Hard carbon negative electrode material precursor, hard carbon negative electrode material, preparation method thereof, and battery

Abstract

The present invention relates to the field of battery technology, and in particular to a hard carbon negative electrode material precursor, a hard carbon negative electrode material, a preparation method thereof, and a battery. The hard carbon negative electrode material precursor includes a cross-linked product, and the cross-linked product includes a cross-linked product of an amide polymer and a hard carbon precursor; the hard carbon precursor includes a carboxyl and / or hydroxyl functional group; the amide group in the amide polymer and the carboxyl functional group, or the amide group and the hydroxyl functional group interact through hydrogen bonds and form a double-network cross-linked three-dimensional structure. The preparation method of the hard carbon negative electrode material precursor comprises: mixing a hard carbon precursor, an amide monomer, a cross-linking agent, and a solvent to obtain a mixture, and subjecting the mixture to a polymerization reaction under the action of photocatalysis to obtain a hard carbon negative electrode material precursor. The hard carbon negative electrode material is obtained by carbonizing the hard carbon negative electrode material precursor. The hard carbon negative electrode material provided by the present invention has the characteristics of high capacity and low potential platform capacity ratio.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a hard carbon negative electrode material precursor, a hard carbon negative electrode material, a preparation method thereof, and a battery. Background Art

[0002] Sodium-ion batteries (SIBs) are expected to become a low-cost alternative to the dominant lithium-ion batteries due to their abundant sodium resources, excellent low-temperature performance, and fast charging capability. In Na-ion batteries, although several cathode materials such as layered oxides, polyanionic compounds, and Prussian blue have been well developed, the lack of high-performance anode materials with high sodium (Na) storage capacity and low cost is a major challenge in the development of high-energy SIBs.

[0003] Typically, graphite is the main negative electrode material for commercial lithium-ion batteries. However, the insertion of sodium ions into graphite to form binary graphite intercalated graphite (b-GICs) is thermodynamically unfavorable. That is, graphite negative electrode materials have been relatively successfully used in lithium-ion batteries, but because sodium ions are difficult to embed into them, the application of graphite in sodium-ion batteries is limited. Therefore, the development of high-capacity sodium ion negative electrode materials is the key to advancing sodium-ion battery technology. Among them, hard carbon is considered to be a very promising sodium-ion battery negative electrode material because of its advantages such as large interlayer spacing, good structural stability and low cost. However, existing hard carbon materials have shortcomings such as low capacity and low first efficiency, which limit their further development in the field of sodium-ion battery negative electrodes.

[0004] Therefore, there is an urgent need to develop a new hard carbon negative electrode material for sodium ion batteries with high capacity and low potential platform capacity ratio. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially address one of the technical problems in the related art. To this end, the present invention provides a hard carbon anode material precursor, a hard carbon anode material, a preparation method thereof, and a battery, wherein the hard carbon anode material has the characteristics of high capacity and low potential plateau capacity ratio.

[0006] In order to solve the above technical problems, this application is implemented as follows:

[0007] According to a first aspect of the present application, the present invention provides a hard carbon negative electrode material precursor, wherein the hard carbon negative electrode material precursor includes a cross-linked product, wherein the cross-linked product includes a cross-linked product of an amide polymer and a hard carbon precursor;

[0008] The hard carbon precursor includes carboxyl and / or hydroxyl functional groups;

[0009] The amide groups and the carboxyl functional groups in the amide polymer interact with each other through hydrogen bonds to form a double-network cross-linked three-dimensional structure, or the amide groups and the hydroxyl functional groups in the amide polymer interact with each other through hydrogen bonds to form a double-network cross-linked three-dimensional structure.

[0010] In any embodiment, the amide polymer comprises polyacrylamide.

[0011] In any embodiment, the hard carbon precursor includes a saccharide.

[0012] In any embodiment, the hard carbon precursor includes at least one of sodium alginate, chitosan, cellulose, or β-cyclodextrin.

[0013] In any embodiment, the mass ratio of the amide polymer to the hard carbon precursor is (1-50):(1-100).

[0014] A second aspect of the present application provides a method for preparing a hard carbon negative electrode material precursor, comprising the following steps:

[0015] Mixing a hard carbon precursor, an amide monomer, a cross-linking agent, and a solvent to obtain a mixture, and subjecting the mixture to a polymerization reaction under photocatalysis to obtain a hard carbon negative electrode material precursor;

[0016] Wherein, the hard carbon precursor includes carboxyl and / or hydroxyl functional groups;

[0017] The amide monomers are polymerized to form amide polymers, and the amide groups and the carboxyl functional groups in the amide polymers interact with each other through hydrogen bonds to form a three-dimensional structure with a double network cross-linking. Alternatively, the amide groups and the hydroxyl functional groups in the amide polymers interact with each other through hydrogen bonds to form a three-dimensional structure with a double network cross-linking.

[0018] In any embodiment, the mixture further includes an initiator.

[0019] In any embodiment, the mass ratio of the hard carbon precursor, the amide monomer, the crosslinking agent and the initiator is (1-100):(1-50):(0.1-10):(0.1-10).

[0020] In any embodiment, the amide monomer includes at least one of acrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N-cyclopropylacrylamide, N-methylacrylamide or N-ethylacrylamide.

[0021] In any embodiment, the hard carbon precursor includes at least one of sodium alginate, chitosan, cellulose, or β-cyclodextrin.

[0022] In any embodiment, the cross-linking agent includes at least one of tetramethylethylenediamine, N,N'-methylenebisacrylamide, or ethylene glycol dimethacrylate.

[0023] In any embodiment, the solvent includes at least one of water, ethanol, acetone, toluene, diethyl ether, N,N'-dimethylformamide or ethylene glycol monomethyl ether.

[0024] In any embodiment, the initiator includes at least one of azobisisobutylcyanide, ammonium persulfate, azobisisoheptanonitrile or hydrogen peroxide.

[0025] In any embodiment, the photocatalytic method includes at least one of ultraviolet light photocatalysis or gamma ray photocatalysis.

[0026] In any embodiment, the photocatalytic time is 10 min to 300 min.

[0027] A third aspect of the present application provides a method for preparing a hard carbon negative electrode material, comprising the following steps: carbonizing a hard carbon negative electrode material precursor to obtain a hard carbon negative electrode material;

[0028] Wherein, the hard carbon negative electrode material precursor includes the hard carbon negative electrode material precursor mentioned above or the hard carbon negative electrode material precursor prepared by the above method.

[0029] In any embodiment, before the carbonization treatment, the method further comprises:

[0030] The hard carbon negative electrode material is dried and pulverized to obtain an intermediate, and then the intermediate is carbonized to obtain the hard carbon negative electrode material.

[0031] In any embodiment, the drying process includes vacuum drying, and the temperature of the vacuum drying is 50°C to 100°C.

[0032] In any embodiment, the pulverization process includes at least one of air flow pulverization, mechanical milling, ball milling or roller milling.

[0033] In any embodiment, the specific surface area of ​​the intermediate is 50 to 200 m 2 / g.

[0034] In any embodiment, the intermediate has a median particle size of 5 μm to 10 μm.

[0035] In any embodiment, the true density of the intermediate is 1.8 to 2.2 g / cm 3 .

[0036] In any embodiment, the temperature of the carbonization treatment is 1000° C. to 1600° C., the heating rate of the carbonization treatment is 0.1 to 10° C. / min, and the holding time of the carbonization treatment is 1 to 10 hours.

[0037] In any embodiment, the specific surface area of ​​the hard carbon negative electrode material is 2 to 10 m 2 / g.

