Hot pressing method and manufacturing process of battery cell, battery cell, battery and hot pressing device

Abstract

The invention provides a hot-pressing method and a manufacturing process of a battery cell, the battery cell, a battery and a hot-pressing device, and relates to the technical field of battery manufacturing. The hot-pressing method comprises the following steps: placing a bare cell to be hot-pressed on the hot-pressing device; carrying out hot pressing on the naked battery cell by utilizing a hot pressing device; wherein the naked battery cell is divided into a plurality of different areas, hot pressing parameters corresponding to the different areas are different, and the hot pressing parameter of the area in the center of the naked battery cell is larger than that of other areas. According to the embodiment of the invention, different hot pressing parameters are adopted for different areas of the battery cell, so that the density of the battery cell center after hot pressing is greater than that of other areas, the expansion degree and temperature of the battery cell center area in the use process are reduced, the consistency of the battery cell is improved, and the attenuation of the battery cell in performance is delayed.

Description

Technical Field

[0001] The present application relates to the technical field of battery manufacturing, and in particular to a hot pressing method for a battery cell, a manufacturing process, a battery cell, a battery and a hot pressing device. Background Art

[0002] In the production process of battery cells, winding or lamination can be used, but no matter which production method is used, hot pressing is required. The hot pressing process is to place the battery cell on a hot pressing device, which heats and pressurizes the battery cell at the same time. The heating temperature and pressure of the entire area of ​​the battery cell are basically the same. However, as lithium batteries continue to develop towards high power and high energy density, the temperature, current and expansion force of each area of ​​the battery cell are different due to different working conditions. The attenuation of each area is different under different working conditions, resulting in too fast attenuation of the overall reversible capacity of the battery cell. Summary of the invention

[0003] The purpose of the embodiments of the present application is to provide a hot pressing method, a manufacturing process, a battery cell, a battery and a hot pressing device for a battery cell, so as to reduce the performance degradation of the battery cell.

[0004] In a first aspect, an embodiment of the present application provides a hot pressing method for a battery cell, comprising:

[0005] Placing the bare battery cell to be hot pressed on the hot pressing device;

[0006] The bare cell is hot pressed using a hot pressing device; wherein the bare cell is divided into a plurality of different regions, the hot pressing parameters corresponding to different regions are different, and the hot pressing parameter of the region at the center of the bare cell is greater than the hot pressing parameters of other regions.

[0007] The embodiment of the present application adopts different hot pressing parameters for different areas of the battery cell, so that the density of the center of the battery cell after hot pressing is greater than that of other areas, thereby reducing the expansion degree and temperature of the center area of ​​the battery cell during use, improving the consistency of the battery cell, and delaying the performance degradation of the battery cell.

[0008] In any embodiment, the bare cell is divided into a plurality of regions along the length direction or the width direction, and the bare cell is hot-pressed by a hot-pressing device, including:

[0009] Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters decrease from the center area to the two side areas of the bare battery cell;

[0010] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0011] During the use of the battery cell, the heat dissipation effect in the central area is the worst, while the heat dissipation effect in the edge area is the best. Therefore, the bare battery cell can be divided into multiple areas along the length direction or the width direction, and the hot pressing parameters in the central area are the largest, and the hot pressing parameters decrease along both sides. As a result, the porosity and wettability of the central area of ​​the battery cell after hot pressing are lower than those of the edge area. During the use of the battery cell, the reaction rate and degree of reaction in each area are adjusted, and then the temperature and expansion force tend to be consistent, which can improve the cycle performance of the battery cell.

[0012] In any embodiment, the bare cell is divided into a plurality of concentric rings with the center as the center; the bare cell is hot-pressed by a hot-pressing device, including:

[0013] Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters of the annular area of ​​the bare battery cell show a decreasing trend from the center of the circle along the radial direction;

[0014] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0015] During the use of the battery cell, the heat dissipation effect in the central area is the worst, and the heat dissipation effect in the edge area is the best. Therefore, the bare battery cell can be divided into multiple concentric rings with the center as the center. The hot pressing parameters in the central area are the largest, and the hot pressing parameters decrease along the edge. Therefore, the porosity and wettability of the central area of ​​the battery cell after hot pressing are lower than those of the edge area. During the use of the battery cell, the reaction rate and degree of reaction in each area are adjusted, and then the temperature and expansion force tend to be consistent, which can improve the cycle performance of the battery cell.

