WO2017121113A1

WO2017121113A1 - Carbon-coated zinc ferrite electrode material, and preparation method and application thereof

Info

Publication number: WO2017121113A1
Application number: PCT/CN2016/095922
Authority: WO
Inventors: 侯贤华; 屈丽娜
Original assignee: 华南师范大学
Priority date: 2016-01-11
Filing date: 2016-08-18
Publication date: 2017-07-20
Also published as: CN105609732A

Abstract

The present application relates to the technical field of new energy materials, and specifically relates to a carbon-coated zinc ferrite electrode material, and a preparation method and an application thereof. The present application uniformly disperses zinc ferrite in an aqueous ethanol solution, adding a silane coupling agent to implement surface treatment; then heating the reaction system to 50 °C to 80 °C, adding an initiator and mixing; then dripping in a mixed monomer and a dispersant to implement in situ graft copolymerisation, collecting the product, washing, drying, and calcining; and thereby obtaining a carbon-coated zinc ferrite electrode material. The preparation method of the present invention is simple, low-cost, and highly efficient, and has good coating effects; the outer layer coating particles of the carbon-coated zinc ferrite electrode material obtained using a coprecipitation method and an in situ graft copolymerisation method are evenly distributed and have a small particle size, showing an excellent electrochemical performance, and good cyclic stability and electrical conductivity.

Description

Carbon coated zinc ferrite electrode material and preparation method and application thereof

Technical field

The invention belongs to the technical field of new energy materials, and particularly relates to a carbon coated zinc ferrite electrode material and a preparation method and application thereof.

Background technique

In the past ten years, as a rechargeable battery, lithium-ion batteries have been widely used in various small portable electronics due to their high voltage platform, high energy density, low self-discharge, good cycle performance, light weight and environmental friendliness. Equipment, electric vehicles and hybrid electric vehicles. Electrode materials are the key factors determining the overall performance of lithium-ion batteries. Commercial graphite is currently used as a common anode material for lithium-ion batteries. It has good reversibility, high capacity and low discharge platform, but the actual specific capacity is close to the theory. The specific capacity of 372mAh/g, pure graphite can not meet the demand of high energy density battery; on the other hand, the lithium-embedded potential platform of graphite is close to the deposition potential of metallic lithium, and it is prone to "deposition of lithium" during rapid charging or low-temperature charging. Therefore, safety hazards are caused; in addition, the graphite material has poor solvent compatibility, and is easily peeled off in a low-temperature electrolyte containing propylene carbonate or the like to cause capacity degradation. Therefore, the development of a lithium ion battery anode material with high capacity, long life, safety and reliability has become one of the key factors for improving battery performance.

The metal oxide lithium storage anode material has a high theoretical capacity and can form various alloys with lithium. The lithium insertion potential is higher than the electrode potential of the graphite anode material, and it is difficult to cause surface lithium deposition during charging, and the safety is poor. . As a negative electrode material for lithium ion batteries, zinc ferrite (ZnFe ₂ O ₄ ), a soft magnetic material with excellent performance, has great commercial value. ZnFe ₂ O ₄ material has a high theoretical capacity (1486 mAh/g), and is inexpensive and free. The advantages of poisoning can be used as a hot spot for replacing graphite electrode materials. At the same time, it has a stable potential platform (about 0.8v), which does not cause lithium deposition, which greatly improves the safety of the battery. At the same time, during the charging and discharging process, the structure of zinc ferrite is stable, which makes the material have good cycle performance as a negative electrode material, which is the basis for developing high-performance zinc ferrite storage electrode materials.

As a negative electrode material of lithium ion battery, the disadvantages and disadvantages of zinc ferrite are: first, low conductivity, resulting in poor high-rate charge and discharge performance, and low actual specific capacity; second, low efficiency for the first time, during the first lithium intercalation reaction, a large number The irreversible Li ₂ O and the formation of the dead lithium phase material cause the active lithium ions to be consumed, so that they cannot be reduced to effective active lithium ions during the subsequent delithiation reaction, thereby reducing the first cycle efficiency, in the actual battery design process. Can not effectively match the positive electrode material and other issues.

