Battery monomer, battery device, power utilization device and energy storage device

Abstract

The invention provides a battery monomer, a battery device, a power utilization device and an energy storage device. Each single battery comprises a shell and an electrode assembly, the electrode assembly is accommodated in the shell, and the shell is made of a soft package material; the electrode assembly comprises a positive electrode plate and a negative electrode plate, the positive electrode plate comprises a positive electrode film layer, the positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises polyanion particles of which at least part of the surface is provided with a carbon coating material; a volume particle size distribution curve of particles in the positive electrode film layer is a bimodal curve, the peak position of a first peak in the bimodal curve is 0.3-0.7 mu m, the peak position of a second peak in the bimodal curve is 0.9-1.5 mu m, and the integral area ratio of the first peak to the second peak is 4: 6-8: 2; the positive electrode film layer further comprises a conductive agent, and the conductive agent comprises a carbon nanotube; and the size of the positive pole piece along the width direction of the battery monomer is less than or equal to 130mm. The battery monomer provided by the invention has good dynamic performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of battery cells, and particularly to a battery cell, a battery device, an electrical device, and an energy storage device. Background Art

[0002] In recent years, battery cells have been widely used in energy storage power systems such as hydraulic, thermal, wind, and solar power stations, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.

[0003] With the market's pursuit of the fast charging performance and service life of batteries, higher requirements are put forward for the kinetic performance and cycling performance of batteries. However, it is difficult for the existing technologies to simultaneously improve the above performances, and how to balance the two has become a technical problem urgently to be solved in this field. Summary of the Invention

[0004] The present application is made in view of the above problems, and its purpose is to provide a battery cell with good kinetic performance and cycling performance.

[0005] In a first aspect of the present application, a battery cell is provided, which includes a housing and an electrode assembly. The electrode assembly is accommodated inside the housing, and the material of the housing is a soft-pack material; the electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive electrode film layer, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes polyanion particles with at least part of their surfaces provided with a carbon coating material; the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve, the peak position of the first peak in the bimodal curve is 0.3 - 0.7 μm, the peak position of the second peak is 0.9 - 1.5 μm, and the integral area ratio of the first peak to the second peak is 4:6 - 8:2; the positive electrode film layer further includes a conductive agent, and the conductive agent includes carbon nanotubes; the size of the positive electrode tab in the width direction of the battery cell is less than or equal to 130 mm.

[0006] In an embodiment of the present application, the positive electrode active material has a bimodal particle size distribution, where the peak position of the first peak is less than the peak position of the second peak. The peak position of the first peak is 0.3 - 0.7 μm, and the peak position of the second peak is 0.9 - 1.5 μm, that is, the positive electrode active material includes small particles with particle sizes mainly located in 0.3 - 0.7 μm and large particles with particle sizes mainly located in 0.9 - 1.5 μm, such as Figure 2As shown. Research shows that large particles have a smaller specific surface area and fewer side reactions, but a longer ion diffusion path and relatively poor kinetics; small particles have a short ion diffusion path and good kinetic performance, but a larger specific surface area and relatively more side reactions. In the embodiments of the present application, the integral area ratio of the first peak to the second peak is controlled to be 4:6 - 8:2, that is, the ratio of the above-mentioned large and small particles is controlled within an appropriate range, which helps to improve the kinetic performance of the positive electrode active material and at the same time takes into account the cycle performance of the soft-pack battery. At the same time, the positive electrode film layer in the embodiments of the present application further includes a conductive agent, and the conductive agent includes carbon nanotubes to make up for the defects of low graphitization degree and insufficient electronic conductivity caused by insufficient sintering temperature or insufficient sintering time of small particles, and further improve the kinetic performance of the battery. Carbon nanotubes are one-dimensional conductive agents with excellent conductivity. At the same time, they can coat the surface of the particles, reduce the direct contact between the particles and the electrolyte, further reduce the degree of side reactions, and improve the cycle performance of the battery. In addition, the size of the positive electrode tab along the width direction of the battery cell is less than or equal to 130 mm in the embodiments of the present application. The smaller battery width is conducive to reducing the gas escape path in the soft-pack battery, thereby alleviating the lithium plating problem caused by the increase of small particles, the aggravation of side reactions, and gas aggregation. In summary, the battery cell provided by the embodiments of the present application has good cycle performance while improving the kinetic performance.

[0007] In any embodiment, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. In the bimodal curve, the peak position of the first peak is less than that of the second peak, and the peak position of the first peak is 0.3 - 0.6 μm.

[0008] The peak position of the first peak being within the above range helps to achieve a balance between the kinetic performance and cycle life of the battery.

[0009] In any embodiment, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. In the bimodal curve, the peak position of the first peak is less than that of the second peak, and the peak position of the second peak is 0.9 - 1.4 μm.

[0010] The peak position of the second peak being within the above range helps to take into account its kinetic performance while reducing the specific surface area of the particles and the degree of side reactions, reducing the resistance of the electrode tab, and taking into account the kinetic performance and cycle performance of the battery.

[0011] In any embodiment, the size of the positive electrode tab along the width direction of the battery cell is 110 - 125 mm.

[0012] In any embodiment, the integral area ratio of the first peak to the second peak is 5:5 - 7:3.

[0013] The integral area ratio of the first peak to the second peak is further within the above range, indicating that the positive electrode film layer has an appropriate ratio of large particles and small particles, which helps to balance the side reaction degree and kinetic performance of the positive electrode film layer, helps to further improve the battery kinetic performance and take into account the cycle performance.

[0014] In any embodiment, based on the total mass of the positive electrode film layer, the mass ratio of the conductive agent is greater than or equal to 0.8%.

[0015] The mass ratio of the conductive agent within the above range helps to improve the conductivity of the positive electrode film layer, reduce the resistance of the positive electrode sheet, and improve the kinetic performance of the battery.

[0016] In any embodiment, based on the total mass of the positive electrode film layer, the mass ratio of the conductive agent is 0.8% - 1.3%.

[0017] The content of the conductive agent is further within the above range, which can improve the kinetic performance of the battery cell while not occupying the space of the active material due to its excessive content, thus taking into account the volume energy density of the battery cell.

[0018] In any embodiment, based on the total mass of the conductive agent, the mass ratio of the carbon nanotubes is greater than or equal to 30%.

[0019] Carbon nanotubes are one-dimensional conductive agents with excellent electronic conductivity. The mass content of carbon nanotubes within the above range helps to form a good three-dimensional network structure in the positive electrode film layer and improve the conductivity of the positive electrode film layer. In addition, carbon nanotubes have a one-dimensional linear morphology, and their covering on the particle surface helps to reduce the direct contact area between the particles and the electrolyte. The mass content of carbon nanotubes within the above range can effectively reduce the contact between the particles and the electrolyte and reduce the degree of side reactions, thus taking into account the cycle performance while improving the battery kinetic performance.

[0020] In any embodiment, based on the total mass of the conductive agent, the mass ratio of the carbon nanotubes is 30% - 70%.

[0021] In any embodiment, based on the total mass of the conductive agent, the mass ratio of the carbon nanotubes is 40% - 70%.

[0022] Carbon nanotubes have poor flexibility. Excessive content of carbon nanotubes in the positive electrode film layer may lead to an increase in the brittleness of the electrode sheet and cause powder falling problems during long-term cycling, thus affecting the cycle performance of the battery. In the embodiments of the present application, the mass content of carbon nanotubes is further within the above range, which takes into account the brittleness of the electrode sheet while reducing the resistance of the electrode sheet, thus further improving the kinetic performance and cycle performance of the battery. In addition, the cost of carbon nanotubes is relatively high. The mass content of carbon nanotubes within the above range helps to reduce the production cost of the battery.

[0023] In any embodiment, the carbon nanotubes include one or more of single-walled carbon nanotubes, oligomeric-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0024] In any embodiment, the carbon nanotubes include oligomeric-walled carbon nanotubes.

[0025] Compared with multi-walled carbon nanotubes, oligomeric-walled carbon nanotubes have good electrical conductivity; compared with single-walled carbon nanotubes, they have better chemical stability and lower cost. In the embodiments of the present application, the carbon nanotubes include oligomeric-walled carbon nanotubes, which helps to balance the production cost while improving the kinetic performance of the battery monomer.

[0026] In any embodiment, the conductive agent further includes conductive carbon black.

[0027] In any embodiment, the conductive carbon black includes one or more of Super P, Ketjen black, and acetylene black.

[0028] The conductive carbon black is a particulate conductive agent, which can be filled into the three-dimensional conductive network of carbon nanotubes. The synergistic effect between the two is beneficial to further improving the electrical conductivity of the electrode sheet, thereby further improving the kinetic performance of the battery.

[0029] In any embodiment, the polyanion particles include the components represented by the following general formula: Li x A y Me a M b P 1-c X c Y z Formula I, where 0.1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.8 ≤ x + y ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or several of Na, K, and Mg; Me includes one or several of Mn, Fe, Co, and Ni; M includes one or several of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or several of S, Si, Cl, B, C, and N; Y includes one or several of O and F.

[0030] In any embodiment, the positive electrode active material includes titanium element, and based on the total mass of the positive electrode active material, the mass ratio of the titanium element is 1000 - 5000 ppm.

[0031] Tetravalent titanium atom Ti 4+ and divalent iron atom Fe2+ With similar ionic radii, titanium can replace some iron sites to form Ti-O bonds. Compared with Fe-O bonds, Ti-O bonds have higher bond energy, which helps to improve the lattice strength and inhibit lattice distortion during charge and discharge processes, thus enhancing the stability of the material and the cycling performance of the battery. In addition, the doping of titanium introduces extra positive charges, and the material system forms an Fe-O-Ti network according to the charge compensation mechanism, promoting electron transition, improving the conductivity of the positive electrode active material, reducing the resistance of the electrode sheet, and enhancing the kinetic performance of the battery.

[0032] In any embodiment, the positive electrode active material includes titanium. Based on the total mass of the positive electrode active material, the mass ratio of titanium is 2000 - 5000 ppm.

