Lithium-ion battery and manufacturing method, battery pack, and electric device

Abstract

A lithium-ion battery. The battery comprises a positive electrode sheet and a negative electrode sheet; the positive electrode sheet comprises a positive electrode active material layer, and the modal pore diameter r1 of the positive electrode sheet is 50-90 nm; the negative electrode sheet comprises a negative electrode active material layer, and the modal pore diameter r2 of the negative electrode sheet is 900-1500 nm.

Description

A lithium-ion battery, its preparation method, battery pack, and electrical equipment.

[0001] Cross-references to related applications

[0002] This disclosure claims Chinese Patent Application No. 202510507506.X, filed with the Chinese Patent Office on April 18, 2025, entitled "A Lithium-ion Battery and its Preparation Method, Battery Pack and Electrical Equipment", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium battery technology, specifically to a lithium-ion battery and its preparation method, battery pack and electrical equipment. Background Technology

[0004] New energy vehicles represent the direction of the global automotive industry. Lithium-ion secondary batteries, as a new type of high-voltage, high-energy-density power battery, have outstanding characteristics such as light weight, high energy density, no pollution, no memory effect, and long service life, and are therefore widely used in new energy vehicles.

[0005] Existing technologies require simultaneous control of the specific surface area and volume of macropores and micropores in the positive and negative electrode sheets during the preparation process to improve the rate performance of lithium-ion batteries. This has high process requirements and is inconvenient to operate in practice. Summary of the Invention

[0006] The purpose of this disclosure is to provide a lithium-ion battery and its preparation method, battery pack and electrical equipment. This lithium-ion battery provides more effective channels for lithium-ion migration by adjusting the most frequent aperture of the positive and negative electrode plates, reducing the diffusion distance and time of lithium ions in the electrodes, improving the charge-discharge performance and rate performance of the battery, with low process requirements, simple operation, easy to scale up production, and improved economic benefits for enterprises.

[0007] To achieve the above objectives, the first aspect of this disclosure provides a lithium-ion battery, the battery comprising a positive electrode and a negative electrode, the positive electrode comprising a positive active material layer, the most frequent aperture r1 of the positive electrode being 50-90 nm; the negative electrode comprising a negative active material layer, the most frequent aperture r2 of the negative electrode being 900-1500 nm.

[0008] A second aspect of this disclosure provides a method for preparing a lithium-ion battery, the method comprising:

[0009] (1) A negative electrode active material layer is formed on the negative electrode current collector to obtain a negative electrode sheet; the maximum aperture of the negative electrode sheet is 900-1500 nm.

[0010] (2) A positive electrode active material layer is formed on the positive electrode current collector to obtain a positive electrode sheet; the maximum aperture of the positive electrode sheet is 50-90 nm.

[0011] The third aspect of this disclosure provides a lithium-ion battery prepared by the method described in the second aspect of this disclosure.

[0012] This disclosure provides a fourth aspect of a battery pack, including the lithium-ion battery described in the first or third aspect of this disclosure.

[0013] The fifth aspect of this disclosure provides an electrical device including a battery as described in the first or third aspect of this disclosure, or a battery pack as described in the fourth aspect of this disclosure.

[0014] Through the above technical solution, this disclosure improves the charge-discharge performance and rate performance of the battery by adjusting the most frequent aperture of the positive and negative electrode sheets within a specific range, thereby providing more effective channels for lithium-ion migration and reducing the diffusion distance and time of lithium-ions in the electrode sheets. At the same time, the appropriate most frequent aperture of the positive and negative electrode sheets helps to maintain the structural stability of the electrode sheets, reduce material breakage and electrode detachment caused by the volume expansion and contraction of the active material during charge and discharge, and extend the cycle life of the battery.

[0015] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0017] Figure 1 is a pore size distribution curve of the positive and negative electrode sheets in Embodiment 2 of this disclosure. Detailed Implementation

[0018] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0019] The first aspect of this disclosure provides a lithium-ion battery, the battery including a positive electrode and a negative electrode, the positive electrode including a positive active material layer, the most frequent pore size r1 of the positive electrode being 50-90 nm; the negative electrode including a negative active material layer, the most frequent pore size r2 of the negative electrode being 900-1500 nm.

[0020] This disclosure improves the battery's charge / discharge performance and rate performance by adjusting the most frequent pore size distribution of the positive and negative electrode sheets within a specific range. This provides more effective channels for lithium-ion migration, reduces the diffusion distance and time of lithium-ions in the electrode sheets, and thus improves the battery's charge / discharge performance and rate performance. Simultaneously, appropriate most frequent pore sizes of the positive and negative electrode sheets help maintain the structural stability of the electrode sheets, reducing the breakage and shedding of active materials due to volume expansion and contraction during charge / discharge, thereby extending the battery's cycle life. It avoids excessively large most frequent pore sizes, which increase the risk of electrolyte loss and reduce the battery's liquid retention capacity, and prevents uneven distribution of lithium-ions within the electrode sheets, thus affecting the battery's cycle life. Conversely, it avoids excessively small most frequent pore sizes, which limit the migration speed of lithium-ions, increase the battery's internal resistance, and reduce the battery's rate performance.

