Battery cells, battery devices, power consumption devices and energy storage devices

Abstract

The application provides a battery monomer, a battery device, a power utilization device and an energy storage device. The battery monomer comprises a shell and an electrode assembly, the electrode assembly is accommodated in the shell, and the material of the shell is a soft package material. The electrode assembly comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode film layer, and the positive electrode film layer comprises a positive electrode active material. The positive electrode active material comprises polyanion particles with carbon-coated materials on at least part of the surfaces. 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 comprises a conductive agent, and the conductive agent comprises carbon nanotubes. The size of the positive electrode sheet along the width direction of the battery monomer is less than or equal to 130 mm. The battery monomer has good kinetic performance and cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery monomer, in particular to a battery monomer, a battery device, a power utilization device and an energy storage device. BACKGROUND

[0002] In recent years, battery monomers are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0003] With the market's pursuit of fast charging performance and service life of batteries, higher requirements are put forward for the kinetic performance and cycle performance of batteries. However, the prior art is difficult to simultaneously improve the above-mentioned performances, and how to balance the two has become a technical problem to be solved in the field. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a battery monomer with good kinetic performance and cycle performance.

[0005] The first aspect of the present application provides a battery monomer, comprising a shell and an electrode assembly, the electrode assembly is contained in the shell, the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a positive electrode film layer, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises polyanion particles with at least part of the surface provided with 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 of 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 comprises a conductive agent, and the conductive agent comprises carbon nanotubes; the size of the positive electrode sheet along the width direction of the battery monomer is less than or equal to 130 mm.

[0006] In the embodiment of the present application, the positive electrode active material has a bimodal particle size distribution, wherein the peak position of the first peak is smaller than that 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, i.e. the positive electrode active material comprises small particles with a particle size mainly located at 0.3-0.7 μm and large particles with a particle size mainly located at 0.9-1.5 μm, such as Figure 2The research shows that the specific surface area of the large particles is small, the side reactions are less, but the ion diffusion path is long, and the kinetics is relatively poor; the ion diffusion path of the small particles is short, and the kinetics is good, but the specific surface area is large, and the side reactions are relatively more. The integral area ratio of the first peak to the second peak is controlled to be 4:6-8:2 in the embodiments of the present application, that is, the ratio of the above-mentioned large particles and small particles is controlled in a suitable range, which is helpful to improve the kinetics performance of the positive active material, and at the same time, the cycle performance of the soft package battery is considered. At the same time, the positive electrode film layer of the embodiments of the present application also includes a conductive agent, and the conductive agent includes carbon nanotubes, so as to make up for the low graphitization degree and insufficient electronic conductivity of the small particles due to insufficient sintering temperature or insufficient sintering time, and further realize the improvement of the battery kinetics performance. The carbon nanotubes are one-dimensional conductive agents, have excellent conductivity, and at the same time can be coated on the surface of the particles, reduce the direct contact of 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 sheet of the embodiments of the present application along the width direction of the battery monomer is less than or equal to 130 mm, the battery width is small, which is helpful to reduce the escape path of the gas in the soft package battery, so as to relieve the lithium precipitation problem caused by the increase of small particles, the increase of side reactions and the gas aggregation. In summary, the battery monomer provided by the embodiments of the present application has good cycle performance while improving the kinetics performance.

[0007] In any embodiment, 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 is less than the peak position 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 is in the above range, which is helpful to realize the consideration of the battery kinetics performance and the cycle life.

[0009] In any embodiment, 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 is less than the peak position 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 is in the above range, which is helpful to reduce the specific surface area of the particles, reduce the degree of side reactions, and at the same time, consider the kinetics performance, reduce the sheet resistance, and consider the kinetics performance and cycle performance of the battery.

[0011] In any embodiment, the size of the positive electrode sheet along the width direction of the battery monomer 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 ratio of the integral areas of the first peak and the second peak is further within the above range, indicating that the positive electrode film layer has a suitable proportion of large particles and small particles, thereby helping to balance the degree of side reaction and kinetic performance of the positive electrode film layer, and helping to further improve the kinetic performance of the battery while taking into account the cycle performance.

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

[0015] The mass percentage of the conductive agent is within the above range, which 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, the mass percentage of the conductive agent is 0.8%-1.3% based on the total mass of the positive electrode film layer.

[0017] The content of the conductive agent is further within the above range, which helps to improve the kinetic performance of the battery monomer while not occupying too much space of the active material due to the high content, thereby taking into account the volume energy density of the battery monomer.

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

[0019] The carbon nanotube is a one-dimensional conductive agent with excellent electronic conductivity. The mass content of the carbon nanotube is within the above range, which 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, the carbon nanotube has a one-dimensional linear morphology, which helps to reduce the direct contact area between the particles and the electrolyte when the carbon nanotube is covered on the surface of the particles. The mass content of the carbon nanotube is within the above range, which can effectively reduce the contact between the particles and the electrolyte and reduce the degree of side reaction, thereby improving the kinetic performance of the battery while taking into account the cycle performance.

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

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

[0022] The carbon nanotube has poor flexibility, and too much content of the carbon nanotube in the positive electrode film layer may increase the brittleness of the sheet and cause powder loss during long-term cycling, thereby affecting the cycle performance of the battery. In the embodiments of the present application, the mass content of the carbon nanotube is further within the above range, which helps to reduce the brittleness of the sheet while reducing the resistance of the sheet, thereby further improving the kinetic performance and cycle performance of the battery. In addition, the carbon nanotube has a high cost, and the mass content of the carbon nanotube is within the above range, which 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-arm carbon nanotubes, they have the characteristics of better chemical stability and lower cost. In the embodiments of the present application, the carbon nanotubes include oligomeric-walled carbon nanotubes, which help to improve the kinetic performance of the battery monomer while taking into account the production cost.

[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 that can be filled into the three-dimensional conductive network of the carbon nanotubes, and the two work together to further improve the electrical conductivity of the electrode sheet, thereby further improving the kinetic performance of the battery.

[0029] In any embodiment, the polyanion particles include a component represented by the following general formula:

[0030] Li x A y Me a M b P 1-c X c Y z Formula I,

[0031] 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 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, Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F.

[0032] In any embodiment, the positive electrode active material includes titanium elements, and the mass fraction of the titanium elements is 1000-5000 ppm based on the total mass of the positive electrode active material.

[0033] Tetravalent titanium atom Ti 4+ With divalent iron atom Fe 2+ With a similar ionic radius, titanium can partially replace iron sites, forming Ti-O bonds. Compared to Fe-O bonds, Ti-O bonds have higher bond energy, which helps improve lattice strength and suppress lattice distortion during charge and discharge, thereby improving material stability and battery cycle performance. Furthermore, titanium doping introduces additional positive charge, and the material system forms an Fe-O-Ti network based on a charge compensation mechanism, promoting electron transitions, improving the conductivity of the positive electrode active material, reducing electrode sheet resistance, and enhancing the battery's kinetic performance.

[0034] In any embodiment, the positive electrode active material includes titanium element, and the mass proportion of the titanium element is 2000-5000 ppm based on the total mass of the positive electrode active material.

[0035] A titanium content within the above range further helps improve the battery's kinetic and cycling performance. Furthermore, excessive titanium content increases the number of iron sites occupied, thereby affecting the battery's energy density. Therefore, in the embodiments of the present application, a titanium content within the above range also helps reduce the energy density loss caused by the introduction of titanium.

[0036] In any embodiment, when the battery cell is fully discharged, the compaction density of the positive electrode film layer is 2.3 g / cm 3 -2.5g / cm 3 .

[0037] A high compaction density helps increase the loading of the positive electrode active material on the positive electrode sheet; a low compaction density helps increase the porosity of the film layer. In the embodiments of the present application, when the battery cell is fully discharged, the compaction density of the positive electrode film layer is within the above range. This helps to ensure that the positive electrode film layer has an appropriate porosity, improves the electrode sheet's liquid retention rate, and enhances the electrolyte infiltration rate, thereby reducing the battery's internal resistance and further improving the battery's dynamic performance. It also helps to ensure that the positive electrode sheet has an appropriate loading of positive electrode active material, while also taking into account the battery's volumetric energy density.

[0038] In any embodiment, the electrode assembly further includes a separator disposed between the positive electrode sheet and the negative electrode sheet, the separator including a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on at least one side of the ceramic layer away from the base film.

[0039] In any embodiment, the base film includes one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), aramid, and polytetrafluoroethylene (PTFE).

[0040] In any embodiment, the base film comprises polyethylene (PE).

