Composite negative electrode material, preparation method thereof, negative electrode sheet, battery and electronic device

Abstract

The present application relates to a kind of composite negative material and its preparation method, negative pole piece, battery and electronic device, the composite negative material includes MXene nanosheet, and NiMoO4 Nanorod in situ growth on the MXene nanosheet;The NiMoO4 Nanorod forms nanorod skeleton on the MXene nanosheet, to support the Mxene nanosheet;The MXene nanosheet is few-layer MXene nanosheet, and the layer number of the MXene nanosheet is ≤3 layers.The composite negative material has high capacity of NiMoO4 Material and high conductivity of MXene material, has excellent battery dynamics performance and electrochemical performance;In addition, the composite negative material obtained by the preparation method provided in the present application has stronger binding force, and the stability of the obtained battery is higher.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, and in particular to a composite negative electrode material and its preparation method, a negative electrode sheet, a battery, and an electronic device. Background Technology

[0002] In recent years, with the increasing maturity of lithium-ion batteries (LIBs), their application scope and demand have gradually expanded. However, lithium-ion batteries still face challenges such as limited lithium reserves, uneven distribution of lithium resources, and high costs. Therefore, given the large-scale market demand, finding a lower-cost, abundant, and safer energy storage system is imperative. Since sodium and lithium share similar physical and chemical properties, and sodium-ion batteries (SIBs) operate on very similar principles to LIBs, they are not only inexpensive but also benefit from the existing technological experience of mature lithium-ion batteries. Therefore, they hold promise as a next-generation rechargeable battery and an effective alternative to lithium-ion batteries. Among sodium-ion battery materials, the development of anode materials has been a major obstacle to commercialization. Traditional graphite anodes are not suitable for the insertion / deintercalation of sodium ions. Therefore, researching and exploring anode materials with high energy density and long cycle life is a crucial issue that needs to be addressed for sodium-ion batteries.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] In view of the above, this application provides a composite negative electrode material and its preparation method, a negative electrode sheet, a battery, and an electronic device to solve at least one problem existing in the background art.

[0005] The first aspect of the present invention provides a composite anode material, the composite anode material comprising MXene nanosheets and NiMoO4 nanorods grown in situ on the MXene nanosheets; the NiMoO4 nanorods form a nanorod framework on the MXene nanosheets to support the MXene nanosheets; the MXene nanosheets are few-layer MXene nanosheets, and the number of layers of the MXene nanosheets is ≤3.

[0006] Preferably, the MXene has the general formula M n+1 X n T x Wherein, M is selected from one or more transition metals chosen from Sc, Ti, V, Cr, or Mo; X is selected from C or N; T x The surface functional group is selected from one or more of hydroxyl, F, Cl and O; n is selected from 1, 2 or 3;

[0007] More preferably, the MXene is Ti3C2T. x .

[0008] Preferably, the length of the NiMoO4 nanorod is 5μm to 10μm, and the aspect ratio of the NiMoO4 nanorod is 12.5 to 100.

[0009] Preferably, the mass ratio of the NiMoO4 nanorods to the MXene nanosheets is (1-3):(0.86-4.2).

[0010] A second aspect of the present invention provides a method for preparing the composite negative electrode material provided in the first aspect of the present invention, the method comprising:

[0011] S1: Provides fewer layers of MXene;

[0012] S2: Dissolve the Ni source, molybdate, and the few-layer MXene obtained in step S1 in water, and perform a hydrothermal reaction to obtain the precursor product. Anneal the precursor product under an inert gas atmosphere to obtain the composite anode material.

[0013] Preferably, step S1 is as follows: LiF and hydrochloric acid are mixed, heated, Ti3AlC2 is added, etched, and ultrasonicated to obtain a few-layer Ti3C2T x .

[0014] Preferably, step S1 satisfies at least one of the following features (1) to (5):

[0015] (1) The ratio of the mass (g) of LiF to the volume (ml) of hydrochloric acid is 1:(2~200), and the concentration of hydrochloric acid is 7mol / L~11mol / L;

[0016] (2) The mass ratio of LiF to Ti3AlC2 is 1:(0.5~2);

[0017] (3) The heating method is water bath heating, the heating temperature is 25℃~35℃, and the heating time is 12h~24h;

[0018] (4) The etching method is magnetic stirring etching, the etching time is 24h to 48h, and the etching process also includes a washing step.

[0019] (5) The ultrasound is ice bath ultrasound; the ultrasound is performed in an inert gas atmosphere, and the inert gas is selected from at least one of argon, nitrogen, helium and neon; the ultrasound time is 1h to 2h; the ultrasound is followed by centrifugation and drying steps.