[0021] In this disclosure, the most frequent pore size refers to the pore size value that appears most frequently in the pore size distribution. For example, in Figure 1, the highest peak on the vertical axis of the pore size distribution obtained by mercury porosimetry is the most frequent pore size of the positive and negative electrode active material layers.

[0022] In this disclosure, the most frequent aperture is tested using the mercury intrusion porosimetry method; it can be tested by cutting a certain area from the positive / negative electrode sheet prepared according to the embodiment, or by cutting an appropriate size from the positive / negative electrode sheet obtained after disassembling the battery.

[0023] In one embodiment, the most frequent aperture r1 of the positive electrode can be any value from 50 to 90 nm, for example, it can be any value within the range of 50 nm, 52 nm, 55 nm, 59 nm, 60 nm, 61 nm, 65 nm, 68 nm, 70 nm, 72 nm, 77 nm, 78 nm, 80 nm, 83 nm, 84 nm, 86 nm, 89 nm, 90 nm or any combination thereof.

[0024] In one embodiment, the most frequent aperture r2 of the negative electrode can be any value in the range of 900 to 1500 nm, for example, it can be any value in the range of 900 nm, 901 nm, 905 nm, 970 nm, 990 nm, 1000 nm, 1005 nm, 1010 nm, 1130 nm, 1170 nm, 1200 nm, 1210 nm, 1280 nm, 1300 nm, 1305 nm, 1350 nm, 1390 nm, 1400 nm, 1450 nm, 1490 nm, 1500 nm or any combination thereof.

[0025] In one embodiment, r1 is 60–85 nm, and / or r2 is 1050–1200 nm. In this embodiment, r1 can be any value between 60 and 85 nm, for example, it can be any value within the range of 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, 66 nm, 67 nm, 69 nm, 70 nm, 71 nm, 72 nm, 74 nm, 75 nm, 76 nm, 77 nm, 79 nm, 80 nm, 81 nm, 83 nm, 84 nm, 85 nm, or any two of these values; r2 can be any value between 1050 and 1200 nm, for example, it can be any value within the range of 1050 nm, 1055 nm, 1058 nm, 1060 nm, 1062 nm, 1069 nm, 1070 nm, 1075 nm, 1080 nm, 1086 nm, 1090 nm, 1100 nm, 1120 nm, 1130 nm, 1150 nm, 1170 nm, 1200 nm, or any two of these values. The above-described embodiments are beneficial for providing more effective channels for lithium-ion migration, reducing the diffusion distance and time of lithium-ions in the electrode sheet, and improving the charge-discharge performance and rate performance of the battery; at the same time, they help maintain the structural stability of the electrode sheet, reduce the breakage of active materials and electrode detachment caused by volume expansion and contraction during charge and discharge, and further improve the cycle life of the battery.

[0026] In one embodiment, the volume of pores with a diameter of 50-90 nm accounts for 50-90% of the total pore volume of the positive electrode sheet, preferably 70-90%. In this disclosure, the ratio of the volume of pores with a diameter of 50-90 nm to the total pore volume of the positive electrode sheet refers to the proportion of the volume of pores with a diameter of 50-90 nm in the total pore volume of the positive electrode active material layer in the pore size distribution curve of the positive electrode sheet. This volume proportion can be calculated from the pore size distribution curve. In this embodiment, the pore size distribution curve of the positive electrode sheet is formed with a sharp peak, resulting in a higher proportion of pores with a diameter of 50-90 nm.

[0027] In one embodiment, in the negative electrode sheet, the volume of pores with a pore size of 900–1500 nm accounts for 50–90% of the total pore volume of the negative electrode sheet, preferably 70–90%. In this disclosure, the ratio of the volume of pores with a pore size of 900–1500 nm to the total pore volume of the negative electrode sheet refers to the proportion of the volume of pores with a pore size of 900–1500 nm in the total pore volume of the negative electrode active material layer in the pore size distribution curve of the negative electrode sheet. This volume proportion can be calculated using the pore size distribution curve. In this embodiment, the pore size distribution curve of the electrode sheet is formed with a sharp peak, resulting in a higher proportion of pores with a pore size of 900–1500 nm.

