Battery

Abstract

The present disclosure provides a battery, which comprises: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the negative electrode sheet has a porosity of φ in %; the separator has a thickness of t in μm and a pore size of R in μm; the ratio of the total mass of the electrolyte to the discharge capacity of the battery is N in g / Ah. The electrolyte comprises an electrolyte additive, and the electrolyte additive comprises a sulfate compound and a first lithium salt, wherein the first lithium salt includes an oxalate-containing lithium salt, the sulfate compound has a structure represented by Formula I, and the mass fraction of the sulfate compound in the electrolyte is C in %. The battery satisfies the expression A, expression A.

Description

Battery

[0001] This application claims priority to the Chinese patent application No. 202411283546.2, filed on September 13, 2024, and entitled "Battery", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of batteries, in particular, to a battery. BACKGROUND

[0003] With the development of the new energy industry, the energy density of higher power batteries has become a research hotspot in the industry. Using high-energy-density negative active materials and high-specific-energy positive active materials can effectively improve the energy density of lithium-ion batteries. However, at present, high-energy-density batteries are prone to produce gas, SEI film (Solid Electrolyte Interface) rupture and other adverse effects under high-temperature conditions, which makes the high-temperature performance of the battery poor. Therefore, there is an urgent need to develop a battery with better high-temperature performance.

[0004] SUMMARY

[0005] In a first aspect of the present application, a battery is provided, comprising: a positive electrode sheet, a negative electrode sheet, a separator film and an electrolyte, the porosity of the negative electrode sheet is unit is %; the thickness of the separator film is t, unit is μm; the pore size of the separator film is R, unit is μm; the ratio of the total mass of the electrolyte to the discharge capacity of the battery is N, unit is g / Ah; the electrolyte comprises an electrolyte additive, the electrolyte additive comprises: a sulfuric acid ester compound and a first lithium salt additive, the first lithium salt additive comprises a lithium salt containing oxalate, the sulfuric acid ester compound has a structure shown in Formula I, R1, R8 are independently selected from hydrogen, C1-C5 hydrocarbon group,

[0006] R2, R3, R4, R5, R6, R7 are each independently selected from C1-C3 alkylene, C1-C3 alkoxy, oxygen atom, n is an integer from 0 to 4, the mass fraction of the sulfuric acid ester compound in the electrolyte is C, unit is %; the battery satisfies Formula A, Formula A. Thus, the battery can effectively alleviate the problems of gas production and SEI film rupture and recombination in high-energy-density batteries, and improve the high-temperature performance of the battery.

[0007] In some embodiments, t is 60% - 80%; and / or, t is 12 pm - 20 pm; and / or, R is 0.03 pm - 0.12 pm; and / or, C is 0.1% - 10%; and / or, N is 2.0 - 5.0. In this way, the high-temperature performance of the battery can be further improved.

[0008] In some embodiments, R1, R8 are each independently selected from hydrogen,

[0009] at least one of R2, R3, R4 is selected from at least one of R2, R3, R4 is selected from an oxygen atom,

[0010] at least one of R5, R6, R7 is selected from at least one of R5, R6, R7 is selected from an oxygen atom,

[0011] n is 2.

[0012] In some embodiments, the sulfate compound has one of the following structures:

[0013] In some embodiments, the first lithium salt additive includes at least one of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium difluorodi(oxalato)phosphate, and lithium tris(oxalato)phosphate. In this way, the high-temperature performance, conductivity performance, and cycle performance of the battery can be improved.

[0014] In some embodiments, the molar ratio of the first lithium salt additive to the sulfate compound is 1: (1-5). In this way, the inhibitory effect of the sulfate compound on the first lithium salt additive can be further improved, so that the hindered first lithium salt additive is less likely to move freely.

[0015] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.1% - 5%, and / or the mass fraction of the sulfate compound in the electrolyte is 1% - 10%. In this way, the stability of the battery under high-temperature long cycle can be improved.

[0016] In some embodiments, the electrolyte additive further includes an electrolyte lithium salt, and the electrolyte lithium salt includes at least one of LiBF4, LiPF6, LiAsF6, and LiN(SO2F)2. In this way, the electrolyte lithium salt can further inhibit the corrosion of hydrogen fluoride on the SEI film and the CEI film.

[0017] In some embodiments, the mass ratio of the electrolyte lithium salt to the first lithium salt additive is 1: (0.4-2).

[0018] In some embodiments, the mass fraction of the electrolyte lithium salt in the electrolyte is 0.1%-1%. In this way, the stability of the battery under high-temperature long cycle can be further improved.

[0019] In some embodiments, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material, the positive electrode active material comprising at least one of lithium iron phosphate and a ternary material, wherein the ternary material satisfies the chemical formula LiNi x Co y M1 z1 M2 z2 O2, M1 and M2 are each independently selected from one of Al, Mn, Fe, and M1 and M2 are different, 0 < x ≤ 1, 0 < y < 1, 0 < z1 < 1, 0 ≤ z2 < 1, and x + y + z1 + z2 = 1.

