Preparation method of secondary battery, secondary battery, energy storage system and electric equipment

Abstract

The invention relates to the field of energy storage battery cells, and provides a preparation method of a secondary battery, the secondary battery, an energy storage system and electric equipment, and the method comprises the following steps: carrying out first liquid injection treatment and high-temperature standing treatment on a battery cell in a battery cell bearing part; after the battery cell is subjected to high-temperature standing treatment, the current moisture value of the target battery cell is detected; under the condition that the current moisture value of the target battery cell is greater than the preset moisture value, performing second liquid injection treatment and / or pre-charging treatment on the battery cell in the battery cell bearing part, so that the moisture value of the battery cell in the battery cell bearing part is smaller than or equal to the preset moisture value; and performing formation treatment on the battery cell in the battery cell bearing part to obtain the secondary battery. According to the method, the moisture in the battery cell is detected after the high-temperature standing of the first liquid injection treatment, the moisture in the battery cell is further monitored, and the water precipitation treatment is carried out on the battery cell in time under the condition that the moisture of the battery cell is too large, so that the moisture value of the battery cell is not too large, and the manufactured battery is enabled to have fewer brown spots.

Description

Technical Field

[0001] The present application relates to the field of energy storage cells, and more specifically, to a method for preparing a secondary battery, a secondary battery, an energy storage system, and electrical equipment. Background Art

[0002] With the development of science and technology, the performance requirements for batteries in existing technologies are becoming more and more stringent, and the brown spot problem of battery cells is a serious defect in battery performance. The generation of brown spots in battery cells will lead to further lithium deposition in the battery cells, thereby affecting the battery capacity and performance. In severe cases, it will cause thermal runaway of the battery, and then cause a battery safety accident. Summary of the invention

[0003] The main purpose of the present application is to provide a method for preparing a secondary battery, a secondary battery, an energy storage system and an electrical device, so as to at least solve the problem that the existing battery preparation method easily causes brown spots on the prepared battery cells, thereby causing a decrease in battery performance.

[0004] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a method for preparing a secondary battery is provided, comprising: performing a first liquid injection treatment on the battery cells in a battery cell carrier, and performing a high-temperature static treatment on the battery cells in the battery cell carrier after performing the first liquid injection treatment; after performing the high-temperature static treatment on the battery cells for a preset period of time, detecting the current moisture value of the target battery cells, wherein the target battery cells are some of the battery cells in the battery cell carrier; when the current moisture value of the target battery cells is greater than a preset moisture value, performing a preset treatment on the battery cells in the battery cell carrier so that the moisture value of the battery cells in the battery cell carrier is less than or equal to the preset moisture value; performing a formation treatment on the battery cells in the battery cell carrier to obtain a secondary battery; wherein the preset treatment includes at least one of the following: performing a second liquid injection treatment on the battery cells, wherein the moisture value of the electrolyte used when performing the first liquid injection treatment on the battery cells in the battery cell carrier is greater than the moisture value of the electrolyte used when performing the second liquid injection treatment on the battery cells in the battery cell carrier; and performing a pre-charging treatment on the battery cells.

[0005] Optionally, before performing the first liquid injection treatment on the battery cells in the battery cell carrier, the method also includes: obtaining basic parameters of each of the battery cells in the battery cell carrier, the basic parameters of the battery cells including the weight of the battery cells and the thickness of the battery cells, the thickness of the battery cells being positively correlated with the width of the electrolyte channel of the battery cells; determining the battery cells whose weight is greater than or equal to a preset weight as the target battery cells, and / or determining the battery cells whose thickness is less than or equal to a preset thickness as the target battery cells; installing the target battery cells at a preset detection position of the battery cell carrier, the preset detection position being a position in the battery cell carrier where the moisture value of the battery cells can be detected.

[0006] Optionally, the battery cells in the battery cell carrier are subjected to a preset treatment, including: performing a first preset treatment on the battery cells in the battery cell carrier; detecting a current moisture value of the target battery cells; when the current moisture value of the target battery cells is greater than the preset moisture value, performing a second preset treatment on the battery cells in the battery cell carrier, wherein the first preset treatment is one of the second liquid injection treatment and the pre-charging treatment, and the second preset treatment is the other of the second liquid injection treatment and the pre-charging treatment; when the current moisture value of the target battery cells is less than or equal to the preset moisture value, determining to perform the formation treatment on the battery cells in the battery cell carrier.

[0007] Optionally, the first preset process is the second injection process, and the second preset process is the pre-charging process.

[0008] Optionally, when the preset treatment includes performing a second liquid injection treatment on the battery cell, and before performing a first liquid injection treatment on the battery cell in the battery cell carrier, the method further includes: determining the saturated liquid absorption of the battery cell; determining a first liquid injection amount and a second liquid injection amount according to the saturated liquid absorption of the battery cell, the first liquid injection amount being the liquid injection amount of the electrolyte used when performing the first liquid injection treatment on the battery cell, and the second liquid injection amount being the liquid injection amount of the electrolyte used when performing the second liquid injection treatment on the battery cell.

[0009] Optionally, when the preset treatment includes pre-charging the battery cells, the battery cells in the battery cell carrier are preset treated, including: determining a reaction film-forming potential of the battery cells, a reaction potential of each substance in a first electrolyte, and a reaction potential of each substance in a second electrolyte, the first electrolyte being the electrolyte used for the first liquid injection treatment, and the second electrolyte being the electrolyte used for the second liquid injection treatment; determining a charging voltage for the pre-charging treatment based on the reaction film-forming potential of the battery cells, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte, the charging voltage for the pre-charging treatment being less than the reaction film-forming potential of the battery cells, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte; and using the charging voltage to pre-charge the battery cells in the battery cell carrier.

[0010] Optionally, the battery cells in the battery cell carrier are subjected to preset processing, including: determining the cell type of the battery cells in the battery cell carrier; determining the number of times the preset processing is performed on the battery cells according to the cell type of the battery cells and the current moisture value of the target battery cells; when the cell type of the battery cells is lithium-replenished batteries, determining the number of times the preset processing is performed on the battery cells is a first number; when the cell type of the battery cells is non-lithium-replenished batteries, determining the number of times the preset processing is performed on the battery cells is a second number, wherein the first number is greater than the second number; performing the preset processing on the battery cells in the battery cell carrier the first number or the second number.

[0011] Optionally, the battery cells in the battery cell carrier are subjected to a formation treatment, including: obtaining the rated capacity of the battery cells in the battery cell carrier; determining a constant current based on the rated capacity of the battery cells, wherein the constant current is less than the rated capacity of the battery cells; and charging the battery cells in the battery cell carrier with the constant current to perform a formation treatment on the battery cells.

[0012] Optionally, the constant current is 0.02~0.2C, where C is the rated capacity of the battery cell.

[0013] Optionally, after performing a formation treatment on the battery cells in the battery cell carrier to obtain a secondary battery, the method further includes: obtaining a brown spot condition of the secondary battery, the brown spot condition including at least the number and size of the brown spots of the secondary battery; and determining the preset moisture value for the next preparation of the secondary battery based on the brown spot condition of the secondary battery and the preset moisture value.

