CN117374210A - Battery negative electrode material, preparation method thereof, battery negative electrode sheet preparation method and battery - Google Patents

Abstract

The invention provides a battery negative electrode material, a preparation method thereof, a battery negative electrode sheet preparation method and a battery, wherein the battery negative electrode material preparation method comprises the following steps: preparing graphene aqueous dispersion liquid, ferric salt solution and vanadate solution; adding ferric salt solution and vanadate solution into graphene aqueous dispersion liquid in sequence to obtain mixed solution, and regulating the mixed solutionLiquid to target pH; carrying out hydrothermal reaction on the mixed solution according to preset conditions to obtain black precipitate; collecting black precipitate and drying; and calcining and annealing the dried black precipitate in protective gas to obtain the ferric vanadate/graphene composite material. According to the method, the graphene is tightly coated on FeVO by generating the ferric vanadate in the graphene aqueous dispersion liquid ₄ The nano-composite is formed on the surface of the nano-particle, and then the FeVO is promoted by using the graphene ₄ Is used for the electrical conductivity and the structural strength of the steel sheet.

Description

Battery negative electrode material and preparation method thereof, battery negative electrode sheet preparation method and battery

Technical field

The present invention relates to the technical characteristics of electrode material preparation, and in particular to a battery negative electrode material and its preparation method, a battery negative electrode sheet preparation method and a battery.

Background technique

Rechargeable lithium-ion batteries (LIBs) have been widely used in industrial and commercial fields (such as laptop computers, mobile communication equipment, and electric vehicles) due to their high energy density and long life. However, traditional commercial graphite anode materials (372mAh g ^-1 ) cannot meet the growing demand, and anode materials with high energy density and long cycle life have become a research hotspot. Therefore, it is particularly important to develop new anode materials with high capacity. Transition metal oxides have been widely studied as anode materials because of their great potential, mainly due to their rich natural reserves and high theoretical capabilities (500-1000mAh g ^-1 ). In recent years, transition metal salt anode materials have attracted widespread attention from researchers due to their series of advantages, such as high theoretical specific capacity, various types, and good cycle stability. Transition metal salts, as a kind of binary metal oxide, have recently attracted the attention of a large number of researchers due to their excellent and unique properties as anode materials for lithium-ion batteries. However, on the one hand, due to the nature of the electrochemical reaction of metal salt materials, metal salt materials will undergo large volume expansion during the charge and discharge process, reducing the stability of the material; on the other hand, the electronic conductivity of metal salt materials The rate is low, which seriously restricts its rate performance.

Therefore, a metal salt electrode material with good electrical conductivity and high strength and a preparation method thereof are urgently needed in this field.

Contents of the invention

In order to improve the conductivity and structural strength of metal salt electrode materials and combine the characteristics of various metal salts, in the first aspect of the present invention, a method for preparing battery negative electrode materials is proposed. The method includes: preparing graphene water dispersion, iron salt solution and vanadate solution; add the iron salt solution and vanadate solution to the graphene aqueous dispersion in sequence to obtain a mixed solution, adjust the mixed solution to the target pH; The mixed solution undergoes a hydrothermal reaction according to preset conditions to obtain a black precipitate; the black precipitate is collected and dried; the dried black precipitate is calcined and annealed in a protective gas to obtain an iron vanadate/graphene composite material .

In one or more embodiments, the concentration range of the graphene aqueous dispersion includes: 1.0 to 2.0 mL·mg-1.

In one or more embodiments, the iron salt includes ferric chloride, ferrous sulfate, ferric nitrate and/or ferrous oxalate; the vanadate includes ammonium metavanadate, vanadyl acetylacetonate, dioxide pentoxide Vanadium, sodium metavanadate and/or potassium metavanadate.

In one or more embodiments, adjusting the mixed solution to a target pH includes: adjusting the pH of the mixed solution to 2-5 using a dilute acid corresponding to the iron salt or vanadate.

In one or more embodiments, performing a hydrothermal reaction on the mixed solution under preset conditions includes: performing a hydrothermal reaction on the mixed solution at a reaction temperature of 150-200°C.

In one or more embodiments, the method further includes washing the black precipitate with deionized water 2 to 5 times before drying the black precipitate.

In one or more embodiments, calcining and annealing the dried black precipitate in a protective gas includes: calcining the dried black precipitate in a protective gas at 350-550°C for 2-4 hours, Then, it is annealed at normal temperature, wherein the protective gas includes nitrogen or argon.

In a second aspect of the present invention, a battery negative electrode material is proposed, which is an iron vanadate/graphene composite material prepared by a battery negative electrode material preparation method in any of the above embodiments.

