Preparation Method and Equipment of Secondary Battery, Secondary Battery and Energy Storage System

Abstract

This application belongs to the field of energy storage technologies, and provides a preparation method of a secondary battery, a preparation device, the secondary battery, and an energy storage system. The preparation method includes: a winding treatment process; a liquid injection process, applying a first positive pressure and a first negative pressure alternately and cyclically to a liquid injection container located above an initial battery cell to inject an electrolyte into the corresponding initial battery cell, and detecting the liquid level of the electrolyte, determining whether the liquid injection is completed according to the liquid level of the electrolyte, if the liquid injection is completed, performing a primary infiltration process, if the liquid injection is not completed, performing a preset operation; performing a primary infiltration process on the initial battery cell after the liquid injection is completed, the steps of the primary infiltration process including applying a second positive pressure and a second negative pressure alternately and cyclically to the initial battery cell to perform primary battery cell infiltration; after the primary battery cell infiltration ends, moving the initial battery cell to a static storage, and performing a secondary infiltration process in the static storage. It solves the problem that the risk of battery cell deformation caused by a relatively high positive pressure in the positive and negative pressure cycle of the equal-pressure liquid injection process is increased.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and in particular, to a preparation method of a secondary battery, a preparation device of a secondary battery, a secondary battery, an energy storage system and an electrical device. Background Art

[0002] Currently, the infiltration of batteries mainly includes two stages, the first stage of liquid injection and the second stage of high-temperature standing before formation. Among them, the effect of the first stage of liquid injection directly affects the time of high-temperature infiltration and has an accelerating effect on the entire infiltration process. Currently, equal-pressure liquid injection is mostly used in the first stage of liquid injection.

[0003] In the equal-pressure liquid injection process, the battery is often evacuated first, and then liquid is injected under a vacuum state. Due to the negative pressure difference, the electrolyte will automatically "flow" into the battery core. Then, the infiltration of the electrolyte in the battery core is realized through positive and negative pressure cycling. The positive and negative pressures applied in this positive and negative pressure cycling are high positive pressures, and the relatively high positive pressure increases the risk of battery core deformation. Summary of the Invention

[0004] The main purpose of the present application is to provide a preparation method of a secondary battery, a preparation device of a secondary battery, a secondary battery, an energy storage system and an electrical device, so as to at least solve the problem that the relatively high positive pressure in the positive and negative pressure cycling of the equal-pressure liquid injection process increases the risk of battery core deformation.

[0005] To achieve the above object, according to the first aspect of the present application, a preparation method of a secondary battery is provided, including: winding a positive electrode sheet, a negative electrode sheet and a separator, and then placing them in a housing to form an initial battery core, where the separator is located between the positive electrode sheet and the negative electrode sheet; performing a liquid injection process on the initial battery core, in the steps of the liquid injection process, alternately and cyclically applying a first positive pressure and a first negative pressure to a liquid injection container located above the initial battery core to inject the electrolyte into the corresponding initial battery core, and detecting the liquid level of the electrolyte, determining whether the liquid injection is completed according to the liquid level of the electrolyte, if the liquid injection is completed, performing a primary infiltration process, if the liquid injection is not completed, performing a preset operation, where the liquid injection container is a container for injecting the electrolyte into the initial battery core and containing the electrolyte; performing the primary infiltration process on the initial battery core after the liquid injection is completed, the steps of the primary infiltration process including alternately and cyclically applying a second positive pressure and a second negative pressure to the initial battery core to perform primary battery core infiltration, where the second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure, applying a positive pressure to make the internal pressure higher than the external pressure, applying a negative pressure to achieve vacuum pumping, the positive pressure includes the first positive pressure and the second positive pressure, and the negative pressure includes the first negative pressure and the second negative pressure; after the primary battery core infiltration is completed, moving the initial battery core to a standing warehouse and performing a secondary infiltration process in the standing warehouse.

[0006] Optionally, a plurality of the initial battery cells are placed on the battery cell carrier, and determining whether the liquid injection is completed according to the liquid level of the electrolyte includes: determining a target battery cell, where the target battery cell is the initial battery cell with the slowest liquid injection speed among the plurality of initial battery cells under the same liquid injection conditions; detecting the liquid level of the target electrolyte, where the target electrolyte is the electrolyte injected into the target battery cell; if the liquid level of the target electrolyte drops below the liquid injection hole, it is determined that the liquid injection of the target battery cell is completed, and the completion of the liquid injection of the target battery cell indicates that the liquid injection of all the initial battery cells on the battery cell carrier is completed, where the liquid injection hole is located on the top cover of the target battery cell.

[0007] Optionally, determining the target battery cell includes: if the weight difference between two battery cells among all the initial battery cells on the battery cell carrier is greater than a preset weight difference, determining the initial battery cell with the largest weight as the target battery cell; if the weight difference between any two battery cells among all the initial battery cells on the battery cell carrier is less than or equal to the preset weight difference, determining the initial battery cell with the smallest thickness among all the initial battery cells on the battery cell carrier as the target battery cell.

[0008] Optionally, during the process of determining whether the liquid injection is completed according to the liquid level of the electrolyte, it further includes: when the liquid level of the target electrolyte is above the liquid injection hole, extending the duration of applying the first positive pressure and / or the first negative pressure to all the liquid injection containers until the liquid level of the target electrolyte is below the liquid injection hole.

[0009] Optionally, detecting the liquid level of the electrolyte includes: acquiring a liquid level image, where the liquid level image is obtained by photographing using a first image acquisition module; determining the liquid level of the electrolyte according to the liquid level image.

[0010] Optionally, the method further includes: during the liquid injection process, determining whether the initial battery cell is deformed according to the side image of the battery cell. If the initial battery cell is deformed, determining the amount of deformation of the deformed initial battery cell to obtain a first amount of battery cell deformation, where the side image of the battery cell is obtained by photographing using a second image acquisition module; determining a reduction amount of the first positive pressure corresponding to the first amount of battery cell deformation, and reducing the first positive pressure according to the reduction amount of the first positive pressure, where there is a positive correlation between the first amount of battery cell deformation and the reduction amount of the first positive pressure.

