Preparation method of lithium battery cell

Abstract

The invention provides a preparation method of a lithium battery cell, which comprises the following steps: a providing step: providing a to-be-welded structure and a top cover structure; a first control step: controlling the heating source to heat the welding area; a determination step: determining a plurality of sequentially increased temperature acquisition moments; obtaining, wherein the surface temperature of the welding area is obtained; an adjusting step: adjusting the operation parameters of the heating source according to the surface temperature and the set temperature; a second control step: controlling the heating source to stop heating, and performing laser welding on the welding area and the pole; and a treatment step: carrying out core combination, surface film coating and shell packaging on the to-be-welded structure after laser welding to obtain a packaging structure, and at least carrying out liquid injection treatment and formation treatment on the packaging structure to obtain a battery core structural member. According to the laser welding device, the welding area of the switching piece is heated, the laser absorptivity is improved, and it is guaranteed that the welding effect of laser welding is good.

Description

Technical Field

[0001] The present application relates to the field of battery manufacturing technology, and in particular, to a method for preparing a lithium battery cell. Background Art

[0002] At present, when laser welding lithium-ion battery adapters, due to the smooth surface of copper and aluminum adapters, when the initial laser is irradiated to the surface of copper and aluminum adapters, the copper and aluminum adapters will have a low absorption rate of the laser, resulting in cold welding between the copper and aluminum adapters and the copper and aluminum poles on the top cover, thereby affecting the performance of the battery cell. Summary of the invention

[0003] The main purpose of the present application is to provide a method for preparing a lithium battery cell, so as to at least solve the problem of incomplete welding and cold welding in the welding of the adapter of the lithium-ion battery in the prior art, which affects the performance of the cell.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for preparing a lithium battery cell is provided, comprising: a providing step, providing a structure to be welded and a top cover structure, the structure to be welded comprising a transfer sheet and a paired bare cell, the transfer sheet being electrically connected to the bare cell, and a partial area of ​​the transfer sheet being a welding area; a first control step, controlling a heating source to heat the welding area when the structure to be welded and the top cover structure are superimposed on a welding station, the projection of the welding area on the welding station overlaps with the projection of the pole of the top cover structure on the welding station; a determining step, determining a plurality of successively increasing temperature acquisition moments according to the length of time the structure to be welded stays at the welding station and the moment when the structure to be welded arrives at the welding station, the maximum temperature acquisition moment being the same as the moment when the structure to be welded arrives at the welding station. The difference in time between the welding stations is less than the dwell time; an acquisition step, when the current time reaches the temperature acquisition time, acquiring the surface temperature of the welding area; an adjustment step, when the surface temperature is within a predetermined range and the deviation between the surface temperature and the set temperature is greater than a first predetermined threshold, adjusting the operating parameters of the heating source according to the surface temperature and the set temperature, and the predetermined range is determined according to the set temperature; a second control step, when the deviation is less than or equal to the first predetermined threshold, controlling the heating source to stop heating, and laser welding the welding area and the pole; a processing step, performing core bonding, surface coating and shell packaging on the structure to be welded after laser welding to obtain a packaging structure, and at least performing liquid injection treatment and chemical formation treatment on the packaging structure to obtain a battery cell structure.

[0005] Optionally, the heating source includes a heating component and a fan, and the operating parameters of the heating source are adjusted according to the surface temperature and the set temperature, including: adjusting at least one of the following according to the relationship between the surface temperature and the set temperature: the heating power of the heating component and the air outlet rate of the fan.

[0006] Optionally, according to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet rate of the fan, including: when the absolute value of the difference between the surface temperature and the set temperature is greater than the first predetermined threshold and less than or equal to the second predetermined threshold, adjusting the air outlet rate according to the relationship between the surface temperature and the set temperature; when the absolute value of the difference is greater than the second predetermined threshold and less than or equal to the third predetermined threshold, adjusting the heating power according to the relationship between the surface temperature and the set temperature; when the absolute value of the difference is greater than the third predetermined threshold, adjusting the air outlet rate and the heating power according to the relationship between the surface temperature and the set temperature.

[0007] Optionally, according to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet rate of the fan, including: when the surface temperature is greater than the set temperature, reducing at least one of the following according to the first step value: the heating power and the air outlet rate; when the surface temperature is lower than the set temperature, increasing at least one of the following according to the second step value: the heating power and the air outlet rate.

[0008] Optionally, before the second control step, the method further includes: when the current moment has not reached the maximum temperature acquisition moment, or when the surface temperature is within the predetermined range and the deviation is greater than the first predetermined threshold, looping the acquisition step and the adjustment step until the current moment reaches the maximum temperature acquisition moment, or until the surface temperature is within the predetermined range and the deviation is less than or equal to the first predetermined threshold.

[0009] Optionally, the determination step includes: according to the dwell time and a plurality of preset multiples, determining the product of the dwell time and each of the preset multiples as the interval time, and the plurality of preset multiples are all less than 1; according to the plurality of interval times and the time when the structure to be welded arrives at the welding station, determining the time when the structure to be welded arrives at the welding station and the sum of each of the interval times as the temperature acquisition time.

[0010] Optionally, the plurality of predetermined multiples include a first predetermined multiple, a second predetermined multiple, a third predetermined multiple, a fourth predetermined multiple and a fifth predetermined multiple which increase in sequence, the first predetermined multiple is in the range of 0% to 10%, the second predetermined multiple is in the range of 10% to 20%, the third predetermined multiple is in the range of 20% to 30%, the fourth predetermined multiple is in the range of 30% to 40%, and the fifth predetermined multiple is in the range of 40% to 50%.

