CN114613955B - Graphene modified silicon anode material and preparation method and application thereof - Google Patents

Graphene modified silicon anode material and preparation method and application thereof Download PDF

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CN114613955B
CN114613955B CN202210220183.2A CN202210220183A CN114613955B CN 114613955 B CN114613955 B CN 114613955B CN 202210220183 A CN202210220183 A CN 202210220183A CN 114613955 B CN114613955 B CN 114613955B
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谢英朋
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Eve Energy Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract

The invention provides a graphene modified silicon anode material, and a preparation method and application thereof, wherein the preparation method comprises the following steps: and mixing the aminated nano silicon source with sulfonated graphene, and performing spray drying to obtain the graphene modified silicon anode material. According to the preparation method, the aminated nano silicon source and the sulfonated graphene are mixed and are matched with a spray drying mode to prepare the graphene modified silicon anode material, and the amino contained in the nano silicon source reacts with the sulfonic group of the graphene to generate the sulfonamide, so that the graphene and the nano silicon are connected through covalent bonds, the compactness and uniformity of graphene coating are improved, the volume expansion of the silicon is effectively reduced, and the multiplying power performance and the cycle performance of the battery are improved.

Description

Graphene modified silicon anode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of batteries, and relates to a graphene modified silicon anode material, and a preparation method and application thereof.
Background
Lithium ion batteries are considered as green power sources suitable for portable electronic products and electric vehicles, and therefore, development of advanced lithium ion batteries with high energy density, high cycle performance, and low cost is essential to meet the increasing demands of next-generation energy storage devices. Silicon has an ultra-high theoretical specific capacity (corresponding to Li 4.4 4200mAh/g of Si) is generally considered as one of the most promising negative electrode materials, however, silicon negative electrode has low ion diffusion and poor electrical conductivity, and particularly has large volume expansion (about 400%) during delithiation and lithium intercalation, which eventually leads to a sharp decrease in the capacity of the material, preventing its application. Meanwhile, the volume expansion inevitably causes cracking of an unstable Solid Electrolyte Interphase (SEI) layer, resulting in rapid capacity decay of the material and poor rate performance. In recent years, many efforts have been made to solve these problems, and it is a relatively efficient way to compound graphene with silicon.
Graphene (Graphene) is a kind of Graphene which is formed by sp 2 The hybridized and connected carbon atoms are closely stacked to form a new material with a single-layer two-dimensional honeycomb lattice structure, and the new material has excellent optical, electrical and mechanical properties. The graphene is used as a novel conductive agent, and because of a unique lamellar structure (two-dimensional structure), the graphene is in point-to-surface contact with an active substance instead of a conventional point-to-point contact form, so that the consumption of the conductive agent can be reduced, and the capacity of a lithium battery can be improved. The graphene is widely applied to a silicon negative electrode, and CN108735990A discloses a preparation method of a graphene modified silicon carbon negative electrode material, which comprises the steps of adding silicon powder and graphite micropowder into graphene oxide dispersion liquid, adding a dispersing agent, performing ultrasonic dispersion treatment to form suspension, performing spray drying and pelletizing on the obtained suspension, and performing heat treatment at 500-800 ℃ in a reducing atmosphere to obtain a graphene coated silicon powder and graphite micropowder composite negative electrode material, so that the cycle performance of a single silicon material is improved. CN107910513A disclosesA graphene/silicon composite lithium ion battery cathode and a preparation method thereof are provided, wherein a multi-layer structure of matching a graphene layer and a silicon/carbon nano tube layer is arranged on a current collector, silicon nano particles are successfully wrapped by adopting graphene and carbon tubes, the volume effect of a silicon material in the charging and discharging process is improved through a layered special structure, and the conductivity and the cycle performance of the material are improved. CN111403723a provides a preparation method of a silicon-carbon negative electrode composite material, which comprises the steps of adding silicon powder into graphene oxide suspension, mixing, drying, and roasting for 1-5 h at 600-1200 ℃ in an inert atmosphere to obtain the silicon-carbon negative electrode composite material, thereby improving the stability of the material.