[0011] Optionally, the method further includes: in the first infiltration process, determining whether the initial battery cell is deformed according to the side image of the battery cell; if the initial battery cell is deformed, determining the deformation amount of the deformed initial battery cell to obtain a second battery cell deformation amount; determining a duration increment of applying the first positive pressure and / or a duration increment of the first negative pressure corresponding to the second battery cell deformation amount, and increasing the first positive pressure and / or the first negative pressure according to the duration increment, and applying the increased first positive pressure and / or the increased first negative pressure to the preparation process of the secondary battery again, wherein there is a positive correlation between the duration increment of the first positive pressure, the duration increment of the first negative pressure and the second battery cell deformation amount respectively.

[0012] Optionally, the pressure value range of the first positive pressure is 0.3~0.4 Mpa, the pressure value range of the first negative pressure is -65~-55 Kpa, the pressure value range of the second positive pressure is 0.75~0.85 Mpa, and the pressure value range of the second negative pressure is -85~-75 Kpa.

[0013] According to a second aspect of the present application, there is provided a preparation device for a secondary battery, including: a winding and encapsulation mechanism for winding a positive electrode sheet, a negative electrode sheet and a separator and then placing them into a housing to form an initial battery cell; a liquid injection mechanism including a liquid injection tank, a pressurizing structure and a first image acquisition module, wherein the liquid injection tank is internally provided with a liquid injection container, and in the liquid injection process, the pressurizing structure alternately and cyclically applies a first positive pressure and a first negative pressure to the liquid injection container to inject electrolyte into the corresponding initial battery cell, wherein the liquid injection container is a container for injecting liquid into the initial battery cell and containing the electrolyte, and in the first infiltration process after the liquid injection is completed, the pressurizing structure alternately and cyclically applies a second positive pressure and a second negative pressure to the initial battery cell to perform primary battery cell infiltration, and the first image acquisition module is used to acquire a liquid level image, and the liquid level image indicates the liquid level of the electrolyte, wherein the second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure; a static storage library, after the primary battery cell infiltration is completed, the initial battery cell is moved to the static storage library, and a secondary infiltration process is performed in the static storage library.

[0014] Optionally, the liquid injection mechanism further includes a second image acquisition module, and the second image acquisition module is used to acquire a side image of the battery cell.

[0015] According to a third aspect of the present application, there is provided a secondary battery, which is prepared by using any one of the preparation methods of the secondary battery, or the secondary battery is prepared by using any one of the preparation devices of the secondary battery.

[0016] According to a fourth aspect of the present application, an energy storage system is provided, which includes a plurality of the secondary batteries.

[0017] According to a fifth aspect of the present application, an electrical device is provided, which includes the secondary battery or the energy storage system.

[0018] The beneficial effects of the present application are as follows: Through the winding process, the liquid injection process, the first infiltration process, and the second infiltration process, the liquid injection and infiltration of the initial battery cells are realized. And under the combined action of the first positive pressure and the first negative pressure in the liquid injection process and the second positive pressure and the second negative pressure in the first infiltration process, better initial infiltration is achieved while reducing the risk of battery cell deformation, and further shortening the duration of the subsequent second infiltration. That is, the overall duration of battery cell infiltration is shortened. Description of the Drawings

[0019] The schematic diagrams of the drawings forming a part of the present application are used to provide a further understanding of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0020] Figure 1 Shows a schematic flow chart of a method for manufacturing a secondary battery provided according to an embodiment of the present application;

[0021] Figure 2 Shows a schematic diagram of a manufacturing device for a secondary battery provided according to an embodiment of the present application;

[0022] Figure 3 Shows Figure 2 a partial structural schematic diagram of the manufacturing device for the secondary battery in

[0023] Among them, the above-mentioned drawings include the following reference numerals:

[0024] 01, liquid injection container; 02, initial battery cell; 21, liquid injection hole; 03, upper cover; 04, fixture tray; 05, first image acquisition module; 06, second image acquisition module. Detailed Embodiments

[0025] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0026] It should be noted that the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they specify the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element can be directly on the other element or there can also be an intermediate element. Also, in the specification and claims, when an element is described as "connected" to another element, the element can be "directly connected" to the other element or "connected" to the other element through a third element.

[0028] In order to enable those skilled in the art to better understand the solution of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0029] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0030] In the description of the embodiments of the present application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0031] In the description of the embodiments of the present application, the term "and / or" is only an associative relationship describing associated objects and indicates that three relationships can exist. For example, A and / or B can represent: the presence of A, the simultaneous presence of A and B, and the presence of B.

[0032] As introduced in the background art, in the isobaric liquid injection process, the infiltration of the electrolyte in the battery cell is realized through positive and negative pressure cycles. The positive and negative pressures applied in this positive and negative pressure cycle are high positive pressures, and the relatively high positive pressure increases the risk of deformation of the battery cell. To solve the problem that the relatively high positive pressure in the positive and negative pressure cycle of the isobaric liquid injection process increases the risk of deformation of the battery cell, the embodiments of the present application provide a method for preparing a secondary battery, a device for preparing a secondary battery, a secondary battery, an energy storage system, and an electrical device.

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

[0034] An embodiment of the present application provides a method for manufacturing a secondary battery. Figure 1 It is a flowchart corresponding to the method for manufacturing a secondary battery provided by the embodiment of the present application.

[0035] Referring to Figure 1 , the method for manufacturing a secondary battery includes:

[0036] Step S101: After winding the positive electrode sheet, the negative electrode sheet, and the separator, place them in a housing to form an initial battery cell, where the separator is located between the positive electrode sheet and the negative electrode sheet.

[0037] The positive electrode sheet may include a positive electrode current collector and a positive electrode material layer covering the surface of the positive electrode current collector. The positive electrode material layer includes a positive electrode material and a positive electrode binder, and the positive electrode material is dispersed in the positive electrode binder.

[0038] The negative electrode sheet may include a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode material and a negative electrode binder, and the negative electrode material is dispersed in the negative electrode binder.

[0039] In a specific implementation, the material of the positive electrode current collector is aluminum foil, and the material of the negative electrode current collector is copper foil.

[0040] The positive electrode material may be selected from lithium iron phosphate, lithium cobaltate, lithium manganate, or ternary materials, etc.

[0041] The negative electrode material may be selected from natural graphite, artificial graphite, soft carbon, or hard carbon, etc.

[0042] Both the positive electrode binder and the negative electrode binder may be selected from sodium carboxymethyl cellulose, polyvinylidene fluoride, or styrene-butadiene rubber.

