Quality control methods for batteries, battery packs, electrical equipment, and batteries

Abstract

This invention provides a battery, battery pack, electrical device, and a quality control method for the battery. The battery includes a positive electrode and a negative electrode; the positive electrode includes a positive active material layer; the negative electrode includes a negative active material layer; the positive active material layer includes a positive active material; the negative active material layer includes a carbon-based negative active material; the battery satisfies: 0.4 ≤ A × C / B ≤ 0.95; where A is the Dv50 of the positive active material, in μm, 3μm ≤ A ≤ 5μm; B is the Dv50 of the carbon-based negative active material, in μm, 6μm ≤ B ≤ 13μm; C is the N / P ratio of the battery, 1.25 ≤ C ≤ 1.6. The battery of this invention has low internal resistance and high capacity recovery rate at high temperatures.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a quality control method for batteries, battery packs, electrical devices, and batteries. Background Technology

[0002] Secondary batteries (i.e., rechargeable batteries) have advantages such as being able to be repeatedly charged and discharged, having high energy conversion efficiency, low long-term use cost, and being conducive to resource conservation and environmental protection. They are widely used in electric vehicles, energy storage systems, and portable electronic devices.

[0003] However, the performance of rechargeable batteries faces many challenges, among which high internal resistance is a key issue. Especially at low temperatures, the ionic conductivity of active metal ions decreases significantly, the diffusion rate of active metal ions in electrode materials slows down, and the interfacial charge transfer impedance increases significantly, leading to a sharp increase in internal resistance. This, in turn, causes a decrease in power output, charging difficulties, and even the risk of lithium plating. At the same time, at high temperatures, although the internal resistance of the battery decreases, the internal side reactions intensify. This not only consumes active metal ions and electrolytes but also causes electrode structure degradation, ultimately resulting in a decrease in battery capacity recovery rate and a shortened battery life, limiting the application of rechargeable batteries in extreme temperature environments.

[0004] Therefore, there is an urgent need for a method to reduce battery internal resistance and improve battery capacity recovery rate at high temperatures in order to expand the application of secondary batteries. Summary of the Invention

[0005] This invention provides a battery, battery pack, electrical equipment, and a battery quality control method, wherein the battery has low internal resistance and high capacity recovery rate at high temperatures.

[0006] This invention provides a battery, including a positive electrode and a negative electrode;

[0007] The positive electrode includes a positive active material layer; the negative electrode includes a negative active material layer;

[0008] The positive electrode active material layer includes a positive electrode active material;

[0009] The negative electrode active material layer includes a carbon-based negative electrode active material;

[0010] The battery satisfies: 0.4 ≤ A × C / B ≤ 0.95;

[0011] Wherein, A is the Dv50 of the positive electrode active material, expressed in μm, and 3μm≤A≤5μm;

[0012] B represents the Dv50 of the carbon-based negative electrode active material, expressed in μm, where 6μm≤B≤13μm;

[0013] C is the N / P ratio of the battery, where 1.25 ≤ C ≤ 1.6.

[0014] In some embodiments of the present invention, 1.4 ≤ C ≤ 1.6.

[0015] In some embodiments of the present invention, the areal density of the positive electrode active material layer is 114 g / m². 2 ~131g / m 2 The area of ​​the positive electrode active material layer is 0.27 m². 2 ~0.32 m 2 .

[0016] In some embodiments of the present invention, the areal density of the negative electrode active material layer is 66 g / m². 2 ~74 g / m 2 The area of ​​the negative electrode active material layer is 0.3 m². 2 ~0.35 m 2 .

[0017] In some embodiments of the present invention, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0018] In some embodiments of the present invention, the carbon-based negative electrode active material includes at least one of natural graphite and artificial graphite.

[0019] This invention also provides a method for preparing the battery as described above, comprising the following steps:

[0020] The method includes controlling the composition of the positive and negative electrode plates to make the N / P ratio of the battery 1.25~1.6, and 0.4≤A×C / B≤0.95.

[0021] Wherein, A is the average particle size of the positive electrode active material, expressed in μm, and 3μm≤A≤5μm;

[0022] B is the average particle size of the carbon-based negative electrode active material, expressed in μm, where 6μm≤B≤13μm;

[0023] C is the N / P ratio of the battery, where 1.25 ≤ C ≤ 1.6.

[0024] This invention also provides a battery pack comprising at least two batteries as described above.

[0025] This invention also provides an electrical device, including the battery as described above, or including a battery pack as described above.

[0026] This invention also provides a battery quality control method, comprising the following steps:

[0027] The current structural parameters of the positive electrode active material layer and the negative electrode active material layer of the battery are detected;

[0028] Determine whether the current structural parameters meet the preset threshold;

[0029] Wherein, the preset threshold is 0.4≤ ≤0.95, the current structural parameter is calculated according to the following formula:

[0030] = A×C / B;

[0031] in, ;

[0032] A represents the Dv50 of the positive electrode active material in the positive electrode active material layer, expressed in μm, where 3μm≤A≤5μm;

[0033] B is the Dv50 of the carbon-based negative electrode active material in the negative electrode active material layer, in μm, where 6μm≤B≤13μm;

[0034] C is the N / P ratio of the battery, where 1.25 ≤ C ≤ 1.6.

