A battery cell and its preparation method, a battery device, and an electrical device thereof.

Abstract

This application relates to the field of battery technology, providing a battery cell and its preparation method, a battery device, and an electrical device. The battery cell provided in this application includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode material, a first binder, and a first conductive agent. The first binder has a fibrous structure, and based on the total mass of the positive electrode film layer, the content of the first binder is less than or equal to 1.2 wt%. In the battery cell of this application, the specific surface area of ​​the positive electrode sheet is controlled at a low level while the compaction density is controlled at a high level. This helps to improve the integrity of the positive electrode material, making it less likely for fresh interfaces to be generated due to particle breakage. This significantly suppresses side reactions in the battery, thereby significantly improving the battery's capacity retention rate, resulting in better high-temperature storage performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, and in particular relates to a battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0002] Lithium-ion batteries are widely used in electronic products, electric vehicles, hybrid vehicles, and energy storage systems due to their advantages of high capacity, high energy density, low environmental pollution, and no memory effect. With significant advancements in the battery field, higher performance requirements are being placed on lithium-ion batteries.

[0003] The above statements are for the purpose of providing background information in relation to this application only and do not necessarily constitute prior art. Summary of the Invention

[0004] The purpose of this application is to provide a battery cell and its preparation method, battery device, and power supply device, aiming to solve the problem of unsatisfactory high-temperature storage performance of battery cells.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a battery cell, wherein the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the positive electrode film layer includes a positive electrode material, a first binder and a first conductive agent, the first binder having a fibrous structure; based on the total mass of the positive electrode film layer, the content of the first binder is less than or equal to 1.2 wt%.

[0007] The aforementioned cathode material includes lithium cobalt oxide, and the specific surface area of ​​the cathode sheet is less than or equal to 0.15 m². 2 / g, the compacted density of the positive electrode sheet is greater than or equal to 4 g / cm³. 3 ;or,

[0008] The chemical formula of the above cathode material is LiNi x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 1, and the specific surface area of ​​the positive electrode is less than or equal to 0.3 m². 2 / g, the compacted density of the positive electrode sheet is greater than or equal to 3.4 g / cm³. 3 .

[0009] In the technical solution of this application, the first binder has a fibrous structure. Multiple first binders with fibrous structures interweave and overlap to form a network structure. These network structures can better bind the positive electrode material, thereby promoting close contact between the positive electrode material particles. This close bonding also enhances the connection strength between the positive electrode material particles, which is beneficial to increasing the compaction density of the positive electrode sheet and reducing the specific surface area of ​​the positive electrode sheet.

[0010] The positive electrode sheet has a high compaction density, which means that the contact between the positive electrode material particles in the positive electrode sheet is closer and the bonding force is enhanced. This allows the positive electrode sheet to better withstand the stress generated by volume changes during charging and discharging, thus effectively reducing the breakage of the positive electrode material particles.

[0011] The positive electrode has a low specific surface area, which means that the surface energy of the positive electrode material is low and the chemical activity is weak. This can significantly reduce the risk of side reactions between the positive electrode material and the electrolyte. Moreover, the low specific surface area also means that there are fewer active sites in contact between the positive electrode material and the electrolyte, which can also effectively suppress the occurrence of side reactions.

[0012] Based on this, this application controls the specific surface area of ​​the positive electrode sheet to a low level and its compaction density to a high level. This helps improve the integrity of the positive electrode material, making it less likely for fresh interfaces to form due to particle breakage, i.e., less likely to generate more active sites. Since the surface of the positive electrode material can serve as a site for side reactions between the electrolyte and the positive electrode material, the suppression of changes in active sites significantly suppresses side reactions in the battery, thereby significantly improving the battery's capacity retention rate. This results in better high-temperature storage performance of the battery.

[0013] In some embodiments, the positive electrode material comprises lithium cobalt oxide, and the positive electrode sheet satisfies at least one of the following features (1) to (3):

[0014] (1) The specific surface area of ​​the above positive electrode is 0.1-0.15 m². 2 The compacted density of the above positive electrode sheet is 4–4.3 g / cm³. 3 ;

[0015] (2) The limiting compaction density of the above-mentioned positive electrode sheet is 4.3–4.45 g / cm³. 3 ;

[0016] (3) The above positive electrode film layer has a porous structure with a pore size of 1μm-20μm.

[0017] In lithium cobalt oxide battery systems, controlling the specific surface area, compaction density, and ultimate compaction density of the positive electrode sheet within the aforementioned ranges results in stronger bonding forces between the positive electrode material particles, making them less prone to cracking and pulverization during charging and discharging. This helps improve the integrity of the positive electrode sheet, enabling the battery to maintain good performance during long-term cycling, especially its high-temperature cycling performance.

[0018] The pore size of the pore structure is within the above range, which provides sufficient space inside the positive electrode sheet to buffer the volume change of the positive electrode material caused by the insertion and extraction of active ions, thereby reducing the risk of the positive electrode material breaking. This plays a positive role in improving the integrity of the positive electrode material.

[0019] In some embodiments, the chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6≤x<1, 0<y<0.4, the positive electrode plate satisfies at least one of the following characteristics (1)~(3):

[0020] (1) The specific surface area of ​​the above-mentioned positive electrode sheet is 0.2-0.3 m². 2 The compacted density of the above positive electrode sheet is 3.4–3.85 g / cm³. 3 ;

[0021] (2) The limiting compaction density of the above-mentioned positive electrode sheet is 3.7–3.9 g / cm³. 3 ;

[0022] (3) The above positive electrode film layer has a porous structure with a pore size of 3μm-40μm.

[0023] In ternary cathode material battery systems, controlling the specific surface area, compaction density, and ultimate compaction density of the cathode sheet within the aforementioned ranges means that the cathode material particles are arranged more tightly and orderly. This tight packing effectively reduces the gaps between the cathode material particles, thereby effectively enhancing the mutual support force between them. This tight packing and mutual support between the cathode material particles can effectively disperse the mechanical stress they experience, making the cathode material less prone to cracking and pulverization during charging and discharging. This has a significant positive effect on improving battery safety and long-life cycle life.

[0024] In some embodiments, at least a portion of the positive electrode material is in contact with the first binder.

[0025] The first binder has a fibrous structure. Multiple first binders with fibrous structures interweave and overlap to form a network structure. Due to the good contact between the positive electrode material and the first binder, the positive electrode material is relatively uniformly filled in the network structure. That is, the network structure formed by the fibrous first binder is relatively uniformly distributed in the positive electrode film layer. These network structures can effectively bind the positive electrode material. In other words, the fibrous first binder can wrap around the surface of the positive electrode material particles and wrap the positive electrode material particles from multiple directions, thereby fixing the positive electrode material particles in space within the network. This further promotes close contact between the positive electrode particles. Thus, when the positive electrode material undergoes volume changes due to the insertion and extraction of active ions during charging and discharging, the network structure can limit the outward expansion of the positive electrode material, preventing it from expanding excessively. This means that the positive electrode material is less prone to particle breakage during charging and discharging. Based on this, a fibrous first binder is used to ensure close contact between the cathode material particles. As a result, the cathode material particles are less likely to move or rub against each other under external stress, which effectively reduces the risk of cathode material breakage. In other words, the cathode material is less likely to generate more fresh interfaces, which also significantly suppresses the side reactions of the battery, thereby significantly improving the battery's cycle performance, especially its high-temperature storage performance.

[0026] In some embodiments, at least a portion of the first conductive agent is coated on the surface of the positive electrode material.

[0027] At least a portion of the first conductive agent is tightly attached to the surface of the positive electrode material particles in a continuous or discontinuous form. This is beneficial for the first conductive agent to fully exert its conductivity, making the migration of electrons in the positive electrode material more rapid. This not only improves the charging and discharging rate of the battery, but also reduces the internal resistance of the battery during high-current charging and discharging, thus reducing energy loss.

[0028] In some embodiments, the areal density of the positive electrode film is 0.052-0.260 mg / mm². 2 .

[0029] Within this range of areal density, it means that the positive electrode film can load more active material per unit area, thereby effectively improving the energy density of the battery.

[0030] In some embodiments, the thickness of the positive electrode layer is 50 μm-200 μm.

[0031] By controlling the thickness of the positive electrode film within the aforementioned range, the internal resistance of the battery is reduced, and the changes to the electrode structure caused by the continuous insertion and extraction of active ions during charge and discharge cycles are minimized. As a result, the cycle performance of the battery is effectively improved.

[0032] In some embodiments, based on the total mass of the positive electrode film, the content of the positive electrode material is 97.5 wt%-98.5 wt%, the content of the first binder is 0.6 wt%-1.2 wt%, and the content of the first conductive agent is 0.9 wt%-1.3 wt%.

[0033] By controlling the content of each component within the above range, each component can exert its best performance, giving the positive electrode film better conductivity and adhesion, making the bonding of the positive electrode material more compact, and thus less likely to break during charging and discharging. This can effectively reduce the occurrence of side reactions between the positive electrode material and the electrolyte, thereby improving the high-temperature storage performance of the battery.

[0034] In some embodiments, the first binder includes at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, and sodium carboxymethyl cellulose. These binders can form a fibrous structure, thereby achieving better confinement of the cathode material and reducing the risk of the cathode material breaking during cycling.

[0035] In some embodiments, the first conductive agent includes at least one of a carbon material and a conductive polymer. These conductive agents possess excellent conductivity, effectively reducing the internal resistance of the positive electrode and increasing the electron transport rate.

[0036] In some embodiments, the D50 particle size of the cathode material is 2μm-10μm.

[0037] The D50 particle size of the cathode material is within the above range, which allows the active ions to have a suitable transport path, thereby improving the transport rate of the active ions.

[0038] In some embodiments, the positive electrode sheet further includes a conductive adhesive layer disposed on at least one surface of the positive current collector, and a positive electrode film layer disposed on the surface of the conductive adhesive layer away from the positive current collector.

[0039] The presence of the conductive adhesive layer enables a more stable bond between the positive electrode film and the positive electrode current collector, thereby helping to improve the integrity of the positive electrode sheet.

[0040] In some embodiments, the thickness of the conductive adhesive layer is 0.3 μm to 1.5 μm. Within this thickness range, the conductive adhesive layer can fully utilize its adhesive and conductive properties.

[0041] In some embodiments, the conductive adhesive layer includes a second adhesive and a second conductive agent, wherein the content of the second adhesive is 70wt%-85wt% and the content of the second conductive agent is 15wt%-30wt% based on the total mass of the conductive adhesive layer.

[0042] Controlling the content of the second adhesive and the second conductive agent within the above range is more conducive to the function of each component, so that the conductive adhesive layer has high bonding performance and conductivity.

[0043] Secondly, this application provides a method for preparing a battery cell, comprising the following steps:

[0044] The positive electrode material and the first conductive agent are subjected to a first mixing treatment at 5℃-25℃, then heated to 40℃-60℃ for a second mixing treatment, and then subjected to a first cooling treatment to obtain the first mixture.

[0045] The first mixture and the initial first binder are subjected to a third mixing treatment at 5℃-25℃, then the temperature is raised to 25℃-40℃ for a fourth mixing treatment, then the temperature is raised to 70℃-90℃ for a fifth mixing treatment, and then a second cooling treatment is performed to obtain the second mixture.

[0046] The second mixture is thinned by hot rolling to obtain the positive electrode film layer;

[0047] A positive electrode film layer is disposed on at least one side of the positive electrode current collector to prepare a positive electrode sheet;

[0048] The positive electrode and the negative electrode are assembled to prepare a single battery cell.

[0049] The method for preparing a battery cell provided in this application firstly disperses the first conductive agent and the initial first binder in a stepwise manner, so that the first conductive agent is uniformly dispersed and coats the positive electrode material, and the initial first binder is uniformly dispersed and fully fibrous. Then, the positive electrode film layer is thinned by hot rolling to obtain a self-supporting positive electrode film layer. The positive electrode film layer is then placed on one side of the positive electrode current collector, thereby obtaining a positive electrode sheet with uniform distribution of components, dense stacking of positive electrode material, and small specific surface area. Finally, the positive electrode sheet and the negative electrode sheet are assembled, thereby effectively preparing a battery cell with the performance of the present application as described above.

