Negative active material, method for manufacturing the same, secondary battery, battery module, battery pack, and electric device

Abstract

The embodiment of the present application provides a kind of negative active material and its preparation method, secondary battery, battery module, battery pack and electric device.The preparation method of negative active material of the present application includes: on amphiphilic polymer material template, first oxide is formed by assembling, wherein the first oxide is selected from one of V2O3, Fe2O3 And CuO;Second oxide precursor is assembled on the assembled first oxide to form amphiphilic polymer material-first oxide-second oxide precursor complex, wherein the second oxide precursor is selected from one of K2SnO3, Na2SiO3, Na2GeO3, NaAlO2, NaBO4·4H2O;The complex is heated to remove the amphiphilic polymer material and make the second oxide precursor form second oxide, obtain the negative active material with hexagonal hollow structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a negative electrode active material, a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0002] In recent years, lithium ion batteries have been more and more widely applied in energy storage power supply systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion batteries have achieved great development, higher requirements have been put forward for their energy density, cycle performance and safety performance, etc. Based on the higher requirements for the energy density of secondary batteries, a large amount of research has been carried out around high-capacity negative electrode active materials.

[0003] Graphite and silicon are commonly used as negative electrode active materials, but the theoretical specific capacity of graphite negative electrode active material is low, and the silicon negative electrode active material has a serious volume effect, which limits the improvement of the energy density of lithium ion batteries and sodium ion batteries, thereby limiting the development of lithium ion batteries and sodium ion batteries. SUMMARY

[0004] The present application is made in view of the above-mentioned problems, and aims to provide a negative electrode active material, a preparation method thereof, a secondary battery, a battery module, a battery pack and a power utilization device, so as to solve the problem of limited specific capacity improvement of existing negative electrode active materials.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a preparation method of a negative electrode active material, comprising:

[0006] assembling a first oxide on the amphiphilic polymer material template, wherein the first oxide is selected from one of V2O3, Fe2O3 and CuO;

[0007] assembling a second oxide precursor on the assembled first oxide to form an amphiphilic polymer material-first oxide-second oxide precursor composite, wherein the second oxide precursor is selected from one of K2SnO3, Na2SiO3, Na2GeO3, NaAlO2 and NaBO4·4H2O; and

[0008] heating the composite to remove the amphiphilic polymer material and make the second oxide precursor form a second oxide, so as to obtain a negative electrode active material with a hexagonal hollow structure.

[0009] The preparation method of the negative electrode active material of the present application uses an amphiphilic polymer material as a template to prepare a negative electrode active material with a hexagonal hollow structure. Generally, during the charging and discharging process, the active ion in the active material is easy to cause volume expansion / contraction during intercalation. However, the hexagonal hollow structure of the negative electrode active material of the present application has a certain buffering effect on volume expansion / contraction, which can overcome the volume change caused by the intercalation of active ions, thereby maintaining the overall structural stability of the negative electrode active material. In addition, the negative electrode active material of the present application is formed by compounding the first oxide and the second oxide, which can better play the complementary advantages and the synergistic effect of making up for each other's shortcomings. Compared with single elements or single oxides, the negative electrode active material of the present application has a larger amount of active ion intercalation and further increases the reversible capacity, thereby improving the gravimetric capacity and specific surface area of the negative electrode active material, and further improving the energy density of the secondary battery.

[0010] In some embodiments of the first aspect of the present application, the negative electrode material comprises one of V2O3-SnO2, Fe2O3-SnO2, Fe2O3-GeO2, Fe2O3-Al2O3, Fe2O3-B2O3 and CuO-SiO2, and is optionally V2O3-SnO2 or Fe2O3-SnO2.

[0011] In these optional embodiments, the specific optional negative electrode materials all have a hexagonal hollow structure, a high specific surface area and a certain buffering effect, which can overcome the volume change caused by the intercalation of active ions, and thus the overall structural stability of the above-mentioned negative electrode active materials is good. In addition, according to the embodiments of the negative electrode material, the first oxide and the second oxide have a better synergistic effect.

[0012] In some embodiments of the first aspect of the present application, the amphiphilic polymer material is selected from polyvinylpyrrolidone.

[0013] In these optional embodiments, polyvinylpyrrolidone is a linear polymer polymerized from monomer vinylpyrrolidone, and is soluble in water and polar solvents such as alcohol, halogenated hydrocarbon, carboxylic acid and alcohol amine. The molecular chain skeleton of polyvinylpyrrolidone and the -CH2- in the pyrrolidone have hydrophobicity, and the amide group in the pyrrolidone ring has hydrophilicity. After dissolving in the dispersion medium, the polyvinylpyrrolidone molecules can aggregate to form micelles, and the outer layer of the micelles is composed of the hydrophilic groups of polyvinylpyrrolidone. The hydrophilic groups of polyvinylpyrrolidone can become the sites for interaction with metal atoms through complexation and / or electrostatic adsorption, so that the polyvinylpyrrolidone micelles can be used as a template for assembling metal oxides.

[0014] In some embodiments of the first aspect of this application, the first oxide is assembled and formed on an amphiphilic polymer material template, specifically including:

[0015] The amphiphilic polymer material and the first oxide precursor are fully dispersed in an alkaline dispersion medium to obtain a dispersion system in which the first oxide precursor is assembled on the amphiphilic polymer material template.

[0016] The dispersion system is heated so that the first oxide precursor forms the first oxide, thereby obtaining the assembled first oxide.

