Battery cell heating method and device

Abstract

The present invention relates to the technical field of new energy battery manufacturing, and specifically to a battery cell heating method and device. The battery cell heating device is utilized to operate according to the following steps: S1, electrically connecting positive and negative electrodes of a battery cell to corresponding wiring terminals of a variable-frequency power supply, respectively; S2, applying an alternating current I or an alternating voltage U of a certain magnitude and frequency to the two electrodes of the battery cell by means of the variable-frequency power supply, to heat the battery cell to a set temperature T; S3, processing the battery cell and / or a sealed cavity where the battery cell is located, by means of evacuating, dry gas charging, or cyclically switching between evacuating and dry gas charging, such that a certain pressure value P is maintained in the battery cell and / or said sealed cavity; S4, when the battery cell reaches the set temperature T, maintaining the temperature for a period of time t; and S5, when the battery cell is heated, cooling the battery cell and / or said sealed cavity and / or the wiring terminals of the variable-frequency power supply. The present invention improves the heating efficiency of battery cells, reduces loss, and synchronously achieves the identification of defective battery cells.

Description

A method and apparatus for heating battery cells Technical Field

[0001] This invention relates to the field of new energy battery manufacturing technology, specifically to a cell heating method and equipment. Background Technology

[0002] With the rapid development of the new energy industry, secondary batteries such as lithium-ion batteries and sodium-ion batteries have developed rapidly and the market has continued to expand. As competition intensifies, battery manufacturers are increasingly demanding to reduce energy consumption such as water, electricity and gas in the battery manufacturing process, shorten process time and improve production efficiency.

[0003] Traditional battery cell heating processes typically employ either ventilated or contact heating. The battery cell is placed in a sealed cavity, and a heating wire or plate is energized to generate heat. In a dry gas atmosphere, heat is transferred or conducted to the battery cell. During the heating process, the entire cavity is evacuated and then purged with nitrogen. This "nitrogen purging and vacuuming" cycle is repeated several times to displace the water vapor that evaporates from the battery cell, thus removing moisture. However, both of these heating methods have several drawbacks. Firstly, the heating and holding times are long, resulting in low heating efficiency and high energy consumption. Both ventilated and contact ovens use resistance wires / heating wires to generate heat, which is then transferred or conducted to the battery cell. Due to the poor thermal conductivity of the battery cell, heating takes a long time, leading to low efficiency and significant energy consumption. Due to the uneven temperature distribution inside the convection oven and the uneven temperature distribution between the contact surface and the inside of the battery cell in the contact oven, the oven cannot be set to a high baking temperature and requires a long holding time. This is to prevent the separator inside the battery cell in the high-temperature area from becoming closed after prolonged high-temperature baking, while moisture inside the battery cell in the low-temperature area cannot be dried out. On the other hand, the oven consumes a lot of gas, suffers significant equipment wear and tear, and poses a risk of cross-contamination by foreign objects. Frequent nitrogen filling and vacuuming steps are required for the entire heating chamber, which not only wastes a large amount of nitrogen but also exacerbates the loss of the negative pressure source, both of which increase the manufacturing cost of the battery. In addition, the "nitrogen filling and vacuuming" breathing cycle may blow foreign objects in the chamber into the battery cell through the battery cell injection hole, causing an increase in the self-discharge failure rate.

[0004] In addition, after the battery cell is heated and dehydrated, a Hipot test is generally required to identify battery cells with defects such as diaphragm damage, electrode edge burrs, and metal foreign objects. Currently, the commonly used detection methods are: (1) DC Hipot test, which involves applying a certain DC voltage to the positive and negative terminals to cause the metal foreign objects or edge burrs on the electrode surface to discharge at the tip, and detecting defective battery cells by recording the leakage current generated under high voltage or calculating the insulation resistance value. (2) AC Hipot test, which involves applying a certain AC voltage to the positive and negative terminals to cause the metal foreign objects or edge burrs on the electrode surface to discharge at the tip, and detecting defects by recording the changes in current and voltage waveforms to identify the tiny discharge phenomena in the battery cell. However, since the battery cell is under static conditions of normal temperature and pressure during the test, and the test time is short, the above detection methods generally have the problem of low defect recognition rate. In addition, the above detection methods are all separate processes performed before and after the battery cell heating process and require separate testing equipment, which will undoubtedly increase the working time and manufacturing cost of the overall battery cell process. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for heating battery cells, which solves the problems of low efficiency and high loss when heating battery cells in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for heating a battery cell, comprising the following steps:

[0007] S1. Connect the positive and negative terminals of the battery cell to the corresponding terminals of the frequency converter power supply.