[0050] In some embodiments, the conditions for the first mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min.

[0051] In some embodiments, the conditions for the second mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 1500 rpm to 2500 rpm, and a time of 5 min to 10 min.

[0052] The conditions of the first mixing process and the second mixing process are controlled within the above range so that the first conductive agent is uniformly dispersed and coated on the surface of the positive electrode material.

[0053] In some embodiments, the conditions for the third mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min.

[0054] In some embodiments, the conditions for the fourth mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 1500 rpm to 2500 rpm, and a time of 5 min to 10 min.

[0055] In some embodiments, the conditions for the fifth mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 3000 rpm to 4000 rpm, and a time of 10 min to 15 min.

[0056] By controlling the conditions of the third, fourth, and fifth mixing processes within the aforementioned range, the first binder is uniformly dispersed and achieves high-quality fibrosis, thereby forming an interlinked network structure in the positive electrode film layer to improve the integrity of the positive electrode material.

[0057] In some embodiments, the conditions for the first cooling process include: a cooling temperature of 5°C to 25°C, a revolution speed of 30 rpm to 50 rpm, and a time of 5 min to 10 min.

[0058] In some embodiments, the conditions for the second cooling process include: a cooling temperature of 5°C to 25°C, a revolution speed of 30 rpm to 50 rpm, and a time of 3 min to 6 min.

[0059] In some embodiments, the conditions for the above-mentioned hot roll thinning include: a roll surface temperature of 90°C-105°C, a linear velocity ratio of the three rolls of 4:7:9-4:9:12, and a gap between adjacent roll shafts of 70μm-500μm.

[0060] A self-supporting positive electrode film layer is formed by using hot roller pressing to thin the mixture obtained by dry mixing.

[0061] In some embodiments, the specific process of disposing the positive electrode film layer on at least one side of the positive electrode current collector is as follows:

[0062] A conductive adhesive layer is formed on at least one surface of the positive current collector;

[0063] The positive electrode film is placed on the surface of the conductive adhesive layer away from the positive electrode current collector, and then composited and cold-pressed to obtain the positive electrode sheet.

[0064] By setting a conductive bonding layer on the surface of the positive electrode current collector, it is beneficial to tightly bond the positive electrode film layer with the positive electrode current collector, thereby obtaining a positive electrode sheet with high structural stability.

[0065] In some embodiments, the temperature of the above composite treatment is 90°C-105°C.

[0066] Under the conditions of this composite treatment, the positive electrode film layer is tightly disposed on the surface of the conductive adhesive layer.

[0067] In some embodiments, the pressure of the cold pressing is 10T-35T.

[0068] Under these cold pressing conditions, a positive electrode sheet with a high compaction density is obtained, thereby improving the energy density of the battery.

[0069] Thirdly, this application provides a battery device including multiple battery cells of the above embodiments.

[0070] Fourthly, this application provides an electrical device, including a battery cell or a battery device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy. Attached Figure Description

[0071] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0072] Figure 1 This is a schematic diagram of the structure of the fifth mixture provided in the embodiments of the present invention / application;

[0073] Figure 2 This is a schematic diagram of the structure of the sixth mixture provided in the embodiments of the present invention / application;

[0074] Figure 3 This is a structural diagram of the mixture provided in the comparative scheme;

[0075] Figure 4 This is an exploded view of the battery device provided in the embodiments of the present invention / application;

[0076] Figure 5 This is an exploded view of a battery cell provided in the embodiments of the present invention / application;

[0077] Figure 6 A schematic diagram of one embodiment of an electrical device that uses a single battery cell as a power source, as described in this application.

[0078] Figure 7 This is a pressure-compaction diagram of the positive electrode sheets prepared in Example 1 and Comparative Example 1;

[0079] Figure 8These are EBSD test images of the positive electrode sheets prepared in Example 1 and Comparative Example 1;

[0080] Figure 9 These are SEM images of the positive electrode sheets prepared in Example 1 and Comparative Example 1.

[0081] The following are the labeling elements in the figure:

[0082] 40. Fifth mixture; 50. Sixth mixture;

[0083] 41. Positive electrode material; 42. First conductive agent; 43. Initial first binder; 44. First binder;

[0084] 100. Battery device;

[0085] 10. Box body; 11. First box body; 12. Second box body;

[0086] 20. Battery cell modules;

[0087] 30. Battery cell, 31. Casing, 32. Electrode assembly, 33. Cover plate. Detailed Implementation

[0088] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0089] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0090] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0091] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0092] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0093] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0094] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0095] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0096] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0097] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0098] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0099] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0100] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0101] In the embodiments of this application, SEI film is short for "solid electrolyte interface", which refers to a solid electrolyte interface film with the characteristics of a solid electrolyte. That is, during the first charge and discharge process of a liquid lithium-ion battery, a passivation layer formed by the reaction between the electrode material and the electrolyte at the solid-liquid interface is formed and covers the surface of the negative electrode material.

[0102] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0103] In this paper, specific surface area refers to the total area of ​​a unit mass of material, which can be tested by nitrogen adsorption method. Specifically, at liquid nitrogen temperature, nitrogen molecules will adsorb on the surface of the positive electrode, forming physical adsorption. When a complete layer of nitrogen molecules is adsorbed on the surface of the positive electrode, the specific surface area of ​​the positive electrode can be obtained by measuring the amount of adsorption.

[0104] In this article, compaction density refers to the mass contained per unit volume, usually calculated by dividing the areal density by the thickness of the material, with units of g / cm³. 3 The following methods can be used for testing:

[0105] For online testing, the thickness of the positive electrode sheet is measured online using laser or X-ray (this thickness does not include the thickness of the positive current collector). In this case, the compaction density of the positive electrode sheet is the areal density of the positive electrode sheet divided by the thickness of the positive electrode sheet. For offline testing, the thickness of the positive electrode sheet is measured using a micrometer or ten-thousand-meter (this thickness does not include the thickness of the positive current collector). In this case, the compaction density of the positive electrode sheet is the areal density of the positive electrode sheet divided by the thickness of the positive electrode sheet.

[0106] In this paper, the ultimate compaction density refers to the density value corresponding to the maximum degree of compaction that a positive electrode sheet can achieve under specific compaction conditions. Typically, by applying a certain amount of pressure, vibration, or other compaction methods to the positive electrode sheet, the compaction density of the positive electrode sheet continuously increases as the compaction process proceeds. When a certain level is reached, no matter how much further the compaction is increased, the compaction density no longer changes significantly. This density is the ultimate compaction density.

[0107] In this article, "area density" refers to the mass per unit area, usually expressed as weight per unit area (e.g., mg / m²). 2 mg / cm 2 mg / mm 2 It is expressed as (). Areal density reflects the weight of active material loaded per unit area in the positive electrode film. The method for testing areal density is as follows:

[0108] Online testing uses beta rays to measure areal density. When beta rays penetrate the positive electrode sheet, some energy is absorbed, and the intensity attenuation of the rays has a negative exponential relationship with the areal density of the target. By detecting the intensity before and after ray penetration, the thickness and areal density of the positive electrode sheet can be estimated. Offline testing uses a stamping machine to obtain a certain number (typically 36) of electrodes with a specific area (typically 1540.25 mm²). 2 The weight of the circular electrode sheet (excluding the weight of the positive current collector) is measured using a high-precision electronic scale. The electrode sheet weight is divided by the electrode sheet area to obtain the electrode sheet surface density.

[0109] In this paper, "D50 particle size" refers to the particle size that, starting from the smallest particle size, represents 50% of the total volumetric particle size distribution. The D50 particle size can be determined by referring to GB / T19077-2016 Particle Size Distribution Laser Diffraction Method, such as using a Malvern 3000 (MasterSizer 3000) laser particle size analyzer.

[0110] In this paper, the pore size of the pore structure can be tested by the following method: obtaining the morphology of the positive electrode cross-section through SEM testing, and measuring the pore size by drawing lines using the SEM scale.

[0111] In this paper, porosity refers to the ratio of the volume of pores in the positive electrode to the total volume of the positive electrode, usually expressed as a percentage. It can be tested using the mercury intrusion porosimetry method. Specifically, mercury does not wet solids, and external pressure must be applied to allow mercury to enter the pores. The greater the external pressure, the smaller the radius of the pore that mercury can enter. By measuring the amount of mercury entering the pores under different external pressures, the pore volume of the corresponding pore size can be determined.

[0112] From a market perspective, the application of power batteries is becoming increasingly widespread, with applications in electric bicycles, electric motorcycles, electric cars, and other electric vehicles. As the application areas of power batteries continue to expand, higher demands are being placed on the lifespan of new energy vehicles under high-temperature conditions. This demand translates into requirements for the high-temperature storage performance of batteries.

[0113] Fully charged batteries are prone to rapid capacity decay under high-temperature storage conditions, leading to a significant reduction in battery life. This is mainly due to the high positive electrode potential and highly reactive electrolyte, resulting in more severe side reactions within the battery. To address this issue, related technologies primarily aim to improve the high-temperature storage performance of fully charged cells by reducing the active sites in the positive electrode material or enhancing the high-temperature performance of the electrolyte. However, most methods have some insurmountable problems. For example, doping or coating the positive electrode material reduces the active sites, thereby reducing side reactions between the positive electrode material and the electrolyte. However, doping or coating the positive electrode material can easily lead to a decrease in specific capacity and an increase in impedance, significantly negatively impacting battery kinetics. Furthermore, the doping and coating processes for raw materials are complex and costly. Another example is reducing the compaction density of the positive electrode sheet to reduce the fragmentation of the positive electrode material particles, thereby reducing the active sites for reaction between the positive electrode material and the electrolyte. However, reducing the compaction density increases the thickness of the positive electrode sheet, significantly deteriorating the battery's energy density. For example, adding electrolyte high-temperature protection additives can preferentially form a passivation film on the surface of positive electrode material particles, reducing side reactions between the electrolyte and the positive electrode material. However, the passivation film formed by the introduction of additives can easily lead to the deterioration of the battery's dynamic performance.

[0114] Based on the above background, this application provides a battery cell that optimizes the positive electrode sheet to achieve a smaller specific surface area and a larger compaction density. This means that there are fewer active sites in the positive electrode sheet that can undergo side reactions with the electrolyte, thereby effectively improving the high-temperature storage performance of the battery cell.

[0115] Typically, a battery cell includes a casing, and electrode assemblies and an electrolyte housed within the casing. The electrode assemblies include a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0116] Next, we will provide a detailed introduction to the positive electrode, negative electrode, separator, and electrolyte components of a single battery cell.

[0117] [Positive electrode plate]

[0118] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode material, a first binder, and a first conductive agent. The first binder has a fibrous structure, and the content of the first binder is less than or equal to 1.2 wt% based on the total mass of the positive electrode film layer.

[0119] The aforementioned positive electrode material includes lithium cobalt oxide, and the specific surface area of ​​the aforementioned positive electrode sheet is less than or equal to 0.15 m². 2 / g, the compacted density of the above positive electrode sheet is greater than or equal to 4 g / cm³. 3 ;or,

[0120] The chemical formula of the above cathode material is LiNi x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 1, and the specific surface area of ​​the above positive electrode is less than or equal to 0.3 m². 2 / g, the compacted density of the above positive electrode sheet is greater than or equal to 3.4 g / cm³. 3 .

[0121] In this article, "fibrous structure" refers to the fibrous morphology of the adhesive, that is, the first adhesive presents a slender fibrous shape, which can be a single fiber or a fiber bundle.

[0122] In the technical solution of this application, the first binder has a fibrous structure. Multiple first binders with fibrous structures interweave and overlap to form a network structure. These network structures can better bind the positive electrode material, thereby promoting close contact between the positive electrode material particles. This close bonding also enhances the connection strength between the positive electrode material particles, which is beneficial to increasing the compaction density of the positive electrode sheet and reducing the specific surface area of ​​the positive electrode sheet.

[0123] Because binders typically have a large specific surface area, under high-temperature full-charge conditions, the large specific surface area of ​​the binder can catalyze side reactions between the positive electrode material and the electrolyte, and between the binder and the electrolyte. Therefore, controlling the content of the first binder to a low level, specifically less than or equal to 1.2 wt%, serves two purposes. First, it allows for the formation of a better network structure in the positive electrode film, thereby increasing the adhesion between the positive electrode material and the first conductive agent. This prevents the positive electrode material from easily detaching or breaking during charging and discharging, effectively improving the structural integrity of the positive electrode sheet and resulting in a higher cycle life for the battery. Second, the low content of the first binder makes the positive electrode sheet less prone to side reactions, allowing the battery to maintain a high capacity during long-term use, thus extending its lifespan.

