Anode material, anode sheet and battery

Abstract

The present invention relates to the field of batteries, and more specifically to negative electrode materials, negative electrode sheets containing the negative electrode materials, and batteries containing the negative electrode materials. The negative electrode materials include MOF@carbon composite materials and silicon-based materials. The negative electrode materials of the present invention exhibit excellent flexibility and scalability, alleviating the problem of negative electrode material expansion during battery charging while also ensuring that the negative electrode maintains good electrical contact during battery discharge and contraction.

Description

Technical Field

[0001] The present invention relates to the field of batteries, and in particular to a negative electrode material, a negative electrode sheet containing the negative electrode material, and a battery containing the negative electrode material. Background Art

[0002] Energy crisis and environmental pollution jointly threaten the survival and development of human society. The development of new energy sources is imminent. Batteries and other energy storage devices play an important role in energy storage and release and have become the focus of new energy. Among them, lithium-ion batteries have attracted the most attention due to their advantages such as high open circuit voltage, high energy density, long service life, no memory effect, no pollution, and low self-discharge rate.

[0003] In the development of battery materials, negative electrode materials have received great attention and research. The theoretical specific capacity of commercial graphite negative electrode is 372mAhg -1 , while the theoretical specific capacity of silicon reaches 4200mAhg -1 . New negative electrode materials can bring more than ten times the capacity increase, but also bring about huge volume changes. For example, the volume expansion of silicon can reach more than 300% after it is fully intercalated with lithium, causing the negative electrode material to pulverize and be destroyed, resulting in a sharp decline in capacity during the cycle. Currently, for silicon negative electrodes and other negative electrode materials with severe volume expansion, the main approach is to design gaps in the structure of the electrode active material or to use loose carbon conductive materials to provide space for volume expansion. Metal-organic framework materials (MOFs) have the potential value in solving the expansion problem of negative electrode materials due to their advantages such as easy functionalization with other heteroatoms or metals and metal oxides. There is an existing technology that uses MOF to modify silicon materials / carbon materials / silicon-carbon composite materials for use as negative electrode materials. However, there are the following problems: when the negative electrode material is intercalated with lithium, MOF cannot completely buffer the volume expansion of the negative electrode material. Excessive volume expansion directly causes the collapse of the MOF skeleton, resulting in poor structure of the formed lithium-ion battery; when the negative electrode material is delithiated, the loose pores of MOF make it difficult for the negative electrode to always maintain good electrical contact during operation.

[0004] Therefore, it is very important to find a negative electrode material with large capacity and small volume expansion rate. Summary of the Invention

[0005] The present invention aims to overcome the aforementioned problems of the prior art by providing a negative electrode material, a negative electrode sheet comprising the negative electrode material, and a battery comprising the negative electrode material. The negative electrode material of the present invention exhibits excellent flexibility and scalability, which not only alleviates the problem of negative electrode material expansion during battery charging but also ensures that the negative electrode maintains good electrical contact during battery discharge and contraction.

[0006] The inventors of the present invention discovered that using MOF with a flexible skeleton structure to modify carbon materials can effectively alleviate the expansion of negative electrode materials and maintain good electrical contact during the operation of the negative electrode. The reason may be that MOF with a flexible skeleton can undergo large-scale reversible deformation, that is, under the stimulation of surrounding environmental factors (such as temperature, pressure, etc.), its skeleton structure will transform between "large pore" and "narrow pore" forms, and accordingly its unit cell volume will also change significantly. In the initial state, the MOF with a flexible skeleton structure exists in a "large pore" form. During the charging process, lithium ions are embedded in the negative electrode, and the volume of the negative electrode expands. At this time, the external pressure increases. Under the stimulation of pressure, the MOF with a flexible skeleton changes from a "large pore" form to a "small pore" form, and its unit cell volume is greatly reduced. The reduced volume of the MOF with a flexible skeleton can offset the expanded volume of the negative electrode, so that the overall volume of the negative electrode does not change much; during the discharge process, lithium ions escape from the negative electrode and the volume of the negative electrode shrinks. At this time, the external pressure returns to normal, and the MOF with a flexible skeleton changes from a "small pore" form to a "large pore" form, and its unit cell volume returns to its initial state. During the battery discharge process, the volume of the negative electrode does not change much, so that the negative electrode always maintains good electrical contact.