[0020] Preferably, step S2 satisfies at least one of the following features (1) to (7):

[0021] (1) The Ni source is selected from at least one of nickel nitrate, nickel chloride, and nickel acetate;

[0022] (2) The molybdate is selected from at least one of sodium molybdate, ammonium molybdate, and potassium molybdate;

[0023] (3) The molar ratio of the Ni source to the molybdate is 1:(0.5~2);

[0024] (4) The concentration of the few-layer MXene in the water is 1 mg / ml to 4 mg / ml;

[0025] (5) In the precursor product, the molar ratio of Ni to the few-layer MXene is (1-3):(2-5);

[0026] (6) The temperature of the hydrothermal reaction is 100℃~160℃, and the time of the hydrothermal reaction is 5h~8h; after the hydrothermal reaction is completed, the steps of centrifugation washing and drying are also included.

[0027] (7) The annealing heating rate is 3℃ / min to 5℃ / min, the annealing temperature is 450℃ to 600℃, and the annealing time is 2h to 5h; the inert gas is selected from at least one of helium, neon, argon and nitrogen.

[0028] A third aspect of the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode active material, wherein the negative electrode active material is a composite negative electrode material provided in the first aspect of the present invention or a composite negative electrode material prepared by the preparation method provided in the second aspect of the present invention.

[0029] A fourth aspect of the present invention provides a battery comprising the negative electrode sheet provided in the third aspect of the present invention.

[0030] A fifth aspect of the present invention provides an electronic device comprising the battery provided in the fourth aspect of the present invention.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention provides a composite anode material, its preparation method, an anode sheet, a battery, and an electronic device. The composite anode material forms a nanosheet structure supported by a nanorod framework by in-situ bonding of few-layer MXene nanosheets with NiMoO4 bimetallic nanorods, thus combining the high capacity of NiMoO4 with the high conductivity of MXene. This composite anode material utilizes the Ni / Ni ratio of NiMoO4... 2+ with Mo / Mo 6+The reversible redox reaction between the two phases results in a high theoretical capacity. Due to the high conductivity of MXene itself, the composite negative electrode material structure is rich in ion and charge transfer channels, which greatly reduces the charge transfer resistance between the solid and liquid phases and thus accelerates the charge transfer rate inside the battery. Furthermore, since this invention uses MXene material with a few-layer nanosheet structure, it not only has excellent conductivity but also does not easily form interlayer stacking, thereby significantly improving the kinetic performance of the battery.

[0033] Furthermore, the composite anode material provided by this invention is prepared by first using a hydrothermal method to bond NiMoO4 and Mxene through van der Waals forces to form a precursor product, and then by medium-temperature sintering to form a NiMoO4 / Mxene composite material. This achieves in-situ bonding between NiMoO4 nanorods and Mxene with a few-layer nanosheet structure, allowing NiMoO4 nanorods to grow in situ on the few-layer Mxene to form a nanorod framework to support the few-layer Mxene nanosheets. As a result, the bonding force between the prepared composite materials is stronger than that of the precursor product, significantly improving the stability of the battery using it as the anode active material. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0035] Figure 1 The Ti3C2T prepared in Example 2 of this invention x SEM image of the sample.

[0036] Figure 2 This is a SEM image of the NiMoO4 nanorods prepared in Comparative Example 2 of this invention.

[0037] Figure 3 The Ti3C2T prepared in Example 2 of this application x SEM image of the / NiMoO4 composite material. Detailed Implementation

[0038] To make the technical solution and beneficial effects of the present invention more apparent and understandable, a detailed description is provided below by listing specific embodiments. The accompanying drawings are not necessarily drawn to scale, and local features may be enlarged or reduced to more clearly show the details of the local features. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional experimental conditions. Unless otherwise specified, all reagents and raw materials used in this invention are commercially available.

[0039] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be practiced without one or more of these details. In other instances, to avoid confusion with this application, some technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and steps described in detail.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0041] To fully understand this application, detailed steps and structures will be presented in the following description to illustrate the technical solution of this application. Preferred embodiments of this application are described in detail below; however, in addition to these detailed descriptions, this application may have other implementation methods.

[0042] Unless otherwise defined, the technical and scientific terms used in this application have the same meanings as those in the technical and scientific field to which this application pertains.

[0043] Unless otherwise specified, the techniques or conditions described in the following embodiments are generally performed in accordance with conventional techniques or conditions described in the literature in this field, or in accordance with the product manual and the manufacturer's recommendations. All numerical ranges in the following embodiments include endpoint values.

[0044] MXenes, as an emerging two-dimensional material, can be etched with hydrofluoric acid to form nanosheets containing functional groups of hydroxyl, oxygen, and fluorine. The diverse chemical composition and abundant functional groups give MXenes excellent interfaces and high conductivity, thus demonstrating great potential in the energy storage field. However, compared with traditional carbon materials, the electrochemical performance of MXenes still needs continuous improvement. Currently, although sulfur-doped MXenes technology is widely used to improve its electrochemical performance, the use of H2S as the sulfur source is highly toxic, environmentally unfriendly, and difficult to recycle. Patent CN109786743B improves the sodium storage performance of MXenes through sulfur doping, but the improvement in kinetics and capacity is not significant. Furthermore, during sodium ion insertion / extraction, due to van der Waals forces and hydrogen bonds, the nanosheets of MXene materials with multilayer nanosheet structures tend to stack, thus hindering sodium ion diffusion.