Summary of the invention

In order to overcome the deficiencies and shortcomings of the prior art, a primary object of the present invention is to provide a method for preparing a carbon coated zinc ferrite electrode material.

Another object of the present invention is to provide a carbon-coated zinc ferrite electrode material prepared by the above preparation method.

It is still another object of the present invention to provide an application of the above carbon coated zinc ferrite electrode material.

The object of the invention is achieved by the following technical solution:

A method for preparing a carbon-coated zinc ferrite electrode material comprises the following steps:

(1) uniformly dispersing zinc ferrite in an aqueous ethanol solution; then adding a silane coupling agent for surface treatment;

(2) heating the reaction system in the step (1) to 50 ° C to 80 ° C, adding an initiator to mix; then adding a mixed monomer and a dispersant to carry out in-situ graft copolymerization, then collecting the product, washing, drying ;

(3) The dried product in the step (2) is calcined at 300 to 600 ° C for 3 to 6 hours in an air atmosphere; a carbon coated zinc ferrite electrode material is obtained;

The zinc ferrite described in the step (1) is preferably nanorod zinc ferrite;

The method for preparing zinc ferrite described in the step (1) (coprecipitation method) preferably comprises the following steps:

Mixing the acid precipitant with the dispersing agent and stirring for 0.5 to 5 hours; then adding the soluble zinc salt and the ferrous salt to be uniformly mixed, stirring for 18 to 24 hours; washing and drying to obtain nano-rod zinc ferrite; the zinc salt is Zinc sulfate, zinc chloride or zinc nitrate; the divalent iron salt is ferrous sulfate or ferrous chloride;

The molar ratio of zinc ions and ferrous ions in the soluble zinc salt and the divalent iron salt is preferably 1:2;

The dispersing agent is a mixture of ethylene glycol, cyclohexane, cetyltrimethylammonium bromide and water;

The acid precipitating agent is citric acid, oxalic acid or acetic acid;

The washing method is preferably washed with anhydrous ethanol and deionized water;

The drying condition is preferably dried at 50 to 80 ° C for 5 to 10 hours;

The ethanol aqueous solution described in the step (1), the mass ratio of ethanol to water is preferably 9:1;

The uniformity of the dispersion described in the step (1) is preferably uniform by stirring and stirring, wherein the stirring speed is preferably 200 to 400 rpm, the stirring time is preferably 10 to 30 minutes, and the zinc ferrite is sufficiently mixed and dispersed uniformly by stirring, which is advantageous for coupling with the coupling agent. Grafting, the more uniform and finer the dispersion, the more the surface of the particles can be graft polymerized, and the area of the polymerization coating is increased;

The silane coupling agent described in the step (1) is KH570 or KH560;

The amount of the silane coupling agent described in the step (1) is not more than 5% by mass of the zinc ferrite;

The silane coupling agent described in the step (1) is preferably added to the reaction system by dropwise addition; the dropping speed is preferably 5 to 10 d / min;

The time of the surface treatment described in the step (1) is preferably 2 to 12 h;

The initiator described in the step (2) is benzoyl peroxide or azobisisobutyronitrile;

The amount of the initiator described in the step (2) is 0.8% to 1.2% of the mass of the mixed monomer;

The mixed monomer described in the step (2) is styrene and acrylonitrile, wherein the mass ratio of styrene to acrylonitrile is (3:7) to (7:3); the mass ratio of styrene to acrylonitrile is preferred. 7:3;

The mass ratio of the zinc ferrite to the mixed monomer in the step (2) is 1: (1 to 3); too much mixed monomer causes mutual polymerization before the polymer, agglomeration causes the particles to increase, and Affect the coating effect;

The mass ratio of the zinc ferrite to the mixed monomer in the step (2) is preferably 1:1;

The dispersing agent described in the step (2) is polyvinylpyrrolidone;

The dispersant is used in the step (2) in an amount of 10% to 20% by mass of the mixed monomer; if the amount of the dispersant is too small, the dispersion is uneven, and since the dispersant PVP is a nonionic polymer, the amount is too large. Will also increase the viscosity of the reaction, which is not conducive to the reaction;