In a third aspect of the present invention, a method for preparing a battery negative electrode sheet is proposed, including: using an iron vanadate/graphene composite material prepared by a battery negative electrode material preparation method in any of the above embodiments as an electrode The active material uses super-P as the conductive agent and polyvinylidene fluoride (PVDF) as the binder. According to the weight ratio of 8:1:1, take the respective masses and add 200 μl of N-methylpyrrolidone (NMP). ), mix it into a slurry; apply the slurry evenly on the Cu foil, dry it in a vacuum drying oven at 80 degrees Celsius for 12 hours, and then punch it into an electrode sheet.

In a fourth aspect of the present invention, a battery is proposed, including: a battery negative electrode, the battery negative electrode is a negative electrode sheet, and the negative electrode sheet is prepared by using a method for preparing a battery negative electrode sheet in the above embodiment; a battery positive electrode, The positive electrode of the battery is a positive electrode sheet, and the positive electrode sheet is a lithium sheet; a separator, the material of the separator is Celgard 2400; and the electrolyte is LiPF ₆ /DMC:DEC:EC.

The beneficial effects of the present invention include:

1. The present invention obtains iron vanadate/graphite with higher purity and better crystallinity by collaboratively controlling the pH value, reaction temperature, reaction time and subsequent annealing process of the hydrothermally synthesized iron vanadate/graphene composite material. The olefin composite material, without other vanadium oxides mixed in it, can obtain a lithium-ion battery anode material with a more obvious charge and discharge platform and better cycle performance;

2. By collaboratively controlling the pH value, reaction temperature and reaction time of the hydrothermal synthesis of iron vanadate/graphene composite materials, the present invention obtains a composite material structure with a special morphology in which nanostructured iron vanadate is wrapped by a graphene layer. , this composite material can effectively reduce the volume expansion during the insertion and extraction of lithium ions, and reduce the capacity drop caused by structural collapse;

3. The iron vanadate/graphene composite material synthesized in the present invention increases the external contact area of the material due to its unique mixed structure, improves the charging and discharging efficiency of lithium-ion batteries, shortens the diffusion path of lithium ions, and improves The transmission efficiency of lithium ions is conducive to improving the electrochemical performance of the material;

4. The iron vanadate/graphene composite material synthesized by the present invention not only has the advantages of high reversible capacity, good cycle performance, and high charge and discharge efficiency, but also has a simple preparation method, green environmental protection, low cost, wide source of raw materials, and Advantages of easy operation.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other embodiments can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a process flow chart of a method for preparing battery negative electrode materials according to an embodiment of the present invention;

Figure 2 is an XRD comparison chart of the lithium-ion battery anode material prepared according to Example 1 and Comparative Example 1 of the present invention;

Figure 3 is a Raman comparison chart of the lithium-ion battery negative electrode material prepared according to Example 1 of the present invention;

Figure 4 is a scanning electron microscope comparison diagram of the lithium-ion battery negative electrode material prepared according to Example 1 and Comparative Example 1 of the present invention;

Figure 5 is a transmission electron microscope image of the lithium-ion battery negative electrode material prepared according to Example 1;

Figure 6 is a comparison chart of cycle test curves of half-cells prepared from lithium-ion battery anode materials prepared according to Example 1 and Comparative Example 1 of the present invention at a current density of 200 mAh g ^-1 ;

Figure 7 is a comparison chart of rate test curves for the preparation of lithium-ion battery negative electrode materials prepared according to Example 1 and Comparative Example 1 of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings.

It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are to distinguish two entities or parameters with the same name but not the same, so it can be seen that "first" and "second" It is only for the convenience of description and should not be understood as a limitation on the embodiments of the present invention, and subsequent embodiments will not describe this one by one.

In order to improve the conductivity and structural strength of metal salt electrode materials, and in view of the fact that metal vanadate electrode materials can form an amorphous VOx array during the charge and discharge cycle, it can effectively alleviate the agglomeration of another metal element; In addition, equally important is that vanadium has multiple valence states and is easy to form acid radicals, and can easily construct nanostructures of metal vanadate through hydrothermal reaction temperature control; iron vanadate is also low-priced, widely available, and environmentally friendly. and many other advantages. Therefore, the present invention proposes a performance improvement scheme based on iron vanadate (FeVO ₄ ) materials, by adding iron salt solution and vanadate solution to the graphene aqueous dispersion and reacting at the preset pH and hydrothermal temperature. The iron vanadate/graphene composite material is generated, thereby greatly improving the electrical conductivity and structural strength of the iron vanadate material. The embodiments of the present invention will be described in more detail below with reference to the accompanying drawings.

