A method and device for heating a battery core

Abstract

The present invention relates to the technical field of new energy battery manufacturing, and specifically to a method and device for heating a battery cell. The battery cell heating device is used to operate according to the following steps: S1, electrically connecting the positive and negative electrodes of the 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 through the variable frequency power supply, and heating the battery cell to a set temperature T; S3, vacuuming the battery cell and / or the sealed cavity where the battery cell is located, filling it with dry gas, or vacuuming and filling it with dry gas in a cyclic switching manner, and maintaining a certain air pressure value P in the battery cell and / or the sealed cavity where the battery cell is located; S4, after the battery cell reaches the set temperature T, keeping it warm for a period of time t; S5, after the battery cell is heated, cooling the battery cell and / or the sealed cavity where the battery cell is located and / or the wiring terminals of the variable frequency power supply; the efficiency of heating the battery cell is improved, the loss is reduced, and the identification of defective battery cells is realized simultaneously.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy battery manufacturing, and in particular to a method and device for heating a battery core. Background Art

[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] The traditional battery cell heating process usually adopts the process of air-conveying heating or contact heating. The battery cell is placed in a closed cavity, and the electric heating wire or electric heating plate is powered on to generate heat. In a dry gas atmosphere, the battery cell is heated by heat transfer or heat conduction. During the heating process, the entire cavity is evacuated and nitrogen-filled. After a certain number of "nitrogen filling and vacuuming" breathing cycles, the water vapor evaporated from the battery cell is replaced to remove the moisture in the battery cell. However, the above two heating methods have many disadvantages. On the one hand, the heating and heat preservation time are long, the heating efficiency is low, and the energy consumption is high. Whether it is an air-conveying oven or a contact oven, the battery cell is heated by heat transfer or heat conduction after heating by means of resistance wire / electric heating wire. Due to the poor thermal conductivity of the battery cell, it takes a long time to heat up, the heating efficiency is low, and a lot of electricity is consumed. Due to the uneven temperature distribution inside the air-conveying oven and the uneven temperature distribution between the contact surface of the contact oven and the inside of the battery cell, the oven cannot be set to a higher baking temperature and needs to be set to a longer insulation time to avoid the diaphragm in the battery cell in the higher temperature area from being closed after being baked at high temperature for a long time, while the moisture in the battery cell in the lower temperature area cannot be baked out. On the other hand, the gas consumption is large, the equipment loss is large, and there is a risk of cross-contamination by foreign matter. The entire heating cavity needs to be frequently filled with nitrogen and vacuumed, which not only wastes a large amount of nitrogen, but also aggravates 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 also blow foreign matter in the cavity 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 the battery cells with defects such as diaphragm damage, electrode edge burrs and metal foreign matter. At present, the commonly used detection methods are: (1) DC Hipot test, by applying a certain DC voltage across the positive and negative terminals, the metal foreign matter or edge burrs on the surface of the electrode will cause tip discharge, and the defective battery cell will be detected by recording the leakage current generated under high voltage or calculating the insulation resistance. (2) AC Hipot test, by applying a certain AC voltage across the positive and negative terminals, the metal foreign matter or edge burrs on the surface of the electrode will cause tip discharge, and the tiny discharge phenomenon in the battery cell will be identified by recording the changes in the current and voltage waveforms to perform defect detection. 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 another independent process performed before and after the battery cell heating process and require separate detection equipment, which will undoubtedly increase the working hours and manufacturing cost of the overall battery cell process. Summary of the invention

[0005] The object of the present invention is to provide a method and device for heating a battery cell, so as to solve the problems of low efficiency and large loss when heating a battery cell in the prior art.

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

[0007] S1. Electrically connect the positive and negative electrodes of the battery cell to the corresponding wiring terminals of the variable frequency power supply respectively;

[0008] S2, connect the variable frequency power supply, apply an alternating current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell through the variable frequency power supply, and heat the battery cell to a set temperature T;

[0009] S3, during the power-on heating process and / or after the power-on heating stops, the battery cell and / or the battery cell is placed in a closed cavity and vacuumed, filled with dry gas, or vacuumed and filled with dry gas in a cyclic switching manner, and a certain air pressure value P is maintained in the closed cavity where the battery cell and / or 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 the power-on heating process in real time. When an abnormality occurs, it indicates that the battery cell is defective. The power-off module 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 the battery cell to a heat preservation bin or by adjusting the frequency conversion power supply parameters to reduce the heating power, and the temperature is maintained for a period of time t;

[0012] S5. After the battery cell is heated, the battery cell and / or the sealed cavity where the battery cell is located and / or the variable frequency power supply terminal are cooled by at least one of natural cooling, forced air cooling or liquid cooling.