[0007] A first aspect of the present invention provides a negative electrode material, which includes a MOF@carbon composite material and a silicon-based material.

[0008] A second aspect of the present invention provides a negative electrode sheet, which includes the negative electrode material described in the first aspect of the present invention.

[0009] A third aspect of the present invention provides a battery, comprising the negative electrode material according to the first aspect of the present invention and / or the negative electrode sheet according to the second aspect of the present invention.

[0010] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0011] (1) The negative electrode material of the present invention includes a MOF@carbon composite material and a silicon-based material. The MOF@carbon composite material has a flexible skeleton structure and good scalability, so that the negative electrode material can not only alleviate the volume expansion of the negative electrode during battery charging, but also provide more active sites for lithium ion insertion and extraction;

[0012] (2) The negative electrode material of the present invention includes MOF@carbon composite material and silicon-based material, which can enable the negative electrode to always maintain good electrical contact during the discharge and shrinkage process of the battery.

[0013] 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 and 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Shown is a schematic structural diagram of six MOFs in one example of the present invention.

[0015] Figure 2 Shown is the XRD pattern of MIL-47(V)@graphene oxide obtained in Example 1.

[0016] Figure 3 Shown is the SEM image of MIL-47(V)@graphene oxide obtained in Example 1.

[0017] Figure 4 Shown is a comparison chart of the cycle capacity retention rate of the battery prepared with the negative electrode sheet obtained in Example 1 and the capacity retention rate of the battery prepared with the negative electrode sheet obtained in Comparative Example 2.

[0018] Figure 5 Shown is a schematic diagram of the preparation method of MIL-47(V)@graphene oxide obtained in Example 1. DETAILED DESCRIPTION

[0019] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0020] A first aspect of the present invention provides a negative electrode material, which may include a MOF@carbon composite material and a silicon-based material.

[0021] In the present invention, the MOF@carbon composite material is a MOF-modified carbon material. For example, the MOF-modified carbon material is a MOF-coated carbon material, or for another example, the MOF-modified carbon material is a MOF-doped carbon material.

[0022] In one embodiment, the MOF has a flexible skeleton structure.

[0023] In the present invention, the term "MOF" has the conventional meaning in the art. The term "MOF" refers to metal-organic framework materials.

[0024] In one example, the MOF@carbon composite material is a carbon material coated with the MOF.

[0025] The MOF is assembled by organic ligands and metal ions through a chemical self-assembly process.

[0026] For example, the metal ion may be selected from Fe 3+ 、Al 3+ 、Co 2+ 、V 5+ 、Ti 4+ 、Zn 2+ 、Cu 2+ Cr 3+ 、Mn 2+ and Ni 2+ The organic ligand may be selected from at least one of terephthalic acid, 2-aminoterephthalic acid, 4,4'-biphenyldicarboxylic acid, 1,4-bis(1H-pyrazol-4-yl)benzene, 4,4'-bipyridine, 3,3',4,4'-tetracarboxylic acid benzophenone and 1,4-diazabicyclo[2.2.2]octane.

[0027] In one example, the MOF includes a metal element, and the metal element is selected from at least one of Fe, Al, Co, V, Ti, Zn, Cu, Cr, Mn, and Ni.

[0028] In one example, the mass of the metal element accounts for 0.72%-7.8% of the total mass of the negative electrode material.

[0029] In one example, the mass of the metal element accounts for 0.8%-6.2% of the total mass of the negative electrode material.

[0030] In one example, the MOF is selected from at least one of MIL-47(V), NH2-MIL-53(Al), DUT-5(Al), Co(BDP), Zn2(btdc)2(bpy) and Zn2(1,4-bdc)2(dabco).

[0031] like Figure 1 The following is a schematic diagram of the structures of six MOFs in one embodiment of the present invention, wherein Figure 1 (a) is a schematic diagram of the structure of MIL-47(V), Figure 1 (b) is a schematic diagram of the structure of NH2-MIL-53(Al), Figure 1 (c) is a schematic diagram of the structure of DUT-5(Al), Figure 1 (d) is the schematic structural diagram of Co(BDP), Figure 1 (e) is a schematic diagram of the structure of Zn2(btdc)2(bpy), Figure 1 (f) is a schematic diagram of the structure of Zn2(1,4-bdc)2(dabco).

