A battery, a battery pack, an electrical device, and a quality control method.

Abstract

This application provides a battery, a battery pack, an electrical device, and a quality control method. The battery includes a negative electrode sheet and an electrolyte. The negative electrode sheet includes a negative electrode active material, and the electrolyte includes a solvent, which includes ethylene carbonate. The battery has a K value of 0.8 to 1.2. K is calculated using Equation 1: Equation 1; In Equation 1, Φ is the porosity of the negative electrode sheet (%), d is the Dv10 of the negative electrode active material (μm), and w is the mass fraction of ethylene carbonate in the solvent (%). The battery of this application satisfies a K value of 0.8 to 1.2, which can effectively improve the problem of decreased charging efficiency of the battery in low-temperature environments without affecting the battery's cycle performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery, battery pack, electrical device and quality control method. Background Technology

[0002] As the core energy carrier for new energy vehicles, energy storage systems, and consumer electronics, the performance of secondary batteries directly affects the range, safety, and lifespan of these devices. In recent years, with the increasing prevalence of new energy vehicles in cold regions (such as the Arctic Circle, Siberia, and northern Canada), the ability to fast-charge batteries in extreme low-temperature environments has become a market necessity. For example, in cold-climate winters, users need vehicles to be charged in a very short time to address the range reduction issue caused by low temperatures.

[0003] However, current rechargeable batteries suffer severe performance degradation at low temperatures, especially in charging efficiency, which significantly hinders their commercial application in cold regions. To alleviate this problem, the industry has proposed various improvement solutions, but the results are often unsatisfactory: some solutions have failed to effectively improve battery charging performance at low temperatures, while others, while improving low-temperature charging performance to some extent, have led to a significant reduction in battery cycle performance.

[0004] Therefore, developing a battery with excellent low-temperature charging performance while maintaining stable battery cycle performance has become an urgent problem to be solved. Summary of the Invention

[0005] This application provides a battery that, by adjusting and matching the porosity of the negative electrode sheet, the Dv10 of the negative electrode active material, and the content of ethylene carbonate in the electrolyte, effectively improves the problem of low charging efficiency of the battery in low-temperature environments while maintaining stable battery cycle performance.

[0006] This application also provides a battery pack comprising at least two of the above-mentioned batteries, thus the battery pack has the advantage of good low-temperature charging performance.

[0007] This application also provides an electrical device including the aforementioned battery or battery pack, thus the electrical device has the advantage of rapid energy replenishment in low-temperature environments.

[0008] This application also provides a quality control method for batteries, which can effectively control the quality of batteries by detecting and judging the porosity of the negative electrode sheet, the Dv10 of the negative electrode active material, and the content of ethylene carbonate in the electrolyte.

[0009] This application provides a battery, including a negative electrode and an electrolyte. The negative electrode includes a negative electrode active material, and the electrolyte includes a solvent, specifically ethylene carbonate. The battery has a K value of 0.8 to 1.2; wherein K is calculated using Equation 1.

[0010] Formula 1;

[0011] In Formula 1, Φ is the porosity of the negative electrode sheet, in units of %; d is the Dv10 of the negative electrode active material, in units of μm; w is the mass fraction of ethylene carbonate in the solvent, in units of %.

[0012] In the battery described above, K is 1 to 1.2.

[0013] In the battery described above, Φ is 15%~35%; and / or, Dv10 is 3μm~15μm; and / or, w is 30%~80%.

[0014] In the battery described above, Φ is 20%~30%; and / or, Dv10 is 5μm~12μm; and / or, w is 35%~60%.

[0015] In the battery described above, the negative electrode active material includes at least one of graphite particles, hard carbon particles, and soft carbon particles.

[0016] As described above, the electrolyte further includes lithium salts, other solvents, and additives. The lithium salts include at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The other solvents include at least one of propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl propionate, trimethyl phosphate, triethyl phosphate, and ethyl acetate. The additives include at least one of vinylene carbonate and fluoroethylene carbonate.