[0013] Preferably, when electrically connecting the positive and negative electrodes of the battery cell to the terminal blocks of the variable frequency power supply in step S1, the positive and negative electrodes of a single battery cell are respectively connected to the two terminal blocks of the variable frequency power supply, or the single battery cell is connected in series, in parallel, or in series and parallel and then electrically connected to the two terminal blocks of the variable frequency power supply.

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

[0015] Preferably, the temperature T in step S2 ranges from 30 to 200° C. to avoid low baking efficiency due to too low a temperature and aging of the material due to too high a temperature.

[0016] Preferably, the air pressure value P in step S3 is in the range of 10 -5 pa~200 Kpa. To avoid the air pressure being too low or too high which may cause the shell to deform and thus affect the sealing performance of the shell.

[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°C.

[0019] A battery cell heating device, the battery cell heating device is applied to the battery cell heating method described in the claim, the heating chamber comprises a chamber body and a chamber door hinged at the open edge of the front end of the chamber body; the tray assembly comprises a trough body and a plate body clamped in the inner cavity of the trough body, the plate body is provided with a plurality of placement grooves for positioning and placing the battery cells; the lifting mechanism is arranged at the bottom of the inner cavity of the chamber body and is used to lift the tray assembly; the heating assembly comprises a support plate fixed to the top of the inner cavity of the chamber body, a power-on column vertically mounted on the support plate and having a bottom end corresponding to a pole ear at the top of the battery cell, a gas connection terminal vertically mounted on the support plate and having a bottom end corresponding to a reserved injection hole at the top of the battery cell, and a temperature sensor vertically mounted on the support plate and having a bottom end corresponding to a battery cell shell, the top ends of the power-on columns are respectively electrically connected to a variable frequency power supply, and a detection module and a power-off module are arranged in the circuit between the power-on columns and the variable frequency power supply, and the top ends of the gas connection terminals are respectively connected to a negative pressure source and a dry gas source through a tee.

[0020] Preferably, a support plate is fixed in the middle of the body cavity of the warehouse, guide plates are vertically fixed at both ends of the support plate, a hole is provided in the middle of the support plate, and slide grooves are respectively provided on both sides of the top surface of the support plate; rollers that roll along the slide grooves are rotatably installed on the front and rear ends of the two side walls of the trough body, threaded holes are respectively provided in the middle of the bottom plate of the trough body near the two sides, and fixing bolts that are threadedly sleeved and matched with the threaded holes are respectively provided in the middle of the plate body near the two sides, and 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 body cavity of the warehouse, and a top plate fixed to the top end of the telescopic cylinder piston rod and slidingly sleeved and matched with the hole.

[0021] Preferably, a pair of pillars and a pair of threaded sleeves are fixed at the four corners of the top surface of the trough body, a cover plate is provided above the trough body, a conductive circuit is inlaid on the cover plate, contacts that are in conductive contact with the top pole ears of the battery cell in a one-to-one correspondence are provided on the bottom surface of the conductive circuit, insulating sheets are provided on the top surface of the conductive circuit corresponding to the contacts, a through hole 1 and a through hole 2 that match the gas connection terminal and the bottom end of the temperature sensor are provided on the cover plate, a pair of conductive connectors are provided at the corners of the cover plate, the conductive connectors include a conductive column whose bottom end is sleeved on the corners of the cover plate and electrically connected to the two ends of the conductive circuit, a threaded column fixedly docked at the bottom end of the conductive column and matching the threaded sleeve, and a knob fixedly sleeved on the conductive column near the top outside, a power-on column is sleeved on the support plate at the position corresponding to the conductive column, and the bottom ends of the power-on column, the gas connection terminal and the temperature sensor are elastic telescopic structures respectively.