[0041] Compared to traditional polymer materials, polyethylene has a relatively high swelling rate and can absorb more electrolyte; it helps to increase the electrolyte infiltration rate in the diaphragm, thereby increasing the diffusion rate of lithium ions; at the same time, the high swelling rate helps to increase the pressure between the electrode and the diaphragm, promotes the release of gas produced by side reactions, and reduces the increase in gas production caused by the increase in small particles, which leads to large-scale lithium precipitation in the battery, thereby improving the battery's cycle performance. In addition, polyethylene-based base films have good internal pore uniformity, which helps to improve the uniformity of lithium ion diffusion and further improve the battery's cycle performance. In addition, polyethylene has good flexibility, which helps to reduce the risk of diaphragm cracking when soft-pack batteries are deformed, further improving the battery's cycle performance.

[0042] In any embodiment, the ceramic layer includes one or more of aluminum oxide (Al 2 O 3 ), zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), calcium oxide (CaO), and magnesium oxide (MgO).

[0043] The ceramic layer has the ability to accommodate electrolyte, which helps increase the electrolyte infiltration rate of the separator, reduce the internal resistance of the battery, and improve the battery's dynamic performance and cycle performance. In addition, polyethylene base films are relatively soft and have 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 and enhance the puncture resistance of the soft-pack battery, thereby improving the battery's safety performance.

[0044] In any embodiment, the tie layer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR).

[0045] The diaphragm includes an adhesive layer, which helps to improve the bonding strength between the diaphragm and the positive electrode sheet and the negative electrode sheet. On the one hand, this helps to reduce the gap between the electrode assemblies, reduce the internal resistance of the battery, and improve the dynamic performance of the battery; on the other hand, it helps to reduce the displacement between the diaphragm and the positive electrode sheet and the negative electrode sheet, increase the stability of the electrode assembly, and thus improve the cycle performance of the battery.

[0046] In any embodiment, the bonding layer includes polyvinylidene fluoride (PVDF), and the bonding layer is porous and continuous.

[0047] In traditional separators, the bonding layer is typically made of aqueous PVDF and typically exhibits a discontinuous island structure. In this application, the bonding layer is continuous and porous, which helps increase the bonding area between the separator and the positive and negative electrode sheets, enhances the bonding strength, improves the tightness of the pouch cell grouping, reduces the interfacial resistance between the separator and the electrode sheets, and lowers the battery impedance, thereby further improving the battery's dynamic performance and cycle performance.

[0048] In any embodiment, the separator comprises a base film, ceramic layers arranged on both sides of the base film, and adhesive layers arranged on the sides of the ceramic layers away from the base film respectively.

[0049] The separator comprising the ceramic layers arranged on both sides of the base film and the adhesive layers arranged on the sides of the ceramic layers away from the base film respectively 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, thereby helping to further improve the kinetic performance and the cycle performance of the battery cell.

[0050] In any embodiment, the porosity of the separator is 30%-45%.

[0051] The porosity of the separator within the above range helps to improve the electrolyte wetting rate of the separator, thereby improving the transmission rate of lithium ions, reducing the internal resistance of the battery, and further improving the kinetic performance of the battery.

[0052] In any embodiment, the battery cell further comprises an electrolyte, and the electrolyte comprises a solvent, and the solvent comprises ethylene carbonate (EC), and the mass fraction of the ethylene carbonate (EC) in the total mass of the solvent is 0.1%-25%.

[0053] The inclusion of ethylene carbonate in the electrolyte helps to dissolve the solute in the electrolyte, and at the initial stage of battery use, the 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 a too high content of ethylene carbonate will affect the transmission rate of lithium ions, and in turn affect the kinetic performance of the battery. In the embodiments of the present application, the mass fraction of the ethylene carbonate is within the above range, which helps to form a good SEI film and CEI film, and at the same time reduces the influence of the ethylene carbonate on the transmission rate of lithium ions, thereby improving the cycle performance of the battery while taking into account the kinetic performance of the battery.

[0054] In any embodiment, the electrolyte further comprises vinylene carbonate (VC), and the mass fraction of the vinylene carbonate (VC) in the total mass of the electrolyte is 0.5%-2%.

[0055] The vinylene carbonate (VC) is preferentially decomposed before the decomposition of the ethylene carbonate (EC) into a film, forming an initial SEI film with high elasticity and low impedance, and to some extent promoting the stability of the positive electrode CEI film. In the embodiments of the present application, the mass content of the VC is within the above range, which helps to reduce the gas generated by the decomposition of the ethylene carbonate, thereby reducing the internal gas content of the battery, alleviating the lithium precipitation phenomenon induced by gas accumulation, and further improving the cycle life of the battery.

[0056] In any embodiment, the electrolyte further comprises lithium difluorophosphate (LiPF2O2) in a mass ratio of 0.03%-0.2% based on the total mass of the electrolyte.

[0057] The decomposition product of lithium difluorophosphate can fill into the SEI film and the CEI film, enhance the elasticity and compactness of the interface film, reduce the direct contact between the electrolyte and the active material, and thus reduce the degree of side reaction. 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 the CEI film, reduce the gas production inside the battery, and thus improve the lithium precipitation caused by gas accumulation, and further improve the cycle performance of the battery.

[0058] In any embodiment, the negative electrode sheet comprises a negative electrode film layer, the negative electrode film layer comprises a negative electrode active material, and the negative electrode active material has a D V 50 is less than or equal to 25 μm.

[0059] The negative electrode active material has a D V 50 is large, indicating that the particle size of the negative electrode active material is large, thereby prolonging the lithium ion diffusion path and further affecting the ion conductivity of the negative electrode sheet. In the embodiments of the present application, the negative electrode active material has a D V 50 is within the above range, indicating that the negative electrode active material has a suitable particle size, which helps to shorten the lithium ion deintercalation path and improve the ion conductivity of the negative electrode film layer, and thus further improve the kinetic performance of the battery.

[0060] In any embodiment, the negative electrode active material comprises artificial graphite, and the negative electrode active material has an orientation degree (OI) less than 3.5, wherein the orientation degree (OI) = I004 / I110, I004 represents the integral area of the diffraction peak of the 004 crystal plane of the crystalline carbon in the X-ray diffraction test, and I110 represents the integral area of the diffraction peak of the 110 crystal plane of the crystalline carbon in the X-ray diffraction test.

[0061] In the embodiments of the present application, the negative electrode active material has an orientation degree (OI) within the above range, and the orientation of the material is relatively disordered, which helps to increase the number of end faces of lithium ion intercalation, and thus helps to improve the kinetic performance of the battery.

[0062] In any embodiment, the compaction density of the negative electrode film layer of the battery monomer is 1.4 g / cm 3 -1.6 g / cm 3 .

[0063] 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.

[0064] In any embodiment, the soft package material comprises an aluminum plastic composite film, the aluminum plastic composite film comprises a composite film of one or more of polypropylene (PP), nylon (PA), polypropylene (CPP), polyimide (PI), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene terephthalate (PET), polyethylene (PE) and aluminum.

[0065] The soft package material has a high ductility, so that the shell thereof is more light and thin, soft, which helps to improve the space utilization of the battery monomer, thereby improving the energy density of the battery monomer. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery, reduce the decomposition of electrolyte and the oxidation degree of electrode material, thereby improving the service life of the battery.

[0066] In any embodiment, the battery monomer comprises a laminated cell, and the laminated cell comprises an electrode assembly.

[0067] Compared with the wound cell, the laminated cell has no corner area, so that the battery comprising the laminated cell helps to improve the space utilization of the battery, thereby improving the volumetric energy density of the battery; however, due to the absence of the constraint of 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 easy to escape, thereby causing the gas to accumulate, the lithium of the electrode sheet to be separated, and the cycle performance of the battery to be affected. In the embodiment of the present application, the laminated cell is used, and 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 monomer are controlled, which helps to improve the kinetic performance and energy density of the battery, while the cycle performance is taken into account.

[0068] The second aspect of the present application provides a battery device, the battery device comprising the battery monomer provided in the first aspect.

[0069] The third aspect of the present application provides a power utilization device, the power utilization device comprising the battery device provided in the second aspect, and the battery device is used to provide electric energy.

[0070] The fourth aspect of the present application provides an energy storage device, the energy storage device comprising the battery device provided in the second aspect, and the battery device is used to store electric energy.

[0071] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the description, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0072] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in this application and should not be construed as limiting the scope of this application.

