CN117214112B - Online consistency monitoring method for battery baking pole piece based on laser moisture tester - Google Patents
Online consistency monitoring method for battery baking pole piece based on laser moisture tester Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 36
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- 238000001514 detection method Methods 0.000 claims abstract description 90
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 58
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 44
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 28
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims abstract description 12
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention provides a battery baking pole piece on-line consistency monitoring method based on a laser moisture tester, which comprises the steps of placing a battery cell into an oven, and performing primary vacuumizing operation on the oven; performing primary nitrogen filling operation on the oven; performing secondary vacuumizing operation on the oven; heating and baking the oven; performing secondary nitrogen filling operation on the oven; extracting a preset volume of gas to be detected in an oven, introducing the gas to be detected into a sample detection chamber, and monitoring a current moisture value by using a laser moisture tester for calculating to obtain the current water content of the battery cell; and carrying out compensation baking operation according to the current water content of the battery cell to obtain the baked battery cell. According to the method, the interference of more volatile substances with low boiling points is avoided, the monitoring accuracy is improved, the consistency of monitoring the moisture of each batch of battery cells is improved, the mixed batch PACK is combined, and the overall qualification rate of the battery is improved.
Description
Technical Field
The invention relates to the technical field of accurate monitoring of current moisture of pole piece baking, in particular to a method for monitoring the consistency of battery baked pole pieces on line based on a laser moisture tester.
Background
At present, the influence of moisture on the performance of a lithium ion battery is critical, the self-discharge of the lithium ion battery is higher due to the fact that the moisture content in the battery exceeds the standard, the circulation performance is poor, and even the explosion-proof valve of the battery is opened and scrapped due to the fact that excessive gas is produced due to the existence of the moisture. Therefore, the control of moisture is particularly important in the lithium ion battery production process, and in general, the lithium ion battery production process needs to be carried out in a low-humidity environment in a whole flow, and residual moisture in the battery needs to be removed as much as possible by vacuum high-temperature baking before battery injection. Meanwhile, the battery also needs to use a card type method to test the moisture content of the baked battery pole piece and the diaphragm before liquid injection.
However, the conventional card test method has several problems in testing the moisture content of the battery pole piece as follows:
1) The water content needs to be tested offline, and the production rhythm of a full-automatic production line is affected;
2) Destructive testing is carried out on the sample, full detection cannot be achieved, and the phenomenon of low monitoring accuracy exists;
3) Because of the difference of the moisture of the pole pieces of the battery cells in different batches, the consistency of the moisture among batches produced by the same baking process is poor, so that the grouping of the mixed batches of PACKs cannot be realized, and the overall qualification rate of the battery is affected;
4) The water separation line test needs manual operation, has the risk of measurement operation errors and inaccurate measurement, and reduces the accuracy rate of water monitoring;
5) The card moisture meter is complex in test and maintenance and long in maintenance time, so that the production cost is increased.
Aiming at the problems, a plurality of novel online testing methods are presented on the market, such as a method for detecting the water content of a lithium ion battery pole piece before liquid injection in China patent CN110797583A, but the pole piece to be monitored still needs to be destroyed, and the efficiency is still low.
And like the on-line moisture detection method in the vacuum drying process of the Chinese patent CN 113358824A-battery, the method can solve the problem that the pole piece to be monitored is not damaged, and can realize on-line monitoring. The vacuum degree and the time are adopted as standard parameters for comparison and analysis so as to deduce the monitoring result, but the method ignores that more volatile substances with low boiling point exist in the pole piece besides moisture, so that the vacuum degree is greatly influenced, and if the difference of the volatile substances such as organic solvents in each batch is large, the consistency monitoring influence is larger, so that the mixed batch PACK grouping cannot be realized, and the overall qualification rate of the battery is influenced.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides the online consistency monitoring method for the battery baking pole piece based on the laser moisture tester, which has higher monitoring efficiency, can avoid damage to the battery core to be monitored, and can reduce interference of non-moisture substances on the monitoring result to a certain extent.
The aim of the invention is realized by the following technical scheme:
a battery baking pole piece online consistency monitoring method based on a laser moisture tester comprises the following steps of
S110: placing the battery cell into an oven, performing primary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a first preset vacuum degree;
S120: performing primary nitrogen filling operation on the oven, and enabling the vacuum degree in the oven to be lower than a second preset vacuum degree;
S130: performing secondary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a third preset vacuum degree;
s140: heating and baking the oven, and enabling the oven to reach a preset baking temperature;
s150: performing secondary nitrogen filling operation on the oven;
s160: extracting a preset volume of gas to be detected in the oven, introducing the gas to be detected into a sample detection chamber, and monitoring a current moisture value by using a laser moisture tester for calculating to obtain the current water content of the battery cell;
S170: and carrying out compensation baking operation according to the current water content of the battery cell to obtain the baked battery cell.