[0017] In these optional embodiments, the amphiphilic polymer material and the first oxide precursor are fully dispersed in an alkaline dispersion medium. Polyvinylpyrrolidone (PVP) molecules can aggregate to form micelles. The outer layer of these micelles is composed of hydrophilic groups of PPVP. These hydrophilic groups can become sites for interaction with metal atoms through complexation and / or electrostatic adsorption, thereby adsorbing the first oxide precursor onto these sites. The dispersion system is heated to form the first oxide from the first oxide precursor. The heating temperature of the dispersion system needs to be such that all the first oxide precursor is formed into the first oxide, improving the conversion rate of the first oxide precursor; however, the heating temperature also needs to be controlled to prevent the amphiphilic polymer material from volatilizing and being removed, maintaining the stability of the amphiphilic polymer material template to ensure the subsequent assembly of the second oxide precursor.

[0018] In some embodiments of the first aspect of this application, the first oxide precursor is selected from one of Co3V2O8, Fe(NO3)3 and Cu(NO3)2.

[0019] In these alternative embodiments, the amphiphilic polymer material has high solubility in an alkaline dispersion medium with one of Co3V2O8, Fe(NO3)3 and Cu(NO3)2, which allows the first oxide precursor to be fully dispersed, avoiding the loss of the first oxide during assembly, thereby ensuring the yield and purity of the product.

[0020] In some embodiments of the first aspect of this application, the mass ratio of the amphiphilic polymer material to the first oxide precursor is 1:(1-2).

[0021] In these alternative embodiments, the amphiphilic polymer material and the first oxide precursor are in a suitable mass ratio, such that the first oxide precursor is fully assembled on the amphiphilic polymer material template. Moreover, the suitable mass ratio ensures that the final obtained negative electrode active material has a hexagonal hollow structure.

[0022] In some embodiments of the first aspect of this application, the temperature for heating the dispersion system is 200°C to 400°C, and the time is 5 hours to 7 hours.

[0023] In these optional embodiments, suitable heating temperature and heating time ensure that the first oxide precursor is completely converted into the first oxide, improving product yield. Furthermore, heating the dispersion system at a temperature of 200°C to 400°C reduces the loss of the amphiphilic polymer material and maintains the stability of the amphiphilic polymer template. In addition, suitable heating temperature and heating time reduce energy consumption and production costs.

[0024] In some embodiments of the first aspect of this application, assembling a second oxide precursor on an assembled first oxide specifically includes:

[0025] The assembled first oxide and second oxide precursors are fully dispersed in a dispersion medium to bring the assembled first oxide and second oxide precursors into contact.

[0026] In these alternative embodiments, the assembled first oxide and the second oxide precursor are fully dispersed in a dispersion medium, and the second oxide precursor is assembled onto the assembled first oxide by physical adsorption.

[0027] In some embodiments of the first aspect of this application, the mass ratio of the assembled first oxide to the second oxide precursor is 1:(1 to 2).

[0028] In these alternative embodiments, the assembled first oxide and second oxide precursors have a suitable mass ratio to ensure that the final obtained negative electrode active material has a hexagonal hollow structure.

[0029] In some embodiments of the first aspect of this application, the mass concentration of the amphiphilic polymer material in the dispersion medium is 15% to 25%.

[0030] In these alternative embodiments, the amphiphilic polymer material has a mass such that polyvinylpyrrolidone molecules can aggregate to form micelles in an alkaline dispersion medium.

[0031] In some embodiments of the first aspect of this application, the temperature of the heating compound is 400°C to 600°C, and the time is 5h to 7h.

[0032] In these alternative embodiments, suitable heating temperature and heating time ensure that the second oxide precursor is completely converted into the second oxide, improving product yield. By heating the composite, the amphiphilic polymer material in the composite can be removed, and the second oxide undergoes an alloying reaction upon heating to combine with the first oxide, forming strong metallic bonds through the electrostatic attraction between metal ions.

[0033] In some embodiments of the first aspect of this application, the average particle size Dv50 of the negative electrode active material is 100 μm to 200 μm, and optionally 120 μm to 180 μm.

[0034] In these alternative embodiments, the average particle size Dv50 of the negative electrode active material is within an appropriate range, which is beneficial for the negative electrode active material layer to obtain a high compaction density, while having a suitable porosity to meet the electrolyte wetting amount required for electrochemical reactions, and also having a shorter migration path for active ions and electrons within the particles, thereby improving the energy density and cycle performance of the negative electrode active material layer.

[0035] The second aspect of this application also provides a negative electrode active material, which is prepared by the preparation method of the first aspect of this application.

[0036] The negative electrode active material of this application is composed of a first oxide and a second oxide. The negative electrode active material has a hexagonal hollow structure, which gives it a high specific capacity and specific surface area, and the secondary battery prepared from it also has a high energy density.

[0037] In any embodiment of the second aspect of this application, the specific surface area of ​​the negative electrode active material is 175 m². 2 / g~400m 2 / g, optionally 300m 2 / g~400m 2 / g.

[0038] In these optional embodiments, the specific surface area of ​​the negative electrode active material is within the above-mentioned range, which ensures that the negative electrode active material has a high active specific surface area, and at the same time helps to reduce the side reactions of the electrolyte on the surface of the negative electrode active material, thereby improving the capacity utilization and cycle life of the negative electrode active material.

[0039] In any embodiment of the second aspect of this application, the specific capacity of the negative electrode active material is 490 mAh / g to 1100 mAh / g, and optionally 500 mAh / g to 700 mAh / g.