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

[0023] Preferably, the inner cavity of the warehouse is provided with auxiliary electric heating equipment and / or cooling equipment.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention relates to a method and device for heating a battery cell, which utilizes the capacitance effect of the battery cell itself to apply a current or voltage signal of a certain size and frequency to the battery cell to generate heat. The battery cell temperature rises faster, the temperature distribution inside the battery cell is more uniform, and the heat transfer efficiency is higher. In addition, the method of vacuuming a single battery cell and filling it with dry gas can achieve faster mass transfer efficiency, reduce the amount of gas used, and avoid the risk of foreign matter and dust in the cabin entering the battery cell.

[0026] 2. The present invention relates to a method and device for heating a battery cell, which has a simple operation process for heating the battery cell, low energy consumption, short time and low cost.

[0027] 3. The present invention relates to a battery cell heating method and device that can monitor the power parameters of the heating circuit in real time while the battery cell is powered on for heating, so as to timely judge whether the quality of the battery cell is qualified or not through the monitoring data, and can promptly stop the power supply and heating of unqualified battery cells to save resources.

[0028] 4. The present invention relates to a method and device for heating a battery cell, which can detect defective batteries while heating the battery cell. During the detection, the temperature inside the battery cell is higher and the gap between the pole pieces changes dynamically due to repeated vacuuming and injection of dry gas. There are several advantages for detection, namely, the position of the foreign matter changes dynamically during this process, and the defect recognition rate is higher than the conventional method due to the increase in the number of long-term detections (traditional HIPOT tests are performed under static conditions of normal temperature and pressure, and the test time is only a few seconds). In addition, high temperature is also conducive to identifying defects. The impact of high temperature on detection is that the increase in temperature will increase the thermal motion of air molecules, making molecular collisions more frequent, thereby increasing the probability of ionization, which is conducive to identifying defects such as diaphragm damage. It not only reduces the investment in additional HIPOT detection equipment before and after baking, improves the recognition rate of battery cell defects, but also improves the overall efficiency of the battery cell heating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the overall three-dimensional structure of the present invention;

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

[0031] Figure 3 It is a schematic diagram of the exploded structure of the tray assembly of the present invention;

[0032] Figure 4is a schematic diagram of the three-dimensional structure of the conductive connecting member of the present invention;

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

[0034] Figure 6 For the present invention Figure 1 A schematic diagram of the enlarged structure at A in the middle;

[0035] Figure 7 is a schematic diagram of the three-dimensional structure of the conductive column of the present invention;

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

[0037] Fig. 9 It is a schematic diagram of the three-dimensional structure of the temperature sensor of the present invention;

[0038] Fig.10 Schematic diagram of the moisture content of the positive and negative electrode sheets at different baking times in Example 3 of the present invention and Comparative Example 1.

[0039] In the figure: 1-heating chamber; 1.1-chamber body; 1.2-chamber door; 1.3-support plate; 1.4-chute; 1.5-guide plate; 1.6-hole;

[0040] 2-tray assembly; 2.1-trough body; 2.1.1-threaded hole; 2.1.2-pillar; 2.1.3-threaded sleeve; 2.1.4-roller; 2.2-plate body; 2.2.1-placement slot; 2.2.2-fixing bolt; 2.3-cover plate; 2.3.1-conductive circuit; 2.3.2-perforation 1; 2.3.3-perforation 2; 2.3.4-insulating sheet; 2.4-conductive connector; 2.4.1-conductive column; 2.4.2-threaded column; 2.4.3-knob;

[0041] 3-lifting mechanism; 3.1-telescopic cylinder; 3.2-base; 3.3-top plate;

[0042] 4-heating assembly; 4.1-support plate; 4.2-power column; 4.3-suction cup; 4.4-temperature sensor. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1: Please refer to Figure 1-9The present invention provides a technical solution, a method for heating a battery core, comprising the following steps:

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

[0046] Among them, the battery cell includes a positive electrode sheet, a diaphragm or a solid electrolyte membrane, and a negative electrode sheet. The battery cell can be a pole core composed of winding or lamination, or a pole core with a pole ear welded, or a battery cell with a shell package completed. The battery cell with a shell package completed can be a soft-packaged battery cell with three sides of aluminum-plastic film packaged and electrolyte not injected, or a square metal shell battery cell with six sides packaged and electrolyte not injected, or a cylindrical battery cell with shell and cover packaged and electrolyte not injected. According to the shape and size of different battery cells, the plate body with corresponding placement slot 2.2.1 can be replaced in the tank body 2.1.