[0008] S2. Connect the frequency converter power supply and apply an alternating current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell to heat the battery cell to the set temperature T.

[0009] S3. During the heating process and / or after the heating process is stopped, the battery cell and / or the battery cell placed in a sealed cavity are treated by vacuuming, filling with dry gas, or alternating between vacuuming and filling with dry gas, and a certain gas pressure value P is maintained in the sealed cavity where the battery cell is located.

[0010] The power-on heating circuit is connected to a detection module and a power-off module. The detection module is used to monitor the circuit parameters in real time during the power-on heating process. When an abnormality occurs, it indicates that there is a defect in the battery cell. The power-off module then cuts off the heating circuit and stops heating.

[0011] S4. After the battery cell reaches the set temperature T, the battery cell is kept warm by transferring it to the insulation chamber or by adjusting the inverter power supply parameters to reduce the heating power, and this temperature is maintained for a period of time t.

[0012] S5. After the battery cell has been heated, the battery cell and / or the sealed cavity where the battery cell is located and / or the inverter power supply terminals shall be cooled by at least one of the following methods: natural cooling, forced air cooling or liquid cooling.

[0013] Preferably, in step S1, when electrically connecting the positive and negative terminals of the battery cell to the terminals of the frequency converter, the positive and negative terminals of a single battery cell are connected to the two terminals of the frequency converter respectively, or the single battery cell is connected in series, in parallel, or in series and in parallel before being electrically connected to the two terminals of the frequency converter.

[0014] Preferably, in step S2, the frequency conversion range of the variable frequency power supply is 1Hz to 200kHz, the current range is 0.5 to 1500A, and the voltage range is 5 to 3000V. The output waveform can be one or more of the following: sine wave, square wave, triangle wave, sawtooth wave, rectangular wave, full wave, half wave, and pulse wave. An nth harmonic can also be applied to the fundamental voltage source, with a harmonic content of u%, to improve heating efficiency; where n is 0 to 200 and u is 0 to 15.

[0015] Preferably, the temperature T in step S2 is in the range of 30–200°C. This is to avoid the baking efficiency being too low due to excessively low temperature, and the material aging due to excessively high temperature.

[0016] Preferably, the air pressure value P in step S3 is in the range of 10. -5 The pressure should be between 100 kPa and 200 kPa to avoid deformation of the casing due to excessively low or high pressure, which could affect the sealing performance of the casing.

[0017] Preferably, the time t in step S4 ranges from 0 to 10 hours.

[0018] Preferably, the drying gas in step S3 is one of nitrogen, argon, carbon dioxide, helium or compressed air, and the dew point temperature of the drying gas is ≤-20℃.

[0019] A battery cell heating device is provided, which is applied to the battery cell heating method of the claim. The heating chamber includes a chamber body and a door hinged to the open edge of the front end of the chamber body. The tray assembly includes a groove and a plate fitted into the inner cavity of the groove. The plate is provided with a plurality of placement grooves for positioning and placing battery cells. The lifting mechanism is located at the bottom of the inner cavity of the chamber and is used to lift the tray assembly. The heating assembly includes a support plate fixed to the top of the inner cavity of the chamber, an energizing post vertically mounted on the support plate with its bottom end corresponding to the top tab of the battery cell, a gas connection terminal vertically mounted on the support plate with its bottom end corresponding to the pre-reserved liquid injection hole on the top of the battery cell, and a temperature sensor vertically mounted on the support plate with its bottom end corresponding to the outer shell of the battery cell. The top ends of the energizing posts are electrically connected to a frequency converter, and a detection module and a power-off module are provided in the circuit between the energizing posts and the frequency converter. The top ends of the gas connection terminals are connected to a negative pressure source and a drying gas source through a tee.