[0033] The content of titanium further within the above range helps to further improve the kinetic performance and cycling performance of the battery. In addition, too high a content of titanium increases the occupied iron sites, thus affecting the energy density of the battery. Therefore, in the embodiments of the present application, the mass content of titanium within the above range also helps to reduce the energy density loss caused by the introduction of titanium.

[0034] In any embodiment, when the battery cell is in a fully discharged state, the tap density of the positive electrode film layer is 2.3 g / cm 3 - 2.5 g / cm 3 .

[0035] A high tap density helps to increase the loading amount of the positive electrode active material on the positive electrode sheet; a low tap density helps to increase the porosity of the film layer. In the embodiments of the present application, when the battery cell is in a fully discharged state, the tap density of the positive electrode film layer within the above range helps to make the positive electrode film layer have a suitable porosity, improve the liquid retention rate of the electrode sheet, enhance the infiltration rate of the electrolyte, thus reducing the internal resistance of the battery and further improving the kinetic performance of the battery. At the same time, it helps to make the positive electrode sheet have an appropriate loading amount of the positive electrode active material, taking into account the volumetric energy density of the battery.

[0036] In any embodiment, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on the side of at least one ceramic layer away from the base film.

[0037] In any embodiment, the base film includes one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), aramid, and polytetrafluoroethylene (PTFE).

[0038] In any embodiment, the base film includes polyethylene (PE).

[0039] Compared with traditional polymer materials, polyethylene has a relatively high swelling rate and can absorb more electrolyte; it helps to improve the wetting rate of the electrolyte in the separator, thereby increasing the diffusion rate of lithium ions; at the same time, the high swelling rate helps to increase the pressure between the electrode sheet and the separator, promoting the release of gas generated by side reactions, reducing the increase in gas production caused by the increase in small particles, and thus improving the cycle performance of the battery. In addition, the polyethylene-based film has good internal pore uniformity, which helps to improve the uniformity of lithium ion diffusion and further improve the cycle performance of the battery. Moreover, polyethylene has good flexibility, which helps to reduce the risk of separator cracking when the soft-pack battery is deformed, further improving the cycle performance of the battery.

[0040] In any embodiment, the ceramic layer comprises one or more of aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), calcium oxide (CaO), and magnesium oxide (MgO).

[0041] The ceramic layer has the ability to accommodate the electrolyte, which helps to improve the wetting rate of the electrolyte in the separator, reduce the internal resistance of the battery, and improve the kinetic performance and cycle performance of the battery. In addition, the polyethylene-based film is relatively soft and has low mechanical strength. In the embodiments of the present application, the separator comprises a base film and a ceramic layer disposed on at least one side of the base film, which helps to improve the mechanical strength of the separator, improve the puncture resistance of the soft-pack battery, and thus improve the safety performance of the battery.

[0042] In any embodiment, the adhesive layer comprises one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR).

[0043] The separator comprises an adhesive layer, which helps to improve the bonding strength between the separator and the positive electrode sheet and the negative electrode sheet. On the one hand, it helps to reduce the gap between the electrode components, reduce the internal resistance of the battery, and improve the kinetic performance of the battery; on the other hand, it helps to reduce the displacement between the separator and the positive electrode sheet and the negative electrode sheet, increase the stability of the electrode components, and thus improve the cycle performance of the battery.

[0044] In any embodiment, the adhesive layer comprises polyvinylidene fluoride (PVDF), and the adhesive layer is in a porous continuous shape.

[0045] In traditional separators, the adhesive layer is generally aqueous PVDF, and the adhesive layer in the separator usually presents a discontinuous island-like structure. In the present application, the adhesive layer is in a continuous porous shape, which helps to increase the bonding area between the separator and the positive electrode sheet and the negative electrode sheet, increase the bonding strength, improve the tightness of the soft-pack battery pack, reduce the interfacial resistance between the separator and the electrode sheet, reduce the battery impedance, and thus further improve the kinetic performance and cycle performance of the battery.

[0046] In any embodiment, the separator includes a base film, ceramic layers disposed on both sides of the base film, and adhesive layers respectively disposed on the sides of the ceramic layers away from the base film on both sides of the base film.

[0047] The separator includes ceramic layers disposed on both sides of the base film and adhesive layers respectively disposed on the sides of the ceramic layers away from the base film on both sides of the base film, which helps to further improve the mechanical strength of the separator and the adhesive strength between the separator and the positive electrode sheet and the negative electrode sheet, thereby helping to further improve the kinetic performance and cycling performance of the battery cell.

[0048] In any embodiment, the porosity of the separator is 30% - 45%.

[0049] When the porosity of the separator is within the above range, it helps to improve the electrolyte infiltration rate of the separator, thereby increasing the lithium ion transmission rate, reducing the battery internal resistance, and further improving the kinetic performance of the battery.

[0050] In any embodiment, the battery cell further includes an electrolyte, the electrolyte includes a solvent, the solvent includes ethylene carbonate (EC), and based on the total mass of the solvent, the mass percentage of ethylene carbonate (EC) is 0.1% - 25%.

[0051] The inclusion of ethylene carbonate in the electrolyte helps the dissolution of the solute in the electrolyte. And at the initial stage of battery use, ethylene carbonate can decompose to form a solid electrolyte interface film (SEI film) at the negative electrode interface and an electrochemical interface film (CEI film) at the positive electrode interface, thereby improving the cycling performance of the battery. However, the viscosity of ethylene carbonate is relatively high, and too high a content will affect the lithium ion transmission rate, thereby affecting the kinetic performance of the battery. In the embodiments of the present application, the mass percentage of ethylene carbonate is within the above range, which not only helps to form good SEI and CEI films, but also reduces its impact on the lithium ion transmission rate, thus taking into account the kinetic performance of the battery while improving the cycling performance of the battery.

[0052] In any embodiment, the electrolyte further includes vinylene carbonate (VC), and based on the total mass of the electrolyte, the mass percentage of vinylene carbonate (VC) is 0.5% - 2%.

[0053] Vinylene carbonate (VC) decomposes preferentially before ethylene carbonate (EC) decomposes to form a primary SEI film with high elasticity and low impedance, and promotes the stability of the positive electrode CEI film to a certain extent. In the embodiments of the present application, the mass content of VC is within the above range, which helps to reduce the gas generated by the decomposition of ethylene carbonate, thereby reducing the gas content inside the battery, alleviating the lithium plating phenomenon induced by gas aggregation, and further improving the cycle life of the battery.

[0054] In any embodiment, the electrolyte further includes lithium difluorophosphate (LiPF2O2), and based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate (LiPF2O2) is 0.03% - 0.2%.

[0055] The decomposition products of lithium difluorophosphate can fill into the SEI film and CEI film, enhancing the elasticity and compactness of the interface film, reducing the direct contact between the electrolyte and the active material, thereby reducing the degree of side reactions. In the embodiments of the present application, the content of lithium difluorophosphate is within the above range, which helps to improve the quality of the SEI film and CEI film, reduce the gas generation inside the battery, thereby improving the lithium deposition caused by gas aggregation, and further improving the cycle performance of the battery.

[0056] In any embodiment, the negative electrode sheet includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, and the D V 50 is less than or equal to 25 μm.

[0057] The D V 50 of the negative electrode active material is large, indicating that the particle size of the negative electrode active material is relatively large, thus extending the lithium ion diffusion path, and further affecting the ionic conductivity of the negative electrode sheet. In the embodiments of the present application, the D V 50 of the negative electrode active material is within the above range, indicating that the negative electrode active material has an appropriate particle size, which helps to shorten the lithium ion insertion / extraction path, improve the ionic conductivity of the negative electrode film layer, and further improve the kinetic performance of the battery.

[0058] In any embodiment, the negative electrode active material includes artificial graphite, and the orientation degree (OI) of the negative electrode active material is less than 3.5, where the orientation degree (OI) = I004 / I110, I004 represents the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the X-ray diffraction test, and I110 represents the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the X-ray diffraction test.

[0059] In the embodiments of the present application, the orientation degree (OI) of the negative electrode active material is within the above range, and the orientation of the material is relatively disordered, which helps to increase the number of end faces for lithium ion insertion, thus helping to improve the kinetic performance of the battery.

[0060] In any embodiment, when the battery cell is in a fully discharged state, the tap density of the negative electrode film layer is 1.4 g / cm 3 - 1.6 g / cm 3 .

[0061] In the embodiments of the present application, the tap density of the negative electrode film layer is within the above range, which helps to improve the kinetic performance of the battery.

[0062] In any embodiment, the pouch material includes an aluminum-plastic composite film, which is a composite film composed of one or more of polypropylene (PP), nylon (PA), cast polypropylene (CPP), polyimide (PI), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene terephthalate (PET), polyethylene (PE) and aluminum.

[0063] The pouch material has a high elongation rate, so its casing is thinner, lighter and softer, which helps to improve the space utilization rate of the battery cell, thereby increasing the energy density of the battery cell. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery interior, reduce the decomposition of the electrolyte and the oxidation degree of the electrode material, thereby increasing the battery life.

[0064] In any embodiment, the battery cell includes a stacked cell, and the stacked cell includes an electrode assembly.

[0065] Compared with the wound cell, the stacked cell has no corner area. Therefore, the battery including the stacked cell helps to improve the space utilization rate of the battery, and further increases the volumetric energy density of the battery. However, due to the lack of restraint in the corner area, the extrusion between the positive electrode sheet, the separator and the negative electrode sheet is small, and the generated gas is not easily escaped, which may lead to gas accumulation and lithium plating on the electrode sheet, affecting the cycle performance of the battery. In the embodiments of the present application, the stacked cell is used, and at the same time, the particle size and proportion of large and small particles in the positive electrode film layer are controlled, the conductive agent includes carbon nanotubes, and the size of the positive electrode sheet along the width direction of the battery cell is controlled, which helps to improve the kinetic performance and energy density of the battery while taking into account the cycle performance.

[0066] In a second aspect of the present application, a battery device is provided, and the battery device includes the battery cell provided in the first aspect.

[0067] In a third aspect of the present application, an electrical device is provided, and the electrical device includes the battery device provided in the second aspect, and the battery device is used to provide electrical energy.

