Battery cells, battery devices, and power-consuming devices

Abstract

The present disclosure provides a battery cell, a battery device and an electric device, wherein the battery cell comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer provided on at least one side of the positive electrode current collector, and a primer layer provided between the positive electrode current collector and at least one side of the positive electrode film layer; the positive electrode film layer comprises a positive electrode active material and a positive electrode film layer conductive agent, and the D V90 The particles in the primer layer have a D V90 The positive electrode film conductive agent includes a carbon nanotube conductive agent.

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, and an electrical 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, aerospace and other fields.

[0003] With the popularization of single-cell battery applications, the market has put forward higher requirements for their energy density and safety. It is difficult to achieve the above-mentioned performance improvements at the same time in the existing technology, which has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0004] In view of the above problems, the present application provides a battery cell, a battery device and an electrical device, which are described below respectively.

[0005] The first aspect of the present application provides a battery cell, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector, a positive electrode film layer disposed on at least one side of the positive electrode current collector, and a primer layer disposed between the positive electrode current collector and at least one side of the positive electrode film layer; the positive electrode film layer comprises a positive electrode active material and a positive electrode film layer conductive agent, and the D V90 16μm-25μm; D of the particles in the primer layer V90 The thickness of the positive electrode film layer is 3μm-8μm; the positive electrode film layer conductive agent includes a carbon nanotube conductive agent.

[0006] In order to improve the compaction density of the electrode, it is necessary to increase the proportion of large particles in the electrode film layer to achieve dense stacking of the film layer through gradation theory. V90 Within this range, the compaction density of the electrode can be increased, thereby improving the energy density of the battery cell. However, the generation of burrs during the cutting process of high-component-density electrode sheets is closely related to large particles in the electrode film layer. During the slicing process, the cutter squeezes large particles, causing them to squeeze the current collector, causing the current collector to deform and fracture due to compression rather than shear fracture, resulting in burrs and affecting battery safety performance.

[0007] In this application, a small D V90 The base coating forms a transition buffer layer between the positive electrode film layer and the current collector, which can evenly disperse the external mechanical stress applied by the blade during the cutting process, or the internal stress generated by expansion / contraction during the cycle, reducing the probability of large particles in the positive electrode film layer directly contacting the positive electrode current collector to form stress concentration, resulting in damage and burrs to the positive electrode current collector, thereby improving the safety of the battery.

[0008] Studies have shown that by providing a primer layer on at least one side of the positive electrode current collector surface, the D V90 A thickness of 3 μm-8 μm is beneficial for improving the problem of burrs on the positive electrode current collector during the slicing process. However, the undercoat layer is mainly composed of small particles, and its ultimate compaction density is much lower than the compaction density of the positive electrode film layer. Therefore, during the compaction process of the positive electrode film layer, the undercoat layer is prone to overpressure, which significantly reduces the porosity in the film layer, increases the rigid contact between the particles, and thus leads to a decrease in the overall flexibility of the electrode sheet and an increase in brittleness, which makes the positive electrode sheet prone to fracture during deformation.

[0009] Carbon nanotube conductive agent is used in the positive electrode film layer in the embodiment of the present application. On the one hand, thanks to the high aspect ratio of carbon nanotubes, a large number of active material particles can be connected in series inside the positive electrode film layer, and a tight connection can be formed across the interface between the positive electrode film layer and the base coating layer, thereby increasing the adhesion between the positive electrode film layer and the base coating layer, improving the flexibility of the electrode sheet, and reducing the probability of brittle fracture of the electrode sheet; on the other hand, its one-dimensional nanostructure provides high specific strength and specific modulus, forming a three-dimensional network structure in the positive electrode film layer, and effectively dissipating external stress through the fiber-matrix interface effect and the bridging effect, reducing the conduction of stress to the base coating layer and the current collector, which can effectively improve the fracture toughness of the material, reduce the rupture of the positive electrode sheet caused by volume expansion or contraction, and comprehensively improve the brittleness problem of the positive electrode sheet.

[0010] In any embodiment, the mass content of the carbon nanotube conductive agent is 0.3%-0.8%, optionally 0.4%-0.7%, based on the total mass of the positive electrode film layer. When the mass content of the carbon nanotube conductive agent is within the above range, the probability of agglomeration of the carbon nanotube conductive agent due to its high specific surface area during the preparation of the positive electrode film slurry is reduced, thereby maximizing the internal bonding and stress conduction of the positive electrode sheet, optimizing brittleness, and reducing the probability of powder loss and particle loosening and shedding during repeated charge-discharge expansion and contraction cycles, which may result in detached particles piercing the diaphragm and causing internal short circuits, thereby improving cycle safety.

[0011] In any embodiment, the positive electrode film layer further includes a binder, and based on the total mass of the positive electrode film layer, the mass proportion of the binder is 0.6%-1.5%, and can be optionally 0.7%-1.3%. The amount of binder used is positively correlated with the internal bonding force of the positive electrode film layer. If the amount of binder used is too small, the internal bonding force of the positive electrode film layer is low; if the amount of binder used is too high, the resistance of the film layer will be deteriorated and the proportion of active material will be reduced. The mass proportion of the binder within the above range can maximize the internal bonding force, strengthen the bonding between the particles inside the positive electrode film layer, facilitate stress conduction and reduce crack propagation, reduce the brittleness of the battery, balance the internal resistance of the film layer, reduce ohmic polarization, and at the same time improve the energy density and cycle performance of the battery.

[0012] In any embodiment, the D of the particles in the base coating is V90 The particle size of the primer layer is 4μm-7μm. V90 Within the above range, the squeezing of the current collector by large particles in the positive electrode film layer during slicing can be further effectively buffered, thereby reducing the probability of burrs being generated during the electrode cutting process.

[0013] In any embodiment, the positive electrode active material includes a lithium-containing transition metal oxide, and the molar proportion of nickel in the lithium-containing transition metal oxide is 80%-95% based on the total molar proportion of the transition metal in the lithium-containing transition metal oxide. When the molar proportion of nickel in the lithium-containing transition metal oxide is 80%-95%, due to the high electrochemical activity of nickel, the increased nickel content helps to achieve the advantages of high energy density and high power performance of the battery.

[0014] In any embodiment, the positive electrode active material includes a component having the following general formula: Li a Ni x Co y M1 z M2 w O 2-b, wherein, M1 includes one or more of Mn and Al, and M2 includes one or more of Zr, B, Mg, Ti, W, Mo, Nb, Ta, Sr, Sb, and K; 0.8 ≤ a ≤ 1.2, 0.8 ≤ x ≤ 1, 0 < y ≤ 0.2, 0 < z ≤ 0.2, 0 ≤ w ≤ 0.1, -0.1 ≤ b ≤ 0.1. The ionic radii of cobalt and nickel elements are similar, and their electron distributions are similar. The local phase transformation of the NiO6 octahedral structure is inhibited by cobalt elements, reducing the non-stoichiometry of LiNiO2 and improving the stability of the layered structure during cycling. M1 does not participate in redox reactions during charge and discharge, so there is no structural change caused by the Jahn-Teller effect, which can play a role in stabilizing the layered structure. Selecting appropriate modifying element M2 can further improve the lattice change rate of the positive electrode active material during lithium deintercalation and insertion, reduce the oxygen activity on the particle surface, improve the structural stability of the material, and further improve the specific capacity performance of the material during cycling, and further improve the cycle life of the lithium-ion secondary battery.

[0015] In any embodiment, the D of the particles in the positive electrode film layer V50 is 5 μm - 12 μm, (D V90 - D V10 ) / D V50 is 0.5 - 3. The D of the particles in the positive electrode film layer v50 , (D v90 - D[[ID=-16]] v10 ) / D v50 Within the above range, a reasonable particle size distribution is formed between the smaller particles and the larger particles, improving the compaction density of the entire positive electrode film layer and the energy density of the battery cell, while forming a complete pore structure in the positive electrode film layer, which is beneficial to accommodating carbon nanotubes and binders, forming good connections between particles, enhancing the adhesion force inside the electrode sheet. During cycling, the internal stress of the positive electrode active material particles is effectively conducted, and the pore structure provides a certain deformation space, reducing the possibility of brittle fracture of the electrode sheet and improving the cycle life of the battery.