[0038] In any embodiment, the median particle size of the hard carbon negative electrode material is 3 μm to 6 μm.

[0039] In any embodiment, the true density of the hard carbon negative electrode material is 1.5 to 1.7 g / cm 3 .

[0040] A fourth aspect of the present application provides a hard carbon negative electrode material, which is prepared using the above-mentioned method for preparing the hard carbon negative electrode material.

[0041] A fifth aspect of the present application provides a battery, comprising a negative electrode sheet, wherein the negative electrode sheet comprises the hard carbon negative electrode material prepared by the above-mentioned preparation method of the hard carbon negative electrode material, or comprises the above-mentioned hard carbon negative electrode material.

[0042] Through the above technical solution, the beneficial technical effects of the present invention are:

[0043] (1) In the embodiment of the present application, the hard carbon negative electrode material precursor and its preparation method are mainly composed of an amide polymer and a cross-linked product of a hard carbon precursor. The hard carbon precursor contains carboxyl and / or hydroxyl functional groups, and the amide polymers therein are interconnected on the surface of the hard carbon precursor to form a bulk molecular chain and a stable network structure, thereby improving the strength and hardness of the material; and the amide functional groups in the side chains of the amide polymer can interact with the hydroxyl or carboxyl groups in the hard carbon precursor material through hydrogen bonds to self-assemble layer by layer to form a double-network cross-linked three-dimensional structure, thereby obtaining a hard carbon negative electrode material precursor with well-developed pores, which is a good preparation for the subsequent Na + Provides larger storage space, which is beneficial for Na + embedding, thereby increasing the capacity of the material and the proportion of low-potential platform capacity.

[0044] (2) In the embodiment of the present application, the hard carbon negative electrode material and its preparation method are mainly obtained by carbonizing the aforementioned hard carbon negative electrode material precursor with a double-grid cross-linked three-dimensional structure. During the carbonization process, the double-network cross-linked three-dimensional structure in the hard carbon negative electrode material precursor, that is, the short-range ordered graphite-like microcrystals gradually form long-range disordered curled carbon chains, which are wound and shrunk to form a large number of closed pores. A large number of closed pores are Na + Provides more storage space, thereby increasing Na +The storage capacity at the low potential platform is increased while the capacity of the material is improved.

[0045] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0047] Figure 1 Shown is a SEM image (scanning electron microscope image) of the hard carbon negative electrode material obtained in Example 1.

[0048] Figure 2 Shown is a TEM image (transmission electron microscope image) of the hard carbon negative electrode material obtained in Example 1.

[0049] Figure 3 Shown is the XRD pattern (X-ray diffraction pattern) of the hard carbon negative electrode material obtained in Example 1.

[0050] Figure 4 Shown is the Raman graph (Raman spectrum) of the hard carbon negative electrode material obtained in Example 1.

[0051] Figure 5 Shown is a schematic structural diagram of sodium alginate in the present invention.

[0052] Figure 6 Shown is a schematic structural diagram of the hard carbon negative electrode material precursor in the present invention.

[0053] Figure 7 Shown is an enlarged schematic diagram of the structure of the hard carbon negative electrode material precursor in the present invention, which represents acrylamide.

[0054] Figure 8 Shown is an enlarged schematic diagram of the structure of the hard carbon negative electrode material precursor in the present invention, which represents a sugar carbon source hard carbon precursor containing a carboxyl functional group.

[0055] Figure 9 Shown is an enlarged schematic diagram of the structure of the hard carbon negative electrode material precursor in the present invention, which represents the cross-linking agent. DETAILED DESCRIPTION

[0056] The present invention discloses a hard carbon negative electrode material precursor, a hard carbon negative electrode material, a preparation method thereof, and a battery. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the desired results. It should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments. It is obvious that relevant personnel can modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0057] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0058] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0059] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0060] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0061] In sodium-ion batteries, although several cathode materials such as layered oxides, polyanionic compounds, and Prussian blue have been well developed, there is a lack of high-performance anode materials with high sodium storage capacity and low cost. Among sodium-ion battery anode materials, "hard carbon", a non-graphitizable carbon, has become the most suitable SIB anode microstructure due to its randomly distributed vortex structure with large interlayer spacing (over 0.37 nm) and closed nanopores. Generally, hard carbon is synthesized by high-temperature carbonization of thermosetting precursors (such as cellulose, peanut shells, sucrose, glucose, phenolic resins, starch, anthracite, etc.). During the pyrolysis process, the carbon layer in the precursor easily forms vortex layers and disordered microstructures consisting of surface defects, nanopores or voids, and graphitic domains. During the curing process, Na ions are first adsorbed in the inclined region (0.1-1 V vs Na / Na + ) on the hard carbon defect sites, and then in the plateau region (0-0.1 V vs Na / Na + ) to form quasi-metallic Na clusters. At present, the extensive research on hard carbon can be summarized as follows: 1) Understanding the charge storage mechanism of hard carbon by introducing heteroatoms (such as O, N, S, P), pores or defects to enhance the Na + transfer kinetics; 2) optimizing the electrode-electrolyte interface; and 3) improving the reversible Na storage capacity and initial Coulombic efficiency by tuning the pore structure. Despite these studies, these hard carbon electrodes have a low reversible Na storage capacity at ≈0.1 V (Na + / Na) still exhibits a rather low plateau capacity, which plays a key role in determining the operating voltage and energy density of a fully charged battery. Therefore, it is urgent to develop a hard carbon anode material for sodium-ion batteries with high capacity and low potential plateau capacity ratio.

[0062] In light of this, the present application proposes a hard carbon anode material precursor, a hard carbon anode material, a preparation method thereof, and a battery. The hard carbon anode material has the characteristics of high capacity and low potential platform capacity ratio. The present application and optional embodiments are described in more detail below.

[0063] [Hard carbon anode material precursor]

[0064] In some embodiments, a hard carbon negative electrode material precursor is provided. The hard carbon negative electrode material precursor includes a cross-linked product. The cross-linked product includes a cross-linked product of an amide polymer and a hard carbon precursor.

[0065] The hard carbon precursor includes carboxyl and / or hydroxyl functional groups; for example, the hard carbon precursor may include carboxyl functional groups, or may include hydroxyl functional groups, or may include both carboxyl functional groups and hydroxyl functional groups.

[0066] The amide group and the carboxyl functional group in the amide polymer interact with each other through hydrogen bonds to form a double network cross-linked three-dimensional structure, or the amide group and the hydroxyl functional group in the amide polymer interact with each other through hydrogen bonds to form a double network cross-linked three-dimensional structure.

[0067] In the present application, the provided hard carbon negative electrode material precursor can be used to prepare a hard carbon negative electrode material. For example, the hard carbon negative electrode material can be obtained by carbonizing the hard carbon negative electrode material precursor. Particularly notably, the hard carbon negative electrode material precursor comprises a crosslinked product of an amide polymer and a hard carbon precursor, which can impart a double-network crosslinked three-dimensional structure to the hard carbon negative electrode material, thereby enabling the hard carbon negative electrode material to be a three-dimensional network hard carbon negative electrode material. The present invention primarily utilizes hydrogen bonding between the amide (or amino) functional groups of the amide polymer side chains and the carboxyl or hydroxyl groups on the hard carbon precursor to form a double-network three-dimensional structure, thereby enhancing the capacity or other electrochemical properties of the resulting hard carbon negative electrode material.