In one embodiment, before step S110, the method further includes: and winding the positive plate, the negative plate and the diaphragm to obtain a winding core, and packaging or bagging the winding core to obtain the battery cell.
In one embodiment, the step of S170 further includes a step of S180: and (5) filling and packaging the baked battery cell to obtain the battery.
In one embodiment, the first preset vacuum degree is 0 Pa-100 Pa; and/or the number of the groups of groups,
The second preset vacuum degree is set according to the production process requirements; and/or the number of the groups of groups,
The third preset vacuum degree is 0 Pa-100 Pa.
In one embodiment, the preset baking temperature is set according to the production process requirements.
In one embodiment, the secondary nitrogen charging operation is a cyclic nitrogen charging operation.
In one embodiment, before the step S160 of monitoring the current moisture value by using the laser moisture tester, the method further includes a cooling operation for the gas to be detected.
In one embodiment, in the step S160, when the laser moisture tester is used for monitoring the current moisture value, the gas to be detected is in a constant temperature state.
In one embodiment, the sample detection chamber is in communication with an evacuated tube of the oven and the laser moisture tester is located within the sample detection chamber.
In one embodiment, the outer wall of the sample detection chamber is provided with a cooling insulation layer.
In one embodiment, the cooling insulation layer comprises a cooling surrounding pipe and an insulation layer, and the insulation layer is connected with the outer wall of the sample detection chamber through the cooling surrounding pipe.
Compared with the prior art, the invention has at least the following advantages:
1. according to the invention, the preset volume of gas to be detected is extracted from the oven, the gas to be detected is introduced into the sample detection chamber, the laser moisture tester is used for monitoring the current moisture value, so that the laser moisture tester can accurately detect the moisture content in the gas to be detected, the interference of more volatile substances with low boiling point is effectively avoided, then the compensation baking operation is performed according to the moisture content of the current battery cell, so that the accurate monitoring of the online current moisture of the battery cell electrode slice baking is realized, the moisture standard of the battery cell of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cell of each batch is improved, the grouping of the mixed batch PACK is realized, and the overall qualification rate of the battery is further improved.
2. When the laser moisture tester monitors the gas to be detected on line, the structure of the battery cell is not required to be damaged, comprehensive monitoring can be realized, and off-line moisture testing is not required, so that the production efficiency is improved; the laser moisture tester has high detection speed, does not need manual operation, and further improves the accuracy of monitoring; and the laser moisture tester basically does not need maintenance, thereby reducing the production cost.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of steps of a method for monitoring on-line consistency of battery baked pole pieces based on a laser moisture tester according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of on-line consistency monitoring of a battery baking pole piece based on a laser moisture tester according to an embodiment of the present invention;
Fig. 3 is a schematic structural diagram of a laser moisture tester according to an embodiment of the present invention.
Reference numerals: 10. a sample detection chamber; 100. the outer peripheral wall of the sample detection chamber; 200. an outer wall of the bottom of the sample detection chamber; 300. a laser moisture tester; 400. cooling the heat preservation layer; 410. cooling the surrounding tube; 411. a first cooling tube; 412. a second cooling tube; 413. a heat preservation layer; 500. a temperature sensor.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. The drawings illustrate preferred embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
The application provides a battery baking pole piece on-line consistency monitoring method based on a laser moisture tester, which comprises the following steps: placing the battery cell into an oven, performing primary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a first preset vacuum degree; performing primary nitrogen filling operation on the oven, and enabling the vacuum degree in the oven to be lower than a second preset vacuum degree; performing secondary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a third preset vacuum degree; ; heating and baking the oven, and enabling the oven to reach a preset baking temperature; performing secondary nitrogen filling operation on the oven; extracting a preset volume of gas to be detected in the oven, introducing the gas to be detected into a sample detection chamber, and monitoring a current moisture value by using a laser moisture tester for calculating to obtain the current water content of the battery cell; and carrying out compensation baking operation according to the current water content of the battery cell to obtain the baked battery cell.
According to the online consistency monitoring method for the battery baking pole piece based on the laser moisture tester, the preset volume of gas to be detected is extracted in the oven, the gas to be detected is introduced into the sample detection chamber, the laser moisture tester is used for monitoring the current moisture value, so that the laser moisture tester can accurately detect the moisture content in the gas to be detected, the interference of more low-boiling-point volatile substances is effectively avoided, then the compensation baking operation is carried out according to the moisture content of the current battery cell, the online current moisture of the battery cell pole piece baking is accurately monitored, the moisture standard of the battery cells of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cells of each batch is improved, the mixed batch PACK is realized, and the overall qualification rate of the battery is improved. Further, when the laser moisture tester monitors the gas to be detected on line, the structure of the battery core is not required to be damaged, comprehensive monitoring can be realized, and off-line moisture testing is not required, so that the production efficiency is improved; the laser moisture tester has high detection speed, does not need manual operation, and further improves the accuracy of monitoring; and the laser moisture tester basically does not need maintenance, thereby reducing the production cost.
