Liquid injection method and system for battery cell and preparation method of battery cell

Abstract

The application discloses a kind of injection method of battery, injection system and preparation method of battery, and the injection method of battery includes the following steps: obtaining the target injection amount M0 of battery, the average injection amount Ma of previous n injected battery of current un-injected battery;According to average injection amount Ma and target injection amount M0, adjust the operating parameter of injection pump, to adjust the actual injection amount M of injection pump;Control injection pump to start, inject electrolyte into the air bag of the un-injected battery, and seal the air bag, obtain semi-finished battery.The injection method of battery provided in the application, according to the average injection amount Ma of previous n injected battery and target injection amount M0, timely adjust the actual injection amount M of injection pump, so that each actual injection amount M is closer to target injection amount M0 than average injection amount Ma of injected battery, can improve injection consistency, and then achieve the effect of improving the consistency of liquid retention, to improve the electrochemical performance and reliability of battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery production, and in particular to a method for injecting electrolyte into a battery, a system for injecting electrolyte into a battery, and a method for manufacturing a battery. BACKGROUND

[0002] With the rapid development of consumer electronics, energy storage, and electric vehicles, the demand for soft-pack lithium batteries is increasing, and the performance requirements for soft-pack lithium batteries are also becoming higher. In a lithium battery, the injection amount is the initial amount of electrolyte injected into the battery during the injection stage of the production process. The electrolyte retention amount refers to the amount of electrolyte actually retained in the battery after the battery is packaged. The consistency of the electrolyte retention amount is an important indicator in the battery manufacturing process, which directly affects the performance and yield of the battery. For example, insufficient electrolyte retention amount can increase the internal resistance of the battery, reducing its cycle life and discharge capacity; and excessive electrolyte retention amount can increase the risk of battery leakage, affecting safety and increasing manufacturing costs.

[0003] Due to the non-uniformity in the injection process, evaporation loss of electrolyte, and leakage in the subsequent packaging process, it is often difficult to accurately control the relationship between the injection amount and the electrolyte retention amount in the prior art, resulting in inconsistent electrolyte retention amount of the battery, affecting the electrochemical performance and reliability of the battery. SUMMARY

[0004] The present application provides a method for injecting electrolyte into a battery, a system for injecting electrolyte into a battery, and a method for manufacturing a battery, to solve the problem of difficult accurate control of the relationship between the injection amount and the electrolyte retention amount, to improve the consistency of the electrolyte retention amount of the battery, and to improve the electrochemical performance and reliability of the battery.

[0005] Specifically, the present application provides a method for injecting electrolyte into a battery, the method comprising the following steps:

[0006] obtaining a target injection amount M0 of the battery, and an average injection amount Ma of n previously injected batteries of the battery;

[0007] adjusting the operating parameters of the injection pump according to the average injection amount Ma and the target injection amount M0, to adjust the actual injection amount M of the injection pump;

[0008] controlling the injection pump to start, injecting electrolyte into the gas bag of the un-injected battery, and sealing the gas bag to obtain a semi-finished battery.

[0009] Optionally, the adjustment of the parameters of the injection pump comprises:

[0010] in response to the average injection amount Ma being higher than the target injection amount M0, reducing the rotation speed or operating time of the injection pump; or

[0011] in response to the average liquid injection amount Ma being lower than the target liquid injection amount M0, increasing the rotation speed or operation time of the liquid injection pump.

[0012] Optionally, the liquid injection method further comprises:

[0013] After obtaining the average liquid injection amount Ma, calculating a difference AM between the target liquid injection amount M0 and the average liquid injection amount Ma.

[0014] adjusting the actual liquid injection amount M according to the formula M=M0+kAM.

[0015] wherein k is an adjustment coefficient, 0.5≤k≤0.8.

[0016] Optionally, 4≤n≤32.

[0017] The application further provides a preparation method of an electric core, comprising the following steps:

[0018] liquid injection to obtain a semi-finished electric core; the liquid injection is performed according to the liquid injection method of any one of the above.

[0019] formation, aging and degassing of the semi-finished electric core to obtain a finished electric core.