[0073] Figure 1 This is a surface morphology diagram of the negative electrode after lithium deposition in the prior art;

[0074] Figure 2 This is a cross-sectional polished electron microscope image of the positive electrode sheet in one embodiment of the present application;

[0075] Figure 3 This is a schematic diagram of an electrical device provided in some embodiments of the present application. DETAILED DESCRIPTION

[0076] Below, the embodiments of the battery cells, battery devices, electrical devices, and energy storage devices of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same 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 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 described in the claims.

[0077] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0078] If not particularly specified, all the 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.

[0079] If not particularly specified, all the 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.

[0080] If not particularly specified, all the steps of the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0081] If not particularly specified, the "comprise" and "include" mentioned in the present application are open-ended, and can also be closed. For example, the "comprise" and "include" can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0082] If not particularly 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 one 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) and B is true (or exists); or both A and B are true (or exist).

[0083] In the present application, the terms "plurality" and "multiple" mean two or more.

[0084] Unless otherwise specified, the terms used in the present application have the commonly known meanings understood by those skilled in the art.

[0085] Unless otherwise specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art

[0086] The determination is carried out, for example, according to the test method given in the examples of the present application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0087] The battery mentioned in the embodiments of the present application can 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 can include a battery cell, a battery module, or a battery pack, etc.

[0088] The battery cell is the smallest unit that constitutes the battery, which can independently realize the function of charging and discharging.

[0089] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in a mixed connection through a busbar component. In some embodiments, the battery can 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 can be a battery pack, which includes a box body and battery cells, and the battery cells or battery modules are contained in the box body. In some embodiments, the box body can be part of the chassis structure of the vehicle. For example, part of the box body can be at least part of the floor of the vehicle, or part of the box body can be at least part of the cross beam and the longitudinal beam of the vehicle.

[0090] In some embodiments, the battery can be an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc.

[0091] In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained 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.

[0092] Optionally, the battery module can further include a shell having an accommodation space, and the multiple battery cells are accommodated in the accommodation space.

[0093] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0094] The battery pack can include a box body and multiple battery modules arranged 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 forms a closed space for accommodating the battery modules. The multiple battery modules can be arranged in the box body in any way.

[0095] The battery provided by the embodiments of the present application can include a lithium ion battery.

[0096] The battery cell includes an electrode assembly and an electrolyte.

[0097] The electrode assembly generally includes a positive electrode tab and a negative electrode tab, the negative electrode tab being an electrode that undergoes a reaction of absorbing or lithiating lithium ions during charging of the battery and releasing or delithiating lithium during discharging, and the positive electrode tab being an electrode that undergoes a reaction of releasing or delithiating lithium ions during charging of the battery and absorbing or lithiating lithium during discharging.

[0098] The polyanion material has good cycle performance and safety, and has been widely used in the positive active material of the battery. However, compared with the ternary material, the specific capacity is relatively low, and the space utilization of the battery can be improved by adopting the soft package battery cell strategy, so as to improve the volume energy density of the battery. The applicant finds that reducing the particle size in the positive electrode film layer helps to improve the lithium ion diffusion rate of the positive electrode tab, which is beneficial to the improvement of the battery dynamics performance. However, the increase of small particles in the positive electrode film layer will increase the ohmic impedance of the positive electrode tab, which has a negative impact on the improvement of the battery dynamics performance. At the same time, the increase of small particles increases the specific surface area of the positive active material, and the degree of side reaction increases, thereby increasing the gas generated in the cycle process of the battery. The shell of the soft package battery cell is relatively soft, and the binding force of the electrode assembly is small, so it cannot effectively extrude the gas generated by the side reaction, thereby causing the gas to gather, the internal gap of the battery cell to become larger, the internal resistance of the battery to increase, and the dynamics of the battery to deteriorate; in addition, a large amount of gas gathering will also cause large-area lithium precipitation, as shown in Figure 1 , which seriously affects the cycle performance of the battery. Therefore, how to improve the dynamics performance of the polyanion system soft package battery while considering the cycle performance has become a technical problem to be solved.

[0099] To solve the above problems, the first aspect of the present application provides a battery monomer, which comprises a shell and an electrode assembly, the electrode assembly is contained in the shell, and the material of the shell is a soft package material; the electrode assembly comprises a positive electrode tab and a negative electrode tab, the positive electrode tab comprises a positive electrode film layer, the positive electrode film layer comprises a positive active material, and the positive active material comprises polyanion particles with at least part of the surface provided with 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 comprises a conductive agent, and the conductive agent comprises carbon nanotubes; the size of the positive electrode tab along the width direction of the battery monomer is less than or equal to 130 mm.

[0100] In the embodiment of the present application, the positive active material has a bimodal particle size distribution, wherein the peak position of the first peak is smaller than that 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, i.e. the positive active material comprises 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 shown in Figure 2The research shows that the specific surface area of large particles is small, the side reaction is less, but the ion diffusion path is long, and the kinetics is relatively poor; the ion diffusion path of small particles is short, and the kinetics is good, but the specific surface area is large, and the side reaction is relatively more. The integral area ratio of the first peak to the second peak is controlled to be 4:6-8:2 in the embodiment of the present application, that is, the ratio of the above-mentioned large and small particles is controlled in a suitable range, which helps to improve the kinetics performance of the positive active material, and at the same time, the cycle performance of the soft package battery is considered. At the same time, the positive electrode film layer of the embodiment of the present application also includes a conductive agent, and the conductive agent includes carbon nanotubes, so as to make up for the low graphitization degree and insufficient electronic conductivity of small particles due to insufficient sintering temperature or insufficient sintering time, and further realize the improvement of the battery kinetics performance. The carbon nanotube is a one-dimensional conductive agent, has excellent conductivity, and can be coated on the surface of the particle, reducing the direct contact of the particle and the electrolyte, further reducing the degree of side reaction, and improving the cycle performance of the battery. In addition, the size of the positive electrode sheet of the embodiment of the present application along the width direction of the battery monomer is less than or equal to 130 mm, the battery width is small, which is beneficial to reduce the escape path of gas in the soft package battery, so as to alleviate the lithium precipitation problem caused by the increase of small particles, the intensification of side reaction and gas aggregation. In summary, the battery monomer provided by the embodiment of the present application has good cycle performance while improving the kinetics performance.

[0101] In the present application, the term "bimodal curve" refers to the existence of two peaks in the curve. This distribution characteristic shows that the particles in the material are mainly concentrated in two particle size intervals with large differences. The peak position of the first peak in the bimodal curve is smaller than that of the second peak, and the peak position refers to the particle size corresponding to the peak in the curve.

[0102] In the present application, the particle size volume distribution curve can be determined by methods and instruments known in the art. As an example, GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method can be referred to for convenient determination by a laser particle size analyzer. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. of the United Kingdom. Examples are as follows: S1: 2 g of positive electrode active material and 5 g of sodium dodecyl sulfate SDS are added to 200 mL of N-methyl pyrrolidone (NMP), and then the mixture is placed in an ultrasonic cleaner for ultrasonic treatment, with a power of 100 W and a time of 30 min. The solution after ultrasonic treatment is taken for particle size testing; S2: 2 g of positive electrode active material and 5 g of sodium dodecyl sulfate SDS are added to 200 mL of N-methyl pyrrolidone (NMP), and then the mixture is placed in an ultrasonic cleaner for ultrasonic treatment, with a power of 100 W and a time of 60 min. The solution after ultrasonic treatment is taken for particle size testing; 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 completely dispersed, the step S2 is repeated and the ultrasonic time is increased by 30 min, until the fluctuation of Dv50 and Dv99 of the two tests with a difference of 30 min in ultrasonic time are both less than or equal to 5%, the testing is stopped, and 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. Wherein, the fluctuation of Dv50 is the difference between the two test results of Dv50 divided by the smaller Dv50 in the two test results; the fluctuation of Dv99 is the difference between the two test results of Dv99 divided by the smaller Dv99 in the two test results.

[0103] It is worth noting that the material used for testing in the present application can be freshly prepared material, or material scraped from the film layer after disassembly of a secondary battery.

[0104] In some embodiments, 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, and the peak position of the first peak can be 0.3 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.4 μm, 0.41 μm, 0.42 μm, 0.43 μm, 0.44 μm, 0.45 μm, 0.46 μm, 0.47 μm, 0.48 μm, 0.49 μm, 0.5 μm, 0.51 μm, 0.52 μm, 0.53 μm, 0.54 μm, 0.55 μm, 0.56 μm, 0.57 μm, 0.58 μm, 0.59 μm, 0.6 μm, 0.61 μm, 0.62 μm, 0.63 μm, 0.64 μm, 0.65 μm, 0.66 μm, 0.67 μm, 0.68 μm, 0.69 μm, 0.7 μm, or any numerical range between any two of these values.

