Negative pressure setting method for battery formation exhaust

Abstract

The invention discloses a negative pressure setting method for battery formation exhaust. The method comprises the following steps: determining a formation process of a battery to be formed; determining an SOC range corresponding to the charging capacity of each formation process stage; searching a vacuum condition parameter corresponding to each formation process stage according to the SOC range; and setting a negative pressure vacuum condition of each formation process stage according to the vacuum condition parameters. The negative pressure and the negative pressure duration time are set according to different SOCs in different formation stages in the battery formation process, so that the waste of resources is reduced, meanwhile, the loss of electrolyte components and solvents can be reduced, and the electrical performance of a battery cell is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery formation, in particular to a negative pressure setting method for battery formation exhaust. BACKGROUND

[0002] Battery formation refers to the process of charging the battery monomer with a charging device. During the formation process, when lithium ions are inserted into the surface layer of the negative electrode material, the Fermi level of the surface layer of the negative electrode material is higher than the lowest unoccupied molecular orbital (LUMO) of the electrolyte. Therefore, the electrolyte is reduced and decomposed on the surface of the negative electrode material. Due to the reduction of additives and solvents, a solid electrolyte interface film (SEI) and byproduct gas are generated. When the generated gas stays between the pole piece and the separator, the pole piece gas path channel will stop the pre-formation reaction due to the insulating nature of the gas, resulting in uneven pole piece formation. The generated bubbles also occupy part of the space of the electrolyte, causing the electrolyte to overflow and resulting in loss of electrolyte. In order to reduce the residence of gas in the pole group and enable it to escape quickly, a negative pressure process is usually used to exhaust the generated gas.

[0003] In order to exhaust the generated gas, the gas guide pipe of the exhaust equipment is usually connected to the exhaust port of the battery, and the gas in the battery is exhausted by setting a negative pressure. In the process of forming large-capacity batteries, different companies will choose different formation charging systems in order to effectively exhaust the gas and form a stable SEI. However, a negative pressure is usually set at each stage of the formation exhaust, and this negative pressure condition is often constant, which seriously wastes energy resources. At the same time, if a negative pressure condition is provided during the non-gas production stage, the volatility of the electrolyte solvent will increase, resulting in changes in the composition of the electrolyte and a decrease in the solvent, which will affect the subsequent electrical performance of the battery

[0004] For example, Chinese patent CN205004414U discloses a method for detecting the pressure in the pipeline and automatically exhausting the gas by using a vacuum gauge and a vacuum pumping device. Chinese patent CN115911616A discloses a method for exhausting gas during the battery formation process, which adjusts and exhausts the negative pressure of the battery in real time according to the real-time correspondence between the state of charge of the battery and the negative pressure. The above technical route is complex and troublesome, and cannot provide a universal, convenient and efficient method for different battery models and different formation systems, which cannot meet the needs of different battery models. For the actual production of large-capacity batteries, a negative pressure is set during the constant current process of each step. There is no need to set a negative pressure when there is no gas production or after the gas production is completed. Moreover, the amount of gas produced is not constant at different formation stages. If the negative pressure condition is set when the amount of gas produced is large, the boiling point of the electrolyte will decrease and the evaporation rate will increase. If the composition of the electrolyte changes, it will damage the subsequent electrical performance of the battery. SUMMARY

[0005] The present application aims to overcome the deficiencies and shortcomings of the prior art, and provides a negative pressure setting method for battery formation exhaust.

[0006] A negative pressure setting method for battery formation exhaust, comprising the steps of:

[0007] determining a formation process for a battery to be formed;

[0008] determining a SOC range corresponding to a charging capacity of each formation process stage;

[0009] According to the SOC range, find the vacuum condition parameters corresponding to each formation process stage;

[0010] According to the vacuum condition parameters, set the negative pressure vacuum condition of each formation process stage.

[0011] Among them, the vacuum condition parameters include different negative pressure intervals and zero pressure.

