A battery

Abstract

The application relates to the technical field of batteries, in particular to a battery. The battery comprises a negative electrode sheet and an electrolyte. The surface of the negative electrode sheet is divided into a single-face area and a double-face area. The double-face area is a double-face coating area, the total thickness of the double-face coating layer is Y mm, the single-face area is a single-face coating area, the other face corresponding to the single-face coating area is a blank foil area, the thickness of the single-face coating layer is X mm, and the ratio A of the thickness of the single-face area to the thickness of the double-face area is 0.5-0.65. The electrolyte comprises an organic solvent, the organic solvent comprises ethyl propionate and / or propyl propionate, the weight content B wt% of the ethyl propionate is 0-50 wt% based on the total weight of the electrolyte, the weight content C wt% of the propyl propionate is 0-60 wt% based on the total weight of the electrolyte, and A, B and C satisfy 2B+C >= 400*(A-0.5). The battery of the application can prevent lithium precipitation during a cycle process above 1C charging rate, improve the stability and safety of the battery, and reduce the self-discharge degree.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a battery. Background Technology

[0002] Lithium-ion batteries have a long cycle life and high energy density, making them widely used in various electronic products, electric vehicles, and energy storage devices. With technological advancements, batteries need to achieve faster charging speeds to reduce charging time and further facilitate user convenience.

[0003] The charging rate is a measure of how fast a battery charges. Numerically, it is equal to the ratio of the charging current to the battery's rated capacity, i.e., "charging current / battery rated capacity = charging rate," and is generally measured in "C." Currently, commercially available lithium-ion batteries, including those for laptops, mobile phones, and automobiles, typically have charging rates of 1C or higher.

[0004] When the charging rate is too high, lithium plating can occur on the negative electrode due to insufficient kinetics, leading to rapid interface deterioration, increased self-discharge, accelerated battery degradation, and even safety accidents such as fires and explosions. Improving the electrolyte conductivity and reducing viscosity can significantly increase the battery's charging rate and prevent lithium plating. However, because the negative electrode has single-sided and double-sided regions, the thinness of the single-sided region often results in actual compaction being less than the designed compaction, leading to poorer kinetics and making it a region more prone to lithium plating.

[0005] Therefore, it is very important to invent a battery that can prevent lithium plating at high rates and has a low self-discharge rate. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a battery. The battery of this invention can prevent lithium plating during cycling at charge rates above 1C, improving battery stability and safety, while simultaneously reducing the battery's self-discharge rate.

[0007] The first aspect of this invention provides a battery comprising a negative electrode and an electrolyte. The surface of the negative electrode is divided into a single-sided region and a double-sided region. The double-sided region is a double-coated area with a total thickness of Y mm. The single-sided region is a single-coated area with an empty foil area on the opposite side, and the thickness of the single-sided coating is X mm. The ratio A of the thickness of the single-sided region to the thickness of the double-sided region is 0.5-0.65. The electrolyte comprises an organic solvent, including ethyl propionate and propyl propionate. Based on the total weight of the electrolyte, the weight content B of ethyl propionate is 0-50 wt%, and the weight content C of propyl propionate is 0-60 wt%. Then A, B, and C satisfy 2B+C≥400*(A-0.5).

[0008] In one example, the electrolyte further includes a first additive having the structure shown in formula (I).

[0009]

[0010] Wherein, R1, R2, R3, R4, R5, R6, R7, R8, and R9 are each independently selected from H, substituted or unsubstituted C1-C10 alkyl groups, and -CN, and at least one of R1, R2, and R3 is -CN; the substituents are selected from halogens, -C(=O)-R a -C(=O)-OC(=O)-R b C 6-14 Aryl, 5-14 heteroaryl, R a and R b Each alkyl group is independently selected from C1-C10.

[0011] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0012] (1) The battery of the present invention can prevent lithium plating during cycling at a charging rate of 1C or higher;

[0013] (2) This battery has a low self-discharge rate;

[0014] (3) This battery has high stability;

[0015] (4) This battery is highly safe.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0017] Figure 1 The image shown is a top view of a negative electrode sheet provided in an embodiment of the present invention.