[0011] Optionally, the method also includes: when the current moment reaches the maximum temperature acquisition moment and the deviation is greater than the first predetermined threshold, sending a first alarm message to the terminal device, the first alarm message indicating that the deviation is greater than the first predetermined threshold and instructing to stop welding; when the surface temperature is not within the predetermined range, sending a second alarm message to the terminal device, the second alarm message indicating that the surface temperature is not within the predetermined range and instructing to stop welding.

[0012] Optionally, obtaining the surface temperature of the welding area includes: obtaining temperature values ​​of multiple positions of the welding area, wherein the temperature weight values ​​corresponding to at least two of the positions are different; and performing weighted summation of the multiple temperature values ​​according to the multiple temperature weight values ​​to obtain the surface temperature.

[0013] Optionally, the first predetermined threshold is 5% of the set temperature, the minimum value of the predetermined range is 80%-100% of the set temperature, and the maximum value of the predetermined range is 100%-120% of the set temperature.

[0014] By applying the technical solution of the present application, the welding area of ​​the adapter is heated before welding, and the surface temperature of the welding area is obtained multiple times. When the surface temperature does not meet the temperature requirements, the operating parameters of the heating source are adjusted according to the surface temperature of the adapter to adjust the surface temperature of the welding area. When the surface temperature meets the temperature requirements, the heating is stopped and the adapter and the pole of the top cover structure are laser welded together. The heating improves the absorption rate of the welding area of ​​the adapter to the laser, thereby ensuring that the laser welding of the adapter has a good welding effect and avoiding the problem of affecting the performance of the battery cell due to incomplete welding, cold welding, etc. in the welding of the adapter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0016] Figure 1A schematic diagram of a process for preparing a lithium battery cell according to an embodiment of the present application is shown;

[0017] Figure 2 A schematic structural diagram of welding a structure to be welded and a top cover structure at a welding station using a heating source according to an embodiment of the present application is shown.

[0018] The above drawings include the following reference numerals:

[0019] 1. Adapter; 2. Top cover structure; 3. Heating source; 11. Welding area; 21. Explosion-proof valve. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims and drawings of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] When the current adapter is welded, since the surface temperature of copper and aluminum is relatively low (room temperature) and relatively smooth, the absorption rate of metal devices (copper and aluminum adapters) to laser energy is low in the initial stage of welding, resulting in incomplete welding and cold welding in the initial stage of welding.

[0024] In order to solve the problem of incomplete welding and cold welding of adapter plates of lithium-ion batteries, which affects the performance of the battery cell, an embodiment of the present application provides a method for preparing a lithium battery cell.

[0025] The present application provides a method for preparing a lithium battery cell. Figure 1 As shown, the preparation method of the lithium battery cell includes:

[0026] Step S101: providing a step of providing a structure to be welded and a top cover structure, wherein the structure to be welded includes a transfer sheet and a paired bare battery cell, the transfer sheet is electrically connected to the bare battery cell, and a part of the transfer sheet is a welding area.

[0027] Step S102: a first control step, in which, when the structure to be welded and the top cover structure are superimposed on the welding station, the heating source is controlled to heat the welding area, and the projection of the welding area on the welding station overlaps with the projection of the pole of the top cover structure on the welding station.

[0028] Step S103: a determination step, according to the residence time of the structure to be welded at the welding station and the time when the structure to be welded arrives at the welding station, a plurality of successively increasing temperature acquisition times are determined, and the difference between the maximum temperature acquisition time and the time when the structure to be welded arrives at the welding station is less than the residence time.

[0029] Step S104: an acquisition step, in which the surface temperature of the welding area is acquired when the current time reaches the temperature acquisition time.

[0030] Step S105: an adjustment step, in which, when the surface temperature is within a predetermined range and the deviation between the surface temperature and the set temperature is greater than a first predetermined threshold, the operating parameters of the heating source are adjusted according to the surface temperature and the set temperature, and the predetermined range is determined according to the set temperature.

[0031] Step S106: a second control step, when the deviation is less than or equal to the first predetermined threshold, controlling the heating source to stop heating, and performing laser welding on the welding area and the pole.

[0032] Step S107: a processing step, performing core bonding, surface coating and shell packaging on the structure to be welded after laser welding to obtain a packaging structure, and at least performing liquid injection processing and chemical formation processing on the packaging structure to obtain a battery cell structure.

[0033] A method for preparing a lithium battery cell, wherein the welding area of ​​an adapter is heated before welding, and the surface temperature of the welding area is obtained multiple times. When the surface temperature does not meet the temperature requirement, the operating parameters of the heating source are adjusted according to the surface temperature of the adapter to adjust the surface temperature of the welding area. When the surface temperature meets the temperature requirement, the heating is stopped and the adapter and the pole of the top cover structure are laser welded together. Heating improves the absorption rate of the welding area of ​​the adapter to the laser, thereby ensuring that the laser welding of the adapter has a good welding effect, and avoiding the problem of affecting the performance of the battery cell due to incomplete welding, false welding, etc. in the welding of the adapter.

[0034] The exemplary embodiments of the method for preparing a lithium battery cell provided in the present application will be described in more detail below. However, these exemplary embodiments can be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art.

[0035] First, if Figure 2 As shown, step S101 is performed: a providing step is performed to provide a structure to be welded and a top cover structure 2, the structure to be welded includes a transfer sheet and a paired bare battery cell, the transfer sheet 1 is electrically connected to the bare battery cell, and a partial area of ​​the transfer sheet 1 is a welding area 11.