[0016] In any embodiment, the positive electrode active material includes single crystal particles and polycrystalline particles, and the mass ratio of the single crystal particles to the polycrystalline particles is 4:6 - 2:8. Controlling the mass ratio of the polycrystalline particles to the single crystal particles to meet the above range, a reasonable particle size distribution is formed between the smaller single crystal particles and the larger polycrystalline particles, which is beneficial to improving the compaction density of the electrode sheet and enabling the battery to have excellent energy density.

[0017] In any embodiment, the carbon nanotube conductive agent comprises one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes. Single-walled and few-walled carbon nanotubes have extremely high electronic conductivity and can efficiently transfer electrons. Even a small amount can effectively reduce the electron transfer impedance within the battery, increasing the active material loading in the electrode and the battery's energy density. Multi-walled carbon nanotubes, due to their multiple carbon layers, provide greater mechanical strength and rigidity, providing stronger support during the charge and discharge process, reducing the effects of electrode expansion and contraction, reducing brittle fracture of the electrode, and thus increasing the battery's service life.

[0018] In any embodiment, the positive electrode film layer conductive agent further includes a spherical conductive agent, and the spherical conductive agent includes one or more of Super-P, acetylene black, and Ketjen black. Due to the one-dimensional structure of the carbon nanotubes, an electron transmission channel can be formed, and a connection can be formed across the layer structure. The spherical conductive carbon particles contact each other, forming a regional network with multiple contact points. When the carbon nanotubes and spherical conductive carbon are combined, the structures of the two are complementary, and their respective advantages can be brought into play to form a more efficient electron conduction network and improve the adhesion inside the pole piece, further reducing the possibility of brittle fracture.

[0019] In any embodiment, the binder includes at least one of a water-based binder, a bio-based binder, a polyimide binder, and a polyurethane binder, and may be polyvinylidene fluoride. Polyvinylidene fluoride has strong chemical resistance and is not easily affected by electrolytes and other chemicals. It also maintains good stability at higher temperatures, adapting to battery operation in different temperature environments.

[0020] In any embodiment, the primer layer comprises polyanionic particles comprising a component having the following general formula:

[0021] Li x A y Me a M b P 1-c X c Y z Formula I,

[0022] Among them, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤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.

[0023] In any embodiment, the polyanion particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadium phosphate, lithium manganese iron phosphate, and modified materials thereof.

[0024] Polyanion active materials generally have an olivine structure and possess superior thermodynamic thermal stability compared to lithium-containing transition metal oxides. They can reduce high-temperature oxygen release, and their use as a basecoat can improve both the safety and service life of battery cells while improving burr formation. Polyanion active materials have a lower hardness and are more susceptible to deformation or shattering under external forces. Furthermore, their lower hardness may cause particles to rearrange more easily during rolling, rather than exerting a significant compression effect on the current collector. Therefore, using polyanions as a basecoat further reduces the likelihood of burrs.

[0025] In any embodiment, the polyanion particles include one or more of lithium manganese iron phosphate and modified materials thereof.

[0026] Research has shown that conventional lithium iron phosphate materials have a voltage platform that is too low (~3.2V) compared to lithium-containing transition metal oxides. This lowers the voltage platform of the battery cell during operation, making it difficult to fully utilize the specific capacity of lithium iron phosphate. Introducing the element manganese into lithium iron phosphate can effectively increase the voltage platform of lithium iron phosphate (~3.7V), matching it with the voltage window of the lithium-containing transition metal oxide in the positive electrode film. This helps maximize the specific capacity of the material and allows the undercoat layer to reduce the probability of burrs while also minimizing the negative impact on battery energy density.

[0027] In any embodiment, the primer layer includes a primer conductive agent, which includes one or more of conductive carbon black and carbon nanotubes. Adding a conductive agent to the primer layer improves the electronic conductivity of the primer layer and enhances contact and adhesion between particles in the coating, which is beneficial for increasing the cycle life of the battery, enhancing power performance, and reducing internal resistance.

[0028] In any embodiment, the thickness of the positive electrode current collector is 7μm-15μm. The positive electrode current collector does not contribute to the capacity of the battery, and its thinning is conducive to making room for the positive electrode active material and improving the energy density of the battery cell. However, the thinning of the positive electrode current collector reduces its ability to withstand large particle extrusion during the slitting process, and the burr phenomenon is more serious. The thickness of the positive electrode current collector within the above range is conducive to improving the yield rate during the electrode cutting process while maintaining the high energy density of the battery cell, meeting the performance and efficiency requirements.

[0029] In any embodiment, the thickness of the primer layer on one side is 5μm-25μm. The thickness of the primer layer on one side within the above range is conducive to reducing the probability of burrs on the pole piece, while also reducing the sacrifice of battery capacity and energy density due to excessive primer layer thickness, thereby meeting the battery's requirements for safety and energy density. Furthermore, because the primer layer is thin and on the same order of magnitude as the length of the carbon nanotubes, the carbon nanotube structure can penetrate most areas of the primer layer after cold pressing, forming connections between the layers and within the layered structure, thereby improving the internal bonding strength of the pole piece, improving the brittleness of the pole piece, and thereby enhancing the high safety of the battery.

[0030] In any embodiment, the thickness of the positive electrode film layer on a single side is 30 μm to 50 μm. Reducing the thickness of the positive electrode film layer helps reduce the diffusion path length of lithium ions and improve the dynamic performance of the battery cell. However, the thinner the thickness, the greater the probability of burrs piercing the positive electrode film layer, increasing safety risks. The battery cell in the embodiments of the present application can optimize the dynamic performance of the battery cell while reducing the risk of burrs, thereby improving the safety performance of the battery.

[0031] In any embodiment, the compaction density of the positive electrode film layer in the full state is 3.40 g / cm 3 -3.60g / cm 3 The compaction density of the positive electrode film layer within the above range is conducive to maintaining the high energy density of the battery cell while improving the yield rate during the electrode cutting process, thereby meeting performance and efficiency requirements.

[0032] A second aspect of the present application provides a battery device comprising the battery cell of the first aspect of the present application.

[0033] A third aspect of the present application provides an electrical device comprising at least one of the battery cell of the first aspect of the present application and the battery device of the third aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] Figure 1 This is an electron microscope morphology image of a polished cross-section of a positive electrode sheet along the thickness direction in one embodiment of the present application;

[0036] Figure 2 This is an electron microscope morphology image of a polished cross section of a positive electrode piece along the thickness direction in the prior art;

[0037] Figure 3 is a schematic diagram of a battery cell according to one embodiment of the present application;

[0038] Figure 4 yes Figure 3 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0039] Figure 5 is a schematic diagram of a battery module according to one embodiment of the present application;

[0040] Figure 6 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0041] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0042] Figure 8 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0043] Description of reference numerals:

[0044] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly; 62 positive electrode sheet, 621 positive electrode current collector; 622 positive electrode film layer; 623 bottom coating layer. DETAILED DESCRIPTION

[0045] 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, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially the same structures may be 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 to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0046] " 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.

[0047] 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.

[0048] 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.

[0049] 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), which means 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), which means 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.

[0050] In this application, the terms "plurality" and "multiple" refer to two or more.

[0051] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0052] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0053] 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.

[0054] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. A battery cell can be cylindrical, rectangular or other shapes, etc., which is not limited in the present embodiment. Figure 3 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0055] A battery cell includes an electrode assembly and an electrolyte.

[0056] 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).

[0057] In some embodiments, as Figure 4 As shown, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 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.

[0058] 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 during charging and releases or delithiates lithium during discharging. The positive electrode sheet is the electrode that releases or delithiates lithium ions during charging and absorbs or lithiates lithium during discharging.

[0059] When there are multiple battery cells, they 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 crossbeams or longitudinal beams.

[0060] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0061] 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 5 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 5 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.

[0062] 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.

[0063] 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.

[0064] Figure 6 and Figure 7 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 6 and Figure 7 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.