[0016] In any embodiment, the method further comprises:

[0017] Obtain the temperature distribution diagram of the test cell during use;

[0018] The temperature distribution map is analyzed by using a temperature detection model to generate a temperature distribution map including multiple temperature gradient marks; the temperature detection model is obtained by training using the labeled training temperature distribution map;

[0019] The bare battery cell is hot pressed by using a hot pressing device, comprising:

[0020] Setting a hot pressing parameter of a hot pressing device based on a temperature gradient identifier; wherein the hot pressing parameter is negatively correlated with a temperature corresponding to the temperature gradient identifier;

[0021] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0022] The embodiment of the present application is based on the temperature distribution diagram of the test battery cell during use, which can understand the heating situation of the battery cell, and use the temperature detection model to analyze the temperature distribution diagram to generate a temperature distribution diagram with multiple temperature gradient identifiers. Then, the hot pressing parameters can be set based on the temperature gradient identifier, and larger hot pressing parameters can be used in high temperature areas to reduce the porosity and reaction rate of the battery cell after hot pressing, so that the overall consistency of the battery cell during use is better, thereby improving the cycle performance of the battery cell.

[0023] In any embodiment, the hot pressing parameters include at least one of temperature, pressure, and hot pressing time.

[0024] In a second aspect, an embodiment of the present application provides a process for manufacturing a battery cell, including:

[0025] The positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form a bare battery cell;

[0026] Place the bare battery cell on the lower pressing plate, and drive the upper pressing plate downward to pre-press the bare battery cell;

[0027] The pre-pressed bare battery cell is placed in a heating furnace for preheating to obtain a bare battery cell to be hot pressed;

[0028] The bare battery cell to be hot pressed is hot pressed using the method of the first aspect to obtain a formed battery cell.

[0029] The embodiment of the present application uses different hot pressing parameters to hot press different areas of the battery cell, thereby improving the overall consistency of the battery cell after hot pressing, and further improving the cycle performance of the battery cell.

[0030] In a third aspect, an embodiment of the present application provides a battery cell, which is manufactured using the battery cell manufacturing process described in the second aspect.

[0031] In a fourth aspect, an embodiment of the present application provides a battery, comprising the battery cell described in the third aspect.

[0032] In a fifth aspect, an embodiment of the present application provides a hot pressing device, which is used to hot press the bare battery cell in the hot pressing method described in the third aspect; the hot pressing device includes multiple pressure driving devices, multiple heating devices, a pressure controller and a temperature controller; wherein:

[0033] The number of the pressure driving devices and the number of the heating devices are the same;

[0034] The heating device comprises a first heater, a second heater, a first hot pressing plate and a second hot pressing plate; the first heater is used to heat the first hot pressing plate, and the second heater is used to heat the second hot pressing plate; the first hot pressing plate and the second hot pressing plate are arranged opposite to each other;

[0035] The pressure controllers are respectively connected to the multiple pressure driving devices;

[0036] The temperature controller is connected to the first heater and the second heater of the plurality of heating devices, respectively.

[0037] The hot pressing device in the embodiment of the present application can implement hot pressing of different areas of the battery cell using different hot pressing parameters, so that the overall consistency of the battery cell after hot pressing is better, thereby improving the performance of the battery cell.

[0038] In any embodiment, the hot pressing device also includes a central controller; the central controller is connected to the pressure controller and the temperature controller; the central controller is used to send pressure parameters to the pressure controller; the central controller is also used to send temperature parameters to the temperature controller.

[0039] The embodiment of the present application improves the hot pressing accuracy of the hot pressing device by controlling the pressure controller and the temperature controller through a central controller.

[0040] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by practicing the embodiments of the present application. The purpose and other advantages of the present application can be realized and obtained by the structures specifically pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0042] Figure 1 A schematic diagram of the cell division provided in an embodiment of the present application;

[0043] Figure 2 A schematic diagram of a hot pressing method for a battery cell provided in an embodiment of the present application;

[0044] Figure 3 This is a schematic diagram of dividing a bare cell into four regions in the width direction according to an embodiment of the present application;

[0045] Figure 4 A temperature distribution diagram of the battery cell provided in an embodiment of the present application during use;

[0046] Figure 5 The temperature distribution diagram of multiple groups of battery cells after hot pressing using the traditional hot pressing method;

[0047] Figure 6 A temperature distribution diagram of multiple groups of battery cells after hot pressing using the hot pressing method provided by the present application;

[0048] Figure 7 A schematic diagram of the capacity retention rate of different groups of cells during cyclic use after hot pressing using the hot pressing method provided by the present application with gradient hot pressing parameters;

[0049] Figure 8 A schematic diagram of the structure of a hot pressing device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0050] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0052] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0053] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0055] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0056] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0057] With the continuous consumption of non-renewable energy such as oil and the urgent demand for environmental protection, new energy has gradually become the main force to replace traditional energy. Lithium-ion batteries have become the favorite of all countries and industries due to their high specific energy and long life, and are widely used in various consumer batteries, energy storage power stations and new energy vehicles.

