Silicon / graphene composite material and preparation method and application thereof
By preparing silicon/graphene composite materials, the problems of volume expansion and poor conductivity of silicon anode materials in lithium-ion batteries were solved, thereby improving the performance of lithium-ion batteries.
Patent Information
- Application Number
- CN202510860158.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2025-11-18
AI Technical Summary
Silicon anode materials have limited performance in lithium-ion batteries due to volume expansion and poor conductivity, and existing technologies have difficulty effectively solving this problem.
Silicon/graphene composite materials were prepared by in-situ electrostatic self-assembly and post-annealing reduction process. Graphene nanosheets encapsulated silicon nanoparticles to form a strongly coupled structure, which suppressed volume changes and provided additional electron channels.
It significantly suppresses stress/strain caused by volume changes, improves electron migration efficiency, and enhances the kinetic performance of lithium-ion batteries.
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a silicon / graphene composite material and a preparation method and application thereof. BACKGROUND
[0002] With the growing demand for power of emerging portable electronic devices and electric vehicles, higher energy and power requirements are put forward for the energy output of lithium ion batteries (LIB). Alloy-type anodes (such as aluminum, phosphorus, silicon, tin, etc.) can provide extremely high specific capacity by reacting with cations. Silicon anode material has an ultra-high theoretical specific capacity (4200 mAh / g), so introducing a high-capacity silicon anode into a lithium ion battery is an effective method to improve the energy density thereof. However, the huge volume expansion (300%) of silicon during the entire alloying and de-alloying process must be controlled, and in addition, the poor conductivity of silicon is also an important factor hindering its development.
[0003] Based on this, the application designs a strongly coupled silicon / graphene composite material (Si@G) prepared by in-situ electrostatic self-assembly and post-annealing reduction process. The composite structure greatly suppresses the stress / strain caused by volume change and effectively relieves the pulverization of the anode material during the charging and discharging process. SUMMARY
[0004] One of the purposes of the application is to provide a preparation method of a silicon / graphene composite material, comprising the following steps:
[0005] Step 1, adding silicon powder into water, then adding cationic polymer, ultrasonic dispersion, and centrifugation to obtain silicon precipitate;
[0006] Step 2, adding graphene oxide into water to obtain a graphene oxide solution;
[0007] Step 3, adding the aqueous solution of the silicon precipitate into the graphene oxide solution, stirring, and filtering to obtain Si@GO;
[0008] Step 4, calcining the Si@GO to obtain the silicon / graphene composite material.
[0009] Further, the cationic polymer is a polyquaternary ammonium salt cationic polymer, selected from polydimethyl diallyl ammonium chloride (PDDA), polymethyl acryloyl ethyl trimethyl ammonium chloride (PMETAC), poly(2-methyl acryloyl ethyl trimethyl ammonium chloride) (PTAC), and poly(3-methyl acryloyl propyl trimethyl ammonium chloride) (PAPTAC).
[0010] Further, in step 1, the mass ratio of the silicon powder to the cationic polymer is 1-1.5:1.
[0011] In one embodiment of the present application, the cationic polymer is added to water to form an aqueous solution before being added.
[0012] Further, in step 3, the mass ratio of the silicon precipitate and graphene oxide is 5:1.
[0013] Further, in step 4, the calcination is performed under a protective atmosphere, preferably a 10% H2 / Ar atmosphere.
[0014] Further, in step 4, the calcination is performed at 800-1000℃ for 1-3h.
[0015] Further, the heating rate is 5℃ / min.
[0016] The second object of the present application is to provide a silicon / graphene composite material prepared by the above preparation method.
[0017] The third object of the present application is to provide a negative electrode sheet comprising a current collector and an active layer on the surface of the current collector, wherein the active layer comprises the above negative electrode material or the above negative electrode material.
[0018] The fourth object of the present application is to provide a battery comprising the above negative electrode sheet.
[0019] The above technical solutions have at least the following advantages:
[0020] The present application provides a strong coupling silicon / graphene composite material (Si@G) prepared by in-situ electrostatic self-assembly and post-annealing reduction process. The composite structure greatly suppresses the stress / strain caused by volume change. The silicon nanoparticles are completely wrapped by graphene nanosheets. The aggregation of silicon and the folding and stacking of graphene nanosheets form many voids, which are beneficial to the penetration of electrolyte and the transmission of Li + ions. At the same time, the silicon-loaded nanosheets are connected to each other, providing additional electronic channels.