The speed of the dropwise addition described in the step (2) is preferably 5 to 10 d / min;

The time of the in-situ graft copolymerization reaction described in the step (2) is preferably from 12 h to 24 h;

The drying condition described in the step (2) is preferably: drying at 50 to 80 ° C for 5 to 10 hours;

A carbon-coated zinc ferrite electrode material prepared by the above preparation method;

The carbon-coated zinc ferrite electrode material has good dispersibility, small outer layer coating particle size and uniform particles;

The carbon coated zinc ferrite electrode material can be applied to the field of lithium ion battery preparation;

The principle of the invention: the invention disperses zinc ferrite uniformly in an aqueous solution of ethanol, and then adds a silane coupling agent for surface treatment: the silane coupling agent undergoes hydrolysis reaction under water condition, and the hydrolyzed silane One type of coupling agent will produce a hydroxyl group at one end, and this hydroxyl group will have a hydrogen bond with the zinc ferrite, that is, the hydroxyl group on the surface of the precursor, and in the subsequent heating process, the dehydration condensation bond is formed to function as a graft;

In the subsequent heating process, the benzoyl peroxide contains a peroxy group (—O—O—), and after heating, the —O—O— bond is broken and splits into two corresponding radicals, thereby initiating polymerization of the monomer. Forming a unique structure of polymer-coated zinc ferrite rod-shaped particles; in this process, the initiator does not directly initiate the reaction and needs to be decomposed into a radical to initiate the reaction, and the chain initiation is a rapid step, so the initiator The half-life has great significance. The invention firstly adds an initiator, and when the half life is reached, the monomer which is dripped is more completely polymerized, which is equivalent to less monomer in the atmosphere of more initiator radicals, The titrated monomer is fully polymerized. Further, after the initiator is added, the mixed monomer is added dropwise, and the grafting reaction is completed, and then the polymerization is carried out to obtain the polymer-coated zinc ferrite particles (Fig. 1);

The present invention has the following advantages and effects over the prior art:

(1) The invention adopts the method of coprecipitation and in-situ graft copolymerization to prepare nanometer-polymer coated zinc ferrite particles, and the product has uniform dispersion and good crystallinity, and the aspect ratio is 2:1 to 3: 1. The outer coating is evenly distributed, the particle size is small, the electrochemical performance is excellent, the first charging and discharging efficiency is high, the cycle performance is good, and the specific capacity is high (for the first time, it is more than 1600mAh/g, and the theoretical commercial capacity of graphite is 372mAh. /g), thereby solving the problem of the first inefficiency, large irreversible capacity loss, and poor conductivity of the zinc ferrite electrode material.

(2) The preparation method of the invention is simple, low in cost and green and environmentally friendly.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the preparation of a carbon-coated zinc ferrite electrode material of the present invention.

2 is an XRD pattern of a carbon-coated zinc ferrite electrode material prepared in Example 1.

3 is an SEM chart of a carbon-coated zinc ferrite electrode material prepared in Example 1.

4 is a graph showing the charge and discharge cycle performance of the carbon-coated zinc ferrite electrode material obtained in Example 1.

5 is an XRD pattern of a carbon-coated zinc ferrite electrode material prepared in Example 2.

6 is a SEM image of a carbon-coated zinc ferrite electrode material prepared in Example 2.

Fig. 7 is a graph showing the charge and discharge cycle performance of the carbon-coated zinc ferrite electrode material obtained in Example 2.

8 is an XRD pattern of a carbon-coated zinc ferrite electrode material prepared in Example 3.

9 is a SEM image of a carbon-coated zinc ferrite electrode material prepared in Example 3.

Fig. 10 is a graph showing the charge and discharge cycle performance of the carbon-coated zinc ferrite electrode material obtained in Example 3.

