1. Lithium ion battery cathode Fe₇S₈/Fe₂O₃The preparation method of the composite material is characterized by comprising the following steps: dissolving iron salt, urotropine and sublimed sulfur in water, stirring, carrying out hydrothermal reaction, washing, drying and calcining the obtained product to obtain Fe₇S₈/Fe₂O₃A composite material.

2. The method of claim 1, wherein: the iron salt is Fe (NO)₃)·9H₂The mass ratio of the iron salt to the urotropine to the sublimed sulfur is 0.6: (1.1-1.3): 0.12.

3. the method of claim 1, wherein: the hydrothermal reaction temperature is 160-200 ℃ and the time is 8-16 h.

4. The method of claim 1, wherein: the calcination temperature of the dried product is 450-500 ℃, and the time is 2-3 h.

5. The composite material produced by the production method according to any one of claims 1 to 4, wherein: said Fe₇S₈/Fe₂O₃The composite material is in a pine needle ball shape, and the particle size is uniform.

6. Use of the composite material of claim 5 in a negative electrode material for a lithium ion battery.

7. Use according to claim 6, characterized in that: the battery capacity is up to 1000 mAh/g after charging and discharging circulation for 200 times at 0.1C multiplying power.

Background

At present, the commercial lithium ion battery cathode material is mainly graphite, the graphite has good cycling stability, but the specific capacity is lower (the theoretical specific capacity is only 372 mAh ∙ g)^-1) And the requirements of people on the lithium ion battery with high power density and high energy density cannot be met. Therefore, it is necessary to develop a negative electrode material having a high specific capacity, high cycle stability and high rate performance to replace the existing graphite negative electrode.

Fe. O and S widely exist in the nature, are low in price and friendly to the environment, and iron oxides have the advantages of high energy density, safety, no toxicity, stable structure and low price, and are deeply concerned by researchers. Therefore, iron oxides are ideal negative electrode materials for lithium ion batteries. Wherein Fe₂O₃The theoretical capacity of the catalyst reaches 1008 mAh g^-1However, the practical discharge capacity is very low, about 300 mAh g-1, and the cycling stability and rate performance can not meet the requirements, which are mainly limited by the volume change and the dynamics of the active material. To improve Fe₂O₃Is generally Fe₂O₃Nanocrystallization, or preparation of Fe₂O₃And C, the reversible capacity and the cycle life of the negative electrode material are improved to a certain extent.

Also, iron has poor sulfide stability, Fe₇S₈Theoretical capacity of 667 mAh g^-1The actual discharge capacity is slightly higher than that of Fe₃O₄Actual discharge capacity of (c). However Fe₇S₈The material has the defects of low conductivity, volume expansion in the charge-discharge cycle process, active substance dissolution in electrolyte and the like, so that the cyclicity and the rate capability of the material are poor.

Disclosure of Invention

The invention provides Fe₇S₈/Fe₂O₃The composite material, the preparation method and the application thereof solve the problem of Fe₂O₃And Fe₇S₈Low actual discharge specific capacity and bad cycle capacity and cycle life.

The technical scheme for realizing the invention is as follows:

lithium ion battery cathode Fe₇S₈/Fe₂O₃A process for the preparation of a composite material from 0.6g Fe (NO)₃)·9H₂O, 1.19g of urotropin and 0.12g of sublimed sulfur are dissolved in 30mL of water, the mixture is continuously stirred for 20min, then the obtained solution is poured into an autoclave (50 mL), and the autoclave is placed in an oven for reaction at the temperature of 160 ℃ and 200 ℃ for 8-16 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 450-500 ℃ for 2-3h under the atmosphere, and the heating rate is 5 ℃ min^-1。

Said Fe₇S₈/Fe₂O₃The composite material is in a pine needle ball shape, and the particle size is uniform.

The method takes ferric nitrate, urotropine and sublimed sulfur as raw materials, and prepares the composite lithium ion battery cathode material (Fe) by hydrothermal synthesis and high-temperature calcination₂O₃/Fe₇S₈）。Fe₂O₃/Fe₇S₈Mixing with Super P, PVDF and N-methyl pyrrolidone in proportion, coating on copper foil, and drying at 80 deg.C for 12 hr; then slicing and drying for 4 hours at 80 ℃ to obtain the lithium ion battery negative pole piece.

The invention has the beneficial effects that: fe prepared herein₂O₃/Fe₇S₈The composite material is in a pine needle ball shape, provides a large contact area for the electrolyte and the electrode, and promotes charge and Li⁺Fast transfer of (2); and it makes the composite material form larger space gap, and relieves the body of the material when lithium is embeddedThe volume is expanded, so that the electrochemical performance of the battery is effectively improved. Thereby Fe₂O₃/Fe₇S₈The composite electrode exhibits a high reversible capacity. The charge and discharge cycle is 200 times at 0.1C multiplying power, and the capacity is as high as 1000 mAh/g.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 shows Fe prepared in example 1₇S₈/Fe₂O₃Scanning Electron Microscope (SEM) images of (a).

