A secondary battery and its preparation process, energy storage system and electrical equipment

Abstract

The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and its preparation process, energy storage system and electrical equipment. The secondary battery preparation process comprises: putting active material, thickener and conductive agent into a stirring device and stirring and mixing to form a first mixed material, adding a solvent and stirring and mixing to form a second mixed material and calculating viscosity and stability characterization quantities. When the viscosity and stability characterization quantities meet the requirements, a binder is added and stirred and mixed to form a negative electrode active material and the viscosity and stability characterization quantities are calculated. When both the viscosity and stability characterization quantities meet the requirements, the negative electrode active material is coated on a negative electrode current collector to form a negative electrode sheet and prepared into a secondary battery. The viscosity and stability characterization quantities of the material are calculated in real time during the stirring process, which reduces the process of removing the material, shortens the preparation cycle of the negative electrode active material, reduces the risk of material contamination during the removal process, improves the accuracy of the test results, and reduces the preparation cost.

Description

Technical Field

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

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

[0003] The battery cell assembly consists of a positive electrode sheet, a negative electrode sheet, and a separator. The positive electrode sheet is formed by coating the positive electrode active material on the positive electrode current collector, while the negative electrode sheet is formed by coating the negative electrode active material on the negative electrode current collector. The negative electrode active material is formed by mixing and stirring the active material, thickener, conductive agent, binder, and water. During the stirring process, the viscosity of the negative electrode active material must meet the required level before proceeding to the next step.

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

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

[0006] In a first aspect, the present application provides a secondary battery preparation process, comprising: placing at least an active material, a thickener, and a conductive agent into a stirring device, wherein the stirring device mixes the active material, thickener, and conductive agent to form a first mixed material; adding a first mass of solvent to the first mixed material, wherein the stirring device stirs the solvent and the first mixed material to form a dispersed material; adding a second mass of solvent to the dispersed material, wherein the stirring device stirs the solvent and the dispersed material to form a second mixed material; and calculating the viscosity and stability characteristic of the second mixed material. When the viscosity of the second mixed material is within a first preset range and the stability characteristic of the second mixed material is within a second preset range, a binder is added to the second mixed material, wherein the stirring device stirs the solvent and the second mixed material to form a negative electrode active material; and calculating the viscosity and stability characteristic of the negative electrode active material. The viscosity μ and the stability characteristic S satisfy the following relationship: S = d(μ) / d(t), where t is the stirring time of the stirring device. When the viscosity of the negative electrode active material is within a third preset range and the stability characteristic 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 the negative electrode current collector and dried to form the negative electrode sheet. The positive electrode active material is coated on the positive electrode current collector and dried to form the positive electrode sheet. The positive electrode sheet, separator, and negative electrode sheet are stacked and wound to form a battery cell assembly. The battery cell assembly is placed in a casing, and the electrolyte is injected into the casing to form a secondary battery.

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

[0008] In some possible designs, before the step of calculating the viscosity and stability characterizing the second mixed material, the secondary battery preparation process includes: preparing a first test sample, the first test sample including at least an active substance, a thickener and a conductive agent. Detecting the viscosity of the first test sample, and calculating the first coefficient M1 based on 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 characterizing the negative electrode active material, the secondary battery preparation process includes: preparing a second test sample, the second test sample including at least an active substance, a thickener, a conductive agent and a binder. Detecting the viscosity of the second test sample, and calculating the second coefficient M2 based on 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 portion of the second mixed material as the first test sample. The step of preparing the second test sample includes: taking out a portion of the negative electrode active material as the second test sample.

[0010] In some possible designs, the step of preparing a first test sample includes: prior to the step of preparing the first mixed material, preparing a first test material, the first test material comprising at least an active substance, a thickener, and a conductive agent; adding a solvent to the first test material, and using a stirring device to stir and fully disperse the solvent and the first test material to form a second test material; removing a portion of the second test material for use as the first test sample; and preparing a second test sample includes: adding a solvent to the second test material, and using a stirring device to stir and fully disperse the solvent and the second test material to form a third test material; removing the third test material for use 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 characteristic value of the second mixed material is within a second preset range, the viscosity μ1 of the second mixed material satisfies the following conditions: 5000 mPa·s ≤ μ1 ≤ 10000 mPa·s, and the stability characteristic value S1 of the second mixed material satisfies the following conditions: -10 mPa·s / min ≤ S1 < 0. When the viscosity of the negative electrode active material is within a third preset range and the stability characteristic value of the negative electrode active material is within a fourth preset range, the viscosity μ2 of the negative electrode active material satisfies the following conditions: 5000 mPa·s ≤ μ2 ≤ 10000 mPa·s, and the stability characteristic value S2 of the negative electrode active material satisfies the following conditions: -10 mPa·s / min ≤ S2 < 0.

[0012] In some possible designs, when the stirring device stirs the solvent and the dispersion material, the secondary battery preparation process includes: storing the rotational 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 value of the second mixed material is within a second preset range, the secondary battery preparation process includes: storing the stirring time of the second mixed material by the stirring device in a database. When the stirring device stirs the solvent and the second mixed material, the secondary battery preparation process includes: storing the rotational 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 value of the negative electrode active material is within a fourth preset range, the secondary battery preparation process includes: storing the stirring time of the negative electrode active material by the stirring device in a database.

[0013] A second aspect of the present application provides a secondary battery, prepared by any of the secondary battery preparation processes described above. The secondary battery comprises a housing, a cell assembly, and an electrolyte. The housing comprises a receiving cavity, and the cell assembly and electrolyte are located within the receiving cavity. The cell assembly comprises a positive electrode sheet, a negative electrode sheet, and a separator, wherein the separator is located between the positive and negative electrode sheets. The negative electrode sheet comprises a negative current collector and a negative active material.

[0014] A third aspect of the present application provides an energy storage system, which includes the above-mentioned secondary battery.

[0015] A fourth aspect of the present application provides an electrical device, which includes a load and the above-mentioned energy storage system, and the energy storage system can supply power to the load.

[0016] In the present application, the viscosity of the second mixed material and the negative electrode active material is calculated in real time by a calculation module, which reduces the process of removing the material, and is conducive to shortening the preparation cycle of the negative electrode active material. At the same time, the risk of material contamination during the removal process is reduced, and the accuracy of the test results is improved. In addition, the process of removing the material is reduced, the waste of materials caused by the viscosity test is reduced, the discharge rate of the negative electrode active material is improved, the preparation cost of the negative electrode active material is reduced, the cost of the battery cell assembly and the secondary battery made of the negative electrode active material is reduced, and the cost of the energy storage system containing the secondary battery and the electrical equipment containing the energy storage system is reduced.

[0017] The calculation module calculates the viscosity and stability characterization quantities in real time, and it can be used to determine whether to proceed to the next process or discharge the material, so that the stirring equipment can stir the material within the optimal stirring time, reducing the risk of performance degradation of the negative electrode active material due to excessive stirring time, shortening the stirring time, and reducing the cost of the negative electrode active material, negative electrode sheet, secondary battery, energy storage system and electrical equipment.

