A Si@SiO x @CA composite material, method for preparing the same and use thereof

Abstract

The application discloses Si@SiO x @CA composite material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The preparation method comprises the following steps: dissolving ammonium persulfate and an acid solution with a mass fraction of 98% in deionized water, fully stirring, uniformly mixing, and obtaining a mixed solution; adding silicon powder, heating and stirring, uniformly mixing, and cleaning to neutral, and obtaining modified silicon particles; dissolving chitosan in an acetic acid solution, adding a crosslinking agent imido ester and the modified silicon particles, stirring, and obtaining a uniform suspension; vacuum drying, and obtaining a gel precursor; pyrolyzing in an inert atmosphere, and obtaining the Si@SiO x @CA composite material. The application discloses Si@SiO x @CA composite material and a preparation method and application thereof, and the Si@SiO x @CA composite material is applied to a lithium ion battery, and the high reversibility and long cycle stability of the lithium ion battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a Si@SiO x @CA composite materials, their preparation methods, and applications. Background Technology

[0002] With the rapid development of electric vehicles and grid energy storage technologies, the performance improvement of lithium-ion batteries (LIBs), as a core power source, has become a research focus. The performance of the battery anode material directly determines the energy density, cycle life, and overall efficiency of lithium-ion batteries. Therefore, developing high-performance battery anode materials has always been a major direction of lithium-ion battery research.

[0003] Silicon anode materials, with their theoretical lithium storage capacity of up to 4200 mAh / g, far exceeding that of graphite (approximately 420 mAh / g), a conventional anode material for lithium-ion batteries, demonstrate enormous application potential. However, silicon-based anode materials face significant technical bottlenecks in practical applications, primarily manifested in their cycle stability, which is far inferior to that of commercially available graphite materials. In-depth research reveals that the root cause of this problem lies in the enormous volume changes of silicon anode materials during electrochemical charge and discharge processes, with a volume expansion effect reaching up to 300%. This drastic volume change can lead to mechanical fracture and fragmentation, causing the solid electrolyte interphase (SEI) to rupture. Simultaneously, the resulting stress causes the active electrode material to gradually detach from the current collector and separate from the conductive agent and binder, ultimately resulting in a rapid decline in battery capacity. Furthermore, silicon, as a semiconductor material, has low intrinsic conductivity, leading to slow reaction kinetics, further limiting its performance in direct applications.

[0004] To address these issues, researchers have developed various strategies to mitigate or suppress the volume expansion and stress effects of silicon-based anodes. These include modification schemes such as surface coatings on silicon particles, microstructure design, the application of novel binders, and pre-lithiation. However, silicon-based anode materials currently face numerous challenges. While introducing oxygen to modify silicon-based anode materials can rearrange silicon and oxygen atoms to form silicon oxide as a buffer layer to suppress volume expansion, it also reduces the theoretical specific capacity and initial coulombic efficiency of silicon anode materials. Summary of the Invention

[0005] This invention aims to provide a Si@SiO x @CA composite materials, their preparation methods, and applications; this method improves the Si@SiO₂ composite material... x The structural stability and electrochemical properties of the @CA composite material are improved, solving the problem of poor material performance in existing technologies. This invention also provides the Si@SiO composite material. x The application of @CA composite materials in lithium-ion batteries has improved the high reversibility and long-cycle stability of lithium-ion batteries.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A Si@SiO x The preparation method of @CA composite material includes the following steps:

[0008] S1. Dissolve ammonium persulfate and 98% acid solution in deionized water, stir thoroughly, and mix evenly to obtain a mixed solution;

[0009] S2. Add silicon powder to the mixed solution obtained in S1, heat and stir until uniform, wash until neutral, and obtain modified silicon particles.

[0010] S3. Dissolve chitosan in acetic acid solution, add crosslinking agent imine ester and modified silica particles obtained in S2, stir to obtain a uniform suspension;

[0011] S4. Vacuum dry the suspension obtained in S3 to obtain the gel precursor;

[0012] S5. The gel precursor obtained in S4 is pyrolyzed in an inert atmosphere to obtain Si@SiO x @CA composite materials.