[0047] S2, the lifting mechanism 3 lifts the tray assembly 2 as a whole upward to a certain height from the bottom, so that the positive and negative poles of the battery cell are in electrical contact with the power-on column 4.2 respectively, and at the same time, the reserved liquid injection hole on the top of the battery cell is fitted with the bottom end of the gas connection terminal 4.3, and the probe of the temperature sensor 4.4 is fitted on the outer shell of the battery cell.

[0048] Among them, the power column 4.2 is the connection terminal of the variable frequency power supply.

[0049] S3, connect the variable frequency power supply, apply a current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell through the power-on column 4.2, and heat the battery cell to the set temperature T;

[0050] The frequency conversion range of the variable frequency power supply is 1 Hz~200KHz, the current range is 0.5~1500A, the voltage range is 5~3000 V, and the temperature T range is 30~200 ℃. The power-on heating circuit is connected with a detection module and a power-off module. The detection module is used to monitor the circuit parameters in the power-on heating process in real time. When an abnormality occurs, it indicates that the battery cell is defective. The power-off module cuts off the heating circuit and stops heating.

[0051] S4, during the power-on heating process and / or after the power-on heating stops, the battery cell is evacuated, filled with dry gas, or evacuated and filled with dry gas in a cyclic switching manner, and a certain gas pressure value P is maintained in the battery cell;

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

[0053] S5, after the battery cell reaches the set temperature T, the battery cell is kept warm by transferring the battery cell to a heat preservation bin or by adjusting the frequency conversion power supply parameters to reduce the heating power, and the temperature is maintained for a period of time t;

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

[0055] S6. After the battery cells are heated, at least one of natural cooling, forced air cooling or liquid cooling is used to cool the interior of the warehouse body 1 and / or the power-on column 4.2 of the variable frequency power supply.

[0056] Example 2: Please refer to Figure 1-9 The difference between the second embodiment and the first embodiment is only that steps S1 and S2 are different. Steps S1 and S2 of the second embodiment are respectively:

[0057] S1. Insert the bottom of the battery cell into each placement slot 2.2.1 of the plate body 2.2, cover the cover plate 2.3 on top of the battery cell, so that the four corners of the bottom surface of the cover plate 2.3 are supported on the pillar 2.1.2 or the threaded sleeve 2.1.3 respectively, and then install the conductive connector 2.4, so that the threaded column 2.4.2 at the bottom of the conductive connector 2.4 is screwed into the threaded sleeve 2.1.3, and the conductive column 2.4.1 is electrically connected to the two ends of the wire line 2.3.1 respectively. At this time, the reserved injection hole of the battery cell corresponds to the perforation 1 2.3.2 one by one, and the battery cell shell corresponds to the perforation 2 2.3.3; the insulating sheet 2.3.4 corresponds to the power-on column 4.2 in the middle of the support plate 4.1 of the heating component 4; the two conductive columns 2.4.1 correspond to the two conductive columns 4.2 at the corners of the support plate 4.1 respectively.

[0058] Then the tray assembly 2 is inserted as a whole into the middle of the inner cavity of the bin body 1.1, and the bin door 1.2 is closed.

[0059] S2, the lifting mechanism 3 lifts the tray assembly 2 as a whole to a certain height from the bottom, so that the two conductive columns 2.4.1 are respectively in electrical contact with the two power-carrying columns 4.2 at the corners of the support plate 4.1, and at the same time, the bottom end of the gas connection terminal 4.3 passes through the through hole 1 2.3.2 and fits with the reserved liquid injection hole on the top of the battery cell, and the probe of the temperature sensor 4.4 passes through the through hole 2.3.3 and fits on the outer shell of the battery cell.

[0060] In order to realize the single battery cell being connected in series, in parallel or in series and in parallel and then being electrically connected to the two terminals of the variable frequency power supply. The series and parallel connection method is adopted, so that the battery cells with different electrical parameters can be heated at one time.

[0061] Example 3: The battery cell is a square aluminum shell lithium-ion battery cell with six-sided packaging. The length × width × height of the battery cell is 173mm × 71mm × 208mm. After excluding the volume of the dry battery cell inside the battery cell, the redundant space is about 0.2L. There are positive and negative poles and a circular injection hole with a diameter of 3mm on the top cover. The heating process steps used are as follows:

[0062] S1. Place the battery cells into the tray assembly 2, and seal the tray assembly 2 carrying the battery cells as a whole in the bin body 1.1. The lifting mechanism 3 lifts up the tray assembly 2 as a whole, so that the positive and negative ends of the battery cells are pressed against the power-on columns 4.2 of the variable frequency power supply respectively, and the equipment automatically detects the capacitance value of the dry battery cells; at the same time, the gas connection terminal 4.3 is pressed against the reserved injection hole on the top of the battery cell, and the temperature sensor 4.4 is fitted against the battery cell shell.