[0068] In detail, the hard carbon negative electrode material precursor of the present invention is mainly composed of an amide polymer and a cross-linked product of a hard carbon precursor, wherein the amide polymer can be formed by polymerizing an amide monomer. After polymerization, the amide monomer forms a linear molecular chain, which is interconnected under the action of a cross-linking agent to gradually form a three-dimensional molecular chain and form a stable network structure, thereby enhancing the strength and hardness of the material; at the same time, the side chain in the amide polymer carries an amide (or amino) functional group, and the hard carbon precursor includes a carboxyl and / or hydroxyl functional group. The carboxyl or hydroxyl group in the hard carbon precursor can interact with the amide group in the side chain of the amide polymer through hydrogen bonding to self-assemble layer by layer to form a double-network cross-linked three-dimensional structure, that is, the amide polymer has a network structure, and at the same time, the amide polymer and the hard carbon precursor can cross-link to form a network structure, thereby obtaining a double-network cross-linked three-dimensional structure, and then obtaining a hard carbon negative electrode material precursor with developed pores, providing conditions for the subsequent preparation of a hard carbon negative electrode material with a large number of closed pores.

[0069] Therefore, the hard carbon negative electrode material precursor provided in the present application selects a hard carbon precursor containing carboxyl and / or hydroxyl groups, and introduces an amide polymer at the same time, wherein the amide group in the amide polymer and the carboxyl group or hydroxyl group in the hard carbon precursor form a double-network cross-linked three-dimensional structure through hydrogen bonding, providing a large number of pore structures for the hard carbon negative electrode material precursor, providing conditions for the subsequent preparation of a hard carbon negative electrode material with a large number of closed pores, and helping to improve the low-potential platform capacity of the hard carbon negative electrode material.

[0070] In this application, the term "amide polymer" refers to a type of high molecular weight compound containing an amide bond (-CONH-) in the main chain of the molecule.

[0071] In this application, the term "carboxyl" refers to a -COOH group.

[0072] In this application, the term "hydroxyl" refers to an -OH group.

[0073] In the present application, the term "cross-linked product" refers to a product in which cross-linked polymer molecular chains are connected by chemical bonds or other strong interactions to form a three-dimensional network structure.

[0074] In some embodiments, the amide polymer includes, but is not limited to, polyacrylamide. The polyacrylamide can be polymerized from amide monomers. Polyacrylamide has a stable network structure. The addition of polyacrylamide can improve the sodium ion storage performance of the resulting hard carbon anode material, thereby increasing the capacity of the hard carbon anode material.

[0075] In some embodiments, the hard carbon precursor includes, but is not limited to, sugars.

[0076] Optionally, in some embodiments, the hard carbon precursor includes but is not limited to at least one of sodium alginate, chitosan, cellulose, or β-cyclodextrin.

[0077] Preferably, the hard carbon precursor is selected from sodium alginate, which is easier to cross-link with polyacrylamide to produce a hard carbon negative electrode material precursor with better performance.

[0078] Of course, it is not limited thereto, and other similar sugar carbon sources may also be used, as long as they do not limit the purpose of this application.

[0079] In the present application, a carbohydrate carbon source rich in carboxyl or hydroxyl functional groups is selected as a hard carbon precursor. These carbohydrate carbon sources are mixed with amide monomers such as acrylamide, and then a polymerization reaction of acrylamide is initiated under the action of photocatalysis to form a three-dimensional structural polymer chain with an amide functional group on the side chain; at the same time, the amide group on the side chain and the carboxyl or hydroxyl group on the biomass-derived hard carbon precursor such as the carbohydrate carbon source are self-assembled layer by layer through hydrogen bonds or chemical bonds to form a double-network cross-linked three-dimensional structure, thereby obtaining a hard carbon negative electrode material precursor with well-developed pores.

[0080] In some specific embodiments, the mass ratio of the amide polymer to the hard carbon precursor is (1-50): (1-100). Preferably, the mass ratio of the amide polymer to the hard carbon precursor is (5-30): (1-100). As an example, the mass ratio of the amide polymer to the hard carbon precursor can be any one of 1:1, 1:2, 5:22, 8:35, 10:55, 15:63, 35:52, 40:75, 50:92 or a range value between any two of them. By controlling the mass of the amide polymer and the hard carbon precursor within the above range, the hard carbon precursor material can have a large number of porous structures, and thus a material with a large amount of Na can be prepared. + The hard carbon negative electrode material with storage space can improve the storage capacity of sodium ions at low potential platforms. If the content of amide polymer is too high, the cross-linking density of the cross-linked product formed by amide polymer and hard carbon precursor will be too large, and the grid in the three-dimensional structure will be densely stacked, thereby reducing the pores in the cross-linked product and causing the subsequent Na in the hard carbon negative electrode material to be too large. + The storage space decreases, so the platform capacity decreases, and the first discharge capacity also decreases significantly; if the content of amide polymer is too low, the cross-linking density of the cross-linked product formed by the amide polymer and the hard carbon precursor will be too low, and the grid in the three-dimensional structure will be relatively sparse, which will lead to the formation of a small number of large pores in the cross-linked product, and the specific surface area will be relatively large, resulting in a decrease in the first efficiency of the subsequent hard carbon negative electrode material.

[0081] That is, by controlling the mass ratio of the amide polymer and adjusting the crosslinking degree of the amide polymer and the hard carbon precursor, it is ensured that the hard carbon negative electrode material precursor has a large number of pore structures, providing conditions for the subsequent hard carbon negative electrode material with a large number of closed pores, so that the hard carbon negative electrode material has a large amount of Na + Storage space, increasing the storage capacity of sodium ions on the low potential platform, thereby increasing the capacity of the hard carbon negative electrode material and the proportion of low potential platform capacity.

[0082] [Preparation method of hard carbon negative electrode material precursor]

[0083] In some embodiments, the present application provides a method for preparing a hard carbon negative electrode material precursor, comprising the following steps:

[0084] A hard carbon precursor, an amide monomer, a cross-linking agent, and a solvent are mixed to obtain a mixture, and the mixture is polymerized under a photocatalytic action to obtain a hard carbon negative electrode material precursor;

[0085] Wherein, the hard carbon precursor includes carboxyl and / or hydroxyl functional groups;

[0086] The amide monomers are polymerized to form amide polymers, in which the amide groups and the carboxyl functional groups in the amide polymers interact with each other through hydrogen bonds to form a three-dimensional structure with a double network crosslinking, or the amide groups and the hydroxyl functional groups interact with each other through hydrogen bonds to form a three-dimensional structure with a double network crosslinking.

[0087] In the present application, a hard carbon precursor, an amide monomer, a cross-linking agent and a solvent are mixed, and a polymerization reaction is initiated under the action of photocatalysis to prepare a hard carbon negative electrode material precursor. This provides a method for photocatalytically constructing a three-dimensional network hard carbon negative electrode material precursor, which can improve the reversible specific capacity, low potential platform capacity, first effect and other properties of the final hard carbon negative electrode material.

[0088] This preparation method has simple process, easy operation, strong feasibility and is easy to industrialize. Through this method, a hard carbon negative electrode material precursor with a double network three-dimensional structure can be prepared, which has good structural stability, more sodium storage space and good electrochemical properties.

[0089] It should be understood that all the features and advantages described above for the “hard carbon negative electrode material precursor” are also applicable to the “method for preparing the hard carbon negative electrode material precursor” and will not be described in detail here.