[0020] Preferably, a support plate is fixed in the middle of the inner cavity of the silo, guide plates are fixed at both ends of the support plate along the vertical direction, an opening is provided in the middle of the support plate, and sliding grooves are provided on both sides of the top surface of the support plate; rollers that roll along the sliding grooves are rotatably installed at the front and rear ends of the two side walls of the silo, and threaded holes are provided in the middle of the bottom plate of the silo near the two sides, and fixing bolts that are threaded and matched with the threaded holes are respectively fitted in the middle of the plate near the two sides. The lifting mechanism includes a telescopic cylinder arranged vertically, a base that fixes the bottom of the telescopic cylinder piston cylinder to the bottom surface of the inner cavity of the silo, and a top plate that is fixed to the top of the telescopic cylinder piston rod and slidably matched with the opening.

[0021] Preferably, a pair of support pillars and a pair of threaded sleeves are fixed at the four corners of the top surface of the tank. A cover plate is provided above the tank, and conductive lines are embedded in the cover plate. The bottom surface of the conductive lines is provided with contacts that make one-to-one conductive contact with the top tabs of the battery cells. Insulating sheets are provided on the top surface of the conductive lines corresponding to the positions of the contacts. The cover plate is provided with a first through hole and a second through hole that are matched with the bottom end of the gas connection terminal and the temperature sensor. A pair of conductive connectors are provided at the corners of the cover plate. The conductive connectors include conductive posts whose bottom ends are fitted into the corners of the cover plate and electrically connected to both ends of the conductive lines, threaded posts that are fixedly connected to the bottom ends of the conductive posts and threadedly fitted with the threaded sleeves, and knobs that are fixedly fitted into the outer part of the conductive posts near the top. A power-conducting post is fitted on the support plate at the position corresponding to the conductive post. The bottom ends of the power-conducting post, the gas connection terminal, and the temperature sensor are all elastic telescopic structures.

[0022] Preferably, the conductive circuit is one of a series circuit, a parallel circuit, or a series-parallel circuit.

[0023] Preferably, the internal cavity of the chamber is equipped with auxiliary electric heating equipment and / or cooling equipment.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. The present invention relates to a cell heating method and device that utilizes the capacitance effect of the cell itself to apply a current or voltage signal of a certain magnitude and frequency to generate heat, resulting in a faster temperature rise rate, a more uniform internal temperature distribution, and higher heat transfer efficiency. Furthermore, the method of vacuuming and filling a single cell with dry gas achieves faster mass transfer efficiency, reduces gas consumption, and avoids the risk of foreign dust entering the cell from the chamber.

[0026] 2. The battery cell heating method and equipment involved in this invention have a simple operation process, low energy consumption, short time and low cost.

[0027] 3. The battery cell heating method and equipment of the present invention can monitor the power parameters of the heating circuit in real time while heating the battery cell, so as to judge whether the quality of the battery cell is qualified in a timely manner through monitoring data, and can stop the heating of unqualified battery cells in a timely manner to save resources.

[0028] 4. The battery cell heating method and equipment involved in this invention can simultaneously heat the battery cell and detect defects. During detection, the internal temperature of the battery cell is higher, and the gaps between the electrodes dynamically change due to repeated vacuuming and injection of dry gas. This offers several advantages for detection: the dynamic change in the position of foreign objects during this process, combined with the increased number of tests over a long period, results in a higher defect identification rate than conventional methods (traditional HIPOT testing is conducted under static conditions at room temperature and pressure, and the test time is only a few seconds). Furthermore, the high temperature also facilitates defect identification. Specifically, the increased temperature increases the thermal motion of air molecules, leading to more frequent molecular collisions and thus increasing the ionization probability, which is beneficial for identifying defects such as diaphragm damage. This not only reduces the investment in additional HIPOT testing equipment before and after baking and improves the defect identification rate of the battery cell, but also improves the overall efficiency of the battery cell heating process. Attached Figure Description

[0029] Figure 1 is a three-dimensional structural diagram of the present invention;

[0030] Figure 2 is a three-dimensional structural diagram of the heating chamber of the present invention;

[0031] Figure 3 is an exploded structural diagram of the tray assembly of the present invention;

[0032] Figure 4 is a three-dimensional structural schematic diagram of the conductive connector of the present invention;

[0033] Figure 5 is a three-dimensional structural schematic diagram of the lifting mechanism of the present invention;

[0034] Figure 6 is an enlarged structural schematic diagram of point A in Figure 1 of the present invention;

[0035] Figure 7 is a three-dimensional structural diagram of the conductive pillar of the present invention;

[0036] Figure 8 is a three-dimensional structural schematic diagram of the gas connection terminal of the present invention;

[0037] Figure 9 is a three-dimensional structural schematic diagram of the temperature sensor of the present invention;

[0038] Figure 10 is a schematic diagram of the moisture content of the positive and negative electrode sheets of Embodiment 3 and Comparative Example 1 under different baking times.