[0045] On the other hand, ternary metal molybdates, as electrode materials, have also attracted researchers' attention due to their high theoretical capacity and tunable morphology. However, molybdates themselves have poor conductivity and undergo significant volume expansion during cycling, making them prone to structural collapse and thus leading to a deterioration in cycle life. Patent CN110350184B synthesizes NiMoO4 using Ni-MOF as a substrate, which solves the problem of poor conductivity, but does not provide good protection for the structure. Patent CN109911947B produces core-shell structured NiCo2O4@NiMoO4 materials to ensure structural variation, but the core-shell structure increases the ion transport distance, and the thickness of the core and shell layers cannot be precisely controlled.

[0046] In view of the above, the present invention provides the following technical solution:

[0047] [Composite Anode Materials]

[0048] The first aspect of the present invention provides a composite anode material, the composite anode material comprising MXene nanosheets and NiMoO4 nanorods grown in situ on the MXene nanosheets; the NiMoO4 nanorods form a nanorod framework on the MXene nanosheets to support the MXene nanosheets; the MXene nanosheets are few-layer MXene nanosheets, and the number of layers of the MXene nanosheets is ≤3.

[0049] The composite anode material provided by this invention forms a nanosheet structure supported by a nanorod framework by in-situ bonding of few-layer MXene nanosheets with NiMoO4 bimetallic nanorods, thus combining the high capacity of NiMoO4 with the high conductivity of MXene. This composite anode material utilizes the Ni / Ni ratio of NiMoO4... 2+ with Mo / Mo6+ The reversible redox reaction between the two phases results in a high theoretical capacity. Due to the high conductivity of MXene itself, the composite negative electrode material structure is rich in ion and charge transfer channels, which greatly reduces the charge transfer resistance between the solid and liquid phases and thus accelerates the charge transfer rate inside the battery. Furthermore, since this invention uses MXene material with a few-layer nanosheet structure, it not only has excellent conductivity but also does not easily form interlayer stacking, thereby significantly improving the kinetic performance of the battery.

[0050] In this invention, by selecting MXene nanosheets with ≤3 layers, the severe self-stacking phenomenon caused by a large number of MXene nanosheet layers can be avoided. This effectively solves the problem that when combined with NiMoO4 nanorods, the nanorods only combine on the surface of the MXene material and are difficult to enter the middle stacking part, thus failing to support the composite structure and affecting the cycle performance of the battery.

[0051] In some embodiments, the MXene has the general formula M n+1 X n T x Wherein, M is selected from one or more transition metals chosen from Sc, Ti, V, Cr, or Mo; X is selected from C or N; T x The surface functional group is selected from one or more of hydroxyl, F, Cl and O; n is selected from 1, 2 or 3.

[0052] In some implementations, the MXene is Ti3C2T x .

[0053] In some embodiments, the length of the NiMoO4 nanorod is 5 μm to 10 μm, such as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In this invention, when the length of the NiMoO4 nanorods is within the above-mentioned range, it can avoid the problem that the nanorod skeleton is not effectively formed due to the length being too small, which would weaken its support effect on the MXene material and affect the capacity retention rate of the battery; it can also avoid the problem of unevenness and easy breakage during material composite due to the length of the nanorods being too long.

[0055] In some embodiments, the aspect ratio of the NiMoO4 nanorods is 12.5 to 100, for example, 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, 35, 37.5, 40, 42.5, 45, 47.5, 50, 52.5, 55, 57.5, 60, 62.5, 65, 67.5, 70, 72.5, 75, 77.5, 80, 82.5, 85, 87.5, 90, 92.5, 95, 97.5 or 100, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0056] In this invention, when the aspect ratio of the NiMoO4 nanorods is within the above-mentioned range, it can avoid the problem that a large number of nanorods are exposed during material composite due to an excessively small aspect ratio, which weakens the effect of MXene nanosheets in inhibiting the expansion of NiMoO4 nanorods, leading to structural collapse and deterioration of cycle life; it can also avoid the problem of unevenness and easy breakage during material composite due to an excessively large aspect ratio.

[0057] In some embodiments, the mass ratio of the NiMoO4 nanorods to the MXene nanosheets is (1-3):(0.86-4.2), for example 1:0.86, 1:1, 1:2, 1:3, 1:4, 1:4.2, 2:0.86, 2:1, 2:3, 2:4.2, 3:0.86, 3:1, 3:2, 3:4 or 3:4.2, but is not limited to the listed ratios. Other unlisted ratios within the range are also applicable.

[0058] In this invention, when the mass ratio of the NiMoO4 nanorods to the MXene nanosheets is within the above-mentioned range, it can avoid the problem that an excessively large proportion of MXene nanosheets would prevent the nanorods from providing effective support, causing accumulation problems and hindering sodium ion diffusion. It can also avoid the problem that an excessively large proportion of NiMoO4 nanorods would lead to a decrease in the conductivity of the material, and that the relatively small proportion of MXene material during cycling would not effectively suppress the volume expansion of the nanorods, leading to structural collapse and a deterioration in cycle life.

