Lithium ion battery electrolyte and lithium ion battery

Abstract

The invention relates to a lithium ion battery electrolyte and a lithium ion battery. The electrolyte comprises a first additive and a second additive, the first additive comprises a lithium sulfonate compound, the mass percentage content of the first additive in the electrolyte is A%, and A is larger than or equal to 0.1 and smaller than or equal to 4; the second additive comprises a boron-nitrile-containing compound, the mass percentage content of the second additive in the electrolyte is B%, and B is greater than or equal to 0.2 and less than or equal to 2; the battery satisfies: 0.1 < = A / B < = 10; 0.01 < = (A + B) / X < = 0.1; wherein X is the single-sided density of the negative electrode active material layer in the negative electrode, the unit is g / m < 2 >, and X is more than or equal to 30 and less than or equal to 80. According to the scheme provided by the invention, a compact and thin organic-inorganic composite SEI film can be formed on a negative electrode interface through the synergistic effect of the first additive and the second additive, so that the stability of the negative electrode interface is effectively enhanced, and the comprehensive requirements of high and low temperature cycle performance and safety performance of the lithium ion battery under high voltage are comprehensively met.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more particularly to lithium-ion battery electrolytes and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, with their advantages of high energy density, low self-discharge rate, and long cycle life, have become the core power source for portable electronic devices and new energy vehicles. Their normal operation depends on the synergistic effect between the positive electrode, negative electrode, electrolyte, and separator. During charging and discharging, a solid electrolyte interphase (SEI) film forms on the surface of the negative electrode, which has a decisive influence on battery performance. However, traditional SEI films have a loose structure and poor stability, making them prone to rupture and reconstruction during cycling. This not only triggers continuous interfacial side reactions and electrolyte decomposition but may also lead to solvent molecules co-intercalating into the graphite negative electrode, damaging the electrode structure and thus limiting the battery's cycle life and safety under harsh conditions such as high voltage and extreme temperatures. Summary of the Invention

[0003] To address or partially address the problems existing in related technologies, this application provides a lithium-ion battery electrolyte and a lithium-ion battery, which can form a dense and thin organic-inorganic composite SEI film at the negative electrode interface through the synergistic effect of the first additive and the second additive, effectively enhancing the stability of the negative electrode interface and fully meeting the comprehensive requirements of lithium-ion batteries for high and low temperature cycle performance and safety performance under high voltage.

[0004] This application provides a lithium-ion battery electrolyte, comprising a first additive and a second additive. The first additive comprises a lithium sulfonate compound, and the mass percentage of the first additive in the electrolyte is A%, 0.1≤A≤4. The second additive comprises a boron-containing nitrile compound, and the mass percentage of the second additive in the electrolyte is B%, 0.2≤B≤2. The battery satisfies the following: 0.1 ≤ A / B ≤ 10; 0.01 ≤ (A+B) / X ≤ 0.1; Where X is the one-sided density of the negative electrode active material layer in the negative electrode, in g / m². 2 , 30≤X≤80.

[0005] In some embodiments of the present invention, 0.015 ≤ (A+B) / X ≤ 0.08.

[0006] In some embodiments of the present invention, 0.5 ≤ A / B ≤ 8.

[0007] In some embodiments of the present invention, 0.5 ≤ A ≤ 4; and / or, 0.2 ≤ B ≤ 1.

[0008] In some embodiments of the present invention, the structural formula of the lithium sulfonate compound is as follows:

[0009] R1 is selected from one of fluorine atoms, fluorinated alkane groups, amino groups, and fluorinated amino groups.

[0010] In some embodiments of the present invention, the lithium sulfonate compound is selected from at least one of the following compounds:

[0011] Compound 1

[0012] Compound 2

[0013] Compound 3

[0014] Compound 4

[0015] Compound 5

[0016] Compound 6

[0017] Compound 7

[0018] Compound 8.

[0019] In some embodiments of the present invention, the structural formula of the boron-containing nitrile compound is as follows:

[0020] Where m, n1, and n2 are all natural numbers greater than or equal to 0. R2 to R9 are each independently selected from -CH3, -F, -C=O, -O-, fluorinated alkane groups, nitrile alkane groups, and fluorinated nitrile alkane groups, and at least one side chain of R2 to R9 contains a nitrile group.

