Formation process of a soft-pack lithium battery

Abstract

The present invention relates to the technical field of soft-pack lithium battery production, and in particular to a formation process for soft-pack lithium batteries, comprising the following steps: A. performing pre-formation treatment on the soft-pack lithium battery to form a dense SEI film, and performing exhaust treatment on the soft-pack lithium battery during and / or after the pre-formation treatment; B. performing n times of formation treatment on the soft-pack lithium battery, with the formation temperature being T n , and the formation current being I n ; both the formation temperature T n and the formation current In increase with the increase of n; C. performing aging treatment on the soft-pack lithium battery, and simultaneously monitoring the voltage change and appearance change of the soft-pack lithium battery; D. performing sorting treatment on the soft-pack lithium battery. The present invention uses low temperature and small current to perform pre-formation on the soft-pack lithium battery, so that the soft-pack lithium battery generates a dense SEI film for protection. Subsequently, during formation, a segmented formation method is adopted to generate SEI films with different densities to improve the conductivity, so that the present invention has two advantages at the same time, thereby improving the quality of the soft-pack lithium battery.

Description

Technical Field

[0001] The present invention relates to the technical field of production of soft-pack lithium batteries, and in particular to a formation process for soft-pack lithium batteries. Background Art

[0002] The formation process is one of the very important processes in the production of soft-pack lithium batteries. Its purpose is to activate the electrolyte of the soft-pack lithium battery and generate a SEI film on the soft-pack lithium battery. In the existing formation processes, the following contradictions are often encountered: If high temperature and large current are used for pre-formation and formation, although the rate of SEI film formation is fast, the density of the SEI film is relatively low, which cannot play a protective role but can increase the ionic conductivity (cited from: Yang Juan, Influence of Lithium Ion Battery Formation Conditions on Formation Effect); if low temperature and small current are used for pre-formation and formation, the generated SEI film has a large density, but the required time is relatively long. Summary of the Invention

[0003] The present invention provides a formation process for soft-pack lithium batteries to solve the problems of the prior art, which can combine the above two contradictory points to generate a dense and loose SEI film.

[0004] To solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A formation process for soft-pack lithium batteries provided by the present invention includes the following steps:

[0006] A. Perform pre-treatment on the soft-pack lithium battery to form a dense SEI film, and perform exhaust treatment on the soft-pack lithium battery during and / or after the pre-treatment process;

[0007] B. Perform n formation treatments on the soft-pack lithium battery, the formation temperature is Tn, and the formation current is In; where n is a natural number and 2≤n≤6, the unit of the formation temperature Tn is °C, the unit of the formation current In is mA, and both the formation temperature Tn and the formation current In increase with the increase of n;

[0008] C. Perform aging treatment on the soft-pack lithium battery, and simultaneously monitor the voltage change and appearance change of the soft-pack lithium battery;

[0009] D. Perform sorting treatment on the soft-pack lithium battery.

[0010] Further, step A specifically includes:

[0011] A1. Perform a primary air extraction treatment on the soft-pack lithium battery;

[0012] A2. Charge the soft-pack lithium battery and sense the change in air pressure inside the soft-pack lithium battery; if the air pressure inside the soft-pack lithium battery exceeds the threshold, execute step A3, otherwise execute step A4;

[0013] A3. Perform secondary evacuation on the soft-pack lithium battery, and then execute step A4;

[0014] A4. Sense the air pressure change rate of the soft-pack lithium battery. If the air pressure change rate is less than the preset value, perform vacuum evacuation on the soft-pack lithium battery;

[0015] A5. Keep charging the soft-pack lithium battery until the preset time is reached.