[0018] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 A schematic structural diagram of a vehicle provided in some embodiments of the present application;

[0021] Figure 2 A schematic diagram of the structure of an energy storage box provided in some embodiments of the present application;

[0022] Figure 3 An exploded view of a secondary battery provided in some embodiments of the present application;

[0023] Figure 4 A schematic diagram of the structure of the top cover provided in some embodiments of the present application;

[0024] Figure 5 A schematic diagram of the structure of a battery cell assembly provided in some embodiments of the present application;

[0025] Figure 6 A schematic diagram of the stacked structure of a battery cell assembly provided in some embodiments of the present application;

[0026] Figure 7 A schematic diagram of a secondary battery preparation process according to some embodiments of the present application;

[0027] Figure 8 Schematic diagram of the process for preparing negative electrode active materials in related technologies;

[0028] Figure 9 A schematic diagram of a process for preparing negative electrode active materials according to some embodiments of the present application;

[0029] Figure 10 is a schematic diagram of a process for mixing the solvent and the first mixed material in batches;

[0030] Figure 11 A schematic diagram of a flow chart for calculating a first coefficient provided in some embodiments of the present application;

[0031] Figure 12 A schematic diagram of a flow chart for calculating a second coefficient provided in some embodiments of the present application;

[0032] Figure 13 A schematic diagram of a flow chart for calculating a first coefficient and a second coefficient provided in some embodiments of the present application.

[0033] Reference numerals:

[0034] 1-battery pack; 2-energy storage box; 21-cabinet;

[0035] 3-secondary battery; 31-housing; 32-top cover; 321-positive electrode column; 322-negative electrode column; 323-pressure relief valve; 33-cell assembly; 331-positive electrode sheet; 332-negative electrode sheet; 333-diaphragm; 334-positive electrode tab; 335-negative electrode tab. DETAILED DESCRIPTION

[0036] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0037] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0039] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0040] In a first aspect, embodiments of the present application provide a secondary battery that can be used, but is not limited to, in electrical devices such as vehicles, ships, or aircraft. Exemplary electrical devices include mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, and the like. Electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and spacecraft can include airplanes, rockets, space shuttles, and spacecraft.

[0041] For the convenience of explanation, the electric equipment is taken as a vehicle as an example.

[0042] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle provided in some embodiments of the present application. The vehicle can be a fuel-powered vehicle, a gas-powered vehicle, or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle, or an extended-range vehicle. A battery pack 1 is disposed within the vehicle and can be located at the bottom, front, or rear of the vehicle. Battery pack 1 can be used to power the vehicle.

[0043] 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, the energy storage system is taken as an energy storage box as an example.

[0044] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the energy storage box provided in some embodiments of the present application. The energy storage box 2 includes a cabinet 21, an inverter, and at least one battery pack. The cabinet 21 has a housing, within which the inverter and battery pack are housed. The inverter converts direct current (DC) into alternating current (AC). It offers advantages such as high conversion efficiency, fast startup, and enhanced safety. It also provides protection against short circuits, overloads, over / under voltage, and over-temperature conditions.

[0045] Some large energy storage boxes may also include a battery management system, which is used to enable the battery pack to operate within a safe working range. It can control the charge and discharge power of the battery pack according to factors such as ambient temperature, battery status, and power demand, thereby improving the safety of the battery pack and making the working state of the battery pack more reasonable, which is conducive to improving the battery life and service life of the battery pack.

[0046] The battery pack includes a housing and multiple secondary batteries 3, which are housed within the housing. The housing can be made of aluminum, aluminum alloy, or other metal materials, or it can also be made of non-metallic materials. The housing provides space for the secondary batteries 3 and can adopt a variety of structures.

[0047] In some embodiments, the case may include a bottom cover and an upper cover. The bottom cover is open at the top, and the upper cover is sized to match the top opening of the bottom cover. The upper cover can be attached to the bottom cover in the height direction of the battery pack, and the upper and bottom covers can be connected by bolts or other fasteners. The upper and bottom covers enclose a storage space for accommodating the secondary battery. The case may have various shapes, such as a cylinder, a rectangular parallelepiped, etc.

[0048] A sealing member may be provided between the upper cover and the bottom cover to seal the accommodating space.

[0049] In a battery pack, multiple secondary batteries 3 can be connected in series, in parallel, or in a hybrid configuration. Hybrid configuration refers to a combination of series and parallel connections. In some embodiments, multiple secondary batteries 3 can be directly connected in series, in parallel, or in a hybrid configuration, and then housed within a housing. Multiple secondary batteries 3 can be arranged side by side along the length or width of the battery pack.

[0050] In other embodiments, multiple secondary batteries 3 may be first connected in series, parallel, or hybrid to form a battery module, and then the multiple battery modules may be connected in series, parallel, or hybrid to form a whole unit and housed in a housing. The battery module includes a frame structure, which may include interconnected end plates, side plates, a top plate, and a bottom plate. The multiple secondary batteries are located within the inner cavity of the frame structure and are stacked one on top of the other within the inner cavity of the frame structure. The stacking direction may be the length, width, or height direction.

[0051] In addition, the battery pack may also include other structures, such as a busbar component, for achieving electrical connection between multiple secondary batteries.

[0052] The secondary battery may be cylindrical, flat, rectangular or in other shapes.

[0053] Please refer to Figure 3 , Figure 3This is an exploded view of a secondary battery 3 provided in some embodiments of the present application. The secondary battery 3 includes a housing 31, a top cover 32, a cell assembly 33, and other functional components.

[0054] In some embodiments, the housing 31 and the top cover 32 can be independent components. The housing 31 has an opening, and the top cover 32 covers the opening of the housing to isolate the internal environment of the secondary battery 3 from the external environment. The internal environment enclosed by the housing 31 and the top cover 32 can be used to accommodate the battery cell assembly 33, electrolyte, and other components. In other embodiments, the housing 31 and the top cover 32 can also be integrated. Specifically, the housing 31 and the top cover 32 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 31 needs to be encapsulated, the top cover 32 can cover the housing 31.

[0055] The housing 31 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 31 can be determined based on the specific shape and size of the battery cell assembly 33. The housing 31 can also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., which are not particularly limited in this embodiment of the present application.

[0056] Please refer to Figure 4 , Figure 4 A schematic structural diagram of a top cover 32 provided for some embodiments of the present application. The shape of the top cover 32 can be adapted to the shape of the shell. A positive pole 321 and a negative pole 322 can be provided on the top cover 32. The positive pole 321 and the negative pole 322 can be electrically connected to the battery cell assembly 33 for outputting or inputting electrical energy of the secondary battery 3. In some embodiments, a pressure relief valve 323 for releasing internal pressure when the internal pressure or temperature of the secondary battery 3 reaches a threshold value may also be provided on the top cover 32. In some embodiments, an insulating member may also be provided on the inner side of the top cover 32, and the insulating member may be used to isolate the conductive components in the shell 31 from the top cover 32 to reduce the risk of short circuit. Exemplarily, the insulating member may be plastic, rubber, etc.

[0057] The top cover 32 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any particular limitation thereto. Optionally, the top cover 32 can be made of a material with a certain degree of hardness and strength (such as an aluminum alloy) to prevent the top cover 32 from deforming when subjected to compression or collision, thereby providing the secondary battery 3 with higher structural strength and safety performance.