[0021] In some embodiments of the present invention, the boron-containing nitrile compound is selected from at least one of the following compounds:

[0022] compound a

[0023] Compound b

[0024] Compound C

[0025] compound d

[0026] compound e

[0027] compound f

[0028] compound g

[0029] compound h

[0030] Compound i.

[0031] A second aspect of this application provides a lithium-ion battery, including a negative electrode, a positive electrode, and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0032] In some embodiments of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active substance, which includes natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured lithium-ion TiO2-Li4Ti5O. 12 At least one of Li-Al alloys.

[0033] The technical solution provided in this application may include the following beneficial results: This application specifies A (0.1%~4%), B (0.2%~2%), and X (30g / m 2 ~80g / m 2 The specific numerical range of (A+B) was determined, and two key ratio constraints, 0.01≤(A+B) / X≤0.1 and 0.1≤A / B≤10, were introduced to achieve multi-dimensional and precise control of the negative electrode interface chemistry. This enabled the two types of additives to exert a synergistic effect under high voltage conditions, and successfully constructed a composite SEI film with high ionic conductivity, dense structure, oxidation resistance and thermal stability. This fully meets the comprehensive requirements of lithium-ion batteries for low-temperature cycle performance, high-temperature cycle performance and thermal shock safety performance under high voltage.

[0034] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Detailed Implementation

[0035] The embodiments of this application will now be described in more detail. It should be understood that this application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this application more thorough and complete, and to fully convey the scope of this application to those skilled in the art.

[0036] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0037] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0038] In related technologies, functional additives, such as film-forming additives, are often used to regulate the composition and structure of the SEI film in order to improve the stability of the negative electrode interface. However, a single functional additive is difficult to fully meet the comprehensive requirements of lithium-ion batteries for high and low temperature cycling performance and safety performance under high voltage.

[0039] To address the aforementioned issues, this application provides a lithium-ion battery electrolyte that, through the synergistic effect of a first additive and a second additive, forms a dense and thin organic-inorganic composite SEI film at the negative electrode interface, effectively enhancing the stability of the negative electrode interface and fully meeting the comprehensive requirements of lithium-ion batteries for high and low temperature cycle performance and safety performance under high voltage.

[0040] This application provides a lithium-ion battery electrolyte, comprising a first additive and a second additive. The first additive comprises a lithium sulfonate compound, and the mass percentage of the first additive in the electrolyte is A%, 0.1≤A≤4. The second additive comprises a boron-containing nitrile compound, and the mass percentage of the second additive in the electrolyte is B%, 0.2≤B≤2. This battery satisfies the following conditions: 0.1 ≤ A / B ≤ 10; 0.01 ≤ (A+B) / X ≤ 0.1; Where X is the one-sided density of the negative electrode active material layer in the negative electrode, in g / m². 2 , 30≤X≤80.

[0041] In this embodiment, the first additive, with its unique -SO3 group, can preferentially reduce and form a dense and uniform SEI film on the negative electrode surface. This film is rich in components such as Li2S and ROSO2Li, which can effectively inhibit the continuous decomposition of the electrolyte and the growth of lithium dendrites, while possessing both high ionic conductivity and electrochemical stability. Simultaneously, it reduces interfacial impedance and improves lithium-ion migration efficiency. Therefore, the first additive helps improve the low-temperature and high-temperature cycling performance of the battery.

[0042] However, when the content of the first additive is too high (e.g., A > 4%), most of the lithium sulfonate compounds that do not participate in film formation will worsen the electrolyte viscosity, deteriorate kinetic performance, and lead to a decrease in low-temperature cycling performance; at the same time, they may decompose and generate heat at high temperatures, worsening thermal shock performance and compromising battery safety. If the content is too low (e.g., A < 0.1%), it is insufficient to form a complete and dense SEI film, failing to effectively suppress side reactions and solvent co-intercalation, and making it difficult to meet the cycling stability requirements under high voltage.