[0039] In the diagram: 1-Heating chamber; 1.1-Chamber body; 1.2-Chamber door; 1.3-Support plate; 1.4-Slide groove; 1.5-Guide plate; 1.6-Opening;

[0040] 2-Tray assembly; 2.1-Slot; 2.1.1-Threaded hole; 2.1.2-Support; 2.1.3-Threaded sleeve; 2.1.4-Roller; 2.2-Plate; 2.2.1-Placement slot; 2.2.2-Fixing bolt; 2.3-Cover plate; 2.3.1-Conductive circuit; 2.3.2-Through hole one; 2.3.3-Through hole two; 2.3.4-Insulating sheet; 2.4-Conductive connector; 2.4.1-Conductive post; 2.4.2-Threaded post; 2.4.3-Knob;

[0041] 3-Lifting mechanism; 3.1-Telescopic cylinder; 3.2-Base; 3.3-Top plate;

[0042] 4-Heating component; 4.1-Support plate; 4.2-Power column; 4.3-Suction cup; 4.4-Temperature sensor. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1: Please refer to Figures 1-9. This invention provides a technical solution, a method for heating a battery cell, comprising the following steps:

[0045] S1. Insert the bottom of the battery cell into each placement slot 2.2.1 of the plate 2.2, and then insert the entire tray assembly 2 into the middle of the inner cavity of the compartment 1.1.

[0046] The battery cell includes a positive electrode, a separator or solid electrolyte membrane, and a negative electrode. The battery cell can be an electrode core assembled by winding or stacking, an electrode core with soldered tabs, or a battery cell with a fully encapsulated casing. Specifically, a fully encapsulated battery cell can be a soft-pack battery cell with three sides encapsulated with aluminum-plastic film but no electrolyte injected, a square metal-cased battery cell with six sides encapsulated but no electrolyte injected, or a cylindrical battery cell with both casing and cover encapsulated but no electrolyte injected. Depending on the shape and size of the battery cell, a plate with a corresponding placement slot 2.2.1 can be replaced within the tank 2.1.

[0047] S2, the lifting mechanism 3 lifts the tray assembly 2 upwards to a certain height from the bottom, so that the positive and negative terminals of the battery cell are electrically connected to the power-conducting post 4.2 respectively. At the same time, the reserved liquid injection hole on the top of the battery cell is attached to the bottom end of the gas connection terminal 4.3, and the probe of the temperature sensor 4.4 is attached to the outer shell of the battery cell.

[0048] Among them, the power supply post 4.2 is the wiring terminal of the frequency converter power supply.

[0049] S3. Connect the frequency converter power supply and apply a current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell through the energizing column 4.2 to heat the battery cell to the set temperature T.

[0050] The frequency converter has a frequency range of 1Hz to 200kHz, a current range of 0.5 to 1500A, a voltage range of 5 to 3000V, and a temperature range of 30 to 200℃. The heating circuit is connected to a detection module and a power-off module. The detection module monitors the circuit parameters in real time during the heating process; if an abnormality occurs, it indicates a defect in the battery cell, and the power-off module cuts off the heating circuit, stopping heating.

[0051] S4. During the heating process and / or after the heating process is stopped, the battery cell is evacuated and filled with dry gas, or the evacuation and dry gas filling are alternately switched to maintain a certain gas pressure value P inside the battery cell.

[0052] Among them, the air pressure value P ranges from 10. -5 The dry gas is between 200 kPa and 200 kPa, and is one or more of nitrogen, argon, carbon dioxide, helium or compressed air, with a dew point temperature of ≤-20℃.