[0016] Furthermore, provide a preconditioning device for executing step A. The preconditioning device includes a vacuum pump, a filter, a switching valve, a pressure sensor, a charging module, and a temperature control module. The vacuum pump is connected to the soft-pack lithium battery through the filter and the switching valve. The pressure sensor is used to insert into the soft-pack lithium battery to sense the air pressure. The charging module is used to charge the soft-pack lithium battery, and the temperature control module is used to control the temperature of the soft-pack lithium battery;

[0017] In step A2, it also includes sensing the air pressure change rate inside the soft-pack lithium battery. If the air pressure change rate is greater than the preset value, cool down the soft-pack lithium battery through the temperature control module;

[0018] If the air pressure change rate of the soft-pack lithium battery does not exceed the lower threshold within a specific time, heat up the soft-pack lithium battery through the temperature control module;

[0019] In step A5, it specifically includes:

[0020] Cool down the soft-pack lithium battery so that the temperature of the soft-pack lithium battery is reduced to T';

[0021] Keep the temperature of the soft-pack lithium battery at T', and then continuously charge the soft-pack lithium battery until the preset time is reached.

[0022] Furthermore, the preconditioning device also includes a weighing module and a liquid supplementing module. The switching valve has a first input port, a second input port, and an output port. The first input port is connected to the filter, the second input port is connected to the liquid supplementing module, and the output port is used to connect to the soft-pack lithium battery;

[0023] Step A also includes:

[0024] A6. Weigh the weight change of the soft-pack lithium battery through the weighing module;

[0025] A7. Control the switching valve to switch to connect the second input port and the output port;

[0026] A8. The liquid supplementing module replenishes the electrolyte of the soft-pack lithium battery until the weight of the soft-pack lithium battery returns to the weight before preconditioning;

[0027] A9. Discharge the soft-pack lithium battery.

[0028] Further, step B specifically includes:

[0029] B1. Heat the temperature of the soft-pack lithium battery to Tn; Tn = k’ * n, where k’ is a constant and the value range of k’ is 15 - 20;

[0030] B2. Charge the soft-pack lithium battery with a current value of In until the current battery charge of the soft-pack lithium battery becomes of the total battery charge; where In = n * I, and I is a preset rated current value;

[0031] B3. Repeat steps B1 and B2 for n times;

[0032] where k = 1 + 2 + …… + n.

[0033] Furthermore, when n > 1, execute step B1, then while maintaining the state of charging the soft-pack lithium battery with a current value of In-1, heat up the soft-pack lithium battery until the temperature of the soft-pack lithium battery is heated from Tn-1 to Tn, and then increase the current value to In.

[0034] Furthermore, provide a formation device for executing step B, including an exhaust module, a temperature adjustment module, a power supply module, and a sealing module,

[0035] The exhaust module is used to communicate with the inside of the soft-pack lithium battery and exhaust the soft-pack lithium battery, so as to form a negative pressure inside the soft-pack lithium battery;

[0036] The temperature adjustment module is used to adjust the temperature of the soft-pack lithium battery;

[0037] The power supply module is used to charge the soft-pack lithium battery;

[0038] The sealing module is used to perform a sealing treatment on the soft-pack lithium battery.

[0039] Furthermore, the sealing module is used to perform a sealing treatment on the soft-pack lithium battery, and specifically includes:

[0040] Clamp the tube of the soft-pack lithium battery;

[0041] Cut the tube of the soft-pack lithium battery to reduce the length of the tube;

[0042] Ultrasonically weld the tube of the soft-pack lithium battery to keep the tube in a closed state;

[0043] Seal the position of the tube of the soft-pack lithium battery to block and cover the tube.

[0044] Further, step C specifically includes:

[0045] C1. Place the soft-pack lithium battery for aging and monitor the voltage change of the soft-pack lithium battery;

[0046] C2. During the placement aging process, obtain the appearance changes of the soft-pack lithium battery;

[0047] C3. Infer the aging state of the soft-pack lithium battery based on the appearance changes and voltage changes of the soft-pack lithium battery and record it.