[0059] [Preparation Method of Composite Anode Materials]

[0060] A second aspect of the present invention provides a method for preparing the composite negative electrode material provided in the first aspect of the present invention, the method comprising:

[0061] S1: Provides fewer layers of MXene;

[0062] S2: Dissolve the Ni source, molybdate, and the few-layer MXene obtained in step S1 in water, and perform a hydrothermal reaction to obtain the precursor product. Anneal the precursor product under an inert gas atmosphere to obtain the composite anode material.

[0063] In this invention, a hydrothermal method is first used to bond NiMoO4 and Mxene through van der Waals forces to form a precursor product. Then, a NiMoO4 / Mxene composite material is formed by medium-temperature sintering. This achieves in-situ bonding between NiMoO4 nanorods and Mxene with a few-layer nanosheet structure, allowing NiMoO4 nanorods to grow in situ on the few-layer Mxene to form a nanorod framework to support the few-layer Mxene nanosheets. As a result, the bonding force between the prepared composite material is stronger than that of the precursor product, significantly improving the stability of the battery using it as the negative electrode active material.

[0064] In some embodiments, step S1 is as follows: LiF and hydrochloric acid are mixed, heated, Ti3AlC2 is added, etched, and ultrasonicated to obtain a few-layer Ti3C2T x .

[0065] In some embodiments, in step S1, the ratio of the mass (g) of LiF to the volume (ml) of hydrochloric acid is 1:(2-200), for example 1:2, 1:20, 1:40, 1:60, 1:80, 1:100, 1:120, 1:140, 1:160, 1:180 or 1:200, but is not limited to the listed ratios. Other unlisted ratios within the range are also applicable.

[0066] In some embodiments, in step S1, the concentration of hydrochloric acid is 7 mol / L to 11 mol / L, for example, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L or 11 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, in step S1, the mass ratio of LiF to Ti3AlC2 is 1:(0.5 to 2), for example 1:0.5, 1:1, 1:1.5 or 1:2, but not limited to the listed ratios. Other unlisted ratios within the range are also applicable.

[0068] In some embodiments, in step S1, the heating method is water bath heating, and the heating temperature is 25℃~35℃, such as 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃ or 35℃, but not limited to the listed values, and other unlisted values ​​within the range are also applicable; the heating time is 12h~24h, such as 12h, 14h, 16h, 18h, 20h, 22h or 24h, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, in step S1, the etching method is magnetic stirring etching, and the etching time is 24h to 48h, such as 24h, 28h, 32h, 36h, 40h, 44h or 48h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, step S1 further includes a washing step after etching, wherein the washing is centrifugal washing until pH≈6.

[0071] In some embodiments, in step S1, the ultrasound is ice bath ultrasound; the ultrasound is performed in an inert gas atmosphere, the inert gas being selected from at least one of argon, nitrogen, helium, and neon; the ultrasound duration is 1 to 2 hours, for example 1 hour, 1.5 hours, or 2 hours, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, step S1 further includes centrifugation and drying after ultrasounding. The centrifugation time is 0.5h to 1h; the drying is freeze drying, and the drying time is 24h to 36h, for example, 24h, 28h, 32h or 36h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, in step S2, the Ni source is selected from at least one of nickel nitrate, nickel chloride, and nickel acetate.

[0074] In some embodiments, in step S2, the molybdate is selected from at least one of sodium molybdate, ammonium molybdate, and potassium molybdate.

[0075] In some embodiments, in step S2, the molar ratio of the Ni source to the molybdate is 1:(0.5 to 2), for example 1:0.5, 1:1, 1:1.5 or 1:2, but not limited to the listed ratios. Other unlisted ratios within the range are also applicable.

[0076] In some embodiments, in step S2, the concentration of the few-layer MXene in the water is 1 mg / ml to 4 mg / ml, for example, 1 mg / ml, 2 mg / ml, 3 mg / ml or 4 mg / ml, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, in step S2, the molar ratio of Ni to the few-layer MXene in the precursor product is (1-3):(2-5), for example 1:2, 1:3, 1:4, 1:5, 2:2, 2:3, 2:5, 3:2, 3:4 or 3:5, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, in step S2, the temperature of the hydrothermal reaction is 100℃ to 160℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or 160℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable; the time of the hydrothermal reaction is 5h to 8h, for example, 5h, 6h, 7h or 8h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, step S2 further includes centrifugal washing and drying after the hydrothermal reaction is completed. The washing consists of 3 to 6 washes with water followed by 2 to 5 washes with ethanol, for example, 3 washes with water followed by 2 washes with ethanol. The drying temperature is 50°C to 80°C, for example, 50°C, 60°C, 70°C, or 80°C, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The drying time is 10 to 12 hours, for example, 10 hours, 11 hours, or 12 hours, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, in step S2, the heating rate of the annealing is 3°C / min to 5°C / min, for example, 3°C / min, 4°C / min, or 5°C / min, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The annealing temperature is 450°C to 600°C, for example, 450°C, 500°C, 550°C, or 600°C, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The annealing time is 2h to 5h, for example, 2h, 3h, 4h, or 5h, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. The inert gas is selected from at least one of helium, neon, argon, and nitrogen.

