CN107706417B - A kind of preparation method of spherical carbon anode material for lithium ion battery - Google Patents

Abstract

The invention relates to a preparation method of a spherical carbon negative electrode material of a lithium ion battery. The method comprises the steps of taking starch as a raw material, uniformly mixing the starch with iron powder according to a certain proportion, carrying out stabilization treatment in an air atmosphere at the temperature of 200-250 ℃, then carrying out high-temperature carbonization in an inert atmosphere, and obtaining the spherical carbon negative electrode material through acid washing, water washing, suction filtration and drying. The iron powder is added to separate starch granules from each other, so that the phenomenon that the starch granules are heated unevenly is avoided, the stabilization time is greatly shortened, and the prepared carbon microspheres keep the original shape of the starch granules and have the grain diameter of 2-40 mu m. The method has simple process and low requirement on equipment, and the obtained carbon microspheres have excellent appearance and show excellent electrochemical performance when being used as the cathode material of the lithium ion battery.

Description

A kind of preparation method of spherical carbon anode material for lithium ion battery

technical field

The invention relates to a preparation method of spherical carbon and its application in lithium ion batteries, and belongs to the technical field of negative electrode materials of lithium ion batteries.

Background technique

Electronic products play an increasingly important role in our daily life. The battery market is highly competitive. Lithium-ion batteries have high energy density, high average output voltage, good cycle stability, long service life, small size and light weight. It has the advantages of no memory effect, safety and reliability, and is widely used in consumer electronics, electric vehicles and energy storage.

The improvement of the capacity of anode materials for lithium-ion batteries is one of the keys to the improvement of their energy density. Carbon material is an ideal choice for lithium-ion battery anode material, and currently, graphite-based materials are the most widely used. With the expansion of the application field of lithium-ion batteries, the performance requirements of lithium-ion batteries have been continuously improved, and the limitations of graphite anode materials in terms of specific energy, cycle performance and safety have become more and more prominent. Carbon microspheres have good thermal stability, thermal conductivity, high bulk density, and low surface area-to-volume ratio, which can reduce irreversible capacity loss caused by side reactions such as SEI films, thereby improving the electrochemical performance of lithium-ion batteries. hot spot.

In the document "Non-catalytic CVD preparation of carbon spheres with a specific size (Carbon, 2004, 42(4), 761-766)", the author used toluene as a raw material and used a self-made double-furnace chemical vapor deposition device in a catalyst-free environment. Spherical carbon materials were prepared under the conditions. In the document "The production of carbonmaterials by hydrothermal carbonization of cellulose Carbon, 2009.47(9):2281-2289", carbon microspheres were prepared by hydrothermal method and KOH activation using cellulose, eucalyptus wood chips, etc. as carbon sources. Li Yongfeng et al. used coal as raw material and changed the plasma conditions to prepare carbon microspheres. The preparation process was completed on a DC arc plasma evaporation experimental device (a novel coal-based spherical carbon and its formation mechanism. Journal of Dalian University of Technology, 2002, 42(6):663-668). In the literature "Monodispersed hard carbon spherules with uniform nanopores", sucrose was used as the carbon source, dehydrated at 190 °C in a closed condition, and carbonized at high temperature in an argon atmosphere to prepare monodisperse carbon microparticles with a specific surface area of 400 m ² /g. ball. In summary, many preparation methods of carbon microspheres have high requirements on experimental conditions and equipment, which greatly limits the commercialization process of carbon microsphere anode materials, and most of the precursors for preparing carbon microspheres are non-renewable. or environmentally unfriendly precursors. Therefore, simplifying the preparation process, using environmentally friendly precursors, and improving the yield have become the research directions of carbon microspheres. Starch is rich in sources and low in cost. Through the early oxidation treatment, carbon microsphere materials that maintain the original spherical shape of starch granules can be obtained, which not only reduces the difficulty of the sphere-forming process, but also reduces the preparation cost of negative electrode materials for lithium ion batteries. Green, environmentally friendly and renewable, alleviating the problem of shortage of fossil resources.