[0035] In some embodiments of the present invention, the battery quality control method further includes: if the current structural parameters of the battery do not meet the preset threshold, adjusting the coating quality of the positive electrode active material, the coating quality of the carbon-based negative electrode active material, the coating area of ​​the positive electrode active material layer, and the coating area of ​​the negative electrode active material layer until the current structural parameters of the battery meet the preset threshold.

[0036] This invention provides a quality control method for batteries, battery packs, electrical devices, and batteries. By controlling the Dv50 of the positive electrode active material and the Dv50 of the carbon-based negative electrode active material, and ensuring that the battery satisfies 0.4≤A×C / B≤0.95, the internal resistance of the battery can be reduced, resulting in a higher capacity recovery rate at high temperatures. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0038] Figure 1 This is a SEM image of the negative electrode active material layer in Example 1 of the present invention;

[0039] Figure 2 This is a SEM image of the positive electrode active material of Example 1 of the present invention.

[0040] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Currently, rechargeable batteries suffer from low rate performance and low capacity recovery rate at high temperatures. The inventors analyzed that the rate performance of rechargeable batteries is limited by the overall internal resistance of the battery, while the low capacity recovery rate is closely related to the decomposition of the electrolyte under high-temperature conditions, increased interfacial side reactions leading to the consumption of active metal ions, and increased impedance.

[0043] Through long-term research, the inventors discovered that the transport rate of active metal ions and their insertion / extraction efficiency in positive and negative electrode materials have a significant impact on the internal resistance of secondary batteries. Simultaneously, the structural stability of the positive and negative electrode active materials during cycling directly affects the battery's capacity recovery capability under high-temperature conditions. However, existing technologies typically optimize only a single material or a specific performance indicator independently, lacking a systematic design considering the synergistic effects between multiple components in the battery. This often exacerbates side reactions and active material degradation when reducing battery internal resistance, resulting in a significant decrease in battery capacity recovery rate. Conversely, improving the battery's capacity recovery rate may sacrifice ion transport capability, increasing the battery's internal resistance.

[0044] Therefore, the inventors aimed to improve the battery's internal resistance and capacity recovery rate at high temperatures, taking into account both the transport rate of active metal ions and the stability of active materials.

[0045] Based on this, embodiments of the present invention provide a battery, including a positive electrode sheet and a negative electrode sheet; the positive electrode sheet includes a positive active material layer; the negative electrode sheet includes a negative active material layer; the positive active material layer includes a positive active material; the negative active material layer includes a carbon-based negative active material; the battery satisfies: 0.4≤A×C / B≤0.95; where A is the Dv50 of the positive active material, in μm, 3μm≤A≤5μm; B is the Dv50 of the carbon-based negative active material, in μm, 6μm≤B≤13μm; C is the N / P ratio of the battery, 1.25≤C≤1.6.

[0046] In the battery of this invention, active metal ions have a high transport rate in the positive and negative electrode plates, and the positive electrode active material and carbon-based negative electrode active material have high stability. Therefore, the battery has low internal resistance and high capacity recovery rate.

[0047] The inventors analyzed that the battery of the present invention has low internal resistance and high capacity recovery rate because: First, by controlling the N / P ratio of the battery within the above-mentioned range, the present invention ensures that the negative electrode has sufficient capacity for the insertion of active metal ions during the process of insertion, avoiding the problem that some active metal ions cannot be inserted due to insufficient negative electrode capacity and are reduced to elemental metals, thus causing increased internal resistance and decreased capacity recovery rate at high temperatures. Secondly, controlling the N / P ratio of the battery within the above-mentioned range also takes into account the energy density of the battery. Furthermore, by controlling the Dv50 of the positive electrode active material and the Dv50 of the carbon-based negative electrode active material, the present invention provides a shorter diffusion path for active metal ions, which is beneficial to improving the transport rate of active metal ions. Moreover, when the Dv50 of the positive electrode active material and the carbon-based negative electrode active material are within the above-mentioned range, it is beneficial to improve the stability of the active materials and mitigate the problem of side reactions with the electrolyte, thus improving the battery's internal resistance and capacity recovery rate at high temperatures. The embodiments of the present invention also take into account the balance between the active metal ion transport rate and the stability of the active material by controlling 0.4≤A×C / B≤0.95, so that the battery can improve both the internal resistance of the battery and the capacity recovery rate at high temperature.

[0048] In detail, the positive electrode includes a positive current collector and a positive active material layer present on at least one side of the positive current collector; the negative electrode includes a negative current collector and a negative active material layer located on at least one side of the negative current collector.

