Silicon-carbon negative electrode material and preparation method thereof, all-solid-state battery and electric equipment

Abstract

The invention provides a silicon-carbon negative electrode material and a preparation method thereof, an all-solid-state battery and electric equipment, and relates to the field of secondary batteries. The preparation method of the silicon-carbon negative electrode material comprises the following steps: mixing a lithium source, dilute nitric acid, a complexing agent and water to obtain a mixed solution; mixing a dispersing agent, a carbon source, a silicon source and water to obtain turbid liquid; mixing the mixed solution with the turbid liquid to obtain sol; heating the sol to obtain gel; and sintering the gel to obtain the silicon-carbon negative electrode material. The silicon-carbon negative electrode material prepared by the preparation method has relatively high charging specific capacity and excellent cycling stability at the same time.

Description

Silicon-carbon anode materials and their preparation methods, all-solid-state batteries and electrical devices Technical Field

[0001] This application relates to the field of secondary batteries, and more particularly to a silicon-carbon anode material and its preparation method, an all-solid-state battery, and an electrical device thereof. Background Technology

[0002] With the rapid development of electric vehicles, higher demands are being placed on battery energy density. Traditional graphite anode materials, due to their limited theoretical specific capacity (approximately 372 mAh / g), are insufficient to meet the requirements of high-energy-density batteries.

[0003] Silicon, as an anode material, is considered an ideal choice for next-generation high-energy-density batteries due to its extremely high theoretical specific capacity (4200 mAh / g). However, silicon undergoes severe volume expansion (up to 300%) during charge and discharge. This volume change leads to increased mechanical stress, which damages the battery structure. Even silicon materials prepared through crushing and grinding are difficult to avoid silicon atom aggregation in practical applications, resulting in material densification. This densification further exacerbates volume expansion, increases internal stress within the anode, leads to mechanical damage and lithium-ion deactivation, and ultimately manifests as a sharp decline in battery cycle life.

[0004] To mitigate the volume effect of silicon, existing technologies typically employ silicon-carbon composite materials. However, existing silicon-carbon anode materials suffer from problems such as low specific charge capacity, poor cycle stability, and complex fabrication processes. Therefore, developing a silicon-carbon anode material with high specific charge capacity, long cycle life, and ease of industrial production has become an urgent technical challenge. Summary of the Invention

[0005] The purpose of this application is to provide a silicon-carbon anode material and its preparation method, an all-solid-state battery, and an electrical device to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: a method for preparing a silicon-carbon anode material, comprising: mixing a lithium source, dilute nitric acid, a complexing agent, and water to obtain a mixed solution; mixing a dispersant, a carbon source, a silicon source, and water to obtain a suspension; mixing the mixed solution with the suspension to obtain a sol; heating the sol to obtain a gel; and sintering the gel to obtain the silicon-carbon anode material.

[0007] According to embodiments of this application, the lithium source includes at least one of lithium oxide, lithium hydroxide, and lithium nitrate; and / or, the complexing agent includes at least one of an aminocarboxyl complexing agent, a mercapto complexing agent, and citric acid monohydrate, wherein the mercapto complexing agent includes at least one of dimercaprol, dimercaptosuccinic acid, sodium dimercaptopropanesulfonate, and mercaptoacetic acid, and the aminocarboxyl complexing agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

[0008] According to embodiments of this application, the carbon source includes at least one of graphite and graphene; and / or, the silicon source includes at least one of nano-silicon and micron-silicon; and / or, the mass of lithium in the lithium source accounts for 0.1-0.5% of the total mass of the carbon source and silicon source; and / or, the dispersant includes at least one of polyvinyl alcohol, polycarboxylate, styrene-acrylic acid copolymer, and polyacrylamide; and / or, the mass of the dispersant accounts for 1.9-5.7% of the mass of the carbon source.

[0009] According to embodiments of this application, the mass fraction of the dilute nitric acid is 5-10%; and / or, the molar ratio of the lithium source to the dilute nitric acid and the complexing agent is 1:3:(10-15).

[0010] According to an embodiment of this application, the mass ratio of the carbon source to the silicon source is (5-10):1.