[0036] Specifically, the structure to be welded includes an adapter 1 and a paired bare cell, wherein the paired bare cell is obtained by pairing bare cells A and B with similar electrochemical performance parameters; the material of the adapter is a conductive material, one adapter is used to electrically connect the positive ears of the bare cells A and B, as the positive electrode of the paired bare cell, and the other adapter is used to electrically connect the negative ears of the bare cells A and B, as the negative electrode of the paired bare cell. The top cover structure 2 includes structures such as poles, bare aluminum sheets, upper plastic, lower plastic, explosion-proof valve 21 and sealing rings. The top cover structure and the shell cooperate to provide sealing protection for the paired bare cells. The electrodes of the paired bare cells are electrically connected to the poles of the top cover structure through the adapter, so that the paired cells can be electrically connected to the external circuit through the poles to achieve the transmission and exchange of electrical energy.

[0037] After providing the steps, such as Figure 2 As shown, step S102 is performed: the first control step, when the structure to be welded and the top cover structure 2 are superimposed on the welding station, the heating source 3 is controlled to heat the welding area 11, and the projection of the welding area 11 on the welding station overlaps with the projection of the pole of the top cover structure 2 on the welding station.

[0038] Specifically, the poles of the top cover structure and the adapter plate of the structure to be welded are stacked in sequence on the welding station. The projection of the welding area of ​​the adapter plate on the welding station overlaps with the projection of the poles of the top cover structure on the welding station. The heating source is controlled to heat the welding area so that the temperature of the welding area meets the temperature requirement. This can improve the laser absorption rate of the surface of the adapter plate, thereby ensuring the subsequent laser welding quality.

[0039] After the first control step, step S103 is performed: a determination step, in which a plurality of successively increasing temperature acquisition moments are determined according to the length of time the structure to be welded stays at the welding station and the moment when the structure to be welded arrives at the welding station, and the difference between the maximum temperature acquisition moment and the moment when the structure to be welded arrives at the welding station is less than the length of the stay.

[0040] Specifically, the moment when the structure to be welded arrives at the welding station refers to the moment when the turntable carrying the stacked structure to be welded and the top cover structure arrives at the welding station. After the structure to be welded and the top cover structure of the present application arrive at the welding station, a heating operation needs to be performed before a welding operation is performed. The heating operation process needs to perform temperature acquisition operations multiple times. The difference between the maximum temperature acquisition moment and the moment of arrival at the welding station is controlled to be less than the dwell time, so that time can be reserved for the next welding operation to avoid welding abnormalities caused by insufficient welding time of the adapter and the pole.

[0041] After the determination step, step S104 is performed: an acquisition step, in which the surface temperature of the welding area is acquired when the current moment reaches the temperature acquisition moment.

[0042] Specifically, by obtaining the surface temperature of the welding area, temperature control during the heating process can be ensured. The surface temperature of the welding area can be obtained by a temperature sensor or a temperature acquisition device such as an infrared thermal imager. When the surface temperature meets the temperature requirements, that is, the surface temperature is within a predetermined range and the deviation between the surface temperature and the set temperature is not greater than a first predetermined threshold, the adapter and the pole are laser welded in time. When the surface temperature does not meet the temperature requirements, the heating operation is continued. This ensures that the surface temperature of the welding area of ​​the adapter meets the temperature requirements before welding begins, and avoids the problem of inefficient welding workstations caused by excessive heating time, thereby ensuring that the timing of starting welding is more accurate.

[0043] After the acquisition step, step S105 is performed: an adjustment step. When the surface temperature is within a predetermined range and the deviation between the surface temperature and the set temperature is greater than a first predetermined threshold, the operating parameters of the heating source are adjusted according to the surface temperature and the set temperature. The predetermined range is determined according to the set temperature.

[0044] Specifically, when the surface temperature is within a predetermined range and the deviation from the set temperature exceeds a certain threshold, it means that the surface temperature is high, but there is still some deviation from the set temperature. At this time, the temperature deviation can be corrected by adjusting the operating parameters of the heating source, so that the laser absorption rate of the welding area of ​​the adapter after the temperature deviation is corrected is higher, providing better welding conditions for subsequent laser welding operations. The deviation between the surface temperature and the set temperature can be a negative value, indicating that the surface temperature after heating has not reached the set temperature. At this time, by adjusting the operating parameters of the heating source, the heating intensity of the welding area is increased, thereby increasing the surface temperature.

[0045] After the adjustment step, step S106 is performed: a second control step, in which, when the deviation is less than or equal to the first predetermined threshold, the heating source is controlled to stop heating, and laser welding is performed on the welding area and the pole.

[0046] Specifically, by monitoring deviations and performing laser welding when the requirements are met, the heating temperature and duration can be effectively controlled to avoid excessive heating resulting in insufficient subsequent welding time or low overall cell preparation efficiency. At the same time, by controlling the heating temperature, the welding area can have the laser absorption rate required for welding, thereby avoiding the occurrence of cold welds or incomplete welds during subsequent welding.

[0047] After the second control step, step S107 is performed: a processing step, in which the structure to be welded after laser welding is subjected to core bonding, surface coating and shell packaging to obtain a packaging structure, and the packaging structure is at least subjected to liquid injection processing and chemical formation processing to obtain a battery cell structure.