[0043] The second additive preferentially forms a dense and stable solid electrolyte film, mainly composed of lithium oxalate and lithium borate, at the positive / negative electrode interface. This effectively isolates the electrolyte and electrodes, reduces continuous electrolyte decomposition, inhibits solvent co-intercalation, and significantly improves the battery's cycle life. Furthermore, its strongly polar -C≡N groups can complex with transition metal ions dissolved from the positive electrode, enhancing the electrolyte's oxidation resistance, reducing side reactions, further strengthening the stability of the SEI film, and simultaneously improving battery safety.

[0044] However, when the content of the second additive is too high (e.g., B > 2%), it will significantly increase the viscosity of the electrolyte, deteriorate the ion transport kinetics, and lead to a deterioration in low-temperature cycling performance. If the content is too low (e.g., B < 0.2%), it will not be able to effectively form an interface film of sufficient thickness or stability, nor will it be able to fully complex transition metal ions, making it difficult to maintain long-term cycling stability and safety under high voltage.

[0045] Therefore, it is difficult to fully meet the comprehensive requirements of high and low temperature cycling performance and safety performance under high voltage by using any single additive alone. The embodiments of this application utilize the synergistic effect of two types of additives to form a dense and thin organic-inorganic composite SEI film at the negative electrode interface. This film inherits the high ionic conductivity and electrochemical stability formed by lithium sulfonate compounds, while also incorporating the structural density, oxidation resistance, and transition metal ion capture ability brought by boron-nitrile compounds. This effectively enhances the stability of the negative electrode interface, thereby achieving a synergistic improvement in the battery's low-temperature cycling performance, high-temperature cycling performance, and thermal shock safety performance under high voltage.

[0046] Furthermore, in this embodiment of the application, 0.1 ≤ A / B ≤ 10 is set.

[0047] A / B reflects the relative contribution of the two types of additives to interfacial film formation. When A / B < 0.1 (i.e., B is much greater than A), there is an excess of inorganic borate components and an insufficient amount of organic conductive components in the SEI film, leading to increased interfacial impedance and deterioration of low-temperature performance. When A / B > 10 (i.e., A is much greater than B), the lack of sufficient -C≡N groups to complex transition metal ions will lead to intensified oxidation of the cathode under high voltage, decreased high-temperature cycling capacity retention, and poor thermal stability.

[0048] Therefore, setting 0.1≤A / B≤10 ensures that lithium sulfonate compounds provide high ion conductivity, while boron-containing nitrile compounds provide structural compactness, antioxidant properties, and metal ion capture capabilities. The two complement each other and work together to support high and low temperature cycling and safety performance.

[0049] In this embodiment, X represents the loading of the negative electrode active material per unit area on one side of the negative electrode. When X < 30 g / m² 2 When the negative electrode load is too low, although film formation is easy, the battery volumetric energy density is insufficient, making it difficult to meet the requirements of high-energy-density applications; when X > 80 g / m 2 At this time, the negative electrode has a high compaction density and low porosity. Under a fixed electrode thickness, the ion diffusion path is extended and the local current density is increased, resulting in a significant deterioration in kinetic performance.

[0050] Therefore, setting 30≤X≤80 ensures the formation of a uniform, dense, and fully functional organic-inorganic composite SEI film on a high-load negative electrode, taking into account energy density, cycle life, and safety.

[0051] Furthermore, in this embodiment, 0.01≤(A+B) / X≤0.1 is set. This formula correlates the total amount of additives (A+B) with the surface density X of the negative electrode, reflecting the matching relationship between the interfacial film formation requirements and the negative electrode loading.

[0052] If (A+B) / X < 0.01, the total amount of additive is severely insufficient relative to the high areal density of the negative electrode, resulting in a discontinuous SEI film that is prone to breakage and reconstruction during high-voltage cycling, leading to a surge in impedance and a decline in low-temperature performance. If (A+B) / X > 0.1, the additive is excessive, and the accumulation of residues increases viscosity, hinders ion migration, and may decompose at high temperatures to produce gas or exothermic gases, thus worsening thermal stability. Therefore, when 0.01 ≤ (A+B) / X ≤ 0.1, a better balance between SEI film thickness, density, and ion conductivity can be achieved.