[0032] The inventors of the present invention have discovered that when the organic ligand contains a benzene ring structure, during the charge and discharge process of the battery, lithium ions will be partially embedded in the benzene ring of the organic ligand in the MOF pores, which can further improve the capacity performance of the battery.

[0033] In one embodiment, the organic ligand contains a benzene ring.

[0034] The inventors of the present invention have found that the organic ligand of MIL-47(V) is terephthalic acid, which contains a benzene ring structure, and MIL-47(V) has a large volume change rate (about 40%), which can effectively improve the capacity performance and cycle performance of the battery.

[0035] Preferably, the MOF is MIL-47(V).

[0036] More preferably, in the XRD diffraction pattern of the MOF, characteristic peaks appear at 8.2°-8.8°, 16.3°-17.3°, and 24.5°-25.5°.

[0037] In one example, the MOF is a combination of MIL-47(V) and one or more of NH2-MIL-53(Al), DUT-5(Al), Co(BDP), Zn2(btdc)2(bpy) and Zn2(1,4-bdc)2(dabco).

[0038] Due to their unique pore structure, MOFs with flexible skeletons have a certain degree of spatial freedom in their coordination bonds, allowing them to undergo large, reversible deformations. In response to environmental stimuli (such as temperature and pressure), the MOF's skeleton can transition between "large-pore" and "narrow-pore" states, with the unit cell volume also changing significantly. For example, MIL-47(V) can experience a volume change of up to 40%.

[0039] In the present invention, the volume change rate of the MOF may be 20%-60%, for example, 20%, 21%, 27%, 30%, 36%, 40%, 45%, 50%, 59% or 60%.

[0040] In the present invention, the volume change rate of the MOF can be obtained by a Monte Carlo (MC) simulation method.

[0041] In the present invention, the silicon-based materials include silicon, silicon carbon and SiO x At least one of (0<x<2).

[0042] Preferably, the silicon-based material is nano-silicon.

[0043] In one example, the particle size of the silicon-based material may be 100 nm-400 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0044] The particle size of the MOF@carbon composite material may be 100 nm-400 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0045] The particle size of the negative electrode material may be 100 nm-400 nm, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm or 400 nm.

[0046] In the present invention, the particle size of the MOF@carbon composite material, the particle size of the silicon-based material, and the particle size of the negative electrode material can be measured by a laser diffraction particle size analyzer, specifically referring to the national standard GB / T24533-2019 "Graphite Anode Materials for Lithium-ion Batteries".

[0047] In the present invention, the carbon material can be selected from conventional carbon materials in the art, for example, at least one selected from graphene materials, carbon nanotubes, carbon black, soft carbon, hard carbon, and graphite. The graphene material can be graphene and graphene oxide. The carbon nanotubes can be single-walled carbon nanotubes and multi-walled carbon nanotubes.

[0048] The inventors of the present invention found that when the carbon material is graphene oxide, the conductivity and stability of the negative electrode material are even better. The reason may be that the carboxyl and hydroxyl groups of graphene oxide can coordinate and bond with the metal ions of MOF, thereby strengthening the contact between the MOF and the graphite particle interface, facilitating the insertion and removal of lithium ions, and improving the electrochemical capacity performance and stability.

[0049] In one embodiment, the carbon material is graphene oxide.

[0050] In one embodiment, the XRD diffraction pattern of the carbon material shows a characteristic peak at 8.5-9.5°.

[0051] Based on the total weight of the negative electrode material, the content of the MOF@carbon composite material can be 16-26 weight % (e.g., 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 or 26 weight %), and the content of the silicon-based material can be 74-84 weight % (e.g., 84, 83, 82, 81, 80, 79, 78, 77, 76, 75 or 74 weight %).

[0052] In one example, based on the total weight of the negative electrode material, the content of the MOF@carbon composite material is 19-22% by weight, and the content of the silicon-based material is 78-81% by weight.

[0053] In one example, based on the total weight of the negative electrode material, the content of the MOF@carbon composite material is 19.5-20.5 wt %, and the content of the silicon-based material is 79.5-80.5 wt %.

[0054] Based on the total weight of the MOF@carbon composite material, the content of the MOF can be 80-99.9 wt% (e.g., 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 99.9 wt%), and the content of the carbon material can be 0.1-20 wt% (e.g., 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.1 wt%).