[0020] In some embodiments, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, the mass fraction of silicon in the negative electrode active material being greater than 8%. DETAILED DESCRIPTION

[0021] The following examples are illustrative only and are not intended to limit the present application in any way.

[0022] 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 belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; and various parameters recited in the specification of the present application can be measured using any method known to one of ordinary skill in the art (e.g., the methods given in the examples of the present application).

[0023] The terms "comprise" and "have" and any variations thereof in the specification and claims of the present application are open-ended, i.e., including not only the recited elements but also equivalents thereof.

[0024] In a first aspect of the present application, the present application provides a battery comprising: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, the porosity of the negative electrode sheet being The unit is %; the thickness of the separator film is t, the unit is μm; the pore size of the separator film is R, the unit is μm; the ratio of the total mass of the electrolyte to the discharge capacity of the battery is N, the unit is g / Ah; the electrolyte comprises an electrolyte additive, and the electrolyte additive comprises: a sulfuric ester compound and a first lithium salt additive, the first lithium salt additive comprises a lithium salt containing oxalate, and the sulfuric ester compound has a structure shown in Formula I, R1, R8 are independently selected from hydrogen, C1-C5 hydrocarbon group,

[0025] R2, R3, R4, R5, R6, R7 are each independently selected from C1-C3 hydrocarbylene, C1-C3 alkoxy, oxygen atom, n is an integer from 0 to 4, the mass fraction of the sulfuric ester compound in the electrolyte is C, the unit is %; the battery satisfies formula A, Formula A. Thus, the battery can effectively alleviate the problems of gas production, SEI film rupture and recombination in high energy density batteries, and improve the high temperature performance of the battery.

[0026] In the present application, the sulfuric ester compound has a tongs structure, and the tongs structure is surrounded by multiple double bond oxygen (such as carbonyl, sulfur-oxygen double bond, etc.) and single bond oxygen atom. The lithium salt containing oxalate has a similar "X" type structure, and the molecular structure also has multiple carbonyl groups. When the two polar molecules are mixed, based on the spatial stereostructure of the two polar molecules, the lithium salt containing oxalate molecules can be inserted into the structure gap of the large group structure of the carbonyl and sulfur-oxygen double bond in the sulfuric ester compound, to limit the free movement of the lithium salt containing oxalate to a certain extent; on the other hand, when mixed, the two polar molecules will repel each other due to the large number of carbonyl groups and / or sulfur-oxygen double bonds in their structures. The orientation force of this mutual repulsion makes the molecules of the lithium salt containing oxalate and the sulfuric ester compound rotate with each other to balance the repulsion between them, that is, the planar configuration of the two substances tends to be from a parallel state to an intersecting state, which is beneficial to the large group structure of the carbonyl and sulfur-oxygen double bond in the sulfuric ester compound to tend to insert into the structure gap of the lithium salt containing oxalate molecule, thereby producing steric hindrance to the lithium salt containing oxalate. The repulsion between the two polar molecules is beneficial to the tongs structure of the sulfuric ester to limit the free movement of the molecules of the lithium salt containing oxalate; under the dual action of molecular repulsive force and spatial limitation, the hindered lithium salt containing oxalate is less likely to move freely.

[0027] When the electrolyte additive is used in a battery, the hindered free movement of lithium salt containing oxalate is reduced, thereby reducing the direct contact of oxalate with the electrode plate, making the gas generation reaction of oxalate not easy to occur, and also reducing the damage to the SEI film caused by the swelling of the battery due to gas generation, thereby improving the stability under high temperature and long cycle of the battery.

[0028] Further, t x R in formula A can indicate the total influence of the adverse factors, specifically, when the thickness t of the separator is too thick, or when the pore size R of the separator is too large, the internal impedance of the battery will be large, and the macromolecular impurities will pass through the separator and cause side reactions at the electrode plate, which will deteriorate the performance of the battery. Therefore, when t x R is too small, the internal impedance of the battery is too high, and the adverse side reactions are intensified; when t x R is too large, the output voltage of the battery is unstable, and toxic gas may be generated. The total mass of the electrolyte and the discharge capacity of the battery can reflect that the discharge capacity of the sulfonate compound is strong; t x R in formula A can indicate the total influence of the adverse factors, specifically, when the thickness t of the separator is too thick, or when the pore size R of the separator is too large, the internal impedance of the battery will be large, and the macromolecular impurities will pass through the separator and cause side reactions at the electrode plate, which will deteriorate the performance of the battery. Therefore, when t x R is too small, the internal impedance of the battery is too high, and the adverse side reactions are intensified; when t x R is too large, the output voltage of the battery is unstable, and toxic gas may be generated.