[0124] The positive electrode material includes lithium cobalt oxide, meaning the battery is a lithium cobalt oxide battery system. In this case, the specific surface area of ​​the positive electrode sheet in the battery system is less than or equal to 0.15 m². 2 / g, the compacted density of the positive electrode sheet is greater than or equal to 4 g / cm³. 3 The chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 1, indicates that the battery is a ternary cathode material battery system. As an example, the cathode material includes, but is not limited to, LiNi. 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.92 Co 0.04 Mn 0.04 O2LiNi 0.96 Co 0.02 Mn 0.02 At least one of O2, where the specific surface area of ​​the positive electrode in the battery system is less than or equal to 0.3 m². 2 / g, the compacted density of the positive electrode sheet is greater than or equal to 3.4 g / cm³.3 This indicates that the positive electrode has a low specific surface area and a high compaction density. The high compaction density means that the contact between the positive electrode material particles is tighter, and the bonding force is stronger. This allows the positive electrode to better withstand the stress generated by volume changes during charging and discharging, effectively reducing the breakage of the positive electrode material particles. The low specific surface area of ​​the positive electrode means that the surface energy of the positive electrode material is lower and its chemical activity is weaker, which significantly reduces the risk of side reactions between the positive electrode material and the electrolyte. Moreover, the lower specific surface area also means that there are fewer active sites in contact with the electrolyte, which also effectively suppresses the occurrence of side reactions.

[0125] Based on this, this application controls the specific surface area of ​​the positive electrode sheet to a low level and its compaction density to a high level. This helps improve the integrity of the positive electrode material, making it less likely for fresh interfaces to form due to particle breakage, i.e., less likely to generate more active sites. Since the surface of the positive electrode material can serve as a site for side reactions between the electrolyte and the positive electrode material, the suppression of changes in active sites significantly suppresses side reactions in the battery, thereby significantly improving the battery's capacity retention rate. This results in better high-temperature storage performance of the battery.

[0126] The aforementioned "positive electrode film layer disposed on at least one side of the positive electrode current collector" means that the positive electrode film layer can be disposed on one side of the positive electrode current collector along its own thickness direction, or it can be disposed on both sides of the positive electrode current collector along its own thickness direction.

[0127] This application does not impose any particular limitation on the positive electrode current collector, as long as it can achieve the purpose of this application. 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 material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0128] In some embodiments, the positive electrode material includes lithium cobalt oxide, in which case the specific surface area of ​​the positive electrode sheet is 0.1-0.15 m². 2 The compacted density of the positive electrode sheet is 4–4.3 g / cm³. 3 .

[0129] As an example, the specific surface area of ​​the positive electrode can be 0.1 m². 2 / g, 0.12m 2 / g, 0.13m2 / g, 0.14m 2 / g, 0.15m 2 / g and other typical but non-restrictive values.

[0130] As an example, the compaction density of the positive electrode sheet can be 4 g / cm³. 3 4.1g / cm 3 4.2g / cm 3 4.3g / cm 3 Typical but not restrictive values.

[0131] In lithium cobalt oxide battery systems, the specific surface area of ​​the positive electrode is within the aforementioned range, meaning that the contact area between the positive electrode and the electrolyte is relatively small. This significantly reduces the occurrence of side reactions between the positive electrode material and the electrolyte. Moreover, the positive electrode with a relatively small specific surface area has higher structural stability because the bonding force between the positive electrode material particles is stronger, making it less prone to cracking and pulverization during charging and discharging. This helps improve the integrity of the positive electrode, enabling the battery to maintain good performance during long-term cycling, especially its high-temperature cycling performance.

[0132] In lithium cobalt oxide battery systems, controlling the compaction density of the positive electrode sheet within the aforementioned range means that more positive electrode material can be accommodated per unit volume of the positive electrode sheet. This allows the battery to store more electrical energy, thereby increasing the battery's volumetric energy density. Furthermore, within this compaction density range, the contact between the positive electrode materials within the positive electrode sheet is tighter, and the bonding force is enhanced. This makes the positive electrode material less prone to breakage during charge and discharge, and less likely to generate fresh interfaces. Consequently, side reactions in the battery are significantly suppressed, improving the battery's cycle performance.

[0133] In addition, the increased contact area between cathode material particles makes the transport path of ions / electrons in the cathode material smoother, and can also significantly reduce the contact resistance during electron transport, thereby improving the charging and discharging efficiency of the battery.

[0134] In some embodiments, the positive electrode active material includes lithium cobalt oxide, in which case the limiting compaction density of the positive electrode sheet is 4.3–4.45 g / cm³. 3 For example, in a lithium cobalt oxide battery system, the limiting compaction density of the positive electrode sheet can be 4.3 g / cm³. 3 4.32 g / cm 3 4.35g / cm 3 4.38g / cm 3 4.4 g / cm 3 4.42 g / cm 3 4.45g / cm 3 Typical but not restrictive values.

[0135] When the ultimate compaction density is reached, the cathode material particles can be considered to have reached their most compact state. At this point, the gaps between the particles are compressed to their limit, meaning there are almost no extra gaps between the cathode material particles that can be compressed further. The higher the ultimate compaction density, the more tightly the cathode material particles can be compressed, resulting in a more densely packed structure. This dense packing structure is beneficial for improving the battery's energy density. Simultaneously, the denser packing of the cathode material also enhances the bonding force between the cathode materials, making them less prone to breakage during battery use, thus contributing to improved long-term cycle stability.

[0136] In some embodiments, the positive electrode active material includes lithium cobalt oxide, and the positive electrode sheet has a porous structure with a pore size of 1μm-20μm.

[0137] As an example, the pore size of the pore structure can be a typical but non-limiting value such as 1μm, 5μm, 10μm, 15μm, 20μm, etc.

[0138] In lithium cobalt oxide battery systems, the pores in the positive electrode sheet can provide a certain buffer space for the volume change of the positive electrode material during battery charging and discharging. Thus, within this pore size range, there is enough space inside the positive electrode sheet to buffer the volume change of the positive electrode material caused by the insertion and extraction of active ions, thereby reducing the risk of positive electrode material breakage. This effectively reduces the structural changes and side reactions of the positive electrode sheet during cycling, thereby improving the cycle life of the battery.

[0139] In some embodiments, the positive electrode active material includes lithium cobalt oxide, in which case the porosity of the positive electrode sheet is 10%-14%.

[0140] As an example, in a lithium cobalt oxide battery system, the porosity of the positive electrode can be a typical but not limiting value such as 10%, 11%, 12%, 13%, or 14%.

[0141] Controlling the porosity of the positive electrode sheet within the above-mentioned range means that the particles of the positive electrode material in the positive electrode sheet are more densely arranged, which is beneficial to improving the compaction density of the positive electrode sheet. That is, it is necessary to further compress the gaps between particles under a smaller external force to achieve the required compaction degree. This can suppress the breakage of the positive electrode material particles, thereby improving the structural integrity of the positive electrode material and the positive electrode sheet, and significantly suppressing side reactions, thus effectively improving the cycle performance of the battery.

[0142] In this application, the presence of a fibrous binder creates an overlapping network structure within the positive electrode film. This network structure provides uniform support for the positive electrode material particles and the first conductive agent, and restricts the distribution of the active material and the first conductive agent, resulting in a more uniform distribution of the components within the positive electrode film. This, in turn, promotes a more uniform distribution of pores within the positive electrode sheet. This relatively uniform pore structure leads to more even stress distribution on the positive electrode sheet, reducing the likelihood of localized stress concentration. Consequently, the positive electrode material is less prone to particle breakage, effectively suppressing side reactions and resulting in higher cycle performance of the battery.

[0143] In some embodiments, the chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 0.4, the specific surface area of ​​the positive electrode is 0.2-0.3 m² / g. 2 The compacted density of the positive electrode sheet is 3.4–3.85 g / cm³. 3 .

[0144] For example, in a ternary cathode material battery system, the specific surface area of ​​the cathode sheet can be 0.2 m². 2 / g, 0.22m 2 / g, 0.23m 2 / g, 0.24m 2 / g, 0.25m 2 / g, 0.26m 2 / g, 0.28m 2 / g, 0.3m 2 / g and other typical but non-restrictive values.

[0145] As an example, in a ternary cathode material battery system, the compaction density of the cathode sheet can be 3.4 g / cm³. 3 3.5g / cm 3 3.6g / cm 3 3.7g / cm 3 3.8g / cm 3 3.85g / cm 3 Typical but not restrictive values.

[0146] In ternary cathode material battery systems, the specific surface area and compaction density of the cathode sheet are within the aforementioned range, which means that the contact area between the cathode sheet and the electrolyte is relatively small. This can significantly reduce the occurrence of side reactions between the cathode material and the electrolyte, and the contact between the cathode materials is tighter, and the bonding force between the cathode material particles is significantly enhanced. As a result, the cathode material is not easy to break during charging and discharging, and it is not easy to generate fresh interfaces. This allows the battery to maintain good performance during long-term cycling, especially the high-temperature cycling performance of the battery.

[0147] In some embodiments, the chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 0.4, the limiting compaction density of the positive electrode sheet is 3.7–3.9 g / cm³. 3 .

[0148] For example, in a ternary cathode material battery system, the ultimate compaction density of the cathode sheet can be 3.7 g / cm³. 3 3.75g / cm 3 3.8g / cm 3 3.85g / cm 3 3.9g / cm 3 Typical but not restrictive values.

[0149] In a ternary cathode material battery system, the ultimate compaction density of the cathode sheet is within the above range, which means that the cathode material particles can be stacked in a more compact manner. This makes the bonding between the cathode material particles tighter and the bonding force between the particles higher. As a result, it can better resist the stress caused by volume changes during battery cycling, reduce the pulverization and shedding of the cathode material, and thus improve the cycle life of the battery.

[0150] In some embodiments, the chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6≤x<1, 0<y<0.4, at this time, the positive electrode plate has a porous structure with a pore size of 3μm-40μm.

[0151] For example, in a ternary cathode material battery system, the pore size can be typical but not limiting values ​​such as 3μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, and 40μm.

[0152] In some embodiments, at least a portion of the positive electrode material is in contact with the first binder.

[0153] In one embodiment, the fibrous binder forms a mesh structure that can wrap around and encapsulate the positive electrode material particles, which makes the bonding force between the positive electrode material particles higher and the contact tighter, thereby effectively suppressing the positive electrode material from cracking or falling off due to volume changes during charging and discharging.

[0154] In another embodiment, the fibrous structure of the binder can be interwoven into the gaps between the positive electrode material particles, filling the voids and effectively reducing the porosity and specific surface area of ​​the positive electrode sheet. Moreover, this tight physical bond also enhances the connection strength between the positive electrode material particles, thus effectively reducing the problem of relative movement and friction of the positive electrode material under external stress, and also effectively reducing the risk of positive electrode material breakage.

[0155] The first binder with a fibrous structure can form a fibrous network structure, that is, multiple first binders with fibrous structures interlock and overlap to form a network structure. Due to the good contact between the positive electrode material and the first binder, the positive electrode material is relatively uniformly filled in this network structure; that is, the network structure formed by the fibrous first binder is relatively uniformly distributed in the positive electrode film layer. On the one hand, this network structure can relatively uniformly distribute the external forces it receives throughout the entire positive electrode area. In other words, the external forces acting on the positive electrode sheet, such as the stress generated by volume changes during charging and discharging, and external mechanical pressure, can be effectively dispersed by this network structure, making the positive electrode sheet less prone to stress concentration, thereby reducing the breakage of the positive electrode material and the peeling of the positive electrode film layer. On the other hand, the mesh structure can effectively bind the positive electrode material, which means that the mesh structure formed by the fibrous binder can be tightly bonded to the positive electrode material, thereby reducing the gaps between the positive electrode particles. This results in the positive electrode sheet having a smaller porosity and a lower specific surface area. At the same time, this tight bonding also enhances the connection strength between the positive electrode material particles, making it less likely for the positive electrode material particles to move relative to each other and rub against each other under external stress, further reducing the risk of the positive electrode material breaking and effectively improving the structural integrity of the positive electrode sheet under stress.

