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

Abstract

The present application provides a battery cell, a battery device, an electrical device, and an energy storage device. The battery cell includes a positive electrode plate, a negative electrode plate, and an electrolyte; the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer includes a first positive electrode film layer arranged on the side close to the positive electrode current collector and a second positive electrode film layer arranged on the side of the first positive electrode film layer away from the positive electrode current collector, the Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18μm; the Dv99 of the particles in the first positive electrode film layer is less than or equal to 18μm, and the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1-1.5μm. The battery cell provided by the present application has good safety performance and energy density.

Description

Technical Field

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

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

[0003] As the market pursues higher battery capacity and safety performance, higher requirements are being placed on battery energy density and safety performance. However, existing technologies have difficulty achieving simultaneous improvements in these performances. How to strike a balance between the two has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its object is to provide a battery cell having both high energy density and good safety performance.

[0005] In a first aspect, the present application provides a battery cell, comprising a positive electrode plate, a negative electrode plate and an electrolyte; the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector, the positive electrode film layer comprises a first positive electrode film layer arranged on a side close to the positive electrode current collector and a second positive electrode film layer arranged on a side of the first positive electrode film layer away from the positive electrode current collector, the Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18 μm; the Dv99 of the particles in the first positive electrode film layer is less than or equal to 18 μm, and the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1-1.5 μm.

[0006] The battery cell provided in the present application adds a first positive electrode film layer between the current collector and the second positive electrode film layer. Among them, the Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18μm, and has certain large-sized particles to increase the compaction density of the positive electrode plate and improve the energy density of the battery. However, the large particles in the second positive electrode film layer are prone to squeeze the current collector, causing burr problems. By setting a first positive electrode film layer with a Dv99 less than or equal to 18μm between the positive current collector and the second positive electrode film layer, the particles in the first positive electrode film layer are smaller in size than those in the second positive electrode film layer, which effectively reduces the probability of large particles in the second positive electrode film layer directly contacting and squeezing the current collector during the plate cutting process, thereby reducing the probability of burrs, improving the yield rate of plate cutting and the safety performance of the battery.

[0007] At the same time, the particle size volume distribution curve of the first positive electrode film layer particles of the battery cell in this application is set to present a bimodal distribution, with the particles mainly concentrated in two particle size ranges with large differences. The smaller particles can effectively fill the gaps between the larger particles, achieving dense particle stacking and reducing the loss of positive electrode sheet compaction density caused by the addition of the first positive electrode film layer. At the same time, the peak position of the first peak is located at 0.1-1.5μm, increasing the content of small particles in the first positive electrode film layer in contact with the current collector, so that the surface is coated with more binder and the contact points with the current collector are increased, thereby improving the bonding strength between the positive electrode film layer and the current collector, improving the burr phenomenon, and reducing the probability of the film layer easily falling off during the cutting of the electrode sheet, thereby exposing the current collector, further improving the safety performance of the battery.

[0008] In any embodiment, the Dv90 of the particles in the second positive electrode film layer is 20-28 μm.

[0009] In any embodiment, the Dv99 of the particles in the first positive electrode film layer is 1-18 μm.

[0010] In any embodiment, the peak position of the first peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is 0.3-1 μm.

[0011] In any embodiment, the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 0.5-7 μm.

[0012] The peak positions of the two characteristic peaks of the particle size volume distribution of the particles in the first positive electrode film layer are controlled within the above range, that is, a large difference between the two particle size ranges is maintained, and smaller particles fill the gaps between larger particles, which can improve the gap filling rate between larger particles, thereby maintaining a high compaction density of the positive electrode sheet and a high energy density of the battery cell.

[0013] In any embodiment, the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 1-5 μm.

[0014] Furthermore, controlling the peak position of the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer within the range of 1-5 μm helps to increase the specific surface area of ​​the larger particles in the first positive electrode film layer, increase the amount of surface binder coating, reduce the probability of collector leakage during electrode cutting and improve the cycle performance of the battery; at the same time, the larger particle size in the first positive electrode film layer is within the above range, and the particle size is appropriate, which helps to maintain a higher compaction density of the positive electrode film layer, and the battery has a higher volume energy density.

[0015] In any embodiment, the first positive electrode film layer includes lithium-containing transition metal oxide single crystal particles and polyanion particles, the volume distribution particle size Dv50 of the lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer is 0.5-7μm, optionally 1-5μm, and the volume distribution particle size Dv50 of the polyanion particles is 0.1-1.5μm, optionally 0.3-1μm.

[0016] The size of lithium-containing transition metal oxide single crystal particles is smaller than that of polycrystalline particles, which can reduce the size of large particles in the first positive electrode film layer and reduce the probability of burrs on the positive electrode plate. However, due to the small size of the single crystal particles in the first positive electrode film layer, the compaction density of the plate is reduced, thereby losing the volume energy density of the battery cell; at the same time, the smaller lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer have limited effect on the bonding force between the positive electrode film layer and the current collector, and powder shedding and current collector leakage problems will still occur during the plate cutting process. In the embodiment of the present application, the first positive electrode film layer includes lithium-containing transition metal oxide single crystal particles and polyanion particles with a smaller particle size. On the one hand, the polyanion particles fill the gaps between the single crystal particles, increasing the compaction density of the plate; on the other hand, the polyanion fills the gaps between the single crystal particles, thereby increasing the number of particles in contact with the current collector in the first positive electrode film layer, increasing the binder content and area, and increasing the bonding strength between the positive electrode film layer and the current collector, further reducing the probability of current collector leakage and improving the yield rate of the plate.

[0017] In any embodiment, based on the total mass of the first positive electrode film layer, the mass proportion of the polyanion particles is 0.1%-10%.

[0018] The mass proportion of polyanions is in the range of 0.1%-10%, which helps to improve the volume energy density of battery cells; at the same time, compared with lithium-containing transition metal oxides, polyanions have a lower voltage platform and low-temperature voltage platform stability. The mass proportion of polyanions is in the above range, which helps to improve the power deterioration problem of the battery at low temperature and low SOC.

[0019] In any embodiment, based on the total mass of the first positive electrode film layer, the mass proportion of the polyanion particles is 2%-8%.

[0020] Furthermore, the mass proportion of polyanions is in the range of 2%-8%, which helps to further reduce the probability of collector leakage when the electrode is divided and improve the cycle performance of the battery; at the same time, the polyanion particles can fully fill the gaps between the lithium-containing transition metal oxide single crystal particles, while reducing the non-gap space occupied by excessive polyanion particles, thereby increasing the compaction density of the positive electrode film layer and further optimizing the energy density of the battery; in addition, the mass proportion of polyanions is in the above range, which helps to further improve the problem of power deterioration of the battery at low temperature and low SOC.

[0021] In any embodiment, the polyanionic particles include components represented by the following general formula:

[0022] Li x A y Me a M b P 1-c X c Y z Formula I,

[0023] 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.

[0024] In any embodiment, the polyanion includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate, lithium fluoride phosphate, lithium manganese iron phosphate, and modified materials thereof.

[0025] Polyanions often have a smaller particle size, which is beneficial for filling the gaps in the first positive electrode film layer, and is beneficial for increasing the adhesive adhesion to the current collector by utilizing its small particle size, thereby improving the leakage of the current collector from the electrode.

[0026] In any embodiment, the polyanion includes one or more of lithium manganese iron phosphate and modified materials thereof.

[0027] Compared to other polyanions, lithium iron manganese phosphate (LiMnFePO4) has a higher voltage platform and a smaller voltage difference with lithium-containing transition metal oxides, which facilitates the full utilization of the polyanion's specific capacity, thereby further improving the volumetric energy density of the battery cell. Furthermore, the polyanion, through its lower voltage platform, forms a voltage complement with the lithium-containing transition metal oxide, allowing the lithium-containing transition metal oxide to maintain a high voltage at low states of charge (SOC), effectively alleviating the power degradation problem of lithium-containing transition metal oxide materials at low temperatures and low SOCs.

[0028] In any embodiment, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-6 μm and the second peak is located at 5-14 μm.

[0029] In any embodiment, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-6 μm and the second peak is located at 6-10 μm.