In order to better understand the online consistency monitoring method of the battery baking pole piece based on the laser moisture tester, the online consistency monitoring method of the battery baking pole piece based on the laser moisture tester is further explained as follows:
Referring to fig. 1 and 2, an embodiment of a method for monitoring on-line consistency of battery baked pole pieces based on a laser moisture tester includes the following steps:
s110: the electric core is placed into the oven, the first vacuumizing operation is carried out on the oven, and the vacuum degree in the oven is lower than the first preset vacuum degree, so that moisture in air in the oven is extracted, the electric core is ensured to be in the vacuum condition for carrying out the baking operation, and the interference of the moisture in the air in the oven to the moisture monitoring of the electric core is effectively avoided.
In one embodiment, the first preset vacuum degree is 0 Pa-100 Pa, so that the vacuum degree in the oven is well ensured, the interference of moisture in the air in the oven is effectively avoided, the moisture in the battery cell is easier to occur, the moisture in the gas to be detected with the preset volume is extracted in the oven later to be the moisture of the battery cell, and the monitoring accuracy is ensured. Specifically, the first preset vacuum degree may be 0Pa, 10Pa, 50Pa, 100Pa, and a person skilled in the art may select the first preset vacuum degree to be adapted according to actual production needs.
In a preferred embodiment, the first preset vacuum degree is 10 Pa-50 Pa, so as to better ensure the vacuum degree in the oven, to more effectively avoid the interference of moisture in the air in the oven, and to effectively ensure the accuracy of the subsequent monitoring of the laser moisture tester while providing better vacuum conditions for the battery cell.
It is worth mentioning that when the electric core is in vacuum condition, the boiling point of water can be reduced, the water is easy to evaporate, the gas to be detected of the preset volume amount is easier to extract, and the phenomenon that the electric core is oxidized in the baking process can be avoided, so that the baking consistency of the electric core is ensured, the mixed PACK is better realized, and the overall qualification rate of the battery is improved
S120: and (3) performing primary nitrogen filling operation on the oven, and enabling the vacuum degree in the oven to be lower than a second preset vacuum degree so as to ensure that the filled nitrogen can be replaced with gas in the oven, so as to realize extraction of gas to be detected in the oven, and simultaneously ensure that the vacuum degree in the oven meets the production process requirements of baking the battery cell, so as to provide vacuum drying conditions for baking the battery cell, ensure that moisture in the battery cell can be quickly evaporated and is not easy to oxidize under the vacuum drying conditions, and ensure the baking quality of the battery cell.
In one embodiment, the second preset vacuum degree can be set according to the production process requirements of baking of the specific battery cells, so that the flexibility of the online consistency monitoring method of the battery baked pole pieces based on the laser moisture tester is improved.
In this embodiment, the second preset vacuum degree is 30kPa to 80kPa, so that better vacuum conditions can be provided for the battery cell, and meanwhile, the accuracy of monitoring by the subsequent laser moisture tester is effectively ensured
S130: the secondary vacuumizing operation is carried out on the oven, and the vacuum degree in the oven is lower than the third preset vacuum degree, so that moisture in air in the oven is extracted more comprehensively, the vacuum degree of the oven is well ensured, the interference of the moisture in the air in the oven on the monitoring of the moisture of the battery cell is well avoided, and the monitoring accuracy is further improved. Meanwhile, after the secondary vacuumizing operation of the oven is completed, the empty volume of the oven is calculated, defined as V 1,, and transmitted to a computer terminal.
In one embodiment, the third preset vacuum degree is 0Pa to 100Pa. Specifically, the third preset vacuum degree may be 0Pa, 10Pa, 50Pa, 100Pa, and a person skilled in the art may select an adapted third preset vacuum degree according to actual production needs.
S140: and heating and baking the oven, and enabling the oven to reach a preset baking temperature.
It can be understood that when the temperature rising and baking operation is performed on the oven, the moisture in the battery cell can be well evaporated, so that the moisture in the battery cell can be effectively removed, and the drying effect is achieved.