[0014] Optionally, according to the brown spot situation of the secondary battery and the preset moisture value, determining the preset moisture value for preparing the secondary battery next time, including: calculating the brown spot coverage rate of the secondary battery according to the number and size of the brown spots of the secondary battery; when the brown spot coverage rate of the secondary battery is less than or equal to the preset coverage rate, determining the preset moisture value when preparing the secondary battery this time as the preset moisture value when preparing the secondary battery next time; when the brown spot coverage rate of the secondary battery is greater than the preset coverage rate, determining the preset moisture value when preparing the secondary battery next time according to the preset moisture value when preparing the secondary battery this time, wherein the preset moisture value when preparing the secondary battery next time is less than the preset moisture value when preparing the secondary battery this time.

[0015] Optionally, detecting the current moisture value of the target battery cell includes: detecting the moisture value of the gas in the target battery cell at the current moment to obtain the gas moisture value; determining the electrolyte moisture value of the target battery cell at the current moment based on the gas moisture value of the target battery cell at the current moment to obtain the current moisture value of the target battery cell, wherein the gas moisture value of the target battery cell is positively correlated with the electrolyte moisture value of the target battery cell.

[0016] Optionally, the preset moisture value is 50 ppm~55 ppm.

[0017] According to another aspect of the present application, a secondary battery is provided. The secondary battery is prepared by using any one of the methods for preparing a secondary battery.

[0018] According to another aspect of the present application, there is provided an energy storage system, comprising: at least one secondary battery as described above.

[0019] According to another aspect of the present application, there is provided an electrical device, comprising: at least one of the secondary batteries or the energy storage system.

[0020] Effects of the present application: The above-mentioned secondary battery preparation method first performs a first liquid injection treatment and a high-temperature static treatment on the battery cells in the battery cell carrier; after the high-temperature static treatment, the current moisture value of the target battery cell is detected; when the current moisture value of the target battery cell is greater than the preset moisture value, the battery cells in the battery cell carrier are subjected to a second liquid injection treatment and / or a pre-charging treatment, so that the moisture value of the battery cells in the battery cell carrier is less than or equal to the preset moisture value; finally, the battery cells in the battery cell carrier are subjected to a formation treatment to obtain a secondary battery. The method detects the moisture in the battery cell after the high-temperature static treatment of the first liquid injection treatment, further monitors the moisture in the battery cell, and timely performs a moisture reduction treatment on the battery cell when the moisture content of the battery cell is too high, so as to ensure that the moisture value of the battery cell is not too high, thereby ensuring that the manufactured battery has no brown spots or less brown spots, and does not affect the performance of the battery cell, solving the problem that the existing battery preparation method easily causes brown spots in the prepared battery cell, thereby causing the battery performance to decline. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 A schematic diagram of a process for preparing a secondary battery provided in an embodiment of the present application is shown;

[0023] Figure 2A schematic structural diagram of a battery cell assembly provided according to an embodiment of the present application is shown;

[0024] Figure 3 A schematic structural diagram of a liquid injection mechanism provided according to an embodiment of the present application is shown;

[0025] Figure 4 A schematic diagram of a formation charging process according to an embodiment of the present application is shown;

[0026] Figure 5 A schematic structural diagram of a formation device provided according to an embodiment of the present application is shown.

[0027] The above drawings include the following reference numerals:

[0028] 10. Battery cell tray; 20. Battery cell; 21. Target battery cell; 30. Liquid injection mechanism; 40. Cup body; 50. Negative pressure nozzle; 60. Buffer cup; 70. Bus bar; 80. Buffer tank. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] In the prior art, the generation of brown spots in the battery cell mainly refers to the chemical reaction between the battery structure layers when the internal moisture of the battery environment is high, resulting in the generation of black metal oxides on the surface of the positive electrode material of the battery, thereby affecting the battery capacity and performance. In severe cases, it will cause thermal runaway of the battery, and then cause a battery safety accident. The inner circle brown spots of the battery cell are generally formed during the battery formation process. Battery formation is the process of charging the battery cell at a certain voltage to activate the battery cell material and structure. If the battery has a large amount of water inside the battery during the formation process, the chemical reaction between the internal structure of the battery cell is more intense, and the inner circle brown spots are easily formed. That is, in the battery preparation process of the prior art, when the battery cell structural parameters change, the chemical reaction of the internal structure during the battery cell formation process has a greater impact, which is easy to cause the generation of inner circle brown spots, and the excessive water content of the battery cell is the main reason for the generation of inner circle brown spots. In order to solve the problem that the existing battery preparation method is easy to cause the prepared battery cell to produce brown spots, thereby causing the battery performance to decline, the embodiments of the present application provide a secondary battery preparation method, a secondary battery, an energy storage system and an electrical device.

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0034] In this embodiment, a method for preparing a secondary battery is provided. It should be noted that, although a logical sequence is shown in the flow chart, in some cases, the steps shown or described may be performed in a different order than that shown here.

[0035] Figure 1 FIG. 1 is a flow chart of a method for preparing a secondary battery according to an embodiment of the present application. Figure 1 As shown, the method comprises the following steps:

[0036] Step S101, performing a first liquid injection treatment on the battery cells in the battery cell carrier, and performing a high-temperature static treatment on the battery cells in the battery cell carrier after the first liquid injection treatment;

[0037] Specifically, the battery cell carrier is generally a battery cell tray. Figure 2 It is a structural schematic diagram of a battery cell assembly disk, such as Figure 2As shown, the battery cell tray is composed of a battery cell tray 10 and a plurality of battery cells 20. The battery cell tray 10 stores a plurality of battery cells 20. Generally, the number of battery cells 20 stored in the battery cell tray 10 is 24. The first liquid injection treatment is the process of injecting electrolyte into the battery cell after the electrode production, battery cell assembly (winding or lamination) and the first baking (pre-baking) are completed. The electrolyte is the carrier of the electrochemical reaction inside the battery cell. It contains lithium salts, organic solvents and possible additives, and provides the necessary medium for the movement of lithium ions between the positive and negative electrodes, thereby realizing the charging and discharging function of the battery cell. The high-temperature static treatment is to place the battery cell in a specific temperature environment higher than room temperature and keep the battery in a static state for a period of time at this temperature. The high-temperature static treatment is to bake the battery cell to reduce the moisture value of the battery cell for the first time.

[0038] like Figure 2 As shown, the target battery cell 21 is installed in the preset detection position of the battery cell carrier, and then all the battery cells 20 in the battery cell tray 10 are simultaneously subjected to the first liquid injection treatment and the high-temperature static treatment.

[0039] Step S102, after the battery cells are subjected to the high-temperature static treatment for a preset time, detecting the current moisture value of the target battery cells, where the target battery cells are some of the battery cells in the battery cell carrier;

[0040] Specifically, the battery cell with higher moisture content is determined as the target battery cell, and the moisture content of other battery cells in the battery cell carrier can be determined subsequently by detecting the moisture value of the target battery cell. That is, if the moisture value of the target battery cell is less than the preset moisture value, it proves that the moisture values ​​of the battery cells with higher moisture content are all less than the preset moisture value, and then the moisture values ​​of other battery cells with lower moisture content in the battery cell carrier must also be less than the preset moisture value.

[0041] If each battery cell is tested for moisture, it will not only be time-consuming and costly. Therefore, setting a preset detection position only requires testing the moisture value of the battery cell at the preset detection position to reflect the moisture situation of the battery cells in the entire battery cell carrier, reducing the number of unnecessary detections, greatly improving detection efficiency, shortening production time, and effectively reducing production costs.