[0030] In any embodiment, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-5 μm and the second peak is located at 6-10 μm.

[0031] In any embodiment, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-5 μm and the second peak is located at 5-14 μm.

[0032] The particles in the second positive electrode film layer show a bimodal distribution, which is similar to the bimodal distribution of the particles in the first positive electrode film layer. This is conducive to smaller particles filling the gaps between larger particles, achieving close stacking of particles, and increasing the compaction density of the second positive electrode film layer, thereby further improving the energy density of the battery.

[0033] In any embodiment, the second positive electrode film layer includes lithium-containing transition metal oxide polycrystalline particles and lithium-containing transition metal oxide single crystal particles.

[0034] In any embodiment, the volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 20-30 μm.

[0035] In any embodiment, the volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 22-28 μm.

[0036] In any embodiment, the volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 5-14 μm.

[0037] In any embodiment, the volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 6-10 μm.

[0038] The Dv99 and Dv50 of the polycrystalline particles in the second positive electrode film layer are within the above ranges, and the particles have a larger size, which is beneficial to improving the compaction density of the second positive electrode film layer, thereby further improving the energy density of the battery.

[0039] In any embodiment, the volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-13 μm.

[0040] In any embodiment, the volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-12 μm.

[0041] In any embodiment, the volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-6 μm.

[0042] In any embodiment, the volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-5 μm.

[0043] The combination of polycrystalline particles and single crystal particles that meet the above-mentioned particle size range is beneficial to improving the particle grading, achieving close stacking of particles in the positive electrode film layer, and further increasing the compaction density of the electrode, thereby increasing the energy density of the battery.

[0044] In any embodiment, the mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 5:5-9:1.

[0045] Controlling the mass ratio of polycrystalline particles and single crystal particles to meet the above range and mixing smaller-sized single crystals with larger-sized polycrystalline particles can help improve the space utilization of the second positive electrode film layer, thereby increasing the compaction density of the electrode sheet and giving the battery excellent energy density.

[0046] In any embodiment, the mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 6:4-8:2.

[0047] The mass ratio of polycrystalline particles to single crystal particles in the second positive electrode film layer is in the range of 6:4-8:2, which is conducive to better grading between particles to further improve space utilization, increase the compaction density of the electrode, and improve the volume energy density of the battery.

[0048] In any embodiment, the lithium-containing transition metal oxide in the positive electrode film layer includes nickel element. Based on the total molar number of transition metals in the lithium-containing transition metal oxide in the positive electrode film layer, the molar proportion of nickel element in the lithium-containing transition metal oxide in the positive electrode film layer is 80%-96%, and can be optionally 90%-96%.

[0049] Lithium-containing transition metal oxides with a molar percentage of 80%-96% nickel have high gram capacity, which is beneficial for further improving the energy density of battery cells. However, this also increases the hardness of the particles in the positive electrode film, exacerbating the compression of the large particles on the current collector, making it more likely to generate burrs during the slicing of the positive electrode sheets. The technical solutions in the embodiments of this application are particularly suitable for such positive electrode sheets, further improving the high energy density of the battery while increasing the yield rate during the sheet cutting process, meeting performance and efficiency requirements.

[0050] In any embodiment, the lithium-containing transition metal oxide in the first positive electrode film layer and the second positive electrode film layer independently comprises a component Li represented by the following general formula: a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1, wherein M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0051] In any embodiment, based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 5%-50%, and can be optionally 20%-40%.

[0052] The thickness of the first positive electrode film layer is within the above range, which can reduce the contact between large particles in the second positive electrode film layer and the current collector, reduce the probability of burrs on the electrode during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the electrode compression loss caused by adding the first positive electrode film layer, while taking into account the energy density of the battery.

[0053] In any embodiment, the thickness of a single surface of the positive electrode film layer is 25-60 μm.

[0054] In any embodiment, the thickness of a single surface of the positive electrode film layer is 30-50 μm.

[0055] Reducing the thickness of the cathode film helps reduce the diffusion path of lithium ions and improve the dynamic performance of battery cells. However, as the thickness of the cathode film decreases, the electrode sheet compaction density increases, which makes the current collector more severely squeezed by large particles during slicing, increasing the probability of burrs. At the same time, burrs are more likely to protrude from the edge of the cathode film, exacerbating the safety risks of burrs.

[0056] In any embodiment, the bonding strength between the positive electrode film layer and the positive electrode current collector is 10-30 N / m.

[0057] In any embodiment, the bonding strength between the positive electrode film layer and the positive electrode current collector is 15-25 N / m.

[0058] The bonding strength in the embodiment of the present application is within the above range, the positive electrode film layer has good adhesion to the current collector, can effectively improve the current collector leakage phenomenon during the cutting process, and improve the cycle performance of the battery.

[0059] In any embodiment, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-2.5%.

[0060] In any embodiment, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-0.8%.

[0061] In any embodiment, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-2.1%.

[0062] In any embodiment, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-0.05%.

[0063] As the electrode sheets become thinner and the compaction density increases, when the electrode sheets are cut, large particles squeeze the current collector to produce burrs. In the embodiment of the present application, a first positive electrode film layer is added between the second positive electrode film layer and the current collector, and the proportion of electrode sheets with burrs can be reduced to within the above range, which is beneficial to improving the yield of the electrode sheets and improving the safety performance of the battery.

[0064] In any embodiment, the charge capacity of the positive electrode is 232-238.5 mAh g -1 .

[0065] In any embodiment, at -25°C, the time required to discharge the battery cell from 5% SOC to 0% SOC at a discharge rate of 5C is 41-65 seconds.

[0066] At -25°C, the longer the time required to discharge the battery cell from 5% SOC to 0% SOC at a discharge rate of 5C, the better the power performance of the battery cell at low temperature and low SOC, and the more energy can be supplied at low power.

[0067] A second aspect of the present application provides a battery device, which includes the battery cell provided by the first aspect.

[0068] A third aspect of the present application provides an electrical device, which includes the battery device provided in the second aspect, and the battery device is used to provide electrical energy.

[0069] A fourth aspect of the present application provides an energy storage device, which includes the battery device provided in the second aspect, and the battery device is used to store electrical energy.

[0070] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] 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.

[0072] Figure 1 This is a cross-sectional polished electron microscope image of the positive electrode piece in the prior art;

[0073] Figure 2 This is a cross-sectional polished electron microscope morphology image of a pair of proportional positive electrode pieces of the present application;

[0074] Figure 3 This is a cross-sectional polished electron microscope image of the positive electrode sheet in one embodiment of the present application;

[0075] Figure 4 This is a graph showing the electrode bonding test data of an embodiment of the present application and a pair of proportional figures;

[0076] Figure 5 is a schematic diagram of a battery cell provided in some embodiments of the present application;

[0077] Figure 6 is a schematic diagram of a battery module provided in some embodiments of the present application;

[0078] Figure 7 is a schematic diagram of a battery pack provided in some embodiments of the present application;

[0079] Figure 8 yes Figure 7 An exploded schematic diagram of the battery pack shown;

[0080] Figure 9 is an exploded schematic diagram of a battery cell provided in some embodiments of the present application;

[0081] Figure 10 This is a schematic diagram of an electrical device provided in some embodiments of the present application.

[0082] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0083] Explanation of the accompanying drawings: 1. battery pack; 2. upper case; 3. lower case; 4. battery module; 5. battery cell; 51. shell; 52. electrode assembly; 53. cover plate; 6. positive electrode sheet; 61. positive electrode current collector; 62. positive electrode film layer; 621. first positive electrode film layer; 622. second positive electrode film layer. DETAILED DESCRIPTION

[0084] Below, the embodiments of the battery cells, battery devices, and electrical 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 understanding by 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.

[0085] " 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.

[0086] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0087] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0088] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0089] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0090] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0091] In this application, the terms "plurality" and "multiple" refer to two or more.

[0092] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0093] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be obtained by various test methods commonly used in the art.

[0094] The measurement can be performed, for example, according to the test method given in the examples of this application. Unless otherwise specified, the test temperature of each parameter is 25°C.