[0090] In the present application, a hard carbon precursor containing carboxyl and / or hydroxyl functional groups and an amide monomer are mixed, wherein the amide monomer undergoes polymerization reaction under the action of photocatalysis to generate linear amide polymer molecular chains, and then under the action of a cross-linking agent, the linear amide polymer molecular chains are interconnected to form a three-dimensional molecular chain and form a stable network structure, thereby further enhancing the strength and hardness of the material; at the same time, the amide groups in the side chains of the amide polymer and the carboxyl or hydroxyl functional groups in the hard carbon precursor are self-assembled layer by layer through hydrogen bonding to form a double-network cross-linked three-dimensional structure, thereby obtaining a hard carbon negative electrode material precursor with well-developed pores, providing conditions for the subsequent preparation of a hard carbon negative electrode material with a large number of closed pores, and improving the Na in the hard carbon negative electrode material. + storage space, which is beneficial to Na + embedding, thereby increasing the capacity of the material and the proportion of low-potential platform capacity.

[0091] In some specific embodiments, the mixture further includes an initiator. That is, the hard carbon precursor, the amide monomer, the crosslinking agent, the initiator, and the solvent are mixed to obtain a mixture.

[0092] As an example, a hard carbon precursor, an amide monomer, a cross-linking agent, and an initiator are sequentially added to a stirring tank containing a solvent and uniformly dispersed, and then transferred to a reactor and amide monomers such as acrylamide are polymerized under the action of photocatalysis to form a three-dimensional structural polymer chain with an amide functional group on the side chain; at the same time, the amide group on the side chain and the carboxyl group or hydroxyl group on the biomass-derived hard carbon precursor are self-assembled layer by layer through hydrogen bonding to obtain a three-dimensional network cross-linked hard carbon negative electrode material precursor with well-developed pores.

[0093] Optionally, the initiator includes, but is not limited to, any one of azobisisobutyl cyanide, ammonium persulfate, azobisisoheptonitrile or hydrogen peroxide, or a combination of two or more of them in any proportion.

[0094] In some specific embodiments, the mass ratio of the hard carbon precursor, the amide monomer, the crosslinking agent, and the initiator is (1-100):(1-50):(0.1-10):(0.1-10). As an example, the mass ratio of the hard carbon precursor, amide monomer, crosslinker and initiator can be any one of 1:1:0.1:0.1, 2:1:0.1:0.1, 5:1:0.1:0.1, 10:1:0.1:0.1, 35:1:0.1:0.1, 50:1:0.1:0.1, 100:1:0.1:0.1, 100:5:0.1:0.1, 100:10:0.1:0.1, 100:30:0.1:0.1, 100:50:0.1:0.1, 100:50:1:1, 100:50:10:10, or a range value between any two of them. By adjusting the mass ratio of the hard carbon precursor, amide monomer, crosslinking agent and initiator within the above range, the pore size and quantity of the hard carbon negative electrode material precursor can be increased, providing a basis for the subsequent Na + The embedding of the hard carbon precursor provides a large amount of storage space, thereby increasing the capacity of the material and the proportion of low-potential platform capacity. In addition, by keeping the usage ratio of the hard carbon precursor and the amide monomer within the above range, conditions can be provided for the subsequent sintering of the hard carbon negative electrode material precursor to prepare the hard carbon negative electrode material. The usage of the hard carbon precursor and the amide monomer has a direct impact on the molecular weight of the cross-linked product. The larger the molecular weight of the cross-linked product, the greater the cross-linking strength of the cross-linked product, and thus the strength of the cross-linked product will also increase. The structural change during the sintering process is small, which can ensure that the double-network cross-linked three-dimensional structure in the hard carbon negative electrode material precursor is not destroyed during the sintering process.

[0095] In some specific embodiments, the amide monomers include, but are not limited to, any one of acrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N-cyclopropylacrylamide, N-methylacrylamide or N-ethylacrylamide, or a combination of two or more in any proportion.

[0096] Preferably, the amide monomer is selected from acrylamide. The main reason for using acrylamide monomer is that it has a cross-linkable double bond and can easily undergo a cross-linking reaction to form a polymer through photoinduction, which is simple and safe.

[0097] In some embodiments, the hard carbon precursor includes, but is not limited to, any one of sodium alginate, chitosan, cellulose, or β-cyclodextrin, or a combination of two or more of them in any ratio.

[0098] In some embodiments, the cross-linking agent includes, but is not limited to, any one of tetramethylethylenediamine, N,N'-methylenebisacrylamide, or ethylene glycol dimethacrylate, or a combination of two or more of them in any ratio.

[0099] In some embodiments, the solvent includes, but is not limited to, any one of water, ethanol, acetone, toluene, diethyl ether, N,N'-dimethylformamide or ethylene glycol monomethyl ether, or a combination of two or more of them in any proportion.

[0100] However, the present application is not limited to these amide monomers, hard carbon precursors, crosslinking agents, initiators, and solvents. Other amide monomers, hard carbon precursors, crosslinking agents, solvents, initiators, etc. that can be used as precursors for hard carbon negative electrode materials may also be used in the present application. These substances may be used alone or in combination of two or more.

[0101] In some embodiments, the photocatalytic method includes, but is not limited to, at least one of ultraviolet light photocatalysis and gamma ray photocatalysis.

[0102] In some specific embodiments, the photocatalytic time is 10 min to 300 min. As an example, the photocatalytic time can be any one of 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 150 min, 200 min, 250 min, and 300 min, or a range therebetween.

[0103] Therefore, controlling the aforementioned process parameters within the given ranges facilitates the preparation of a high-quality hard carbon negative electrode material precursor, provides favorable conditions for the final preparation of the hard carbon negative electrode material, and further improves the performance of the hard carbon negative electrode material of the present application. Those skilled in the art can selectively adjust one or more of the aforementioned process parameters based on actual production conditions.

[0104] As an example, the preparation of a hard carbon negative electrode material precursor includes:

[0105] 1-100 g of a hard carbon precursor such as sodium alginate, chitosan, cellulose or β-cyclodextrin, 1-50 g of an amide monomer such as acrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N-cyclopropylacrylamide, N-methylacrylamide or N-ethylacrylamide, 0.1-10 g of a cross-linking agent such as tetramethylethylenediamine, N,N'-methylenebisacrylamide or ethylene glycol dimethacrylate, 0.1-10 g of an initiator such as azobisisobutyl cyanide, ammonium persulfate, azobisisoheptanenitrile or hydrogen peroxide and a solvent such as water, ethanol, acetone, toluene, ether, N,N'-dimethylformamide or ethylene glycol monomethyl ether are mixed and dispersed, and then photocatalyzed, such as using ultraviolet light photocatalysis or gamma ray photocatalysis, to carry out polymerization reaction for 10-300 minutes to obtain a hard carbon negative electrode material precursor.

[0106] Optionally, the structural diagram of sodium alginate is as follows Figure 5 shown.

[0107] Taking sodium alginate as the hard carbon precursor and acrylamide as the amide monomer as an example, the double-network cross-linked three-dimensional structure of the hard carbon negative electrode material precursor is described. It should be understood that sodium alginate is used as an example here, and other carbohydrate carbon source precursors containing carboxyl or hydroxyl functional groups also have similar structures. The structure of the hard carbon negative electrode material precursor with a double-network cross-linked three-dimensional structure is as follows Figure 6 As shown; the enlarged schematic diagram of the structure of the hard carbon negative electrode material precursor is shown Figures 7 to 9 shown.

[0108] Figure 6 In the figure, the -NHO- structure indicated by the arrow is a three-dimensional network cross-linked structure formed by the carboxyl functional group on the hard carbon precursor and the amide group on the acrylamide connected together through hydrogen bonds.