[0058] However, the application of lithium-ion batteries in new energy vehicles, the consistency and reliability of batteries are the main aspects that consumers are concerned about. The main factors affecting the reliability and quality of lithium-ion batteries are the many steps and complex processes in the lithium-ion battery production process. It is very important to ensure the consistency of semi-finished products and finished products in the process.

[0059] At present, bare cells of power lithium batteries are generally heat-pressed and shaped by hot pressing machines. The upper and lower plates are usually heated by embedded heating wires. The bare cells are placed between the upper and lower heating plates and are pushed and pressed by the oil cylinder to achieve the hot pressing process of the bare cells. During the hot pressing process, the temperature and pressure applied to each area of ​​the cell are kept consistent as much as possible, so that the density of the cell after hot pressing is more uniform.

[0060] However, in the actual use of the battery cell, the temperature, current and expansion force of different parts of the battery cell are different, resulting in different attenuation degrees in different areas of the battery cell, which causes the overall reversible capacity of the battery cell to decay too quickly. For ease of description, the battery cell is divided into the upper, middle and lower parts along the length direction. Figure 1As shown. Since the heat cannot be effectively dissipated in the middle of the battery cell, the temperature is the highest and the expansion force is the largest, which causes the capacity in the middle of the battery cell to be consumed first, so the reversible capacity decays the fastest. Due to the presence of the pole ear, the upper part of the battery cell will receive a large current, so the temperature is also high, but there is a certain amount of spare structure in this part, and it is at the edge, so the heat dissipation is better, the electrolyte infiltration is low, and it will not fully participate in the cycle of the battery cell, so the temperature, expansion force and performance decay are small. Relatively speaking, there is no spare structure in the lower part of the battery cell, and the temperature, expansion force and performance decay are between the upper and middle parts. Therefore, during the use of the battery cell, the temperature in the middle will be high and the temperature on both sides will be relatively low. This phenomenon will cause the battery to decay faster.

[0061] In order to solve this technical problem, an embodiment of the present application provides a hot pressing method for a battery cell. This method adopts different hot pressing parameters for different areas of the battery cell so that the temperature, expansion force, etc. of each area of ​​the hot pressed battery cell are as consistent as possible during use, thereby delaying the performance degradation of the battery cell.

[0062] It should be noted that the hot pressing method of the present application is applicable to battery cells manufactured by winding or lamination processes.

[0063] Figure 2 A schematic diagram of a hot pressing method for a battery cell provided in an embodiment of the present application is shown in FIG. Figure 2 As shown, the method includes:

[0064] Step 201: placing the bare battery cell to be hot pressed on a hot pressing device;

[0065] Step 202: hot pressing the bare cell using a hot pressing device; wherein the bare cell is divided into a plurality of different regions, the hot pressing parameters corresponding to different regions are different, and the hot pressing parameter of the region at the center of the bare cell is greater than the hot pressing parameter of other regions.

[0066] In the specific implementation process, the bare battery cell refers to the positive electrode plate, the negative electrode plate and the isolation film made by winding or lamination process, and the bare battery cell to be hot pressed refers to the bare battery cell that needs to be hot pressed in the next step in the manufacturing process.

[0067] The hot pressing device is mainly used to perform hot pressing and shaping on the battery cell to improve the flatness of the battery, eliminate diaphragm wrinkles, expel the air inside the battery cell, and make the diaphragm and the positive and negative pole pieces fit tightly together.

[0068] The working principle of the hot pressing device mainly includes the following steps:

[0069] Battery cell positioning: Place the battery cell to be hot pressed on the workbench of the hot pressing device and accurately position it through the positioning mechanism.