[0020] Optionally, the degassing step comprises the following steps performed in sequence:

[0021] placing the semi-finished electric core after aging into a vacuum generating device and puncturing the air bag of the semi-finished electric core;

[0022] controlling the vacuum degree of the vacuum generating device to be a first threshold value P1 and maintaining for a first time T1;

[0023] controlling the vacuum degree of the vacuum generating device to be a second threshold value P2 and maintaining for a second time T2; wherein the second threshold value P2 is greater than the first threshold value P1.

[0024] sealing the air bag to obtain a finished electric core.

[0025] Optionally, the first threshold value P1 is-60Kpa to-80Kpa.

[0026] and / or, the second threshold value P2 is-80Kpa to-90Kpa.

[0027] Optionally, after maintaining for the second time, controlling the vacuum degree of the vacuum generating device to be a third threshold value P3 and maintaining for a third time T3; wherein the third threshold value P3 is greater than the second threshold value P2.

[0028] Optionally, T2+T3>T1.

[0029] Optionally, the first threshold P1 is -40 Kpa to -60 Kpa.

[0030] Optionally, the second threshold P2 is -60 Kpa to -80 Kpa.

[0031] Optionally, the third threshold P3 is -80 Kpa to -90 Kpa.

[0032] Optionally, the first time T1 is 1 s to 4 s.

[0033] Optionally, the second time T2 is 1 s to 3 s.

[0034] Optionally, the third time T3 is 1 s to 3 s.

[0035] Optionally, the formation includes charging and activating the semi-finished battery cell.

[0036] Optionally, the aging includes placing the charged semi-finished battery cell in a cartridge and standing.

[0037] Optionally, before the formation, the air bag of the semi-finished battery cell is squeezed, and then the semi-finished battery cell is placed in the cartridge and stood.

[0038] Optionally, the squeezing of the air bag of the semi-finished battery cell includes:

[0039] A clamping plate is arranged on both sides of the air bag, and a pressure F is applied to the clamping plate for a holding time T4.

[0040] Wherein, F is 10 N to 500 N, and T4 is 0.2 s to 2 s.

[0041] Optionally, the total contact area of the air bag and the clamping plates on both sides thereof is S1, and S1 and the area S2 of the air bag satisfy: 0.5S2≤S1≤0.8S2.

[0042] Optionally, the cartridge includes a bottom plate and side plates arranged at both ends of the bottom plate, and two side plates are used to accommodate a plurality of semi-finished battery cells.

[0043] At least one side of the side plate close to the other side plate is provided with a elastic layer; or at least one side plate is made of elastic material.

[0044] The step of placing the semi-finished battery cell in the cartridge and standing includes:

[0045] A plurality of semi-finished battery cells are arranged and placed on the bottom plate of the cartridge along the thickness direction and between the side plates.

[0046] The side plates clamp all the semi-finished battery cells in the magazine, and the elastic layer or the side plates made of elastic material is pressed against the outermost surface of the semi-finished battery cells arranged at the outermost side.

[0047] The magazine is stationary and clamps the semi-finished battery cells.

[0048] Optionally, the elastic layer is made of elastic material, and the elastic material is a foam or a silica gel pad.

[0049] The application further provides an injection system, which comprises:

[0050] A liquid storage tank is configured to store electrolyte.

[0051] An injection pump is in communication with the liquid storage tank and is configured to inject the electrolyte into the gas bag of an un-injected battery cell.

[0052] A controller is in communication connection with the injection pump.

[0053] An upper computer is configured to store a machine executable program, and the machine executable program is configured to implement the injection method according to any one of the above when executed by the controller.

[0054] The application has the following advantages:

[0055] In the injection method, the preparation method and the related device of the battery cell, the actual injection amount M of the injection pump is adjusted in time according to the average injection amount Ma of the first n battery cells and the target injection amount M0, so that the actual injection amount M is closer to the target injection amount M0 than the average injection amount Ma of the injected battery cell. Since the liquid retention amount = injection amount - liquid loss amount, the consistency of the injection amount can be improved by adjusting the actual injection amount M, and the consistency of the liquid retention amount is improved, so that the electrochemical performance and the reliability of the battery cell are improved. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the application. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0057] Figure 1 is a schematic principle diagram of an injection system in an embodiment of the application;

[0058] Figure 2 is a schematic diagram of the semi-finished battery cells placed in the magazine in an embodiment of the application.

