Secondary battery and preparation process thereof, energy storage system and electric equipment

Abstract

The invention relates to the technical field of secondary batteries, in particular to a secondary battery and a preparation process thereof, an energy storage system and electric equipment. The preparation process of the secondary battery comprises the following steps: putting the active substance, the thickening agent and the conductive agent into stirring equipment, stirring and mixing to form a first mixed material, adding the solvent, stirring and mixing to form a second mixed material, and calculating the viscosity and stability characterization quantity. When the viscosity and the stability characterization quantity meet the requirements, adding a binder, stirring and mixing to form a negative electrode active material, calculating the viscosity and the stability characterization quantity, and when the viscosity and the stability characterization quantity meet the requirements, coating a negative electrode current collector with the negative electrode active material to prepare a negative electrode piece and prepare the secondary battery. The viscosity and stability characterization quantity of the material are calculated in real time in the stirring process, the process of taking out the material is reduced, the preparation period of the negative electrode active material is shortened, the risk that the material is polluted in the taking-out process is reduced, the accuracy of a test result is improved, and the preparation cost is reduced.

Description

Technical Field

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

[0002] A secondary battery includes a housing, a battery cell assembly, and an electrolyte located inside the housing. The battery cell assembly and the electrolyte are used to carry out an electrochemical reaction, so that the battery cell assembly outputs electric energy to an external circuit or obtains electric energy from the external circuit.

[0003] The battery cell assembly includes a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate is prepared by coating a positive electrode active material on a positive electrode current collector, and the negative electrode plate is prepared by coating a negative electrode active material on a negative electrode current collector. The negative electrode active material is formed by mixing and stirring an active substance, a thickener, a conductive agent, a binder, water, etc. During the stirring process, the viscosity of the negative electrode active material needs to meet the requirements to proceed to the next process.

[0004] Therefore, how to detect the viscosity of the negative electrode active material is an important problem to be solved in this field. Summary of the Invention

[0005] In view of this, the present application provides a secondary battery, a preparation process thereof, an energy storage system, and an electrical device, which can detect the viscosity of the negative electrode active material in real time during the stirring process.

[0006] The first aspect of the present application provides a preparation process for a secondary battery, including: at least putting an active material, a thickening agent, and a conductive agent into a stirring device, and the stirring device mixes the active material, the thickening agent, and the conductive agent to form a first mixed material. Adding a first mass of a solvent into the first mixed material, and the stirring device stirs the solvent and the first mixed material to form a dispersed material. Adding a second mass of the solvent into the dispersed material, and the stirring device stirs the solvent and the dispersed material to form a second mixed material, and calculating the viscosity and the stability characterization quantity of the second mixed material. When the viscosity of the second mixed material is within a first preset range and the stability characterization quantity of the second mixed material is within a second preset range, adding a binder into the second mixed material, and the stirring device stirs the solvent and the second mixed material to form a negative electrode active material, and calculating the viscosity and the stability characterization quantity of the negative electrode active material. The viscosity μ and the stability characterization quantity S satisfy: S = d(μ) / d(t), where t is the stirring duration of the stirring device. When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the negative electrode active material is discharged. Coating the negative electrode active material on a negative electrode current collector, and drying to form a negative electrode plate. Coating a positive electrode active material on a positive electrode current collector, and drying to form a positive electrode plate. Stacking the positive electrode plate, a separator, and the negative electrode plate, and winding to form a battery cell assembly. Placing the battery cell assembly into a housing, and injecting an electrolyte into the housing to form a secondary battery.

[0007] In some possible designs, the stirring device includes a stirring member and a driving motor, and the driving motor drives the stirring member to rotate at a preset speed. The rotation speed n of the stirring member, the real-time current value I of the driving motor, and the viscosity μ satisfy: μ = M×(I / n), where M is a coefficient.

[0008] In some possible designs, before the step of calculating the viscosity and the stability characterization quantity of the second mixed material, the preparation process for the secondary battery includes: preparing a first test sample, where the first test sample at least includes an active material, a thickening agent, and a conductive agent. Detecting the viscosity of the first test sample, and calculating a first coefficient M1 according to the viscosity of the first test sample, the rotation speed of the stirring member when stirring the first test sample, and the current value of the driving motor. Before the step of calculating the viscosity and the stability characterization quantity of the negative electrode active material, the preparation process for the secondary battery includes: preparing a second test sample, where the second test sample at least includes an active material, a thickening agent, a conductive agent, and a binder. Detecting the viscosity of the second test sample, and calculating a second coefficient M2 according to the viscosity of the second test sample, the rotation speed of the stirring member when stirring the second test sample, and the current value of the driving motor.

[0009] In some possible designs, the step of preparing the first test sample includes: taking out a part of the second mixed material as the first test sample. The step of preparing the second test sample includes: taking out a part of the negative electrode active material as the second test sample.

[0010] In some possible designs, the steps of preparing the first test sample include: before the step of preparing the first mixed material, preparing a first test material, which at least includes an active substance, a thickening agent, and a conductive agent. Adding a solvent into the first test material, and a stirring device stirs and fully disperses the solvent and the first test material to form a second test material. Taking out a part of the second test material as the first test sample. The steps of preparing the second test sample include: adding a solvent into the second test material, and the stirring device stirs and fully disperses the solvent and the second test material to form a third test material. Taking out the third test material as the second test sample.

[0011] In some possible designs, when the viscosity of the second mixed material is within a first preset range and the stability characterization quantity of the second mixed material is within a second preset range, the viscosity μ1 of the second mixed material satisfies: 5000 millipascal·seconds ≤ μ1 ≤ 10000 millipascal·seconds, and the stability characterization quantity S1 of the second mixed material satisfies: -10 millipascal·seconds per minute ≤ S1 < 0. When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the viscosity μ2 of the negative electrode active material satisfies: 5000 millipascal·seconds ≤ μ2 ≤ 10000 millipascal·seconds, and the stability characterization quantity S2 of the negative electrode active material satisfies: -10 millipascal·seconds per minute ≤ S2 < 0.

[0012] In some possible designs, when the stirring device stirs the solvent and the dispersing material, the secondary battery manufacturing process includes: storing the rotation speed of the stirring member and the current of the driving motor in a database. When the viscosity of the second mixed material is within a first preset range and the stability characterization quantity of the second mixed material is within a second preset range, the secondary battery manufacturing process includes: storing the stirring time of the stirring device for the second mixed material in the database. When the stirring device stirs the solvent and the second mixed material, the secondary battery manufacturing process includes: storing the rotation speed of the stirring member and the current of the driving motor in a database. When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the secondary battery manufacturing process includes: storing the stirring time of the stirring device for the negative electrode active material in the database.

[0013] The second aspect of the present application provides a secondary battery, which is manufactured by the secondary battery manufacturing process described in any one of the above. The secondary battery includes a housing, an electrode assembly, and an electrolyte. The housing includes a receiving cavity, and the electrode assembly and the electrolyte are located in the receiving cavity. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a separator, and the separator is located between the positive electrode plate and the negative electrode plate. The negative electrode plate includes a negative electrode current collector and a negative electrode active material.

[0014] In a third aspect of the present application, an energy storage system is provided, and the energy storage system includes the above secondary battery.

[0015] In a fourth aspect of the present application, an electrical equipment is provided, and the electrical equipment includes a load and the above energy storage system, and the energy storage system can supply power to the load.

[0016] In the present application, by calculating the viscosities of the second hybrid material and the anode active material in real time through a calculation module, the process of taking out the materials is reduced, which is beneficial to shortening the preparation cycle of the anode active material. At the same time, the risk of material contamination during the taking-out process is reduced, and the accuracy of the test results is improved. In addition, the process of taking out the materials is reduced, the waste of materials caused by viscosity testing is reduced, the discharge rate of the anode active material is increased, the preparation cost of the anode active material is reduced, the costs of the battery cell assembly and the secondary battery made of the anode active material are reduced, and the costs of the energy storage system including the secondary battery and the electrical equipment including the energy storage system are reduced.

[0017] By calculating the viscosity and the stability characterization quantity in real time through the calculation module, it can be judged whether to enter the next process or discharge according to the viscosity and the stability characterization quantity, so that the stirring equipment can stir the materials within the optimal stirring duration, reducing the risk of performance degradation of the anode active material caused by too long stirring time, shortening the stirring duration, and reducing the costs of the anode active material, the anode electrode sheet, the secondary battery, the energy storage system, and the electrical equipment.

[0018] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to illustrate the technical solutions of the embodiments of the present application more clearly, the drawings required to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic structural diagram of a vehicle provided by some embodiments of the present application; Figure 2 It is a schematic structural diagram of an energy storage box provided by some embodiments of the present application; Figure 3 It is an exploded view of a secondary battery provided by some embodiments of the present application; Figure 4 It is a schematic structural diagram of a top cover provided by some embodiments of the present application; Figure 5 It is a schematic structural diagram of a battery cell assembly provided by some embodiments of the present application; Figure 6Schematic diagram of the stacked structure of the battery cell assembly provided by some embodiments of the present application; Figure 7 Schematic diagram of the process flow of the secondary battery manufacturing process provided by some embodiments of the present application; Figure 8 Schematic diagram of the process flow of the preparation process of the negative electrode active material in the related art; Figure 9 Schematic diagram of the process flow of the preparation process of the negative electrode active material provided by some embodiments of the present application; Figure 10 Schematic diagram of the process flow when the solvent and the first mixed material are mixed in batches; Figure 11 Schematic diagram of the process flow for calculating the first coefficient provided by some embodiments of the present application; Figure 12 Schematic diagram of the process flow for calculating the second coefficient provided by some embodiments of the present application; Figure 13 Schematic diagram of the process flow for calculating the first coefficient and the second coefficient provided by some embodiments of the present application.