[0029] Further, when the sulfonate compound is used in combination with the first lithium salt additive, the foregoing battery is suitable for a battery system using a medium-nickel positive electrode and a silicon-based negative electrode, and can exert an advantageous effect under the battery system.

[0030] It should be noted that in the electrolyte additive of the present application, the mutual repulsion between polar molecules produces orienting force and space limitation, which does not completely prevent the lithium salt containing oxalate from exerting its advantages, but effectively slows down the movement of the lithium salt containing oxalate, so that the gas generation reaction is not easy to occur, thereby reducing the damage to the SEI film, and thereby promoting the performance stability of the battery under high temperature and long cycle.

[0031] The term C1-C5 hydrocarbon group refers to a saturated linear or branched carbon hydrogen compound group containing 1-5 carbon atoms, such as CH3-, C2H5-, etc.

[0032] The term C1-C3 alkylene group refers to a linear saturated hydrocarbon group containing 1-3 carbon atoms, such as methylene, ethylene, etc.

[0033] The term C1-C3 alkoxy group refers to a group of -OR, wherein R is a C1-C3 alkyl group, such as ethoxy, n-propoxy, etc.

[0034] ​​​As an example, n is an integer from 0 to 4, such as 0, 1, 2, 3, 4, etc.

[0035] The sulfate compound has a pincer structure, and the pincer structure is surrounded by multiple double-bond oxygen (such as carbonyl, sulfur-oxygen double bond, etc.) and single-bond oxygen atoms.

[0036] When the first lithium salt additive is used in the electrolyte of the battery, the high-temperature performance, the conductivity performance, and the cycle performance of the battery are improved, which is because the oxalate in the first lithium salt additive has a large electronegativity for fluorine elements and can form a covalent bond with carbon elements to increase the boiling point of the electrolyte; meanwhile, the compounds in the electrolyte can form small solvent clusters to promote the flowability and the conductivity performance of the electrolyte.

[0037] In some embodiments, 60% to 80%; and / or, t is 12 μm to 20 μm; and / or, R is 0.03 μm to 0.12 μm; and / or, C is 0.1% to 10%; and / or, N is 2.0 to 5.0. In this way, the high-temperature performance of the battery can be further improved.

[0038] When the porosity of the negative electrode sheet is located in the foregoing range, more space for expansion can be provided, effectively relieving the volume expansion of the negative active material, such as a silicon-based material, and effectively maintaining the integrity of the negative SEI film.

[0039] When the thickness t of the separator film is located in the foregoing range, the movement of the oxalate-containing lithium salt can be hindered, and the negative impact on the lithium ion transmission rate is less.

[0040] When the ratio of the total mass of the electrolyte to the discharge capacity of the battery is N located in the foregoing range, the discharge capacity of the battery is better.

[0041] When the pore size R of the separator film is located in the foregoing range, the migration ability of lithium ions in the electrolyte is better.

[0042] In some embodiments, R1, R8 are each independently selected from hydrogen,

[0043] at least one of R2, R3, R4 is selected from and at least one of R2, R3, R4 is selected from an oxygen atom,

[0044] at least one of R5, R6, R7 is selected from and at least one of R5, R6, R7 is selected from an oxygen atom,

[0045] n is 2.

[0046] In some embodiments, the sulfate compound has one of the following structures:

[0047] In some embodiments, the first lithium salt additive includes at least one of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium difluorodi(oxalato)phosphate, and lithium tris(oxalato)phosphate. Thereby, the high temperature performance, the conductivity performance, and the cycle performance of the battery are improved.

[0048] As an example, the first lithium salt additive is lithium difluoro(oxalato)borate. Lithium difluoro(oxalato)borate is beneficial to improve the conductivity, to optimize the high and low temperature performance, and to improve the thermal stability.

[0049] In some embodiments, the molar ratio of the first lithium salt additive to the sulfate compound is 1:(1-5). Thereby, the inhibition of the first lithium salt additive by the sulfate compound is further improved, so that the hindered first lithium salt additive is less likely to move freely.

[0050] In some embodiments, the molar ratio of the first lithium salt additive to the sulfate compound is 1:(1-5), such as 1:1, 1:1.6, 1:2, 1:3, 1:3.4, 1:4, 1:5, etc.

[0051] In some embodiments, the molar ratio of the first lithium salt additive to the sulfate compound is 1:(2-4). Thereby, the sulfate compound is in a slight excess state relative to the first lithium salt additive, and the inhibition of the first lithium salt additive by the sulfate compound is further improved, so that the hindered first lithium salt additive is less likely to move freely.

[0052] In some embodiments, the mass fraction of the first lithium salt additive in the electrolyte is 0.1%-5%.