[0059] In the figure: 100, liquid storage tank, 200, liquid injection pump, 300, controller, 400, upper computer, 500, buffer cup, 600, magazine, 610, bottom plate, 620, side plate, 700, un-injected battery cell, 800, semi-finished battery cell. DETAILED DESCRIPTION

[0060] In order to make the technical problems solved by the present application, technical solutions and beneficial effects more clearly, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0061] The present application will be further described below through examples.

[0062] The present application provides a liquid injection method of battery cell, the liquid injection method comprising the following steps:

[0063] Obtaining the target injection amount M0 of the battery cell, the average injection amount Ma of the previous n injected battery cells before the un-injected battery cell 700;

[0064] According to the average injection amount Ma and the target injection amount M0, adjusting the operation parameters of the liquid injection pump 200 to adjust the actual injection amount M of the liquid injection pump 200;

[0065] Controlling the liquid injection pump 200 to start, injecting electrolyte into the air bag of the un-injected battery cell 700, and sealing the air bag to obtain the semi-finished battery cell 800.

[0066] For the same liquid injection system, the liquid loss caused by each link is relatively close, so the actual injection amount M and the liquid retention amount are relatively close. According to the average injection amount Ma of the previous n injected battery cells and the target injection amount M0, the actual injection amount M of the liquid injection pump 200 is adjusted in time in the embodiment of the present application, so that each actual injection amount M is closer to the target injection amount M0 than the average injection amount Ma of the injected battery cells. Since the liquid retention amount = injection amount - liquid loss, by adjusting the actual injection amount M, the consistency of the injection amount can be improved, and the effect of improving the consistency of the liquid retention amount is achieved, so as to improve the electrochemical performance and reliability of the battery cell.

[0067] Wherein, 4≤n≤32, if the injection amount of a battery cell in the production process suddenly changes when n takes a too small value, the actual injection amount M of the subsequent battery cell is greatly affected, which easily leads to a large deviation of the injection amount of the subsequent battery cell and reduces the consistency of the liquid retention amount; if n takes a too large value, the actual injection amount M of the subsequent battery cell is not greatly affected when the injection amount of a battery cell in the production process suddenly changes, which makes it difficult to adjust the actual injection amount M of the subsequent battery cell in time, resulting in poor consistency of the liquid retention amount.

[0068] Further, the liquid injection method further comprises:

[0069] After the average injection amount Ma is obtained, a difference AM between the target injection amount M0 and the average injection amount Ma is calculated; wherein, a weight M1 of the non-injection battery cell 700 before injection is obtained; the electrolyte is injected into the battery cell by the injection pump 200 according to the set parameters, the injection is sealed, and the weight M2 is obtained after weighing, so that the injection amount M' of the battery cell is calculated as M2-M1; the average value of the injection amount M' of the first n battery cells is the average injection amount Ma;

[0070] The actual injection amount M is adjusted according to the formula M=M0+kAM; wherein, k is an adjustment coefficient, 0.5≤k≤0.8.

[0071] In the embodiment of the application, by adjusting the difference AM between the target injection amount M0 and the average injection amount Ma according to a certain proportion, the influence of the sudden change of the injection amount of a certain battery cell on the actual injection amount M of the subsequent battery cell can be further reduced, and the consistency of the liquid retention amount is improved.

[0072] Specifically, the parameters of the injection pump 200 are adjusted, including: in response to the average injection amount Ma being higher than the target injection amount M0, the rotation speed or running time of the injection pump 200 is reduced; or, in response to the average injection amount Ma being lower than the target injection amount M0, the rotation speed or running time of the injection pump 200 is increased.

[0073] In the embodiment of the application, the actual injection amount M of the injection pump 200 is reduced or increased by reducing or increasing the rotation speed or running time of the injection pump 200, so as to achieve the effect of making the liquid retention amount consistent by adjusting the actual injection amount M.

[0074] The application also provides a preparation method of a battery cell, comprising:

[0075] injecting electrolyte to obtain a semi-finished battery cell 800; the injection is performed according to the injection method of any one of the above;

[0076] forming, aging and exhausting the semi-finished battery cell 800 to obtain a finished battery cell.