[0021] Reference numerals: 1 - battery pack; 2 - energy storage box; 21 - cabinet body; 3 - secondary battery; 31 - housing; 32 - top cover; 321 - positive electrode terminal; 322 - negative electrode terminal; 323 - pressure relief valve; 33 - battery cell assembly; 331 - positive electrode plate; 332 - negative electrode plate; 333 - separator; 334 - positive electrode tab; 335 - negative electrode tab. Detailed description of the specific embodiments

[0022] In order to better understand the technical solutions of the present application, the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0023] It should be clear that the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0024] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms of "a", "the" and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0025] It should be understood that the term "and / or" used herein is merely a description of the relationship between associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0026] In a first aspect, embodiments of the present application provide a secondary battery, which can be but is not limited to being used in power-consuming devices such as vehicles, ships, or aircraft. Exemplarily, the power-consuming device can be a mobile phone, a tablet computer, a laptop computer, an electric toy, an electric tool, a battery-powered vehicle, an electric vehicle, a ship, a spacecraft, and so on. Among them, the electric toy can include stationary or mobile electric toys, such as a game console, an electric vehicle toy, an electric ship toy, and an electric aircraft toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, and a spaceship, etc.

[0027] For the sake of convenience of description, the power-consuming device is taken as an example of a vehicle for illustration.

[0028] Please refer to Figure 1 , Figure 1 which is a schematic structural diagram of a vehicle provided by some embodiments of the present application. The vehicle can be a fuel vehicle, a gas vehicle, or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or an extended-range electric vehicle, etc. A battery pack 1 is disposed inside the vehicle, and the battery pack 1 can be disposed at the bottom, head, or tail of the vehicle. The battery pack 1 can be used for power supply of the vehicle.

[0029] The secondary battery disclosed in the embodiments of the present application can also be used in energy storage systems such as energy storage boxes. For the sake of convenience of description, the energy storage system is taken as an example of an energy storage box.

[0030] Please refer to Figure 2 , Figure 2 which is a schematic structural diagram of an energy storage box provided by some embodiments of the present application. The energy storage box 2 includes a cabinet body 21, an inverter, and at least one battery pack. The cabinet body 21 has a receiving cavity, and the inverter and the battery pack are received in the receiving cavity. The inverter is used to convert direct current into alternating current. The inverter has advantages such as high conversion efficiency, fast start-up speed, and high safety, and can also have functions such as short-circuit protection, overload protection, over / under voltage protection, and over-temperature protection.

[0031] In some large energy storage boxes, a battery management system can also be included. The battery management system is used to make the battery pack work within a safe working range, and can control the charge and discharge power of the battery pack according to factors such as environmental temperature, battery state, and power consumption demand, etc., to improve the safety of the battery pack, make the working state of the battery pack more reasonable, and thus be beneficial to improving the endurance and service life of the battery pack.

[0032] The battery pack includes a box body and a plurality of secondary batteries 3, and the plurality of secondary batteries 3 are accommodated in the box body. Among them, the box body can be made of aluminum, aluminum alloy or other metal materials, or can also be made of non-metal materials. The box body is used to provide an accommodation space for the secondary batteries 3, and the box body can adopt various structures.

[0033] In some embodiments, the box body may include a bottom cover and an upper box cover. The bottom cover is a structure with an open top. The size of the upper box cover is equivalent to the size of the top opening of the bottom cover. The upper box cover can be covered on the bottom cover in the height direction of the battery pack, and the upper box cover and the bottom cover can be connected by fixing parts such as bolts. The upper box cover and the bottom cover enclose an accommodation space for accommodating the secondary batteries. The box body can be of various shapes, such as a cylinder, a cuboid, etc.

[0034] A seal can also be provided between the upper box cover and the bottom cover for sealing the accommodation space.

[0035] In the battery pack, the plurality of secondary batteries 3 can be connected in series, in parallel or in a mixed connection. A mixed connection means that there are both series and parallel connections among the plurality of secondary batteries 3. In some embodiments, the plurality of secondary batteries 3 can be directly connected in series, in parallel or in a mixed connection together, and then the whole formed by the plurality of secondary batteries 3 is accommodated in the box body. The plurality of secondary batteries 3 can be arranged side by side along the length direction of the battery pack, or can also be arranged side by side along the width direction of the battery pack.

[0036] In other embodiments, it can also be that a plurality of secondary batteries 3 are first connected in series, in parallel or in a mixed connection to form battery modules, and then the plurality of battery modules are connected in series, in parallel or in a mixed connection to form a whole and are accommodated in the box body. Among them, the battery module includes a frame structure. The frame structure can include end plates, side plates, top plates and bottom plates that are connected to each other. A plurality of secondary batteries are located in the inner cavity of the frame structure and are stacked on each other in the inner cavity of the frame structure. The stacking direction can be the length direction, the width direction or the height direction.

[0037] In addition, other structures can also be included in the battery pack, such as a busbar component for realizing the electrical connection between the plurality of secondary batteries.

[0038] Among them, the secondary battery can be in the shape of a cylinder, a flat body, a cuboid or other shapes, etc.

[0039] Please refer to Figure 3 , Figure 3 , which is an exploded view of the secondary battery 3 provided in some embodiments of the present application. The secondary battery 3 includes a housing 31, a top cover 32, a battery cell assembly 33 and other functional components.

[0040] In some embodiments, the housing 31 and the top cover 32 may be separate components. The housing 31 has an opening, and the top cover 32 is closed at the opening of the housing to isolate the internal environment of the secondary battery 3 from the external environment. The internal environment surrounded by the housing 31 and the top cover 32 can be used to accommodate the battery cell assembly 33, the electrolyte, and other components. In other embodiments, the housing 31 and the top cover 32 may also be integrated. Specifically, the housing 31 and the top cover 32 may first form a common connection surface before other components are placed into the housing, and when it is necessary to encapsulate the interior of the housing 31, the top cover 32 is then closed on the housing 31.

[0041] The housing 31 can be of various shapes and sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined according to the specific shape and size of the battery cell assembly 33. The material of the housing 31 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special restrictions on this.

[0042] Please refer to Figure 4 , Figure 4 which is a schematic structural diagram of the top cover 32 provided by some embodiments of the present application. The shape of the top cover 32 can be adapted to the shape of the housing. The top cover 32 may be provided with a positive electrode terminal 321 and a negative electrode terminal 322. The positive electrode terminal 321 and the negative electrode terminal 322 can be electrically connected to the battery cell assembly 33 for outputting or inputting the electrical energy of the secondary battery 3. In some embodiments, the top cover 32 may also be provided with a pressure relief valve 323 for releasing the internal pressure when the internal pressure or temperature of the secondary battery 3 reaches a threshold. In some embodiments, an insulating member may also be provided on the inner side of the top cover 32, and the insulating member can be used to isolate the conductive components in the housing 31 from the top cover 32 to reduce the risk of short circuit. Exemplarily, the insulating member can be plastic, rubber, etc.

[0043] The material of the top cover 32 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special restrictions on this. Optionally, the top cover 32 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the top cover 32 is not easily deformed when being squeezed or collided, and the secondary battery 3 can have higher structural strength and safety performance.

[0044] Please refer to Figure 5 , Figure 5 which is a schematic structural diagram of the battery cell assembly 33 provided by some embodiments of the present application. The battery cell assembly 33 is a component in the secondary battery 3 that generates electrical energy through an electrochemical reaction. The housing 31 may contain one or more battery cell assemblies 33.

[0045] Please refer to Figure 6 , Figure 6Schematic diagram of the stacked structure of the battery cell assembly 33 provided by some embodiments of the present application. The battery cell assembly 33 includes a positive electrode tab 331, a negative electrode tab 332, and a separator 333. The separator 333 is located between the positive electrode tab 331 and the negative electrode tab 332, and is used to isolate the positive electrode tab 331 and the negative electrode tab 332. The positive electrode tab 331, the separator 333, and the negative electrode tab 332 are stacked and wound in sequence.

[0046] The negative electrode tab 332 includes a negative current collector and a negative active material coated on the surface of the negative current collector. The positive electrode tab 331 includes a positive current collector and a positive active material coated on the surface of the positive current collector. After winding, the negative active material, the positive active material, and the separator 333 located between the two form a wound structure. The positive current collector can be cut to form a positive electrode tab 334, and the negative current collector can be cut to form a negative electrode tab 335. The positive electrode tab 334 and the negative electrode tab 335 can be located at one end of the wound structure together, or the positive electrode tab 334 and the negative electrode tab 335 can be located at both ends of the wound structure respectively.

[0047] The positive electrode tab 334 is electrically connected to the positive electrode terminal 321 through a positive connection member, and the negative electrode tab 335 is electrically connected to the negative electrode terminal 322 through a negative connection member. During the charging and discharging process of the secondary battery 3, the positive active material and the negative active material in the wound structure react with the electrolyte to generate electric energy, which is conducted to the positive electrode terminal 321 through the positive electrode tab 334 and the positive connection member, and is conducted to the negative electrode terminal 322 through the negative electrode tab 335 and the negative connection member, and the electric energy is output through the positive electrode terminal 321 and the negative electrode terminal 322.