In one embodiment, the preset baking temperature is set according to the production process requirement, so that the moisture in the battery cell is removed more comprehensively, and a good drying effect on the battery cell is achieved. Specifically, the preset baking temperature is 80 ℃ to 150 ℃, for example, the preset baking temperature can be 80 ℃, 100 ℃, 105 ℃, 120 ℃, 125 ℃, 135 ℃ and 150 ℃, i.e. the person skilled in the art can select the adaptive third preset vacuum degree according to the actual production requirement.
S150: and performing secondary nitrogen filling operation on the oven. It can be appreciated that it is difficult to ensure that the moisture inside the cell has reached the production process requirements, since only the first nitrogen filling operation is performed. Therefore, in order to ensure the accuracy of monitoring the moisture of the battery cell, the invention also carries out secondary nitrogen filling operation on the oven so as to realize the accurate monitoring of the moisture of the battery cell during baking.
In one embodiment, the secondary nitrogen charging operation is a cyclic nitrogen charging operation. It can be understood that the secondary nitrogen filling operation is a circulating nitrogen filling operation, so that the circulating nitrogen filling operation can be better replaced with the gas in the oven continuously and circularly, and the online accurate monitoring of the moisture of the battery cell during baking can be better realized. Further, the number of times of the circulating nitrogen filling operation can be 2 times, 3 times or 4 times, and a person skilled in the art can select the number of times of the circulating nitrogen filling operation according to the actually produced battery cell so as to realize online accurate monitoring of the moisture of the battery cell.
S160: and extracting a preset volume of gas to be detected in the oven, introducing the gas to be detected into a sample detection chamber, and monitoring the current moisture value by using a laser moisture tester for calculating to obtain the current water content of the battery cell.
It can be understood that, because the electric core is in a vacuum drying environment, the boiling points of the organic solvent and the moisture in the pole piece of the electric core are reduced, and especially when the temperature rising and baking operation is performed on the oven, a plurality of low-boiling organic solvents and the moisture are more easily evaporated, if the traditional vacuum degree and the traditional time are used as standard parameters for comparison and analysis, the moisture value in the pole piece of the electric core cannot be accurately detected, so that the monitoring effect is poor, the consistency of the moisture value of each batch of electric core is poor, and the mixed batch PACK grouping cannot be realized, so that the overall qualification rate of the battery is affected.
Therefore, the method comprises the steps of extracting a preset volume of gas to be detected in an oven, introducing the gas to be detected into a sample detection chamber, monitoring the current moisture value by using a laser moisture tester to obtain the water content of the gas to be detected, defining H 1, transmitting H 1 to a computer end, calculating the water content in the empty volume of the oven by using a computer program, and finally calculating to obtain the water content of a battery cell, defining H 2 as the current water content of the battery cell. Specifically, the calculation formula of the computer program is H 2＝η*H1, wherein eta is a conversion coefficient, and eta is required to be subjected to fitting calibration by testing a certain number of H 1 and H 2.
The laser moisture tester adopts the wavelength modulation absorption spectrum technology to test the water content in the gas to be detected. The basic principle is lambert beer's law; the expression is as follows:
A=epsilon bc, wherein a is the absorption rate; epsilon is the molar absorptivity of the target sample gas, and b is the optical path; c is the concentration of the sample gas. There is a significant linearity between the concentration of moisture and the absorptivity of light, and the different substances have a strong selectivity for the absorption of light energy, usually yielding a maximum absorption only at their characteristic wavelength. The characteristic absorption wavelength of water molecules is 1.877um. When water molecules collide with a certain energy source with a certain wavelength, the water molecules vibrate, so that energy is absorbed, and the concentration of the water molecules can be determined by measuring the change of the energy. Therefore, the laser moisture tester has higher accuracy in detecting moisture, and can effectively improve the interference of low-boiling-point gas so as to better ensure the accuracy of monitoring.
Further, when the laser moisture tester monitors the gas to be detected on line, the structure of the battery core is not required to be damaged, comprehensive monitoring can be realized, and off-line moisture testing is not required, so that the production efficiency is improved; the laser moisture tester has high detection speed, does not need manual operation, and further improves the accuracy of monitoring; and the laser moisture tester basically does not need maintenance, thereby reducing the production cost.
In one embodiment, the gas flow pump is arranged in the gas inlet pipe of the sample detection chamber and is communicated with the vacuumizing pipe of the oven so as to ensure that the extracted preset volume of gas to be detected can enter the sample detection chamber, and the gas flow pump can calculate the extracted gas to be detected so as to ensure the accuracy of the extracted gas to be detected and the accuracy of subsequent monitoring.