[0077] Further, the exhausting step comprises the following steps performed in sequence:

[0078] placing the semi-finished battery cell 800 after aging into a vacuum generating device, and puncturing the air bag of the semi-finished battery cell 800;

[0079] controlling the vacuum degree of the vacuum generating device to be a first threshold value P1, and maintaining the first threshold value P1 for a first time T1;

[0080] controlling the vacuum degree of the vacuum generating device to be a second threshold value P2 and keeping for a second time T2; wherein the second threshold value P2 is greater than the first threshold value P1;

[0081] sealing the air bag to obtain the finished product battery cell.

[0082] Through secondary vacuumizing, the electrolyte can be fully infiltrated into the positive and negative active materials in the air bag, avoiding the electrolyte being extracted with the gas, reducing the liquid loss of the battery cell, and improving the consistency of the liquid loss. Since the liquid retention of the battery cell = the liquid injection amount - the liquid loss, controlling the consistency of the liquid retention requires controlling the consistency of the liquid injection amount and the consistency of the liquid loss. The technical solution improves the liquid injection method to improve the consistency of the liquid injection amount, and through the secondary vacuumizing in the embodiment, the consistency of the liquid loss is improved, and finally the consistency of the liquid retention is improved.

[0083] Specifically, the first threshold value P1 is -60Kpa to -80Kpa; and the second threshold value P2 is -80Kpa to -90Kpa.

[0084] Further, after keeping for the second time, the vacuum degree of the vacuum generating device is controlled to be a third threshold value P3 and kept for a third time T3; wherein the third threshold value P3 is greater than the second threshold value P2. Through three times of vacuumizing, the liquid loss of the battery cell can be further reduced, and the consistency of the liquid loss is improved.

[0085] In the three times of vacuumizing, the first threshold value P1 is -40Kpa to -60Kpa; the second threshold value P2 is -60Kpa to -80Kpa; and the third threshold value P3 is -80Kpa to -90Kpa. If the first time T1 is relatively long, and the second time T2 and the third time T3 are relatively short, the battery cell is kept in a low vacuum degree for a relatively long time, which is easy to cause more gas to be retained in the battery cell, and the appearance of the battery cell shows a slight swelling / floating liquid. Therefore, in order to avoid too much gas being retained in the battery cell, the embodiment of the present application limits T2+T3>T1.

[0086] In some embodiments of the present application, the formation includes charging and activating the semi-finished product battery cell 800; and the aging includes placing the charged semi-finished product battery cell 800 in the magazine 600 for standing. Further, before the formation, the air bag of the semi-finished product battery cell 800 is squeezed to accelerate the electrolyte remaining in the air bag to quickly infiltrate into the positive and negative active materials. Then the semi-finished product battery cell 800 is placed in the magazine 600 for standing, which is carried out at room temperature or high temperature environment. By standing the battery cell for a period of time, it is ensured that the electrolyte is fully infiltrated into the positive and negative active materials.

[0087] As Figure 2As shown, the clip includes a bottom plate 610 and side plates 620 arranged at both ends of the bottom plate 610, and two side plates 620 are used to accommodate a plurality of semi-finished battery cells 800;

[0088] At least one side of the side plate 620 close to the other side plate 620 is provided with an elastic layer made of elastic material, and the elastic material is a foam or a silica gel pad; or at least one side plate 620 is made of elastic material.

[0089] The step of placing the semi-finished battery cells in the clip 600 includes:

[0090] A plurality of semi-finished battery cells are arranged and placed on the bottom plate 610 of the clip 600 along the thickness direction and between the side plates 620;

[0091] The side plates 620 cooperate to clamp all the semi-finished battery cells in the clip 600, and the elastic layer or the side plates 620 made of elastic material are pressed on the outermost surface of the semi-finished battery cells arranged on the outermost side;

[0092] The clip 600 clamped with the semi-finished battery cells 800 is placed and rested.

[0093] Specifically, the step of extruding the air bag of the semi-finished battery cell 800 includes:

[0094] Clamping plates are arranged on both sides of the air bag, and a pressure F is applied to the clamping plates for a holding time T4;

[0095] Wherein, F is 10N to 500N, and T4 is 0.2s to 2s.

[0096] The total contact area of the air bag and the clamping plates on both sides thereof is S1, and S1 and the area S2 of the air bag satisfy: 0.5S2≤S1≤0.8S2.