[0063] S2. Turn on the negative pressure source to evacuate the battery cell to a vacuum degree below 1 KPa, and then use the dry gas source to fill the battery cell with dry nitrogen through the gas connection terminal 4.3 to normal pressure.

[0064] S3, apply 24V / 20A / 500HZ variable frequency 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] In the vacuum heating stage, the battery cell is evacuated to below 1KPa, and the temperature and pressure are maintained for 20 minutes;

[0066] During the dry nitrogen replacement phase, the battery cell is filled with dry nitrogen to 70KPa~90KPa, and the temperature and pressure are maintained for 2 minutes;

[0067] Breathing cycle stage: Repeat the vacuum heating stage and dry nitrogen replacement stage 10 times, and maintain the battery cell temperature in 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: The same battery cell as in Example 3 is placed in a sealed cavity with a cavity volume of about 500L. A single cavity can hold 50 battery cells of 173×71×208 size (the redundant volume inside the cavity is about 375L). The heating and baking process of the battery cell is as follows:

[0070] S1. Place the battery cell in a well-sealed contact oven and heat it with an electric heating plate.

[0071] S2. Evacuate the cavity until the vacuum degree inside is below 50Pa.

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

[0073] S4, vacuum baking stage: evacuate until the vacuum degree inside the cavity is below 50Pa, and keep the temperature and pressure under low vacuum for 2 hours.

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

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

[0076] S7. After heating and baking, dry nitrogen is used to break the vacuum, the hatch is opened, and the battery cell is taken out of the oven;

[0077] The cells of Example 3 and Comparative Example 1 were sampled respectively, and the moisture content of the positive and negative electrodes of the cells at different baking times was tested (moisture content of the positive electrode: <450ppm, moisture content of the negative electrode: <200ppm). Fig.10 shown.

[0078] Both baking processes can meet the moisture index requirements, but the baking process of the present invention can achieve the purpose of rapid water removal.

[0079] The comparison of process indicators is shown 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 Process index comparison table

[0081] project Embodiment 3 Comparative Example 1 Total process time 4.6h 19.3h Vacuum times 11 7 Nitrogen filling times 11 7 Nitrogen consumption (single battery) 2.2L 67.5L

[0082] Embodiment 4: In another embodiment of the present invention, the battery cell is a cylindrical aluminum shell sodium ion battery cell with two ends encapsulated, the battery cell diameter is 46mm, the height is 120mm, and after excluding the volume of the dry battery cell inside the battery cell, the redundant space is about 80mL. There are positive and negative poles and a circular injection hole with a diameter of 3mm on the top cover. The heating process steps are as follows:

[0083] S1. Place the battery cells into the tray assembly 2, and seal the tray assembly 2 carrying the battery cells as a whole in the bin body 1.1. The lifting mechanism 3 lifts up the tray assembly 2 as a whole, so that the positive and negative ends of the battery cells are pressed against the power-on columns 4.2 of the variable frequency power supply respectively, and the equipment automatically detects the capacitance value of the dry battery cells; at the same time, the gas connection terminal 4.3 is pressed against the reserved injection hole on the top of the battery cell, and the temperature sensor 4.4 is fitted against the battery cell shell.

[0084] S2. Turn on the negative pressure source to evacuate the battery cell to a vacuum degree below 1 KPa, and then use the dry gas source to fill the battery cell with dry nitrogen through the gas connection terminal 4.3 to normal pressure.

[0085] S3, apply 12V / 10A / 300HZ variable frequency 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;

[0086] In the vacuum heating stage, the battery cell is evacuated to below 1KPa, and the temperature and pressure are maintained for 10 minutes;

[0087] During the dry nitrogen replacement stage, fill the battery cell with nitrogen to 70KPa~90KPa and keep the temperature and pressure for 2 minutes;

[0088] Breathing cycle stage: Repeat the vacuum heating stage and dry nitrogen replacement stage 20 times, maintaining the battery cell temperature in the range of 110±2℃ during the process.