[0053] S5. After the battery cell reaches the set temperature T, the battery cell is kept warm by transferring it to the insulation chamber or by adjusting the inverter power supply parameters to reduce the heating power, and this temperature is maintained for a period of time t.

[0054] The time t ranges from 0 to 10 hours.

[0055] S6. After the battery cell has finished heating, the power supply column 4.2 of the inverter power supply inside the housing 1 and / or the housing 1 is cooled by at least one of the following methods: natural cooling, forced air cooling or liquid cooling.

[0056] Example 2: Please refer to Figures 1-9. The difference between Example 2 and Example 1 lies only in steps S1 and S2. Steps S1 and S2 in Example 2 are as follows:

[0057] S1. Insert the bottom of the battery cell into each of the placement slots 2.2.1 of the plate 2.2, and cover the battery cell with the cover plate 2.3, so that the four corners of the bottom surface of the cover plate 2.3 are respectively supported on the support column 2.1.2 or the threaded sleeve 2.1.3. Then install the conductive connector 2.4, so that the threaded post 2.4.2 at the bottom of the conductive connector 2.4 is screwed into the threaded sleeve 2.1.3, and the conductive post 2.4.1 is electrically connected to both ends of the wire line 2.3.1. At this time, the reserved liquid injection hole of the battery cell corresponds one-to-one with the perforation 2.3.2, the battery cell shell corresponds to the perforation 2.3.3; the insulating sheet 2.3.4 corresponds one-to-one with the energizing post 4.2 in the middle of the heating assembly 4 support plate 4.1; the two conductive posts 2.4.1 correspond to the two conductive posts 4.2 at the corners of the support plate 4.1.

[0058] Then insert the entire pallet assembly 2 into the middle of the inner cavity of the compartment 1.1 and close the compartment door 1.2.

[0059] S2, the lifting mechanism 3 lifts the tray assembly 2 upwards to a certain height from the bottom, so that the two conductive posts 2.4.1 make electrical contact with the two energized posts 4.2 at the corner of the support plate 4.1 respectively. At the same time, the bottom end of the gas connection terminal 4.3 passes through the first perforation 2.3.2 and is attached to the reserved liquid injection hole on the top of the cell, and the probe of the temperature sensor 4.4 passes through the second perforation 2.3.3 and is attached to the outer shell of the cell.

[0060] This allows for the connection of individual battery cells in series, parallel, or series-parallel configurations before electrical connection to the two terminals of the frequency converter. The series-parallel configuration enables the simultaneous heating of battery cells with different electrical parameters.

[0061] Example 3: A six-sided encapsulated square aluminum-cased lithium-ion cell was selected. The cell's dimensions (length × width × height) are 173mm × 71mm × 208mm. After excluding the internal dry cell volume, the redundant space is approximately 0.2L. The top cover has positive and negative terminals and a 3mm diameter circular injection hole. The heating process steps are as follows:

[0062] S1. Place the battery cell into the tray assembly 2, and seal the entire tray assembly 2 containing the battery cell inside the chamber 1.1. The lifting mechanism 3 lifts the entire tray assembly 2, so that the positive and negative ends of the battery cell are pressed against the power-on post 4.2 of the frequency converter power supply. The equipment automatically detects the capacitance value of the battery cell. At the same time, the gas connection terminal 4.3 is pressed against the pre-reserved liquid injection hole on the top of the battery cell, and the temperature sensor 4.4 is attached to the outer shell of the battery cell.

[0063] S2. Turn on the negative pressure source to evacuate the battery cell to a vacuum level below 1 kPa. Then, through the gas connection terminal 4.3, fill the battery cell with dry nitrogen gas to atmospheric pressure.

[0064] S3. Apply a 24V / 20A / 500HZ inverter current to both ends of the battery cell, set the heating temperature to 110℃, and after 35 minutes, the battery cell reaches the set temperature.

[0065] Among them, the vacuum heating stage involves evacuating the inside of the battery cell to below 1 kPa and maintaining the temperature and pressure for 20 minutes.

[0066] During the drying nitrogen replacement stage, the inside of the battery cell is filled with dry nitrogen to 70KPa~90KPa and kept at the temperature and pressure for 2 minutes.

[0067] Breathing cycle stage: Repeat the vacuum heating stage and the dry nitrogen replacement stage 10 times, maintaining the cell temperature within the range of 110±2℃ during the process.