[0068] In a fourth aspect of the present application, an energy storage device is provided, and the energy storage device includes the battery device provided in the second aspect, and the battery device is used to store electrical energy.

[0069] The above description is only an overview of the technical solutions of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other objects, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are hereinafter specifically exemplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the several views denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings merely depict some embodiments disclosed in accordance with the present application and should not be regarded as limiting the scope of the present application.

[0071] Figure 1 is a surface topography diagram of a negative electrode tab after lithium plating in the prior art; Figure 2 is a cross-sectional polished electron microscopy topography diagram of a positive electrode tab in an embodiment of the present application; Figure 3 is a schematic diagram of an electrical device provided in some embodiments of the present application. Detailed Embodiments

[0072] Hereinafter, embodiments of the battery cell, battery device, electrical device, and energy storage device of the present application will be specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary details are omitted. For example, there are cases where the detailed description of well-known matters and the repeated description of actually identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0073] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a particular range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0074] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0075] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0076] Unless otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or can also include steps (a), (c) and (b), or can also include steps (c), (a) and (b), etc.

[0077] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present application mean open-ended or can also be closed-ended. For example, the "comprising" and "including" can mean that other components not listed can also be included or contained, or can also mean only including or containing the listed components.

[0078] Unless otherwise specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0079] In the present application, the terms "a plurality of" and "a variety of" mean two or more than two.

[0080] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art.

[0081] Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used testing methods in the art For example, they can be measured according to the testing methods given in the embodiments of the present application. Unless otherwise specified, the testing temperature of each parameter is 25°C.

[0082] In the embodiments of the present application, the battery mentioned may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include battery cells, battery modules, battery packs, etc.

[0083] A battery cell is the smallest unit that makes up a battery and can independently perform the functions of charging and discharging.

[0084] When there are multiple battery cells, the multiple battery cells are connected in series, parallel or in a hybrid connection through a busbar component. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, and the battery pack includes a box body and battery cells, and the battery cells or battery modules are accommodated in the box body. In some embodiments, the box body may be part of the chassis structure of a vehicle. For example, part of the box body may become at least part of the vehicle floor, or part of the box body may become at least part of the crossbeam and longitudinal beam of the vehicle.

[0085] In some embodiments, the battery may be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0086] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. In the battery module, the multiple battery cells can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other way. Further, the multiple battery cells can be fixed by fasteners.

[0087] Optionally, the battery module may further include a housing having an accommodation space, and the multiple battery cells are accommodated in the accommodation space.

[0088] In some embodiments, the above battery module can be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0089] The battery pack may include a box body and multiple battery modules disposed in the box body. The box body includes an upper box body and a lower box body. The upper box body is used to cover the lower box body and form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in the box body in any way.

[0090] The battery provided in the embodiments of the present application may include a lithium-ion battery.

[0091] A battery cell includes an electrode assembly and an electrolyte.

[0092] An electrode assembly generally includes a positive electrode sheet and a negative electrode sheet. The negative electrode sheet is the electrode where the reaction of absorbing or lithiating lithium ions occurs during battery charging and releasing or delithiating lithium occurs during discharging. The positive electrode sheet is the electrode where the reaction of releasing or delithiating lithium ions occurs during battery charging and occluding or lithiating lithium occurs during discharging.

[0093] Polyanion materials have characteristics such as good cycle performance and safety, and have been widely used as the positive active material of batteries. However, compared with ternary materials, their specific capacity is relatively low. Adopting a soft-pack battery cell strategy can improve the space utilization rate of the battery, thereby increasing the volumetric energy density of the battery. The applicant found that reducing the particle size in the positive electrode film layer helps to improve the lithium ion diffusion rate of the positive electrode sheet, which is beneficial to the improvement of battery kinetics performance. However, the increase in small particles in the positive electrode film layer will lead to an increase in the ohmic impedance of the positive electrode sheet, which has a negative impact on the improvement of battery kinetics performance. At the same time, the increase in small particles makes the specific surface area of the positive active material increase, and the degree of side reactions increases, resulting in an increase in the gas generated during the battery cycle. The shell of the soft-pack battery cell is relatively soft, with a small binding force on the electrode assembly, and cannot effectively extrude the gas generated by side reactions, resulting in gas accumulation, an increase in the internal gap of the battery cell, an increase in the battery internal resistance, and deterioration of the battery kinetics performance; in addition, a large amount of gas accumulation will also cause large-area lithium deposition, as Figure 1 shown, seriously affecting the cycle performance of the battery. Therefore, how to balance the cycle performance while improving the kinetics performance of the polyanion-based soft-pack battery has become an urgent technical problem to be solved.

[0094] To solve the above problems, in the first aspect of the present application, a battery cell is provided, including a shell and an electrode assembly. The electrode assembly is accommodated inside the shell, and the material of the shell is a soft-pack material; the electrode assembly includes a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode film layer, the positive electrode film layer includes a positive active material, and the positive active material includes polyanion particles with at least part of the surface provided with a carbon coating material; the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve, the peak position of the first peak in the bimodal curve is 0.3 - 0.7 μm, the peak position of the second peak is 0.9 - 1.5 μm, and the integral area ratio of the first peak to the second peak is 4:6 - 8:2; the positive electrode film layer further includes a conductive agent, and the conductive agent includes carbon nanotubes; the size of the positive electrode sheet in the width direction of the battery cell is less than or equal to 130 mm.

[0095] In the embodiment of the present application, the positive active material has a bimodal particle size distribution, where the peak position of the first peak is less than the peak position of the second peak. The peak position of the first peak is 0.3 - 0.7 μm, and the peak position of the second peak is 0.9 - 1.5 μm, that is, the positive active material includes small particles with a particle size mainly located in 0.3 - 0.7 μm and large particles with a particle size mainly located in 0.9 - 1.5 μm, as Figure 2As shown. Research shows that large particles have a smaller specific surface area and fewer side reactions, but a longer ion diffusion path and relatively poor kinetics; small particles have a short ion diffusion path and good kinetic performance, but a larger specific surface area and relatively more side reactions. In the embodiment of the present application, the integral area ratio of the first peak to the second peak is controlled to be 4:6 - 8:2, that is, the ratio of the above-mentioned large and small particles is controlled within an appropriate range, which helps to improve the kinetic performance of the cathode active material and at the same time takes into account the cycle performance of the soft-pack battery. At the same time, the cathode film layer in the embodiment of the present application further includes a conductive agent, and the conductive agent includes carbon nanotubes to make up for the defects of low graphitization degree and insufficient electronic conductivity caused by insufficient sintering temperature or insufficient sintering time of small particles, and further improve the kinetic performance of the battery. Carbon nanotubes are one-dimensional conductive agents with excellent conductivity. At the same time, they can be coated on the surface of the particles to reduce the direct contact between the particles and the electrolyte, further reducing the degree of side reactions and improving the cycle performance of the battery. In addition, the size of the cathode electrode sheet in the embodiment of the present application along the width direction of the battery cell is less than or equal to 130 mm. The smaller battery width is beneficial to reducing the gas escape path in the soft-pack battery, thereby alleviating the lithium deposition problem caused by the increase of small particles, the aggravation of side reactions, and gas aggregation. In summary, the battery cell provided by the embodiment of the present application has good cycle performance while improving the kinetic performance.

[0096] In the present application, the term "bimodal curve" refers to a curve with two peaks. This distribution characteristic indicates that the particles in the material are mainly concentrated in two significantly different particle size ranges. The peak position of the first peak in the bimodal curve is less than that of the second peak, and the peak position refers to the particle size corresponding to the peak in the curve.

[0097] In this application, the particle size volume distribution curve can be measured by methods and instruments known in the art. As an example, reference can be made to GB / T 19077-2016 Laser diffraction method for particle size distribution, and it can be conveniently measured using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 laser particle size analyzer of Malvern Instruments Limited, UK. The example is as follows: S1: Add 2 g of the positive electrode active material and 5 g of sodium dodecyl sulfate (SDS) to 200 mL of N-methylpyrrolidone (NMP), then place it in an ultrasonic cleaner for ultrasonic treatment, set the power to 100 W and the time to 30 min, and take the solution after the ultrasonic treatment to measure the particle size; S2: Re-take 2 g of the positive electrode active material and 5 g of sodium dodecyl sulfate (SDS) and add them to 200 mL of N-methylpyrrolidone (NMP), then place it in an ultrasonic cleaner for ultrasonic treatment, set the power to 100 W and the time to 60 min, and take the solution after the ultrasonic treatment to measure the particle size; If the Dv50 measured in steps S1 and S2 is greater than 5% or the fluctuation of Dv99 is greater than 5%, it is considered that the positive electrode active material is not fully dispersed. Repeat step S2 and increase the ultrasonic time by 30 min until the fluctuations of Dv50 and Dv99 in two tests with an ultrasonic time difference of 30 min are both less than or equal to 5%, then stop the test. The particle size distribution test result of the solution with the longest ultrasonic time is the particle size distribution of the positive electrode active material. Among them, the fluctuation of Dv50 is the ratio of the difference between the Dv50 values of the two tests to the smaller Dv50 value in the two test results; the fluctuation of Dv99 is the ratio of the difference between the Dv99 values of the two tests to the smaller Dv99 value in the two test results.

[0098] It should be noted that the materials used for testing in this application can be freshly prepared materials or materials obtained by scraping powder from the film layer after disassembling a secondary battery.

[0099] In some embodiments, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve, and the peak position of the first peak in the bimodal curve is less than the peak position of the second peak. The peak position of the first peak can be 0.3μm, 0.31μm, 0.32μm, 0.33μm, 0.34μm, 0.35μm, 0.36μm, 0.37μm, 0.38μm, 0.39μm, 0.4μm, 0.41μm, 0.42μm, 0.43μm, 0.44μm, 0.45μm, 0.46μm, 0.47μm, 0.48μm, 0.49μm, 0.5μm, 0.51μm, 0.52μm, 0.53μm, 0.54μm, 0.55μm, 0.56μm, 0.57μm, 0.58μm, 0.59μm, 0.6μm, 0.61μm, 0.62μm, 0.63μm, 0.64μm, 0.65μm, 0.66μm, 0.67μm, 0.68μm, 0.69μm, 0.7μm or the numerical range between any two of them.