[0105] In some embodiments, 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, and the peak position of the first peak is 0.3-0.6 μm.

[0106] The peak position of the first peak in the above range helps to achieve a balance between battery kinetics and cycle life.

[0107] In some embodiments, 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, and the peak position of the second peak can be 0.9 μm, 0.91 μm, 0.92 μm, 0.93 μm, 0.94 μm, 0.95 μm, 0.96 μm, 0.97 μm, 0.98 μm, 0.99 μm, 1.0 μm, 1.01 μm, 1.02 μm, 1.03 μm, 1.04 μm, 1.05 μm, 1.06 μm, 1.07 μm, 1.08 μm, 1.09 μm, 1.1 μm, 1.11 μm, 1.12 μm, 1.13 μm, 1.14 μm, 1.15 μm, 1.16 μm, 1.17 μm, 1.18 μm, 1.19 μm, 1.2 μm, 1.21 μm, 1.22 μm, 1.23 μm, 1.24 μm, 1.25 μm, 1.26 μm, 1.27 μm, 1.28 μm, 1.29 μm, 1.3 μm, 1.31 μm, 1.32 μm, 1.33 μm, 1.34 μm, 1.35 μm, 1.36 μm, 1.37 μm, 1.38 μm, 1.39 μm, 1.4 μm, 1.41 μm, 1.42 μm, 1.43 μm, 1.44 μm, 1.45 μm, 1.46 μm, 1.47 μm, 1.48 μm, 1.49 μm, 1.5 μm, or any range of values between any two of these values.

[0108] In some embodiments, 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, and the peak position of the second peak is 0.9-1.4 μm.

[0109] The peak position of the second peak in the above range helps to reduce the specific surface area of the particles, reduce the degree of side reactions, and at the same time take into account the kinetic performance, reduce the electrode resistance, and take into account the kinetic performance and cycle performance of the battery.

[0110] In this application, the integral area ratio of the first peak to the second peak can be tested using methods and instruments known in the art. As an example, according to the method above, the 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 the “Volume (%)” view, click “Band Analysis” in the top menu bar, find the option “User-defined Bands”, click “Add Band”, and set the interval to obtain the integral area ratio of the two peaks. The interval set is adjusted according to the two peaks of the positive electrode active material to ensure that the set interval only includes the full range of the first peak or the second peak.

[0111] In some embodiments, the ratio of the integrated area 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.

[0112] In the present application, the dimension of the positive electrode tab along the battery monomer width direction can be tested using methods and instruments known in the art. As an example, a micrometer (e.g., Mitutoyo 293-100, accuracy of 0.1 μm) can be used for testing.

[0113] In some embodiments, the dimension of the positive electrode tab along the battery monomer width direction 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.

[0114] In some embodiments, the dimension of the positive electrode tab along the battery monomer width direction is 110-125 mm.

[0115] In the present application, the presence of carbon nanotubes in the positive electrode film layer 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 can be taken for observation and determination.

[0116] In some embodiments, the ratio of the integrated area of the first peak to the second peak is 5:5-7:3.

[0117] The ratio of the integrated area of the first peak to the second peak is further within the above range, indicating that the positive electrode film layer has a suitable proportion of large particles and small particles, thereby helping to balance the degree of side reaction and kinetic performance of the positive electrode film layer, and further improving the battery kinetic performance while taking into account the cycle performance.

[0118] In some embodiments, the mass percentage of the conductive agent based on the total mass of the positive electrode film layer is greater than or equal to 0.8%.

[0119] In some embodiments, the mass percentage of the conductive agent based on the total mass of the positive electrode film layer 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.

[0120] The mass percentage of the conductive agent in the above range helps to improve the conductivity of the positive electrode film layer, reduce the resistance of the positive electrode tab, and improve the kinetic performance of the battery.

[0121] In some embodiments, the mass percentage of the conductive agent based on the total mass of the positive electrode film layer is 0.8%-1.3%.

[0122] The content of the conductive agent is further in the above range, which helps to improve the kinetic performance of the battery cell while not occupying too much space of the active material due to the high content, thereby balancing the volume energy density of the battery cell.

[0123] In some embodiments, the mass percentage of the carbon nanotubes based on the total mass of the conductive agent is greater than or equal to 30%.

[0124] In some embodiments, the mass percentage of the carbon nanotubes based on the total mass of the conductive agent can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any numerical range between any two of them.

[0125] The carbon nanotubes are one-dimensional conductive agents with excellent electronic conductivity. The mass content of the carbon nanotubes in the above range helps to form a good three-dimensional network structure in the positive electrode film layer, improving the conductivity of the positive electrode film layer. In addition, the carbon nanotubes have a one-dimensional linear morphology, which helps to reduce the direct contact area between the particles and the electrolyte when the carbon nanotubes are covered on the surface of the particles. The mass content of the carbon nanotubes in the above range can effectively reduce the contact between the particles and the electrolyte, reduce the degree of side reactions, and thus improve the kinetic performance of the battery while balancing the cycle performance.

[0126] In some embodiments, the mass percentage of the carbon nanotubes based on the total mass of the conductive agent is 30%-70%.

[0127] In some embodiments, the mass percentage of the carbon nanotubes based on the total mass of the conductive agent is 40%-70%.

[0128] The carbon nanotubes have poor flexibility, and too much content of the carbon nanotubes in the positive electrode film layer may increase the brittleness of the tab and cause the problem of powder falling during long-term cycling, thereby affecting the cycle performance of the battery. In the embodiments of the present application, the mass content of the carbon nanotubes is further in the above range, which helps to reduce the brittleness of the tab while reducing the resistance of the tab, thereby further improving the kinetic performance and cycle performance of the battery. In addition, the carbon nanotubes have a high cost, and the mass content of the carbon nanotubes in the above range helps to reduce the production cost of the battery.

[0129] In some embodiments, the carbon nanotubes include one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0130] In some embodiments, the carbon nanotubes include oligowall carbon nanotubes.

[0131] Compared with multiwall carbon nanotubes, oligowall carbon nanotubes have good electrical conductivity; compared with single-arm carbon nanotubes, they have the characteristics of better chemical stability and lower cost. The carbon nanotubes in the embodiments of the present application include oligowall carbon nanotubes, which help to improve the kinetic performance of the battery monomer while taking into account the production cost.

[0132] In some embodiments, the conductive agent further includes conductive carbon black.

[0133] In some embodiments, the conductive carbon black includes one or more of Super P, Ketjen black, and acetylene black.

[0134] The conductive carbon black is a particulate conductive agent that can be filled into the three-dimensional conductive network of the carbon nanotubes, and the two work together to further improve the electrical conductivity of the electrode sheet, thereby further improving the kinetic performance of the battery.

[0135] In some embodiments, the polyanion particles include a component represented by the following general formula:

[0136] Li x A y Me a M b P 1-c X c Y z Formula I,

[0137] 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 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, Ce; X includes one or more of S, Si, Cl, B, C, and N; and Y includes one or more of O and F.

[0138] In some embodiments, x can be selected as 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.

[0139] In some embodiments, y can be selected from 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 these values.

[0140] In some embodiments, x+y can be selected from 0.8, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, or any range between any two of these values.

[0141] In some embodiments, a can be selected from 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 these values.

[0142] In some embodiments, b can be selected from 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 these values.

[0143] In some embodiments, a+b can be selected from 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 these values.

[0144] In some embodiments, c can be selected from 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 these values.

[0145] In some embodiments, z can be selected from 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 these values.

[0146] In the present application, the type and content of elements in the polyanion particles in the positive electrode film layer can be tested by any known method in the art.

[0147] In some embodiments, the polyanion particles comprise one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluorophosphate, lithium manganese iron phosphate, lithium iron fluorophosphate, lithium manganese iron fluorophosphate, and modified materials thereof.

[0148] In some embodiments, the polyanion particles comprise one or more of lithium iron phosphate and modified materials thereof.

[0149] In some embodiments, the positive electrode active material comprises titanium element, and the mass percentage of the titanium element is 1000-5000 ppm based on the total mass of the positive electrode active material.

[0150] The type and content of elements in the lithium-containing transition metal phosphate particles in the positive electrode active material can be tested by any publicly known method in the art. As an example, the titanium element and content are tested by inductively coupled plasma emission spectrometry according to Appendix C of GB / T 33822-2017.