[0018] Figure 2 The image shown is a side view of a negative electrode sheet provided in an embodiment of the present invention. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] The first aspect of this invention provides a battery comprising a negative electrode and an electrolyte. The surface of the negative electrode is divided into a single-sided region and a double-sided region. The double-sided region is a double-coated area with a total thickness of Y mm. The single-sided region is a single-coated area with an empty foil area on the other side, and the thickness of the single-sided coating is X mm. The ratio A of the thickness of the single-sided region to the thickness of the double-sided region is 0.5-0.65. The electrolyte comprises an organic solvent, including ethyl propionate and / or propyl propionate. Based on the total weight of the electrolyte, the weight content B of ethyl propionate is 0-50 wt%, and the weight content C of propyl propionate is 0-60 wt%. Then A, B, and C satisfy 2B+C≥400*(A-0.5).

[0021] The inventors of this invention have discovered that by improving the kinetics of the negative electrode single-sided region, lithium plating can be prevented during battery cycling at rates above 1C. Although carboxylic acid esters in the electrolyte can reduce the viscosity and increase the conductivity of the electrolyte, lithium plating can still occur during battery cycling at rates above 1C due to the smaller compaction and poorer kinetics of the negative electrode single-sided region.

[0022] After further in-depth research, the inventors of this invention discovered that in order to improve the kinetics of the single-sided region of the negative electrode, the compaction of the single-sided region can be correlated with the carboxylic acid esters (i.e., ethyl propionate (EP) and propyl propionate (PP)) in the electrolyte, thereby improving the kinetics of the single-sided region, preventing lithium plating in the battery, improving the stability and safety of the battery, and reducing the self-discharge level of the battery.

[0023] By setting the thickness ratio A of the single-sided to double-sided regions on the negative electrode surface, along with the weight content Bwt% of ethyl propionate (EP) and the weight content Cwt% of propyl propionate (PP), to satisfy 2B+C≥400*(A-0.5), the battery can achieve higher safety and lower discharge levels than existing technologies. To further improve the performance, one or more of these technical features can be further optimized.

[0024] The surface of the negative electrode 10 is divided into a single-sided region 30 and a double-sided region 20, and the division can be performed in accordance with conventional methods in the art. One division method is as follows: Figure 1 As shown, the single-sided area 30 is located at the beginning of the cell (the starting end of the winding).

[0025] In one instance, such as Figure 2As shown, the double-sided area 20 is a double-sided coated area, that is, there is a coating layer on both sides of the negative electrode 10. The thickness of the coating layer on one side of the negative electrode 10 is amm, and the thickness of the coating layer on the other side is bmm. Here, a and b can be the same or different. The total thickness Ymm of the double-sided coating layer is Ymm = amm + bmm, which refers to the sum of the thicknesses of the coating layers on both sides of the double-sided coated area.

[0026] In one instance, such as Figure 2 As shown, the single-sided area 30 is the area coated on one side of the negative electrode 10, that is, on the surface of the negative electrode 10, there is a coating layer on one side, the thickness of the coating layer is cmm, and there is no coating layer on the other side, which is an empty foil area; the thickness of the single-sided coating layer Xmm = cmm, that is, the thickness of the coating layer on the side with the coating layer.

[0027] In one example, the thickness of the single-sided coating layer, X mm = c mm, can be the same as or different from a mm or b mm.

[0028] In one example, the thickness of the single-sided coating layer is Xmm = cmm > amm, or the thickness of the single-sided coating layer is Xmm = cmm > bmm.

[0029] In one instance, such as Figure 2 As shown, the ratio A = cmm / (a+b)mm of the thickness of the single-sided area 30 (i.e., the thickness of the single-sided coating layer Xmm = cmm) to the thickness of the double-sided area 20 (i.e., the total thickness of the double-sided coating layer Ymm = amm + bmm) is 0.5-0.75 (e.g., 0.52, 0.53, 0.55, 0.57, 0.6, 0.62, 0.65, 0.67, 0.7, 0.73, 0.75).