[0028] In one embodiment, the positive electrode active material layer includes a positive electrode active substance, a first binder, and a first conductive agent; the first conductive agent includes carbon nanotubes, carbon black, and graphite flakes, wherein the diameter of the carbon nanotubes is 10–25 nm, preferably 15–20 nm; the carbon black has a D… 50 The particle size is 50–100 nm, preferably 60–90 nm; the thickness of the graphite microsheets is 200–400 nm, preferably 200–300 nm; and the sheet diameter is 0.5–4.5 μm, preferably 1–3 μm. This embodiment facilitates the construction of a conductive network within the battery using carbon nanotubes, improving the conductivity of the positive electrode active material, reducing the internal resistance of the lithium battery, reducing the expansion and contraction of the positive electrode active material during charging and discharging, and improving battery life. It also improves the adhesion strength of the electrode sheets and reduces the amount of binder added. Furthermore, the mixing of multiple conductive agents further facilitates keeping the most frequent pore size of the positive electrode sheet within a suitable range, providing more effective channels for lithium-ion migration, reducing the diffusion distance and time of lithium ions in the electrode material, thereby improving the battery's charge / discharge performance and rate performance.

[0029] In this disclosure, the mass ratio of the positive electrode active material, the first binder, and the first conductive agent in the positive electrode active material layer is not specifically limited and can be a conventional ratio in the art. For example, in one embodiment, the mass ratio of the positive electrode active material, the first binder, and the first conductive agent can be (85-97):1:(1.5-5). In a further embodiment, the mass ratio of the positive electrode active material, the first binder, and the first conductive agent can be calculated based on the feeding ratio in the preparation method.

[0030] In one embodiment, the positive electrode active material layer may further include a first dispersant. This disclosure does not specifically limit the type of dispersant, which may be a conventional type in the art, such as one or more of carboxymethyl cellulose, polyacrylic acid, polymethyl methacrylate and polyvinylpyrrolidone. The amount of dispersant added is not specifically limited, and may be a conventional proportion in the art.

[0031] In one embodiment, the positive electrode active material comprises nano-sized lithium iron phosphate particles and micron-sized lithium iron phosphate particles, wherein the nano-sized lithium iron phosphate particles have a D... 50 The particle size is 0.1–0.4 μm, and the D of the micron-sized lithium iron phosphate particles is... 50 The particle size is 1–4 μm. In this disclosure, D 50 Particle size can be measured using a particle size diffractometer or a scanning electron microscope. In this disclosure, D 50 This refers to Dv50, which is the volume median diameter of the particle.

[0032] In this disclosure, the composition of lithium iron phosphate particles is not specifically limited, and can be any conventional lithium iron phosphate material in the art, such as LiFe. (1-x) MxPO4 0≤x≤0.1. In one embodiment, the lithium iron phosphate particles of this disclosure may be doped with a modifying element M, which may be one or more of Ti, Zr, Mo, Mn, Mg, V, and C. The doping amount of the modifying element M in the lithium iron phosphate particles may be 2000-6000 ppm, preferably 2000-3000 ppm. In a specific embodiment, the doping amount of the modifying element in the lithium iron phosphate particles can be tested by inductively coupled plasma (ICP).

[0033] In one embodiment, the mass ratio of the nano-sized lithium iron phosphate particles to the micron-sized lithium iron phosphate particles in the positive electrode active material layer is 1:(0.67-2.33), preferably 1:(1.50-2.33). This embodiment facilitates the gradation of particles with different sizes, ensuring that the most frequent pore size of the positive electrode sheet is within a suitable range. This provides more effective channels for lithium ion migration, reduces the diffusion distance and time of lithium ions in the electrode sheet, and improves the charge / discharge performance and rate performance of the battery. Simultaneously, it helps maintain the structural stability of the electrode sheet, reducing the breakage and shedding of the active material due to volume expansion and contraction during charge / discharge, further improving the cycle life of the battery.

[0034] In one embodiment, the positive electrode further includes a positive current collector and a positive conductive coating. The positive conductive coating is located between the positive current collector and the positive active material layer. The thickness of the positive conductive coating is 0.3–1.8 μm, preferably 0.3–1 μm. In this disclosure, the thickness of the conductive coating refers to the thickness of one side of the conductive coating. In a specific embodiment, the thickness of the conductive coating can be measured by scanning electron microscopy. The above embodiments are beneficial for reducing the interfacial impedance between the positive current collector and the positive active material layer, enhancing conductivity, improving the problem of electrochemical corrosion on the surface of the current collector, reducing polarization, improving the adhesion between the positive active material and the current collector, and preventing corrosion of the current collector by the electrolyte.

[0035] In one embodiment, the negative electrode active material layer comprises a negative electrode active substance, a second binder, and a second conductive agent; the negative electrode active substance comprises primary graphite particles and secondary graphite particles, wherein the primary graphite particles have a D... 50 The secondary graphite particles have a particle size of 3–5 μm and a D0 50 The particle size is 20–40 μm. In this disclosure, the D of the negative electrode active material... 50Particle size can be measured using a particle size diffractometer or a scanning electron microscope (SEM). The above-described implementation facilitates the gradation of particles of different sizes, ensuring that the most frequent pore size of the negative electrode active material layer is within a suitable range. This provides more effective channels for lithium-ion migration, reduces the diffusion distance and time of lithium-ions in the electrode sheet, and improves the battery's charge / discharge performance and rate performance. Simultaneously, it helps maintain the structural stability of the electrode sheet, reducing the breakage and shedding of active material due to volume expansion and contraction during charge / discharge, further improving the battery's cycle life.

