CN114057488B

CN114057488B - Preparation method of porous SiOC ceramic and application of porous SiOC ceramic in negative electrode material of lithium ion battery

Info

Publication number: CN114057488B
Application number: CN202210046585.5A
Authority: CN
Inventors: 夏克东; 刘晓; 段凌瑶; 李芸玲; 侯振雨
Original assignee: Henan Institute of Science and Technology
Current assignee: Henan Institute of Science and Technology
Priority date: 2022-01-17
Filing date: 2022-01-17
Publication date: 2022-04-15
Anticipated expiration: 2042-01-17
Also published as: CN114057488A

Abstract

The invention discloses a preparation method of porous SiOC ceramic and application thereof in a lithium ion battery cathode material. According to the invention, phenyl triethoxysilane is used as a sol-gel precursor, starch is used as a template, and 3-aminopropyl triethoxysilane (KH 540) is used as a surface modifier, so that the porous SiOC ceramic is successfully synthesized. Amount of starch, KH540, EtOH/H₂The O ratio influences the synthesis of porous SiOC ceramics, the specific surface area of the SiOC ceramics is 207.3m at a starch content of 2.5g²g^‑1Has better rate performance and cycle performance at 37.2mAg^‑1And 372mAg^‑1The discharge capacities after passing through the material for 200 times of circulation under the current are 745mAhg respectively^‑1、483 mAhg^‑1。

Description

Preparation method of porous SiOC ceramic and application of porous SiOC ceramic in negative electrode material of lithium ion battery

Technical Field

The invention belongs to the technical field of preparation of lithium ion battery cathode materials, and particularly relates to synthesis and application of porous SiOC ceramic.

Background

The lithium ion battery as a rechargeable battery for energy storage and conversion has the characteristics of light weight, high working voltage, no memory effect, environmental friendliness and the like, and is widely applied to the fields of mobile phones, notebook computers, electric vehicles and the like. Graphite is used as a common lithium ion battery cathode material, the theoretical capacity is only 372 mAh/g, the current energy requirement is difficult to meet, and carbon materials such as carbon nanotubes and graphene are easy to contact and react with electrolyte in the charging and discharging processes. In addition, materials such as transition metal oxides, Si-based, Ge-based, and Sn-based have been developed to increase specific capacity, but these materials undergo severe volume expansion during cycling, resulting in capacity loss. Therefore, there is a need to develop a lithium ion battery negative electrode material that is inexpensive, has a stable structure, has a high specific capacity, and has excellent cycle performance.

SiOC ceramics are concerned by having better chemical stability, structural stability and electrochemical performance, and the SiOC ceramics mainly comprise SiO_xC_4-xIn combination with the free C phase, which is commonly considered to be the primary lithium storage site for use as a lithium ion battery anode material. The content of free C is improved, and SiO can be stabilized_xC_4-xCan improve the lithium storage performance of the material. The C content of the SiOC ceramic can be effectively increased by using the siloxane containing unsaturated substituent groups, the C-rich precursor and the cross-linking agent. In addition, the specific surface area of the SiOC ceramic is increased, and the electrochemical performance of the material can be improved by designing a porous structure. The mesopores are favorable for the transmission of lithium ions and electrons, and the micropores can increase the lithium storage capacity of the material.

In the prior art, the preparation method of the SiOC porous ceramic CN102311275A adopts the modes of wrapping, briquetting, cross-linking and foaming, requires high pressure for operation, and has complex process; CN107262028A discloses a preparation method and application of an ultra-light massive super-hydrophobic magnetic shaddock peel carbon material, wherein a fruit residue shaddock peel is used as a carbon precursor, and the ultra-light massive super-hydrophobic magnetic shaddock peel carbon material is prepared by carbonization/magnetization and surface low-energy substance modification; CN104752691A A silicon/carbon composite negative electrode material for lithium ion battery and its preparation method, the structure includes: the lithium ion battery comprises a graphite framework material, an intermediate buffer layer SiOC material, a carbon fiber conductive network and a silicon-containing material (carbon-coated silicon-containing material) SiOz @ AC, wherein the specific capacity of the material is adjusted by adjusting the amount of an added active silicon-containing material; CN107910554A A SiOC composite negative electrode material for lithium ion batteries and a preparation method thereof, wherein wood powder and solid polysiloxane are used for preparing porous SiOC ceramic powder, the porous SiOC ceramic is compounded with graphene oxide, and by utilizing the synergistic effect among the components of the composite material, the porous structure can buffer the volume change of SiOC in the charging and discharging processes of the lithium ion batteries, but the morphology is difficult to control in the pores made by the wood powder, and the prepared porous SiOC ceramic has poor stability.