[0013] Preferably, in S1, the 98% acid solution by mass fraction is either a sulfuric acid solution or a nitric acid solution.

[0014] Preferably, in S1, the amount of ammonium persulfate added is 2-10g, and the amount of 98% acid solution is 10-50mL.

[0015] Preferably, in S2, the silicon powder particle size is 100 nm.

[0016] Preferably, in S2, the amount of silicon powder added is 0.2-1.0g.

[0017] Preferably, in S2, the heating and stirring temperature is 60-100℃, and the heating and stirring time is 2-5h.

[0018] Preferably, in S3, the amount of chitosan added is 2-10g, the amount of crosslinking agent imide added is 0.1-0.5g, and the ratio of chitosan to imide is 20:1.

[0019] Preferably, in step S3, the stirring speed is 500-800 rpm and the stirring time is 2-5 hours.

[0020] Preferably, in step S4, the vacuum drying temperature is 80-120℃, the vacuum drying time is 12-24h, and the vacuum degree is -0.1MPa.

[0021] Preferably, in S5, the heating rate is 2-10℃ / min, the pyrolysis temperature is 500-700℃, and the pyrolysis time is 2-5h.

[0022] This invention also provides Si@SiO prepared by the preparation method described above. x @CA composite materials.

[0023] This invention also provides Si@SiO prepared by the preparation method described above. x @CA composite material or the aforementioned Si@SiO x Application of @CA composite material in the preparation of silicon-based negative electrode sheets for lithium-ion batteries.

[0024] The present invention also provides a silicon-based negative electrode sheet for lithium-ion batteries, characterized in that it comprises the aforementioned Si@SiO x @CA composite materials, binders, and conductive agents.

[0025] The present invention also provides a method for preparing the silicon-based negative electrode sheet of the lithium-ion battery, comprising the following steps:

[0026] T1, Si@SiO x @CA composite material, conductive agent and binder are mixed and stirred thoroughly to obtain a uniform slurry;

[0027] T2. The slurry obtained in T1 is evenly coated onto copper foil and vacuum dried to obtain a dried electrode sheet.

[0028] T3. Roll and cut the dried electrode sheet obtained in T2 to obtain the silicon-based negative electrode sheet for lithium-ion batteries.

[0029] Preferably, in T1, the Si@SiO x The mass ratio of the @CA composite material, binder, and conductive agent is 7:1:2.

[0030] Preferably, in T1, the conductive agent is Super P and the binder is polyacrylic acid.

[0031] Preferably, in T2, the vacuum drying temperature is 80°C, the vacuum drying time is 24 hours, and the vacuum degree is -0.1 MPa.

[0032] Preferably, in T3, the diameter of the silicon-based negative electrode sheet of the lithium-ion battery is 12mm.

[0033] Preferably, in T3, the silicon-based negative electrode sheet of the lithium-ion battery contains Si@SiO x The mass of the @CA composite material is 0.6-1.2 g / cm³. 2 .

[0034] Compared with the prior art, the present invention has the following advantages and technical effects:

[0035] This invention discloses a Si@SiO x @CA composite materials, their preparation methods, and applications, including the construction of SiO2 on the surface of Si particles. X The layers are embedded in a carbon gel with high mechanical and elastic strength to form Si@SiO. x @CA composite material. This structural design effectively mitigates the volume expansion effect of Si particles during electrochemical charge and discharge, reduces mechanical stress caused by volume expansion, thereby reducing silicon particle pulverization and electrode structure damage, and improving battery cycle stability. Si@SiO X @CA composite materials, when assembled into lithium-ion batteries, exhibit excellent reversibility and long-cycle stability. They maintain high reversible capacity at various current densities and retain good capacity even at high current densities. Furthermore, the introduction of carbon gel not only provides mechanical support but also constructs a continuous conductive network, effectively improving the conductivity of the silicon-based anode material. This compensates for the low intrinsic conductivity of silicon, accelerates electron transport, and enhances the battery's rate performance. Simultaneously, the carbon gel layer and SiO2... X The synergistic effect of the layers can reduce interfacial impedance, suppress direct contact between the electrolyte and silicon particles, reduce the occurrence of side reactions, and form a more stable solid electrolyte layer (SEI), thereby improving the initial coulombic efficiency and cycle life of the battery. The preparation method of this invention is simple, efficient, and easy to industrialize. The prepared Si@SiO x @CA composite materials have broad application prospects in the field of lithium-ion batteries and can meet the demand for high-performance batteries in electric vehicles and grid energy storage.