[0109] [Preparation method of hard carbon negative electrode material]

[0110] In some embodiments, the present application provides a method for preparing a hard carbon negative electrode material, comprising the following steps: carbonizing a hard carbon negative electrode material precursor to obtain a hard carbon negative electrode material;

[0111] Wherein, the hard carbon negative electrode material precursor includes the hard carbon negative electrode material precursor mentioned above or the hard carbon negative electrode material precursor prepared by the above method.

[0112] The hard carbon negative electrode material of the present invention can be obtained by carbonizing the hard carbon negative electrode material precursor mentioned above, and thus has at least all the characteristics and advantages of the hard carbon negative electrode material precursor mentioned above.

[0113] In the present application, a hard carbon precursor containing carboxyl and / or hydroxyl functional groups and an amide monomer are mixed, wherein the amide monomer undergoes polymerization reaction under the action of photocatalysis to generate linear amide polymer molecular chains, and then under the action of a cross-linking agent, the linear amide polymer molecular chains are interconnected to form a three-dimensional molecular chain and form a stable network structure, further enhancing the strength and hardness of the material; at the same time, the amide groups in the side chains of the amide polymer and the carboxyl or hydroxyl functional groups in the hard carbon precursor self-assemble layer by layer through hydrogen bonding to form a double-network cross-linked three-dimensional structure, and then the double-network cross-linked three-dimensional structure is carbonized to obtain a hard carbon negative electrode material with developed pores. During the preparation process, the cross-linking degree of the hard carbon negative electrode material can be controlled by adjusting the mass proportion of amide monomers such as acrylamide, and during the carbonization process, as the temperature increases, the short-range ordered graphite-like crystallites gradually form long-range disordered curled carbon chains, and coil and shrink to form a large number of closed pores, and a large number of closed pores are Na + Provides more storage space, thereby increasing Na + The storage capacity at the low potential platform is increased while the capacity of the material is improved.

[0114] In some specific embodiments, before the carbonization treatment, the method further comprises:

[0115] The hard carbon negative electrode material is dried and pulverized to obtain an intermediate, and then the intermediate is carbonized to obtain a hard carbon negative electrode material.

[0116] As an example, after preparing the hard carbon negative electrode material precursor, the hard carbon negative electrode material precursor is first placed in an oven for vacuum drying treatment, and then crushed to obtain an intermediate. The intermediate is then placed in a high-temperature carbonization furnace and subjected to high-temperature carbonization treatment under the protection of an inert atmosphere to obtain a hard carbon negative electrode material.

[0117] In some specific embodiments, the drying process includes, but is not limited to, vacuum drying, and the vacuum drying temperature is 50° C. to 100° C. As an example, the vacuum drying temperature can be any one of 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., and 100° C., or a range therebetween.

[0118] In some embodiments, the pulverization process comprises at least one of air flow pulverization, mechanical milling, ball milling, or roller milling.

[0119] In some embodiments, the specific surface area of ​​the intermediate is 50 to 200 m 2 / g; the median particle size of the intermediate is 5μm to 10μm; the true density of the intermediate is 1.8 to 2.2g / cm 3As an example, the specific surface area of ​​the intermediate can be 50m 2 / g、80m 2 / g、100m 2 / g, 120m 2 / g, 150m 2 / g, 160m 2 / g, 180m 2 / g, 200m 2 / g or any range between them; the median particle size of the intermediate can be any point value among 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or any range between them; the true density of the intermediate can be 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 By regulating the surface area, median particle size and vacuum density of the intermediate within the above range, conditions are provided for the subsequent preparation of hard carbon anode materials with a large number of closed pores, so that the hard carbon precursor can be Na + Provide more storage space and increase Na + The storage capacity at the low potential platform is increased while the capacity of the material is improved.

[0120] In some specific embodiments, the temperature of the carbonization treatment is 1000° C. to 1600° C., the heating rate of the carbonization treatment is 0.1 to 10° C. / min, and the holding time of the carbonization treatment is 1 hour to 10 hours. As an example, the temperature of the carbonization treatment can be any one of 1000, 1080, 1100, 1200, 1500, 1200, 1500, 1300, 1360, 1400, 1480, 1500, 1550, and 1600°C, or a range between any two of them; the heating rate of the carbonization treatment can be any one of 0.1°C / min, 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, and 10°C / min, or a range between any two of them; the holding time of the carbonization treatment can be any one of 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, and 10h, or a range between any two of them. By adjusting the carbonization parameters within the above range, the double-network cross-linked three-dimensional structure formed by the amide polymer and the hard carbon precursor with carboxyl and / or hydroxyl groups can gradually form a long-range disordered coiled carbon chain and shrink to form a large number of closed pores, which are Na +Provides a large amount of storage space, thereby increasing Na + Storage capacity at a low potential platform. If the carbonization temperature is too high, the double-network cross-linked three-dimensional structure formed by the amide polymer and the hard carbon precursor with carboxyl and / or hydroxyl groups will be destroyed at high temperature, resulting in the inability to obtain a double-grid structure; if the carbonization temperature is too low, the double-network cross-linked three-dimensional structure will not be able to gradually form long-range disordered coiled carbon chains, and thus cannot shrink to form a large number of closed pores.

[0121] In some specific embodiments, the specific surface area of ​​the hard carbon negative electrode material is 2 to 10 m 2 / g, the median particle size of the hard carbon negative electrode material is 3μm~6μm, and the true density of the hard carbon negative electrode material is 1.5~1.7g / cm 3 As an example, the specific surface area of ​​the hard carbon negative electrode material can be 2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g or any range between them; the median particle size of the hard carbon negative electrode material can be any point value among 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm or any range between them; the true density of the hard carbon negative electrode material can be 1.5g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 By regulating the surface area, median particle size and vacuum density of the hard carbon negative electrode material within the above range, it can be ensured that the hard carbon negative electrode material can be Na + Provide more storage space and increase Na + The storage capacity at the low potential platform is increased while the capacity of the material is improved.

[0122] Therefore, controlling the above process parameters within the given range is conducive to preparing high-quality hard carbon negative electrode materials, which can further improve the hard carbon negative electrode material Na + The storage capacity and capacity at the low potential platform. Those skilled in the art can selectively adjust one or more of the above process parameters according to actual production conditions.

[0123] [Hard carbon anode material]

[0124] In some embodiments, the present application provides a hard carbon negative electrode material, which is prepared using the above-mentioned method for preparing the hard carbon negative electrode material.

[0125] It should be understood that all the features and advantages described above for the “hard carbon negative electrode material precursor” or “method for preparing hard carbon negative electrode material” are also applicable to the “hard carbon negative electrode material” and will not be repeated here.

[0126] [Battery]

[0127] In some embodiments, the present application provides a battery, including a negative electrode sheet, which includes a hard carbon negative electrode material prepared by the above-mentioned preparation method of the hard carbon negative electrode material, or includes the above-mentioned hard carbon negative electrode material.

[0128] Since the negative electrode sheet includes the hard carbon negative electrode material provided in the embodiments of the present application, it can exhibit good electrochemical properties, such as a higher initial charge and discharge capacity, excellent initial coulombic efficiency, and the like.

[0129] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is disposed on the two opposing surfaces of the negative electrode current collector. It is understood that the negative electrode active material layer can also be laminated on either surface of the negative electrode current collector.

[0130] The present application does not specifically limit the material of the negative electrode current collector, as long as it can achieve the purpose of this application, and can be selected according to actual needs. As an example, the negative electrode current collector can be made of a metal material such as aluminum, copper, nickel, stainless steel, nickel-plated steel, or a foil with a surface coating layer made of a related foil.