[0081] In this invention, the size of the NiMoO4 nanorods can be controlled by changing the amount of molybdate added in step S2 and the process parameters (such as hydrothermal reaction temperature and time); the size, length, aspect ratio of the NiMoO4 nanorods, and the number of layers of the MXene nanosheets can all be obtained directly or indirectly by scanning electron microscopy (SEM).

[0082] [Negative electrode plate]

[0083] A third aspect of the present invention provides a negative electrode sheet, the negative electrode sheet comprising a negative electrode active material, wherein the negative electrode active material is a composite negative electrode material provided in the first aspect of the present invention or a composite negative electrode material prepared by the preparation method provided in the second aspect of the present invention.

[0084] The negative electrode sheet includes a negative electrode current collector and a layer of negative electrode active material disposed on the negative electrode current collector. The negative electrode current collector can be aluminum foil, copper foil, titanium foil, nickel foil, iron foil, zinc foil, etc. The negative electrode active material layer includes negative electrode active material. In this invention, the negative electrode active material is the negative electrode material provided in the second aspect of this invention.

[0085] The negative electrode active material layer may also include one or both selected from conductive agents and binders. Conductive agents are used to improve the electrode conductivity. Examples of negative electrode conductive agents include conductive carbon black, conductive graphite, vapor-deposited carbon fiber (VGCF), carbon nanotubes, and graphene. The binder in the negative electrode improves the adhesion between the negative electrode active material particles and between the negative electrode active material particles and the current collector. Examples of negative electrode binders include polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC-Na), cyclodextrin, gelatin, polyvinyl alcohol, polyacrylate, and acrylonitrile copolymers. The mass ratio of the components in the negative electrode active material layer can be conventional.

[0086] This application does not impose any particular limitation on the preparation method of the negative electrode sheet; any preparation method known in the art can be used, as long as it achieves the purpose of this application. For example, the preparation method of the negative electrode sheet includes, but is not limited to, the following steps: dispersing and mixing the negative electrode active material, conductive agent, and binder in a solvent to form a uniform negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector; and obtaining the negative electrode sheet after drying, cold pressing, cutting, slitting, and re-drying. The solvent for the negative electrode slurry can be a conventional solvent in the art, such as deionized water.

[0087] It should be understood that, since the negative electrode sheet provided in this application includes a negative electrode active material, which is the composite negative electrode material provided in the first aspect of the present invention or the composite negative electrode material prepared by the preparation method provided in the second aspect of the present invention, the beneficial effects of the composite negative electrode material and its preparation method described in any of the above embodiments are applicable to the negative electrode sheet.

[0088] [Battery]

[0089] A fourth aspect of the present invention provides a battery comprising the negative electrode sheet provided in the third aspect of the present invention.

[0090] In some embodiments, the battery can be a secondary battery or a primary battery, preferably a secondary battery. For example, the battery can be a sodium-ion battery, but it is not limited to this. The battery structures of this application include, but are not limited to, pouch-type sodium-ion batteries, square hard-case batteries, or cylindrical hard-case batteries.

[0091] In some embodiments, the battery further includes a positive electrode, an electrolyte, and a separator. Typically, a battery includes a positive electrode, a negative electrode, an electrolyte, and a separator, with the separator disposed between the positive and negative electrodes. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and extracting. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0092] The positive electrode sheet includes a positive current collector and a layer of positive active material disposed on the positive current collector. The positive current collector can be aluminum foil, copper foil, titanium foil, nickel foil, iron foil, zinc foil, etc. The positive active material layer includes the positive active material. The positive active material suitable for this invention can be any known positive active material that can be used in sodium-ion batteries, capable of reversibly inserting and de-intercalating sodium ions. The positive active material can be a sodium-ion positive active material commonly used in the art, preferably selected from sodium-iron composite oxides (such as NaFeO2), sodium-cobalt composite oxides (such as NaCoO2), sodium-chromium composite oxides (such as NaCrO2), sodium-manganese composite oxides (such as NaMnO2), sodium-nickel composite oxides (such as NaNiO2), and sodium-nickel-titanium composite oxides (such as NaNiO2). .5 Ti 0.5 O2), sodium-nickel-manganese composite oxides (such as NaNi) 0.5 Mn 0.5 O2), sodium iron manganese composite oxides (such as Na) 2 / 3 Fe 1 / 3 Mn 2 / 3 O2), sodium-nickel-cobalt-manganese composite oxides (such as NaNi) 1 / 3 Co 1 / 3 Mn 1 / 3 One or more of the following: O2), sodium iron phosphate (such as NaFePO4), sodium manganese phosphate (such as NaMnPO4), and sodium cobalt phosphate (such as NaCoPO4).