In order to ensure that the laser moisture tester monitors the gas to be detected more accurately, in one embodiment, a high-precision balance is further arranged in the sample detection chamber, and the high-precision balance is arranged adjacent to an air inlet pipe of the sample detection chamber, so that the high-precision balance can accurately test the gas to be detected just coming in, the volume number of the gas to be detected actually entering the sample detection chamber is calculated, and the accuracy of the monitoring result of the laser moisture tester on the gas to be detected is improved.
S170: and carrying out compensation baking operation according to the current water content of the battery cell to obtain the baked battery cell.
It can be understood that, according to the comparison between the water content H 2 of the electric core calculated in step S160 and the water content H 0 preset in the process, if H 2<H0, the control program of the oven will execute the baking stopping operation on the electric core; otherwise, the baking operation is continued until H 2<H0 is reached, and the baking is stopped; for example, a compensation baking program can be added in an oven running program and is linked with a control system of a computer, so that the linkage operation of the oven, the computer and a laser moisture tester is realized, the accurate monitoring of the online current moisture of the battery cell baking pole piece is realized, the moisture standard of the battery cells of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cells of each batch is improved, the grouping of the mixed batch PACKs is realized, and the overall qualification rate of the battery is further improved.
Specifically, the preset water content H 0 of the process can be set according to the requirement of actually producing the battery cells, for example, H 0 can be set to H0≤500ppm、H0≤300ppm、H0≤250ppm、H0≤200ppm、H0≤100ppm、H0≤150ppm、H0≤50ppm or the like, so that the water content value of each batch of battery cells can be controlled within a quite narrow range, and the consistency of the water content of each batch of battery cells is improved.
According to the method, the preset volume of gas to be detected is extracted from the oven, the gas to be detected is introduced into the sample detection chamber, the laser moisture tester is used for monitoring the current moisture value, so that the laser moisture tester can accurately detect the moisture content in the gas to be detected, the interference of more volatile substances with low boiling point is effectively avoided, then the compensation baking operation is performed according to the moisture content of the current battery cell monitored by the laser moisture tester, the accurate monitoring of the on-line current moisture of the battery cell pole piece baking is realized, the moisture standard of the battery cells of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cells of each batch is improved, the mixed batch PACK is realized, and the overall qualification rate of the battery is improved.
Further, when the laser moisture tester monitors the gas to be detected on line, the structure of the battery core is not required to be damaged, comprehensive monitoring can be realized, and off-line moisture testing is not required, so that the production efficiency is improved; the laser moisture tester has high detection speed, does not need manual operation, and further improves the accuracy of monitoring; and the laser moisture tester basically does not need maintenance, thereby reducing the production cost.
In one embodiment, before step S110, the method further includes: and winding the positive plate, the negative plate and the diaphragm to obtain a winding core, and packaging or bagging the winding core to obtain the battery cell.
In one embodiment, before the step S160 of monitoring the current moisture value by using the laser moisture tester, the method further includes a cooling operation for the gas to be detected.
It can be understood that in practical application, the laser moisture tester is simply applied to online monitoring of the battery cell baking pole piece, and the high temperature of the gas to be detected entering the sample detection chamber easily causes the too fast speed of movement of water molecules in the gas to be detected so as to influence the accuracy of the laser moisture tester on moisture detection. Therefore, in the invention, the cooling operation is carried out on the gas to be detected, so that the movement speed of water molecules in the gas to be detected is ensured to be slower, the collision probability of the water molecules in the gas to be detected and the laser beam is improved, and the accuracy of the laser moisture tester for detecting the moisture in the gas to be detected is improved.
In one embodiment, in the step S160, when the laser moisture tester is used for monitoring the current moisture value, the gas to be detected is in a constant temperature state.
It can be understood that although the probability of collision between the water molecules in the gas to be detected and the laser beam can be improved through the cooling operation, the probability of collision between the water molecules in the gas to be detected and the laser beam is reduced because the speed of movement of the water molecules in the gas to be detected is high and low due to the fact that the temperature fluctuation of the gas to be detected is large, and the accuracy of detecting the water in the gas to be detected by the laser moisture tester is further affected. Therefore, in the invention, when the gas to be detected is in a constant temperature state, the constant and uniform movement speed of the water molecules in the gas to be detected can be ensured, so that the collision probability of the water molecules and the laser beam is improved, and the accuracy of the water detection result in the gas to be detected by the laser water content tester is further improved.
As shown in fig. 3, in one embodiment, the sample detection chamber further includes a temperature sensor 500, where a temperature probe of the temperature sensor 500 is located in the sample detection chamber to realize real-time monitoring of a temperature in the sample detection chamber, and if the temperature in the sample detection chamber reaches a constant set value, the cooling tube may stop delivering the cooling liquid, so as to better ensure that the sample detection chamber can be maintained in a relatively constant temperature state.