[0049] For example, the value of C is, for example, 1.25, 1.3, 1.4, 1.5, 1.6 or any combination thereof; the value of A×C / B is, for example, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95 or any combination thereof; the Dv50 of the positive electrode active material is, for example, 3μm, 4μm, 5μm or any combination thereof; the Dv50 of the carbon-based negative electrode active material is, for example, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm or any combination thereof.

[0050] The embodiments of this invention can use conventional testing methods and instruments in the art to test the Dv50 of the positive electrode active material and the carbon-based negative electrode active material, such as using SEM. Specifically, the testing can be performed as follows: After the battery is fully discharged, it is disassembled, and the positive and negative electrode sheets are separated and placed in a drying oven for approximately 12 hours to remove moisture. Taking the positive electrode sheet as an example, a sample of the positive electrode sheet is cut using an argon ion beam to obtain a cross-section. The cross-section of the positive electrode sheet is observed using an SEM. The SEM voltage and magnification are adjusted according to actual needs. Using the measurement tools provided with the SEM, the Dv50 of the positive electrode active material in the positive electrode active material layer is measured. At least 100 positive electrode active material particles are sampled, and the Dv50 of the positive electrode active material is statistically obtained. The Dv50 testing of the carbon-based negative electrode active material is similar and will not be described in detail here.

[0051] The N / P ratio of a battery can be tested using conventional testing methods and instruments in the art, such as the mass calculation method. Specifically, the test can be performed as follows: After the battery is fully discharged, it is disassembled to separate the positive and negative electrode plates, which are then placed in a drying oven for approximately 12 hours to remove moisture. The positive and negative electrode plates are then cut using a cutting tool and weighed, denoted as m. 正 and m 负 Remove the positive active material layer from the surface of the positive electrode and the negative active material layer from the surface of the negative electrode. Then, use the same cutting tool to take out the positive current collector and the negative current collector and weigh them, denoted as m. 箔正 and m 箔负 Calculate the positive electrode surface load: Positive electrode surface load = (m 正 -m 箔正 ) / positive electrode area, similarly, negative electrode surface loading = (m 负 -m 箔负 N / P = (Negative electrode surface loading × Negative electrode reversible specific capacity) / (Positive electrode surface loading × Positive electrode reversible specific capacity).

[0052] The areas of the positive and negative electrodes can be obtained using a laser rangefinder. The reversible specific capacity of the negative and positive active materials can be obtained through the following methods:

[0053] Positive electrode coin cell assembly: Place the positive electrode sheet in a drying oven to remove moisture for approximately 12 hours. Then, cut the electrode sheet with single-sided auxiliary material to the coin cell adapter size (usually φ12-14). In a glove box, assemble the electrodes in the following order: positive electrode shell → positive electrode sheet → separator → lithium sheet → electrolyte → spring contact → gasket → negative electrode shell. Seal the coin cell assembly and let it stand for 4 hours. Negative electrode coin cell assembly: Place the negative electrode sheet in a drying oven to remove moisture for 12 hours. Then, cut the electrode sheet with single-sided auxiliary material to the coin cell adapter size (usually φ12-14). In a glove box, assemble the electrodes in the following order: positive electrode shell → negative electrode sheet → separator → lithium sheet → electrolyte → spring contact → gasket → negative electrode shell. Seal the coin cell assembly and let it stand for 4 hours.

[0054] Reversible specific capacity test: Positive electrode coin cell test: Charge at 0.1C constant current and constant voltage to 4.3V, cut-off current 0.01C, rest for 5 minutes, discharge at 0.1C constant current to 2.8V, rest for 5 minutes. Repeat the above steps 3 times, and use the capacity of the 3rd test as the standard. Negative electrode coin cell test: Discharge at 0.05C constant current to 0.01V, rest for 5 minutes, charge at 0.1C constant current to 1.5V, rest for 5 minutes, then repeat the following steps 3 times: discharge at 0.1C constant current and constant voltage to 0.01V, cut-off current 0.01C → rest for 5 minutes → charge at 0.1C to 1.5V, rest for 5 minutes. Use the capacity of the 3rd test as the standard.

[0055] In some embodiments of the present invention, 1.4≤C≤1.6, which further improves the internal resistance of the battery and the capacity recovery rate at high temperatures.

[0056] In some embodiments, the areal density of the positive electrode active material layer is 114 g / m². 2 ~131g / m 2 The area of ​​the positive electrode active material layer is 0.27 m². 2 ~0.32 m 2 This helps to better control the N / P ratio of the battery.

[0057] In some embodiments, the areal density of the negative electrode active material layer is 66 g / m². 2 ~74 g / m 2 The area of ​​the negative electrode active material layer is 0.3 m². 2 ~0.35 m 2 This helps to better control the N / P ratio of the battery.