[0042] Figure 3 is a structural schematic diagram of a liquid injection mechanism, such as Figure 3 As shown, the liquid injection mechanism 30 includes a cup body 40, and the cup body 40 is connected to the interior of the battery cell through a pipeline. Figure 3The injection mechanism 30 shown is a self-enclosed structure, which maintains gas communication with the inside of the battery cell through the cup body 40. When detecting the moisture value of the target battery cell, the moisture value of the gas in the cup body 40 of the target battery cell can be directly detected to obtain the moisture value of the target battery cell. Specifically, the moisture value of the target battery cell is determined by detecting the dew point of the target battery cell monitored by the pipeline. The dew point monitored by the pipeline refers to the temperature when water vapor in the gas condenses into dew (or frost) when it is cold. The dew point is an important indicator for measuring the moisture content in the gas. The lower the dew point, the less moisture content in the gas.

[0043] Step S103, when the current moisture value of the target battery cell is greater than the preset moisture value, performing preset processing on the battery cell in the battery cell carrier so that the moisture value of the battery cell in the battery cell carrier is less than or equal to the preset moisture value;

[0044] Specifically, since the inner circle brown spots of the battery cell are generally formed during the battery formation process, if the water content inside the battery is large during the formation process and the chemical reaction between the internal structures of the battery cell is more intense, the inner circle brown spots are easily formed. Therefore, controlling the water content of the battery cell before formation can further ensure that the water content of the battery cell is not too large during the formation process, thereby ensuring that the gas production of the battery cell during the formation process is small, so as to reduce the brown spot problem of the battery cell.

[0045] The setting of the preset moisture value needs to be at least based on the different sensitivities of the battery cell material, electrolyte, etc. to moisture. For example, lithium metal negative electrodes and certain high-nickel ternary positive electrode materials are prone to violent reactions when exposed to water, so a lower preset moisture value needs to be set accordingly.

[0046] The above-mentioned preset processing includes at least one of the following:

[0047] The battery cell is subjected to a second liquid injection treatment, and the moisture content of the electrolyte used in the first liquid injection treatment of the battery cell in the battery cell carrier is greater than the moisture content of the electrolyte used in the second liquid injection treatment of the battery cell in the battery cell carrier; generally, a larger moisture content of the battery cell means that the moisture content of the electrolyte of the battery cell is larger, and an electrolyte with a lower moisture content can be used for neutralization. For example, if the moisture content of the electrolyte used in the first liquid injection treatment is 90ppm, then the moisture content of the electrolyte used in the second liquid injection treatment is 4ppm, that is, the moisture content of the electrolyte used in the first liquid injection treatment is less than 100ppm, and the moisture content of the electrolyte used in the second liquid injection treatment is less than 10ppm.

[0048] The above-mentioned battery cell is pre-charged. Specifically, during the pre-charging process, the voltage change inside the battery cell will cause some water and impurities to decompose or be removed, which helps to reduce the water content inside the battery cell and reduce impurities, thereby improving the performance and reliability of the battery. Therefore, the pre-charging process can be used to reduce the water content of the battery cell.

[0049] It should be noted that different preset treatments can be selected to reduce the moisture value of the battery cell in different situations, and the type and number of preset treatments can be selected according to the current moisture value of the target battery cell. For example, if the current moisture value of the target battery cell is small, only one of the second liquid injection treatment and the pre-charging treatment can be used to reduce the moisture of the battery cell in the battery cell carrier; if the current moisture value of the target battery cell is large, the battery cell can be subjected to both the second liquid injection treatment and the pre-charging treatment. If the current moisture value of the target battery cell still cannot be less than the preset moisture value, the battery cell can be subjected to multiple second liquid injection treatments or multiple pre-charging treatments.

[0050] Step S104, performing a formation treatment on the battery cell in the battery cell carrier to obtain a secondary battery;

[0051] Figure 4 Schematic diagram of a formation charging process. Figure 4 As shown, the formation treatment steps mainly include battery cell positioning, needle bed pressing, charging start, charging termination and needle bed lifting. First, the battery cell is positioned, then the needle bed is pressed, and it is in a negative pressure environment of -80±5kpa. Then, charging is started, and the negative pressure of -80±5kpa is also maintained. After charging is terminated, it returns to normal pressure 0kpa, and finally the needle bed is lifted.

[0052] Figure 5 is a schematic diagram of the structure of a chemical formation device, such as Figure 5 As shown, under negative pressure environment, the negative pressure nozzle 50 absorbs the electrolyte in the battery cell 20 and stores the electrolyte in the buffer cup 60, so that the electrolyte can flow in the device, and the gas in the battery cell 20 can also be removed. The negative pressure nozzle 50 can accurately control the flow direction of the electrolyte under negative pressure; the bus 70 collects the electrolyte in each buffer cup 60, and allows the electrolyte to flow to the buffer tank 80 through the bus 70. The buffer tank 80 is externally connected to a vacuum and stores electrolyte, which can prevent external impurities from contaminating the electrolyte, provide a buffer space, stabilize the electrolyte supply, and ensure continuous and stable operation of the device. In this embodiment, the following is adopted: Figure 4 The formation charging process steps shown and Figure 5 The formation device shown performs formation treatment on the battery cell.

[0053] The preparation method of the above-mentioned secondary battery of the present application first performs a first liquid injection treatment and a high-temperature static treatment on the battery cells in the battery cell carrier; after the high-temperature static treatment is performed on the battery cells, the current moisture value of the target battery cells is detected; when the current moisture value of the target battery cells is greater than the preset moisture value, the battery cells in the battery cell carrier are subjected to a second liquid injection treatment and / or a pre-charging treatment, so that the moisture value of the battery cells in the battery cell carrier is less than or equal to the preset moisture value; finally, the battery cells in the battery cell carrier are subjected to a formation treatment to obtain a secondary battery. The method detects the moisture in the battery cells after the high-temperature static treatment of the first liquid injection treatment, further monitors the moisture in the battery cells, and timely performs a moisture reduction treatment on the battery cells when the moisture in the battery cells is too high, so as to ensure that the moisture value of the battery cells is not too high, thereby ensuring that the manufactured battery has less brown spots, and solves the problem that the existing battery preparation method easily causes brown spots in the prepared battery cells, thereby causing the battery performance to decline.

[0054] Wherein, detecting the current moisture value of the target battery cell includes the following steps:

[0055] Step S1021, detecting the moisture value of the gas in the target battery cell at the current moment to obtain the moisture value of the gas;

[0056] Step S1022, according to the gas moisture value of the above-mentioned target battery cell at the current moment, determine the electrolyte moisture value of the above-mentioned target battery cell at the current moment, and obtain the current moisture value of the above-mentioned target battery cell, wherein the gas moisture value of the above-mentioned target battery cell is positively correlated with the electrolyte moisture value of the above-mentioned target battery cell.

[0057] During the high-temperature static process of the battery cell, the water in the electrolyte will evaporate into the gas. The higher the water content in the gas, the higher the water content in the electrolyte. By detecting the water content in these gases, the original water content of the electrolyte can be inferred.

[0058] Among them, detecting the moisture value of the gas in the battery cell does not require destroying the battery cell structure. It is a non-destructive detection method that is suitable for online detection in mass production and will not affect the subsequent use of the battery cell. Compared with directly detecting the moisture in the electrolyte, detecting the moisture value in the gas can provide results faster. The moisture value in the gas can quickly reflect the changes in the moisture inside the battery cell, especially after standing at high temperature, the evaporation of moisture is accelerated, making the moisture detection in the gas more timely.

