WO2019024221A1 - Preparation method for high-first-efficiency long-life silicon-carbon cathode material - Google Patents

Abstract

A preparation method for a high-first-efficiency long-life silicon-carbon cathode material: first heating, mixing, sieving and grading SiOX and asphalt, to obtain an SiOX/C material; then using aluminum nitrate, urea and SiOX/C to prepare a precursor Al(OH)3-SiOX/C; finally, obtaining an Al2O3-SiOX/C material by means of heat treatment. With the present invention, carbon cladding treatment is firstly performed on the SiOX to alleviate a volume effect generated during electrical charging and discharging of the SiOX, and the process is simple, with low manufacturing costs and high yield. The Al2O3 cladding layer may effectively reduce contact between an electrolyte and SiOX and between the electrolyte and the carbon layer, thus reducing the side reaction of the material and the electrolyte, while reducing formation of an SEI film. In addition, the Al2O3 cladding layer may act as an SEI film, which conducts Li+ but does not conduct electrons, and which may also increase Li+ migration speed.

Description

Method for preparing silicon-carbon anode material with high initial effect and long life Technical field

The invention belongs to the field of lithium ion battery materials, and particularly relates to a method for preparing a silicon carbon anode material with high initial effect and long life.

Background technique

Lithium-ion batteries with high energy and long cycle life are in greater demand in the fields of electronic equipment and electric vehicles. In the field of anode materials research, the material silicon has a theoretical specific capacity (4200 mAh/g, Li ₂₂ Si ₅ ) and a large volumetric energy density (9786 mAh/cm ³ ) exceeding 10 times of graphite, which has become a hot research object. There is a huge volume effect (about 300% change in volume), and the internal stress generated easily causes the silicon to be powdered and peeled off, which limits its commercial application. Compared with silicon materials, the theoretical specific capacity of SiO materials is about 2000mAh/g. Because of the mixed phase structure of silicon and oxide, it can effectively alleviate the volume effect of silicon during charge and discharge process and improve the cycle stability of materials. This makes it easier to implement commercial applications. However, SiO is also facing the disadvantages of low coulombic efficiency, poor conductivity, and rapid decay of the cycle process.

In view of the shortcomings of SiO, the current technical solutions are roughly disproportionation treatment, CVD carbon coating treatment, stencil etching treatment and the like. The above disproportionation treatment and etching are mainly aimed at alleviating the volume expansion of SiO. On the one hand, carbon coating relieves volume expansion, on the other hand, it reduces contact between SiO and electrolyte, and forms a stable SEI film in the carbon layer. After the treatment of these methods, the first efficiency and cycle performance of SiO are still not ideal, and there is still room for improvement.

Summary of the invention

The object of the present invention is to break through the bottleneck of the prior art, and to provide a method for preparing a silicon carbon anode material which is superior in performance, low in cost, and suitable for industrialization.

In order to solve the above technical problems, the technical solution adopted by the present invention is: a high-effect long-life silicon carbon anode material preparation method, and the innovation is that the specific steps are as follows:

(1) Under a nitrogen atmosphere, the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 700-1000 ° C, and kept for 1-4 h, and after cooling to room temperature, the material is classified. Sieve treatment gave a SiO _X /C composite.

(2) The SiO _X /C composite was added to deionized water, then added with aluminum nitrate for 20 min, then a weak aqueous alkali solution was added, and stirred in a water bath at 60-80 ° C for 1-5 h.

(3) The mixed liquid obtained above was subjected to a drying treatment to obtain a precursor Al(OH) ₃ -SiO _X /C material.

(4) The precursor material is heat-treated at 800-1100 ° C for 1-4 h in a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material.

Further, the SiO _X raw material in the step (1) has a median diameter of 4-8 μm and 0<X<2, and the pitch is one of coal pitch or petroleum pitch.

Further, the weak base in the step (2) is one of ammonia water, urea or ammonium hydrogencarbonate, and the molar ratio of the weak base to the aluminum nitrate is 1:1 to 3:1.

Further, the drying treatment in the step (3) is any one of blast drying, spray drying, and freeze drying.

Further, the mass ratio of the final material Al ₂ O ₃ -SiO _X /C of Al ₂ O _{3 to} the SiO _X /C material in the step (4) is 0.1% to 5%.

The beneficial effects of the present invention are as follows:

(1) The present invention firstly performs carbon coating treatment on SiO _X to alleviate the volume effect generated when SiO _{X is} charged and discharged, and has a simple process, low manufacturing cost, and high yield.

(2) The Al ₂ O ₃ coating layer can effectively reduce the contact between the electrolyte and the SiO _X and the carbon layer, and reduce the side reaction of the material and the electrolyte, and also reduce the formation of the SEI film.

(3) The Al ₂ O ₃ cladding layer can act as an SEI film, which itself leads to Li ⁺ non-conductors and can also increase the Li ⁺ migration rate.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a scanning electron micrograph of a SiO _X /C material provided in Example 1 of the present invention.

2 is a scanning electron micrograph of an Al ₂ O ₃ -SiO _X /C material provided in Example 1 of the present invention.