[0011] According to an embodiment of this application, the heating temperature is 50~85°C, and the heating time is 20-40 minutes.

[0012] According to an embodiment of this application, the sintering temperature is 300~500℃; and / or the sintering time is 1.5~5h.

[0013] This application also provides a silicon-carbon anode material, which is prepared by the silicon-carbon anode material preparation method described above.

[0014] This application also provides an all-solid-state battery, which includes a silicon-carbon anode material prepared by the method described above, or includes the silicon-carbon anode material described above.

[0015] This application also provides an electrical device, including the all-solid-state battery described above.

[0016] Compared with existing technologies, the beneficial effects of this application include: the silicon-carbon anode material prepared in this application simultaneously possesses high charge specific capacity and excellent cycle stability. Specifically, the anode material prepared in this application has a rich porous structure, providing sufficient space for the volume expansion of silicon material during charge and discharge. These pores can absorb and buffer the volume changes of silicon material, reduce internal stress, and prevent material cracking and agglomeration. Moreover, in the anode material prepared in this application, lithium ions are uniformly distributed in the silicon-carbon anode material, ensuring uniform distribution of lithium ions within the anode material. During charge and discharge cycles, the uniformly distributed lithium ions can rapidly replenish the active lithium ions lost due to side reactions, maintaining the battery's high capacity and long cycle life. The uniform distribution and immediate replenishment mechanism of lithium ions help maintain the stability and activity of the anode, reducing battery performance degradation caused by insufficient lithium ions. Furthermore, the preparation method of this application also has the advantages of low cost and simple operation, which is conducive to large-scale industrial production. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0018] Figure 1 shows the curves of the specific charging capacity of Example 1 and Comparative Example 1 as a function of the number of cycles. Detailed Implementation

[0019] As used herein, “prepared from” is synonymous with “comprising”. The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0020] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0021] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0022] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0023] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0024] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0025] To better illustrate the technical solution provided in this application, the technical solution will be described in its entirety before the embodiments, as follows: A method for preparing a silicon-carbon anode material includes: mixing a lithium source, dilute nitric acid, a complexing agent, and water to obtain a mixed solution; mixing a dispersant, a carbon source, a silicon source, and water to obtain a suspension; mixing the mixed solution with the suspension to obtain a sol; heating the sol to obtain a gel; and sintering the gel to obtain the silicon-carbon anode material.

[0026] According to an embodiment of this application, the lithium source includes at least one of lithium oxide, lithium hydroxide, and lithium nitrate. In this application, a lithium source is added before the preparation of the sol. As the gel gradually forms, lithium ions will be uniformly attached to the silicon carbon particles. This uniformly distributed lithium ions can replenish the active lithium ions lost due to side reactions in a timely manner during charge and discharge cycles, maintaining the high capacity and long cycle life of the battery.

[0027] And / or, the complexing agent includes at least one of an aminocarboxylic acid complexing agent, a mercapto complexing agent, and citric acid monohydrate; the mercapto complexing agent includes at least one of dimercaprol, dimercaptosuccinic acid, sodium dimercaptopropanesulfonate, and mercaptoacetic acid; and the aminocarboxylic acid complexing agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

[0028] According to embodiments of this application, the carbon source includes at least one of graphite and graphene; and / or, the silicon source includes at least one of nano-silicon and micron-silicon.

[0029] And / or, the mass of lithium in the lithium source accounts for 0.1-0.5% of the total mass of the carbon source and silicon source; for example, the mass of lithium in the lithium source accounts for any value between 0.1%, 0.2%, 0.3%, 0.4%, 0.5% or 0.1-0.5% of the total mass of the carbon source and silicon source.

[0030] And / or, the dispersant includes at least one of polyvinyl alcohol, polycarboxylate, styrene-acrylic acid copolymer, and polyacrylamide; and / or, the mass of the dispersant accounts for 1.9-5.7% of the mass of the carbon source.

[0031] For example, the mass of the dispersant can be any value between 1.9%, 2%, 3%, 4%, 5%, 5.7% or 1.9-5.7% of the mass of the carbon source.