[0156] Based on this, since the first binder has a fibrous structure, the positive electrode sheet is less prone to stress concentration, which helps to improve the integrity of the positive electrode material. This makes it less likely for the positive electrode material to generate fresh interfaces due to particle breakage, thereby significantly suppressing the side reactions of the battery. As a result, the battery exhibits better cycle performance, especially high-temperature storage performance.

[0157] In some embodiments, at least a portion of the first conductive agent is coated on the surface of the positive electrode material.

[0158] At least a portion of the first conductive agent is tightly attached to the surface of the positive electrode material particles in a continuous or discontinuous form. This is beneficial for the first conductive agent to fully exert its conductivity, making the migration of electrons in the positive electrode material more rapid. This not only improves the charging and discharging rate of the battery, but also reduces the internal resistance of the battery during high-current charging and discharging, thus reducing energy loss.

[0159] In some embodiments, the areal density of the positive electrode film is 0.052-0.260 mg / mm². 2 For example, the areal density of the positive electrode film can be 0.052 mg / mm². 2 0.1 mg / mm 2 0.15 mg / mm 2 0.194 mg / mm 2 0.26 mg / mm 2 Typical but not restrictive values.

[0160] Controlling the areal density within this range means, on the one hand, that the positive electrode film can load more active material per unit area, thereby effectively improving the energy density of the battery; on the other hand, it helps maintain the structural stability of the positive electrode during the charging and discharging process, making it less likely for the positive electrode to experience stress concentration due to volume changes during cycling, thus having a positive effect on the battery's capacity and cycle life.

[0161] In some embodiments, the thickness of the positive electrode film is 50 μm-200 μm. For example, the thickness of the positive electrode film can be a typical but non-limiting value such as 50 μm, 100 μm, 150 μm, or 200 μm.

[0162] By controlling the thickness of the positive electrode film within the aforementioned range, the internal resistance of the battery is reduced, and the changes to the electrode structure caused by the continuous insertion and extraction of active ions during charge and discharge cycles are minimized. As a result, the cycle performance of the battery is effectively improved.

[0163] In some embodiments, based on the total mass of the positive electrode film, the content of the positive electrode material is 97.5 wt%-98.5 wt%, the content of the first binder is 0.6 wt%-1.2 wt%, and the content of the first conductive agent is 0.9 wt%-1.3 wt%.

[0164] As an example, the content of the cathode material can be typical but not limiting values ​​such as 97.5 wt%, 97.8 wt%, 98 wt%, 98.2 wt%, and 98.5 wt%.

[0165] As an example, the content of the first binder can be typical but not limiting values ​​such as 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.1wt%, 1.2wt%.

[0166] As an example, the content of the first conductive agent can be a typical but non-limiting value such as 0.9wt%, 1wt%, 1.1wt%, 1.2wt%, 1.3wt%.

[0167] Controlling the content of the cathode material within the aforementioned range means that more lithium ions or active materials participating in electrochemical reactions can be stored in the same volume or mass of the cathode sheet. This results in a higher battery capacity, effectively increasing the battery's energy density. Simultaneously, a higher content of cathode material allows for a more compact structure, making the cathode material less prone to breakage due to volume changes during cycling. This effectively suppresses changes in the active sites of the cathode material, thereby improving the battery's cycle stability, particularly its high-temperature storage performance.

[0168] Conductive agents typically have a large specific surface area. Under high-temperature, full-charge conditions, these large surface areas can catalyze side reactions between the positive electrode material and the electrolyte, and between the conductive agent and the electrolyte. Therefore, controlling the content of the first conductive agent within the aforementioned range can effectively reduce the specific surface area of ​​the positive electrode, thus helping to suppress internal side reactions and significantly improving cycle life and safety. Furthermore, the network structure formed by the fibrous first binder provides effective physical support for the first conductive agent, allowing the conductive agent particles to adhere to the surface of the fibrous binder. Simultaneously, the network structure tightly wraps around the conductive agent particles, effectively preventing agglomeration and sedimentation. This results in a more uniform distribution of the first conductive agent within the positive electrode, contributing to the construction of an effective conductive network, fully utilizing its conductivity, and improving electron transport rates.

[0169] Binders typically have a large specific surface area. Under high-temperature, full-charge conditions, this large surface area often catalyzes side reactions between the cathode material and the electrolyte, as well as between the binder and the electrolyte. Therefore, controlling the content of the first binder within the aforementioned range allows for the formation of a better network structure in the cathode film, thereby increasing the adhesion between the cathode material and the first conductive agent. This makes the cathode material less prone to detachment or breakage during charging and discharging, effectively improving the structural integrity of the cathode sheet and resulting in a higher cycle life for the battery.

[0170] Therefore, by controlling the content of each component within the above range, the components can synergistically enhance each other and exert better performance, giving the positive electrode sheet higher structural integrity and better electron transport rate. In this way, the positive electrode material is not easy to break, and the side reactions between the positive electrode material and other components and the electrolyte can be effectively suppressed, thereby significantly improving the battery's service life, especially the battery's high-temperature storage performance.

[0171] In some embodiments, the first binder includes at least one selected from polytetrafluoroethylene, polyvinylidene fluoride, and sodium carboxymethyl cellulose. These binders can form a good fibrous structure, thereby achieving better confinement of the cathode material and reducing the risk of the cathode material breaking during cycling.

[0172] In some embodiments, the first conductive agent comprises at least one of a carbon material and a conductive polymer. These conductive agents exhibit excellent conductivity, reducing the internal resistance of the positive electrode and increasing the electron transport rate.

[0173] As an example, carbon materials include, but are not limited to, at least one of artificial graphite, natural graphite, carbon black, carbon nanotubes, and vapor-grown carbon fibers.

[0174] As an example, the conductive polymer includes at least one of polyaniline, polypyrrole, polythiophene, polyphenylenevinylene, and polyacetylene.

[0175] In some embodiments, the D50 particle size of the cathode material is 2μm-10μm.

[0176] As an example, the D50 particle size of the cathode material can be a typical but non-limiting value such as 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm.

[0177] Controlling the D50 particle size of the cathode material within the aforementioned range ensures that active ions have suitable transport paths, thereby increasing their transport rate. Furthermore, the fibrous first binder forms a network structure that effectively binds the cathode material. This network structure restricts the outward expansion of the cathode material during charging and discharging due to the insertion and extraction of active ions, preventing excessive expansion and thus reducing the likelihood of breakage. This suppresses side reactions, resulting in higher high-temperature storage performance of the battery.

[0178] In some embodiments, in the electron backscatter diffraction (EBSD) test of the positive electrode, the KAM value is 2, and the corresponding Counts ≤ 250.

[0179] KAM is an abbreviation for Kernel Average Misorientation, a parameter used to characterize the local orientation difference or degree of plastic deformation in a material. The KAM value is obtained by calculating the average orientation deviation between a point and its surrounding neighbors. In other words, by calculating the number of sites with local orientation deviations in the positive electrode sheet, it can reflect whether there is significant local stress on the surface of the positive electrode sheet. A higher KAM value indicates a larger local deviation; under a given KAM value, a higher number of such sites means there are more deviation sites. Therefore, in the technical solution of this application, the local deviation of the positive electrode sheet is small, meaning that local stress concentration is less likely to occur.

[0180] In some embodiments, the positive electrode sheet further includes a conductive adhesive layer disposed on at least one surface of the positive current collector, and a positive electrode film layer disposed on the surface of the conductive adhesive layer away from the positive current collector.

[0181] The conductive adhesive layer has good conductivity, which can form a continuous and good conductive path between the positive electrode film and the positive electrode current collector. This helps to reduce the internal resistance of the positive electrode and improve the charge and discharge efficiency and rate performance of the battery.

[0182] The conductive adhesive layer has a high bonding ability, which can firmly bond the positive electrode film and the positive electrode current collector together. This helps to improve the mechanical strength and structural stability of the positive electrode sheet, making the positive electrode film less likely to fall off or break during charging and discharging, thereby extending the battery's service life.

[0183] In some embodiments, the thickness of the conductive adhesive layer is 0.3 μm-1.5 μm. As an example, the thickness of the conductive adhesive layer can be a typical but non-limiting value such as 0.3 μm, 0.5 μm, 1.0 μm, or 1.5 μm.

[0184] Within this thickness range, its conductivity and adhesion properties can be fully utilized, not only constructing a continuous and uniform conductive path between the positive electrode current collector and the positive electrode film layer, but also firmly bonding the positive electrode film layer and the positive electrode current collector together, thereby improving the integrity of the positive electrode sheet.

[0185] In some embodiments, the conductive adhesive layer includes a second adhesive and a second conductive agent, wherein the content of the second adhesive is 70wt%-85wt% and the content of the second conductive agent is 15wt%-30wt% based on the total mass of the conductive adhesive layer.

[0186] For example, the content of the second adhesive can be typical but not limiting values ​​such as 70wt%, 72wt%, 75wt%, 78wt%, 80wt%, 85wt%.

[0187] For example, the content of the second conductive agent can be typical but not limiting values ​​such as 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%.

[0188] Controlling the content of the second adhesive and the second conductive agent within the above range is more conducive to the function of each component, so that the conductive adhesive layer has high bonding performance and conductivity.

[0189] In some embodiments, the second conductive agent comprises a carbon material. As an example, the carbon material includes, but is not limited to, at least one of conductive carbon, carbon nanotubes, activated carbon, Ketjen black, acetylene black, graphene, graphite sheets, graphite particles, carbon fibers, and intermediate carbon microspheres.

[0190] These conductive agents have good conductivity and can form a good conductive network between the positive electrode current collector and the positive electrode film, so that the positive electrode has high electronic conductivity.

[0191] In some embodiments, the second adhesive includes, but is not limited to, at least one of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, polyacrylate, silicone resin, epoxy resin, polyurethane, phenolic resin, polyimide resin, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, and acrylonitrile multi-component copolymer.

[0192] These adhesives have good bonding ability and can firmly bond the positive electrode film layer to the surface of the positive electrode current collector, thereby improving the integrity of the positive electrode sheet.

[0193] [Negative electrode plate]

[0194] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The aforementioned "negative electrode film layer disposed on at least one surface of the negative current collector" means that the negative electrode film layer can be disposed on one surface of the negative current collector along its own thickness direction, or it can be disposed on two surfaces of the negative current collector along its own thickness direction.

[0195] This application does not impose any particular limitation on the negative electrode current collector, as long as it achieves the purpose of this application. 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 material base film and a metal layer formed on at least one side of the polymer material 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, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art.

[0196] In some embodiments, the negative electrode film layer contains a negative electrode active material, which may include negative electrode active materials known in the art for use in batteries. 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, and lithium titanate, etc. However, this application is not limited to these materials, and other conventional 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.

[0197] In some embodiments, the negative electrode film layer may optionally include an adhesive. As an example, the adhesive in the negative electrode film layer 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).

[0198] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent in the negative electrode film may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0199] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0200] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0201] [Septum]

[0202] The separator is used to separate the positive electrode and the negative electrode to prevent short circuits inside the secondary battery, allow electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process.

[0203] This application does not impose any particular restrictions on the diaphragm, as long as it can achieve the purpose of this application, any well-known porous diaphragm with good chemical and mechanical stability can be selected.

[0204] In some embodiments, the diaphragm material may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The diaphragm may be a single-layer film or a multi-layer composite film, without particular limitation. When the diaphragm is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0205] [Electrolytes]

[0206] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0207] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0208] Taking lithium-ion batteries as an example, 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0209] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0210] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0211] The second aspect of this application provides a method for preparing a battery cell, comprising the following steps:

[0212] Step S10: The positive electrode material and the first conductive agent are subjected to a first mixing treatment at 5℃-25℃, then heated to 40℃-60℃ for a second mixing treatment, and then subjected to a first cooling treatment to obtain the first mixture.

[0213] The first mixture and the initial first binder are subjected to a third mixing treatment at 5℃-25℃, then the temperature is raised to 25℃-40℃ for a fourth mixing treatment, then the temperature is raised to 70℃-90℃ for a fifth mixing treatment, and then a second cooling treatment is performed to obtain the second mixture.