[0048] Furthermore, step D specifically includes:

[0049] D1. Obtain the voltage change of the soft-pack lithium battery. If the voltage change is within the preset range, determine that the lithium battery is in the first state; otherwise, determine it as the second state;

[0050] D2. Obtain the image of the soft-pack lithium battery, and obtain the volume change of the soft-pack lithium battery and whether there are any damage marks from the image of the soft-pack lithium battery;

[0051] D3. Compare the volume change of the soft-pack lithium battery with the pre-stored data. When the volume change of the soft-pack lithium battery is within the preset range, determine that the soft-pack lithium battery is in the third state; otherwise, determine it as the fourth state;

[0052] D4. Determine the damage length and depth through the pixel marks in the image. If there are no damage marks, determine that the soft-pack lithium battery is in the fifth state; if both the damage length and depth are within the preset range, determine that the soft-pack lithium battery is in the sixth state; if the damage length and / or depth exceed the preset range, determine that the soft-pack lithium battery is in the seventh state;

[0053] D5. Sort the soft-pack lithium batteries as follows:

[0054] When the soft-pack lithium battery is in any one of the second state, the fourth state, and the seventh state, sort the soft-pack lithium battery to the unqualified station;

[0055] Sort the soft-pack lithium batteries that are simultaneously in the first state, the third state, and the fifth state to the qualified station;

[0056] Sort the soft-pack lithium batteries that are simultaneously in the first state, the third state, and the sixth state to the repair station.

[0057] Advantages of the present invention: In the pre-forming stage, the present invention uses low temperature and small current to process the soft-pack lithium battery, so that the soft-pack lithium battery generates a dense SEI film and is protected. Subsequently, during forming, a segmented forming method is adopted to generate SEI films with different densities to improve the conductivity, so that the present invention has two advantages at the same time, thereby improving the quality of the soft-pack lithium battery. Brief Description of the Drawings

[0058] Figure 1 It is a flowchart of the present invention.

[0059] Figure 2 Schematic diagram of the pre - formation device described in the present invention.

[0060] Figure 3 Schematic diagram of the formation device described in the present invention.

[0061] Reference numerals:

[0062] 1 - Pre - formation device, 11 - Vacuum pump, 12 - Filter, 13 - Switch valve, 14 - Pressure sensor, 15 - Charging module, 16 - Temperature control module, 17 - Weighing module, 18 - Liquid supplement module;

[0063] 2 - Formation device, 21 - Exhaust module, 22 - Temperature adjustment module, 23 - Power supply module, 24 - Sealing module, 25 - Clamping and welding mechanism, 26 - Shearing mechanism, 27 - Glue sealing mechanism. Detailed implementation manners

[0064] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments and the accompanying drawings. The content mentioned in the implementation manners does not limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0065] As Figures 1 to 3 shown, a formation process for a soft - package lithium battery provided by the present invention includes the following steps:

[0066] A. Perform pre - formation treatment on the soft - package lithium battery to form a dense SEI film, and exhaust the soft - package lithium battery during and / or after the pre - formation treatment;

[0067] B. Perform n times of formation treatment on the soft - package lithium battery, the formation temperature is Tn, and the formation current is In; where n is a natural number and 2 ≤ n ≤ 6, the unit of the formation temperature Tn is °C, the unit of the formation current In is mA, and both the formation temperature Tn and the formation current In increase with the increase of n;

[0068] C. Perform aging treatment on the soft - package lithium battery, and simultaneously monitor the voltage change and appearance change of the soft - package lithium battery;

[0069] D. Perform sorting treatment on the soft - package lithium battery.

[0070] That is, the present invention adopts a forming method combining low temperature and small current with high temperature and large current. In the pre-forming stage, a dense SEI film is formed by using a low temperature and small current method. For example, it is maintained at room temperature or even lower temperature, and a charge-discharge current of 0.05C or even lower is used for pre-forming, so that the SEI film in contact with both electrodes (mainly the cathode) formed during pre-forming has a high density, thereby avoiding the reaction of the electrolyte with both electrodes and eroding both electrodes during subsequent use; after the pre-forming is completed, a segmented forming process is used to process the soft-pack lithium battery, that is, as the number of forming times increases, the temperature and current are continuously increased, so that the soft-pack lithium battery has SEI films with various densities on the basis of a dense SEI film. This method can make the structure inside the dense SEI film rough and loose, which is beneficial to improving the ionic conductivity, thereby making the soft-pack lithium battery discharge stably and efficiently.