[0058] The areal density of the positive electrode active material layer and the areal density of the negative electrode active material layer can be tested using conventional testing methods and instruments in the art. Taking the areal density test of the positive electrode active material layer as an example, the testing process may include: disassembling the battery after it is fully discharged, separating the positive electrode sheet and the negative electrode sheet, and placing them in a drying oven to remove water for about 12 hours. Take the above positive electrode sheet sample, and test the total mass m1 of the positive electrode sheet sample and the surface area S of one side in the thickness direction of the whole electrode sheet sample; then scrape off the positive electrode active material layer on the positive electrode sheet sample, and test the mass m2 of the obtained positive electrode current collector. Then the areal density of the positive electrode active material layer = (m1 - m2) / S.

[0059] In some embodiments of the present invention, the reversible specific capacity of the positive electrode active material can be 148 mAh / g, which is beneficial for better control of the N / P ratio of the battery.

[0060] In some embodiments, the reversible specific capacity of the negative electrode active material can be 363 mAh / g, which is beneficial for better control of the N / P ratio of the battery.

[0061] The battery in this embodiment of the invention can be a lithium-ion battery (such as a lithium-ion power battery), a sodium-ion battery, or other novel energy storage batteries, preferably a lithium-ion battery.

[0062] In detail, when the above conditions are met, the kinetic performance of the positive and negative electrodes of lithium-ion batteries is more matched, which can better suppress lithium plating on the negative electrode and is conducive to improving the internal resistance and capacity recovery rate of lithium-ion batteries at high temperatures.

[0063] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector. Specifically, the positive active material layer can be provided on one side surface in the thickness direction of the positive current collector, or positive active material layers can be provided on both opposite sides surface in the thickness direction of the positive current collector.

[0064] In some embodiments, the battery is a sodium-ion battery, and the positive electrode active material includes, but is not limited to, one or a combination of transition metal oxides, polyanionic compounds, organic compounds, and Prussian blue materials. The transition metal oxides may be, but are not limited to, NaMO2 (M may be Fe, Co, Ni, Mn, etc.); the polyanionic compounds may be, but are not limited to, Na3V2(PO4)3, NaFePO4, Na2FePO4F, etc.; the Prussian blue materials may be, but are not limited to, Na2Fe(CN)6, etc.; and the organic compounds may be, but are not limited to, sodium terephthalic acid salts, etc.

[0065] In some embodiments, the battery is a lithium-ion battery, and the positive electrode active material may include LiCoO2, LiNiO2, or LiCo. x Ni1-x O2 (0≤x≤1), LiCo x Ni 1-x-y Al y O2 (0≤x≤1, 0≤y≤1), LiMn2O4, LiFe x Mn y M z O4 (M is one or more of Al, Mg, Ga, Cr, Co, Ni, Cu, Zn or Mo, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1), Li 1＋ x L 1－y－z M y N z O2 (L, M, N are one or more of Li, Co, Mn, Ni, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, F, I, S, B, -0.1≤x≤0.2, 0≤y≤1, 0≤z≤1, 0≤y+z≤1), LiFePO4, Li3V2(PO4)3, Li3V3(PO4)3, LiVPO4F, Li2CuO2, Li5FeO4, and metal sulfides and oxides (such as TiS2, V2S3, FeS, FeS2, LiMS) x (M is at least one of the transition metal elements such as Ti, Fe, Ni, Cu, Mo, etc., 1≤x≤2.5), TiO2, Cr3O8, V2O5, MnO2, etc.

[0066] In some embodiments, the positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate, which is more conducive to improving the stability of the positive electrode active material and further improving the internal resistance of the battery and the capacity recovery rate at high temperatures.

[0067] In some embodiments, the carbon-based negative electrode active material includes at least one of natural graphite and artificial graphite, which is more conducive to improving the stability of the negative electrode active material, and further reducing the internal resistance of the battery and improving the capacity recovery rate of the battery at high temperatures.

[0068] The positive electrode active material layer also includes a positive electrode active material, a conductive agent, and a binder. In the positive electrode active material layer, the mass percentage of the positive electrode active material can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass fraction of the conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The mass fraction of the binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0069] In this embodiment of the invention, the conductive agent in the positive electrode active material layer can be a conventional conductive material in the art. For example, the conductive agent in the positive electrode active material layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0070] In this embodiment of the invention, the binder in the positive electrode active material layer can be a conventional binder in the art. For example, the binder in the positive electrode active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0071] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0072] Specifically, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be provided on one side surface of the negative electrode current collector, or negative electrode active material layers can be provided on both opposite sides of the negative electrode current collector in the thickness direction.

[0073] Specifically, the negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite, and the conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; the binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0074] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0075] This invention also provides a method for preparing the above-mentioned battery, comprising the following steps: controlling the composition of the positive electrode and the negative electrode to make the N / P ratio of the battery 1.25~1.6, and 0.4≤A×C / B≤0.95; wherein, A is the average particle size of the positive electrode active material in μm, 3μm≤A≤5μm; B is the average particle size of the carbon-based negative electrode active material in μm, 6μm≤B≤13μm; and C is the N / P ratio of the battery, 1.25≤C≤1.6.