FIG. 2 shows Fe prepared in example 1₇S₈/Fe₂O₃X-ray diffraction (XRD) pattern of (A) and (B) Fe₂O₃And Fe₇S₈Standard card drawings.

FIG. 3 is Fe prepared in example 1₇S₈/Fe₂O₃X-ray photoelectron spectroscopy (XPS).

FIG. 4 shows Fe prepared in example 1₇S₈/Fe₂O₃And a 0.1C constant current charge and discharge curve diagram of the battery assembled by the negative electrode material prepared by the sample.

FIG. 5 shows Fe prepared in example 1₇S₈/Fe₂O₃Cyclic Voltammetry (CV) curves after the sample prepared negative electrode material was assembled into a battery.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.

Example 1

0.6g of Fe (NO)₃)·9H₂O, 1.19g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, and the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 180 ℃ for reaction for 10 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 500 deg.C for 2h at a temperature of 5 deg.C/min^-1。

Example 2

0.6g of Fe (NO)₃)·9H₂O, 1.12g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, and the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 180 ℃ for reaction for 10 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 500 deg.C for 2h at a temperature of 5 deg.C/min^-1。

Example 3

0.6g of Fe (NO)₃)·9H₂O, 1.26g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 180 ℃ for reaction for 10 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 500 deg.C for 2h at a temperature of 5 deg.C/min^-1。

Example 4

0.6g of Fe (NO)₃)·9H₂Dissolving O, 1.19g urotropin and 0.12g sublimed sulfur in 30mL water, stirring the mixture for 20min, and adding sodium chlorideThe resulting solution was poured into an autoclave (50 mL) and placed in an oven at 180 ℃ for 8 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 500 deg.C for 2h at a temperature of 5 deg.C/min^-1。

Example 5

0.6g of Fe (NO)₃)·9H₂O, 1.19g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 180 ℃ for reaction for 12 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 500 deg.C for 2h at a temperature of 5 deg.C/min^-1。

Example 6

0.6g of Fe (NO)₃)·9H₂O, 1.1g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 160 ℃ for reaction for 8 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder was dried in a vacuum oven at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 450 deg.C for 2.5h in the atmosphere, and heating rate of 5 deg.C/min^-1。

Example 7

0.6g of Fe (NO)₃)·9H₂O, 1.30g of urotropin and 0.12g of sublimed sulfur were dissolved in 30mL of water, the mixture was stirred for 20min, and then the resulting solution was poured into an autoclave (50 mL) and placed in an oven at 200 ℃ for reaction for 16 h. After cooling to room temperature, the obtained precipitate was washed with water and ethanol 2-3 times, respectively. Finally, Fe₇S₈/Fe₂O₃The powder is placed in a vacuum drying ovenDrying at 80 ℃ for 8 hours. Then transferred to a tube furnace in N₂Annealing at 550 ℃ for 3h under the atmosphere, wherein the heating rate is 5 ℃ per minute^-1。

Examples of the effects of the invention

Mixing the black magnetic powder obtained in the above embodiment with Super P, PVDF and N-methylpyrrolidone in proportion, coating the mixture on a copper foil, and drying the copper foil at 80 ℃ for 12 hours; then slicing and drying for 4 hours at 80 ℃ to obtain the lithium ion battery negative pole piece. And assembling the pole piece, the sodium metal, the diaphragm and the electrolyte into a battery, and testing, wherein the composite lithium ion battery negative electrode material Fe prepared in the embodiment 1 is₇S₈/Fe₂O₃The best results of the charge and discharge performance test after the battery is assembled (as shown in fig. 3).

FIG. 1 shows sample Fe₂O₃/Fe₇S₈The Scanning Electron Microscope (SEM) image shows that the composite material is like a pine needle ball and has a relatively large surface area to be contacted with the electrolyte.

FIG. 2 is a view showing the sequence of Fe prepared by the present invention from top to bottom₇S₈/Fe₂O₃X-ray diffraction (XRD) pattern of (A) and (B) Fe₂O₃And Fe₇S₈Standard card drawing, which shows that the invention successfully prepares Fe₇S₈/Fe₂O₃A material.

FIG. 3 shows Fe prepared by the present invention₇S₈/Fe₂O₃Further illustrating the successful preparation of Fe by the present invention, X-ray photoelectron spectroscopy (XPS)₇S₈/Fe₂O₃A material.

FIG. 4 shows Fe in sample₇S₈/Fe₂O₃A0.1C constant-current charge-discharge curve diagram after the negative electrode material prepared by the sample is assembled into a battery shows that the discharge capacity reaches 1000 mAh/g after 200 cycles.

FIG. 5 shows Fe in sample₇S₈/Fe₂O₃Cyclic Voltammetry (CV) curves after the sample prepared negative electrode material was assembled into a battery.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.