[0151] In some embodiments, the positive electrode active material comprises titanium element, and the mass percentage of the titanium element is selected from 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 numerical range between any two of them, based on the total mass of the positive electrode active material.

[0152] tetravalent titanium atom Ti 4+ with divalent iron atom Fe 2+ Having similar ionic radii, the titanium element can replace part of the iron element 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 the lattice distortion during charging and discharging, thereby improving the stability of the material and the cycle performance of the battery. In addition, the titanium element doping introduces additional positive charge, and the material system forms a Fe-O-Ti network according to the charge compensation mechanism, promotes electron transition, improves the conductivity of the positive electrode active material, reduces the electrode resistance, and enhances the kinetic performance of the battery.

[0153] In some embodiments, the positive electrode active material comprises titanium element, and the mass percentage of the titanium element is 2000-5000 ppm based on the total mass of the positive electrode active material.

[0154] The content of the titanium element is further within the above range, which helps to improve the kinetic performance and cycle performance of the battery. In addition, the content of the titanium element is too high to occupy the iron element sites, thereby affecting the energy density of the battery. Therefore, in the embodiments of the present application, the mass content of the titanium element is within the above range, which also helps to reduce the energy density loss caused by the introduction of the titanium element.

[0155] In some embodiments, the compaction density of the positive electrode film layer of the battery cell under full discharge state is 2.3 g / cm3 2.5 g / cm2 3 .

[0156] In the present application, the full discharge state refers to placing the battery in a 25℃ oven environment, standing for 2h, waiting for the battery temperature to remain 25℃, discharging the battery at 1 / 3C constant current to 2.5V, then standing for 30min, and then discharging at 0.04C constant current to 2.5V.

[0157] In the present 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 a 25℃ oven environment, stand for 2h, wait for the battery temperature to remain 25℃, discharge the battery at 1 / 3C constant current to 2.5V, then stand for 30min, and then discharge at 0.04C constant current to 2.5V, disassemble the battery, obtain the positive electrode sheet, treat the residual electrolyte with dimethyl carbonate solvent, dry the sheet, cut into small round pieces with an area of S, obtain its mass W1, and measure the thickness T1 of the positive electrode sheet using a micrometer, then wipe off the positive electrode film layer of the above weighed sheet, weigh the mass of the current collector, denoted as W2, and measure the thickness T2 of the current collector using a micrometer, then the compaction density PD of the positive electrode film layer = (W1-W2) / [(T1-T2)×S].

[0158] In some embodiments, the compaction density of the positive electrode film layer of the battery cell in the full discharge state can be 2.3g / cm2 3 , 2.31g / cm2 3 , 2.32g / cm2 3 , 2.33g / cm2 3 , 2.34g / cm2 3 , 2.35g / cm2 3 , 2.36g / cm2 3 , 2.37g / cm2 3 , 2.38g / cm2 3 , 2.39g / cm2 3 , 2.40g / cm2 3 , 2.41g / cm2 3 , 2.42g / cm2 3 , 2.43g / cm2 3 , 2.44g / cm2 3 , 2.45g / cm2 3 , 2.46g / cm2 3 , 2.47g / cm2 3 , 2.48g / cm2 3 , 2.49g / cm2 3 , 2.5g / cm2 3 or any numerical range between any two of them.

[0159] The high compaction density helps to increase the loading of the positive active material on the positive electrode sheet; and the low compaction density helps to increase the porosity of the membrane layer. In the embodiments of the present application, the compaction density of the positive electrode membrane layer of the battery monomer in the full discharge state is within the above range, which helps to make the positive electrode membrane layer have a suitable porosity, improve the liquid retention rate of the electrode sheet, and 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 a suitable loading of the positive active material, and balance the volume energy density of the battery.

[0160] In some embodiments, the electrode assembly further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet, the separator comprising a base film, a ceramic layer disposed on at least one side of the base film, and a bonding layer disposed on the side of the at least one ceramic layer away from the base film.

[0161] In some embodiments, the separator comprises a base film, a ceramic layer disposed on one side of the base film.

[0162] In some embodiments, the separator comprises a base film, ceramic layers disposed on both sides of the base film.

[0163] In some embodiments, the base film comprises one or more of polyethylene (PE), polypropylene (PP), polyimide (PI), aramid, and polytetrafluoroethylene (PTFE).

[0164] In some embodiments, the base film comprises polyethylene (PE).

[0165] 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, reduce the increase in small particles caused by the increase in gas production, and thus improve the cycle performance of the battery. In addition, the polyethylene-based base 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 soft package battery deforms, and further improves the cycle performance of the battery.

[0166] In some embodiments, the ceramic layer comprises one or more of aluminum oxide (Al2O3), zirconium oxide (ZrO2), titanium oxide (TiO2), calcium oxide (CaO), and magnesium oxide (MgO).

[0167] In some embodiments, the ceramic layer comprises aluminum oxide (Al2O3).

[0168] The ceramic layer has the ability to contain electrolyte, which helps to improve the electrolyte infiltration rate 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 base film is relatively soft and has low mechanical strength. The separator in the embodiments of the present application includes a base film and a ceramic layer arranged on at least one side of the base film, which helps to improve the mechanical strength of the separator and the puncture resistance of the soft package battery, thereby improving the safety performance of the battery.

[0169] In some embodiments, the adhesive layer includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and styrene-butadiene rubber (SBR).

[0170] The separator includes an adhesive layer, which helps to improve the adhesion strength between the separator and the positive and negative electrode sheets. On the one hand, this helps to reduce the gap between the electrode assemblies, 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 and negative electrode sheets, increase the stability of the electrode assemblies, and thus improve the cycle performance of the battery.

[0171] In some embodiments, the adhesive layer includes polyvinylidene fluoride (PVDF), and the adhesive layer is in a porous and continuous form.

[0172] In traditional separators, the adhesive layer is generally water-based PVDF, and the adhesive layer in the separator usually has a discontinuous island structure. In the present application, the adhesive layer is in a continuous and porous form, which helps to increase the bonding area between the separator and the positive and negative electrode sheets, increase the adhesion strength, improve the tightness of the soft package battery, reduce the interface resistance between the separator and the electrode sheets, reduce the battery impedance, and thus further improve the kinetic performance and cycle performance of the battery.

[0173] In some embodiments, the separator includes a base film, a ceramic layer arranged on one side of the base film, and an adhesive layer arranged on the side of the ceramic layer away from the base film.

[0174] In some embodiments, the separator includes a base film, ceramic layers arranged on both sides of the base film, and adhesive layers arranged on the sides of the two ceramic layers away from the base film, respectively.

[0175] The separator includes ceramic layers arranged on both sides of the base film and adhesive layers arranged on the sides of the two ceramic layers away from the base film, respectively, which helps to further improve the mechanical strength of the separator and the adhesion strength between the separator and the positive and negative electrode sheets, thereby further improving the kinetic performance and cycle performance of the battery monomer.

[0176] In some embodiments, the porosity of the separator is 30%-45%.

[0177] As used herein, the porosity of the separator is of 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 to measure the porosity according to GB / T 24586-2009. The porosity ε = (V1-V2) / V1x100%, wherein V1 is the apparent volume of the sample and V2 is the true volume of the sample.

[0178] In some embodiments, the porosity of the separator can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 30%, 41%, 42%, 43%, 44%, 45% or any range between any two of the values.

[0179] The porosity of the separator within the above range helps to improve the electrolyte wetting rate of the separator, thereby improving the transmission rate of lithium ions, reducing the internal resistance of the battery, and further improving the kinetic performance of the battery.

[0180] In some embodiments, the battery cell further comprises an electrolyte, and the electrolyte comprises a solvent, and the solvent comprises ethylene carbonate (EC), and the mass fraction of ethylene carbonate (EC) in the total mass of the solvent is 0.1%-25%.