[0070] Heating and pressurizing: Start the hot pressing device, the heating element heats the battery cell, and the pressure applying mechanism applies a certain pressure to the battery cell. Under the action of heating and pressurizing, the diaphragm and the positive and negative pole pieces inside the battery cell gradually fit closely together. It should be noted that the hot pressing device provided in the embodiment of the present application can apply different hot pressing parameters to different areas of the bare battery cell, and the hot pressing parameters of the central area of ​​the bare battery cell are greater than the hot pressing parameters of other areas, so that the porosity and electrolyte infiltration degree of the central area of ​​the bare battery cell after hot pressing are low. The hot pressing parameters may include at least one of temperature, pressure and hot pressing duration. If the hot pressing parameters include temperature, then a large hot pressing parameter means a high temperature; if the hot pressing parameters include pressure, then a large hot pressing parameter means a high pressure; if the hot pressing parameters include hot pressing duration, then a large hot pressing parameter means a long hot pressing duration. If the hot pressing parameters include multiple items of heat, pressure and hot pressing duration, then a large hot pressing parameter means a high temperature, a high pressure or a long hot pressing duration. It is understandable that the bare battery cell that is hot pressed with larger hot pressing parameters has a higher density, lower porosity and electrolyte infiltration. During the use of the battery cell, the ion reaction rate in this area is lower and less heat is generated.

[0071] Pressure holding and cooling: After reaching the set hot pressing time and temperature, a certain pressure is maintained to hold the battery cell for pressure treatment to ensure the tight fit between the diaphragm and the pole piece. Subsequently, the temperature of the battery cell is lowered by natural cooling or forced cooling.

[0072] Removing the battery cells: After the battery cells cool to room temperature, the battery cells are removed from the hot pressing device through the material removal mechanism for subsequent testing and assembly.

[0073] The embodiment of the present application adopts different hot pressing parameters for different areas of the battery cell, so that the density of the center of the battery cell after hot pressing is greater than that of other areas, thereby reducing the expansion degree and temperature of the center area of ​​the battery cell during use, improving the consistency of the battery cell, and delaying the performance degradation of the battery cell.

[0074] On the basis of the above embodiment, the bare cell is divided into a plurality of regions along the length direction or the width direction, and the bare cell is hot pressed by a hot pressing device, including:

[0075] Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters decrease from the center area to the two side areas of the bare battery cell;

[0076] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0077] In a specific implementation process, the large surface of the bare cell can be divided into multiple areas in the length direction or the width direction, such as Figure 1 As shown, Figure 1 For the embodiment of the present application, the bare battery cell is divided into three areas in the length direction; Figure 3 For the present embodiment, the bare cell is divided into four regions in the width direction, such as Figure 3 As shown. It should be noted that the bare cell can also be divided into more areas, and the embodiments of the present application do not specifically limit this. In addition, the area divisions on the two opposite large surfaces of the bare cell are the same, and the heating parameters are also the same. And, the side of the bare cell can also be divided into areas, and the heating parameters of the relative areas are the same.

[0078] Set the hot pressing parameters of the hot pressing device, assuming that the hot pressing parameters include temperature and pressure. Figure 1 For example, the temperature corresponding to the upper part of the battery cell is T1, the temperature in the middle is T2, and the temperature in the lower part is T3. T2>T3>T1, the temperature range of T2 can be 150-180°C, the temperature range of T3 can be 90-120°C, and the temperature range of T1 can be 60-80°C. The pressure corresponding to the upper part of the battery cell is P1, the pressure in the middle is P2, and the pressure in the lower part is P3. P2>P3>P1, the pressure range of P2 is 8-10MPa, the pressure range of P3 is 4-6MPa, and the pressure range of P1 is 1-2MPa. It can be understood that T1 can be equal to T3, and P1 can be equal to P3.

[0079] like Figure 3 As shown, for the case of being divided into four parts, the temperature and pressure of the two middle areas can be set to be the same. The temperature and pressure of the two side areas are lower than that of the middle area.

[0080] After the hot pressing parameters of the hot pressing device are set, the hot pressing device can be used to perform hot pressing on the bare battery cell based on the hot pressing parameters.

[0081] The embodiments of the present application enable the bare battery cell to be hot-pressed using different temperatures and pressure gradients according to different actual working conditions, control parameters such as the closed pores of the diaphragm and the porosity and degree of wetting after compaction of the anode and cathode in the bare battery cell, and adjust the performance of the bare battery cell to be more uniform, thereby avoiding the overall performance degradation of the battery cell due to rapid capacity decay in the middle part, reducing safety risks such as internal short circuits caused by lithium plating, and enhancing the capacity retention performance of the battery during the discharge cycle.