[0055] The inventors of the present invention have discovered that in the MOF@carbon composite material, the MOF and the carbon material have specific contents, so that the MOF@carbon composite material can have both a large deformation amount and good electrical contact performance.

[0056] In one example, based on the total weight of the MOF@carbon composite material, the content of the MOF is 90-99 weight %, and the content of the carbon material is 1-10 weight %.

[0057] The ratio of the mass of the MOF in the negative electrode material to the mass of the silicon-based material in the negative electrode material may be 1:(3.1-5.5), for example, 1:3.1, 1:3.5, 1:4, 1:4.5, 1:5 or 1:5.5.

[0058] The inventors of the present invention have discovered that there is a specific ratio between the mass proportion of the MOF in the negative electrode material and the mass proportion of the silicon-based material in the negative electrode material, so that the MOF can alleviate the volume expansion of the silicon-based material and keep the volume of the negative electrode material from changing suddenly.

[0059] In one example, the ratio of the mass of the MOF in the negative electrode material to the mass of the silicon-based material in the negative electrode material is 1:(3.8-4.6).

[0060] In one example, the ratio of the mass of the MOF in the negative electrode material to the mass of the silicon-based material in the negative electrode material is 1:(4.0-4.5).

[0061] The negative electrode material of the present invention includes a MOF@carbon composite material and a silicon-based material. The MOF@carbon composite material is a carbon material modified with MOF. The MOF has good scalability and can provide more active sites for lithium ion insertion and extraction. It can alleviate the volume expansion of the negative electrode during battery charging and can enable the negative electrode to always maintain good electrical contact during battery discharge and contraction.

[0062] A second aspect of the present invention provides a negative electrode sheet, which includes the negative electrode material described in the first aspect of the present invention.

[0063] The negative electrode sheet includes a negative electrode current collector and a coating layer coated on one side or both sides of the negative electrode current collector, wherein the coating layer includes the negative electrode material according to the first aspect of the present invention.

[0064] The coating may further include additives conventionally used in coatings, such as conductive agents and binders.

[0065] In one embodiment, the coating layer includes the negative electrode material, a conductive agent, and a binder. The conductive agent may include at least one of Super P, acetylene black, and Ketjen black. The binder may include at least one of sodium carboxymethyl cellulose, carboxymethyl cellulose, polyvinylidene fluoride, and styrene-butadiene rubber.

[0066] The mass of the negative electrode material may account for 80%-99.5% of the total weight of the coating, for example 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 99.5%.

[0067] In one example, the mass of the negative electrode material accounts for 95%-98.5% of the total weight of the coating.

[0068] In one example, the mass of the negative electrode material accounts for 96.2%-97.4% of the total weight of the coating.

[0069] Based on the total weight of the coating, the content of the negative electrode material can be 80-99.5 weight % (for example, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 99.5 weight %), the content of the conductive agent can be 0.2-10 weight % (for example, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5 or 0.2 weight %), and the content of the binder can be 0.2-10 weight % (for example, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5 or 0.2 weight %).

[0070] In one example, based on the total weight of the coating, the content of the negative electrode material is 95-98.5 wt %, the content of the conductive agent is 0.5-2.5 wt %, and the content of the binder is 0.5-2.5 wt %.

[0071] In one example, based on the total weight of the coating, the content of the negative electrode material is 96.2-97.4 wt %, the content of the conductive agent is 1.3-1.9 wt %, and the content of the binder is 1.3-1.9 wt %.

[0072] A third aspect of the present invention provides a battery, comprising the negative electrode material according to the first aspect of the present invention and / or the negative electrode sheet according to the second aspect of the present invention.

[0073] The components of the battery other than the negative electrode (such as the positive electrode, separator, electrolyte, etc.) can be selected from conventional options in the art.

[0074] In one example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0075] The positive electrode active material can be a conventional choice in the art. For example, the positive electrode active material is selected from at least one of lithium cobalt oxide (LCO), nickel cobalt manganese ternary material (NCM), nickel cobalt aluminum ternary material (NCA), nickel cobalt manganese aluminum quaternary material (NCMA), lithium iron phosphate (LFP), lithium manganese phosphate (LMP), lithium vanadium phosphate (LVP), lithium manganese oxide (LMO), lithium nickel oxide, lithium manganese oxide, lithium-rich manganese base and lithium iron manganese phosphate.

