Single crystal Fe 1-x Composite material of s and carbon, method for preparing the same, negative electrode sheet, and lithium battery

Abstract

A single crystal Fe 1‑x The application relates to a composite material of single crystal Fe 1‑x The preparation method of the composite material of single crystal Fe 1‑x The application provides a composite material of single crystal Fe 1‑x The application provides a composite material of single crystal Fe

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a single-crystal Fe 1-x S and carbon, a preparation method thereof, a negative plate and a lithium battery. BACKGROUND

[0002] Since 1991, when the rechargeable lithium-ion batteries (LIBs) were commercialized, graphite has been used as a key anode material for lithium-ion batteries. Graphite has been widely used as an anode material, and its mature preparation process has been developed, which has laid a solid foundation for the commercial application of lithium-ion batteries. Although graphite is the most mature anode material, its small interlayer spacing (0.334 nm) and anisotropic ion transport channels seriously limit the further improvement of ion transport capacity, and the low theoretical specific capacity (372 mAh / g) of graphite cannot meet the growing demand for high-capacity fast-charging lithium-ion batteries for 3C electronic devices and electric vehicles.

[0003] Over the past few decades, scientists and researchers have been exploring anode materials to replace graphite, and have conducted a large number of studies on materials such as silicon and its oxides, transition metal oxides, transition metal sulfides, and graphene. Among these anode materials, Fe 1-x S has attracted great attention from researchers due to its high theoretical lithium storage capacity, abundant reserves, and environmental protection characteristics. Unfortunately, Fe 1-x S as an anode material for lithium-ion batteries faces serious capacity decay and unsatisfactory rate capability. These problems are mainly due to the conversion reaction of Fe 1-x S to Fe and polysulfides during charging and discharging, the shuttle effect of polysulfides, and the irreversibility of the conversion reaction, which inevitably leads to volume changes, thereby causing poor cycle stability of Fe 1-x S. In addition, as a transition metal sulfide, Fe 1-x S has low electrical conductivity, resulting in slow electrode charge transport and thus poor rate performance of Fe 1-x S.

[0004] Therefore, it is crucial to develop a preparation technology for single-crystal Fe 1-x S material suitable for lithium-ion batteries. SUMMARY

[0005] Based on the above-mentioned deficiencies, the present application provides a single-crystal Fe 1-x S and carbon, a preparation method thereof, a negative plate and a lithium battery, to partially or completely improve the problems in the related art.

[0006] The present application is achieved in the following manner:

[0007] In a first aspect, examples of the present application provide a single-crystal Fe 1-x A method for preparing a composite material of Fe

[0008] A precursor solution is obtained, the precursor solution comprising an iron-containing organic salt and a sulfur-containing organic solvent;

[0009] The precursor solution is placed in a sealed container and heated in a protective gas environment to convert the precursor solution into a gas phase and maintain for more than 5 minutes, and then cooled to room temperature to obtain a single-crystal Fe 1-x S nanosheet and carbon composite material, 0 < x < 1.

[0010] In the above implementation process, the iron-containing organic salt in the precursor solution can provide an iron source and a carbon source, and the sulfur-containing organic solvent can provide a sulfur source and a carbon source. After heating, the temperature and pressure in the sealed container can be increased to make the iron ions in the precursor solution form Fe e1-x S, and after cooling, thin and flat single-crystal Fe 1-x S nanosheets. At the same time, in the high-pressure gas phase environment in the sealed container, the precursor solution can form gaseous groups, which can form a dense and uniform carbon layer on the surface of Fe 1-x S. Moreover, due to the high pressure in the sealed container, the increase in the thickness of the carbon coating layer can be inhibited and the crystallization of the carbon coating layer can be promoted, forming a graphene-like carbon coating layer, thereby obtaining a single-crystal Fe 1-x S nanosheet structure composite material.

[0011] In the composite material obtained by the above preparation method, when applied to a lithium battery system, the graphene-like carbon layer is coated on the surface of the single-crystal Fe 1-x S nanosheet, which can effectively improve the electrical conductivity of the composite material, and the dense and uniform graphene-like carbon layer can effectively prevent the agglomeration and stacking of single-crystal Fe 1-x S nanosheets, and can also prevent direct contact between single-crystal Fe 1-x S nanosheets and electrolyte, thereby enhancing the structural stability and rate performance of the composite material during the cycle process. Therefore, the single-crystal Fe 1-x S nanosheet and carbon composite material prepared by the examples of the present application can be used as the anode of a lithium ion battery, which can improve the capacity, rate performance and cycle stability of the lithium ion battery.

[0012] In combination with the first aspect, in a possible implementation, the iron-containing organic salt is selected from iron iso-octoate; and the sulfur-containing organic solvent is selected from at least one of dimethyl sulfoxide dimethyl sulfide or sulfolane.

