Wound battery

Abstract

The invention relates to the field of batteries, and provides a coiled battery, a positive electrode active material in the coiled battery contains an aluminum element, the volume particle size of the positive electrode active material is in bimodal distribution, the particle sizes corresponding to two peak values are respectively F1 and F2, F1 is 2-8, F2 is 12-25, and the unit is [mu] m; the negative electrode active material comprises a silicon-based material and a carbon-based material; wherein Ac is the mass content of the aluminum element in the positive electrode active material, Ac is 5000-9000, and the unit is ppm; ws is the mass content of the silicon element in the negative electrode active material and is 1%-20%; f3 is the particle size corresponding to the highest peak value in the volume particle size distribution curve of the negative electrode active material, F3 is 6-20, and the unit is [mu] m; sigma is the breaking strength of the negative electrode current collector, sigma is greater than or equal to 400, and the unit is MPa. The battery provided by the invention has high energy density, and also has relatively good cycling stability and electrochemical performance.

Description

Technical Field

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

[0002] Lithium-ion batteries have brought convenience to people, and to meet the ever-increasing demands, lithium battery technology is developing rapidly, with the main development directions being performance improvement and safety assurance. The key performance characteristics of lithium batteries are high-rate charging and higher energy density. How to select various materials and coordinate them to achieve optimal performance is also an essential research topic. However, a single battery system often cannot cover all battery performance aspects; therefore, for specific needs, battery systems can be designed to achieve the desired results.

[0003] To improve battery energy density, materials can be used to increase the specific capacity of active materials, such as using high-cutoff-voltage lithium cobalt oxide for the positive electrode and silicon-based materials for the negative electrode. In terms of core structure, methods like increasing areal density and compaction density can be employed. However, these methods all introduce side effects. High cutoff voltage may lead to irreversible phase transitions in the materials, causing capacity decay, while silicon-based materials may cause the negative electrode sheet to expand and stretch. Overcoming these side effects and showcasing the superior performance of the materials requires designing a robust battery structure that minimizes the interactions between various materials through overall design. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned problems existing in the prior art and provide a wound battery with high energy density, as well as good cycle stability and electrochemical performance.

[0005] To achieve the above objectives, the present invention provides a wound battery comprising a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material containing aluminum, and the volumetric particle size of the positive electrode active material exhibits a bimodal distribution. The volumetric particle size of the positive electrode active material also exhibits a bimodal distribution, with the two peaks corresponding to particle sizes F1 and F2, where F1 is 2-8 μm and F2 is 12-25 μm. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer comprises a negative electrode active material, which includes silicon-based materials and carbon-based materials. Wherein, Ac is the mass content of aluminum in the positive electrode active material, and Ac is 5000-9000, with the unit being ppm; Ws is the mass content of silicon in the negative electrode active material, and Ws is 1%-20%; F3 is the particle size corresponding to the highest peak value in the volume particle size distribution curve of the negative electrode active material. F3 is 6-20, and the unit is μm. σ is the fracture strength of the negative electrode current collector, σ≥400, and the unit is MPa.

[0006] The present invention, by adopting the above technical solution, has the following beneficial effects: This invention increases the surface density and compaction density of the positive electrode by controlling the particle size and Al content of the positive electrode active material, stabilizing the structure of the positive electrode active material, reducing side reactions with the electrolyte, alleviating battery gas generation and active lithium consumption, and improving battery cycle stability. By controlling the particle size, silicon content, and fracture strength of the negative electrode current collector, it alleviates the volume expansion caused by silicon-based materials, thereby mitigating gas generation and lithium plating problems caused by expansion. It also improves the yield of battery cores, avoids problems such as excessive electrode stretching and electrode breakage during cycling, and improves the battery's rate charging performance and cycle performance. By controlling the particle size of the positive electrode active material containing two different particle sizes, the peak particle size of the negative electrode active material, the amount of Al added to the positive electrode active material and the amount of silicon added to the negative electrode active material, and the fracture strength of the negative electrode current collector, the invention achieves a battery with high energy density, good cycle stability, and excellent electrochemical performance.