In the prior art, graphene and a silicon material are combined in a plurality of ways to improve the electrochemical performance of silicon, but in the technical scheme, the coating compactness and uniformity of the graphene are poor, the electrolyte is in contact with the silicon to form an SEI film due to the poor coating compactness, and the poor uniformity can reduce the rate capability of a battery; in addition, in the circulation process, graphene is easily stretched due to the huge volume expansion of silicon, so that exposed silicon is contacted with electrolyte, more SEI films are formed to consume active lithium, and the circulation performance is deteriorated.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a graphene modified silicon anode material and a preparation method and application thereof. According to the preparation method, the aminated nano silicon source and the sulfonated graphene are mixed and are matched with a spray drying mode to prepare the graphene modified silicon anode material, and the amino contained in the nano silicon source reacts with the sulfonic group of the graphene to generate the sulfonamide, so that the graphene and the nano silicon are connected through covalent bonds, the compactness and uniformity of graphene coating are improved, the volume expansion of the silicon is effectively reduced, and the multiplying power performance and the cycle performance of the battery are improved.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a preparation method of a graphene modified silicon anode material, where the preparation method includes:
and mixing the aminated nano silicon source with sulfonated graphene, and performing spray drying to obtain the graphene modified silicon anode material.
According to the preparation method, the aminated nano silicon source and the sulfonated graphene are mixed, and the graphene modified silicon anode material is prepared in a spray drying mode, so that the prepared material has good multiplying power performance and circulation performance.
The technical principle of the invention is as follows: the amino on the first nano silicon source reacts with the sulfonic group on the sulfonated graphene to form sulfonamide, so that the graphene can uniformly coat the nano silicon, and compared with the traditional coating means, the coating layer prepared by the chemical reaction coating method is more compact and uniform, the SEI film formed by directly contacting electrolyte with silicon can be reduced, and the improvement of the rate capability of the battery is facilitated; secondly, the chemical reaction coating method enables the graphene and the nano silicon to be connected through covalent bonds, and when the silicon undergoes huge volume expansion, the graphene is tightly adhered to the surface of the silicon negative electrode, so that the volume expansion rate of the silicon negative electrode is reduced, and the cycle performance of the battery is improved; thirdly, the aminated nano silicon source is adopted to react with the sulfonated graphene, so that the aminated nano silicon source has higher reactivity, is more beneficial to the reaction with the sulfonated graphene, has better matching effect with the sulfonated graphene, and the prepared material has better multiplying power performance and cycle performance, and meanwhile, the addition of the graphene reduces the consumption of the conductive agent and improves the energy density of the battery.
Preferably, the molar ratio of the aminated nano-silicon source to the sulfonated graphene is (1-30): 1, for example, 1:1, 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, 24:1, 26:1, 28:1 or 30:1, etc., and preferably (20-30): 1.
The most suitable proportion exists between the aminated nano silicon source and the sulfonated graphene, the proportion is too low, the aminated nano silicon content is low, the energy density of a battery can be reduced, the proportion is too high, the sulfonated graphene content is low, the thickness of a coating layer is small, the buffer effect is difficult to play, and the buffer layer is easy to spread due to silicon expansion.
Preferably, the aminated nanosilicon source is aminated nanosilicon.
As a preferable technical scheme of the preparation method, the aminated nano-silicon is prepared according to the following mode:
stirring the nano silicon in an acid solution, drying, mixing with a first solvent and a second solvent, and heating to obtain the aminated nano silicon.
The particle diameter D50 of the nano-silicon is preferably 5 to 80nm, and may be, for example, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, or the like, and preferably 28 to 32nm.