[0095] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0096] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. The battery cell can be cylindrical, rectangular or other shapes, etc., and the embodiments of the present application are not limited to this. Figure 5 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0097] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0098] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0099] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 6 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 6 As shown, in the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0100] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0101] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0102] Figure 7 and Figure 8 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 7 and Figure 8 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0103] The battery provided in the embodiments of the present application may include a lithium-ion battery.

[0104] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly can be a wound structure or a laminated structure, which is not limited in the present embodiment.

[0105] Battery cells may also include an outer packaging, which can be used to encapsulate the electrode assembly and electrolyte. This outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, or steel shell. Alternatively, it can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0106] In some embodiments, as Figure 9 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0107] The electrode assembly usually includes a positive electrode sheet and a negative electrode sheet. The negative electrode sheet is the electrode that absorbs or lithiates lithium ions when the battery is charged and releases or delithiates lithium when the battery is discharged. The positive electrode sheet is the electrode that releases or delithiates lithium ions when the battery is charged and absorbs or lithiates lithium when the battery is discharged.

[0108] As market demands for faster-charging performance and higher energy density increase, the thickness of cold-pressed electrode sheets is required to be reduced, while the density of the positive electrode film layer is increased. However, researchers have found that such electrode sheets are prone to burrs during slitting, and the thickness of the positive electrode film is insufficient to completely cover the burrs. In electrode assemblies, burred electrode sheets can easily penetrate the separator, triggering self-discharge in the battery cell and even causing short-circuit failure, compromising battery safety and making them unsuitable for use.

[0109] The first aspect of the present application provides a battery cell, comprising a positive electrode sheet, a negative electrode sheet and an electrolyte; Figure 3 As shown, the positive electrode plate 6 includes a positive electrode collector 61 and a positive electrode film layer 62 arranged on at least one side of the positive electrode collector 61, the positive electrode film layer 62 includes a first positive electrode film layer 621 arranged on the side close to the positive electrode collector 61 and a second positive electrode film layer 622 arranged on the side of the first positive electrode film layer 621 away from the positive electrode collector 61, the Dv90 of the particles in the second positive electrode film layer 622 is greater than or equal to 18μm; the Dv99 of the particles in the first positive electrode film layer 621 is less than or equal to 18μm, and the particle size volume distribution curve of the particles in the first positive electrode film layer 621 presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1-1.5μm.

[0110] Studies have shown that the burrs generated during the slitting process of high compaction density electrodes are closely related to the large particles in the electrode film layer. In order to increase the compaction density of the electrode, it is necessary to increase the particle size of the particles in the electrode to increase the compaction density of the electrode. However, during the slitting process, the squeezing effect of the cutter on the large particles will be transmitted to the current collector, causing local deformation or even fracture of the current collector. The stress distribution at the fracture is uneven, which in turn produces burrs, such as Figure 1 As shown, it affects the safety performance of the battery.

[0111] The battery cell provided in this application adds a first positive electrode film layer between the current collector and the second positive electrode film layer, such as Figure 3 As shown. Among them, the Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18μm, and there are certain large-sized particles to increase the compaction density of the positive electrode sheet and improve the energy density of the battery. However, the large particles in the second positive electrode film layer are prone to squeeze the current collector, causing burr problems. By setting a first positive electrode film layer with a Dv99 less than or equal to 18μm between the positive electrode current collector and the second positive electrode film layer, the particles in the first positive electrode film layer are smaller in size than those in the second positive electrode film layer, which effectively reduces the probability of large particles in the second positive electrode film layer directly contacting and squeezing the current collector during the electrode sheet cutting process, thereby reducing the probability of burrs, improving the yield rate of electrode sheet cutting and the safety performance of the battery.

[0112] At the same time, the particle size volume distribution curve of the first positive electrode film layer particles of the battery cell in this application is set to present a bimodal distribution, with the particles mainly concentrated in two particle size ranges with large differences. The smaller particles can effectively fill the gaps between the larger particles, achieving dense particle stacking and reducing the loss of positive electrode sheet compaction density caused by the addition of the first positive electrode film layer. At the same time, the peak position of the first peak is located at 0.1-1.5μm, increasing the content of small particles in the first positive electrode film layer in contact with the current collector, so that the surface is coated with more binder and the contact points with the current collector are increased, thereby improving the bonding strength between the positive electrode film layer and the current collector, improving the burr phenomenon, and reducing the probability of the film layer easily falling off during the cutting of the electrode sheet, thereby exposing the current collector, further improving the safety performance of the battery.

[0113] In some embodiments, the Dv90 of the particles in the second positive electrode film layer may be 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, or any range therebetween.

[0114] In some embodiments, the Dv90 of the particles in the second positive electrode film layer is 20-28 μm.

[0115] In some embodiments, the Dv99 of the particles in the first positive electrode film layer can be selected as 1 μm, 3 μm, 5 μm, 6 μm, 10 μm, 11 μm, 12 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm or any range of values ​​therebetween.

[0116] In some embodiments, the Dv99 of the particles in the first cathode film layer is 1-18 μm.

[0117] In some embodiments, the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, 1.2 μm, 1.5 μm or any numerical range therebetween.

[0118] As used in this article, the term "burr" refers to the provisions of the IEEE1725 battery safety performance review and testing standard, such as Figure 1 As shown, the metal protrusions or protrusions extend outward from the current collector; the extension direction can be any direction, such as the thickness direction or the pole piece plane direction, and the reasons for its occurrence include but are not limited to cutting, tearing, etc.

[0119] As used herein, a bimodal particle size volume distribution curve refers to the presence of two characteristic peaks. This distribution characteristic indicates that the particles in the material are primarily concentrated in two significantly different particle size ranges.

[0120] As used herein, the particle size volume distribution curve exhibits a bimodal distribution, and the peak position of the first peak refers to the particle size corresponding to the smaller characteristic peak in the curve.

[0121] The Dv90 and Dv99 of particles are well known in the art, and represent the particle sizes corresponding to when the cumulative volume distribution percentage of the particles reaches 90% and 99%, respectively.

[0122] The particle size volume distribution curve, Dv90 and Dv99 of the particles can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer with reference to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method. The testing instrument can be the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK. The examples are as follows: S1: Add 2g of positive electrode active material and 5g of sodium dodecyl sulfate SDS to 200mL of N-methylpyrrolidone (NMP), and then place it in an ultrasonic cleaner for ultrasonic treatment, set the power to 100W and the time to 30min, and take the solution after the ultrasonic treatment for particle size test; S2: Take 2g of positive electrode active material and 5g of sodium dodecyl sulfate SDS again and add them to 200mL of N-methylpyrrolidone (NMP), and then place it in an ultrasonic cleaner for ultrasonic treatment, set the power to 100W and the time to 30min, and take the solution after the ultrasonic treatment for particle size test; S2: Take 2g of positive electrode active material and 5g of sodium dodecyl sulfate SDS again and add them to 200mL of N-methylpyrrolidone (NMP), and then place it in an ultrasonic cleaner for ultrasonic treatment, set the power to 100W and the time to 30min, and take the solution after the ultrasonic treatment for particle size test; Set the power to 100W and the time to 60 minutes. Take the solution after the ultrasonic treatment 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. Repeat step S2 and increase the ultrasonic time by 30 minutes until the fluctuation of Dv50 and Dv99 in two tests with an ultrasonic time difference of 30 minutes is less than or equal to 5%. Stop the test. The particle size distribution test result of the solution with the longest ultrasonic time is the particle size distribution of the positive electrode active material. Among them, the fluctuation of Dv50 is the ratio of the difference between the Dv50 of the two tests to the smaller Dv50 of the two test results; the fluctuation of Dv99 is the ratio of the difference between the Dv99 of the two tests to the smaller Dv99 of the two test results.

[0123] It is worth noting that the materials used for testing in this application can be freshly prepared materials or obtained by scraping powder from the film layer after disassembling the secondary battery.

[0124] In some embodiments, the peak position of the first peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is 0.3-1 μm.

[0125] In some embodiments, the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm or any numerical range therebetween.