[0065] In recent years, the market demand for high energy density batteries has become increasingly strong. In order to obtain high compaction density electrodes and high energy density batteries, the industry's common method is to increase the particle size and proportion of large particles to improve the grading, form a dense stack, and increase the compaction density of the electrode to increase the load of active materials per unit volume. When the positive electrode is cut, the particles are squeezed against the positive current collector by force, and large particles are difficult to disperse the pressure. Stress concentration is prone to occur at the contact point with the positive current collector, causing the current collector to be squeezed and deformed and fractured instead of cut and fractured, thereby generating burrs, such as Figure 2 As demand for fast charging (4C and above) grows, the thinner the electrode film, the shorter the distance lithium ions have to diffuse within it, and the faster the diffusion rate. Consequently, the film thickness decreases, making it impossible to cover burrs. These burrs can then be exposed and pierce the separator, creating an internal short circuit. Therefore, how to avoid burrs while maintaining energy density and improving battery safety is a pressing technical issue in this field.

[0066] The first aspect of the present application provides a battery cell, wherein the battery cell includes a positive electrode sheet, such as Figure 1 As shown, the positive electrode sheet 62 includes a positive electrode current collector 621, a positive electrode film layer 622 disposed on at least one side of the positive electrode current collector 621, and a primer layer 623 disposed between the positive electrode current collector 621 and at least one side of the positive electrode film layer 622; the positive electrode film layer includes a positive electrode active material and a positive electrode film layer conductive agent, and the D of the particles in the positive electrode film layer is V90 16μm-25μm; D of the particles in the primer layer V90 The thickness of the positive electrode film layer is 3μm-8μm; the positive electrode film layer conductive agent includes a carbon nanotube conductive agent.

[0067] In order to improve the compaction density of the electrode, it is necessary to increase the proportion of large particles in the electrode film layer to achieve dense stacking of the film layer through gradation theory. V90 Within this range, the compaction density of the electrode can be increased, thereby improving the energy density of the battery cell. However, the generation of burrs during the cutting process of high-component-density electrode sheets is closely related to large particles in the electrode film layer. During the slicing process, the cutter squeezes large particles, causing them to squeeze the current collector, causing the current collector to deform and fracture due to compression rather than shear fracture, resulting in burrs and affecting battery safety performance.

[0068] In this application, a small D V90The base coating forms a transition buffer layer between the positive electrode film layer and the current collector, which can evenly disperse the external mechanical stress applied by the blade during the cutting process, or the internal stress generated by expansion / contraction during the cycle, reducing the probability of large particles in the positive electrode film layer directly contacting the positive electrode current collector to form stress concentration, resulting in damage and burrs to the positive electrode current collector, thereby improving the safety of the battery.

[0069] Studies have shown that by providing a primer layer on at least one side of the positive electrode current collector surface, the D V90 A thickness of 3 μm-8 μm is beneficial for improving the problem of burrs on the positive electrode current collector during the slicing process. However, the undercoat layer is mainly composed of small particles, and its ultimate compaction density is much lower than the compaction density of the positive electrode film layer. Therefore, during the compaction process of the positive electrode film layer, the undercoat layer is prone to overpressure, which significantly reduces the porosity in the film layer, increases the rigid contact between the particles, and thus leads to a decrease in the overall flexibility of the electrode sheet and an increase in brittleness, which makes the positive electrode sheet prone to fracture during deformation.

[0070] Carbon nanotube conductive agent is used in the positive electrode film layer in the embodiment of the present application. On the one hand, thanks to the high aspect ratio of carbon nanotubes, a large number of active material particles can be connected in series inside the positive electrode film layer, and a tight connection can be formed across the interface between the positive electrode film layer and the base coating layer, thereby increasing the adhesion between the positive electrode film layer and the base coating layer, improving the flexibility of the electrode sheet, and reducing the probability of brittle fracture of the electrode sheet; on the other hand, its one-dimensional nanostructure provides high specific strength and specific modulus, forming a three-dimensional network structure in the positive electrode film layer, and effectively dissipating external stress through the fiber-matrix interface effect and the bridging effect, reducing the conduction of stress to the base coating layer and the current collector, which can effectively improve the fracture toughness of the material, reduce the rupture of the positive electrode sheet caused by volume expansion or contraction, and comprehensively improve the brittleness problem of the positive electrode sheet.

[0071] In this application, the term "particle" refers to particles with identifiable complete boundaries in the field of view of the positive electrode film layer at a certain magnification, such as 10,000 times. Defects and scratches may exist inside the particles, but complete boundaries sufficient to separate the particles cannot be identified inside the particles.

[0072] In this application, the term "D V90" has a well-known meaning in the art and can be tested using methods known in the art. For example, the method is as follows: 2 g of sample is added to 200 ml of NMP solution and 5 g of sodium dodecyl sulfate (SDS), and ultrasonically dispersed at 60°C for 30 min, 60 min, 90 min, etc. The solutions obtained at different dispersion times are then measured using a laser particle size analyzer (e.g., Malvern 2000 (MasterSizer 2000) laser particle size analyzer) with reference to GB / T 19077-2016 / ISO 13320:2009. If the particle size distribution fluctuation is greater than 5%, the ultrasonic dispersion time is further increased. If the particle size distribution fluctuation of the solution measured at the last two dispersion times is ≤5%, it indicates that the dispersion is complete and the test results are accurate. The results can be output to obtain a particle size distribution graph based on volume distribution." V10 ”, “D V50 ” and “D V90 ” respectively correspond to the particle sizes when the percentages of the particle size distribution graph reach 10%, 50%, and 90%.

[0073] In some embodiments, the D of the particles in the positive electrode film layer is V90 It is 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, 20.5μm, 21μm, 21.5μm, 22μm, 22.5μm, 23μm, 23.5μm, 24μm, 24.5μm, 25μm or a numerical range between any two of the above.

[0074] In some embodiments, the D of the particles in the base coating is V90 The thickness may be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm or a range between any two of the above values.

[0075] In this application, the term "burr" refers to a metal protrusion or protrusion extending outward from the current collector in accordance with the IEEE1725 battery cell safety performance review and testing standard; the extension direction can be in any direction, such as the thickness direction or the pole piece plane direction, and the causes of its occurrence include but are not limited to cutting, tearing, etc.

[0076] In some embodiments, the positive electrode film layer conductive agent includes a carbon nanotube conductive agent.

[0077] In this application, the term "carbon nanotube" refers to a carbon nanotube composed of carbon atoms in the form of sp 2A nanomaterial consisting of several to dozens of coaxial hollow tubes formed by the curling of hybrid-bonded graphene sheets. Diameters typically range from a few to tens of nanometers, and lengths can range from microns to centimeters, exhibiting a high aspect ratio. Based on the number of graphene layers, they can be classified as single-walled carbon nanotubes (SWCNTs), few-walled carbon nanotubes (FWCNTs), and multi-walled carbon nanotubes (MWCNTs).

[0078] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the carbon nanotube conductive agent is 0.3%-0.8%, and can be optionally 0.4%-0.7%.

[0079] In some embodiments, based on the total mass of the positive electrode film layer, the mass content of the carbon nanotube conductive agent can be selected as 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or a numerical range between any two of the above.

[0080] Based on the total mass of the positive electrode film layer, the mass content of the carbon nanotube conductive agent is within the above range, which reduces the probability of carbon nanotube conductive agent agglomeration due to high specific surface area during the preparation of the positive electrode film layer slurry, maximizes the internal bonding force and stress conduction of the positive electrode plate, optimizes brittleness, and reduces the probability of powder loss and loose particles falling off during repeated charge and discharge expansion and contraction cycles, and the probability of falling particles piercing the diaphragm and causing internal short circuits, thereby improving cycle safety.

[0081] In some embodiments, based on the total mass of the positive electrode film layer, the mass proportion of the binder is 0.6%-1.5%, and can be optionally 0.7%-1.3%.

[0082] In some embodiments, the positive electrode film layer further includes a binder. Based on the total mass of the positive electrode film layer, the mass proportion of the binder can be selected to be 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5% or a numerical range between any two of the above.