[0068] S4. The heating and baking process of the battery cell is completed.

[0069] Comparative Example 1: Using the same battery cells as in Example 3, the cells were placed in a sealed cavity with a volume of approximately 500L. Each cavity could hold 50 battery cells with dimensions of 173×71×208 (with an internal redundant volume of approximately 375L). The heating and baking process for the battery cells was as follows:

[0070] S1. Place the battery cells in a well-sealed contact oven, and heat them using an electric heating plate.

[0071] S2. Evacuate the cavity until the internal vacuum level is below 50Pa.

[0072] S3. Preheating and baking: Fill with dry nitrogen until the internal pressure of the oven is 70KPa~90KPa, turn on the heating, raise the oven temperature to 100℃, keep it warm and pressurized for 3 hours until the internal temperature of the battery cell reaches 100℃.

[0073] S4. Vacuum baking stage: Evacuate the cavity until the vacuum level inside the cavity is below 50Pa, and keep it warm and pressurized under low vacuum for 2 hours.

[0074] S5. Vacuum breathing: Fill the oven with dry nitrogen until the vacuum level inside the oven is 70-90 kPa, and maintain the pressure for 20 minutes.

[0075] S6. Repeat steps S4 to S5 6 times.

[0076] S7. After heating and baking is completed, dry nitrogen is used to break the vacuum, the door is opened, and the battery cells are taken out of the oven.

[0077] Samples were taken from the cells of Example 3 and Comparative Example 1, and the moisture content of the positive and negative electrodes of the cells was tested at different baking times (positive electrode moisture standard: <450ppm, negative electrode moisture standard <200ppm), as shown in Figure 10.

[0078] Both baking processes can meet the moisture requirements, but the baking process of this invention can achieve rapid dehydration.

[0079] The process parameters are compared in Table 1. The baking process of the present invention has lower gas consumption and shorter baking time than the conventional baking process.

[0080] Table 1 Comparison of Process Indicators

[0081] Example 4: In another embodiment of this invention, the battery cell is a cylindrical aluminum-cased sodium-ion battery cell with encapsulation at both ends. The battery cell diameter is 46mm and the height is 120mm. After excluding the dry battery cell volume, the redundant space is approximately 80mL. The top cover has positive and negative electrode posts and a circular liquid injection hole with a diameter of 3mm. The heating process steps are as follows:

[0082] S1. Place the battery cell into the tray assembly 2, and seal the entire tray assembly 2 containing the battery cell inside the chamber 1.1. The lifting mechanism 3 lifts the entire tray assembly 2, so that the positive and negative ends of the battery cell are pressed against the power-on post 4.2 of the frequency converter power supply. The equipment automatically detects the capacitance value of the battery cell. At the same time, the gas connection terminal 4.3 is pressed against the pre-reserved liquid injection hole on the top of the battery cell, and the temperature sensor 4.4 is attached to the outer shell of the battery cell.

[0083] S2. Turn on the negative pressure source to evacuate the battery cell to a vacuum level below 1 kPa. Then, through the gas connection terminal 4.3, fill the battery cell with dry nitrogen gas to atmospheric pressure.

[0084] S3. Apply a 12V / 10A / 300HZ frequency converter current to both ends of the battery cell, set the heating temperature to 110℃, and after 10 minutes, the battery cell reaches the set temperature.

[0085] Among them, the vacuum heating stage involves evacuating the inside of the battery cell to below 1 kPa and maintaining the temperature and pressure for 10 minutes.

[0086] During the drying and nitrogen replacement stage, nitrogen is purged into the battery cell to 70 kPa to 90 kPa, and the temperature and pressure are maintained for 2 minutes.

[0087] Breathing cycle stage: Repeat the vacuum heating stage and the dry nitrogen replacement stage 20 times, maintaining the cell temperature within the range of 110±2℃ during the process.

[0088] S4. The heating and baking process of the battery cell is completed.

[0089] Comparative Example 2: Using the same battery cells as in the example, they were placed in a sealed cavity with a volume of approximately 500L. Each cavity could hold 250 46×120 size battery cells (with an internal redundant volume of approximately 250L). The battery cell heating and baking process was as follows:

[0090] S1. Place the battery cells in a well-sealed contact oven, and heat them using an electric heating plate.