Please refer to Figure 1, which shows a process flow of a battery negative electrode material preparation method according to an embodiment of the present invention, including: step S1, preparing a graphene aqueous dispersion, an iron salt solution and a vanadate solution; step S2, preparing The iron salt solution and the vanadate solution are sequentially added to the graphene aqueous dispersion to obtain a mixed solution, and the mixed solution is adjusted to the target pH; Step S3, perform a hydrothermal reaction on the mixed solution according to preset conditions to obtain a black precipitate; Step S4, collect the black precipitate Precipitate and perform drying treatment; Step S5: Calculate and anneal the dried black precipitate in a protective gas to obtain an iron vanadate/graphene composite material.

Specifically, the graphene aqueous dispersion in this embodiment can be prepared by adding graphene oxide to deionized water for ultrasonic dispersion. The iron salt solution and the vanadate solution are added to the deionized water by adding iron salt and vanadate solution respectively. And stir thoroughly to dissolve. The key to the process flow of this embodiment is to form iron vanadate in the graphene aqueous dispersion so that graphene can be tightly coated on the surface of FeVO ₄ nanoparticles to form a nanocomposite, thereby using graphene to improve the conductive properties of FeVO ₄ and Structural strength, and the improvement of structural strength can effectively reduce the volume expansion of the battery negative electrode during the process of lithium ion insertion and extraction, thereby greatly extending the service life and cycle times of the battery negative electrode material.

In a further embodiment, the concentration range of the graphene aqueous dispersion includes: 1.0 to 2.0 mL·mg ^-1 .

In further embodiments, iron salts include: ferric chloride, ferrous sulfate, ferric nitrate and/or ferrous oxalate.

In further embodiments, the vanadate salts include: ammonium metavanadate, vanadyl acetylacetonate, vanadium pentoxide, sodium metavanadate, and/or potassium metavanadate.

In a further embodiment, adjusting the mixed solution to the target pH includes: using a dilute acid corresponding to iron salt or vanadate to adjust the pH of the mixed solution to 2-5.

In a further embodiment, performing a hydrothermal reaction on the mixed solution according to preset conditions includes: performing a hydrothermal reaction on the mixed solution at a reaction temperature of 150-200°C.

In a further embodiment, the method of the present invention further includes washing the black precipitate with deionized water 2 to 5 times before drying the black precipitate.

In a further embodiment, calcining and annealing the dried black precipitate in a protective gas includes: calcining the dried black precipitate in a protective gas at 350-550°C for 2-4 hours, and then calcining it at room temperature. Annealing, wherein the protective gas includes nitrogen or argon.

In a specific embodiment, the complete process flow of a battery negative electrode material preparation method of the present invention is as follows:

S1. Add graphene oxide to deionized water for ultrasonic dispersion to obtain a graphene aqueous dispersion;

S2. Add the iron salt and vanadate to deionized water respectively, perform magnetic stirring, and after complete dissolution, obtain iron salt and vanadate solutions respectively;

S3. Add the iron salt and vanadate solutions in step S2) dropwise to the graphene aqueous dispersion, and then adjust the pH value with dilute acid under magnetic stirring;

S4. Subject the mixed solution obtained in step S3) to a hydrothermal reaction;

S5. Collect the black precipitate obtained by the hydrothermal reaction in step S4);

S6. Dry the black precipitate obtained in step S5);

S7. Perform annealing treatment on the dried precipitate in step S6) under a protective atmosphere.

Specifically, in step S1, the concentration of the graphene dispersion is 1.0-2.0 mL·mg ^-1 . Graphene uses graphite powder as raw material and is prepared using an improved Hummers method. Graphene is ultrasonically exfoliated in deionized water to form a graphene suspension to disperse the graphene evenly and prevent graphene agglomeration during the hydrothermal reaction.

In step S2, the iron source is selected from at least one of ferric chloride, ferrous sulfate, ferric nitrate, and ferrous oxalate; the vanadium source is selected from ammonium metavanadate, vanadyl acetylacetonate, vanadium pentoxide, and metavanadium. At least one of sodium phosphate and potassium metavanadate; add the iron salt and vanadate solutions drop by drop to the graphene aqueous dispersion. The concentration of vanadium ions in the hydrothermal reaction will affect the aggregation state of vanadium, and different aggregation states will lead to different product morphologies. Therefore, controlling the concentration of vanadate in the hydrothermal solution has an important impact on the morphology of the prepared products.