[0040] In these alternative embodiments, the negative electrode active material of this application has a large specific capacity, thereby enabling the secondary battery to have a large energy density.

[0041] A third aspect of this application provides a secondary battery, comprising a negative electrode active material prepared by the preparation method of the first aspect of this application or a negative electrode active material of the second aspect of this application.

[0042] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0043] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0044] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0046] Figure 1 A flowchart of a method for preparing a negative electrode active material according to an embodiment of this application is shown.

[0047] Figure 2 A diagram showing the lithium intercalation state of the negative electrode active material during charge and discharge according to an embodiment of this application is illustrated.

[0048] Figure 3 A flowchart illustrating an exemplary process for forming a first oxide in a method for preparing a negative electrode active material is shown.

[0049] Figure 4 An SEM image of the negative electrode active material according to an embodiment of this application is shown.

[0050] Figure 5 An SEM image of a negative electrode active material according to another embodiment of this application is shown.

[0051] Figure 6 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0052] Figure 7 yes Figure 6 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0053] Figure 8 This is a schematic diagram of a battery module according to one embodiment of this application.

[0054] Figure 9 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0055] Figure 10 yes Figure 9 An exploded view of a battery pack according to one embodiment of this application is shown.

[0056] Figure 11 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0057] Explanation of reference numerals in the attached figures:

[0058] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Cover plate. Detailed Implementation

[0059] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material, its preparation method, electrode sheet, secondary battery, battery module, battery pack, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0060] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0061] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0062] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0063] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0064] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0065] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0066] With the significant advancements in both lithium-ion and sodium-ion batteries, higher demands have been placed on their energy density, cycle performance, and safety. Among these, the negative electrode active material is one of the main factors affecting the performance of lithium-ion or sodium-ion batteries. Lithium-ion batteries are widely used in electronic products such as mobile phones, tablets, and drones, and there are increasingly higher requirements for battery capacity in these products, aiming to maximize battery capacity within limited space. Currently used graphite negative electrode active materials have a theoretical specific capacity of approximately 370 mAh / g, which cannot meet the demand for higher energy density lithium-ion batteries. Although the theoretical specific capacity of silicon materials is significantly higher than that of currently commercially available graphite negative electrode active materials, silicon materials exhibit very significant volume expansion (>300%) during high-level lithium intercalation. This expansion of the negative electrode sheet leads to pulverization and material loss, severely affecting the cycle stability and cycle life of the battery. Based on this, the inventors prepared a composite negative electrode active material with excellent electrochemical performance and high capacity through a thermal reduction method of silicon and graphite. However, the above-mentioned composite anode active materials have complex synthesis routes and stringent process requirements, and also suffer from significant volume expansion during lithium intercalation.

[0067] Based on the problems identified by the applicant, the applicant improved the preparation method of the negative electrode active material by using a template method to synthesize the negative electrode active material. The preparation method is simple, and the prepared negative electrode active material has a high active ion intercalation amount, which improves the specific capacity and specific surface area of ​​the negative electrode active material, and further improves the energy density of the secondary battery.

[0068] Preparation method of negative electrode active material

[0069] Figure 1 A flowchart of a method for preparing a negative electrode active material according to an embodiment of this application is shown.

[0070] like Figure 1 As shown, the first aspect of this application provides a method for preparing a negative electrode active material, comprising:

[0071] S1. The first oxide is assembled on an amphiphilic polymer material template;

[0072] The first oxide is selected from one of V2O3, Fe2O3 and CuO;

[0073] S2. Assemble a second oxide precursor on the assembled first oxide to form an amphiphilic polymer material-first oxide-second oxide precursor complex;

[0074] The second oxide precursor is selected from one of K2SnO3, Na2SiO3, Na2GeO3, NaAlO2, and NaBO4·4H2O; and

[0075] S3. Heating the composite removes the amphiphilic polymer material and causes the second oxide precursor to form the second oxide, thereby obtaining a negative electrode active material with a hexagonal hollow structure.

[0076] The method for preparing the negative electrode active material in this application uses an amphiphilic polymer material as a template to prepare a negative electrode active material with a hexagonal hollow structure. Normally, during charge and discharge, the insertion of active ions easily causes volume expansion / contraction in negative electrode active materials. However, the hexagonal hollow structure of the negative electrode active material in this application has a certain buffering effect on volume expansion / contraction, which can overcome the volume changes caused by the insertion of active ions, thereby maintaining the overall structural stability of the negative electrode active material. Furthermore, this application forms the negative electrode active material by combining a first oxide and a second oxide, which can better leverage their complementary advantages and synergistic effects to compensate for each other's shortcomings. Compared with elemental or single oxide materials, the negative electrode active material in this application has a greater amount of inserted active ions, further increasing the reversible capacity, thereby improving the specific capacity and specific surface area of ​​the negative electrode active material, and further improving the energy density of the secondary battery.

[0077] According to embodiments of this application, the amphiphilic polymer is a polymer that is both hydrophobic and hydrophilic. Not intended to be limited to any particular theory or explanation, when dissolved in a dispersion medium, the amphiphilic polymer molecules can associate to form micelles. The hydrophobic groups of the amphiphilic polymer molecules can attract each other to form the micelle core, while the hydrophilic groups form the micelle outer layer. The hydrophilic groups on the outer layer of the micelles can undergo electrostatic adsorption and / or complexation with metal atoms, becoming sites capable of binding metal atoms. This allows the amphiphilic polymer material to serve as a template for assembling and forming metal oxides.