Fig. 3 is a cycle diagram of a button battery when the Al ₂ O ₃ -SiO _X /C material provided in Example 1 of the present invention is used as a negative electrode.

Detailed ways

The embodiments of the present invention are described below by way of specific embodiments, and those skilled in the art can readily understand other advantages and functions of the present invention from the disclosure.

A high-effect long-life silicon carbon anode material preparation method, the specific steps are as follows:

(1) Under a nitrogen atmosphere, the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 700-1000 ° C, and kept for 1-4 hours (h), and after cooling to room temperature, The material was subjected to classification and sieving treatment to obtain a SiO _X /C composite material.

(2) The SiO _X /C composite was added to deionized water, and then aluminum nitrate was added and stirred for 20 minutes (min), followed by addition of a weak aqueous alkali solution, and stirred in a water bath at 60-80 ° C for 1-5 h.

(3) The mixed liquid obtained above was subjected to a drying treatment to obtain a precursor Al(OH) ₃ -SiO _X /C material.

(4) The precursor material is heat-treated at 800-1100 ° C for 1-4 h in a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material.

It is feasible that the SiO _X raw material in the step (1) has a median diameter of 4-8 μm and 0<X<2, and the pitch is one of coal pitch or petroleum pitch.

Preferably, the weak base in the step (2) is one of ammonia water, urea or ammonium hydrogencarbonate, and the molar ratio of the weak base to the aluminum nitrate is 1:1 to 3:1.

Feasible, the drying treatment in step (3) is blast drying, spray drying, freeze drying Any of them.

It is feasible that the mass ratio of the final material Al ₂ O ₃ -SiO _X /C of Al ₂ O _{3 to} the SiO _X /C material in the step (4) is 0.1% to 5%.

Example 1

Under a nitrogen atmosphere, the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 700 ° C, and kept for 2 h. After cooling to room temperature, the material is subjected to classification and sieving treatment to obtain SiO _X / C composite material. The SiO _X /C composite was added to deionized water, then added with aluminum nitrate for 20 min, then aqueous ammonia solution was added and stirred in a water bath at 70 ° C for 1 h. The mixed liquid obtained above was subjected to a drying treatment to obtain a precursor Al(OH) ₃ -SiO _X /C material. The precursor material was heat-treated at 1100 ° C for 3 h under a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material.

Preparation of negative electrode sheet: The electrode sheet is prepared by stirring and then coated on a copper foil by an automatic coating film dryer. The solvent of the slurry is deionized water, the conductive agent is Super P, and the binder is carboxymethyl fiber. The butyl rubber emulsion has a ratio of active material, conductive agent and binder of 8:1:1.

Battery preparation: The button type half-cell uses lithium sheet as the counter electrode, and the CR2032 button battery is assembled in the glove box according to the order of the positive electrode shell, the electrode sheet, the separator, the lithium sheet, the stainless steel gasket, the foamed nickel and the negative electrode shell. 1 mol/L of LiPF _{6 was} used as the electrolyte, the solvent was 1:1:1 EC/EMC/DMC, and 10% FEC was added.

Battery test: The charge and discharge curve of the blue battery test button battery is charged and discharged at 0.1C rate, and the cut-off voltage is 0.005-1.5V.

Referring to Figures 1 and 2, they are SiO _X /C electron micrographs of the asphalt coated SiO _X of Example 1 and a scanning electron micrograph of the final Al ₂ O ₃ -SiO _X /C material, respectively. It can be seen that the material has a regular shape, uniform distribution and smooth surface.

The charge ratio of the button cell prepared by using the Al ₂ O ₃ -SiO _X /C material of the present invention as a negative electrode material for 50 cycles is shown in Fig. 3. It can be seen that the first charging capacity is 1481.2 mAh/g, and the capacity after 20 cycles is still 876.1 mAh/g, and the capacity retention rate is 59.15%.

Example 2

Under a nitrogen atmosphere, the SiO _X raw material and the pitch are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 900 ° C, and kept for 1 h. After cooling to room temperature, the material is subjected to classification and sieving treatment to obtain SiO _X / C composite material. The SiO _X /C composite was added to deionized water, then added with aluminum nitrate for 20 min, then aqueous urea solution was added and stirred in a water bath at 60 ° C for 2 h. The mixed liquid obtained above was subjected to a drying treatment to obtain a precursor Al(OH) ₃ -SiO _X /C material. The precursor material was heat-treated at 1000 ° C for 1 h in a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material.

Preparation of negative electrode sheet: The electrode sheet is prepared by stirring and then coated on a copper foil by an automatic coating film dryer. The solvent of the slurry is deionized water, the conductive agent is Super P, and the binder is carboxymethyl fiber. The butyl rubber emulsion has a ratio of active material, conductive agent and binder of 8:1:1.

Battery preparation: The button type half-cell uses lithium sheet as the counter electrode, and the CR2032 button battery is assembled in the glove box according to the order of the positive electrode shell, the electrode sheet, the separator, the lithium sheet, the stainless steel gasket, the foamed nickel and the negative electrode shell. 1 mol/L of LiPF _{6 was} used as the electrolyte, the solvent was 1:1:1 EC/EMC/DMC, and 10% FEC was added.