[0012] Among them, when the battery is formed, the vacuum condition parameters are the corresponding negative pressure interval, otherwise the vacuum condition parameters are zero pressure.

[0013] Among them, in the initial stage of the formation process, it is zero pressure, then it is negative pressure formation according to the preset multiple negative pressure intervals, and it is restored to zero pressure when the battery no longer produces gas, until the formation ends.

[0014] Among them, the higher the SOC range corresponding to the charging capacity of each formation stage, the greater the negative pressure of the vacuum condition parameters.

[0015] Among them, in the formation process, the negative pressure values of different negative pressure intervals are set from low to high, that is, as the formation proceeds, the negative pressure values corresponding to the negative pressure intervals tend to increase.

[0016] Among them, the vacuum condition parameters corresponding to each formation process stage are determined by experiment in advance and stored in the form of a table for looking up when forming similar batteries.

[0017] Among them, setting the negative pressure vacuum condition of each formation process stage according to the vacuum condition parameters comprises:

[0018] determining the start and end time of each formation process stage;

[0019] According to the start and end time, the negative pressure vacuum condition is set, including negative pressure opening and negative pressure closing.

[0020] Among them, the determination of the vacuum condition parameters corresponding to each formation process stage comprises:

[0021] Connect the exhaust port of the test battery to a gas flow meter, perform negative pressure formation on the test battery according to the preset formation process steps, and collect the volumetric flow rate data of the gas produced at different formation stages.

[0022] Based on the collected volumetric flow rate data, a graph showing the change in the volume of produced gas with SOC corresponding to a unit change in SOC state is obtained.

[0023] Based on the graph showing the change in gas production volume with SOC corresponding to the unit change in SOC, the gas production variation law of the test battery at different SOCs is obtained.

[0024] Based on the gas production variation pattern of the test battery at different SOCs, corresponding vacuum condition parameters were set.

[0025] Specifically, when setting the negative pressure vacuum conditions for each formation process stage, a corresponding negative pressure value is selected from the negative pressure range for setting.

[0026] This invention sets the negative pressure and duration of negative pressure according to the different SOC at different stages of battery formation, thereby reducing resource waste and minimizing the loss of electrolyte components and solvents, thus ensuring the electrical performance of the battery cell. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of the negative pressure setting method for battery formation venting according to the present invention.

[0028] Figure 2 This is a graph showing the change in the volume of produced gas with SOC corresponding to a unit change in SOC state, obtained by the present invention.

[0029] Figure 3 This is a schematic diagram of gas pressure as a function of SOC in a unit-changing state of charge, obtained by the present invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] See Figure 1 As shown, a negative pressure setting method for battery formation venting includes the following steps:

[0032] S1. Determine the formation process of the battery to be formed;

[0033] S2. Determine the SOC range corresponding to the charging capacity of each formation process stage;

[0034] S3. Based on the SOC range, find the vacuum condition parameters corresponding to each formation process stage;

[0035] S4. Set the negative pressure vacuum conditions for each formation process stage according to the vacuum condition parameters.

[0036] The vacuum condition parameters include different negative pressure ranges and zero pressure.

[0037] This invention sets the corresponding negative pressure and duration of negative pressure according to the different SOC at different formation stages during the battery formation process. This achieves the goal of not setting negative pressure when the battery is not producing gas, but only when the battery is producing gas. This avoids the waste of resources caused by applying negative pressure when the battery is not producing gas. At the same time, it can also reduce the loss of electrolyte components and solvents, and ensure the electrical performance of the battery cell.

[0038] After determining the negative pressure vacuum conditions for each formation process stage through the above steps, automatic control can be implemented. The negative pressure vacuum conditions for different stages can be automatically controlled through automatic equipment detection. When the controller detects that a corresponding formation stage is about to begin, it automatically controls the activation of the corresponding negative pressure to exhaust gas. This can be monitored through formation charging equipment, such as monitoring the battery's state of charge (SOC) or the start and end times of each formation stage. The opening or closing of the negative pressure vacuum can be controlled according to the set vacuum conditions, thereby achieving the purpose of this invention.