[0058] Please refer to Figure 5 , Figure 5This is a schematic diagram of the structure of a battery cell assembly 33 provided in some embodiments of the present application. The battery cell assembly 33 is the component in the secondary battery 3 that generates electricity through electrochemical reactions. The housing 31 may contain one or more battery cell assemblies 33.

[0059] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the stacked structure of a battery cell assembly 33 provided in some embodiments of the present application. The battery cell assembly 33 includes a positive electrode sheet 331, a negative electrode sheet 332, and a separator 333. The separator 333 is located between the positive electrode sheet 331 and the negative electrode sheet 332 and is used to separate the positive electrode sheet 331 and the negative electrode sheet 332. The positive electrode sheet 331, the separator 333, and the negative electrode sheet 332 are stacked and wound in sequence.

[0060] The negative electrode sheet 332 includes a negative electrode current collector and a negative electrode active material coated on the surface of the negative electrode current collector. The positive electrode sheet 331 includes a positive electrode current collector and a positive electrode active material coated on the surface of the positive electrode current collector. After winding, the negative electrode active material, the positive electrode active material, and the separator 333 located between the two form a wound structure. The positive electrode current collector can be cut to form a positive electrode tab 334, and the negative electrode 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 together at one end of the wound structure, or the positive electrode tab 334 and the negative electrode tab 335 can be located at each end of the wound structure.

[0061] The positive electrode tab 334 is electrically connected to the positive electrode post 321 via a positive electrode connector, and the negative electrode tab 335 is electrically connected to the negative electrode post 322 via a negative electrode connector. During the charge and discharge process of the secondary battery 3, the positive and negative electrode active materials in the wound structure react with the electrolyte to generate electrical energy. This energy is then transferred to the positive electrode post 321 via the positive electrode tab 334 and the positive electrode connector, and to the negative electrode post 322 via the negative electrode tab 335 and the negative electrode connector. The electrical energy is then output through the positive electrode post 321 and the negative electrode post 322.

[0062] The positive poles 321 of the multiple secondary batteries 3 can be electrically connected through the positive connecting piece, and the negative poles 322 of the multiple secondary batteries 3 can be electrically connected through the negative connecting piece, so as to realize the series connection, parallel connection or mixed connection of the multiple secondary batteries 3.

[0063] In a second aspect, an embodiment of the present application provides a secondary battery preparation process.

[0064] Please refer to Figure 7 , Figure 7 A schematic diagram of a secondary battery manufacturing process provided in some embodiments of the present application. The secondary battery manufacturing process includes:

[0065] Prepare positive electrode sheets and negative electrode sheets;

[0066] Winding the positive electrode sheet, separator and negative electrode sheet to form a battery cell assembly;

[0067] The battery cell assembly is installed into the shell, and the electrolyte is injected into the shell to form a secondary battery.

[0068] The steps of preparing the positive electrode sheet include:

[0069] preparing a positive electrode active material;

[0070] The positive electrode active material is coated on the positive electrode current collector and dried to form a positive electrode sheet.

[0071] 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 compounds such as lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium iron phosphate, and lithium nickel cobalt aluminum oxide.

[0072] The steps of preparing the negative electrode sheet include:

[0073] preparing a negative electrode active material;

[0074] The negative electrode active material is coated on the negative electrode current collector and dried to form a negative electrode sheet.

[0075] The negative electrode current collector may include, but is not limited to, copper foil, and the negative electrode active material may include, but is not limited to, graphite, silicon-based materials (such as silicon or carbon-silicon compounds), lithium metal, and the like.

[0076] Please refer to Figure 8 , Figure 8 The figure is a flow chart of the preparation process of negative electrode active materials in related technologies. In related technologies, the preparation process of negative electrode active materials includes:

[0077] An active material, a thickener and a conductive agent are put into a stirring device. The active material includes but is not limited to graphite, the thickener includes but is not limited to CMC (Carboxymethyl Cellulose), and the conductive agent includes but is not limited to SP (Super P). The stirring device is used to mix and stir to form a first mixed material.

[0078] A solvent is added into the stirring device, the solvent includes but is not limited to water, and the stirring device performs mixing and stirring to form a second mixed material. As the stirring time increases, the viscosity of the second mixed material gradually decreases.

[0079] After stirring for a certain period of time, a portion of the second mixed material is taken out and the viscosity of the second mixed material is tested. If the viscosity of the second mixed material meets the requirements, the next step is performed; otherwise, the stirring device continues to stir the second mixed material.

[0080] After the viscosity of the second mixed material meets the requirement, a binder is added to the stirring device. The binder includes but is not limited to SBR (Styrene Butadiene Rubber). The stirring device is used to mix and stir to form a negative electrode active material. As the stirring time increases, the viscosity of the negative electrode active material gradually decreases.

[0081] After stirring for a certain period of time, a portion of the negative electrode active material is taken out and the viscosity of this portion of the negative electrode active material is tested. 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.

[0082] In the related art, in the process of taking out a portion of the second mixed material and the negative electrode active material, foreign matter such as dust and water vapor in the external environment enters the second mixed material and the negative electrode active material and affects the test results. Moreover, the taken out portion of the second mixed material and the negative electrode active material cannot be used, resulting in material waste and increasing the manufacturing cost of the secondary battery.

[0083] In view of this, please refer to Figure 9 , Figure 9 Schematic diagram of the process for preparing negative electrode active materials provided in some embodiments of the present application. The process for preparing negative electrode active materials provided in the present application includes:

[0084] At least the active material, the thickener and the conductive agent are added into the stirring device according to a preset ratio, and the stirring device mixes the active material, the thickener and the conductive agent to form a first mixed material.

[0085] The total mass of the first mixed material is G1, the mass of the active material 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.

[0086] 0.96≤g11 / G1≤0.965, that is, the mass proportion of the active substance is between 96% and 96.5%. Exemplarily, the mass proportion of the active substance can be 96%, 96.1%, 96.2%, 96.3%, 96.4%, 96.5%, etc.

[0087] Illustratively, 0.96≤g11 / G1≤0.961, and the mass proportion 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%, and 96.1%.

[0088] Illustratively, 0.961≤g11 / G1≤0.963, and the mass proportion 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.

[0089] Illustratively, 0.963≤g11 / G1≤0.965, and the mass proportion 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.

[0090] 0.015≤g12 / G1≤0.02, that is, the mass proportion of the thickener is between 1.5% and 2%. Exemplarily, the mass proportion of the thickener can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, etc.

[0091] Illustratively, 0.015≤g12 / G1≤0.017, and the mass proportion 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.

[0092] Illustratively, 0.017≤g12 / G1≤0.019, and the mass proportion 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.

[0093] For example, 0.019≤g12 / G1≤0.02, the mass proportion 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.

[0094] 0.01≤g13 / G1≤0.015, that is, the mass proportion of the conductive agent is between 1% and 1.5%. Exemplarily, the mass proportion of the conductive agent can be 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc.

[0095] For example, 0.01≤g13 / G1≤0.011, and the mass proportion 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.

[0096] Illustratively, 0.011≤g13 / G1≤0.013, and the mass proportion 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.

[0097] For example, 0.013≤g13 / G1≤0.015, the mass proportion 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.

[0098] The above is merely an example of the mixing ratio of the active substance, the thickener, and the conductive agent. The embodiments of the present application do not impose any special restrictions on the specific mixing ratio of the active substance, the thickener, and the conductive agent.