[0076] The present invention provides a battery that combines high active metal ion transport rate and active material stability through the above-described battery preparation method, resulting in a battery with low internal resistance and high capacity recovery rate at high temperatures.

[0077] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the positive electrode active material, conductive agent, and binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0078] In practice, the positive electrode slurry can be prepared at a temperature of 20℃~45℃; the positive electrode slurry can be coated onto the surface of the positive electrode current collector using conventional coating equipment in the field, such as continuous coating equipment.

[0079] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, components used to form the negative electrode active material layer, such as carbon-based negative electrode active material, solid electrolyte material, conductive agent, and binder, can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0080] In practice, the negative electrode slurry can be prepared at a temperature of 20℃~45℃; conventional coating equipment in the field, such as continuous coating equipment, can be used to coat the surface of the negative electrode current collector with the negative electrode slurry.

[0081] In detail, embodiments of the present invention can regulate the N / P ratio of the battery by controlling parameters such as the mass ratio of positive active material in the positive electrode slurry, the coating area of ​​the positive active material layer during coating, the mass ratio of carbon-based negative active material in the negative electrode slurry, and the coating area of ​​the negative active material layer during coating.

[0082] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), diethyl carbonate (DEC) and propylene carbonate (PC). Additives include, for example, fluoroethylene carbonate (FEC) and vinylene carbonate (VC). Electrolyte salts may include lithium salts (if it is a lithium-ion battery). Lithium salts include, for example, lithium hexafluorophosphate (LiPF6), LiFSI, LiTFSI, etc., but are not limited thereto.

[0083] In this embodiment of the invention, the separator is used to separate the positive electrode and the negative electrode to prevent short circuits caused by contact between the positive and negative electrode. Conventional separators in the art can be used in this embodiment of the invention, and there are no particular limitations. For example, the separator material can be a separator made of one or more of the following substances: high-density polyethylene (PE), ultra-high-density polyethylene, low-density polyethylene, linear low-density polyethylene, high-density polypropylene (PP), ultra-high-density polypropylene, polyimide, and polyvinylidene fluoride.

[0084] In this embodiment of the invention, the battery cell can be packaged using conventional housing materials in the art, such as flexible packaging materials like aluminum-plastic film, but is not limited thereto.

[0085] The embodiments of the present invention can assemble components such as positive electrode, separator and negative electrode into a battery using conventional methods in the art. For example, positive electrode, separator and negative electrode can be stacked in an alternating manner to obtain a stacked cell (or wound into a wound cell); then the cell is placed in a casing (outer packaging) and after conventional processes such as electrolyte injection (i.e., injection of electrolyte) and encapsulation, the battery is obtained.

[0086] The battery in this embodiment of the invention can be a solid-state battery, which further includes a solid electrolyte membrane disposed between the positive electrode and the negative electrode.

[0087] Specifically, the solid electrolyte membrane can be a conventional solid electrolyte membrane in the art, and the solid electrolyte membrane includes a solid electrolyte material. The solid electrolyte material in the solid electrolyte membrane may include at least one of sulfide solid electrolyte and halide solid electrolyte, preferably a sulfide solid electrolyte. In some embodiments, the sulfide solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 Li3 .25 Ge 0 .25 P 0 .75 One or more of S4.

[0088] Generally, the aforementioned solid-state battery includes a cell and a casing for encapsulating the cell. A solid electrolyte membrane is located between the positive and negative electrodes of the solid-state battery and is assembled within the cell inside the casing. The negative electrode includes a negative electrode sheet, and the positive electrode includes a positive electrode sheet. The cell can be a stacked cell, meaning it is composed of alternating layers of a positive electrode sheet, a solid electrolyte membrane, and a negative electrode sheet; or it can be a wound cell, meaning it is composed of stacked positive electrode sheets, a solid electrolyte membrane, and a negative electrode sheet, which are then wound together.

[0089] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a solid electrolyte material, a conductive agent, and a binder. The positive electrode active material layer has a mass percentage content of 40% to 90%, for example, 40%, 50%, 70%, 80%, 85%, 90%, or any combination thereof. The solid electrolyte material has a mass percentage content of 9% to 50%, for example, 10%, 20%, 30%, 40%, 50%, or any combination thereof. The conductive agent has a mass fraction of 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The binder has a mass fraction of 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0090] In this embodiment of the invention, the solid electrolyte material in the positive electrode active material layer may include at least one of a sulfide solid electrolyte and a halide solid electrolyte, preferably a sulfide solid electrolyte. In some embodiments, the sulfide solid electrolyte includes Li3PS4 and Li7P3S. 11 Li 11 GeP2S 12 Li6PS5Cl, Li7P2S8I, Li 10 SnP2S 12 Li 3 .25 Ge 0 .25 P 0 .75 One or more of S4. In the positive electrode active material layer of the solid-state battery, the selection of binder, conductive agent and positive electrode active material is as described above, and will not be repeated here.