[0013] In the implementation process, iron (III) 2-ethylhexanoate and dimethyl sulfoxide can form a solution, so that the precursor solution contains corresponding iron source, sulfur source and carbon source, and the precursor solution formed by iron (III) 2-ethylhexanoate and dimethyl sulfoxide can be converted into gaseous groups in a high-pressure gas phase environment in a closed environment, and can form single-crystal Fe 1-x The surface of the single-crystal Fe

[0014] In combination with the first aspect, in a possible implementation, the precursor solution contains iron (III) 2-ethylhexanoate and dimethyl sulfoxide in a mass ratio of 1:0.6-1.2.

[0015] In the implementation process, the mass ratio of iron (III) 2-ethylhexanoate and dimethyl sulfoxide is controlled in the range of 1:0.6-1.2, so that single-crystal Fe 1-x S nanosheet and carbon composite material.

[0016] If the content of iron (III) 2-ethylhexanoate is relatively high and the content of dimethyl sulfoxide is relatively low, the content of Fe is relatively high and the content of S is insufficient, under the high-temperature gas phase condition in the closed container, in addition to the generation of single-crystal Fe 1-x In addition to the single-crystal Fe 1-x S nanosheet, the excess Fe will form Fe3O4 impurity nanoparticles with O in the precursor. The Fe3O4 nanoparticles will adhere to the Fe

[0017] If the content of iron (III) 2-ethylhexanoate is relatively low and the content of dimethyl sulfoxide is relatively high, the content of Fe is insufficient and the content of S is excessive, under the high-pressure gas phase environment in the closed container, part of the iron ions will be completely sulfurized to form FeS, forming impurities. Compared with Fe 1-x S, the nanosheet formed by FeS is thicker, and the single-crystal Fe 1-x S nanosheet is thin and flat, which can realize faster lithium storage. At the same time, too much dimethyl sulfoxide will provide excess carbon source, resulting in an excessively thick carbon coating layer, which may affect the lithium storage capacity of the composite material.

[0018] In combination with the first aspect, in a possible implementation, the temperature of the closed heating in the protective gas environment is 550-750°C, and the time is 10-30 min.

[0019] In the implementation process, the precursor solution is heated to 550-750°C, so that the precursor solution can be converted into gaseous groups, and the single-crystal Fe 1-x The surface of the single-crystal Fe

[0020] In the second aspect, the present application provides a single-crystal Fe1-x The composite material of S nanosheets and carbon was prepared according to the preparation method provided in the first aspect.

[0021] In the above-described process, the single-crystal Fe obtained by the preparation method provided in the first aspect... 1-x In the application of S nanosheets and carbon composite materials in lithium battery systems, a graphene-like carbon layer is coated on a single-crystal Fe. 1-x The surface of S nanosheets can effectively improve the electrical conductivity of composite materials, and the dense and uniform graphene-like carbon layer can effectively prevent single-crystal Fe from being absorbed. 1-x The aggregation and stacking of S nanosheets can also block single-crystal Fe 1-x The direct contact between the Fe nanosheets and the electrolyte enhances the structural stability and rate performance of the composite material during cycling. Therefore, the single-crystal Fe nanosheets prepared in this application example... 1-x Composite materials of S nanosheets and carbon can be used as negative electrodes for lithium-ion batteries to improve the capacity, rate performance and cycle stability of lithium-ion batteries.

[0022] In a third aspect, this application provides an example of a single-crystal Fe... 1-x Composite materials of S nanosheets and carbon, including single-crystal Fe 1-x S nanosheets and coated single-crystal Fe 1-x Carbon nanofiber coating on S nanosheets.

[0023] In the above implementation process, the composite material includes single-crystal Fe. 1-x S nanosheets and coated single-crystal Fe 1-x Carbon nanosheet coating of S nanosheets, single-crystal Fe 1-x S nanosheets possess high theoretical lithium storage capacity, and nano-sized single-crystal Fe... 1-x S can shorten the lithium-ion transport path, thus improving the high-capacity fast-charging efficiency of lithium-ion batteries. Furthermore, in single-crystal Fe... 1-x The surface of S nanosheets is coated with a thin carbon nanotube layer, which effectively inhibits the lithium storage capacity of single-crystal Fe nanosheets without significantly affecting the lithium storage capacity of the composite material. 1-x The aggregation and stacking of S nanosheets can suppress polysulfide shuttle, improve the electrical conductivity of the material, alleviate the volume expansion of the material during lithium storage, enhance the charge transport capacity and structural stability of the electrode, and also block single-crystal Fe. 1-x The direct contact between the S nanosheets and the electrolyte enhances the structural stability and rate performance of the composite material during cycling.

[0024] In conjunction with the third aspect, in one possible implementation, the carbon nanotube coating is a graphene-like coating, and the thickness of the carbon nanotube coating is 5-10 nm.

[0025] In the implementation process, the thickness of the carbon nanocoating layer is 5-10 nm, which can reduce the influence of the nanocoating layer on the lithium storage capacity of the negative electrode material.

[0026] In combination with the third aspect, in a possible implementation, the single-crystal Fe 1-x The length of the FeS nanosheet is 2-8 microns.