[0099] After the first mixed material is formed, 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. The calculation module calculates the viscosity and stability characterization value of the second mixed material in real time.

[0100] The total mass of the solvent is G2, 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.

[0101] Illustratively, 1≤G1 / G2≤1.1, and 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.

[0102] Illustratively, 1.1≤G1 / G2≤1.2, and 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.

[0103] The above is merely an example of the mixing ratio of the solvent and the first mixed material. The embodiment of the present application does not impose any special limitation on the mixing ratio of the solvent and the first mixed material.

[0104] When the viscosity of the second mixed material is within the first preset range and the stability characterization value of the second mixed material is within the second preset range, exemplarily, the viscosity μ1 of the second mixed material satisfies: 5000 millipascal·second ≤ μ1 ≤ 10000 millipascal·second, and the stability characterization value S1 of the second mixed material satisfies: -10 millipascal·second per minute ≤ S1 < 0, the binder is added to the second mixed material, the stirring equipment stirs the solvent and the second mixed material to form a negative electrode active material, and the calculation module calculates the viscosity and stability characterization value of the negative electrode active material in real time.

[0105] The mass of the adhesive is G3, the mass of the second mixed material is G4, 0.012≤G3 / G4≤0.018. Exemplarily, the mass ratio of the adhesive to the second mixed material can be 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, or 0.018.

[0106] Illustratively, 0.012≤G3 / G4≤0.014, and the mass ratio of the adhesive to the second mixed material may be 0.012, 0.0122, 0.0124, 0.0126, 0.0128, 0.013, 0.0132, 0.0134, 0.0136, 0.0138, 0.014, etc.

[0107] Illustratively, 0.014≤G3 / G4≤0.016, and the mass ratio of the adhesive to the second mixed material may be 0.014, 0.0142, 0.0144, 0.0146, 0.0148, 0.015, 0.0152, 0.0154, 0.0156, 0.0158, 0.016, etc.

[0108] Illustratively, 0.016≤G3 / G4≤0.018, and the mass ratio of the adhesive to the second mixed material may be 0.016, 0.0162, 0.0164, 0.0166, 0.0168, 0.017, 0.0172, 0.0174, 0.0176, 0.0178, 0.018, etc.

[0109] The above is merely an example of the mixing ratio of the adhesive and the second mixed material. The embodiment of the present application does not impose any special limitation on the mixing ratio of the adhesive and the second mixed material.

[0110] The viscosity μ and the stability characterization quantity S satisfy: S=d(μ) / d(t), where t is the stirring time of the stirring equipment.

[0111] When the viscosity of the negative electrode active material is within the third preset range and the stability characterization value of the negative electrode active material is within the fourth preset range, illustratively, the viscosity μ2 of the negative electrode active material satisfies: 5000 millipascal·second ≤ μ2 ≤ 10000 millipascal·second, and the stability characterization value S2 of the negative electrode active material satisfies: -10 millipascal·second per minute ≤ S2 < 0, the negative electrode active material is discharged.

[0112] Exemplarily, the material viscosity can be 5000 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, 7000 mPa·s, 7500 mPa·s, 8000 mPa·s, 8500 mPa·s, 9000 mPa·s, 9500 mPa·s, 10000 mPa·s, etc.

[0113] For example, the viscosity μ of the material satisfies the following: 5000 mPa·s≤μ≤6000 mPa·s. The viscosity μ may be 5000 mPa·s, 5100 mPa·s, 5200 mPa·s, 5300 mPa·s, 5400 mPa·s, 5500 mPa·s, 5600 mPa·s, 5700 mPa·s, 5800 mPa·s, 5900 mPa·s, 6000 mPa·s, etc.

[0114] For example, the viscosity μ of the material satisfies the following: 6000 mPa·s≤μ≤7000 mPa·s. The viscosity μ may be 6000 mPa·s, 6100 mPa·s, 6200 mPa·s, 6300 mPa·s, 6400 mPa·s, 6500 mPa·s, 6600 mPa·s, 6700 mPa·s, 6800 mPa·s, 6900 mPa·s, 7000 mPa·s, etc.

[0115] For example, the viscosity μ of the material satisfies the following: 7000 mPa·s≤μ≤8000 mPa·s. The viscosity μ may be 7000 mPa·s, 7100 mPa·s, 7200 mPa·s, 7300 mPa·s, 7400 mPa·s, 7500 mPa·s, 7600 mPa·s, 7700 mPa·s, 7800 mPa·s, 7900 mPa·s, 8000 mPa·s, etc.

[0116] For example, the viscosity μ of the material satisfies the following: 8000 mPa·s≤μ≤9000 mPa·s. The viscosity μ may be 8000 mPa·s, 8100 mPa·s, 8200 mPa·s, 8300 mPa·s, 8400 mPa·s, 8500 mPa·s, 8600 mPa·s, 8700 mPa·s, 8800 mPa·s, 8900 mPa·s, 9000 mPa·s, etc.

[0117] For example, the viscosity μ of the material satisfies the following: 9000 mPa·s≤μ≤10000 mPa·s. The viscosity μ may be 9000 mPa·s, 9100 mPa·s, 9200 mPa·s, 9300 mPa·s, 9400 mPa·s, 9500 mPa·s, 9600 mPa·s, 9700 mPa·s, 9800 mPa·s, 9900 mPa·s, 10000 mPa·s, etc.

[0118] 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·second per minute, -4.5 milliPascal·second per minute, -4 milliPascal·second per minute, -3.5 milliPascal·second per minute, -3 milliPascal·second per minute, -2.5 milliPascal·second per minute, -2 milliPascal·second per minute, -1.5 milliPascal·second per minute, -1 milliPascal·second per minute, -0.5 milliPascal·second per minute, -0.01 milliPascal·second per minute, etc.

[0119] For example, the stability characterization value S of the material satisfies: -10 milliPascal seconds per minute ≤ S ≤ -9 milliPascal seconds per minute. The stability characterization value 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.

[0120] For example, the stability characterization value S of the material satisfies: -9 milliPascal seconds per minute ≤ S ≤ -8 milliPascal seconds per minute. The stability characterization value 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.

[0121] For example, the stability characterization value S of the material satisfies: -8 milliPascal seconds per minute ≤ S ≤ -7 milliPascal seconds per minute. The stability characterization value 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.

[0122] For example, the stability characterization value S of the material satisfies: -7 milliPascal seconds per minute ≤ S ≤ -6 milliPascal seconds per minute. The stability characterization value 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.

[0123] For example, the stability characterization value S of the material satisfies: -6 milliPascal seconds per minute ≤ S ≤ -5 milliPascal seconds per minute. The stability characterization value 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.

[0124] For example, the stability characterization value S of the material satisfies: -5 milliPascal seconds per minute ≤ S ≤ -4 milliPascal seconds per minute. The stability characterization value 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.

[0125] For example, the stability characterization value S of the material satisfies: -4 milliPascal seconds per minute ≤ S ≤ -3 milliPascal seconds per minute. The stability characterization value 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] In the step of adding the solvent into the first mixed material, the solvent may be added all at once or in batches.