Patent CN103647082A prepares hard carbon microsphere negative electrode material through low temperature stabilization and high temperature carbonization under reduced pressure. This method can avoid the agglomeration of carbon microspheres after carbonization, reduce the irreversible capacity of hard carbon microspheres, and improve the material's performance. Cyclic Stability. In order to eliminate the foaming and agglomeration phenomenon of carbon microspheres, this method requires a long time (8-100h) of low temperature stabilization treatment, which makes the preparation time of carbon microspheres too long and reduces the preparation efficiency. Patent CN102364727A combines starch-based hard carbon microspheres with expanded graphite to form an artificial solid space conductive network structure, which improves the voltage hysteresis of hard carbon materials and improves the first efficiency of the material. In this method, the composite process of carbon microspheres and expanded graphite is complicated, and the preparation cost of the material is increased.

SUMMARY OF THE INVENTION

In view of the problems in the prior art, the present invention aims to provide a method for preparing spherical carbon for lithium ion battery negative electrode by adding iron powder as a precursor to shorten the stabilization time by using starch as a precursor.

Technical scheme used in the present invention: a preparation method of spherical carbon, the concrete steps are as follows:

1. Mix the raw starch and iron powder uniformly in a certain proportion, and perform heating stabilization pretreatment in the temperature range of 200-250 °C;

2. Place the stabilized sample in step 1 in a high-temperature tube furnace, and perform high-temperature carbonization in the temperature range of 600-1200 °C under an inert atmosphere for 0.5-3 hours, and obtain a carbonized product after cooling;

3. Pickling the carbonized product in step 2, washing with deionized water, suction filtration, and drying to obtain a spherical carbon negative electrode material for lithium ion batteries.

Preferably, the starch raw material in the step 1 is at least one of potato starch, corn starch, wheat starch, tapioca starch, rice starch, sweet potato starch, and mung bean starch.

Preferably, the iron powder in the step 1 is high-purity iron powder, and the particle size is 300-1000 mesh.

Preferably, the mixing ratio of starch and iron powder in the step 1 is 1:1-100:1.

Preferably, the stabilization treatment time in the step 1 is 1-12h.

Preferably, the inert atmosphere in step 2 is high-purity nitrogen.

Preferably, the carbonization temperature in step 2 is 700-1000°C.

Preferably, the carbonization time in step 2 is 1-2h.

Preferably, the acid used in step 3 is 1% dilute hydrochloric acid.

The invention has the characteristics of abundant raw material sources, low cost, simple preparation process, no pollution and the like. By adding iron powder to the starch for stabilization treatment, the starch granules are separated from each other. At the same stabilization temperature, the fusion of starch granules and the uneven heating of starch granules due to mutual accumulation can be avoided. The pre-stabilization time of starch is shortened, resources are saved, and the preparation efficiency is improved.

By adding iron powder to separate the starch granules from each other, for stabilization or carbonization treatment, the starch granules are heated evenly, which improves the consistency of the prepared samples. The operation process is simple, the equipment requirements are low, and the large-scale preparation and production are easy. The starch-based carbon microspheres prepared by the invention have good spherical morphology, and show excellent cycle stability and rate performance when used as negative electrode materials for lithium ion batteries.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) picture of the raw material potato starch used in the present invention.

2 is a scanning electron microscope image of the starch-based carbon microsphere negative electrode material prepared in Example 1 of the present invention.

3 is a scanning electron microscope image of the starch-based carbon microsphere negative electrode material prepared in Comparative Example 1 of the present invention.

4 is a cycle performance curve of the carbon microsphere negative electrode material prepared in Example 1 at a current density of 50 mA/g.

5 is a rate performance curve of the carbon microsphere negative electrode material prepared in Example 1 at a current density of 0.05-2 A/g.

Detailed ways

The present invention will be further described below by way of examples, but it does not constitute a limitation of the present invention.

Example 1

10g potato starch and 10g iron powder were fully stirred and mixed, and the mixture was put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized material is placed in a beaker, treated with 1% dilute hydrochloric acid, washed with deionized water for several times, suction filtered, and dried to obtain potato starch-based carbon microspheres with a particle size range of 5.5-32.6 μm.

The obtained carbon microspheres were used as negative electrode materials for lithium ion batteries to assemble batteries, and their cycle performance and rate performance were tested. The test conditions are: 25°C, current density 0.05-2A/g, voltage range 0.01-3V.

As shown in FIG. 5 , the obtained carbon microspheres were used as negative electrode materials for lithium-ion batteries, and at a current density of 50 mA/g, the reversible specific capacity was 323.2 mAh/g. At a current density of 2 A/g, the reversible specific capacity was 82.7 mAh/g. The cycle performance is excellent. When the current density returns to 50 mA/g, the reversible specific capacity reaches 336.3 mAh/g.