[0053] As an example, the mass fraction of the first lithium salt additive in the electrolyte is 0.1%, 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, etc. Thereby, the stability of the battery under high temperature and long cycle is further improved.

[0054] In some embodiments, the mass fraction C of the sulfate compound in the electrolyte is 1%-10%.

[0055] As an example, the mass fraction of the sulfate compound in the electrolyte is 1%, 1.07%, 1.4%, 1.7%, 2%, 3%, 3.4%, 4%, 5%, 6%, 6.9%, 7%, 8%, 8.7, 9%, 10%, etc. Thereby, the stability of the battery under high temperature and long cycle is further improved.

[0056] The electrolyte contains fluorine element. With the battery reaction, fluorine element produces hydrogen fluoride, which corrodes SEI film and CEI film, causing the capacity attenuation and gas swelling of the battery in high-temperature storage.

[0057] In some embodiments, the electrolyte additive further comprises an electrolyte lithium salt, which comprises at least one of LiBF4, LiPF6, LiAsF6, LiN(SO2F)2. Thus, the electrolyte lithium salt can further inhibit the corrosion of hydrogen fluoride to SEI film and CEI film. Thus, the first lithium salt additive, the sulfuric acid ester compound and the electrolyte lithium salt interact with each other, not only making the hindered oxalate-containing lithium salt not easy to move freely. The first lithium salt additive can also inhibit the hydrolysis of the oxalate-containing lithium salt, and for the fluorine-containing lithium salt therein, the generation of fluoride ions can be reduced, the generation of hydrogen fluoride is reduced, thereby reducing the corrosion of hydrogen fluoride to SEI film and CEI film, increasing the high-temperature storage capacity of the battery, and facilitating the reduction of the gas swelling of the battery.

[0058] Further, the electrolyte lithium salt is LiBF4. LiBF4 has strong stability at high temperature, which is conducive to further inhibiting the generation of hydrogen fluoride and improving the high-temperature performance of the battery.

[0059] In some embodiments, the mass ratio of the electrolyte lithium salt to the first lithium salt additive is 1:(0.4-2).

[0060] In some embodiments, the mass ratio of the electrolyte lithium salt to the first lithium salt additive is 1:(0.4-2), for example, 1:0.4, 1:0.5, 1:1, 1:1.5, 1:75, 1:1, etc.

[0061] In some embodiments, the mass fraction of the electrolyte lithium salt in the electrolyte is 0.1%-1%. Thus, the stability of the battery in high-temperature long cycle can be further improved.

[0062] For example, the mass fraction of the electrolyte lithium salt in the electrolyte is 0.1%, 0.15%, 0.3%, 0.5%, 0.8%, 1%, etc. Thus, the stability of the battery in high-temperature long cycle can be further improved.

[0063] In the present application, the electrolyte can also optionally comprise a second additive, which can be selected according to the specific application of the electrolyte in different batteries.

[0064] In some embodiments, the second additive includes at least one of vinyl sulfate (DTD), vinylene carbonate, fluoroethylene carbonate (FEC), vinyl ethylene carbonate, ethylene sulfate, 1,3-propane sultone, 1,3-propene sultone, vinyl sulfite, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphate. Thus, the electrolyte is particularly suitable for use in a silicon negative electrode battery to further improve the cycle performance and high-temperature storage performance of the battery.

[0065] In some embodiments, the mass fraction of the second additive in the electrolyte is 0.5%-20%, such as 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, etc.

[0066] In the present application, the electrolyte can be a non-aqueous electrolyte, and the solvent of the non-aqueous electrolyte is an organic solvent.

[0067] In some embodiments, the organic solvent includes at least one of vinyl carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate, diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone.

[0068] In some embodiments, the mass fraction of the organic solvent in the electrolyte is 10%-80%.

[0069] In some embodiments, the organic solvent includes EC, PC, EMC, and DEC. EC has a high dielectric constant, which can ensure that the lithium salt is fully dissolved and ionized, and is conducive to improving the electrical conductivity of the electrolyte and ensuring the cycle life; EMC and DEC are linear carbonates, which have the advantages of low viscosity and low melting point compared with cyclic carbonates (EC), and thus the use of PC, EMC, DEC, and EC as electrolyte solvents improves the battery performance.

[0070] In some embodiments, the mass ratio of the organic solvent to the sulfate compound in the electrolyte is (8-170):1, such as 8:1, 15:1, 30:1, 40:1, 75:1, 95:1, 120:1, 140:1, 170:1, etc. Thus, the stability of the battery under high-temperature long cycle is further improved.

[0071] In the present application, the electrolyte can further include a third lithium salt. The third lithium salt further includes at least one of lithium perchlorate, lithium bisfluorosulfonylimide, lithium difluorophosphate, lithium hexafluoroarsenate.

[0072] In some embodiments, the mass fraction of the third lithium salt in the electrolyte is 10%-20%, such as 10%, 13%, 15%, 18%, 20%, etc.