[0007] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In this document, unless otherwise specified, data ranges include endpoints. Attached Figure Description

[0008] Figure 1 This is a volumetric particle size distribution diagram of the positive electrode active material in Example 1. Detailed Implementation

[0009] 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.

[0010] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0011] This invention provides a battery comprising a positive electrode and a negative electrode. The positive electrode comprises a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer comprises a positive active material containing aluminum, and the volumetric particle size of the positive active material exhibits a bimodal distribution. The positive active material layer contains an Al-containing positive active material, and the volumetric particle size of the positive active material exhibits a bimodal distribution, with the two peaks corresponding to particle sizes F1 and F2, respectively, in μm; F1 < F2. The negative electrode comprises a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The negative active material layer comprises a negative active material, and the negative active material comprises silicon-based material and carbon-based material.

[0012] Ac represents the mass content of aluminum in the positive electrode active material, expressed in ppm. Ws is the mass content of silicon in the negative electrode active material; F3 is the particle size corresponding to the highest peak value in the volume particle size distribution curve of the negative electrode active material, in μm; σ is the fracture strength of the negative electrode current collector, in MPa.

[0013] The particle size distribution of the positive electrode active material exhibits two peaks, indicating that it is composed of particles of two different sizes. This composition enhances the compactness of the particle packing, increases the areal density and compaction density of the positive electrode sheet, and allows for a greater load of active material within a limited space, thus providing more energy to the battery. Simultaneously, the combination of large and small particle sizes also improves the performance of the positive electrode sheet, such as enhancing its processing performance, improving the adhesion between particles and adhesive, improving its flexibility, and increasing its rate performance. Al doping significantly impacts the performance of the positive electrode active material, increasing its cutoff voltage, improving its high-temperature stability, ensuring a larger specific capacity, and maintaining capacity during high-temperature cycling of the battery cell. Adding silicon-based materials to the negative electrode active material further increases its specific capacity, reduces its coating areal density, and decreases the space occupied by the negative electrode sheet, thereby increasing the battery's energy density. The silicon content affects the expansion and stretching of the negative electrode. During charging and discharging, the repeated expansion and recovery of silicon particles in the negative electrode can easily lead to relative displacement between particles and between particles and the current collector. This ultimately increases the electrode surface resistance, causes powder shedding, and increases electrode expansion and stretching, increasing pressure on the membrane and ultimately leading to battery failure. A solution can effectively alleviate the stress effect of silicon expansion on the electrode, reducing electrode expansion and stretching. This allows the user to benefit from the high specific capacity provided by silicon while preventing electrode expansion and stretching caused by silicon particles.

[0014] In some embodiments, Ac is 5000-9000, such as 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, and 9000. The type and content of doping elements in the cathode active material have a significant impact on its performance. The presence of Al increases the operating voltage of the cathode active material, thereby increasing its specific capacity. Simultaneously, the Al-O bond is more stable, playing a stabilizing role in the structure of the cathode active material and inhibiting the dissolution of elements such as cobalt, thus enhancing the high-temperature and cycle stability of the cathode active material. Too little Al doping leads to poor cycle stability; too much Al doping reduces the specific capacity of the cathode active material, thereby reducing the battery energy density.

[0015] In this invention, the content of elements can be obtained using ICP testing.

[0016] In some embodiments, F1 is 2-8, such as 2, 3, 4, 5, 6, 7, 8. In some embodiments, F2 is 12-25, such as 12, 14, 16, 18, 20, 22, 25. The volumetric particle size distribution of the positive electrode active material is bimodal, allowing small particles to fill the gaps between large particles, increasing the areal density of the positive electrode sheet. This facilitates the rolling of the positive electrode sheet, thereby increasing the compaction density and increasing the energy density of the battery cell, while reducing electrode thickness rebound. It also increases the contact area between the positive electrode surface and the electrolyte, increases the contact area between the positive electrode active material particles, increases the ion transfer rate, and prevents gas generation and active lithium consumption caused by excessively large particle surface area and increased side reactions with the electrolyte. If F1 is too large or F2 is too small, it will lead to problems such as insufficient electrode compaction density, thicker electrodes, and reduced electrode flexibility, affecting energy density and process yield. If F1 is too small or F2 is too large, it will lead to increased battery side reactions or decreased rate performance.