[0017] In the battery described above, the mass ratio of the lithium salt, ethylene carbonate, other solvents, and additives is 5~30:10~90:10~80:0~15.

[0018] In the battery described above, the compaction density of the negative electrode sheet is 1.1 g / cm³. 3 ~1.8g / cm 3 ; and / or, the areal density of the negative electrode sheet on one side is 70 g / m³. 2 ~200g / m 2 ; and / or, the Dv50 of the negative electrode active material is 5μm~25μm; and / or, the Dv90 of the negative electrode active material is 10μm~40μm.

[0019] The battery as described above further includes a positive electrode sheet, the positive electrode sheet comprising a positive electrode active material; the porosity of the positive electrode sheet is 5% to 30%; and / or, the Dv10 of the positive electrode active material is 2 μm to 10 μm; and / or, the Dv50 of the positive electrode active material is 5 μm to 20 μm; and / or, the Dv90 of the positive electrode active material is 5 μm to 30 μm.

[0020] This application also provides a battery pack comprising at least two batteries as described in any one of the above claims.

[0021] This application also provides an electrical device, including any of the batteries described above, or the battery packs described above.

[0022] This application also provides a battery quality control method, comprising the following steps: 1) detecting the actual K value of the battery to be evaluated; 2) determining whether the actual K value meets a preset threshold; wherein the preset threshold is 0.8~1.2, and the actual K value is calculated according to Formula 1:

[0023] Formula 1;

[0024] In Equation 1, Φ is the porosity of the negative electrode sheet, in %; d is the Dv10 of the negative electrode active material, in μm; w is the mass fraction of ethylene carbonate in the electrolyte solvent, in %.

[0025] The battery provided in this application satisfies K as 0.8~1.2, where K is calculated by the porosity of the negative electrode sheet, the Dv10 of the negative electrode active material, and the mass fraction of ethylene carbonate in the electrolyte solvent. When the battery satisfies K, the above parameters can be mutually adapted, thereby effectively improving the problem of low charging efficiency of the battery at low temperatures while maintaining stable battery cycle performance. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] In low-temperature environments, rechargeable batteries generally suffer from low charging efficiency, which not only prolongs charging time but also limits charging capacity, making it difficult to meet current application requirements. Through analysis of the battery structure, the inventors discovered that the porosity of the electrodes and the particle size of the active material directly affect the liquid-phase or solid-phase diffusion resistance and electrochemical transfer resistance, while the electrolyte viscosity directly affects conductivity. Therefore, the inventors attempted to improve low-temperature charging performance by increasing electrode porosity, reducing the particle size of the active material, or decreasing electrolyte viscosity, but found that it was difficult to simultaneously achieve good low-temperature charging performance and cycle performance. Further research showed that these parameters do not act in isolation; only when they are appropriately matched can the overall charging performance of the battery be effectively improved.

[0028] Based on this, this application provides a battery, including a negative electrode sheet and an electrolyte, wherein the negative electrode sheet includes a negative electrode active material, the electrolyte includes a solvent, the solvent includes ethylene carbonate, and the battery has a K of 0.8~1.2.

[0029] Wherein, K is calculated using Equation 1:

[0030] Formula 1;

[0031] In Equation 1, Φ is the porosity of the negative electrode sheet, in %; d is the Dv10 of the negative electrode active material, in μm; w is the mass fraction of ethylene carbonate in the solvent, in %.

[0032] When calculating the K value, Φ and w, carrying the unit % (%), need to be substituted into the formula. For example, when Φ is 24.5% and w is 60%, 0.245 and 0.6 should be substituted into Equation 1 to calculate the K value.

[0033] It is worth noting that the negative electrode active material may include at least one of primary particles and secondary particles formed by the agglomeration of primary particles. The Dv10 of the negative electrode active material in this application does not distinguish between primary particles and secondary particles, that is, it is the Dv10 of all particles therein.

