Battery cell hot-pressing method and battery cell

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a battery cell hot-pressing method and a battery cell. The battery cell hot-pressing method comprises the following steps: applying a down force with a first preset value to a battery cell so as to pre-press the battery cell; carrying out electromagnetic heating on the battery cell for a first preset time; and increasing the downward pressure on the battery core until the standard pressure value is reached, and maintaining the pressure for a second preset time. The method comprises the following steps: pre-pressing and fixing a battery cell by adopting a small force, then generating an eddy current in the battery cell through electromagnetic heating, generating heat by the battery cell through a Joule heating effect under the action of the eddy current, and since a variable magnetic field can penetrate through the whole battery cell, the heating efficiency is higher, the diaphragm glue is fully dissolved, and the battery cell is pre-pressed and fixed at the moment; the structure, except for the diaphragm, of the battery cell can be prevented from being influenced by high temperature; after electromagnetic heating is finished, the battery cell starts to be subjected to hot pressing, at the moment, the battery cell has waste heat, the battery cell can be subjected to hot pressing through the waste heat of the battery cell, and the attaching effect of the diaphragm and the positive and negative pole pieces is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a battery cell hot pressing method and a battery cell. Background Art

[0002] Lithium-ion batteries include battery cells, which are mainly composed of positive electrodes, negative electrodes and separators that are wound or stacked. After the positive electrodes, negative electrodes and separators are wound or stacked into battery cells, the gaps between the battery cells make the battery cells fluffy, which is not convenient for subsequent assembly and use. Therefore, a battery cell hot pressing process needs to be introduced. The main purpose is to heat the adhesive on the separator so that it can be bonded to the positive and negative electrodes under the combined action of temperature and pressure, and the distance between each layer of electrodes is kept highly consistent, so that during the use of the lithium-ion battery, the lithium ions from the negative electrode sheet can penetrate to the positive electrode sheet at a consistent distance, thereby improving the performance of the lithium-ion battery.

[0003] The current hot pressing process uses upper and lower hot pressing plates to apply pressure to the battery cells. At the same time, the upper and lower hot pressing plates heat up and transfer the temperature to the battery cells. However, due to the low thermal conductivity and large specific heat capacity of the battery cells themselves, the temperature rise inside the battery cells lags behind, which in turn leads to insufficient dissolution of the diaphragm glue, making it impossible for the diaphragm to fit tightly with the positive and negative electrodes. Summary of the invention

[0004] The object of the present invention is to provide a battery cell hot pressing method and a battery cell, which can ensure the lamination effect between the diaphragm and the positive and negative electrode sheets.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] A cell hot pressing method, comprising:

[0007] Applying a first preset downward pressure to the battery cell to pre-press the battery cell;

[0008] Electromagnetically heating the battery cell for a first preset time;

[0009] The downward pressure on the battery cell is increased until the standard pressure value is reached, and the pressure is maintained for a second preset time.

[0010] The battery cell is formed by the battery cell hot pressing method as described in the above scheme.

[0011] Beneficial effects of the present invention:

[0012] The battery cell hot pressing method provided by the present invention includes: applying a downward pressure of a first preset value to the battery cell to pre-press the battery cell; electromagnetically heating the battery cell for a first preset time; increasing the downward pressure on the battery cell until the standard pressure value is reached, and maintaining the pressure for a second preset time. First, a smaller force is used to pre-press and fix the battery cell, and then electromagnetic heating is used to generate eddy currents inside the battery cell. Under the action of the eddy currents, the battery cell generates heat through the Joule heat effect to heat the battery cell. Since the variable magnetic field can penetrate the entire battery cell, the entire battery cell generates heat evenly, so the heating efficiency is higher, and then the diaphragm glue is fully dissolved. In addition, the battery cell is pre-pressed and fixed at this time, which can prevent the structure of the battery cell other than the diaphragm from being affected by high temperature. After the electromagnetic heating is completed, the battery cell begins to be hot pressed. At this time, the battery cell still has residual heat, and the residual heat of the battery cell can be used to hot press the battery cell, ensuring the bonding effect between the diaphragm and the positive and negative electrodes.