[0036] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated by the following embodiments.

[0038] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0039] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0040] Example 1

[0041] A Si@SiO x The preparation method of @CA composite material includes the following steps:

[0042] S1. Dissolve 6g of ammonium persulfate and 30mL of 98% nitric acid solution in 100mL of deionized water, stir thoroughly and mix evenly to obtain a mixed solution;

[0043] S2. Add 0.6g of silicon powder with a particle size of 100nm to the mixed solution obtained in S1, heat and stir at 80℃ for 3h, mix evenly, and wash repeatedly with deionized water until the pH is neutral to obtain modified silicon particles.

[0044] S3. Dissolve 6g of chitosan in 100mL of acetic acid solution, add 0.3g of crosslinking agent imide ester and modified silicon particles obtained in S2, stir at 500rpm for 5h to obtain a uniform suspension.

[0045] S4. The suspension obtained in S3 is dried under vacuum at 80°C for 24 hours, with a vacuum degree of -0.1 MPa, to obtain the gel precursor.

[0046] S5. The gel precursor obtained in S4 was pyrolyzed at 600℃ for 2 hours in an inert atmosphere at a heating rate of 5℃ / min to obtain Si@SiO. x @CA composite materials.

[0047] Example 2

[0048] The preparation method is the same as in Example 1, except that the amount of ammonium persulfate added is 2g and the amount of nitric acid solution added is 10mL.

[0049] Example 3

[0050] The preparation method is the same as in Example 1, except that the amount of ammonium persulfate added is 4g and the amount of nitric acid solution added is 20mL.

[0051] Example 4

[0052] The preparation method is the same as in Example 1, except that the amount of ammonium persulfate added is 8g and the amount of nitric acid solution added is 40mL.

[0053] Example 5

[0054] The preparation method is the same as in Example 1, except that the amount of ammonium persulfate added is 10g and the amount of nitric acid solution added is 50mL.

[0055] Example 6

[0056] The preparation method is the same as in Example 1, except that the amount of silicon powder added is 0.2g.

[0057] Example 7

[0058] The preparation method is the same as in Example 1, except that the amount of silicon powder added is 0.4g.

[0059] Example 8

[0060] The preparation method is the same as in Example 1, except that the amount of silicon powder added is 0.8g.

[0061] Example 9

[0062] The preparation method is the same as in Example 1, except that the amount of silicon powder added is 1.0g.

[0063] Example 10

[0064] The preparation method is the same as in Example 1, except that the amount of chitosan added is 2g and the amount of crosslinking agent imide ester added is 0.1g.

[0065] Example 11

[0066] The preparation method is the same as in Example 1, except that the amount of chitosan added is 4g and the amount of crosslinking agent imide ester added is 0.2g.

[0067] Example 12

[0068] The preparation method is the same as in Example 1, except that the amount of chitosan added is 8g and the amount of crosslinking agent imide ester added is 0.4g.

[0069] Example 13

[0070] The preparation method is the same as in Example 1, except that the amount of chitosan added is 10g and the amount of crosslinking agent imide ester added is 0.5g.

[0071] Example 14

[0072] The preparation method is the same as in Example 1, except that in S5, the pyrolysis temperature is 500℃.

[0073] Example 15

[0074] The preparation method is the same as in Example 1, except that in S5, the pyrolysis temperature is 700℃.

[0075] Comparative Example 1

[0076] Material: Silicon powder with a particle size of 100nm, without any processing, and available through commercial channels.

