Battery negative pressure formation method and device

Abstract

The invention relates to the technical field of batteries, and provides a battery negative pressure formation method which comprises the following steps: S1, sequentially communicating a battery to be formed, a trace gas measuring device and a negative pressure source by adopting a pipeline, S2, charging the battery, enabling the battery to generate gas, starting the negative pressure source and enabling the gas generated by the battery to be sucked into the pipeline, and S3, starting the negative pressure source. The trace gas measuring device measures the gas production rate and the gas production rate of gas passing through the trace gas measuring device, S4, according to the gas production rate and the gas production rate measured by the trace gas measuring device and in combination with the negative pressure of the negative pressure source, the negative pressure pumping time is calculated, and S5, the working duration of the negative pressure source is set according to the pumping time. The invention further provides a battery negative pressure formation device. According to the invention, the trace gas measuring device is introduced into the battery negative pressure formation process, and the trace gas measuring device is adopted to obtain the gas volume of the gas released by the battery, so that the gas extraction time of the battery negative pressure formation can be calculated, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a negative pressure formation method and device for batteries. Background Art

[0002] Battery formation refers to the first charging process of the battery after the battery is filled with liquid. This process can activate the active substances in the battery and activate the battery. During the formation process, a solid electrolyte interface (SEI) film can be generated on the negative electrode side of the battery, which can prevent further side reactions.

[0003] Today's lithium battery formation process is generally carried out in a high temperature, low dew point environment. During the formation process, as the chemical reaction inside the battery proceeds, a certain amount of gas will be produced. If the gas cannot be discharged in time, the accumulation of gas will cause the battery shell to swell, the formation to be poor, or even scrapped, posing a great potential risk.

[0004] The existing process has the following problems:

[0005] (1) At present, the negative pressure source and the pipeline arranged between the negative pressure source and the battery injection hole are mainly used to directly evacuate the battery to eliminate the gas produced inside the battery. The negative pressure remains constant during the entire negative pressure formation process. In addition, in the existing battery negative pressure formation operation, most of the negative pressure evacuation time is estimated based on experience. In order to ensure that the gas can be completely evacuated, a longer negative pressure evacuation time is set, which is usually longer than the actual evacuation time. At the same time, the battery formation gas production rate is not a constant process, which leads to low negative pressure formation efficiency and prolonged process time. If the formation gas production can be accurately measured, it will help optimize the formation process, reduce the formation cycle, and improve production efficiency. However, due to the black box characteristics of the battery, its gas production in the formation stage cannot be accurately predicted. At present, it can only be set based on experience. Longer negative pressure evacuation time, which will also lead to a longer negative pressure evacuation process time, prolonging the process time and reducing production efficiency.

[0006] (2) When the negative pressure is drawn, the electrolyte may be drawn out, causing the electrolyte to be dispersed in the pipeline and enter the vacuum source, thereby causing electrolyte loss and increasing production costs. In addition, the electrolyte dispersed in the pipeline is prone to crystallization and block the exhaust pipeline, or even damage the negative pressure source equipment. At present, a gas-liquid separation device is generally used to filter the extracted electrolyte, but this method cannot prevent the electrolyte from being drawn out.

[0007] (3) In addition, the entire system works under negative pressure conditions. In actual operation, gas leakage in the negative pressure system due to poor sealing of pipes and joints is difficult to avoid. However, accurate and quantitative detection of the gas leakage in the system can ensure accurate measurement of the gas production. The prior art generally uses a negative pressure gauge to monitor the negative pressure in the system, but the negative pressure gauge can only qualitatively monitor whether there is a gas leak in the system based on the pressure change, and cannot accurately detect the gas leakage. Therefore, it is impossible to accurately measure the gas production. Summary of the invention

[0008] The object of the present invention is to provide a battery negative pressure formation method and device, which can at least solve some of the defects in the prior art.