[0059] In some embodiments, a hygrometer may be used to directly detect the moisture value of the electrolyte in the target battery cell to obtain the current moisture value of the target battery cell.

[0060] Among them, the above preset moisture value is 50 ppm~55ppm. 50 ppm~55ppm is 50%~55% moisture. Among them, the current moisture value of the target battery cell refers to the moisture volatilized into the cavity by the electrolyte of the battery cell at the current moment, that is, the moisture value of the volatilized electrolyte. Therefore, the preset moisture value is for the moisture value of the volatilized electrolyte (that is, the moisture value of the air in the battery cell cavity), that is, the preset moisture value is the maximum moisture value of the volatilized electrolyte in the battery cell.

[0061] Since trace amounts of moisture (such as 50 ppm~55 ppm) are beneficial to battery performance in some cases, it can promote the formation of SEI film and make the film structure more stable, thereby improving the battery's cycle performance and storage performance. Therefore, setting the maximum moisture value of the battery cell to 50 ppm~55 ppm is the result of comprehensive consideration of battery performance, safety and cost-effectiveness. This moisture value range helps to form a stable and efficient SEI film, reduce side reactions, and ensure the stability of the chemical environment inside the battery, thereby improving the overall performance of the battery and extending its service life. In the manufacturing process of lithium-ion batteries, humidity control is one of the most critical steps to ensure high quality and safety of the battery. It should be pointed out that this value may be adjusted depending on the battery type, application environment and formation process, but strict control of moisture content is a generally followed principle.

[0062] Before the first liquid injection process is performed on the battery cells in the battery cell carrier, the method further comprises the following steps:

[0063] Step S201, obtaining basic parameters of each of the battery cells in the battery cell carrier, the basic parameters of the battery cells including the weight of the battery cells and the thickness of the battery cells, the thickness of the battery cells being positively correlated with the width of the electrolyte channel of the battery cells;

[0064] Step S202, determining the battery cell having a weight greater than or equal to a preset weight as the target battery cell, and / or determining the battery cell having a thickness less than or equal to a preset thickness as the target battery cell;

[0065] Step S203 , installing the target battery cell at a preset detection position of the battery cell carrier, wherein the preset detection position is a position in the battery cell carrier where the moisture value of the battery cell can be detected.

[0066] Specifically, the target battery cell may be one or more. The target battery cell may be determined by detecting the weight of the battery cell and / or the thickness of the battery cell. The target battery cell is a battery cell with a large amount of water.

[0067] Since the weight of the battery cell with a larger moisture value will also be larger, the weight is used as the selection condition of the target battery cell. In addition, the smaller the thickness of the battery cell, the more compact the battery cell is, that is, the thinner the battery cell is, the closer the distance between the positive and negative electrodes is, and the shorter the diffusion path of water inside the battery cell. However, this also means that when water penetrates from one side of the battery cell to the other side, it needs to pass through a narrower channel, the so-called moisture channel. As the thickness of the battery cell decreases, the degree of compression of the electrodes and diaphragms may increase, resulting in a narrower width of the moisture channel. Narrow channels increase the resistance to moisture diffusion, making the distribution of moisture inside the battery cell uneven, especially the difference in moisture between the edge and the center area may be more significant. Before entering the production process, the battery cell usually needs to be baked to remove moisture (i.e., high-temperature static treatment). The thinner the battery cell thickness, although the baking efficiency may appear to be higher on the surface (because heat can penetrate more easily), in fact, the existence of narrow channels may make it difficult to completely remove moisture in certain areas inside the battery cell, especially those parts with tighter structures or difficult for heat to reach. That is, a battery cell with a smaller thickness may make it more difficult to completely remove moisture from the inside of the battery cell, thereby increasing the moisture value of the battery cell. Therefore, in addition to weight, thickness can also be used as a selection condition for the target battery cell.

[0068] Therefore, by detecting the weight of the battery cell and / or the thickness of the battery cell, the battery cell with a larger moisture value can be accurately determined, that is, the target battery cell can be accurately determined.

[0069] Based on the above reasons, in addition to the weight and thickness of the battery cells, the compaction pressure of the battery cells can also be used to screen out the target battery cells, because the compaction pressure mainly reflects the compactness of the internal materials of the battery cells. The greater the compaction pressure, the denser the internal materials of the battery cells, and the smaller the thickness of the battery cells.

[0070] In addition, in some embodiments, the internal resistance of the battery cell can also be used to screen the target battery cell. The battery cell with a larger moisture value tends to have a higher internal resistance, because the moisture will react with the lithium salt in the electrolyte to form a non-conductive SEI film, which increases the resistance of the battery cell. Therefore, by measuring the internal resistance of the battery cell, the battery cell with a higher moisture value can be indirectly screened out.

[0071] In some embodiments, the battery cell in the battery cell carrier is subjected to a preset process, comprising the following steps:

[0072] Step S301, performing a first preset process on the battery cell in the battery cell carrier;

[0073] Step S302, detecting the current moisture value of the target battery cell;

[0074] Step S303, when the current moisture value of the target battery cell is greater than the preset moisture value, performing a second preset process on the battery cell in the battery cell carrier, wherein the first preset process is one of the second liquid injection process and the pre-charging process, and the second preset process is the other of the second liquid injection process and the pre-charging process;

[0075] Step S304 , when the current moisture value of the target battery cell is less than or equal to the preset moisture value, determining to perform the formation treatment on the battery cell in the battery cell carrier.

[0076] Specifically, by detecting the current moisture value of the target battery cell and comparing it with the preset moisture value, it can be ensured that the moisture content of the battery cell is at the optimal level before formation. The setting of the preset moisture value takes into account the balance between battery performance and safety, ensuring that there is not too much moisture to cause side reactions, nor too little moisture to affect the normal formation of the SEI film. The above step dynamically determines whether to adopt the first preset treatment or the second preset treatment based on the current moisture value of the battery cell. This means that the processing flow can be adjusted according to the actual state of the battery cell. By pre-treating the battery cell (the first preset treatment or the second preset treatment), the moisture value of the battery cell can be reduced before the formation treatment, thereby reducing the generation of brown spots in the battery cell.

[0077] In some embodiments, the first preset process is the second injection process, and the second preset process is the pre-charging process.

[0078] Among them, in the above embodiment, the first preset treatment is the above second liquid injection treatment, and the above second preset treatment is the above pre-charging treatment. Combining steps S301 to S304, it can be obtained that in the above embodiment, the second liquid injection treatment is first performed on the battery cell, and then the pre-charging treatment is performed on the battery cell. Performing the second liquid injection treatment on the battery cell first can first physically treat the battery cell. If the moisture value of the battery cell is reduced to below the preset moisture value after the second liquid injection treatment, the pre-charging treatment of the battery cell is not required, thereby avoiding the slight influence of the charging treatment on the chemical reaction in the battery cell.

[0079] In addition, after the injection, bubbles may remain inside the battery cell, which will affect the internal environment of the battery cell and reduce the uniformity of the electrolyte distribution. Pre-charging the battery cell after the second injection treatment can promote a slight chemical reaction inside the battery cell, which helps to eliminate the bubbles inside the battery cell and optimize the electrolyte distribution, thereby improving the overall performance and consistency of the battery cell.