[0076] The positive electrode active material also includes doped and / or coated positive electrode active materials.

[0077] The battery can be assembled in accordance with conventional methods in the art.

[0078] The battery can be a liquid electrolyte battery, a semi-solid battery, or an all-solid battery.

[0079] The battery of the present invention can not only maintain stable interface contact between the negative electrode material and the separator or between the negative electrode material and the solid electrolyte during the charge and discharge process, but also has excellent charge and discharge cycle stability and capacity performance.

[0080] The present invention will be described in detail below through examples. The examples described in the present invention are only some examples of the present invention, not all examples. All other examples obtained by persons of ordinary skill in the art based on the examples of the present invention without creative work are within the scope of protection of the present invention.

[0081] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0082] The following examples are used to illustrate the negative electrode sheet of the present invention.

[0083] Example 1

[0084] (1) Preparation of MOF@carbon composite materials:

[0085] 10 mg of graphene oxide, 0.12 g of NH4VO3 (ammonium metavanadate), 0.33 g of H2BDC (terephthalic acid) and 7 mL of DMF (N, N-dimethylformamide) were dispersed in 50 mL of deionized water and stirred for 30 min. The mixture was then transferred to a 100 mL reactor and placed in a forced air drying oven. The mixture was maintained at 140° C. for 12 h, and then separated and dried to obtain MIL-47(V)@graphene oxide. The content of graphene oxide in MIL-47(V)@graphene oxide was 3% by weight, the content of MIL-47(V) was 97% by weight, the particle size of MIL-47(V)@graphene oxide was 200 nm, and the volume change rate of MIL-47(V) was 40%.

[0086] (2) Preparation of negative electrode sheet:

[0087] The MIL-47(V)@graphene oxide and nano-silicon dioxide (particle size 200 nm) obtained in step (1) are mixed to obtain a negative electrode material, and then conductive carbon black (Super P), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are added, wherein the mass ratio of MIL-47(V)@graphene oxide, nano-silicon dioxide, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber is 19.3:77.5:1.6:0.8:0.8, and deionized water is added to obtain a negative electrode material slurry with a solid content of 45%; the negative electrode material slurry is coated on both sides of a copper foil, dried in a vacuum oven at 60°C, and then rolled and sliced ​​to obtain a negative electrode sheet.

[0088] Example 2

[0089] (1) Preparation of MOF@carbon composite materials:

[0090] 17 mg of graphene oxide, 1.5 g of NH2-BDC (2-aminoterephthalic acid), and 3.1 g of Al(NO3)3·9H2O (aluminum nitrate nonahydrate) were dispersed in 23 mL of deionized water and stirred for 30 min. The mixture was then transferred to a 50 mL reactor and placed in a forced air drying oven. The mixture was maintained at 150° C. for 5 h, filtered and separated, and then refluxed in DMF (N,N-dimethylformamide) at 150° C. for 8 h to obtain NH2-MIL-53(Al)@graphene oxide. The graphene oxide content in NH2-MIL-53(Al)@graphene oxide was 1% by weight, the content of NH2-MIL-53(Al) was 99% by weight, the particle size of NH2-MIL-53(Al)@graphene oxide was 100 nm, and the volume change rate of NH2-MIL-53(Al) was 27%.

[0091] (2) Preparation of negative electrode sheet:

[0092] After mixing the NH2-MIL-53(Al)@graphene oxide and nano-silicon dioxide (particle size 100 nm) obtained in step (1) to obtain a negative electrode material, conductive carbon black (Super P), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are added, wherein the mass ratio of NH2-MIL-53(Al)@graphene oxide, nano-silicon dioxide, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber is 19.2:78:1.4:0.7:0.7, and deionized water is added to obtain a negative electrode material slurry with a solid content of 45%; the negative electrode material slurry is coated on both sides of a copper foil, dried in a vacuum oven at 60°C, and then rolled and sliced ​​to obtain a negative electrode sheet.