In step S3, after the iron salt and vanadate solutions are added dropwise to the graphene aqueous dispersion, dilute acid is used to adjust the pH value to 3-4. The acid can be selected from at least one of hydrochloric acid, sulfuric acid, and phosphoric acid, and a dilute solution of the acid is used, with a concentration of 0.5-1 mol·L ^-1 . The pH value of the hydrothermal solution has a very significant impact on the aggregation state of vanadium ions in the solution, and the morphology of the products obtained with different pH values is significantly different. When the pH value is 3-4, nanostructures with uniform sizes can be obtained. When the pH value is lower than 2, as the pH value decreases, the product is mainly vanadium oxide compound. When the pH value is too high, the product will be dominated by iron oxide, and too many oxidation states of vanadium compounds will make it more difficult to obtain products with high purity and uniform morphology. The present invention can obtain an iron vanadate/graphene composite material with higher purity and better crystallinity by keeping the pH of the mixed solution between 3 and 4.

In step 4, the mixed solution obtained in step S3 is moved to a hydrothermal reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is controlled at 150-200°C, and the time of the hydrothermal reaction is controlled at 12-36 hours. The time of hydrothermal reaction has an important influence on the morphology of the product. When the hydrothermal reaction time is short, the crystallinity of the product is poor and the shape is irregular. As the hydrothermal time prolongs, the grain formation rate accelerates, the crystallinity of the product increases and the shape gradually changes to a regular shape.

In step S5, the solution after the hydrothermal reaction is cooled to room temperature, and the black precipitate obtained by the hydrothermal reaction in step S4 is collected by suction filtration, and the obtained precipitate is washed 2-5 times.

In step S6, the black precipitate washed in step S5 is dried.

In step S7, the dried precipitate in step S6 is annealed under a protective atmosphere. The protective atmosphere is selected from at least one of nitrogen and argon. Annealing treatment includes calcination at 350-550℃ for 2-4h. Thus, the battery negative electrode material-iron vanadate/graphene composite material is obtained.

In order to verify the structural characteristics and electrical characteristics of the iron vanadate/graphene composite material of the present invention, as well as using different concentrations of graphene water dispersion, different pH reaction conditions, different hydrothermal temperatures and/or different calcination temperatures to generate vanadium The present invention also conducted the following comparative tests on the structural properties and electrical properties of acid iron/graphene composite materials:

Example 1

Add 40 mg of graphene oxide to 40 mL of deionized water and disperse it ultrasonically for 60 min (performed in three steps). Add 0.001mol FeCl ₃ ·6H ₂ O and 0.001mol NH ₄ VO ₃ to 5.0mL deionized H ₂ O respectively, stir at room temperature for 20 minutes to form a clear solution; add FeCl ₃ solution and NH ₄ VO ₃ solution respectively Add dropwise to the graphene oxide dispersion solution, continue stirring for 30 minutes, adjust the pH to 3.0 with 0.5 mol/L alkene HCl; transfer to a 100 ml high-pressure reactor, react at 180°C for 24 hours, and naturally cool to room temperature; Then, centrifuge, wash several times with absolute ethanol and deionized water, and dry at 80°C for 8 hours; finally, calcined at 500°C for 2 hours in an argon atmosphere to obtain FeVO ₄ /rGO nanocomposite.

Example 2

Add 50 mg of graphene oxide to 40 mL of deionized water and disperse it ultrasonically for 60 min (performed in three steps). Add 0.0015mol Fe(NO ₃ ) ₃ ·6H ₂ O and 0.0015mol NH ₄ VO ₃ to 5.0mL deionized H ₂ O respectively, stir at room temperature for 30 minutes to form a clear solution; add Fe(NO ₃ ) ₃ respectively The solution and NH4VO3 solution were added dropwise to the graphene oxide dispersion. After continuing to stir for 30 minutes, adjust the pH to 4.0 with 0.5 mol/L alkene HNO ₃ ; transfer to a 100 ml high-pressure reactor and react at 200°C for 18 hours. Naturally cool to room temperature; then, centrifuge, wash several times with absolute ethanol and deionized water, and dry at 80°C for 8h; finally, calcined at 450°C for 3h in an argon atmosphere to obtain FeVO ₄ /rGO nanocomposite.

Example 3

Add 40 mg of graphene oxide to 40 mL of deionized water and disperse it ultrasonically for 60 min (performed in three steps). Add 0.0015mol Fe(NO ₃ ) ₃ ·6H2O and 0.0015mol vanadyl acetylacetonate to 5.0mL H ₂ O respectively, stir at room temperature for 30 minutes to form a clear solution; add Fe(NO ₃ ) ₃ solution and acetylacetone respectively. Add the vanadium solution drop by drop to the graphene oxide dispersion. After continuing to stir for 30 minutes, adjust the pH to 3.5 with 0.5 mol/L alkene HNO ₃ ; transfer to a 100 ml high-pressure reactor and react at 180°C for 36 hours. Naturally Cool to room temperature; then, centrifuge, wash several times with absolute ethanol and deionized water, and dry at 80°C for 8h; finally, calcined at 550°C for 2h in an argon atmosphere to obtain FeVO ₄ /rGO nanocomposite.