[0077] Comparative Example 2

[0078] A Si@SiO x The preparation method of @CA silicon-based materials includes the following steps:

[0079] S1. Dissolve 6g of ammonium persulfate and 30mL of 98% nitric acid solution in 100mL of deionized water, stir thoroughly and mix evenly to obtain a mixed solution;

[0080] S2. Add 0.6g of silicon powder with a particle size of 100nm to the mixed solution obtained in S1, heat and stir at 80℃ for 3h, mix evenly, and wash repeatedly with deionized water until the pH is neutral to obtain modified silicon particles.

[0081] S3. The modified silicon particles obtained in S2 are dried under vacuum at 80℃ for 24 hours, with a vacuum degree of -0.1MPa, to obtain Si@SiO. X Silicon-based materials.

[0082] Comparative Example 3

[0083] A method for preparing Si@CA silicon-based material includes the following steps:

[0084] S1. Dissolve 6g of chitosan in 100mL of acetic acid solution, add 0.3g of crosslinking agent imide ester and 0.6g of silicon powder with a particle size of 100nm, stir at 500rpm for 5h to obtain a uniform suspension;

[0085] S2. The suspension obtained in S1 is dried under vacuum at 80°C for 24 hours, with a vacuum degree of -0.1 MPa, to obtain the gel precursor.

[0086] S3. The gel precursor obtained in S3 was pyrolyzed in an inert atmosphere at 600℃ for 2 hours at a heating rate of 5℃ / min to obtain the Si@CA composite material.

[0087] The effects of the composite materials provided in Examples 1-15 and Comparative Examples 1-3 were verified through the following experiments.

[0088] The Si@SiO provided in Example 1 above x @CA composite material is used as the negative electrode active material in the preparation of negative electrode sheets, including the following steps:

[0089] T1, Si@SiO x @CA composite material, Super P and polyacrylic acid are mixed in a mass ratio of 7:2:1 and stirred thoroughly to obtain a uniform slurry;

[0090] T2. The slurry obtained in T1 is evenly coated onto copper foil using a coater and dried under vacuum at 80°C for 24 hours. The vacuum degree is -0.1MPa, resulting in a dried electrode sheet.

[0091] T3. The dried electrode sheets obtained in T2 are rolled and cut to obtain silicon-based negative electrode sheets for lithium-ion batteries with a diameter of 12 mm. The negative electrode active material loading of each silicon-based negative electrode sheet is 0.7 mg / cm³. -2 .

[0092] The materials provided in Examples 2-15 and Comparative Examples 1-3 were used to prepare silicon-based negative electrode sheets for lithium-ion batteries, and the preparation method was the same as above.

[0093] The above-mentioned silicon-based negative electrode sheet for lithium-ion batteries is used to prepare lithium-ion coin cells, as follows:

[0094] The button cell assembly was completed in a glove box (where water and oxygen content were both below 0.01 ppm).

[0095] The prepared silicon-based negative electrode sheet for lithium-ion batteries is used as the negative electrode, the positive electrode is a lithium sheet (15 mm in diameter and 2 mm thick), the separator is polypropylene (PP), and the electrolyte is 1.0 M LiPF6 in EC+DMC. The negative electrode sheet, electrolyte, separator, and positive electrode sheet are assembled in that order, and then sealed using a hydraulic sealing machine to obtain the lithium-ion battery.

[0096] The electrochemical performance of the above-mentioned lithium-ion batteries was tested. The test results are shown in Tables 1 and 2.

[0097] Table 1. Performance Test Results by Rate Capacity

[0098]

[0099]

[0100] Table 2 shows the results of the long-cycle stability test.