[0021] The in-situ electrostatic self-assembly synthesis process is simple to operate and low in energy consumption. The graphene layer attached to the surface of Si nanospheres can weaken the volume expansion and prevent the aggregation of Si particles with high surface energy. The high conductivity of graphene promotes the electron migration during the charging and discharging process, greatly improving the kinetic performance of the Si@G negative electrode. DETAILED DESCRIPTION
[0022] In order to make the above objectives, features and advantages of the present application more clear and easily understood, the specific embodiments of the present application are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in many different ways from those described herein, and should not be construed as being limited to the embodiments set forth herein, as one of ordinary skill in the art would understand from the description that various modifications are possible in the present application without departing from the scope of the present application.
[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.
[0024] In addition, the terms "first", "second", etc. are used herein only to describe various conditions, and should not be construed as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically limited.
[0025] The alloying reaction of silicon can cause a volume expansion of more than 300%, and the present application alleviates the stress / strain caused by the volume change through material design. The graphene layer attached to the surface of the silicon nanosphere can reduce the volume expansion and prevent the aggregation of silicon particles with high surface energy. The high conductivity of graphene promotes the migration of electrons during the charging and discharging process, so that the kinetic performance of the silicon / graphene composite (Si@G) negative electrode is greatly improved.
[0026] Specifically, the present application provides a preparation method of a silicon / graphene composite material, comprising the following steps:
[0027] Step 1, adding silicon powder into water, then adding cationic polymer, ultrasonic dispersion, and centrifuging to obtain silicon precipitate;
[0028] Step 2, adding graphene oxide into water to obtain a graphene oxide solution;
[0029] Step 3, adding the aqueous solution of the silicon precipitate into the graphene oxide solution, stirring, and filtering to obtain Si@GO;
[0030] Step 4, calcining the Si@GO to obtain the silicon / graphene composite material.
[0031] Further, in step 1, the cationic polymer is a polyquaternary ammonium salt cationic polymer selected from polydimethyl diallyl ammonium chloride (PDDA), polymethyl acryloxyethyl trimethyl ammonium chloride (PMETAC), poly(2-methyl acryloxyethyl trimethyl ammonium chloride) (PTAC), poly(3-methyl acryloxypropyl trimethyl ammonium chloride) (PAPTAC).
[0032] Cationic polymers are an important class of functional polymers, due to their special structure, widely used in textile (antistatic agent), papermaking (paper strength agent), petroleum chemical industry (long-acting clay stabilizer), cosmetics, water treatment (flocculant), environmental governance (non-oxidizing bactericide), corrosion science (antirust agent), material surface modification and other technical fields. At present, the cationic polymers commonly used are quaternary ammonium salt polymers, quaternary phosphonium salt polymers and quaternary sulfonium salt polymers; among them, the most widely used and the most numerous products are quaternary ammonium salt polymers.
[0033] Quaternary ammonium salt polymers are an important type of cationic polymers, with the characteristics of the most varieties and the most widely used. Polydimethyl diallyl ammonium chloride, as a typical representative of quaternary ammonium salt polymers, has attracted much attention. It contains a pyrrole ring in its molecular structure, has high positive charge density, good water solubility, controllable molecular weight, high efficiency and no toxicity, low cost, and good development prospects. It has been widely used in water treatment, oil extraction, papermaking, daily chemicals, textiles, sterilization and metal corrosion prevention and other fields. The present application utilizes the special structure of quaternary ammonium salt polymers to modify the surface of silicon powder, thereby facilitating the subsequent wrapping of graphene nanosheets on silicon nanoparticles.
[0034] Further, in step 1, the mass ratio of the silicon powder to the cationic polymer is 1-1.5:1.
[0035] In a specific embodiment of the present application, the cationic polymer is added to water to form an aqueous solution before being added.
[0036] Further, in step 3, the mass ratio of the silicon precipitate to graphene oxide is 5:1.
[0037] Further, in step 4, the calcination is carried out under a protective atmosphere, preferably a 10% H2 / Ar atmosphere.
[0038] Further, in step 4, the calcination conditions are 800-1000℃ for 1-3h.
[0039] Further, the heating rate is 5℃ / min.