[0131] Please refer to Figure 10 , Figure 10 This is a schematic diagram of the process of mixing the solvent and the first mixed material in batches. The steps of adding the solvent to the first mixed material and stirring the solvent and the first mixed material with a stirring device to form the second mixed material include:

[0132] Adding a first mass g21 of solvent into the first mixed material, and stirring the solvent and the first mixed material with a stirring device to form a dispersed material;

[0133] A second mass g22 of solvent is added to the dispersed material, and the stirring device stirs the solvent and the dispersed material to form a second mixed material.

[0134] 8:12≤g21:g22≤18:12. For example, the ratio of the first mass to the second mass may be 8:12, 9:12, 10:12, 11:12, 12:12, 13:12, 14:12, 15:12, 16:12, 17:12, 18:12, etc.

[0135] Exemplarily, 8:12≤g21:g22≤10:12, and the ratio of the first mass to 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.

[0136] Exemplarily, 10:12≤g21:g22≤12:12, and the ratio of the first mass to 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.

[0137] Exemplarily, 12:12≤g21:g22≤14:12, and the ratio of the first mass to 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.

[0138] Exemplarily, 14:12≤g21:g22≤16:12, and the ratio of the first mass to 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.

[0139] Exemplarily, 16:12≤g21:g22≤18:12, and the ratio of the first mass to the second mass 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.

[0140] The above is only an example of the ratio of the first mass to the second mass. The embodiment of the present application does not specifically limit the relationship between the first mass and the second mass. For example, the first mass is less than the second mass, that is, a small amount of solvent is added for the first time and the remaining solvent is added for the second time.

[0141] In this embodiment, the initial addition of a small amount of solvent allows for initial wetting and dispersion of the solid components of the first mixed material. This pre-addition of a small amount of solvent allows them to fully swell, reducing the potential for agglomeration when a larger amount of solvent is subsequently added. Adding the solvent in at least two separate additions facilitates adjustment of the overall viscosity and fluidity of the negative electrode active material, thereby facilitating uniform dispersion of the individual materials and improving the performance of the negative electrode active material.

[0142] 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, which reduces the process of removing a portion of the second mixed material and the negative electrode active material, thereby 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 removal process is reduced, thereby improving the accuracy of the test results, and reducing the risk of affecting the performance of the negative electrode active material due to excessive stirring time, thereby improving the performance of the negative electrode active material. In addition, the process of removing a portion of the second mixed material and the negative electrode active material is reduced, reducing the waste of materials caused by viscosity testing, 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 cost of the battery cell assembly and secondary battery made of the negative electrode active material, and reducing the cost of the energy storage system containing the secondary battery and the electrical equipment containing the energy storage system.

[0143] During the stirring and dispersion process, viscosity gradually decreases over time. When the dispersion of the individual materials stabilizes, the rate of viscosity decreases toward a constant value. If the dispersion is uneven, the viscosity may fluctuate. Therefore, the calculation module detects and calculates the viscosity of the second mixed material and the negative electrode active material in real time, obtains a viscosity-over-time curve, and takes the differential of the viscosity with respect to time to obtain a stability indicator used to characterize the rate of viscosity change.

[0144] The stability characterization quantities of the second mixed material and the negative electrode active material are calculated to determine 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 by the calculation module. It can be determined whether to enter the next process or discharge the material based on the viscosity and stability characterization quantities, so that the stirring equipment can stir the material within the optimal stirring time, reducing the risk of performance degradation of the negative electrode active material due to excessive stirring time, thereby shortening the stirring time and reducing the cost of the negative electrode active material, negative electrode plate, secondary battery, energy storage system and electrical equipment.

[0145] The stirring equipment can also upload the stirring parameters of the second mixed material and the negative electrode active material to the database. The stirring parameters include but are not limited to the type of material, the mixing ratio of the materials, the stirring speed of the stirring element, the current feedback value of the driving motor that drives the stirring element to rotate, the stirring time, the real-time viscosity and the real-time stability characterization value, etc.

[0146] When the stirring equipment performs stirring processing on the same kind of negative electrode active material in batches, the same here means that the parameters such as material type and mixing ratio are exactly the same. During the production of the first batch of negative electrode active materials, the stirring equipment uploads the relevant stirring parameters to the database. In the production of subsequent batches, the stirring equipment can directly extract the stirring parameters in the database, thereby selecting the optimal parameters such as rotation speed and stirring time, so as to improve the processing efficiency of subsequent batches of negative electrode active materials.

[0147] The process of removing a portion of the second mixed material and the negative electrode active material is reduced, which helps shorten 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 removal process is reduced, thereby improving the accuracy of the test results and reducing the risk of affecting the performance of the negative electrode active material due to excessive stirring time, which helps improve the performance of the negative electrode active material. In addition, the process of removing a portion of the second mixed material and the negative electrode active material is reduced, reducing the waste of materials caused by viscosity testing, thereby improving the discharge rate of the negative electrode active material and reducing the preparation cost of the negative electrode active material. This in turn reduces the cost of the battery cell assembly and secondary battery made of the negative electrode active material, and reduces the cost of the energy storage system containing the secondary battery and the electrical equipment containing the energy storage system.

[0148] Taking a dual planetary mixer as an example, the mixer's drive motor controls the rotation of agitators, such as paddles or a dispersion disc. These agitators apply shear stress to the material, driving it to flow, mix, and evenly disperse. From a fluid mechanics perspective, the viscosity and rotational speed of the fluid are directly related to the shear stress, which in turn is related to the motor's current.

[0149] For example, during the stirring process of the second mixed material and the negative electrode active material by the stirring equipment, the viscosity of the material gradually decreases as the stirring time increases, and the stirring element maintains a uniform rotation speed at a preset speed. As the viscosity decreases, the shear stress value required to stir the material gradually decreases, that is, the feedback current value of the drive motor gradually decreases, that is, the viscosity of the material can be directly reflected from the feedback current value of the drive motor.

[0150] Taking the process of stirring the second mixed material by the stirring equipment as an example, the following Table 1 illustrates the relationship between the feedback current value of the drive motor and the stirring time. As shown in Table 1, as the stirring time increases, the viscosity of the material gradually decreases. When maintaining the stirring element to rotate at a constant speed, the feedback current value of the drive motor gradually decreases.

[0151]

[0152] During the stirring process, the calculation module can obtain the real-time current value I of the drive motor. Based on the stirring element's speed n and the real-time current value I of the drive motor, the calculation module can calculate the material viscosity in real time using the viscosity formula μ = M × (I / n), thereby determining whether the next process or material discharge can be carried out. In the viscosity formula, μ is the viscosity of the material, the coefficient M = k / b, where k is the torque constant of the drive motor and b is the conversion factor.

[0153] In this embodiment, the real-time viscosity of the material is calculated by the real-time change of the feedback current value of the driving motor, which reduces the difficulty of the viscosity test and further improves the accuracy and reliability of the viscosity test result.

[0154] 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 calculating the viscosity and stability characterization quantity of the material, the coefficient M needs to be determined first.

[0155] The secondary battery preparation process includes:

[0156] A first test sample is prepared. The components and component ratios of the first test sample are completely the same as those of the second mixed material, that is, the first test sample at least includes an active substance, a thickener, a conductive agent, and a solvent.

[0157] At least a portion of the first test sample is taken out, and the viscosity of the taken out portion of the first test sample is measured using a viscometer (μ01).