[0034] The electrolyte may contain one or more solvents. When one solvent is present, the solvent is ethylene carbonate, and w is 100%. When multiple solvents are present, w is the mass fraction of ethylene carbonate in all solvents.

[0035] In addition, the porosity of the negative electrode refers to the proportion of pore volume in the total volume of the negative electrode.

[0036] In detail, when charging batteries at low temperatures, the deposition rate of active ions on the negative electrode surface exceeds their embedding rate into the material, easily triggering irreversible lithium plating. Increasing the porosity of the negative electrode effectively enhances the wetting effect of the electrolyte, expands the active interface area involved in the reaction, and constructs a more complete liquid-phase ion diffusion channel. This helps reduce the liquid-phase diffusion impedance and electrochemical transfer impedance under low-temperature conditions, thereby increasing the negative electrode potential during charging and effectively suppressing lithium plating. To increase particle packing density, negative electrode active materials are typically composed of particles of different sizes. Under low-temperature conditions, electrolyte viscosity increases, and diffusion impedance rises. Particles with larger Dv10 have smaller active surface areas and longer solid-phase diffusion paths, limiting their reaction kinetics. At this time, particles with smaller Dv10 can provide lower electrochemical transfer impedance and solid-phase diffusion impedance, helping to increase the negative electrode potential and thus effectively suppressing lithium plating.

[0037] However, increasing the porosity of the negative electrode or reducing the Dv10 of the negative electrode active material increases the contact interface between the negative electrode and the electrolyte, promoting the formation of more SEI film. This not only leads to a decrease in the initial coulombic efficiency but also increases the risk of SEI film rupture and reconstruction during cycling, ultimately having an adverse effect on the long-term cycling stability of the battery.

[0038] Ethylene carbonate (EC) plays a crucial role in the formation and maintenance of a stable SEI film and is typically an indispensable component of the electrolyte. However, EC has a high melting point of 36°C, and its viscosity increases significantly at low temperatures. This leads to a decrease in the ionic conductivity of the electrolyte, hinders ion desolvation, and consequently exacerbates battery polarization. Furthermore, when dealing with high-viscosity electrolytes, even increasing the porosity of the negative electrode or reducing the Dv10 of the negative electrode active material is insufficient to improve the battery's charging performance at low temperatures. Therefore, it is necessary to rationally control the proportion of EC to ensure stable SEI film formation while balancing low-temperature charging performance and long-term cycle stability.

[0039] In summary, the compatibility between the porosity of the negative electrode, the Dv10 of the negative electrode active material, and the mass fraction of ethylene carbonate in the solvent is crucial for balancing the low-temperature charging performance and cycle performance of the battery. After extensive research, the inventors concluded that only when these parameters are properly matched and K is between 0.8 and 1.2 can the charging performance of the battery in low-temperature environments be effectively improved while maintaining high cycle stability.

[0040] When testing parameters in a battery, the discharged battery is disassembled and the negative electrode and electrolyte are removed. The porosity of the negative electrode can be tested, for example, by mercury porosimetry, and the mass fraction of ethylene carbonate in the electrolyte can be tested, for example, by gas chromatography.

[0041] When testing the Dv10 of the negative electrode active material, for example, the negative electrode sheet can be immersed in water to deactivate the binder, thereby separating the negative electrode active layer from the negative electrode current collector. The negative electrode active layer is then dissolved in NMP by grinding and pulverizing, heated at 120°C and stirred at 1200 rpm for 2 hours to fully dissolve the binder. The mixture is then filtered to obtain a solid material. After washing three times with NMP and then filtering again, the residual binder can be completely removed. Subsequently, the remaining system is added to water. Since the density of the negative electrode active material is greater than that of the conductive agent, the denser negative electrode active material sinks to the bottom, while the less dense conductive agent floats in the supernatant. By centrifuging the system at different speeds (5000-8000-10000-15000 rpm) and continuously removing the supernatant until no negative electrode active material is visible in the SEM of the supernatant and no conductive agent is visible in the lower layer, it can be determined that the conductive agent has been completely removed. The remaining solid material is then mixed, washed three times with deionized water, and dried to obtain the pure negative electrode active material. Subsequently, the Dv10 of the negative electrode active material was detected using a laser diffraction particle size analyzer.