[0078] In some embodiments, the amphiphilic polymer material is polyvinylpyrrolidone.

[0079] Polyvinylpyrrolidone (PVP) is a linear polymer synthesized from the monomer ethylenepyrrolidone. It is soluble in water and polar solvents such as alcohols, halogenated hydrocarbons, carboxylic acids, and alkanolamines. The molecular chain backbone of PPVP and the -CH2- group in pyrrolidone are hydrophobic, while the amide groups in the pyrrolidone ring are hydrophilic. After dissolving in a dispersion medium, PPVP molecules can aggregate to form micelles. The outer layer of these micelles is composed of the hydrophilic groups of PPVP. These hydrophilic groups can become sites for binding metal atoms through complexation and / or electrostatic adsorption, thus allowing PPVP micelles to serve as templates for the assembly of metal oxides.

[0080] In some embodiments of this application, the first oxide is selected from V2O3, Fe2O3 and CuO. These first oxides contain transition metal elements. When applied to secondary batteries, they have good ion insertion and extraction reversibility, stable chemical properties in the electrolyte, and a large lithium-ion storage density.

[0081] In some embodiments of this application, the second oxide precursor is selected from one of K2SnO3, Na2SiO3, Na2GeO3, NaAlO2, and NaBO4·4H2O. These second oxides are readily soluble in the dispersion medium.

[0082] In some embodiments of this application, the amphiphilic polymer material-first oxide-second oxide precursor composite is heated in step S3. On the one hand, heating can remove the amphiphilic polymer material to obtain a negative electrode active material composed of the first oxide and the second oxide. On the other hand, the second oxide precursor is heated to form the second oxide, and the second oxide undergoes an alloying reaction after heating to combine with the first oxide, and a strong metal bond is formed through the electrostatic attraction between metal ions.

[0083] Figure 2 A diagram showing the lithium intercalation state of the negative electrode active material during charge and discharge according to an embodiment of this application is illustrated. See also: Figure 2 , Figure 2 The hexagonal hollow structure of the negative electrode active material in this application has a relatively large amount of embedded active ions.

[0084] In some embodiments, the negative electrode material includes one of V2O3-SnO2, Fe2O3-SnO2, Fe2O3-GeO2, Fe2O3-Al2O3, Fe2O3-B2O3, and CuO-SiO2.

[0085] Optionally, the negative electrode material is V2O3-SnO2 or Fe2O3-SnO2. Tin, as a negative electrode, has the advantages of high theoretical specific capacity and high packing density. However, tin negative electrodes exhibit large volume expansion (greater than 300%) during charge and discharge, and the electrode material structure is prone to pulverization, significantly reducing the cycle performance of the battery. The negative electrode active material of this application is based on the preparation of a hexagonal hollow structure using a template method, achieving tin doping. Furthermore, transition metal elements such as V, Fe, and Cu are introduced to stabilize the structure of the negative electrode active material through alloying. Moreover, the alloying of transition metal elements can serve as a supporting framework to reduce the expansion ratio of the negative electrode active material.

[0086] In these optional embodiments, these specific optional anode materials all exhibit a hexagonal hollow structure, which has a high specific surface area and a certain buffering effect, and can overcome the volume change caused by the insertion of active ions. Therefore, the overall structural stability of the above-mentioned anode active materials is good.

[0087] See Figure 3 , Figure 3 A flowchart illustrating an exemplary process for forming a first oxide in a method for preparing a negative electrode active material is shown.

[0088] In some embodiments, such as Figure 3 As shown, in step S1, the first oxide is assembled and formed on the amphiphilic polymer material template, specifically including:

[0089] S11. The amphiphilic polymer material template and the first oxide precursor are fully dispersed in an alkaline dispersion medium to obtain a dispersion system in which the first oxide precursor is assembled on the amphiphilic polymer material template.

[0090] S12. The dispersion system is heated so that the first oxide precursor forms the first oxide, thereby obtaining the assembled first oxide.

[0091] In step S11 of this application, the amphiphilic polymer material and the first oxide precursor are fully dispersed in an alkaline dispersion medium. Polyvinylpyrrolidone molecules can aggregate to form micelles. The outer layer of the micelles is composed of hydrophilic groups of polyvinylpyrrolidone. The hydrophilic groups of polyvinylpyrrolidone can become sites for interaction with metal atoms through complexation and / or electrostatic adsorption, thereby assembling the first oxide on the amphiphilic polymer material template.

[0092] In some embodiments of this application, step S11 specifically includes: dispersing the amphiphilic polymer material and the first oxide precursor in an alkaline dispersion medium and stirring for at least 5 hours. Under the condition of thorough stirring, the amphiphilic polymer material can be fully dispersed in the dispersion medium and aggregate to form micelles, exposing more sites and assembling more first oxide precursors on the amphiphilic polymer material template.

[0093] Alternatively, magnetic stirring can be used.

[0094] Optionally, the stirring time is 5 to 8 hours.

[0095] In step S12 of this application, the dispersion system in step S11 is heated to form the first oxide from the first oxide precursor. It is necessary to control the heating temperature in step S12 to ensure that all the first oxide precursor is formed into the first oxide, thereby improving the conversion rate of the first oxide precursor; however, it is also necessary to control the heating temperature of the dispersion system in S12 to prevent the amphiphilic polymer material from being removed, thus maintaining the stability of the amphiphilic polymer material template and ensuring the subsequent assembly of the second oxide precursor.