[0027] In the implementation process, the length of the single-crystal Fe 1-x S nanosheet is 2-8 microns, which can shorten the ion transmission distance and improve the electrical performance of the lithium battery.

[0028] In the fourth aspect, examples of the present application provide a negative electrode sheet, and the raw material for forming the negative electrode sheet includes the composite material improved in the second aspect or the third aspect.

[0029] In the fifth aspect, examples of the present application provide a lithium battery, which includes the negative electrode sheet provided in the fourth aspect.

[0030] In the implementation process, the negative electrode sheet is made of the composite material provided in the second aspect or the third aspect, which can enhance the structural stability and rate performance of the lithium battery. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0032] Figure 1 The preparation process of the single-crystal Fe 1-x S nanosheet and the carbon composite material provided in the examples of the present application is shown in the schematic diagram.

[0033] Figure 2 The SEM diagram of the single-crystal Fe 1-x S nanosheet and the carbon composite material provided in Embodiment 1 of the present application is shown in the SEM diagram.

[0034] Figure 3 The TEM diagram of the single-crystal Fe 1-x S nanosheet and the carbon composite material provided in Embodiment 1 of the present application is shown in the TEM diagram.

[0035] Figure 4 The enlarged diagram of the boundary structure of the FeS nanosheet is shown in the diagram. Figure 3 The enlarged diagram of the graphite-like carbon layer coating is shown in the diagram.

[0036] Figure 5 The enlarged diagram of the graphite-like carbon layer coating is shown in the diagram. Figure 4 The enlarged diagram of the graphite-like carbon layer coating is shown in the diagram.

[0037] Figure 6 The TEM diffraction diagram of the single-crystal Fe 1-x S nanosheet and the carbon composite material provided in Embodiment 1 of the present application is shown in the TEM diagram.

[0038] Figure 7 XRD pattern of the composite material provided for Example 1 of the present application;

[0039] Figure 8 Raman pattern of the composite material provided for Example 1 of the present application;

[0040] Figure 9 SEM image of the composite material provided for Example 2 of the present application;

[0041] Figure 10 XRD pattern of the composite material provided for Example 2 of the present application;

[0042] Figure 11 Raman pattern of the composite material provided for Example 2 of the present application;

[0043] Figure 12 SEM image of the composite material provided for Example 3 of the present application;

[0044] Figure 13 XRD pattern of the composite material provided for Example 3 of the present application;

[0045] Figure 14 Raman pattern of the composite material provided for Example 3 of the present application;

[0046] Figure 15 SEM image of the composite material provided for Example 4 of the present application;

[0047] Figure 16 XRD pattern of the composite material provided for Example 4 of the present application;

[0048] Figure 17 SEM image of the composite material provided for Example 5 of the present application;

[0049] Figure 18 XRD pattern of the composite material provided for Example 5 of the present application;

[0050] Figure 19 SEM image of the composite material provided for Example 6 of the present application;

[0051] Figure 20 XRD pattern of the composite material provided for Example 6 of the present application;

[0052] Figure 21 SEM image of the composite material provided for Example 7 of the present application;

[0053] Figure 22 XRD pattern of the composite material provided for Example 7 of the present application;

[0054] Figure 23The first cycle charge-discharge curve of the lithium battery negative electrode provided for Example 8 of the present application under 0.1C rate charge-discharge;

[0055] Figure 24 The cycle curve of the lithium battery negative electrode provided for Example 8 of the present application under 1C rate charge-discharge;

[0056] Figure 25 The cycle curve of the lithium battery negative electrode provided for Example 8 of the present application under 10C rate charge-discharge;

[0057] Figure 26 The rate performance curve of the lithium battery negative electrode provided for Example 8 of the present application. DETAILED DESCRIPTION

[0058] The embodiments of the present application will be described in detail with examples, but those skilled in the art will understand that the following examples are only for illustration of the present application and should not be regarded as limiting the scope of the present application. The specific conditions are not specified in the examples, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0059] Fe 1-x S as a negative electrode material applied in lithium ion batteries faces serious capacity decay and unsatisfactory rate capability. These problems are mainly due to the formation of Fe and polysulfides from Fe1-xS due to the conversion reaction during charge-discharge, the polysulfides have a shuttle effect, and the conversion reaction is irreversible, leading to inevitable volume change, which leads to Fe 1- x S poor cycle stability. In addition, as a transition metal sulfide, Fe 1-x S has low electrical conductivity, leading to slow electrode charge transport, thereby reducing the rate performance of Fe 1-x S.

[0060] In order to improve the rate performance of Fe 1-x S, the inventors believe that adjusting the morphology and structure of Fe 1-x S at the nanoscale can improve its electrochemical performance. By reducing the F e1-xThe size of the S material can shorten the transmission path of lithium ions, and at the same time, can help to reduce the strain caused by volume expansion, thereby increasing the rate performance and cycle stability. Moreover, by constructing a carbon coating, the shuttle of polysulfides can be inhibited, the electrical conductivity of the material can be improved, the volume expansion of the material during lithium storage can be alleviated, and the self-aggregation of nanoparticles can be reduced, thereby improving the charge transport capacity and structural stability of the electrode, and further improving the rate performance and cycle stability of the electrode. In addition, the inventors believe that, since the single crystal material has no grain boundary and the crystal structure is very ordered, the single crystal Fe 1-x S can improve the rate performance of the battery.