[0009] To achieve the above object, the embodiment of the present invention provides the following technical solution: a battery negative pressure formation method, comprising the following steps:

[0010] S1, use pipelines to connect the battery to be formed, the trace gas measuring device and the negative pressure source in sequence,

[0011] S2, charging the battery, the battery generates gas, starting the negative pressure source, and the negative pressure source sucks the gas generated by the battery into the pipeline,

[0012] S3, the trace gas measuring device measures the amount of gas passing through it,

[0013] S4, calculating the negative pressure pumping time according to the gas volume measured by the trace gas measuring device and the negative pressure of the negative pressure source,

[0014] S5, setting the working time of the negative pressure source according to the air extraction time.

[0015] Furthermore, the trace gas measuring device obtains the dynamic gas production of the battery and outputs an instantaneous flow rate according to the gas production dynamics, and the instantaneous flow rate displays the peak and valley values ​​of the gas production rate of the battery.

[0016] Furthermore, a control system is used to receive and analyze the instantaneous flow rate, and control the negative pressure source to adjust the negative pressure in real time.

[0017] Furthermore, when the pipeline leaks, the trace gas measuring device and the negative pressure source are used to measure the leakage flow.

[0018] Furthermore, a first valve is provided on the pipeline between the battery and the trace gas measuring device. The first valve is closed and the negative pressure source is turned on. There is a pressure difference between the air inlet and the air outlet of the trace gas measuring device, and the trace gas measuring device can measure the leakage gas flow.

[0019] Furthermore, a liquid conductivity sensor is arranged at the pipeline near the battery, and the liquid conductivity sensor is used to monitor whether the electrolyte in the battery is extracted.

[0020] Furthermore, when a control system is used, when the liquid conductivity sensor detects that the conductivity is higher than a threshold value, a signal is fed back to the control system, and the control system controls the negative pressure source to adjust the negative pressure in real time.

[0021] Further, the priority of the control system controlling the negative pressure source according to the liquid conductivity sensor is greater than the priority of the control system controlling the negative pressure source according to the instantaneous flow rate.

[0022] Furthermore, the trace gas measuring device uses a bubble method to measure tiny gas flow rates.

[0023] An embodiment of the present invention provides another technical solution: a battery negative pressure formation device, comprising a negative pressure source and a trace gas measuring device, wherein the air inlet end of the trace gas measuring device is connected to the battery to be formed through a pipeline, and the air outlet end of the trace gas measuring device is connected to the negative pressure source through a pipeline.

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

[0025] 1. Introduce a trace gas measuring device into the battery negative pressure formation process. The trace gas measuring device can be used to obtain the amount of gas released by the battery formation in real time, and the gas extraction time of the battery negative pressure formation can be calculated, thereby improving production efficiency.

[0026] 2. According to the real-time gas production rate, the control system can dynamically adjust the negative pressure in real time. When the gas production rate is in a slower stage, the control system will increase the negative pressure, so that the negative pressure source can continue to maintain the optimal negative pressure during the entire pumping process, thereby shortening the process time and improving production efficiency. At the same time, it can also keep the pressure within the upper and lower limit thresholds allowed by the process, reducing the probability of electrolyte being accidentally sucked out.

[0027] 3. The trace gas measuring device measures the volume of gas flowing through the system based on the pressure difference between the air inlet and the air outlet. By combining the trace gas measuring device with a negative pressure source, the system leakage and leakage rate can be accurately measured. This value can be used as a leakage background value to improve the accuracy of the gas volume of the battery output gas measured by the trace gas measuring device.