[0089] S4, the heating and baking process of the battery cell is completed.

[0090] Comparative Example 2: The same battery cells as in the embodiment are placed in a sealed cavity with a cavity volume of about 500L. A single cavity can hold 250 battery cells of 46×120 size (the redundant volume inside the cavity is about 250L). The heating and baking process of the battery cells is as follows:

[0091] S1. Place the battery cell in a well-sealed contact oven and heat it with an electric heating plate.

[0092] S2. Evacuate the cavity until the vacuum degree inside is below 50Pa.

[0093] S3. Preheating and baking: Fill with dry nitrogen until the internal pressure of the oven is 70KPa-90KPa, turn on the heating, raise the temperature of the oven to 100℃, keep the temperature and pressure for 2h until the temperature inside the battery cell reaches 100℃.

[0094] S4, vacuum baking stage: evacuate until the vacuum degree inside the cavity is below 50Pa, and keep the temperature and pressure under low vacuum for 2 hours.

[0095] S5, vacuum breathing: fill with dry nitrogen until the vacuum degree inside the oven is 70~90KPa, and maintain the pressure for 10 minutes;

[0096] S6. Repeat steps S4 to S5 8 times.

[0097] S7. After heating and baking is completed, dry nitrogen is used to break the vacuum, the hatch is opened, and the battery cells are taken out of the oven.

[0098] The battery cells of Example 4 and Comparative Example 2 were sampled respectively, and the moisture content of the positive and negative electrodes of the battery cells was tested as shown in Table 2, and both met the moisture index requirements.

[0099] Table 2 Moisture content of positive and negative electrodes of the tested battery cells

[0100] project Embodiment 4 Comparative Example 2 Positive electrode moisture content (standard: <200ppm) 109.6ppm 112.1ppm Moisture content of negative electrode (standard: <200ppm) 127.2ppm 135.6ppm Total process time 3.4h 12.5h Vacuum times 16 9 Nitrogen filling times 16 9 Nitrogen consumption (single battery) 1.3L 9L

[0101] By comparing the baking effects of the embodiment and the comparative example on square / cylindrical batteries, it can be seen that the embodiment of the present invention can not only effectively remove moisture from the battery cell, but also shorten the total baking process time, saving energy consumption. In addition, the present invention only performs vacuuming and nitrogen filling cycles inside the battery cell, and the vacuum and nitrogen consumption are small, while the comparative example performs vacuuming / nitrogen filling on the entire oven cavity, which not only reduces nitrogen consumption, but also avoids the loss of negative pressure source due to frequent vacuuming, thereby reducing the manufacturing cost of the battery cell.

[0102] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0103] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for heating a battery core, characterized in that: The following steps are involved: S1. Electrically connect the positive and negative electrodes of the battery cell to the corresponding wiring terminals of the variable frequency power supply respectively; S2, connect the variable frequency power supply, apply a current I or voltage U of a certain magnitude and frequency to the two poles of the battery cell through the variable frequency power supply, and heat the battery cell to a set temperature T; S3, during the power-on heating process and / or after the power-on heating stops, the battery cell and / or the battery cell is placed in a closed cavity and vacuumed, filled with dry gas, or vacuumed and filled with dry gas in a cyclic switching manner, and a certain air pressure value P is maintained in the closed cavity where the battery cell and / or 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 the power-on heating process in real time. When an abnormality occurs, it indicates that the battery cell is defective. The power-off module 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 the battery cell to a heat preservation bin or by adjusting the frequency conversion power supply parameters to reduce the heating power, and the temperature is maintained for a period of time t; S5. After the battery cell is heated, the battery cell and / or the sealed cavity where the battery cell is located and / or the variable frequency power supply terminal are cooled by at least one of natural cooling, forced air cooling or liquid cooling.

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

3. A battery core heating method according to claim 1, characterized in that: When electrically connecting the positive and negative electrodes of the battery cell to the variable frequency power supply terminals in step S1, the positive and negative electrodes of a single battery cell are respectively connected to the two terminals of the variable frequency power supply, or the single battery cell is connected in series, in parallel, or in series and parallel and then electrically connected to the two terminals of the variable frequency power supply.