[0036] In one embodiment, the mass ratio of the primary graphite particles to the secondary graphite particles in the negative electrode active material layer is 1:(2.33-9), preferably 1:(4-9). This embodiment facilitates the gradation of particles of different sizes, ensuring that the most frequent pore size of the negative electrode sheet is within a suitable range. This provides more effective channels for lithium-ion migration, reduces the diffusion distance and time of lithium-ions in the electrode sheet, and improves the charge-discharge performance and rate performance of the battery. Simultaneously, it helps maintain the structural stability of the electrode sheet, reducing the breakage and shedding of the active material due to volume expansion and contraction during charge-discharge, further improving the cycle life of the battery.

[0037] In this disclosure, primary graphite particles and secondary graphite particles have the same meaning as those known in the art; primary graphite particles refer to unprocessed raw graphite particles; secondary graphite particles refer to primary graphite particles agglomerated to form secondary particles. This disclosure does not impose any special limitations on the preparation method of secondary graphite particles, which can be obtained by conventional methods in the art.

[0038] In one embodiment, this disclosure does not specifically limit the mass ratio of the negative electrode active material, the second binder, and the second conductive agent in the negative electrode active material layer, and it can be a conventional ratio in the art. For example, in one embodiment, the mass ratio of the negative electrode active material, the second binder, and the second conductive agent can be (90-97):(1-5):1. In a specific embodiment, the mass ratio of the negative electrode active material, the second binder, and the second conductive agent can be calculated based on the feeding ratio in the preparation method.

[0039] In one embodiment, the negative electrode active material layer of this disclosure may further include a second dispersant. This disclosure does not specifically limit the type of dispersant, which may be a conventional type in the art, such as one or more of carboxymethyl cellulose, polyacrylic acid, polymethyl methacrylate and polyvinylpyrrolidone. The amount of dispersant added is not specifically limited, and may be a conventional proportion in the art.

[0040] In one embodiment, this disclosure does not specifically limit the first and second binders, and they can be conventional types in the art, such as one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. This disclosure also does not specifically limit the first and second conductive agents, and they can be conventional types in the art, such as one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0041] A second aspect of this disclosure provides a method for preparing a lithium-ion battery, the method comprising:

[0042] (1) A negative electrode active material layer is formed on the negative electrode current collector to obtain a negative electrode sheet; the maximum aperture of the negative electrode sheet is 900-1500 nm.

[0043] (2) A positive electrode active material layer is formed on the positive electrode current collector to obtain a positive electrode sheet; the maximum aperture of the positive electrode sheet is 50-90 nm.

[0044] In one embodiment, the most frequent aperture of the positive electrode is 60–85 nm; and / or, the most frequent aperture of the negative electrode is 1050–1200 nm.

[0045] The method disclosed herein improves the battery's charge-discharge performance and rate performance by adjusting the most frequent aperture of the positive and negative electrode sheets within a specific range, thereby providing more effective channels for lithium-ion migration and reducing the diffusion distance and time of lithium-ions in the electrode sheets. Simultaneously, appropriate aperture sizes of the positive and negative electrode sheets help maintain the structural stability of the electrode sheets, reducing the breakage and shedding of active materials due to volume expansion and contraction during charge and discharge, and extending the battery's cycle life. The method disclosed herein has low process requirements, is easy to operate, and is easily scaled up for production, thus improving the economic benefits for enterprises.

[0046] In one embodiment, in step (1), the negative electrode active material layer is formed using a negative electrode slurry comprising a negative electrode active material, a second binder, and a second conductive agent; the negative electrode active material comprises primary graphite particles and secondary graphite particles, wherein the primary graphite particles have a D... 50 The particle size is 3-5 μm; the D of the secondary graphite particles 50The particle size is 20–40 μm. The above-described embodiments help to keep the most frequent pore size of the negative electrode within a suitable range, providing more effective channels for lithium-ion migration, reducing the diffusion distance and time of lithium-ions in the electrode, and improving the battery's charge / discharge performance and rate performance. Simultaneously, it helps maintain the structural stability of the electrode, reducing the breakage and shedding of active materials due to volume expansion and contraction during charge / discharge, further improving the battery's cycle life.

[0047] In one embodiment, in step (1), the mass ratio of the primary graphite particles to the secondary graphite particles in the negative electrode slurry is 1:(2.33-9), preferably 1:(4-9). This embodiment facilitates the gradation of particles of different sizes, ensuring that the most frequent pore size of the negative electrode sheet is within a suitable range. This provides more effective channels for lithium-ion migration, reduces the diffusion distance and time of lithium-ions in the electrode sheet, and improves the charge / discharge performance and rate performance of the battery. Simultaneously, it helps maintain the structural stability of the electrode sheet, reducing the breakage and shedding of active materials due to volume expansion and contraction during charge / discharge, further improving the cycle life of the battery.