In one embodiment, the test conditions of the laser moisture tester: the pressure in the sample detection chamber is 0.8 Bar-1.5 Bar, and the temperature of the sample detection chamber is 20-40 ℃, so that the temperature in the sample detection chamber is relatively suitable, the constant and uniform movement speed of water molecules of the gas to be detected entering the sample detection chamber is better ensured, and the accuracy of the laser moisture tester for detecting the moisture in the gas to be detected is better improved.
In one embodiment, the sample detection chamber is communicated with the vacuumizing tube of the oven, so that the gas to be detected in the oven can enter the sample detection chamber, and the laser moisture tester is positioned in the sample detection chamber, so that the laser moisture tester can detect water molecules in the gas to be detected. Specifically, the evacuation tube may communicate with the sample detection chamber through a three-way valve.
As shown in fig. 3, in one embodiment, the outer wall of the sample detection chamber 10 is provided with a cooling insulation 400. It can be appreciated that the cooling insulation layer 400 additionally arranged can rapidly cool the gas to be detected entering the sample detection chamber 10, so as to improve the probability of collision between water molecules in the gas to be detected and laser beams, and meanwhile, the cooling insulation layer 400 can also ensure that the sample detection chamber 10 can be maintained in a constant temperature state, so that the constant and uniform speed of movement of the water molecules in the gas to be detected is ensured, and further, the accuracy of detecting the moisture in the gas to be detected by the laser moisture tester 300 is better improved.
In one embodiment, the cooling and insulating layer 400 includes a cooling surrounding pipe 410 and an insulating layer 413, and the insulating layer 413 is connected to the outer wall of the sample detection chamber 10 through the cooling surrounding pipe 410, so as to ensure that the cooling surrounding pipe 410 can rapidly cool the gas to be detected in the sample detection chamber 10, so as to better adapt to monitoring of the online continuous production of the battery baking pole piece. Specifically, the heat insulating layer 413 may be an asbestos layer to achieve a heat insulating effect. Of course, the specific material of the insulating layer 413 is not limited, and those skilled in the art can select and use according to actual requirements.
In one embodiment, the sample detection chamber 10 is a high thermal conductivity sample detection chamber 10 to ensure that the cooling surrounding tube 410 can rapidly transfer cold gas into the sample detection chamber 10 to achieve rapid cooling of the gas to be detected in the sample detection chamber 10. Specifically, the high thermal conductivity sample detection chamber 10 may be a copper alloy sample detection chamber 10. Of course, the high thermal conductivity sample detection chamber 10 is not limited to the copper alloy material, and may be other materials capable of realizing high thermal conductivity.
It should be noted that, if the temperature of the gas to be detected in the sample detection chamber 10 is not uniform, the probability of collision between the water molecules in the gas to be detected and the laser beam is reduced, so that the detection result of the laser moisture tester 300 is inaccurate. Therefore, in the present invention, the cooling surrounding pipe 410 includes a plurality of first cooling pipes 411 and a plurality of second cooling pipes 412, each of the first cooling pipes 411 is uniformly distributed on the outer wall 200 of the bottom of the sample detection chamber, and each of the second cooling pipes 412 is uniformly distributed on the outer peripheral wall 100 of the sample detection chamber; so as to ensure that the first cooling pipes 411 and the second cooling pipes 412 can rapidly and uniformly cool the gas to be detected in the sample detection chamber 10, so as to better adapt to the monitoring of the online continuous production of the battery baking pole pieces, and ensure that the moisture value of each batch of cells produced online continuously can be controlled in a quite narrow range, thereby improving the consistency of the moisture of each batch of cells.
It should be noted that, in order to make the gas to be detected reach quick and even cooling in the sample room, generally all be provided with the cooling tube at the periphery wall, bottom and the top of sample detection room to realize treating the gas to be detected and cooling down fast and evenly better, but the cooling tube adopts above-mentioned way then can bring another new problem: the phenomenon that part of water molecules in the gas to be detected are condensed on the inner wall of the sample detection chamber 10 affects the accuracy of the detection result of the laser moisture tester 300. Therefore, in the invention, the plurality of first cooling pipes 411 are uniformly arranged on the outer wall 200 at the bottom of the sample detection chamber, the plurality of second cooling pipes 412 are uniformly arranged on the outer peripheral wall 100 of the sample detection chamber, so that the phenomenon that water molecules in the entering gas to be detected are condensed on the inner wall of the sample detection chamber 10 can be effectively avoided, the phenomenon that water molecules in the gas to be detected enter the sample detection chamber 10 are condensed on the inner wall of the sample detection chamber 10 can be effectively avoided under the condition of realizing rapid and uniform cooling, the accuracy of the detection result of the laser moisture tester 300 is improved, more accurate calculation basis is provided for subsequent calculation, the accurate monitoring of the current moisture of the baking of the battery cell pole pieces is realized, the moisture standard of the battery cells of each batch is better ensured to be at the same level, the consistency of the moisture monitoring of the battery cells of each batch is improved, the group of the mixed batch PACKs is realized, and the overall qualification rate of the battery is further improved.