[0042] Furthermore, when the K of the battery is 1~1.2, the porosity of the negative electrode sheet, the Dv10 of the negative electrode active material and the ethylene carbonate content are more matched, and the charging performance of the battery at low temperature is further improved.

[0043] In one specific implementation, Φ is 15%~35%.

[0044] In detail, when the porosity of the negative electrode is within the above range, the liquid phase diffusion resistance of the battery is better matched with the stability of the SEI film, and the low-temperature charging performance and cycle performance of the battery are further balanced.

[0045] In one specific implementation, Dv10 is 3μm~15μm.

[0046] In detail, when the Dv10 of the negative electrode active material is within the above range, the solid-phase diffusion impedance of the battery is better matched with the stability of the SEI film, and the low-temperature charging performance and cycle performance of the battery are further balanced.

[0047] In one specific implementation, w is 30% to 80%.

[0048] In detail, when the mass fraction of ethylene carbonate in the electrolyte solvent is within the above range, the ionic conductivity of the electrolyte and the stability of the SEI film are better matched, and the low-temperature charging performance and cycle performance of the battery are further balanced.

[0049] In one specific implementation, Φ is 15%~35%, which further improves the low-temperature charging performance of the battery.

[0050] In one specific implementation, Dv10 is 3μm~15μm, further improving the low-temperature charging performance of the battery.

[0051] In one specific implementation, w is 30%~80%, which further improves the low-temperature charging performance of the battery.

[0052] In one specific embodiment, the negative electrode active material includes at least one of graphite particles, hard carbon particles, and soft carbon particles.

[0053] In detail, the negative electrode active material can be primary particles, secondary particles, or a combination of both. When the negative electrode active material is selected as described above, it is a better match with ethylene carbonate, which is more conducive to improving the low-temperature charging performance of the battery.

[0054] In one specific embodiment, the electrolyte further includes lithium salts, other solvents, and additives. The lithium salts include at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The other solvents include at least one of propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl propionate, trimethyl phosphate, triethyl phosphate, and ethyl acetate. The additives include at least one of vinylene carbonate and fluoroethylene carbonate.

[0055] In detail, when the electrolyte includes lithium salt, the battery is more suitable for lithium-ion batteries. When the electrolyte composition is as selected above, the compatibility between the electrolyte and the negative electrode is higher, further improving the battery's low-temperature charging performance.

[0056] In one specific embodiment, the mass ratio of lithium salt, ethylene carbonate, other solvents and additives is 5~30:10~90:10~80:0~15.

[0057] In detail, when the proportions of the components in the electrolyte are selected as described above, the ion transport performance of the electrolyte and its effect on the stability of the SEI membrane are further improved, and the low-temperature charging performance of the battery is further improved.

[0058] In one specific embodiment, the compaction density of the negative electrode sheet is 1.1 g / cm³. 3 ~1.8g / cm 3 .

[0059] In detail, when the compaction density of the negative electrode sheet is within the above range, it is more conducive to improving the porosity of the negative electrode sheet, thereby improving the low-temperature charging performance of the battery.

[0060] In one specific embodiment, the areal density of the negative electrode sheet on one side is 70 g / m². 2 ~200g / m 2 .

[0061] In detail, when the areal density of the negative electrode is within the above range, the energy density of the negative electrode is further improved.

[0062] In one specific embodiment, the Dv50 of the negative electrode active material is 5μm~25μm.

[0063] In detail, when the Dv50 of the negative electrode active material is within the above range, the particle size distribution of the negative electrode active material is more suitable and more conducive to improving the low-temperature charging performance of the battery.