[0091] This invention also provides a battery pack comprising at least two of the above-described batteries, which has advantages corresponding to the above-described negative electrode sheet, and will not be described in detail here.

[0092] 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.

[0093] This invention also provides an electrical device, including the battery or battery pack described above. This electrical device has advantages corresponding to the negative electrode sheet described above, which will not be elaborated further.

[0094] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, 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., and there are no particular limitations on this.

[0095] This invention also provides a battery quality control method, comprising the following steps: detecting the current structural parameters of the positive electrode active material layer and the negative electrode active material layer of the battery;

[0096] Determine whether the current structural parameters meet the preset threshold;

[0097] The preset threshold is 0.4≤ ≤0.95, the current structural parameters are calculated according to the following formula:

[0098] = A×C / B;

[0099] in, ;

[0100] A represents the Dv50 of the positive electrode active material in the positive electrode active material layer, expressed in μm, where 3μm≤A≤5μm;

[0101] B represents the Dv50 of the carbon-based anode active material in the anode active material layer, expressed in μm, where 6μm≤B≤13μm;

[0102] C is the N / P ratio of the battery, 1.25≤C≤1.6.

[0103] The present invention, through the above-described battery quality control method, can screen out batteries with lower internal resistance and higher capacity recovery rate.

[0104] In some embodiments of the present invention, the quality control method for the battery further includes: if the current structural parameters of the battery do not meet a preset threshold, adjusting the coating quality of the positive electrode active material, the coating quality of the carbon-based negative electrode active material, the coating area of ​​the positive electrode active material layer, and the coating area of ​​the negative electrode active material layer until the current structural parameters of the battery meet the preset threshold. Through the above operations, it is beneficial to obtain a battery that meets the above conditions.

[0105] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0106] Example 1

[0107] The battery in this embodiment is prepared by the following method:

[0108] 1) Positive electrode preparation: 93% NCM111 material (positive electrode active material) with a Dv50 of 3 μm, 5% carbon black (conductive agent), and 2% PVDF (binder) are added to N-methylpyrrolidone solvent at a mass ratio. The rotation speed and time are adjusted, and a positive electrode slurry is prepared using a high-speed dispersion device. The positive electrode slurry is then coated onto the current collector, controlling its areal density to be 131 g / m³. 2 After drying, rolling, and slitting, it is made into an electrode sheet with an area of ​​0.277m². 2 The positive electrode sheet is prepared by drying, rolling, and slitting. 2) Negative electrode sheet preparation: First, graphite (carbon-based negative electrode active material) and carbon black (conductive agent) are thoroughly mixed, then an appropriate amount of deionized water is added to prepare a negative electrode slurry. Then, 1% sodium carboxymethyl cellulose and 1% styrene-butadiene rubber (binder) are added and the mixture is dispersed using a high-speed dispersion device to prepare a negative electrode slurry. This negative electrode slurry is then uniformly coated on both sides of the current collector copper foil, and its surface density is controlled to be 66 g / m². 2 After drying, rolling, and slitting, it is made into electrode sheets with an area of ​​0.305m². 2 The negative electrode.

[0109] 3) Electrolyte: by mass percentage, it includes 9% EP, 17% EC, 34% EMC, 26% DMC, 9% lithium hexafluorophosphate, 5% lithium difluorosulfonylimide, 0.5% vinylene carbonate, 0.5% vinyl sulfate, and 0.5% lithium difluorophosphate.

[0110] 4) The positive electrode, negative electrode and separator (PE separator) are wound together using a winding machine to obtain the core, and then successively go through welding, packaging, baking, liquid injection, aging, formation and capacity testing to obtain the finished lithium-ion battery.

[0111] The Dv50 of the positive electrode active material (referred to as A in the table), the Dv50 of the carbon-based negative electrode active material (referred to as B in the table), the N / P ratio of the battery (referred to as C in the table), A×C / B, the areal density of the positive electrode active material layer, the area of ​​the positive electrode active material layer, the areal density of the negative electrode active material layer, the area of ​​the negative electrode active material layer, the reversible capacity of the positive electrode active material, and the reversible capacity of the negative electrode active material are shown in Table 1.

[0112] The differences between Examples 2-9, Comparative Examples 1-9 and the Examples are the differences in parameters such as the Dv50 of the positive electrode active material, the Dv50 of the carbon-based negative electrode active material, the N / P ratio of the battery, the areal density of the positive electrode active material layer, the area of ​​the positive electrode active material layer, the areal density of the negative electrode active material layer, the area of ​​the negative electrode active material layer, the reversible capacity of the positive electrode active material, and the reversible capacity of the negative electrode active material. See Table 1 for details.