[0080] In some optional embodiments, there is no limit on the number of times the first preset processing and the second preset processing are performed, that is, the current moisture value of the target battery cell is detected after each preset processing (the first preset processing or the second preset processing), and when the current moisture value of the target battery cell is greater than the preset moisture value, the preset processing (the first preset processing or the second preset processing) is continued to be performed on the battery cell until the current moisture value of the target battery cell is less than or equal to the preset moisture value, then the preset processing of the battery cell is stopped and the formation processing of the battery cell is started.

[0081] It should be noted that the first preset processing can be set as the above-mentioned second liquid injection processing, and the above-mentioned second preset processing can be set as the above-mentioned pre-charging processing, or the first preset processing can be set as the above-mentioned pre-charging processing, and the above-mentioned second preset processing can be set as the above-mentioned second liquid injection processing. The types of the first preset processing and the second preset processing are not limited here. Moreover, when the battery cell is subjected to this preset processing, the first preset processing can be performed multiple times first, and then the second preset processing can be performed multiple times, or the second preset processing can be performed multiple times first, and then the first preset processing can be performed multiple times, or the first preset processing and the second preset processing can be performed alternately.

[0082] Wherein, when the preset treatment includes performing a second liquid injection treatment on the battery cell, and before performing a first liquid injection treatment on the battery cell in the battery cell carrier, the method further includes the following steps:

[0083] Step S401, determining the saturated liquid absorption amount of the battery cell;

[0084] Step S402, determining a first injection volume and a second injection volume according to the saturated liquid absorption volume of the above-mentioned battery cell, wherein the first injection volume is the injection volume of the electrolyte used when the above-mentioned battery cell is subjected to the above-mentioned first injection treatment, and the second injection volume is the injection volume of the electrolyte used when the above-mentioned battery cell is subjected to the above-mentioned second injection treatment.

[0085] Specifically, the saturated liquid absorption of the battery cell refers to the maximum volume of electrolyte that the battery cell can absorb when it is fully soaked. Determining the injection volume of the two stages based on this volume can ensure that the positive and negative electrodes, diaphragms and other components inside the battery cell are fully soaked, but not excessively, thus avoiding waste of electrolyte and possible safety issues.

[0086] In some embodiments, the first injection amount is the sum of the saturated liquid absorption amount of the battery cell and the first preset value, and the second injection amount is pre-set. That is, if the saturated liquid absorption amount of the battery cell is 840g, and the amount of electrolyte actually to be injected into the battery cell is 1000g, then the first preset value can be set to 20g, that is, the first injection amount can be 860g, and the second injection amount can be set to 100g, that is, 860g is injected in the first injection treatment, and 100g is injected in the second injection treatment, and a total of 960g is injected, then the remaining 40g is injected after the battery cell is formed. The amount of electrolyte injected after the battery cell is formed is related to the first injection amount and the second injection amount. The larger the first injection amount and the second injection amount, the smaller the amount of electrolyte injected after the battery cell is formed, and the smaller the first injection amount and the second injection amount, the larger the amount of electrolyte injected after the battery cell is formed, that is, the electrolyte injected after the battery cell is formed only needs to be injected with the difference between the current injection amount and 1000g. It should be noted that the first injection amount and the second injection amount are not limited to the above values ​​and can be adjusted according to actual conditions, but the first injection amount must be greater than the saturated liquid absorption amount of the battery cell.

[0087] Wherein, in the case where the preset process includes pre-charging the battery cell, the preset process is performed on the battery cell in the battery cell carrier, comprising the following steps:

[0088] Step S501, determining the reaction film forming potential of the battery cell, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte, wherein the first electrolyte is the electrolyte used in the first liquid injection process, and the second electrolyte is the electrolyte used in the second liquid injection process;

[0089] Step S502, determining a charging voltage for the pre-charging process according to a reaction film forming potential of the battery cell, a reaction potential of each substance in the first electrolyte, and a reaction potential of each substance in the second electrolyte, wherein the charging voltage for the pre-charging process is less than the reaction film forming potential of the battery cell, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte;

[0090] Step S503 , using the charging voltage to pre-charge the battery cells in the battery cell carrier.

[0091] Specifically, the reaction film forming potential refers to the potential level at which lithium ions can form a SEI film on the surface of the negative electrode. Different substances in the electrolyte have different reaction potentials. If the pre-charge voltage is too high, it may trigger the decomposition reaction of other substances in the electrolyte. By controlling the pre-charge voltage below the reaction film forming potential, it is possible to reduce the moisture in the battery cell while ensuring that no unnecessary chemical reactions occur in the battery cell, thereby ensuring the stability and safety of the battery.

[0092] In some embodiments, the charging voltage of the pre-charging process is a preset value. For example, the reaction film forming potential of the battery cell, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte are all in the range of 2.5V~3V, then the charging voltage is set to 1.3V~2.5V.

[0093] The step of performing a chemical treatment on the battery cell in the battery cell carrier comprises the following steps:

[0094] Step S601, obtaining the rated capacity of the battery cell in the battery cell carrier;

[0095] Step S602, determining a constant current according to the rated capacity of the battery cell, wherein the constant current is less than the rated capacity of the battery cell;

[0096] Step S603 , using the constant current to charge the battery cell in the battery cell carrier to perform a formation process on the battery cell.

[0097] Specifically, the formation process is a key step in the manufacture of lithium-ion batteries, mainly to form the SEI (Solid Electrolyte Interface) film. The SEI film is a protective layer formed on the surface of the negative electrode, which is crucial to the performance and life of the battery. Small current formation can ensure the uniform deposition of lithium ions, forming a more uniform and stable SEI film. When the SEI film is well formed, it can effectively prevent the further decomposition of solvent molecules in the electrolyte, thereby reducing the generation of brown spots. In addition, during high current formation, local overheating may occur inside the battery, which will accelerate the decomposition of the electrolyte and the occurrence of side reactions, leading to the formation of brown spots and other deposits. Small current formation can avoid local overheating, reduce side reactions, and thus reduce the generation of brown spots.

[0098] In some embodiments, the constant current is 0.02-0.2C, where C is the rated capacity of the battery cell.

[0099] For example, if the rated capacity of a battery is 1000mAh (1Ah), then the formation current of 0.1C is 100mA, and the formation current of 0.5C is 500mA. The specific current setting also depends on the manufacturer's process requirements, formation time, and considerations for battery performance and safety. Usually, the formation process is divided into multiple stages, and different current and voltage settings may be used in different stages.

[0100] Specifically, 0.02~0.2C is a relatively small current, that is, a small current is used to perform the formation treatment on the above-mentioned battery cell, and the lithium ion deposition rate is slow, which helps the lithium ions to deposit evenly on the negative electrode surface, avoiding side reactions caused by excessive local concentration, such as the precipitation of metallic lithium, and thus reducing the generation of brown spots. In addition, the small current formation provides a relatively mild electrochemical environment, which helps to control the reaction rate inside the battery cell, reduce local overheating, avoid electrolyte decomposition and the generation of harmful substances under high temperature conditions, and effectively reduce the brown spots of the battery cell.