[0028] 4. The liquid conductivity sensor can be used to measure the electrolyte that is accidentally sucked out. If combined with the control system, the negative pressure can be automatically adjusted in real time, thereby reducing the negative pressure pumping rate, ensuring that the electrolyte will not be pumped away, and avoiding the problem of electrolyte crystallization in the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a negative pressure formation device for a battery provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of a trace gas measuring device for a battery negative pressure formation device provided by an embodiment of the present invention;

[0031] Figure 3 A schematic side view of a trace gas measuring device for a negative pressure formation device for a battery provided by an embodiment of the present invention;

[0032] Figure 4 A schematic diagram of the cumulative flow rate of gas produced during the formation process of a negative pressure formation device for a battery provided by an embodiment of the present invention;

[0033] Figure 5 A schematic diagram of the instantaneous flow rate of gas produced during the formation process of a battery negative pressure formation device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] See also Figure 1 , an embodiment of the present invention provides a battery negative pressure formation device, specifically, the device includes a negative pressure source and a trace gas measuring device, the air inlet end of the trace gas measuring device is connected to the battery to be formed through a pipeline, and the air outlet end of the trace gas measuring device is connected to the negative pressure source through a pipeline. The existing data of gas production and pumping time are statistically analyzed, and the calculation model of gas production and pumping time is obtained through software analysis. The trace gas measuring device is introduced into the battery negative pressure formation process, and the real-time gas production released by the battery measured by the trace gas measuring device can be used to calculate and predict the pumping time of the battery negative pressure formation according to the calculation model of gas production and pumping time. At the same time, the control system can adjust the negative pressure of the negative pressure source in real time according to the real-time gas production of the battery, thereby improving production efficiency. This embodiment cleverly uses a trace gas measuring device to measure the gas volume, so that the specific pumping time can be calculated, and then the working time of the negative pressure source can be set according to the pumping time, so that the pumping time of the batch of batteries to be formed can be set.

[0036] See also Figure 1 , Figure 4 and Figure 5The trace gas measuring device obtains the dynamic gas production of the battery, which is the cumulative flow rate, and outputs the instantaneous gas production flow curve according to the dynamic gas production. The instantaneous gas production flow curve shows the changing trend of the gas production rate of the battery. The amount of gas produced during the formation process of the battery is not constant, and the gas production will change in different process stages.

[0037] See also Figure 1 , Figure 2 and Figure 3 The trace gas measuring device uses a bubble method to measure the flow of tiny gases. The trace gas measuring device measures the volume flow of the gas flowing through the gas based on the pressure difference between the gas inlet and the gas outlet. The bubble method can accurately measure the gas production volume of the battery. Preferably, the trace gas measuring device includes a V-shaped tube ( Figure 2), the tube body includes a first section 1, a second section 2 and a third section 3 connected to the first section 1, the third section 3 is arranged vertically, the connection between the first section 1 and the second section 2 is a gas production port, and the second section 2 is arranged vertically. The angle between the first section 1 and the second section 2 is controlled to be between 25° and 75°, which can ensure that the liquid medium in the first section 1 can be smoothly pressed to the second section 2 due to the intake pressure and form bubbles at the gas production port. If the angle is too large, the flow resistance of the liquid medium is too large, resulting in uneven flow rate, which in turn leads to uneven rate and size of bubble generation. If the angle is too small, it is difficult for the generated bubbles to cross the gas production port and enter the second section 2, which will also lead to inaccurate measurement. An imaging sensor 4 is used to calculate the size and volume of the bubble. The fixed range of the sensor and the gas production port on the vertical surface is between -5 and +5 mm, so that the volume of the bubble can be better controlled and the measurement accuracy can be improved. The sensor is fixed on the vertical surface near the gas production port. The transmission signal of the sensor needs to be calibrated and adjusted by the software algorithm according to the shape and position of the gas production port to ensure accurate detection of bubbles and sizes, and the range should be between -5 and +5 mm. The third section 3 has an air inlet end, which is designed as a vertical air inlet end 30 to facilitate the entry of gas into the present trace gas measurement device. Preferably, the second section 2 has an air outlet end 20 connected to a negative pressure source; the intersection of the two geometric bodies of the first section 1 and the second section 2 at the upper end is a gas production port, and the shape of the gas production port is one of linear, serrated, hyperbolic, and parabolic. The shape of the gas production port will affect the size of the bubble formed. The flowing gas enters the tube body from the air inlet end 30, and the liquid at the air inlet end 30 is pressed to the air outlet end 20; due to the low gas flow rate, the liquid column pressure generated by the increase in the liquid level at the air outlet end 20 is greater than the pressure generated by the flowing gas entering the tube body, thereby causing the gas to be squeezed into the liquid; when the gas enters the liquid through the gas production port, a local low-pressure area is formed, causing the surrounding liquid to move toward the low-pressure area, forming a flow vortex, which causes the gas-liquid interface film to swell, and when it accumulates to a certain volume (usually more than a hemisphere), the opening closes under the action of surface tension, thereby forming a bubble. The size of the bubble is affected by the angle design between the first section 1 and the second section 2 and the shape design of the gas outlet. Under the conditions that the angle between the first section 1 and the second section 2 is fixed and the shape of the gas outlet is fixed, the size of the generated bubble is also constant. The bubble enters the second section 2 from the gas outlet and moves upward until the liquid surface breaks. When the bubble is formed at the gas outlet, the bubble can be measured by sensor 4. Sensor 4 can be an imaging sensor, which calculates the volume by the size of the bubble. Sensor 4 can also be an optical, ultrasonic, electromagnetic or other sensor, which accumulates the volume by measuring the number of bubbles and further obtains the instantaneous flow rate. An optical sensor is preferably used.