[0082] On the basis of the above embodiment, the bare cell is divided into a plurality of concentric rings with the center as the center of the circle; the bare cell is hot-pressed by a hot-pressing device, including:

[0083] Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters of the annular area of ​​the bare battery cell show a decreasing trend from the center of the circle along the radial direction;

[0084] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0085] In the specific implementation process, Figure 4 The temperature distribution diagram of the battery cell provided in the embodiment of the present application during use. Figure 4 It can be seen that the temperature at the center of the battery cell is the highest and the temperature gradient is circular. Therefore, based on the temperature distribution diagram, the center of the bare battery cell can be divided into multiple concentric rings with the center of the circle as the center. When setting the hot pressing parameters of the hot pressing device, starting from the center of the circle, the hot pressing parameters gradually decrease along the radial direction. It should be noted that the hot pressing plate used for hot pressing the battery cell in the hot pressing device can be one-piece or can be made up of multiple pieces. For the one-piece hot pressing plate, different hot pressing parameters can be set for different areas, and the regional division of the one-piece hot pressing plate corresponds to the regional division of the battery cell. The hot pressing parameters of multiple spliced ​​hot pressing plates can also be set separately, and the arrangement of the spliced ​​areas corresponds to the divided areas of the battery cell.

[0086] During the use of the battery cell, the heat dissipation effect in the central area is the worst, and the heat dissipation effect in the edge area is the best. Therefore, the bare battery cell can be divided into multiple concentric rings with the center as the center. The hot pressing parameters in the central area are the largest, and the hot pressing parameters decrease along the edge. Therefore, the porosity and wettability of the central area of ​​the battery cell after hot pressing are lower than those of the edge area. During the use of the battery cell, the reaction rate and degree of reaction in each area are adjusted, so that the temperature and expansion force areas are consistent, which can improve the cycle performance of the battery cell.

[0087] Based on the above embodiment, the method further includes:

[0088] Obtain the temperature distribution diagram of the test cell during use;

[0089] The temperature distribution map is analyzed by using a temperature detection model to generate a temperature distribution map including multiple temperature gradient marks; the temperature detection model is obtained by training using the labeled training temperature distribution map;

[0090] The bare battery cell is hot pressed using a hot pressing device, including:

[0091] Setting a hot pressing parameter of the hot pressing device based on the temperature gradient identifier; wherein the hot pressing parameter is negatively correlated with the temperature corresponding to the temperature gradient identifier;

[0092] Based on the hot pressing parameters, the bare battery cell is hot pressed using a hot pressing device.

[0093] In the specific implementation process, the temperature distribution diagram of the test cell under various working conditions during use can be obtained, and the temperature distribution diagram can be manually annotated to obtain multiple temperature gradient marks, which are approximately circular and have approximately the same temperature values ​​on the circle. The temperature distribution diagram is used as the input of the model, and the temperature gradient mark is used as a label to train the model to obtain a temperature detection model.

[0094] Therefore, when it is necessary to divide the bare battery cells into regions, the battery cells of the same model that are hot pressed using the traditional hot pressing method can be used as test cells, the temperature distribution diagram of the test battery cells during use can be obtained, and the temperature gradient mark of the temperature distribution diagram can be generated using the temperature detection model.

[0095] The hot pressing parameters of each area of ​​the hot pressing device are set based on the temperature gradient identifier. The hot pressing parameters of the high temperature area can be set higher, and the hot pressing parameters of the low temperature area can be set lower. After the hot pressing parameters are set, the hot pressing device is used to hot press the bare battery cell.

[0096] The embodiment of the present application is based on the temperature distribution diagram of the test battery cell during use, which can understand the heating situation of the battery cell, and use the temperature detection model to analyze the temperature distribution diagram to generate a temperature distribution diagram with multiple temperature gradient identifiers. Then, the hot pressing parameters can be set based on the temperature gradient identifier, and larger hot pressing parameters can be used in high temperature areas to reduce the porosity and reaction rate of the battery cell after hot pressing, so that the overall consistency of the battery cell during use is better, thereby improving the cycle performance of the battery cell.

[0097] The present application embodiment is tested by dividing the battery cell into three parts: upper part, middle part and lower part, and records the gradient hot pressing parameters and battery cell parameters corresponding to the battery cells of multiple groups, as shown in the following table:

[0098]

[0099]

[0100] Figure 5 This is the temperature distribution diagram of multiple groups of battery cells after hot pressing using the traditional hot pressing method. Figure 6 The temperature distribution diagram of multiple groups of battery cells after hot pressing using the hot pressing method provided by the present application; by comparing Figure 5 and Figure 6 It can be seen that the temperature of each area of ​​the battery cell hot-pressed by the hot-pressing method provided in the embodiment of the present application is more uniform than that of the battery cell hot-pressed by the traditional hot-pressing method.

[0101] Figure 7 This is a schematic diagram of the capacity retention rate of different groups of cells in cyclic use after hot pressing with gradient hot pressing parameters after hot pressing using the hot pressing method provided in the present application. Figure 7 As shown, based on Figure 7 A better heat pressing parameter can be selected.