[0096] Optionally, the temperature at which the dispersion system is heated is less than or equal to 400°C.

[0097] In these alternative embodiments, the method of assembling the first oxide onto an amphiphilic polymer material template is simple and easy to operate, and the prepared assembled first oxide has the characteristics of uniform chemical composition and large specific surface area.

[0098] In some embodiments, the first oxide precursor is selected from one of Co3V2O8, Fe(NO3)3 and Cu(NO3)2.

[0099] In these alternative embodiments, one of Co3V2O8, Fe(NO3)3 and Cu(NO3)2 has high solubility in an alkaline dispersion medium, which allows the first oxide precursor to be fully dispersed, avoiding the loss of the first oxide during assembly, thereby ensuring the yield and purity of the product.

[0100] In some embodiments, the mass ratio of the amphiphilic polymer material to the first oxide precursor is 1:(1-2).

[0101] In these alternative embodiments, the amphiphilic polymer material and the first oxide precursor are in a suitable mass ratio, such that the first oxide precursor is fully assembled on the amphiphilic polymer material template. Moreover, the suitable mass ratio ensures that the final obtained negative electrode active material has a hexagonal hollow structure.

[0102] In some embodiments, the mass concentration of the amphiphilic polymer material in the dispersion medium is 15% to 25%.

[0103] In these alternative embodiments, the amphiphilic polymer material has a certain mass, so that polyvinylpyrrolidone molecules can aggregate to form micelles in an alkaline dispersion medium.

[0104] In some embodiments, the temperature for heating the dispersion system is 200°C to 400°C, and the time is 5 hours to 7 hours.

[0105] In some embodiments of this application, the temperature for heating the dispersion system is 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, or other ranges consisting of any two of the above endpoints.

[0106] Optionally, the temperature for heating the dispersion system is 280℃~350℃.

[0107] Alternatively, the dispersion system may be heated in an oven or calcining furnace.

[0108] In these optional embodiments, suitable heating temperature and heating time ensure that the first oxide precursor is completely converted into the first oxide, improving product yield. Furthermore, heating the dispersion system at a temperature of 200°C to 400°C reduces the loss of the amphiphilic polymer material and maintains the stability of the amphiphilic polymer template. In addition, suitable heating temperature and heating time reduce energy consumption and production costs.

[0109] In some embodiments, assembling a second oxide precursor on the assembled first oxide in step S2 specifically includes:

[0110] The assembled first oxide and second oxide precursors are fully dispersed in a dispersion medium to allow the assembled first oxide and second oxide precursors to come into contact.

[0111] Optionally, the dispersion medium is water or ethanol.

[0112] In these alternative embodiments, the assembled first oxide and the second oxide precursor are fully dispersed in a dispersion medium, and the second oxide precursor is assembled onto the assembled first oxide by physical adsorption.

[0113] In some embodiments, the mass ratio of the assembled first oxide to the second oxide precursor is 1:(1-2).

[0114] In these alternative embodiments, the assembled first oxide and second oxide precursors have a suitable mass ratio to ensure that the final obtained negative electrode active material has a hexagonal hollow structure.

[0115] In some embodiments, the temperature of the heating compound is 400°C to 600°C, and the time is 5h to 7h.

[0116] In some embodiments of this application, the temperature of the heating compound is 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or other ranges consisting of any two of the above endpoints.

[0117] Optionally, the temperature of the heated composite is 480°C to 550°C.

[0118] Alternatively, the compound can be heated in an oven or calcining furnace.

[0119] In these alternative embodiments, suitable heating temperature and heating time ensure that the second oxide precursor is completely converted into the second oxide, improving product yield. Heating removes the amphiphilic polymer material from the composite, and the second oxide undergoes an alloying reaction upon heating, combining with the first oxide and forming strong metallic bonds through electrostatic attraction between metal ions.

[0120] Thus, a negative electrode active material composed of two metal oxides is obtained.

[0121] In some embodiments, the average particle size Dv50 of the negative electrode active material is 100 μm to 200 μm.

[0122] In some embodiments of this application, the average particle size Dv50 of the negative electrode active material is 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, or other ranges consisting of any two of the above endpoints.

[0123] Optionally, the average particle size Dv50 of the negative electrode active material is 120 μm to 180 μm.

[0124] In some embodiments of this application, the average particle size Dv50 of the negative electrode active material is controlled during the preparation process to ensure that the particle size is between 100 μm and 200 μm. According to this application, the volume average particle size Dv50 of the negative electrode active material can be measured using conventional methods in the art. For example, it can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK, in accordance with GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method.

[0125] If the average particle size Dv50 of the negative electrode active material is too large, there will still be large gaps between the particles, which will reduce the compaction density of the negative electrode sheet, resulting in low energy density of the secondary battery. If the average particle size Dv50 of the negative electrode active material is too small, undesirable agglomeration will occur, which will also reduce the compaction density of the negative electrode sheet. Moreover, the lack of sufficient gaps between the particles to retain electrolyte will reduce the cycle performance of the negative electrode active material layer.

[0126] In these alternative embodiments, the average particle size Dv50 of the negative electrode active material is within an appropriate range, which is beneficial for the negative electrode active material layer to obtain a high compaction density, while having a suitable porosity to meet the electrolyte wetting amount required for electrochemical reactions, and also having a shorter migration path for active ions and electrons within the particles, thereby improving the energy density and cycle performance of the negative electrode active material layer.