[0048] The positive electrode terminals 321 of multiple secondary batteries 3 can be electrically connected through a positive connection plate, and the negative electrode terminals 322 of multiple secondary batteries 3 can be electrically connected through a negative connection plate to achieve series or parallel or mixed connection of multiple secondary batteries 3.

[0049] In a second aspect, an embodiment of the present application provides a manufacturing process for a secondary battery.

[0050] Please refer to Figure 7 , Figure 7 , which is a schematic flow chart of the manufacturing process for a secondary battery provided by some embodiments of the present application. The manufacturing process for a secondary battery includes: Preparing a positive electrode tab and a negative electrode tab; Winding the positive electrode tab, the separator, and the negative electrode tab to form a battery cell assembly; Placing the battery cell assembly into a housing and injecting an electrolyte into the housing to form a secondary battery.

[0051] Among them, the step of preparing the positive electrode tab includes: Preparing a positive active material; Coat the positive electrode active material on the positive electrode current collector and dry it to form the positive electrode plate.

[0052] The materials that can be used for the positive electrode current collector include, but are not limited to, aluminum foil, and the positive electrode active materials include, but are not limited to, lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium iron phosphate, lithium nickel cobalt aluminum oxide and other lithium compounds.

[0053] The steps for preparing the negative electrode plate include: Prepare the negative electrode active material; Coat the negative electrode active material on the negative electrode current collector and dry it to form the negative electrode plate.

[0054] The materials that can be used for the negative electrode current collector include, but are not limited to, copper foil, and the negative electrode active materials that can be used include, but are not limited to, graphite, silicon-based materials (such as silicon or carbon silicon compounds), lithium metal, etc.

[0055] Please refer to Figure 8 , Figure 8 , which is a schematic flow chart of the preparation process of the negative electrode active material in the related technology. In the related technology, the preparation process of the negative electrode active material includes: Put the active substance, thickening agent and conductive agent into the stirring equipment. The active substance includes, but is not limited to, graphite, the thickening agent includes, but is not limited to, CMC (Carboxymethyl Cellulose), and the conductive agent includes, but is not limited to, SP (Super P). The stirring equipment performs mixing and stirring to form the first mixed material.

[0056] Add a solvent to the stirring equipment. The solvent includes, but is not limited to, water. The stirring equipment performs mixing and stirring to form the second mixed material. As the stirring time increases, the viscosity of the second mixed material gradually decreases.

[0057] After stirring for a certain time, take out a part of the second mixed material and test the viscosity of this part of the second mixed material. If the viscosity of the second mixed material meets the requirements, proceed to the next step; otherwise, the stirring equipment continues to stir the second mixed material.

[0058] After the viscosity of the second mixed material meets the requirements, add a binder to the stirring equipment. The binder includes, but is not limited to, SBR (Styrene Butadiene Rubber). The stirring equipment performs mixing and stirring to form the negative electrode active material. As the stirring time increases, the viscosity of the negative electrode active material gradually decreases.

[0059] After stirring for a certain time, take out a part of the negative electrode active material and test the viscosity of this part of the negative electrode active material. If the viscosity of the negative electrode active material meets the requirements, the negative electrode active material is discharged; otherwise, the stirring equipment continues to stir the negative electrode active material.

[0060] In the related art, during the process of taking out a part of the second mixed material and the negative electrode active material, foreign matters such as dust and water vapor in the external environment enter the second mixed material and the negative electrode active material, which affects the test results. Moreover, this part of the second mixed material and the negative electrode active material taken out cannot be used, resulting in material waste and increasing the manufacturing cost of the secondary battery.

[0061] In view of this, please refer to Figure 9 , Figure 9 which is a schematic flowchart of the preparation process of the negative electrode active material provided in some embodiments of the present application. The preparation process of the negative electrode active material provided in the present application includes: At least put the active substance, the thickener and the conductive agent into the stirring equipment according to a preset ratio, and the stirring equipment mixes the active substance, the thickener and the conductive agent to form a first mixed material.

[0062] The total mass of the first mixed material is G1, the mass of the active substance contained in the first mixed material is g11, the mass of the thickener contained in the first mixed material is g12, and the mass of the conductive agent contained in the first mixed material is g13.

[0063] 0.96 ≤ g11 / G1 ≤ 0.965, that is, the mass ratio of the active substance is between 96% and 96.5%. Exemplarily, the mass ratio of the active substance can be 96%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, etc.

[0064] Exemplarily, 0.96 ≤ g11 / G1 ≤ 0.961, and the mass ratio of the active substance can be 96%, 96.01%, 96.02%, 96.03%, 96.04%, 96.05%, 96.06%, 96.07%, 96.08%, 96.09%, 96.1%.

[0065] Exemplarily, 0.961 ≤ g11 / G1 ≤ 0.963, and the mass ratio of the active substance can be 96.1%, 96.11%, 96.13%, 96.15%, 96.17%, 96.19%, 96.2%, 96.21%, 96.23%, 96.25%, 96.27%, 96.29%, 96.3%, etc.

[0066] Exemplarily, 0.963 ≤ g11 / G1 ≤ 0.965, and the mass ratio of the active substance can be 96.3%, 96.31%, 96.33%, 96.35%, 96.37%, 96.39%, 96.4%, 96.41%, 96.43%, 96.45%, 96.47%, 96.49%, 96.5%, etc.

[0067] 0.015 ≤ g12 / G1 ≤ 0.02, that is, the mass ratio of the thickener is between 1.5% and 2%. Exemplarily, the mass ratio of the thickener can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc.

[0068] Exemplarily, 0.015 ≤ g12 / G1 ≤ 0.017, and the mass ratio of the thickener can be 1.5%, 1.51%, 1.53%, 1.57%, 1.59%, 1.6%, 1.61%, 1.63%, 1.65%, 1.67%, 1.69%, 1.7%, etc.

[0069] Exemplarily, 0.017 ≤ g12 / G1 ≤ 0.019, and the mass ratio of the thickener can be 1.7%, 1.71%, 1.73%, 1.77%, 1.79%, 1.8%, 1.81%, 1.83%, 1.85%, 1.87%, 1.89%, 1.9%, etc.

[0070] Exemplarily, 0.019 ≤ g12 / G1 ≤ 0.02, and the mass ratio of the thickener can be 1.9%, 1.91%, 1.92%, 1.93%, 1.94%, 1.95%, 1.96%, 1.97%, 1.98%, 1.99%, 2%, etc.

[0071] 0.01 ≤ g13 / G1 ≤ 0.015, that is, the mass ratio of the conductive agent is between 1% and 1.5%. Exemplarily, the mass ratio of the conductive agent can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc.

[0072] Exemplarily, 0.01 ≤ g13 / G1 ≤ 0.011, and the mass ratio of the conductive agent can be 1%, 1.01%, 1.02%, 1.03%, 1.04%, 1.05%, 1.06%, 1.07%, 1.08%, 1.09%, 1.1%, etc.

[0073] Exemplarily, 0.011 ≤ g13 / G1 ≤ 0.013, and the mass ratio of the conductive agent can be 1.1%, 1.11%, 1.13%, 1.15%, 1.17%, 1.19%, 1.2%, 1.21%, 1.23%, 1.25%, 1.27%, 1.29%, 1.3%, etc.

[0074] Exemplarily, 0.013 ≤ g13 / G1 ≤ 0.015, and the mass ratio of the conductive agent can be 1.3%, 1.31%, 1.33%, 1.35%, 1.37%, 1.39%, 1.4%, 1.41%, 1.43%, 1.45%, 1.47%, 1.49%, 1.5%, etc.

[0075] The above are only examples of the mixing ratios of the active material, thickener, and conductive agent. The embodiments of the present application do not impose special restrictions on the specific mixing ratios of the active material, thickener, and conductive agent.

[0076] After forming the first mixed material, a solvent is added to the first mixed material, and a stirring device stirs the solvent and the first mixed material to form a second mixed material. A calculation module calculates the viscosity and stability characterization quantity of the second mixed material in real time.

[0077] The total mass of the solvent is G2, and the total mass of the first mixed material is G1. 1:1 ≤ G2:G1 ≤ 1:1.2, that is, 1 ≤ G1 / G2 ≤ 1.2. Exemplarily, the mass ratio of the first mixed material to the solvent can be 1, 1.05, 1.1, 1.15, 1.2, etc.

[0078] Exemplarily, 1 ≤ G1 / G2 ≤ 1.1. The mass ratio of the first mixed material to the solvent can be 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, etc.

[0079] Exemplarily, 1.1 ≤ G1 / G2 ≤ 1.2. The mass ratio of the first mixed material to the solvent can be 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.2, etc.

[0080] The above are only examples of the mixing ratios of the solvent and the first mixed material. The embodiments of the present application do not impose special limitations on the mixing ratios of the solvent and the first mixed material.

[0081] When the viscosity of the second mixed material is within the first preset range and the stability characterization quantity of the second mixed material is within the second preset range, exemplarily, the viscosity μ1 of the second mixed material satisfies: 5000 millipascal·seconds ≤ μ1 ≤ 10000 millipascal·seconds, and the stability characterization quantity S1 of the second mixed material satisfies: -10 millipascal·seconds per minute ≤ S1 < 0, a binder is added to the second mixed material, and a stirring device stirs the solvent and the second mixed material to form a negative electrode active material. A calculation module calculates the viscosity and stability characterization quantity of the negative electrode active material in real time.