The preparation of porous SiOC ceramics usually adopts chemical etching and template method. The chemical etching method uses HF, NaOH, or KOH for etching. HF is more corrosive, while NaOH and KOH require high temperature etching. The template method for synthesizing the SiOC ceramic is relatively simple and adopts CaCO₃、SiO₂And waiting for the inorganic template, and simultaneously carrying out subsequent etching treatment. The present invention has been made to solve the above problems.

Disclosure of Invention

In order to solve the problems in the prior art, the invention takes starch as a template and phenyltriethoxysilane (PhTES) as a sol-gel precursor, porous SiOC ceramic is obtained by impregnation and high-temperature heat treatment, the porous SiOC ceramic is used as a lithium ion battery anode material, and the starch dosage and H are explored₂The influence of O/EtOH solvent and starch modifier gamma-aminopropyl triethoxysilane (KH 540) on the synthesis and performance of the material. The material synthesis steps are as follows:

1) preparation of PhTES Sol

Adding PhTES into EtOH, stirring, dropwise adding deionized water, and sealing and stirring for 9-12 h to obtain PhTES sol;

the volume ratio of the PhTES to the EtOH to the deionized water is 2-2.5:5-6: 0.9-1.5;

2) pretreatment of starch

Weighing starch and adding into H₂Adding a certain amount of KH540 into the O/EtOH mixed solution, and stirring at room temperature for 30 min to obtain a starch solution;

wherein the mass ratio of the KH540 to the starch is 1: 10-15; said H₂The volume ratio of O/EtOH is 1:1, and the starch and the H are₂The mass ratio of the O/EtOH mixed solution is 1: 2-10;

3) synthesis of porous SiOC ceramics

Adding the PhTES sol to the starch solution at 80-95 deg.C^oC, stirring to dry to obtain white powder, and then placing the white powder in a place of 95-100 DEG C^oC, drying in an oven for 16-48 h, grinding after drying, and performing high-temperature heat treatment after grinding, wherein the high-temperature heat treatment is performed by 4-6^oRaising the temperature to 800-^oC, preserving the heat for 2-3 h to obtain the porous SiOC ceramic;

the mass ratio of the PhTES in the PhTES sol to the starch in the starch solution is 0.6-2.

4. Assembly of lithium ion batteries

Dissolving polyvinylidene fluoride in an N-methyl pyrrolidone solution, adding porous SiOC ceramic and acetylene black, and grinding into uniform slurry, wherein the mass ratio of the porous SiOC ceramic to the acetylene black to the polyvinylidene fluoride is 8:1: 1; coating the slurry on the rough surface of the copper foil, vacuum-drying at 80-90 deg.C for 24-36 h, cutting out electrode sheet with diameter of 10 mm by using a slicer, and weighing. Assembling the button cell in a vacuum glove box according to the sequence of an active electrode, a cell diaphragm Celgard 2325, a lithium sheet and a gasket, wherein the electrolyte adopts 1-1.5mol/L LiPF₆Solution of said LiPF₆The solvent of the solution is a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 1: 1.