[0013] The battery cell provided by the present invention is formed by adopting the battery cell hot pressing method provided by the present invention. By adopting the battery cell hot pressing method provided by the present invention, the yield rate of the battery cell can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a flow chart of a battery cell hot pressing method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0016] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0017] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0018] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0019] Lithium-ion batteries include battery cells, which are mainly composed of positive electrodes, negative electrodes and separators that are wound or stacked. After the positive electrodes, negative electrodes and separators are wound or stacked into battery cells, the gaps between the battery cells make the battery cells fluffy, which is not convenient for subsequent assembly and use. Therefore, a battery cell hot pressing process needs to be introduced. The main purpose is to heat the adhesive on the separator so that it can be bonded to the positive and negative electrodes under the combined action of temperature and pressure, and the distance between each layer of electrodes is kept highly consistent, so that during the use of the lithium-ion battery, the lithium ions from the negative electrode sheet can penetrate to the positive electrode sheet at a consistent distance, thereby improving the performance of the lithium-ion battery.

[0020] The current hot pressing process uses upper and lower hot pressing plates to apply pressure to the battery cells. At the same time, the upper and lower hot pressing plates heat up and transfer the temperature to the battery cells. However, due to the low thermal conductivity and large specific heat capacity of the battery cells themselves, the temperature rise inside the battery cells lags behind, which in turn leads to insufficient dissolution of the diaphragm glue, making it impossible for the diaphragm to fit tightly with the positive and negative electrodes.

[0021] In view of the above problems, the present invention provides a method for hot pressing a battery cell, such as Figure 1 As shown, the battery cell heating method includes:

[0022] S1. Apply a first preset downward pressure to the battery cell to pre-press the battery cell.

[0023] Applying a first preset value of downward pressure on the battery cell specifically includes placing the battery cell under a pressing plate, and pressing the pressing plate downward until the pressure value on the battery cell reaches the first preset value.

[0024] In this embodiment, the first preset value is 8kgf-12kgf, and optionally, the first preset value is 8kgf, 9kgf, 10kgf, 11kgf or 12kgf. The first preset value is much smaller than the standard pressure value, that is, a smaller force is used to pre-press and fix the battery cell.

[0025] In this embodiment, a pressure sensor is provided on the pressing plate, and the pressure sensor is used to detect the pressure value of the pressing plate on the battery cell. The pressing plate is driven downward by a pressing plate driving device, and the pressing plate driving device is in communication connection with the pressure sensor. When the pressing plate pre-presses the battery cell, the pressure sensor detects the pressure value of the pressing plate on the battery cell in real time. When the pressure sensor detects that the pressure value of the pressing plate on the battery cell reaches a first preset value, the pressing plate driving device stops driving.

[0026] S2. Electromagnetic heating is performed on the battery cell for a first preset time to preheat the battery cell.

[0027] Electromagnetic heating generates eddy currents inside the battery cell. Under the action of the eddy currents, the battery cell generates heat through the Joule heating effect, thereby heating the battery cell. Since the variable magnetic field can penetrate the entire battery cell, the entire battery cell generates heat evenly, so the heating efficiency is higher, and the diaphragm glue is fully dissolved. Since the battery cell is pre-pressed and fixed when it is preheated, the structure of the battery cell other than the diaphragm can be prevented from being affected by high temperature, which improves the bonding effect between the diaphragm and the positive and negative electrodes during the subsequent hot pressing of the battery cell.

[0028] In this embodiment, an electromagnetic coil is disposed on the pressing plate, and the electromagnetic coil is electrically connected to a power source, and the power source can apply an alternating frequency current of a certain power to the electromagnetic coil, so that the electromagnetic coil generates an alternating magnetic field.

[0029] The battery core is subjected to electromagnetic heating for a first preset time, specifically: the electromagnetic coil on the pressure plate is powered on, and the electromagnetic coil is powered off after the first preset time.

[0030] Optionally, the first preset time is 70s-200s. Optionally, the first preset time can be 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s or 200s. The first preset time depends on the battery cell model. Different battery cell models require different first preset times.

[0031] S3, increasing the downward pressure on the battery cell until it reaches a standard pressure value, and maintaining the pressure for a second preset time.

[0032] At this time, the electromagnetic heating has ended, but the battery cell still has residual heat. At this time, the downward pressure on the battery cell is increased until the standard pressure value is reached and the pressure is maintained for the second preset time. The residual heat of the battery cell can be used to hot press the battery cell to ensure that the diaphragm fits well with the positive and negative electrodes.

[0033] Increasing the downward pressure on the battery cell until the standard pressure value is reached is specifically: continuing to press the pressing plate downward until the pressure value on the battery cell reaches the standard pressure value.