[0126] Furthermore, the peak position of the first peak of the particle size volume distribution curve of the particles in the first positive electrode film layer is controlled within the range of 0.3-1 μm. The particles have a larger specific surface area, which helps to reduce the probability of collector leakage caused by electrode cutting. At the same time, the particle size is appropriate and the battery has good cycle performance.

[0127] In some embodiments, the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 0.5-7 μm.

[0128] In some embodiments, the peak position of the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or any numerical range therebetween.

[0129] The peak positions of the two characteristic peaks of the particle size volume distribution of the particles in the first positive electrode film layer are controlled within the above range, that is, a large difference between the two particle size ranges is maintained, and smaller particles fill the gaps between larger particles, which can improve the gap filling rate between larger particles, thereby maintaining a high compaction density of the positive electrode sheet and a high energy density of the battery cell.

[0130] In some embodiments, the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 1-5 μm.

[0131] In some embodiments, the peak position of the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is located at 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any numerical range therebetween.

[0132] Furthermore, controlling the peak position of the second peak in the particle size volume distribution curve of the particles in the first positive electrode film layer within the range of 1-5 μm helps to increase the specific surface area of ​​the larger particles in the first positive electrode film layer, increase the amount of surface binder coating, reduce the probability of collector leakage during electrode cutting and improve the cycle performance of the battery; at the same time, the larger particle size in the first positive electrode film layer is within the above range, and the particle size is appropriate, which helps to maintain a higher compaction density of the positive electrode film layer, and the battery has a higher volume energy density.

[0133] In some embodiments, the first positive electrode film layer includes lithium-containing transition metal oxide single crystal particles and polyanion particles. The volume distribution particle size Dv50 of the lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer is 0.5-7 μm, which can be optionally 1-5 μm, and the volume distribution particle size Dv50 of the polyanion particles is 0.1-1.5 μm, which can be optionally 0.3-1 μm.

[0134] In some embodiments, the volume distribution particle size Dv50 of the lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer can be selected as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or any two numerical ranges.

[0135] In some embodiments, the volume distribution particle size Dv50 of the polyanion particles in the first positive electrode film layer can be selected as 0.1μm, 0.2μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm or any two of the numerical ranges.

[0136] As used herein, the term "single crystal particle" refers to the smallest unit of a particle within a certain observation range. A single crystal particle may contain any form of defects, but it is impossible to define smaller particles within it. It should be understood that the single crystal particle described herein does not necessarily mean a single crystal without grain boundaries, or a continuous and consistent periodic arrangement of atoms, molecules, or ions in three-dimensional space. Rather, it refers to a single crystal in which, at a certain observation scale, it is impossible to define smaller particles within the single crystal by grain boundaries.

[0137] As used herein, the term "polyanionic" particles refers to particles whose crystal structure contains a plurality of anions (e.g. etc.) through oxygen atom bridging to form a stable three-dimensional framework structure.

[0138] The Dv50 of a particle is a well-known term in the art and represents the particle size at which the cumulative volume distribution percentage of the particle reaches 50%. The Dv50 of a particle can be determined by referring to the Dv90 test method for the particle.

[0139] Lithium-containing transition metal oxides are an important class of cathode materials for lithium-ion batteries. They are characterized by transition metals (such as cobalt, nickel, and manganese) combined with oxygen to form a layered or spinel structure. Examples include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, the ternary material lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, and lithium-rich manganese-based oxides.

[0140] The size of lithium-containing transition metal oxide single crystal particles is smaller than that of polycrystalline particles, which can reduce the size of large particles in the first positive electrode film layer and reduce the probability of burrs on the positive electrode plate. However, due to the small size of the single crystal particles in the first positive electrode film layer, the compaction density of the plate is reduced, thereby losing the volume energy density of the battery cell; at the same time, the smaller lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer have limited effect on the bonding force between the positive electrode film layer and the current collector, and powder shedding and current collector leakage problems will still occur during the plate cutting process. In the embodiment of the present application, the first positive electrode film layer includes lithium-containing transition metal oxide single crystal particles and polyanion particles with a smaller particle size. On the one hand, the polyanion particles fill the gaps between the single crystal particles, increasing the compaction density of the plate; on the other hand, the polyanion fills the gaps between the single crystal particles, thereby increasing the number of particles in contact with the current collector in the first positive electrode film layer, increasing the binder content and area, and increasing the bonding strength between the positive electrode film layer and the current collector, further reducing the probability of current collector leakage and improving the yield rate of the plate.

[0141] In some embodiments, based on the total mass of the first cathode film layer, the mass proportion of the polyanion particles is 0.1%-10%.

[0142] In some embodiments, the mass proportion of the polyanion particles based on the total mass of the first positive electrode film layer can be selected as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10% or any numerical range therebetween.

[0143] The mass proportion of polyanions is in the range of 0.1%-10%, which helps to improve the volume energy density of battery cells; at the same time, compared with lithium-containing transition metal oxides, polyanions have a lower voltage platform and low-temperature voltage platform stability. The mass proportion of polyanions is in the above range, which helps to improve the power deterioration problem of the battery at low temperature and low SOC.

[0144] In some embodiments, based on the total mass of the first positive electrode film layer, the mass proportion of the polyanion particles is 2%-8%.

[0145] Furthermore, the mass proportion of polyanions is in the range of 2%-8%, which helps to further reduce the probability of collector leakage when the electrode is divided and improve the cycle performance of the battery; at the same time, the polyanion particles can fully fill the gaps between the lithium-containing transition metal oxide single crystal particles, while reducing the non-gap space occupied by excessive polyanion particles, thereby increasing the compaction density of the positive electrode film layer and further optimizing the energy density of the battery; in addition, the mass proportion of polyanions is in the above range, which helps to further improve the problem of power deterioration of the battery at low temperature and low SOC.

[0146] In some embodiments, the polyanionic particles include components represented by the following formula:

[0147] Li x A y Me a M b P 1-c X c Y z Formula I,

[0148] 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.

[0149] In some embodiments, x can be selected from 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, or any range therebetween.

[0150] In some embodiments, y can be selected to be 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 therebetween.

[0151] In some embodiments, x+y may be selected to be 0.8, 0.9, 0.95, 1.0, 1.1, 1.2, 1.3, or any range therebetween.

[0152] 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 therebetween.

[0153] In some embodiments, b can be selected to be 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 therebetween.

[0154] In some embodiments, a+b may be selected to be 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, or any range therebetween.

[0155] In some embodiments, c can be selected as 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 therebetween.

[0156] In some embodiments, z can be selected as 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 therebetween.

[0157] In some embodiments, the polyanion includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadium phosphate, lithium manganese iron phosphate, lithium fluoro iron phosphate, lithium fluoro manganese iron phosphate, and modified materials thereof.

[0158] Polyanions often have a smaller particle size, which is beneficial for filling the gaps in the first positive electrode film layer, and is beneficial for increasing the adhesive adhesion to the current collector by utilizing its small particle size, thereby improving the leakage of the current collector from the electrode.

[0159] In some embodiments, the polyanion includes one or more of lithium manganese iron phosphate and modified materials thereof.

[0160] Compared to other polyanions, lithium iron manganese phosphate (LiMnFePO4) has a higher voltage platform and a smaller voltage difference with lithium-containing transition metal oxides, which facilitates the full utilization of the polyanion's specific capacity, thereby further improving the volumetric energy density of the battery cell. Furthermore, the polyanion, through its lower voltage platform, forms a voltage complement with the lithium-containing transition metal oxide, allowing the lithium-containing transition metal oxide to maintain a high voltage at low states of charge (SOC), effectively alleviating the power degradation problem of lithium-containing transition metal oxide materials at low temperatures and low SOCs.

[0161] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-6 μm and the second peak is located at 5-14 μm.

[0162] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-6 μm and the second peak is located at 6-10 μm.

[0163] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-5 μm and the second peak is located at 6-10 μm.

[0164] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, wherein the first peak of the bimodal distribution is located at 1-5 μm and the second peak is located at 5-14 μm.

[0165] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, and the first peak of the bimodal distribution can be located at 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or any numerical range therebetween.

[0166] In some embodiments, the particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, and the second peak of the bimodal distribution can be located at 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11 μm, 12μm, 14μm or any numerical range therebetween.