[0091] S2. Evacuate the cavity until the internal vacuum level is below 50Pa.

[0092] S3. Preheating and baking: Fill with dry nitrogen until the internal pressure of the oven is 70KPa-90KPa, turn on the heating, raise the oven temperature to 100℃, keep it warm and pressurized for 2 hours until the internal temperature of the battery cell reaches 100℃.

[0093] S4. Vacuum baking stage: Evacuate the cavity until the vacuum level inside the cavity is below 50Pa, and keep it warm and pressurized under low vacuum for 2 hours.

[0094] S5. Vacuum breathing: Fill the oven with dry nitrogen until the vacuum level inside the oven is 70-90 kPa, and maintain the pressure for 10 minutes;

[0095] S6. Repeat steps S4 to S5 8 times.

[0096] S7. After heating and baking is completed, dry nitrogen is used to break the vacuum, the chamber door is opened, and the battery cells are taken out of the oven.

[0097] Samples were taken from the cells of Example 4 and Comparative Example 2, and the moisture content of the positive and negative electrodes of the cells was tested. The results are shown in Table 2, and all samples met the moisture content requirements.

[0098] Table 2. Moisture content of positive and negative electrodes of the battery cell.

[0099] By comparing the baking effects of the embodiments and comparative examples on square / cylindrical batteries, it can be seen that the embodiments using this invention patent can not only effectively remove moisture from the battery cells, but also have a shorter total baking time, saving energy consumption. Furthermore, this invention only performs vacuuming and nitrogen circulation inside the battery cell, resulting in low vacuum and nitrogen consumption. In contrast, the comparative example vacuums and purifies the entire oven cavity, reducing nitrogen consumption and avoiding the damage to the negative pressure source caused by frequent vacuuming, thus lowering the manufacturing cost of the battery cells.

[0100] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0101] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for heating a battery cell, characterized in that, Includes the following steps: S1. Connect the positive and negative terminals of the battery cell to the corresponding terminals of the frequency converter power supply. S2. Connect the frequency converter power supply and apply a current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell to heat the battery cell to the set temperature T. S3. During the heating process and / or after the heating process is stopped, the battery cell and / or the battery cell placed in a sealed cavity are treated by vacuuming, filling with dry gas, or alternating between vacuuming and filling with dry gas, and a certain gas pressure value P is maintained in the sealed cavity where the battery cell is located. The power-on heating circuit is connected to a detection module and a power-off module. The detection module is used to monitor the circuit parameters in real time during the power-on heating process. When an abnormality occurs, it indicates that there is a defect in the battery cell. The power-off module then cuts off the heating circuit and stops heating. S4. After the battery cell reaches the set temperature T, the battery cell is kept warm by transferring it to the insulation chamber or by adjusting the inverter power supply parameters to reduce the heating power, and this temperature is maintained for a period of time t. S5. After the battery cell has been heated, the battery cell and / or the sealed cavity where the battery cell is located and / or the inverter power supply terminals shall be cooled by at least one of the following methods: natural cooling, forced air cooling or liquid cooling.

2. The cell heating method according to claim 1, characterized in that: In step S2, the frequency conversion range of the variable frequency power supply is 1Hz to 200KHz, the current range is 0.5 to 1500A, the voltage range is 5 to 3000V, and the temperature range is 30 to 200℃.

3. The cell heating method according to claim 1, characterized in that: In step S1, when electrically connecting the positive and negative terminals of the battery cell to the terminals of the frequency converter, the positive and negative terminals of a single battery cell can be connected to the two terminals of the frequency converter respectively, or the single battery cell can be connected in series, in parallel, or in series and in parallel before being electrically connected to the two terminals of the frequency converter.

4. The cell heating method according to claim 1, characterized in that: In step S3, the air pressure value P ranges from 10. -5 The dry gas is between 200 kPa and 200 kPa, and is one or more of nitrogen, argon, carbon dioxide, helium or compressed air, with a dew point temperature of ≤-20℃.