[0048] In one embodiment, the positive electrode active material layer is formed using a positive electrode slurry comprising a positive electrode active material, a first binder, and a first conductive agent; the positive electrode active material includes nano-sized lithium iron phosphate particles and micron-sized lithium iron phosphate particles, wherein the nano-sized lithium iron phosphate particles have a D... 50 The particle size is 0.1–0.4 μm, and the D of the micron-sized lithium iron phosphate particles is... 50 The particle size is 1–4 μm. The above-described embodiments are beneficial in keeping the most frequent pore size of the positive electrode sheet within a suitable range, which helps to provide more effective channels for lithium ion migration, reduces the diffusion distance and time of lithium ions in the electrode sheet, and improves the charge-discharge performance and rate performance of the battery; at the same time, it helps to maintain the structural stability of the electrode sheet, reduces the breakage and shedding of active materials due to the volume expansion and contraction of active materials during charge-discharge, and further improves the cycle life of the battery.

[0049] In the positive electrode slurry, the mass ratio of the nano-sized lithium iron phosphate particles to the micron-sized lithium iron phosphate particles is 1:(0.67~2.33), preferably 1:(1.50~2.33). This embodiment facilitates the gradation of particles of different sizes, ensuring that the most frequent pore size of the positive electrode sheet is within a suitable range. This provides more effective channels for lithium ion migration, reduces the diffusion distance and time of lithium ions in the electrode sheet, and improves the charge / discharge performance and rate performance of the battery. Simultaneously, it helps maintain the structural stability of the electrode sheet, reducing the breakage and shedding of active materials due to volume expansion and contraction during charge / discharge, further improving the cycle life of the battery.

[0050] In this disclosure, the preparation methods of the nano-sized lithium iron phosphate particles and the micron-sized lithium iron phosphate particles can be conventional methods in the art, such as low-temperature liquid-phase synthesis, hydrothermal synthesis, high-temperature solid-phase synthesis, carbothermal reduction, etc. 50 Lithium iron phosphate particles with particle size within the scope of this disclosure.

[0051] In one embodiment, in step (2), the first conductive agent comprises carbon nanotubes, carbon black, and graphite flakes; the diameter of the carbon nanotubes is 10–25 nm, preferably 15–20 nm; the D of the carbon black is… 50 The particle size is 50–100 nm, preferably 60–90 nm; the thickness of the graphite microsheets is 200–400 nm, preferably 200–300 nm; and the sheet diameter is 0.5–4.5 μm, preferably 1–3 μm. This embodiment facilitates the construction of a conductive network within the battery using carbon nanotubes, improving the conductivity of the positive electrode active material, reducing the internal resistance of the lithium battery, reducing the expansion and contraction of the positive electrode active material during charging and discharging, improving battery life, and simultaneously improving the adhesion strength of the electrode sheets while reducing the amount of binder required.

[0052] This disclosure does not specifically limit the mass ratio of carbon nanotubes, carbon black, and graphite flakes in the positive electrode slurry, and it can vary within a wide range, for example, it can be (10-5):(3-0.5):1. The above embodiments facilitate the formation of a conductive network of carbon nanotubes inside the battery, improving the conductivity of the positive electrode active material, reducing the internal resistance of the lithium battery, reducing the expansion and contraction of the positive electrode active material during charging and discharging, improving battery life, and simultaneously improving the adhesion strength of the electrode sheets and reducing the amount of binder added.

[0053] In one embodiment, the method further includes: mixing a third conductive agent and a third binder to form a conductive coating slurry; coating the conductive coating slurry onto the positive electrode current collector to form a positive electrode conductive coating; then coating the positive electrode slurry onto the positive electrode conductive coating to form the positive electrode active material layer on the positive electrode conductive coating, thereby obtaining a positive electrode comprising the positive electrode active material layer and the conductive coating; wherein the thickness of the conductive coating is 0.3–1.8 μm.

[0054] This disclosure does not specifically limit the third conductive agent and the third binder used in the positive electrode conductive coating, and they can be conventional types in the art. For example, the third conductive agent can be one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the third binder can be one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0055] The third aspect of this disclosure provides a lithium-ion battery prepared by the method described in the second aspect of this disclosure.

[0056] In one embodiment, the battery includes a separator, which can be of conventional types in the art and is not specifically limited thereto. For example, it can include a base film, a coating, and an adhesive layer. The base film can be one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride; the coating can be a polyvinylidene fluoride coating (PVDF) and / or a pseudo-boehmite coating (ALOOH); and the adhesive layer can be an adhesive layer formed of polyvinylidene fluoride.

[0057] The battery disclosed herein may include, but is not limited to, single cells, battery modules, battery packs, etc. That is, the actual application form of the battery provided herein may be, but is not limited to, the listed products, or other application forms. When the battery is a single cell, it includes at least one of cylindrical cells, prismatic cells, etc.

[0058] This disclosure provides a fourth aspect of a battery pack, including the battery described in the first or third aspect of this disclosure.