In the invention, the nano silicon with the specific particle size is preferably used for preparing the amination nano silicon to participate in the reaction with the sulfonated graphene, and the nano silicon with the particle size of 5-80 nm has higher activity, is easier to aminate, has higher activity of an amination product, and has good combination property with the sulfonated graphene and good dispersibility. Preferably, the acid solution comprises HCl solution.
Illustratively, the solute content in the acid solution is 20-30%, for example, 20%, 22%, 24%, 26%, 28%, 30%, or the like, based on 100% by mass of the acid solution.
The drying temperature is 60 to 80℃and may be 60℃62℃64℃66℃68℃70℃72℃74℃76℃78℃80℃or the like, for example.
Preferably, the first solvent comprises toluene, which acts as a dispersing solvent for the nano-silicon, and the use amount of the first solvent is 1 (1-10) of the mass ratio of the nano-silicon to the toluene, for example, 1:1, 1:2, 1:4, 1:6, 1:8 or 1:10, etc.
Preferably, the second solvent includes 3-aminopropyl triethoxysilane (APTES) as a reactant for the aminated nano-silicon.
Preferably, the molar ratio of the nano-silicon to the second solvent is 1 (0.2-5), for example, 1:0.2, 1:0.5, 1:1, 1:2, 1:3, 1:4, or 1:5, etc.
Preferably, the heating temperature is 80 to 120 ℃, for example, 80 ℃, 85 ℃,90 ℃, 95 ℃, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃ or the like, and the heating time is 6 to 24 hours, for example, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours or the like.
Preferably, the gas in the heated atmosphere comprises nitrogen.
The aminated nano silicon prepared by the preparation method is more suitable for being combined with sulfonated graphene, and the synergistic effect of the aminated nano silicon and the sulfonated graphene has better electrochemical performance.
In a preferred embodiment of the production method of the present invention, the sulfonated graphene has a particle diameter D50 of 1.2 to 4. Mu.m, for example, 1.2. Mu.m, 1.5. Mu.m, 2.5. Mu.m, 3. Mu.m, 3.5. Mu.m, 4. Mu.m, or the like.
Preferably, the number of layers of the sulfonated graphene is less than 5, for example, 1 layer, 2 layers, 3 layers or 4 layers, and preferably 2 to 4 layers.
According to the invention, sulfonated graphene with a specific size is preferable, when the particle size D50 of the sulfonated graphene is smaller, the sulfonated graphene is unfavorable for dispersing with the aminated nano silicon, is easy to agglomerate, and the size of the sulfonated graphene is not easy to change in a larger range, otherwise, the sulfonated graphene is unfavorable for being matched with the aminated nano silicon; meanwhile, the number of the sulfonated graphene layers is preferably 2-4, and the volume expansion cannot be restrained when the sulfonated graphene is thinner, and the lithium ion transmission is not facilitated when the sulfonated graphene is thicker.
Preferably, a third solvent and a catalyst are also added during the mixing of the aminated silicon source with the sulfonated graphene.
Preferably, the third solvent comprises thionyl chloride.
Preferably, the catalyst comprises N, N-Dimethylformamide (DMF).
The catalyst may be added in an amount of 0.5 to 2mL, for example, 0.5mL, 0.8mL, 1mL, 1.2mL, 1.5mL, 1.8mL, 2mL, or the like.
Preferably, the temperature at which the aminated silicon source is mixed with the sulfonated graphene is 60 to 100 ℃, and for example, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃,90 ℃, 95 ℃, 100 ℃, or the like can be used.
Preferably, the mixing time of the aminated silicon source and the sulfonated graphene is 12-36 h, for example, 12h, 15h, 20h, 25h, 30h, 35h or 36h, etc.
Preferably, the process of mixing the aminated silicon source with the sulfonated graphene is performed in a nitrogen atmosphere.
As a preferable mode of the production method of the present invention, the inlet temperature of the spray drying is 150 to 300℃and may be, for example, 150℃180℃200℃220℃240℃260℃280℃300℃or the like.