[0043] The separator may be selected from polypropylene (PP) microporous membranes, polyethylene (PE) microporous membranes, PE / PP composite microporous membranes, copolymers of propylene and ethylene membranes, or polyethylene homopolymer membranes, etc.

[0044] The winding process is a process of sequentially laminating the positive electrode sheet, the separator, and the negative electrode sheet and then winding them into a core roll in a certain order, mainly used for producing square and cylindrical lithium batteries. The battery cells involved in the present application include square and cylindrical battery cells.

[0045] In addition to the above winding process, the initial battery cell can be formed by stacking the components and then placing them into the housing. The stacking process is an assembly method for constructing the battery cell by stacking components such as the positive electrode sheet, separator, and negative electrode sheet layer by layer. The stacking process can generally be divided into a lamination type and a folding type. Compared with the winding process, the stacking and winding process requires higher tension control. The stacking process is mainly used for the manufacture of large square batteries, ultra-thin batteries, and special-shaped batteries.

[0046] Step S102: Perform a liquid injection process on the above initial battery cell. In the steps of the liquid injection process, a first positive pressure and a first negative pressure are alternately and cyclically applied to the liquid injection container located above the above initial battery cell to inject the electrolyte into the corresponding above initial battery cell, and the liquid level of the electrolyte is detected. Whether the liquid injection is completed is determined according to the liquid level of the electrolyte. If the liquid injection is completed, a soaking process is performed once. If the liquid injection is not completed, a preset operation is executed. Among them, the above liquid injection container is a container for injecting the electrolyte into the above initial battery cell and containing the above electrolyte;

[0047] See Figure 2 , a first positive pressure and a first negative pressure are alternately and cyclically applied to the liquid injection container 01 located above the above initial battery cell 02 to inject the electrolyte into the corresponding above initial battery cell 02;

[0048] The above preset operation is an operation that causes the liquid level of the electrolyte to drop until the liquid injection is completed;

[0049] Among them, the liquid injection container can be a liquid injection cup. A hole is opened at the bottom of the liquid injection container, and a liquid injection hole is provided at the top of the initial battery cell, specifically on the top cover of the initial battery cell. After controlling the hole at the bottom of the liquid injection container to communicate with the liquid injection hole at the top of the initial battery cell, the electrolyte in the liquid injection container is injected into the corresponding initial battery cell;

[0050] See Figure 3 , a liquid injection hole 21 is provided at the top of the initial battery cell 02, specifically on the top cover of the initial battery cell 02.

[0051] Among them, the electrolyte components include: vinylene carbonate, lithium salt, and non-aqueous organic solvent. The first electrolyte mainly composed of a low-concentration additive combination is beneficial to form a low-polarization, uniform and dense SEI film in the subsequent formation process, and effectively discharge the side reaction gas, which avoids the problem that a large amount of additives are difficult to fully react when used once. In addition, by controlling the combination and ratio of the additives, it is beneficial to generate a better interface layer, that is, the SEI film.

[0052] For the initial battery cell formed in application step S101, the liquid injection process in step S102 is carried out. Specifically, the first positive pressure and the first negative pressure are alternately cycled to inject the electrolyte into the corresponding initial battery cell. This liquid injection process is different from the normal pressure liquid injection process and the vacuum liquid injection process. Among them, the normal pressure liquid injection process is: without vacuum pumping, the electrolyte is directly injected into the battery cell through an air bag or a liquid injection port; the vacuum liquid injection process is: first, the inside of the battery cell is evacuated, and the liquid is injected under a vacuum state. Due to the negative pressure difference, the electrolyte will automatically "flow" into the battery cell. The liquid injection speed of the liquid injection process in step S102 is faster than that of the normal pressure liquid injection process and the vacuum liquid injection process;

[0053] Moreover, the magnitudes of the first positive pressure and the first negative pressure in step S102 are also different from the positive pressure and the negative pressure in the positive and negative pressure cycles of the conventional equal-pressure liquid injection process. The first positive pressure in step S102 is less than the positive pressure in the positive and negative pressure cycles of the conventional equal-pressure liquid injection process, and the absolute value of the first negative pressure in step S102 is less than the absolute value of the negative pressure in the positive and negative pressure cycles of the conventional equal-pressure liquid injection process. One reason for this setting is that the positive and negative pressure cycles here are for liquid injection, not infiltration, so a smaller positive and negative pressure can meet the process requirements. Another reason is to cooperate with the second positive pressure and the second negative pressure in step S103 to achieve liquid injection and primary infiltration while reducing the risk of battery cell deformation.

[0054] Further explanation is as follows. In the existing solutions, directly applying a large second positive pressure is likely to cause deformation of the battery cell. By first applying a small first positive pressure and then applying a large second positive pressure, the gradual increase of the air pressure is realized, enabling the battery cell to adapt to the change of the air pressure and reducing the risk of deformation;

[0055] In addition, in the prior art, one way to reduce the risk of deformation is to gradually increase the air pressure entering the cavity by controlling the opening degree of the intake valve. However, this method is difficult to create a large pressure difference in a short time, affecting the infiltration effect, but the solution of this application overcomes this defect.

[0056] This solution applies this pressure difference during the equal-pressure liquid injection and standing process to strengthen the filling of the electrolyte between layers and in the voids along the thickness direction of the electrode plate, and to accelerate the suction process from the bottom during the standing step after the liquid injection is completed.

[0057] Step S103: Perform the above-mentioned primary infiltration process on the above-mentioned initial battery cell after liquid injection. The steps of the above-mentioned primary infiltration process include alternately and cyclically applying a second positive pressure and a second negative pressure to the above-mentioned initial battery cell to perform primary battery cell infiltration. Among them, the above-mentioned second positive pressure is greater than the above-mentioned first positive pressure, and the absolute value of the above-mentioned second negative pressure is greater than the absolute value of the above-mentioned first negative pressure. Applying a positive pressure makes the internal pressure higher than the external pressure, and applying a negative pressure realizes vacuum pumping. The above-mentioned positive pressure includes the above-mentioned first positive pressure and the above-mentioned second positive pressure, and the above-mentioned negative pressure includes the above-mentioned first negative pressure and the above-mentioned second negative pressure;

[0058] Specifically, alternately and cyclically applying the first positive pressure and the first negative pressure to the liquid injection container located above the above-mentioned initial battery cell is achieved by alternately and cyclically applying the first positive pressure and the first negative pressure to the cavity communicated with the liquid injection container; alternately and cyclically applying the second positive pressure and the second negative pressure to the above-mentioned initial battery cell is achieved by alternately and cyclically applying the second positive pressure and the second negative pressure to the cavity communicated with the initial battery cell; that is, the first positive pressure and the second positive pressure use the same gas source. The first positive pressure and the second positive pressure are generated by controlling the pressure of the gas source;