[0061] The inventors attempted to prepare a carbon-coated single crystal Fe 1-x S by a hydrothermal method, but the synthesized single crystal Fe 1-x S is prone to agglomeration, and the carbon layer coating is relatively thick, which is not conducive to rapid lithium storage. Alternatively, polyacrylonitrile is used to prepare a spinning solution, and then Fe 1-x S dispersed in a carbon nanofiber matrix structure is obtained by electrospinning and carbonization. Alternatively, a single crystal Fe 1-x S is formed by sulfidation growth on the basis of Fe and a carbon substrate, but such a carbon substrate is composed of amorphous carbon, which can cause the overall single crystal Fe 1-x S nanosheet and carbon composite material has poor electronic / ionic conductivity.

[0062] In order to further improve the rate performance of the Fe 1-x S, the present application provides a single crystal Fe 1-x S nanosheet and carbon composite material and a preparation method thereof, which can prepare a composite material of single crystal Fe 1-x S nanosheet coated with a carbon nanocoating layer to improve the rate performance of a lithium ion battery.

[0063] The single crystal Fe 1-x S nanosheet and carbon composite material and the preparation method thereof provided in the examples of the present application are further described in detail below in conjunction with the accompanying drawings.

[0064] Referring to Figure 1 , the single crystal Fe 1-x S nanosheet and carbon composite material provided in the examples of the present application is prepared by the following method.

[0065] S1, a precursor solution is obtained, and the precursor solution includes an organic salt of iron and an organic solvent containing a sulfur element.

[0066] The iron source in the precursor solution and the sulfur source provided by the organic solvent containing a sulfur element interact under high-temperature and high-pressure gas phase conditions in a sealed environment, and after cooling, a single crystal Fe 1-xS nanosheet. Meanwhile, the precursor solution can be converted into gaseous radicals under high-temperature and high-pressure gas phase conditions in a sealed container, and the carbon source in the gaseous radicals can form a carbon nanocoating layer on the surface of the single-crystal Fe 1-x S nanosheet. Meanwhile, the precursor solution can be converted into gaseous radicals under high-temperature and high-pressure gas phase conditions in a sealed container, and the carbon source in the gaseous radicals can form a carbon nanocoating layer on the surface of the single-crystal Fe

[0067] The present application does not limit the specific types of the organic iron salt and the organic sulfur-containing solvent, and the relevant personnel can make corresponding selection according to the needs.

[0068] In a possible implementation, the organic iron salt can be selected from iron isooctanoate.

[0069] In a possible implementation, the organic sulfur-containing solvent is selected from at least one of dimethyl sulfoxide, dimethyl sulfide or sulfolane.

[0070] For example, the organic iron salt can be selected from iron isooctanoate, and the organic sulfur-containing solvent can be selected from dimethyl sulfoxide. The dimethyl sulfoxide contains a phosphorus source and a carbon source, is a good solvent for iron isooctanoate, and can form a precursor solution, so that the precursor solution can be converted into gaseous radicals at a lower temperature.

[0071] Further, the present application does not limit the specific ratio of iron isooctanoate and dimethyl sulfoxide in the precursor solution, and the relevant personnel can make corresponding selection according to the needs.

[0072] The mass ratio of iron isooctanoate and dimethyl sulfoxide needs to be controlled within a suitable range. If the content of iron isooctanoate is relatively high and the content of dimethyl sulfoxide is relatively low, the content of Fe is relatively high and the content of S is insufficient. Under high-temperature gas phase conditions in a sealed environment, in addition to the formation of Fe 1-x In addition to the S nanosheet, the excess Fe will form Fe3O4 nanoparticles with O in the precursor, forming impurities. The Fe3O4 nanoparticles will adhere to the Fe 1-x In addition to the S nanosheet, the excess Fe will form Fe3O4 nanoparticles with O in the precursor, forming impurities. The Fe3O4 nanoparticles will adhere to the Fe 1-x Compared with FeS, the nanosheet formed by FeS is thicker, and the single-crystal Fe 1-x Compared with FeS, the nanosheet formed by FeS is thicker, and the single-crystal Fe 1-x Compared with FeS, the nanosheet formed by FeS is thicker, and the single-crystal Fe

[0073] In one possible implementation, the precursor solution contains iron isooctoate and dimethyl sulfoxide in a mass ratio of 1:0.6-1.2.

[0074] For example, the mass ratio of iron isooctoate and dimethyl sulfoxide in the precursor solution can be one of 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, or 1:1.2, or a range between any two of them.