[0059] The fifth aspect of this disclosure provides an electrical device including a battery as described in the first or third aspect of this disclosure, or a battery pack as described in the fourth aspect of this disclosure.

[0060] It should be noted that the aforementioned electrical equipment can be any equipment that conventionally requires electricity, such as, but not limited to, computers, electric vehicles, air conditioners, refrigerators, washing machines, microwave ovens, printers, fax machines, etc.

[0061] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto. Unless otherwise specified, all reagents used in this disclosure are battery-grade and commercially available.

[0062] In the following embodiments of this disclosure, the positive electrode active material, the negative electrode active material, and the carbon black D 50Particle size was measured using scanning electron microscopy (SEM). The method included: cutting a 0.5cm x 0.5cm portion of the positive electrode sheet, magnifying it 2000x under a scanning electron microscope, and taking 50 SEM images. For each SEM image, the particle size of 50 positive electrode active material particles was measured, and the average value was taken to obtain the D value of the positive electrode active material. 50 Particle size;

[0063] D of negative electrode active material 50 Particle size was measured using scanning electron microscopy (SEM). The method included: cutting a 0.5cm x 0.5cm section of the negative electrode sheet, magnifying it 2000x under a scanning electron microscope, and taking 50 SEM images. In each SEM image, the particle size of 50 negative electrode active material particles was measured, and the average value was taken to obtain the D value of the negative electrode active material. 50 Particle size;

[0064] D of carbon black 50 Particle size was measured using scanning electron microscopy (SEM). The method involved cutting a 0.5cm x 0.5cm section of the positive electrode sheet, magnifying it 2000x under a scanning electron microscope, and taking 50 SEM images. In each SEM image, the particle size of 50 carbon black particles was measured, and the average value was taken to obtain the D value of the carbon black. 50 ;

[0065] The diameter of carbon nanotubes is measured by scanning electron microscopy (SEM). The testing method includes: observing the cross-section of the positive electrode under SEM, selecting at least 5 different locations, testing no less than 3 discrete carbon nanotubes in each location, and the total sample size must be ≥15. The average diameter of the carbon nanotubes is then calculated.

[0066] The diameter of the graphite microflakes was measured using scanning electron microscopy (SEM). This involved cutting a 0.5cm x 0.5cm portion of the positive electrode, magnifying it 2000x under a scanning electron microscope, and taking 50 SEM images. The length of each of the 50 graphite microflakes in each SEM image was measured, and the average value was taken to determine the diameter of the graphite microflakes. The thickness of the graphite microflakes was also measured using SEM. The method involved cutting a 0.5cm x 0.5cm portion of the positive electrode, magnifying it 2000x under a scanning electron microscope, and taking 50 SEM images. The thickness of each of the 50 graphite microflakes in each SEM image was measured, and the average value was taken to determine the thickness of the graphite microflakes.

[0067] The most frequent pore size and pore volume ratio of the positive and negative electrode sheets are tested by mercury intrusion porosimetry (test standard is GB / T 21650.1-2008).

[0068] Example 1

[0069] Negative electrode preparation:

[0070] Artificial graphite active material, conductive agent (conductive carbon black SP), dispersant (carboxymethyl cellulose CMC), and binder (styrene-butadiene rubber SBR) were mixed in a mass ratio of 95:1:1.5:2.5. The powder and deionized water were stirred using a homogenizer to form a negative electrode slurry, which was then uniformly coated onto copper foil. After drying, a negative electrode active material layer was formed. The artificial graphite particles used in Example 1 included: D 50 Primary artificial graphite particles with a particle size of 3 μm, D 50 Secondary artificial graphite particles with a particle size of 20 μm, at a mass ratio of 1:9; conductive carbon black SP with D 50 The particle size is 50 nm.

[0071] Preparation of positive electrode sheet:

[0072] The preparation of the conductive coating includes: mixing a binder (PVDF) and a conductive agent (carbon black) at a mass ratio of 19:1 to form a conductive coating slurry, coating it on an aluminum foil, and drying it to form a conductive coating with a single-sided thickness of 1.8 μm;

[0073] Lithium iron phosphate active material, conductive agent, and binder (polyvinylidene fluoride PVDF) are mixed in a mass ratio of 97:2:1. The powder and NMP are then stirred in a homogenizer to form a positive electrode slurry, which is then uniformly coated onto a conductive coating. After drying, a positive electrode consisting of a positive electrode active material layer and a conductive coating is formed. The lithium iron phosphate used is LiFePO4, with a Ti content of 2500 ppm. The lithium iron phosphate includes D... 50 Nanoscale lithium iron phosphate particles with a particle size of 0.1 μm and D 50 The lithium iron phosphate particles are micron-sized (4 μm) with a mass ratio of nano-sized to micron-sized particles of 1:2.33. The positive electrode conductive agent includes carbon nanotubes (CNTs), conductive carbon black, and graphite flakes. The carbon nanotubes have a diameter of 20 nm, and the conductive carbon black has a diameter of D... 50 The particle size is 100 nm, the graphite microplate diameter is 0.5 μm, the thickness is 300 nm, and the mass ratio of carbon nanotubes, conductive carbon black and graphite microplates is 8:1:1.