[0158] Based on the viscosity μ01 of the first test sample, the speed n01 of the stirring element during stirring, and the current I01 of the drive motor, the first coefficient M1 required for calculating the second mixed material is calculated according to μ01 = M1 × (I01 / n01). Here, n01 and I01 are the real-time speed and current values ​​at the moment the first test sample was taken.

[0159] For example, the viscosity μ01 of the first test sample is 10,000 mPa·s, the rotation speed n01 of the stirring member when stirring the first test sample is 25 rpm, and the current value I01 of the driving motor when stirring the first test sample is 70 A. Then, the calculation process of M1 is as follows:

[0160] First, 10000=M1×(70 / 25), second, M1=10000 / (70 / 25), and finally, M1=3571.

[0161] The secondary battery preparation process includes:

[0162] A second test sample is prepared. The components and component ratios of the second test sample are completely the same as those of the negative electrode active material, that is, the second test sample at least includes an active material, a thickener, a conductive agent, a solvent, and a binder.

[0163] At least a portion of the second test sample is taken out, and the viscosity μ02 of the taken out portion of the second test sample is measured using a viscometer.

[0164] Based on the viscosity μO2 of the second test sample, the speed nO2 of the stirring element during stirring, and the current IO2 of the drive motor, the second coefficient M2 required for calculating the negative electrode active material is calculated according to μO2 = M2 × (IO2 / nO2). Here, nO2 and IO2 are the real-time speed and current values ​​at the time the second test sample was taken.

[0165] For example, the viscosity μO2 of the second test sample is 11280.6 mPa·s, the rotation speed nO2 of the stirring member when stirring the second test sample is 925 rpm, and the current value IO2 of the driving motor when stirring the second test sample is 102.3 A. The calculation process of M2 is as follows:

[0166] First, 11280.6=M2×(102.3 / 925), second, M2=11280.6 / (102.3 / 925), and finally, M2≈102000.

[0167] In this embodiment, the first coefficient M1 is calculated using a first test sample that is exactly the same as the second mixed material, and the second coefficient M2 is calculated using a second test sample that is exactly the same as the negative electrode active material. This improves the accuracy of the calculation results of the first coefficient M1 and the second coefficient M2, thereby improving the accuracy of the calculation results of the viscosity of the second mixed material and the negative electrode active material.

[0168] The first test sample can be directly taken out from the second mixed material or prepared separately. The second test sample can be directly taken out from the negative electrode active material or prepared separately.

[0169] Figure 11 Schematic diagram of the process of calculating the first coefficient provided in some embodiments of the present application. When the first test sample is taken directly from the second mixed material, please refer to Figure 11 The step of preparing the first test sample includes:

[0170] A portion of the second mixed material is taken out as a first test sample. At this time, the rotation speed n01 of the stirring member is the real-time rotation speed when the first test sample is taken out, and the current value I01 of the driving motor is the real-time current when the first test sample is taken out.

[0171] When the second test sample is taken directly from the negative electrode active material, please refer to Figure 11 The step of preparing the second test sample includes:

[0172] A portion of the negative electrode active material is taken out as a second test sample. At this time, the rotation speed n02 of the stirring member is the real-time rotation speed when the second test sample is taken out, and the current value I02 of the driving motor is the real-time current when the second test sample is taken out.

[0173] In this embodiment, a portion of the second mixed material and the negative electrode active material is directly taken out and used as a test sample, which improves the consistency of the test sample with the second mixed material and the negative electrode active material, thereby improving the accuracy and reliability of viscosity calculation.

[0174] Figure 13 Schematic diagram of the process of calculating the first coefficient and the second coefficient provided in some embodiments of the present application. When the first test sample is prepared separately, please refer to Figure 13 The step of preparing the first test sample includes:

[0175] Before the step of preparing the first mixed material, a first test material is prepared. The composition and proportion of the first test material are exactly the same as those of the first mixed material. The first test material at least includes an active substance, a thickener, and a conductive agent.

[0176] The solvent is added 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.

[0177] A portion of the second test material is removed and used as a first test sample.

[0178] When preparing the first test sample separately, please refer to Figure 13 The step of preparing the second test sample includes:

[0179] adding a solvent to the remaining second test material, and using a stirring device to stir and fully disperse the solvent and the second test material to form a third test material;

[0180] The third test material is removed and used as a second test sample.

[0181] In this embodiment, before the formal preparation of the negative electrode active material, a small amount of the first test sample and the second test sample are prepared, and the conversion coefficient is determined by the first test sample and the second test sample. Thereafter, during the formal preparation of the negative electrode active material, the real-time viscosity of the material can be directly calculated based on the conversion coefficient, which is beneficial to shortening the preparation cycle of the negative electrode active material and reducing the preparation cost.

[0182] The first coefficient and the second coefficient can be stored in a database and correspond to parameters such as the composition and mixing ratio of the negative electrode active material. When the stirring equipment processes the same negative electrode active material in other batches, it can directly extract the first coefficient and the second coefficient from the database, thereby further shortening the preparation cycle.

[0183] In summary, exemplary, the preparation process of the secondary battery provided in some examples of this application includes:

[0184] Graphite, CMC and SP are put into a stirring device, and the stirring device mixes the graphite, CMC and SP at a first preset speed to form a first mixed material.

[0185] Taking the stirring paddle as an example, the first speed is between 15 rpm and 25 rpm. For example, the first 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.

[0186] Exemplarily, the first speed is between 15rpm and 20rpm, and the first speed can be 15rpm, 15.2rpm, 15.4rpm, 15.6rpm, 15.8rpm, 16rpm, 16.2rpm, 16.4rpm, 16.6rpm, 16.8rpm, 17rpm, 17.2rpm, 17.4rpm, 17.6rpm, 17.8rpm, 18rpm, 18.2rpm, 18.4rpm, 18.6rpm, 18.8rpm, 19rpm, 19.2rpm, 19.4rpm, 19.6rpm, 19.8rpm, 20rpm, etc.

[0187] Exemplarily, the first speed is between 20rpm and 25rpm, and the first speed can be 20rpm, 20.2rpm, 20.4rpm, 20.6rpm, 20.8rpm, 21rpm, 21.2rpm, 21.4rpm, 21.6rpm, 21.8rpm, 22rpm, 22.2rpm, 22.4rpm, 22.6rpm, 22.8rpm, 23rpm, 23.2rpm, 23.4rpm, 23.6rpm, 23.8rpm, 24rpm, 24.2rpm, 24.4rpm, 24.6rpm, 24.8rpm, 25rpm, etc.

[0188] First water addition and stirring: a first mass of water is added to the first mixed material, and the stirring device stirs the water and the first mixed material at a second speed for a first preset time to form a dispersed material.

[0189] Taking the stirring paddle as an example, the second speed is between 15 rpm and 25 rpm. For example, the second 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.

[0190] Exemplarily, the second speed is between 15rpm and 20rpm, and the second speed can be 15rpm, 15.2rpm, 15.4rpm, 15.6rpm, 15.8rpm, 16rpm, 16.2rpm, 16.4rpm, 16.6rpm, 16.8rpm, 17rpm, 17.2rpm, 17.4rpm, 17.6rpm, 17.8rpm, 18rpm, 18.2rpm, 18.4rpm, 18.6rpm, 18.8rpm, 19rpm, 19.2rpm, 19.4rpm, 19.6rpm, 19.8rpm, 20rpm, etc.