[0131] In some embodiments, the negative electrode active material layer includes the hard carbon negative electrode material described above as provided herein. Furthermore, the negative electrode active material layer may optionally include a conductive agent. Furthermore, the negative electrode active material layer may optionally include a binder. The embodiments of this application do not particularly limit the types of conductive agents and binders in the negative electrode active material layer, as long as they can achieve the objectives of this application.

[0132] In some embodiments, the battery further comprises a positive electrode sheet, an electrolyte, and a separator. That is, the battery comprises a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator.

[0133] In the embodiments of the present application, in the battery, there is no limitation on the specific materials and structures of the positive electrode sheet, separator, and electrolyte. Components and structures that are well known in the art and can be used for secondary batteries can be selected as long as the purpose of the present application can be achieved.

[0134] The battery mentioned in the embodiments of this application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may be a battery cell, or the battery may include a battery module (or battery module) or a battery pack.

[0135] In some embodiments, a battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet. The electrode assembly can be a wound structure or a stacked structure, which is not limited in the present embodiment.

[0136] In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0137] In some embodiments, the battery may be a battery pack, which may include a case and battery cells, wherein the battery cells or battery modules are housed in the case.

[0138] It should be understood that multiple battery cells can be assembled into a battery module or a battery pack. The number of battery cells contained in a battery module or a battery pack can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module or battery pack.

[0139] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0140] In the embodiments of the present application, the preparation method of the battery cell or battery is well known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with electrolyte, and then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell. Optionally, multiple battery cells can be further connected in series, in parallel or in a mixed connection to form a battery module. Optionally, multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. Optionally, in some embodiments, multiple battery cells can also directly form a battery pack.

[0141] The present invention is further described in detail below by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0142] Example 1

[0143] The preparation of hard carbon negative electrode material includes the following steps:

[0144] Sodium alginate, acrylamide, tetramethylethylenediamine, and azobisisobutyl cyanide were added to a stirring tank containing deionized water in a mass ratio of 100:35:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 35 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 4.53 μm and a specific surface area of ​​50.07 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 3.58 μm and a specific surface area of ​​3.96 m 2 / g, true density is 1.57 g / cm 3 hard carbon negative electrode materials.

[0145] The SEM image of the hard carbon negative electrode material obtained in Example 1 (SEM model: Tescan Mira3, Czech Tescan Company) is as follows: Figure 1 As shown. Figure 1 It can be seen that the hard carbon negative electrode material prepared in Example 1 is irregular block-shaped black particles with uniform particle size.

[0146] The TEM image of the hard carbon negative electrode material obtained in Example 1 (TEM model: Talos F200X, ThermoFisher, USA) is as follows: Figure 2 As shown. Figure 2 It can be seen from the transmission electron microscope that the hard carbon negative electrode material prepared in Example 1 has abundant nanopores and graphite-like interlayer structure, which is conducive to the migration and storage of sodium ions. Figure 2 It can be seen that the formation process of the short-range ordered graphite-like crystallites of the product prepared in the embodiment of the present invention is mainly that the short-range ordered graphite-like crystallites gradually grow into long-range disordered coiled carbon chains.

[0147] The XRD pattern of the hard carbon negative electrode material obtained in Example 1 (XRD model: D8 ADVANCE, BRUKER, Germany) is as follows: Figure 3 As shown. Figure 3It can be seen that the XRD peak positions of the sample material include two broad peaks located at 2θ ≈ 23° (002) and 2θ ≈ 43° (100), that is, the hard carbon negative electrode material obtained in Example 1 has two typical characteristic peaks at positions of 25° and 43°, which are related to the (002) and (100) crystal planes of hard carbon, respectively.

[0148] The Raman pattern of the hard carbon negative electrode material obtained in Example 1 (Raman model: HR800, Horiba JobinYvon, France) is as follows: Figure 4 As shown. Figure 4 It can be seen that the Raman spectrum of the hard carbon negative electrode material obtained in Example 1 shows two typical peaks, representing disordered or defective graphite bands (D peak, 1350 cm -1 ) and crystalline graphite bands (G peak, 1580 cm -1 ), the integrated intensity ratio (ID / IG) shows that the degree of structural ordering of carbon is 1.05.

[0149] The hard carbon negative electrode material obtained in Example 1 was assembled into a half-cell to test its electrochemical performance. The specific steps are as follows:

[0150] Weigh 19g of active material (also known as hard carbon negative electrode material), 5.0g of conductive carbon black Super P and 5.0g of binder (2.5% carboxymethyl cellulose CMC), stir magnetically at a speed of 500rpm to mix the slurry, and after coating, place it in a vacuum oven at 80℃ and dry it for 8h to remove moisture; use sodium sheet as counter electrode, polypropylene microporous membrane as diaphragm, and use 1M NaClO4 three-component mixed solvent with electrolyte mixed in a volume ratio of EC:DMC:PC=1:1:1 to assemble the battery to obtain a battery. The battery test conditions are as follows: voltage range 0.0-2.0V, during the first cycle, the working steps are set to 0.1C constant current discharge, 0.05C constant current discharge, 0.02C constant current discharge, and 0.1C constant current charge; during subsequent cycles, the working steps are set to 0.2C constant current discharge, 0.1C constant current discharge, 0.05C constant current discharge, 0.02C constant current discharge, and 0.2C constant current charge; the electrochemical performance test results are shown in Table 1.

[0151] Example 2

[0152] The preparation of hard carbon negative electrode material includes the following steps:

[0153] Chitosan, acrylamide, tetramethylethylenediamine, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:20:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 20 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 4.04 μm and a specific surface area of ​​70.57 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 3.53 μm and a specific surface area of ​​5.07 m 2 / g, true density is 1.5 g / cm 3 hard carbon negative electrode materials.

[0154] The hard carbon negative electrode material obtained in Example 2 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0155] Example 3

[0156] The preparation of hard carbon negative electrode material includes the following steps:

[0157] Chitosan, acrylamide, N, N'-methylenebisacrylamide, and azobisisobutyl cyanide were added to a stirring tank containing deionized water in a mass ratio of 100:25:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 25 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 4.53 μm and a specific surface area of ​​40.07 m 2 / g, true density is 2.0 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 4.36μm and a specific surface area of ​​4.89m 2 / g, true density is 1.5 g / cm 3 hard carbon negative electrode materials.

[0158] The hard carbon negative electrode material obtained in Example 3 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0159] Example 4

[0160] The preparation of hard carbon negative electrode material includes the following steps:

[0161] Cellulose, acrylamide, ethylene glycol dimethacrylate, and azobisisoheptyl cyanide were added to a stirring kettle containing deionized water in a mass ratio of 100:30:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 30 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 3.53 μm and a specific surface area of ​​44.87 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 4.37 μm and a specific surface area of ​​3.88 m 2 / g, true density is 1.5 g / cm 3 hard carbon negative electrode materials.

[0162] The hard carbon negative electrode material obtained in Example 4 was assembled into a half-cell. The test conditions were the same as in Example 1. The electrochemical performance test results are shown in Table 1.