[0113] Test case

[0114] Test methods for Dv50 of positive electrode active material and Dv50 of carbon-based negative electrode active material: The positive and negative electrode sheets from the above examples and comparative examples were disassembled from the battery (empty state: discharged to 2.8V) and placed in a drying oven for 12 hours to remove moisture. Taking the positive electrode sheet as an example, a sample of the positive electrode sheet was cut, and the cross-section of the positive electrode sheet was obtained by argon ion beam cutting. The cross-section of the positive electrode sheet was observed in an SEM. The particle size of the positive electrode active material was measured on the disassembled positive electrode sheet cross-section using the built-in scale of the SEM at a magnification of 1000-5000. The Dv50 of the positive electrode active material was taken as the average particle size of 100 positive electrode active material particles. The Dv50 method for carbon-based negative electrode active material is similar. The SEM test of the positive electrode active material layer in Example 1 of this invention is as follows: Figure 2 As shown, the SEM test results of the negative electrode active material layer are as follows: Figure 1 As shown. By Figure 1 and Figure 2 It can be seen that the particle size of carbon-based anode active materials is larger than that of cathode active materials.

[0115] N / P Test: The test was conducted using a mass calculation method, specifically including the following steps: The positive and negative electrode sheets from the above examples and comparative examples were disassembled from the finished battery and placed in a drying oven to remove moisture for about 12 hours. The positive and negative electrode sheets were then removed using a sheet cutter and weighed, and the weight was recorded as m. 正 and m 负 Remove the positive active material layer from the surface of the positive electrode and the negative active material layer from the surface of the negative electrode. Then, use the same cutting tool to take out the positive current collector and the negative current collector and weigh them, denoted as m. 箔正 and m 箔负 Calculate the positive electrode surface load: Positive electrode surface load = (m 正 -m 箔正 ) / positive electrode area, similarly, negative electrode surface loading = (m 负 -m 箔负 N / P = (Negative electrode surface area × Theoretical specific capacity of negative electrode) / (Positive electrode surface area × Theoretical specific capacity of positive electrode). The areas of the positive and negative electrodes can be obtained using a laser rangefinder.

[0116] The reversible specific capacity of the negative electrode active material and the reversible specific capacity of the positive electrode active material can be obtained as follows: Positive electrode coin cell assembly: Place the positive electrode sheet in a drying oven to remove moisture for approximately 12 hours. Then, cut the electrode sheet with single-sided auxiliary material to the coin cell adapter size (usually φ12-14). Assemble in a glove box in the following order: positive electrode shell → positive electrode sheet → separator → lithium sheet → electrolyte → spring sheet → gasket → negative electrode shell. Seal the coin cell and let it stand for 4 hours. Negative electrode coin cell assembly: Place the negative electrode sheet in a drying oven to remove moisture for 12 hours. Then, cut the electrode sheet with single-sided auxiliary material to the coin cell adapter size (usually φ12-14). Assemble in a glove box in the following order: positive electrode shell → negative electrode sheet → separator → lithium sheet → electrolyte → spring sheet → gasket → negative electrode shell. Seal the coin cell and let it stand for 4 hours.

[0117] Reversible specific capacity test: Positive electrode coin cell test: 0.1C constant current and constant voltage charging to 4.3V, cutoff current 0.01C, rest for 5 min, 0.1C constant current discharging to 2.8V, rest for 5 min, repeat the above steps 3 times, and use the third capacity as the standard. Negative electrode coin cell test: 0.05C constant current discharging to 0.01V, rest for 5 min, 0.1C constant current charging to 1.5V, rest for 5 min, then repeat the following steps 3 times: 0.1C constant current and constant voltage discharging to 0.01V, cutoff current 0.01C → rest for 5 min → 0.1C charging to 1.5V, rest for 5 min. Use the third capacity as the standard. In the embodiments and comparative examples of this invention, the reversible specific capacity of the positive electrode active material is 148mAh / g, and the reversible specific capacity of the negative electrode active material is 363mAh / g.

[0118] Low-temperature internal resistance test of the battery: At 25℃, the batteries in the above examples and comparative examples were first discharged to 2.8V at 1C, left to stand for 600s, and then charged at 1C constant current and constant voltage with a 0.05C cutoff to adjust the battery SOC to 50%. The batteries were then cooled to -40℃ and held for 3 hours. The following process was then used for testing: the battery was left to stand for 600s, charged at 2C for 5s (the voltage in the first second of charging is recorded as V1, and the voltage in the last second of charging is recorded as V2), left to stand for 600s, discharged at 0.1C for 100s, left to stand for 600s, discharged at 18C for 10s (the voltage in the first second of discharge is recorded as V3, and the voltage in the last second of discharge is recorded as V4), and left to stand for 600s. The charging impedance calculation formula is (V2-V1) / charging current, and the results (charging impedance at -40℃) are shown in Table 2; the discharging impedance calculation formula is (V3-V4) / discharging current, and the results (discharging impedance at -40℃) are shown in Table 2.