[0191] Exemplarily, the second speed is between 20rpm and 25rpm, and the second speed can be 20rpm, 20.2rpm, 20.4rpm, 20.6rpm, 20.8rpm, 21rpm, 21.2rpm, 21.4rpm, 21.6rpm, 21.8rpm, 22rpm, 22.2rpm, 22.4rpm, 22.6rpm, 22.8rpm, 23rpm, 23.2rpm, 23.4rpm, 23.6rpm, 23.8rpm, 24rpm, 24.2rpm, 24.4rpm, 24.6rpm, 24.8rpm, 25rpm, etc.

[0192] The first preset time is between 30 minutes and 60 minutes. Exemplarily, the first preset time can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.

[0193] Exemplarily, the first preset time is between 30min and 45min, and the first preset time can be 30min, 31min, 32min, 33min, 34min, 35min, 36min, 37min, 38min, 39min, 40min, 41min, 42min, 43min, 44min, 45min, etc.

[0194] Exemplarily, the first preset time is between 45min and 60min, and the first preset time can be 45min, 46min, 47min, 48min, 49min, 50min, 51min, 52min, 53min, 54min, 55min, 56min, 57min, 58min, 59min, 60min, etc.

[0195] Second water addition and stirring: a second mass of water is added to the dispersed material, and the stirring device stirs the water and the dispersed material at a third speed for a second preset time to form a second mixed material.

[0196] Taking the stirring paddle as an example, the third speed is between 15 rpm and 25 rpm. For example, the third 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.

[0197] Exemplarily, the third speed is between 15rpm and 20rpm, and the third speed can be 15rpm, 15.2rpm, 15.4rpm, 15.6rpm, 15.8rpm, 16rpm, 16.2rpm, 16.4rpm, 16.6rpm, 16.8rpm, 17rpm, 17.2rpm, 17.4rpm, 17.6rpm, 17.8rpm, 18rpm, 18.2rpm, 18.4rpm, 18.6rpm, 18.8rpm, 19rpm, 19.2rpm, 19.4rpm, 19.6rpm, 19.8rpm, 20rpm, etc.

[0198] Exemplarily, the third speed is between 20rpm and 25rpm, and the third speed can be 20rpm, 20.2rpm, 20.4rpm, 20.6rpm, 20.8rpm, 21rpm, 21.2rpm, 21.4rpm, 21.6rpm, 21.8rpm, 22rpm, 22.2rpm, 22.4rpm, 22.6rpm, 22.8rpm, 23rpm, 23.2rpm, 23.4rpm, 23.6rpm, 23.8rpm, 24rpm, 24.2rpm, 24.4rpm, 24.6rpm, 24.8rpm, 25rpm, etc.

[0199] Taking the dispersion disk as an example, the third rotational speed is between 800 rpm and 1200 rpm. For example, 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.

[0200] Exemplarily, the third speed is between 800rpm and 1000rpm, and the third speed can be 800rpm, 810rpm, 820rpm, 830rpm, 840rpm, 850rpm, 860rpm, 870rpm, 880rpm, 890rpm, 900rpm, 910rpm, 920rpm, 930rpm, 940rpm, 950rpm, 960rpm, 970rpm, 980rpm, 990rpm, 1000rpm, etc.

[0201] Exemplarily, the third speed is between 1000rpm and 1200rpm. The third speed may be 1000rpm, 1010rpm, 1020rpm, 1030rpm, 1040rpm, 1050rpm, 1060rpm, 1070rpm, 1080rpm, 1090rpm, 1100rpm, 1110rpm, 1120rpm, 1130rpm, 1140rpm, 1150rpm, 1160rpm, 1170rpm, 1180rpm, 1190rpm, 1200rpm, etc.

[0202] The second preset time is between 60 minutes and 120 minutes. Exemplarily, the second preset time can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes, etc.

[0203] Exemplarily, the second preset time is between 60min and 90min, and the second preset time can be 60min, 62min, 64min, 66min, 68min, 70min, 72min, 74min, 76min, 78min, 80min, 82min, 84min, 86min, 88min, 90min, etc.

[0204] Exemplarily, the second preset time is between 90min and 120min, and the second preset time can be 90min, 92min, 94min, 96min, 98min, 100min, 102min, 104min, 106min, 108min, 110min, 112min, 114min, 116min, 118min, 120min, etc.

[0205] During the stirring process of the second mixed material, the real-time viscosity μ1 of the second mixed material is calculated according to the rotation speed n1, the real-time feedback current value I1 of the drive motor and the first coefficient M1 using the formula μ1=M1×(I1 / n1), where M1 is 3571.

[0206] For example, taking the state after stirring for 20 minutes as an example, the calculation process of the viscosity μ1 of the second mixed material is as follows:

[0207] μ1=3571×(I1 / n1)=3571×(77.1 / 22)≈12515.

[0208] 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.

[0209]

[0210] According to the viscosity μ1 of the second mixed material, the stability characterizing quantity S1 of the second mixed material is calculated using the formula S1=d(μ1) / d(t1).

[0211] For example, taking the state after stirring for 20 minutes as an example, the calculation process of the stability characteristic value S1 of the second mixed material is as follows:

[0212] S1=d(μ1) / d(t1)=Δ(μ1) / Δ(t1)=(μ12-μ11) / (t12-t11)=(12515-13943) / (20-10)≈-143.

[0213] When 5000 millipascal·second ≤ μ1 ≤ 10000 millipascal·second and -10 millipascal·second per minute ≤ S1 < 0, the stirring time 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 device stirs the solvent and the second mixed material to form a negative electrode active material.

[0214] During the stirring process of the negative electrode active material, the viscosity μ2 of the negative electrode active material is calculated according to the rotation speed n2, the real-time feedback current value I2 of the drive motor and the second coefficient M2 using the formula μ2=M2×(I2 / n2), where M2 is 102000.

[0215] For example, taking the state after stirring for 20 minutes as an example, the calculation process of the viscosity μ2 of the second mixed material is as follows:

[0216] μ2=102000×(I2 / n2)=102000×(115.6 / 925)≈12747.2.

[0217] According to the above calculation, the real-time viscosity comparison table of the negative electrode active material is obtained as shown in Table 3, and the real-time feedback current value I2 of the driving motor and the real-time viscosity μ2 of the negative electrode active material are uploaded to the database.

[0218]

[0219] 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).

[0220] For example, taking the state of stirring for 20 minutes as an example, the calculation process of the stability characteristic value S2 of the negative electrode active material is as follows:

[0221] S2=d(μ2) / d(t2)=Δ(μ2) / Δ(t2)=(μ21-μ22) / (t22-t21)=(12747.2-13309.6) / (20-10)≈-56.2.

[0222] When 5000 milliPascal·second ≤ μ2 ≤ 10000 milliPascal·second and -10 milliPascal·second per minute ≤ S2 < 0, the negative electrode active material is discharged, and the stirring time t2 of the negative electrode active material is uploaded to the database.

[0223] The negative electrode active material is coated on the negative electrode current collector and dried to form a negative electrode sheet.

[0224] The positive electrode sheet, separator and negative electrode sheet are wound to form a battery cell assembly.