[0030] In a preferred embodiment, the ratio A = cmm / (a+b)mm of the thickness Xmm = cmm of the single-sided area 30 to the thickness Ymm = amm + bmm of the double-sided area 20 is 0.53-0.57.

[0031] The organic solvent includes ethyl propionate (EP) and propyl propionate (PP). Based on the total weight of the electrolyte, the weight content of ethyl propionate (Bwt%) is 0-50wt%, and the weight content of propyl propionate (Cwt%) is 0-60wt%, and B and C are not both 0.

[0032] According to a preferred embodiment, based on the total weight of the electrolyte, the weight content of ethyl propionate (Bwt%) is 5-25wt%, and the weight content of propyl propionate (Cwt%) is 5-35wt%.

[0033] The condition A, B, and C satisfy 2B+C≥400*(A-0.5), indicating that the values ​​of A, B, and C satisfy the above formula.

[0034] The inventors of this invention control the ethyl propionate (EP) and propyl propionate (PP) in the electrolyte based on the thickness ratio of the single-sided and double-sided regions on the surface of the negative electrode. This improves the kinetics of the single-sided region at high rates, thereby preventing lithium plating, reducing the self-discharge of the battery, and enhancing the stability and safety of the battery.

[0035] According to one specific embodiment, the electrolyte further includes a first additive having the structure shown in formula (Ⅰ).

[0036]

[0037] Among them, R1, R2, R3, R4, R5, R6, R7, R8 and R9 may be the same or different, and each is independently selected from H, substituted or unsubstituted C1-C10 alkyl groups, and -CN.

[0038] C1-C10 alkyl groups can be represented as straight-chain or branched saturated alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms.

[0039] In one example, the alkyl group is selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl or 1,2-dimethylbutyl or isomers of the above alkyl groups.

[0040] In a preferred embodiment, the substituted or unsubstituted alkyl group is a C1-C6 alkyl group selected from methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl.

[0041] More preferably, the substituted or unsubstituted alkyl group can be a C1-C3 alkyl group, selected from methyl, ethyl, n-propyl, and isopropyl.

[0042] "Substituted or unsubstituted C1-C10 alkyl" means that the alkyl group can be substituted or can be left unsubstituted. For example, when the alkyl group is substituted by a halogen, one H in the alkyl group can be substituted by a halogen, multiple H can be substituted by a halogen, or all H can be substituted by a halogen.

[0043] At least one of R1, R2, and R3 is -CN, indicating that the number of -CN groups in R1, R2, and R3 can be 1, 2, or 3.

[0044] The substituent can be selected from halogens, -C(=O)-R a -C(=O)-OC(=O)-R b C 6-14 Aryl, 5-14 heteroaryl.

[0045] Halogens can be selected from one or more of F, Cl, Br and I.

[0046] R a and R b They may be the same or different, and each is independently selected from C1-C10 alkyl groups.

[0047] According to a preferred embodiment, R4, R5, R6, R7, R8, and R9 are each independently selected from the substituted C1-C6 alkyl groups, and R1, R2, and R3 are all -CN; the substituents are selected from -C(=O)-R a -C(=O)-OC(=O)-R b R a and R b Each alkyl group is independently selected from C1-C6.

[0048] In a preferred example, R a and R b Each alkyl group is independently selected from C1-C3.

[0049] In one instance, the first additive is selected from one or more of the following structures:

[0050]

[0051]

[0052] According to one specific embodiment, based on the total weight of the electrolyte, the weight content of the first additive is 0.1-5 wt% (e.g., 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%).

[0053] In one example, the weight content of the first additive is 0.5-2 wt% based on the total weight of the electrolyte.

[0054] The electrolyte may or may not include a second additive.

[0055] In one example, the electrolyte further includes a second additive selected from one or more of fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, succinic acid, adiponitrile, triacrylonitrile, 1,3,6-hexanetrionitrile, lithium difluorooxalate borate, lithium difluorophosphate, and lithium difluorodioxalate phosphate.