[0163] Example 5

[0164] The preparation of hard carbon negative electrode material includes the following steps:

[0165] Cellulose, acrylamide, N, N'-methylenebisacrylamide, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:40:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 40 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 5.93 μm and a specific surface area of ​​39.65 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 4.69 μm and a specific surface area of ​​7.56 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0166] The hard carbon negative electrode material obtained in Example 5 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0167] Example 6

[0168] The preparation of hard carbon negative electrode material includes the following steps:

[0169] Sodium alginate, acrylamide, N, N'-methylenebisacrylamide and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:50:0.1:0.1 and uniformly dispersed. Then they were transferred to a reactor and catalytically initiated to polymerize acrylamide under ultraviolet light for 50 minutes. After the reaction was complete, they were placed in a 60°C oven for vacuum drying, and the dried material was crushed by a jet mill to obtain an intermediate with a median particle size of 4.94 μm, a specific surface area of ​​44.07 m2 / g and a true density of 1.9 g / cm3. The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere, and the carbonization temperature was increased from room temperature to 1400°C at a heating rate of 2°C / min for 4 hours. After cooling to room temperature, the particles were sieved through 300 mesh to obtain a median particle size of 5.34 μm and a specific surface area of ​​6.99 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0170] The hard carbon negative electrode material obtained in Example 6 was assembled into a half-cell. The test conditions were the same as in Example 1. The electrochemical performance test results are shown in Table 1.

[0171] Example 7

[0172] The preparation of hard carbon negative electrode material includes the following steps:

[0173] Sodium alginate, N-propyl acrylamide, N, N'-methylenebisacrylamide, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:35:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of N-propyl acrylamide under ultraviolet light for 50 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 4.53 μm and a specific surface area of ​​50.07 m 2 / g, true density is 1.9 g / cm 3The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 5.34 μm and a specific surface area of ​​6.99 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0174] The hard carbon negative electrode material obtained in Example 7 was assembled into a half-cell. The test conditions were the same as in Example 1. The electrochemical performance test results are shown in Table 1.

[0175] Example 8

[0176] The preparation of hard carbon negative electrode material includes the following steps:

[0177] Sodium alginate, acrylamide, tetramethylethylenediamine, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:5:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 5 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 7.53 μm and a specific surface area of ​​35.07 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1100°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 7.63 μm and a specific surface area of ​​15.74 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0178] The hard carbon negative electrode material obtained in Example 8 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0179] Example 9

[0180] The preparation of hard carbon negative electrode material includes the following steps:

[0181] Sodium alginate, acrylamide, ethylene glycol dimethacrylate, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:10:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 120 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 7.53 μm and a specific surface area of ​​80.14 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1200°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 8.34 μm and a specific surface area of ​​1.68 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0182] The hard carbon negative electrode material obtained in Example 9 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0183] Example 10

[0184] The preparation of hard carbon negative electrode material includes the following steps:

[0185] Sodium alginate, acrylamide, N, N'-methylenebisacrylamide, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:60:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 150 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a particle size of 6.65 μm and a specific surface area of ​​23.04 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1500°C at a heating rate of 2°C / min and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 8.99 μm and a specific surface area of ​​1.25 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0186] The hard carbon negative electrode material obtained in Example 10 was assembled into a half-cell. The test conditions were the same as in Example 1. The electrochemical performance test results are shown in Table 1.

[0187] Example 11

[0188] The preparation of hard carbon negative electrode material includes the following steps:

[0189] Sodium alginate, acrylamide, N, N'-methylenebisacrylamide, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:100:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 180 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 9.53 μm and a specific surface area of ​​46.24 m 2 / g, true density is 1.9 g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1500°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 9.38um and a specific surface area of ​​0.92m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0190] The hard carbon negative electrode material obtained in Example 11 was assembled into a half-cell. The test conditions were the same as in Example 1. The electrochemical performance test results are shown in Table 1.

[0191] Comparative Example 1

[0192] The preparation of hard carbon negative electrode material includes the following steps:

[0193] Sodium alginate was placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min and the holding time was 4 hours. After cooling to room temperature, the sodium alginate was sieved through 300 mesh to obtain a median particle size of 1.38 μm and a specific surface area of ​​1.86 m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0194] The hard carbon negative electrode material obtained in Comparative Example 1 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0195] Comparative Example 2

[0196] The preparation of hard carbon negative electrode material includes the following steps:

[0197] Coconut shell, acrylamide, N, N'-methylenebisacrylamide, and ammonium persulfate were added to a stirring tank containing deionized water in a mass ratio of 100:100:0.1:0.1 and uniformly dispersed. The mixture was then transferred to a reactor and catalyzed to initiate polymerization of acrylamide under ultraviolet light for 180 minutes. After the reaction was complete, the mixture was placed in a 60°C oven and vacuum dried. The dried material was pulverized by a jet mill to obtain a median particle size of 7.53 μm and a specific surface area of ​​61.57 m 2 / g, true density is 1.9g / cm 3 The intermediate was then placed in a high-temperature carbonization furnace filled with nitrogen atmosphere. The carbonization temperature was raised from room temperature to 1400°C at a heating rate of 2°C / min, and the holding time was 4 hours. After cooling to room temperature, the intermediate was sieved through 300 mesh to obtain a median particle size of 7.88um and a specific surface area of ​​5.92m 2 / g, true density is 1.5g / cm 3 hard carbon negative electrode materials.

[0198] The hard carbon negative electrode material obtained in Comparative Example 2 was assembled into a half-cell. The test conditions were the same as those in Example 1. The electrochemical performance test results are shown in Table 1.

[0199] Performance Testing

[0200] The batteries prepared in the above embodiments and comparative examples were subjected to performance tests, specifically including:

[0201] (1) Specific surface area test: The test is carried out using the nitrogen adsorption-desorption method. Specifically, the hard carbon negative electrode material is adsorbed below the boiling point of the adsorbate and a P / P value is given. After reaching adsorption equilibrium, the adsorption volume V is measured (the adsorption amount of the gas is obtained by measuring the volume difference of a known amount of gas before and after adsorption). Through a series of P / Po and V measurement values, many points are obtained, and the data points are connected to obtain the isothermal adsorption line; conversely, the vacuum is reduced and the adsorbed gas is removed to obtain the desorption line. The specific surface area and pore size distribution information are calculated by introducing different statistical models based on the adsorption-desorption curve.

[0202] (2) First discharge capacity and first charge capacity test:

[0203] 0.1C discharge capacity test: Discharge at 0.1C constant current to 0V and let it stand for 5 minutes. The capacity measured in this step is the 0.1C discharge capacity (denoted as C0), which is the first discharge capacity.

[0204] 0.1C charging capacity: Charge to 2.0V with a 0.1C constant current and constant voltage, with a cut-off current of 0.05C and let stand for 5 minutes. The capacity measured in this step is the 0.1C charging capacity (denoted as C1), which is the first charging capacity.

[0205] (3) Low-potential platform capacity test: The low-potential platform capacity corresponds to the gram capacity between 0-0.1V of the charging curve; the data of the low-potential platform capacity is directly read from the charge and discharge test data, which is the capacity data corresponding to the charging curve at 0.1V.

[0206] (4) First coulombic efficiency: First coulombic efficiency = first discharge capacity / first charge capacity*100%.

[0207] The test results are shown in Table 1.