[0064] In one specific embodiment, the Dv90 of the negative electrode active material is 10 μm to 40 μm.

[0065] In detail, when the Dv50 of the negative electrode active material is within the above range, the particle size distribution of the negative electrode active material is more suitable and more conducive to improving the low-temperature charging performance of the battery.

[0066] In one specific embodiment, the battery further includes a positive electrode sheet, which comprises a positive electrode active material; the porosity of the positive electrode sheet is 5% to 30%.

[0067] In detail, when the porosity of the positive electrode is within the above range, the positive and negative electrodes are more well matched, and the low-temperature charging performance of the battery is further improved. The detection method for the porosity of the positive electrode can refer to the aforementioned detection method for the porosity of the negative electrode.

[0068] This application does not strictly limit the selection of positive electrode active materials. Taking lithium-ion batteries as an example, the materials can be, specifically, commonly used positive electrode active materials in lithium-ion batteries, such as at least one composite oxide of lithium with cobalt, manganese, nickel, or combinations thereof. More specifically, the materials can be at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0069] This application does not strictly limit the choice of separator material. Taking lithium-ion batteries as an example, it can be a separator material commonly used in lithium-ion batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, or separator with ceramic coating.

[0070] In the preparation of lithium-ion batteries, the positive electrode, separator, and negative electrode are wound or stacked to obtain a bare cell, which is then packaged into a pre-stamped aluminum-plastic film bag. After the packaged battery is dried, electrolyte is injected into the dried battery. The battery undergoes resting, formation, and secondary sealing to complete the battery preparation process.

[0071] In one specific embodiment, the Dv10 of the positive electrode active material is 2μm~10μm.

[0072] In detail, when the Dv10 of the positive electrode active material is within the above range, the positive and negative electrodes are more well matched, and the low-temperature charging performance of the battery is further improved.

[0073] In one specific embodiment, the Dv50 of the positive electrode active material is 5μm~20μm.

[0074] In detail, when the Dv50 of the positive electrode active material is within the above range, the positive and negative electrodes are more well matched, and the low-temperature charging performance of the battery is further improved.

[0075] In one specific embodiment, the Dv90 of the positive electrode active material is 5μm~30μm.

[0076] In detail, when the Dv90 of the positive electrode active material is within the above range, the positive and negative electrodes are more well matched, and the low-temperature charging performance of the battery is further improved.

[0077] This application also provides a battery pack comprising at least two of the aforementioned batteries, which has advantages corresponding to the aforementioned batteries, and will not be elaborated here.

[0078] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0079] This application also provides an electrical device including the aforementioned battery or the aforementioned battery pack, which has advantages corresponding to the aforementioned battery, and will not be elaborated here.

[0080] The electrical equipment used in this application can be conventional electrical equipment in the field, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without any particular limitation.

[0081] This application also provides a battery quality control method, comprising the following steps:

[0082] 1) Detect the actual K value of the battery to be evaluated;

[0083] 2) Determine whether the actual K value meets the preset threshold;

[0084] The preset threshold is 0.8~1.2, and the actual K value is calculated according to Equation 1:

[0085] Formula 1;

[0086] In Equation 1, Φ is the porosity of the negative electrode sheet, in %; d is the Dv10 of the negative electrode active material, in μm; w is the mass fraction of ethylene carbonate in the electrolyte solvent, in %.

[0087] This application does not limit the order of measurement of the parameters in the battery K-value formula. For example, the porosity Φ of the negative electrode sheet can be measured first, then the Dv10 of the negative electrode active material to be tested can be measured, and finally the mass fraction w of ethylene carbonate in the electrolyte solvent can be measured. The K-value can be calculated by Equation 1. This K-value is the actual K-value of the battery.

[0088] Then, the K values ​​obtained from different test samples are compared. If the K value is any value between 0.8 and 1.2, then the test sample is a battery that meets the high-quality requirements and is classified as a high-quality product; otherwise, it is classified as a general product.