[0053] In summary, the embodiments of this application limit A (0.1%~4%), B (0.2%~2%), and X (30g / m³) to... 2 ~80g / m 2 The specific numerical range of (A+B) was determined, and two key ratio constraints, 0.01≤(A+B) / X≤0.1 and 0.1≤A / B≤10, were introduced to achieve multi-dimensional and precise control of the negative electrode interface chemistry. This enabled the two types of additives to exert a synergistic effect under high voltage conditions, and successfully constructed a composite SEI film with high ionic conductivity, dense structure, oxidation resistance and thermal stability. This fully meets the comprehensive requirements of lithium-ion batteries for low-temperature cycle performance, high-temperature cycle performance and thermal shock safety performance under high voltage.

[0054] In some embodiments of the present invention, 0.015 ≤ (A+B) / X ≤ 0.08.

[0055] This implementation further optimizes the range of the ratio of total additive amount to negative electrode areal density. If (A+B) / X < 0.015, it will lead to local defects in the SEI film, low low-temperature capacity retention, and accelerated high-temperature cycling degradation; if (A+B) / X > 0.08, it will lead to deterioration of electrolyte kinetics, decreased low-temperature performance, and significant thermal shock temperature rise. Therefore, setting 0.015 ≤ (A+B) / X ≤ 0.08 can further ensure film integrity while taking into account both low-temperature performance and thermal safety.

[0056] In some embodiments of the present invention, 0.5 ≤ A / B ≤ 8.

[0057] By further setting 0.5≤A / B≤8 in this embodiment, the complementary functions of the two types of additives can be further ensured, thereby further synergistically supporting high and low temperature cycling and safety.

[0058] In some embodiments of the present invention, 0.5 ≤ A ≤ 4.

[0059] By further setting 0.5≤A≤4 in the embodiments of this application, the cycle performance of the battery under low temperature and high temperature conditions can be further improved.

[0060] In some embodiments of the present invention, 2≤B≤1.

[0061] By further setting 2≤B≤1, the battery cycle life and battery safety can be further improved in the embodiments of this application.

[0062] In some embodiments of the present invention, the structural formula of lithium sulfonate compounds is as follows:

[0063] R1 is selected from one of fluorine atoms, fluorinated alkane groups, amino groups, and fluorinated amino groups.

[0064] In the embodiments of this application, when R1 is a fluorine atom or a fluorinated alkane group, it can preferentially form a film, generating a high LiF content SEI, which significantly improves high and low temperature performance.

[0065] When R1 is a fluorinated amino group (such as -NHCF3), it can have both electron-donating and electron-withdrawing effects, which can adjust the molecular polarity and moderately improve solubility without sacrificing film-forming ability. If it is a common amino group (–NH2), its thermal stability is relatively poor, and it is easy to decompose at high temperatures, which is detrimental to safety performance.

[0066] Therefore, limiting R1 to a fluorine atom, a fluorinated alkane group, an amino group, or a fluorinated amino group can maintain high film-forming activity while ensuring molecular stability, with fluorinated alkane groups and fluorinated amino groups showing better results.

[0067] In some embodiments of the present invention, the lithium sulfonate compound is selected from at least one of the following compounds:

[0068] Compound 1

[0069] Compound 2

[0070] Compound 3

[0071] Compound 4

[0072] Compound 5

[0073] Compound 6

[0074] Compound 7

[0075] Compound 8.

[0076] In some embodiments of the present invention, the structural formulas of boron-nitrile compounds are as follows:

[0077] Where m, n1, and n2 are all natural numbers greater than or equal to 0. R2 to R9 are each independently selected from -CH3, -F, -C=O, -O-, fluorinated alkane groups, nitrile alkane groups, and fluorinated nitrile alkane groups, and at least one side chain of R2 to R9 contains a nitrile group.

[0078] This structure defines the core framework of the second additive. Boron atoms are key to the formation of the lithium borate inorganic film; -C≡N groups are necessary for complexing transition metal ions and improving oxidation resistance; fluorinated alkane groups (such as -CH2CF3) can enhance molecular hydrophobicity and inhibit HF corrosion.