[0032] According to embodiments of this application, the mass fraction of the dilute nitric acid is 5-10%; for example, the mass fraction concentration of the dilute nitric acid is 5%, 6%, 7%, 8%, 9%, 10%, or any value between 5 and 10%.

[0033] And / or, the molar ratio of the lithium source to the dilute nitric acid and the complexing agent is 1:3:(10-15).

[0034] For example, the molar ratio of lithium source to dilute nitric acid and complexing agent can be any value between 1:3:10, 1:3:11, 1:3:12, 1:3:13, 1:3:14, 1:3:15 or 1:3: (10-15).

[0035] According to an embodiment of this application, the mass ratio of the carbon source to the silicon source is (5-10):1.

[0036] For example, the mass ratio of carbon source to silicon source can be any value between 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or (5-10):1.

[0037] In some embodiments, when preparing the mixed solution, the mass ratio of the complexing agent to water is 1:(6-12), for example, any value between 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12 or 1:(6-12).

[0038] According to an embodiment of this application, the heating temperature is 50~85°C, and the heating time is 20-40 minutes.

[0039] For example, the heating temperature is any value between 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 50~85℃, and the heating time is any value between 20min, 25min, 30min, 35min, 40min or 20-40min.

[0040] During heating, as water evaporates, the solution gradually concentrates and forms a uniform gel. In this process, the carbon source and silicon source are uniformly dispersed in the gel network.

[0041] According to an embodiment of this application, the sintering temperature is 300~500℃; for example, the sintering temperature can be any value between 300℃, 350℃, 400℃, 450℃, 500℃ or 300~500℃.

[0042] During sintering, the gel expands, burns, and decomposes at high temperatures. The organic components in the gel decompose to generate large amounts of gases (such as CO2 and H2O), which escape and leave behind a rich porous structure. This porous structure provides a large number of internal pores for the final material, which can effectively accommodate the volume changes of the silicon material during charging and discharging, thereby alleviating mechanical stress.

[0043] And / or, the sintering treatment time is 1.5~5h.

[0044] For example, the sintering time can be any value between 1.5h, 1h, 2h, 3h, 4h, 5h, or 1.5h and 5h.

[0045] In some embodiments, the sintering atmosphere is air.

[0046] This application also provides a silicon-carbon anode material, which is prepared by the silicon-carbon anode material preparation method described above.

[0047] The silicon-carbon anode material of this method includes a matrix and a coating layer covering the matrix. The matrix includes silicon, the coating layer includes carbon, and lithium elements are distributed in both the matrix and the coating layer. Therefore, the silicon-carbon anode material of this application not only enhances the conductivity of the material but also provides better mechanical support, further mitigating the impact of the volume expansion of the silicon material on the overall structure.

[0048] In some embodiments, the silicon-carbon anode material has at least one shape, including cylindrical and spherical forms. This morphology allows the material to retain a large amount of porosity when fabricated as a solid-state battery anode. Specifically, both the carbon material of the coating layer and the coated silicon retain sufficient porosity. Therefore, this material can significantly reduce volume expansion and internal stress during charge and discharge, thereby effectively mitigating mechanical damage and improving the cycle stability and lifespan of the battery.

[0049] This application also provides an all-solid-state battery, which includes a silicon-carbon anode material prepared by the method described above, or includes the silicon-carbon anode material described above.

[0050] Furthermore, the all-solid-state battery of this application also includes the structures necessary for conventional all-solid-state batteries, such as a positive electrode and an electrolyte layer.

[0051] This application also provides an electrical device, including the all-solid-state battery described above.

[0052] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0053] Example 1 Example 1 provides a silicon-carbon anode material, the preparation method of which includes: (1) adding lithium oxide, 5% dilute nitric acid and citric acid monohydrate in a molar ratio of 1:3:14 to water to prepare 50g of solution A, wherein the mass ratio of citric acid monohydrate to water is 1:9; (2) mixing graphite, nano-silicon powder, water and dispersant to obtain a suspension, wherein the mass ratio of graphite to nano-silicon powder is 7:1, the dispersant is polyvinyl alcohol, and the mass of the dispersant accounts for 2% of the mass of graphite, to prepare 50g of suspension. The total mass of graphite and nano-silicon powder in the suspension is 5g; the mass of lithium element in lithium oxide in step (1) accounts for 0.47% of the total mass of graphite and nano-silicon powder in step (2); (3) the suspension is slowly added to solution A to obtain a sol; (4) the sol is evaporated and stirred at 75°C for 30min to obtain a gel; (5) the gel is transferred to a crucible, the muffle furnace is preheated to 450°C, the gel is placed in an air atmosphere and sintered at 450°C for 2h; after crushing and sieving, silicon-carbon anode material is obtained.