[0083] The amount of binder used is positively correlated with the internal cohesion of the positive electrode film. Too little binder results in low internal cohesion; too much binder deteriorates the film's resistance and reduces the active material content. A binder mass percentage within the above range maximizes internal cohesion, strengthening the bond between particles within the positive electrode film. This facilitates stress conduction, reduces crack propagation, and reduces battery brittleness. It also balances the film's internal resistance, reduces ohmic polarization, and improves the battery's energy density and cycle performance.

[0084] In some embodiments, the D of the particles in the base coating is V90 4μm-7μm.

[0085] D of particles in the base coat V90 Within the above range, the squeezing of the current collector by large particles in the positive electrode film layer during slicing can be further effectively buffered, thereby reducing the probability of burrs being generated during the electrode sheet cutting process.

[0086] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide, and the molar proportion of nickel in the lithium-containing transition metal oxide is 80%-95% based on the total molar number of transition metals in the lithium-containing transition metal oxide.

[0087] Lithium-containing transition metal oxides are an important type of positive electrode active material for lithium-ion batteries. When the molar proportion of nickel in the lithium-containing transition metal oxides is 80%-95%, due to the high electrochemical activity of nickel, the increase in nickel content helps to make the battery have the advantages of high energy density and high power performance.

[0088] In some embodiments, the positive electrode active material has the following chemical formula: Li a Ni x Co y M1 z M2 w O 2-b , 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≤a≤1.2, 0.8≤x≤1, 0 <y≤0.2,0<z≤0.2,0≤w≤0.1,-0.1≤b≤0.1。

[0089] In some embodiments, a can be selected as 0.80, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98, 1.00, 1.02, 1.04, 1.06, 1.08, 1.10, 1.12, 1.14, 1.16, 1.18, 1.20 or a range of values ​​therebetween.

[0090] In some embodiments, x can be 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, or a range of values ​​therebetween.

[0091] In some embodiments, y can be selected as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, or a range of values ​​therebetween.

[0092] In some embodiments, z can be selected as 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, or a range of values ​​therebetween.

[0093] In some embodiments, w can be selected as 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, or a range of values ​​therebetween.

[0094] In some embodiments, b can be selected as -0.10, -0.09, -0.08, -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 or a numerical range therebetween.

[0095] Li a Ni x Co y M1 z M2 w O 2-bThe ionic radius of cobalt and nickel in the NiO6 are similar, and their electron distribution is similar. The local phase change of the NiO6 octahedral structure is suppressed by cobalt, which reduces the non-stoichiometric ratio of LiNiO2 and improves the stability of the layered structure during the cycle. M1 does not participate in the redox reaction during the charge and discharge process, so there is no structural change caused by the Jan-Taylor effect, which can play a role in stabilizing the layered structure. Selecting an appropriate modifying element M2 can further improve the lattice change rate of the positive electrode active material during the lithium insertion and extraction process, reduce the oxygen activity on the particle surface, improve the structural stability of the material, and thus improve the material's gram capacity during the cycle, further improving the cycle life of the lithium-ion secondary battery.

[0096] In some embodiments, the D of the particles in the positive electrode film layer is V50 5μm-12μm, (D V90 -D V10 ) / D V50 0.5-3.

[0097] In some embodiments, the D of the particles in the positive electrode film layer is V50 Optional 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm, 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8 1 0.6μm, 10.7μm, 10.8μm, 10.9μm, 11μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm, 12μm or a numerical range between any two of the above.

[0098] In some embodiments, the particles in the positive electrode film layer (D V90 -D V10 ) / D V50The optional values ​​can be 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0 or a numerical range between any two of the above.

[0099] In this application, the term "D V50 、D V10 " has a well-known meaning in the art and can be tested using methods known in the art. Please refer to the above-mentioned particle size distribution test method.

[0100] D of particles in the positive electrode film v50 ,(D v90 -D v10 ) / D v50 Within the above range, a reasonable particle grading is formed between smaller particles and larger particles, which improves the compaction density of the entire positive electrode film layer and increases the energy density of the battery cell. At the same time, the positive electrode film layer forms a complete pore structure, which is conducive to accommodating carbon nanotubes and binders, forming a good connection between the particles, and enhancing the bonding force inside the electrode. During the cycle, the internal stress of the positive electrode active material particles is effectively conducted, and the pore structure provides a certain deformation space, which reduces the possibility of brittle fracture of the electrode sheet and improves the cycle life of the battery.

[0101] In some embodiments, the positive electrode active material includes single crystal particles and polycrystalline particles, and a mass ratio of the single crystal particles to the polycrystalline particles is 4:6-2:8.

[0102] In some embodiments, the positive electrode active material includes single crystal particles and polycrystalline particles, and the mass ratio of the single crystal particles to the polycrystalline particles can be selected from 4:6, 3.9:6.1, 3.8:6.2, 3.7:6.3, 3.6:6.4, 3.5:6.5, 3.4:6.6, 3.3:6.7, 3.2:6.8, 3.1:6.9, 3:7, 2.9:7.1, 2.8:7.2, 2.7:7.3, 2.6:7.4, 2.5:7.5, 2.4:7.6, 2.3:7.7, 2.2:7.8, 2.1:7.9, 2:8 or a numerical range between any two of the above.

[0103] In this application, the term "single crystal" refers to a crystal whose internal structure generally conforms to a lattice structure. A single crystal contains no or a small number of grain boundaries on a macroscopic scale, and the crystal orientation remains generally consistent throughout the crystal.

[0104] In this application, the term "polycrystalline" refers to a crystal composed of many single crystal particles with different orientations. The entire structure is not permeated by a single lattice. The hard agglomeration of single crystal particles caused by chemical bonding results in a large number of grain boundaries within the polycrystalline particles.

[0105] In the present application, the mass ratio of polycrystalline particles and single crystal particles 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. Randomly select a number of points for shooting, and the number of points is ≥10, which can be 10, 20, 50, 100, etc. The area ratio of the polycrystalline particles and single crystal particles in the captured picture to the size of the positive electrode film layer is calculated, and the average value is obtained. The area ratio between polycrystalline particles and single crystal particles can be equivalent to the mass ratio of polycrystalline particles to single crystal particles.

[0106] Controlling the mass ratio of polycrystalline particles and single crystal particles to meet the above range and forming a reasonable particle grading between smaller single crystal particles and larger polycrystalline particles is beneficial to improving the compaction density of the electrode and making the battery have excellent energy density.

[0107] In some embodiments, the D of the single crystal particles V50 1μm-5μm; and / or D of polycrystalline particles V50 5μm-11μm.

[0108] In some embodiments, the D of the single crystal particles V50 The options include 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm or a numerical range between any two of the above.

[0109] In some embodiments, the D of the single crystal particles V50Optional 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm, 6μm, 6.1μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6 .6μm, 6.7μm, 6.8μm, 6.9μm, 7μm, 7.1μm, 7.2μm, 7.3μm, 7.4μm, 7.5μm, 7.6μm, 7.7μm, 7.8μm, 7.9μm, 8μm, 8.1μm, 8.2μm , 8.3μm, 8.4μm, 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, 10μm, 10μm, 10.1μm, 10.2μm, 10.3μm, 10.4μm, 10.5μm, 10.6μm, 10.7μm, 10.8μm, 10.9μm, 11μm or a numerical range between any two of the above.

[0110] The D of the single crystal particles and the polycrystalline particles V50 Within the above range, the single crystal particles can fill the pores formed by the accumulation of polycrystalline particles, making more effective use of space, increasing the compaction density of the entire positive electrode sheet, and increasing the energy density of the battery cell.

[0111] In some embodiments, the carbon nanotube conductive agent in the positive electrode film layer includes one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0112] Single-walled and few-walled carbon nanotubes have extremely high electronic conductivity and can efficiently transfer electrons. Even a small amount can effectively reduce the electron transfer impedance within the battery, increasing the active material loading in the electrode and the battery's energy density. Multi-walled carbon nanotubes, due to their multiple carbon layers, provide greater mechanical strength and rigidity. They can provide stronger support during the charge and discharge process, mitigate the effects of electrode expansion and contraction, reduce brittle fracture of the electrode, and thus extend the battery's lifespan.