[0167] The particles in the second positive electrode film layer show a bimodal distribution, which is similar to the bimodal distribution of the particles in the first positive electrode film layer. This is conducive to smaller particles filling the gaps between larger particles, achieving close stacking of particles, and increasing the compaction density of the second positive electrode film layer, thereby further improving the energy density of the battery.

[0168] In some embodiments, the second positive electrode film layer includes lithium-containing transition metal oxide polycrystalline particles and lithium-containing transition metal oxide single crystal particles.

[0169] When used in this article, the term "polycrystalline particles" refers to agglomerates of single crystal particles. The agglomeration here is a hard agglomeration caused by chemical bonding of single crystal particles, which makes the polycrystalline particles have more clear grain boundaries and inconsistent atomic arrangement orientations. After cutting the cross section of the polycrystalline particles, it can be seen that the polycrystalline particles are formed by the agglomeration of many single crystal particles.

[0170] In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 20-30 μm.

[0171] In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 22-28 μm.

[0172] In some embodiments, the volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer can be selected as 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm or any numerical range therebetween.

[0173] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 5-14 μm.

[0174] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 6-10 μm.

[0175] In some embodiments, the volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer can be selected as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm or any numerical range therebetween.

[0176] The Dv99 and Dv50 of the polycrystalline particles in the second positive electrode film layer are within the above ranges, and the particles have a larger size, which is beneficial to improving the compaction density of the second positive electrode film layer, thereby further improving the energy density of the battery.

[0177] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-13 μm.

[0178] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-12 μm.

[0179] In some embodiments, the volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer can be 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or any numerical range therebetween.

[0180] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-6 μm.

[0181] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-5 μm.

[0182] In some embodiments, the volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm or any numerical range therebetween.

[0183] The combination of polycrystalline particles and single crystal particles that meet the above-mentioned particle size range is beneficial to improving the particle grading, achieving close stacking of particles in the positive electrode film layer, and further increasing the compaction density of the electrode, thereby increasing the energy density of the battery.

[0184] In some embodiments, the mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 5:5-9:1.

[0185] As used herein, the mass ratio of polycrystalline particles to single crystal particles in the second positive electrode film layer can be selected as 5:5, 5.5:4.5, 6:4, 6.5:3.5, 7:3, 7.5:2.5, 8:2, 8.5:1.5, 9:1 or any value therebetween.

[0186] When used in this article, the mass ratio of polycrystalline particles and single crystal particles in the second positive electrode film layer can be determined by the following method: take a prepared positive electrode sheet, or a positive electrode sheet disassembled from a battery, and perform a CP-SEM test. In the obtained image, it can be clearly observed that there is a clear dividing line between the first positive electrode film layer and the second positive electrode film layer. The film layer close to the current collector has smaller particles and has a combination of two particles with large differences in particle size. This layer is the first positive electrode film layer; the film layer away from the positive electrode current collector has larger particles. This layer is the second positive electrode film layer. Randomly select a number of points in the second positive electrode film layer for photography. The number of points is ≥10, which can be 10, 20, 50, 100, etc. Calculate the area ratio of the polycrystalline particles and single crystal particles to the size of the positive electrode film layer in the photographed image, and calculate the average value. The area ratio between polycrystalline particles and single crystal particles can be equivalent to the mass ratio of polycrystalline particles to single crystal particles.

[0187] Controlling the mass ratio of polycrystalline particles and single crystal particles to meet the above range and mixing smaller-sized single crystals with larger-sized polycrystalline particles can help improve the space utilization of the second positive electrode film layer, thereby increasing the compaction density of the electrode sheet and giving the battery excellent energy density.

[0188] In some embodiments, the mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 6:4-8:2.

[0189] The mass ratio of polycrystalline particles to single crystal particles in the second positive electrode film layer is in the range of 6:4-8:2, which is conducive to better grading between particles to further improve space utilization, increase the compaction density of the electrode, and improve the volume energy density of the battery.

[0190] In some embodiments, the lithium-containing transition metal oxide in the positive electrode film layer includes nickel element. Based on the total molar number of transition metals in the lithium-containing transition metal oxide in the positive electrode film layer, the molar proportion of nickel element in the lithium-containing transition metal oxide in the positive electrode film layer is 80%-96%, and can be optionally 90%-96%.

[0191] In some embodiments, the lithium-containing transition metal oxide in the positive electrode film layer includes nickel element. Based on the total molar number of transition metal in the lithium-containing transition metal oxide in the positive electrode film layer, the molar proportion of nickel element in the lithium-containing transition metal oxide in the positive electrode film layer can be selected to be 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96% or any numerical range therebetween.

[0192] As used herein, the molar fraction of nickel in the lithium-containing transition metal oxide can be determined by instruments and methods known in the art based on the total molar fraction of transition metals in the lithium-containing transition metal oxide. As an example, the following method can be used for measurement: 0.5 g of the material to be tested is immersed in 100 mL of aqua regia solution for digestion at a digestion temperature of 50° C., and then the completely dissolved solution is subjected to inductively coupled plasma (ICP) testing to detect the content of transition metals (such as Ni, Co, Mn ions) in the solution. The molar fraction of nickel in the lithium-containing transition metal oxide is calculated by dividing the molar fraction of nickel by the total molar fraction of transition metals based on the total molar fraction of transition metals in the lithium-containing transition metal oxide.

[0193] Lithium-containing transition metal oxides with a molar percentage of 80%-96% nickel have high gram capacity, which is beneficial for further improving the energy density of battery cells. However, this also increases the hardness of the particles in the positive electrode film, exacerbating the compression of the large particles on the current collector, making it more likely to generate burrs during the slicing of the positive electrode sheets. The technical solutions in the embodiments of this application are particularly suitable for such positive electrode sheets, further improving the high energy density of the battery while increasing the yield rate during the sheet cutting process, meeting performance and efficiency requirements.

[0194] In some embodiments, the lithium-containing transition metal oxide in the first cathode film layer and the second cathode film layer independently comprises a component Li represented by the following general formula: a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 , wherein M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.1.

[0195] In some embodiments, a1 can be selected as 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, or any range therebetween.

[0196] In some embodiments, x1 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, or any range therebetween.

[0197] In some embodiments, y1 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, or any range therebetween.

[0198] In some embodiments, z1 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, or any range therebetween.

[0199] In some embodiments, w1 may be selected as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any range therebetween.

[0200] In some embodiments, b1 may be selected as -0.1, -0.05, 0, 0.05, 0.1, or any range therebetween.

[0201] When the positive electrode film layer includes the above-mentioned lithium-containing transition metal oxide, the gram capacity of the positive electrode active material can be further increased, thereby further improving the energy density of the battery cell.

[0202] In some embodiments, based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 5%-50%, and can be optionally 20%-40%.

[0203] The thickness ratio of the first positive electrode film layer can be tested by methods and equipment known in the art, as shown below: Take a prepared positive electrode sheet, or a positive electrode sheet disassembled from a battery, and perform a CP-SEM test. In the obtained picture, it can be clearly observed that there is a clear dividing line between the first positive electrode film layer and the second positive electrode film layer. The film layer close to the current collector has smaller particles and has a combination of two particles with large differences in particle size. This layer is the first positive electrode film layer; the film layer away from the positive current collector has larger particles. This layer is the second positive electrode film layer. Mark the interface between the first positive electrode film layer and the second positive electrode film layer. The vertical distance H1 from the interface to the positive electrode current collector is the thickness of the first positive electrode film layer. The vertical distance H2 from the surface of the second positive electrode film layer away from the current collector to the current collector is the single-sided thickness of the positive electrode film layer. The thickness ratio of the first positive electrode film layer is H1 / H2.

[0204] In some embodiments, based on the total thickness of the positive electrode film layer, the thickness proportion of the first positive electrode film layer can be selected as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or any numerical range therebetween.

[0205] The thickness of the first positive electrode film layer is within the above range, which can reduce the contact between large particles in the second positive electrode film layer and the current collector, reduce the probability of burrs on the electrode during cutting, and further improve the safety performance of the battery cell; at the same time, it can reduce the electrode compression loss caused by adding the first positive electrode film layer, while taking into account the energy density of the battery.