[0089] This quality control method can be used to evaluate battery quality, select products that meet the K value of 0.8~1.2, and ensure that the selected products have high cycle stability while effectively improving charging performance in low-temperature environments.

[0090] The battery provided in this application will be described in detail below through specific embodiments.

[0091] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0092] Example 1

[0093] The battery preparation method of this embodiment includes the following steps:

[0094] 1) The binder (PVDF) and solvent (NMP) are dispersed evenly, followed by the addition of the conductive agent (carbon black) and further dispersion. Finally, the positive electrode active material (LFP, Dv10 5μm, Dv50 10μm, Dv90 20μm) is added and dispersed evenly. After vacuum defoaming, the positive electrode slurry is obtained. The mass ratio of the positive electrode active material, binder, conductive agent, and solvent is 95.5:2.5:2:60. The positive electrode slurry is evenly coated on both surfaces of the positive electrode current collector (aluminum foil) using a coating machine, controlling the areal density of the positive electrode sheet to be 400 g / m². 2 After drying and rolling, the compacted density is 2.5 g / cm³. 3 A positive electrode with a porosity of 20%;

[0095] 2) Disperse the dispersant (CMC) and solvent (deionized water) evenly, then add the conductive agent (carbon black), negative electrode active material (secondary graphite particles, Dv10 is 6μm, Dv50 is 11μm, Dv90 is 18μm), solvent (NMP), and binder (SBR) in sequence and disperse evenly. After vacuum defoaming, a negative electrode slurry is obtained. The mass ratio of negative electrode active material, dispersant, binder, conductive agent, solvent (NMP), and solvent (deionized water) is 94:2:2:2:5:100. Use a coating machine to evenly coat the negative electrode slurry on both surfaces of the negative electrode current collector (copper foil), controlling the areal density of the negative electrode sheet to be 185g / m². 2 After drying and rolling, the compacted density was 1.45 g / cm³. 3 The negative electrode plate;

[0096] 3) The above positive electrode sheet, negative electrode sheet and separator (PP) are stacked in sequence to obtain a bare cell. The bare cell is then packaged into a pre-stamped aluminum-plastic film bag. After drying, the electrolyte is injected into the dried battery. The battery is then vacuum-sealed, left to stand, formed and tested for capacity to obtain the battery. The electrolyte is a mixture of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate) and additive (ethylene carbonate) in a mass ratio of 10:60:40:2.

[0097] Example 2

[0098] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the compaction density of the negative electrode sheet is controlled to be 1.43 g / cm³. 3 .

[0099] Example 3

[0100] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 4 μm, the Dv50 is 8 μm, and the Dv90 is 12 μm, and the compaction density of the negative electrode sheet is controlled to be 1.55 g / cm³. 3The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:40:60:2.

[0101] Example 4

[0102] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the electrolyte is lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate) and additive (ethylene carbonate) in a mass ratio of 10:50:50:2.

[0103] Example 5

[0104] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 7 μm, the Dv50 is 13 μm, and the Dv90 is 23 μm, and the compaction density of the negative electrode sheet is controlled to be 1.4 g / m³. 2 The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:50:50:2.

[0105] Example 6

[0106] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 4 μm, the Dv50 is 8 μm, and the Dv90 is 12 μm, and the compaction density of the negative electrode sheet is controlled to be 1.5 g / m³. 2 The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:75:25:2.

[0107] Example 7

[0108] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 10 μm, the Dv50 is 16 μm, and the Dv90 is 27 μm, and the compaction density of the negative electrode sheet is controlled to be 1.35 g / m³. 2 The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:75:25:2.

[0109] Example 8

[0110] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 10 μm, the Dv50 is 16 μm, and the Dv90 is 27 μm, and the compaction density of the negative electrode sheet is controlled to be 1.5 g / m³. 2The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:35:65:2.