[0048] Specifically, the core is to turn over and bend the battery cell AB in the structure to be welded with the top cover structure, and fix it by bundling. Surface coating is to coat the outer surface of the structure to be welded after welding with Mylar film (a polyester film), and fix the Mylar film on the lower plastic of the top cover structure by hot melting. The corrosion resistance and insulation performance of the battery cell can be guaranteed by surface coating. Shell packaging is to push the battery cell coated with Mylar film into the metal shell (usually aluminum shell) in sections to complete the battery cell into the shell, and pre-weld and fully seal the metal shell and the top cover structure in turn by laser welding. Shell packaging can ensure the sealing of the battery cell, protect the internal structure of the battery cell, and ensure that the battery cell is not affected by the external environment during operation. Liquid injection treatment refers to injecting electrolyte into the battery cell to provide a channel for ion transmission, so as to realize the normal charging and discharging function of the battery. Formation treatment refers to the first charging and activation of the battery cell to form a stable SEI film, and remove the gas generated during the film formation process by negative pressure. Liquid injection treatment and formation treatment can realize the electrochemical properties of the battery cell structure and ensure the normal charging and discharging function and long-term stability of the battery cell.

[0049] According to some optional solutions of the present application, the set temperature is 120° C. to 150° C. For example, the set temperature is set to 120° C., 130° C., 135° C., 140° C., or 150° C.

[0050] In some embodiments, the injection treatment includes a primary injection before the formation treatment and a secondary injection after the formation treatment. In the primary injection process, after the interior of the battery cell is evacuated, the electrolyte is injected into the shell through the injection hole, and the electrolyte is quickly absorbed by the battery cell through repeated vacuum / positive pressure operations. After a certain period of high temperature and normal temperature stillness, it is ensured that all materials are fully infiltrated with the electrolyte. In the secondary injection process, the battery cell after formation is replenished with electrolyte through vacuum extraction and positive pressure operations to ensure that the battery cell has sufficient electrolyte to support future enteric circulation use.

[0051] In addition to the liquid injection and formation treatment, the packaging structure is also subjected to the following procedures before the liquid injection: a helium inspection to test the sealing of the battery cell; a baking treatment to remove the moisture inside the battery cell by contact baking the battery cell. After the formation treatment, the following procedures are also performed: sealing pin welding to isolate the inside of the battery cell from the outside world; a secondary helium inspection; a capacity separation treatment to fully discharge the battery cell after full charge to test the actual capacity of the battery cell; and an insulating film coating to coat the outer surface of the battery cell shell with an insulating film and affix an insulating sheet on the top to leave the pole and explosion-proof valve exposed.

[0052] In some optional embodiments, the heating source includes a heating component and a fan, and the operating parameters of the heating source are adjusted according to the surface temperature and the set temperature, including: adjusting at least one of the following according to the relationship between the surface temperature and the set temperature: the heating power of the heating component and the air outlet rate of the fan.

[0053] In an optional embodiment, the heating power of the heating component and / or the air outlet rate of the fan are adjusted according to the relationship between the surface temperature and the set temperature, so that the heating temperature can be quickly adjusted so that the deviation between the adjusted surface temperature and the set temperature is no greater than a first predetermined threshold value, thereby further ensuring that the welding area of ​​the adapter after heating control has a high absorption rate of the laser.

[0054] Specifically, the heating component can be located in the air duct of the fan, and compressed air is provided to the air duct by an external connection. The compressed air entering the air duct is heated by the heating component and then blown to the welding area to heat the welding area. At the same time, the surface temperature of the welding area of ​​the adapter is monitored in real time by an infrared temperature measuring probe. According to the temperature fed back in real time by the infrared temperature measuring probe and the real-time temperature of the surface of the adapter, the heating power and the compressed air flow rate are adjusted in a closed loop in a timely manner. The heating component can be a heating rod or a heating element such as a heating plate. The heating component in the present application is specifically selected as a resistance wire. The interior of the fan is composed of a resistance wire.

[0055] In some optional embodiments, according to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet rate of the fan, including: when the absolute value of the difference between the surface temperature and the set temperature is greater than a first predetermined threshold and less than or equal to a second predetermined threshold, adjusting the air outlet rate according to the relationship between the surface temperature and the set temperature; when the absolute value of the difference is greater than the second predetermined threshold and less than or equal to a third predetermined threshold, adjusting the heating power according to the relationship between the surface temperature and the set temperature; when the absolute value of the difference is greater than the third predetermined threshold, adjusting the air outlet rate and the heating power according to the relationship between the surface temperature and the set temperature.

[0056] In an optional embodiment, considering that the temperature rise rate achieved by adjusting the air outlet rate is different from the temperature rise rate achieved by adjusting the heating power, a graded adjustment method is adopted to implement different control strategies for different temperature difference thresholds. When the absolute value of the temperature difference is small, there is no need to adjust the heating power, and only the air outlet rate of the fan is adjusted, which can save energy; when the absolute value of the temperature difference is relatively large, the heating power is adjusted to achieve rapid temperature regulation and reduce energy waste to a certain extent; and when the absolute value of the temperature difference is larger, the heating power and the air outlet rate are adjusted at the same time, so that the surface temperature rises rapidly, and the surface temperature of the welding area is efficiently regulated. Through regulation, the laser absorption rate of the welding area before welding is higher, thereby further ensuring that the laser welding effect is better during welding and the welding reliability is higher.

[0057] According to some exemplary solutions of the present application, the second predetermined threshold is 10% of the set temperature; and the third predetermined threshold is 15% of the set temperature.