[0113] In some embodiments, the positive electrode film layer conductive agent further comprises a spherical conductive agent, and the spherical conductive agent comprises one or more of Super-P, acetylene black, and Ketjen black.

[0114] The one-dimensional structure of carbon nanotubes allows for the formation of electron transport channels that can span layers of the structure, creating connections. The spherical conductive carbon particles come into contact with each other, forming a regional network with multiple contact points. When carbon nanotubes and spherical conductive carbon are combined, their complementary structures leverage their respective strengths, forming a more efficient electron conduction network and improving the internal bonding strength of the electrode, further reducing the likelihood of brittle fracture.

[0115] In some embodiments, the adhesive includes at least one of a water-based adhesive, a biological adhesive, a polyimide adhesive, and a polyurethane adhesive, and may be polyvinylidene fluoride.

[0116] The binders used in this application include, but are not limited to, the aforementioned types of binders, which are capable of bonding active materials, conductive agents, and other components together within the positive electrode film layer, and possess a certain degree of bonding strength that meets the requirements of this application. Polyvinylidene fluoride has strong chemical resistance and is not easily affected by electrolytes and other chemicals. It also maintains good stability at higher temperatures, making it suitable for battery operation in different temperature environments.

[0117] In some embodiments, the primer layer comprises polyanionic particles comprising a component having the following general formula:

[0118] Li x A y Me a M b P 1-c X c Y z Formula I,

[0119] Among them, 0.1≤x≤1.3, 0≤y≤1.3, and 0.9≤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.

[0120] In some embodiments, x can 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, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, or a range of values ​​therebetween.

[0121] In some embodiments, y can be selected as 0, 0.05, 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, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3 or a range of values ​​therebetween.

[0122] In some embodiments, x+y can be selected as 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, or a range of values ​​therebetween.

[0123] In some embodiments, a can be selected as 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a range of values ​​therebetween.

[0124] In some embodiments, b can be selected as 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5 or a range of values ​​therebetween.

[0125] In some embodiments, a+b can be selected as 0.9, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, or a range of values ​​therebetween.

[0126] In some embodiments, c can be selected as 0, 0.01, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 0.38, 0.4, 0.42, 0.44, 0.46, 0.48, 0.5 or a range of values ​​therebetween.

[0127] 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 a range of values ​​therebetween.

[0128] When used herein, "the polyanionic particles include components having the following general formula I" is not limited to the substances represented by the molecular general formula, but also includes other substances formed after further appropriate modification on the basis of the molecular general formula, which is not limited here. The use of "general formula" is only for the convenience of description and is not intended to limit this application. It is understood that new materials or new substances obtained by appropriate modification on the basis of the listed materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to acceptable modification methods for the materials, and non-limiting examples include coating modification.

[0129] Polyanion active materials generally have an olivine structure and possess superior thermodynamic thermal stability compared to lithium-containing transition metal oxides. They can reduce high-temperature oxygen release, and their use as a basecoat can improve both the safety and service life of battery cells while improving burr formation. Polyanion active materials have a lower hardness and are more susceptible to deformation or shattering under external forces. Furthermore, their lower hardness may cause particles to rearrange more easily during rolling, rather than exerting a significant compression effect on the current collector. Therefore, using polyanions as a basecoat further reduces the likelihood of burrs.

[0130] In some embodiments, the polyanionic particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadium phosphate, lithium manganese iron phosphate, and modified materials thereof.

[0131] In some embodiments, the polyanionic particles include one or more of lithium manganese iron phosphate and modified materials thereof.

[0132] Research has shown that conventional lithium iron phosphate materials have a voltage platform that is too low (~3.2V) compared to lithium-containing transition metal oxides. This lowers the voltage platform of the battery cell during operation, making it difficult to fully utilize the specific capacity of lithium iron phosphate. Introducing the element manganese into lithium iron phosphate can effectively increase the voltage platform of lithium iron phosphate (~3.7V), matching it with the voltage window of the lithium-containing transition metal oxide in the positive electrode film. This helps maximize the specific capacity of the material and allows the undercoat layer to reduce the probability of burrs while also minimizing the negative impact on battery energy density.

[0133] In some embodiments, the primer layer includes a primer conductive agent, and the primer conductive agent includes one or more of conductive carbon black and carbon nanotubes.

[0134] By adding a conductive agent to the base coating, the electronic conductivity of the base coating is improved, and the contact and adhesion between the particles in the coating are improved, which is beneficial for increasing the cycle life of the battery, improving power performance and reducing internal resistance.

[0135] In some embodiments, the thickness of the positive electrode current collector is 7 μm-15 μm.

[0136] In some embodiments, the thickness of the positive electrode current collector may be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or a range of values ​​between any two of the above.

[0137] In this application, the thickness of the positive electrode current collector can be measured by the following method: cutting the positive electrode film layer along the thickness direction of the electrode piece using an argon ion beam (for example, equipment model: Leica EMTIC 3X CP, operating voltage: 6kV, operating time: 6h), exposing the cross section, and observing the cross section of the positive electrode film layer along the thickness direction of the electrode piece using a scanning electron microscope (for example, equipment model: Hitachi SU8230, operating voltage: 3kV, beam current: high, probe model: U (LA100), working distance <5mm). The thickness of the positive electrode current collector is measured using the scale in the electron microscope image as a reference.

[0138] The positive electrode current collector does not contribute to battery capacity, so reducing its thickness helps free up space for the positive electrode active material, thereby increasing the energy density of the battery cell. However, this thinning reduces its ability to withstand large particle extrusion during the slitting process, exacerbating burring. Maintaining the positive electrode current collector thickness within the above range helps improve the yield rate during the electrode sheet cutting process while maintaining high battery cell energy density, thereby meeting performance and efficiency requirements.

[0139] In some embodiments, the thickness of the primer layer on one side is 5 μm to 25 μm.

[0140] In some embodiments, the thickness of the primer layer on one side may be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm or a numerical range between any two of the above.

[0141] A single-sided primer coating thickness within the aforementioned range helps reduce the probability of burrs on the electrode, while also minimizing the sacrifice in battery capacity and energy density caused by excessive primer thickness, thereby meeting the battery's safety and energy density requirements. Furthermore, because the primer coating is thin, on the same order of magnitude as the carbon nanotube length, the carbon nanotube structure can penetrate most areas of the primer coating after cold pressing, forming connections between layers and within the layered structure. This improves internal bonding strength within the electrode, reduces its brittleness, and ultimately enhances battery safety.

[0142] In some embodiments, the thickness of the bottom positive electrode film layer on one side is 30 μm-50 μm.

[0143] In some embodiments, the thickness of the primer layer on one side may be 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm or a numerical range between any two of the above.

[0144] Reducing the thickness of the positive electrode film helps reduce the diffusion path length of lithium ions and improve the dynamic performance of the battery cell. However, the thinner the thickness, the greater the probability of burrs piercing the positive electrode film, increasing safety risks. The battery cell in the embodiment of the present application can optimize the dynamic performance of the battery cell while reducing the risk of burrs, thereby improving the safety performance of the battery.

[0145] In some embodiments, the cold pressed density of the positive electrode film layer is 3.50 g / cm 3 -3.75g / cm 3 .

[0146] In some embodiments, the cold pressed density of the positive electrode film layer can be 3.50 g / cm 3 、3.51g / cm 3 、3.52g / cm 3 、3.53g / cm 3 、3.54g / cm 3 、3.55g / cm 3 、3.56g / cm 3 、3.57g / cm 3 、3.58g / cm 3 、3.59g / cm 3 、3.6g / cm 3 、3.61g / cm 3 、3.62g / cm 3 、3.63g / cm 3 、3.64g / cm3 、3.65g / cm 3 、3.66g / cm 3 、3.67g / cm 3 、3.68g / cm 3 、3.69g / cm 3 、3.7g / cm 3 , 3.71g / cm3, 3.72g / cm3, 3.73g / cm3, 3.74g / cm3, 3.75g / cm3 or a numerical range between any two of the above.