[0214] Step S20: The second mixture is thinned by hot rolling to obtain the positive electrode film layer;

[0215] Step S30: The positive electrode film layer is disposed on at least one side of the positive electrode current collector to prepare the positive electrode sheet;

[0216] Step S40: Assemble the positive electrode and the negative electrode to prepare a single battery cell.

[0217] The method for preparing a battery cell provided in this application firstly disperses the first conductive agent and the initial first binder in a stepwise manner, so that the first conductive agent is uniformly dispersed and coats the positive electrode material, and the initial first binder is uniformly dispersed and fully fibrous. Then, the positive electrode film layer is thinned by hot rolling to obtain a self-supporting positive electrode film layer. Then, the self-supporting positive electrode film layer is placed on one side of the positive electrode current collector, thereby obtaining a positive electrode sheet with uniform distribution of each component, dense stacking of positive electrode material, and small specific surface area. Finally, the positive electrode sheet and the negative electrode sheet are assembled, thereby effectively preparing a battery cell with the performance of the present application as described above.

[0218] In some embodiments, in step S10, the first conductive agent and the initial first binder are dispersed in a stepwise manner, specifically: firstly, the positive electrode material and the first conductive agent are macroscopically mixed at room temperature, and then, under medium-high temperature conditions, the diffusion rate is enhanced by temperature conditions to increase the interfacial contact between the positive electrode material and the first conductive agent, so that the first conductive agent is uniformly dispersed and coated on the surface of the positive electrode material. Then, a cooling treatment is performed to suppress the agglomeration of the second mixture particles. Next, the initial first binder is added to premix the components. Then, under conditions of 25℃-40℃, the unfibrillated initial first binder is adhered to the surface of the positive electrode material particles and the first conductive agent particles. Under conditions of 70℃-90℃, the mixing treatment is continued to allow the initial first binder to fully fibrillate to form a first binder with a good fiber structure, thereby promoting the close packing of the positive electrode material particles. Finally, a cooling treatment is performed to make the sixth mixture particles less prone to agglomeration, thus obtaining a mixture with more uniform dispersion of each component.

[0219] In this article, "revolutionary speed" refers to the speed at which the entire stirring device rotates around a central axis. During the stirring process, the stirring container is usually stationary, while the stirring device revolves through mechanical transmission or other means. This revolving motion allows the stirring paddle to cover a larger area within the container, thereby achieving more uniform mixing of the materials.

[0220] In this application, the revolution speed refers to the rotational speed of the stirring rotor in the mixing device, such as the stirring rotor speed of a double planetary mixer.

[0221] In this article, "rotation speed" refers to the speed at which the agitator rotates around its axis. The rotation of the agitator is the primary means of shearing, mixing, and dispersing materials. The magnitude of the rotation speed directly affects the intensity of the agitator's action on the materials.

[0222] In this application, the rotation speed refers to the rotation speed of the material dispersion device in the mixing equipment, such as the dispersion disc speed of a double planetary mixer.

[0223] In some embodiments, in step S11, the conditions for the first mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min.

[0224] By controlling the conditions of the first mixing process within the above range, the positive electrode material and the first conductive agent are premixed, that is, the positive electrode material particles and the first conductive agent particles are fully dispersed on a macroscopic scale, so that the positive electrode material and the first conductive agent are macroscopically uniformly mixed.

[0225] In some embodiments, in step S12, the conditions for the second mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 1500 rpm to 2500 rpm, and a time of 5 min to 10 min.

[0226] Under the conditions of the second mixing treatment, the molecular thermal motion intensifies, and the diffusion rate of the positive electrode material and the first conductive agent particles accelerates. This helps the first conductive agent to better penetrate into the interparticle gaps of the positive electrode material, achieving a more uniform mixture. For example, the first conductive agent can more fully coat the positive electrode material particles, forming a good conductive network.

[0227] In some embodiments, in step S13, the conditions for the first cooling process include: a cooling temperature of 5°C to 25°C, a revolution speed of 30 rpm to 50 rpm, and a time of 5 min to 10 min.

[0228] The uniformly mixed positive electrode material and the first conductive agent are cooled slowly to prevent particle agglomeration in the second mixture, thus providing a basis for the uniform mixing of the first binder.

[0229] In some embodiments, in step S14, the conditions for the third mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min.

[0230] Under room temperature conditions, the initial first binder, the first conductive agent, and the positive electrode material are macroscopically mixed, that is, the positive electrode material particles, the first conductive agent particles, and the initial first binder are fully dispersed on a macroscopic scale.

[0231] In some embodiments, in step S15, the conditions for the fourth mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 1500 rpm to 2500 rpm, and a time of 5 min to 10 min.

[0232] Under certain temperature conditions, such as 25℃-40℃, the diffusion rate of each component can be increased. Then, under shear force conditions of 1500rpm-2500rpm, the initial first binder can be further dispersed, which effectively increases the specific surface area of ​​the initial first binder, thereby enabling it to better contact with the cathode material and the first conductive agent, improving the bonding effect. Moreover, smaller particles of the initial first binder are more likely to be evenly distributed between the cathode material and the first conductive agent, thus achieving better macroscopic uniform mixing.

[0233] In some embodiments, in step S16, the conditions for the fifth mixing process include: a revolution speed of 30 rpm to 50 rpm, a rotation speed of 3000 rpm to 4000 rpm, and a time of 10 min to 15 min.

[0234] Under shear force of 3000-4000 rpm, the initial first binder particles are broken into smaller particles, increasing their dispersion and further improving their contact area with the positive electrode material and the first conductive agent. Furthermore, under this shear force, the molecular chains of the initial first binder are gradually elongated and oriented, beginning to form a preliminary fibrous morphology. With continued shear force, the fibrous structure continuously develops and improves. Controlling the temperature of the fifth mixing process at 70℃-90℃ increases the fluidity of the initial first binder, making the molecular chains easier to move and align. Thus, the initial first binder molecules can better respond to shear force, forming a high-quality fibrous structure.

[0235] In some embodiments, the conditions for the second cooling process include: a cooling temperature of 5°C to 25°C, a revolution speed of 30 rpm to 50 rpm, and a time of 3 min to 6 min.

[0236] The sixth mixture, which has formed a high-quality fiber structure, is cooled slowly to prevent particle agglomeration.

[0237] In some embodiments, the conditions for the above-mentioned hot roll thinning include: a roll surface temperature of 90°C-105°C, a linear velocity ratio of the three rolls of 4:7:9-4:9:12, and a gap between adjacent roll shafts of 70μm-500μm.

[0238] The hot roll forming method is used to form a self-supporting positive electrode film layer from the dry-mixed materials. By adjusting parameters such as the temperature of the roll surface, the linear speed and the roll spacing, not only can the positive electrode film layer be fine-tuned, but it also helps to improve the consistency and performance stability of the battery and reduce local performance differences caused by uneven thickness.

[0239] Please see Figure 1 , Figure 1 As an example, the structural diagram of the initial mixture of the first binder, the first conductive agent, and the positive electrode material is shown below. Specifically, the structural diagram of the fifth mixture 40 after step S15 is shown below. Figure 1 As shown. Figure 1 In the mixture 40, the fifth mixture includes a positive electrode material 41, a first conductive agent 42 and an initial first binder 43. At this time, the first conductive agent 42 is uniformly distributed in the interparticle gaps of the positive electrode material 41, and the initial first binder 43 is uniformly distributed in the interparticle gaps of the positive electrode material 41. That is, the positive electrode material 41, the first conductive agent 42 and the initial first binder 43 are in a relatively uniform distribution state.

[0240] Please see Figure 2 , Figure 2 As an example, the structural diagram of the initial first adhesive after fiberization, i.e., the structural diagram of the sixth mixture 50 after step S16, is shown below. Figure 2 As shown. In step S16, the initial first adhesive 43 is fiberized to form a first adhesive 44 with a fibrous structure. Figure 2 In the mixture 50, the sixth mixture includes a positive electrode material 41, a first conductive agent 42 and a first binder 44. At this time, the first conductive agent 42 is uniformly distributed in the interparticle gaps of the positive electrode material 41, and the first binder 44 overlaps with each other to form a mesh structure. The positive electrode material 41 and the first conductive agent 42 are relatively uniformly filled in the mesh structure.

[0241] Based on this, this application uses a stepwise dispersion method for the first conductive agent and the first binder, combined with a specific dispersion temperature, to make the first conductive agent uniformly dispersed and coated on the surface of the positive electrode material, and the initial first binder can undergo high-quality fiberization to form a network structure, which promotes the close packing of the positive electrode material particles, thus obtaining a mixture in which the components are more uniformly dispersed.

[0242] In contrast, if the positive electrode material, the first conductive agent, and the initial first binder are mixed according to the following comparative scheme:

[0243] The positive electrode material and the first conductive agent were mixed and treated for 5 minutes at a temperature of 5℃-25℃ and a rotation speed of 30rpm-50rpm. Then, the initial first binder was added and the mixture was treated for 5 minutes at a temperature of 5℃-25℃ and a rotation speed of 30rpm-50rpm. Subsequently, the mixture was treated for 30 minutes at a temperature of 90℃-105℃, a rotation speed of 30rpm-50rpm, and a rotation speed of 3000rpm-4000rpm. Finally, the mixture was cooled for 5 minutes at a temperature of 5℃-25℃ and a rotation speed of 30rpm-50rpm to obtain the mixture.

[0244] In the aforementioned comparative schemes, the dispersion process of the initial first binder and the first conductive agent is simply completed in one step, making it difficult for the first conductive agent and the initial first binder to be sufficiently and uniformly dispersed. Furthermore, using a high temperature of 90-105℃, the first conductive agent, due to its large specific surface area, is prone to agglomeration and difficult to disperse. At this temperature, the initial first binder is also close to its glass transition temperature, resulting in the inability to form a high-quality fibrous structure. A schematic diagram of the mixture is shown below. Figure 3 As shown. Figure 3 -A is a schematic diagram of the structure of the initial first binder before it undergoes fibrosis after the positive electrode material, the first conductive agent, and the initial first binder are mixed. Figure 3 -B is a schematic diagram of the structure after the initial first adhesive 43 has been fiberized. From Figure 3 As can be seen, the distribution uniformity of the first conductive agent 42 is poor, and the distribution uniformity of the initial first binder 43 is also poor. As a result, even if the initial first binder 43 forms a fibrous structure first binder 44, it cannot effectively promote the formation of a dense distribution of the positive electrode material 41. Furthermore, the fibrous structure first binder 44 is not easy to form a network structure in the entire positive electrode sheet, and it is easy to form a local cluster structure.

[0245] In some embodiments, the specific process of disposing the positive electrode film layer on at least one surface of the positive electrode current collector is as follows:

[0246] A conductive adhesive layer is formed on at least one surface of the positive current collector;

[0247] The positive electrode film is placed on the surface of the conductive adhesive layer away from the positive electrode current collector, and then composited and cold-pressed to obtain the positive electrode sheet.

[0248] By setting a conductive bonding layer on the surface of the positive electrode current collector, it is beneficial to tightly bond the positive electrode film layer with the positive electrode current collector, thereby obtaining a positive electrode sheet with high structural stability.

[0249] In some embodiments, the specific process of forming a conductive adhesive layer on at least one surface of the positive current collector is as follows:

[0250] The second binder and the second conductive agent are dispersed in a solvent to form a conductive adhesive slurry, which is then coated on at least one surface of the positive electrode current collector to form a conductive adhesive layer.

[0251] Specifically, the selection of the second adhesive and the second conductive agent is as described above, and will not be repeated here.

[0252] Specifically, the solvent includes at least one of deionized water, ethanol, acetone, N-methylpyrrolidone, N-dimethylacetamide, and N-dimethylformamide.

[0253] Specifically, the solid content of the conductive adhesive paste is 20% to 40%.

[0254] In some embodiments, the temperature of the above composite treatment is 90°C-105°C.

[0255] Under the conditions of this composite treatment, the positive electrode film layer is tightly disposed on the surface of the conductive adhesive layer.

[0256] In some embodiments, the pressure of the above-mentioned cold pressing process is 10T-35T.