[0054] Example 2 Example 2 provides a silicon-carbon anode material, the preparation method of which includes: (1) adding lithium oxide, 5% dilute nitric acid and citric acid monohydrate in a molar ratio of 1:3:10 to water to prepare 50g of solution A; (2) mixing graphite, nano-silicon powder, water and dispersant to obtain a suspension, wherein the mass ratio of graphite to nano-silicon powder is 9:1, the dispersant is polyvinyl alcohol, the mass of the dispersant accounts for 2% of the mass of graphite, and 50g of suspension is prepared, the total mass of graphite and nano-silicon powder in the suspension is 5g; the mass of lithium element in lithium oxide in step (1) accounts for 0.47% of the total mass of graphite and nano-silicon powder in step (2); (3) slowly adding the suspension to solution A to obtain a sol; (4) evaporating and stirring the sol at 75°C for 30min to obtain a gel; (5) transferring the gel to a crucible, preheating the muffle furnace to 450°C, placing the gel in an air atmosphere, and sintering at 450°C for 1.5h. Silicon-carbon anode material is obtained after crushing and sieving.

[0055] Example 3 Example 3 provides a silicon-carbon anode material, the preparation method of which includes: (1) adding lithium nitrate, 5% dilute nitric acid and citric acid monohydrate to water in a molar ratio of 1:3:10 to obtain 50g of solution A, wherein the mass ratio of citric acid monohydrate to water is 1:9; (2) mixing graphite, nano-silicon powder, water and dispersant to obtain a suspension, wherein the mass ratio of graphite to nano-silicon powder is 7:1, the dispersant is polyvinyl alcohol, and the mass of the dispersant accounts for 2% of the mass of graphite. Prepare 50g of suspension, the total mass of graphite and nano-silicon powder in the suspension is 5g; the mass of lithium element in lithium nitrate in step (1) accounts for 0.24% of the total mass of graphite and nano-silicon powder in step (2); (3) slowly add the suspension to solution A to obtain a sol; (4) evaporate and stir the sol at 75℃ for 30min to obtain a gel; (5) transfer the gel to a crucible, preheat the muffle furnace to 450℃, place the gel in an air atmosphere, and sinter at 450℃ for 1.5h. After crushing and sieving, silicon-carbon anode material is obtained.

[0056] Example 4 Example 4 provides a silicon-carbon anode material, the preparation method of which includes: (1) adding lithium nitrate, 5% dilute nitric acid and citric acid monohydrate in water at a molar ratio of 1:3:15 to prepare 50g of solution A; (2) mixing graphite, nano-silicon powder, water and dispersant to obtain a suspension, wherein the mass ratio of graphite to nano-silicon powder is 5:1, the dispersant is polyvinyl alcohol, the mass of the dispersant accounts for 2% of the mass of graphite, and 50g of suspension is prepared, the total mass of graphite and nano-silicon powder in the suspension is 5g; the mass of lithium element in lithium nitrate in step (1) accounts for 0.24% of the total mass of graphite and nano-silicon powder in step (2); (3) slowly adding the suspension to solution A to obtain a sol; (4) evaporating and stirring the sol at 75°C for 30min to obtain a gel; (5) transferring the gel to a crucible, preheating the muffle furnace to 500°C, placing the gel in an air atmosphere, and sintering at 500°C for 1.5h. Silicon-carbon anode material is obtained after crushing and sieving.

[0057] Comparative Example 1: Silicon and glucose were mixed at a mass ratio of 1:15 and sintered at 250°C for 3 hours to obtain silicon-carbon material.

[0058] Comparative Example 2 uses silicon-carbon 550 type materials.