[0074] Electrolyte preparation:

[0075] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0076] Separator: Polyethylene film is used as the separator.

[0077] Preparation of lithium-ion batteries: The above-mentioned positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrode sheets. Then, they are wound to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0078] Examples 2-12

[0079] The methods in Examples 2 to 12 are the same as those in Example 1, except that the particle size and mass ratio of the positive and negative electrode active materials used are different. The specific differences are shown in Table 1.

[0080] Comparative Examples 1-5

[0081] The methods of Comparative Examples 1 to 5 are the same as those of Example 1, except that the particle size and mass ratio of the positive and negative electrode active materials used are different. The specific differences are shown in Table 1.

[0082] Table 1

[0083] Test case

[0084] The pore size distribution of the positive and negative electrode sheets obtained in the above embodiments and comparative examples was tested. At the same time, the lithium-ion batteries assembled in the embodiments and comparative examples were also tested. The test results are shown in Table 2. The pore size distribution test results of the positive and negative electrode sheets in Embodiment 2 are shown in Figure 1.

[0085] The method for testing battery power performance is as follows:

[0086] (1) Battery DC internal resistance test: The battery was discharged to 2.0V at a constant current of 0.33C (0.6A) at room temperature, and then charged to 50% SOC at a constant current of 0.33C (charging capacity 0.9A). It was then discharged at a constant current of 1.5C (2.7A) for 30s, and the voltage before and after discharge was recorded. The discharge DCIR (mΩ) was calculated as (voltage before discharge - voltage after discharge) / discharge current * 1000.

[0087] (2) Cyclic performance test: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were charged at a rate of 3C and discharged at a rate of 1C to conduct a full charge and discharge cycle test until the capacity of the lithium-ion battery decayed to 80% of the initial capacity, and the number of cycles was recorded.

[0088] Table 2

[0089] According to the data in Table 2, compared with Comparative Examples 1 to 5, Examples 1 to 12 have lower DC internal resistance and better cycle performance in the most frequent aperture range of the positive and negative electrode plates of this disclosure.

[0090] Compared with Examples 7 and 11, it can be seen that the particle size of the primary and secondary graphite particles in the negative electrode active material of Example 2 is within the preferred range of this disclosure, and the most frequent pore size of the negative electrode is within the preferred range of this disclosure. As a result, the battery has a smaller DC internal resistance and better cycle performance.

[0091] Compared with Example 8, it can be seen that the mass ratio of nano-sized particles to micro-sized particles of the positive electrode active material in Example 2 is within the preferred range of this disclosure, the most frequent pore size of the positive electrode is within the preferred range of this disclosure, the DC internal resistance of the battery is smaller, and the cycle performance is better.

[0092] By comparison with Example 9, it can be seen that the mass ratio of primary graphite particles to secondary graphite particles in the negative electrode active material of Example 2 is within the preferred range of this disclosure, the maximum pore size of the negative electrode is within the preferred range of this disclosure, the DC internal resistance of the battery is smaller, and the cycle performance is better.

[0093] By comparing with Example 10, it can be seen that the particle size range of the nano-sized and micro-sized particles of the positive electrode active material in Example 2 is within the preferred range of this disclosure, the most frequent pore size of the positive electrode is within the preferred range of this disclosure, the DC internal resistance of the battery is smaller, and the cycle performance is better.

[0094] By comparison with Example 12, it can be seen that the thickness range of the positive electrode conductive coating in Example 2 is within the preferred range of this disclosure, the maximum frequency aperture of the positive electrode is within the preferred range of this disclosure, the DC internal resistance of the battery is smaller, and the cycle performance is better.

[0095] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0096] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0097] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A lithium-ion battery, characterized by, The battery includes a positive electrode and a negative electrode. The positive electrode includes a positive active material layer and the most frequent aperture r1 of the positive electrode is 50-90 nm. The negative electrode includes a negative active material layer and the most frequent aperture r2 of the negative electrode is 900-1500 nm.

2. The lithium-ion battery of claim 1, wherein, r1 is 60–85 nm; and / or r2 is 1050–1200 nm.

3. The lithium-ion battery of claim 1 or 2, wherein, In the positive electrode sheet, the volume of pores with a diameter of 50–90 nm accounts for 50–90% of the total pore volume of the positive electrode sheet, preferably 70–90%; and / or, In the negative electrode sheet, the volume of pores with a pore size of 900-1500 nm accounts for 50%-90% of the total pore volume of the negative electrode sheet, preferably 70%-90%.