[0038] See also Figure 1, a control system is used to receive and analyze the instantaneous flow rate of gas production, and the control system can adjust the negative pressure of the negative pressure source in real time according to the instantaneous flow rate. After the instantaneous flow rate is obtained, since the instantaneous flow rate is also real-time, the automatic dynamic adjustment of the negative pressure formation of the battery can be realized by cooperating with the control system, and the negative pressure will no longer be a fixed value, and can be adjusted in real time. When the gas production of batteries in the same batch varies greatly, the formation efficiency is always kept at the highest state. For example, when the gas production rate is in a faster stage, the negative pressure is too high, and the control system will reduce the negative pressure. The negative pressure can be adjusted to reduce the negative pressure, and the electrolyte can be prevented from being extracted and lost too much; when the gas production rate gradually slows down, the negative pressure can be appropriately increased to accelerate the gas extraction process, so that the negative pressure source continues to maintain the optimal negative pressure during the entire gas extraction process, thereby shortening the process time and improving production efficiency. Negative pressure formation is a common formation process. The gas pressure inside the battery is adjusted by a negative pressure source. The gas generated during the formation of the battery is extracted from the liquid injection port of the battery through a negative pressure vacuum system. The gas generated during the formation process can be discharged in time to ensure the stability and consistency of the SEI film, and also accelerate the infiltration effect of the electrolyte. At present, the process time is relatively long, ranging from a few hours to more than ten hours depending on the size and capacity of the battery. Because the gas production of the battery can generally only be calculated based on the empirical data of the previous laboratory stage, there are still differences from the actual production process. In order to ensure that the expected effect of fully exhausting the gas production is achieved, the process time is generally designed to be longer. After real-time monitoring of the gas production of the battery during the negative pressure formation process, the negative pressure of the exhaust can be dynamically adjusted to effectively optimize the negative pressure formation time and improve production efficiency.

[0039] See also Figure 1 When the pipeline leaks, the trace gas measuring device and the negative pressure source can be used to measure the leakage flow. In the prior art, a negative pressure gauge is generally connected in the pipeline to evaluate the pipeline leakage through the pressure drop over a certain period of time. However, this method cannot accurately know the amount of pipeline leakage, which will cause the leaked gas to be included in the gas production when measuring the gas production, resulting in inaccurate data. By using a trace gas measuring device and a negative pressure source, the leakage flow can be accurately measured, which can be used as a leakage background value to improve the accuracy of the gas volume of the battery output gas measured by the trace gas measuring device.