[0073] Generally, in addition to the electrolyte, the battery also includes a positive electrode sheet, a negative electrode sheet, and a separator. During the charging and discharging of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuiting between the positive electrode and the negative electrode, while allowing ions to pass through.

[0074] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material including at least one of lithium iron phosphate and a ternary material, wherein the ternary material satisfies the chemical formula LiNi x Co y M1 z1 M2 z2 O2, M1 and M2 are each independently selected from one of Al, Mn, Fe, and M1 and M2 are different, 0

[0075] In some embodiments, when the ternary material is a cobalt-containing positive electrode active material, the spatial restriction and the repulsive intermolecular forces between the sulfate compound and the first lithium salt additive cause the oxalate structure near the electrode to be significantly reduced, thereby greatly reducing the probability of the dissolved Co element forming cobalt oxalate precipitation with oxalate, and further reducing the damage of the precipitation to the electrode and reducing the impedance of the battery; the sulfate compound can also undergo complexation reaction with the dissolved Co element, reducing the occurrence of side reactions of the dissolved Co element in the battery system, and further improving the stability of the battery under high temperature and long cycle; the negative electrode of the battery will also partially decompose the sulfate compound and form a solid electrolyte interface film, which can limit the Co element from being released. Thus, the electrolyte containing the electrolyte additive of the first aspect or the electrolyte of the second aspect is particularly suitable for use with cobalt-containing positive electrode active materials in the battery system.

[0076] As an example, the positive electrode active material includes LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.6 Co 0.1 Mn 0.3 O2(NCM613), LiNi 0.5 Co 0.2Mn 0.3 O2(NCM523) and the like.

[0077] In some embodiments, the positive active material comprises lithium iron phosphate. Thus, the sulfate compound can also undergo complexation reaction with the dissolved metal elements (such as Fe elements), reducing the occurrence of side reactions of the dissolved metal elements in the battery system, thereby improving the stability of the battery under high temperature and long cycle; the negative electrode of the battery will also undergo partial decomposition of the sulfate compound and form a solid electrolyte interface film, which can limit the metal element from being released.

[0078] In some embodiments, the positive active material layer can further comprise a binder. Specific examples of the binder include, but are not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene-fluoride-tetrafluoroethylene-propylene terpolymer, and styrene butadiene rubber (SBR).

[0079] In some embodiments, the positive active material layer can further comprise a conductive agent. Specific examples of the conductive agent include, but are not limited to, super-conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and the like.

[0080] In some embodiments, the positive current collector can be a metal foil, such as an aluminum foil.

[0081] In some embodiments, the negative electrode tab comprises a negative current collector and a negative active material layer located on at least one side of the negative current collector, the negative active material layer comprising a negative active material, the mass fraction of silicon in the negative active material being greater than 8%. By increasing the specific capacity of the negative active material, the energy density of the battery can be effectively improved. The specific capacity of the current graphite-based material has reached the upper limit of its theoretical capacity (372 mAh / g), while the highest theoretical specific capacity of the silicon-based negative active material can reach 4200 mAh / g, and the silicon-based negative active material has great application prospects. The silicon-based negative active material has a large volume change during the charging and discharging process of the battery. During repeated charging and discharging cycles, the SEI film on the surface of the silicon-based negative electrode will repeatedly break and form, constantly consuming the electrolyte, resulting in poor cycle performance of the battery. In the present application, by optimizing the composition of the electrolyte additive, the corrosion problem and the gas production problem of the SEI can be effectively improved.

[0082] In some embodiments, the negative active material layer can further comprise a binder. Specific examples of the binder include, but are not limited to, one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylamide (PAM), and polyvinylidene fluoride (PVDF).

[0083] In some embodiments, the negative active material layer can further include a conductive agent. Specific examples of the conductive agent include, but are not limited to, super P, acetylene black, carbon black, graphene, and the like.

[0084] In some embodiments, the negative active material layer can further include a thickening agent, such as sodium carboxymethyl cellulose (CMC-Na).

[0085] The type of the separator film is not particularly limited in the present application, and various porous structure separator films with good stability can be selected, such as polyethylene separator film, polypropylene separator film, PE ceramic coated separator film, and the like.

[0086] The scheme of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application.

[0087] In the following embodiments:

[0088] Compound 1 is: CAS: 2520352-94-5;

[0089] Compound 2 is: CAS: 201419-80-9.

[0090] Compound 3 is:

[0091] Compound 4 is:

[0092] Compound 5 is:

[0093] The following embodiments are used to illustrate the application of the electrolyte additive and the electrolyte containing the same in the lithium ion battery of NCM613 positive electrode.