[0101]

[0102]

[0103] Tables 1 and 2 show the Si@SiO X Performance testing of lithium-ion batteries prepared from Si@SiO3 composite materials, comparing the examples with comparative examples, shows that Si@SiO3... X The @CA composite material exhibits excellent rate performance and cycle stability, primarily because in this invention, SiO₂ is constructed on the surface of silicon particles by varying the amount of oxidant. X The thickness of the layer is selected by optimizing the amount of oxidant to obtain a suitable SiO2 layer. X Layer, then SiO X The layer generates lithium silicate and lithium oxide during charging and discharging, which can buffer the volume expansion effect of silicon particles, and then Si@SiO is applied. X Embedded within carbon gels, nitrogen-containing carbon gels constructed from chitosan can integrate Si@SiO2. X The coating forms a continuous conductive network structure, which allows for the modulation of the electronic structure and the formation of Li. + High-speed transmission channel improves electron transport efficiency and compensates for SiO XThe low conductivity improves rate performance. As shown in Table 1, Example 1's rate performance in the range of 0.2 A / g to 3.0 A / g is significantly higher than that of other examples and comparative examples, even providing a reversible capacity of 652 mAh / g at a current density of 3.0 A / g. Simultaneously, the carbon gel layer and SiO... X The synergistic effect reduces interfacial impedance, inhibits direct contact between the electrolyte and silicon particles, reduces side reactions, and forms a more stable SEI film, thus improving the initial coulombic efficiency of the lithium-ion battery. Simultaneously, the elastic properties of the carbon gel disperse the stress effects of the lithiation / delithiation process, preventing silicon particle pulverization through physical constraint and improving the cycle stability of the lithium-ion battery, resulting in 95% capacity retention after 800 cycles at a current density of 1.0 A / g. These data demonstrate the excellent kinetic performance of Example 1, proving the effectiveness of the Si@SiO prepared in this invention. X The superior properties of @CA composite materials.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A Si@SiO x Method for the production of a Si@SiO The method comprises the following steps: S1, dissolving ammonium persulfate and 98% acid solution with mass fraction of 0.1% in deionized water, fully stirring and mixing uniformly to obtain a mixed solution; S2, adding silicon powder to the mixed solution obtained in S1, heating and stirring, mixing uniformly, washing to neutral, and obtaining modified silicon particles; S3, dissolving chitosan in acetic acid solution, adding crosslinking agent imido ester and the modified silicon particles obtained in S2, and stirring to obtain a uniform suspension; S4, vacuum drying the suspension obtained in S3 to obtain a gel precursor; S5, pyrolyzing the gel precursor obtained in S4 in an inert atmosphere to obtain Si@SiO x @CA composite material; In S1, the acid solution is one of sulfuric acid solution or nitric acid solution; In S2, the heating and stirring temperature is 60-100℃, and the heating and stirring time is 2-5h.

2. The production method according to claim 1, characterized by, In S3, the stirring speed is 500-800rpm, and the stirring time is 2-5h.

3. The preparation method according to claim 1, characterized in that, In S4, the vacuum drying temperature is 80-120℃, the vacuum drying time is 12-24h, and the vacuum degree is-0.1MPa.

4. The method of claim 1, wherein, In S5, the heating rate is 2-10℃ / min, the pyrolysis temperature is 500-700℃, and the pyrolysis time is 2-5h.

5. The Si@SiO2@CA composite material prepared according to the preparation method of any one of claims 1-4. x @CA composite material.

6. The Si@SiOx@CA composite material or the Si@SiOx@CA composite material prepared by the preparation method according to any one of claims 1-4 for use in the preparation of a silicon-based anode sheet for a lithium ion battery. x @CA composite material or the Si@SiOx@CA composite material according to claim 5 for use in the preparation of a silicon-based anode sheet for a lithium ion battery. x @CA composite material or the Si@SiOx@CA composite material according to claim 5 for use in the preparation of a silicon-based anode sheet for a lithium ion battery.

7. A silicon-based anode sheet for a lithium-ion battery, characterized in that, Si@SiO x @CA composite, binder, and conductive agent.

8. A method for preparing a silicon-based negative electrode sheet for a lithium-ion battery as described in claim 7, characterized in that, The method comprises the following steps: T1, Si@SiO x @The CA composite, conductive agent and binder are mixed and stirred thoroughly to obtain a uniform slurry; T2, uniformly coating the slurry obtained in T1 on a copper foil, and vacuum drying to obtain a dry electrode sheet; T3, rolling and cutting the dry electrode sheet obtained in T2 to obtain a lithium ion battery silicon-based negative electrode sheet.

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