[0093] Example 3

[0094] (1) Preparation of MOF@carbon composite materials:

[0095] 20 mg of graphene oxide, 0.26 g of H2BPDC (4,4'-biphenyldicarboxylic acid), and 0.52 g of Al(NO3)3·9H2O (aluminum nitrate nonahydrate) were dispersed in 30 mL of DMF (N,N-dimethylformamide) and stirred for 40 min, then transferred to a 50 mL reactor and placed in a blast drying oven. The mixture was maintained at 120° C. for 24 h, filtered and dried to obtain DUT-5(Al)@graphene oxide, wherein the content of graphene oxide in DUT-5(Al)@graphene oxide was 10% by weight, the content of DUT-5(Al) was 90% by weight, the particle size of DUT-5(Al)@graphene oxide was 400 nm, and the volume change rate of DUT-5(Al) was 59%.

[0096] (2) Preparation of negative electrode sheet:

[0097] The DUT-5(Al)@graphene oxide and nano-silicon dioxide (particle size 400 nm) obtained in step (1) are mixed to obtain a negative electrode material, and then conductive carbon black (Super P), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are added, wherein the mass ratio of DUT-5(Al)@graphene oxide, nano-silicon dioxide, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber is 19.4:77:1.8:0.9:0.9, and deionized water is added to obtain a negative electrode material slurry with a solid content of 45%; the negative electrode material slurry is coated on both sides of a copper foil, dried in a vacuum oven at 60°C, and then rolled and sliced ​​to obtain a negative electrode sheet.

[0098] Example 4

[0099] This set of examples is used to illustrate the impact of changes in MOF on negative electrode materials and negative electrode sheets.

[0100] This group of examples was carried out with reference to Example 1, except that the MOF was changed, specifically:

[0101] Example 4a: (1) 24 mg of graphene oxide, 1.8 g of Co(CF3SO3)2 (copper trifluoromethanesulfonate), and 0.9 g of H2BDP (1,4-bis(1H-pyrazol-4-yl)benzene) were dispersed in 30 mL of DEF (N,N-diethylformamide) and stirred for 30 min. The mixture was then transferred to a 50 mL reactor and placed in a forced air drying oven at 1,50°C for 6 days. The mixture was separated and dried to obtain Co(BDP)@graphene oxide, wherein the content of graphene oxide in the Co(BDP)@graphene oxide was 3 wt %, the content of Co(BDP) was 97 wt %, the particle size of the Co(BDP)@graphene oxide was 200 nm, and the volume change rate of Co(BDP) was 21%;

[0102] Example 4b: (1) 75 mg of graphene oxide, 2.1 g of Zn(NO3)2·6H2O (zinc nitrate hexahydrate), 1.1 g of H4BTDC (3,3',4,4'-tetracarboxylic acid benzophenone) and 1.1 g of bpy (4,4'-bipyridine) was dispersed in 70 mL of deionized water and stirred for 30 min, then transferred to a 100 mL reactor, placed in a blast drying oven, maintained at 160° C. for 4 days, separated and dried to obtain Zn2(btdc)2(bpy)@graphene oxide, wherein the content of graphene oxide in Zn2(btdc)2(bpy)@graphene oxide was 3% by weight, the content of Zn2(btdc)2(bpy) was 97% by weight, the particle size of Zn2(btdc)2(bpy)@graphene oxide was 400 nm, and the volume change rate of Zn2(btdc)2(bpy) was 36%;

[0103] Example 4c: (1) 30 mg of graphene oxide, 3.2 g of Zn(NO3)2·6H2O (zinc nitrate hexahydrate), 1.6 g of H2BDC (terephthalic acid) and 0.6 g of DABCO (1,4-diazabicyclo[2.2.2]octane) were dispersed in 120 mL of The reaction mixture was stirred in DMF (N,N-dimethylformamide) for 30 minutes, then transferred to a 250 mL reactor, placed in a forced air drying oven, maintained at 140°C for 48 hours, separated and dried to obtain Zn2(1,4-bdc)2(dabco)@graphene oxide, wherein the content of graphene oxide in Zn2(1,4-bdc)2(dabco)@graphene oxide was 3 weight percent, the content of Zn2(1,4-bdc)2(dabco) was 97 weight percent, the particle size of Zn2(1,4-bdc)2(dabco)@graphene oxide was 200 nm, and the volume change rate of Zn2(1,4-bdc)2(dabco) was 45%.

[0104] Example 5

[0105] This set of examples is used to illustrate the effects of changes in carbon materials.