[0147] In this application, the compaction density after cold pressing can be tested using methods known in the art. As an example, the positive electrode sheet obtained after cold pressing is cut into small discs with an area of ​​S, and its mass is obtained as W1. The thickness of the positive electrode sheet is measured using a caliper to obtain T1. The positive electrode film layer of the weighed electrode sheet is then wiped off, the mass of the current collector is weighed, recorded as W2, and the thickness of the current collector is measured using a caliper to obtain T2. ​​The compaction density of the positive electrode film layer is PD = (W1-W2) / [(T1-T2)×S].

[0148] In some embodiments, the compaction density of the positive electrode film layer in the full state is 3.40 g / cm 3 -3.60g / cm 3 .

[0149] In some embodiments, the compaction density of the positive electrode film layer in the full state is 3.40 g / cm 3 、3.41g / cm 3 、3.42g / cm 3 、3.43g / cm 3 、3.44g / cm 3 、3.45g / cm 3 、3.46g / cm 3 、3.47g / cm 3 、3.48g / cm 3 、3.49g / cm 3 、3.50g / cm 3 、3.51g / cm 3 、3.52g / cm 3 、3.53g / cm 3 、3.54g / cm 3 、3.55g / cm 3 、3.56g / cm 3 、3.57g / cm 3 、3.58g / cm 3 、3.59g / cm 3 、3.60g / cm3 Or a numerical range between any two of the above.

[0150] In this application, the full discharge state means that the battery is placed at 25℃, left to stand for 2 hours, and when the battery temperature remains at 25℃, the battery is discharged at a constant current of 1 / 3C to 2.8V, then left to stand for 30 minutes, and then continued to discharge at a constant current of 0.04C to 2.8V.

[0151] In the present application, the compaction density of the positive electrode film layer in the full state can be tested by methods known in the art. As an example, the battery is placed in a 25°C oven environment and allowed to stand for 2 hours. After the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.8V and then allowed to stand for 15 minutes. It is then discharged at a constant current of 0.04C to 2.8V. The battery is disassembled to obtain the positive electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the sheet is dried, and cut into small discs with an area of ​​S. The mass is W1, and the thickness T1 of the positive electrode sheet is measured using a micrometer. Then, the positive electrode film layer of the weighed sheet is wiped off, the mass of the current collector is weighed, recorded as W2, and the thickness T2 of the current collector is measured using a micrometer. The compaction density PD of the positive electrode film layer is PD = (W1-W2) / [(T1-T2)×S].

[0152] The compaction density of the positive electrode film layer within the above range is beneficial for maintaining the high energy density of the battery cell while improving the yield rate in the electrode cutting process, thereby meeting performance and efficiency requirements.

[0153] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0154] In some embodiments, the primer layer may further include a binder. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0155] In some embodiments, the positive electrode plate can be prepared by the following method: the components for preparing the above-mentioned primer layer, such as lithium-containing transition metal phosphate, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a primer layer slurry; the components such as lithium-containing transition metal oxide, conductive agent, binder are dispersed in a solvent to form a positive electrode film layer slurry; the primer layer slurry is first coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode film layer slurry is then coated on the surface of the primer layer, and after drying, cold pressing and other processes, the positive electrode plate can be obtained.

[0156] [Negative electrode]

[0157] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector.

[0158] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0159] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0160] In some embodiments, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0161] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0162] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0164] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0165] [Electrolytes]

[0166] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0167] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0168] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0169] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0170] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0171] [Isolation film]

[0172] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0173] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0174] [Battery Cell]

[0175] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0176] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0177] In some embodiments, the volume energy density of the battery cell is 650Wh / L-720Wh / L.

[0178] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape.

[0179] [Battery device]

[0180] The present invention also provides a battery device, which includes the battery cell provided in the present invention. In some embodiments, the battery device is one or more of a battery module, a battery pack, and an energy storage device.

[0181] [Electrical devices]

[0182] In addition, an embodiment of the present application further provides an electrical device, the electrical device comprising at least one of the battery cells, battery modules, or battery packs provided in the embodiments of the present application. The battery cells, battery modules, or battery packs can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0183] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0184] Figure 8 This is an example of an 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 the battery cells in this device, a battery pack or battery module can be used.

[0185] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0186] Example

[0187] 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.

[0188] Example 1

[0189] 1) Preparation of positive electrode sheet

[0190] Preparation of base coating slurry: D V90 6μm lithium manganese iron phosphate (LiMn 0.6 Fe 0.4 PO4), carbon nanotube conductive agent, conductive carbon black, and binder PVDF were mixed in a mass ratio of 98:05:0.5:1, and solvent N-methyl-2-pyrrolidone (NMP) was added, and stirred under a vacuum stirrer until the system became uniform to obtain a primer slurry;

[0191] Preparation of positive electrode film slurry: D V90 25μm, D V50 9μm, D V102.5μm polycrystalline lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Mn 0.04 O2, D V90 11μm, D V50 0 is 4.5μm, D V10 1.5μm single crystal lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Mn 0.04 A positive electrode active material mixture was weighed in a mass ratio of 7:3 (the mass ratio of polycrystalline to single crystal was 7:3), and the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF were mixed in a mass ratio of 97.7:0.5:0.5:1.3. A solvent NMP was added, and the mixture was stirred in a vacuum mixer until the system became uniform to obtain a positive electrode film slurry.

[0192] The primer slurry is evenly coated on both sides of the positive electrode current collector and then dried to form a primer layer, wherein the coating mass on one side is 40 mg / 1540.25 mm 2 ; The positive electrode film slurry is evenly coated on the surface of the base coating away from the positive electrode current collector, and the single-sided coating mass is 160mg / 1540.25mm 2 After drying at room temperature, the film is transferred to an oven for further drying and then cold pressed to obtain the positive electrode sheet. The single-sided coating mass here does not include the solvent mass, but only the solid content mass in the coating.

[0193] Among them, after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10μm, and the volume distribution particle size D of the particles in the bottom coating is V90 6μm;

[0194] The thickness of the positive electrode film on one side of the positive electrode sheet is 40 μm, and the D V90 22μm, D V50 8μm, (D V90 -D V10 ) / D V50 The cold pressing density of the positive electrode film is 3.7g / cm 3 .

[0195] Pole sheet slitting (one out of two): the positive electrode sheet is cut on the slitting machine, the slitting speed is 0.5m / s, the slitting knife is made of steel knife, and the negative pressure of the slitting machine is -10KPa

[0196] Pole piece cutting: The slit pole pieces are wound and cut, with a winding speed of 0.6m / s, a core length of 3m, a steel blade as the cutting blade, and a negative pressure of -10KPa inside the winding machine.

[0197] 2) Preparation of negative electrode sheet

[0198] The graphite negative electrode active material, polyvinyl alcohol binder, and SP-Li conductive agent were fully mixed and ball-milled in a deionized water solvent system at a mass ratio of 90:5:5 to obtain a negative electrode slurry. The negative electrode slurry was mixed and milled at a mass ratio of 148 mg / 1540.25 mm 2 The single-sided coating weight was double-sided coated on the surface of the copper foil, and vacuum dried overnight at a temperature of 110°C to obtain a negative electrode sheet.

[0199] 3) Preparation of diaphragm

[0200] A polyethylene film with a thickness of 13 μm was used as the separator.

[0201] 4) Preparation of electrolyte

[0202] Lithium hexafluorophosphate (LiPF6) was dissolved in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 to form a uniform solution, thereby obtaining an electrolyte with a LiPF6 concentration of 1 mol / L.

[0203] 5) Battery assembly

[0204] The cells are arranged in the order of "diaphragm - negative electrode sheet - separator - positive electrode sheet". One end of the positive electrode sheet, negative electrode sheet, and two separators are fixed to the discharge roller, and the other end is fixed to the winding shaft after being stacked together. A motor rotates the winding shaft, winding the positive electrode sheet, negative electrode sheet, and two separators to form a wound bare cell. The bare cell is placed in an outer packaging, injected with the above-mentioned electrolyte, and encapsulated to form a battery cell.

[0205] The preparation method of Example 2 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.7:0.8:0.2:1.3, and other parameter conditions remain unchanged.