[0093] The positive electrode active material layer may also include one or both selected from conductive agents and binders. Conductive agents are used to improve the electrode conductivity. Examples of conductive agents for the positive electrode include one or more of conductive carbon black, carbon fiber (CF), acetylene black, Ketjen black, graphene, carbon nanotubes, and carbon microspheres. The binder for the positive electrode improves the adhesion between the positive electrode active material particles and between the positive electrode active material particles and the current collector. Examples of binders for the positive electrode include at least one selected from fluorinated resins, polypropylene resins, fiber-type binders, rubber-type binders, and polyimide-type binders. The mass ratio of the components in the positive electrode active material layer can be conventional.

[0094] The positive electrode active material layer is obtained by coating a positive electrode slurry containing the components of the positive electrode active material layer and a solvent onto a positive electrode current collector, followed by rolling and slitting. The solvent for the positive electrode slurry can be N-methylpyrrolidone (NMP).

[0095] The separator can be a polymer porous separator, an inorganic porous separator, or a polymer-inorganic composite porous separator. Polymer porous separators include single-layer polymer porous separators and multi-layer polymer porous separators.

[0096] The electrolyte typically comprises a solvent and a sodium salt. The electrolyte suitable for this invention can be conventional; for example, the solvent can be one or more selected from dimethyl carbonate (DMC), propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), or 1,4-butylpropyl carbonate, more preferably one or more selected from PC, EC, and EMC. The sodium salt can be one or more selected from sodium tetrafluoroborate, sodium hexafluorophosphate, sodium trifluoromethanesulfonate, or sodium perchlorate.

[0097] The battery of this application also includes a packaging shell for housing the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the art for sodium-ion batteries. This application does not limit the aforementioned other components. This application does not impose any particular limitation on the packaging shell; it can be a packaging shell known in the art, as long as it achieves the purpose of this application.

[0098] This invention does not impose any special restrictions on the battery preparation method; any technical solution known to those skilled in the art for preparing a battery, such as a secondary battery, from a negative electrode material can be used.

[0099] It should be understood that, since the battery provided in this application includes the negative electrode sheet described in the third aspect of the present invention, the beneficial effects of the composite negative electrode material described in any of the above embodiments are applicable to the battery.

[0100] [Electronic Devices]

[0101] A fifth aspect of the present invention provides an electronic device comprising the battery provided in the fourth aspect of the present invention.

[0102] The application of the battery in this application is not particularly limited, and it can be used in any electronic device known in the prior art. In some embodiments, the battery of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, drones, and sodium-ion capacitors, etc.

[0103] It should be understood that since the electronic device provided in this application includes the battery described in the fourth aspect of the present invention, the beneficial effects of the composite negative electrode material described in any of the above embodiments are applicable to the electronic device.

[0104] The method of the present invention will be described below through specific embodiments. It should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0105] Example 1

[0106] Step S101: First, place 1g of lithium fluoride (LiF) and 40ml of 9M hydrochloric acid (HCl) in a plastic beaker / PTFE bottle and stir magnetically for 30min. Transfer the plastic bottle to a 35℃ water bath. After the temperature stabilizes, add 1g of titanium aluminum carbide (Ti3AlC2, MAX phase) in batches and stir magnetically for 36h for etching. After the water bath reaction is complete, centrifuge and wash the product until pH≈6, sonicate in an ice bath under argon atmosphere for 1h, centrifuge for 1h, and freeze-dry for 36h to obtain a few-layer Ti3C2T x (i.e., few-layer MXene).

[0107] Step S102: Mix 2 mmol of nickel nitrate (Ni(NO3)2·6H2O) with 2 mmol of sodium molybdate (Na2MoO4·2H2O) and the few-layer Ti3C2T obtained in step S101. x Dissolve in 60 mL of deionized water (deionized water contains a small layer of Ti3C2T) xThe concentration of the precursor was 4 mg / mL. After magnetic stirring for 1 hour, the mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally reacted at 160 °C for 8 hours. After the hydrothermal reaction, the solution was centrifuged, washed three times with water and twice with ethanol, and dried at 60 °C for 12 hours to obtain the precursor product (Ti3C2T in the precursor product). x The molar ratio of NiMoO4 to NiMoO4 is 2:1. Under an argon atmosphere, at 3℃ for [time missing] min... -1 Ti3C2T was obtained by annealing at 450℃ for 2 hours. x / NiMoO4 composite material (i.e. composite anode material).

[0108] Example 2

[0109] The only difference between Example 2 and Example 1 is that in step S102, the Ti3C2T layer in the deionized water is... x The concentration was 2 mg / mL; the aspect ratio of NiMoO4 nanorods ranged from 35 to 40, and the length was 7 μm; the obtained precursor product contained Ti3C2T x The molar ratio of NiMoO4 to NiMoO4 is 1:1.

[0110] Example 3

[0111] The only difference between Example 3 and Example 1 is that in step S102, the amount of nickel nitrate added is 4 mmol; the amount of sodium molybdate added is 4 mmol; and the amount of Ti3C2T in deionized water is... x The concentration was 2 mg / mL; the obtained precursor product contained Ti3C2T x The molar ratio of NiMoO4 to NiMoO4 is 1:2.

[0112] Example 4

[0113] The only difference between Example 4 and Example 2 is that the length of the NiMoO4 nanorod is 5 μm.