Example 2

10g potato starch and 0.1g iron powder were fully stirred and mixed, the mixture was put into a muffle furnace, and in an air atmosphere, the temperature was raised to 230°C at a heating rate of 5°C/min for 8 hours, and then stabilized. The chemical samples were placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized material is placed in a beaker, treated with 1% dilute hydrochloric acid, washed with deionized water for several times, suction filtered, and dried to obtain potato starch-based carbon microspheres with a particle size range of 6.0-30.66 μm. The obtained carbon material was assembled into a battery and tested for electrochemical performance. At a current density of 50mAh/g, the first discharge specific capacity was 645.6mAh/g, the reversible specific capacity was 350.5mAh/g, and the capacity retention rate after 50 cycles was 70. %.

Example 3

10g of potato starch and 1g of iron powder were fully stirred and mixed, and the mixture was put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized product was placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain potato starch-based carbon microspheres. Its particle size range is 3.9-28.13 μm.

Example 4

10g potato starch and 1g iron powder were fully stirred and mixed, and the mixture was put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized product was placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain potato starch-based carbon microspheres.

Example 5

10g potato starch and 1g iron powder are fully stirred and mixed, and the mixture is put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized product was placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain potato starch-based carbon microspheres.

Example 6

10g of potato starch and 1g of iron powder were fully stirred and mixed, and the mixture was put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 1000 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized product was placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain potato starch-based carbon microspheres. Its particle size range is 6-32 μm.

Example 7

10g cornstarch and 10g iron powder are fully stirred and mixed, and the mixture is put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized material is placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain a cornstarch-based carbon material.

Example 8

10g wheat starch and 10g iron powder were fully stirred and mixed, and the mixture was put into a muffle furnace. The sample was placed in a carbonization furnace, and in a nitrogen atmosphere, the temperature was raised to 700 °C at a heating rate of 1.5 °C/min for 1 h. The carbonized material is placed in a beaker, treated with 1% dilute hydrochloric acid, washed several times with deionized water, suction filtered, and dried to obtain a wheat starch-based carbon material.

Comparative Example 1

Put 10 g of potato starch into a muffle furnace, and in an air atmosphere, raise the temperature to 230 °C for 8 h at a heating rate of 5 °C/min for stabilization treatment. At the heating rate of 1.5°C/min, the temperature was raised to 700°C for 1 h, and the potato starch-based carbon material was obtained after cooling. Compared with Example 1, the potato starch was directly stabilized in this example. During the later carbonization process, the starch granules were melted and adhered, and the spherical shape of the potato starch granules could not be completely preserved.

Some embodiments of the present invention have been specifically described above, but the present invention is not limited to the above-mentioned embodiments. Those skilled in the art can make equivalent modifications or substitutions without departing from the spirit of the present invention. Variations or substitutions of the above are all included within the scope defined by the claims of the present application.

Claims (4)

1. A preparation method of a spherical carbon negative electrode material of a lithium ion battery is provided, the particle diameter of the spherical carbon negative electrode material is 2-40 μm, and the preparation method is characterized by comprising the following steps:

(1) the starch raw material is at least one of potato starch, corn starch, wheat starch, tapioca starch, rice starch and mung bean starch, the starch raw material and iron powder are fully and uniformly mixed according to a certain proportion, and the mixture is subjected to heating stabilization pretreatment for 1-12h within the temperature range of 200-;

(2) placing the stabilized sample in the step (1) in an inert atmosphere, carbonizing at the temperature of 600-1200 ℃ for 0.5-3h, and cooling to obtain a carbonized product;

(3) and (3) pickling the carbide obtained in the step (2), washing with deionized water, performing suction filtration, and drying to obtain the spherical carbon negative electrode material of the lithium ion battery.

2. The preparation method of the spherical carbon negative electrode material of the lithium ion battery according to claim 1, characterized by comprising the following steps: the particle size of the iron powder is 300-1000 meshes.

3. The preparation method of the spherical carbon negative electrode material of the lithium ion battery according to claim 1, characterized by comprising the following steps: the mixing ratio of the starch and the iron powder in the step (1) is 1: 1-500: 1.

4. the preparation method of the spherical carbon negative electrode material of the lithium ion battery according to claim 1, characterized by comprising the following steps:

the acid in the step (3) is 1% dilute hydrochloric acid.

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