[0101] The battery cells in the battery cell carrier are subjected to a preset process, including:

[0102] Determining the cell type of the cell in the cell carrier;

[0103] Determining the number of times the preset treatment is performed on the battery cell according to the battery cell type of the battery cell and the current moisture value of the target battery cell;

[0104] In the case where the cell type of the cell is a lithium supplemented cell, determining that the number of times the preset processing is performed on the cell is the first number; wherein the number of preset processing is the total number of the first preset processing and the second preset processing;

[0105] In the case that the cell type of the cell is a non-lithium supplemented cell, determining that the number of times the preset process is performed on the cell is a second number, wherein the first number is greater than the second number;

[0106] The first number or the second number of preset processes are performed on the battery cells in the battery cell carrier.

[0107] Specifically, since the cell properties of lithium-supplemented cells and non-lithium-supplemented cells are known, lithium-supplemented cells are more likely to produce brown spots. Therefore, when other conditions are the same, the number of preset treatments implemented on lithium-supplemented cells is greater than the number of preset treatments implemented on non-lithium-supplemented cells, so as to better reduce the moisture value of lithium-supplemented cells, thereby better reducing the brown spots of lithium-supplemented cells. Commonly used lithium supplements include metallic lithium, lithium alloys, and lithium compounds. The choice of which lithium supplement depends on the design of the battery, the required electrochemical properties, and the production process.

[0108] The beneficial effects of the present application will be further illustrated below in conjunction with embodiments.

[0109] Example 1

[0110] A secondary battery was prepared using the first target battery cell, the first target battery cell was a lithium-supplemented battery cell, the lithium supplement agent used was metallic lithium, and the lithium supplement amount was 10 mAh / g. The first target battery cell was sequentially subjected to a first liquid injection treatment, a high-temperature static treatment, a second liquid injection treatment, and a normal current formation treatment to prepare a secondary battery. The first liquid injection treatment used an electrolyte with a moisture value of 90 ppm for liquid injection, and the second liquid injection treatment used an electrolyte with a moisture value of 4 ppm for liquid injection. The current used in the normal current formation treatment was 0.5 C, and the secondary battery finally prepared had circular brown spots with a diameter of 4 mm.

[0111] Example 2

[0112] A secondary battery is prepared by using the first target battery cell, the first target battery cell is a lithium supplement battery cell, the lithium supplement agent used is metallic lithium, the lithium supplement amount is 10 mAh / g, the first target battery cell is sequentially subjected to the first liquid injection treatment, high temperature static treatment, second liquid injection treatment, pre-charge treatment, and normal current formation treatment to prepare a secondary battery, the first liquid injection treatment uses an electrolyte with a moisture value of 90ppm for liquid injection, the second liquid injection treatment uses an electrolyte with a moisture value of 4ppm for liquid injection, the first target battery cell is charged for five minutes with a 0.1C current during the pre-charge treatment, and the current used during the normal current formation treatment is 0.5C, and the secondary battery finally prepared has a circular brown spot with a diameter of 3mm. Among them, the difference between Example 2 and Example 1 is that Example 2 has one more pre-charge treatment step than Example 1.

[0113] Example 3

[0114] A secondary battery is prepared using the first target battery cell, the first target battery cell is a lithium supplement battery cell, the lithium supplement agent used is metallic lithium, the lithium supplement amount is 10 mAh / g, the first target battery cell is sequentially subjected to a first liquid injection treatment, a high temperature static treatment, a second liquid injection treatment, a pre-charge treatment, and a small current formation treatment to prepare a secondary battery, the first liquid injection treatment uses an electrolyte with a moisture value of 90ppm for liquid injection, the second liquid injection treatment uses an electrolyte with a moisture value of 4ppm for liquid injection, the first target battery cell is charged for five minutes with a 0.1C current during the pre-charge treatment, the current used during the small current formation treatment is 0.02C, and the secondary battery finally prepared has a circular brown spot with a diameter of 1mm or no brown spot. Among them, the difference between Example 3 and Example 2 is only that Example 3 uses a small current formation treatment, while Example 2 uses a normal current formation treatment.

[0115] Comparative Example 1

[0116] A secondary battery is prepared using the first target battery cell, the first target battery cell is a lithium supplement battery cell, the lithium supplement agent used is metallic lithium, the lithium supplement amount is 10 mAh / g, the first target battery cell is sequentially subjected to a first liquid injection treatment, a high temperature static treatment, and a normal current formation treatment to prepare a secondary battery, the formation current used in the above-mentioned normal current formation treatment is 0.5C, and the secondary battery finally prepared has a circular brown spot with a diameter of 7 mm. Among them, the difference between Comparative Example 1 and Examples 1, 2, and 3 is that the second liquid injection treatment, the pre-charging treatment, and the small current formation treatment are not used.

[0117] Example 4

[0118] A secondary battery is prepared using the second target battery cell, which is a non-lithium-supplemented battery cell. The second target battery cell is sequentially subjected to a first liquid injection treatment, a high-temperature static treatment, a second liquid injection treatment, and a normal current formation treatment to prepare a secondary battery. The first liquid injection treatment uses an electrolyte with a moisture content of 90 ppm for liquid injection, and the second liquid injection treatment uses an electrolyte with a moisture content of 4 ppm for liquid injection. The current used in the normal current formation treatment is 0.5 C, and the secondary battery finally prepared has circular brown spots with a diameter of 3 mm.

[0119] Example 5

[0120] A secondary battery is prepared by using the second target battery cell, which is a non-lithium supplemented battery cell. The second target battery cell is sequentially subjected to a first liquid injection treatment, a high-temperature static treatment, a second liquid injection treatment, a pre-charge treatment, and a normal current formation treatment to prepare a secondary battery. The first liquid injection treatment uses an electrolyte with a moisture value of 90ppm for liquid injection, and the second liquid injection treatment uses an electrolyte with a moisture value of 4ppm for liquid injection. During the pre-charge treatment, a 0.1C current is used to charge the first target battery cell for five minutes, and a current of 0.5C is used during the normal current formation treatment. The secondary battery finally prepared has a circular brown spot with a diameter of 1mm or no brown spot. Among them, the difference between Example 5 and Example 4 is that Example 5 has an additional pre-charge treatment step compared with Example 4.

[0121] Example 6

[0122] A secondary battery is prepared by using the second target battery cell, which is a non-lithium supplemented battery cell. The second target battery cell is sequentially subjected to a first liquid injection treatment, a high-temperature static treatment, a second liquid injection treatment, a pre-charging treatment, and a small current formation treatment to prepare a secondary battery. The first liquid injection treatment uses an electrolyte with a moisture value of 90ppm for liquid injection, and the second liquid injection treatment uses an electrolyte with a moisture value of 4ppm for liquid injection. During the pre-charging treatment, a 0.1C current is used to charge the first target battery cell for five minutes, and a current of 0.02C is used during the small current formation treatment. The secondary battery finally prepared has no brown spots. Among them, the difference between Example 6 and Example 5 is that Example 6 uses a small current formation treatment, while Example 5 uses a normal current formation treatment.

[0123] Comparative Example 2

[0124] A secondary battery is prepared by using the second target battery cell, the second target battery cell is a non-lithium supplemented battery cell, and the second target battery cell is sequentially subjected to a first liquid injection treatment, a high temperature static treatment, and a normal current formation treatment to prepare a secondary battery, the formation current used in the above-mentioned normal current formation treatment is 0.5C, and the secondary battery finally prepared has a circular brown spot with a diameter of 6mm. Among them, the difference between Comparative Example 2 and Example 4, Example 5, and Example 6 is that the second liquid injection treatment, the pre-charging treatment, and the low current formation treatment are not used.