[0094] Example 1a

[0095] Preparation of positive electrode sheet:

[0096] The positive active material NCM613, the binder polyvinylidene fluoride (PVDF), the conductive agent SP, and the conductive agent CNT are mixed in a weight ratio of 95:3:0.5:1.5, N-methyl pyrrolidone (NMP) is added to form a slurry, the solid content is controlled at 55%, and the mixture is stirred under the action of a vacuum stirrer until the mixture becomes a positive electrode slurry with uniform fluidity; the positive electrode slurry is uniformly coated on an aluminum foil with a thickness of 16 μm; the aluminum foil coated with the positive electrode slurry is dried in an oven at 120°C for 8h. Finally, the positive electrode sheet is obtained by rolling, and the positive electrode sheet is controlled to have a compacted density of 3.5g / cm 3 , and is cut to obtain a positive electrode sheet.

[0097] Negative electrode sheet preparation:

[0098] The graphite / Zichen silicon carbon 550-M5-230415 negative electrode active material, conductive agent SP, binder SBR (JSR-104A), thickening agent CMC (crt30000PA) were mixed according to the weight ratio of 95:1.5:2:1.5, water was added to form a slurry, the solid content of the slurry was controlled at 45%, and the slurry was stirred under the action of a vacuum stirrer to obtain a negative electrode slurry; the negative electrode slurry was uniformly coated on a copper foil with a thickness of 9 μm; the copper foil coated with the negative electrode slurry was dried at 85°C for 5 h. Finally, after rolling, the compaction density of the negative electrode sheet was controlled at 1.6 g / cm 3 , and the negative electrode sheet was slitted to obtain a negative electrode sheet with a porosity of 70%.

[0099] Preparation of electrolyte:

[0100] In an argon-filled glove box (moisture <10 ppm, oxygen <1 ppm), the solvent EC:PC:DEC:EMC was mixed uniformly according to the mass percentage of 3:3:4:10 to obtain an organic solvent. The organic solvent was added with: electrolyte additive (compound 1 and first lithium salt additive (lithium difluoro(oxalato)borate)), electrolyte lithium salt (LiBF4), second additive (FEC and DTD), and stirred uniformly to obtain a non-aqueous electrolyte. The mass of the electrolyte was 9 g.

[0101] Preparation of separator film:

[0102] A double-layer PP ceramic-coated separator film was selected, the thickness t of the separator film was 16 μm, and the pore size R of the separator film was 0.08 μm.

[0103] Preparation of lithium ion battery:

[0104] The above prepared positive electrode sheet, separator film, and negative electrode sheet were wound to obtain a non-liquid-injected bare cell; the bare cell was placed in an outer package, the above prepared electrolyte was injected into the dried bare cell, and the lithium ion battery was obtained after vacuum packaging, standing, formation, shaping, sorting, and other processes. The battery discharge capacity was obtained by first fully charging the battery, then discharging at 0.5C of half the battery capacity, and recording the discharge time multiplied by the discharge current, which was the discharge capacity.

[0105] The differences between Examples 2a-19a, Comparative Examples 1a-3a, and Example 1a are shown in Table 1-1.

[0106] Table 1-1

[0107] The differences between Examples 20a-27a and Example 1a are shown in Table 1-2.

[0108] Table 1-2

[0109] The following tests were performed on the aforementioned examples and comparative examples, and the test results are shown in Table 2.

[0110] (1) High-temperature storage performance test: The lithium ion battery was placed in a 60°C constant-temperature oven for 6 h, and then charged at 1C constant current and constant voltage to an upper limit voltage of 4.4 V, with a cutoff current of 0.05C. After the battery was fully charged, it was left to stand for 5 min, and then discharged at 1C constant current to a cutoff voltage of 2.75 V. The gas production (drainage method) at full charge (100% SOC) before storage was measured; the capacity retention rate and the gas production by the drainage method were measured after 60 days of storage, wherein

[0111] Capacity retention rate (%) = residual capacity after discharge / initial capacity x 100%.

[0112] Drainage gas production (m 3 ) = (initial weight - weight after drainage) / density of water.

[0113] (2) High-temperature cycle performance test:

[0114] At 45°C, the lithium ion battery was first charged at 1C constant current to a voltage of 4.5 V, and the thickness of the lithium ion battery at this time was recorded as H0. Then, the lithium ion battery was discharged at 1C constant current to 2.75 V, and the initial capacity C0 before storage was recorded. The lithium ion battery was first charged at 0.3C constant current to a voltage of 4.5 V, and the initial capacity Q0 was recorded. The capacity at 800 cycles was recorded as Q1, and the 1C, 500-cycle capacity retention rate was calculated by formula (1):

[0115] 45°C storage 500-cycle capacity retention rate (%) = Q1 / Q0 x 100%

[0116] (3) Normal-temperature cycle performance test:

[0117] The prepared lithium ion battery was placed in a 25°C environment, and charged at 1C constant current to a voltage of 4.5 V, and then discharged at 1C constant current to 2.75 V. The initial capacity Q0 was recorded, and the capacity at 800 cycles was recorded as Q1. The 1C, 500-cycle capacity retention rate was calculated by formula (1):

[0118] 500-cycle capacity retention rate (%) = Q1 / Q0 x 100%

[0119] The relevant test results of the above examples and comparative examples are shown in Table 2.