[0114] Example 5

[0115] The only difference between Example 5 and Example 2 is that the aspect ratio of the NiMoO4 nanorods is 12.5.

[0116] Comparative Example 1

[0117] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 only includes step S101 in Example 1, to obtain the few-layer Ti3C2T x As a negative electrode material.

[0118] Comparative Example 2

[0119] Step S102*: Dissolve 2 mmol of nickel nitrate (Ni(NO3)2·6H2O) and 2 mmol of sodium molybdate (Na2MoO4·2H2O) in 60 mL of deionized water. After magnetic stirring for 1 h, transfer the solution to a 100 mL polytetrafluoroethylene-lined reactor and hydrothermally react at 160 °C for 8 h. After the hydrothermal reaction, centrifuge, wash three times with water and twice with ethanol, and dry at 60 °C for 12 h to obtain the precursor product. Then, under an argon atmosphere, heat the precursor product at 3 °C for 1 min. -1 NiMoO4 nanorods (i.e., anode materials) were obtained by annealing at 450℃ for 2 hours.

[0120] Comparative Example 3

[0121] The only difference between Comparative Example 3 and Example 1 is that in step S102, the few-layer Ti3C2T in the deionized water... x The concentration is 10 mg / mL.

[0122] Comparative Example 4

[0123] The only difference between Comparative Example 4 and Example 1 is that in step S102, the deionized water contains a few layers of Ti3C2T. x The concentration was 2 mg / mL; and the annealing step was not included, and the resulting precursor product was used as the negative electrode material only.

[0124] Electrochemical performance testing

[0125] Preparation of sodium-ion batteries:

[0126] (1) Preparation of negative electrode sheet: The negative electrode materials prepared in Examples 1-5 and Comparative Examples 1-4 above are used as negative electrode active materials, carbon black is used as a conductive agent, and CMC is used as a binder. They are mixed in a ratio of negative electrode active material: conductive agent: binder = 8:1:1 and uniformly coated on negative electrode current collector (Cu foil) on a coating machine. The negative electrode sheet is then formed by rolling and cutting.

[0127] (2) Preparation of positive electrode: Sodium metal sheet is used as positive electrode;

[0128] (3) Separator: Glass fiber diaphragm is selected as the diaphragm;

[0129] (4) Electrolyte: The electrolyte is prepared by dissolving 1.0 mol / L NaPF6 in diethylene glycol dimethyl ether;

[0130] (5) Battery assembly: Assemble the negative electrode, separator and positive electrode in sequence and immerse them in electrolyte. Assemble the CR2032 button cell in an argon glove box.

[0131] The performance of CR2032 button batteries using the negative electrode materials prepared in Examples 1-5 and Comparative Examples 1-4 as negative electrode active materials was tested. The test results are shown in Table 1.

[0132] 1. Testing of initial discharge capacity, initial charge capacity, and initial coulombic efficiency: Using the Wuhan Landian CT200A battery testing system, the battery was discharged to 0V at a constant current density of 0.1A / g under 25℃ conditions, and the discharge capacity at this point was recorded as the initial discharge capacity; then, it was charged to 3V at a constant current density of 0.1A / g, and the charging capacity at this point was recorded as the initial charge capacity; Initial coulombic efficiency = Initial charge capacity / Initial discharge capacity * 100%.

[0133] 2. 100-cycle capacity retention test: Using the Wuhan Landian CT200A battery testing system, the battery was discharged to 0V at a constant current density of 0.1A / g under 25℃ conditions, and then charged to 3V at a constant current density of 0.1A / g. The charging capacity at this point was recorded as the first cycle charging capacity. This constitutes one cycle. After repeating this process for 100 cycles, the charging capacity of the 100th cycle was recorded. The capacity retention rate = charging capacity of the 100th cycle / charging capacity of the first cycle * 100%.

[0134] Table 1

[0135]

[0136]

[0137] As shown in Table 1, comparing Example 2 with Example 4 reveals that the 100-cycle capacity retention of Example 4 decreased by 10% compared to Example 2. This is because the composite NiMoO4 nanorods in Example 4 are short rods of 5 μm. Short rods prevent the formation of an internally connected framework, resulting in poorer support for Mxene and reduced effectiveness of MXene in inhibiting nanorod volume expansion, thus affecting cycle life. Comparing Example 2 with Example 5, Example 5 has a higher initial efficiency than Example 2, but its capacity retention is significantly lower. This is because the NiMoO4 nanorods in Example 5 have a smaller aspect ratio, causing most of the nanorods to be exposed on the surface of the Mxene nanosheets during composite formation. This results in more active sites and thus a better initial efficiency. However, it also weakens the effect of MXene nanosheets in inhibiting NiMoO4 nanorod expansion, leading to a lower capacity retention. Comparing Comparative Example 1 with Examples 1-5 reveals that only Ti3C2T... xThe charge / discharge capacity of the negative electrode material is significantly lower than that of the negative electrode material in the examples. Comparing Comparative Example 2 with Examples 1-5 reveals that after 100 cycles at a current density of 0.1 A / h, the capacity retention of the negative electrode material obtained in Comparative Example 2 is only about 20%, far lower than the 90% of Example 2, and the initial coulombic efficiency is also significantly reduced. Comparing Comparative Example 3 with Examples 1-5 reveals that significantly increasing the added Ti3C2T... x After material quality adjustments, the initial charge-discharge capacity of the resulting anode materials significantly decreased. Furthermore, comparing Examples 1-5 revealed that Example 2 exhibited the best initial coulombic efficiency and capacity retention after 100 cycles. This indicates that while higher NiMoO4 content leads to a higher initial discharge specific capacity, excessive NiMoO4 can cause structural instability. By controlling the ratio of MXene to NiMoO4 to that in Example 2, the resulting battery demonstrated superior electrochemical performance. A direct comparison between Comparative Example 4 and Example 2 revealed that high-temperature sintering of the obtained precursor products can form a NiMoO4 / MXene composite material, thereby achieving in-situ bonding of NiMoO4 nanorods with MXene possessing a few-layer nanosheet structure, resulting in higher stability of the obtained anode material.