[0071] In this embodiment, step A specifically includes:

[0072] A1. Perform a primary air extraction treatment on the soft-pack lithium battery;

[0073] A2. Charge the soft-pack lithium battery and sense the change in air pressure inside the soft-pack lithium battery; if the air pressure inside the soft-pack lithium battery exceeds the threshold value, execute step A3, otherwise execute step A4;

[0074] A3. Perform a secondary air extraction treatment on the soft-pack lithium battery, and then execute step A4;

[0075] A4. Sense the air pressure change rate of the soft-pack lithium battery. If the air pressure change rate is less than the preset value, perform a vacuum air extraction treatment on the soft-pack lithium battery;

[0076] A5. Keep charging the soft-pack lithium battery until the preset time is reached.

[0077] That is, for the soft-pack lithium battery after the injection of electrolyte is completed, it is necessary to perform a vacuum treatment on it so that the pre-forming is carried out under a negative pressure state, thereby effectively avoiding the influence and interference of oxygen on the pre-forming; during the pre-forming, the gas inside the electrolyte and the gas generated by the reaction will be released into the soft-pack lithium battery. Therefore, the present invention needs to monitor the change in air pressure inside the soft-pack lithium battery at all times and perform a secondary air extraction treatment when the air pressure reaches a certain value to avoid the soft-pack lithium battery from bulging or cracking; when the air pressure change of the soft-pack lithium battery is lower than the preset value (which can be determined by conventional multiple tests), it proves that the gas generation is basically over. At this time, the final air extraction treatment in the pre-forming process is performed on the soft-pack lithium battery, and then the pre-forming is continued until the preset pre-forming time is reached to ensure that the generated dense SEI film is thick enough.

[0078] Specifically, the present invention provides a preconditioning device 1 for performing step A. The preconditioning device 1 includes a vacuum pump 11, a filter 12, a switching valve 13, a pressure sensor 14, a charging module 15, and a temperature control module 16. The vacuum pump 11 is connected to the soft-pack lithium battery through the filter 12 and the switching valve 13. The pressure sensor 14 is used to insert into the soft-pack lithium battery and sense the air pressure. The charging module 15 is used to charge the soft-pack lithium battery, and the temperature control module 16 is used to control the temperature of the soft-pack lithium battery;

[0079] In step A2, it further includes sensing the rate of change of the air pressure inside the soft-pack lithium battery. If the rate of change of the air pressure is greater than a preset value, the temperature control module 16 is used to cool down the soft-pack lithium battery;

[0080] If the rate of change of the air pressure of the soft-pack lithium battery does not exceed the lower threshold within a specific time, the temperature control module 16 is used to heat up the soft-pack lithium battery;

[0081] In step A5, it specifically includes:

[0082] Cool down the soft-pack lithium battery so that the temperature of the soft-pack lithium battery is reduced to T';

[0083] Keep the temperature of the soft-pack lithium battery at T', and then continuously charge the soft-pack lithium battery until the preset time is reached.

[0084] That is, during the preconditioning process of the soft-pack lithium battery, heat generation is inevitably involved. At this time, in order to ensure that the preconditioning effect meets the expectations, the temperature control module 16 is used to cool down the soft-pack lithium battery; and in order to ensure the preconditioning efficiency, when the temperature of the soft-pack lithium battery is too low, it is also necessary to heat it up to maintain the preconditioning within a preset temperature range.

[0085] The temperature control module 16 preferably includes a heating wire and a water cooling module. When heating is required, the heating wire is used to increase the temperature around the soft-pack lithium battery, and when cooling is required, the water cooling module is used to cool down the temperature around the soft-pack lithium battery.

[0086] It should also be noted that for the soft-pack lithium battery described in the present invention, it has a tube inserted into the inside of the aluminum-plastic film. This tube is integrated with the aluminum-plastic film and is used for operations such as liquid injection, air extraction, and liquid replenishment. In the preconditioning device 1 of the present invention, the vacuum pump 11 is connected to the tube through the filter 12 and the switching valve 13. That is, the extracted gas is filtered and absorbed by the filter 12 for impurities such as electrolyte, and then extracted by the vacuum pump 11 to the outside to ensure the safety of the vacuum pump 11 and avoid environmental pollution.