[0059] Referring to the previous content, under the combined action of the first positive pressure and the first negative pressure in step S102 and the second positive pressure and the first negative pressure in step S103, the effect of primary battery cell infiltration of alternately and cyclically applying the second positive pressure and the second negative pressure to the above-mentioned initial battery cell in step S103 can be fully exerted. And because the first positive pressure and the first negative pressure have been alternately and cyclically applied before alternately and cyclically applying the second positive pressure and the second negative pressure, rather than directly applying the larger second positive pressure and the first negative pressure, the risk of battery cell deformation is reduced while achieving the effect of primary battery cell infiltration;

[0060] Step S104: After the above-mentioned primary battery cell infiltration is completed, move the above-mentioned initial battery cell to a static storage library and perform a secondary infiltration process in the above-mentioned static storage library.

[0061] The secondary infiltration performed in the static storage library is high-temperature infiltration, which generally takes a long time; specifically, the high-temperature infiltration temperature range can be 45°C to 60°C, such as 45°C to 50°C, 50°C to 55°C or 55°C to 60°C, and specifically can be 45°C, 48°C, 50°C, 53°C, 56°C or 60°C; the time range can be 24h to 36h, such as 24h to 28h, 28h to 32h or 32h to 36h, and specifically can be 24h, 26h, 28h, 30h, 32h, 34h, 36h. High-temperature formation above 40°C can accelerate the speed of the electrochemical reaction and the growth speed of the SEI film, and reduce the time required for formation;

[0062] The degree of high-temperature infiltration is related to factors such as infiltration temperature, infiltration time, and the placement direction of the battery cell.

[0063] Combined with the analysis in the previous text, the combined effect of step S102 and step S103 achieves a better wetting effect for the battery cell once, shortening the time of secondary wetting in the static storage in step S104, that is, shortening the duration of high-temperature wetting.

[0064] The above method for manufacturing a secondary battery, including step S101, step S102, step S103, and step S104, realizes the injection and wetting of the initial battery cell through a winding process, a liquid injection process, a primary wetting process, and a secondary wetting process. Moreover, under the combined action of the first positive pressure and the first negative pressure in the liquid injection process and the second positive pressure and the second negative pressure in the primary wetting process, a better initial wetting is achieved while reducing the risk of battery cell deformation, and further shortening the duration of subsequent secondary wetting. That is, overall, the duration of battery cell wetting is shortened.

[0065] Multiple of the above-mentioned initial battery cells are placed on the battery cell carrier. To determine whether the liquid injection is completed, in the embodiments of the present application, it is determined whether the liquid injection is completed according to the liquid level of the above-mentioned electrolyte, including:

[0066] Determine the target battery cell, where the target battery cell is the slowest-injecting one among multiple of the above-mentioned initial battery cells under the same liquid injection conditions;

[0067] Among them, the same liquid injection conditions include: the same specification of the liquid injection container, the same content of the initial electrolyte in the liquid injection container, the same first positive pressure and first negative pressure applied, the same size of the top liquid injection hole of the initial battery cell, and the same processes of multiple of the above-mentioned initial battery cells on the same battery cell carrier before the liquid injection process, including the battery cell baking process, etc.;

[0068] That is to say, multiple initial battery cells on the same battery cell carrier are not all the same. Therefore, to determine whether the liquid injection is completed, a convenient way is to find the initial battery cell with the slowest injection speed. As long as the initial battery cell with the slowest injection speed has not completed the liquid injection, the other initial battery cells on the same battery cell carrier have not completed the liquid injection either;

[0069] Detect the liquid level of the target electrolyte, where the target electrolyte is the electrolyte injected into the above-mentioned target battery cell;

[0070] The liquid level of the target electrolyte here, that is, the highest position of the liquid surface of the target electrolyte, may be in the target liquid injection container or in the target battery cell, and most likely in the target battery cell;

[0071] If the liquid level of the above-mentioned target electrolyte drops below the liquid injection hole, it is determined that the above-mentioned target battery cell has completed the liquid injection. The completion of the liquid injection of the above-mentioned target battery cell indicates that all of the above-mentioned initial battery cells on the battery cell carrier have completed the liquid injection, where the above-mentioned liquid injection hole is located on the top cover of the above-mentioned target battery cell.

[0072] As described above, below the liquid injection hole means below the upper surface of the liquid injection hole;

[0073] The liquid injection hole is generally a circular liquid injection hole. Of course, in some cases, other shapes of liquid injection holes other than circular liquid injection holes can be selected, for example, an irregularly shaped liquid injection hole;

[0074] That is, taking the upper surface of the liquid injection hole as a critical point to judge whether the target battery cell has completed liquid injection, that is, judging whether the liquid injection is completed through the judgment of the liquid level, that is, a quantitative index is found to achieve an accurate judgment of whether the liquid injection is completed.

[0075] As described above, the main reason for controlling the liquid level of the target electrolyte to drop below the liquid injection hole and then applying the second positive pressure and the second negative pressure is that: the liquid level of the target electrolyte dropping below the liquid injection hole ensures the balance of the internal and external pressure differences of the battery cell, that is, solves the defect of the asynchronous internal and external pressure differences caused by liquid sealing. On the premise of the balance of the internal and external pressure differences, even if the second positive pressure and the second negative pressure are applied subsequently, the battery cell will not deform.

[0076] For further explanation, the principle that the liquid level of the target electrolyte dropping below the liquid injection hole ensures the balance of the internal and external pressure differences of the battery cell is that: the liquid level of the target electrolyte dropping below the liquid injection hole makes the inside and outside of the housing of the battery cell communicate, and a larger positive pressure and negative pressure can be applied synchronously; if the inside and outside of the housing of the battery cell (equivalent to the initial battery cell in this article) do not communicate, applying a larger positive pressure and negative pressure synchronously will cause the housing of the battery cell to bulge or collapse;

[0077] For further explanation, the aperture of the liquid injection hole on the battery cell cover is relatively small. For example, the aperture is 4 mm, but the diameter of the air pipe connected to the liquid injection container is relatively large. For example, the aperture is 8 mm, and the diameter of the air pipe connected to the outside cavity is even larger, generally with an aperture of twenty or thirty centimeters. This large aperture difference causes that if a relatively large air pressure is directly provided, it is easy to form liquid sealing.