[0082] The mass of the binder is G3, and the mass of the second mixed material is G4. 0.012 ≤ G3 / G4 ≤ 0.018. Exemplarily, the mass ratio of the binder to the second mixed material can be 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018.

[0083] Exemplarily, 0.012 ≤ G3 / G4 ≤ 0.014, and the mass ratio of the adhesive to the second mixed material can be 0.012, 0.0122, 0.0124, 0.0126, 0.0128, 0.013, 0.0132, 0.0134, 0.0136, 0.0138, 0.014, etc.

[0084] Exemplarily, 0.014 ≤ G3 / G4 ≤ 0.016, and the mass ratio of the adhesive to the second mixed material can be 0.014, 0.0142, 0.0144, 0.0146, 0.0148, 0.015, 0.0152, 0.0154, 0.0156, 0.0158, 0.016, etc.

[0085] Exemplarily, 0.016 ≤ G3 / G4 ≤ 0.018, and the mass ratio of the adhesive to the second mixed material can be 0.016, 0.0162, 0.0164, 0.0166, 0.0168, 0.017, 0.0172, 0.0174, 0.0176, 0.0178, 0.018, etc.

[0086] The above are only examples of the mixing ratio of the adhesive to the second mixed material, and the embodiments of the present application do not make special limitations on the mixing ratio of the adhesive and the second mixed material.

[0087] The viscosity μ and the stability characterization quantity S satisfy: S = d(μ) / d(t), where t is the stirring duration of the stirring equipment.

[0088] When the viscosity of the negative electrode active material is within the third preset range and the stability characterization quantity of the negative electrode active material is within the fourth preset range, exemplarily, when the viscosity μ2 of the negative electrode active material satisfies: 5000 millipascal·seconds ≤ μ2 ≤ 10000 millipascal·seconds, and the stability characterization quantity S2 of the negative electrode active material satisfies: -10 millipascal·seconds per minute ≤ S2 < 0, the negative electrode active material is discharged.

[0089] Exemplarily, the material viscosity can be 5000 millipascal·seconds, 5500 millipascal·seconds, 6000 millipascal·seconds, 6500 millipascal·seconds, 7000 millipascal·seconds, 7500 millipascal·seconds, 8000 millipascal·seconds, 8500 millipascal·seconds, 9000 millipascal·seconds, 9500 millipascal·seconds, 10000 millipascal·seconds, etc.

[0090] Exemplarily, the viscosity μ of the material satisfies: 5000 millipascal - seconds ≤ μ ≤ 6000 millipascal - seconds. The viscosity μ can be 5000 millipascal - seconds, 5100 millipascal - seconds, 5200 millipascal - seconds, 5300 millipascal - seconds, 5400 millipascal - seconds, 5500 millipascal - seconds, 5600 millipascal - seconds, 5700 millipascal - seconds, 5800 millipascal - seconds, 5900 millipascal - seconds, 6000 millipascal - seconds, etc.

[0091] Exemplarily, the viscosity μ of the material satisfies: 6000 millipascal - seconds ≤ μ ≤ 7000 millipascal - seconds. The viscosity μ can be 6000 millipascal - seconds, 6100 millipascal - seconds, 6200 millipascal - seconds, 6300 millipascal - seconds, 6400 millipascal - seconds, 6500 millipascal - seconds, 6600 millipascal - seconds, 6700 millipascal - seconds, 6800 millipascal - seconds, 6900 millipascal - seconds, 7000 millipascal - seconds, etc.

[0092] Exemplarily, the viscosity μ of the material satisfies: 7000 millipascal - seconds ≤ μ ≤ 8000 millipascal - seconds. The viscosity μ can be 7000 millipascal - seconds, 7100 millipascal - seconds, 7200 millipascal - seconds, 7300 millipascal - seconds, 7400 millipascal - seconds, 7500 millipascal - seconds, 7600 millipascal - seconds, 7700 millipascal - seconds, 7800 millipascal - seconds, 7900 millipascal - seconds, 8000 millipascal - seconds, etc.

[0093] Exemplarily, the viscosity μ of the material satisfies: 8000 millipascal - seconds ≤ μ ≤ 9000 millipascal - seconds. The viscosity μ can be 8000 millipascal - seconds, 8100 millipascal - seconds, 8200 millipascal - seconds, 8300 millipascal - seconds, 8400 millipascal - seconds, 8500 millipascal - seconds, 8600 millipascal - seconds, 8700 millipascal - seconds, 8800 millipascal - seconds, 8900 millipascal - seconds, 9000 millipascal - seconds, etc.

[0094] Exemplarily, the viscosity μ of the material satisfies: 9000 millipascal - seconds ≤ μ ≤ 10000 millipascal - seconds. The viscosity μ can be 9000 millipascal - seconds, 9100 millipascal - seconds, 9200 millipascal - seconds, 9300 millipascal - seconds, 9400 millipascal - seconds, 9500 millipascal - seconds, 9600 millipascal - seconds, 9700 millipascal - seconds, 9800 millipascal - seconds, 9900 millipascal - seconds, 10000 millipascal - seconds, etc.

[0095] The stability characterization quantity of the material can be -10 millipascal - seconds per minute, -9.5 millipascal - seconds per minute, -9 millipascal - seconds per minute, -8.5 millipascal - seconds per minute, -8 millipascal - seconds per minute, -7.5 millipascal - seconds per minute, -7 millipascal - seconds per minute, -6.5 millipascal - seconds per minute, -6 millipascal - seconds per minute, -5.5 millipascal - seconds per minute, -5 millipascal - seconds per minute, -4.5 millipascal - seconds per minute, -4 millipascal - seconds per minute, -3.5 millipascal - seconds per minute, -3 millipascal - seconds per minute, -2.5 millipascal - seconds per minute, -2 millipascal - seconds per minute, -1.5 millipascal - seconds per minute, -1 millipascal - seconds per minute, -0.5 millipascal - seconds per minute, -0.01 millipascal - seconds per minute, etc.

[0096] Exemplarily, the stability characterization quantity S of the material satisfies: -10 millipascal - seconds per minute ≤ S ≤ -9 millipascal - seconds per minute. The stability characterization quantity S of the material can be -10 millipascal - seconds per minute, -9.9 millipascal - seconds per minute, -9.8 millipascal - seconds per minute, -9.7 millipascal - seconds per minute, -9.6 millipascal - seconds per minute, -9.5 millipascal - seconds per minute, -9.4 millipascal - seconds per minute, -9.3 millipascal - seconds per minute, -9.2 millipascal - seconds per minute, -9.1 millipascal - seconds per minute, -9 millipascal - seconds per minute, etc.

[0097] Exemplarily, the stability characterization quantity S of the material satisfies: -9 millipascal - seconds per minute ≤ S ≤ -8 millipascal - seconds per minute. The stability characterization quantity S of the material can be -9 millipascal - seconds per minute, -8.9 millipascal - seconds per minute, -8.8 millipascal - seconds per minute, -8.7 millipascal - seconds per minute, -8.6 millipascal - seconds per minute, -8.5 millipascal - seconds per minute, -8.4 millipascal - seconds per minute, -8.3 millipascal - seconds per minute, -8.2 millipascal - seconds per minute, -8.1 millipascal - seconds per minute, -8 millipascal - seconds per minute, etc.

[0098] Exemplarily, the stability characterization quantity S of the material satisfies: -8 millipascal - seconds per minute ≤ S ≤ -7 millipascal - seconds per minute. The stability characterization quantity S of the material can be -8 millipascal - seconds per minute, -7.9 millipascal - seconds per minute, -7.8 millipascal - seconds per minute, -7.7 millipascal - seconds per minute, -7.6 millipascal - seconds per minute, -7.5 millipascal - seconds per minute, -7.4 millipascal - seconds per minute, -7.3 millipascal - seconds per minute, -7.2 millipascal - seconds per minute, -7.1 millipascal - seconds per minute, -7 millipascal - seconds per minute, etc.

[0099] Exemplarily, the stability characterization quantity S of the material satisfies: -7 millipascal·seconds per minute ≤ S ≤ -6 millipascal·seconds per minute. The stability characterization quantity S of the material can be -7 millipascal·seconds per minute, -6.9 millipascal·seconds per minute, -6.8 millipascal·seconds per minute, -6.7 millipascal·seconds per minute, -6.6 millipascal·seconds per minute, -6.5 millipascal·seconds per minute, -6.4 millipascal·seconds per minute, -6.3 millipascal·seconds per minute, -6.2 millipascal·seconds per minute, -6.1 millipascal·seconds per minute, -6 millipascal·seconds per minute, etc.

[0100] Exemplarily, the stability characterization quantity S of the material satisfies: -6 millipascal·seconds per minute ≤ S ≤ -5 millipascal·seconds per minute. The stability characterization quantity S of the material can be -6 millipascal·seconds per minute, -5.9 millipascal·seconds per minute, -5.8 millipascal·seconds per minute, -5.7 millipascal·seconds per minute, -5.6 millipascal·seconds per minute, -5.5 millipascal·seconds per minute, -5.4 millipascal·seconds per minute, -5.3 millipascal·seconds per minute, -5.2 millipascal·seconds per minute, -5.1 millipascal·seconds per minute, -5 millipascal·seconds per minute, etc.