Preferably, the outlet temperature of the spray drying is 110 to 190 ℃, and may be 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃ or the like, for example.
As a preferable technical scheme of the preparation method, the preparation method comprises the following steps:
(1) Stirring nano silicon with the particle size D50 of 5-80 nm in an acid solution, drying at 60-80 ℃, mixing with a first solvent and a second solvent, and heating at 80-120 ℃ for 6-24 hours to obtain aminated nano silicon;
(2) Performing ultrasonic dispersion on the aminated nano silicon and a third solvent in the step (1), adding 0.5-2 mL of catalyst, dropwise adding sulfonated graphene with the particle size D50 of 1.2-4 mu m in a nitrogen atmosphere at the temperature of 60-100 ℃, mixing for 12-36 h to obtain a mixed solution, wherein the molar ratio of the aminated nano silicon to the sulfonated graphene is (20-30): 1;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 150-300 ℃, and the outlet temperature of spray drying is 110-190 ℃, so as to obtain the graphene modified silicon anode material.
In a second aspect, the invention provides a graphene modified silicon anode material, which is prepared by the preparation method according to the first aspect, and comprises graphene and silicon loaded on the surface of the graphene.
In the graphene modified silicon anode material prepared by the method, graphene and silicon are connected through covalent bonds, and the graphene is coated more uniformly and compactly, so that the volume expansion of the silicon anode can be reduced, and the silicon anode material has better stability.
In a third aspect, the invention provides a lithium ion battery, wherein the negative electrode of the lithium ion battery comprises the graphene modified silicon negative electrode material according to the first aspect.
The lithium ion battery prepared by the method has higher energy density and better cycle performance.
Compared with the prior art, the invention has the following beneficial effects:
according to the preparation method, the aminated nano silicon source and the sulfonated graphene are mixed and are matched with a spray drying mode to prepare the graphene modified silicon anode material, and the amino contained in the nano silicon source reacts with the sulfonic group of the graphene to generate the sulfonamide, so that the graphene and the nano silicon are connected through covalent bonds, the compactness and uniformity of graphene coating are improved, the volume expansion of the silicon is effectively reduced, and the multiplying power performance and the cycle performance of the battery are improved.
Drawings
Fig. 1 is a flow chart of preparation of graphene-modified silicon anode material in one embodiment of the present invention.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
The embodiment of the invention provides a preparation method of a graphene modified silicon anode material, which comprises the following steps:
and mixing the aminated nano silicon source with sulfonated graphene, and performing spray drying to obtain the graphene modified silicon anode material.
In some embodiments, the molar ratio of the aminated nanosilicon source to the sulfonated graphene is (1-30): 1, preferably (20-30): 1.
In some embodiments, the aminated nanosilicon source is aminated nanosilicon.
In some embodiments, the aminated nanosilicon is prepared as follows:
stirring the nano silicon in an acid solution, drying, mixing with a first solvent and a second solvent, and heating to obtain the aminated nano silicon.
In some embodiments, the nanosilicon has a particle size D50 of from 5 to 80nm, preferably from 28 to 32nm.
In some embodiments, the acid solution comprises HCl solution.
In some embodiments, the first solvent comprises toluene.
In some embodiments, the second solvent comprises 3-aminopropyl triethoxysilane.
In some embodiments, the molar ratio of the nanosilicon to the second solvent is 1 (0.2-5).
In some embodiments, the heating is at a temperature of 80 to 120 ℃ for a time of 6 to 24 hours.
In some embodiments, the gas in the heated atmosphere comprises nitrogen.
In some embodiments, the sulfonated graphene has a particle size D50 of 1.2 to 4 μm.
In some embodiments, the number of layers of the sulfonated graphene is less than 5 layers.
In some embodiments, the sulfonated graphene has 2 to 4 layers.
In some embodiments, a third solvent and catalyst are also added during the mixing of the aminated silicon source with the sulfonated graphene.