[0056] In one example, the weight content of the second additive is 0.01-15 wt% (e.g., 0.01 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 12 wt%, 15 wt%), based on the total weight of the electrolyte.

[0057] In one example, the weight content of the second additive is 5-12 wt%, based on the total weight of the electrolyte.

[0058] According to one specific embodiment, the electrolyte in the electrolyte is selected from lithium salts.

[0059] In one example, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(trifluoromethylsulfonyl)imide, lithium difluorobis(oxalate)phosphate, lithium tetrafluoroborate, lithium bis(oxalate)borate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium di(trifluoromethylsulfonyl)imide, lithium di(pentafluoroethylsulfonyl)imide, lithium tri(trifluoromethylsulfonyl)methyl, and lithium di(trifluoromethylsulfonyl)imide.

[0060] In one example, the electrolyte content is 11-18% by weight (e.g., 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%), based on the total weight of the electrolyte.

[0061] According to one specific embodiment, the organic solvent further includes carbonates and / or carboxylic esters.

[0062] In one example, the carbonate is selected from one or more of the following solvents, either fluorinated or unsubstituted: ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate.

[0063] In one example, the carboxylic acid ester is selected from one or more of the following solvents, either fluorinated or unsubstituted: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, methyl butyrate, and ethyl butyrate.

[0064] The content of the carbonate and / or carboxylate can be adjusted within a wide range. For example, when the sum of the weight contents of the above components is less than 100%, the insufficient part to 100% can be supplemented with carbonate and / or carboxylate.

[0065] The negative electrode plate comprises a negative electrode current collector and an active material layer coated on the surface of the negative electrode current collector, and the negative electrode material comprises a negative electrode active material, a conductive agent and a binder.

[0066] In one example, the negative electrode current collector is copper foil.

[0067] According to a specific embodiment, the negative electrode active material comprises a carbon-based active material and / or a silicon-based active material.

[0068] In one example, the carbon-based active material comprises one or more of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon and soft carbon.

[0069] In one example, the silicon-based active material is selected from nano-silicon, silicon-oxygen material (SiO x (0<x<2)) or one or more of silicon-carbon materials.

[0070] According to a specific embodiment, the negative electrode active material comprises a carbon-based active material and a silicon-based active material.

[0071] In one example, in the negative electrode active material, the mass ratio of the carbon-based active material to the silicon-based active material is 1:(0.1-19) (for example, 1:19, 1:18, 1:17, 1:16, 1:15, 1:14, 1:13, 1:12, 1:11, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 1:0.7, 1:0.5, 1:0.3, 1:0.1).

[0072] According to a specific embodiment, based on the total weight of the negative electrode material, the content of the negative electrode active material is 80-99.8wt%, the content of the conductive agent is 0.1-10wt%, and the content of the binder is 0.1-10wt%.

[0073] Preferably, based on the total weight of the negative electrode material, the content of the negative electrode active material is 90-99.6wt%, the content of the conductive agent is 0.2-5wt%, and the content of the binder is 0.2-5wt%.

[0074] According to a specific embodiment, the battery further comprises a positive electrode plate containing a positive active material and a separator.

[0075] The positive electrode sheet can be a conventional positive electrode sheet in the art. For example, the positive electrode sheet includes a positive current collector and a positive electrode material coated on one or both surfaces of the positive current collector. The positive electrode material includes a positive active material, a conductive agent, and a binder.

[0076] In one example, the positive electrode active material is selected from one or more of transition metal lithium oxides, lithium iron phosphate, and lithium-rich manganese-based materials.

[0077] In one example, the chemical formula of the transition metal lithium oxide is Li. 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; where M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr, such as lithium cobalt oxide.

[0078] In one example, the positive electrode material of the battery includes lithium cobalt oxide.

[0079] In one example, the conductive agent is selected from one or more of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0080] In one example, the adhesive is selected from one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0081] According to one specific embodiment, based on the total weight of the positive electrode material, the content of the positive electrode active material is 80-99.8 wt%, the content of the conductive agent is 0.1-10 wt%, and the content of the binder is 0.1-10 wt%.