[0101] Exemplarily, the stability characterization quantity S of the material satisfies: -5 millipascal·seconds per minute ≤ S ≤ -4 millipascal·seconds per minute. The stability characterization quantity S of the material can be -5 millipascal·seconds per minute, -4.9 millipascal·seconds per minute, -4.8 millipascal·seconds per minute, -4.7 millipascal·seconds per minute, -4.6 millipascal·seconds per minute, -4.5 millipascal·seconds per minute, -4.4 millipascal·seconds per minute, -4.3 millipascal·seconds per minute, -4.2 millipascal·seconds per minute, -4.1 millipascal·seconds per minute, -4 millipascal·seconds per minute, etc.

[0102] Exemplarily, the stability characterization quantity S of the material satisfies: -4 millipascal·seconds per minute ≤ S ≤ -3 millipascal·seconds per minute. The stability characterization quantity S of the material can be -4 millipascal·seconds per minute, -3.9 millipascal·seconds per minute, -3.8 millipascal·seconds per minute, -3.7 millipascal·seconds per minute, -3.6 millipascal·seconds per minute, -3.5 millipascal·seconds per minute, -3.4 millipascal·seconds per minute, -3.3 millipascal·seconds per minute, -3.2 millipascal·seconds per minute, -3.1 millipascal·seconds per minute, -3 millipascal·seconds per minute, etc.

[0103] For example, the stability characterization value S of the material satisfies: -3 millipascal seconds per minute ≤ S ≤ -2 millipascal seconds per minute. The stability characterization value S of the material can be -3 millipascal seconds per minute, -2.9 millipascal seconds per minute, -2.8 millipascal seconds per minute, -2.7 millipascal seconds per minute, -2.6 millipascal seconds per minute, -2.5 millipascal seconds per minute, -2.4 millipascal seconds per minute, -2.3 millipascal seconds per minute, -2.2 millipascal seconds per minute, -2.1 millipascal seconds per minute, -2 millipascal seconds per minute, etc.

[0104] For example, the stability characterization value S of the material satisfies: -2 millipascal seconds per minute ≤ S ≤ -1 millipascal seconds per minute. The stability characterization value S of the material can be -2 millipascal seconds per minute, -1.9 millipascal seconds per minute, -1.8 millipascal seconds per minute, -1.7 millipascal seconds per minute, -1.6 millipascal seconds per minute, -1.5 millipascal seconds per minute, -1.4 millipascal seconds per minute, -1.3 millipascal seconds per minute, -1.2 millipascal seconds per minute, -1.1 millipascal seconds per minute, -1 millipascal seconds per minute, etc.

[0105] For example, the stability characterizing value S of the material satisfies: -1 milliPascal second per minute ≤ S < 0. The stability characterizing value S of the material may be -1 milliPascal second per minute, -0.9 milliPascal second per minute, -0.8 milliPascal second per minute, -0.7 milliPascal second per minute, -0.6 milliPascal second per minute, -0.5 milliPascal second per minute, -0.4 milliPascal second per minute, -0.3 milliPascal second per minute, -0.2 milliPascal second per minute, -0.1 milliPascal second per minute, etc.

[0106] If the viscosity and stability characterization values of the material are large, the fluidity of the negative electrode active material is poor. When the negative electrode active material with high viscosity is coated on the negative electrode current collector, there is a higher risk of inconsistent coating thickness. If the viscosity and stability characterization values of the material are small, the fluidity of the negative electrode active material is too strong, and the coating of the negative electrode active material on the negative electrode current collector is more difficult. Therefore, 5000 millipascal·second ≤ μ ≤ 10000 millipascal·second, -10 millipascal·second per minute ≤ S < 0, which reduces the difficulty of coating the negative electrode active material, improves the coating uniformity of the negative electrode active material, and thus improves the performance of the negative electrode sheet.

[0107] In the step of adding the solvent into the first mixed material, the solvent may be added all at once or in batches.

[0108] Please refer to Figure 10 ,Figure 10 It is a schematic flow diagram when the solvent and the first mixed material are mixed in batches. The steps of adding the solvent into the first mixed material and the stirring device stirring the solvent and the first mixed material to form the second mixed material include: Adding a solvent with a first mass g21 into the first mixed material, and the stirring device stirs the solvent and the first mixed material to form a dispersed material; Adding a solvent with a second mass g22 into the dispersed material, and the stirring device stirs the solvent and the dispersed material to form the second mixed material.

[0109] 8:12 ≤ g21:g22 ≤ 18:12. Exemplarily, the proportional relationship between the first mass and the second mass can be 8:12, 9:12, 10:12, 11:12, 12:12, 13:12, 14:12, 15:12, 16:12, 17:12, 18:12, etc.

[0110] Exemplarily, 8:12 ≤ g21:g22 ≤ 10:12. The proportional relationship between the first mass and the second mass can be 8:12, 8.2:12, 8.4:12, 8.6:12, 8.8:12, 9:12, 9.2:12, 9.4:12, 9.6:12, 9.8:12, 10:12, etc.

[0111] Exemplarily, 10:12 ≤ g21:g22 ≤ 12:12. The proportional relationship between the first mass and the second mass can be 10:12, 10.2:12, 10.4:12, 10.6:12, 10.8:12, 11:12, 11.2:12, 11.4:12, 11.6:12, 11.8:12, 12:12, etc.

[0112] Exemplarily, 12:12 ≤ g21:g22 ≤ 14:12. The proportional relationship between the first mass and the second mass can be 12:12, 12.2:12, 12.4:12, 12.6:12, 12.8:12, 13:12, 13.2:12, 13.4:12, 13.6:12, 13.8:12, 14:12, etc.

[0113] Exemplarily, 14:12 ≤ g21:g22 ≤ 16:12. The proportional relationship between the first mass and the second mass can be 14:12, 14.2:12, 14.4:12, 14.6:12, 14.8:12, 15:12, 15.2:12, 15.4:12, 15.6:12, 15.8:12, 16:12, etc.

[0114] Exemplarily, 16:12 ≤ g21:g22 ≤ 18:12, and the ratio relationship between the first quality and the second quality can be 16:12, 16.2:12, 16.4:12, 16.6:12, 16.8:12, 17:12, 17.2:12, 17.4:12, 17.6:12, 17.8:12, 18:12, etc.

[0115] The above are only examples of the ratio of the first quality and the second quality. The embodiments of the present application do not make special limitations on the relationship between the first quality and the second quality. Exemplarily, the first quality is less than the second quality, that is, a small amount of solvent is added for the first time, and the remaining solvent is added for the second time.

[0116] In this embodiment, when a small amount of solvent is added for the first time, the solid components of the first mixed material can be preliminarily wetted and dispersed. Adding a small amount of solvent in advance allows them to fully expand first, reducing the agglomeration phenomenon that may occur when a large amount of solvent is added subsequently. The solvent is added at least in two times, which can facilitate the adjustment of the overall viscosity and fluidity of the negative electrode active material, thereby facilitating the uniform dispersion of each material and being beneficial to improving the performance of the negative electrode active material.

[0117] In this embodiment, the viscosity of the second mixed material and the negative electrode active material is calculated in real time by the calculation module, reducing the process of taking out a part of the second mixed material and the negative electrode active material, which is beneficial to shortening the preparation cycle of the negative electrode active material. At the same time, the risk of contamination of the second mixed material and the negative electrode active material during the taking-out process is reduced, thereby improving the accuracy of the test results, reducing the risk that the performance of the negative electrode active material is affected by too long stirring time, and being beneficial to improving the performance of the negative electrode active material. In addition, the process of taking out a part of the second mixed material and the negative electrode active material is reduced, the waste of materials caused by viscosity testing is reduced, thereby improving the discharge rate of the negative electrode active material, reducing the preparation cost of the negative electrode active material, and further reducing the costs of the battery cell assembly and the secondary battery made of the negative electrode active material, and reducing the costs of the energy storage system including the secondary battery and the electrical equipment including the energy storage system.

[0118] During the stirring and dispersion process, the viscosity will gradually decrease with time. When the dispersion of each material tends to be stable, the rate of decrease of the viscosity tends to a constant value. If the dispersion is uneven, the viscosity may jump. Therefore, by the calculation module, the viscosity of the second mixed material and the negative electrode active material is detected and calculated in real time, the curve of the viscosity changing with time is obtained, and the differential of the viscosity with respect to time is taken, and the stability characterization quantity for characterizing the rate of change of the viscosity can be obtained.

[0119] Calculate the stability characterization quantities of the second mixed material and the negative electrode active material, based on which it can be judged whether the ability of the negative electrode active material to maintain its viscosity characteristics during storage, transportation and use meets the requirements. The viscosity and stability characterization quantities are calculated in real time through a calculation module, and it can be judged whether to enter the next process or discharge according to the viscosity and stability characterization quantities, so that the mixing equipment can mix the materials within the optimal mixing duration, reducing the risk of performance degradation of the negative electrode active material caused by too long mixing time, thereby shortening the mixing duration and reducing the costs of the negative electrode active material, the negative electrode sheet, the secondary battery, the energy storage system and the electrical equipment.