[0087] Specifically, the pre-conditioning device 1 further includes a weighing module 17 and a liquid replenishing module 18. The switching valve 13 has a first input port, a second input port, and an output port. The first input port is communicated with the filter 12, the second input port is communicated with the liquid replenishing module 18, and the output port is used to communicate with the soft-pack lithium battery.

[0088] Step A further includes:

[0089] A6. Weigh the weight change of the soft-pack lithium battery through the weighing module 17;

[0090] A7. Control the switching valve 13 to switch to the state where the second input port is communicated with the output port;

[0091] A8. The liquid replenishing module 18 replenishes the electrolyte of the soft-pack lithium battery until the weight of the soft-pack lithium battery returns to the weight before pre-conditioning;

[0092] A9. Perform a discharging process on the soft-pack lithium battery.

[0093] When pumping air, a part of the liquid will inevitably be pumped out. Therefore, the weight of the soft-pack lithium battery will change. In response to this, the present invention uses a three-way three-position valve as the switching valve 13, so that the switch has three states: a sealed tube, a control tube communicated with the vacuum pump 11, and a control injection module communicated with the tube. After the pre-conditioning is completed, according to the weight loss of the soft-pack lithium battery, its weight is supplemented by means of liquid replenishment. The preferred rule for this supplement is that the mass of the supplemented electrolyte is greater than the weight of the lost electrolyte: if the weight loss is 100 g, then 105 - 110 g of electrolyte is supplemented, and the subsequent weight loss problem encountered during formation is solved by the extra 5 - 10 g of electrolyte, avoiding secondary liquid replenishment.

[0094] In this embodiment, step B specifically includes:

[0095] B1. Heat the temperature of the soft-pack lithium battery to Tn; Tn = k' * n, where k' is a constant and the value range of k' is 15 - 20;

[0096] B2. Charge the soft-pack lithium battery with a current value of In until the current power of the soft-pack lithium battery becomes of the total power; where In = n * I, and I is a preset rated current value;

[0097] B3. Repeat steps B1 and B2 for n times;

[0098] Where k = 1 + 2 +... + n.

[0099] Taking the formation times as four times as an example, k is equal to 1 + 2 + 3 + 4 = 10. The temperature of the first formation is 20 °C, and the formation current is I;

[0100] When the current power of the soft-pack lithium battery becomes 1 / 10 of the total power, the second formation is performed. At this time, the formation temperature is 40°C and the formation current is 2I.

[0101] When the current power of the soft-pack lithium battery becomes 3 / 10 of the total power, the third formation is performed. At this time, the formation temperature is 60°C and the formation current is 3I;

[0102] When the current power of the soft-pack lithium battery becomes 6 / 10 of the total power, the fourth formation is performed, at which the formation temperature is 80°C and the formation current is 4I.

[0103] In the above manner, the soft-pack lithium battery produced by the present invention can form a loose and uneven sei membrane structure. Since the dense sei membrane formed by pre-forming realizes the protection of the cathode, the sei membrane structure formed subsequently is mainly used to ensure the conductivity at the cathode, so as to achieve the two effects of avoiding cathode corrosion as much as possible and improving conductivity.

[0104] Specifically, when n>1, step B1 is executed, and the temperature of the soft-pack lithium battery is increased while the soft-pack lithium battery is charged at a current value of In-1 until the temperature of the soft-pack lithium battery is heated from Tn-1 to Tn, and then the current value is increased to In.

[0105] For example, in the second formation, the current I is maintained to charge and discharge the soft-pack lithium battery, and then the temperature is raised in this state until the temperature of the soft-pack lithium battery reaches 40°C, and then the current is increased to 2I. In this way, there is a transition between the two formations of the soft-pack lithium battery, avoiding the impact of the formation result caused by the one-time jump of the two parameters.

[0106] Specifically, the present invention provides a formation device 2 for performing step B, comprising an exhaust module 21, a temperature adjustment module 22, a power supply module 23 and a sealing module 24.

[0107] The exhaust module 21 is used to communicate with the inside of the soft-pack lithium battery and exhaust the soft-pack lithium battery so that a negative pressure is formed inside the soft-pack lithium battery;

[0108] The temperature adjustment module 22 is used to adjust the temperature of the soft-pack lithium battery;

[0109] The power supply module 23 is used to charge the soft-pack lithium battery;

[0110] The sealing module 24 is used to seal the soft-pack lithium battery.