[0059] Comparative Example 3 uses nano-silicon.

[0060] The preparation method of the negative electrode material in Comparative Example 4 includes: adding 0.06g of lithium nitrate to 50ml of water, adding excess dilute nitric acid (5% by mass) to dissolve it, heating at 60℃ to evaporate the excess dilute nitric acid, adding 2.94g of high-purity graphite, stirring continuously to evaporate until the material is completely dry, and then grinding and sieving to obtain the negative electrode material.

[0061] The negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-4 were assembled into all-solid-state half-cells. Specifically, the process included: first, adding about 85 mg of intermediate electrolyte powder and pressing it into an intermediate electrolyte layer in a 0.85 cm² mold at a pressure of 2.5 tons for 2 minutes; then, adding the negative electrode layer prepared by the negative electrode material of Examples 1-4 or Comparative Examples 1-4 to one side and pressing it with 5 tons for 3 minutes; and then adding indium sheets, lithium sheets, and stainless steel sheets to the other side and pressing it with 1 ton for 2 minutes.

[0062] The assembled batteries underwent performance testing, which involved charge-discharge testing at a constant temperature of 50°C. The capacity data in Table 1 represents the specific charge capacity.

[0063] The test results are shown in Table 1.

[0064] Table 1. Comparison of electrochemical rate of change and cycling performance between Examples 1-4 and Comparative Examples 1-4

[0065] As can be seen from Table 1, Examples 1-4 simultaneously possess high charge specific capacity, excellent rate performance, and excellent cycle performance, and their overall performance is significantly better than that of Comparative Examples 1-4.

[0066] Figure 1 shows the charging specific capacity of Example 1 and Comparative Example 1 as a function of the number of cycles. As can be seen from Figure 1, the charging specific capacity of Example 1 is significantly better than that of Comparative Example 1.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0068] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, include: A mixed solution is obtained by mixing a lithium source, dilute nitric acid, a complexing agent, and water; a suspension is obtained by mixing a dispersant, a carbon source, a silicon source, and water; the mixed solution and the suspension are mixed to obtain a sol; the sol is heated to obtain a gel; and the gel is sintered to obtain a silicon-carbon anode material.

2. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, The lithium source includes at least one of lithium oxide, lithium hydroxide, and lithium nitrate; and / or, the complexing agent includes at least one of an aminocarboxylic acid complexing agent, a mercapto complexing agent, and citric acid monohydrate, wherein the mercapto complexing agent includes at least one of dimercaprol, dimercaptosuccinic acid, sodium dimercaptopropanesulfonate, and mercaptoacetic acid, and the aminocarboxylic acid complexing agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

3. The method for preparing the silicon-carbon anode material according to claim 2, characterized in that, The carbon source includes at least one of graphite and graphene; and / or, the silicon source includes at least one of nano-silicon and micron-silicon; and / or, the lithium element in the lithium source accounts for 0.1-0.5% of the total mass of the carbon source and silicon source; and / or, the dispersant includes at least one of polyvinyl alcohol, polycarboxylate, styrene-acrylic acid copolymer, and polyacrylamide; and / or, the dispersant accounts for 1.9-5.7% of the mass of the carbon source.

4. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, The mass fraction of the dilute nitric acid is 5-10%; and / or the molar ratio of the lithium source to the dilute nitric acid and the complexing agent is 1:3:(10-15).

5. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, The mass ratio of the carbon source to the silicon source is (5-10):

1.

6. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, The heating temperature is 50~85℃, and the heating time is 20-40min.

7. The method for preparing the silicon-carbon anode material according to any one of claims 1-6, characterized in that, The sintering temperature is 300~500℃; and / or the sintering time is 1.5~5h.

8. A silicon-carbon anode material, characterized in that, The silicon-carbon anode material is prepared by the method for preparing silicon-carbon anode material according to any one of claims 1-7.

9. An all-solid-state battery, characterized in that, The all-solid-state battery includes silicon-carbon anode material prepared by the method for preparing silicon-carbon anode material according to any one of claims 1-7, or includes silicon-carbon anode material according to claim 8.

10. An electrical appliance, characterized in that, Including the all-solid-state battery as described in claim 9.

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