Compared with the prior art, the invention has the following advantages:

in the invention, KH540 is used for pretreating starch, so that the binding force of the starch and the PhTES sol can be enhanced, and the starch is regulated and controlledThe SiOC ceramics with different morphologies are obtained by using the amount; regulating and controlling H along with the increase of the using amount of starch₂The proportion of the O/EtOH mixed solution is 1:1, porous SiOC ceramics can be obtained, the specific surface area of the SiOC ceramics can be increased, and the lithium storage performance of the material can be improved; compared with the preparation process of other battery materials, the preparation method has the advantages of simple operation method, obvious modification process effect, cheap modified raw materials and strong practicability, and the prepared ceramic material has good rate discharge performance and cycle discharge performance; the specific surface area of the SiOC ceramic prepared when the starch content is 2.5g is 207.3m2g-1, the ceramic material shows better rate performance and cycle performance, the discharge capacity of the cycle material after 200 times under the current of 37.2mAg-1 and 372 mAg-1 is 745mAhg-1 and 483mAhg-1 respectively, the performance of the lithium ion battery can be greatly improved, and the application significance is wide.

Drawings

FIG. 1 is an SEM image of sample No. 1-1;

FIG. 2 is an SEM image of sample Nos. 1-2;

FIG. 3 is an SEM image of samples Nos. 1-3;

FIG. 4 is an SEM image of sample Nos. 1-4;

FIG. 5 is an SEM image of sample number 2-1;

FIG. 6 is an SEM image of sample number 2-2;

FIG. 7 is an SEM image of sample number 3-1;

FIG. 8 is an SEM image of sample number 3-2;

FIG. 9 is an SEM image of sample number 4-1;

FIG. 10 is an SEM image of sample number 5-1;

FIG. 11 is an SEM image of sample number 6-1;

FIG. 12 is a graph of sorption-desorption isotherms of the sample of example 1;

FIG. 13 is a graph of rate capability for samples 1-1, 1-2 versus 1-3, 5-1, 6-1, 1-4;

FIG. 14 shows that the sample sizes of 1-3 are 37.2mAg^-1The cycle performance of (c);

FIG. 15 shows the results of 1-3 samples at 372mAg^-1The cycle performance of (c).

Detailed Description

Example 1

Adding 2 ml of PhTES into 5 ml of EtOH, stirring, dropwise adding 0.9 ml of deionized water, and then sealing and stirring for 9-12 h to obtain PhTES sol;

1.5 g, 2.0 g, 2.5g, 3.0 g starch were weighed out separately and added to 10 mL H₂Adding 0.15 g, 0.20 g, 0.25 g and 0.30 g KH540 into the O/EtOH mixed solution (v/v =1: 1), stirring for 30 min, adding PhTES sol solution, and stirring at 80 deg.C^oC stirring until it is dried to obtain white powder, and placing at 100 deg.C^oAfter drying in oven C for 24 h, at 900^oC, heat treatment is carried out for 2 h. The synthesized samples were numbered, 1-1, 1-2, 1-3, 1-4 corresponding to 1.5 g, 2.0 g, 2.5g, 3.0 g starch synthesized SiOC material, respectively.

Comparative example 1

2.0 g and 2.5g of starch were weighed out separately and added to 10 mL of H₂Adding 0.20 g KH540 and 0.25 g KH540 into O, stirring for 30 min, adding the PhTES sol solution prepared in example 1, and stirring at 80 deg.C^oC stirring until it is dried to obtain white powder, and placing at 100 deg.C^oAfter drying in oven C for 24 h, at 900^oC, heat treatment is carried out for 2 h. The samples synthesized are numbered, 2-1, 2-2 corresponding to 2.0 g, 2.5g starch synthesized SiOC material, respectively.

Comparative example 2

2.0 g and 2.5g of starch were weighed into 10 mL of EtOH, 0.20 g and 0.25 g of KH540 were added, respectively, and stirred for 30 min, after which the PhTES sol solution prepared in example 1 was added at 80%^oC stirring until it is dried to obtain white powder, and placing at 100 deg.C^oAfter drying in oven C for 24 h, at 900^oC, heat treatment is carried out for 2 h. The samples synthesized were numbered, 3-1, 3-2 corresponding to 2.0 g, 2.5g starch synthesized SiOC material, respectively.