[0102] A manufacturing process of a battery cell provided in an embodiment of the present application includes:

[0103] Making a bare cell: The positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form a bare cell;

[0104] Pre-pressing: placing the bare cell on the lower pressing plate, and driving the upper pressing plate downward to pre-press the bare cell;

[0105] Preheating: The pre-pressed bare cell is placed in a heating furnace for preheating to obtain a bare cell to be hot-pressed; specifically, the bare cell can be heated in a heating furnace for 300-600 seconds to maintain the temperature of the bare cell at about 100°C.

[0106] Hot pressing: Use the bare cells to be hot pressed to obtain the formed cells. The loose bare cells that have been heated are transferred to the lower hot pressing plate. Figure 1 As shown, the upper and lower hot pressing plates of the three parts are heated to the specified temperatures T1, T2 and T3 by a heating device (T2>T3>T1, the temperature range of T2 is 150~180℃, the temperature range of T3 is 90~120℃, and the temperature range of T1 is 60~80℃), and then the hot pressing plates are pressed down by a pressing device to compact the bare battery cells, and the pressing forces used are P1, P2 and P3 respectively (P2>P3>P1, the pressure range of P2 is 8-10MPa, the pressure range of P3 is 4-6MPa, and the pressure range of P1 is 1-2MPa).

[0107] Molding: Raise the upper pressing plate and take out the hot-pressed battery cells.

[0108] The embodiments of the present application enable the bare cell to be hot-pressed with different temperature and pressure gradients according to different actual working conditions, control the parameters such as the porosity and degree of wetting of the diaphragm closed pores and the compacted anode and cathode in the bare cell, and adjust the performance of the bare cell to be more uniform, thereby avoiding the overall performance decay of the cell due to the rapid capacity decay in the middle part, reducing the safety risks such as internal short circuit caused by lithium precipitation, enhancing the capacity retention performance of the battery in the discharge cycle, and improving the cycle life of the battery. The use of a high-temperature, high-pressure hot pressing process in the middle of the cell will reduce the porosity of the diaphragm and the specific surface area of ​​the active material, and will also reduce the degree of wetting of the electrolyte at this position, so that the reaction rate of the cell is reduced during high-power use, and the temperature and capacity of each part of the cell are promoted to remain consistent as much as possible without affecting the capacity, thereby reducing the capacity decay of the cell.

[0109] An embodiment of the present application provides a battery cell, which is manufactured using the above-mentioned battery cell manufacturing process.

[0110] Battery cells (also known as battery cells) include but are not limited to lithium-ion batteries, sodium-ion batteries, sodium-lithium-ion batteries, lithium metal batteries, sodium metal batteries, lithium-sulfur batteries, magnesium-ion batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0111] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and removed between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to reduce the risk of short circuit between the positive and negative electrodes, while allowing active ions to pass through.

[0112] In some embodiments, the positive electrode may be a positive electrode sheet, and the positive electrode sheet may include a positive electrode current collector and a positive electrode active material disposed on at least one surface of the positive electrode current collector.

[0113] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0114] As an example, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum with a silver-plated surface, stainless steel with a silver-plated surface, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. may be used. The composite current collector may include a polymer material base and a metal layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0115] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of two or more. Among them, examples of lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 )、LiNi0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc.

[0116] In some embodiments, the positive electrode may be a foamed metal. The foamed metal may be a nickel foam, a copper foam, an aluminum foam, an alloy foam, or a carbon foam. When the foamed metal is used as the positive electrode, the positive electrode active material may not be provided on the surface of the foamed metal, but of course, the positive electrode active material may also be provided. As an example, a lithium source material, potassium metal or sodium metal may also be filled or / and deposited in the foamed metal, and the lithium source material is lithium metal and / or a lithium-rich material.

[0117] In some embodiments, the negative electrode may be a negative electrode sheet, and the negative electrode sheet may include a negative electrode current collector.

[0118] As an example, the negative electrode current collector can be a metal foil, a foamed metal or a composite current collector. For example, as a metal foil, aluminum or stainless steel treated with silver, stainless steel, copper, aluminum, nickel, carbon electrode, carbon, nickel or titanium, etc. can be used. The foamed metal can be a foamed nickel, a foamed copper, a foamed aluminum, a foamed alloy, or a foamed carbon, etc. The composite current collector can include a polymer material base and a metal layer. The composite current collector can 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, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0119] As an example, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material disposed on at least one surface of the negative electrode current collector.

[0120] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0121] As an example, the negative electrode active material may adopt the negative electrode active material for battery cells known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0122] In some embodiments, the material of the positive electrode current collector may be aluminum, and the material of the negative electrode current collector may be copper.