[0039] During battery formation and venting, the vacuum condition parameter is the corresponding negative pressure range; otherwise, the vacuum condition parameter is zero pressure, i.e., when no gas is generated, the corresponding vacuum condition parameter is 0. As shown in Table 1, the negative pressure range includes, for example, the first negative pressure range -80 to -90, the second negative pressure range -20 to -30, and the third negative pressure range -10 to -20, which correspond to the SOC of different formation stages, such as 1.9 to 3.7, 3.7 to 3.5, and 8 to 18, respectively. The zero pressure is at both ends of the negative pressure range, corresponding to the SOC of the formation stages of 0 to 1.9 and 18 to 100, respectively.

[0040] Specifically, when setting the negative pressure vacuum conditions for each formation process stage, the corresponding negative pressure value can be selected from the negative pressure range for setting.

[0041] More preferably, the initial stage of the battery formation process is at zero pressure, followed by negative pressure formation according to multiple preset negative pressure intervals. The pressure is restored to zero when the battery stops producing gas, until formation is complete. This setup allows the negative pressure to adapt to the gas production situation or rate, making the negative pressure setting more scientific and consistent with the purpose of negative pressure venting. It achieves dynamic adaptive adjustment of negative pressure and gas production or venting. Specifically, the higher the SOC range corresponding to the charging capacity of each formation stage, the greater the negative pressure of the vacuum condition parameters. In the formation process, the negative pressure values ​​of different negative pressure intervals are set from low to high, meaning that as formation progresses, the negative pressure value corresponding to the negative pressure interval tends to increase.

[0042] Preferably, the vacuum condition parameters corresponding to each formation process stage are pre-determined through experiments and stored in the form of a table for reference when forming similar batteries, as shown in Table 1 below. Specifically, the corresponding negative pressure value can be selected in the negative pressure range according to the situation.

[0043] Table 1

[0044]

[0045] In this application, the negative pressure vacuum conditions for each formation process stage are set according to the vacuum condition parameters, including: determining the start and end times of each formation process stage; and setting the negative pressure vacuum conditions according to the start and end times, including negative pressure activation and negative pressure deactivation.

[0046] In this application, a corresponding start and end time node is set for each formation stage of the battery. The formation stage is controlled and determined based on the time. Based on the formation time node, the formation stage is determined, and then the negative pressure is controlled to start and end, as well as the negative pressure value at which it is started.

[0047] In some implementation schemes, the vacuum condition parameters corresponding to each formation process stage are determined by testing the test cell. The test steps include:

[0048] Connect the exhaust port of the test battery to a gas flow meter, and perform negative pressure formation on the test battery according to the preset formation process steps, collecting the volumetric flow rate data of the gas produced at different formation stages; based on the collected volumetric flow rate data, obtain a graph showing the change in gas production volume with SOC corresponding to a unit change in SOC state; based on the graph showing the change in gas production volume with SOC corresponding to a unit change in SOC state, obtain the gas production variation law of the test battery at different SOCs; based on the gas production variation law of the test battery at different SOCs, set the corresponding vacuum condition parameters.

[0049] The vacuum condition parameters are selected and set according to the battery properties and formation requirements. Generally, they are set to a range of values, and the value within the range can meet the formation negative pressure requirements during formation.

[0050] Specifically, during the experiment, the exhaust port of the battery undergoing formation was connected to a gas flow meter to collect the velocity and volume of gas produced by the battery at different formation stages. Data processing was then used to obtain... Figure 2 The graph shows the relationship between D(ml) / D(SOC) and SOC. It can be seen that in the range of 0%–1.9% SOC, no gas is generated, as the reduction potential of the electrolyte additive has not been reached. In the range of 1.9%–3.7% SOC, the electrolyte additive begins to undergo reduction, forming an SEI film on the negative electrode surface, resulting in a large amount of gas production. In the range of 3.7%–5% SOC, the gas production rate decreases significantly. In the range of 5%–18% SOC, the gas production rate reaches its lowest point because the formation of the SEI film, to some extent, prevents the electrolyte additive from further contacting electrons on the negative electrode for reduction. After 18% SOC, no more gas is produced. Through the above analysis, the variation of battery gas production rate with SOC is obtained.