[0206] In some embodiments, the thickness of a single surface of the positive electrode film layer is 25-60 μm.

[0207] In some embodiments, the thickness of a single surface of the positive electrode film layer is 30-50 μm.

[0208] In some embodiments, the thickness of the positive electrode film layer may be 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, or any range therebetween.

[0209] Reducing the thickness of the cathode film helps reduce the diffusion path of lithium ions and improve the dynamic performance of battery cells. However, as the thickness of the cathode film decreases, the electrode sheet compaction density increases, which makes the current collector more severely squeezed by large particles during slicing, increasing the probability of burrs. At the same time, burrs are more likely to protrude from the edge of the cathode film, exacerbating the safety risks of burrs.

[0210] In some embodiments, the bonding strength between the positive electrode film layer and the positive electrode current collector is 10-30 N / m.

[0211] In some embodiments, the bonding strength between the positive electrode film layer and the positive electrode current collector is 15-25 N / m.

[0212] As used herein, the term "bonding strength" has a well-known meaning in the art and can be tested using methods and instruments known in the art. An example is as follows: prepare a positive electrode sheet or disassemble a battery to obtain a positive electrode sheet, and cut the positive electrode sheet into a rectangular sample to be tested with a long side width of a and a short side width of b; use double-sided tape to stick the sample to be tested to the surface of a steel plate and compact it with a pressure roller to make it completely fit the electrode sheet; bend one end of the positive current collector 180° in the opposite direction, that is, bend the long side of the positive current collector; use the lower clamp of the high-speed rail tensile testing machine to fix the steel plate and the upper clamp to fix the bent end (short side) of the positive current collector, adjust the angle of the current collector so that the upper and lower ends are in a vertical position, and stretch the sample at a speed of 50 mm / min until the current collector is completely peeled off from the surface of the electrode sheet, record the displacement and force during the process, and the force when the forces are balanced is the bonding force F of the electrode sheet. The bonding strength is = bonding force F / b, unit N / m.

[0213] The bonding strength in the embodiment of the present application is within the above range, the positive electrode film layer has good adhesion to the current collector, can effectively improve the current collector leakage phenomenon during the cutting process, and improve the cycle performance of the battery.

[0214] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-2.5%.

[0215] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-0.8%.

[0216] In some embodiments, the percentage of positive electrode sheets with leaking current collectors can be selected as 0.1%, 0.2%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.7%, 0.75%, 0.8%, 0.9%, 1%, 1.2%, 1.5%, 18%, 2%, 2.15%, 2.35%, 2.5% or any numerical range therebetween.

[0217] As used herein, the term "current collector leakage" refers to the phenomenon in which a film layer does not completely cover a surface of the current collector, thereby exposing the current collector. The percentage of positive electrode sheets with current collector leakage after slitting at a slitting speed of 0.5 m / s can be tested using methods and instruments known in the art. An example is as follows: After the positive electrode sheets are slid at a slitting speed of 0.5 m / s, a high-resolution electron microscope (CCD) is used to capture micrographs of 1,000 positive electrode film surfaces facing away from the current collector. If a bright spot or bright edge appears at the slitting point of the sheet in the micrograph, it is identified as a positive electrode sheet with current collector leakage. The number of current collector sheets with current collector leakage is calculated as n2, and the percentage of positive electrode sheets with current collector leakage is (n2 / 1000)×100%.

[0218] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-2.1%.

[0219] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-0.05%.

[0220] In some embodiments, after the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the proportion of positive electrode sheets with burrs can be selected as 0, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.1% or any numerical range therebetween.

[0221] As used herein, a positive electrode sheet with burrs refers to a sheet of positive electrode sheet that has been slit, and the size of the burrs on the sheet is calibrated. Burrs with a size greater than or equal to 40% of the thickness of the positive electrode sheet are included in the statistical range and are calibrated as positive electrode sheets with burrs. The proportion of positive electrode sheets with burrs can be tested using methods known in the art. As an example, the following method can be used to test: a certain number of slit electrode sheets are observed through a CCD using the burr size measurement method described above, and the frequency K1 of electrode sheets with burrs is counted. The proportion of electrode sheets with burrs is calculated as K1 / total number of electrode sheets × 100%.

[0222] When used in this article, the term "burr size" refers to the absolute length of the burr (not limited to the vertical distance). The burr size can be tested using instruments and methods known in the art. As an example, the following test method can be used: use a CCD instrument to observe the burrs after cutting (such as Keyence 600), the test temperature is 25°C, the test electrode size is 80mm×60mm, the magnification is 300x, the light input opening is 30%, and the burr size is calibrated.

[0223] As the electrode sheets become thinner and the compaction density increases, when the electrode sheets are cut, large particles squeeze the current collector to produce burrs. In the embodiment of the present application, a first positive electrode film layer is added between the second positive electrode film layer and the current collector, and the proportion of electrode sheets with burrs can be reduced to within the above range, which is beneficial to improving the yield of the electrode sheets and improving the safety performance of the battery.

[0224] In some embodiments, the charge capacity of the positive electrode is 232-238.5 mAh g -1 .

[0225] In some embodiments, the charge capacity of the positive electrode sheet can be selected to be 232 mAh g -1 , 233 mAh g -1 , 233.7mAh g -1 , 234 mAh g -1 , 234.5 mAh g -1 , 235 mAh g -1 , 235.5 mAh g -1 , 236 mAh g -1 , 236.5 mAhg -1 , 237 mAh g -1 , 237.3 mAh g -1 , 238mAh g -1 , 238.5 mAh g -1 or any range of values ​​between them.

[0226] As used herein, the charge capacity in grams of a positive electrode can be measured using methods and instruments known in the art. A specific example is as follows: a button cell was prepared according to the preparation method described in the Examples of this application. The prepared button cell was allowed to rest for 3 hours at 25°C, then charged to 4.25V at a constant current of 0.1C, then charged to 50μA at a constant voltage, and allowed to rest for 5 minutes. The charge capacity in grams of the button cell at 25°C was recorded. The charge capacity in grams of the positive electrode active material at 25°C, Cl, is calculated as: charge capacity of the button cell at 25°C / mass of the positive electrode active material.

[0227] In some embodiments, at -25°C, the time required to discharge a battery cell from 5% SOC to 0% SOC at a discharge rate of 5C is 41-65 seconds.

[0228] In some embodiments, at -25°C, the time required to discharge a battery cell from 5% SOC to 0% SOC at a discharge rate of 5C may be selected as 41s, 42s, 43s, 44s, 45s, 46s, 47s, 48s, 49s, 50s, 51s, 52s, 53s, 54s, 55s, 56s, 57s, 58s, 59s, 60s, 61s, 62s, 63s, 64s, 65s or any range of values ​​therebetween.

[0229] As used herein, the time required to discharge a battery cell from 5% SOC to 0% SOC at a discharge rate of 5C at -25°C can be tested using methods and instruments known in the art. The battery cell is left at -25°C for 2 hours to ensure the temperature of the battery cell is -25°C. The battery is discharged at a discharge rate of 5C to 5% SOC, and the timing begins. Discharge at a 5C rate continues until the discharge voltage is less than 2.8V, and the timing is stopped, indicating that the battery has been discharged to 0% SOC. The timing duration T is the time required to discharge the battery cell from 5% SOC to 0% SOC at a discharge rate of 5C at -25°C.

[0230] At -25°C, the longer the time required to discharge the battery cell from 5% SOC to 0% SOC at a discharge rate of 5C, the better the power performance of the battery cell at low temperature and low SOC, and the more energy can be supplied at low power.

[0231] Battery device

[0232] An embodiment of the present application further provides a battery device, which includes the battery cell provided in the embodiment of the present application.

[0233] The battery device includes one or more of a battery module, a battery pack, and an energy storage battery.

[0234] Electrical devices

[0235] The present application also provides an electrical device, comprising a battery device provided in the present application, for providing electrical energy. The battery device can be used as a power source for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, and satellites.

[0236] The electrical device can select a specific type of battery, such as a battery cell, a battery module, or a battery pack, according to its usage requirements.

