example 4 is named 11#.

[0107] The battery sample prepared using the electrolyte provided in Example 5 is named 12#.

[0108] The battery sample prepared using the electrolyte provided in Example 6 is named 13#.

[0109] The battery samples prepared using the electrolyte provided in Example 7 were named 14# and 15#, respectively.

[0110] The battery samples prepared using the electrolyte provided in Example 8 were named 16# and 17#, respectively.

[0111] The battery samples prepared using the electrolyte provided in Example 9 were named 18# and 19#, respectively.

[0112] Comparative Example 1

[0113] Battery 20# was prepared according to the method described in Example 1, except that the electrolyte additive used was 3% of the first additive.

[0114] Comparative Example 2

[0115] Battery 21# was prepared according to the method described in Example 1, except that the electrolyte additive used was 1% of a second additive (Formula 2-1).

[0116] Comparative Example 3

[0117] Battery 22# was prepared according to the method described in Example 1, except that the electrolyte additive used was 3% PS (1,3-propanesulfonate lactone).

[0118] The differences in electrolyte additives in batteries #1 to #22 are shown in Table 1.

[0119] Table 1

[0120]

[0121] Performance testing

[0122] I. Testing Methods.

[0123] 1.45℃ 0.5C / 0.5C Cyclic Test

[0124] The battery was charged at 45℃ with a constant current of 0.5C to 4.85V, then charged with a constant voltage to a cutoff current of 0.05C. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C1. This charge-discharge cycle was repeated 250 times, and the discharge capacity was recorded as C1. 250 The capacity retention rate of a battery after 250 cycles = C 250 / C1*100%.

[0125] Tested after 15 days of storage at 2.45℃.

[0126] The battery was charged at 25℃ with a constant current of 0.5C to 4.85V, and then charged at a constant voltage of 4.85V until the cutoff current of 0.05C. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C2. The battery was then charged again with a constant current of 0.5C to 4.85V, and then charged at a constant voltage of 4.85V until the cutoff current of 0.05C, i.e., fully charged. It was then transferred to a 45℃ environment and stored for 15 days. After storage, the battery was removed and allowed to cool to room temperature. It was then discharged at a constant current of 0.5C, and the discharge capacity was recorded as C3. The battery was cycled three times at 0.5C, and the discharge capacity of the last cycle was recorded as C4. The capacity retention rate after 15 days of storage at 45℃ = C3 / C2 * 100%. The capacity recovery rate = C4 / C2 * 100%.

[0127] II. Test Results.

[0128] The performance test results are shown in Table 2.

[0129] Table 2

[0130]

[0131] The results show that, compared to batteries 20 and 21 (Comparative Examples 1 and 2), batteries 1#-13# (Examples 1-6) show that the compounds shown in Formula I and Formula II, when used alone as additives, can effectively improve the high-temperature cycling and storage performance of batteries under high voltage conditions. However, the batteries with the addition of both Formula I and Formula II exhibit significantly better high-temperature cycling and storage performance than the comparative examples. This indicates that substances with the structure of Formula II can synergistically work with compounds of Formula I to form a stable and high-voltage resistant interfacial film on the electrode surface, suppressing side reactions of the electrolyte under high temperature and high pressure conditions, and ultimately improving the cycling and storage performance of the batteries under these conditions. Among these, the combination of compound 2-1 and the compound shown in Formula I shows the best performance at the same dosage. Furthermore, comparing the test results of batteries 14#-19#, it is clear that the amount of compound I or Formula II added to the electrolyte and the mass ratio of compounds I and Formula II have a significant impact on the cycling and storage performance of the batteries under high temperature and high pressure conditions. When the amount of these compounds added is insufficient or excessive, or when the mass ratio of the two compounds is too small or too large, the battery performance will be adversely affected. Only by precisely controlling the amount of compounds shown in Formula I and Formula II added to the electrolyte and the mass ratio of the two compounds can the battery's cycle performance and storage performance under high temperature and high pressure be effectively improved.

[0132] Compared to battery 22 (Comparative Example 3), batteries 1#-13# (Examples 1-6) exhibit improved high-temperature cycling and high-temperature storage performance under high voltage conditions. This is because the increased number of O atoms in the structure of compound 2-1 effectively slows down the decomposition process of the second additive, resulting in a more complete SEI film. Furthermore, it encourages the formation of interfacial film components such as ROSO3Li, ROSO2Li, and Li2SO3, reducing SEI film impedance, minimizing irreversible capacity loss during the first cycle, and improving battery capacity retention.

[0133] 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.

[0134] 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 additive for lithium-ion battery electrolytes, characterized in that, include: The first additive comprises a compound represented by Formula I. Formula I; and The second additive comprises a compound represented by Formula II. Equation II, where, A1 is selected from C x H 2x O y x = 0 or 1, y = 0 or 1; A2 is selected from C n H 2n n = 0 or 1; The mass ratio of the first additive to the second additive is (1-30):

1. Based on the total mass of the electrolyte, the mass percentage of the first additive is 1-5%, and the mass percentage of the second additive is 0.1-2%.

2. The electrolyte additive according to claim 1, characterized in that, The mass ratio of the first additive to the second additive is (1-10):

1.

3. The electrolyte additive according to claim 2, characterized in that, The second additive includes at least one of the following substances: 2-1、 2-2、 2-3。 4. An electrolyte for lithium-ion batteries, characterized in that, It includes the electrolyte additive as described in any one of claims 1 to 3.

5. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and a membrane located between the positive electrode and the negative electrode, as well as the electrolyte according to claim 4.

6. The lithium-ion battery according to claim 5, characterized in that, The positive electrode includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector; The positive electrode material layer includes a positive electrode active material, which includes lithium nickel manganese oxide, and the chemical formula of the lithium nickel manganese oxide is LiNi. x Mn 2-x O4, 0 <x≤0.5。 7. The lithium-ion battery according to claim 5 or 6, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on at least one side surface of the negative electrode current collector; the negative electrode material layer includes a negative electrode active material, which includes at least one of silicon-based materials and carbon-based materials.

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