Comparative example 3

2.5g of starch are weighed into 10 mL of H₂To the O/EtOH mixed solution (v/v =1: 1), after stirring for 30 min the PhTES sol solution prepared in example 1 was added at 80^oC stirring until it is dried to obtain white powder, and placing at 100 deg.C^oAfter drying in oven C for 24 h, at 900^oC, heat treatment is carried out for 2 h. To pairThe samples synthesized are numbered, 4-1 corresponding to the SiOC material synthesized.

Comparative example 4

Adding 2.00 mL PhTES into 5 mL EtOH, stirring, adding 0.90 mL deionized water dropwise, sealing and stirring for 10 h to obtain PhTES sol, and placing at 100^oC drying in an oven for 24 h to obtain a gel, 5^oHeating to 900 deg.C/min^oC, preserving the heat for 2 hours, wherein the sample number is 5-1.

2.5g of starch was added to 10 mL of H₂O/EtOH mixed solution (v/v =1: 1), 80^oC stirring until it is dried to obtain white powder, and placing at 100 deg.C^oAfter drying in oven C for 24 h, at 900^oC, heat treatment is carried out for 2 h, and the sample number is 6-1.

Morphology characterization of materials

The synthesized material is adhered to a sample stage of a scanning electron microscope, and appearance observation is carried out by vacuumizing, so that the influence of the solvent ratio and KH540 on the appearance of the material is obvious. At H₂In the O/EtOH mixed solution, porous SiOC ceramics can be obtained with increasing amount of starch, and FIGS. 1 to 4 are SEM images of SiOC ceramics prepared in example 1. At H₂In O, bulk SiOC ceramic was obtained, no porous structure was formed on the surface, and FIGS. 5 and 6 are the morphologies of the samples prepared in comparative example 1. However, comparative example 2 is EtOH, whereas fig. 7 and 8 show that the morphology of the material is significantly changed, and a random sheet-like morphology is obtained after heat treatment. In addition, comparative example 3 was made without adding KH540, and the obtained sample was in the form of a sheet, indicating that the sample obtained without adding KH540 had a dispersed structure. Comparative example 4 is the heat treatment of pure SiOC ceramic without starch and KH540 and starch without KH540, and FIGS. 10 and 11 observe that the samples after heat treatment are amorphous blocks and sheets, which shows that the porous structure of the SiOC ceramic material is realized by the modification of starch to the morphology of the SiOC ceramic.

Specific surface area and pore size analysis of materials

The specific surface area of the material was measured by the BET method and the pore size distribution was measured by the BJH method. Fig. 12 is a sorption-desorption isotherm of the sample in example 1. Although FIG. 1 shows bulk material, the surface has a porous structure, of SiOC ceramicsSpecific surface area of 181.9 m²g^-1. The specific surface area of SiOC ceramics increases with increasing amounts of starch. The specific surface areas of the SiOC ceramics obtained with 2.0 g and 2.5g of starch were 193.7 m²g^-1And 207.3m²g^-1. However, as the amount of starch was increased to 3.0 g, the specific surface area of the SiOC ceramic was slightly decreased to 194.6 m²g^-1. In addition, at a lower P/P₀The temperature line of adsorption and desorption is increased sharply, and more micropores exist in the surface material. P/P₀When the temperature is more than 0.3, a hysteresis loop appears on the adsorption and desorption isotherm, which indicates that the interior of the material contains mesopores.

Lithium ion battery performance testing

The materials of example 1 and comparative example were used to assemble a button cell. The rate capability test was performed on the assembled cells at room temperature using the novyi lithium ion battery test system, first at 37.2mAg^-1Circulate 5 times, then respectively at 74.4mAg^-1、186mAg^-1、372mAg^-1、744mAg^-1Circulating for 10 times, passing through 744mAg^-1After circulation, the current returns to 37.2mAg^-1And 5 times of recycling. At 37.2mAg^-1、74.4mAg^-1、186mAg^-1、372mAg^-1、744mAg^-1The discharge capacities at current were 415mAhg, respectively^-1、370mAhg^-1、270mAhg^-1、180mAhg^-1、80mAhg^-1. The best rate performance of the 1-3 samples, at 37.2mAg^-1、74.4mAg^-1、186mAg^-1、372mAg^-1、744mAg^-1The discharge capacities at current were 710mAhg, respectively^-1、730mAhg^-1、590mAhg^-1、490mAhg^-1、390mAhg^-1(ii) a The effect of the modified starch on the electrical property of the SiOC ceramic is obvious, and the specific surface areas of the SiOC ceramic under different starch dosages are different, so that the lithium storage property of the material can be improved by the larger specific surface area.