[0040] The electrostatic self-assembly technology is a bottom-up, small-to-large fabrication method, i.e., starting from the atomic or molecular level to completely construct a device. The present application prepares a strong-coupling silicon / graphene composite material (Si@G) through in-situ electrostatic self-assembly and post-annealing reduction process. The composite structure greatly suppresses the stress / strain caused by volume change, the silicon nanoparticles are completely wrapped by the graphene nanosheets, the aggregation of silicon and the folding and stacking of graphene nanosheets form many voids, which are conducive to the penetration of electrolyte and the transmission of Li + ions. Meanwhile, the silicon-loaded nanosheets are connected to each other, providing additional electronic channels.
[0041] The preferred embodiments of the present application will be described in detail below with reference to the embodiments. It should be understood that the following embodiments are given only for the purpose of illustration and are not intended to limit the scope of the present application. Those skilled in the art can make various modifications and replacements to the present application without departing from the spirit and principles of the present application.
[0042] The experimental methods used in the following examples are conventional methods unless otherwise specified.
[0043] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.
[0044] Example 1
[0045] 1. Preparation of Si-PDDA: First, 0.5 g of silicon powder was weighed and stirred in 50 mL of deionized water for 30 min, then 2 mL of 20 wt% polydimethyl diallyl ammonium chloride (PDDA) solution was added and ultrasonically dispersed for 1 h. Then, the above solution was centrifuged at 10000 rpm / min for 5 min, washed with deionized water three times to remove excess PDDA, and a positively charged silicon precipitate was obtained, denoted as Si-PDDA.
[0046] 2. Preparation of GO solution: 0.1 g of graphite oxide (GO) was weighed and added to 100 mL of deionized water, mixed and stirred and treated with ultrasonic for 1 h to obtain a 1 mg / mL GO solution.
[0047] 3. The prepared aqueous Si-PDDA solution (solvent is deionized water, concentration is 0.01 g / mL, 0.5 g of Si-PDDA was weighed and stirred in 50 mL of deionized water for 1 h) was slowly added to the GO solution and stirred for 12 h. The solution was filtered to obtain Si@GO, and then vacuum dried at 80℃ for 12 h.
[0048] 4. The dried Si@GO was calcined at 900℃ for 2 h under a 10% H2 / Ar atmosphere. Finally, the Si@G sample was obtained.
[0049] The Si@G material (active material), SP and PVDF are stirred uniformly in a mass ratio of 8:1:1, then applied on a copper foil, and then vacuum dried and sheeted to obtain a negative electrode sheet.
[0050] Battery assembly: Celgard 2400 polypropylene microporous membrane is used as a separator, a mixed solution of 1 mol / L LiPF6 in ethylene carbonate (EC), dimethyl carbonate (DMC) and methyl ethyl carbonate (EMC) (volume ratio 1:1:1) is used as an electrolyte, lithium iron phosphate (LiFePO4) is used as a positive electrode material to prepare a positive electrode sheet, and in an argon-filled glove box, the prepared negative electrode sheet and the positive electrode sheet are assembled into a CR2032 type button cell.
[0051] Meanwhile, a silicon powder is used as a negative electrode material to prepare a negative electrode sheet and assemble a battery as a control for testing.
[0052] Full charge expansion test: first, the initial thickness H0 of the negative electrode sheet is measured using a micrometer, then the negative electrode sheet is assembled into a battery, and after constant current charging to full lithium state, the negative electrode sheet is disassembled and the full charge thickness H1 is quickly measured using a micrometer, and the full charge expansion rate is calculated according to the formula (H1-H0) / H0*100%.
[0053] Powder resistivity and conductivity test: first, the powder sample to be tested is placed in a cylindrical mold, and a powder sheeting machine is used to press the powder into a dense sheet body with fixed size and shape under a constant pressure of 10 MPa, to ensure that the sample is uniform and has good conductivity. Subsequently, four-probe or two-electrode method is used for measurement, in the four-probe method, the outer two probes apply a constant current, and the inner two probes measure the voltage drop, and the resistivity is calculated according to the formula ρ=(V / I)*(A / L) (ρ is the resistivity, V is the voltage, I is the current, A is the cross-sectional area of the sample, and L is the probe spacing); and the conductivity σ is the inverse of the resistivity, i.e. σ=1 / ρ.