The working principle of the method is as follows: firstly, performing primary vacuumizing operation on the oven to remove moisture in air in the oven so as to ensure the accuracy of a monitoring result; secondly, performing primary nitrogen filling operation on the oven to ensure that the vacuum degree in the oven meets the production process requirements of electric core baking, and extracting gas to be detected in the oven; secondly, performing secondary vacuumizing operation on the oven to more comprehensively extract moisture in the air in the oven so as to prevent the moisture in the air in the oven from interfering with the monitoring of the moisture of the battery cell, and further improving the monitoring accuracy; at this point, the empty volume of the oven, defined as V 1, is calculated for subsequent calculation; Then, heating and baking the oven to evaporate the moisture in the battery core so as to facilitate the subsequent extraction and replacement; then, performing secondary nitrogen filling operation on the oven to provide a continuous vacuum drying environment for the battery cell so as to ensure that the moisture in the battery cell meets the production process requirement; next, extracting a preset volume of gas to be detected in the oven, specifically, because the vacuumizing tube of the oven is communicated, the vacuumizing tube is communicated with the air inlet pipe of the sample detection chamber, so that the extracted preset volume of gas to be detected can enter the sample detection chamber, and the laser moisture tester can detect the gas; Because the sample detection chamber is provided with the cooling heat preservation layer, the gas to be detected entering the sample detection chamber can be rapidly cooled and kept in a constant temperature state, so that the laser moisture tester can accurately detect the moisture of the gas to be detected to obtain the moisture content of the gas to be detected, which is defined as H 1, then H 1 is transmitted to a computer end, the moisture content in the vacant volume of the oven is calculated through a computer program, finally, calculating to obtain the water content of the battery cell, and defining the water content as H 2; finally, comparing the water content H 2 of the battery cell with the preset water content H 0, and stopping baking the battery cell if the water content H 2<H0 is the same; and otherwise, performing compensation baking operation until H 2<H0 is reached, so that the accurate monitoring of the online current moisture of the battery cell baking pole piece is realized, the moisture standard of the battery cells of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cells of each batch is improved, the grouping of the PACK of mixed batches is realized, and the overall qualification rate of the battery is improved.
Compared with the prior art, the invention has at least the following advantages:
1. according to the invention, the preset volume of gas to be detected is extracted from the oven, the gas to be detected is introduced into the sample detection chamber, the laser moisture tester is used for monitoring the current moisture value, so that the laser moisture tester can accurately detect the moisture content in the gas to be detected, the interference of more volatile substances with low boiling point is effectively avoided, then the compensation baking operation is performed according to the moisture content of the current battery cell, so that the accurate monitoring of the online current moisture of the battery cell electrode slice baking is realized, the moisture standard of the battery cell of each batch is ensured to be at the same level, the consistency of the moisture monitoring of the battery cell of each batch is improved, the grouping of the mixed batch PACK is realized, and the overall qualification rate of the battery is further improved.
2. When the laser moisture tester monitors the gas to be detected on line, the structure of the battery cell is not required to be damaged, comprehensive monitoring can be realized, and off-line moisture testing is not required, so that the production efficiency is improved; the laser moisture tester has high detection speed, does not need manual operation, and further improves the accuracy of monitoring; and the laser moisture tester basically does not need maintenance, thereby reducing the production cost.
The examples are listed below, but it should be noted that the examples below are not exhaustive of all possible cases and that the materials used in the examples below are commercially available unless otherwise specified.
Example 1
Placing batch of electric cores into an oven, performing primary vacuumizing operation (the vacuum degree is 50 Pa) on the oven, performing primary nitrogen filling operation (the vacuum degree is 80 kPa) on the oven, and performing secondary vacuumizing operation (the vacuum degree is 80 Pa) on the oven; next, the oven is subjected to a heating baking operation to reach a preset baking temperature (105 ℃); performing secondary nitrogen filling operation (the vacuum degree is 80 kPa) on the oven so as to meet the production requirement of the battery cell process; the vacuumizing tube is used for extracting a preset volume of gas to be detected in the oven, introducing the gas to be detected into the sample detection chamber, and monitoring the current moisture value by adopting the laser moisture tester for calculating to obtain the current water content of the battery cell; then, performing compensation baking operation according to the current water content of the battery cell to obtain a baked battery cell; and obtaining the batch of battery cells. Wherein, the moisture standard value is set to 250ppm.