[0017] In this invention, the particle size of the material can be determined by a laser particle size analyzer.

[0018] Yc is the compaction density of the positive electrode, in g / cm³. 3 Mc is the areal density of the positive electrode active material layer, in mg / cm³. 2 .

[0019] In some embodiments, Yc is 3-5, such as 3, 3.5, 4, 4.5, 5.

[0020] In some embodiments, Mc is 11.2-19.8, such as 11.2, 12, 13, 14, 15, 16, 17, 18, 19, 19.8.

[0021] In this invention, the areal density of the electrode sheet can be calculated by cutting a 15.0425 cm² circular sheet, weighing it, subtracting the weight of the foil, and dividing the weight by the area. The compacted density can be calculated by dividing the areal density by the coating thickness.

[0022] In some embodiments, the positive electrode active material comprises at least one of the following substances, either doped with aluminum or undoped with aluminum: lithium nickel cobalt manganese oxide, lithium nickel cobalt oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, preferably comprising lithium cobalt oxide, either doped with aluminum or undoped with aluminum, and / or lithium nickel cobalt manganese oxide, either doped with aluminum or undoped with aluminum.

[0023] In some embodiments, the positive electrode active material layer further comprises a conductive agent and a binder. The conductive agent and binder can be conventional conductive agents and binders in the art. In one embodiment, the conductive agent comprises, but is not limited to, at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber. In one embodiment, the binder comprises, but is not limited to, at least one of carboxymethyl cellulose (CMC) (or its sodium salt), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyethylene oxide, and polyvinylidene fluoride.

[0024] In some embodiments, the content of the positive electrode active material in the positive electrode active material layer is 94 wt% to 98.5 wt%, for example, 94 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 98.5 wt%; the content of the binder is 0.7 wt% to 5 wt%, for example, 0.7 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%; and the content of the conductive agent is 0.8 wt% to 5 wt%, for example, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0025] In some embodiments, the positive current collector may be aluminum foil or composite aluminum foil.

[0026] In some embodiments, F3 is 6-20, such as 6, 8, 10, 12, 14, 16, 18, or 20. The particle size of the negative electrode active material affects the compaction density and thickness rebound of the negative electrode sheet. When F3 is smaller, the particle gaps are smaller, the expansion space is smaller, and the thickness rebound of the electrode sheet after rolling is larger, which can easily lead to poor cell manufacturing thickness and excessive cycle expansion. When F3 is larger, it will affect the rate performance of the cell, increase the lithium-ion insertion distance, and increase the polarization internal resistance of the battery. If the F3 size does not meet the range, it will lead to increased expansion of the negative electrode sheet and increased process defect rate due to the thickness of the core, and will also affect the rate charging performance and cycle performance of the battery.

[0027] In this invention, a laser diffraction particle size analyzer is used for measurement.

[0028] In some embodiments, Ws is 1%-20%, such as 1%, 5%, 10%, 15%, and 20%. Doping silicon into the negative electrode can effectively increase its specific capacity, thereby reducing the areal density of the negative electrode and the amount of active material used, thus improving the battery's energy density. However, the presence of silicon can cause a series of problems, including expansion and stretching of the negative electrode, battery volume expansion, gas generation, and lithium plating, reducing the battery's cycle life. Using silicon content and particle size within a suitable range, combined with a negative electrode current collector of appropriate strength, and integrating it with the positive electrode, can leverage the advantages of high energy density and good material stability of both electrodes while avoiding the risk of cycle failure caused by electrode expansion and stretching. This mitigates problems such as volume expansion, gas generation, and lithium plating, resulting in a battery with excellent cycle performance and rate charging performance.

[0029] In this invention, the test method for Ws can be as follows: negative electrode ash content test, weigh more than 2g of negative electrode active material, record the weight W1, keep it at 800℃ in air for 10 hours, cool it to room temperature, and record the weight W2, Ws=W2 / W1.

[0030] In some embodiments, σ ​​≥ 400, such as 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, or 900, preferably σ ≥ 500. The strength of the negative electrode current collector affects the yield of the core manufacturing process and the occurrence of problems such as excessive electrode stretching and electrode breakage that may occur during battery cycling. In some embodiments, the negative electrode current collector can be copper foil or a composite current collector.