[0097] As Figure 1 The application also provides an injection system, which includes:

[0098] A liquid storage tank 100 for storing electrolyte;

[0099] An injection pump 200 in communication with the liquid storage tank 100, for injecting the electrolyte into the air bag of an un-injected battery cell 700;

[0100] A controller 300 in communication connection with the injection pump 200,

[0101] The host computer 400 stores a machine executable program, and when the machine executable program is executed by the controller 300, the machine executable program is used to realize the liquid injection method of any one of the above.

[0102] In application, the electrolyte enters and is stored in the liquid storage tank 100 through the conveying pipeline. In the first liquid injection, the weight M1 of the un-injected battery cell 700 is obtained first; the host computer 400 transmits the set target liquid injection amount M0 to the controller 300, the controller 300 converts the target liquid injection amount M0 into the operation parameters (the rotation speed, the flow rate and the time) of the liquid injection pump 200, and sends the operation parameters to the liquid injection pump 200, the liquid injection pump 200 operates according to the operation parameters, the electrolyte is poured into the buffer cup 500, the buffer cup 500 pours the electrolyte into the un-injected battery cell 700, the liquid injection is completed, the sealing is completed, the weight M2 is obtained after weighing, and the liquid injection amount of the battery cell is M' = M2-M1. The liquid injection pump 200 adopts a mode of one pump controlling one needle, and the amount of electrolyte poured into the buffer cup 500 by the liquid injection pump 200 each time is the amount of electrolyte to be injected into the battery cell.

[0103] In subsequent liquid injection, the host computer 400 calculates the average liquid injection amount Ma of the previous n injected battery cells, and calculates the actual liquid injection amount M according to the formula M = M0+kΔM, ΔM = M0-Ma, further transmits the actual liquid injection amount M to the controller 300, the controller 300 converts the actual liquid injection amount M into the operation parameters (the rotation speed, the flow rate and the time) of the liquid injection pump 200, and sends the operation parameters to the liquid injection pump 200, the liquid injection pump 200 operates according to the operation parameters, the electrolyte is poured into the buffer cup 500, the buffer cup 500 pours the electrolyte into the un-injected battery cell 700, the liquid injection is completed, the sealing is completed, the weight M2 is obtained after weighing, and the liquid injection amount of the battery cell is M' = M2-M1. The host computer 400 obtains the weight M2 of the battery cell and calculates the liquid injection amount M' of the battery cell, and further calculates the average liquid injection amount Ma of the previous n battery cells.

[0104] As shown in Figure 2 The present application also provides a magazine 600, which comprises a bottom plate 610 and side plates 620 arranged at both ends of the bottom plate 610, and two side plates 620 are used to accommodate semi-finished battery cells; at least one side of the side plate 620 close to the other side plate 620 is provided with an elastic layer; or at least one side plate 620 is made of elastic material. Through the arrangement of the elastic layer, a certain extrusion force can be applied to the battery cell when the battery cell is at rest, so that a better infiltration effect is achieved.

[0105] Further, the elastic layer is made of elastic material, and the elastic material is foam or silica gel pad. The elasticity generated by the foam or silica gel pad makes the extrusion force between the battery cell and the adjacent battery cell <10N, so as to ensure that the electrolyte has sufficient flow channel in the air bag.

[0106] The application is further illustrated by the following examples. However, the application is not limited to the examples described. The experimental methods in the following examples, for which no specific conditions are indicated, are carried out according to conventional methods and conditions, or according to the instructions of the commercial suppliers.

[0107] Liquid injection amount test:

[0108] Example 1

[0109] S1, injection: the weight M1 of the current dried non-injection battery cell 700 and the target injection amount M0 are obtained, the host computer 400 calculates the average injection amount Ma of the previous n (n = 8) battery cells before the current non-injection battery cell, and calculates ΔM according to the formula ΔM = M0-Ma, and calculates the actual injection amount M according to the formula M = M0+kΔM (k = 0.5), and transmits the actual injection amount M to the controller 300, the controller 300 converts the actual injection amount M into the running parameters of the injection pump 200 (the rotation speed, flow and time of the injection pump 200), and sends the running parameters to the injection pump 200, the injection pump 200 runs according to the running parameters, and the electrolyte is poured into the buffer cup 500, and the buffer cup 500 pours the electrolyte into the air bag of the battery cell, completes the injection sealing and weighing, and obtains the weight M2 of the battery cell.