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

5. A battery core heating device, characterized in that: The battery cell heating device is applied to the battery cell heating method according to any one of claims 1 to 4, comprising: A heating chamber (1), the heating chamber (1) comprising a chamber body (1.1) and a chamber door hinged to a front open edge of the chamber body (1.1); A tray assembly (2), the tray assembly (2) comprising a trough body (2.1) and a plate body (2.2) mounted in an inner cavity of the trough body (2.1), the plate body (2.2) being provided with a plurality of placement grooves (2.2.1) for positioning and placing battery cells; A lifting mechanism (3), the lifting mechanism (3) being arranged at the bottom of the inner cavity of the warehouse body (1.1) and being used for lifting the tray assembly (2); A heating component (4), the heating component (4) comprising a support plate (4.1) fixed to the top of the inner cavity of the bin body (1.1), a power-on column (4.2) vertically mounted on the support plate (4.1) and having a bottom end corresponding one-to-one with a pole ear at the top of a battery cell, a gas connection terminal (4.3) vertically mounted on the support plate (4.1) and having a bottom end corresponding one-to-one with a reserved injection hole at the top of the battery cell, and a temperature sensor (4.4) vertically mounted on the support plate (4.1) and having a bottom end corresponding one-to-one with a battery cell shell, the top ends of the power-on columns (4.2) being electrically connected to a variable frequency power supply, and a detection module and a power-off module being provided in the circuit between the power-on columns (4.2) and the variable frequency power supply, and the top ends of the gas connection terminals (4.3) being respectively connected to a negative pressure source and a dry gas source through a tee.

6. The electric core 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 bin body (1.1), guide plates (1.5) are vertically fixed at both ends of the support plate (1.3), a hole (1.6) is provided in the middle of the support plate (1.3), and slide grooves (1.4) are respectively provided on both sides of the top surface of the support plate (1.3); rollers (2.1.4) that roll along the slide grooves (1.4) are rotatably mounted at the front and rear ends of the two side walls of the trough body (2.1), and threaded holes (2.1.4) are respectively provided in the middle of the bottom plate of the trough body (2.1) near the two sides. 2.1.1), the middle of the plate body (2.2) near both sides are respectively provided with fixing bolts (2.2.2) threadedly sleeved and matched with the threaded holes (2.1.1), the lifting mechanism (3) comprises a telescopic cylinder (3.1) arranged vertically, a base (3.2) for fixing the bottom of the piston cylinder of the telescopic cylinder (3.1) to the bottom surface of the inner cavity of the warehouse body (1.1), and a top plate (3.3) fixed to the top end of the piston rod of the telescopic cylinder (3.1) and slidingly sleeved and matched with the hole (1.6).

7. The electric core heating device according to claim 6, characterized in that: A pair of 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 trough body (2.1); a cover plate (2.3) is provided above the trough body; a conductive circuit (2.3.1) is embedded on the cover plate (2.3); contacts that are in conductive contact with the top pole ears of the battery cell in a one-to-one correspondence are provided on the bottom surface of the conductive circuit (2.3.1); insulating sheets (2.3.4) are provided at positions corresponding to the contacts on the top surface of the conductive circuit (2.3.1); a through hole 1 (2.3.2) and a through hole 2 (2.3.3) that are matched with the bottom sleeves of the gas connection terminal (4.3) and the temperature sensor (4.4) are provided on the cover plate (2.3); a pair of conductive connection terminals (2.3.1) are provided at the corners of the cover plate (2.3); The conductive connecting member (2.4) comprises a conductive column (2.4.1) whose bottom end is sleeved on the corner of the cover plate (2.3) and is electrically connected to two ends of the conductive circuit (2.3.1), a threaded column (2.4.2) fixedly connected to the bottom of the conductive column (2.4.1) and threadedly sleeved with the threaded sleeve (2.1.3), and a knob (2.4.3) fixedly sleeved on the conductive column (2.4.1) near the top outside, and a power-on column (4.2) is sleeved on the support plate (4.1) at a position corresponding to the conductive column (2.4.1), and the bottom ends of the power-on column (4.2), the gas connection terminal (4.3) and the temperature sensor (4.4) are elastic telescopic structures.

8. The electric core heating device according to claim 7, characterized in that: The conductive circuit (2.3.1) is a series circuit, a parallel circuit or a series-parallel circuit.

9. The electric core heating device according to claim 8, characterized in that: The inner cavity of the warehouse body (1.1) is provided with auxiliary electric heating equipment and / or cooling equipment.

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