[0031] In this invention, the breaking strength of the negative electrode current collector can be tested as follows: The current collector (foil) is cut into strips of 15mm ± 0.2mm. Using a WD-D3 electronic universal testing machine with a 50mm gap between the upper and lower clamps, both ends of the foil are clamped in the clamps. The test is started at a speed of 100mm / min and continues until the equipment stops. The breaking strength σ is recorded. The error of three tests should not exceed 10%, and the average value is taken.

[0032] In some embodiments, the negative electrode active material layer further comprises a conductive agent. The type of conductive agent can be the same as that in the positive electrode active material layer, and may be the same or different in specific applications.

[0033] Ya is the compaction density of the negative electrode, in g / cm³. 3 Ma represents the density of the negative electrode active material layer, in mg / cm³. 2 Wa represents the total mass content of negative electrode active material and conductive agent in the negative electrode active material layer.

[0034] In some embodiments, Ya is 0.9-1.9, such as 0.9, 1, 1.2, 1.4, 1.6, 1.8, or 1.9.

[0035] In some embodiments, Ma is 4-12, such as 4, 6, 8, 10, or 12.

[0036] In some embodiments, Wa is 96%-99%, such as 96%, 97%, 98%, or 99%.

[0037] In this invention, Wa can be tested using a thermogravimetric analyzer. The sample is kept at 80°C for 2 hours, and 0.05g of the sample is placed in an alumina crucible and heated to 600°C at 10°C / min under nitrogen atmosphere. The remaining weight is Wa.

[0038] In some embodiments, the carbon-based material comprises at least one of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon.

[0039] In some embodiments, silicon-based materials include silicon-carbon materials and silicon-oxygen materials (SiO2). x At least one of (x < 2) and nano-silicon materials.

[0040] In some embodiments, the negative electrode active material comprises artificial graphite and silicon carbide.

[0041] In some embodiments, the negative electrode active material layer further comprises a binder. The type of binder can be the same as that in the positive electrode active material layer, and may be the same or different in specific applications.

[0042] In some embodiments, the negative electrode active material layer contains 95 wt% to 99 wt% of the negative electrode active material, for example, 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 99 wt%; the binder contains 0.5 wt% to 3 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, or 3 wt%; and the conductive agent contains 0.5 wt% to 2 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, or 2 wt%.

[0043] In some embodiments, the battery is a lithium-ion battery.

[0044] In some embodiments, the battery further includes a separator and an electrolyte, with the positive electrode, separator, and negative electrode stacked together.

[0045] In some embodiments, the diaphragm comprises a base membrane. The base membrane may be made of materials conventional in the art, including but not limited to at least one of polyethylene, polypropylene, glass fiber, and nonwoven fabric. The diaphragm may be a single-layer film or a multi-layer composite film.

[0046] In some embodiments, the battery includes a battery assembly and a housing formed by stacking a positive electrode, a separator, and a negative electrode, with the battery assembly located within the housing. The housing may be an aluminum-plastic film. The battery may be a pouch cell battery.

[0047] In some embodiments, the electrolyte comprises an organic solvent and a lithium salt.

[0048] In some embodiments, the organic solvent comprises carbonates and / or carboxylic acid esters.

[0049] In some embodiments, the organic solvent comprises at least one of the following solvents, either fluorinated or unsubstituted: propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate, propyl propionate (PP), ethyl propionate (EP), methyl butyrate, ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate, diethyl carbonate (DEC), and methyl ethyl carbonate.

[0050] In some embodiments, the lithium salt comprises at least one 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.

[0051] In some embodiments, the concentration of lithium salt in the electrolyte is 0.8 mol / L-2 mol / L, for example, it can be 0.8 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, or 2 mol / L.

[0052] In some embodiments, the electrolyte further comprises functional additives.

[0053] In some embodiments, the functional additives include one or more of nitrile additives, carbonate additives, and organosulfur additives.

[0054] In some embodiments, the nitrile additives include at least one of ethylene glycol bis(propionitrile) ether, adiponitrile, butadionitrile (SN), 1,3,6-hexanetrionitrile (HTCN), glutaronitrile, trans-butenedionitrile, and trans-hexenedionitrile.