[0040] See also Figure 1 , a first valve a is provided on the pipeline between the battery and the trace gas measuring device A, the first valve a is closed, and the negative pressure source B is turned on. There is a pressure difference between the air inlet and the air outlet of the trace gas measuring device A, and the trace gas measuring device A can measure the leakage gas flow. After starting the negative pressure source B, a uniform negative pressure is formed in the entire pipeline, and the negative pressure is preferably between -20 and -100 kPa. Figure 1, the left side of the negative pressure source B is the first negative pressure port c1, which provides negative pressure for the air inlet of the trace gas measuring device A, and the right side of the negative pressure source B is the second negative pressure port c2, which provides negative pressure for the air outlet of the trace gas measuring device A. At this time, the first valve a is closed. When there is a leak in the pipeline, it will cause a pressure difference between the air inlet and the air outlet of the trace gas measuring device A. The pressure difference can produce bubbles in the trace gas measuring device A, and the trace gas measuring device A can measure the leaked gas flow, thereby obtaining the leakage background value. Preferably, it also includes a three-way and a second valve b, wherein the three ports of the three-way are respectively connected to the air inlet of the first valve a, the second valve b and the trace gas measuring device A, open the first valve a, close the second valve b, and charge and discharge control of the battery. Specifically, when the pipeline system is leaked, it is necessary to close the first valve a and open the second valve b. After the battery is connected for the formation process, it is necessary to open the first valve a and close the second valve b. At this time, the battery starts to produce gas, resulting in a high pressure at the inlet end of the trace gas measuring device A, and a pressure difference between the inlet end and the outlet end of the trace gas measuring device A. The trace gas measuring device A can measure the gas flow rate passing through, deduct the leakage background value, and obtain the gas production during the formation process of the battery under negative pressure conditions. Preferably, the first valve a can be set at a position close to the battery in the pipeline, or it can be directly connected to the battery to avoid failure to detect when a leak occurs in the pipeline between the battery and the first valve a.

[0041] See also Figure 1 , a liquid conductivity sensor is arranged near the battery in the pipeline, and the liquid conductivity sensor monitors whether the electrolyte in the battery is extracted. Preferably, when a control system is adopted, when the liquid conductivity sensor detects that the conductivity is higher than the set threshold value, that is, electrolyte flows out, a signal is fed back to the control system, and the control system controls the negative pressure source B to adjust the negative pressure in real time. When the negative pressure is too high and electrolyte leaks from the battery, since the electrolyte is a high-conductivity liquid, the liquid conductivity sensor detects that the conductivity is higher than the threshold value, that is, a signal is fed back to the control system to adjust the negative pressure of the air extraction, thereby reducing the negative pressure extraction rate, ensuring that the electrolyte is not extracted, and avoiding the problem of electrolyte crystallization in the pipeline. The control system can automatically adjust the negative pressure to ensure that the electrolyte is not extracted.

[0042] See also Figure 1, the priority of the control system to control the negative pressure source B according to the liquid conductivity sensor is greater than the priority of the control system to control the negative pressure source B according to the instantaneous flow rate. By limiting the control priority, when the magnitude of the negative pressure controlled by the liquid conductivity sensor conflicts with the magnitude of the negative pressure controlled by the instantaneous flow rate, for example, when the gas production at this time point is high and the negative pressure needs to be increased, but the electrolyte is extracted after the increase, then the negative pressure should be reduced according to the priority to ensure that the electrolyte is not lost. This priority can also make the gas extraction of this method more reasonable and reliable, and can also make the efficiency of this negative pressure formation operation higher.