[0138] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations included in the claims. Various modifications and changes can be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments can be arbitrarily combined to form other embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments only illustrate several implementations of the present invention and do not limit the scope of protection of this patent.

Claims

1. A method for preparing a sodium-ion battery composite negative electrode material, characterized in that, The sodium-ion battery composite anode material includes MXene nanosheets and NiMoO4 nanorods grown in situ on the MXene nanosheets; the NiMoO4 nanorods form a nanorod framework on the MXene nanosheets to support the MXene nanosheets; the MXene nanosheets are few-layer MXene nanosheets, and the number of layers of the MXene nanosheets is ≤3. The MXene is Ti3C2T x ;T x The functional group is a surface functional group, which is selected from one or more of hydroxyl, F, Cl and O; The mass ratio of the NiMoO4 nanorods to the MXene nanosheets is (1~3):(0.86~4.2), and the aspect ratio of the NiMoO4 nanorods is 35~40; The preparation method includes: S1: Provides fewer layers of MXene; S2: Dissolve the Ni source, molybdate, and the few-layer MXene obtained in step S1 in water, and perform a hydrothermal reaction to obtain the precursor product. Anneal the precursor product under an inert gas atmosphere to obtain the sodium-ion battery composite anode material.

2. The preparation method according to claim 1, characterized in that, The length of the NiMoO4 nanorods is 5μm~10μm.

3. The preparation method according to claim 1, characterized in that, Step S1 is as follows: LiF and hydrochloric acid are mixed, heated, Ti3AlC2 is added, etched, and ultrasonicated to obtain a few-layer Ti3C2T. x .

4. The preparation method according to claim 3, characterized in that, Step S1 satisfies at least one of the following features (1) to (5): (1) The ratio of the mass of LiF (g) to the volume of hydrochloric acid (ml) is 1:(2~200), and the concentration of the hydrochloric acid is 7mol / L~11mol / L; (2) The mass ratio of LiF to Ti3AlC2 is 1:(0.5~2); (3) The heating method is water bath heating, the heating temperature is 25℃~35℃, and the heating time is 12h~24h; (4) The etching method is magnetic stirring etching, the etching time is 24h~48h, and the etching process also includes a washing step; (5) The ultrasound is ice bath ultrasound; the ultrasound is performed in an inert gas atmosphere, and the inert gas is selected from at least one of argon, helium and neon; the ultrasound time is 1h to 2h; the ultrasound is followed by centrifugation and drying steps.

5. The preparation method according to claim 1, characterized in that, Step S2 satisfies at least one of the following features (1) to (7): (1) The Ni source is selected from at least one of nickel nitrate, nickel chloride, and nickel acetate; (2) The molybdate is selected from at least one of sodium molybdate, ammonium molybdate, and potassium molybdate; (3) The molar ratio of the Ni source to the molybdate is 1:(0.5~2); (4) The concentration of the few-layer MXene in the water is 1 mg / ml to 4 mg / ml; (5) In the precursor product, the molar ratio of Ni to the few-layer MXene is (1~3):(2~5); (6) The temperature of the hydrothermal reaction is 100℃~160℃, and the time of the hydrothermal reaction is 5h~8h; after the hydrothermal reaction is completed, the steps of centrifugation, washing and drying are also included; (7) The annealing heating rate is 3℃ / min~5℃ / min, the annealing temperature is 450℃~600℃, and the annealing time is 2h~5h; the inert gas is selected from at least one of helium, neon and argon.

6. A sodium-ion battery negative electrode sheet, characterized in that, The sodium-ion battery negative electrode sheet includes a negative electrode active material, which is a sodium-ion battery composite negative electrode material prepared by the preparation method according to any one of claims 1-5.

7. A sodium-ion battery, characterized in that, The sodium-ion battery includes the sodium-ion battery negative electrode sheet as described in claim 6.

8. An electronic device, characterized in that, The electronic device includes the sodium-ion battery as described in claim 7.

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