[0106] This group of examples was carried out with reference to Example 1, except that the carbon material was changed, specifically:

[0107] Example 5a: Using single-walled carbon nanotubes of equal mass to replace graphene oxide;

[0108] Example 5b: Using equal mass of multi-walled carbon nanotubes to replace graphene oxide;

[0109] Example 5c: Using an equal amount of carbon black to replace graphene oxide.

[0110] Example 6

[0111] This group of embodiments is used to illustrate the impact of changes in "the ratio of the mass of the MOF in the negative electrode material to the mass of the nano-silicon oxide in the negative electrode material".

[0112] This group of examples is carried out with reference to Example 1, except that the ratio of the mass of the MOF in the negative electrode material to the mass of the nano-silicon oxide in the negative electrode material is changed. Specifically:

[0113] Example 6a: The MIL-47(V)@graphene oxide obtained in step (1) and nano-silicon dioxide (particle size 200 nm) were mixed to obtain a negative electrode material, and conductive carbon black (Super P), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) were added, wherein the mass ratio of MIL-47(V)@graphene oxide, nano-silicon dioxide, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber was 16:79:2.5:1.2:1.3;

[0114] Example 6b: The MIL-47(V)@graphene oxide and nano-silicon dioxide (particle size 200 nm) obtained in step (1) are mixed to obtain a negative electrode material, and then conductive carbon black (Super P), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) are added, wherein the mass ratio of MIL-47(V)@graphene oxide, nano-silicon dioxide, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber is 20.5:64:8:3.5:4.

[0115] Example 7

[0116] This set of examples is used to illustrate the impact of whether the MOF organic ligand contains a benzene ring.

[0117] This group of examples was carried out with reference to Example 1, except that the MOF was changed, specifically: (1) Preparation of MOF@carbon composite material:

[0118] 10 mg of graphene oxide, 2.94 g of AlCl3·6H2O (aluminum chloride hexahydrate), and 1.68 g of C4H4O4 (fumaric acid) were dispersed in 60 mL of DMF (N,N-dimethylformamide), then transferred to a 100 mL reactor and placed in a forced air drying oven at 130°C for 4 days. The mixture was separated and dried to obtain A520@graphene oxide, wherein the graphene oxide content in A520@graphene oxide was 3 wt %, the A520 content was 97 wt %, the particle size of A520@graphene oxide was 200 nm, and the volume change rate of A520 was 40%.

[0119] Comparative Example 1

[0120] The same method is carried out with reference to Example 1, except that step (1) is different, specifically:

[0121] (1) Preparation of composite materials: 3 mL of methanol, 0.05 g of nano-silicon dioxide particles, 0.26 g of H2BPDC (4,4'-biphenyldicarboxylic acid), and 0.52 g of Al(NO3)3·9H2O (aluminum nitrate nonahydrate) were dispersed in 27 mL of DMF (N,N-dimethylformamide) and stirred for 40 min. The mixture was then transferred to a 50 mL reactor and placed in a forced air drying oven at 120°C for 24 h. The mixture was filtered and dried, and then carbonized under inert gas for 3 h at a carbonization temperature of 800°C and a heating rate of 1°C / min.

[0122] Comparative Example 2

[0123] The same method is carried out with reference to Example 1, except that step (1) is different, specifically:

[0124] (1) Preparation of composite materials: 30 mg of graphene oxide, 0.4 g of ZrCl4 (zirconium tetrafluoride), and 0.28 g of H2BDC (terephthalic acid) were dispersed in 60 mL of DMF (N,N-dimethylformamide) and stirred for 30 min. The mixture was then transferred to a 100 mL reactor and placed in a forced air drying oven at 120°C for 24 h. The mixture was separated and dried to obtain UiO-66@graphene oxide.

[0125] Capacity retention test

[0126] The negative electrode sheets and positive electrode sheets (metal lithium) prepared in the examples and comparative examples were assembled into button cells in an argon atmosphere glove box. The electrochemical charge and discharge performance of the button cells was tested. The specific test method is as follows:

[0127] At 0.5Ag -1 The cycle capacity retention rate was tested under the current density and the test voltage range of 0.01-3.0V. The test results are recorded in Table 1. The capacity retention rate of the batteries prepared by the negative electrode sheets obtained in Example 1 and Comparative Example 2 is shown in the curves of the change with the number of cycles. Figure 4 shown.