[0120] Table 2

[0121] According to Table 2 above, the gas generation amount of the lithium ion battery of Examples 1a-27a is lower than that of the lithium ion battery of Comparative Examples 1a-3a, and the cycle performance and high-temperature performance of the lithium ion battery of Examples 1a-27a are also better than those of the lithium ion battery of Comparative Examples 1a-3a, indicating that when the electrolyte additive or electrolyte of the present application is used in the battery, the hindered free movement of the lithium salt containing oxalate is reduced, thereby reducing the contact of oxalate with the battery electrode, making the gas generation reaction of oxalate not easy to occur, and also reducing the damage to the SEI caused by the swelling of the battery due to gas generation, thereby improving the stability of the battery under high-temperature long cycle.

[0122] Compared with Example 16a, the lithium ion battery of Example 16a has a slightly increased gas generation amount, slightly reduced cycle performance and slightly reduced high-temperature performance, indicating that the electrolyte lithium salt helps to improve the high-temperature long cycle performance of the battery and reduce gas generation. Compared with Comparative Example 1a, the lithium ion battery of Example 1a has better high-temperature performance and cycle performance than Comparative Example 1a, which is because when the electrolyte additive or electrolyte does not contain the first lithium salt additive (such as lithium difluorooxalate borate), it will cause the first lithium salt additive to be used to improve the high-temperature performance and cycle performance of the battery to decrease. Compared with Comparative Example 2a, the lithium ion battery of Example 1a has a lower gas generation amount than that of Comparative Example 2a, and the cycle performance and high-temperature performance of the lithium ion battery of Example 1a are also better than those of the lithium ion battery of Comparative Example 2a, which is because when the electrolyte additive or electrolyte does not contain the sulfuric acid ester compound, it will cause the restriction between the sulfuric acid ester compound and the first lithium salt additive to weaken, thereby causing the gas generation reaction of the first lithium salt additive to intensify, affecting the high-temperature long cycle performance of the battery. Compared with Comparative Example 3a, the lithium ion battery of Example 1a has a lower gas generation amount than that of Comparative Example 3a, and the cycle performance and high-temperature performance of the lithium ion battery of Example 1a are also better than those of the lithium ion battery of Comparative Example 3a, indicating that the presence of the two components in the electrolyte additive or electrolyte can improve the high-temperature and room-temperature cycle performance of the battery.

[0123] The following examples are used to illustrate the application of the electrolyte additive and the electrolyte containing the same in the lithium ion battery of LiFePO4 cathode.

[0124] Example 1b

[0125] Example 1b is the same as Example 1a, except that the cathode electrode sheet is prepared as follows:

[0126] The lithium iron phosphate positive electrode active material, the conductive agent carbon black SP, the binder polyvinylidene fluoride, and the dispersant polyacrylate are dispersed at a mass ratio of 97.2:0.8:1.8:0.2 by high-speed stirring to obtain a positive electrode slurry, and the positive electrode slurry obtained is used to prepare a positive electrode sheet, and the single-sided area density of the positive electrode sheet is 230 g / m 2 , and the compacted density is 2.50 g / cm 3 .

[0127] The differences between Examples 2b-11b, Comparative Examples 1b-3b and Example 1b are shown in Table 3.

[0128] Table 3

[0129] The aforementioned examples and comparative examples are subjected to the aforementioned high-temperature storage performance test, high-temperature cycle performance test, and room-temperature cycle performance test, and the test results are shown in Table 4.

[0130] Table 4

[0131] As shown in Table 4, the gas production of the lithium ion batteries of Examples 1b-11b is lower than that of the lithium ion batteries of Comparative Examples 1b-3b, and the cycle performance and high-temperature performance of the lithium ion batteries of Examples 1b-11b are also better than those of the lithium ion batteries of Comparative Examples 1b-3b, which indicates that the electrolyte additive or electrolyte of the present application can improve the stability of the battery under high-temperature long cycle and reduce gas production when used in the battery.

[0132] Compared with Example 8b, the gas production of the lithium ion battery of Example 1b-7b is slightly increased, and the cycle performance and high-temperature performance are slightly reduced, which indicates that the electrolyte lithium salt helps to improve the high-temperature long cycle performance of the battery and reduce gas production.