[0054] Full charge expansion Powder resistivity (Ω*cm) Electrical conductivity (S / cm) Si 287％ 1.35*10 5 ]]> 7.41*10 -6 ]]> Si@G 224％ 6.31*10 3 ]]> 1.58*10 -4 ]]>
[0055] From the above results, it can be seen that the kinetic performance of the Si@GO negative electrode prepared by the application is much better than that of the silicon powder. The graphene layer attached to the surface of the Si nanosphere can weaken the volume expansion and prevent the aggregation of Si particles with high surface energy, and the high conductivity of graphene promotes the electron migration in the charging and discharging process, so that the kinetic performance of the Si@G negative electrode is greatly improved.
[0056] Example 2
[0057] 1. Preparation of Si-PDDA: First, 0.4 g of silicon powder was weighed and stirred in 40 mL of deionized water for 30 min, then 2 mL of 20 wt% polydimethyl diallyl ammonium chloride (PDDA) solution was added and ultrasonic dispersed for 1 h. Then, the above solution was centrifuged at 10000 rpm / min for 5 min, washed with deionized water for three times to remove the excess PDDA, and a positively charged silicon precipitate was obtained, denoted as Si-PDDA.
[0058] 2. Preparation of GO solution: 0.1 g of graphite oxide (GO) was weighed and added to 100 mL of deionized water, mixed and stirred and treated with ultrasonic for 1 h to obtain a GO solution of 1 mg / mL.
[0059] 3. The prepared aqueous Si-PDDA solution (solvent: deionized water, concentration: 0.01 g / mL, 0.5 g of Si-PDDA was weighed and stirred in 50 mL of deionized water for 1 h) was slowly added to the GO solution and stirred for 12 h. The solution was filtered to obtain Si@GO, which was then vacuum dried at 80°C for 12 h.
[0060] 4. The dried Si@GO was calcined at 800°C for 3 h under a 10% H2 / Ar atmosphere. Finally, the Si@G sample was obtained.
[0061] The Si@G material (active material), SP and PVDF were stirred uniformly at a mass ratio of 8:1:1 and then applied to a copper foil, followed by vacuum drying and tabletting to obtain a negative electrode sheet. The battery was assembled according to the procedure of Example 1, and its lithium storage performance was tested.
[0062] Example 3
[0063] 1. Preparation of Si-PDDA: First, 0.6 g of silicon powder was weighed and stirred in 60 mL of deionized water for 30 min, then 2 mL of 20 wt% polydimethyl diallyl ammonium chloride (PDDA) solution was added and ultrasonic dispersed for 1 h. Then, the above solution was centrifuged at 10000 rpm / min for 5 min, washed with deionized water for three times to remove the excess PDDA, and a positively charged silicon precipitate was obtained, denoted as Si-PDDA.
[0064] 2. Preparation of GO solution: 0.1 g of graphite oxide (GO) was weighed and added to 100 mL of deionized water, mixed and stirred and treated with ultrasonic for 1 h to obtain a GO solution of 1 mg / mL.
[0065] 3. The prepared aqueous Si-PDDA solution (solvent: deionized water, concentration: 0.01 g / mL, 0.5 g Si-PDDA was weighed and stirred in 50 mL deionized water for 1 h) was slowly added to the GO solution and stirred for 12 h. The solution was filtered to obtain Si@GO, which was then vacuum dried at 80 °C for 12 h.
[0066] 4. The dried Si@GO was calcined at 900 °C for 2 h under a 10% H2 / Ar atmosphere. Finally, the Si@G sample was obtained.
[0067] The Si@G material (active material), SP and PVDF were stirred uniformly at a mass ratio of 8:1:1, then applied to a copper foil, vacuum dried and sheeted to obtain a negative electrode sheet. The battery was assembled according to the procedure of Example 1, and its lithium storage performance was tested.
[0068] Example 4
[0069] 1. Si-PDDA preparation: First, 0.5 g of silicon powder was weighed and stirred in 50 mL deionized water for 30 min, then 2 mL of 20 wt% polydimethyl diallyl ammonium chloride (PDDA) solution was added and ultrasonically dispersed for 1 h. Then, the above solution was centrifuged at 10000 rpm / min for 5 min, washed with deionized water three times to remove excess PDDA, and a positively charged silicon precipitate was obtained, denoted as Si-PDDA.