[0100] In some embodiments, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve, and the peak position of the first peak in the bimodal curve is less than the peak position of the second peak. The peak position of the first peak is 0.3 - 0.6μm.

[0101] The peak position of the first peak being within the above range helps to achieve a balance between the battery kinetic performance and the cycle life.

[0102] In some embodiments, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. In the bimodal curve, the peak position of the first peak is less than that of the second peak. The peak position of the second peak can be 0.9μm, 0.91μm, 0.92μm, 0.93μm, 0.94μm, 0.95μm, 0.96μm, 0.97μm, 0.98μm, 0.99μm, 1.0μm, 1.01μm, 1.02μm, 1.03μm, 1.04μm, 1.05μm, 1.06μm, 1.07μm, 1.08μm, 1.09μm, 1.1μm, 1.11μm, 1.12μm, 1.13μm, 1.14μm, 1.15μm, 1.16μm, 1.17μm, 1.18μm, 1.19μm, 1.2μm, 1.21μm, 1.22μm, 1.23μm, 1.24μm, 1.25μm, 1.26μm, 1.27μm, 1.28μm, 1.29μm, 1.3μm, 1.31μm, 1.32μm, 1.33μm, 1.34μm, 1.35μm, 1.36μm, 1.37μm, 1.38μm, 1.39μm, 1.4μm, 1.41μm, 1.42μm, 1.43μm, 1.44μm, 1.45μm, 1.46μm, 1.47μm, 1.48μm, 1.49μm, 1.5μm or the numerical range between any two of them.

[0103] In some embodiments, the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. In the bimodal curve, the peak position of the first peak is less than that of the second peak. The peak position of the second peak is 0.9 - 1.4μm.

[0104] The peak position of the second peak being within the above range helps to balance its kinetic performance while reducing the specific surface area of the particles and the degree of side reactions, reducing the resistance of the electrode sheet, and balancing the kinetic performance and cycling performance of the battery.

[0105] In the present application, the integral area ratio of the first peak to the second peak can be measured using methods and instruments well-known in the art. As an example, according to the above method, a volume particle size distribution curve of the particles in the positive electrode film layer is obtained using a Mastersizer 3000 laser particle size analyzer. In the software, open "Size Distribution", select to display the "Volume(%)" view, click "Band Analysis" in the top menu bar, find the option "User-defined Bands", click "Add Band", and perform interval setting to obtain the integral area ratio of the two peaks. Among them, the set interval is adjusted adaptively according to the two peaks of the positive electrode active material to ensure that the set interval only includes the entire range of the first peak or the second peak.

[0106] In some embodiments, the integral area ratio of the first peak to the second peak can be 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, or a numerical range between any two of them.

[0107] In the present application, the dimension of the positive electrode tab along the width direction of the battery cell can be tested using methods and instruments known in the art. As an example, it can be tested using a micrometer (e.g., Mitutoyo 293-100 type, with a precision of 0.1 μm).

[0108] In some embodiments, the dimension of the positive electrode tab along the width direction of the battery cell can be 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm, or a numerical range between any two of them.

[0109] In some embodiments, the dimension of the positive electrode tab along the width direction of the battery cell is 110-125 mm.

[0110] In the present application, whether the positive electrode film layer contains carbon nanotubes can be determined using methods and instruments known in the art. As an example, a cross-section polished-scanning electron microscope (CP-SEM) image of the positive electrode film layer is taken for observation and determination.

[0111] In some embodiments, the integral area ratio of the first peak to the second peak is 5:5-7:3.

[0112] The integral area ratio of the first peak to the second peak further within the above range indicates that the positive electrode film layer has an appropriate ratio of large particles and small particles, which helps to balance the side reaction degree and kinetic performance of the positive electrode film layer, helps to further improve the battery kinetic performance and take into account the cycle performance.

[0113] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the conductive agent is greater than or equal to 0.8%.

[0114] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the conductive agent can be 0.8%, 0.85%, 0.9%, 0.95%, 1%, 1.05%, 1.1%, 1.15%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.65%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, or a numerical range between any two of them.

[0115] When the mass proportion of the conductive agent is within the above range, it helps to improve the conductivity of the positive electrode film layer, reduce the resistance of the positive electrode sheet, and improve the kinetic performance of the battery.

[0116] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the conductive agent is 0.8% - 1.3%.

[0117] When the content of the conductive agent is further within the above range, while improving the kinetic performance of the battery cell, it will not occupy the space of the active material due to its excessive content, thus taking into account the volume energy density of the battery cell.

[0118] In some embodiments, based on the total mass of the conductive agent, the mass proportion of carbon nanotubes is greater than or equal to 30%.

[0119] In some embodiments, based on the total mass of the conductive agent, the mass proportion of carbon nanotubes can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or any value range between any two of them.

[0120] Carbon nanotubes are one-dimensional conductive agents with excellent electronic conductivity. When the mass content of carbon nanotubes is within the above range, it helps to form a good three-dimensional network structure in the positive electrode film layer and improve the conductivity of the positive electrode film layer. In addition, carbon nanotubes have a one-dimensional linear morphology, and their covering on the particle surface helps to reduce the direct contact area between the particles and the electrolyte. When the mass content of carbon nanotubes is within the above range, it can effectively reduce the contact between the particles and the electrolyte and reduce the degree of side reactions, thus taking into account the cycle performance while improving the battery kinetic performance.

[0121] In some embodiments, based on the total mass of the conductive agent, the mass proportion of carbon nanotubes is 30% - 70%.

[0122] In some embodiments, based on the total mass of the conductive agent, the mass proportion of carbon nanotubes is 40% - 70%.

[0123] Carbon nanotubes have poor flexibility. Excessive content of carbon nanotubes in the positive electrode film layer may lead to an increase in the brittleness of the electrode sheet and cause powder falling problems during long-term cycling, thus affecting the cycle performance of the battery. In the embodiments of the present application, when the mass content of carbon nanotubes is further within the above range, while reducing the resistance of the electrode sheet, the brittleness of the electrode sheet is taken into account, thus further improving the kinetic performance and cycle performance of the battery. In addition, the cost of carbon nanotubes is relatively high. When the mass content of carbon nanotubes is within the above range, it helps to reduce the production cost of the battery.

[0124] In some embodiments, the carbon nanotubes include one or more of single-walled carbon nanotubes, oligomeric-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0125] In some embodiments, the carbon nanotubes include few-walled carbon nanotubes.

[0126] Compared with multi-walled carbon nanotubes, few-walled carbon nanotubes have good electrical conductivity; compared with single-walled carbon nanotubes, they have better chemical stability and lower cost. In the embodiments of the present application, the carbon nanotubes include few-walled carbon nanotubes, which helps to balance the production cost while improving the kinetic performance of the battery cell.

[0127] In some embodiments, the conductive agent further includes conductive carbon black.

[0128] In some embodiments, the conductive carbon black includes one or more of Super P, Ketjenblack, and acetylene black.

[0129] The conductive carbon black is a particulate conductive agent, which can be filled into the three-dimensional conductive network of carbon nanotubes. The synergistic effect of the two is beneficial to further improving the electrical conductivity of the electrode sheet, thereby further improving the kinetic performance of the battery.

[0130] In some embodiments, the polyanion particles include the components represented by the following general formula: Li x A y Me a M b P 1-c X c Y z Formula I where 0.1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.8 ≤ x + y ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or more of Na, K, and Mg; Me includes one or more of Mn, Fe, Co, and Ni; M includes one or more of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or more of S, Si, Cl, B, C, and N; Y includes one or more of O and F.

[0131] In some embodiments, x can be selected from 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3 or any range between any two of them.

[0132] In some embodiments, y can be optionally 0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3 or any range between any two of them.

[0133] In some embodiments, x + y can be optionally 0.8, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3 or any range between any two of them.

[0134] In some embodiments, a can be optionally 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5 or any range between any two of them.

[0135] In some embodiments, b can be optionally 0, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 or any range between any two of them.

[0136] In some embodiments, a + b can be optionally 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5 or any range between any two of them.

[0137] In some embodiments, c can be optionally 0, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 or any range between any two of them.

[0138] In some embodiments, z can be optionally 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 or any range between any two of them.

[0139] In the present application, the types and contents of elements in the polyanion particles in the positive electrode film layer can be tested by any well-known method in the art.

[0140] In some embodiments, the polyanion particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate fluoride, lithium manganese iron phosphate, lithium iron phosphate fluoride, lithium manganese iron phosphate fluoride and their modified materials.

[0141] In some embodiments, the polyanion particles include one or more of lithium iron phosphate and its modified materials.

[0142] In some embodiments, the positive electrode active material includes titanium element, and based on the total mass of the positive electrode active material, the mass ratio of the titanium element is 1000 - 5000 ppm.

[0143] The types and contents of elements in the lithium-containing transition metal phosphate particles in the positive electrode active material can be tested by any well-known method in the art. As an example, inductively coupled plasma emission spectrometry is used to test the titanium element and its content with reference to Appendix C of GB / T 33822-2017.

[0144] In some embodiments, the positive electrode active material includes titanium element, and based on the total mass of the positive electrode active material, the mass ratio of the titanium element can be optionally 1000 ppm, 1100 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2100 ppm, 2200 ppm, 2300 ppm, 2400 ppm, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm, 2900 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm or any value range between any two of them.

[0145] Tetravalent titanium atom Ti 4+ and divalent iron atom Fe 2+ have similar ionic radii. The titanium element can replace some iron element sites to form Ti-O bonds. Compared with the Fe-O bond, the Ti-O bond has a higher bond energy, which helps to improve the lattice strength and inhibit lattice distortion during charge and discharge, thereby enhancing the stability of the material and the cycle performance of the battery. In addition, the doping of titanium element introduces additional positive charges, and the material system forms a Fe-O-Ti network according to the charge compensation mechanism, promoting electron transition, improving the conductivity of the positive electrode active material, reducing the resistance of the electrode sheet, and enhancing the kinetic performance of the battery.