[0123] In some embodiments, the separator is a separator membrane, which can be any known porous separator membrane with good chemical stability and mechanical stability.

[0124] As an example, the material of the separator may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different. The separator may be a separate component located between the positive and negative electrodes, or may be attached to the surface of the positive and negative electrodes.

[0125] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode and the negative electrode and serves to transmit ions and isolate the positive and negative electrodes.

[0126] In some embodiments, the battery cell further includes an electrolyte, which plays a role in conducting ions between the positive and negative electrodes. The electrolyte can be liquid, gel or solid. Among them, the liquid electrolyte includes an electrolyte salt and a solvent.

[0127] In some embodiments, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0128] In some embodiments, the solvent may include at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent may also be an ether solvent. The ether solvent may include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether and crown ether.

[0129] Among them, gel electrolytes include polymers

[0130] It is the skeleton network of the electrolyte, combined with ionic liquid-lithium salt.

[0131] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0132] As an example, the polymer solid electrolyte may be polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, polyionic liquid-lithium salt, cellulose, and the like.

[0133] As an example, the inorganic solid electrolyte may include an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

[0134] As an example, the composite solid electrolyte is formed by adding an inorganic solid electrolyte filler to a polymer solid electrolyte.

[0135] In some embodiments, the electrode assembly is a wound structure, wherein the positive electrode sheet and the negative electrode sheet are wound into the wound structure.

[0136] In some embodiments, the electrode assembly is a laminate structure.

[0137] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0138] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet may be folded to form a plurality of stacked folded segments, with a positive electrode sheet being sandwiched between adjacent folded segments.

[0139] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of folded sections that are stacked.

[0140] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0141] As an example, the separator may be disposed continuously, and disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0142] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

[0143] In some embodiments, the electrode assembly is provided with tabs, which can lead current out of the electrode assembly. The tabs include a positive tab and a negative tab.

[0144] In some embodiments, the battery cell may include a housing. The housing is used to encapsulate components such as the electrode assembly and the electrolyte. The housing may be a steel housing, an aluminum housing, a plastic housing (such as polypropylene), a composite metal housing (such as a copper-aluminum composite housing), or an aluminum-plastic film.

[0145] As an example, the battery cell may be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a polygonal prismatic battery, such as a hexagonal prismatic battery.

[0146] The battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide higher voltage and capacity.

[0147] In some embodiments, the battery may be a battery module. When there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0148] In some embodiments, the battery may be a battery pack, which includes a case and battery cells, wherein the battery cells or battery modules are accommodated in the case.

[0149] In some embodiments, the box body can be used as a part of the chassis structure of the vehicle. For example, part of the box body can become at least a part of the floor of the vehicle, or part of the box body can become at least a part of the cross beam and longitudinal beam of the vehicle.

[0150] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0151] An embodiment of the present application also provides a battery, which includes the battery cells provided by the above embodiments.

[0152] The embodiment of the present application provides a hot pressing device, which includes: a plurality of pressure driving devices, a plurality of heating devices, a pressure controller and a temperature controller; wherein:

[0153] The number of the pressure driving devices and the number of the heating devices are the same;

[0154] The heating device comprises a first heater, a second heater, a first hot pressing plate and a second hot pressing plate; the first heater is used to heat the first hot pressing plate, and the second heater is used to heat the second hot pressing plate; the first hot pressing plate and the second hot pressing plate are arranged opposite to each other;

[0155] The pressure controllers are respectively connected to the multiple pressure driving devices;

[0156] The temperature controller is connected to the first heater and the second heater of the plurality of heating devices, respectively.

[0157] In the specific implementation process, Figure 8 A schematic diagram of the structure of a hot pressing device provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, the hot pressing device includes three pressure driving devices, namely drive 1, drive 2 and drive 3; it also includes three heating devices, each of which includes a first heater, a second heater, a first hot pressing plate and a second hot pressing plate. Among them, the first heater is used to heat the first hot pressing plate, and the second heater is used to heat the second hot pressing plate. The first hot pressing plate and the second hot pressing plate are arranged opposite to each other, and the middle is used to place the bare battery cell and hot press the bare battery cell. The pressure controller is respectively connected to a plurality of pressure driving devices to control the downward pressure of the pressure driving device. The temperature control controller is respectively connected to each heater to control the heating temperature of the heater. It should be noted that the above is only an example. The number, shape and arrangement of the specific pressure driving device and heating device can be set according to the actual situation, and the present application does not make specific restrictions on this.