[0043] See also Figure 1 , an embodiment of the present invention provides a battery negative pressure formation method, which is used for the above-mentioned device. It includes the following steps S1, using a pipeline to connect the battery to be formed, a trace gas measuring device and a negative pressure source in sequence, S2, charging the battery, the battery generates gas, starting the negative pressure source, and the negative pressure source sucks the gas generated by the battery into the pipeline, S3, the trace gas measuring device measures the amount of gas passing through it, S4, according to the amount of gas measured by the trace gas measuring device and combined with the negative pressure of the negative pressure source, calculate the negative pressure exhaust time, S5, according to the exhaust time, set the working time of the negative pressure source. The trace gas measuring device is introduced into the battery negative pressure formation process, and the trace gas measuring device is used to obtain the amount of gas released by the battery, so that the exhaust time of the battery negative pressure formation can be calculated, thereby improving production efficiency. Specifically, in the existing battery negative pressure formation operation, most of them are based on experience to estimate the negative pressure pumping time, and in order to ensure that the gas can be completely pumped out, a longer negative pressure pumping time is set, which is usually longer than the actual pumping time, thereby reducing production efficiency. The present embodiment cleverly uses a trace gas measuring device to measure the gas volume, so that the specific pumping time can be calculated, and then the working time of the negative pressure source is set according to the pumping time, so that the pumping time of the batch of batteries to be formed can be set.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A battery negative pressure formation method, characterized in that: The steps include: S1, use pipelines to connect the battery to be formed, the trace gas measuring device and the negative pressure source in sequence, S2, charging the battery, the battery generates gas, starting the negative pressure source, and the negative pressure source sucks the gas generated by the battery into the pipeline, S3, the trace gas measuring device measures the amount of gas passing through it, S4, calculating the negative pressure pumping time according to the gas volume measured by the trace gas measuring device and the negative pressure of the negative pressure source, S5, setting the working time of the negative pressure source according to the air extraction time.

2. The negative pressure formation method for a battery as claimed in claim 1, characterized in that: The trace gas measuring device obtains the dynamic gas production of the battery and outputs an instantaneous flow rate according to the gas production dynamics. The instantaneous flow rate displays the peak and valley values ​​of the gas production rate of the battery.

3. The negative pressure formation method for a battery as claimed in claim 2, characterized in that: A control system is used to receive and analyze the instantaneous flow rate, and control the negative pressure source to adjust the negative pressure in real time.

4. The negative pressure formation method for a battery as claimed in claim 1, characterized in that: When the pipeline leaks, the trace gas measuring device and the negative pressure source are used to measure the leakage flow.

5. The negative pressure formation method for a battery as claimed in claim 4, characterized in that: A first valve is arranged on the pipeline between the battery and the trace gas measuring device. The first valve is closed and the negative pressure source is opened. There is a pressure difference between the air inlet and the air outlet of the trace gas measuring device. The trace gas measuring device can measure the leakage gas flow.

6. The negative pressure formation method for a battery as claimed in claim 1 or 3, characterized in that: A liquid conductivity sensor is arranged near the battery in the pipeline, and the liquid conductivity sensor is used to monitor whether the electrolyte in the battery is extracted.

7. The negative pressure formation method for a battery as claimed in claim 6, characterized in that: When a control system is used, when the liquid conductivity sensor detects that the conductivity is higher than a threshold value, a signal is fed back to the control system, and the control system controls the negative pressure source to adjust the negative pressure in real time.

8. The battery negative pressure formation method according to claim 7, characterized in that: The priority of the control system controlling the negative pressure source according to the liquid conductivity sensor is greater than the priority of the control system controlling the negative pressure source according to the instantaneous flow rate.

9. The battery negative pressure formation method according to claim 1, characterized in that: The trace gas measuring device adopts a bubble method to measure the tiny gas flow.

10. A battery negative pressure formation device, characterized in that: It comprises a negative pressure source and a trace gas measuring device, wherein the air inlet end of the trace gas measuring device is connected to the battery to be formed through a pipeline, and the air outlet end of the trace gas measuring device is connected to the negative pressure source through a pipeline.

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