[0058] Furthermore, the specific manner of adjusting the air outlet rate according to the magnitude relationship between the surface temperature and the set temperature may be: increasing or decreasing the air outlet rate according to a predetermined step value according to the magnitude relationship between the surface temperature and the set temperature. The specific manner of adjusting the air outlet rate according to the magnitude relationship between the surface temperature and the set temperature may also be: setting a corresponding relationship between the temperature difference and the air outlet rate, determining the air outlet rate corresponding to the temperature difference as the target air outlet rate according to the temperature difference between the surface temperature and the set temperature from the corresponding relationship, and adjusting the air outlet rate of the heating source to the target air outlet rate.

[0059] Furthermore, the specific manner of adjusting the heating power according to the magnitude relationship between the surface temperature and the set temperature may be: increasing or decreasing the heating power according to a predetermined step value according to the magnitude relationship between the surface temperature and the set temperature. The specific manner of adjusting the heating power according to the magnitude relationship between the surface temperature and the set temperature may also be: setting a corresponding relationship between the temperature difference and the heating power, determining the heating power corresponding to the temperature difference as the target heating power according to the temperature difference between the surface temperature and the set temperature from the corresponding relationship, and adjusting the heating power of the heating source to the target heating power.

[0060] In some optional embodiments, according to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet rate of the fan, including: when the surface temperature is greater than the set temperature, reducing at least one of the following according to the first step value: the heating power and the air outlet rate; when the surface temperature is lower than the set temperature, increasing at least one of the following according to the second step value: the heating power and the air outlet rate.

[0061] In an optional embodiment, according to the relationship between the surface temperature and the set temperature, the heating power and / or the air outlet rate are gradually increased or decreased by step adjustment, so that the temperature control accuracy is higher, and the surface temperature of the welding area is further accurately controlled. By adjusting the laser absorption rate of the welding area before welding, the laser welding effect is better during welding, the welding reliability is higher, and the preparation quality and performance of the lithium battery cell are further improved.

[0062] In some optional embodiments, before the second control step, the method further includes: when the current moment has not reached the maximum temperature acquisition moment, or when the surface temperature is within a predetermined range and the deviation is greater than a first predetermined threshold, looping the acquisition step and the adjustment step until the current moment reaches the maximum temperature acquisition moment, or until the surface temperature is within a predetermined range and the deviation is less than or equal to the first predetermined threshold.

[0063] In an optional embodiment, when the maximum temperature acquisition moment is not reached at the current moment, or when the surface temperature does not meet the temperature requirement, the acquisition step and the adjustment step are executed cyclically to achieve closed-loop control of the surface temperature of the welding area, thereby further ensuring that the surface temperature of the welding area before welding is within a predetermined range and the deviation is less than or equal to a first predetermined threshold value, thereby further ensuring that the laser absorption rate of the welding area before welding meets the laser welding requirements.

[0064] In some optional embodiments, the determination step includes: determining the product of the dwell time and each predetermined multiple as the interval time based on the dwell time and multiple preset multiples, and the multiple preset multiples are all less than 1; determining the time when the structure to be welded arrives at the welding station and the sum of each interval time as the time to obtain each temperature based on multiple interval time and the time when the structure to be welded arrives at the welding station.

[0065] In an optional embodiment, the stay time of the structure to be welded at the welding station is divided according to multiple predetermined multiples less than 1, and multiple temperature acquisition moments are obtained. The multiple temperature acquisition moments are divided into multiple temperature adjustment stages, which ensures that the determined temperature acquisition moments are more reasonable, provides a suitable control time for the heating operation, and reserves time for subsequent welding operations.

[0066] Specifically, the multiple predetermined multiples increase in sequence and are all greater than 0. For example, the multiple predetermined multiples may be 10%, 20%, 30% or 40%, and so on.

[0067] In some optional embodiments, the multiple predetermined multiples include a first predetermined multiple, a second predetermined multiple, a third predetermined multiple, a fourth predetermined multiple and a fifth predetermined multiple which increase in sequence, the first predetermined multiple is in the range of 0% to 10%, the second predetermined multiple is in the range of 10% to 20%, the third predetermined multiple is in the range of 20% to 30%, the fourth predetermined multiple is in the range of 30% to 40%, and the fifth predetermined multiple is in the range of 40% to 50%.

[0068] In an optional embodiment, at most 50% of the dwell time is used for heating, further ensuring that there is sufficient time after heating to weld the structure to be welded and the top cover structure, and further avoiding welding abnormalities caused by insufficient welding time of the adapter and the pole; and, within at most 50% of the dwell time, it is divided into five temperature adjustment stages according to five predetermined multiples. In these five temperature adjustment stages, the welding area can be heated and the temperature can be controlled according to the obtained surface temperature, so that the regulated surface temperature meets the temperature requirements.

[0069] Exemplarily, taking the first predetermined multiple as 10%, the second predetermined multiple as 20%, the third predetermined multiple as 30%, the fourth predetermined multiple as 40%, the fifth predetermined multiple as 50% and the dwell time as t as an example, the heating time of the heating operation first performed at the welding station is at most 50%t, and the welding available time of the welding operation performed later is at least 50%t. Specifically, after the structure to be welded and the top cover structure arrive at the welding station, the heating source is controlled to start heating the welding area of ​​the adapter, and when the heating time reaches 10%t, the surface temperature is obtained once, and when the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is greater than the first predetermined threshold, the operating parameters of the heating source are adjusted; when the heating time reaches 20%t, the surface temperature is obtained once, and when the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is greater than the first predetermined threshold, the operating parameters of the heating source are continued to be adjusted; when the heating time reaches 30%t, the surface temperature is obtained once, and in the table When the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is greater than the first predetermined threshold, the operating parameters of the heating source are continuously adjusted; when the heating time reaches 40%t, the surface temperature is acquired once, and when the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is greater than the first predetermined threshold, the operating parameters of the heating source are continuously adjusted; when the heating time reaches 50%t, the surface temperature is acquired once, and when the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is less than or equal to the first predetermined threshold, the heating of the welding area is stopped, and the welding area and the pole are welded together by laser welding. During the heating time greater than 10%t and less than 50%t, if the surface temperature is within the predetermined range and the deviation between the surface temperature and the set temperature is less than or equal to the first predetermined threshold, the heating of the welding area is stopped immediately, and the welding operation is performed. During the heating time greater than 10%t and less than 50%t, if the surface temperature is not within the predetermined range, the heating is stopped immediately, and the welding operation is not performed.