[0034] When the pressure plate continues to press down, the pressure sensor detects the pressure value of the pressure plate on the battery cell in real time. When the pressure sensor detects that the pressure value of the pressure plate on the battery cell reaches the standard pressure value, the pressure plate driving device stops driving.

[0035] Optionally, the standard pressure value is 3T-7.5T. Optionally, the standard pressure value may be 3T, 3.5T, 4T, 4.5T, 5T, 5.5T, 6T, 6.5T, 7T or 7.5T. The standard pressure value depends on the battery cell model. Different battery cell models require different standard pressure values.

[0036] In this embodiment, the second preset time is 30 seconds. For different types of battery cells, after the hot pressing time reaches 30 seconds, the separator and the positive and negative electrode sheets can all be ensured to achieve a good bonding effect.

[0037] The battery cell hot pressing method provided by the present invention first uses a relatively small force to pre-press and fix the battery cell, and then generates eddy currents inside the battery cell through electromagnetic heating. Under the action of the eddy currents, the battery cell generates heat through the Joule heating effect, thereby heating the battery cell. Since the variable magnetic field can penetrate the entire battery cell, the entire battery cell generates heat evenly, so the heating efficiency is higher, the diaphragm glue is fully dissolved, and the battery cell is pre-pressed and fixed at this time, which can prevent the structure of the battery cell other than the diaphragm from being affected by high temperature. After the electromagnetic heating is completed, the battery cell is started to be hot pressed. At this time, the battery cell still has residual heat, and the residual heat of the battery cell can be used to hot press the battery cell, thereby ensuring the fitting effect of the diaphragm and the positive and negative electrode sheets.

[0038] The present invention also provides a battery cell formed by the battery cell hot pressing method. By adopting the battery cell hot pressing method, the bonding effect between the diaphragm and the positive and negative electrode sheets can be ensured, and the yield rate of the battery cell can be improved.

[0039] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A battery cell hot pressing method, characterized in that: include: Applying a first preset downward pressure to the battery cell to pre-press the battery cell; Electromagnetically heating the battery cell for a first preset time; The downward pressure on the battery cell is increased until the standard pressure value is reached, and the pressure is maintained for a second preset time.

2. The battery core hot pressing method according to claim 1, characterized in that: Applying a first preset value of downward pressure on the battery cell specifically includes placing the battery cell under a pressing plate, and pressing the pressing plate downward until the pressure value on the battery cell reaches the first preset value.

3. The battery core hot pressing method according to claim 2, characterized in that: An electromagnetic coil is arranged on the pressing plate; the battery core is electromagnetically heated for a first preset time, specifically: the electromagnetic coil on the pressing plate is powered on, and the electromagnetic coil is powered off after the first preset time.

4. The battery core hot pressing method according to claim 2, characterized in that: Increasing the downward pressure on the battery cell until the standard pressure value is reached is specifically: continuing to press the pressing plate downward until the pressure value on the battery cell reaches the standard pressure value.

5. The battery core hot pressing method according to claim 4, characterized in that: The pressure plate is provided with a pressure sensor, and the pressure sensor is used to detect the pressure value of the pressure plate on the battery cell.

6. The battery core hot pressing method according to claim 5, characterized in that: The pressing plate is driven downward by a pressing plate driving device, and the pressing plate driving device is in communication connection with the pressure sensor; When the pressing plate pre-presses the battery cell, the pressure sensor detects the pressure value of the pressing plate on the battery cell in real time. When the pressure sensor detects that the pressure value of the pressing plate on the battery cell reaches a first preset value, the pressing plate driving device stops driving; When the pressure plate continues to press down, the pressure sensor detects the pressure value of the pressure plate on the battery cell in real time. When the pressure sensor detects that the pressure value of the pressure plate on the battery cell reaches the standard pressure value, the pressure plate driving device stops driving.

7. The battery core hot pressing method according to any one of claims 1 to 6, characterized in that: The first preset value is 8kgf-12kgf.

8. The battery core hot pressing method according to any one of claims 1 to 6, characterized in that: The first preset time is 70s-200s.

9. The battery core hot pressing method according to any one of claims 1 to 6, characterized in that: The standard pressure value is 3T-7.5T, and the second preset time is 30s.

10. A battery cell, characterized in that: The battery is formed by hot pressing method according to any one of claims 1 to 9.

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