[0079] In some embodiments of the present invention, the boron-containing nitrile compound is selected from at least one of the following compounds:

[0080] compound a

[0081] Compound b

[0082] Compound C

[0083] compound d

[0084] compound e

[0085] compound f

[0086] compound g

[0087] compound h

[0088] Compound i.

[0089] Corresponding to the aforementioned application function implementation method embodiments, this application also provides a lithium-ion battery, an electrical device, and corresponding embodiments.

[0090] This application provides a lithium-ion battery, including a negative electrode, a positive electrode, and an electrolyte, wherein the electrolyte is the aforementioned electrolyte.

[0091] In some embodiments of the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which includes natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 At least one of Li-Al alloys.

[0092] In this invention, there are no particular limitations on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or composite current collector, etc.

[0093] In some preferred embodiments, the negative current collector comprises copper foil.

[0094] In some embodiments, the negative electrode further includes a negative electrode active material layer disposed on at least one side surface of the current collector, and the negative electrode active material layer further includes a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent.

[0095] The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene. The negative electrode binder includes styrene-butadiene latex, and the thickener includes CMC. The solvent includes deionized water.

[0096] In some embodiments, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active substance.

[0097] In this application, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material.

[0098] In some embodiments, the positive electrode active material layer further includes a positive electrode conductive agent, a positive electrode binder, and a solvent.

[0099] In some embodiments, the type of positive conductive agent mentioned in this invention is not limited, and any known conductive agent can be used.

[0100] In some embodiments, the positive electrode conductive agent mentioned in this invention includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0101] In one embodiment, the type of positive electrode binder mentioned in this invention is not limited, and any known positive electrode binder can be used.

[0102] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0103] In the lithium-ion batteries mentioned in this application, a separator is typically provided between the positive and negative electrodes to prevent short circuits. There are no particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application.

[0104] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties. The diaphragm includes resin or glass fiber diaphragm materials, including but not limited to polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0105] In some embodiments, the lithium-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte described above.

[0106] In some implementations, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of a lithium-ion battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0107] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0108] On the other hand, one embodiment of this application provides an electrical device including the lithium-ion battery described above.

[0109] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0110] To further understand the present invention, the following embodiments are provided to illustrate the present application. These embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0111] Example 1 I. Preparation of Lithium-ion Batteries 1. Preparation of positive electrode sheet The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent acetylene black (SuperP) and polyvinylidene fluoride (PVDF) binder are mixed evenly at a mass ratio of 97:1.5:1.5, and then evenly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry. The mixed slurry is coated on both sides of the aluminum foil current collector, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0112] 2. Preparation of negative electrode sheet Artificial graphite (anode active material), acetylene black (Super P) (anode conductive agent), CMC (thickener), and SBR (anode binder) (anode binder) are mixed evenly in a mass ratio of 94:2:1.2:2.8 and then evenly dispersed with deionized water to form a uniform anode slurry. The mixed slurry is coated on both sides of a copper foil current collector, and then baked, rolled, and cut into sheets to obtain the anode sheet.

[0113] 3. Preparation of electrolyte a. Mix ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (EP), and diethyl carbonate (DEC) in a mass ratio of 10:20:40:30 to form a mixed solvent. Remove water using a molecular sieve and set aside. Add 1M LiPF6 and mix thoroughly. b. Add additives (the types and amounts of additives are shown in Table 1) to the colorless and transparent liquid obtained in step a to obtain the electrolyte.

[0114] 4. Assembly of lithium-ion batteries The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrodes. After winding and welding the tabs, a bare cell is obtained. The bare cell is placed in an aluminum-plastic film for liquid injection and encapsulation to obtain a lithium-ion battery.

[0115] The method for testing the single-sided areal density in the negative electrode active material layer is as follows: First, prepare a high-precision balance, a dedicated cutter, and other tools, and operate in a low-humidity environment. Then, using the dedicated cutter, cut multiple circular samples (area S) from the uncoated copper foil, weigh them to obtain the average mass of the copper foil current collector, and record it as m1. Next, using the same cutter, cut multiple circular samples from the coated negative electrode sheet (both sides coated with active material), weigh them to obtain the average mass of the negative electrode sheet, and record it as m2. The surface density of the negative electrode on one side is calculated using the formula X=((m2-m1) / 2) / S. The entire process must be performed according to standardized procedures to ensure data accuracy.