Figure 11 is a SEM image of a carbon coated zinc ferrite electrode material prepared in Comparative Example.

detailed description

The present invention will be further described in detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

Example 1

(1) Preparation of precursor zinc ferrite: 100 mL of cyclohexane, 16.5 mL of ethylene glycol and 16.5 mL of deionized water were separately mixed, and then 10.68 g of cetyltrimethylammonium bromide was added, and the mixture was stirred for 30 minutes; Then add 10 g of oxalic acid as a precipitant and continue to stir for 1 h; then weigh 1.15 g of zinc sulfate, respectively. 2.23 g of ferrous sulfate is dissolved in the above mixed solution, wherein the molar concentration of zinc sulfate is 0.08 mol/liter, the molar concentration of ferrous sulfate is 0.16 mol/liter, and the molar ratio of zinc sulfate to ferrous sulfate is 1:2. The mixture was stirred at room temperature for 24 hours; the yellow liquid after the stirring was alternately washed with anhydrous ethanol and deionized water for 3 times, and then dried in an oven at 60 ° C for 8 hours to obtain a yellow zinc ferrite powder;

(2) 5 g of the zinc ferrite powder prepared in the step (1) and the aqueous ethanol solution (45 g of absolute ethanol and 5 g of deionized water are uniformly mixed), and stirred at 300 rpm for 10 min to uniformly disperse the zinc ferrite in the aqueous ethanol solution. Then adding KH570 ethanol solution (0.25g KH570 dissolved in 5g absolute ethanol), the dropping rate is 10d/min, after the completion of the dropwise addition, the surface treatment is carried out for 12h;

(3) heating the reaction system in the step (2) to 70 ° C, adding benzoyl peroxide solution (0.05 g of benzoyl peroxide dissolved in 5 g of absolute ethanol), stirring at 300 rpm for 10 min; 5 g of mixed monomer (3.5 g of styrene and 1.5 g of acrylonitrile) and 2.3 g of polyvinylpyrrolidone having a mass fraction of 25.18% were dissolved in 10 g of absolute ethanol, and added dropwise to the above reaction system at a rate of 6 d/min. In situ graft copolymerization at 70 ° C for 24 h; after completion of the reaction, the product was washed alternately with ethanol and deionized water for 3 times, and dried at 60 ° C for 8 h;

(4) The dried product in the step (3) is sintered in a muffle furnace at 450 ° C for 5 hours in an air atmosphere to obtain a carbon-coated zinc ferrite electrode material; wherein, FIG. 2 is obtained in the present embodiment. The XRD pattern of the carbon-coated zinc ferrite electrode material is consistent with the zinc ferrite standard card JCPDSno.22-1012, and there is no diffraction peak of impurities such as ZnO or Fe ₂ O ₃ , and the crystallinity is good. 3 is a scanning electron micrograph of the carbon-coated zinc ferrite electrode material prepared in the present embodiment, which shows that the coated zinc ferrite surface coating particles are uniform and have good dispersibility, and the average diameter is 20 to 50 nm.

The carbon-coated zinc ferrite electrode material prepared in the present embodiment is used as a negative electrode active material, and is mixed with a binder LA132 and a conductive agent Super-P in a weight ratio of 5:2:3 to prepare a slurry and coated thereon. On a copper foil, vacuum drying, rolling, and slicing were carried out to prepare a negative electrode sheet. A three-component mixed solvent of 1 mol/L LiPF _{6 was} used: EC:DMC:EMC=1:1:1, and the v/v/v solution was The electrolyte, the polypropylene microporous membrane is a membrane, and is assembled into a half-cell. The cycle performance was tested using a constant current charge and discharge test using a current of 100 mA, and the charge and discharge voltage ranged from 0.01 V to 3 V. The electrochemical performance of the experimental battery fabricated by the carbon coated zinc ferrite electrode material prepared in this example was tested by LAND battery test system (Wuhan Jinnuo Electronics Co., Ltd.) and tested under normal temperature conditions. 4 is a graph showing the charge-discharge cycle performance of a carbon-coated zinc ferrite electrode material prepared in the present embodiment as a negative electrode material for a lithium ion battery, which can be obtained from FIG. 4, and the coated zinc ferrite nano-powder material is used as a lithium battery. The specific capacity of the negative electrode material is high, the first discharge specific capacity is 1644 mAh/g, the first charge specific capacity is 1280 mAh/g, and the first cycle efficiency is 77.86%. After circulating for 20 weeks, the specific capacity was maintained at 1100 mAh/g or more, and the cycle performance was excellent.