[0070] In some optional embodiments, the method further includes: when the maximum temperature acquisition moment is reached at the current moment and the deviation is greater than a first predetermined threshold, sending a first alarm message to the terminal device, the first alarm message indicating that the deviation is greater than the first predetermined threshold and instructing to stop welding; when the surface temperature is not within the predetermined range, sending a second alarm message to the terminal device, the second alarm message indicating that the surface temperature is not within the predetermined range and instructing to stop welding.

[0071] In an optional implementation, when the maximum temperature acquisition moment is reached at the current moment and the deviation is greater than the first predetermined threshold, it means that the surface temperature cannot be adjusted to a smaller deviation from the set temperature within the prescribed heating time. At this time, the laser absorption rate of the welding area cannot meet the subsequent welding requirements and the subsequent welding effect cannot be guaranteed. At this time, a first alarm message is issued so that relevant personnel can be informed of the situation in time and take corresponding measures, such as adjusting and optimizing some processes; when the surface temperature is not within the predetermined range, it means that the surface temperature is significantly different from the temperature requirement and cannot be increased to meet the temperature requirement through subsequent heating operations. At this time, a second alarm message is issued so that relevant personnel can be informed of the situation in time and take corresponding measures, such as adjusting and optimizing the overall process. Both alarms avoid welding adapters that do not meet the welding requirements, resulting in poor welding and wasted work time.

[0072] In some optional embodiments, obtaining the surface temperature of the welding area includes: obtaining temperature values ​​at multiple positions of the welding area, wherein the temperature weight values ​​corresponding to at least two positions are different; and performing weighted summation on the multiple temperature values ​​according to the multiple temperature weight values ​​to obtain the surface temperature.

[0073] In an optional embodiment, by acquiring temperature values ​​at multiple locations in the welding area and performing weighted summation on the temperature values ​​according to weight values ​​at different locations, the obtained surface temperature can more accurately reflect the overall temperature condition of the welding area.

[0074] For example, the welding area includes a central area and a non-central area located on the periphery of the central area. The central area is the projection area of ​​the fan outlet of the heating source on the welding area, and the temperature weight value corresponding to the central area is smaller than the temperature weight value corresponding to the non-central area. The surface temperature obtained in this way can reflect the temperature of the non-central area, avoiding the problem of poor welding effect in the non-central area due to ignoring the laser absorption rate in the non-central area.

[0075] In some optional embodiments, the first predetermined threshold is 5% of the set temperature, the minimum value of the predetermined range is 80%~100% of the set temperature, and the maximum value of the predetermined range is 100~120% of the set temperature. In other words, the difference between the minimum value of the predetermined range and the set temperature is -20%~0, and the difference between the maximum value of the predetermined range and the set temperature is 0~20%. In this embodiment, considering that the heating source has limited temperature control capabilities for the adapter, the predetermined range is set to 80%~100% of the set temperature and 100~120% of the set temperature, ensuring that the predetermined range is more reasonable.

[0076] Specifically, when the surface temperature is not within the predetermined range, the surface temperature cannot be adjusted to the predetermined range even if the operating parameters of the heating source are adjusted, so welding is stopped to save resources and avoid waste of work time; when the surface temperature is within the predetermined range, the operating parameters of the heating source can be adjusted to ensure that the adjusted deviation is no greater than the first predetermined threshold value, so the heating source is regulated in this case to ensure the subsequent welding quality.

[0077] Exemplarily, the predetermined range may be 80% to 120% of the set temperature. When the surface temperature of the welding area of ​​the adapter plate in each temperature adjustment stage is within the fluctuation range of 80% to 120% of the set temperature, if the surface temperature is lower than the set temperature (the value lower than is greater than the first predetermined threshold), the heating power and the air outlet rate are increased; if the surface temperature is higher than the set temperature (the value higher than is greater than the first predetermined threshold), the heating power and the air outlet rate are reduced.

[0078] In the present application, the adapter welded to one tab of the battery cell AB is a copper sheet, and the adapter welded to the other tab of the battery cell AB is an aluminum sheet. Experimental verification shows that compared with the solution of directly welding the welding areas of the copper sheet and the aluminum sheet at room temperature, the copper sheet and the aluminum sheet are heated by the method of the present application so that the surface temperature of the copper sheet welding area reaches 120℃~150℃, and the surface temperature of the aluminum sheet welding area reaches 120℃~150℃ before welding. The copper sheet's absorption rate of 1060nm wavelength laser increases by nearly one-fold, and the aluminum sheet's absorption rate of laser increases from 5%~7% to 15%~18%, an increase of nearly three times, which can effectively avoid the occurrence of cold welding or incomplete welding lines.