[0206] The preparation method of Example 3 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.7:0.7:0.3:1.3, and other parameter conditions remain unchanged.

[0207] The preparation method of Example 4 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.7:0.4:0.6:1.3, and other parameter conditions remain unchanged.

[0208] The preparation method of Example 5 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.7:0.3:0.7:1.3, and other parameter conditions remain unchanged.

[0209] The preparation method of Example 6 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry. V90 19μm, D V50 7μm, D V10 2.2μm polycrystalline lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Mn 0.04 O2 replaces the original polycrystalline lithium-containing transition metal oxide; after cold pressing, the thickness of the positive electrode film on one side of the positive electrode sheet is 40 μm, and the D V90 16μm, D V50 6.2μm, (D V90 -D V10 ) / D V50 The cold pressed density of the positive electrode film is 3.67 g / cm 3 , other parameters remain unchanged.

[0210] The preparation method of Example 7 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry. V90 27μm, D V50 10μm, D V10 4μm polycrystalline lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Mn 0.04 O2 replaces the original polycrystalline lithium-containing transition metal oxide; after cold pressing, the thickness of the positive electrode film on one side of the positive electrode sheet is 40 μm, and the D V90 25μm, D V50 8.7μm, (D V90 -D V10 ) / D V50 The cold compaction density of the positive electrode film is 3.65g / cm 3 , other parameters remain unchanged.

[0211] The preparation method of Example 8 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the undercoat slurry. V90The original lithium manganese iron phosphate is replaced by lithium manganese iron phosphate with a thickness of 8 μm; after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10 μm, and the volume distribution particle size D of the particles in the bottom coating is V90 The thickness is 8 μm, and other parameters remain unchanged.

[0212] The preparation method of Example 9 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the undercoat slurry. V90 7μm lithium manganese iron phosphate replaces the original lithium manganese iron phosphate; after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10μm, and the volume distribution particle size D of the particles in the bottom coating is V90 The other parameters remain unchanged.

[0213] The preparation method of Example 10 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the undercoat slurry. V90 4μm lithium manganese iron phosphate replaces the original lithium manganese iron phosphate; after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10μm, and the volume distribution particle size D of the particles in the bottom coating is V90 The other parameters remain unchanged.

[0214] The preparation method of Example 11 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the undercoat slurry. V90 3μm lithium manganese iron phosphate replaces the original lithium manganese iron phosphate; after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10μm, and the volume distribution particle size D of the particles in the bottom coating is V90 The thickness is 3 μm, and other parameters remain unchanged.

[0215] The preparation method of Example 12 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.5:0.5:0.5:1.5, and other parameter conditions remain unchanged.

[0216] The preparation method of Example 13 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 97.8:0.5:0.5:1.2, and other parameter conditions remain unchanged.

[0217] The preparation method of Example 14 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 98.3:0.5:0.5:0.7, and other parameter conditions remain unchanged.

[0218] The preparation method of Example 15 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 98.4:0.5:0.5:0.6, and other parameter conditions remain unchanged.

[0219] The preparation method of Example 16 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, carbon nanotube conductive agent, conductive carbon black, and binder PVDF is adjusted to 98.5:0.5:0.5:0.5, and other parameter conditions remain unchanged.

[0220] The preparation method of Example 17 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the undercoat slurry. V90 The original lithium manganese iron phosphate is replaced by 6μm lithium iron phosphate (LiFePO4, LFP), and other parameters remain unchanged.

[0221] The preparation method of Example 18 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry, polycrystalline lithium-containing transition metal oxide LiNi is used. 0.92 Co 0.04 Al 0.04 O2 replaces the original polycrystalline lithium-containing transition metal oxide and the single crystal lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Al 0.04 O2 replaces the original single crystal lithium-containing transition metal oxide, and other parameter conditions remain unchanged.

[0222] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that, in the preparation steps of the positive electrode sheet, no primer slurry is prepared and no coating is applied.

[0223] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that D V90 The original lithium manganese iron phosphate is replaced by lithium manganese iron phosphate with a thickness of 10 μm; after cold pressing, the thickness of the bottom coating on one side of the positive electrode sheet is 10 μm, and the volume distribution particle size D of the particles in the bottom coating is V90 The cold pressing density of the positive electrode film is 3.68g / cm 3 Other parameters remain unchanged.

[0224] The preparation method of Comparative Example 3 is basically the same as that of Example 1, except that, in the preparation of the positive electrode sheet and the preparation step of the positive electrode film slurry, the mass ratio of the positive electrode active material mixture, conductive carbon black, and binder PVDF is adjusted to 97.7:1:1.3, and other parameter conditions remain unchanged.

[0225] The preparation method of Comparative Example 4 is basically the same as that of Example 1, except that D is used in the preparation of the positive electrode sheet and the preparation of the positive electrode film slurry. V90 15μm, D V50 6.4μm, D V10 2.0μm polycrystalline lithium-containing transition metal oxide LiNi 0.92 Co 0.04 Mn 0.04 O2 replaces the original polycrystalline lithium-containing transition metal oxide; after cold pressing, the thickness of the positive electrode film on one side of the positive electrode sheet is 40 μm, and the D V90 14μm, D V50 6μm, (D V90 -D V10 ) / D V50 2; the cold pressed density of the positive electrode film is 3.60g / cm 3 , other parameters remain unchanged.

[0226] Performance Testing

[0227] 1. CP-SEM characterization method of the cross section of the positive electrode

[0228] The sample to be characterized was prepared as follows: First, the positive electrode sheet was cut into 2 cm × 2 cm specimens and secured to the sample stage with paraffin wax. The sample stage was then placed in the sample holder and locked securely. The argon ion cross-section polisher IB-19500CP was powered on and vacuumed. The argon flow rate was set to 0.15 MPa, the control voltage to 8 kV, and the polishing time to 2 hours. The sample stage was then set to rocking mode and polishing began. After polishing, the sample to be characterized was obtained.

[0229] Micromorphology Characterization: Samples were characterized using a ZEISS Sigma300 scanning electron microscope. Sample testing can refer to JY / T010-1996. To ensure the accuracy of the test results, multiple randomly selected areas of the sample were scanned and cross-sectional morphology images were captured at a fixed magnification of 5kx.

[0230] 2. Characterization method of burr test on the cross section of positive electrode

[0231] At 25°C, the cut positive electrode sheets from each example and comparative example were characterized using a CCD instrument (Keyence 600). The test sheet size was 80 mm × 60 mm, the magnification was 300x, and the light aperture was 30%. Burrs were observed and calibrated on the cross-section of the sheet. Burrs with a size greater than or equal to 40% of the thickness of the positive electrode sheet were included in the statistics and were calibrated as positive electrode sheets with burrs.

[0232] Burr size statistics: 2000 cut electrodes were observed by CCD, and the frequency K1 of electrodes with burrs was counted. The burr ratio was calculated to be K1 ÷ 2000 × 100%.

[0233] 3. Pole powder shedding test

[0234] At 25°C, the cold-pressed positive electrode sheets prepared in each embodiment and comparative example were taken and sheared using a die-cutting and wrapping integrated machine. The slitting speed was set to 0.5 m / s, the pressure of the slitting machine was set to -10 Kpa, and the number of shearing knives was set to 2000. The powder after shearing was collected, its weight was weighed and recorded as W, and the metal leakage ratio was recorded as W g / 2000 knives.

[0235] 4. Pole piece bonding strength test method

[0236] At 25°C, take the cold-pressed positive electrode sheets prepared in each embodiment and comparative example, cut them into test specimens with a length of L: 100 mm and a width of W: 20 mm, and set them aside; stick one side of the double-sided tape to the surface of the steel plate, and adhere the electrode to be tested on the other side, and compact it with a pressure roller to make it completely fit with the electrode; bend one end of the collector in the opposite direction with a bending angle of 180°; use a high-speed rail tensile testing machine for testing, fix one end of the steel plate to the clamp below the tensile testing machine, and fix the bent end of the collector to the upper clamp, adjust the angle of the collector to ensure that the upper and lower ends are in a vertical position, and then stretch the sample at a speed of 50 mm / min until the current collector is completely peeled off from the surface of the electrode, record the displacement and force during the process, and record the strength when the force is balanced as the bonding force of the electrode as N1. The bonding strength of the electrode can be calculated using the formula N1 / W.