[0181] In this document, the types and mass contents of the components in the electrolyte can be obtained by detecting the electrolyte by any method known to those skilled in the art. As an example, the components and contents 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). For example, according to GB / T-9722-2006 "General rules for gas chromatography of chemical reagents" and / or GB / T 6041-2002 "General rules for mass spectrometry", gas chromatography and mass spectrometry are used. After the components in the sample are separated by gas chromatography, the components are broken into ion fragments in the mass spectrometer, separated according to the mass-to-charge ratio (m / z) to form a specific mass spectrum, and the qualitative analysis of the organic components in the electrolyte is obtained. Then, the organic components in the electrolyte are separated in the chromatographic column and generate component detection signal spectrum, the components are qualitatively analyzed by using retention time, the peak area is corrected by calibration, and the quantitative test analysis of the organic components in the electrolyte is obtained. According to JY / T-020, the anion types of the electrolyte salt in the electrolyte are detected by ion chromatography and quantitatively tested. According to JY / T 0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0182] In this document, the mass fraction of ethylene carbonate (EC) based on the total mass of the solvent can be obtained by the above-mentioned method for testing the types and mass contents of the components in the electrolyte. The mass fraction of ethylene carbonate (EC) based on the total mass of the solvent is the ratio of the mass of ethylene carbonate obtained by the above-mentioned method to the total mass of the solvent in the electrolyte.

[0183] It is worth noting that the electrolyte referred to in this document can be either fresh electrolyte or electrolyte obtained by disassembling a battery cell. The electrolyte obtained by disassembling a battery cell can be either electrolyte free in the battery shell or electrolyte obtained by centrifugation from the electrode sheet.

[0184] In some embodiments, the battery cell further comprises an electrolyte, and the electrolyte comprises a solvent, and the solvent comprises ethylene carbonate (EC), and the mass fraction of ethylene carbonate (EC) based on the total mass of the solvent 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 any numerical range between any two of them.

[0185] The inclusion of ethylene carbonate in the electrolyte helps to dissolve 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 a too high content of ethylene carbonate will affect the transmission rate of lithium ions, and thus affect the dynamic performance of the battery. In the embodiments of the present application, the mass fraction of ethylene carbonate is within the above-mentioned range, which helps to form good SEI film and CEI film, and at the same time reduces the influence of ethylene carbonate on the transmission rate of lithium ions, thereby improving the cycle performance of the battery while taking into account the dynamic performance of the battery.

[0186] In some embodiments, the electrolyte further comprises vinylene carbonate (VC), and the mass fraction of vinylene carbonate (VC) based on the total mass of the electrolyte is 0.5%-2%.

[0187] In this document, the mass fraction of vinylene carbonate (VC) based on the total mass of the electrolyte can be tested using methods and instruments known in the art. As an example, the above-mentioned testing method for testing the types and mass contents of the components in the electrolyte can be used for testing.

[0188] In some embodiments, the electrolyte further comprises vinylene carbonate (VC) in an amount of 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 range between any two of the aforementioned values, based on the total mass of the electrolyte.

[0189] Vinylene carbonate (VC) preferentially decomposes before the decomposition of ethylene carbonate (EC) into a film, forms an initial SEI film with high elasticity and low impedance, and to some extent promotes the stability of the positive CEI film. In the embodiments of the present application, the mass content of VC in the above range helps to reduce the gas generated by the decomposition of ethylene carbonate, thereby reducing the gas content inside the battery, relieving the lithium precipitation phenomenon induced by gas accumulation, and further improving the cycle life of the battery.

[0190] In some embodiments, the electrolyte further comprises lithium difluorophosphate (LiPF2O2) in an amount of 0.03%-0.2%, based on the total mass of the electrolyte.

[0191] In this document, the amount of lithium difluorophosphate (LiPF2O2) can be tested based on the total mass of the electrolyte using methods and instruments known in the art. As an example, the test method for the type and mass content of each component in the above-mentioned electrolyte can be used for testing.

[0192] In some embodiments, the electrolyte further comprises lithium difluorophosphate (LiPF2O2) in an amount of 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 range between any two of the aforementioned values, based on the total mass of the electrolyte.

[0193] The decomposition product of lithium difluorophosphate can fill into the SEI film and the CEI film, enhance the elasticity and density of the interface film, reduce the direct contact between the electrolyte and the active material, and thus reduce the degree of side reactions. In the embodiments of the present application, the content of lithium difluorophosphate in the above range helps to improve the quality of the SEI film and the CEI film, reduce the gas production inside the battery, thereby improving the lithium precipitation caused by gas accumulation, and further improving the cycle performance of the battery.

[0194] In some embodiments, the negative electrode sheet comprises a negative electrode film layer, and the negative electrode film layer comprises a negative electrode active material, and the D50 of the negative electrode active material is less than or equal to 25 μm. V 50 less than or equal to 25 μm.

[0195] In this paper, the 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. V 50 can be measured using methods and instruments known in the art. For example, it can be conveniently measured using a laser particle size analyzer, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0196] In some embodiments, the 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 any range therebetween.

[0197] D of negative electrode active material V 50 is large, indicating that the particle size of the negative electrode active material is large, thereby extending the lithium ion diffusion path, thereby affecting the ionic conductivity of the negative electrode sheet. V 50 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 and extraction path, improve the ionic conductivity of the negative electrode film layer, and thus further improve the kinetic performance of the battery.

[0198] 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, wherein 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.

[0199] As used herein, orientation degree (OI) has a meaning known in the art. The orientation degree (OI) of the negative electrode active material can be tested using methods and instruments known in the art. As an example, an X-ray diffractometer (such as Bruker D8 Discover) is used for testing. The test can refer to JIS K0131-1996 and JB / T 4220-2011 to obtain an X-ray diffraction pattern of the negative electrode active material. According to the OI value = I 004 / I 110 The orientation degree (OI) of the negative electrode active material is calculated. 004I is the integral area of the diffraction peak of the 004 crystal face of the crystalline carbon in the material 110 I is the integral area of the diffraction peak of the 110 crystal face of the crystalline carbon in the material. In the ray diffraction analysis test of the present application, a copper target can be used as an anode target, CuK a ray is used as a radiation source, the ray wavelength is 2 = 1.5418 Å, the scanning 2 theta angle range is 20°-80°, and the scanning rate is 4° / min. The orientation degree (OI) represents the ordered degree of the arrangement of the crystals or particles in the material. The higher the orientation degree (OI), the more ordered the arrangement of the grains of the material; the lower the orientation degree (OI), the more disordered the orientation of the material.

[0200] In some embodiments, the negative active material comprises artificial graphite, and the orientation degree (OI) of the negative active material can be selected as 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 any numerical range between any two of them.

[0201] In the embodiments of the present application, the orientation degree (OI) of the negative active material is within the above range, the orientation of the material is more disordered, which is helpful to increase the number of end faces of lithium ion insertion, thereby helping to improve the kinetic performance of the battery.

[0202] In some embodiments, the compaction density of the negative electrode film layer of the battery cell in the full discharge state can be 1.4 g / cm 3 -1.6 g / cm 3 .

[0203] In the present application, the compaction density of the negative electrode film layer can be tested by referring to the test method of the compaction density of the positive electrode film layer.

[0204] In some embodiments, the compaction density of the negative electrode film layer of the battery cell in the full discharge state 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 / cm3 3 1.55 g / cm3 3 1.56 g / cm3 3 1.57 g / cm3 3 1.58 g / cm3 3 1.59 g / cm3 3 1.6 g / cm3 3 or any numerical range between any two of the above values.

[0205] 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.

[0206] In some embodiments, 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), polypropylene (CPP), polyimide (PI), polybutylene terephthalate (PBT), polybutylene succinate (PBS), polyethylene terephthalate (PET), and polyethylene (PE) and aluminum.

[0207] The soft package material has a high ductility, so that the shell is more light and thin, and soft, which helps to improve the space utilization of the battery monomer, thereby improving the energy density of the battery monomer. In addition, the high barrier property of aluminum can effectively reduce the penetration of water and oxygen into the battery, reduce the decomposition of electrolyte and the oxidation degree of electrode material, thereby improving the service life of the battery.

[0208] In some embodiments, the battery monomer includes a laminated cell, and the laminated cell includes an electrode assembly.

[0209] In some embodiments, the battery monomer includes a laminated cell, and the laminated 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.

[0210] Compared with the wound cell, the laminated cell has no corner area, so that the battery including the laminated cell helps to improve the space utilization of the battery, thereby improving the volumetric energy density of the battery. However, due to the absence of the constraint of 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 easy to escape, thereby causing gas aggregation and lithium precipitation of the electrode sheet, which affects the cycle performance of the battery. In the embodiments of the present application, the laminated cell is used, and 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 monomer are controlled, which helps to improve the kinetic performance and energy density of the battery while taking into account the cycle performance.

[0211] Battery device

[0212] The application further provides a battery device, which comprises the battery cell provided by the application.

[0213] The battery device comprises one or more of a battery module, a battery pack, and an energy storage battery.

[0214] A power consuming device

[0215] The application further provides a power consuming device, which comprises the battery device provided by the application and is used for providing electric energy. The battery can be used as a power supply 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 notebook 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.