Comparative example 1
And (3) performing an online moisture detection method of the batch battery cells by adopting a detection method in CN113358824A, and setting a moisture standard value to be 400ppm to obtain the batch battery cells.
The test of moisture of the positive and negative electrode plates before baking and the positive and negative electrode plates after baking was performed on the different batches of cells (designated A, B, C, D, E, F) in example 1, respectively, wherein the test results were average values of 20 cells sampled in each batch, to obtain the test data of table 1 below:
TABLE 1
The test of moisture of the positive and negative electrode plates before baking and the positive and negative electrode plates after baking was performed on the different batches of cells (designated A, B, C, D, E, F) in comparative example 1, respectively, wherein the test result is an average value of 20 cells sampled in each batch, so as to obtain the test data of the following table 2:
TABLE 2
As can be seen from the range of the different batches in tables 1 and 2, the range of the different batches in example 1 is smaller than that in comparative example 1, and the consistency of the cells in the different batches is good, so that the PACK grouping of mixed batches is realized, and the overall qualification rate of the battery is improved.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (5)
1. The method for monitoring the on-line consistency of the battery baking pole piece based on the laser moisture tester is characterized by comprising the following steps:
S110: placing the battery cell into an oven, performing primary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a first preset vacuum degree;
S120: performing primary nitrogen filling operation on the oven, and enabling the vacuum degree in the oven to be lower than a second preset vacuum degree;
S130: performing secondary vacuumizing operation on the oven, and enabling the vacuum degree in the oven to be lower than a third preset vacuum degree;
s140: heating and baking the oven, and enabling the oven to reach a preset baking temperature;
s150: performing secondary nitrogen filling operation on the oven;
S160: extracting a preset volume of gas to be detected in the oven, introducing the gas to be detected into a sample detection chamber, and cooling the gas to be detected; monitoring the current moisture value by using a laser moisture tester, and calculating to obtain the current water content of the battery cell; the laser moisture tester adopts a wavelength modulation absorption spectrum technology to test the water content in the gas to be detected, and the gas to be detected is in a constant-temperature state; and the characteristic absorption wavelength of the water molecules is 1.877um; test conditions of the laser moisture tester: the pressure in the sample detection chamber is 0.8Bar to 1.5bar, and the temperature of the sample detection chamber is 20 ℃ to 40 ℃;
The sample detection chamber is communicated with the vacuumizing tube of the oven, and the laser moisture tester is positioned in the sample detection chamber; the outer wall of the sample detection chamber is provided with a cooling heat-insulating layer; the cooling heat preservation layer comprises a cooling surrounding pipe and a heat preservation layer, and the heat preservation layer is connected with the outer wall of the sample detection chamber through the cooling surrounding pipe; the cooling surrounding pipes comprise a plurality of first cooling pipes and a plurality of second cooling pipes, the first cooling pipes are uniformly distributed on the outer wall of the bottom of the sample detection chamber, and the second cooling pipes are uniformly distributed on the outer peripheral wall of the sample detection chamber;
the sample detection chamber is a copper alloy sample detection chamber;
the sample detection chamber also comprises a temperature sensor, and a temperature probe of the temperature sensor is positioned in the sample detection chamber;
S170: and carrying out compensation baking operation according to the current water content of the battery cell to obtain the baked battery cell.
2. The method for monitoring the on-line consistency of battery baking pole pieces based on the laser moisture tester according to claim 1, further comprising, before step S110: and winding the positive plate, the negative plate and the diaphragm to obtain a winding core, and packaging or bagging the winding core to obtain the battery cell.
3. The method for monitoring the on-line consistency of the battery baking pole piece based on the laser moisture tester according to claim 1, wherein the first preset vacuum degree is 0 Pa-100 Pa; and/or the number of the groups of groups,
The second preset vacuum degree is set according to the production process requirements; and/or the number of the groups of groups,
The third preset vacuum degree is 0 Pa-100 Pa.
4. The method for monitoring the on-line consistency of the battery baking pole piece based on the laser moisture tester according to claim 1, wherein the preset baking temperature is set according to the production process requirement.
5. The method for monitoring the on-line consistency of battery baking pole pieces based on the laser moisture tester according to claim 1, wherein the secondary nitrogen filling operation is a circulating nitrogen filling operation.
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| CN113358824A (en) * | 2021-06-02 | 2021-09-07 | 合肥国轩高科动力能源有限公司 | Online moisture detection method in vacuum drying process of battery |
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| CN113358824A (en) * | 2021-06-02 | 2021-09-07 | 合肥国轩高科动力能源有限公司 | Online moisture detection method in vacuum drying process of battery |
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