[0237] Energy storage device

[0238] The present application also provides an energy storage device, comprising a battery device according to the present application. The battery device is configured to store electrical energy. The battery device can serve 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.

[0239] Figure 10 The diagram is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0240] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0241] Example

[0242] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0243] 1. Preparation method

[0244] Example 1

[0245] (1) Preparation of positive electrode

[0246] Preparation of the first cathode film slurry: LiNi 0.92 Co 0.04 Mn 0.04 O2 single crystal, LiMn 0.3 Fe0.7 PO4, conductive carbon, and binder PVDF are dissolved in NMP (N-methylpyrrolidone) solvent in a mass ratio of 95:3:1:1, fully stirred and mixed, and then wetted, kneaded, and dispersed to obtain the first film layer positive electrode slurry.

[0247] Preparation of the second cathode film slurry: LiNi 0.92 Co 0.04 Mn 0.04 O2 polycrystalline, LiNi 0.92 Co 0.04 Mn 0.04 The O2 single crystal, conductive carbon, and binder PVDF are dissolved in NMP (N-methylpyrrolidone) solvent in a weight ratio of 68.6:29.4:1:1, stirred and mixed thoroughly, and then wetted, kneaded, and dispersed to obtain the second film layer positive electrode slurry.

[0248] The first positive electrode slurry is coated on the aluminum foil to form a first positive electrode slurry coating, and the second positive electrode slurry is coated on the surface of the first positive electrode slurry to form a second positive electrode slurry coating; then, the positive electrode sheets are obtained by drying, cold pressing, and slitting on a slitting machine at a slitting speed of 0.5 m / s.

[0249] In the second cathode film layer, the polycrystalline particles have a Dv99 of 25μm and a Dv50 of 7μm; the single-crystal particles have a Dv99 of 12μm and a Dv50 of 2.5μm; the mass ratio of polycrystalline to single-crystal particles is 7:3; the particle size distribution in the second cathode film layer is bimodal, with the first peak at 2.5μm and the second peak at 7μm. The bond strength between the cathode film layer and the current collector is 23N / m; the thickness of the single-sided cathode film layer is 50μm; and the charge capacity of the positive electrode sheet is 237.5mAh / g.

[0250] (2) Preparation of negative electrode sheet

[0251] The negative electrode active material graphite, binder (polyvinyl alcohol), and conductive agent SP-Li are mixed in a mass ratio of 90:5:5, and deionized water solvent 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 current collector copper foil, and the negative electrode current 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.

[0252] (3) Preparation of electrolyte

[0253] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) were mixed uniformly in a volume ratio of 1:1:1, a certain amount of LiPF6 lithium salt was dissolved in the organic solvent, the concentration of the lithium salt was controlled to be 1 mol / L, and the mixture was stirred uniformly to obtain an electrolyte.

[0254] (4) Isolation film

[0255] Polyethylene film with a thickness of 13 μm.

[0256] (5) Battery preparation

[0257] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide insulation. The electrode assembly is then wound to form an electrode assembly. The electrode assembly is placed in a battery casing, dried, and then injected with the electrolyte. The lithium-ion battery is then manufactured through formation and resting processes.

[0258] Example 2-3

[0259] The preparation method of the lithium-ion battery is similar to that of Example 1, except that the Dv99 of the first positive electrode film layer is different, see Table 1 for details.

[0260] Examples 4-6

[0261] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiNi 0.92 Co 0.04 Mn 0.04 The Dv50 of O2 single crystal is different, see Table 1 for details.

[0262] Examples 7-9

[0263] The preparation method of the lithium-ion battery is similar to that of Example 1, except that the LiMn 0.3 Fe 0.7 The Dv50 of PO4 is different, see Table 1 for details.

[0264] Example 10

[0265] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiNi 0.92 Co 0.04 Mn 0.04 O2 single crystal, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon, and binder PVDF is 97:1:1:1, see Table 1 for details.

[0266] Example 11

[0267] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiNi 0.92 Co 0.04 Mn 0.04 O2 single crystal, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon, and binder PVDF is 93:5:1:1, see Table 1 for details.

[0268] Example 12

[0269] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiNi 0.92 Co 0.04 Mn 0.04 O2 single crystal, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon, and binder PVDF is 90:8:1:1, see Table 1 for details.

[0270] Example 13

[0271] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiNi 0.92 Co 0.04 Mn 0.04 O2 single crystal, LiMn 0.3 Fe 0.7 The mass ratio of PO4, conductive carbon, and binder PVDF is 88:10:1:1, see Table 1 for details.

[0272] Example 14

[0273] The preparation method of the lithium-ion battery is similar to that of Example 1, except that the thickness of the first positive electrode film layer is 8 μm. Based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 16.7%, see Table 1 for details.

[0274] Example 15

[0275] The preparation method of the lithium ion battery is similar to that of Example 1, except that the LiMn 0.3 Fe 0.7 PO4 was replaced by LiFePO4, see Table 1 for details.

[0276] Comparative Example 1

[0277] The preparation method of the lithium-ion battery is similar to that of Example 1, except that the positive electrode film layer does not include the first positive electrode film layer, as shown in Table 1 for details.

[0278] Comparative Example 2

[0279] The preparation method of the lithium ion battery is similar to that of Example 1, except that the first positive electrode film does not contain LiMn 0.3 Fe 0.7 PO4, LiNi in the first positive electrode slurry 0.92 Co 0.04 Mn 0.04 The mass ratio of O2 single crystal, conductive carbon, and binder PVDF is 98:1:1:1, see Table 1 for details.

[0280] Comparative Example 3

[0281] The preparation method of the lithium-ion battery is similar to that of Example 1, except that the Dv99 of the first positive electrode film layer is different, see Table 1 for details.

[0282] 2. Performance Testing

[0283] 1. Battery volume energy density test

[0284] Allow the lithium-ion secondary battery to rest at 25°C for 2 hours, ensuring the temperature is 25°C. Charge the lithium-ion secondary battery at 0.33C at 25°C to a charge cutoff voltage of 4.25V. Continue constant voltage charging at this charge cutoff voltage until the current reaches 0.05C, at which point charging is terminated (where C represents the rated capacity of the lithium-ion secondary battery). Allow the lithium-ion secondary battery to rest at 25°C for 1 hour, then discharge it at 0.33C at 25°C to a discharge cutoff voltage of 2.8V. Record the total discharge energy of the lithium-ion secondary battery as E0. Measure the length, width, and height of the lithium-ion secondary battery and calculate its volume (V0) = length × width × height. The volumetric energy density of a lithium-ion secondary battery = discharge energy E0 / volume V0.

[0285] 2. Cycle capacity retention rate

[0286] At 25°C, charge the battery to 4.25V at a charge rate of 0.33C of the nominal capacity, then charge it to 0.05C at a constant voltage of 4.25V, let it stand for 10 minutes, and then discharge it to 2.8V at a discharge rate of 1C and let it stand for 10 minutes. The above charge and discharge is one cycle. Based on the total capacity of the nominal capacity, the percentage of the battery capacity after 1000 cycles is recorded as the capacity retention rate.

[0287] 3. Test Results

[0288] The test results of the above embodiments and comparative examples are shown in Tables 1 to 7.

[0289] Table 1

[0290]

[0291] Table 2

[0292]

[0293] From the comparison of the embodiment and the comparative example, it can be seen that the positive electrode film layer includes a first positive electrode film layer arranged close to the positive electrode current collector side and a second positive electrode film layer arranged on the first positive electrode film layer away from the positive electrode current collector side, the Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18 μm, the Dv99 of the particles in the first positive electrode film layer is less than or equal to 18 μm, and the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1-1.5 μm, which is beneficial to reducing the burrs generated by the electrode during the cutting process, improving the yield of the electrode cutting and the safety performance of the battery, and at the same time reducing the probability of the positive electrode film layer falling off during the cutting process and exposing the current collector.

[0294] Table 3

[0295]

[0296] From the comparison between Example 1, Example 5 and Example 4, Example 6, it can be seen that the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, and the second peak in the bimodal distribution is located in the range of 1-5 μm, which helps to further reduce the probability of collector leakage caused by electrode cutting, while improving the volume energy density of the battery while taking into account the cycle performance.