Example 2

(1) Preparation of precursor zinc ferrite: 100 mL of cyclohexane, 16.5 mL of ethylene glycol and 16.5 mL of deionized water were separately mixed, and then 10.68 g of cetyltrimethylammonium bromide was added, and the mixture was stirred for 30 minutes; Further, 10 g of oxalic acid was added as a precipitant, and stirring was continued for 2 hours; then, 1.15 g of zinc sulfate and 2.23 g of ferrous sulfate were respectively weighed and dissolved in the above mixed solution, wherein the molar concentration of zinc sulfate was 0.08 mol/liter, and the mole of ferrous sulfate The concentration is 0.16 mol / liter, the molar ratio of zinc sulfate to ferrous sulfate is 1:2, and stirring is continued for 24 hours at normal temperature; the yellow liquid after stirring is alternately washed with anhydrous ethanol and deionized water for 3 times at 60 ° C. Drying in an oven for 8 h to obtain a yellow powder of zinc ferrite;

(2) 2 g of the zinc ferrite powder prepared in the step (1) is mixed with an aqueous ethanol solution (45 g of absolute ethanol and 5 g of deionized water), and stirred at 400 rpm for 15 minutes to uniformly disperse the zinc ferrite in the aqueous ethanol solution. Then, KH570 ethanol solution (0.1 g KH570 dissolved in 5 g of absolute ethanol) was added dropwise, and the dropping rate was 8 d/min. After the completion of the dropwise addition, the surface treatment was carried out for 10 hours;

(3) heating the reaction system in the step (2) to 80 ° C, adding a benzoyl peroxide solution (0.04 g of benzoyl peroxide dissolved in 5 g of absolute ethanol), stirring at 300 rpm for 10 min; 4 g (2.8 g of styrene and 1.2 g of acrylonitrile) and 1.9 g of a polyvinylpyrrolidone having a mass fraction of 25.18% were added to 10 g of absolute ethanol at a rate of 6 d/min to the above reaction system. °C in-situ graft copolymerization reaction for 18h; after completion of the reaction, the product was washed alternately with ethanol and deionized water for 3 times and dried at 60 ° C for 8 h;

(4) The dried product in the step (3) is sintered in a muffle furnace at 300 ° C for 6 hours in an air atmosphere to obtain a carbon-coated zinc ferrite electrode material; wherein, FIG. 5 is obtained in the present embodiment. The XRD pattern of the carbon-coated zinc ferrite electrode material is consistent with the zinc ferrite standard card JCPDSno.22-1012, and there is no diffraction peak of impurities such as ZnO and Fe2O3, and the crystallinity is good. 6 is a scanning electron micrograph of the carbon-coated zinc ferrite electrode material prepared in the present embodiment, which shows that the surface of the coated zinc ferrite has uniform particles and good dispersibility, and the average diameter is 20 to 50 nm.

The carbon-coated zinc ferrite electrode material prepared in the present embodiment is used as a negative electrode active material, and is mixed with a binder LA132 and a conductive agent Super-P in a weight ratio of 5:2:3 to prepare a slurry and coated thereon. On a copper foil, vacuum drying, rolling, and slicing were carried out to prepare a negative electrode sheet. A three-component mixed solvent of 1 mol/L LiPF _{6 was} used: EC:DMC:EMC=1:1:1, and the v/v/v solution was The electrolyte, the polypropylene microporous membrane is a membrane, and is assembled into a half-cell. The cycle performance was tested using a constant current charge and discharge test using a current of 100 mA, and the charge and discharge voltage ranged from 0.01 V to 3 V. The electrochemical performance of the experimental battery fabricated by the carbon coated zinc ferrite electrode material prepared in this example was tested using a LAND battery test system (Wuhan Jinnuo Electronics Co., Ltd.) and tested under normal temperature conditions. 7 is a graph showing the charge and discharge cycle performance of a carbon-coated zinc ferrite electrode material prepared in the present embodiment as a negative electrode material for a lithium ion battery, which can be obtained from FIG. 7 , and the polymer coated zinc ferrite material is used as a lithium battery. The specific capacity of the negative electrode material is high. The first specific capacity is 1364 mAh/g, the first charge specific capacity is 1084 mAh/g, and the first cycle efficiency is 79.47%. After 5 weeks, the specific capacity is increasing. After 20 weeks, the charge-discharge specific capacity is average. At 1100 mAh/g or more, the cycle performance is excellent.