[0111] Example 9

[0112] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 6 μm, the Dv50 is 11 μm, and the Dv90 is 18 μm, and the compaction density of the negative electrode sheet is controlled to be 1.55 g / m³. 2 The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:63:37:2.

[0113] Example 10

[0114] The preparation method of the battery in this embodiment is basically the same as that in Example 1. The difference is that the Dv10 of the negative electrode active material is 6 μm, the Dv50 is 11 μm, and the Dv90 is 18 μm. The electrolyte is a lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:37:63:2.

[0115] Example 11

[0116] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that the Dv10 of the negative electrode active material is 6 μm, the Dv50 is 11 μm, and the Dv90 is 18 μm, and the compaction density of the negative electrode sheet is controlled to be 1.43 g / m³. 2 The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:66:34:2.

[0117] Example 12

[0118] The preparation method of the battery in this embodiment is basically the same as that in Example 1, except that primary graphite particles are used instead of secondary graphite particles, ethyl methyl carbonate is used instead of ethyl acetate, lithium bis(fluorosulfonyl)imide is used instead of lithium hexafluorophosphate, and fluoroethylene carbonate is used instead of vinylene carbonate.

[0119] Comparative Example 1

[0120] The preparation method of this comparative battery is basically the same as that of Example 1, except that the Dv10 of the negative electrode active material is 10 μm, the Dv50 is 16 μm, and the Dv90 is 27 μm, and the compaction density of the negative electrode sheet is controlled to be 1.5 g / m³. 2The electrolyte consists of lithium salt (lithium hexafluorophosphate), solvent (ethylene carbonate), solvent (ethyl acetate), and additive (ethylene carbonate) in a mass ratio of 10:75:25:2.

[0121] Experimental Example 1

[0122] At 25°C, charge the battery to 3.8V with a constant current and constant voltage of 1C / 0.05C and let it rest for 30 minutes; then discharge it to 2V with a constant current of 1C and let it rest for 30 minutes; repeat the above charging and discharging steps 3 times, and record the discharge capacity of the third discharge as C0.

[0123] The porosity, ethylene carbonate mass fraction in the electrolyte, battery K-value, low-temperature charging capability, low-temperature rate performance, and cycle performance of the negative electrode sheets in all examples and comparative examples were measured. The results are shown in Table 1.

[0124] Porosity Φ of negative electrode: The negative electrode is cut into 5mm diameter discs using a mold, vacuum dried until the weight is constant, and then the discs are tested in an automated mercury porosimeter (Autopore IV 9500) to obtain the cumulative mercury intrusion volume Vp and the apparent volume of the disc Vb. The porosity ɸ of the negative electrode is Vp / Vb.

[0125] The mass fraction of ethylene carbonate in the electrolyte, w: (mass of ethylene carbonate in the electrolyte / total mass of the electrolyte) × 100%;

[0126] The K value of the battery is calculated according to Equation 1.

[0127] Low-temperature charging capability: The battery was discharged to 2V at 1C constant current at 25℃, the ambient temperature was adjusted to -20℃, and it was left to stand for 2 hours. Then it was charged to 3.8V at 1C constant current. The charging capacity was recorded as C1. The low-temperature charging capacity retention rate of the battery was expressed as (C1 / C0)×100%.

[0128] Low-temperature fast charging efficiency: Using a three-electrode cell with a lithium-plated copper wire reference electrode, the battery was discharged to 2V at 1C constant current at 25℃. The ambient temperature was adjusted to -20℃ and left for 2 hours. Then, it was charged to 0mV at a constant current at different decreasing rates (starting from 3C, switching to the next lower rate each time the negative electrode potential reached 0mV, the rates being 3C / 2C / 1C / 0.5C / 0.1C respectively). The total charging time at different rates was recorded as t, and t represents the low-temperature charging time of the battery.