Example 4

Add 40 mg of graphene oxide to 40 mL of deionized water and disperse it ultrasonically for 60 min (performed in three steps). Add 0.001 mol FeCl ₃ ·6H ₂ O and 0.001 mol vanadyl acetylacetonate respectively to 5.0 mL of deionized H2O, stir at room temperature for 20 minutes to form a clear solution; add FeCl ₃ solution and vanadyl acetylacetonate solution drop by drop. into the graphene oxide dispersion solution, continue stirring for 30 minutes, adjust the pH to 4.0 with 0.5 mol/L ene HCl; transfer to a 100 ml high-pressure reactor, react at 180°C for 24 hours, and naturally cool to room temperature; then, centrifuge , washed several times with absolute ethanol and deionized water, dried at 80°C for 8h; finally calcined at 350°C for 4h in an argon atmosphere to obtain FeVO ₄ /rGO nanocomposite.

Example 5

Add 40 mg of graphene oxide to 40 mL of deionized water and disperse it ultrasonically for 60 min (performed in three steps). Add 0.002mol Fe(NO ₃ ) ₃ ·6H ₂ O and 0.001mol V ₂ O ₅ to 5.0mL deionized H ₂ O respectively, and stir for 30 minutes at room temperature to form a clear solution; add the Fe(NO3)3 solution to Add the vanadium and vanadium solution drop by drop to the graphene oxide dispersion. After continuing to stir for 45 minutes, adjust the pH to 4.0 with 1.0 mol/L alkene HNO ₃ ; transfer to a 100 ml high-pressure reactor and react at 200°C for 18 hours. Naturally Cool to room temperature; then, centrifuge, wash several times with absolute ethanol and deionized water, and dry at 80°C for 8h; finally, calcined at 500°C for 2h in an argon atmosphere to obtain FeVO ₄ /rGO nanocomposite.

Comparative example 1

Add 0.001mol FeCl ₃ ·6H ₂ O and 0.001mol NH ₄ VO ₃ to 15mL H ₂ O respectively, stir at room temperature for 20 minutes to form a clear solution; transfer the FeCl ₃ solution to the NH ₄ VO ₃ solution dropwise After continuing to stir for 30 minutes, adjust the pH to 3.0 with 0.5 mol/L alkene HCl; transfer to a 50 ml high-pressure reaction kettle, react at 180°C for 24 hours, and naturally cool to room temperature; then, centrifuge and separate with absolute ethanol. Wash with deionized water several times, dry at 80°C for 8h; finally calcined in an air atmosphere at 500°C for 2h to obtain FeVO ₄ nanomaterials.

Comparative example 2

Add 0.001mol FeCl ₃ ·6H ₂ O and 0.001mol NH ₄ VO ₃ to 15mL H ₂ O respectively, stir at room temperature for 20 minutes to form a clear solution; transfer the FeCl ₃ solution to the NH ₄ VO ₃ solution dropwise After continuing to stir for 30 minutes, adjust the pH to 2.0 with 1.0 mol/L alkene HCl; transfer to a 50 ml high-pressure reaction kettle, react at 180°C for 24 hours, and naturally cool to room temperature; then, centrifuge and separate with absolute ethanol. Wash with deionized water several times, dry at 80°C for 8 hours; finally calcined in an air atmosphere at 500°C for 2 hours to obtain the sample of Comparative Example 2.

Comparative example 3

Add 0.001 mol Fe(NO ₃ ) ₃ ·6H ₂ O and 0.001 mol vanadyl acetylacetonate to 15 mL H ₂ O respectively, stir at room temperature for 20 min to form a clear solution; transfer the FeCl ₃ solution dropwise to the acetyl acetate solution. Acetone vanadyl solution, continue stirring for 30 minutes; transfer to a 50 ml high-pressure reactor, react at 200°C for 24 hours, and naturally cool to room temperature; then, centrifuge, wash several times with absolute ethanol and deionized water, and Drying at 80°C for 8 hours; finally calcining in an air atmosphere at 500°C for 2 hours to obtain the sample of Comparative Example 3.