[0127] The negative electrode active material in this application has a hexagonal hollow structure. Figure 4 A scanning electron microscope (SEM) image of the negative electrode active material according to an embodiment of this application is shown. This SEM image can be obtained, for example, by scanning the negative electrode active material using a ZEISS Gemini SEM 300 scanning electron microscope at 15k magnification in backscattered electron mode.

[0128] like Figure 4 As shown, the negative electrode active material with a hexagonal hollow structure is a composite of the first oxide V2O3 (smaller particle size and lighter color in the figure) and the second oxide SnO2 (larger particle size and darker color in the figure).

[0129] Figure 5 A SEM image of the negative electrode active material according to another embodiment of this application is shown. This scanning electron microscope (SEM) image can be obtained, for example, by scanning the negative electrode active material using a ZEISS Gemini SEM 300 scanning electron microscope at 80k magnification in backscattered electron mode.

[0130] like Figure 5 As shown, the negative electrode active material with a hexagonal hollow structure is a composite of the first oxide Fe2O3 (smaller particle size and lighter color in the figure) and the second oxide SnO2 (larger particle size and darker color in the figure).

[0131] Negative electrode active materials

[0132] The second aspect of this application also provides a negative electrode active material, which is prepared by the preparation method of the first aspect of this application.

[0133] The negative electrode active material of this application is composed of a first oxide and a second oxide. The negative electrode active material has a hexagonal hollow structure, which gives it a high specific capacity and specific surface area, and the secondary battery prepared from it also has a high energy density.

[0134] In some embodiments, the specific surface area of ​​the negative electrode active material is 175 m². 2 / g~400m 2 / g.

[0135] The available location is 300m. 2 / g~400m 2 / g.

[0136] In these optional embodiments, the specific surface area of ​​the negative electrode active material is within the above-mentioned range, which ensures that the negative electrode active material has a high active specific surface area, and at the same time helps to reduce the side reactions of the electrolyte on the surface of the negative electrode active material, thereby improving the capacity utilization and cycle life of the negative electrode active material.

[0137] In some embodiments, the specific capacity of the negative electrode active material is 490 mAh / g to 1100 mAh / g.

[0138] The capacity is optionally 500mAh / g to 700mAh / g.

[0139] In these alternative embodiments, the negative electrode active material of this application has a large specific capacity, thereby enabling the secondary battery to have a large energy density.

[0140] In addition, please refer to the appendix as appropriate below. Figures 6 to 11 This application describes the secondary battery, battery module, battery pack, and electrical device. Figure 6 This is a schematic diagram of a secondary battery according to one embodiment of this application. Figure 7 yes Figure 6 An exploded view of a secondary battery according to one embodiment of this application is shown. Figure 8 This is a schematic diagram of a battery module according to one embodiment of this application. Figure 9 This is a schematic diagram of a battery pack according to one embodiment of this application. Figure 10 yes Figure 9 An exploded view of a battery pack according to one embodiment of this application is shown. Figure 11 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0141] A third aspect of this application provides a secondary battery, comprising a negative electrode active material prepared by the preparation method of the first aspect of this application or a negative electrode active material of the second aspect of this application.

[0142] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0143] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0144] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0145] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0146] In some embodiments, the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode. This application does not impose specific limitations on the type of conductive agent, which can be selected according to actual needs. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.

[0147] In some embodiments, the positive electrode active material layer may further include an adhesive to firmly bond the positive electrode active material and an optional conductive agent to the positive electrode current collector. This application does not impose specific limitations on the type of adhesive, which can be selected according to actual needs. As an example, the adhesive may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMCS).

[0148] In some embodiments, the positive electrode current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers. The metal material of the metal foil, carbon-coated metal foil, and porous metal plate can each be independently selected from at least one of copper, aluminum, nickel, and stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil with a polymer base film. The positive electrode current collector is, for example, one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil, with aluminum foil being preferred.

[0149] The above-mentioned positive electrode sheet is prepared according to conventional methods in the art. Typically, the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry. The positive electrode slurry is coated on the positive electrode current collector, and after drying and cold pressing, the positive electrode sheet is obtained.

[0150] In some embodiments of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer including a negative active material.

[0151] The negative electrode active material is either the negative electrode active material prepared by the preparation method of the first aspect of this application or the negative electrode active material of the second aspect of this application. Therefore, the foregoing description of the embodiments of the negative electrode active material according to this application is also applicable to the negative electrode active material in secondary batteries, and the same content will not be repeated.

[0152] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0153] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0154] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0155] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0156] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0157] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0158] In some embodiments of this application, the electrolyte acts as a conductor of ions between the positive and negative electrode plates. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0159] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0160] In some embodiments, the electrolyte salt may be selected from one or more of NaPF6, NaClO4, NaBF4, KPF6, KClO4, KBF4, LiPF6, LiClO4, LiBF4, Zn(PF6)2, Zn(ClO4)2, and Zn(BF4)2.

[0161] In some embodiments, the electrolyte salt may be selected from one or more of NaPF6, NaClO4, and NaBF4.

[0162] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0163] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0164] In some embodiments of this application, there are no particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0165] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0166] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly by a winding process or a stacking process.

[0167] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0168] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0169] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 A square-structured secondary battery 5 is shown as an example.