[0297] Table 4

[0298]

[0299] From the comparison between Example 1, Example 8, Example 7 and Example 9, it can be seen that the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, and the first peak in the bimodal distribution is located in the range of 0.3-1 μm, which helps to reduce the probability of collector leakage caused by electrode cutting and improve the volume energy density of the battery.

[0300] Table 5

[0301]

[0302] From the comparison between Example 1, Example 11 and Example 10, and Examples 11-12, it can be seen that based on the total mass of the first positive electrode film layer, the mass of the polyanion particles accounts for 2%-8%, which helps to reduce the probability of collector leakage caused by electrode cutting, while taking into account the volume energy density of the battery, the cycle performance of the battery, and the power performance of the battery at low temperature and low SOC.

[0303] Table 6

[0304]

[0305] From the comparison between Example 1 and Example 14, it can be seen that based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 20%-40%, which helps to further reduce the probability of burrs after the electrode sheet is cut, and at the same time improve the cycle performance and low-temperature power performance of the battery.

[0306] Table 7

[0307]

[0308] From the comparison between Example 1 and Example 15, it can be seen that the polyanion includes lithium manganese iron phosphate, which helps to further increase the charging capacity of the positive electrode, improve the power performance at low SOC, and increase the volume energy density of the battery.

[0309] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell, characterized in that: Including positive electrode sheet, negative electrode sheet and electrolyte; The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector, wherein the positive electrode film layer includes a first positive electrode film layer provided on a side close to the positive electrode current collector and a second positive electrode film layer provided on a side of the first positive electrode film layer away from the positive electrode current collector. The Dv90 of the particles in the second positive electrode film layer is greater than or equal to 18 μm; The Dv99 of the particles in the first positive electrode film layer is 1-18 μm, and the particle size volume distribution curve of the particles in the first positive electrode film layer presents a bimodal distribution, wherein the peak position of the first peak is located at 0.1-1.5 μm, and the peak position of the second peak is located at 1-5 μm, The first positive electrode film layer includes lithium-containing transition metal oxide single crystal particles and polyanion particles. Based on the total mass of the first positive electrode film layer, the mass proportion of the polyanion particles is 2%-8%, The lithium-containing transition metal oxide in the positive electrode film layer includes nickel element. Based on the total molar number of transition metals in the lithium-containing transition metal oxide in the positive electrode film layer, the molar proportion of nickel element in the lithium-containing transition metal oxide in the positive electrode film layer is 80%-96%.

2. The battery cell according to claim 1, wherein: The Dv90 of the particles in the second positive electrode film layer is 20-28 μm.

3. The battery cell according to claim 1, wherein: The peak position of the first peak in the particle size volume distribution curve of the particles in the first positive electrode film layer is 0.3-1 μm.

4. The battery cell according to claim 1, wherein: The volume distribution particle size Dv50 of the lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer is 0.5-7 μm.

5. The battery cell according to claim 4, characterized in that The volume distribution particle size Dv50 of the lithium-containing transition metal oxide single crystal particles in the first positive electrode film layer is 1-5 μm.

6. The battery cell according to claim 4, characterized in that The volume distribution particle size Dv50 of the polyanion particles is 0.1-1.5 μm.

7. The battery cell according to claim 4, characterized in that The volume distribution particle size Dv50 of the polyanion particles is 0.3-1 μm.

8. The battery cell according to claim 4, characterized in that The polyanionic particles include components shown in the following general formula: 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.

9. The battery cell according to claim 4, characterized in that The polyanion includes one or more of lithium iron phosphate, lithium manganese phosphate, lithium vanadium fluoride phosphate, lithium manganese iron phosphate, lithium fluoride phosphate, lithium manganese iron phosphate and modified materials thereof.

10. The battery cell according to claim 4, characterized in that The polyanion includes one or more of lithium manganese iron phosphate and modified materials thereof.

11. The battery cell according to claim 1, wherein The particle size volume distribution curve of the particles in the second positive electrode film layer presents a bimodal distribution, and the peak position of the first peak in the particle size volume distribution curve of the particles in the second positive electrode film layer is located at 1-6 μm.

12. The battery cell according to claim 11, characterized in that The peak position of the first peak in the particle size volume distribution curve of the particles in the second positive electrode film layer is located at 1-5 μm.

13. The battery cell according to claim 11, characterized in that The peak position of the second peak in the particle size volume distribution curve of the particles in the second positive electrode film layer is located at 5-14 μm.

14. The battery cell according to claim 11, characterized in that The peak position of the second peak in the particle size volume distribution curve of the particles in the second positive electrode film layer is located at 6-10 μm.

15. The battery cell according to claim 1, characterized in that The second positive electrode film layer includes lithium-containing transition metal oxide polycrystalline particles and lithium-containing transition metal oxide single crystal particles.

16. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 20-30 μm.

17. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv99 of the polycrystalline particles in the second positive electrode film layer is 22-28 μm.

18. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 5-14 μm.

19. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv50 of the polycrystalline particles in the second positive electrode film layer is 6-10 μm.

20. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-13 μm.

21. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv99 of the single crystal particles in the second positive electrode film layer is 6-12 μm.

22. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-6 μm.

23. The battery cell according to claim 15, characterized in that The volume distribution particle size Dv50 of the single crystal particles in the second positive electrode film layer is 1-5 μm.

24. The battery cell according to claim 15, characterized in that The mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 5:5-9:

1.

25. The battery cell according to claim 15, characterized in that The mass ratio of the polycrystalline particles in the second positive electrode film layer to the single crystal particles in the second positive electrode film layer is 6:4-8:

2.

26. The battery cell according to claim 1, characterized in that The molar proportion of nickel element in the lithium-containing transition metal oxide in the positive electrode film layer is 90%-96%.

27. The battery cell according to claim 15, characterized in that The lithium-containing transition metal oxide in the first positive electrode film layer and the second positive electrode film layer independently comprises a component Li represented by the following general formula: a1 Ni x1 Co y1 M1 z1 M2 w1 O 2-b1 , wherein M1 includes one or more of Mn and Al, M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K, 0.8≤a1≤1.2, 0≤x1≤1, 0≤y1≤1, 0≤z1≤1, 0≤w1≤0.1, and -0.1≤b1≤0.

1.

28. The battery cell according to claim 1, characterized in that Based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 5%-50%.

29. The battery cell according to claim 1, characterized in that Based on the total thickness of the positive electrode film layer, the thickness of the first positive electrode film layer accounts for 20%-40%.

30. The battery cell according to claim 1, characterized in that The thickness of a single surface of the positive electrode film layer is 25-60 μm.

31. The battery cell according to claim 1, characterized in that The thickness of a single surface of the positive electrode film layer is 30-50 μm.

32. The battery cell according to claim 1, characterized in that The bonding strength between the positive electrode film layer and the positive electrode current collector is 10-30 N / m.

33. The battery cell according to claim 1, characterized in that The bonding strength between the positive electrode film layer and the positive electrode current collector is 15-25 N / m.

34. The battery cell according to claim 1, characterized in that After the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-2.5%.

35. The battery cell according to claim 1, characterized in that After the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with leaking current collectors accounts for 0.1%-0.8%.

36. The battery cell according to claim 1, characterized in that After the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-2.1%.

37. The battery cell according to claim 1, characterized in that After the positive electrode sheets are cut at a cutting speed of 0.5 m / s, the number of positive electrode sheets with burrs accounts for 0-0.05%.

38. The battery cell according to claim 1, characterized in that The charging capacity of the positive electrode plate is 232-238.5 mAh / g.

39. The battery cell according to any one of claims 1 to 38, characterized in that: At -25°C, the time required to discharge the battery cell from 5% SOC to 0% SOC at a discharge rate of 5C is 41-65s.

40. A battery device, characterized in that: The invention comprises a battery cell according to any one of claims 1 to 39.

41. An electrical device, characterized in that: The electrical device comprises the battery device as claimed in claim 40, and the battery device is used to provide electrical energy.

42. An energy storage device, characterized in that: The energy storage device comprises the battery device as claimed in claim 40, wherein the battery device is used to store electrical energy.

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