[0078] In a more specific implementation manner, determining the target battery cell includes:

[0079] If the weight difference between two battery cells among all the initial battery cells on the above-mentioned battery cell carrier is greater than the preset weight difference, then the initial battery cell with the largest weight is determined as the above-mentioned target battery cell;

[0080] Among them, the weight of the initial battery cell can be measured by a weighing mechanism;

[0081] That is, if the weight difference between multiple initial cells on the same cell carrier is large, the cell with the largest weight is determined as the target cell. It should be noted that the thicknesses of multiple initial cells on the same cell carrier are the same, or not exactly the same but with very small differences, that is, it is difficult to distinguish the initial cells from the thickness. Therefore, among these initial cells, the one with the largest weight has the smallest gap and is the slowest to be injected with liquid;

[0082] If the weight difference between any two cells among all the initial cells on the above-mentioned cell carrier is less than or equal to the above-mentioned preset weight difference, then the initial cell with the smallest thickness among all the initial cells on the above-mentioned cell carrier is determined as the above-mentioned target cell.

[0083] Among them, the thickness of the initial cell can be measured by a thickness measuring instrument, or the determination of the thickness can be achieved through image acquisition combined with subsequent image processing algorithms;

[0084] That is, if the weight difference between multiple initial cells on the same cell carrier is not large, or the weights are exactly the same, but different initial cells can be distinguished from the thickness, then the one with the smallest thickness has the smallest gap among the initial cells and is the slowest to be injected with liquid;

[0085] To ensure the effect of liquid injection, in the embodiments of the present application, when determining whether the liquid injection is completed according to the liquid level of the above-mentioned electrolyte, it further includes:

[0086] When the liquid level of the above-mentioned target electrolyte is above the above-mentioned liquid injection hole, the duration of applying the above-mentioned first positive pressure and / or the above-mentioned first negative pressure to all the above-mentioned liquid injection containers is extended until the liquid level of the above-mentioned target electrolyte is lower than the above-mentioned liquid injection hole.

[0087] The higher the liquid level of the target electrolyte, the longer the duration of applying the above-mentioned first positive pressure and / or the above-mentioned first negative pressure to all the above-mentioned liquid injection containers;

[0088] The above-mentioned extension of the duration of applying the above-mentioned first positive pressure and / or the above-mentioned first negative pressure to all the above-mentioned liquid injection containers includes three situations:

[0089] The first: Extend the duration of applying the first positive pressure to all the above-mentioned liquid injection containers;

[0090] The second: Extend the duration of applying the first negative pressure to all the above-mentioned liquid injection containers;

[0091] The third: Extend the duration of applying the first positive pressure and the first negative pressure to all the above-mentioned liquid injection containers; The probability of selecting the third situation is relatively large.

[0092] Specifically, the extended duration is directly related to the liquid level of the target electrolyte, and a real-time control method can be adopted. That is, if it is detected in real time that the liquid level of the target electrolyte is above the liquid injection hole, the duration of the first positive pressure and / or the first negative pressure is appropriately extended, and then the liquid level of the target electrolyte is continuously detected. If it is found that the liquid level of the target electrolyte is still above the liquid injection hole, the duration of the first positive pressure and / or the first negative pressure is continuously extended. An empirical value can also be used to pre-determine the corresponding relationship between the liquid level of the target electrolyte and the extended duration, and control is performed based on this corresponding relationship.

[0093] In a specific implementation manner, detecting the liquid level of the electrolyte includes:

[0094] Obtaining a liquid level image, which is obtained by shooting with a first image acquisition module;

[0095] See Figure 2 and Figure 3 , a liquid level image is obtained by shooting with the first image acquisition module 05; the installation position of the first image acquisition module 05 is a position where the liquid level can be shot, neither too high nor too low; that is, the camera of the first image acquisition module 05 is aligned between the battery cell and the top liquid injection container;

[0096] Determining the liquid level of the electrolyte according to the liquid level image.

[0097] Specifically, image preprocessing of the liquid level image includes grayscale conversion, binarization, denoising, etc.; edge detection and line detection are used to determine the liquid level of the electrolyte. Among them, Sobel operator, Canny edge detection and Laplacian operator can be used for edge detection; Hough transform and probabilistic Hough transform can be used for line detection; horizontal lines can be detected by Hough transform.

[0098] In some embodiments of the present application, the method further includes:

[0099] In the above liquid injection process, determining whether the initial battery cell is deformed according to the side image of the battery cell. If the initial battery cell is deformed, determining the amount of deformation of the deformed initial battery cell to obtain the first amount of battery cell deformation, and the side image of the battery cell is obtained by shooting with a second image acquisition module;

[0100] Wherein, the side of the battery cell is the side of the aluminum shell, and for a square battery cell, the side of the aluminum shell can be the side with a larger area or the side with a smaller area;

[0101] See Figure 2 and Figure 3 , the side image of the battery cell is obtained by shooting with the second image acquisition module 06, and the camera of the second image acquisition module 06 is aligned with the side of the battery cell;

[0102] Determine whether the initial battery cell is deformed by edge detection, feature extraction, and deformation evaluation. Specifically, use an edge detection algorithm (such as the Canny algorithm) to extract the contour of the battery cell; calculate the geometric features of the battery cell contour, such as the area shape factor, perimeter shape factor, aspect ratio, fillet radius, etc.; compare the extracted features with the preset features of a normal battery cell and calculate the deviation. For example, determine whether there is deformation by comparing the aspect ratio or area change of the battery cell contour.

[0103] Among them, the area shape factor is usually used to describe the degree of approximation of the shape of the battery cell contour to an ideal shape (such as a circle or a square);

[0104] The perimeter shape factor is used to describe the ratio of the perimeter of the battery cell contour to the perimeter of the ideal shape;

[0105] The aspect ratio is the ratio of the length to the width of the battery cell and is used to describe the shape ratio of the battery cell. For a square battery cell, the aspect ratio is an important design parameter;

[0106] The fillet radius refers to the fillet design at the edge of the battery cell, which is used to avoid structural damage caused by stress concentration.