[0125] The comparison results of the final embodiment and the comparative example are shown in Table 1:

[0126] Table 1. Comparison results of the embodiments and comparative examples

[0127]

[0128] It can be seen from Table 1 that when the types of target cells are the same, the more preset treatments (secondary liquid injection before formation, pre-charging treatment) and low-current formation processes are used, the fewer brown spots on the cells; and when the preset treatments (secondary liquid injection before formation, pre-charging treatment) and low-current formation processes are the same, it is more difficult to remove moisture from lithium-supplemented cells than non-lithium-supplemented cells, and more brown spots are produced accordingly.

[0129] In some other embodiments, after the battery cell in the battery cell carrier is subjected to a formation treatment to obtain a secondary battery, the method further comprises the following steps:

[0130] Step S701, obtaining the brown spot condition of the secondary battery, wherein the brown spot condition at least includes the number and size of the brown spots of the secondary battery;

[0131] Step S702, determining the preset moisture value for preparing the secondary battery next time according to the brown spot condition of the secondary battery and the preset moisture value.

[0132] Specifically, the above steps can determine the size of the above preset moisture value when preparing the above secondary battery next time according to the preset moisture value used this time and the corresponding brown spot situation of the secondary battery, so that a more accurate preset moisture value can be set, thereby more effectively improving the brown spot situation of the battery cell in the subsequent production process. For example, the preset moisture value prepared this time is 50ppm, but the prepared secondary battery has a small amount of brown spots, then the preset moisture value needs to be reduced accordingly in the next preparation.

[0133] According to the brown spot condition of the secondary battery and the preset moisture value, determining the preset moisture value when preparing the secondary battery next time comprises the following steps:

[0134] Step S7021, calculating the brown spot coverage rate of the secondary battery according to the number and size of the brown spots of the secondary battery;

[0135] Step S7022, when the brown spot coverage of the secondary battery is less than or equal to the preset coverage, determining the preset moisture value when preparing the secondary battery this time as the preset moisture value when preparing the secondary battery next time;

[0136] Step S7023, when the brown spot coverage of the above-mentioned secondary battery is greater than the above-mentioned preset coverage, determine the above-mentioned preset moisture value when preparing the above-mentioned secondary battery next time according to the above-mentioned preset moisture value when preparing the above-mentioned secondary battery this time, wherein the above-mentioned preset moisture value when preparing the above-mentioned secondary battery next time is smaller than the above-mentioned preset moisture value when preparing the above-mentioned secondary battery this time.

[0137] Specifically, by monitoring the brown spot coverage of the secondary battery, the preset moisture value for the next production is automatically adjusted. This method can dynamically optimize the moisture content based on feedback data from actual production, avoid battery performance problems caused by setting too much or too little preset moisture value, and ensure that moisture management is always in the best state. Traditional moisture control may be based on empirical values, and this closed-loop adjustment mechanism provides a more precise process control method by quantifying the relationship between brown spot coverage and moisture value, helping manufacturers to more accurately determine the boundaries of moisture control and optimize the production process.

[0138] An embodiment of the present application further provides a secondary battery, and the secondary battery is prepared by any one of the above-mentioned secondary battery preparation methods.

[0139] The above-mentioned secondary battery is prepared by adopting any one of the above-mentioned secondary battery preparation methods. Since the above-mentioned preparation method detects the moisture in the battery cell after the high-temperature standing of the first liquid injection treatment, further monitors the moisture in the battery cell, and timely reduces the moisture content of the battery cell when the moisture content of the battery cell is too high, it is ensured that the moisture value of the battery cell is not too high, thereby ensuring that the manufactured battery has fewer brown spots, which solves the problem that the existing battery preparation method easily causes brown spots on the prepared battery cell, thereby causing the battery performance to decline. Therefore, the secondary battery prepared by the above-mentioned preparation method has fewer brown spots.

[0140] An embodiment of the present application further provides an energy storage system, comprising: at least one of the above-mentioned secondary batteries.

[0141] In energy storage systems, battery consistency is critical to system performance. Reducing the number of brown spots helps reduce differences in battery performance, improves the overall consistency of the battery pack, and ensures the stability and smoothness of the system during charging and discharging. The above energy storage system uses secondary batteries with fewer brown spots. Batteries with fewer brown spots have longer life and higher efficiency, which not only reduces the replacement cost of the battery itself, but also reduces the system adjustment and optimization costs caused by battery performance fluctuations, thereby reducing the overall operating cost of the energy storage system.

[0142] In summary, fewer brown spots on secondary batteries mean longer service life, higher energy efficiency, more stable operation, lower safety risks, better charge and discharge performance, better battery pack consistency and more economical system cost for energy storage systems. These factors work together to significantly improve the reliability and economic benefits of energy storage systems.

[0143] An embodiment of the present application further provides an electrical device, comprising: at least one of the above-mentioned secondary batteries or the above-mentioned energy storage system.

[0144] Among them, the reliability of the battery directly affects the overall reliability of electronic equipment. Fewer brown spots means that the battery performs more stably under various environmental conditions, reduces the failure rate of electronic equipment caused by battery failure, and improves the durability and reliability of the equipment. Using secondary batteries with fewer brown spots to make electronic equipment can significantly improve the performance, safety and reliability of the equipment, extend the service life of the equipment, reduce maintenance costs, and be more environmentally friendly, in line with the concept of green manufacturing and sustainable development.

[0145] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0146] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0147] 1) The preparation method of the above-mentioned secondary battery of the present application first performs a first liquid injection treatment and a high-temperature static treatment on the battery cells in the battery cell carrier; after the high-temperature static treatment, the current moisture value of the target battery cell is detected; when the current moisture value of the target battery cell is greater than the preset moisture value, the battery cells in the battery cell carrier are subjected to a second liquid injection treatment and / or a pre-charging treatment, so that the moisture value of the battery cells in the battery cell carrier is less than or equal to the preset moisture value; finally, the battery cells in the battery cell carrier are subjected to a formation treatment to obtain a secondary battery. The method further monitors the moisture content in the battery cells by detecting the moisture content in the battery cells after the high-temperature static treatment of the first liquid injection treatment, and timely performs a moisture reduction treatment on the battery cells when the moisture content of the battery cells is too high, so as to ensure that the moisture value of the battery cells is not too high, thereby ensuring that the manufactured battery has fewer brown spots, solving the problem that the existing battery preparation method easily causes brown spots in the prepared battery cells, thereby causing a decrease in battery performance.

[0148] 2) The above-mentioned secondary battery of the present application is prepared by adopting any one of the above-mentioned secondary battery preparation methods. Since the above-mentioned preparation method detects the moisture in the battery cell after the high-temperature standing of the first liquid injection treatment, further monitors the moisture in the battery cell, and timely reduces the moisture content of the battery cell when the moisture content of the battery cell is too high, it is ensured that the moisture value of the battery cell is not too high, thereby ensuring that the manufactured battery has fewer brown spots, which solves the problem that the existing battery preparation method easily causes brown spots on the prepared battery cell, thereby causing the battery performance to deteriorate. Therefore, the secondary battery prepared by the above-mentioned preparation method has fewer brown spots.