[0158] The hot pressing device in the embodiment of the present application can implement hot pressing of different areas of the battery cell using different hot pressing parameters, so that the overall consistency of the battery cell after hot pressing is better, thereby improving the performance of the battery cell.

[0159] On the basis of the above embodiment, the hot pressing device further includes a central controller; the central controller is connected to the pressure controller and the temperature controller; the central controller is used to send a pressure parameter to the pressure controller; after receiving the pressure parameter, the pressure controller controls the pressure driving device based on the pressure parameter. The central controller is also used to send a temperature parameter to the temperature controller, and after receiving the temperature parameter, the temperature controller controls the heating device to heat based on the temperature parameter.

[0160] The embodiment of the present application improves the hot pressing accuracy of the hot pressing device by controlling the pressure controller and the temperature controller through a central controller.

[0161] In the embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some communication interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0162] In addition, the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0163] Furthermore, the functional modules in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0164] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0165] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A hot pressing method for a battery cell, characterized in that: include: Placing the bare battery cell to be hot pressed on the hot pressing device; The bare cell is hot pressed using a hot pressing device; wherein the bare cell is divided into a plurality of different regions, the hot pressing parameters corresponding to different regions are different, and the hot pressing parameter of the region at the center of the bare cell is greater than the hot pressing parameter of other regions.

2. The method according to claim 1, characterized in that: The bare battery cell is divided into a plurality of regions along a length direction or a width direction, and the bare battery cell is hot-pressed by a hot-pressing device, comprising: Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters show a decreasing trend from the central area to the two side areas of the bare battery cell; Based on the hot pressing parameters, the bare battery cell is hot pressed using the hot pressing device.

3. The method according to claim 1, characterized in that The bare cell is divided into a plurality of concentric rings with the center as the center of the circle; the bare cell is hot-pressed by a hot-pressing device, comprising: Setting the hot pressing parameters of the hot pressing device, wherein the hot pressing parameters of the annular region of the bare battery cell show a decreasing trend along the radial direction from the center of the circle; Based on the hot pressing parameters, the bare battery cell is hot pressed using the hot pressing device.

4. The method according to claim 1, characterized in that: The method further comprises: Obtain the temperature distribution diagram of the test cell during use; The temperature distribution map is analyzed by using a temperature detection model to generate a temperature distribution map including a plurality of temperature gradient marks; the temperature detection model is obtained by training using the labeled training temperature distribution map; The step of hot pressing the bare battery cell using a hot pressing device comprises: Setting a hot pressing parameter of the hot pressing device based on the temperature gradient identifier; wherein the hot pressing parameter is negatively correlated with the temperature corresponding to the temperature gradient identifier; Based on the hot pressing parameters, the bare battery cell is hot pressed using the hot pressing device.

5. The method according to any one of claims 1 to 4, characterized in that: The hot pressing parameters include at least one of temperature, pressure, and hot pressing time.

6. A process for manufacturing a battery cell, characterized in that: include: The positive electrode sheet, the separator and the negative electrode sheet are stacked or wound to form a bare battery cell; Placing the bare cell on the lower pressing plate, and driving the upper pressing plate downward to pre-press the bare cell; The pre-pressed bare battery cell is placed in a heating furnace for preheating to obtain a bare battery cell to be hot pressed; The bare battery cell to be hot pressed is hot pressed using the method according to any one of claims 1 to 5 to obtain a formed battery cell.

7. A battery cell, characterized in that: The battery cell is manufactured using the battery cell manufacturing process as claimed in claim 6.

8. A battery, characterized in that: Comprising the battery cell as claimed in claim 7.

9. A hot pressing device, characterized in that: The hot pressing device is used to hot press the bare battery cell in the hot pressing method according to any one of claims 1 to 5; the hot pressing device comprises a plurality of pressure driving devices, a plurality of heating devices, a pressure controller and a temperature controller; wherein: The number of the pressure driving devices and the number of the heating devices are the same; The heating device comprises a first heater, a second heater, a first hot pressing plate and a second hot pressing plate; the first heater is used to heat the first hot pressing plate, and the second heater is used to heat the second hot pressing plate; the first hot pressing plate and the second hot pressing plate are arranged opposite to each other; The pressure controllers are respectively connected to the multiple pressure driving devices; The temperature controller is connected to the first heater and the second heater of the plurality of heating devices, respectively.

10. The hot pressing device according to claim 9, characterized in that: The hot pressing device also includes a central controller; the central controller is connected to the pressure controller and the temperature controller; the central controller is used to send pressure parameters to the pressure controller; the central controller is also used to send temperature parameters to the temperature controller.

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