[0107] The geometric features of the battery cell contour also include the rectangular shape factor, elliptical shape factor, etc. Among them, the rectangular shape factor is used to describe the degree of approximation of the battery cell contour to a rectangle; the elliptical shape factor is used to describe the degree of approximation of the battery cell contour to an ellipse.

[0108] Determine the reduction amount of the first positive pressure corresponding to the first battery cell deformation amount, and reduce the first positive pressure according to the reduction amount of the first positive pressure. Among them, there is a positive correlation between the first battery cell deformation amount and the reduction amount of the first positive pressure.

[0109] That is to say, in the liquid injection process, the corresponding relationship between the first battery cell deformation amount and the reduction amount of the first positive pressure is determined in advance, and then this corresponding relationship is applied to determine the reduction amount of the first positive pressure. Achieve the accurate determination of the reduction amount of the first positive pressure.

[0110] In some embodiments of the present application, the above method further includes:

[0111] In the above primary infiltration process, determine whether the initial battery cell is deformed according to the side image of the battery cell. If the initial battery cell is deformed, determine the battery cell deformation amount of the deformed initial battery cell to obtain the second battery cell deformation amount;

[0112] Among them, the side of the battery cell is the side of the aluminum shell, and for a square battery cell, the side of the aluminum shell can be the side with a larger area or the side with a smaller area;

[0113] Among them, the side image of the battery cell is obtained by shooting with the second image acquisition module, and the camera of the second image acquisition module is aligned with the side of the battery cell;

[0114] The determination of whether the initial battery cell is deformed is realized through edge detection, feature extraction and deformation evaluation. Specifically, the edge detection algorithm (such as Canny algorithm) is used to extract the contour of the battery cell; calculate the geometric features of the battery cell contour, such as area, perimeter, aspect ratio, shape factor, etc.; compare the extracted features with the preset normal battery cell features, and calculate the deviation amount. For example, by comparing the aspect ratio or area change of the battery cell contour, it is judged whether there is deformation.

[0115] Determine the duration increment of applying the first positive pressure and / or the duration increment of the first negative pressure corresponding to the above-mentioned second battery cell deformation amount, and increase the first positive pressure and / or the first negative pressure according to the above-mentioned duration increment, and apply the first positive pressure with the increased duration and / or the first negative pressure with the increased duration to the preparation process of the secondary battery again, wherein, there is a positive correlation between the duration increment of the first positive pressure, the duration increment of the first negative pressure and the above-mentioned second battery cell deformation amount respectively.

[0116] That is to say, in a single infiltration process, the corresponding relationship between the duration increment of the first positive pressure, the duration increment of the first negative pressure and the above-mentioned second battery cell deformation amount is determined in advance, and then this corresponding relationship is applied to determine the duration increment of the first positive pressure and the duration increment of the first negative pressure. The accurate determination of the duration increment of the first positive pressure and the duration increment of the first negative pressure is realized.

[0117] Specifically, the pressure value range of the first positive pressure is 0.3~0.4 Mpa, the pressure value range of the first negative pressure is -65~-55 Kpa, the pressure value range of the second positive pressure is 0.75~0.85 Mpa, and the pressure value range of the second negative pressure is -85~-75 Kpa.

[0118] Specifically, when the pressure value of the first positive pressure is 0.3 Mpa, the pressure value of the first negative pressure can be -60 Kpa; when the pressure value of the first positive pressure is 0.35 Mpa, the pressure value of the first negative pressure can be -55 Kpa; when the pressure value of the first positive pressure is 0.38 Mpa, the pressure value of the first negative pressure can be -58 Kpa; and so on; combinations can be made according to actual needs;

[0119] Specifically, when the pressure value of the second positive pressure is 0.75 Mpa, the pressure value of the second negative pressure can be -80 Kpa; when the pressure value of the second positive pressure is 0.70 Mpa, the pressure value of the second negative pressure can be -75 Kpa; when the pressure value of the second positive pressure is 0.80 Mpa, the pressure value of the second negative pressure can be -80 Kpa; and so on; combinations can be made according to actual requirements.

[0120] The selection of the pressure value range of the first positive pressure and the pressure value range of the first negative pressure can accelerate the liquid injection speed, and the combined action with the pressure value range of the second positive pressure and the pressure value range of the second negative pressure makes good use of the advantage of the pressure difference, ensures the effect of the initial infiltration, and reduces the risk of cell deformation.

[0121] Moreover, the pressure value of the first positive pressure and the pressure value of the first negative pressure determine the number of times of alternately applying the first positive pressure and the first negative pressure in a cycle; when the pressure value of the first positive pressure is the same, the lower the pressure value of the first negative pressure, the fewer the number of alternately applying cycles; conversely, when the pressure value of the first negative pressure is the same, the higher the pressure value of the first positive pressure, the fewer the number of alternately applying cycles.

[0122] Similarly, the pressure value of the second positive pressure and the pressure value of the second negative pressure determine the number of times of alternately applying the second positive pressure and the second negative pressure in a cycle. When the pressure value of the second positive pressure is the same, the lower the pressure value of the second negative pressure, the fewer the number of alternately applying cycles; conversely, when the pressure value of the second negative pressure is the same, the higher the pressure value of the second positive pressure, the fewer the number of alternately applying cycles.

[0123] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0124] Embodiment 1

[0125] After winding the positive electrode sheet, the negative electrode sheet and the separator and placing them in a housing to form an initial cell, the separator is located between the positive electrode sheet and the negative electrode sheet; a liquid injection process is performed on the initial cell. In the steps of the liquid injection process, the first positive pressure and the first negative pressure are alternately applied to the liquid injection container located above the initial cell to inject the electrolyte into the corresponding initial cell, and the liquid level of the electrolyte is detected. Whether the liquid injection is completed is determined according to the liquid level of the electrolyte. If the liquid injection is completed, a wetting process is performed once. If the liquid injection is not completed, a preset operation is executed, where the liquid level of the electrolyte being lower than the liquid injection hole indicates the completion of the liquid injection.

[0126] Perform a primary infiltration process on the initial battery cell after the injection process is completed. The steps of the primary infiltration process include alternately and cyclically applying a second positive pressure and a second negative pressure to the initial battery cell to perform primary battery cell infiltration. Among them, the second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure. Applying the positive pressure makes the internal pressure higher than the external pressure, and applying the negative pressure realizes vacuum pumping. The positive pressure includes the first positive pressure and the second positive pressure, and the negative pressure includes the first negative pressure and the second negative pressure; among them, the pressure value range of the above-mentioned first positive pressure is 0.3~0.4 Mpa, the pressure value range of the above-mentioned first negative pressure is -65~-55 Kpa, the pressure value range of the above-mentioned second positive pressure is 0.75~0.85 Mpa, and the pressure value range of the above-mentioned second negative pressure is -85~-75 Kpa;

[0127] After the primary battery cell infiltration is completed, move the initial battery cell to the static storage library and perform a secondary infiltration process in the static storage library.