[0216] The power consuming device can select a specific type of battery (such as a battery cell, a battery module, or a battery pack) according to its use requirement.

[0217] An energy storage device

[0218] The application further provides an energy storage device, which comprises the battery device provided by the application and is used for storing electric energy. The battery device can be used as an 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.

[0219] Figure 3 FIG. 1 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 requirement of high power and high energy density of the power consuming device, a battery pack or a battery module can be used.

[0220] The power consuming device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The power consuming device usually requires thinness and lightness, and a battery cell can be used as a power supply.

[0221] Example

[0222] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used for explaining the application, and cannot be understood as a limitation of the application. If a specific technology or condition is not mentioned in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not mentioned by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0223] I. Preparation method

[0224] Example 1

[0225] (1) Preparation of positive electrode

[0226] Preparation of the first particles: Iron phosphate, lithium carbonate, polyethylene glycol, glucose, and titanium dioxide are mixed and ground in methanol to obtain a mixed raw material; the mixed raw material is fully ground in a sand mill to obtain a uniform mixed slurry. The mixed slurry is spray-dried to obtain a dry precursor powder, which is placed in a sintering furnace and heated to 400°C and maintained for 3 hours under a nitrogen atmosphere, then heated to 780°C and maintained for 6 hours. After cooling, the mixture is pulverized using airflow to obtain the first particles; wherein, the D of the first particles is V 50 is 0.4 μm, and the mass content of titanium element is 2500 ppm based on the total mass of the first particles.

[0227] The preparation method of the second particle is basically the same as that of the first particle, except that the sintering temperature and holding time are adjusted to obtain the second particle; wherein, the D V 50 is 1 μm, and the mass content of titanium element is 2500 ppm based on the total mass of the second particles.

[0228] Preparation of positive electrode slurry: 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 at a mass ratio of 68.6:29.4:1:1, and the mixture is thoroughly stirred and mixed. Then, the mixture is wetted, kneaded, and dispersed to obtain a positive electrode slurry; wherein the conductive agent includes oligo-walled carbon nanotubes and conductive carbon black in a mass ratio of 1:1.

[0229] The positive electrode slurry is coated on aluminum foil, and then dried, cold pressed, and cut to obtain positive electrode sheets. Among them, the compaction density of the positive electrode film layer is 2.35g / cm3 when the battery cell is fully discharged. 3 ; The dimension of the positive electrode sheet along the width direction of the battery cell is 118mm.

[0230] (2) Preparation of negative electrode sheet

[0231] The negative electrode active material artificial graphite, the binder polyvinyl alcohol, and the conductive agent SP-Li are mixed in a mass ratio of 90:5:5, and the solvent deionized water is added. The mixture is stirred evenly under the action of a vacuum mixer to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode collector copper foil, and the negative electrode collector coated with the slurry is dried in a vacuum environment at 110°C, and then cold pressed and cut to obtain the negative electrode sheet.

[0232] Among them, the D of the negative electrode active material artificial graphite V50 is 20 pm, and the orientation degree (OI) is 3.2; the compaction density of the negative electrode film layer is 1.45 g / cm 3 .

[0233] (3) Preparation of electrolyte

[0234] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and vinylene carbonate (VC) are mixed uniformly according to a volume ratio of 17.76:29.64:49.4:1.2, LiPF6 and LiPF2O2 with a mass ratio of 98:2 are dissolved in the organic solvents, the concentration of lithium ions is controlled to be 1 mol / L, and stirring is uniform to obtain the electrolyte.

[0235] (4) Preparation of separator

[0236] Porous alumina is added to an NMP (N-methyl pyrrolidone) solvent, stirred uniformly, and then sprayed on both sides of a polyethylene-based film and dried. PVDF is dissolved in an NMP (N-methyl pyrrolidone) solvent, stirred uniformly, and then sprayed on both surfaces of the porous alumina layer away from the base film, and dried to obtain a separator with a porous continuous morphology adhesive layer.

[0237] The thickness of the polyethylene-based film is 7 pm, the single side of the porous alumina layer is 1.5 pm, the single side thickness of the PVDF layer is 0.5 pm, and the porosity of the separator is 38%.

[0238] (5) Preparation of battery

[0239] The above positive electrode sheet, separator and negative electrode sheet are stacked according to the Z-type stacking method, so that the separator is between the positive and negative electrode sheets to play a role of isolation. The electrode assembly is placed in an aluminum-plastic composite film, the above electrolyte is injected, vacuum pumping and heat sealing are performed to form airtight packaging, and a lithium ion battery is obtained.

[0240] The aluminum-plastic composite film is composed of an inner layer of polyethylene, an intermediate layer of aluminum foil and an outer layer of polyethylene terephthalate.

[0241] Example 2

[0242] The preparation method of the lithium ion battery is similar to that of Example 1, except that the above first particles, the above second particles, a conductive agent and a binder (PVDF 5130) are dissolved in an NMP (N-methyl pyrrolidone) solvent according to a mass ratio of 78.4:19.6:1:1 during preparation of the positive electrode slurry.

[0243] Example 3

[0244] The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode slurry, the first particles, the second particles, the conductive agent, and the binder (PVDF 5130) are dissolved in NMP (N-methylpyrrolidone) solvent at a mass ratio of 44.1:53.9:1:1.

[0245] Example 4

[0246] 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 oligo-walled carbon nanotubes and conductive carbon black in a mass ratio of 8:2.

[0247] Example 5

[0248] 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 oligo-walled carbon nanotubes and conductive carbon black in a mass ratio of 3.5:6.5.

[0249] Example 6

[0250] The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode sheet, the amount of titanium dioxide added when preparing the first particles and the second particles is adjusted so that the mass content of the titanium element is 4500 ppm based on the total mass of the first particles, and the mass content of the titanium element is 4500 ppm based on the total mass of the second particles.

[0251] Example 7

[0252] The preparation method of the lithium-ion battery is similar to that of Example 1, except that when preparing the positive electrode sheet, the amount of titanium dioxide added when preparing the first particles and the second particles is adjusted so that the mass content of the titanium element is 1500 ppm based on the total mass of the first particles, and the mass content of the titanium element is 1500 ppm based on the total mass of the second particles.

[0253] Example 8

[0254] 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.

[0255] Example 9

[0256] The preparation method of the lithium ion battery is similar to that of Example 1, except that when the separator is prepared, the porous alumina is added to the NMP (N-methyl pyrrolidone) solvent, and after stirring uniformly, it is sprayed on both sides of the polyethylene-based film and then dried. The PVDF is dissolved in the NMP (N-methyl pyrrolidone) solvent, and after stirring uniformly, it is sprayed on one surface of the porous alumina layer away from the base film, and dried to obtain the separator. During the preparation of the battery, the side with the PVDF layer is arranged close to the negative electrode plate.

[0257] Example 10

[0258] The preparation method of the lithium ion battery is similar to that of Example 1, except that when the separator is prepared, the porous alumina is added to the NMP (N-methyl pyrrolidone) solvent, and after stirring uniformly, it is sprayed on both sides of the polyethylene-based film and then dried. The PVDF is dissolved in the NMP (N-methyl pyrrolidone) solvent, and after stirring uniformly, it is sprayed on one surface of the porous alumina layer away from the base film, and dried to obtain the separator. During the preparation of the battery, the side with the PVDF layer is arranged close to the negative electrode plate.

[0259] Example 11

[0260] 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: the porous alumina is added to the NMP (N-methyl pyrrolidone) solvent, and after stirring uniformly, it is sprayed on both sides of the polyethylene-based film and then dried to obtain the separator.

[0261] Example 12

[0262] The preparation method of the lithium ion battery is similar to that of Example 1, except that the separator only includes a polyethylene-based film.

[0263] Example 13

[0264] The preparation method of the lithium ion battery is similar to that of Example 1, except that the separator only includes a polyethylene-based film.

[0265] Comparative Example 1

[0266] The preparation method of the lithium ion battery is similar to that of Example 13, except that when the positive electrode slurry is prepared, the above-mentioned first particles, the above-mentioned second particles, the conductive agent, and the binder (PVDF 5130) are dissolved in the NMP (N-methyl pyrrolidone) solvent in a mass ratio of 88.2:9.8:1:1.

[0267] Comparative Example 2

[0268] The preparation method of the lithium-ion battery is similar to that of Example 13, except that when preparing the positive electrode slurry, the first particles, the second particles, the conductive agent, and the binder (PVDF 5130) are dissolved in NMP (N-methylpyrrolidone) solvent at a mass ratio of 19.6:78.4:1:1.