[0075] For further information, please refer to Figure 1 The single-crystal Fe 1-x The method for preparing the composite material of Fe

[0076] S2, the precursor solution is placed in a sealed container and heated in a protective gas environment to convert the precursor solution into a gas phase and keep it for more than 5 minutes, and then cooled to room temperature to obtain single-crystal Fe 1-x S nanosheet and carbon, 0

[0077] The precursor solution containing reactants such as iron isooctoate and dimethyl sulfoxide is placed in a sealed container and heated in a protective gas environment to increase the temperature and pressure in the sealed container. After iron isooctoate in the precursor solution is miscible with dimethyl sulfoxide, iron ions are generated, which form Fe 1-x S with S sources in dimethyl sulfoxide. After cooling, thin and flat single-crystal Fe 1-x S nanosheet is formed. At the same time, gaseous groups formed by dimethyl sulfoxide and iron isooctoate in the sealed container under a high-pressure gas phase environment are converted into a carbon coating layer. Under the action of a high-pressure gas phase, a dense and uniform carbon layer is formed to coat the surface of Fe 1-x S. Due to the high pressure in the sealed container, the increase in the thickness of the carbon layer is inhibited, and the crystallization of the carbon layer is promoted, thereby forming a graphene-like carbon layer, and a single-crystal Fe e1-x S nanosheet structure is obtained, and a composite material is obtained.

[0078] Further, the present application does not limit the specific type of the sealed container. Related personnel can make corresponding selection according to needs as long as the gaseous groups formed after the precursor solution is converted under high temperature do not leak out of the sealed container and the gas pressure in the sealed container can be increased.

[0079] For example, the sealed container can be the furnace tube of a tubular heating furnace.

[0080] Alternatively, the sealed container can be a high-temperature reaction kettle.

[0081] Further, the present application does not limit the specific type of the protective gas, and related personnel can make corresponding selection according to needs.

[0082] For example, the protective gas can be at least one of nitrogen or argon.

[0083] Further, the present application does not limit the specific temperature of heating, and the relevant personnel can make corresponding selection according to the need under the condition of ensuring that the precursor solution can be converted to form gaseous groups.

[0084] For example, the temperature of heating the precursor solution in the protective gas environment can be 550-750℃, and the heating time is 10-30min.

[0085] For example, the heating temperature can be one of 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃, or a range between any two of them.

[0086] For example, the heating time can be one of 10min, 15min, 20min, 25min or 30min, or a range between any two of them.

[0087] Further, the present application does not limit the specific heating rate and cooling rate, and the relevant personnel can make corresponding selection according to the need.

[0088] For example, the temperature can be raised to 600℃ at a heating rate of 10℃ / min, and then maintained for 20min, and then cooled to room temperature at a cooling rate of 10℃ / min.

[0089] For example, the temperature can be raised to 550℃ at a heating rate of 5℃ / min, and then maintained for 30min, and then cooled to room temperature by furnace cooling.

[0090] Further, the present application provides a single crystal Fe 1-x S nanosheet and carbon composite material.

[0091] The single crystal Fe 1-x S nanosheet and carbon composite material includes a single crystal Fe 1-x S nanosheet and a carbon nanocoating layer covering the single crystal Fe 1-x S nanosheet.

[0092] In one possible implementation, the carbon nanocoating layer is a graphene-like coating layer, and the thickness thereof can be one of 5nm, 6nm, 7nm, 8nm, 9nm or 10nm, or a range between any two of them.

[0093] The graphene-like coating layer refers to a carbon material having a two-dimensional single-layer or few-layer crystal structure.

[0094] In one possible implementation, the single-crystal Fe 1-x The thickness of the FeS nanosheet is in nanometer scale, and the length or width thereof can be one of 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm or 8 μm, or a range between any two of them.

[0095] Further, the examples of the present application also provide a negative electrode material, which comprises the single-crystal Fe 1-x S nanosheet and carbon.

[0096] Further, the negative electrode material can further comprise a conductive agent and a binder.

[0097] Further, the negative electrode material can further comprise a dispersant, the single-crystal Fe 1-x S nanosheet and carbon, a conductive agent and a binder are dispersed in the dispersant to form a negative electrode slurry.

[0098] Further, the examples of the present application also provide a negative electrode sheet, which is formed by coating the negative electrode slurry on a current collector.

[0099] Illustratively, the current collector can be a copper foil.

[0100] Further, the examples of the present application also provide a lithium battery comprising the negative electrode sheet.

[0101] Further, the lithium battery further comprises a positive electrode sheet.

[0102] Illustratively, the positive electrode sheet comprises a positive electrode current collector and a positive electrode material coated on the positive electrode current collector.

[0103] Illustratively, the positive electrode current collector can be selected from an aluminum foil.

[0104] Illustratively, the positive electrode material can be selected from at least one of lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel-manganese oxide, lithium nickel-cobalt oxide, lithium iron phosphate, lithium nickel-cobalt-aluminum oxide or lithium nickel-cobalt-manganese oxide.

[0105] Illustratively, the positive electrode material can further comprise a conductive agent. For example, the conductive agent of the positive electrode material can comprise at least one of conductive carbon black, flake graphite, graphene or carbon nanotube.