[0110] The host computer 400 obtains the weight M2 of the battery cell and calculates the injection amount M' of the battery cell, and then calculates the average injection amount Ma of the battery cell and the previous 7 injection battery cells, and then performs injection on the next battery cell.

[0111] Repeat the above steps to prepare 1000 battery cells. Among them, the target injection amount M0 is the set injection amount (Target); the average value Mean of the actual injection amount of the 1000 battery cells, the average value (average deviation ΔMean) between the actual injection amount and the target injection amount of the 1000 battery cells, and the mean square error Sigma of the actual injection amount of the 1000 battery cells are calculated 注 .

[0112] Examples 2 to 12 are only different from example 1 in that n or k is changed. In the comparative example 1, the actual injection amount of each battery cell is not adjusted during injection, and the injection is directly performed. The condition variables and test data of examples 1 to 12 and comparative example 1 are shown in table 1:

[0113] Table 1 injection data table of examples 1 to 12 and comparative example 1

[0114]

[0115] From the test results in table 1, it can be seen that:

[0116] Comparing the test results of Examples 1 to 12 and Comparative Example 1, it can be seen that by adjusting the actual liquid injection volume M of each cell in real time during continuous production using the liquid injection method of the present invention, the actual liquid injection volume M of each cell is made closer to the target liquid injection volume M0 compared to the average liquid injection volume Ma of the already liquid-injected cells. Therefore, the mean deviation ΔMean and the root mean square deviation Sigma of each embodiment are relatively small. 注 Both are superior to Comparative Example 1, achieving the effect of improving the consistency of injection volume.

[0117] Comparing the test results of Examples 1 to 6, it can be seen that values ​​of n from 4 to 32 are more effective. When n is 2, a sudden change in the electrolyte injection volume of a certain cell during production will significantly affect the actual electrolyte injection volume M of subsequent cells. Therefore, the mean deviation ΔMean and the root mean square deviation Sigma of the actual electrolyte injection volume of 1000 cells are also affected. 注 The amount of liquid injected is relatively large, and the consistency of the liquid injection volume is poor. When n is 64, a sudden change in the liquid injection volume of a certain cell during the production process has too little impact on the actual liquid injection volume M of subsequent cells, making it difficult to adjust the actual liquid injection volume M of subsequent cells in a timely manner. This results in a large deviation in the average actual liquid injection volume of 1000 cells and poor consistency of the liquid injection volume.

[0118] Comparing the test results of Examples 1 and 7 to 12, it can be seen that a value of k between 0.5 and 0.8 yields better results. When k is below 0.5, after a sudden change in the electrolyte injection volume of a certain cell during production, the adjustment of the actual electrolyte injection volume M of subsequent cells is not timely enough. Therefore, the root mean square error (Sigma) of the actual electrolyte injection volume of 1000 cells is high. 注 The standard deviation (σ) of the liquid injection volume is relatively large, resulting in poor consistency. When k is higher than 0.8, if the liquid injection volume of a certain cell changes abruptly during production, although the actual liquid injection volume M of the cell can be adjusted in time, the impact on the actual liquid injection volume M of subsequent cells is too large. Therefore, the standard deviation (σ) of the actual liquid injection volume of 1000 cells is high. 注 The volume is relatively large, and the consistency of the injection volume is poor.

[0119] Example 13

[0120] Based on Example 1, further processing is carried out on the liquid-filled battery cells:

[0121] S2, Compressed air bag: Clamping plates are set on both sides of the air bag, and a pressure of 20N is applied to the clamping plates for 2s; the contact area is S1, which is equal to 0.55S2.

[0122] S3. Standing: Place the battery cell in the 600 magazine and stand for 12 hours at a high temperature of 45°C to ensure that the electrolyte fully wets the bare battery cell.

[0123] S4, Formation: Charging and activating the battery cell;

[0124] S5, aging: the battery cell is placed in the clip 600 or the clamp, and is left for 8 hours at room temperature 25℃;

[0125] S6, exhaust and two-sealing: the aged battery cell is placed in a vacuum generating device, and the air bag of the battery cell is punctured; the vacuum degree of the vacuum generating device is controlled to be -60 Kpa and is kept for 1 second; then the vacuum degree of the vacuum generating device is controlled to be -90 Kpa and is kept for a second time 4 seconds, the gas in the battery cell is exhausted, and two-sealing is completed. Then, the weight is measured, and the liquid retention amount is calculated.