[0055] In some embodiments, the carbonate additive comprises at least one of fluoroethylene carbonate (FEC), difluoroethylene carbonate, vinylene carbonate (VC), and ethylene ethylene carbonate (VEC).

[0056] In some embodiments, the organosulfur additive comprises at least one of 1,3-propanesulfonate lactone (PS), 1,3-propenesulfonate lactone, 2,4-butanesulfonate lactone, 1,4-butanesulfonate lactone, and methylene disulfonate.

[0057] In some embodiments, the content of each component in the electrolyte can be the amount conventionally used in the art, and will not be elaborated further here. The electrolyte can be commercially available.

[0058] Unless otherwise specified, the other options for the lithium battery are conventional choices in the art. The battery assembly methods can all be performed in accordance with conventional methods in the art.

[0059] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0060] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0061] The present invention will now be described in detail with reference to specific embodiments, which are intended to understand rather than limit the invention.

[0062] The methods for measuring various parameters of the positive and negative electrodes in the battery in this embodiment include: (1) Breaking strength of negative electrode: Cut copper foil into strips of 15mm ± 0.2mm. Use a WD-D3 electronic universal testing machine with a 50mm gap between the upper and lower clamps. Clamp both ends of the foil in the clamps and start testing at a speed of 100mm / min until the equipment stops testing. Record the breaking strength σ. The error of 3 tests should not exceed 10%, and take the average value.

[0063] (2) Aluminum content in the positive electrode: ICP test was used.

[0064] (3) Particle size distribution test of positive electrode active material in positive electrode sheet: measured using laser diffraction particle size analyzer.

[0065] (4) Electrode surface density: Cut a 15.0425cm² circular sheet, weigh it, subtract the weight of the foil, divide the weight by the area, and calculate the surface density.

[0066] (5) Compacted density of the electrode: Divide the areal density by the thickness of the active material layer.

[0067] (6) Test method for Ws: Ash content test of negative electrode sheet. Weigh more than 2g of negative electrode active material and record the weight W1. Keep it at 800℃ in air for 10 hours. After cooling to room temperature, record the weight W2. Ws=W2 / W1.

[0068] (7) Test method for Wa: The thermogravimetric analyzer is used. The sample is kept at 80℃ for 2 hours. 0.05g of the sample is placed in an alumina crucible and heated to 600℃ at 10℃ / min under nitrogen atmosphere. The remaining weight is Wa.

[0069] Example 1 Group This embodiment is used to illustrate the method for preparing the battery according to the present invention.

[0070] In Examples 1-1 to 1-4, copper foils with different fracture strengths σ were used as negative electrode current collectors. The specific preparation methods of the batteries are shown below.

[0071] Positive electrode sheet: The positive electrode active material (two types of lithium cobalt oxide with different particle sizes, their particle size distribution diagrams are shown in the figure) Figure 1 The positive electrode sheet is prepared by mixing conductive carbon black, carbon nanotubes, and PVDF in NMP at a weight ratio of 95:1:1.5:2.5 (as shown), coating the mixture on aluminum foil, drying, rolling, cutting, soldering tabs, and applying adhesive tape. The lithium cobalt oxide is doped with aluminum.

[0072] Negative electrode sheet: CMC is added to deionized water, then graphite, silicon carbide particles, conductive carbon black, and carbon nanotubes are added and stirred to form a slurry. Finally, PAA and SBR are added and stirred to obtain a slurry (the weight ratio of graphite, silicon carbide, conductive carbon black, carbon nanotubes, CMC, PAA, and SBR is 88:10:0.1:0.1:0.3:1:0.5, i.e., Wa is 98.20%). The slurry is coated onto the negative electrode current collector, and then baked, rolled, cut, with tabs soldered, and adhesive tape applied to prepare the negative electrode sheet. The compaction density Ya of the negative electrode sheet is 1.62 g / cm³. 3 The density (Ma) of the negative electrode active material layer is 6.33 mg / cm³. 2 .