[0106] The positive electrode material can further include a binder. The binder can be at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, a polyamide, a polyacrylonitrile, a polyacrylate, a polyacrylic acid, a polyacrylate salt, carboxymethyl cellulose sodium, polyvinyl acetate, polyvinylpyrrolidone, a polyvinyl ether, a polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0107] Further, the lithium battery further includes a separator.

[0108] The separator can be at least one of polyethylene, polypropylene, or polyvinylidene fluoride.

[0109] Further, the lithium battery further includes an electrolyte.

[0110] The electrolyte can include a solvent and a lithium salt.

[0111] The solvent can be at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, or propyl propionate.

[0112] The lithium salt can be at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, or lithium bisfluorosulfonylimide.

[0113] Further, the electrolyte can further include an additive.

[0114] The additive can be at least one of vinylene carbonate or fluoroethylene carbonate.

[0115] The single-crystal FeS nanosheet and carbon composite material of the present application is further described below in conjunction with examples. 1-x The single-crystal FeS nanosheet and carbon composite material is further described below in conjunction with examples.

[0116] Example 1

[0117] Example 1 provides a single-crystal FeS nanosheet and carbon composite material, which is prepared as follows: 1-x The single-crystal FeS nanosheet and carbon composite material is further described below in conjunction with examples.

[0118] A mixture of iron isooctoate and dimethyl sulfoxide is prepared as a precursor solution at a mass ratio of 1:0.8. The precursor solution is then added to a high-pressure reaction device, which is sealed and then transferred to a tube furnace under an argon atmosphere. The high-pressure reaction device is heated to a reaction temperature of 600°C at a heating rate of 10°C / min, and then cooled to room temperature after being kept at the reaction temperature for 20 min. The high-pressure reaction device is then removed and opened to obtain a black powder-shaped composite material.

[0119] Example 2

[0120] Example 2 provides a single-crystal FeS nanosheet and carbon composite material, which is prepared as follows: 1-xThe composite of S nanosheet and carbon differs from Example 1 in that:

[0121] The iron isooctoate and dimethyl sulfoxide are mixed in a mass ratio of 1:1.2 to form a precursor liquid. The reaction temperature is 550°C.

[0122] Example 3

[0123] Example 3 provides a single-crystal Fe 1-x The composite of S nanosheet and carbon differs from Example 1 in that:

[0124] The iron isooctoate and dimethyl sulfoxide are mixed in a mass ratio of 1:0.6 to form a precursor liquid. The reaction temperature is 750°C.

[0125] Example 4

[0126] Example 4 provides a composite material, which differs from Example 1 in that the reaction temperature is 500°C.

[0127] Example 5

[0128] Example 5 provides a composite material, which differs from Example 1 in that the reaction temperature is 800°C.

[0129] Example 6

[0130] Example 6 provides a composite material, which differs from Example 1 in that the mass ratio of iron isooctoate and dimethyl sulfoxide is 1:0.5.

[0131] Example 7

[0132] Example 7 provides a composite material, which differs from Example 1 in that the mass ratio of iron isooctoate and dimethyl sulfoxide is 1:1.3.

[0133] Example 8

[0134] Example 8 provides a lithium battery negative electrode, which is prepared according to the following method:

[0135] The specific process of the lithium battery negative electrode is as follows:

[0136] The composite material in Example 1 is mixed with acetylene black and polyvinylidene fluoride, and is added to N-methyl pyrrolidone for magnetic stirring. After 24 hours, it is uniformly coated on a copper foil current collector, and is then transferred to a vacuum drying oven. First, it is dried at normal pressure and 70°C for 5 hours to remove macromolecular solvents, and then is dried at 100°C under vacuum for 10 hours. After the end of the drying, a disc with a diameter of 12 mm is cut out and is placed in a glove box.

[0137] Test Example 1

[0138] Test Example 1 performed microstructure and XRD analysis on the composite materials provided in Examples 1-8, and Raman analysis on the composite materials provided in Examples 1-3.

[0139] The SEM image of the composite material provided in Example 1 is as follows: Figure 2 As shown, the TEM image is as follows Figure 3 As shown. Figure 4 for Figure 3 Magnified view of the boundary structure of medium and nanosheets. Figure 5 for Figure 4 A magnified image of a graphene-like carbon coating. Figure 6 The single-crystal Fe in Example 1 of this application 1-x TEM diffraction pattern of S nanosheets and carbon composite material Figure 7 The XRD pattern and Raman diagram of the composite material provided in Example 1 of this application are shown below. Figure 8 As shown.