The above-mentioned Examples 1-5 are all schemes for generating iron vanadate in graphene aqueous dispersion, while Comparative Examples 1-3 are all schemes for generating iron vanadate under conventional conditions. Based on the above-mentioned Examples 1-5 and Comparative Examples The points for scale 1-3 are as follows:

Please refer to Figure 2, which shows an XRD comparison chart of the lithium-ion battery anode material prepared according to Example 1 and Comparative Example 1 of the present invention. As shown in Figure 2, the diffraction peaks of both samples correspond one-to-one with the standard spectrum of orthorhombic FeVO ₄ (JCPDS No: 38-1372); indicating that FeVO ₄ can be successfully synthesized in aqueous graphene dispersion. And no impurities are produced, and the sample generated in the graphene aqueous dispersion has high crystallinity. No Graphene peak was found in the XRD pattern of FeVO ₄ /rGO nanocomposite. At the same time, compared with pure FeVO ₄ , the diffraction peak of FeVO ₄ /rGO nanocomposite was lower.

Please refer to Figure 3, which shows a Raman comparison chart of the lithium-ion battery anode material prepared according to Embodiment 1 of the present invention; the peaks at 1333 cm ^-1 and 1594 cm ^-1 in Figure 3 correspond to the D-band of graphene and G-band; the ratio of D-band to G-band (ID/IG) of FeVO ₄ /rGO nanocomposite is greater than 1, indicating that the graphene in the sample has lower crystallinity consistent with the XRD results (FeVO ₄ /rGO nanocomposites have higher purity).

Please refer to Figure 4, which shows a scanning electron microscope comparison diagram of the lithium-ion battery negative electrode material prepared according to Example 1 and Comparative Example 1 of the present invention; it can be seen from the figure that the morphology of FeVO ₄ is uniform nanoparticles with a diameter of It is about 100nm; the morphology of the FeVO ₄ /rGO sample is consistent with that of pure FeVO ₄ and has not changed; graphene is tightly coated on the surface of FeVO ₄ nanoparticles to form a nanocomposite.

Please refer to Figure 5, which shows a transmission electron microscope image of the lithium-ion battery negative electrode material prepared according to Example 1; the diameter of the FeVO ₄ nanoparticles is about 100 nm, which is consistent with the FESEM image analysis results; the graphene is tightly coated on the surface of FeVO ₄ nanoparticles. FeVO ₄ /rGO nanocomposite materials have better mechanical strength and can effectively reduce the volume expansion of FeVO ₄ /rGO during the process of lithium ion insertion and extraction.

Please refer to Figure 6, which shows a comparison chart of the cycle test curves of the half-cell prepared from the lithium-ion battery anode material prepared according to Example 1 and Comparative Example 1 of the present invention at a current density of mAh g ^-1 , and the voltage range is 0.01–3.0V(Li+/Li). As can be seen from Figure 6, FeVO ₄ and FeVO4/rGO electrodes exhibit relatively high initial discharge specific capacities of 1077mAh g ^-1 and 1135mAh g ^-1 , initial charge specific capacities of 748mAh g ^-1 and 1095mAh g ^-1 , and Coulombic efficiencies. (CE) are 69.4% and 96.4% respectively. The initial capacity loss may be due to the decomposition of the electrolyte and the formation of the SEI film. Compared with pure FeVO ₄ electrode, FeVO ₄ /rGO electrode shows higher capacity and better cycle performance. After 100 cycles, the reversible discharge specific capacity of FeVO ₄ /rGO is 1250mAh g ^-1 ; while FeVO ₄ The reversible discharge specific capacity is 721mAh g ^-1 , which is 66.9% of the initial discharge specific capacity. It is obvious that FeVO ₄ /rGO has good cycle stability. This is because the FeVO ₄ /rGO nanocomposite has better mechanical strength and can effectively reduce the volume expansion during the insertion and extraction process of lithium ions.