[0079] The preparation method of the lithium battery cell of the present application will be specifically described below in combination with specific embodiments and comparative examples.

[0080] Example 1

[0081] This embodiment provides a method for preparing a lithium battery cell, comprising the following steps:

[0082] Step S1: providing a structure to be welded and a top cover structure, wherein the structure to be welded includes an adapter and a paired bare cell, wherein the adapter is electrically connected to the bare cell, and a part of the adapter is a welding area, and executing step S2;

[0083] Step S2: When the structure to be welded and the top cover structure are superimposed on the welding station, the heating source is controlled to heat the welding area, and the projection of the welding area on the welding station overlaps with the projection of the pole of the top cover structure on the welding station, and step S3 is executed;

[0084] Step S3: according to the residence time of the structure to be welded at the welding station and the time when the structure to be welded arrives at the welding station, a plurality of successively increasing temperature acquisition times are determined; if the difference between the maximum temperature acquisition time and the time when the structure to be welded arrives at the welding station is less than the residence time, step S4 is executed;

[0085] Step S4: When the temperature acquisition time is reached at the current moment, the surface temperature of the welding area is acquired. When the surface temperature is within the temperature range [96°C, 144°C] and the deviation between the surface temperature and the set temperature 120°C is greater than the threshold value 6°C, step S5 is executed; when the surface temperature is within the temperature range [96°C, 144°C] and the deviation is not greater than the threshold value 6°C, step S6 is executed; when the surface temperature is not within the temperature range [96°C, 144°C], an alarm is issued and the process is terminated; when the maximum temperature acquisition time is reached at the current moment and the deviation is greater than the threshold value 6°C, an alarm is issued and the process is terminated;

[0086] Step S5: adjusting the operating parameters of the heating source according to the surface temperature and the set temperature, the operating parameters including the heating power of the heating component in the heating source and / or the air outlet rate of the fan in the heating source, and returning to step S4;

[0087] Step S6: Control the heating source to stop heating, and perform laser welding on the welding area and the pole, and then perform core bonding, surface coating, shell packaging, liquid injection treatment and chemical treatment on the structure to be welded after laser welding to obtain a battery cell structure.

[0088] Example 2

[0089] This embodiment provides a method for preparing a solar cell. The only difference between this method and Embodiment 1 is that the set temperature is 150°C.

[0090] Example 3

[0091] This embodiment provides a method for preparing a solar cell. The only difference between this method and Embodiment 1 is that the set temperature is 130°C.

[0092] Comparative Example 1

[0093] This embodiment provides a method for preparing a lithium battery cell, comprising the following steps:

[0094] Step S1: providing a structure to be welded and a top cover structure, wherein the structure to be welded includes an adapter and a paired bare cell, wherein the adapter is electrically connected to the bare cell, and a part of the adapter is a welding area, and executing step S2;

[0095] Step S2: When the structure to be welded and the top cover structure are stacked on the welding station, the welding area and the pole are laser welded, and then the structure to be welded after laser welding is subjected to core bonding, surface coating, shell packaging, liquid injection treatment and chemical treatment to obtain a battery cell structure.

[0096] Comparative Example 2

[0097] This embodiment provides a method for preparing a solar cell. The only difference between this method and Embodiment 1 is that the temperature range is [70°C, 90°C] and the set temperature is 80°C.

[0098] The performance of the solar cells prepared by the methods of the above-mentioned Example 1 and Comparative Examples 1 and 2 was tested, and the test results are shown in Table 1:

[0099] Table 1

[0100]

[0101] From the above experimental data, it can be seen that the laser absorption rate of the welding area of ​​the adapter sheet of Example 1 is significantly higher than that of Comparative Example 1, and the welding yield rate of the adapter sheet and the pole of Example 1 is significantly higher than that of Comparative Example 1, indicating that compared with the solution of not heating before welding, the solution of heating before welding of the present application can effectively improve the absorption rate of the welding area of ​​the adapter sheet to the laser and improve the welding yield rate of the adapter sheet. Moreover, compared with Comparative Example 2, the laser absorption rate of the welding area of ​​the adapter sheet of Example 1 is higher and the welding yield rate is higher, indicating that the present application samples a higher temperature range and a higher set temperature to control the surface temperature after welding, which can make the absorption rate of the welding area of ​​the adapter sheet to the laser higher and the welding yield rate of the adapter sheet better. In addition, according to the welding yield data of Example 1, it can be seen that if a higher temperature range (for example, the minimum value of the temperature range is greater than 120°C, and the maximum value of the temperature range is greater than 144°C) and a larger set temperature (for example, the set temperature is 180°C) are used to control the surface temperature, the welding yield effect achieved will not be significantly better than that of Example 1, and the energy consumption and man-hour consumption caused will be much higher than that of Example 1. Therefore, the temperature range and threshold value set in this application are relatively reasonable, which can not only ensure the welding yield, but also avoid the waste of energy and man-hours.

[0102] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0103] Obviously, those skilled in the art should understand that each module or each step of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0104] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0105] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0106] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0107] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0108] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0109] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0110] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0111] From the above description, it can be seen that the embodiments of the present application achieve the following technical effects:

[0112] The preparation method of the lithium battery cell of the present application heats the welding area of ​​the adapter before welding, and obtains the surface temperature of the welding area multiple times. When the surface temperature does not meet the temperature requirements, the operating parameters of the heating source are adjusted according to the surface temperature of the adapter to adjust the surface temperature of the welding area. When the surface temperature meets the temperature requirements, the heating is stopped and the adapter and the pole of the top cover structure are laser welded together. The heating improves the absorption rate of the welding area of ​​the adapter to the laser, thereby ensuring that the laser welding of the adapter has a good welding effect, and avoiding the problem of affecting the performance of the battery cell due to incomplete welding, false welding, etc. in the welding of the adapter.