[0126] The above steps are repeated to prepare 1000 battery cells. Whether each battery cell is inflated is observed, and if inflated, the proportion of the inflated battery cells is calculated. The mean square deviation Sigma of the liquid retention amount of the 1000 battery cells is calculated. 保 .

[0127] Examples 14 to 19 differ from Example 13 only in that the vacuum degree and the keeping time of the vacuum extraction stage are changed; Examples 30 to 32 differ from Example 13 only in that the number of times, the vacuum degree and the keeping time of the vacuum extraction stage are changed; in Comparative Example 2, each battery cell is extracted once in the vacuum extraction stage, and is not segmented. The condition variables and the test data of Examples 13 to 32 and Comparative Example 2 are shown in Table 2:

[0128] Table 2: Vacuum extraction data table of Examples 13 to 22 and Comparative Example 2

[0129]

[0130]

[0131] From the test results in Table 2, it can be seen that:

[0132] From the test results of Examples 13 to 32 and Comparative Example 2, it can be seen that by segmenting the vacuum extraction, the amount of electrolyte entering the air bag with the gas can be reduced in the vacuum extraction process, so that the mean square deviation Sigma of each example 保 is better than that of Comparative Example 2, achieving the effect of improving the consistency of the liquid loss amount, and further improving the consistency of the liquid retention amount. And when the first threshold P1 is the same and the first keeping time is the same, increasing the number of vacuum extractions can further improve the Sigma 保 , but the improvement is limited, so it is more appropriate to divide the vacuum extraction into two or three stages, and further increasing the number of vacuum extractions has a limited improvement on Sigma 保 and is relatively high in cost.

[0133] From the test results of Comparative Example 15, Example 17 to Example 19, it can be seen that when the holding time of the two-stage vacuumizing is the same, changing the vacuum degree of the vacuumizing will cause the liquid loss of the battery cell to change, thus Sigma 保 There is a small change; specifically, reducing the vacuum degree is beneficial to reduce the amount of electrolyte entering the air bag with the gas, thus being able to improve the consistency of the liquid loss, and further improve the consistency of the liquid retention. However, as in Example 18, reducing the vacuum degree of the last stage of vacuumizing is easy to cause the gas residue to increase, thus the appearance of some battery cells has slight swelling / gas floating.

[0134] From the test results of Comparative Example 20 to Example 25, it can be seen that when T1 is long and T2&T3 is short (Example 25), the holding time of the battery cell in the low vacuum degree is relatively long, it is difficult to extract all the gas inside the battery cell, and the gas residue is more, thus the appearance of some battery cells has slight swelling / gas floating.

[0135] From the test results of Comparative Example 23, Example 26 to Example 32, it can be seen that when the holding time of each stage of vacuumizing is the same, reducing the vacuum degree is beneficial to reduce the amount of electrolyte entering the air bag with the gas, thus being able to improve the consistency of the liquid loss, and further improve the consistency of the liquid retention. However, as in Example 26, 29, 32, reducing the vacuum degree of the last stage of vacuumizing is easy to cause the gas residue to increase, thus the appearance of some battery cells has slight swelling / gas floating.

[0136] The above-described examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for injecting electrolyte into a battery cell, characterized in that, The injection method includes the following steps: Get the target electrolyte injection volume M0 of the battery cell and the average electrolyte injection volume Ma of the n electrolyte-injected battery cells before the current uninjected battery cell, where 4≤n≤32; Based on the average injection volume Ma and the target injection volume M0, the operating parameters of the injection pump (200) are adjusted to adjust the actual injection volume M of the injection pump (200); The injection pump (200) is started to inject electrolyte into the air bag of the unfilled battery cell and the air bag is sealed to obtain a semi-finished battery cell (800). The injection method further includes: After obtaining the average injection volume Ma, the difference ∆M between the target injection volume M0 and the average injection volume Ma is calculated. Adjust the actual injection volume M according to the formula M=M0+k∆M; Where k is an adjustment coefficient, 0.5≤k≤0.

8.

2. The injection method according to claim 1, characterized in that, The adjustment of the parameters of the injection pump (200) includes: In response to the average injection volume Ma being higher than the target injection volume M0, the speed or running time of the injection pump (200) is reduced; or, In response to the average injection volume Ma being lower than the target injection volume M0, the rotational speed or running time of the injection pump (200) is increased.