[0116] Examples 2-29 and Comparative Examples 1-18 Examples 2-29 and Comparative Examples 1-18 are mostly the same as Example 1, except that the types and amounts of additives in the electrolyte are different, as shown in Table 1.

[0117]

[0118]

[0119] II. Performance Testing The lithium-ion batteries prepared in the above embodiments and comparative examples were tested as follows, and the test results are shown in Table 2.

[0120] 1. 45℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 45°C at a rate of 1C / 1C within the charge and discharge cutoff voltage range. The discharge capacity of the first cycle was recorded as Z1, and the discharge capacity of the Mth cycle was recorded as Z2. The capacity of the Mth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate of the Mth cycle, Z3 = Z2 / Z1. The cycle number M of the lithium-ion battery when the cycle capacity retention rate Z3 was 80% was recorded.

[0121] 2. 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 0°C within the charge and discharge cutoff voltage range at a rate of 0.5C / 0.5C. The discharge capacity of the first cycle was recorded as Y1, and the discharge capacity of the Nth cycle was recorded as Y2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate of the Nth cycle, Y3 = Y2 / Y1. The cycle number N of the lithium-ion battery was recorded when the cycle capacity retention rate Y3 was 80%.

[0122] 3. Thermal shock performance test First, the lithium-ion batteries were charged to full charge voltage at a constant current and voltage of 0.5C in a constant temperature chamber at 25±2℃, with a cutoff current of 0.05C. Then, the fully charged cells / batteries were placed in the same thermal shock device, and the temperature was increased from room temperature to 132±5℃ at a rate of 5℃ / min, and held at this temperature for 1 hour. The center temperature of the cells / batteries was recorded throughout the entire heating and holding process, with 10 batteries in each group. The safety standard was: no fire, no explosion, and the highest center temperature of the cells / batteries during the entire heating and holding process was recorded.

[0123]

[0124]

[0125] By comparing Examples 1 to 21 and Comparative Examples 1 to 16 with Tables 1 and 2, it can be seen that when 0.1≤A≤4, 0.2≤B≤2, 30≤X≤80, 0.1≤A / B≤10, and 0.01≤(A+B) / X≤0.1 are satisfied, the comprehensive requirements of lithium-ion batteries for low-temperature cycling performance, high-temperature cycling performance, and thermal shock safety performance under high voltage can be fully met.

[0126] Comparing Examples 1 to 5, and Comparative Examples 5 and 6, it is evident that when A is too high (e.g., A > 4%), most of the lithium sulfonate compounds that do not participate in film formation will deteriorate the electrolyte viscosity, worsen kinetic performance, and lead to a decrease in low-temperature cycling performance. Simultaneously, at high temperatures, they may decompose and generate heat, worsening thermal shock performance and compromising battery safety. If A is too low (e.g., A < 0.1%), it is insufficient to form a complete and dense SEI film, failing to effectively suppress side reactions and solvent co-intercalation, making it difficult to meet the cycling stability requirements under high voltage. Therefore, when 0.1 ≤ A ≤ 4%, the high and low temperature cycling performance and safety performance of the battery can be synergistically improved.

[0127] Comparing Examples 6 to 9, and Comparative Examples 7 and 8, it is evident that when B is too low (e.g., B < 0.2%), an interface film of sufficient thickness or stability cannot be effectively formed, nor can transition metal ions be sufficiently complexed, making it difficult to maintain long-term cycle stability and safety under high voltage. When B is excessive (e.g., B > 2), thermal shock performance is better, but electrolyte viscosity and impedance deteriorate, leading to reduced cycle performance. Therefore, when 0.2 ≤ B ≤ 2, the high and low temperature cycle performance and safety performance of the battery can be synergistically improved. Comparing Examples 10 to 13, and Comparative Example 4, it is evident that setting 30 ≤ X ≤ 8 is the basis for ensuring the comprehensive requirements of low-temperature cycle performance, high-temperature cycle performance, and thermal shock safety performance of the battery under high voltage.