[0208] Table 1 Electrochemical performance test results of examples and comparative examples

[0209]

[0210] From the data in Table 1, it can be seen that the capacity and initial efficiency of Examples 1-11 are better than those of Comparative Examples 1-2, and the maximum capacity can reach 330 mAh·g -1 As shown above, the initial efficiency of Example 1 can reach over 90%, indicating that the capacity and initial efficiency of the hard carbon negative electrode material prepared by constructing a double-network cross-linked three-dimensional structure and then controlling more closed pores are significantly improved. The specific reasons are analyzed as follows:

[0211] It can be seen from Examples 1 to 6 and Examples 8 to 11 that with the increase in the mass ratio of hard carbon precursor to acrylamide, the reversible capacity of the hard carbon negative electrode material shows a trend of first increasing and then decreasing, and the change trend of the low potential platform capacity ratio also corresponds to it. This is because acrylamide undergoes a polymerization reaction under the action of photocatalysis, cross-links on the surface of the hard carbon precursor to form a three-dimensional structure, and self-assembles with the carboxyl functional groups on its surface to form a double-network cross-linked three-dimensional structure. During the high-temperature carbonization process, this double-network cross-linked structure gradually forms a long-range disordered coiled carbon chain, which winds and shrinks to form a large number of closed pores, thereby increasing the storage capacity of sodium ions on the low potential platform. When the mass ratio of acrylamide continues to increase, due to the excessive cross-linking density of its molecular chain, the carbon layer is densely stacked after high-temperature carbonization, and the closed pore volume is greatly reduced, resulting in platform capacity, so the first discharge capacity also decreases significantly; when the mass ratio of acrylamide is too low, the cross-linking is too low, resulting in a relatively sparse network. After high-temperature carbonization, a small number of large pores are formed on the surface of the hard carbon negative electrode material, and the specific surface area is relatively large, resulting in a decrease in the first efficiency. Among them, the change in photocatalytic time is mainly due to the increase in the amount of acrylamide used, and the photocatalytic time is also increased to ensure sufficient polymerization.

[0212] It can be seen from Comparative Examples 1 to 2 that in Comparative Example 1, sodium alginate is directly carbonized to obtain a hard carbon negative electrode material. The first charge and discharge capacity, low potential platform capacity and coulombic efficiency of the hard carbon negative electrode material are all lower than those in Example 1, indicating that the capacity and first efficiency of the hard carbon negative electrode material prepared by constructing a double-network cross-linked three-dimensional structure and then regulating more closed pores are significantly improved; the first charge and discharge capacity, low potential platform capacity and coulombic efficiency of the hard carbon negative electrode material in Comparative Example 2 are all lower than those in Example 1. This is because coconut shell is used as the hard carbon precursor. Since the content of oxygen-containing functional groups in coconut shell is relatively low, the oxygen-containing functional groups therein are almost non-existent after subsequent carbonization treatment, and cannot be interconnected with amide polymers on the surface of the hard carbon precursor to form a bulk molecular chain and form a stable network structure, thereby failing to improve the capacity and first efficiency of the material.

[0213] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A hard carbon negative electrode material precursor, characterized in that: The hard carbon negative electrode material precursor includes a cross-linked product, and the cross-linked product includes a cross-linked product of an amide polymer and a hard carbon precursor; The mass ratio of the amide polymer to the hard carbon precursor is 1:1 to 10:55; The hard carbon precursor includes carboxyl and / or hydroxyl functional groups; The amide groups and the carboxyl functional groups in the amide polymer interact with each other through hydrogen bonds to form a double-network cross-linked three-dimensional structure, or the amide groups and the hydroxyl functional groups in the amide polymer interact with each other through hydrogen bonds to form a double-network cross-linked three-dimensional structure.

2. The hard carbon negative electrode material precursor according to claim 1, characterized in that The amide polymer includes polyacrylamide; and / or, The hard carbon precursor includes sugars.

3. The hard carbon negative electrode material precursor according to claim 1 or 2, characterized in that: The hard carbon precursor includes at least one of sodium alginate, chitosan, cellulose or beta-cyclodextrin.

4. A method for preparing a hard carbon negative electrode material precursor, characterized in that: The following steps are involved: Mixing a hard carbon precursor, an amide monomer, a cross-linking agent, and a solvent to obtain a mixture, and subjecting the mixture to a polymerization reaction under photocatalysis to obtain a hard carbon negative electrode material precursor; Wherein, the hard carbon precursor includes carboxyl and / or hydroxyl functional groups; The amide monomers are polymerized to form amide polymers, and the mass ratio of the amide polymer to the hard carbon precursor is 1:1~10:55; the amide groups and the carboxyl functional groups in the amide polymer interact with each other through hydrogen bonds and form a double-network cross-linked three-dimensional structure, or the amide groups and the hydroxyl functional groups in the amide polymer interact with each other through hydrogen bonds and form a double-network cross-linked three-dimensional structure.

5. The method for preparing a hard carbon negative electrode material precursor according to claim 4, characterized in that: The mixture also includes an initiator; The mass ratio of the hard carbon precursor, the amide monomer, the crosslinking agent and the initiator is (1-100): (1-50): (0.1-10): (0.1-10).

6. The method for preparing a hard carbon negative electrode material precursor according to claim 5, characterized in that: The preparation method satisfies at least one of the following conditions (1) to (7): (1) The amide monomer includes at least one of acrylamide, N-n-propylacrylamide, N-isopropylacrylamide, N,N-diethylacrylamide, N-cyclopropylacrylamide, N-methylacrylamide or N-ethylacrylamide; (2) The hard carbon precursor includes at least one of sodium alginate, chitosan, cellulose or β-cyclodextrin; (3) The cross-linking agent includes at least one of tetramethylethylenediamine, N,N'-methylenebisacrylamide or ethylene glycol dimethacrylate; (4) The solvent includes at least one of water, ethanol, acetone, toluene, ether, N,N'-dimethylformamide or ethylene glycol monomethyl ether; (5) The initiator includes at least one of azobisisobutyl cyanide, ammonium persulfate, azobisisoheptanonitrile or hydrogen peroxide; (6) The photocatalytic method includes at least one of ultraviolet photocatalysis and gamma ray photocatalysis; (7) The photocatalytic time is 10 min to 300 min.

7. A method for preparing a hard carbon negative electrode material, characterized in that: Carbonizing a hard carbon negative electrode material precursor to obtain a hard carbon negative electrode material; Wherein, the hard carbon negative electrode material precursor includes the hard carbon negative electrode material precursor according to any one of claims 1 to 3 or the hard carbon negative electrode material precursor prepared by the method according to any one of claims 4 to 6.

8. The method for preparing a hard carbon negative electrode material according to claim 7, wherein: The preparation method satisfies at least one of the following conditions (1) to (8): (1) Before the carbonization treatment, the method further comprises: drying and pulverizing the hard carbon negative electrode material to obtain an intermediate, and then carbonizing the intermediate to obtain the hard carbon negative electrode material; (2) The drying process includes vacuum drying, and the temperature of the vacuum drying is 50°C to 100°C; (3) The pulverization process includes at least one of air flow pulverization, mechanical grinding, ball milling or roller milling; (4) The specific surface area of ​​the intermediate is 50 to 200 m 2 / g; and / or, The median particle size of the intermediate is 5 μm to 10 μm; and / or, The true density of the intermediate is 1.8 to 2.2 g / cm 3 ; (5) The temperature of the carbonization treatment is 1000°C to 1600°C, the heating rate of the carbonization treatment is 0.1 to 10°C / min, and the holding time of the carbonization treatment is 1 hour to 10 hours; (6) The specific surface area of ​​the hard carbon negative electrode material is 2 to 10 m 2 / g; (7) The median particle size of the hard carbon negative electrode material is 3 μm to 6 μm; (8) The true density of the hard carbon negative electrode material is 1.5 to 1.7 g / cm 3 .

9. A hard carbon negative electrode material, characterized in that: The hard carbon negative electrode material is prepared by the preparation method of the hard carbon negative electrode material according to any one of claims 7 to 8.

10. A battery comprising a negative electrode sheet, characterized in that: The negative electrode sheet comprises a hard carbon negative electrode material prepared by the method for preparing a hard carbon negative electrode material according to any one of claims 7 to 8, or comprises the hard carbon negative electrode material according to claim 9.

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