[0073] Electrolyte: An organic solvent is prepared by mixing ethylene carbonate (EC), fluoroethylene carbonate (FEC), and diethyl carbonate (DEC) in a weight ratio of 2.5:0.5:7, and then lithium hexafluorophosphate with a final concentration of 1 mol / L is added to it.

[0074] Separator: PE base membrane is used.

[0075] The positive and negative electrode sheets are separated by a separator, wound into a core, and then sealed in an aluminum-plastic film shell. The battery is then prepared by baking, liquid injection, formation, and secondary sealing.

[0076] The positive electrode active material exhibits a bimodal particle size distribution, with the two peaks corresponding to particle sizes F1 and F2, respectively, in μm; F1 < F2; Ac is the mass content of aluminum in the positive electrode active material, in ppm; Ws is the mass content of silicon in the negative electrode active material; F3 is the particle size corresponding to the highest peak in the volume particle size distribution curve of the negative electrode active material, in μm; σ is the fracture strength of the negative electrode current collector, in MPa; Yc is the compaction density of the positive electrode sheet, in g / cm³. 3 Mc is the areal density of the positive electrode active material layer, in mg / cm³. 2 The specific values ​​are shown in Table 1.

[0077] Comparative Example 1 The operation is carried out according to the method described in Example 1-1, except that the fracture strength σ of the negative electrode current collector is different, as shown in Table 1.

[0078] Example 2 and Comparative Example 2 The operation was carried out according to the method described in Example 1-1, except that the content of aluminum doped in the lithium cobalt oxide was different, as shown in Table 1.

[0079] Example 3 and Comparative Example 3 The operation is carried out according to the method described in Example 1-1, except that F1 is different, as shown in Table 1.

[0080] Example 4 and Comparative Example 4 The operation is carried out according to the method described in Example 1-1, except that F2 is different, as shown in Table 1.

[0081] Example 5 and Comparative Example 5 The operation is carried out according to the method described in Example 1-1, except that the mass content Ws of silicon element in the negative electrode active material is different, as shown in Table 1.

[0082] Example 6 and Comparative Example 6 The operation is carried out according to the method described in Example 1-1, except that F3 is different, as shown in Table 1.

[0083] Example 7 The operation is carried out according to the method described in Example 1-1, except that Wa is different, being 94%, while Ya and Ma remain unchanged.

[0084] Table 1 Note: In Table 1, the "*" designation is the same as in Example 1-1.

[0085] Test case The following describes the performance tests performed on the batteries prepared in the examples and comparative examples.

[0086] (1) Negative electrode elongation test: The battery was cycled at 25℃, charged at 1C constant current to 4.5V, charged at 4.5V constant voltage to 0.2C, and discharged at 0.7C to 3V. After 500 cycles, the battery was discharged to 3V. The battery was dissected, and the width of the electrode was measured using a 2.5D micrometer. The width of the electrode furthest from the active material layer in the double-sided empty foil area was recorded as S1, and the width of the active material layer area was recorded as S2. The electrode elongation was (S2-S1) / S1. The average of the five values ​​was taken.

[0087] (2) Battery energy density: Using a Newway battery tester, charge at 0.2C to the upper limit voltage (cutoff at 0.02C) / discharge at 0.2C to the lower limit voltage, repeat 3 times, and take the discharge energy of the 3rd discharge as the cell energy Q. Use a 2.5D microscope to measure the width W and height H of the cell, and use a PPG thickness tester to measure the full-charge thickness L of the cell. Then the energy density is Q / (W×H×L).

[0088] (3) Battery room temperature cycle performance test: At 25℃, charge at 1C to the cutoff voltage, charge at constant voltage to the 0.05C cutoff current, discharge at 1C to the lower limit voltage, and repeat the above charge and discharge steps 800 times.

[0089] The method for calculating the expansion rate after 50 cycles is as follows: Fully charge the incoming battery, test the full-charge thickness H1, cycle it for 50T according to the cycle regime, fully charge the battery, and test the thickness H2 after the cycle. The cycle expansion rate = (H2-H1) / H1×100%.

[0090] Capacity retention rate after 200 cycles: The capacity of the battery after 1 cycle is denoted as R1, and the capacity after 200 cycles is denoted as R2. The capacity retention rate = R2 / R1 × 100%.