[0257] Under these cold-pressing conditions, a positive electrode sheet with a higher compaction density is obtained, thereby improving the energy density of the battery.

[0258] A third aspect of this application provides a battery device comprising a plurality of battery cells described in the above embodiments.

[0259] The battery device mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0260] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0261] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0262] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cell assemblies housed within the housing.

[0263] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0264] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0265] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0266] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0267] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0268] A fourth aspect of this application provides an electrical device, including a battery cell or a battery device as described in the above embodiments, wherein the battery cell or battery device is used to store or provide electrical energy.

[0269] The technical solutions described in the embodiments of this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft.

[0270] The following description, with appropriate reference to the accompanying drawings, describes the battery cell, battery device, and power consumption device provided in the embodiments of this application.

[0271] Figure 4 This is an exploded view of a battery device 100 as an example. The battery device 100 includes a housing 10 and battery cell assemblies 20, with the battery cell assemblies 20 housed within the housing 10. The housing 10 provides a space for housing the battery cell assemblies 20 and can have various structures. In some embodiments, the housing 10 may include a first housing 11 and a second housing 12, which overlap each other, collectively defining a closed space for housing the battery cell assemblies 20. Of course, the housing 10 formed by the first housing 11 and the second housing 12 can have various shapes, such as a cylinder, a cuboid, etc. Multiple battery cell assemblies 20 can be arranged in any manner within the battery housing.

[0272] In the battery device 100, there can be one or more battery cell components 20. Multiple battery cell components 20 can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cell components 20 are connected in both series and parallel. Multiple battery cell components 20 can be directly connected in series, parallel, or in a mixed manner, and then the whole formed by multiple battery cell components 20 is housed in the housing 10. Of course, the battery device 100 can also be formed by first connecting multiple battery cell components 20 in series, parallel, or in a mixed manner to form a battery module, such as a battery module or battery pack. Multiple battery modules are then connected in series, parallel, or in a mixed manner to form a whole and housed in the housing 10.

[0273] Battery cell assembly 20 includes multiple battery cells 30. Figure 5 This is an exploded view of a single battery cell 30 as an example. The single battery cell 30 includes a housing 31, a cover plate 33, an electrode assembly 32, and other functional components.

[0274] The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 is a hollow structure with an opening at one end, and the housing 31 is used to cooperate with the cover plate 33 to form an internal environment for accommodating the electrode assembly 32, electrolyte, and other functional components. The housing 31 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined according to the specific shape and size of the electrode assembly 32. The material of the housing 31 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here. The cover plate 33 is a component that covers the opening of the housing 31 to isolate the internal environment of the battery cell 30 from the external environment. The material of the cover plate 33 can be, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and is not limited here.

[0275] Figure 6 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0276] Example

[0277] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0278] Lithium cobalt oxide battery system

[0279] Example 1

[0280] This embodiment provides a single battery cell.

[0281] [Preparation of the positive electrode sheet]

[0282] The preparation method of the positive electrode sheet includes the following steps:

[0283] Step 1: Weigh out the positive electrode material (lithium cobalt oxide, D50 particle size of 6μm), conductive agent (conductive carbon SP and conductive carbon nanotubes CNT in a mass ratio of 7:6) and binder (polytetrafluoroethylene PTFE) in a mass ratio of 97.5:1.3:1.2.

[0284] Step 2: Add the positive electrode material and conductive agent to a double planetary mixer and mix for 2 minutes at 20°C and a stirring bar speed of 50 rpm; then mix for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disc speed of 2000 rpm; finally, cool for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0285] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0286] Step 3: The mixture is heated by three rollers to gradually decrease the self-supporting positive electrode film layer to the target areal density. The roller surface temperature is 100℃, the linear speed ratio of the three rollers is 3:5:12, and the gap between each roller is adjusted according to the actual target areal density (range 100μm).

[0287] Step 4: Form a 0.5 μm thick conductive adhesive layer on both surfaces of the positive electrode current collector aluminum foil (9 μm thick). Then, place the self-supporting positive electrode film layer on the surface of the conductive adhesive layer and laminate it at 100°C. After cold pressing and cutting, a surface density of 0.0194 g / cm³ is finally obtained. 2 The compaction density is 4.2 g / cm³. 3 The positive electrode sheet.

[0288] [Preparation of the negative electrode sheet]

[0289] Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose binder, and water solvent were mixed in a weight ratio of 95:2:3:100 and stirred until the system was homogeneous to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both surfaces of a 6 μm thick copper foil current collector to form a negative electrode film. After cold pressing, slitting, and cutting (5 cm x 5 cm) into sheets, a negative electrode sheet was obtained with a compaction density of 1.75 g / cm³. 3 .

[0290] [Septum]

[0291] The separator includes a base membrane, which has a first surface and a second surface disposed opposite to each other along its thickness direction. The first surface is located on the side of the base membrane closer to the positive electrode, and the second surface is located on the side of the base membrane away from the positive electrode. A ceramic layer and a first adhesive layer are sequentially stacked on the first surface of the base membrane, and a second adhesive layer is disposed on the second surface of the base membrane.

[0292] The base film is a 13μm polyethylene film.

[0293] The ceramic layer is made of alumina and has a thickness of 3 μm.

[0294] Both the first and second adhesive layers are made of polyvinylidene fluoride (PVDF), and are formed by spraying at a rate of 0.7 g / m². 2 .

[0295] Electrolyte

[0296] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixed solvent to obtain an electrolyte in which the concentration of lithium salt was 1 mol / L.

[0297] Preparation of battery cells:

[0298] Following the sequence of "separator-positive electrode-separator-negative electrode," the positive electrode, negative electrode, and two separators are fixed at one end to the discharge roller, and the other ends are stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft, winding the positive electrode, negative electrode, and two separators to obtain a wound bare cell. Tabs are welded to the bare cell, and the cell is then placed in an aluminum casing and baked at 100°C to remove water. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation (0.02C current formation for 10 hours), shaping, and capacity testing to obtain a single battery cell.

[0299] Example 2

[0300] This embodiment provides a battery cell, which differs from Embodiment 1 in that the content of each raw material in the positive electrode sheet is different. Specifically, the mass ratio of positive electrode material, conductive agent and binder is 98.5:0.9:0.6.

[0301] Example 3

[0302] This embodiment provides a battery cell, which differs from Embodiment 1 in that the content of each raw material in the positive electrode sheet is different. Specifically, the mass ratio of positive electrode material, conductive agent and binder is 98:1:1.

[0303] Example 4

[0304] This embodiment provides a single battery cell, which differs from Embodiment 1 in the preparation method of the positive electrode sheet. Specifically, the temperature conditions in the mixing method of the mixed materials are different, and the specific process is as follows:

[0305] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 15°C and 50 rpm. Then, they were mixed for 5 minutes at 60°C, 50 rpm, and 2000 rpm. Finally, they were cooled for 5 minutes at 15°C and 50 rpm.

[0306] The binder was placed in a double planetary mixer and mixed for 2 minutes at 15°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 40°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 90°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 15°C and a stirring speed of 50 rpm to obtain the mixture.

[0307] Example 5

[0308] This embodiment provides a single battery cell, which differs from Embodiment 1 in the preparation method of the positive electrode sheet. Specifically, the temperature conditions in the mixing method of the mixed materials are different, and the specific process is as follows:

[0309] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 5°C and 50 rpm. Then, they were mixed for 5 minutes at 40°C, 50 rpm, and 2000 rpm. Finally, they were cooled for 5 minutes at 5°C and 50 rpm.

[0310] The binder was placed in a double planetary mixer and mixed for 2 minutes at 5°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 25°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 70°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 5°C and a stirring speed of 50 rpm to obtain the mixture.

[0311] Example 6

[0312] This embodiment provides a single battery cell, which differs from Embodiment 1 in the preparation method of the positive electrode sheet. Specifically, the shear rate in the mixing method of the mixed materials is different, and the specific process is as follows:

[0313] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 20°C and a stirring bar speed of 50 rpm. Then, they were mixed for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disk speed of 2500 rpm. Subsequently, they were cooled for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0314] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2500 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 4000 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0315] Example 7

[0316] This embodiment provides a single battery cell, which differs from Embodiment 1 in the preparation method of the positive electrode sheet. Specifically, the shear rate in the mixing method of the mixed materials is different, and the specific process is as follows:

[0317] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 20°C and a stirring bar speed of 50 rpm. Then, they were mixed for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disc speed of 1500 rpm. Subsequently, they were cooled for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0318] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 1500 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3000 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0319] Ternary cathode material battery system

[0320] Example 8

[0321] This embodiment provides a single battery cell.

[0322] [Preparation of the positive electrode sheet]

[0323] The preparation method of the positive electrode sheet includes the following steps:

[0324] Step 1: Weigh out the cathode materials (LiNi) according to the mass ratio of 97.5:1.3:1.2. 0.8 Co 0.1 Mn 0.1 O2 (D50 particle size of 6μm), conductive agent (conductive carbon SP and conductive carbon nanotubes CNT in a mass ratio of 7:6) and binder (polytetrafluoroethylene PTFE).

[0325] Step 2: Add the positive electrode material and conductive agent to a double planetary mixer and mix for 2 minutes at 20°C and a stirring bar speed of 50 rpm; then mix for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disc speed of 2000 rpm; finally, cool for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0326] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0327] Step 3: The mixture is heated by three rollers to gradually decrease the self-supporting positive electrode film layer to the target areal density. The roller surface temperature is 100℃, the linear speed ratio of the three rollers is 3:5:12, and the gap between each roller is adjusted according to the actual target areal density (range 100μm).

[0328] Step 4: Form a 0.5 μm thick conductive adhesive layer on both surfaces of the positive electrode current collector aluminum foil (9 μm thick). Then, place the self-supporting positive electrode film layer on the surface of the conductive adhesive layer and laminate it at 100°C. After cold pressing and cutting, a surface density of 0.0194 g / cm³ is finally obtained. 2 The compaction density is 3.6 g / cm³. 3 The positive electrode sheet.

[0329] [Preparation of the negative electrode sheet]

[0330] Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose binder, and water solvent were mixed in a weight ratio of 95:2:3:100 and stirred until the system was homogeneous to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both surfaces of a 6 μm thick copper foil current collector to form a negative electrode film. After cold pressing, slitting, and cutting (5 cm x 5 cm) into sheets, a negative electrode sheet was obtained with a compaction density of 1.75 g / cm³. 3 .

[0331] [Septum]

[0332] Separator: A polyethylene membrane with a thickness of 13μm is used.

[0333] Electrolyte

[0334] Ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in the mixed solvent to obtain an electrolyte in which the concentration of lithium salt was 1 mol / L.

[0335] Preparation of battery cells:

[0336] Following the sequence of "separator-positive electrode-separator-negative electrode," the positive electrode, negative electrode, and two separators are fixed at one end to the discharge roller, and the other ends are stacked together and fixed to the winding shaft. A motor is used to rotate the winding shaft, winding the positive electrode, negative electrode, and two separators to obtain a wound bare cell. Tabs are welded to the bare cell, and the cell is then placed in an aluminum casing and baked at 100°C to remove water. Electrolyte is then injected and the casing is sealed, resulting in a non-charged battery. The non-charged battery then undergoes a series of processes including settling, hot and cold pressing, formation (0.02C current formation for 10 hours), shaping, and capacity testing to obtain a single battery cell.

[0337] Example 9

[0338] This embodiment provides a battery cell, which differs from Embodiment 8 in that the content of each raw material in the positive electrode sheet is different. Specifically, the mass ratio of positive electrode material, conductive agent and binder is 98.5:0.9:0.6.

[0339] Example 10

[0340] This embodiment provides a battery cell, which differs from Embodiment 8 in that the content of each raw material in the positive electrode sheet is different. Specifically, the mass ratio of positive electrode material, conductive agent and binder is 98:1:1.

[0341] Example 11

[0342] This embodiment provides a single battery cell, which differs from Embodiment 8 in the preparation method of the positive electrode sheet. Specifically, the temperature conditions in the mixing method of the mixed materials are different, and the specific process is as follows:

[0343] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 15°C and 50 rpm. Then, they were mixed for 5 minutes at 60°C, 50 rpm, and 2000 rpm. Finally, they were cooled for 5 minutes at 15°C and 50 rpm.