[0269] Comparative Example 3

[0270] The preparation method of the lithium-ion battery is similar to that of Comparative Example 1, except that, when preparing the positive electrode slurry, the conductive agent is conductive carbon black, and oligo-walled carbon nanotubes are not included.

[0271] Comparative Example 4

[0272] The preparation method of the lithium-ion battery is similar to that of Comparative Example 3, except that the dimension of the positive electrode sheet along the width direction of the battery cell is 145 mm.

[0273] 2. Performance Testing

[0274] 1. DC internal resistance DCR test

[0275] Refer to the method in GB / T31467, "Performance Test Specification for High-Power Lithium-Ion Power Batteries for HEVs." For example, at room temperature, charge a battery cell to 3.75V at a constant current of 0.33C, let it rest for 10 minutes, then charge it again at a constant voltage of 3.75V to 0.05C, let it rest for 30 minutes, and then discharge it at a discharge rate of 0.33C to 2.50V. Record the discharge capacity (A0). Then, charge it at a constant current of 0.5A0 at 0.33C, adjusting the SOC to 50%. After the battery cell is left at 25°C for 2 hours, discharge it at a constant current of 3C for 10 seconds. Record ∆U discharge and ∆I discharge. Calculate the lithium-ion battery's discharge DCR data using the following formula: R discharge = ∆U discharge / ∆I discharge, where ∆U discharge represents the voltage change within the first 10 seconds of discharge, and ∆I discharge represents the current value within the first 10 seconds of discharge.

[0276] 2. Battery cycle retention rate test

[0277] The lithium-ion battery was left at rest at 25°C for 2 hours. At 25°C, it was charged to 3.75V at a charge rate of 0.33C, the nominal capacity of the battery. Then, it was charged to 0.05C at a constant voltage of 3.75V, left at rest for 10 minutes, and then discharged to 2.50V at a discharge rate of 0.33C. The reversible capacity was measured as C0. The above charge and discharge is one cycle. After repeating the charge and discharge for 1000 times, the battery capacity C1 was recorded. The capacity retention rate at this number of cycles is (C1 / C0)×100%.

[0278] 3. Test Results

[0279] The test results of the above examples and comparative examples are shown in Tables 1-5.

[0280] Table 1

[0281]

[0282] As can be seen from the comparison of the examples and the comparative examples, the battery cell comprises a shell and an electrode assembly, the electrode assembly is accommodated inside the shell, and the material of the shell is a soft package material; the electrode assembly comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet 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 with at least part of the surfaces provided with carbon coating materials; 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 is smaller than that of the second peak in the bimodal curve, the peak position of the first peak 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 comprises a conductive agent, and the conductive agent comprises carbon nanotubes; and the size of the positive electrode sheet along the width direction of the battery cell is less than or equal to 130 mm, which helps to improve the battery dynamics performance while taking into account the cycle performance.

[0283] As can be seen from the comparison of Example 1 and Examples 2-3, the area ratio of the first peak to the second peak is in the range of 5:5-7:3, which helps to further optimize the comprehensive performance of the battery and take into account the dynamics and cycle performance of the battery.

[0284] Table 2

[0285]

[0286] As can be seen from the comparison of Example 1 and Examples 4-5, the mass proportion of the carbon nanotubes based on the total mass of the conductive agent is in the range of 40%-70%, which helps to further improve the cycle performance of the battery while taking into account the dynamics performance.

[0287] Table 3

[0288]

[0289] As can be seen from the comparison of Example 1, Example 6 and Example 7, the mass proportion of titanium based on the total mass of the positive electrode active material is in the range of 2000-5000 ppm, which helps to further improve the dynamics performance and cycle performance of the battery.

[0290] Table 4

[0291]

[0292] As can be seen from the comparison of Example 1 and Example 8, the orientation degree (OI) of the negative electrode active material is less than 3.5, which helps to further improve the dynamics performance and cycle performance of the battery.

[0293] Table 5

[0294]

[0295] As can be seen from the comparison between Example 12 and Example 13, the base film of the separator includes a polyethylene material, which helps to further improve the kinetic performance and cycle performance of the battery.

[0296] As can be seen from the comparison between Example 11 and Example 12, the separator includes a ceramic layer, which helps to further improve the kinetic performance and cycle performance of the battery.

[0297] As can be seen from the comparison between Example 10 and Example 11, the separator includes a bonding layer, which helps to further improve the kinetic performance and cycle performance of the battery.

[0298] As can be seen from the comparison between Example 9 and Example 10, the bonding layer of the separator is in a porous continuous form, which helps to further improve the kinetic performance and cycle performance of the battery.

[0299] As can be seen from the comparison between Example 1 and Example 9, the separator includes a bonding layer arranged on both sides of the ceramic layer away from the base film, which helps to further improve the kinetic performance and cycle performance of the battery.

[0300] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration and playing the same role and effects as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, other modes constructed by combining part of the configuration elements of the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: It includes a shell and an electrode assembly, wherein the electrode assembly is accommodated inside the shell, and the shell is made of 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 electrode active material, and the positive electrode active material includes polyanion particles with a carbon coating material provided on at least a portion of the surface; 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 integrated 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 dimension of the positive electrode sheet along 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, wherein: The second peak has a peak position of 0.9-1.4 μm.

4. The battery cell according to claim 1, wherein: The dimension of the positive electrode sheet along the width direction of the battery cell is 110-125 mm.

5. The battery cell according to claim 1, characterized in that The integrated 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 of the carbon nanotubes accounts for 30%-70%.

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

11. The battery cell according to claim 1, characterized in that The carbon nanotubes include one or more of single-walled carbon nanotubes, oligo-walled carbon nanotubes, and multi-walled carbon nanotubes.

12. The battery cell according to claim 1, wherein The carbon nanotubes include oligo-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, characterized in that 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 polyanionic particles have the following components: Li x A y Me a M b P 1-c X c Y z Formula I Among them, 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; and Y includes one or more of O and F.

16. The battery cell according to claim 1, characterized in that The positive electrode active material includes titanium element, and 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, and 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 The compaction density of the positive electrode film layer of the battery cell is 2.3g / cm 3 -2.5g / 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, the separator including a base film, a ceramic layer disposed on at least one side of the base film, and an adhesive layer disposed on at least one side of the 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, polypropylene, polyimide, aramid, and polytetrafluoroethylene.

21. The battery cell according to claim 19, characterized in that The base film includes polyethylene.

22. The battery cell according to claim 19, characterized in that The ceramic layer includes one or more of aluminum oxide, zirconium oxide, titanium oxide, calcium oxide, and magnesium oxide.

23. The battery cell according to claim 19, characterized in that The bonding layer includes one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, and styrene-butadiene rubber.

24. The battery cell according to claim 19, characterized in that The bonding layer comprises polyvinylidene fluoride and is porous and continuous.

25. The battery cell according to claim 19, characterized in that The diaphragm includes a base film, ceramic layers respectively arranged on both sides of the base film, and adhesive layers respectively arranged on both sides of the ceramic layers away from the base film.

26. The battery cell according to claim 19, characterized in that The porosity of the diaphragm is 30%-45%.

27. The battery cell according to claim 1, characterized in that The battery cell further includes an electrolyte, the electrolyte includes a solvent, and the solvent includes ethylene carbonate. Based on the total mass of the solvent, the mass proportion of the ethylene carbonate is 0.1%-25%.

28. The battery cell according to claim 27, characterized in that The electrolyte further includes vinylene carbonate, and based on the total mass of the electrolyte, the mass proportion of the vinylene carbonate is 0.5%-2%.

29. The battery cell according to claim 27, characterized in that The electrolyte further includes lithium difluorophosphate, and based on the total mass of the electrolyte, the mass proportion of the lithium difluorophosphate 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 25μm.

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

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

33. The battery cell according to claim 1, characterized in that The soft package material comprises an aluminum-plastic composite film, which comprises a composite film composed of one or more of polypropylene, nylon, polyimide, polybutylene terephthalate, polybutylene succinate, polyethylene terephthalate, and polyethylene and aluminum.

34. The battery cell according to any one of claims 1 to 33, characterized in that: The battery cell includes a laminated battery core, and the laminated battery core 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 comprises the battery device as claimed in claim 35, and the battery device is used to provide electrical energy.

37. An energy storage device, characterized in that: The energy storage device comprises the battery device as claimed in claim 35, wherein the battery device is used to store electrical energy.

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