[0146] In some embodiments, the positive electrode active material includes titanium element, and based on the total mass of the positive electrode active material, the mass ratio of the titanium element is 2000 - 5000 ppm.

[0147] The content of the titanium element further within the above range helps to improve the kinetic performance and cycle performance of the battery further. In addition, too high a content of the titanium element increases the occupied iron element sites, thus affecting the energy density of the battery. Therefore, in the embodiments of the present application, the mass content of the titanium element within the above range also helps to reduce the energy density loss caused by the introduction of the titanium element.

[0148] In some embodiments, when the battery cell is in a fully discharged state, the tap density of the positive electrode film layer is 2.3 g / cm3 -2.5 g / cm 3 。

[0149] In this application, the fully discharged state means placing the battery in an oven environment at 25°C, standing still for 2 h, waiting for the battery temperature to reach 25°C, discharging the battery at a constant current of 1 / 3C until 2.5V, then standing still for 30 min, and then discharging at a constant current of 0.04C until 2.5V.

[0150] In this application, the compaction density of the positive electrode film layer can be tested by methods known in the art. As an example, place the battery in an oven environment at 25°C, stand still for 2 h, wait for the battery temperature to reach 25°C, discharge the battery at a constant current of 1 / 3C until 2.5V, then stand still for 30 min, and then discharge at a constant current of 0.04C until 2.5V. Disassemble the battery to obtain the positive electrode plate, treat the residual electrolyte with dimethyl carbonate solvent, dry the electrode plate, cut it into small round pieces with an area of S, obtain its mass W1, and use a micrometer to measure the thickness T1 of the positive electrode plate. Then wipe off the positive electrode film layer of the weighed electrode plate, weigh the mass of the current collector, denoted as W2, and use a micrometer to measure the thickness T2 of the current collector. Then the compaction density PD of the positive electrode film layer = (W1 - W2) / [(T1 - T2)×S].

[0151] In some embodiments, when the battery cell is in the fully discharged state, the compaction density of the positive electrode film layer can be 2.3 g / cm 3 、2.31 g / cm 3 、2.32 g / cm 3 、2.33 g / cm 3 、2.34 g / cm 3 、2.35 g / cm 3 、2.36 g / cm 3 、2.37 g / cm 3 、2.38 g / cm 3 、2.39 g / cm 3 、2.40 g / cm 3 、2.41 g / cm 3 、2.42 g / cm 3 、2.43 g / cm 3 、2.44 g / cm 3 、2.45 g / cm 3 、2.46 g / cm 3 、2.47 g / cm 3 、2.48 g / cm 3 、2.49 g / cm 3 、2.5 g / cm 3 or any numerical range between any two of them.

[0152] A high compaction density helps to increase the loading amount of the positive active material on the positive electrode sheet; a low compaction density helps to increase the porosity of the film layer. In the embodiments of the present application, when the battery cell is in a fully discharged state, the compaction density of the positive electrode film layer is within the above range, which helps to make the positive electrode film layer have an appropriate porosity, improve the liquid retention rate of the electrode sheet, enhance the infiltration rate of the electrolyte, thereby reducing the internal resistance of the battery and further improving the kinetic performance of the battery. At the same time, it helps to make the positive electrode sheet have an appropriate loading amount of the positive active material, taking into account the volumetric energy density of the battery.

[0153] In some embodiments, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet. The separator includes a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on the side of at least one ceramic layer away from the base film.

[0154] In some embodiments, the separator includes a base film and a ceramic layer disposed on one side of the base film.

[0155] In some embodiments, the separator includes a base film and ceramic layers disposed on both sides of the base film.

[0156] In some embodiments, the base film includes one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), aramid, and polytetrafluoroethylene (PTFE).

[0157] In some embodiments, the base film includes polyethylene (PE).

[0158] Compared with traditional polymer materials, polyethylene has a relatively high swelling rate and can absorb more electrolyte; it helps to improve the infiltration rate of the electrolyte in the separator, thereby increasing the diffusion rate of lithium ions; at the same time, the high swelling rate helps to increase the pressure between the electrode sheet and the separator, promote the release of gas generated by side reactions, and reduce the increase in gas production caused by the increase in small particles, thereby reducing large-area lithium deposition in the battery and improving the cycle performance of the battery. In addition, the polyethylene-based film has good internal pore uniformity, which helps to improve the uniformity of lithium ion diffusion and further improve the cycle performance of the battery. In addition, polyethylene has good flexibility, which helps to reduce the risk of separator cracking when the flexible battery deforms, further improving the cycle performance of the battery.

[0159] In some embodiments, the ceramic layer includes one or more of aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), calcium oxide (CaO), and magnesium oxide (MgO).

[0160] In some embodiments, the ceramic layer includes aluminum oxide (Al2O3).

[0161] The ceramic layer has the ability to hold the electrolyte, which helps to improve the wetting rate of the electrolyte in the separator, reduce the internal resistance of the battery, and enhance the kinetic performance and cycling performance of the battery. Additionally, the polyethylene-based film is relatively soft and has low mechanical strength. In the embodiments of the present application, the separator includes a base film and a ceramic layer disposed on at least one side of the base film, which helps to improve the mechanical strength of the separator, enhance the puncture resistance of the soft-pack battery, and thus improve the safety performance of the battery.

[0162] In some embodiments, the adhesive layer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR).

[0163] The separator includes an adhesive layer, which helps to improve the adhesion strength between the separator and the positive electrode plate and the negative electrode plate. On the one hand, this helps to reduce the gap between the electrode components, lower the internal resistance of the battery, and improve the kinetic performance of the battery; on the other hand, it helps to reduce the displacement between the separator and the positive electrode plate and the negative electrode plate, increase the stability of the electrode components, and thus improve the cycling performance of the battery.

[0164] In some embodiments, the adhesive layer includes polyvinylidene fluoride (PVDF), and the adhesive layer is in a porous continuous shape.

[0165] In traditional separators, the adhesive layer is generally aqueous PVDF, and the adhesive layer in the separator usually presents a discontinuous island-like structure. In the present application, the adhesive layer is in a continuous porous shape, which helps to increase the adhesion area between the separator and the positive electrode plate and the negative electrode plate, increase the adhesion strength, improve the tightness of the soft-pack battery module, reduce the interfacial resistance between the separator and the electrode plate, lower the battery impedance, and thus further improve the kinetic performance and cycling performance of the battery.

[0166] In some embodiments, the separator includes a base film, a ceramic layer disposed on one side of the base film, and an adhesive layer disposed on the side of the ceramic layer away from the base film.

[0167] In some embodiments, the separator includes a base film, ceramic layers disposed on both sides of the base film, and adhesive layers respectively disposed on the sides of the ceramic layers away from the base film.

[0168] The separator includes ceramic layers disposed on both sides of the base film and adhesive layers respectively disposed on the sides of the ceramic layers away from the base film, which helps to further improve the mechanical strength of the separator and the adhesion strength between the separator and the positive electrode plate and the negative electrode plate, and thus helps to further improve the kinetic performance and cycling performance of the battery cell.

[0169] In some embodiments, the porosity of the separator is 30% - 45%.

[0170] When used in this article, the porosity of the separator has the meaning well-known in the art and can be measured using methods and instruments known in the art. As an example, the gas displacement method is used for measurement with reference to GB / T24586-2009. The porosity ε = (V1 - V2) / V1×100%, where V1 is the apparent volume of the sample and V2 is the true volume of the sample.

[0171] In some embodiments, the porosity of the separator can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45% or any value range between any two of them.

[0172] When the porosity of the separator is within the above range, it helps to improve the electrolyte infiltration rate of the separator, thereby increasing the lithium ion transport rate, reducing the battery internal resistance, and further improving the kinetic performance of the battery.

[0173] In some embodiments, the battery cell further includes an electrolyte, the electrolyte includes a solvent, the solvent includes ethylene carbonate (EC), and based on the total mass of the solvent, the mass fraction of ethylene carbonate (EC) is 0.1% - 25%.

[0174] In this article, the types and mass contents of the components in the electrolyte can be obtained by detecting the electrolyte through any method well-known to those skilled in the art. As an example, the composition and content of the electrolyte can be characterized by one or more of gas chromatography - mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography - mass spectrometry (GC-MS). Exemplarily, with reference to GB / T - 9722-2006 "General Rules for Gas Chromatography of Chemical Reagents" and / or GB / T6041-2002 "General Rules for Mass Spectrometry Analysis Methods", gas chromatography and mass spectrometry are used in combination. After the components in the sample are separated by gas chromatography, each component is broken into ion fragments in the mass spectrometer and separated according to the mass-to-charge ratio (m / z) to form a specific mass spectrum, obtaining the qualitative analysis of each organic component in the electrolyte. Then, each organic component in the electrolyte is separated in the chromatographic column to generate a detection signal spectrum of each component, and the components are qualitatively analyzed using the retention time, and the peak area is corrected with a standard to achieve quantification, obtaining the quantitative test analysis of the organic components in the electrolyte. With reference to JY / T - 020, the anion types of the electrolyte salts in the electrolyte are detected by ion chromatography and quantitatively tested. With reference to JY / T 0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain the qualitative and quantitative analysis of the components in the electrolyte.

[0175] In this text, based on the total mass of the solvent, the mass percentage of ethylene carbonate (EC) can be obtained by the method of detecting the types and mass contents of each component in the electrolyte. Based on the total mass of the solvent, the mass percentage of ethylene carbonate (EC) is the ratio of the mass of ethylene carbonate obtained by testing according to the above method to the total mass of the solvent in the electrolyte.

[0176] It should be noted that the electrolyte referred to in this text can be either a fresh electrolyte or an electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be either the free electrolyte in the battery case or the electrolyte centrifuged from the electrode sheet.

[0177] In some embodiments, the battery cell further includes an electrolyte. The electrolyte includes a solvent, and the solvent includes ethylene carbonate (EC). Based on the total mass of the solvent, the mass percentage of ethylene carbonate (EC) can be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a numerical range between any two of them.