[0120] The mixing equipment can also upload the mixing parameters of the second mixed material and the negative electrode active material to the database. The mixing parameters include but are not limited to the types of materials, the mixing ratios of the materials, the mixing speed of the mixing parts, the current feedback value of the drive motor driving the mixing parts to rotate, the mixing duration, the real-time viscosity and the real-time stability characterization quantities, etc.

[0121] When the mixing equipment processes the same negative electrode active material in batches, the same here means that the parameters such as the material type and the mixing ratio are exactly the same. During the production of the first batch of the negative electrode active material, the relevant mixing parameters are uploaded to the database. In the production of subsequent batches, the mixing equipment can directly extract the mixing parameters from the database, so as to select the optimal parameters such as the rotation speed and the mixing duration to improve the processing efficiency of the negative electrode active material in subsequent batches.

[0122] The process of taking out a part of the second mixed material and the negative electrode active material is reduced, which is beneficial to shortening the preparation cycle of the negative electrode active material. At the same time, the risk of contamination of the second mixed material and the negative electrode active material during the taking-out process is reduced, thereby improving the accuracy of the test results, reducing the risk of affecting the performance of the negative electrode active material due to too long mixing time, which is beneficial to improving the performance of the negative electrode active material. In addition, the process of taking out a part of the second mixed material and the negative electrode active material is reduced, the waste of materials caused by viscosity testing is reduced, thereby improving the discharge rate of the negative electrode active material, reducing the preparation cost of the negative electrode active material, and further reducing the costs of the cell assembly and the secondary battery made of the negative electrode active material, and reducing the costs of the energy storage system including the secondary battery and the electrical equipment including the energy storage system.

[0123] Taking a double planetary mixing equipment as an example, the drive motor of the mixing equipment controls the rotation of mixing parts such as mixing paddles or dispersion discs. The mixing parts apply shear stress to the materials, and the mixing parts drive the materials to flow, mix and disperse evenly. From the perspective of fluid mechanics, the viscosity and rotation speed of the fluid are directly related to the value of the shear stress received, and the value of the shear stress is related to the current of the motor.

[0124] Exemplarily, during the stirring process of the stirring device for the second mixed material and the negative electrode active material, as the stirring duration increases, the viscosity of the material gradually decreases, and the stirring member rotates uniformly at a preset rotational speed. As the viscosity decreases, the shear stress value required to stir the material gradually decreases, that is, the feedback current value of the driving motor gradually decreases. That is, the viscosity of the material can be directly reflected from the feedback current value of the driving motor.

[0125] Taking the process of the stirring device stirring the second mixed material as an example, Table 1 below exemplifies the relationship between the feedback current value of the driving motor and the stirring duration. As shown in Table 1, as the stirring duration increases, the viscosity of the material gradually decreases. When maintaining the stirring member rotating at a constant rotational speed, the feedback current value of the driving motor gradually decreases.

[0126]

[0127] During the stirring process of the stirring device, the calculation module can obtain the real-time current value I of the driving motor. The calculation module, based on the rotational speed n of the stirring member and the real-time current value I of the driving motor, and then through the viscosity formula μ = M×(I / n), can achieve the real-time calculation of the viscosity of the material, so as to determine whether the next process or discharging can be carried out. In the viscosity formula, μ is the viscosity of the material, the coefficient M = k / b, k is the torque constant of the driving motor, and b is the conversion coefficient.

[0128] In this embodiment, by calculating the real-time viscosity of the material through the real-time change of the feedback current value of the driving motor, the difficulty of viscosity testing is reduced, and thus the accuracy and reliability of the viscosity test results are improved.

[0129] The torque constant of the driving motor can be obtained from the parameters of the driving motor according to the model of the driving motor. Therefore, before the steps of calculating the viscosity and stability characterization quantity of the material, it is necessary to first determine the coefficient M.

[0130] The secondary battery preparation process includes: Preparing a first test sample, the composition and composition ratio of the first test sample are exactly the same as those of the second mixed material, that is, the first test sample at least includes an active substance, a thickening agent, a conductive agent, and a solvent.

[0131] Taking out at least a part of the first test sample, and using a viscometer to detect the viscosity μ01 of the taken-out part of the first test sample.

[0132] According to the viscosity μ01 of the first test sample, the rotational speed n01 of the stirring member when stirring the first test sample, and the current value I01 of the driving motor, according to μ01 = M1×(I01 / n01), the first coefficient M1 required for calculating the second mixed material is obtained. Here, both n01 and I01 are the real-time rotational speed and current value at the moment of taking out the first test sample.

[0133] Exemplarily, the viscosity μ01 of the first test sample is 10,000 millipascal - seconds, the rotational speed n01 of the stirring member when stirring the first test sample is 25 rpm, and the current value I01 of the drive motor when stirring the first test sample is 70 A. Then the calculation process of M1 is as follows: First, 10000 = M1×(70 / 25). Second, M1 = 10000 / (70 / 25). Finally, M1 = 3571.

[0134] The secondary battery preparation process includes: Preparing a second test sample, the composition components and component ratios of the second test sample are exactly the same as those of the negative electrode active material, that is, the second test sample includes at least active substances, thickeners, conductive agents, solvents, and binders.

[0135] Taking out at least a part of the second test sample and detecting the viscosity μ02 of the taken - out part of the second test sample by using a viscometer.

[0136] According to the viscosity μ02 of the second test sample, the rotational speed n02 of the stirring member when stirring the second test sample, and the current value I02 of the drive motor, based on μ02 = M2×(I02 / n02), the second coefficient M2 required for calculating the negative electrode active material is obtained. Here, n02 and I02 are the real - time rotational speed and current value at the moment of taking out the second test sample.

[0137] Exemplarily, the viscosity μ02 of the second test sample is 11280.6 millipascal - seconds, the rotational speed n02 of the stirring member when stirring the second test sample is 925 rpm, and the current value I02 of the drive motor when stirring the second test sample is 102.3 A. Then the calculation process of M2 is as follows: First, 11280.6 = M2×(102.3 / 925). Second, M2 = 11280.6 / (102.3 / 925). Finally, M2≈102000.

[0138] In this embodiment, the first coefficient M1 is calculated by using the first test sample that is exactly the same as the second mixed material, and the second coefficient M2 is calculated by using the second test sample that is exactly the same as the negative electrode active material, which improves the accuracy of the calculation results of the first coefficient M1 and the second coefficient M2, thereby improving the accuracy of the viscosity calculation results of the second mixed material and the negative electrode active substance.

[0139] The first test sample can be directly taken out from the second mixed material or can be prepared separately. The second test sample can be directly taken out from the negative electrode active material or can be prepared separately.

[0140] Figure 11Schematic flow chart for calculating the first coefficient provided by some embodiments of the present application. When the first test sample is directly taken out from the second mixed material, please refer to Figure 11 , the steps for preparing the first test sample include: Take out a part of the second mixed material as the first test sample. At this time, the rotation speed n01 of the stirring member is the real-time rotation speed when taking out the first test sample, and the current value I01 of the driving motor is the real-time current when taking out the first test sample.

[0141] When the second test sample is directly taken out from the negative electrode active material, please refer to Figure 11 , the steps for preparing the second test sample include: Take out a part of the negative electrode active material as the second test sample. At this time, the rotation speed n02 of the stirring member is the real-time rotation speed when taking out the second test sample, and the current value I02 of the driving motor is the real-time current when taking out the second test sample.

[0142] In this embodiment, directly taking out a part of the second mixed material and the negative electrode active material as the test sample improves the consistency between the test sample and the second mixed material and the negative electrode active material, thereby improving the accuracy and reliability of viscosity calculation.

[0143] Figure 13 Schematic flow chart for calculating the first coefficient and the second coefficient provided by some embodiments of the present application. When the first test sample is prepared separately, please refer to Figure 13 , the steps for preparing the first test sample include: Before the step of preparing the first mixed material, prepare the first test material. The composition components and component ratios of the first test material are exactly the same as those of the first mixed material. The first test material at least includes active substances, thickeners, and conductive agents.

[0144] Add the solvent into the first test material, and the stirring device stirs and fully disperses the solvent and the first test material to form the second test material.

[0145] Take out a part of the second test material as the first test sample.

[0146] When the first test sample is prepared separately, please refer to Figure 13 , the steps for preparing the second test sample include: Add the solvent into the remaining second test material, and the stirring device stirs and fully disperses the solvent and the second test material to form the third test material; Take out the third test material as the second test sample.

[0147] In this embodiment, before the negative electrode active material is formally prepared, a small amount of the first test sample and the second test sample are prepared first, and the conversion coefficient is determined through the first test sample and the second test sample. Thereafter, during the formal preparation process of the negative electrode active material, the real-time viscosity of the material can be directly calculated according to the conversion coefficient, which is beneficial to shortening the preparation cycle of the negative electrode active material and reducing the preparation cost.

[0148] The first coefficient and the second coefficient can be stored in a database and corresponding to parameters such as the composition and mixing ratio of the negative electrode active material. When the stirring device processes the same negative electrode active material in other batches, the first coefficient and the second coefficient can be directly extracted from the database, thereby further shortening the preparation cycle.

[0149] In summary, by way of example, the preparation process of the secondary battery provided in some examples of the present application includes: Put graphite, CMC and SP into a stirring device, and the stirring device mixes graphite, CMC and SP at a first preset rotation speed to form a first mixed material.