[0129] Cycling performance: The battery was charged and discharged at a constant current of 0.5C for 800 cycles at 60℃, with a cycle voltage range of 2V-3.8V. The capacity retention rate was recorded as (discharge capacity at the 800th cycle / discharge capacity at the first cycle) × 100%.

[0130] Table 1

[0131]

[0132] As shown in Table 1, the battery of this application can maintain high cycle performance and has the advantage of good low-temperature charging performance.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A battery, characterized in that, The battery includes a negative electrode sheet and an electrolyte, wherein the negative electrode sheet includes a negative electrode active material, the electrolyte includes a solvent, the solvent includes ethylene carbonate, and the K of the battery is 0.8~1.

2. Wherein, K is calculated using Equation 1: Formula 1; In Formula 1, Φ represents the porosity of the negative electrode sheet (%), d represents the Dv10 of the negative electrode active material (μm), and w represents the mass fraction of ethylene carbonate in the solvent (%). The Φ is 15%~35%, the Dv10 is 3μm~15μm, and the w is 30%~80%.

2. The battery according to claim 1, characterized in that, The K value of the battery is 1 to 1.

2.

3. The battery according to claim 1 or 2, characterized in that, The Φ is 20%~30%; and / or, The Dv10 is 5μm~12μm; and / or, The value of w is 35% to 60%.

4. The battery according to claim 1 or 2, characterized in that, The negative electrode active material includes at least one of graphite particles, hard carbon particles, and soft carbon particles; and / or, The electrolyte further includes lithium salts, other solvents, and additives. The lithium salts include at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The other solvents include at least one of propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl propionate, trimethyl phosphate, triethyl phosphate, and ethyl acetate. The additives include at least one of vinylene carbonate and fluoroethylene carbonate.

5. The battery according to claim 3, characterized in that, The negative electrode active material includes at least one of graphite particles, hard carbon particles, and soft carbon particles; and / or, The electrolyte further includes lithium salts, other solvents, and additives. The lithium salts include at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate. The other solvents include at least one of propylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl acetate, ethyl propionate, trimethyl phosphate, triethyl phosphate, and ethyl acetate. The additives include at least one of vinylene carbonate and fluoroethylene carbonate.

6. The battery according to claim 4, characterized in that, The mass ratio of the lithium salt, ethylene carbonate, other solvents and additives is 5~30:10~90:10~80:0~15.

7. The battery according to claim 5, characterized in that, The mass ratio of the lithium salt, ethylene carbonate, other solvents and additives is 5~30:10~90:10~80:0~15.

8. The battery according to claim 7, characterized in that, The compacted density of the negative electrode sheet is 1.1 g / cm 3 1.8 g / cm 3 ; and / or, The areal density of the negative electrode sheet is 70 g / m². 2 ~200g / m 2 ; and / or, The Dv50 of the negative electrode active material is 5μm~25μm; and / or, The Dv90 of the negative electrode active material is 10μm~40μm.

9. The battery according to claim 8, characterized in that, The battery also includes a positive electrode sheet, which includes a positive electrode active material; The porosity of the positive electrode is 5%~30%; and / or, The Dv10 of the positive electrode active material is 2μm~10μm; and / or, The Dv50 of the positive electrode active material is 5μm~20μm; and / or, The Dv90 of the positive electrode active material is 5μm~30μm.

10. A battery pack, characterized in that, It includes at least two batteries as described in any one of claims 1-9.

11. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 1-9, or the battery pack as described in claim 10.

12. A method for quality control of a battery, characterized in that, Includes the following steps: 1) Detect the actual K value of the battery to be evaluated; 2) Determine whether the actual K value meets the preset threshold; The preset threshold is 0.8 to 1.2, and the actual K value is calculated according to Equation 1: Formula 1; In Equation 1, Φ is the porosity of the negative electrode sheet, in %; d is the Dv10 of the negative electrode active material, in μm; w is the mass fraction of ethylene carbonate in the electrolyte solvent, in %.

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