FIG. 14 shows that the sample sizes of 1-3 are 37.2mAg^-1The cycle performance of (c). The first-circle discharge capacity and the coulombic efficiency are 1864mAhg^-185.1 percent. After 200 cycles, the material discharge capacity is745mAhg^-1(ii) a FIG. 15 shows the results of 1-3 samples at 372mAg^-1The discharge capacity of the material after 200 cycles is 483mAhg^-1. As a lithium ion battery cathode material, the first turn of the cycle performance test process is a discharge process, the charge and discharge process, along with the insertion and separation process of lithium ions, the coulombic efficiency is gradually increased, and the first turn of the coulombic efficiency (the first turn of the coulombic efficiency) is a standard for measuring the performance of the lithium ion battery. At 37.2mAg^-1The discharge capacity was 1864mAhg^-1. As can be seen from FIGS. 14 and 15, the discharge capacity was 37.2mAg^-1And 372mAg^-1The discharge capacities of the materials after 200 cycles were 745mAhg, respectively^-1、483 mAhg^-1。

Claims

1. A preparation method of porous SiOC ceramic is characterized by comprising the following steps:

step 1) preparation of PhTES Sol

step 2) pretreatment of starch

step 3) Synthesis of porous SiOC ceramics

Adding the PhTES sol into the starch solution, stirring at 80-95 ℃ until drying to obtain white powder, then placing the white powder in a baking oven at 95-100 ℃ for drying for 16-48 h, grinding after drying, and performing high-temperature heat treatment after grinding, wherein the high-temperature heat treatment is performed at 4-6 DEG C^oRaising the temperature to 800-^oC, preserving the heat for 2-3 h to obtain the porous SiOC ceramic;

the volume ratio of PhTES, EtOH and deionized water in the step 1) is (2-2.5): (5-6): (0.9-1.5), and the mass ratio of KH540 to starch in the step 2) is 1: 10-15; said H₂H in O/EtOH mixed solution₂The volume ratio of O to EtOH is 1:1, and the starch and the H are₂The mass ratio of the O/EtOH mixed solution is 1:2-10, and the mass ratio of the PhTES in the PhTES sol in the step 3) to the starch in the starch solution is 0.6-2.

2. The use of the porous SiOC ceramic prepared by the method of claim 1 in the negative electrode material of a lithium ion battery.

3. The application of the porous SiOC ceramic in the negative electrode material of the lithium ion battery, which is described in claim 2, is characterized in that the preparation method of the lithium ion battery comprises the following steps: dissolving polyvinylidene fluoride in an N-methyl pyrrolidone solution, adding porous SiOC ceramic and acetylene black, and grinding into uniform slurry; coating the slurry on the rough surface of the copper foil, vacuum-drying at 80-90 ℃ for 24-36 h, cutting an electrode plate with the diameter of 10 mm by using a slicing machine, and weighing; assembling the button cell in a vacuum glove box according to the sequence of an active electrode, a Celgard 2325 diaphragm, a lithium sheet and a gasket, wherein the electrolyte adopts 1-1.5mol/L LiPF₆And (3) solution.

4. The application of the porous SiOC ceramic in the negative electrode material of the lithium ion battery, which is disclosed by claim 3, is characterized in that the mass ratio of the porous SiOC ceramic to the acetylene black to the polyvinylidene fluoride is 8:1: 1.

5. The use of the porous SiOC ceramic of claim 3, wherein said LiPF is used as a negative electrode material in a lithium ion battery₆The solvent of the solution is a mixed solvent of ethylene carbonate and diethyl carbonate, wherein the volume ratio of the ethylene carbonate to the diethyl carbonate is 1: 1.