[0170] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0171] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0172] Figure 6 Battery module 4 is shown as an example. (See reference...) Figure 6 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0173] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0174] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0175] Figure 7 and Figure 8 Battery pack 1 is shown as an example. (See reference...) Figure 7 and Figure 8 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0176] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0177] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0178] Figure 9 An example electrical device is shown. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0179] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0180] Example

[0181] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0182] Example 1

[0183] 3.8 g of polyvinylpyrrolidone (PVP) and 2.5 g of Co3V2O8 were dispersed in 20 ml of 0.05 mol NaOH solution, magnetically stirred for 5 h, and then heated in an oven at 300 °C for 6 h to obtain the assembled first oxide.

[0184] The assembled first oxide and 0.12 g of potassium stannate trihydrate were dispersed in 20 ml of deionized water and magnetically stirred for 5 min to obtain the complex;

[0185] The composite was then placed in an oven and heated at 500°C for 6 hours to obtain the negative electrode active material.

[0186] Other Examples 2-23 and Comparative Examples 1-12 are obtained using the same or similar methods as the adhesive in Example 1.

[0187] The negative electrode active materials of Examples 1-23 and Comparative Examples 1-12 were prepared according to Table 1 below.

[0188] In addition, the negative electrode active materials of Examples 1 to 23 and Comparative Examples 1 to 12 were prepared into secondary batteries as shown below, and corresponding tests were performed.

[0189] (1) Preparation of positive electrode sheet

[0190] The positive electrode slurry was coated onto a 10 μm thick aluminum foil, and an external magnetic field was applied to coat it to a thickness of 500 μm. After drying and pressing, a positive electrode sheet with a thickness of 400 μm was obtained. The positive electrode slurry was composed of NCM96: magnetic modification material: SP: SWCNT: PVDF = 96%: 2%: 0.6%: 0.2%: 1.2%; the viscosity of the positive electrode slurry was 7500 mPa·s, and the solid content was 68%.

[0191] (2) Preparation of negative electrode sheet

[0192] The above-prepared negative electrode active material, conductive agent Super P, binder SBR, and thickener CMC-Na are thoroughly mixed in an appropriate amount of deionized water at a mass ratio of 95:2:2:1 to form a uniform negative electrode slurry. The negative electrode slurry is coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode sheet is obtained.

[0193] (3) Separating membrane

[0194] A PP / PE composite separator is used.

[0195] (4) Preparation of electrolyte

[0196] Ethyl carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1, and then LiPF6 was uniformly dissolved in the mixture to obtain the electrolyte. The concentration of LiPF6 in this electrolyte was 1 mol / L, and the ionic conductivity of the electrolyte at 25°C was 10 mS / cm.

[0197] (5) Preparation of secondary batteries

[0198] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, and the electrolyte prepared above is added. After processes such as encapsulation, settling, capacity testing, and aging, a secondary battery is obtained.

[0199] The negative electrode active materials and secondary batteries of each embodiment and comparative example were tested according to the following test methods.

[0200] (1) Specific capacity of the negative electrode active material:

[0201] At 25℃, the material was discharged at a constant current of 0.05C to 0.005V, allowed to stand for 10 minutes, and then discharged again at a constant current of 50μA to 0.005V. After standing for 10 minutes, it was discharged again at a constant current of 10μA to 0.005V. Then, it was charged at a constant current of 0.1C to 2V, and the charging capacity was recorded. The ratio of the charging capacity to the mass of the negative electrode active material is the specific capacity of the prepared negative electrode active material.

[0202] (2) Specific surface area of ​​negative electrode active material

[0203] Referring to GB / T 19587-2017, the nitrogen adsorption specific surface area was tested using the nitrogen adsorption specific surface area analysis method and calculated using the BET (Brunauer Emmett Teller) method. The nitrogen adsorption specific surface area analysis can be performed using the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0204] Table 1. Parameter results of Examples 1-23 and Comparative Examples 1-12

[0205]

[0206]

[0207] Based on the above results, Examples 1 to 23 all achieved good results, with high specific capacity and specific surface area of ​​the negative electrode active material, and the secondary battery formed by the above-mentioned negative electrode active material has a high energy density. This application prepared a negative electrode active material with a hexagonal hollow structure by using an amphiphilic polymer material as a template. Normally, during the charging and discharging process, the insertion of active ions easily causes volume expansion / contraction in negative electrode active materials. However, the hexagonal hollow structure of the negative electrode active material in this application has a certain buffering effect on volume expansion / contraction, which can overcome the volume change caused by the insertion of active ions, thereby maintaining the overall structural stability of the negative electrode active material. Furthermore, this application forms a negative electrode active material by combining a first oxide and a second oxide, which can better leverage their complementary advantages and synergistic effect of compensating for each other's shortcomings. Compared with elemental or single oxide materials, the negative electrode active material in this application inserts more active ions, further increasing the reversible capacity, thereby improving the specific capacity and specific surface area of ​​the negative electrode active material, and further improving the energy density of the secondary battery.

[0208] Comparative Example 1 uses graphite. Compared to graphite, the anode active material of this application has higher specific capacity and energy density.

[0209] Comparative Examples 2 and 3 are negative electrode active materials of metal oxides, with low specific capacity and energy density. This shows that the negative electrode active material formed by the composite of the first oxide and the second oxide in this application can better leverage their complementary advantages and synergistic effect of compensating for each other's shortcomings. Compared with elemental or single oxides, the negative electrode active material of this application has a greater amount of embedded active ions, which further increases the reversible capacity, thereby improving the specific capacity and specific surface area of ​​the negative electrode active material.