4. The lithium-ion battery of any one of claims 1-3, wherein, The positive electrode active material layer includes a positive electrode active substance, a first binder, and a first conductive agent; The first conductive agent includes carbon nanotubes, carbon black and graphite microsheets, the carbon nanotubes have a tube diameter of 10-25 nm, the carbon black has a D 50 particle diameter of 50-100 nm, and the graphite microsheets have a thickness of 200-400 nm and a flake diameter of 0.5-4.5 μm.

5. The lithium-ion battery of any one of claims 1-4, wherein, The positive active material includes nanoscale lithium iron phosphate particles and microscale lithium iron phosphate particles, the nanoscale lithium iron phosphate particles having a D 50 particle diameter of 0.1 to 0.4 μm, and the microscale lithium iron phosphate particles having a D 50 particle diameter of 1 to 4 μm.

6. The lithium-ion battery of any one of claims 1-5, wherein, In the positive electrode active material layer, the mass ratio of the nano-sized lithium iron phosphate particles to the micro-sized lithium iron phosphate particles is 1:(0.67~2.33), preferably 1:(1.50~2.33).

7. The lithium-ion battery of any one of claims 1-6, wherein, The positive electrode also includes a positive electrode current collector and a positive electrode conductive coating. The positive electrode conductive coating is located between the positive electrode current collector and the positive electrode active material layer, and the thickness of the positive electrode conductive coating is 0.3 to 1.8 μm.

8. The lithium-ion battery of any one of claims 1-7, wherein, The negative electrode active material layer includes a negative electrode active substance, a second binder, and a second conductive agent; The negative active material includes primary graphite particles and secondary graphite particles, the primary graphite particles have a D50 of 3 to 5 μm, and the secondary graphite particles have a D50 of 20 to 40 μm. 50 The negative active material includes primary graphite particles and secondary graphite particles, the primary graphite particles have a D50 of 3 to 5 μm, and the secondary graphite particles have a D50 of 20 to 40 μm. 50 The negative active material includes primary graphite particles and secondary graphite particles, the primary graphite particles have a D50 of 3 to 5 μm, and the secondary graphite particles have a D50 of 20 to 40 μ In the negative electrode active material layer, the mass ratio of the primary graphite particles to the secondary graphite particles is 1:(2.33-9), preferably 1:(4-9).

9. The lithium-ion battery of any one of claims 1-8, wherein, The lithium iron phosphate particles are doped with a modifying element M; the modifying element M includes one or more of Ti, Zr, Mo, Mn, Mg, V and C; The doping amount of modified element M in the lithium iron phosphate particles is 2000-6000 ppm, preferably 2000-3000 ppm.

10. A method of producing a lithium ion battery as defined in any one of claims 1 to 9, characterized in that, The method includes: (1) A negative electrode active material layer is formed on the negative electrode current collector to obtain a negative electrode sheet; the maximum aperture of the negative electrode sheet is 900-1500 nm. (2) A positive electrode active material layer is formed on the positive electrode current collector to obtain a positive electrode sheet; the maximum aperture of the positive electrode sheet is 50-90 nm.

11. The method of claim 10, wherein, The most frequent aperture of the positive electrode is 60–85 nm; and / or, the most frequent aperture of the negative electrode is 1050–1200 nm.

12. The method of claim 10 or 11, wherein, In step (1), the negative electrode active material layer is formed by using a negative electrode slurry containing a negative electrode active material, a second binder, and a second conductive agent; The negative electrode active material comprises primary graphite particles and secondary graphite particles, wherein the primary graphite particles have a D... 50 The secondary graphite particles have a particle size of 3–5 μm and a D0 50 The particle size is 20-40 μm. In the negative electrode active material layer, the mass ratio of the primary graphite particles to the secondary graphite particles is 1:(2.33-9), preferably 1:(4-9).

13. The method of any of claims 10-12, wherein, In step (2), the positive electrode active material layer is formed using a positive electrode slurry containing a positive electrode active material, a first binder, and a first conductive agent; The positive active material includes nanoscale lithium iron phosphate particles and microscale lithium iron phosphate particles, the nanoscale lithium iron phosphate particles having a D 50 particle diameter of 0.1 to 0.4 μm, and the microscale lithium iron phosphate particles having a D 50 particle diameter of 1 to 4 μm.

14. The battery according to any one of claims 10-13, wherein in the positive electrode active material layer, the mass ratio of the nano-sized lithium iron phosphate particles to the micro-sized lithium iron phosphate particles is 1:(0.67-2.33), preferably 1:(1.5-2.33).

15. The method of any of claims 10-14, wherein, In step (2), the first conductive agent includes carbon nanotubes, carbon black, and graphite flakes; The carbon nanotube has a tube diameter of 10-25 nm, and the carbon black has a D 50 The graphite microsheet has a thickness of 200-400 nm and a flake diameter of 0.5-4.5 μm.

16. A battery pack, characterized by Including the lithium-ion batteries described in claims 1 to 9.

17. An electrical device, characterized by A lithium-ion battery comprising the anode of any one of claims 1 to 9 or the battery pack of claim 16.

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