[0150] Taking the stirring paddle as an example, the first rotation speed is between 15 rpm and 25 rpm. By way of example, the first rotation speed can be 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm, 20 rpm, 21 rpm, 22 rpm, 23 rpm, 24 rpm, 25 rpm, etc.

[0151] By way of example, the first rotation speed is between 15 rpm and 20 rpm. The first rotation speed can be 15 rpm, 15.2 rpm, 15.4 rpm, 15.6 rpm, 15.8 rpm, 16 rpm, 16.2 rpm, 16.4 rpm, 16.6 rpm, 16.8 rpm, 17 rpm, 17.2 rpm, 17.4 rpm, 17.6 rpm, 17.8 rpm, 18 rpm, 18.2 rpm, 18.4 rpm, 18.6 rpm, 18.8 rpm, 19 rpm, 19.2 rpm, 19.4 rpm, 19.6 rpm, 19.8 rpm, 20 rpm, etc.

[0152] Exemplarily, the first rotational speed is between 20 rpm and 25 rpm. The first rotational speed can be 20 rpm, 20.2 rpm, 20.4 rpm, 20.6 rpm, 20.8 rpm, 21 rpm, 21.2 rpm, 21.4 rpm, 21.6 rpm, 21.8 rpm, 22 rpm, 22.2 rpm, 22.4 rpm, 22.6 rpm, 22.8 rpm, 23 rpm, 23.2 rpm, 23.4 rpm, 23.6 rpm, 23.8 rpm, 24 rpm, 24.2 rpm, 24.4 rpm, 24.6 rpm, 24.8 rpm, 25 rpm, etc.

[0153] First water addition and stirring: Add water of the first mass to the first mixture material, and the stirring device stirs the water and the first mixture material at the second rotational speed for the first preset time to form a dispersed material.

[0154] Taking the stirring paddle as an example, the second rotational speed is between 15 rpm and 25 rpm. Exemplarily, the second rotational speed can be 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm, 20 rpm, 21 rpm, 22 rpm, 23 rpm, 24 rpm, 25 rpm, etc.

[0155] Exemplarily, the second rotational speed is between 15 rpm and 20 rpm. The second rotational speed can be 15 rpm, 15.2 rpm, 15.4 rpm, 15.6 rpm, 15.8 rpm, 16 rpm, 16.2 rpm, 16.4 rpm, 16.6 rpm, 16.8 rpm, 17 rpm, 17.2 rpm, 17.4 rpm, 17.6 rpm, 17.8 rpm, 18 rpm, 18.2 rpm, 18.4 rpm, 18.6 rpm, 18.8 rpm, 19 rpm, 19.2 rpm, 19.4 rpm, 19.6 rpm, 19.8 rpm, 20 rpm, etc.

[0156] Exemplarily, the second rotational speed is between 20 rpm and 25 rpm. The second rotational speed can be 20 rpm, 20.2 rpm, 20.4 rpm, 20.6 rpm, 20.8 rpm, 21 rpm, 21.2 rpm, 21.4 rpm, 21.6 rpm, 21.8 rpm, 22 rpm, 22.2 rpm, 22.4 rpm, 22.6 rpm, 22.8 rpm, 23 rpm, 23.2 rpm, 23.4 rpm, 23.6 rpm, 23.8 rpm, 24 rpm, 24.2 rpm, 24.4 rpm, 24.6 rpm, 24.8 rpm, 25 rpm, etc.

[0157] The first preset time is between 30 min and 60 min. Exemplarily, the first preset time can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0158] Exemplarily, the first preset time is between 30 min and 45 min. The first preset time can be 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, 41 min, 42 min, 43 min, 44 min, 45 min, etc.

[0159] Exemplarily, the first preset time is between 45 min and 60 min. The first preset time can be 45 min, 46 min, 47 min, 48 min, 49 min, 50 min, 51 min, 52 min, 53 min, 54 min, 55 min, 56 min, 57 min, 58 min, 59 min, 60 min, etc.

[0160] Second water addition and stirring: Add water of the second mass to the dispersing material, and the stirring device stirs the water and the dispersing material at the third rotation speed for the second preset time to form the second mixed material.

[0161] Taking the stirring paddle as an example, the third rotation speed is between 15 rpm and 25 rpm. Exemplarily, the third rotation speed can be 15 rpm, 16 rpm, 17 rpm, 18 rpm, 19 rpm, 20 rpm, 21 rpm, 22 rpm, 23 rpm, 24 rpm, 25 rpm, etc.

[0162] Exemplarily, the third rotation speed is between 15 rpm and 20 rpm. The third rotation speed can be 15 rpm, 15.2 rpm, 15.4 rpm, 15.6 rpm, 15.8 rpm, 16 rpm, 16.2 rpm, 16.4 rpm, 16.6 rpm, 16.8 rpm, 17 rpm, 17.2 rpm, 17.4 rpm, 17.6 rpm, 17.8 rpm, 18 rpm, 18.2 rpm, 18.4 rpm, 18.6 rpm, 18.8 rpm, 19 rpm, 19.2 rpm, 19.4 rpm, 19.6 rpm, 19.8 rpm, 20 rpm, etc.

[0163] Exemplarily, the third rotational speed is between 20 rpm and 25 rpm. The third rotational speed can be 20 rpm, 20.2 rpm, 20.4 rpm, 20.6 rpm, 20.8 rpm, 21 rpm, 21.2 rpm, 21.4 rpm, 21.6 rpm, 21.8 rpm, 22 rpm, 22.2 rpm, 22.4 rpm, 22.6 rpm, 22.8 rpm, 23 rpm, 23.2 rpm, 23.4 rpm, 23.6 rpm, 23.8 rpm, 24 rpm, 24.2 rpm, 24.4 rpm, 24.6 rpm, 24.8 rpm, 25 rpm, etc.

[0164] Taking the dispersion disc as an example, the third rotational speed is between 800 rpm and 1200 rpm. Exemplarily, the third rotational speed can be 800 rpm, 850 rpm, 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm, etc.

[0165] Exemplarily, the third rotational speed is between 800 rpm and 1000 rpm. The third rotational speed can be 800 rpm, 810 rpm, 820 rpm, 830 rpm, 840 rpm, 850 rpm, 860 rpm, 870 rpm, 880 rpm, 890 rpm, 900 rpm, 910 rpm, 920 rpm, 930 rpm, 940 rpm, 950 rpm, 960 rpm, 970 rpm, 980 rpm, 990 rpm, 1000 rpm, etc.

[0166] Exemplarily, the third rotational speed is between 1000 rpm and 1200 rpm. The third rotational speed can be 1000 rpm, 1010 rpm, 1020 rpm, 1030 rpm, 1040 rpm, 1050 rpm, 1060 rpm, 1070 rpm, 1080 rpm, 1090 rpm, 1100 rpm, 1110 rpm, 1120 rpm, 1130 rpm, 1140 rpm, 1150 rpm, 1160 rpm, 1170 rpm, 1180 rpm, 1190 rpm, 1200 rpm, etc.

[0167] The second preset time is between 60 min and 120 min. Exemplarily, the second preset time can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.

[0168] Exemplarily, the second preset time is between 60 min and 90 min. The second preset time can be 60 min, 62 min, 64 min, 66 min, 68 min, 70 min, 72 min, 74 min, 76 min, 78 min, 80 min, 82 min, 84 min, 86 min, 88 min, 90 min, etc.

[0169] Exemplarily, the second preset time is between 90 min and 120 min. The second preset time can be 90 min, 92 min, 94 min, 96 min, 98 min, 100 min, 102 min, 104 min, 106 min, 108 min, 110 min, 112 min, 114 min, 116 min, 118 min, 120 min, etc.

[0170] During the process of stirring the second mixed material, according to the rotational speed n1, the real-time feedback current value I1 of the driving motor, and the first coefficient M1, the real-time viscosity μ1 of the second mixed material is calculated using the formula μ1 = M1×(I1 / n1), where M1 is 3571.

[0171] Exemplarily, taking the state at 20 minutes of stirring as an example, the calculation process of the viscosity μ1 of the second mixed material is as follows: μ1 = 3571×(I1 / n1) = 3571×(77.1 / 22) ≈ 12515.

[0172] According to the above calculation, the real-time viscosity comparison table of the second mixed material shown in Table 2 is obtained, and the real-time feedback current value I1 of the driving motor and the real-time viscosity μ1 of the second mixed material are uploaded to the database.

[0173]

[0174] According to the viscosity μ1 of the second mixed material, the stability characterization quantity S1 of the second mixed material is calculated using the formula S1 = d(μ1) / d(t1).

[0175] Exemplarily, taking the state at 20 minutes of stirring as an example, the calculation process of the stability characterization quantity S1 of the second mixed material is as follows: S1 = d(μ1) / d(t1) = Δ(μ1) / Δ(t1) = (μ12 - μ11) / (t12 - t11) = (12515 - 13943) / (20 - 10) ≈ -143.

[0176] When 5000 mPa·s ≤ μ1 ≤ 10000 mPa·s and -10 mPa·s per minute ≤ S1 < 0, the stirring duration t1 of the second mixed material is uploaded to the database, and a preset mass of SBR is added to the second mixed material. The stirring equipment stirs the solvent and the second mixed material to form the negative electrode active material.

[0177] During the process of stirring the negative electrode active material, according to the rotational speed n2, the real-time feedback current value I2 of the drive motor, and the second coefficient M2, the viscosity μ2 of the negative electrode active material is calculated using the formula μ2 = M2 × (I2 / n2), where M2 is 102000.