Battery test: The charge and discharge curve of the blue battery test button battery is charged and discharged at 0.1C rate, and the cut-off voltage is 0.005-1.5V.

Example 3

Under a nitrogen atmosphere, the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 850 ° C, and kept for 4 hours. After cooling to room temperature, the material is subjected to classification and sieving treatment to obtain SiO _X / C composite material. The SiO _X /C composite was added to deionized water, then added with aluminum nitrate for 20 min, then aqueous ammonium hydrogencarbonate solution was added, and stirred in a water bath at 80 ° C for 5 h. The mixed liquid obtained above was subjected to a drying treatment to obtain a precursor Al(OH) ₃ -SiO _X /C material. The precursor material was heat-treated at 800 ° C for 1 h in a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material.

Preparation of negative electrode sheet: The electrode sheet is prepared by stirring and then coated on a copper foil by an automatic coating film dryer. The solvent of the slurry is deionized water, the conductive agent is Super P, and the binder is carboxymethyl fiber. The butyl rubber emulsion has a ratio of active material, conductive agent and binder of 8:1:1.

Battery preparation: The button type half-cell uses lithium sheet as the counter electrode, and the CR2032 button battery is assembled in the glove box according to the order of the positive electrode shell, the electrode sheet, the separator, the lithium sheet, the stainless steel gasket, the foamed nickel and the negative electrode shell. 1 mol/L of LiPF _{6 was} used as the electrolyte, the solvent was 1:1:1 EC/EMC/DMC, and 10% FEC was added.

Battery test: The charge and discharge curve of the blue battery test button battery is charged and discharged at 0.1C rate, and the cut-off voltage is 0.005-1.5V.

Comparative example 1

Preparation of silicon carbon anode material: the step of removing Al ₂ O ₃ coating, only to keep “the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio in a nitrogen atmosphere, and then heated to 700 ° C, and After heat preservation for 2 h, after cooling to room temperature, the material was classified and sieved to obtain a SiO _X /C composite material.

The parameters related to material deduction of Examples 1-3 and Comparative Example 1 are shown in Table 1:

First reversible capacity First efficiency 20 cycle capacity retention rate Example 1 1481.2mAh/g 81.86% 80.01% Example 2 1469.1mAh/g 82.14% 78.84% Example 3 1487.6mAh/g 80.62% 79.76% Comparative example 1 1477.4mAh/g 79.02% 70.37%

Table 1

The invention firstly performs carbon coating treatment on SiO _X to alleviate the volume effect generated when SiO _{X is} charged and discharged, and has the advantages of simple process, low manufacturing cost and high yield. The Al ₂ O ₃ coating layer can effectively reduce the contact between the electrolyte and the SiO _X and the carbon layer, and reduce the side reaction of the material and the electrolyte, and also reduce the formation of the SEI film. In addition, the Al ₂ O ₃ cladding layer can act as an SEI film, which itself leads to Li ⁺ non-conductors and can also increase the Li ⁺ migration rate.

The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the technical solutions of the present invention. Any technical solutions that can be implemented on the basis of the above embodiments without creative work should be considered as falling into the present invention. The scope of protection of rights.

Claims (5)

A high-efficiency long-life silicon carbon anode material preparation method, characterized in that the specific steps are as follows: (1) Under a nitrogen atmosphere, the SiO _X raw material and the asphalt are uniformly mixed in a heating mixer according to a certain ratio, and then heated to 700-1000 ° C, and kept for 1-4 h, and after cooling to room temperature, the material is classified. Sieve treatment to obtain SiO _X /C composite material; (2) adding SiO _X / C composite material to deionized water, then adding aluminum nitrate for 20min, then adding a weak alkaline aqueous solution, and stirring in a water bath at 60-80 ° C for 1-5h; (3) drying the mixture obtained above to obtain a precursor Al(OH) ₃ -SiO _X /C material; (4) The precursor material is heat-treated at 800-1100 ° C for 1-4 h in a nitrogen atmosphere, and naturally cooled to obtain a final Al ₂ O ₃ -SiO _X /C material. The method according to claim 1, wherein the SiO _X raw material in the step (1) has a median diameter of 4-8 μm, and 0<X< 2. The asphalt is one of coal pitch or petroleum pitch. The method for preparing a high-efficiency long-life silicon carbon anode material according to claim 1, wherein the weak base in the step (2) is one of ammonia water, urea or ammonium hydrogencarbonate, and the weak base The molar ratio to aluminum nitrate is 1:1 to 3:1. The method for preparing a high-efficiency long-life silicon carbon negative electrode material according to claim 1, wherein the drying treatment in the step (3) is any one of blast drying, spray drying, and freeze drying. Kind. The method for preparing a high-efficiency long-life silicon carbon anode material according to claim 1, characterized in that: the final material Al ₂ O ₃ -SiO _X /C Al ₂ O ₃ in the step (4) The mass ratio of the SiO _X /C material is from 0.1% to 5%.

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