[0344] The binder was placed in a double planetary mixer and mixed for 2 minutes at 15°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 40°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 90°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 15°C and a stirring speed of 50 rpm to obtain the mixture.

[0345] Example 12

[0346] This embodiment provides a single battery cell, which differs from Embodiment 8 in the preparation method of the positive electrode sheet. Specifically, the temperature conditions in the mixing method of the mixed materials are different, and the specific process is as follows:

[0347] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 5°C and 50 rpm. Then, they were mixed for 5 minutes at 40°C, 50 rpm, and 2000 rpm. Finally, they were cooled for 5 minutes at 5°C and 50 rpm.

[0348] The binder was placed in a double planetary mixer and mixed for 2 minutes at 5°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 25°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2000 rpm. Next, it was mixed for 10 minutes at 70°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3500 rpm. Finally, it was cooled for 5 minutes at 5°C and a stirring speed of 50 rpm to obtain the mixture.

[0349] Example 13

[0350] This embodiment provides a single battery cell, which differs from Embodiment 8 in the preparation method of the positive electrode sheet. Specifically, the shear rate in the mixing method of the mixed materials is different, and the specific process is as follows:

[0351] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 20°C and a stirring bar speed of 50 rpm. Then, they were mixed for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disk speed of 2500 rpm. Subsequently, they were cooled for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0352] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 2500 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 4000 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0353] Example 14

[0354] This embodiment provides a single battery cell, which differs from Embodiment 8 in the preparation method of the positive electrode sheet. Specifically, the shear rate in the mixing method of the mixed materials is different, and the specific process is as follows:

[0355] The positive electrode material and conductive agent were added to a double planetary mixer and mixed for 2 minutes at 20°C and a stirring bar speed of 50 rpm. Then, they were mixed for 5 minutes at 50°C, a stirring bar speed of 50 rpm, and a dispersion disc speed of 1500 rpm. Subsequently, they were cooled for 5 minutes at 20°C and a stirring bar speed of 50 rpm.

[0356] The binder was placed in a double planetary mixer and mixed for 2 minutes at 20°C and a stirring speed of 50 rpm. Then, it was mixed for 5 minutes at 30°C, a stirring speed of 50 rpm, and a dispersing disc speed of 1500 rpm. Next, it was mixed for 10 minutes at 80°C, a stirring speed of 50 rpm, and a dispersing disc speed of 3000 rpm. Finally, it was cooled for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0357] Comparative Example 1

[0358] This comparative example provides a single battery cell, which differs from Example 1 in that the positive electrode is different.

[0359] The preparation process of the positive electrode sheet in this comparative example is as follows:

[0360] The positive electrode material (lithium cobalt oxide, D50 particle size of 6 μm), conductive agent (conductive carbon SP and conductive carbon nanotubes CNT in a mass ratio of 7:6), binder (polytetrafluoroethylene PTFE), and solvent (N-methylpyrrolidone) were mixed in a mass ratio of 97.5:1.3:1.2:50 and stirred until the system was homogeneous to obtain a positive electrode slurry. The positive electrode slurry was then extruded and coated onto both surfaces of a 9 μm thick aluminum foil current collector to form a positive electrode film. After drying, cold pressing, and cutting, a final areal density of 0.0194 g / cm³ was obtained. 2 The compaction density is 4.2 g / cm³. 3 The positive electrode sheet.

[0361] Comparative Example 2

[0362] This comparative example provides a single battery cell, which differs from Example 1 in that the positive electrode is different.

[0363] The preparation process of the positive electrode sheet in this comparative example is as follows:

[0364] Step 1: Weigh the positive electrode material (lithium cobalt oxide, D50 particle size of 6μm), conductive agent (conductive carbon SP and conductive carbon nanotubes CNT in a mass ratio of 1:1) and binder (polytetrafluoroethylene PTFE) according to a mass ratio of 95:2:3.

[0365] Step 2: Add the positive electrode material and conductive agent to a double planetary mixer and mix for 5 minutes at 20°C and a stirring speed of 50 rpm. Then add the binder to the double planetary mixer and mix for 5 minutes at 20°C and a stirring speed of 50 rpm. After that, mix for 30 minutes at 100°C, a stirring speed of 50 rpm, and a dispersing disk speed of 3500 rpm. Finally, cool for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0366] Step 3: The mixture is heated by three rollers to gradually decrease the self-supporting positive electrode film layer to the target areal density. The roller surface temperature is 100℃, the linear speed ratio of the three rollers is 3:5:12, and the gap between each roller is adjusted according to the actual target areal density (range 100μm).

[0367] Step 4: Form a 0.5 μm thick conductive adhesive layer on both surfaces of the positive electrode current collector aluminum foil (9 μm thick). Then, place the self-supporting positive electrode film layer on the surface of the conductive adhesive layer and laminate it at 100°C. After cold pressing and cutting, a surface density of 0.0194 g / cm³ is finally obtained. 2 The compaction density is 4.2 g / cm³. 3 The positive electrode sheet.

[0368] Comparative Example 3

[0369] This comparative example provides a single battery cell, which differs from Example 8 in that the positive electrode is different.

[0370] The preparation process of the positive electrode sheet in this comparative example is as follows:

[0371] The cathode material (LiNi) 0.8 Co 0.1 Mn 0.1 O2 (D50 particle size 6μm), conductive agent (conductive carbon SP, conductive carbon nanotubes CNT mass ratio 7:6), binder (polytetrafluoroethylene PTFE), and solvent (N-methylpyrrolidone) were mixed at a mass ratio of 97.5:1.3:1.2:50 and stirred until the system was homogeneous to obtain the positive electrode slurry. The positive electrode slurry was then extruded and coated onto both surfaces of a 9μm thick aluminum foil current collector to form a positive electrode film. After drying, cold pressing, and cutting, a final areal density of 0.0194 g / cm³ was obtained. 2 The compaction density is 4.2 g / cm³. 3 The positive electrode sheet.

[0372] Comparative Example 4

[0373] This comparative example provides a single battery cell, which differs from Example 8 in that the positive electrode is different.

[0374] The preparation process of the positive electrode sheet in this comparative example is as follows:

[0375] Step 1: Weigh the cathode materials (LiNi) according to a mass ratio of 95:2:3. 0.8 Co 0.1 Mn 0.1 O2 (D50 particle size of 6μm), conductive agent (conductive carbon SP and conductive carbon nanotubes CNT in a mass ratio of 1:1) and binder (polytetrafluoroethylene PTFE).

[0376] Step 2: Add the positive electrode material and conductive agent to a double planetary mixer and mix for 5 minutes at 20°C and a stirring speed of 50 rpm. Then add the binder to the double planetary mixer and mix for 5 minutes at 20°C and a stirring speed of 50 rpm. After that, mix for 30 minutes at 100°C, a stirring speed of 50 rpm, and a dispersing disk speed of 3500 rpm. Finally, cool for 5 minutes at 20°C and a stirring speed of 50 rpm to obtain the mixture.

[0377] Step 3: The mixture is heated by three rollers to gradually decrease the self-supporting positive electrode film layer to the target areal density. The roller surface temperature is 100℃, the linear speed ratio of the three rollers is 3:5:12, and the gap between each roller is adjusted according to the actual target areal density (range 100μm).

[0378] Step 4: Form a 0.5 μm thick conductive adhesive layer on both surfaces of the positive electrode current collector aluminum foil (9 μm thick). Then, place the self-supporting positive electrode film layer on the surface of the conductive adhesive layer and laminate it at 100°C. After cold pressing and cutting, a surface density of 0.0194 g / cm³ is finally obtained. 2 The compaction density is 4.2 g / cm³. 3 The positive electrode sheet.

[0379] Performance testing

[0380] (1) Pressure-compression test

[0381] The cold pressing conditions and compaction density of the positive electrode sheets in Example 1 and Comparative Example 1 during the preparation of the positive electrode sheet are as follows: Figure 7 As shown.

[0382] from Figure 7 As can be seen, compared with Comparative Example 1, under the same compaction density conditions, Example 1 uses a lower pressure. This may be because there is no problem of particle agglomeration caused by capillary force when the solvent evaporates in Example 1. This makes the particle gap size of the positive electrode material highly consistent, the porosity is also smaller, the particles in the electrode are packed more tightly, and the same compaction is achieved with less cold pressure.

[0383] (2) Stress test

[0384] The positive electrode sheets prepared in Example 1 and Comparative Example 1 were subjected to electron backscatter diffraction (EBSD) tests to evaluate the local stress changes of the positive electrode sheets. The results are as follows: Figure 8 As shown.

[0385] EBSD test: Adjust the angle between the positive electrode and the EBSD probe to 70°, adjust the probe working distance to 15-25mm, perform EBSD test and data acquisition calibration (select 3-7 Kikuchi flower patterns for automatic calibration, check the reliability and error of the calibration, and correct the working distance), and finally determine the corresponding parameters for orientation imaging measurement, such as step size, number of measurement points in the X / Y direction, and magnification, and start the "Automatic" button to perform orientation imaging.

[0386] Figure 8 In this context, KAMD represents the KAM value, where KAM is an abbreviation for Kernel Average Misorientation. It's a parameter used to characterize local orientation differences or the degree of plastic deformation in a material. The KAM value is obtained by calculating the average orientation deviation between a point and its surrounding neighbors. Figure 8 It is evident that Comparative Example 1 has a greater number of deviation sites, indicating that after cold pressing, the residual strain in the positive electrode sheet of Comparative Example 1 is more pronounced, and the local stress concentration is more prominent. This may be because the positive electrode sheet prepared in Example 1 has a more uniform structure, such as a narrower pore size distribution, resulting in a more uniform stress distribution after cold pressing. This significantly reduces the stress concentration of the positive electrode sheet, making it less likely for the positive electrode material particles to break and expose fresh interfaces.

[0387] (3) SEM testing

[0388] The positive electrode sheets prepared in Example 1 and Comparative Example 1 were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 9 As shown. Figure 9 -A is a SEM image of the positive electrode sheet prepared in Example 1. Figure 9 -B is the SEM image of the positive electrode sheet prepared in Comparative Example 1.

[0389] As can be clearly seen from the figure, the positive electrode sheet prepared in this application has a smaller degree of particle breakage, a more compact particle packing of the positive electrode material, and smaller gaps between the positive electrode material particles.

[0390] (4) Adhesion test

[0391] The positive electrode sheets prepared in Example 1 and Comparative Examples 1-2 were subjected to adhesion force tests, and the results are shown in Table 1 below. Adhesion force can be found in the 180° peel membrane adhesion force test, the specific procedure of which is as follows:

[0392] Cutting the electrode sheet: Cut the positive electrode sheet (400mm in length and 50mm in width).

[0393] Fixing the electrode: Take a flat, thin steel plate, 250mm long and 50mm wide. First, apply a strip of double-sided tape (length > the test length of the sample, width equal to the electrode width) to the center of the steel plate, smoothing it firmly to ensure the tape adheres tightly to the center of the steel plate. Peel off the double-sided tape and attach the cut positive electrode to the tape, ensuring the electrode and tape are perfectly matched and adhered.

[0394] Installation and testing: The tensile testing machine has two clamps, one above the other. The steel plate with the adhesive-bonded electrode is inserted into the lower clamp and fixed vertically. The electrode without adhesive is inserted into the upper clamp and fixed, so that the electrode with adhesive paper is at 180° with the electrode fixed in the upper clamp. After fixing the sample, first calibrate and zero the sample, set the test width and peel speed of 50-100mm / min, and then conduct the test to obtain the adhesive force (remove the start and end values ​​of the test and take the average value).

[0395] Table 1

[0396]

[0397] Note: In Table 1, the adhesion test data for Example 1 refers to the test results obtained by preparing the positive electrode sheet using the preparation method provided in Example 1, i.e., preparing 8 positive electrode sheets using Example 1 and performing adhesion tests. Similarly, the adhesion test data for Comparative Example 1 refers to the test results obtained by preparing the positive electrode sheet using the preparation method provided in Comparative Example 1; the adhesion test data for Comparative Example 2 refers to the test results obtained by preparing the positive electrode sheet using the preparation method provided in Comparative Example 2.