[0082] Preferably, based on the total weight of the positive electrode material, the content of the positive electrode active material is 90-99.6 wt%, the content of the conductive agent is 0.2-5 wt%, and the content of the binder is 0.2-5 wt%.

[0083] In one example, the battery is a lithium-ion battery, such as a lithium cobalt oxide battery, a ternary lithium battery, or a lithium iron phosphate battery.

[0084] In a preferred embodiment, the battery is a lithium cobalt oxide battery.

[0085] In one example, the battery has a charge / discharge range of 3.0-4.45V.

[0086] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0087] The following examples illustrate the battery of the present invention.

[0088] Example 1

[0089] (1) Preparation of ingredients

[0090] Organic solvents: 20 parts by weight of ethyl propionate (EP), 10 parts by weight of propyl propionate (PP);

[0091] First additive: 1 part by weight of the first additive having the structure shown in formula (Ⅰ-2);

[0092] Second additive: 3 parts by weight of 1,3-propanesulfonyl lactone, 2 parts by weight of 1,3,6-hexanetrionitrile;

[0093] Lithium salt: 12.5 parts by weight of lithium hexafluorophosphate (LiPF6);

[0094] Other organic solvents: 6.5 parts by weight of fluoroethylene carbonate, 22.5 parts by weight of ethylene carbonate (EC), and 22.5 parts by weight of propylene carbonate (PC).

[0095] (2) Electrolyte preparation

[0096] In an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), EC / PC / EP / PP are mixed evenly, and then fully dried lithium hexafluorophosphate (LiPF6) is quickly added to dissolve it. After dissolution, fluoroethylene carbonate, 1,3-propane sulpholol, 1,3,6-hexanetrionitrile, and the first additive with the structure shown in formula (I-2) are added. The mixture is stirred evenly, and after passing the tests for moisture and free acid, the desired electrolyte is obtained.

[0097] (3) Negative electrode preparation

[0098] Artificial graphite, sodium carboxymethyl cellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP), and single-walled carbon nanotubes (SWCNTs) were mixed in a mass ratio of 96:1.5:1.5:0.95:0.05, and deionized water was added. The mixture was stirred in a vacuum mixer to obtain an anode active slurry. The anode active slurry was uniformly coated on both surfaces of a copper foil. The coated copper foil was dried at room temperature and then transferred to an 80°C oven for 10 hours. After adjusting the cold pressing parameters, the foil was slit to obtain anode sheets with a single-sided thickness X (mm) and a double-sided thickness Y (mm). The ratio A is shown in Table 1.

[0099] Example 2 group

[0100] This set of examples illustrates the effects of changing the weight percentage (Bwt%) of ethyl propionate (EP).

[0101] This set of examples is based on Example 1, except that the weight content of ethyl propionate (EP) is changed to Bwt%, and the total weight is adjusted to 100 by ethylene carbonate (EC) and propylene carbonate (PC) (i.e., ethylene carbonate (EC) (75-BC) / 2 parts by weight, propylene carbonate (PC) (75-BC) / 2 parts by weight), while the weight parts of other substances remain unchanged. See Table 1 for details.

[0102] Example 3 Group

[0103] This set of examples illustrates the effects of changing the weight content (Cwt%) of propyl propionate (PP).

[0104] This set of examples is based on Example 1, except that the weight content of propyl propionate (PP) (Cwt%) is changed, and the total weight is adjusted to 100 by ethylene carbonate (EC) and propylene carbonate (PC) (i.e., ethylene carbonate (EC) (75-BC) / 2 parts by weight, propylene carbonate (PC) (75-BC) / 2 parts by weight), while the weight parts of other substances remain unchanged. See Table 1 for details.

[0105] Example 4 group

[0106] This set of examples is used to illustrate the effect of changing the ratio A of the coating thickness of the single-sided area to the coating thickness of the double-sided area of ​​the negative electrode.

[0107] This set of embodiments is based on Embodiment 1, except that by adjusting the cold pressure generation, A is changed while the components of the electrolyte remain unchanged, as detailed in Table 1.