[0149] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a secondary battery, characterized in that: include: Performing a first liquid injection treatment on the battery cells in the battery cell carrier, and performing a high-temperature static treatment on the battery cells in the battery cell carrier after performing the first liquid injection treatment; After the battery cells are subjected to the high-temperature static treatment for a preset period of time, detecting current moisture values ​​of target battery cells, wherein the target battery cells are some of the battery cells in the battery cell carrier; When the current moisture value of the target battery cell is greater than a preset moisture value, performing a preset process on the battery cell in the battery cell carrier so that the moisture value of the battery cell in the battery cell carrier is less than or equal to the preset moisture value; Performing a formation treatment on the battery cell in the battery cell carrier to obtain a secondary battery; The preset processing includes at least one of the following: Performing a second liquid injection treatment on the battery cell, wherein the moisture value of the electrolyte used when performing the first liquid injection treatment on the battery cell in the battery cell carrier is greater than the moisture value of the electrolyte used when performing the second liquid injection treatment on the battery cell in the battery cell carrier; The battery cell is pre-charged.

2. The method for preparing a secondary battery according to claim 1, characterized in that: Before performing the first liquid injection process on the battery cells in the battery cell carrier, the method further includes: Obtaining basic parameters of each of the battery cells in the battery cell carrier, wherein the basic parameters of the battery cells include the weight of the battery cells and the thickness of the battery cells, and the thickness of the battery cells is positively correlated with the width of the electrolyte channel of the battery cells; Determine the battery cell whose weight is greater than or equal to a preset weight as the target battery cell, and / or determine the battery cell whose thickness is less than or equal to a preset thickness as the target battery cell; The target battery cell is installed at a preset detection position of the battery cell carrier, where the preset detection position is a position in the battery cell carrier where the moisture value of the battery cell can be detected.

3. The method for preparing a secondary battery according to claim 1, characterized in that: Performing a preset process on the battery cell in the battery cell carrier includes: Performing a first preset process on the battery cell in the battery cell carrier; Detecting the current moisture value of the target battery cell; When the current moisture value of the target battery cell is greater than the preset moisture value, performing a second preset process on the battery cell in the battery cell carrier, wherein the first preset process is one of the second liquid injection process and the pre-charging process, and the second preset process is the other of the second liquid injection process and the pre-charging process; When the current moisture value of the target battery cell is less than or equal to the preset moisture value, it is determined to perform the formation treatment on the battery cell in the battery cell carrier.

4. The method for preparing a secondary battery according to claim 3, characterized in that: The first preset process is the second liquid injection process, and the second preset process is the pre-charging process.

5. The method for preparing a secondary battery according to claim 1, characterized in that: In the case where the preset treatment includes performing a second liquid injection treatment on the battery cell, and before performing a first liquid injection treatment on the battery cell in the battery cell carrier, the method further includes: Determining the saturated liquid absorption of the battery cell; The first injection amount and the second injection amount are determined according to the saturated liquid absorption amount of the battery cell, wherein the first injection amount is the injection amount of the electrolyte used when the battery cell is subjected to the first injection treatment, and the second injection amount is the injection amount of the electrolyte used when the battery cell is subjected to the second injection treatment.

6. The method for preparing a secondary battery according to claim 1, characterized in that: In the case where the preset process includes pre-charging the battery cell, the preset process is performed on the battery cell in the battery cell carrier, including: Determining a reaction film forming potential of the battery cell, a reaction potential of each substance in a first electrolyte, and a reaction potential of each substance in a second electrolyte, wherein the first electrolyte is an electrolyte used in the first liquid injection treatment, and the second electrolyte is an electrolyte used in the second liquid injection treatment; Determine the charging voltage of the pre-charging process according to the reaction film forming potential of the battery cell, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte, wherein the charging voltage of the pre-charging process is less than the reaction film forming potential of the battery cell, the reaction potential of each substance in the first electrolyte, and the reaction potential of each substance in the second electrolyte; The charging voltage is used to pre-charge the battery cell in the battery cell carrier.

7. The method for preparing a secondary battery according to claim 1, characterized in that: Performing a preset process on the battery cell in the battery cell carrier includes: Determining the cell type of the cell in the cell carrier; Determining the number of times the preset process is performed on the battery cell according to the battery cell type of the battery cell and the current moisture value of the target battery cell; In the case where the battery cell type is a lithium supplemented battery cell, determining that the number of times the preset processing is performed on the battery cell is the first number; In the case where the cell type of the cell is a non-lithium supplemented cell, determining that the number of times the preset process is performed on the cell is a second number, wherein the first number is greater than the second number; The preset process is performed on the battery cell in the battery cell carrier for the first or second times.

8. The method for preparing a secondary battery according to claim 1, characterized in that: Performing a formation treatment on the battery cell in the battery cell carrier comprises: Obtaining the rated capacity of the battery cell in the battery cell carrier; Determining a constant current according to the rated capacity of the battery cell, wherein the constant current is less than the rated capacity of the battery cell; The constant current is used to charge the battery cell in the battery cell carrier to perform a formation process on the battery cell.

9. The method for preparing a secondary battery according to claim 8, characterized in that: The constant current is 0.02~0.2C, where C is the rated capacity of the battery cell.

10. The method for preparing a secondary battery according to claim 1, characterized in that: After the battery cell in the battery cell carrier is subjected to a formation treatment to obtain a secondary battery, the method further comprises: Acquiring a brown spot condition of the secondary battery, wherein the brown spot condition at least includes the number and size of the brown spots of the secondary battery; The preset moisture value when preparing the secondary battery next time is determined according to the brown spot condition of the secondary battery and the preset moisture value.

11. The method for preparing a secondary battery according to claim 10, characterized in that: Determining the preset moisture value when preparing the secondary battery next time according to the brown spot condition of the secondary battery and the preset moisture value comprises: Calculating the brown spot coverage rate of the secondary battery according to the number and size of the brown spots of the secondary battery; When the brown spot coverage of the secondary battery is less than or equal to the preset coverage, the preset moisture value when preparing the secondary battery this time is determined as the preset moisture value when preparing the secondary battery next time; When the brown spot coverage of the secondary battery is greater than the preset coverage, the preset moisture value for preparing the secondary battery next time is determined according to the preset moisture value for preparing the secondary battery this time, wherein the preset moisture value for preparing the secondary battery next time is smaller than the preset moisture value for preparing the secondary battery this time.

12. The method for preparing a secondary battery according to claim 1, characterized in that: Detect the current moisture value of the target battery cell, including: Detecting the moisture value of the gas in the target battery cell at the current moment to obtain the moisture value of the gas; According to the gas moisture value of the target battery cell at the current moment, the electrolyte moisture value of the target battery cell at the current moment is determined to obtain the current moisture value of the target battery cell, wherein the gas moisture value of the target battery cell is positively correlated with the electrolyte moisture value of the target battery cell.

13. The method for preparing a secondary battery according to claim 1, characterized in that: The preset moisture value is 50ppm~55ppm.

14. A secondary battery, characterized in that: The secondary battery is prepared by the method for preparing a secondary battery according to any one of claims 1 to 13.

15. An energy storage system, characterized in that: include: At least one secondary battery as claimed in claim 14.

16. An electrical equipment, characterized in that: include: At least one secondary battery according to claim 14 or the energy storage system according to claim 15.

Images