[0225] The battery cell assembly is installed into the shell, and the electrolyte is injected into the shell to form a secondary battery.

[0226] In the related art, during the preparation of negative electrode active materials, the materials need to be taken out and the viscosity of the taken out materials is tested to determine whether to proceed to the next process. During the process of taking out the materials, there is a risk that foreign matter such as dust and water vapor in the external environment enters the materials and affects the test results. Moreover, the taken out materials cannot be used any further, resulting in material waste and increasing the manufacturing cost of secondary batteries.

[0227] In the preparation process provided in the embodiment of the present application, the real-time viscosity of the material is calculated based on the real-time current of the drive motor, which reduces the process of removing the material and shortens the preparation cycle of the negative electrode active material. At the same time, the risk of material contamination caused by removing the material is reduced, the accuracy of the test results is improved, and the risk of excessive stirring time affecting the performance of the negative electrode active material is reduced, which is conducive to improving the performance of the negative electrode active material. In addition, the process of removing the material is shortened, the waste of material caused by viscosity testing is reduced, the discharge rate of the negative electrode active material is improved, and the preparation cost of the negative electrode active material is reduced.

[0228] Based on the secondary battery made by the above preparation process, in the third aspect, the embodiment of the present application provides an energy storage system, which includes a plurality of the above secondary batteries. The energy storage system includes but is not limited to an energy storage box. For example, the energy storage system can be Figure 2 The energy storage box 2 shown includes a cabinet 21 and a plurality of secondary batteries installed in the cabinet 21 .

[0229] In a fourth aspect, the present application provides an electrical device, which 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, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc. For example, the electrical device is Figure 1 In the vehicle shown, the battery pack 1 of the vehicle is an energy storage system, and the battery pack 1 has multiple secondary batteries connected in series and parallel. The power module on the vehicle is a load.

Claims

1. A secondary battery preparation process, characterized in that: The secondary battery preparation process includes: At least an active material having a mass of g11, a thickener having a mass of g12, and a conductive agent having a mass of g13 are added to a stirring device, and the stirring device mixes them to form a first mixed material having a mass of G1, 0.96≤g11 / G1≤0.965, 0.015≤g12 / G1≤0.02, and 0.01≤g13 / G1≤0.015; Adding a first mass g21 of solvent into the first mixed material, and stirring with a stirring device to form a dispersed material; Add the second mass g22 of solvent to the dispersed material and stir with a stirring device to form a second mixed material with a mass G4, 1≤G1 / (g21+g22)≤1.2, 8:12≤g21:g22≤1812; The viscosity μ1 of the second mixed material is calculated according to the formula μ1=M1×(I1 / n1), where M1 is a first coefficient, the stirring device includes a stirring member and a drive motor, the drive motor drives the stirring member to rotate at a preset speed, and when the stirring member stirs the second mixed material, n1 is the speed of the stirring member, and I1 is the real-time current value of the drive motor; the stability characteristic value S1 of the second mixed material is calculated according to the formula S1=d(μ1) / d(t1), where t1 is the stirring time of the second mixed material; When 5000 millipascal·second ≤ μ1 ≤ 10000 millipascal·second, and when -10 millipascal·second per minute ≤ S1 < 0, adding a binder with a mass of G3 to the second mixed material, 0.012 ≤ G3 / G4 ≤ 0.018, and stirring with a stirring device to form a negative electrode active material; The viscosity μ2 of the negative electrode active material is calculated according to the formula μ2=M2×(I2 / n2), where M2 is the second coefficient, n2 is the speed of the stirring member when the stirring member stirs the negative electrode active material, and I2 is the real-time current value of the driving motor; the stability characteristic value S2 of the negative electrode active material is calculated according to the formula S2=d(μ2) / d(t2), where t2 is the stirring time of the negative electrode active material; When 5000 milliPascal·second ≤ μ2 ≤ 10000 milliPascal·second, and when -10 milliPascal·second per minute ≤ S2 < 0, the negative electrode active material is discharged; The negative electrode active material is coated on the negative electrode current collector and dried to form a negative electrode sheet; The positive electrode active material is coated on the positive electrode current collector and dried to form a positive electrode sheet; The positive electrode sheet, the separator and the negative electrode sheet are stacked and wound to form a battery cell assembly; The battery cell assembly is installed into the shell, and the electrolyte is injected into the shell to form a secondary battery.

2. The secondary battery preparation process according to claim 1, characterized in that: Before the step of calculating the viscosity and stability characterizing amount of the second mixed material, the secondary battery preparation process includes: preparing a first test sample, the first test sample comprising at least an active substance, a thickener, 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 stability characterizing amount of the negative electrode active material, the secondary battery preparation process includes: preparing a second test sample, the second test sample comprising at least an active substance, a thickener, a conductive agent, and a binder; The viscosity of the second test sample is measured, and the second coefficient M2 is calculated 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.

3. The secondary battery preparation process according to claim 2, characterized in that: The step of preparing the first test sample includes: taking out a portion of the second mixed material as a first test sample; The step of preparing the second test sample includes: A portion of the negative electrode active material was taken out and used as a second test sample.

4. The secondary battery preparation process according to claim 2, characterized in that: The step of preparing the first test sample includes: Before the step of preparing the first mixed material, a first test material is prepared, wherein the first test material at least includes an active substance, a thickener, and a conductive agent; adding a solvent into the first test material, and using a stirring device to stir and fully disperse the solvent and the first test material to form a second test material; removing a portion of the second test material to serve as a first test sample; The step of preparing the second test sample includes: adding a solvent into the second test material, and using a stirring device to stir and fully disperse the solvent and the second test material to form a third test material; The third test material is removed and used as a second test sample.

5. The secondary battery preparation process according to any one of claims 1 to 4, characterized in that: When the stirring device stirs the solvent and the dispersed material, the secondary battery preparation process includes: The rotation speed of the stirring element and the current of the driving motor are stored in a database; When 5000 milliPascal·second ≤ μ1 ≤ 10000 milliPascal·second, and when -10 milliPascal·second per minute ≤ S1 < 0, the secondary battery preparation process includes: storing the stirring time of the second mixed material by the stirring device in a database; When the stirring device stirs the solvent and the second mixed material, the secondary battery preparation process includes: The rotation speed of the stirring element and the current of the driving motor are stored in a database; When 5000 milliPascal·second ≤ μ2 ≤ 10000 milliPascal·second, and when -10 milliPascal·second per minute ≤ S2 < 0, the secondary battery preparation process includes: The stirring time of the negative electrode active material by the stirring equipment is stored in the database.

6. A secondary battery, characterized in that: A secondary battery is prepared by the secondary battery preparation process according to any one of claims 1 to 5; The secondary battery comprises a shell, a battery cell assembly and an electrolyte, wherein the shell comprises 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 sheet, a negative electrode sheet and a separator, and the separator is located between the positive electrode sheet and the negative electrode sheet; The negative electrode sheet includes a negative electrode current collector and a negative electrode active material.

7. An energy storage system, characterized in that: An energy storage system comprises a plurality of secondary batteries according to claim 6.

8. An electrical device, characterized in that: The electrical equipment includes a load and the energy storage system of claim 7, and the energy storage system is capable of supplying power to the load.

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