[0119] Battery internal resistance test at room temperature: At 25℃, the batteries from the above examples and comparative examples were first discharged at 1C to 2.8V, left to stand for 600s, and then charged at 1C constant current and constant voltage with a 0.05C cutoff to adjust the battery SOC to 50%. The test then proceeded as follows: 600s standing, 50C charging for 5s, 600s standing, 1C discharge for 250s, 600s standing, 50C discharge for 10s, and 600s standing. The impedance calculation method was the same as above.

[0120] High-temperature cycling test:

[0121] First, a capacity test was conducted: At 25°C, the batteries from the above examples and comparative examples were first discharged at 1C to 3V, left to rest for 600s, then charged at 1C constant current and constant voltage to 4.1V, cut off at 0.05C, left to rest for 600s, then discharged at 1C to 3V, left to rest for 600s. The final discharge capacity was equal to 1 times the battery capacity. Then, a cycle test was performed, followed by a post-cycle capacity test.

[0122] Cyclic test: 1) Discharge the battery to 3V at 1C at 25℃; 2) Let it stand for 600s; 3) Let it stand in a 60℃ environment for 3h; 4) Charge it to 80% SOC using 10C constant current; 5) Let it stand for 600s; 6) Discharge it to 30% SOC using 10C constant current; 7) Let it stand for 600s; 8) Cycle the process from step 4) to step 7) 1000 times.

[0123] The capacity test was performed again: at 25℃, the battery was first discharged at 1C to 3V and left to stand for 600s. Then, it was charged at 1C constant current and constant voltage to 4.1V, cut off at 0.05C, and left to stand for 600s. Then, it was discharged at 1C to 3V and left to stand for 600s. The discharge capacity of the last step was 2 times the battery capacity.

[0124] Capacity recovery rate = (Battery capacity² / Battery capacity¹) × 100%. Test results are shown in Table 2.

[0125]

[0126]

[0127] As shown in the table, compared with the comparative example, the embodiments of the present invention control the battery to meet the conditions of 0.4≤A×C / B≤0.95, 3μm≤A≤5μm, 6μm≤B≤13μm, and 1.25≤C≤1.6, thereby reducing the internal resistance of the battery at low and normal temperatures, and improving the capacity recovery rate of the battery at high temperatures.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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; and these 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 the present invention.

Claims

1. A battery, characterized in that, Including positive electrode plates and negative electrode plates; The positive electrode includes a positive active material layer; the negative electrode includes a negative active material layer; The positive electrode active material layer includes a positive electrode active material; The negative electrode active material layer includes a carbon-based negative electrode active material; The battery satisfies: 0.4 ≤ A × C / B ≤ 0.95; Wherein, A is the Dv50 of the positive electrode active material, expressed in μm, and 3μm≤A≤5μm; B represents the Dv50 of the carbon-based negative electrode active material, expressed in μm, where 6μm≤B≤13μm; C is the N / P ratio of the battery, where 1.25 ≤ C ≤ 1.

6.

2. The battery according to claim 1, characterized in that, 1.4≤C≤1.6。 3. The battery according to claim 1 or 2, characterized in that, The areal density of the positive electrode active material layer is 114 g / m³. 2 ~131g / m 2 The area of ​​the positive electrode active material layer is 0.27 m². 2 ~0.32 m 2 .

4. The battery according to any one of claims 1-3, characterized in that, The areal density of the negative electrode active material layer is 66 g / m². 2 ~74 g / m 2 The area of ​​the negative electrode active material layer is 0.3 m². 2 ~0.35 m 2 .

5. The battery according to any one of claims 1-4, characterized in that, The positive electrode active material includes at least one of lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

6. The battery according to any one of claims 1-5, characterized in that, The carbon-based negative electrode active material includes at least one of natural graphite and artificial graphite.

7. A battery pack, characterized in that, It includes at least two batteries as described in any one of claims 1-6.

8. An electrical appliance, characterized in that, It includes the battery as described in any one of claims 1-6, or the battery pack as described in claim 7.

9. A method for quality control of a battery, characterized in that, Includes the following steps: The current structural parameters of the positive electrode active material layer and the negative electrode active material layer of the battery are detected; Determine whether the current structural parameters meet the preset threshold; Wherein, the preset threshold is 0.4≤ ≤0.95, the current structural parameter is calculated according to the following formula: = A×C / B; in, ; A represents the Dv50 of the positive electrode active material in the positive electrode active material layer, expressed in μm, where 3μm≤A≤5μm; B is the Dv50 of the carbon-based negative electrode active material in the negative electrode active material layer, in μm, where 6μm≤B≤13μm; C is the N / P ratio of the battery, where 1.25 ≤ C ≤ 1.

6.

10. The battery quality control method according to claim 9, characterized in that, Also includes: If the current structural parameters of the battery do not meet the preset threshold, the coating quality of the positive electrode active material, the coating quality of the carbon-based negative electrode active material, the coating area of ​​the positive electrode active material layer, and the coating area of ​​the negative electrode active material layer are adjusted until the current structural parameters of the battery meet the preset threshold.

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