Example 3

(1) Preparation of precursor zinc ferrite: 100 mL of cyclohexane, 16.5 mL of ethylene glycol and 16.5 mL of deionized water were separately mixed, and 10.68 g of cetyltrimethylammonium bromide was added thereto, and the mixture was stirred for 30 minutes and uniformly mixed. Further, 10 g of oxalic acid was added as a precipitant, and stirring was continued for 1 hour; then, 1.15 g of zinc sulfate and 2.23 g of ferrous sulfate were respectively weighed and dissolved in the above mixed solution, wherein the molar concentration of zinc sulfate was 0.08 mol/liter, and the mole of ferrous sulfate The concentration is 0.16 mol / liter, the molar ratio of zinc sulfate to ferrous sulfate is 1:2, and stirring is continued for 24 hours at normal temperature; the yellow liquid after stirring is alternately washed with anhydrous ethanol and deionized water for 3 times at 60 ° C. Drying in an oven for 8 h to obtain a yellow powder of zinc ferrite;

(2) 1 g of the zinc ferrite powder prepared in the step (1) is mixed with an aqueous ethanol solution (45 g of absolute ethanol and 5 g of deionized water), and stirred at 200 rpm for 30 minutes to uniformly disperse the zinc ferrite in the aqueous ethanol solution. Then, KH570 ethanol solution (0.05 g KH570 dissolved in 5 g of absolute ethanol) was added dropwise, and the dropping rate was 5 d/min, and the mixture was stirred for 2 hours after the completion of the dropwise addition;

(3) heating the reaction system in the step (2) to 60 ° C, adding benzoyl peroxide solution (0.03 g of benzoyl peroxide dissolved in 5 g of absolute ethanol), stirring at 300 rpm for 10 min; The mixed monomer (2.1 g styrene and 0.9 g acrylonitrile) and 1.4 g of the mass fraction of 25.18% polyvinylpyrrolidone were dissolved in 10 g of absolute ethanol, and added dropwise to the above reaction system at a rate of 6 d/min, 70 ° C In-situ graft copolymerization reaction for 12 h; after completion of the reaction, the product was washed alternately with ethanol and deionized water for 3 times and dried at 60 ° C for 8 h;

(4) in the air atmosphere, the dried product in step (3) is sintered in a muffle furnace at 600 ° C for 3 h to obtain a carbon coated zinc ferrite electrode material;

8 is an XRD pattern of the carbon-coated zinc ferrite electrode material prepared in the present embodiment, which is consistent with the zinc ferrite standard card JCPDSno. 22-1012, and has no diffraction peak of impurities such as ZnO and Fe ₂ O ₃ , The crystallinity of the product was good. 9 is a scanning electron micrograph of the carbon-coated zinc ferrite electrode material prepared in the present embodiment, which shows that the surface of the coated zinc ferrite has uniform particles and good dispersibility, and the average particle diameter is 20 to 50 nm.