[0133] Compared with Comparative Example 1b, the high-temperature performance and cycle performance of the lithium ion battery of Example 1b are better than those of Comparative Example 1b, which is because when the electrolyte additive or electrolyte does not contain the first lithium salt additive (such as lithium difluoro(oxalato)borate), the first lithium salt additive for improving the high-temperature performance and cycle performance of the battery is reduced.

[0134] Compared with Comparative Example 2b, the lithium ion battery of Example 1b has lower gas production, better cycle performance and better high-temperature performance, which is because the presence of the sulfuric acid ester compound in the electrolyte additive or electrolyte weakens the restriction between the sulfuric acid ester compound and the first lithium salt additive, thereby intensifying the gas production reaction of the first lithium salt additive and affecting the high-temperature long cycle performance of the battery.

[0135] Compared with Comparative Example 3b, the lithium ion battery of Example 1b has lower gas production, better cycle performance and better high-temperature performance, which indicates that the presence of the two components in the electrolyte additive or electrolyte can improve the high-temperature and room-temperature cycle performance of the battery.

[0136] 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 belongs. All patents and publications referred to in this application are incorporated herein by reference in their entirety. The terms “comprising” or “including” are intended to be open-ended, that is, to include, but not to be limited to, other aspects as well.

[0137] In the description of the specification, the description of the terms “one embodiment”, “another embodiment” and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment are included in at least one embodiment of the application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction. In addition, it should be noted that in the specification, the terms “first”, “second” are for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features.

[0138] Although the embodiments of the application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be understood as limiting the application, and those of ordinary skill in the art can make changes and modifications to the above embodiments within the scope of the application.

Claims

1. A battery, wherein, Comprising: a positive electrode tab, a negative electrode tab, a separator film, and an electrolyte solution; The porosity of the negative electrode tab is unit: %; a thickness of the separator film is t, unit: μm, and a pore size of the separator film is R, unit: μm; a ratio of a total mass of the electrolyte solution to a discharge capacity of the battery is N, unit: g / Ah; The electrolyte includes an electrolyte additive, the electrolyte additive includes: a sulfato compound and a first lithium salt additive, the first lithium salt additive includes a lithium salt containing oxalate, the sulfato compound has a structure shown in formula I, R1, R8 are independently selected from hydrogen, C1-C5 hydrocarbon groups, R2, R3, R4, R5, R6, R7are each independently selected from C1-C3 alkylene, C1-C3 alkoxy, an oxygen atom, n is an integer from 0 to 4, and a mass fraction of the sulfate compound in the electrolyte solution is C, unit: %; The battery satisfies formula A, 2. The battery of claim 1, wherein, t is 12 μm - 20 μm; and / or, R is 0.03 μm - 0.12 μm; and / or, C is 0.1% - 10%; and / or, N is 2.0 - 5.

0.

3. The battery according to claim 1 or 2, wherein, R1, R8 are independently selected from hydrogen, at least one of R2, R3, R4is selected from and at least one of R2, R3, R4 is selected from an oxygen atom, at least one of R5, R6, R7is selected from and at least one of R5, R6, R7 is selected from an oxygen atom, n is 2.

4. The battery of any one of claims 1-3, wherein, The sulfate compound has one of the following structures:

5. The battery of any one of claims 1-4, wherein, The first lithium salt additive includes at least one of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium difluorodioxalato phosphate, and lithium tris(oxalato)phosphate.

6. The battery of any one of claims 1-5, wherein, A molar ratio of the first lithium salt additive to the sulfate compound is 1:(1-5).

7. The battery of any one of claims 1-6, wherein, A mass fraction of the first lithium salt additive in the electrolyte solution is 0.1%-5%, and / or a mass fraction of the sulfate compound in the electrolyte solution is 1%-10%.

8. The battery of any one of claims 1-7, wherein, The electrolyte solution additive further includes an electrolyte lithium salt, and the electrolyte lithium salt includes at least one of LiBF4, LiPF6, LiAsF6, and LiN(SO2F)2.

9. The battery of claim 8, wherein, A mass ratio of the electrolyte lithium salt to the first lithium salt additive is 1:(0.4-2).

10. The battery of claim 8 or 9, wherein, A mass fraction of the electrolyte lithium salt in the electrolyte solution is 0.1%-1%.

11. The battery of any one of claims 1-10, wherein, The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer located on at least one side of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material including at least one of lithium iron phosphate and a ternary material, wherein the ternary material satisfies the chemical formula LiNi x Co y M1 z1 M2 z2 O2, M1 and M2 are each independently selected from one of Al, Mn, Fe, and M1 and M2 are different, 0 < x ≤ 1, 0 < y < 1, 0 < z1 < 1, 0 ≤ z2 < 1, and x + y + z1 + z2 = 1.

12. The battery of any one of claims 1-11, wherein, The negative electrode tab includes a negative electrode current collector and a negative electrode active material layer located on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material, and a mass fraction of silicon in the negative electrode active material is greater than 8%.

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