[0128] Table 1

[0129]

[0130]

[0131] Figure 2 The figure shows the XRD pattern of the MIL-47(V)@graphene oxide obtained in Example 1. The figure shows characteristic peaks of MIL-47(V) near 2Theta of 8.5°, 16.8°, and 25°, and a characteristic peak of graphene oxide near 2Theta of 9°, indicating that the MIL-47(V)@graphene oxide composite material was prepared in Example 1.

[0132] Figure 3 The figure shows the SEM image of the MIL-47(V)@graphene oxide obtained in Example 1. The figure shows that the MIL-47(V)@graphene oxide is a spherical particle with a uniform particle size of approximately 200 nm, close to that of nano-silicon oxide, which can improve the uniformity of the blending.

[0133] Figure 4 The figure shows a comparison of the cycle capacity retention rate of the battery prepared with the negative electrode sheet obtained in Example 1 and the capacity retention rate of the battery prepared with the negative electrode sheet obtained in Comparative Example 2. It can be seen from the figure that the cycle capacity retention rate of Example 1 is significantly higher than that of Comparative Example 2.

[0134] As can be seen from Table 1, the capacity retention rate of the battery prepared with the negative electrode material of the present invention is significantly improved compared with the comparative example.

[0135] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A negative electrode material, characterized in that The negative electrode material includes a MOF@carbon composite material and a silicon-based material; the MOF@carbon composite material includes a MOF-coated carbon material and / or a MOF-doped carbon material; the MOF is selected from at least one of MIL-47(V), DUT-5(Al), Zn2(btdc)2(bpy) and Zn2(1,4-bdc)2(dabco); the MOF has a flexible skeleton structure that can transform between "macroporous" and "microporous" forms; and the volume change rate of the MOF is 20%-60%. The ratio of the mass of the MOF in the negative electrode material to the mass of the silicon-based material in the negative electrode material is 1:(3.1-5.5); based on the total weight of the MOF@carbon composite material, the content of the MOF is 90-99 weight%, and the content of the carbon material is 1-10 weight%.

2. The negative electrode material according to claim 1, wherein The MOF includes metal elements, and the mass of the metal accounts for 0.72%-7.8% of the total mass of the negative electrode material.

3. The negative electrode material according to claim 1, wherein The MOF is MIL-47(V).

4. The negative electrode material according to claim 1, wherein The MOF is a combination of MIL-47(V) and one or more of DUT-5(Al), Zn2(btdc)2(bpy), and Zn2(1,4-bdc)2(dabco).

5. The negative electrode material according to claim 1, wherein The silicon-based materials include silicon, silicon carbon and SiO x At least one of , x is greater than 0 and less than 2.

6. The negative electrode material according to claim 5, wherein The particle size of the silicon-based material is 100nm-400nm.

7. The negative electrode material according to any one of claims 1 to 6, wherein The particle size of the MOF@carbon composite material is 100nm-400nm; and / or, The particle size of the negative electrode material is 100nm-400nm.

8. The negative electrode material according to claim 1, wherein The carbon material is selected from at least one of graphene materials, carbon nanotubes, carbon black, soft carbon, hard carbon and graphite.

9. The negative electrode material according to claim 8, wherein The graphene material is graphene oxide.

10. The negative electrode material according to claim 8, wherein In the XRD diffraction pattern of the carbon material, a characteristic peak appears at 8.5° to 9.5°.

11. The negative electrode material according to claim 1, wherein Based on the total weight of the negative electrode material, the content of the MOF@carbon composite material is 16-26% by weight, and the content of the silicon-based material is 74-84% by weight.

12. The negative electrode material according to claim 11, wherein Based on the total weight of the negative electrode material, the content of the MOF@carbon composite material is 19.5-20.5% by weight, and the content of the silicon-based material is 79.5-80.5% by weight.

13. The negative electrode material according to claim 1, wherein The ratio of the mass of the MOF in the negative electrode material to the mass of the silicon-based material in the negative electrode material is 1:(4.0-4.5).

14. A negative electrode sheet, characterized in that: The negative electrode sheet comprises the negative electrode material according to any one of claims 1 to 13.

15. A battery, characterized in that: The battery comprises the negative electrode material according to any one of claims 1 to 13 and / or the negative electrode sheet according to claim 14.

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