[0128] Comparative Example 1

[0129] The difference from Example 1 is that there is no step of determining whether the injection is completed according to the liquid level of the electrolyte, that is, the liquid level is not monitored. That is to say, although the second positive pressure and the second negative pressure are applied after the first positive pressure and the first negative pressure are applied, there is no strict boundary between the application of the second positive pressure and the second negative pressure and the application of the first positive pressure and the first negative pressure;

[0130] In this implementation method without monitoring the liquid level, during the process of applying the first positive pressure and the first negative pressure, the liquid level of the electrolyte does not drop below the injection hole of the battery cell, and then the second positive pressure and the second negative pressure are applied, resulting in an asynchronous internal and external pressure difference of the battery cell. If the inside of the battery cell is still under negative pressure but the outside of the battery cell is under positive pressure, the battery will be crushed, or if the inside of the battery cell is under positive pressure but the outside of the battery cell is under negative pressure, the battery will bulge, and if the bulge is too large, it will cause the cover plate of the battery cell to crack; while the implementation method of Example 1 makes the liquid level of the electrolyte drop below the injection hole of the battery cell during the process of applying the first positive pressure and the first negative pressure, and then applying the second positive pressure and the second negative pressure solves the defect of asynchronous internal and external pressure difference caused by liquid sealing.

[0131] The comparison table of the battery cell yield of Example 1 and Comparative Example 1 is shown in Table 1. That is, there is a certain probability that the time spent in the high-temperature infiltration stage of the implementation method without monitoring the liquid level is the same as that of Example 1, and there is also a certain probability that the time spent in the high-temperature infiltration stage of Comparative Example 1 is longer; the main difference between these two implementation methods lies in the different battery cell yields. It can be seen from the above analysis that the battery cell yield of Comparative Example 1 is lower than that of Example 1.

[0132] Table 1 Comparison table of battery cell yield

[0133]

[0134] Comparative Example 2

[0135] The difference from Example 1 is that there is no step of applying the first positive pressure and the first negative pressure, and the normal pressure injection process and the vacuum injection process are adopted.

[0136] For the comparison table of the time spent in the secondary infiltration process, i.e., the high-temperature infiltration stage, between Example 1 and Comparative Example 2, see Table 2. It can be seen that the time spent by Example 1 in the high-temperature infiltration stage is significantly reduced compared to Comparative Example 2.

[0137] Table 2 Comparison of the time spent in the high-temperature infiltration stage

[0138]

[0139] Therefore, Example 1 of the present application has technical advantages both in terms of the cell yield and the time spent in the high-temperature infiltration stage.

[0140] The embodiment of the present application also provides a preparation device for a secondary battery, as Figure 2 and Figure 3 shown, including a winding and encapsulation mechanism and an injection mechanism. The winding and encapsulation mechanism winds the positive electrode sheet, the negative electrode sheet, and the separator and then places them in a shell to form an initial cell. The injection mechanism includes an injection tank, and an injection container 01 is disposed inside the injection tank. The injection container 01 is located above the initial cell 02, and the hole at the bottom of the injection container 01 is aligned with the injection hole 21 on the top cover of the initial cell 02. The injection mechanism further includes an upper cover 03 and a fixture tray 04;

[0141] The injection mechanism further includes a first image acquisition module 05;

[0142] In the injection process, the above-mentioned pressurizing structure alternately and cyclically applies a first positive pressure and a first negative pressure to the above-mentioned injection container 01 to inject the electrolyte into the corresponding initial cell 02,

[0143] The installation position of the first image acquisition module 05 is a position where the liquid level can be photographed, neither too high nor too low; that is, the camera of the first image acquisition module 05 is aligned between the cell and the top injection container;

[0144] Wherein, the above-mentioned injection container is a container for injecting the above-mentioned initial cell and containing the above-mentioned electrolyte. In the primary infiltration process after the injection is completed, the above-mentioned pressurizing structure alternately and cyclically applies a second positive pressure and a second negative pressure to the above-mentioned initial cell for primary cell infiltration. The first image acquisition module is used to acquire a liquid level image, and the liquid level image indicates the liquid level of the electrolyte. Wherein, the second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure;

[0145] A static storage. After the primary cell infiltration is completed, the above-mentioned initial cell is moved to the above-mentioned static storage, and a secondary infiltration process is performed in the above-mentioned static storage.

[0146] The winding process is achieved through a winding encapsulation mechanism, the liquid injection and primary infiltration are achieved in the liquid injection mechanism, and the secondary infiltration is achieved in the static storage library. Under the combined action of the first positive pressure and the first negative pressure in the liquid injection process and the second positive pressure and the second negative pressure in the primary infiltration process, better primary infiltration is achieved while reducing the risk of cell deformation, and further shortening the duration of subsequent secondary infiltration. That is, the overall infiltration time of the cell is shortened.

[0147] See Figure 2 and Figure 3 As mentioned above, the liquid injection mechanism further includes a second image acquisition module 06, and the second image acquisition module 06 is used to acquire the side image of the cell. The side image of the cell is obtained by shooting with the second image acquisition module 06, and the camera of the second image acquisition module 06 is aligned with the side of the cell.

[0148] The embodiment of the present application also provides a secondary battery, which is prepared by using the preparation method of the above-mentioned secondary battery, or the above-mentioned secondary battery is prepared by using the preparation equipment of the above-mentioned secondary battery.

[0149] The embodiment of the present application also provides an energy storage system, including the above-mentioned secondary battery.

[0150] The embodiment of the present application also provides an electrical equipment, including the above-mentioned secondary battery or the above-mentioned energy storage system.

[0151] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, commodity or equipment. Without further limitation, the element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, commodity or equipment including the element.