3. A liquid injection system, characterized in that, The injection system includes: A storage tank (100) for storing electrolyte; The injection pump (200) is connected to the storage tank (100) and is used to inject the electrolyte into the air bag of the unfilled battery cell (700); A controller (300) is communicatively connected to the injection pump (200). The host computer (400) stores a machine-executable program, which, when executed by the controller (300), is used to implement the injection method according to any one of claims 1 to 2.

4. A method for preparing a battery cell, characterized in that, Includes the following steps: Liquid injection is performed to obtain a semi-finished battery cell (800); the liquid injection is carried out in accordance with the liquid injection method according to any one of claims 1 to 2; The semi-finished battery cell (800) is formed, aged, and degassed to obtain the finished battery cell.

5. The preparation method according to claim 4, characterized in that, The exhaust step includes the following steps performed sequentially: The aged semi-finished battery cell (800) is placed in a vacuum generator and the air bag of the semi-finished battery cell (800) is punctured. The vacuum level of the vacuum generating device is controlled to a first threshold P1 and maintained for a first time T1; The vacuum level of the vacuum generating device is controlled to a second threshold P2 and maintained for a second time T2; wherein the second threshold P2 is greater than the first threshold P1; The air bag is sealed to obtain the finished battery cell.

6. The preparation method according to claim 5, characterized in that, The first threshold P1 is -60 kPa to -80 kPa; And / or, the second threshold P2 is -80 kPa to -90 kPa.

7. The preparation method according to claim 5, characterized in that, Also includes: After maintaining the second time, the vacuum level of the vacuum generating device is controlled to a third threshold P3 and maintained for a third time T3; wherein the third threshold P3 is greater than the second threshold P2.

8. The preparation method according to claim 7, characterized in that, T2+T3>T1.

9. The preparation method according to claim 7, characterized in that, The first threshold P1 is -40 kPa to -60 kPa; And / or, the second threshold P2 is -60 kPa to -80 kPa; And / or, the third threshold P3 is -80 kPa to -90 kPa.

10. The preparation method according to claim 7, characterized in that, The first time interval T1 is from 1 second to 4 seconds; And / or, the second time T2 is 1s to 3s; And / or, the third time T3 is 1s to 3s.

11. The preparation method according to claim 4, characterized in that, The formation process includes: charging and activating the semi-finished battery cell (800); And / or, the aging process includes: placing the charged semi-finished battery cell (800) in a magazine (600) and allowing it to stand.

12. The preparation method according to claim 11, characterized in that, Also includes: Before the formation, the air bag of the semi-finished battery cell (800) is squeezed, and then the semi-finished battery cell (800) is placed in the magazine (600) and left to stand.

13. The preparation method according to claim 12, characterized in that, The air bag for compressing the semi-finished battery cell (800) includes: Clamping plates are installed on both sides of the air bag, and pressure F is applied to the clamping plates for a holding time T4; Where F ranges from 10 N to 500 N, and T4 ranges from 0.2 s to 2 s.

14. The preparation method according to claim 13, characterized in that, The total contact area between the air bag and the clamps on both sides is S1, and S1 and the area S2 of the air bag satisfy: 0.5S2≤S1≤0.8S2.

15. The preparation method according to claim 12, characterized in that, The magazine includes a base plate (610) and side plates (620) disposed at both ends of the base plate (610), with the space between the two side plates (620) used to accommodate a plurality of the semi-finished battery cells (800). At least one of the side plates (620) has an elastic layer on the side closest to the other side plate (620); or, at least one side plate (620) is made of an elastic material. The step of placing the semi-finished battery cell in the magazine (600) and letting it stand includes: Multiple semi-finished battery cells are arranged along their thickness direction on the base plate (610) of the magazine (600) and located between the side plates (620); The side plate (620) cooperates to hold all the semi-finished battery cells in the clip (600), so that the elastic layer or the side plate (620) made of elastic material is pressed against the outermost surface of the semi-finished battery cells arranged on the outermost side. The magazine (600) holds the semi-finished battery cell (800) in a stationary clamp.

16. The preparation method according to claim 15, characterized in that, The elastic layer is made of an elastic material, such as foam or silicone pad.

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