[0051] Verify the above-mentioned relationship between battery gas production rate and SOC:

[0052] A pressure sensor test was conducted on the gas produced by the battery: The pressure sensor was connected to the battery's vent. When connected to the pressure sensor, the battery was in a sealed state. Due to the accumulation of gas produced during battery formation, the pressure on the pressure sensor gradually increased. The gas pressure change data throughout the process was collected. The pressure data was differentiated to obtain the gas pressure D(MPa) / D(SOC) per unit change in state of charge. Finally, a graph showing the change in gas pressure per unit change in state of charge as a function of SOC was obtained, and the pattern was found to be consistent with the test results of the gas flow meter.

[0053] As can be seen from the above description, the method of this invention calculates the State of Charge (SOC) for each formation stage of the battery according to the different formation methods of the battery, determines the start and end time points of different formation stages of the formation method, and sets different negative pressure vacuum conditions based on the different SOC of different formation stages. The negative pressure is turned on when gas production begins and turned off when gas production ends. The negative pressure setting is linked to the gas production rate of the battery, which can greatly save resources and ensure the electrical performance of the battery cell.

[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0055] Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0056] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method of setting a negative pressure of battery formation exhaust gas, characterized by, The method comprises the steps of: determining a formation process of a battery to be formed; determining an SOC range corresponding to a charging capacity of each formation process stage; looking up a vacuum condition parameter corresponding to each formation process stage according to the SOC range; setting a negative pressure vacuum condition of each formation process stage according to the vacuum condition parameter.

2. The method of claim 1, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. The vacuum condition parameter comprises different negative pressure intervals and zero pressure.

3. The method of claim 2, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. When the battery is being formed, the vacuum condition parameter is a corresponding negative pressure interval, otherwise the vacuum condition parameter is zero pressure.

4. The method of claim 2, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. In the initial stage of the formation process, the vacuum condition parameter is zero pressure, then the battery is formed under negative pressure according to a plurality of preset negative pressure intervals, and when the battery no longer produces gas, the vacuum condition parameter is restored to zero pressure until the formation is completed.

5. The method of claim 1, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. The higher the SOC range corresponding to the charging capacity of each formation stage is, the greater the negative pressure of the vacuum condition parameter is.

6. The method of claim 2, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. In the formation process, the negative pressure values of different negative pressure intervals are set from low to high, that is, the negative pressure values corresponding to the negative pressure intervals increase with the progress of the formation.

7. The method of claim 1, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. The vacuum condition parameter corresponding to each formation process stage is determined in advance through experiments and stored in the form of a table for looking up when forming similar batteries.

8. The method of claim 1, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. The setting of the negative pressure vacuum condition of each formation process stage according to the vacuum condition parameter comprises: determining the start and end time of each formation process stage; setting the negative pressure vacuum condition according to the start and end time, including negative pressure opening and negative pressure closing.

9. The method of claim 1, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. The determination of the vacuum condition parameter corresponding to each formation process stage comprises: connecting the exhaust port of a test battery to a gas flow meter, forming the test battery under negative pressure according to a preset formation process step, and collecting the volume flow data of the gas produced in different formation stages; obtaining a graph of the change of the volume of the produced gas corresponding to a unit change of SOC state with respect to SOC according to the collected volume flow data; obtaining the gas production change rule of the test battery at different SOCs according to the graph of the change of the volume of the produced gas corresponding to a unit change of SOC state with respect to SOC; setting the corresponding vacuum condition parameter according to the gas production change rule of the test battery at different SOCs.

10. The method of claim 2, wherein the negative pressure is set to be - 0.1 to - 0.3 bar. When setting the negative pressure vacuum condition of each formation process stage, a corresponding negative pressure value is selected from the negative pressure intervals for setting.

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