Please refer to FIG. 7 , which shows a comparison chart of the rate test curves of the lithium-ion battery negative electrode materials prepared according to Example 1 and Comparative Example 1 of the present invention. When the current density is 200, 500, 1000, 2000, 5000, 10000 and 15000mA g ^-1 respectively, the reversible capacities of FeVO ₄ /rGO electrode material are 1110, 942, 860, 858, 703, 533 and 478mAhg ^-1 respectively. When the current density returns to 200mAh g ^-1 again, the discharge specific capacity rapidly increases to 1161mAh g ^-1 ; this result further demonstrates that the FeVO ₄ /rGO electrode has better cycle and rate performance. Compared with the FeVO ₄ /rGO nanocomposite electrode material prepared according to the present invention, the FeVO ₄ electrode material without graphene exhibits poor electrochemical performance. It shows that the material provided by the present invention exhibits excellent cycle performance, which is mainly attributed to: (1) The unique hybrid structure of the FeVO ₄ nanocomposite material synthesized by the present invention increases the external contact area of the material and improves the lithium The charge and discharge efficiency of ion batteries shortens the diffusion path of lithium ions and improves the transmission efficiency of lithium ions, which is beneficial to improving the electrochemical performance of the material; (2) The graphene coating layer can promote electron transfer in FeVO ₄ samples and buffer Li -Deformation pressure during the alloying and dealloying process of FeVO ₄ and maintaining the integrity of the electrode; (3) Graphene has the advantages of high surface area, good conductivity, good dynamic properties and stable structure, FeVO ₄ / rGO nanocomposites have better mechanical strength and can effectively reduce volume expansion and material powdering during the insertion and extraction of lithium ions.

In a second aspect of the present invention, a battery negative electrode material is proposed. The battery negative electrode material is an iron vanadate/graphene composite material prepared by any one of the above battery negative electrode material preparation methods.

The FeVO ₄ nanocomposite material synthesized by the present invention increases the external contact area of the material due to its unique mixed structure, improves the charging and discharging efficiency of lithium-ion batteries, shortens the diffusion path of lithium ions, and improves the transmission efficiency of lithium ions. , which is beneficial to improving the electrochemical performance of the material; (2) The graphene coating layer can promote electron transfer of FeVO ₄ samples, buffer the deformation pressure during the alloying and dealloying process of Li-FeVO ₄ and maintain the integrity of the electrode; (3 ) Graphene has the advantages of high surface area, good conductivity, good dynamic properties and stable structure. FeVO ₄ /rGO nanocomposite has better mechanical strength and can effectively reduce the volume during the insertion and extraction process of lithium ions. Expansion and pulverization of material.

In a third aspect of the present invention, a method for preparing a battery negative electrode sheet is proposed, including: using an iron vanadate/graphene composite material prepared by a battery negative electrode material preparation method in any of the above embodiments as an electrode. Active material, with super-P as the conductive agent and polyvinylidene fluoride (PVDF) as the binder, take their respective masses according to the weight ratio of 8:1:1 and add to 200 μl of N-methylpyrrolidone (NMP) , mix it into a slurry; apply the slurry evenly on the Cu foil, dry it in a vacuum drying oven at 80 degrees Celsius for 12 hours, and then punch it into electrode sheets.

The FeVO ₄ nanocomposite material synthesized by the present invention increases the external contact area of the material due to its unique mixed structure, improves the charging and discharging efficiency of lithium-ion batteries, shortens the diffusion path of lithium ions, and improves the transmission efficiency of lithium ions. , which is beneficial to improving the electrochemical performance of the material; (2) The graphene coating layer can promote electron transfer of FeVO ₄ samples, buffer the deformation pressure during the alloying and dealloying process of Li-FeVO ₄ and maintain the integrity of the electrode; (3 ) Graphene has the advantages of high surface area, good conductivity, good dynamic properties and stable structure. FeVO ₄ /rGO nanocomposite has better mechanical strength and can effectively reduce the volume during the insertion and extraction process of lithium ions. Expansion and pulverization of materials greatly extend the life of the battery negative electrode.

In a fourth aspect of the present invention, a battery is proposed, including: a battery negative electrode, the battery negative electrode is a negative electrode sheet, the negative electrode sheet is prepared by using a method for preparing a battery negative electrode sheet in the above embodiment; a battery positive electrode, the battery positive electrode is a positive electrode sheet, the positive electrode sheet is sodium sheet or lithium sheet; the separator, the material of the separator is Celgard 2400; the electrolyte, the electrolyte is LiPF ₆ /DMC:DEC:EC.

Example 6

The FeVO ₄ /rGO nanocomposite material prepared by the preparation method of lithium ion battery negative electrode material according to the present invention was used as the negative electrode and assembled into a battery, and its electrochemical performance was tested. The specific preparation and testing methods are as follows:

The FeVO ₄ /rGO nanocomposite prepared above is used as the active material of the electrode, super-P is used as the conductive agent, and polyvinylidene fluoride (PVDF) is used as the binder. The weight ratio is 8:1:1. After mass, add it to 200 μl of N-methylpyrrolidone (NMP), mix it into a slurry and apply it evenly on the Cu foil. Dry in a vacuum drying oven at 80 degrees Celsius for 12 hours, and punch into 12mm electrode sheets. Use this electrode sheet as the positive electrode, the lithium sheet as the negative electrode, Celgard 2400 as the separator, and 1M LiPF ₆ /DMC:DEC:EC (volume ratio 1:1:1) as the electrolyte in an argon-protected glove box. Assembled into a 2032 model button battery. The charge and discharge performance of the battery was tested on the Blue Power CT2001A battery tester, and the measurement voltage range was 0.01-3.0V. It can be seen from the measured voltage range that the battery prepared using the iron vanadate/graphene composite material of the present invention has good discharge performance and can provide stable voltage.