[0111] In actual use, the sealing module 24 includes a clamping and welding mechanism 25, a shearing mechanism 26, and a glue-sealing mechanism 27. Among them, the clamping and welding mechanism 25 can adopt a structure in which two output ends of pneumatic fingers are respectively provided with ultrasonic welders. The shearing mechanism 26 is composed of a conventional cylinder or a motor-driven scissors in cooperation with a robot, and the glue-sealing mechanism 27 is a conventional structure driven by a lifting module.

[0112] Based on the above-mentioned sealing module 24, the sealing module 24 is used for sealing a soft-pack lithium battery, and specifically includes:

[0113] Clamp the tube of the soft-pack lithium battery;

[0114] Cut the tube of the soft-pack lithium battery to reduce the length of the tube;

[0115] Perform ultrasonic welding on the tube of the soft-pack lithium battery to keep the tube in a closed state;

[0116] Perform glue-sealing treatment on the position of the tube of the soft-pack lithium battery to block and cover the tube.

[0117] During formation, gas may also be generated. However, since most of the gas has been generated and drained during pre-formation, the gas generated during formation is not much, and only needs to be discharged uniformly after the formation step is completed; and after exhaust, the soft-pack lithium battery can be sealed. At this time, the method adopted by the present invention is: first clamp the tube of the soft-pack lithium battery to avoid air leakage; then cut the tube of the soft-pack lithium battery short, preferably cut to be flush with or slightly higher than the soft-pack lithium battery; then use the clamping and welding mechanism 25 to perform ultrasonic welding to keep the tube bonded and clamped, and finally perform glue-sealing treatment so that the position of the tube is filled, achieving the effect of secondary sealing and avoiding the exposure of the tube and affecting the appearance.

[0118] After the glue-sealing treatment, the soft-pack lithium battery is transferred to be aged.

[0119] In this embodiment, step C specifically includes:

[0120] C1. Place the soft-pack lithium battery for aging and monitor the voltage change of the soft-pack lithium battery;

[0121] C2. During the aging process, obtain the appearance change of the soft-pack lithium battery;

[0122] C3. According to the appearance change and voltage change of the soft-pack lithium battery, infer the aging state of the soft-pack lithium battery and record it.

[0123] That is, during the aging process, in addition to sensing the voltage change of the soft-pack lithium battery, it is also necessary to observe the appearance of the soft-pack lithium battery. Only when both the appearance and voltage change meet the requirements, the soft-pack lithium battery is qualified.

[0124] Based on the above steps C1 - C3, step D of the present invention specifically includes:

[0125] D1. Obtain the voltage change of the soft - package lithium battery. If the voltage change is within the preset range, determine that the lithium battery is in the first state; otherwise, determine it as the second state.

[0126] D2. Obtain the image of the soft - package lithium battery, and obtain the volume change of the soft - package lithium battery and whether there are any damage marks from the image of the soft - package lithium battery.

[0127] D3. Compare the volume change of the soft - package lithium battery with the pre - stored data. If the volume change of the soft - package lithium battery is within the preset range, determine that the soft - package lithium battery is in the third state; otherwise, determine it as the fourth state.

[0128] D4. Judge the damage length and depth through the pixel marks in the image. If there are no damage marks, determine that the soft - package lithium battery is in the fifth state; if both the damage length and depth are within the preset range, determine that the soft - package lithium battery is in the sixth state; if the damage length and / or depth exceed the preset range, determine that the soft - package lithium battery is in the seventh state.

[0129] D5. Sort the soft - package lithium batteries as follows:

[0130] When the soft - package lithium battery is in any one of the second state, the fourth state, and the seventh state, sort the soft - package lithium battery to the unqualified station.

[0131] Sort the soft - package lithium batteries that are simultaneously in the first state, the third state, and the fifth state to the qualified station.

[0132] Sort the soft - package lithium batteries that are simultaneously in the first state, the third state, and the sixth state to the repair station.