[0128] Comparing Examples 14 to 17, and Comparative Examples 13 and 14, it can be seen that when 0.1 ≤ A / B ≤ 10, the high and low temperature cycle performance and safety performance of the battery can be synergistically improved. Comparing Examples 18 to 21, and Comparative Examples 15 and 16, it can be seen that when 0.01 ≤ (A+B) / X ≤ 0.1, the high and low temperature cycle performance and safety performance of the battery can be synergistically improved.

[0129] By comparing Examples 1, 22 to 25, and Comparative Examples 9 and 10, it can be seen that the lithium sulfonate compounds provided in the embodiments of this application can improve the high and low temperature cycle performance and safety performance of the battery.

[0130] By comparing Examples 1, 26 to 29, and Comparative Examples 11 and 12, it can be seen that using the boron-nitrile compounds provided in the embodiments of this application can improve the high and low temperature cycle performance and safety performance of the battery.

[0131] Although this application has been described with reference to preferred embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for the elements, as long as they do not depart from the scope of this application. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of this application, as long as they do not depart from the essential scope of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed as the best mode of carrying out this application as conceived, but rather this application will include all embodiments falling within the scope of the appended claims.

[0132] All scopes disclosed in this application include endpoints, and endpoints can be combined with each other.

[0133] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A lithium-ion battery electrolyte, characterized in that, The battery comprises a first additive and a second additive. The first additive includes a lithium sulfonate compound, and the mass percentage of the first additive in the electrolyte is A%, 0.1≤A≤4. The second additive includes a boron-containing nitrile compound, and the mass percentage of the second additive in the electrolyte is B%, 0.2≤B≤2. The battery satisfies the following conditions: 0.1 ≤ A / B ≤ 10; 0.01 ≤ (A+B) / X ≤ 0.1; Where X is the one-sided density of the negative electrode active material layer in the negative electrode, in g / m². 2 , 30≤X≤80.

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, 0.015≤(A+B) / X≤0.

08.

3. The lithium-ion battery electrolyte according to claim 1, characterized in that, 0.5≤A / B≤8.

4. The lithium-ion battery electrolyte according to claim 1, characterized in that, 0.5≤A≤4; and / or, 0.2≤B≤1.

5. The lithium-ion battery electrolyte according to claim 1, characterized in that, The structural formula of the lithium sulfonate compound is as follows: R1 is selected from one of fluorine atoms, fluorinated alkane groups, amino groups, and fluorinated amino groups.

6. The lithium-ion battery electrolyte according to claim 5, characterized in that, The lithium sulfonate compound is selected from at least one of the following compounds: Compound 1 Compound 2 Compound 3 Compound 4 Compound 5 Compound 6 Compound 7 Compound 8.

7. The lithium-ion battery electrolyte according to claim 1, characterized in that, The structural formula of the boron-containing nitrile compound is as follows: Where m, n1, and n2 are all natural numbers greater than or equal to 0. When m = 0, R2 and R3 are each independently selected from -CH3, -F, fluorinated alkane groups, nitrile alkane groups, and fluorinated nitrile alkane groups. R7 to R9 are each independently selected from -CH3, -C=O, -O-, fluorinated alkane groups, nitrile alkane groups, and fluorinated nitrile alkane groups. At least one side chain of R2, R3, and R7 to R9 contains a nitrile group. When m > 0, R2 to R9 are each independently selected from -CH3, -C=O, -O-, fluorinated alkane groups, nitrile alkane groups, and fluorinated nitrile alkane groups. At least one side chain of R2 to R9 contains a nitrile group.

8. The lithium-ion battery electrolyte according to claim 7, characterized in that, The boron-containing nitrile compound is selected from at least one of the following compounds: compound a Compound b Compound C compound d compound e compound f compound g compound h Compound i.

9. A lithium-ion battery, characterized in that, It includes a negative electrode, a positive electrode, and an electrolyte, wherein the electrolyte is the electrolyte according to any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that, The negative electrode includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, which includes natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 At least one of Li-Al alloys.

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