[0070] 2. Preparation of GO solution: 0.1 g of graphite oxide (GO) was weighed and added to 100 mL of deionized water, mixed and stirred and treated with ultrasonic waves for 1 h to obtain a 1 mg / mL GO solution.
[0071] 3. The prepared aqueous Si-PDDA solution (solvent: deionized water, concentration: 0.01 g / mL, 0.5 g Si-PDDA was weighed and stirred in 50 mL deionized water for 1 h) was slowly added to the GO solution and stirred for 12 h. The solution was filtered to obtain Si@GO, which was then vacuum dried at 80 °C for 12 h.
[0072] 4. The dried Si@GO was calcined at 800 °C for 3 h under a 10% H2 / Ar atmosphere. Finally, the Si@G sample was obtained.
[0073] The Si@G material (active material), SP and PVDF were stirred uniformly at a mass ratio of 8:1:1, then applied to a copper foil, vacuum dried and sheeted to obtain a negative electrode sheet. The battery was assembled according to the procedure of Example 1, and its lithium storage performance was tested.
[0074] Example 5
[0075] 1. Si-PDDA preparation: First, 0.5 g of silicon powder was weighed and stirred in 50 mL of deionized water for 30 min, then 2 mL of 20 wt% polydimethyl diallyl ammonium chloride (PDDA) solution was added and ultrasonically dispersed for 1 h. Then, the above solution was centrifuged at 10000 rpm / min for 5 min, washed with deionized water three times to remove excess PDDA, and a positively charged silicon precipitate was obtained, denoted as Si-PDDA.
[0076] 2. Preparation of GO solution: 0.1 g of graphite oxide (GO) was weighed and added to 100 mL of deionized water, mixed and stirred and treated with ultrasonic for 1 h to obtain a 1 mg / mL GO solution.
[0077] 3. The prepared aqueous Si-PDDA solution (solvent: deionized water, concentration: 0.01 g / mL, 0.5 g of Si-PDDA was weighed and stirred in 50 mL of deionized water for 1 h) was slowly added to the GO solution and stirred for 12 h. The solution was filtered to obtain Si@GO, which was then vacuum dried at 80°C for 12 h.
[0078] 4. The dried Si@GO was calcined at 1000°C for 1 h under a 10% H2 / Ar atmosphere. Finally, the Si@G sample was obtained.
[0079] The Si@G material (active material), SP and PVDF were stirred uniformly at a mass ratio of 8:1:1, then applied on a copper foil, vacuum dried and sheet pressed to obtain a negative electrode sheet. The battery was assembled according to the procedure of Example 1, and its lithium storage performance was tested.
Claims
1. A method for preparing a silicon / graphene composite material, characterized in that, Includes the following steps: Step 1: Add silicon powder to water, then add cationic polymer, disperse by ultrasonication, and centrifuge to obtain silicon precipitate; Step 2: Add graphene oxide to water to obtain a graphene oxide solution; Step 3: Add the aqueous solution of silicon precipitate to the graphene oxide solution, stir and filter to obtain Si@GO; Step 4: Calcine Si@GO to obtain the silicon / graphene composite material.
2. The preparation method according to claim 1, characterized in that, The cationic polymer is a polyquaternary ammonium salt cationic polymer.
3. The preparation method according to claim 2, characterized in that, The polyquaternary ammonium salt cationic polymer is selected from polydimethyldiallylammonium chloride, polymethacryloyloxyethyltrimethylammonium chloride, poly(2-methacryloyloxyethyltrimethylammonium chloride), and poly(3-methacryloyloxypropyltrimethylammonium chloride).
4. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of silicon powder to cationic polymer is 1-1.5:
1.
5. The preparation method according to claim 1, characterized in that, In step 3, the mass ratio of the silicon precipitate to graphene oxide is 5:
1.
6. The preparation method according to claim 1, characterized in that, In step 4, the calcination is carried out under a protective atmosphere.
7. The preparation method according to claim 1, characterized in that, In step 4, the calcination conditions are 800-1000℃ for 1-3 hours.
8. A silicon / graphene composite material prepared by the preparation method according to any one of claims 1-7.
9. A negative electrode sheet, characterized in that, It includes a current collector and an active layer located on the surface of the current collector, the active layer comprising a negative electrode material prepared by any one of claims 1-7 or the negative electrode material of claim 8.
10. A battery, characterized in that, This includes the negative electrode sheet as described in claim 9.