[0091] (4) Battery high temperature cycle performance test: The battery is kept at a constant temperature of 45°C for 1 hour, then charged at 1C to the cutoff voltage, charged at constant voltage to the 0.05C cutoff current, and discharged at 1C to the lower limit voltage. The above charging and discharging steps are repeated 800 times.

[0092] The method for calculating the expansion rate after 50 cycles is as follows: Fully charge the incoming battery, test the full-charge thickness H1, cycle it for 50T according to the cycle regime, fully charge the battery, and test the thickness H2 after the cycle. The cycle expansion rate = (H2-H1) / H1×100%.

[0093] Capacity retention rate after 200 cycles: The capacity of the battery after 1 cycle is denoted as R1, and the capacity after 200 cycles is denoted as R2. The capacity retention rate = R2 / R1 × 100%.

[0094] (5) 25℃ rate charging performance test Calculation method for constant current charge ratio during 25℃ high-rate charging: 1. Constant current discharge, 0.5C discharge cutoff voltage is 3V; 2. Constant current charging, 1.5C charging, cutoff voltage is 4.5V, the charging capacity in this step is recorded as R3; 3. Constant voltage charging, cutoff current is 0.05C, the charging capacity in this step is recorded as R4; Constant current charge ratio = R3 / (R3+R4).

[0095] The results of the above tests are shown in Table 2.

[0096] Table 2 It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of the present invention is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0097] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A wound battery, characterized in that, The wound battery includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer contains a positive active material, which contains aluminum. The volumetric particle size of the positive active material exhibits a bimodal distribution, with the two peaks corresponding to particle sizes F1 and F2, respectively. F1 is 2-8 μm, and F2 is 12-25 μm. The negative electrode sheet includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The negative active material layer contains a negative active material, which comprises silicon-based materials and carbon-based materials. Wherein, Ac is the mass content of aluminum in the positive electrode active material, and Ac is 5000-9000, with the unit being ppm; Ws is the mass content of silicon in the negative electrode active material, and Ws is 1%-20%; F3 is the particle size corresponding to the highest peak value in the volume particle size distribution curve of the negative electrode active material. F3 is 6-20, and the unit is μm. σ is the fracture strength of the negative electrode current collector, σ≥400, and the unit is MPa.

2. The wound battery according to claim 1, characterized in that, σ≥500.

3. The wound battery according to claim 1 or 2, characterized in that, Yc is the compaction density of the positive electrode, where Yc is 3-5, and the unit is g / cm³. 3 .

4. The wound battery according to claim 1 or 3, characterized in that, Mc is the areal density of the positive electrode active material layer, ranging from 11.2 to 19.8 mg / cm³. 2 .

5. The wound battery according to any one of claims 1-4, characterized in that, The positive electrode active material contains at least one of the following substances, either doped or undoped with aluminum: lithium nickel cobalt manganese oxide, lithium nickel cobalt oxide, lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, preferably containing lithium cobalt oxide, either doped or undoped with aluminum, and / or lithium nickel cobalt manganese oxide, either doped or undoped with aluminum.

6. The wound battery according to any one of claims 1-5, characterized in that, The negative electrode active material layer also contains a conductive agent; Wa is the total mass content of the negative electrode active material and the conductive agent in the negative electrode active material layer, and Wa is 96%-99%.

7. The wound battery according to claim 6, characterized in that, Ya is the compaction density of the negative electrode, ranging from 0.9 to 1.9, with units of g / cm³. 3 ; and / or Ma is the density of the negative electrode active material layer; Ma is 4-12, and the unit is mg / cm³. 2 .

8. The wound battery according to any one of claims 1-7, characterized in that, Carbon-based materials include at least one of the following: artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, and soft carbon; and / or Silicon-based materials include at least one of silicon-carbon particles, silicon-oxygen particles, and nano-silicon particles; Preferably, the negative electrode active material comprises artificial graphite and silicon carbon particles.

9. The wound battery according to any one of claims 1-8, characterized in that, The wound battery is a lithium-ion battery.

10. The wound battery according to any one of claims 1-9, characterized in that, The wound battery also includes a separator and an electrolyte, with the positive electrode, separator and negative electrode stacked and wound into a core.

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