[0108] Example 5

[0109] The procedure was carried out in accordance with Example 1, except that the electrolyte did not contain the first additive, as detailed in Table 1.

[0110] Example 6

[0111] The procedure was carried out in accordance with Example 1, except that the electrolyte did not contain a second additive, as detailed in Table 1.

[0112] Comparative Example 1

[0113] The process was carried out in accordance with Example 1, except that ethyl propionate (EP) was not added to the electrolyte, and ethylene carbonate (EC) and propylene carbonate (PC) were used to make up the amount (i.e., ethylene carbonate (EC) (75-C) / 2 parts by weight, propylene carbonate (PC) (75-C) / 2 parts by weight), while the weight parts of other substances remained unchanged, as detailed in Table 1.

[0114] Comparative Example 2

[0115] The procedure was carried out in accordance with Example 1, except that propyl propionate (PP) was not added to the electrolyte, the weight of ethyl propionate (EP) was changed to 5, and it was made up with ethylene carbonate (EC) and propylene carbonate (PC) (i.e., ethylene carbonate (EC) (75-B) / 2 parts by weight, propylene carbonate (PC) (75-B) / 2 parts by weight), while the weight of other substances remained unchanged, as detailed in Table 1.

[0116] Comparative Example 3

[0117] The procedure was carried out in accordance with Example 1, except that the value of A was changed to 0.68 by adjusting the cold pressure, while the components of the electrolyte remained unchanged, as detailed in Table 1.

[0118] Table 1

[0119]

[0120] Preparation Example

[0121] The electrolytes and negative electrode sheets obtained in the examples and comparative examples were used to prepare batteries in the following manner.

[0122] (1) Preparation of positive electrode

[0123] Lithium cobalt oxide (LiCoO2), polyvinylidene fluoride (PVDF), super P (SP), and carbon nanotubes (CNT) were mixed in a mass ratio of 96:2:1.5:0.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until it formed a uniform and fluid positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil. The coated aluminum foil was dried, and then rolled and slit to obtain the desired positive electrode sheet.

[0124] (2) Preparation of negative electrode

[0125] The negative electrode sheets obtained from the above embodiments and comparative examples were used respectively.

[0126] (3) Electrolyte

[0127] The electrolytes obtained in the above-described embodiments and comparative examples were used respectively.

[0128] (4) Preparation of lithium-ion batteries

[0129] After stacking the positive electrode sheet from step (1), the negative electrode sheet from step (2), and the separator in the order of positive electrode sheet, separator and negative electrode sheet, the cells are then wound to obtain the battery cell. The battery cell is placed in the outer packaging aluminum foil, and the electrolyte from step (3) is injected into the outer packaging. After vacuum sealing, standing, formation, shaping and sorting, the battery is obtained.

[0130] Test case

[0131] The batteries obtained in the examples and comparative examples were subjected to the following tests:

[0132] (1) Lithium plating test at 10℃ and 1C direct charge

[0133] The batteries in Table 1 were charged at 10°C to the cutoff voltage at a rate of 1C and the cutoff current was 0.025C. After standing for 5 minutes, they were discharged at a rate of 1C to the cutoff voltage. This charge-discharge cycle was repeated for 50 cycles. After charging at a rate of 1C to the cutoff voltage and cutoff current, the batteries were left to stand for 1 hour. The batteries were then disassembled, and the presence of obvious lithium plating on the negative electrode was observed. If there was a silvery-white substance on the negative electrode, it indicated "lithium plating". If there was no silvery-white substance on the negative electrode, it indicated "no lithium plating".

[0134] (2) Battery self-discharge k-value test

[0135] The batteries in Table 1 (3 batteries per example) were charged at 25°C at a rate of 1C to the cutoff voltage with a cutoff current of 0.025C. After standing for 5 minutes, the open-circuit voltage OCV1 (in volts V) of the lithium-ion battery was tested. The fully charged cells / batteries were then left open-circuit at (25±2)°C for 24 hours. The voltage OCV2 after the open-circuit period was tested, and the self-discharge coefficient k of the lithium-ion battery was calculated.

[0136] K = (OCV1 - OCV2) / 24.