[0398] As can be seen from Table 1, the bonding strength of the positive electrode sheet provided in this application is comparable to that of Comparative Examples 1-2, that is, the positive electrode sheet with better bonding strength can be obtained by using the preparation method provided in this application.

[0399] (5) Diaphragm resistance test

[0400] The resistance of the positive electrode sheets prepared in Example 1 and Comparative Examples 1-2 was tested, and the results are shown in Table 2.

[0401] Membrane resistance testing procedure: Cut the positive electrode into a square size of 4cm*8cm, then place the positive electrode under the two probes of the four-probe resistance meter. The two probes are connected to the resistance meter through two poles. Rotate the handle of the testing device, and the probes will be subjected to stable pressure to squeeze the electrode. The pressure is set to 20MPa. Read the resistance data of the resistance meter, which is the membrane resistance.

[0402] Table 2

[0403]

[0404] Note: In Table 2, the resistance test data for Example 1 refers to the test results obtained by preparing the positive electrode using the method provided in Example 1, i.e., preparing 10 positive electrode sheets using Example 1 and performing resistance tests. Similarly, the resistance test data for Comparative Example 1 refers to the test results obtained by preparing the positive electrode using the method provided in Comparative Example 1; the resistance test data for Comparative Example 2 refers to the test results obtained by preparing the positive electrode using the method provided in Comparative Example 2.

[0405] As can be seen from Table 2, the film resistance of the positive electrode provided in this application is at the same level as that of Comparative Examples 1-2, that is, the positive electrode with lower film resistance can be obtained by using the preparation method provided in this application.

[0406] (6) Tensile strength test

[0407] The positive electrode sheets prepared in Example 1 and Comparative Examples 1-2 were subjected to tensile strength tests, and the results are shown in Table 3.

[0408] Tensile strength test: According to the mold for tensile testing, the positive electrode sheet is cut into a rectangle with a width of 15mm and an initial distance of 100mm. Then, the electrode sheet is fixed in the upper and lower clamps of the tensile tester and tested at a tensile test speed of 80mm / min. After the test is completed, the tensile strength of the positive electrode sheet is obtained.

[0409] Table 3

[0410]

[0411] Note: In Table 3, the tensile strength data for Example 1 refers to the test results obtained by preparing the positive electrode using the method provided in Example 1, i.e., preparing 6 positive electrode sheets using Example 1 and performing resistance tests. Similarly, the tensile strength data for Comparative Example 1 refers to the test results obtained by preparing the positive electrode using the method provided in Comparative Example 1; the tensile strength data for Comparative Example 2 refers to the test results obtained by preparing the positive electrode using the method provided in Comparative Example 2.

[0412] As can be seen from Table 3, the tensile strength of the positive electrode sheet provided in this application is at the same level as that of Comparative Examples 1-2, that is, the preparation method provided in this application can obtain a positive electrode sheet with high tensile strength.

[0413] Combination Figures 4-6As can be seen from the results in Tables 1-3, the positive electrode sheet provided in this application has a low specific surface area, but also has a high energy density and good mechanical strength. Thus, without deteriorating the battery dynamics, energy density and safety, it can also effectively improve the battery's high-temperature storage performance.

[0414] (7) Specific surface area and compaction density

[0415] The specific surface area of ​​the positive electrode sheets prepared in Examples 1-14 and Comparative Examples 1-4 was tested using the nitrogen adsorption method.

[0416] The compaction density of the positive electrode sheets prepared in Examples 1-14 and Comparative Examples 1-4 was tested, and the testing process is as follows:

[0417] The punching machine obtained 36 pieces with an area of ​​1540.25 mm². 2 The weight of the circular electrode is measured using a high-precision electronic scale (this weight does not include the weight of the positive current collector). The weight of the electrode is divided by the area of ​​the electrode to obtain the electrode surface density.

[0418] The thickness of the positive electrode sheet is measured using a micrometer or ten-thousand-meter (this thickness does not include the thickness of the positive current collector). At this time, the compaction density of the positive electrode sheet is the areal density of the positive electrode sheet divided by the thickness of the positive electrode sheet.

[0419] Table 4

[0420] <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Compaction density (g / cm 3 )]]> Example 1 0.146 4.2 Example 2 0.121 4.2 Example 3 0.136 4.2 Example 4 0.145 4.2 Example 5 0.139 4.2 Example 6 0.149 4.2 Example 7 0.141 4.2 Comparative Example 1 0.238 4.2 Comparative Example 2 0.219 4.2 Example 8 0.294 3.6 Example 9 0.250 3.6 Example 10 0.281 3.6 Example 11 0.291 3.6 Example 12 0.286 3.6 Example 13 0.298 3.6 Example 14 0.288 3.6 Comparative Example 3 0.465 3.6 Comparative Example 4 0.374 3.6

[0421] (8) Storage performance

[0422] The battery cells prepared in Examples 1-14 and Comparative Examples 1-2 were subjected to storage performance tests, and the test results are shown in Table 5. The test process included the following steps:

[0423] 1. At room temperature, charge at a rate of 0.33C to 4.48V, then charge at a constant voltage of 4.48V to 0.05C;

[0424] 2. At room temperature, discharge the battery cell to 3.0V at 0.33C (record the initial capacity C0 of the battery cell);

[0425] 3. At room temperature, charge at a rate of 0.33C to 4.48V, then charge at a constant voltage of 4.48V to 0.05C;

[0426] 4. Store the battery cells at 60℃ for 3 days, 7 days, and 14 days respectively;

[0427] 5. Take out the cells that have been stored at 60℃ for different times, let them stand at room temperature for 6 hours, and then discharge them at 0.33C to 3.0V at room temperature (record the cell capacity C3, C7, C14). Calculate the capacity retention rate for different storage times by calculating C3 / C0, C7 / C0, and C14 / C0.

[0428] Table 5

[0429]

[0430] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, The device includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector. The positive electrode film layer includes a positive electrode material, a first binder, and a first conductive agent. The first binder has a fibrous structure, and the content of the first binder is less than or equal to 1.2 wt% based on the total mass of the positive electrode film layer. The positive electrode material includes lithium cobalt oxide, and the specific surface area of ​​the positive electrode sheet is less than or equal to 0.15 m². 2 / g, the compaction density of the positive electrode sheet is greater than or equal to 4 g / cm³. 3 ;or, The chemical formula of the cathode material is LiNi. x Co y Mn 1-x-y O2, where 0.6 ≤ x < 1, 0 < y < 1, and the specific surface area of ​​the positive electrode is less than or equal to 0.3 m². 2 / g, the compacted density of the positive electrode sheet is greater than or equal to 3.4 g / cm³. 3 .

2. The battery cell as described in claim 1, characterized in that, The positive electrode material includes lithium cobalt oxide, and the positive electrode sheet satisfies at least one of the following characteristics (1) to (3): (1) The specific surface area of ​​the positive electrode sheet is 0.1-0.15 m². 2 The compacted density of the positive electrode sheet is 4–4.3 g / cm³. 3 ; (2) The ultimate compaction density of the positive electrode sheet is 4.3–4.45 g / cm³. 3 ; (3) The positive electrode sheet has a porous structure distributed in it, and the pore size of the porous structure is 1μm-20μm.

3. The battery cell as described in claim 1, characterized in that, The chemical formula of the cathode material is LiNi. x Co y Mn 1-x- y O2, where 0.6≤x<1, 0<y<0.4, the positive electrode plate satisfies at least one of the following characteristics (1)~(3): (1) The specific surface area of ​​the positive electrode sheet is 0.2-0.3 m². 2 The compacted density of the positive electrode sheet is 3.4–3.85 g / cm³. 3 ; (2) The limiting compaction density of the positive electrode sheet is 3.7–3.9 g / cm³. 3 ; (3) The positive electrode sheet has a porous structure distributed in it, and the pore size of the porous structure is 3μm-40μm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, At least the positive electrode material is in contact with the first binder.

5. The battery cell according to any one of claims 1 to 4, characterized in that, At least a portion of the first conductive agent is coated on the surface of the positive electrode material.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The areal density of the positive electrode film is 0.052-0.260 mg / mm². 2 ; and / or, the thickness of the positive electrode layer is 50μm-200μm.

7. The battery cell according to any one of claims 1 to 6, characterized in that, Based on the total mass of the positive electrode film, the content of the positive electrode material is 97.5wt%-98.5wt%, the content of the first binder is 0.6wt%-1.2wt%, and the content of the first conductive agent is 0.9wt%-1.3wt%.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The positive electrode material has a D50 particle size of 2μm-10μm; and / or The first adhesive comprises at least one of polytetrafluoroethylene, polyvinylidene fluoride, and sodium carboxymethyl cellulose; and / or The first conductive agent includes at least one of carbon materials and conductive polymers.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The positive electrode sheet further includes a conductive adhesive layer, which is disposed on at least one surface of the positive current collector, and the positive electrode film layer is disposed on the surface of the conductive adhesive layer away from the positive current collector.

10. The battery cell as described in claim 9, characterized in that, The thickness of the conductive adhesive layer is 0.3 μm-1.5 μm; and / or The conductive adhesive layer includes a second adhesive and a second conductive agent. Based on the total mass of the conductive adhesive layer, the content of the second adhesive is 70wt%-85wt%, and the content of the second conductive agent is 15wt%-30wt%.

11. A method for preparing a single battery cell, characterized in that, Includes the following steps: The positive electrode material and the first conductive agent are subjected to a first mixing treatment at 5℃-25℃, then heated to 40℃-60℃ for a second mixing treatment, and then subjected to a first cooling treatment to obtain the first mixture. The first mixture and the initial first binder are subjected to a third mixing treatment at 5℃-25℃, then the temperature is raised to 25℃-40℃ for a fourth mixing treatment, then the temperature is raised to 70℃-90℃ for a fifth mixing treatment, and then a second cooling treatment is performed to obtain the second mixture. The second mixture is thinned by hot rolling to obtain a positive electrode film layer; The positive electrode film layer is disposed on at least one side of the positive electrode current collector to prepare a positive electrode sheet; The positive electrode and the negative electrode are assembled to prepare a single battery cell.

12. The method for preparing a single battery cell as described in claim 11, characterized in that, The conditions for the first mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min; and / or The conditions for the second mixing process include: a revolution speed of 30-50 rpm, a rotation speed of 1500-2500 rpm, and a time of 5-10 minutes; and / or The conditions for the third mixing process include: a revolution speed of 30 rpm to 50 rpm and a time of 2 min to 5 min; and / or The conditions for the fourth mixing process include: a revolution speed of 30-50 rpm, a rotation speed of 1500-2500 rpm, and a time of 5-10 minutes; and / or The conditions for the fifth mixing process include: a revolution speed of 30-50 rpm, a rotation speed of 3000-4000 rpm, and a time of 10-15 minutes; and / or The conditions for the first cooling process include: a cooling temperature of 5°C to 25°C, a revolution speed of 30 rpm to 50 rpm, and a time of 5 min to 10 min; and / or The conditions for the second cooling process include: a cooling temperature of 5℃-25℃, a revolution speed of 30rpm-50rpm, and a time of 3min-6min.

13. The method for preparing a battery cell according to any one of claims 11 to 12, characterized in that, The conditions for hot roll thinning include: roll surface temperature of 90℃-105℃, linear velocity ratio of the three rolls of 4:7:9-4:9:12, and gap between adjacent roll shafts of 70μm-500μm.

14. The method for preparing a battery cell according to any one of claims 11 to 13, characterized in that, The specific process of disposing the positive electrode film layer on at least one side of the positive electrode current collector is as follows: A conductive adhesive layer is formed on at least one surface of the positive current collector; The positive electrode film is placed on the surface of the conductive adhesive layer away from the positive electrode current collector, and then subjected to composite processing and cold pressing to obtain the positive electrode sheet.

15. The method for preparing a battery cell as described in claim 14, characterized in that, The temperature of the composite treatment is 90℃-105℃; and / or The pressure of the cold pressing process is 10T-35T.

16. A battery device, characterized in that, It includes multiple battery cells as described in any one of claims 1-10 or battery cells prepared by the preparation method described in any one of claims 11-15.

17. An electrical device, characterized in that, This includes the battery cell as described in any one of claims 1-10, the battery cell prepared by the preparation method described in any one of claims 11-15, or the battery device as described in claim 16.

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