[0133] That is, when the voltage change of the soft - package lithium battery is abnormal, or the volume change is abnormal, or there are large damages on the surface, it proves that the soft - package lithium battery has potential safety hazards, such as being unable to charge stably, being prone to bulging or leakage. At this time, the soft - package lithium battery is directly determined as a non - conforming product and needs to be sorted to the unqualified station for subsequent scrapping treatment.

[0134] When the voltage change of the soft - package lithium battery is normal, the volume change is within the required value, and there are no marks on the surface, then the soft - package lithium battery is a qualified product and can be directly sorted for the next process.

[0135] If the voltage change of the soft - package lithium battery is normal, the volume change is within the required value, but there are slight damages on the surface, then the surface of the soft - package lithium battery is repairable. Therefore, it is sorted to the repair station, and the subsequent damage on its surface can be repaired and then continue to be used.

[0136] Through the above sorting, it is possible to repair and reuse the defective soft-pack lithium batteries as much as possible, improve the yield rate, and help save costs.

[0137] It should be noted that the preconditioning device 1 and the formation device 2 described in the present invention can both precondition and form multiple soft-pack lithium batteries at one time. For the convenience of understanding, the drawings only show the structure of one soft-pack lithium battery. In fact, one preconditioning device 1 and one formation device 2 may respectively include multiple Figure 2 、 Figure 3 structures shown.

[0138] The above are only preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention is disclosed above in preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, when making some changes or modifications using the above-disclosed technical content into equivalent embodiments of equivalent changes, but as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical means of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A formation process for a soft-pack lithium battery, characterized in that: It includes the following steps: A. Pre-treat the soft-pack lithium battery to form a dense SEI film, and perform exhaust treatment on the soft-pack lithium battery during and / or after the pre-treatment process; B. The soft-pack lithium battery is subjected to n formation processes at a formation temperature of T n , and the formation current is I n ; where n is a natural number and 2 ≤ n ≤ 6, the unit of the formation temperature T n is °C, and the unit of the formation current In is mA. Both the formation temperature T n and the formation current In increase with the increase of n; C. Age the soft-pack lithium battery while monitoring the voltage change and appearance change of the soft-pack lithium battery; D. Sort the soft-pack lithium batteries; Step A specifically includes: A1. Perform a primary air extraction treatment on the soft-pack lithium battery; A2. Charge the soft-pack lithium battery and sense the air pressure change inside the soft-pack lithium battery; if the air pressure inside the soft-pack lithium battery exceeds the threshold, execute step A3, otherwise execute step A4; A3. Perform a secondary air extraction treatment on the soft-pack lithium battery, and then execute step A4; A4. Sense the air pressure change rate of the soft-pack lithium battery. If the air pressure change rate is less than the preset value, perform vacuum air extraction treatment on the soft-pack lithium battery; A5. Keep charging the soft-pack lithium battery until the preset time is reached; Step B specifically includes: B1. Heat the temperature of the soft-pack lithium battery to T n ; T n = k' * n, where k' is a constant and the value range of k' is 15 - 20; B2. Charge the soft-pack lithium battery with a current value of In until the current power of the soft-pack lithium battery becomes one of the total powers where I n = n*I, where I is a preset rated current value; B3. Repeat steps B1 and B2 for n times; where k = 1 + 2 +... + n; When n > 1, step B1 is executed, and the charging state of the soft-pack lithium battery is maintained with the current value I n-1 while heating the soft-pack lithium battery until the temperature of the soft-pack lithium battery rises from T n-1 to T n and then the current value is increased to I n ; The formation process adopts a formation method combining low temperature and small current with high temperature and large current. In the pre-formation stage, a dense SEI film is formed by using a low temperature and small current method.