[0178] The inclusion of ethylene carbonate in the electrolyte helps with the dissolution of the solute in the electrolyte. And at the initial stage of battery use, ethylene carbonate can decompose to form a solid electrolyte interface film (SEI film) at the negative electrode interface and an electrochemical interface film (CEI film) at the positive electrode interface, thereby improving the cycle performance of the battery. However, the viscosity of ethylene carbonate is relatively high, and an excessive content thereof will affect the lithium ion transport rate, and thus affect the kinetic performance of the battery. In the embodiments of the present application, the mass percentage of ethylene carbonate is within the above range, which not only helps to form good SEI and CEI films, but also reduces its influence on the lithium ion transport rate, thus taking into account the kinetic performance of the battery while improving the cycle performance of the battery.

[0179] In some embodiments, the electrolyte further includes vinylene carbonate (VC). Based on the total mass of the electrolyte, the mass percentage of vinylene carbonate (VC) is 0.5% - 2%.

[0180] In this text, based on the total mass of the electrolyte, the mass percentage of vinylene carbonate (VC) can be tested using methods and instruments known in the art. As an example, the testing method for the types and mass contents of each component in the above electrolyte can be used for testing.

[0181] In some embodiments, the electrolyte further includes vinylene carbonate (VC). Based on the total mass of the electrolyte, the mass percentage of vinylene carbonate (VC) can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value range between any two of them.

[0182] Vinylene carbonate (VC) preferentially decomposes before ethylene carbonate (EC) decomposes and forms a primary SEI film with high elasticity and low impedance, and to a certain extent promotes the stability of the positive electrode CEI film. In the embodiments of the present application, when the mass content of VC is within the above range, it helps to reduce the gas generated by the decomposition of ethylene carbonate, thereby reducing the gas content inside the battery, alleviating the lithium plating phenomenon induced by gas accumulation, and further improving the cycle life of the battery.

[0183] In some embodiments, the electrolyte further includes lithium difluorophosphate (LiPF2O2). Based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate (LiPF2O2) is 0.03% - 0.2%.

[0184] In this article, based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate (LiPF2O2) can be tested using methods and instruments known in the art. As an example, the testing methods for the types and mass contents of each component in the above electrolyte can be used for testing.

[0185] In some embodiments, the electrolyte further includes lithium difluorophosphate (LiPF2O2). Based on the total mass of the electrolyte, the mass percentage of lithium difluorophosphate (LiPF2O2) can be 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, 0.2%, or any value range between any two of them.

[0186] The decomposition products of lithium difluorophosphate can fill into the SEI film and the CEI film, enhance the elasticity and compactness of the interfacial film, reduce the direct contact between the electrolyte and the active material, thereby reducing the degree of side reactions. In the embodiments of the present application, when the content of lithium difluorophosphate is within the above range, it helps to improve the quality of the SEI film and the CEI film, reduce the gas generation inside the battery, thereby improving the lithium plating caused by gas accumulation, and further improving the cycle performance of the battery.

[0187] In some embodiments, the negative electrode tab includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, and the D V 50 is less than or equal to 25 μm.

[0188] In this text, D of the negative electrode active material V 50 represents the particle size corresponding to when the cumulative volume percentage reaches 50% in the volume particle size distribution curve of the material. D of the negative electrode active material V 50 can be measured by methods and instruments known in the art. For example, it can be conveniently measured by referring to GB / T 19077-2016 Laser Diffraction Method for Particle Size Distribution and using a laser particle size analyzer. The test instrument can be the Mastersizer 3000 type laser particle size analyzer of Malvern Instruments Limited, UK.

[0189] In some embodiments, D of the negative electrode active material V 50 can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm or the numerical range between any two of them.

[0190] When D of the negative electrode active material V 50 is large, it means that the particle size of the negative electrode active material is relatively large, thus prolonging the lithium ion diffusion path, and further affecting the ionic conductivity of the negative electrode sheet. In the embodiments of this application, when D of the negative electrode active material V 50 is within the above range, it means that the negative electrode active material has an appropriate particle size, which helps to shorten the lithium ion insertion / extraction path, improve the ionic conductivity of the negative electrode film layer, and further improve the kinetic performance of the battery.

[0191] In some embodiments, the negative electrode active material includes artificial graphite, and the orientation degree (OI) of the negative electrode active material is less than 3.5, where the orientation degree (OI) = I004 / I110, I004 represents the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the X-ray diffraction test, and I110 represents the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the X-ray diffraction test.

[0192] When used in this text, the orientation degree (OI) has the meaning known in the art, and the orientation degree (OI) of the negative electrode active material can be tested by methods and instruments known in the art. As an example, it is tested using an X-ray diffractometer (such as Bruker D8 Discover), and the test can refer to JIS K0131-1996 and JB / T 4220-2011 to obtain the X-ray diffraction pattern of the negative electrode active material. According to the OI value = I 004 / I 110 Calculate the orientation degree (OI) of the negative electrode active material. I 004is the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the material, I 110 is the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the material. In the X-ray diffraction analysis test of this application, a copper target can be used as the anode target, with CuKα rays as the radiation source, the ray wavelength λ = 1.5418 Å, the scanning 2θ angle range is 20° - 80°, and the scanning rate is 4° / min. The orientation degree (OI) represents the degree of order of the crystal or particle arrangement in the material. A higher orientation degree (OI) indicates a more ordered grain arrangement in the material; a lower orientation degree (OI) indicates a more disordered orientation of the material.

[0193] In some embodiments, the negative electrode active material includes artificial graphite, and the orientation degree (OI) of the negative electrode active material can be selected from 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.49 or the numerical range between any two of them.

[0194] In the embodiments of this application, when the orientation degree (OI) of the negative electrode active material is within the above range, the orientation of the material is relatively disordered, which helps to increase the number of end faces for lithium ion insertion, thereby helping to improve the kinetic performance of the battery.

[0195] In some embodiments, when the battery cell is in a fully discharged state, the tap density of the negative electrode film layer is 1.4 g / cm 3 -1.6 g / cm 3 .

[0196] In this application, the tap density of the negative electrode film layer can be tested with reference to the test method of the tap density of the positive electrode film layer.

[0197] In some embodiments, when the battery cell is in a fully discharged state, the tap density of the negative electrode film layer can be 1.4 g / cm 3 , 1.41 g / cm 3 , 1.42 g / cm 3 , 1.43 g / cm 3 , 1.44 g / cm 3 , 1.45 g / cm 3 , 1.46 g / cm 3 , 1.47 g / cm 3 , 1.48 g / cm 3 , 1.49 g / cm 3 , 1.5 g / cm 3 , 1.51 g / cm 3 , 1.52 g / cm 3 , 1.53 g / cm3 、 1.54 g / cm 3 、 1.55 g / cm 3 、 1.56 g / cm 3 、 1.57 g / cm 3 、 1.58 g / cm 3 、 1.59 g / cm 3 、 1.6 g / cm 3 or the numerical range between any two of them.

[0198] In the embodiments of the present application, the compaction density of the negative electrode film layer is within the above range, which helps to improve the kinetic performance of the battery.

[0199] In some embodiments, the soft-pack material includes an aluminum-plastic composite film, and the aluminum-plastic composite film includes a composite film composed of one or more of polypropylene (PP), nylon (PA), cast polypropylene (CPP), polyimide (PI), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene terephthalate (PET), polyethylene (PE) and aluminum.

[0200] The soft-pack material has a high elongation rate, so its shell is thinner and softer, which helps to improve the space utilization rate of the battery cell, thereby increasing the energy density of the battery cell. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery interior, reduce the decomposition of the electrolyte and the oxidation degree of the electrode material, thereby increasing the battery life.

[0201] In some embodiments, the battery cell includes a stacked cell, and the stacked cell includes an electrode assembly.

[0202] In some embodiments, the battery cell includes a stacked cell, and the stacked cell includes an electrode assembly, wherein the separator is continuously arranged between the positive electrode sheet and the negative electrode sheet in a spiral winding or Z-shaped manner.

[0203] Compared with the wound cell, the stacked cell has no corner area. Therefore, the battery including the stacked cell helps to improve the space utilization rate of the battery, thereby increasing the volumetric energy density of the battery; however, due to the lack of restraint in the corner area, the extrusion between the positive electrode sheet, the separator and the negative electrode sheet is small, and the generated gas is not easily escaped, which may lead to gas accumulation and lithium plating on the electrode sheet, affecting the cycle performance of the battery. In the embodiments of the present application, the stacked cell is used, and at the same time, the particle size and proportion of large and small particles in the positive electrode film layer, the conductive agent including carbon nanotubes, and the size of the positive electrode sheet along the width direction of the battery cell are controlled, which helps to improve the kinetic performance and energy density of the battery, while taking into account the cycle performance.

[0204] Battery device The embodiment of the present application further provides a battery device, which includes the battery cell provided by the embodiment of the present application.

[0205] The battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0206] Power-consuming device The embodiment of the present application further provides a power-consuming device, which includes the battery device provided by the embodiment of the present application. The battery device is used to provide electric energy. The battery can be used as the power source of the power-consuming device. The power-consuming device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, etc.

[0207] The power-consuming device can select the specific type of battery according to its usage requirements, such as a battery cell, a battery module, or a battery pack.

[0208] Energy storage device The embodiment of the present application further provides an energy storage device, which includes the battery device provided by the embodiment of the present application. The battery device is used to store electric energy. The battery device can be used as the energy storage unit of the energy storage device. The energy storage unit can be, but is not limited to, an energy storage container, an energy storage cabinet, an energy storage power station, an energy storage battery pack, or a portable energy storage system, etc.

[0209] Figure 3 is a schematic diagram of a power-consuming device as an example. The power-consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the power-consuming device for high power and high energy density, a battery pack or a battery module can be used.

[0210] Another example of the power-consuming device can be a mobile phone, a tablet computer, a laptop computer, etc. This power-consuming device usually requires thin and light, and a battery cell can be used as the power source.