The above are exemplary embodiments disclosed by the present invention, but it should be noted that various changes and modifications can be made without departing from the scope of the disclosed embodiments of the present invention defined by the claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or claimed in individual form, they may also be understood as plural unless expressly limited to the singular.

It will be understood that, as used herein, the singular form "a" and "an" are intended to include the plural form as well, unless the context clearly supports an exception. It will also be understood that as used herein, "and/or" is meant to include any and all possible combinations of one or more of the associated listed items.

The embodiment numbers disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

Those of ordinary skill in the art should understand that the above discussion of any embodiments is only illustrative, and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the thinking of the embodiments of the present invention , the above embodiments or technical features in different embodiments can also be combined, and there are many other changes in different aspects of the above embodiments of the present invention, which are not provided in details for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention shall be included in the protection scope of the embodiments of the present invention.

Claims (10)

1. A method for preparing battery negative electrode materials, characterized in that the method includes: Prepare graphene aqueous dispersion, iron salt solution and vanadate solution; Add the iron salt solution and the vanadate solution to the graphene aqueous dispersion in sequence to obtain a mixed solution, and adjust the mixed solution to the target pH; The mixed solution is subjected to a hydrothermal reaction according to preset conditions to obtain a black precipitate; Collect the black precipitate and dry it; The dried black precipitate is calcined and annealed in a protective gas to obtain an iron vanadate/graphene composite material. 2. A method for preparing battery negative electrode materials according to claim 1, characterized in that the concentration range of the graphene aqueous dispersion includes: 1.0 to 2.0 mL·mg ^-1 . 3. A method for preparing battery negative electrode materials according to claim 1, characterized in that the iron salt includes ferric chloride, ferrous sulfate, ferric nitrate and/or ferrous oxalate; the vanadate includes metaphase Ammonium vanadate, vanadyl acetylacetonate, vanadium pentoxide, sodium metavanadate and/or potassium metavanadate. 4. A method for preparing a battery negative electrode material according to claim 1, wherein said adjusting the mixed solution to a target pH includes: using a dilute acid corresponding to the iron salt or vanadate to adjust the said mixed solution to a target pH. The pH of the mixed solution is adjusted to 2-5. 5. A method for preparing a battery negative electrode material according to claim 1, wherein the hydrothermal reaction of the mixed solution according to preset conditions includes: The mixed solution is subjected to a hydrothermal reaction at a reaction temperature of 150 to 200°C. 6. A method for preparing battery negative electrode materials according to claim 1, characterized in that the method further includes washing the black precipitate with deionized water for 2 to 5 seconds before drying the black precipitate. Second-rate. 7. A battery negative electrode material preparation method according to claim 1, characterized in that the dried black precipitate is calcined and annealed in a protective gas, including: The dried black precipitate is calcined at 350-550°C for 2-4 hours in a protective gas, and then annealed at room temperature, wherein the protective gas includes nitrogen or argon. 8. A battery negative electrode material, characterized in that the battery negative electrode material is an iron vanadate/graphene composite material prepared by a battery negative electrode material preparation method according to any one of claims 1 to 7. 9. A method for preparing a battery negative electrode sheet, which is characterized by comprising: The iron vanadate/graphene composite material prepared by the battery negative electrode material preparation method described in any one of claims 1-7 is used as the active material of the electrode, with super-P as the conductive agent, polyvinylidene fluoride (PVDF) is used as the binder. According to the weight ratio of 8:1:1, take their respective masses and add them to 200 μl of N-methylpyrrolidone (NMP), and mix to form a slurry; The slurry was evenly applied on the Cu foil, dried in a vacuum drying oven at 80 degrees Celsius for 12 hours, and then punched into electrode sheets. 10. A battery, characterized in that it includes: Battery negative electrode, the battery negative electrode is a negative electrode sheet, and the negative electrode sheet is prepared by a method for preparing a battery negative electrode sheet according to claim 9; Battery positive electrode, the battery positive electrode is a positive electrode sheet, and the positive electrode sheet is a lithium sheet; Separator, the material of the separator is Celgard 2400; Electrolyte, the electrolyte is LiPF ₆ /DMC:DEC:EC.