[0113] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity 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, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0114] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a lithium battery cell, characterized in that: include: Providing a step of providing a structure to be welded and a top cover structure, wherein the structure to be welded includes a transfer sheet and a paired bare battery cell, the transfer sheet is electrically connected to the bare battery cell, and a partial area of ​​the transfer sheet is a welding area; A first control step, in which, when the structure to be welded and the top cover structure are superimposed on a welding station, a heating source is controlled to heat the welding area, and a projection of the welding area on the welding station overlaps with a projection of a pole of the top cover structure on the welding station; A determining step, according to the residence time of the structure to be welded at the welding station and the time when the structure to be welded arrives at the welding station, determining a plurality of successively increasing temperature acquisition times, wherein the difference between the maximum temperature acquisition time and the time when the structure to be welded arrives at the welding station is less than the residence time; an acquisition step, when the current moment reaches the temperature acquisition moment, acquiring the surface temperature of the welding area; an adjusting step, in the case where the surface temperature is within a predetermined range and the deviation between the surface temperature and the set temperature is greater than a first predetermined threshold, adjusting the operating parameters of the heating source according to the surface temperature and the set temperature, wherein the predetermined range is determined according to the set temperature; A second control step, when the deviation is less than or equal to the first predetermined threshold, controlling the heating source to stop heating, and performing laser welding on the welding area and the pole; The processing step is to perform core bonding, surface coating and shell packaging on the structure to be welded after laser welding to obtain a packaging structure, and at least perform liquid injection processing and chemical formation processing on the packaging structure to obtain a battery core structure.

2. The method according to claim 1, characterized in that The heating source includes a heating component and a fan, and the operating parameters of the heating source are adjusted according to the surface temperature and the set temperature, including: According to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet speed of the fan.

3. The method according to claim 2, characterized in that According to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet speed of the fan, including: When the absolute value of the difference between the surface temperature and the set temperature is greater than the first predetermined threshold and less than or equal to the second predetermined threshold, adjusting the air outlet rate according to the magnitude relationship between the surface temperature and the set temperature; When the absolute value of the difference is greater than the second predetermined threshold and less than or equal to the third predetermined threshold, adjusting the heating power according to the magnitude relationship between the surface temperature and the set temperature; When the absolute value of the difference is greater than the third predetermined threshold, the air outlet rate and the heating power are adjusted according to the magnitude relationship between the surface temperature and the set temperature.

4. The method according to claim 2, characterized in that: According to the relationship between the surface temperature and the set temperature, at least one of the following is adjusted: the heating power of the heating component and the air outlet speed of the fan, including: When the surface temperature is greater than the set temperature, reducing at least one of the following according to the first step value: the heating power, the air outlet rate; When the surface temperature is lower than the set temperature, at least one of the following is increased according to a second step value: the heating power, the air outlet rate.

5. The method according to any one of claims 1 to 4, characterized in that Before the second control step, the method further comprises: When the current moment has not reached the maximum temperature acquisition moment, or when the surface temperature is within the predetermined range and the deviation is greater than the first predetermined threshold, the acquisition step and the adjustment step are executed in a loop until the current moment reaches the maximum temperature acquisition moment, or until the surface temperature is within the predetermined range and the deviation is less than or equal to the first predetermined threshold.

6. The method according to claim 5, characterized in that The determining step comprises: According to the stay duration and a plurality of preset multiples, determining the product of the stay duration and each of the preset multiples as the interval duration, wherein the plurality of the preset multiples are all less than 1; According to the multiple interval durations and the time when the structure to be welded arrives at the welding station, the sum of the time when the structure to be welded arrives at the welding station and each interval duration is determined as each temperature acquisition time.

7. The method according to claim 6, characterized in that The multiple predetermined multiples include a first predetermined multiple, a second predetermined multiple, a third predetermined multiple, a fourth predetermined multiple and a fifth predetermined multiple which increase in sequence, wherein the first predetermined multiple is in the range of 0% to 10%, the second predetermined multiple is in the range of 10% to 20%, the third predetermined multiple is in the range of 20% to 30%, the fourth predetermined multiple is in the range of 30% to 40%, and the fifth predetermined multiple is in the range of 40% to 50%.

8. The method according to claim 5, characterized in that The method further comprises: When the current moment reaches the maximum temperature acquisition moment and the deviation is greater than the first predetermined threshold, sending a first alarm message to the terminal device, wherein the first alarm message indicates that the deviation is greater than the first predetermined threshold and instructs to stop welding; In the case that the surface temperature is not within the predetermined range, a second alarm message is sent to the terminal device, wherein the second alarm message indicates that the surface temperature is not within the predetermined range and instructs to stop welding.

9. The method according to any one of claims 1 to 4, characterized in that Obtaining the surface temperature of the welding area includes: Acquiring temperature values ​​of a plurality of positions of the welding area, wherein the temperature weight values ​​corresponding to at least two of the positions are different; According to the multiple temperature weight values, a weighted sum is performed on the multiple temperature values ​​to obtain the surface temperature.

10. The method according to claim 1, characterized in that The first predetermined threshold is 5% of the set temperature, the minimum value of the predetermined range is 80%-100% of the set temperature, and the maximum value of the predetermined range is 100%-120% of the set temperature.

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