5. A battery cell heating device, characterized in that, The cell heating device is applied to the cell heating method according to any one of claims 1-4, comprising: A heating chamber (1), the heating chamber (1) comprising a chamber body (1.1) and a door hinged to the front open edge of the chamber body (1.1); The tray assembly (2) includes a groove (2.1) and a plate (2.2) fitted into the cavity of the groove (2.1). The plate (2.2) is provided with a plurality of placement slots (2.2.1) for positioning and placing battery cells. A lifting mechanism (3) is provided at the bottom of the inner cavity of the compartment (1.1) and is used to lift the pallet assembly (2); The heating assembly (4) includes a support plate (4.1) fixed to the top of the inner cavity of the chamber (1.1), a power-conducting post (4.2) vertically mounted on the support plate (4.1) with its bottom end corresponding to the top tab of the battery cell, a gas connection terminal (4.3) vertically mounted on the support plate (4.1) with its bottom end corresponding to the pre-reserved liquid injection hole on the top of the battery cell, and a temperature sensor (4.4) vertically mounted on the support plate (4.1) with its bottom end corresponding to the outer shell of the battery cell. The top of the power-conducting post (4.2) is electrically connected to the frequency converter, and a detection module and a power-off module are provided in the circuit between the power-conducting post (4.2) and the frequency converter. The top of the gas connection terminal (4.3) is connected to the negative pressure source and the dry gas source through a T-junction.

6. The battery cell heating device according to claim 5, characterized in that: A support plate (1.3) is fixed in the middle of the inner cavity of the silo (1.1). Guide plates (1.5) are fixed vertically at both ends of the support plate (1.3). An opening (1.6) is provided in the middle of the support plate (1.3). Sliding grooves (1.4) are provided on both sides of the top surface of the support plate (1.3). Rollers (2.1.4) that roll along the sliding grooves (1.4) are rotatably installed at the front and rear ends of the two side walls of the trough (2.1). Threaded holes (2.1.4) are provided in the middle of the bottom plate of the trough (2.1) near the two sides. 1.1), the plate (2.2) is fitted with fixing bolts (2.2.2) that are threadedly connected to the threaded hole (2.1.1) near the two sides of the middle part. The lifting mechanism (3) includes a telescopic cylinder (3.1) arranged vertically, a base (3.2) that fixes the bottom of the piston cylinder of the telescopic cylinder (3.1) to the bottom surface of the inner cavity of the chamber (1.1), and a top plate (3.3) that is fixed to the top of the piston rod of the telescopic cylinder (3.1) and slidably connected to the opening (1.6).

7. The battery cell heating device according to claim 6, characterized in that: A pair of support pillars (2.1.2) and a pair of threaded sleeves (2.1.3) are fixed at the four corners of the top surface of the tank (2.1). A cover plate (2.3) is provided above the tank. A conductive line (2.3.1) is embedded in the cover plate (2.3). The bottom surface of the conductive line (2.3.1) is provided with contacts that make one-to-one conductive contact with the top tabs of the battery cell. An insulating sheet (2.3.4) is provided on the top surface of the conductive line (2.3.1) at the position corresponding to the contact. The cover plate (2.3) is provided with a through hole one (2.3.2) and a through hole two (2.3.3) that are matched to the bottom end of the gas connection terminal (4.3) and the temperature sensor (4.4). A pair of conductive connections are provided at the corners of the cover plate (2.3). The conductive connector (2.4) includes a conductive post (2.4.1) whose bottom end is fitted onto the corner of the cover plate (2.3) and electrically connected to both ends of the conductive line (2.3.1), a threaded post (2.4.2) fixedly mated to the bottom end of the conductive post (2.4.1) and threadedly fitted into the threaded sleeve (2.1.3), and a knob (2.4.3) fixedly fitted onto the conductive post (2.4.1) near the top outside. A power-conducting post (4.2) is fitted on the support plate (4.1) at a position corresponding to the conductive post (2.4.1). The bottom ends of the power-conducting post (4.2), the gas connection terminal (4.3), and the temperature sensor (4.4) are elastic telescopic structures.

8. The battery cell heating device according to claim 7, characterized in that: The conductive line (2.3.1) is one of a series circuit, a parallel circuit, or a series-parallel circuit.

9. A cell heating device according to claim 8, characterized in that: The inner cavity of the chamber (1.1) is equipped with auxiliary electric heating equipment and / or cooling equipment.

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