[0140] from Figure 7 It can be clearly seen that the diffraction peaks at 29.8°, 33.6°, 43.1°, 47.1°, and 53.1° are attributed to Fe, respectively. 1-x The (200), (206), (2012), (1017), and (220) crystal planes of S indicate the formation of Fe. 1-x S-structure. Figure 6 The TEM diffraction pattern shows a clear lattice diffraction pattern, proving that the prepared Fe... 1-x S nanosheets have a single-crystal structure. From Figure 8 Raman's work shows that at 2713.4cm... -1 The presence of a typical 2D peak for carbon materials, with an intensity ratio of approximately 2.4 between G and the 2D peak, indicates a graphene-like structural characteristic, which is consistent with... Figure 5 The TEM results are consistent. (By...) Figure 2 The SEM images show that carbon-coated single-crystal Fe 1-x S has a nanosheet structure, with nanosheets of 5–10 μm in size uniformly distributed in... Figure 2 middle. Figure 3 It can be seen that single-crystal Fe 1-x The length of the S nanosheets is approximately 2-8 μm. Figure 4 As can be seen, the boundaries of the nanosheets are covered by a carbon layer, as observed under magnification. Figure 5 It can be seen that the thickness of the coated carbon layer is about 6.39 nm and the number of layers is about 17. It has the characteristics of graphene and belongs to graphene-like carbon layers.

[0141] The SEM image of the composite material provided in Example 2 is as follows: Figure 9 As shown, the XRD pattern is as follows Figure 10 As shown, the Raman diagram is as follows:Figure 11 As shown.

[0142] from Figure 10 The diffraction peaks at 29.8°, 33.6°, 43.1°, 47.1°, and 53.1° can be attributed to Fe, respectively. 1-x The (200), (206), (2012), (1017), and (220) crystal planes of S indicate the formation of Fe. 1-x S-structure. From Figure 11 The Raman analysis plot shows that at 2715.5cm -1 The presence of a typical 2D peak for carbon materials, with an intensity ratio of approximately 2.6 between G and the 2D peak, indicates that it possesses graphene-like structural characteristics. Figure 8 In comparison, its higher intensity ratio of the G and 2D peaks indicates a greater number of graphene-like carbon layers. Figure 9 The SEM images show that carbon-coated single-crystal Fe 1-x S nanosheets are arranged in an interlaced pattern to form spherical clusters, with the nanosheets being approximately 5 μm in length. Single-crystal Fe can also be observed. 1-x S nanosheets are uniformly and densely coated with carbon layers.

[0143] The SEM image of the composite material provided in Example 3 is as follows: Figure 12 As shown, the XRD pattern is as follows Figure 13 As shown, the Raman diagram is as follows: Figure 14 As shown.

[0144] from Figure 13 The diffraction peaks at 29.8°, 33.6°, 43.1°, and 53.1° can be attributed to Fe, respectively. 1-x The (200), (206), (2012), and (220) crystal planes of S indicate the formation of Fe. 1-x S-structure. From Figure 14 The Raman analysis plot shows that at 2718.2 cm... -1 The presence of a typical 2D peak for carbon materials, with an intensity ratio of approximately 2.5 between G and the 2D peak, indicates that it possesses graphene-like structural characteristics. Figure 8 In comparison, its higher intensity ratio of the G and 2D peaks indicates a greater number of graphene-like carbon layers. Figure 12 The SEM images show that carbon-coated single-crystal Fe 1-x S nanosheets have been formed, with lengths ranging from 2 to 8 μm.

[0145] The SEM image of the composite material provided in Example 4 is shown below. Figure 15 As shown, the XRD pattern is as follows Figure 16 As shown.

[0146] from Figure 16 The XRD diffraction pattern shows that the diffraction peaks at 29.8°, 43.1°, 47.1°, and 53.1° are attributed to Fe, respectively. 1-x The diffraction peaks at 30.1°, 35.5°, 36.9°, 57°, 62.5°, and 74.1° are attributed to the (220), (311), (222), (511), (440), and (622) crystal planes of Fe3O4. Figure 15 This indicates that the nanoparticles present are Fe3O4. From Figure 15 The SEM images show that in addition to the nanosheet structure, nanoparticles were also formed, indicating that the morphology was not uniform.

[0147] The SEM image of the composite material provided in Example 5 is shown below. Figure 17 As shown, the XRD pattern is as follows Figure 18 As shown.

[0148] from Figure 18 The XRD diffraction pattern shows that the diffraction peaks at 30.1°, 36.9°, 57°, and 62.5° are attributed to the (220), (222), (511), and (440) crystal planes of Fe3O4, respectively. The diffraction peaks at 33.6°, 43.1°, 47.1°, and 53.1° are attributed to Fe... 1-x S has (206), (2012), (1017), and (220) crystal planes. Unlike the composition in Example 1, Example 5 contains not only Fe... 1-x S was also present, along with a small amount of FeS impurity. This is because, at excessively high temperatures, some Fe was completely sulfided, forming FeS, indicating inconsistencies in the composition of the obtained samples. From Figure 17 The SEM images show that nanosheet structures were also obtained under these conditions.

[0149] The SEM image of the composite material provided in Example 6 is shown below. Figure 19 As shown, the XRD pattern is as follows Figure 20 As shown.