[0237] 5. Bending resistance

[0238] At 25°C, the positive electrode sheets cut in each embodiment and comparative example were folded in half at 180°, rolled back and forth at the fold with a 1.5 kg roller, and then unfolded to observe whether the fold appeared cracking and light transmission; then, they were folded in the opposite direction at 180°, rolled back and forth at the fold with a 1.5 kg roller, and then unfolded to observe whether the fold appeared cracking and light transmission. The above reverse folding steps were repeated, and each folding was recorded as 0.5 bending resistance times. The number of folding times that caused cracking and light transmission at the fold was recorded. At least ten samples were tested, and the average value was taken as the bending resistance number of the positive electrode sheet.

[0239] 6. Battery internal resistance DCR test method

[0240] At 25°C, the battery cells prepared in each embodiment and comparative example were charged at a constant current of 1 / 3C to a charge cut-off voltage of 4.25V, and then continued to be charged at a constant voltage at the charge cut-off voltage until the current reached 0.05C. They were then discharged at 1 / 3C to 50% SOC, allowed to stand for 5 minutes, and then pulse-discharged at 3C for 30 seconds.

[0241] The voltage before and after each pulse discharge was recorded, and the DCR under different conditions was calculated. The calculation formula was DCR = (voltage before pulse discharge after the end of static state - voltage before static state after pulse discharge) / pulse current.

[0242] 7. Battery energy density test method

[0243] The battery cells prepared in each example and comparative example were allowed to rest at 25°C for 2 hours to ensure a constant temperature of 25°C. At 25°C, the battery cells were charged at 1 / 3C to a charge cutoff voltage of 4.25V. Constant voltage charging was then continued at this charge cutoff voltage until the current reached 0.05C, at which point charging was terminated (where C represents the rated capacity of the battery cell). After the battery cell pool was allowed to rest at 25°C for 1 hour, the battery cells were discharged at 0.33C at 25°C to a discharge cutoff voltage of 2.8V. The total discharge energy of the battery cells was recorded as E0.

[0244] Measure the length, width and height of the battery cell and calculate the volume of the battery cell V0 = length × width × height.

[0245] The volume energy density of a battery cell = battery cell discharge energy E0 / battery cell volume V0.

[0246] The battery cells of each embodiment and comparative example were prepared according to the above method. The specific parameters and performances are shown in Tables 1 and 2 below.

[0247] Table 1

[0248]

[0249] By comparing the examples and the comparative examples, it can be seen that by controlling the D V90 The particle size is 16 μm-25 μm, and particles D are set between the positive electrode film layer and the positive electrode current collector. V90 The bottom coating is 3 μm-8 μm, and the positive electrode film layer also includes a carbon nanotube conductive agent. While the battery has a higher energy density, it can improve the problem of burrs on the positive electrode sheets during the slitting process, and at the same time reduce the deterioration of the brittleness of the sheets caused by the addition of the bottom coating, thereby comprehensively improving the safety of the battery.

[0250] Table 2

[0251]

[0252] By comparing Examples 1 and 12 to 16, it can be seen that when the binder content in the positive electrode film layer is 0.7%-1.3%, the adhesion and brittleness of the positive electrode sheet, the DC internal resistance and energy density of the battery are balanced, and the safety and polarization problems that may occur during the battery cycle are further improved.

[0253] Comparison of Examples 1 and 17 shows that lithium manganese iron phosphate as the base coating material is more conducive to improving battery energy density. Comparison of Examples 1 and 18 shows that the nickel-cobalt-manganese ternary material system and the nickel-cobalt-aluminum ternary material system have the potential to achieve higher battery energy density and optimize brittleness.

[0254] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments having substantially the same structure as the technical idea and exerting the same effects are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other methods constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A battery cell comprising a positive electrode plate, characterized in that: The positive electrode sheet includes a positive electrode current collector, a positive electrode film layer disposed on at least one side of the positive electrode current collector, and a primer layer disposed between the positive electrode current collector and at least one side of the positive electrode film layer; the positive electrode film layer includes a positive electrode active material and a positive electrode film layer conductive agent, The D of the particles in the positive electrode film layer V90 The cathode active material includes a lithium-containing transition metal oxide, and the compaction density of the cathode film layer in a fully charged state is 3.40 g / cm 3 -3.60g / cm 3 ; The D of the particles in the base coating V90 The thickness is 3 μm to 8 μm, and the primer layer includes polyanionic particles; The positive electrode film layer conductive agent includes a carbon nanotube conductive agent.

2. The battery cell according to claim 1, wherein: Based on the total mass of the positive electrode film layer, the mass content of the carbon nanotube conductive agent is 0.3%-0.8%.

3. The battery cell according to claim 1, wherein: Based on the total mass of the positive electrode film layer, the mass content of the carbon nanotube conductive agent is 0.4%-0.7%.

4. The battery cell according to claim 1, wherein: The positive electrode film layer further includes a binder. Based on the total mass of the positive electrode film layer, the mass proportion of the binder is 0.6%-1.5%.

5. The battery cell according to claim 4, characterized in that Based on the total mass of the positive electrode film layer, the mass proportion of the binder is 0.7%-1.3%.

6. The battery cell according to claim 1, characterized in that The D of the particles in the base coating V90 4μm-7μm.

7. The battery cell according to claim 1, characterized in that Based on the total molar number of transition metals in the lithium-containing transition metal oxide, the molar proportion of nickel element in the lithium-containing transition metal oxide is 80%-95%.

8. The battery cell according to claim 1, wherein: The positive electrode active material includes a component having the following general formula: Li a Ni x Co y M1 z M2 w O 2-b , 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≤a≤1.2, 0.8≤x≤1, 0 <y≤0.2,0<z≤0.2,0≤w≤0.1,-0.1≤b≤0.1。 9. The battery cell according to claim 1, characterized in that The D of the particles in the positive electrode film layer V50 5μm-12μm, (D V90 -D V10 ) / D V50 0.5-3.

10. The battery cell according to claim 1, characterized in that The positive electrode active material includes single crystal particles and polycrystalline particles, and the mass ratio of the single crystal particles to the polycrystalline particles is 4:6-2:

8.

11. The battery cell according to claim 1, characterized in that The carbon nanotube conductive agent includes one or more of single-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

12. The battery cell according to claim 1, wherein The positive electrode film layer conductive agent further includes a spherical conductive agent, and the spherical conductive agent includes one or more of Super-P, acetylene black, and Ketjen black.

13. The battery cell according to claim 4 or 5, characterized in that: The binder includes a water-based binder.

14. The battery cell according to claim 4 or 5, characterized in that: The adhesive includes at least one of a polyimide adhesive and a polyurethane adhesive.

15. The battery cell according to claim 4 or 5, characterized in that: The binder includes polyvinylidene fluoride.

16. The battery cell according to claim 1, characterized in that The polyanionic particles include components having 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 0.9≤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.

17. The battery cell according to claim 16, characterized in that The polyanion particles include one or more of lithium iron phosphate, lithium manganese phosphate, lithium fluorovanadium phosphate, lithium manganese iron phosphate and modified materials thereof.

18. The battery cell according to claim 16, characterized in that The polyanion particles include one or more of lithium manganese iron phosphate and modified materials thereof.

19. The battery cell according to claim 1, characterized in that The primer layer includes a primer conductive agent, and the primer conductive agent includes one or more of conductive carbon black and carbon nanotubes.

20. The battery cell according to claim 1, characterized in that The thickness of the positive electrode current collector is 7 μm-15 μm.

21. The battery cell according to claim 1, characterized in that The thickness of the primer layer on one side is 5 μm to 25 μm.

22. The battery cell according to claim 1, characterized in that The thickness of the positive electrode film layer on one side is 30 μm-50 μm.

23. A battery device, characterized in that: The battery device includes the battery cell according to any one of claims 1 to 22.

24. An electrical device, characterized in that: The battery cell comprises the battery cell according to any one of claims 1 to 22 or the battery device according to claim 23.

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