2. The formation process of the soft-pack lithium battery according to claim 1, characterized in that: Provide a pre-treatment device for performing step A. The pre-treatment device includes a vacuum pump, a filter, a switching valve, a pressure sensor, a charging module, and a temperature control module. The vacuum pump is connected to the soft-pack lithium battery through the filter and the switching valve. The pressure sensor is used to insert into the soft-pack lithium battery to sense the air pressure. The charging module is used to charge the soft-pack lithium battery, and the temperature control module is used to control the temperature of the soft-pack lithium battery; In step A2, it also includes sensing the air pressure change rate inside the soft-pack lithium battery. If the air pressure change rate is greater than the preset value, cool down the soft-pack lithium battery through the temperature control module; If the air pressure change rate of the soft-pack lithium battery does not exceed the lower threshold within a specific time, heat up the soft-pack lithium battery through the temperature control module; In step A5, it specifically includes: Cool down the soft-pack lithium battery so that the temperature of the soft-pack lithium battery is reduced to T'; Keep the temperature of the soft-pack lithium battery at T', and then continuously charge the soft-pack lithium battery until the preset time is reached.

3. The formation process of the soft-pack lithium battery according to claim 2, characterized in that: The pre-treatment device further includes a weighing module and a liquid supplement module. The switching valve has a first input port, a second input port, and an output port. The first input port is connected to the filter, the second input port is connected to the liquid supplement module, and the output port is used to connect to the soft-pack lithium battery; Step A further includes: A6. Weigh the weight change of the soft-pack lithium battery through the weighing module; A7. Control the switching valve to switch to connect the second input port and the output port; A8. The liquid supplement module supplements the electrolyte to the soft-pack lithium battery until the weight of the soft-pack lithium battery is restored to the weight before pre-treatment; A9. Discharge the soft-pack lithium battery.

4. The formation process of the soft-pack lithium battery according to claim 1, characterized in that: Provide a formation device for performing step B, including an exhaust module, a temperature adjustment module, a power supply module, and a sealing module, The exhaust module is used to connect to the inside of the soft-pack lithium battery and exhaust the soft-pack lithium battery to make the inside of the soft-pack lithium battery form a negative pressure; The temperature adjustment module is used to adjust the temperature of the soft-pack lithium battery; The power supply module is used to charge the soft-pack lithium battery; The sealing module is used to seal the soft-pack lithium battery.

5. The formation process of the soft-pack lithium battery according to claim 4, characterized in that: The sealing module is used to seal the soft-pack lithium battery, specifically including: Clamp the tube of the soft-pack lithium battery; Cut the tube of the soft-pack lithium battery to reduce the length of the tube; Ultrasonically weld the tube of the soft-pack lithium battery to keep the tube in a closed state; Seal the position of the tube of the soft-pack lithium battery to block and cover the tube.

6. The formation process of the soft-pack lithium battery according to claim 1, characterized in that: Step C specifically includes: C1. Place the soft-pack lithium battery for aging and monitor the voltage change of the soft-pack lithium battery; C2. During the aging process, obtain the appearance change of the soft-pack lithium battery; C3. Infer and record the aging state of the soft-pack lithium battery based on the appearance change and voltage change of the soft-pack lithium battery.

7. The formation process of the soft-pack lithium battery according to claim 6, characterized in that: Step D specifically includes: D1. Obtain the voltage change of the soft-pack lithium battery. If the voltage change is within the preset range, determine that the lithium battery is in the first state; otherwise, judge it as the second state; D2. Obtain the image of the soft-pack lithium battery, and obtain the volume change of the soft-pack lithium battery and whether there are any damage marks from the image of the soft-pack lithium battery; D3. Compare the volume change of the soft-pack lithium battery with the pre-stored data. If the volume change of the soft-pack lithium battery is within the preset range, determine that the soft-pack lithium battery is in the third state; otherwise, determine it as the fourth state; D4. Judge the damage length and depth through the pixel traces in the image. If there are no damage marks, determine that the soft-pack lithium battery is in the fifth state; if both the damage length and depth are within the preset range, determine that the soft-pack lithium battery is in the sixth state; if the damage length and / or depth exceeds the preset range, determine that the soft-pack lithium battery is in the seventh state; D5. Sort the soft-pack lithium batteries as follows: When the soft-pack lithium battery is in any one of the second state, the fourth state, and the seventh state, sort the soft-pack lithium battery to the unqualified station; Sort the soft-pack lithium batteries that are simultaneously in the first state, the third state, and the fifth state to the qualified station; Sort the soft-pack lithium batteries that are simultaneously in the first state, the third state, and the sixth state to the repair station.

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