[0150] from Figure 20 The XRD diffraction pattern shows that the diffraction peaks at 29.8°, 33.6°, 43.1°, and 53.1° are attributed to Fe, respectively. 1-x The (200), (206), (2012), and (220) crystal planes of S. The diffraction peaks at 35.5°, 36.9°, 57°, 62.5°, and 74.1° are attributed to the (311), (222), (511), (440), and (622) crystal planes of Fe3O4, respectively. Unlike the composition in Example 1, Example 6 contains not only Fe...1-x S was present, along with impurities such as Fe3O4, indicating uneven composition. Figure 19 The SEM images show that excess Fe reacts to form irregular Fe3O4 particles, indicating that the obtained sample has inconsistent composition and uneven morphology.

[0151] The SEM image of the composite material provided in Example 7 is as follows: Figure 21 As shown, the XRD pattern is as follows Figure 22 As shown.

[0152] from Figure 22 The XRD diffraction pattern shows that the diffraction peaks at 36.9°, 56.1°, and 62.5° are attributed to the (222), (511), and (440) crystal planes of Fe3O4, respectively. The diffraction peaks at 29.8°, 33.6°, 43.1°, 47.1°, and 53.1° are attributed to Fe... 1- x The S crystal planes are (200), (206), (2012), (1017), and (220). This indicates that Comparative Example 4 differs from Example 1 in composition, containing not only Fe... 1-x S also contained the impurity Fe3O4. From Figure 21 The SEM images show that when S is in excess, the resulting samples have inconsistent composition and uneven morphology.

[0153] Test Example 2

[0154] Test Example 2: Electrochemical performance testing was performed on the negative electrode of the battery provided in Example 8. Test method: The performance of the lithium battery negative electrode of Example 8 was tested using a constant current charge-discharge method. The test results are as follows: Figure 23-26 As shown.

[0155] from Figure 23 The diagram shows that the reversible capacity of the negative electrode of the battery provided in Example 8 after the first charge and discharge is 1473.5 mAh / g.

[0156] from Figure 24 It can be seen that at a charge / discharge rate of 1C, after 900 cycles, the reversible capacity of the negative electrode of the battery provided in Example 4 is as high as 1465.6 mAh / g, and the corresponding capacity retention rate is 119.3%.

[0157] from Figure 25 It can be seen that at a charge / discharge rate of 10C, after 10,000 cycles, the reversible capacity of the negative electrode of the battery provided in Example 8 is as high as 765.2 mAh / g, with a corresponding capacity retention rate of 94.8%.

[0158] from Figure 26It can be seen that the capacity obtained by the battery negative electrode at the charge-discharge rate of 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C and 20C is 1474.7 mAh / g, 1422.5 mAh / g, 1327.1 mAh / g, 1245.5 mAh / g, 1122.1 mAh / g, 957.5 mAh / g, 821.5 mAh / g and 674.4 mAh / g respectively, and especially when the charge-discharge rate returns to 0.1C, the reversible capacity is still as high as 1476.7 mAh / g.

[0159] By Figure 23 to Figure 26 It can be seen that the single-crystal Fe e1-x The battery negative electrode prepared from the composite material of FeS nanosheet and carbon has super-high lithium storage capacity, outstanding cycle life and rate performance.

[0160] In summary, the single-crystal Fe 1-x The composite material of FeS nanosheet and carbon has good structural stability and conductivity, and can be used for preparing a battery negative electrode to improve the battery performance.

[0161] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A single crystal Fe 1-x A method for producing a composite material of FeS nanosheets and carbon, characterized by comprising: The preparation method comprises the following steps: obtaining a precursor solution, wherein the precursor solution comprises an organic salt of iron and an organic solvent containing sulfur elements; The precursor solution is placed in a closed container and heated in a protective gas environment to convert the precursor solution into a gas phase and maintain for 5 min or more, and then cooled to room temperature to obtain the single crystal Fe 1-x S nanosheet and carbon composite material, 0 < x < 1; the organic salt of iron is selected from iron iso-octoate; and the organic solvent containing sulfur elements is selected from at least one of dimethyl sulfoxide, dimethyl sulfide or sulfolane; the temperature of the closed heating in a protective gas environment is 550-750 ℃; The composite material comprises the single-crystal Fe 1-x S nanosheets and a carbon nanocoating layer of the single-crystal Fe 1-x S nanosheets and a carbon nanocoating layer of the single-crystal Fe 2. The production method according to claim 1, characterized by, the precursor solution contains the iron iso-octoate and the dimethyl sulfoxide in a mass ratio of 1:0.6-1.

2.

3. The production method according to claim 2, characterized by, the time of the closed heating in a protective gas environment is 10-30 min.

4. A single crystal Fe 1-x A composite material of nanosheets of Fe The preparation method is prepared according to any one of claims 1-3.

5. The composite material of claim 4, wherein, The thickness of the carbon nano-coating layer is 5-10 nm.

6. The composite material of claim 4, wherein, The single crystal Fe 1-x The length of the S nanosheet is 2-8 μm.

7. A negative electrode sheet characterized by comprising: The raw material for forming the negative electrode sheet comprises the composite material according to any one of claims 4-6.

8. A lithium battery, characterized by The negative electrode sheet according to claim 7 is provided.

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