[0211] Example Hereinafter, the embodiments of the present application will be described. The following described embodiments are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those not specified in the embodiments about specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified about the manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0212] I. Preparation method Example 1 (1) Preparation of the positive electrode plate Preparation of the first particles: Mix ferric phosphate, lithium carbonate, polyethylene glycol, glucose, and titanium dioxide evenly in methanol and grind to obtain a mixed raw material; fully grind the mixed raw material in a sand mill to obtain a uniform mixed slurry. Spray-dry the mixed slurry to obtain a dried precursor powder. Place the precursor powder in a sintering furnace, heat it to 400 °C under a nitrogen atmosphere and hold for 3 h, then heat it to 780 °C and hold for 6 h. After cooling, use air jet milling to obtain the first particles; among them, the D V 50 of the first particles is 0.4 μm, and the mass content of titanium element based on the total mass of the first particles is 2500 ppm.

[0213] Preparation of the second particles is basically the same as that of the first particles, except that the temperature and holding time during sintering are adjusted to obtain the second particles; among them, the D V 50 of the second particles is 1 μm, and the mass content of titanium element based on the total mass of the second particles is 2500 ppm.

[0214] Preparation of the positive electrode slurry: Dissolve the above-mentioned first particles, the above-mentioned second particles, a conductive agent, and a binder (PVDF 5130) in an NMP (N-methylpyrrolidone) solvent according to a mass ratio of 68.6:29.4:1:1, stir well and mix evenly, and then perform wetting, kneading, and dispersion treatments to obtain the positive electrode slurry; among them, the conductive agent includes oligomeric wall carbon nanotubes and conductive carbon black with a mass ratio of 1:1.

[0215] Coat the positive electrode slurry on an aluminum foil, and then obtain a positive electrode sheet through drying, cold pressing, and slitting. Among them, when the battery cell is in a fully discharged state, the compaction density of the positive electrode film layer is 2.35 g / cm 3 ; the size of the positive electrode sheet along the width direction of the battery cell is 118 mm.

[0216] (2)Preparation of the negative electrode sheet Mix the negative electrode active material artificial graphite, the binder polyvinyl alcohol, and the conductive agent SP-Li in a mass ratio of 90:5:5, add the solvent deionized water, and stir evenly under the action of a vacuum mixer to prepare a negative electrode slurry; evenly coat the negative electrode slurry on the surface of a negative electrode current collector copper foil, dry the coated negative electrode current collector in a vacuum environment at 110 °C, and then obtain a negative electrode sheet through cold pressing and slitting.

[0217] Among them, the D V 50 of the artificial graphite as the negative electrode active material is 20 μm, and the orientation degree (OI) is 3.2; when the battery cell is in a fully discharged state, the compaction density of the negative electrode film layer is 1.45 g / cm 3 .

[0218] (3)Preparation of the electrolyte In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), the organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and vinylene carbonate (VC) were mixed evenly in a volume ratio of 17.76:29.64:49.4:1.2. LiPF6 and LiPF2O2 with a mass ratio of 98:2 were dissolved in the organic solvent, and the concentration of lithium ions was controlled to be 1 mol / L. After stirring evenly, the electrolyte was obtained.

[0219] (4) Separator preparation Porous alumina was added to NMP (N-methylpyrrolidone) solvent, and after stirring evenly, it was sprayed on both sides of the polyethylene film and then dried. PVDF was dissolved in NMP (N-methylpyrrolidone) solvent, and after stirring evenly, it was sprayed on the two surfaces of the porous alumina layer far from the base film and dried to obtain a separator with a porous continuous morphology bonding layer.

[0220] Among them, the thickness of the polyethylene film is 7 μm, the thickness of the porous alumina layer on one side is 1.5 μm, the thickness of the PVDF layer on one side is 0.5 μm, and the porosity of the separator is 38%.

[0221] (5) Preparation of the battery The above positive electrode sheet, separator, and negative electrode sheet were stacked by the Z-type stacking method, and the separator was placed between the positive and negative electrode sheets to play a role in isolation. The electrode assembly was placed in an aluminum-plastic composite film, the above electrolyte was injected, and then vacuumized and heat-pressed to form an airtight package to obtain a lithium-ion battery.

[0222] Among them, the aluminum-plastic composite film is composed of an inner layer of polyethylene, a middle layer of aluminum foil, and an outer layer of polyethylene terephthalate.

[0223] Example 2 The preparation method of the lithium-ion battery is similar to that of Example 1. The difference is that when preparing the positive electrode slurry, the above first particles, the above second particles, the conductive agent, and the binder (PVDF 5130) were dissolved in NMP (N-methylpyrrolidone) solvent in a mass ratio of 78.4:19.6:1:1.

[0224] Example 3 The preparation method of the lithium-ion battery is similar to that of Example 1. The difference is that when preparing the positive electrode slurry, the above first particles, the above second particles, the conductive agent, and the binder (PVDF 5130) were dissolved in NMP (N-methylpyrrolidone) solvent in a mass ratio of 44.1:53.9:1:1.

[0225] Example 4 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode slurry, the conductive agent includes oligomeric wall carbon nanotubes and conductive carbon black with a mass ratio of 8:2.

[0226] Example 5 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode slurry, the conductive agent includes oligomeric wall carbon nanotubes and conductive carbon black with a mass ratio of 3.5:6.5.

[0227] Example 6 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode plate, the addition amount of titanium dioxide during the preparation of the first particles and the second particles is adjusted so that, based on the total mass of the first particles, the mass content of titanium element is 4500 ppm, and based on the total mass of the second particles, the mass content of titanium element is 4500 ppm.

[0228] Example 7 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode plate, the addition amount of titanium dioxide during the preparation of the first particles and the second particles is adjusted so that, based on the total mass of the first particles, the mass content of titanium element is 1500 ppm, and based on the total mass of the second particles, the mass content of titanium element is 1500 ppm.

[0229] Example 8 The preparation method of the lithium-ion battery is similar to that of Example 1, except that the orientation degree (OI) of the artificial graphite as the negative electrode active material is 5.

[0230] Example 9 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the separator, porous alumina is added to the NMP (N-methylpyrrolidone) solvent, stirred evenly, then sprayed on both sides of the polyethylene film and dried. PVDF is dissolved in the NMP (N-methylpyrrolidone) solvent, stirred evenly, then sprayed on one surface of the porous alumina layer away from the base film and dried to obtain the separator. When preparing the battery, the side with the PVDF layer is arranged close to the negative electrode plate.

[0231] Example 10 The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the separator, porous alumina is added to the NMP (N-methylpyrrolidone) solvent, stirred evenly, then sprayed on both sides of the polyethylene film and dried. PVDF is dissolved in deionized water as the solvent, stirred evenly, then sprayed on one surface of the porous alumina layer away from the base film and dried to obtain the separator with an island-like structure morphology of the bonding layer. When preparing the battery, the side with the PVDF layer is arranged close to the negative electrode plate.

[0232] Example 11 The preparation method of the lithium-ion battery is similar to that of Example 1, except that the preparation method of the separator is as follows: porous alumina is added to NMP (N-methylpyrrolidone) solvent, and after stirring evenly, it is sprayed on both sides of the polyethylene film and then dried to obtain the separator.

[0233] Example 12 The preparation method of the lithium-ion battery is similar to that of Example 1, except that the separator only includes a polyethylene film.

[0234] Example 13 The preparation method of the lithium-ion battery is similar to that of Example 1, except that the separator only includes a polypropylene film.

[0235] Comparative Example 1 The preparation method of the lithium-ion battery is similar to that of Example 13, except that when preparing the positive electrode paste, the above-mentioned first particles, the above-mentioned second particles, the conductive agent, and the binder (PVDF 5130) are dissolved in NMP (N-methylpyrrolidone) solvent according to a mass ratio of 88.2:9.8:1:1.

[0236] Comparative Example 2 The preparation method of the lithium-ion battery is similar to that of Example 13, except that when preparing the positive electrode paste, the above-mentioned first particles, the above-mentioned second particles, the conductive agent, and the binder (PVDF 5130) are dissolved in NMP (N-methylpyrrolidone) solvent according to a mass ratio of 19.6:78.4:1:1.

[0237] Comparative Example 3 The preparation method of the lithium-ion battery is similar to that of Comparative Example 1, except that when preparing the positive electrode paste, the conductive agent is conductive carbon black and does not include multi-walled carbon nanotubes.

[0238] Comparative Example 4 The preparation method of the lithium-ion battery is similar to that of Comparative Example 3, except that the size of the positive electrode plate along the width direction of the battery cell is 145 mm.

[0239] II. Performance Testing 1. DC Internal Resistance DCR Test Refer to the method in GB / T 31467 "Performance Test Specification for High-power Lithium-ion Power Batteries for HEV". For example, at room temperature, charge the battery cell at a constant current of 0.33C to 3.75V, let it stand for 10 min, then charge it at a constant voltage of 3.75V to 0.05C, let it stand for 30 min, and then discharge it at a discharge rate of 0.33C to 2.50V. Record the discharge capacity A0 at this time; then charge it at a constant current of 0.33C for 0.5A0 and adjust the SOC to 50%. After the battery cell is placed at 25°C for 2 h, discharge it at a constant current of 3C for 10 s, record ∆U discharge and ∆I discharge, and calculate the discharge DCR data of the lithium-ion battery through the following formula: R discharge = ∆U discharge / ∆I discharge, where ∆U discharge represents the voltage change within the first 10 s of discharge, and ∆I discharge represents the current value within the first 10 s of discharge.

[0240] 2. Battery cycle retention rate test Let the lithium-ion battery stand at 25°C for 2 h. At 25°C, charge it at a charging rate of 0.33C of the battery nominal capacity to 3.75V, then charge it at a constant voltage of 3.75V to 0.05C, let it stand for 10 min, and then discharge it at a discharge rate of 0.33C to 2.50V. The reversible capacity measured is C0. The above one charge-discharge cycle is one cycle. Continuously repeat the charge-discharge until 1000 times, record the battery capacity C1, and the capacity retention rate at this cycle number is (C1 / C0)×100%.

[0241] III. Test results The test results of the above-mentioned examples and comparative examples are shown in Tables 1 - 5.