[0210] The ratio of the added amphiphilic polymer material, the first oxide precursor, and the second oxide precursor has a significant impact on the performance of the formed negative electrode active material. Referring to Comparative Examples 4 to 7, a suitable mass ratio of the amphiphilic polymer material to the first oxide precursor, and of the assembled first oxide to second oxide precursor, ensures that both the first and second oxide precursors can be assembled onto the amphiphilic polymer material template. Furthermore, this suitable mass ratio guarantees that the final negative electrode active material with a hexagonal hollow structure will have a hexagonal particle morphology, thereby improving the specific capacity and specific surface area of ​​the negative electrode active material.

[0211] Referring to Comparative Examples 8 and 9, suitable heating temperature and heating time can ensure that the first oxide precursor is completely converted into the first oxide, thereby improving the product yield. Too high or too low a temperature will affect the specific surface area of ​​the negative electrode active material.

[0212] Referring to Comparative Examples 10 and 11, the second oxide undergoes an alloying reaction upon heating, combining with the first oxide and forming strong metallic bonds through electrostatic attraction between metal ions to ensure the structural stability of the negative electrode active material. Excessively high or low temperatures will affect the specific capacity of the negative electrode active material.

[0213] See Comparative Example 12. Adjusting the order of the preparation methods can also affect the specific surface area and specific capacity of the negative electrode active material.

[0214] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing a negative electrode active material, comprising: A first oxide is assembled on an amphiphilic polymer material template, wherein the first oxide is selected from V2O3, Fe2O3 and CuO; A second oxide precursor is assembled on the assembled first oxide to form an amphiphilic polymer material-first oxide-second oxide precursor composite, wherein the second oxide precursor is selected from one of K2SnO3, Na2SiO3, Na2GeO3, NaAlO2, and NaBO4·4H2O; and The composite is heated to remove the amphiphilic polymer material and to form a second oxide from the second oxide precursor, thereby obtaining a negative electrode active material with a hexagonal hollow structure and a specific surface area of ​​175 m². 2 / g~400m 2 / g.

2. The method for preparing the negative electrode active material according to claim 1, wherein, The negative electrode active material includes one of V2O3-SnO2, Fe2O3-SnO2, Fe2O3-GeO2, Fe2O3-Al2O3, Fe2O3-B2O3, and CuO-SiO2.

3. The method for preparing the negative electrode active material according to claim 2, wherein, The negative electrode active material is V2O3-SnO2 or Fe2O3-SnO2.

4. The method for preparing the negative electrode active material according to any one of claims 1 to 3, wherein, The amphiphilic polymer material is selected from polyvinylpyrrolidone.

5. The method for preparing the negative electrode active material according to any one of claims 1 to 4, wherein, The assembly of the first oxide on the amphiphilic polymer material template specifically includes: The amphiphilic polymer material and the first oxide precursor are fully dispersed in an alkaline dispersion medium to obtain a dispersion system in which the first oxide precursor is assembled on the amphiphilic polymer material template. The dispersion system is heated so that the first oxide precursor forms the first oxide, thereby obtaining the assembled first oxide.

6. The method for preparing the negative electrode active material according to claim 5, wherein, The negative electrode active material satisfies one or more of the following (1) to (4): The first oxide precursor is selected from one of Co3V2O8, Fe(NO3)3 and Cu(NO3)2; The mass ratio of the amphiphilic polymer material to the first oxide precursor is 1:(1-2); The amphiphilic polymer material has a mass concentration of 15% to 25% in the dispersion medium; The dispersion system is heated at a temperature of 200℃ to 400℃ for 5 hours to 7 hours.

7. The method for preparing the negative electrode active material according to any one of claims 1 to 6, wherein, The assembly of the second oxide precursor onto the assembled first oxide specifically includes: The assembled first oxide and second oxide precursors are sufficiently dispersed in a dispersion medium to bring the assembled first oxide and second oxide precursors into contact.

8. The method for preparing the negative electrode active material according to claim 7, wherein, The mass ratio of the assembled first oxide to the second oxide precursor is 1:(1-2).

9. The method for preparing the negative electrode active material according to any one of claims 1 to 8, wherein, The composite is heated at a temperature of 400℃ to 600℃ for 5 to 7 hours.

10. The method for preparing the negative electrode active material according to any one of claims 1 to 9, wherein, The average particle size Dv50 of the negative electrode active material is 100μm to 200μm.

11. The method for preparing the negative electrode active material according to claim 10, wherein, The average particle size Dv50 of the negative electrode active material is 120 μm to 180 μm.

12. A negative electrode active material, prepared by any one of claims 1 to 11.

13. The negative electrode active material according to claim 12, wherein, The specific surface area of ​​the negative electrode active material is 300 m². 2 / g~400m 2 / g.

14. The negative electrode active material according to claim 12 or 13, wherein, The specific capacity of the negative electrode active material is 490 mAh / g to 1100 mAh / g.

15. The negative electrode active material according to claim 14, wherein, The specific capacity of the negative electrode active material is 550mAh / g to 700mAh / g.

16. A secondary battery, characterized in that, This includes the negative electrode active material prepared by any one of claims 1 to 11 or the negative electrode active material prepared by any one of claims 12 to 15.

17. A battery module, characterized in that, Includes the secondary battery as described in claim 16.

18. A battery pack, characterized in that, Includes the battery module as described in claim 17.

19. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 16, the battery module of claim 17, or the battery pack of claim 18.

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