The carbon-coated zinc ferrite electrode material prepared in the present embodiment is used as a negative electrode active material, and is mixed with a binder LA132 and a conductive agent Super-P in a weight ratio of 5:2:3 to prepare a slurry and coated thereon. On the copper foil, Vacuum drying, rolling, and slicing were carried out to prepare a negative electrode sheet. A three-component mixed solvent of 1 mol/L LiPF6 was used. EC:DMC:EMC=1:1:1, the v/v/v solution was an electrolyte, and the polypropylene was obtained. The microporous membrane is a membrane and assembled into a half-cell. The cycle performance was tested using a constant current charge and discharge test using a current of 100 mA, and the charge and discharge voltage ranged from 0.01 V to 3 V. The electrochemical performance of the experimental battery fabricated by the carbon coated zinc ferrite electrode material prepared in this example was tested by LAND battery test system (Wuhan Jinnuo Electronics Co., Ltd.) and tested under normal temperature conditions. Figure 10 is a graph showing the charge-discharge cycle performance of a carbon-coated zinc ferrite electrode material prepared in the present embodiment as a negative electrode material for a lithium ion battery, which is obtained from Figure 10, and the polymer coated zinc ferrite nano-powder material As the anode material of the lithium battery, the specific capacity is high, the first specific capacity is 1619 mAh/g, the first charge specific capacity is 1255 mAh/g, and the first cycle efficiency is 77.52%. After 20 weeks, the specific capacity was maintained at 1100 mAh/g or more, and the cycle performance was excellent.

Comparative Example 1

(2) 1 g of the zinc ferrite powder prepared in the step (1) is mixed with an aqueous ethanol solution (45 g of absolute ethanol and 5 g of deionized water), and stirred at 300 rpm for 10 min to uniformly disperse the zinc ferrite in the aqueous ethanol solution. Then adding KH570 ethanol solution (0.25g KH570 dissolved in 5g absolute ethanol), the dropping rate is 10d/min, and stirring is completed for 12h;

(4) in the air atmosphere, the dried product in step (3) is sintered in a muffle furnace at 450 ° C for 5 h to obtain a carbon coated zinc ferrite electrode material;

11 is a scanning electron micrograph of the carbon-coated zinc ferrite electrode material prepared in the present embodiment, showing The coated surface of the zinc ferrite surface coating is not uniform, and many particles are agglomerated together, the dispersibility is not good, and the morphology is not good. Moreover, the charge-discharge cycle performance of the carbon-coated zinc ferrite electrode material as a negative electrode material for a lithium ion battery is significantly lower than that of the first embodiment.

The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and combinations thereof may be made without departing from the spirit and scope of the invention. Simplifications should all be equivalent replacements and are included in the scope of the present invention.

Claims

A method for preparing a carbon-coated zinc ferrite electrode material, comprising the steps of:

(1) uniformly dispersing zinc ferrite in an aqueous ethanol solution; then adding a silane coupling agent for surface treatment;

(2) heating the reaction system in the step (1) to 50 ° C to 80 ° C, adding an initiator to mix; then adding a mixed monomer and a dispersant to carry out in-situ graft copolymerization, then collecting the product, washing, drying ;

(3) The dried product in the step (2) is calcined at 300 to 600 ° C for 3 to 6 hours in an air atmosphere; and a carbon-coated zinc ferrite electrode material is obtained.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein the silane coupling agent in the step (1) is KH570 or KH560; and the silane coupling agent is The amount does not exceed 5% of the mass of zinc ferrite.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein:

The initiator described in the step (2) is benzoyl peroxide or azobisisobutyronitrile; and the initiator is used in an amount of 0.8% to 1.2% by mass of the mixed monomer.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein:

The mixed monomer described in the step (2) is styrene and acrylonitrile, wherein the mass ratio of styrene to acrylonitrile is (3:7) to (7:3); the iron described in the step (2) The mass ratio of the zinc acid to the mixed monomer is 1: (1 to 3).
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein:

The mass ratio of the zinc ferrite to the mixed monomer described in the step (2) is 1:1.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein:

The dispersing agent described in the step (2) is polyvinylpyrrolidone; and the dispersing agent is used in an amount of 10% to 20% by mass of the mixed monomer.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein:

The in-situ graft copolymerization reaction time in the step (2) is from 12 h to 24 h.
The method for preparing a carbon-coated zinc ferrite electrode material according to claim 1, wherein the surface treatment time in the step (1) is 2 to 12 hours.
A carbon-coated zinc ferrite electrode material obtained by the production method according to any one of claims 1 to 8.
The carbon coated zinc ferrite electrode material of claim 9 for use in the field of lithium ion batteries.