[0137] The results are recorded in Table 2.

[0138] Example 1 Non-lithium plating 0.046 Example 2a Non-lithium plating 0.072 Example 2b Non-lithium plating 0.041 Example 3a Non-lithium plating 0.044 Example 3b Non-lithium plating 0.051 Example 4a Non-lithium plating 0.039 Example 4b Non-lithium plating 0.067 Example 5 Non-lithium plating 0.092 Example 6 Non-lithium plating 0.048 Comparative Example 1 Lithium plating 0.153 Comparative Example 2 Lithium plating 0.151 Comparative Example 3 Lithium plating 0.243

[0139] As can be seen from Table 2, and through the comparative examples and embodiments, the self-discharge level of the battery in the embodiments is significantly reduced, which can prevent lithium plating during the cycling process. This indicates that the present invention improves the kinetics of the single-sided region by combining the compaction of the single-sided region with the carboxylic acid esters (i.e., ethyl propionate (EP) and propyl propionate (PP)) in the electrolyte, thereby preventing lithium plating in the battery, improving battery safety, and reducing the self-discharge level of the battery.

[0140] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a negative electrode and an electrolyte. The surface of the negative electrode is divided into a single-sided area and a double-sided area. The double-sided area is a double-coated area with a total thickness of Y mm. The single-sided area is a single-coated area with an empty foil area on the other side, and the thickness of the single-sided coating is X mm. The thickness ratio A of the single-sided coating thickness in the single-sided area to the total thickness of the double-sided coating in the double-sided area is 0.52-0.

65. The electrolyte includes an organic solvent, which includes ethyl propionate and propyl propionate. Based on the total weight of the electrolyte, the weight content B of ethyl propionate is 5-25 wt%, and the weight content C of propyl propionate is 5-35 wt%. Then A, B, and C satisfy 2B+C≥400×(A-0.5).

2. The battery according to claim 1, wherein, The ratio A of the thickness of the single-sided area to the thickness of the double-sided area is 0.53-0.

57.

3. The battery according to claim 1 or 2, wherein, The electrolyte further includes a first additive having the structure shown in formula (Ⅰ). Equation (Ⅰ), wherein R1, R2, R3, R4, R5, R6, R7, R8and R9are each independently selected from H, substituted or unsubstituted C1-C10alkyl, -CN, and at least one of R1, R2and R3is -CN; the substituents are selected from halogen, -C(=O)-R a , -C(=O)-O-C(=O)-R b , C 6-14 aryl, 5-14 membered heteroaryl, R a and R b are each independently selected from C1-C10alkyl.

4. The battery according to claim 3, wherein, R4, R5, R6, R7, R8, and R9 are each independently selected from substituted C1-C6 alkyl, and R1, R2, and R3 are all -CN; the substituents are selected from -C(=O)-R a , -C(=O)-O-C(=O)-R b , -C(=O)-O-R a , and -C(=O)-R b are each independently selected from C1-C6 alkyl.

5. The battery according to claim 4, wherein, The first additive is selected from one or more of the following structures: (Ⅰ-1)、 (Ⅰ-2)、 (Ⅰ-3)、 (Ⅰ-4)、 (Ⅰ-5)、 (Ⅰ-6)。 6. The battery according to claim 3, wherein, Based on the total weight of the electrolyte, the weight content of the first additive is 0.1-5 wt%.

7. The battery according to claim 6, wherein, Based on the total weight of the electrolyte, the weight content of the first additive is 0.5-2 wt%.

8. The battery according to claim 3, wherein, The electrolyte further includes a second additive selected from one or more of the following: fluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propenesulfonate lactone, succinic acid nitrile, adiponitrile, triacrylonitrile, 1,3,6-hexanetrionitrile, lithium difluorooxalate borate, lithium difluorophosphate, and lithium difluorodioxalate phosphate.

9. The battery according to claim 8, wherein, Based on the total weight of the electrolyte, the weight content of the second additive is 0-15 wt%.

10. The battery according to claim 1, wherein, The positive electrode material of the battery includes lithium cobalt oxide.

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