[0152] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, the present application can have various changes and modifications. 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, Including: After winding the positive electrode sheet, negative electrode sheet and separator and placing them in a housing to form an initial battery cell, the separator is located between the positive electrode sheet and the negative electrode sheet; Performing a liquid injection process on the initial battery cell. In the steps of the liquid injection process, a first positive pressure and a first negative pressure are alternately and cyclically applied to a liquid injection container located above the initial battery cell to inject electrolyte into the corresponding initial battery cell, and the liquid level of the electrolyte is detected. Whether the liquid injection is completed is determined according to the liquid level of the electrolyte. If the liquid injection is completed, a soaking process is performed once. If the liquid injection is not completed, a preset operation is executed. Wherein, the liquid injection container is a container for injecting electrolyte into the initial battery cell and containing the electrolyte. Wherein, if the liquid level of the target electrolyte drops below the liquid injection hole, it is determined that the liquid injection is completed. The target electrolyte is the electrolyte injected into the target battery cell, and the target battery cell is the battery cell with the slowest liquid injection speed among multiple initial battery cells under the same liquid injection conditions; Performing the soaking process once on the initial battery cell after the liquid injection is completed. The steps of the soaking process once include alternately and cyclically applying a second positive pressure and a second negative pressure to the initial battery cell to perform primary battery cell soaking. Wherein, the second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure. Applying a positive pressure makes the internal pressure higher than the external pressure, and applying a negative pressure realizes vacuum pumping. The positive pressure includes the first positive pressure and the second positive pressure, and the negative pressure includes the first negative pressure and the second negative pressure; After the primary battery cell soaking is completed, move the initial battery cell to a static storage and perform a secondary soaking process in the static storage.

2. The method for preparing a secondary battery according to claim 1, wherein Before performing the liquid injection process on the initial battery cell, the method further includes: If the weight difference between any two battery cells among all the initial battery cells on the battery cell carrier is greater than a preset weight difference, determine the initial battery cell with the largest weight as the target battery cell; If the weight difference between any two battery cells among all the initial battery cells on the battery cell carrier is less than or equal to the preset weight difference, determine the initial battery cell with the smallest thickness among all the initial battery cells on the battery cell carrier as the target battery cell.

3. The method for preparing a secondary battery according to claim 1, wherein During the process of determining whether the liquid injection is completed according to the liquid level of the electrolyte, it further includes: When the liquid level of the target electrolyte is above the liquid injection hole, extend the duration of applying the first positive pressure and / or the first negative pressure to all the liquid injection containers until the liquid level of the target electrolyte is lower than the liquid injection hole.

4. The method for preparing a secondary battery according to claim 1, characterized in that, Detecting the liquid level of the electrolyte includes: Obtaining a liquid level image, which is obtained by shooting with a first image acquisition module; Determining the liquid level of the electrolyte according to the liquid level image.

5. The manufacturing method of the secondary battery according to claim 1, characterized in that, The method further includes: During the liquid injection process, determine whether the initial battery cell is deformed according to the side image of the battery cell. If the initial battery cell is deformed, determine the amount of battery cell deformation of the deformed initial battery cell to obtain a first amount of battery cell deformation. The side image of the battery cell is obtained by shooting with a second image acquisition module; Determine the reduction amount of the first positive pressure corresponding to the deformation amount of the first battery cell, and reduce the first positive pressure according to the reduction amount of the first positive pressure, wherein there is a positive correlation between the deformation amount of the first battery cell and the reduction amount of the first positive pressure.

6. The method for preparing a secondary battery according to claim 1, wherein The method further includes: In the primary infiltration process, determine whether the initial battery cell is deformed according to the side image of the battery cell. If the initial battery cell is deformed, determine the deformation amount of the deformed initial battery cell to obtain the second battery cell deformation amount. Determine the duration increment of the first positive pressure and / or the duration increment of the first negative pressure corresponding to the second battery cell deformation amount, and increase the first positive pressure and / or the first negative pressure according to the duration increment, and apply the increased first positive pressure and / or the increased first negative pressure to the preparation process of the secondary battery again, wherein there is a positive correlation between the duration increment of the first positive pressure, the duration increment of the first negative pressure and the second battery cell deformation amount respectively.

7. The manufacturing method of the secondary battery according to claim 1, characterized in that, The pressure value range of the first positive pressure is 0.3 to 0.4 Mpa, the pressure value range of the first negative pressure is -65 to -55 Kpa, the pressure value range of the second positive pressure is 0.75 to 0.85 Mpa, and the pressure value range of the second negative pressure is -85 to -75 Kpa.

8. A preparation device for a secondary battery, characterized in that, It includes: A winding and encapsulating mechanism that winds the positive electrode sheet, negative electrode sheet and separator and then places them in a housing to form an initial battery cell. A liquid injection mechanism, including a liquid injection tank, a pressurizing structure and a first image acquisition module. The liquid injection tank is internally provided with a liquid injection container. In the liquid injection process, the pressurizing structure alternately and cyclically applies a first positive pressure and a first negative pressure to the liquid injection container to inject the electrolyte into the corresponding initial battery cell. The liquid injection container is a container for injecting the electrolyte into the initial battery cell and containing the electrolyte. In the primary infiltration process after the liquid injection is completed, the pressurizing structure alternately and cyclically applies a second positive pressure and a second negative pressure to the initial battery cell for primary battery cell infiltration. The first image acquisition module is used to acquire a liquid level image, and the liquid level image indicates the liquid level of the electrolyte. The second positive pressure is greater than the first positive pressure, and the absolute value of the second negative pressure is greater than the absolute value of the first negative pressure. The completion of the liquid injection is manifested as: the liquid level of the target electrolyte drops below the liquid injection hole. The target electrolyte is the electrolyte injected into the target battery cell, and the target battery cell is the battery cell with the slowest liquid injection speed among multiple initial battery cells under the same liquid injection conditions. A static storage library. After the primary battery cell infiltration is completed, the initial battery cell is moved to the static storage library for secondary infiltration process.

9. The manufacturing apparatus for a secondary battery according to claim 8, wherein, The liquid injection mechanism further includes a second image acquisition module, and the second image acquisition module is used to acquire the side image of the battery cell.

10. A secondary battery, characterized in that, The secondary battery is prepared by using the preparation method of the secondary battery according to any one of claims 1 to 7, or the secondary battery is prepared by using the secondary battery preparation equipment according to claim 8 or 9.

11. An energy storage system, characterized in that, It includes a plurality of secondary batteries according to claim 10.

12. An electrical device, characterized in that, Comprising a secondary battery as described in claim 10 or an energy storage system as described in claim 11.

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