[0242] Table 1

[0243] It can be seen from the comparison between the examples and the comparative examples that the battery cell includes a housing and an electrode assembly. The electrode assembly is accommodated inside the housing, and the material of the housing is a soft-pack material; the electrode assembly includes a positive electrode plate and a negative electrode plate. The positive electrode plate includes a positive electrode film layer, and the positive electrode film layer includes a positive electrode active material. The positive electrode active material includes polyanion particles with at least part of the surface provided with a carbon coating material; the volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. The peak position of the first peak in the bimodal curve is less than the peak position of the second peak. The peak position of the first peak is 0.3 - 0.7μm, and the peak position of the second peak is 0.9 - 1.5μm. The integral area ratio of the first peak to the second peak is 4:6 - 8:2; the positive electrode film layer also includes a conductive agent, and the conductive agent includes carbon nanotubes; the size of the positive electrode plate along the width direction of the battery cell is less than or equal to 130 mm, which helps to balance its cycle performance while improving the battery kinetic performance.

[0244] As can be seen from the comparison between Example 1 and Examples 2 - 3, when the area ratio of the first peak to the second peak is in the range of 5:5 - 7:3, it helps to further optimize the comprehensive performance of the battery, taking into account both the kinetic performance and the cycling performance of the battery.

[0245] Table 2

[0246] As can be seen from the comparison between Example 1 and Examples 4 - 5, when the mass percentage of carbon nanotubes is in the range of 40% - 70% based on the total mass of the conductive agent, it helps to further improve the cycling performance of the battery and take into account the kinetic performance.

[0247] Table 3

[0248] As can be seen from the comparison between Example 1, Example 6 and Example 7, when the mass percentage of titanium element is in the range of 2000 - 5000 ppm based on the total mass of the positive electrode active material, it helps to further improve the kinetic performance and cycling performance of the battery.

[0249] Table 4

[0250] As can be seen from the comparison between Example 1 and Example 8, when the orientation degree (OI) of the negative electrode active material is less than 3.5, it helps to further improve the kinetic performance and cycling performance of the battery.

[0251] Table 5

[0252] As can be seen from the comparison between Example 12 and Example 13, when the base film of the separator includes a polyethylene material, it helps to further improve the kinetic performance and cycling performance of the battery.

[0253] As can be seen from the comparison between Example 11 and Example 12, when the separator includes a ceramic layer, it helps to further improve the kinetic performance and cycling performance of the battery.

[0254] As can be seen from the comparison between Example 10 and Example 11, when the separator includes an adhesive layer, it helps to further improve the kinetic performance and cycling performance of the battery.

[0255] As can be seen from the comparison between Example 9 and Example 10, when the adhesive layer of the separator is in a porous continuous shape, it helps to further improve the kinetic performance and cycling performance of the battery.

[0256] As can be seen from the comparison between Example 1 and Example 9, when the separator includes adhesive layers disposed on both sides of the ceramic layer away from the base film, it helps to further improve the kinetic performance and cycling performance of the battery.

[0257] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same function and effect as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A battery cell, characterized in that, It includes a housing and an electrode assembly, the electrode assembly is accommodated inside the housing, and the material of the housing is a soft-pack material; The electrode assembly includes a positive electrode tab and a negative electrode tab. The positive electrode tab includes a positive electrode film layer, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes polyanion particles with at least part of their surfaces provided with a carbon coating material; The volume particle size distribution curve of the particles in the positive electrode film layer is a bimodal curve. The peak position of the first peak in the bimodal curve is 0.3 - 0.7 μm, the peak position of the second peak in the bimodal curve is 0.9 - 1.5 μm, and the integral area ratio of the first peak to the second peak is 4:6 - 8:2; The positive electrode film layer further includes a conductive agent, and the conductive agent includes carbon nanotubes; The size of the positive electrode tab in the width direction of the battery cell is less than or equal to 130 mm.

2. The battery cell according to claim 1, wherein The peak position of the first peak is 0.3 - 0.6 μm.

3. The battery cell according to claim 1, characterized in that, The peak position of the second peak is 0.9 - 1.4 μm.

4. The battery cell according to claim 1, characterized in that, The size of the positive electrode tab in the width direction of the battery cell is 110 - 125 mm.

5. The battery cell according to claim 1, characterized in that The integral area ratio of the first peak to the second peak is 5:5 - 7:

3.

6. The battery cell according to claim 1, characterized in that, Based on the total mass of the positive electrode film layer, the mass proportion of the conductive agent is greater than or equal to 0.8%.

7. The battery cell according to claim 1, characterized in that, Based on the total mass of the positive electrode film layer, the mass proportion of the conductive agent is 0.8 - 1.3%.

8. The battery cell according to claim 1, wherein Based on the total mass of the conductive agent, the mass proportion of the carbon nanotubes is greater than or equal to 30%.

9. The battery cell according to claim 1, characterized in that, Based on the total mass of the conductive agent, the mass proportion of the carbon nanotubes is 30% - 70%.

10. The battery cell according to claim 1, characterized in that, Based on the total mass of the conductive agent, the mass proportion of the carbon nanotubes is 40% - 70%.

11. The battery cell according to claim 1, wherein The carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

12. The battery cell according to claim 1, wherein The carbon nanotubes include few-walled carbon nanotubes.

13. The battery cell according to claim 1, characterized in that, The conductive agent further includes conductive carbon black.

14. The battery cell according to claim 13, wherein, The conductive carbon black includes one or more of Super P, Ketjen black, and acetylene black.

15. The battery cell according to claim 1, characterized in that, The polyanion particles have the following components represented by the general formula: Li x A y Me a M b P 1-c X c Y z Formula I Wherein, 0.1 ≤ x ≤ 1.3, 0 ≤ y ≤ 1.3, and 0.8 ≤ x + y ≤ 1.3; 0.9 ≤ a ≤ 1.5, 0 ≤ b ≤ 0.5, and 0.9 ≤ a + b ≤ 1.5; 0 ≤ c ≤ 0.5; 3 ≤ z ≤ 5; A includes one or several of Na, K, and Mg; Me includes one or several of Mn, Fe, Co, and Ni; M includes one or several of B, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Cu, Zn, Sr, Y, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, Ta, W, Yb, La, and Ce; X includes one or several of S, Si, Cl, B, C, and N; Y includes one or several of O and F.

16. The battery cell according to claim 1, characterized in that, The positive electrode active material includes titanium element. Based on the total mass of the positive electrode active material, the mass proportion of the titanium element is 1000 - 5000 ppm.

17. The battery cell according to claim 1, characterized in that, The positive electrode active material includes titanium element. Based on the total mass of the positive electrode active material, the mass proportion of the titanium element is 2000 - 5000 ppm.

18. The battery cell according to claim 1, characterized in that, When the battery cell is in a fully discharged state, the compaction density of the positive electrode film layer is 2.3 g / cm 3 - 2.5 g / cm 3 .

19. The battery cell according to claim 1, characterized in that, The electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet, and the separator includes a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on the side of at least one ceramic layer away from the base film.

20. The battery cell according to claim 19, characterized in that, The base film includes one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), aramid, and polytetrafluoroethylene (PTFE).

21. The battery cell according to claim 19, wherein The base film includes polyethylene (PE).

22. The battery cell according to claim 19, characterized in that, The ceramic layer includes one or more of aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), calcium oxide (CaO), and magnesium oxide (MgO).

23. The battery cell according to claim 19, characterized in that, The adhesive layer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR).

24. The battery cell according to claim 19, wherein, The adhesive layer includes polyvinylidene fluoride (PVDF), and the adhesive layer is in a porous continuous shape.

25. The battery cell according to claim 19, wherein, The separator includes a base film, ceramic layers respectively disposed on both sides of the base film, and adhesive layers respectively disposed on the sides of the two ceramic layers away from the base film.

26. The battery cell according to claim 19, wherein, The porosity of the separator is 30% - 45%.

27. The battery cell according to claim 1, wherein The battery cell further includes an electrolyte, the electrolyte includes a solvent, the solvent includes ethylene carbonate (EC), and based on the total mass of the solvent, the mass ratio of the ethylene carbonate (EC) is 0.1% - 25%.

28. The battery cell according to claim 27, wherein The electrolyte further includes vinylene carbonate (VC), and based on the total mass of the electrolyte, the mass ratio of the vinylene carbonate (VC) is 0.5% - 2%.

29. The battery cell according to claim 27, characterized in that, The electrolyte further includes lithium difluorophosphate (LiPF2O2), and based on the total mass of the electrolyte, the mass ratio of the lithium difluorophosphate (LiPF2O2) is 0.03% - 0.2%.

30. The battery cell according to claim 1, characterized in that, The negative electrode sheet includes a negative electrode film layer, the negative electrode film layer includes a negative electrode active material, and the D V 50 is less than or equal to 25 μm.

31. The battery cell according to claim 30, wherein The negative electrode active material includes artificial graphite, and the orientation degree (OI) of the negative electrode active material is less than 3.5, where the orientation degree (OI) = I004 / I110, I004 represents the integrated area of the diffraction peak of the 004 crystal plane of crystalline carbon in the X-ray diffraction test, and I110 represents the integrated area of the diffraction peak of the 110 crystal plane of crystalline carbon in the X-ray diffraction test.

32. The battery cell according to claim 30, wherein, When the battery cell is in a fully discharged state, the compaction density of the negative electrode film layer is 1.4 g / cm 3 - 1.6 g / cm 3 .

33. The battery cell according to claim 1, characterized in that, The soft package material includes an aluminum-plastic composite film, and the aluminum-plastic composite film includes a composite film composed of one or more of polypropylene (PP), nylon (PA), cast polypropylene (CPP), polyimide (PI), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene terephthalate (PET), and polyethylene (PE) and aluminum.

34. The battery cell according to any one of claims 1-33, characterized in that, The battery cell includes a stacked cell, and the stacked cell includes the electrode assembly.

35. A battery device, characterized in that, The battery device includes the battery cell according to any one of claims 1 to 34.

36. An electrical device, characterized in that, The electrical device includes the battery device according to claim 35, and the battery device is used to provide electrical energy.

37. A energy storage device, characterized in that, The energy storage device includes the battery device according to claim 35, and the battery device is used to store electrical energy.

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