[0178] Exemplarily, taking the state at 20 minutes of stirring as an example, the calculation process of the viscosity μ2 of the second mixed material is as follows: μ2 = 102000 × (I2 / n2) = 102000 × (115.6 / 925) ≈ 12747.2.

[0179] According to the above calculation, the real-time viscosity comparison table of the negative electrode active material shown in Table 3 is obtained, and the real-time feedback current value I2 of the drive motor and the real-time viscosity μ2 of the negative electrode active material are uploaded to the database.

[0180]

[0181] According to the viscosity μ2 of the negative electrode active material, the stability characterization quantity S2 of the negative electrode active material is calculated using the formula S2 = d(μ2) / d(t2).

[0182] Exemplarily, taking the state at 20 minutes of stirring as an example, the calculation process of the stability characterization quantity S2 of the negative electrode active material is as follows: S2 = d(μ2) / d(t2) = Δ(μ2) / Δ(t2) = (μ21 - μ22) / (t22 - t21) = (12747.2 - 13309.6) / (20 - 10) ≈ -56.2.

[0183] When 5000 mPa·s ≤ μ2 ≤ 10000 mPa·s and -10 mPa·s per minute ≤ S2 < 0, the negative electrode active material is discharged, and the stirring duration t2 of the negative electrode active material is uploaded to the database.

[0184] The negative electrode active material is coated on the negative electrode current collector and dried to form the negative electrode plate.

[0185] The positive electrode plate, the separator, and the negative electrode plate are wound to form the cell assembly.

[0186] The cell assembly is placed into the housing, and the electrolyte is injected into the housing to form the secondary battery.

[0187] In the related art, during the process of preparing the negative electrode active material, it is necessary to take out the material and judge whether to perform the next process by testing the viscosity of the taken-out material. During the process of taking out the material, there is a risk that foreign substances such as dust and water vapor in the external environment enter the material and affect the test results. Moreover, this part of the taken-out material cannot be used continuously, resulting in waste of materials and increasing the manufacturing cost of the secondary battery.

[0188] In the preparation process provided by the embodiments of the present application, the real-time viscosity of the material is calculated according to the real-time current of the driving motor, reducing the process of taking out the material and shortening the preparation cycle of the negative electrode active material. At the same time, it reduces the risk of the material being contaminated due to taking out the material, improves the accuracy of the test results, reduces the risk that the stirring time is too long and affects the performance of the negative electrode active material, and is beneficial to improving the performance of the negative electrode active material. In addition, it reduces the process of taking out the material, reduces the waste of materials caused by viscosity testing, improves the discharge rate of the negative electrode active material, and reduces the preparation cost of the negative electrode active material.

[0189] Thirdly, based on the secondary battery made of the above preparation process, the embodiments of the present application provide an energy storage system. The energy storage system includes a plurality of the above secondary batteries. The energy storage system includes but is not limited to an energy storage box. Exemplarily, the energy storage system can be Figure 2 the energy storage box 2 shown in the figure. The energy storage box 2 includes a cabinet body 21 and a plurality of secondary batteries installed in the cabinet body 21.

[0190] Fourthly, the embodiments of the present application provide an electrical device. The electrical device includes the above energy storage system and a load, and the energy storage system can supply power to the load. The electrical device includes but is not limited to mobile phones, tablets, laptop computers, electric toys, electric tools, battery cars, electric vehicles, ships, spacecrafts, etc. Exemplarily, the electrical device is Figure 1 the vehicle shown in the figure. The battery pack 1 of the vehicle is an energy storage system, and there are a plurality of series-connected and parallel-connected secondary batteries in the battery pack 1. The electrical modules on the vehicle are loads.

Claims

1. A preparation process for a secondary battery, characterized in that, The secondary battery preparation process includes: At least an active material, a thickening agent, and a conductive agent are put into a stirring device, and the stirring device mixes the active material, the thickening agent, and the conductive agent to form a first mixed material; A first mass of a solvent is added to the first mixed material, and the stirring device stirs the solvent and the first mixed material to form a dispersed material; A second mass of the solvent is added to the dispersed material, and the stirring device stirs the solvent and the dispersed material to form a second mixed material, and the viscosity and stability characterization quantity of the second mixed material are calculated; When the viscosity of the second mixed material is within a first preset range and the stability characterization quantity of the second mixed material is within a second preset range, a binder is added to the second mixed material, and the stirring device stirs the solvent and the second mixed material to form a negative electrode active material, and the viscosity and stability characterization quantity of the negative electrode active material are calculated; The viscosity μ and the stability characterization quantity S satisfy: S = d(μ) / d(t), where t is the stirring duration of the stirring device; When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the negative electrode active material is discharged; The negative electrode active material is coated on a negative electrode current collector and dried to form a negative electrode plate; The positive electrode active material is coated on a positive electrode current collector and dried to form a positive electrode plate; The positive electrode plate, the separator, and the negative electrode plate are stacked and wound to form an electric core assembly; The electric core assembly is placed in a housing, and an electrolyte is injected into the housing to form the secondary battery.

2. The secondary battery manufacturing process according to claim 1, characterized in that, The stirring device includes a stirring member and a driving motor, and the driving motor drives the stirring member to rotate at a preset speed; The rotation speed n of the stirring member, the real-time current value I of the driving motor, and the viscosity μ satisfy: μ = M×(I / n), where M is a coefficient.

3. The secondary battery manufacturing process according to claim 2, characterized in that, Before the step of calculating the viscosity and stability characterization quantity of the second mixed material, the secondary battery preparation process includes: Preparing a first test sample, where the first test sample at least includes the active material, the thickening agent, and the conductive agent; Detecting the viscosity of the first test sample, and calculating a first coefficient M1 according to the viscosity of the first test sample, the rotation speed of the stirring member when stirring the first test sample, and the current value of the driving motor; Before the step of calculating the viscosity and stability characterization quantity of the negative electrode active material, the secondary battery preparation process includes: Preparing a second test sample, where the second test sample at least includes the active material, the thickening agent, the conductive agent, and the binder; Measuring the viscosity of the second test sample, and calculating a second coefficient M2 according to the viscosity of the second test sample, the rotation speed of the stirring member when stirring the second test sample, and the current value of the driving motor.

4. The secondary battery manufacturing process according to claim 3, characterized in that, The step of preparing the first test sample includes: Taking out a part of the second mixed material as the first test sample; The step of preparing the second test sample includes: Take out a part of the negative electrode active material as the second test sample.

5. The secondary battery manufacturing process according to claim 3, characterized in that, The steps of preparing the first test sample include: Before the step of preparing the first composite material, prepare a first test material, which at least includes an active substance, a thickener, and a conductive agent; Add the solvent into the first test material, and the stirring device stirs and fully disperses the solvent and the first test material to form a second test material; Take out a part of the second test material as the first test sample; The steps of preparing the second test sample include: Add the solvent into the second test material, and the stirring device stirs and fully disperses the solvent and the second test material to form a third test material; Take out the third test material as the second test sample.

6. The secondary battery manufacturing process according to any one of claims 1 to 5, characterized in that, When the viscosity of the second composite material is within a first preset range and the stability characterization quantity of the second composite material is within a second preset range, the viscosity μ1 of the second composite material satisfies: 5000 millipascal·seconds ≤ μ1 ≤ 10000 millipascal·seconds, and the stability characterization quantity S1 of the second composite material satisfies: -10 millipascal·seconds per minute ≤ S1 < 0; When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the viscosity μ2 of the negative electrode active material satisfies: 5000 millipascal·seconds ≤ μ2 ≤ 10000 millipascal·seconds, and the stability characterization quantity S2 of the negative electrode active material satisfies: -10 millipascal·seconds per minute ≤ S2 < 0.

7. The secondary battery manufacturing process according to any one of claims 1 to 5, characterized in that, When the stirring device stirs the solvent and the dispersion material, the secondary battery manufacturing process includes: Store the rotation speed of the stirring member and the current of the driving motor in a database; When the viscosity of the second composite material is within a first preset range and the stability characterization quantity of the second composite material is within a second preset range, the secondary battery manufacturing process includes: Store the stirring time of the second composite material by the stirring device in a database; When the stirring device stirs the solvent and the second composite material, the secondary battery manufacturing process includes: Store the rotation speed of the stirring member and the current of the driving motor in a database; When the viscosity of the negative electrode active material is within a third preset range and the stability characterization quantity of the negative electrode active material is within a fourth preset range, the secondary battery manufacturing process includes: Store the stirring time of the negative electrode active material by the stirring device in a database.

8. A secondary battery, characterized in that, The secondary battery is manufactured by the secondary battery manufacturing process according to any one of claims 1 to 7; The secondary battery includes a housing, a battery cell assembly, and an electrolyte. The housing includes a receiving cavity, and the battery cell assembly and the electrolyte are located in the receiving cavity; The battery cell assembly includes a positive electrode plate, a negative electrode plate, and a separator, and the separator is located between the positive electrode plate and the negative electrode plate; The negative electrode plate includes the negative electrode current collector and the negative electrode active material.

9. A energy storage system, characterized in that, The energy storage system includes a plurality of secondary batteries according to claim 8.

10. An electrical device, characterized in that, The electrical device includes a load and the energy storage system according to claim 9, and the energy storage system is capable of supplying power to the load.

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