In some embodiments, the third solvent comprises thionyl chloride.
In some embodiments, the catalyst comprises N, N-Dimethylformamide (DMF).
In some embodiments, the temperature at which the aminated silicon source is mixed with the sulfonated graphene is 60-100 ℃.
In some embodiments, the aminated silicon source is mixed with the sulfonated graphene for a period of 12 to 36 hours.
In some embodiments, the process of mixing the aminated silicon source with the sulfonated graphene is performed in an atmosphere of nitrogen.
In some embodiments, the spray-drying inlet temperature is 150 to 300 ℃.
In some embodiments, the spray-dried outlet temperature is 110 to 190 ℃.
In some embodiments, the flow chart of the preparation method is shown in fig. 1, and includes:
(1) Stirring nano silicon with the particle size D50 of 5-80 nm in an acid solution, drying at 60-80 ℃, mixing with a first solvent and a second solvent, and heating at 80-120 ℃ for 6-24 hours to obtain aminated nano silicon;
(2) Performing ultrasonic dispersion on the aminated nano silicon and a third solvent in the step (1), adding 0.5-2 mL of catalyst, dropwise adding sulfonated graphene with the particle size D50 of 1.2-4 mu m in a nitrogen atmosphere at the temperature of 60-100 ℃, mixing for 12-36 h to obtain a mixed solution, wherein the molar ratio of the aminated nano silicon to the sulfonated graphene is (20-30): 1;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 150-300 ℃, and the outlet temperature of spray drying is 110-190 ℃, so as to obtain the graphene modified silicon anode material.
Example 1
The embodiment provides a graphene modified silicon anode material and a preparation method thereof, wherein the graphene modified silicon anode material comprises graphene and silicon loaded on the surface of the graphene, and the preparation method comprises the following steps:
(1) Stirring 30 nm-diameter nano-silicon in 25% HCl solution at room temperature for 1 hr, vacuum drying at 70deg.C for 5 hr, ultrasonic treating the dried product in anhydrous toluene for 1 hr, adding APTES, reacting in 100 deg.C nitrogen atmosphere for 15 hr, centrifuging, and washing with anhydrous toluene to obtain aminated nano-silicon (denoted as nano-Si-NH) 2 )；
(2) The nano Si-NH of the step (1) 2 Ultrasonically dispersing with thionyl chloride, adding 1.5mL of N, N-Dimethylformamide (DMF) catalyst, dropwise adding 2-4 layers of sulfonated graphene with the particle size D50 of 2.5 mu m and nano Si-NH under the nitrogen atmosphere at 80 DEG C 2 The mol ratio of the sulfonated graphene to the sulfonated graphene is 25:1, and the mixture is reacted for 20 hours to obtain a mixed solution;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 250 ℃, and the outlet temperature of spray drying is 150 ℃, so as to obtain the graphene modified silicon anode material.
Example 2
The embodiment provides a graphene modified silicon anode material and a preparation method thereof, wherein the graphene modified silicon anode material comprises graphene and silicon loaded on the surface of the graphene, and the preparation method comprises the following steps:
(1) Stirring nano silicon with the particle size D50 of 60nm in 30% HCl solution for 1h at room temperature, then drying in vacuum at 70 ℃ for 5h, putting the dried product into anhydrous toluene for ultrasonic treatment for 1h, adding APTES, reacting for 10h in nitrogen atmosphere at 120 ℃, centrifuging and washing with the anhydrous toluene to obtain nano Si-NH 2 ；
(2) The nano Si-NH of the step (1) 2 Ultrasonic dispersing with thionyl chloride, adding 2mL of DMF catalyst, dropwise adding sulfonated graphene with the number of layers of 2-4 and the particle size D50 of 4 mu m in nitrogen atmosphere at 120 ℃, and nano Si-NH 2 The molar ratio of the sulfonated graphene to the sulfonated graphene is 20:1, and the mixture is reacted for 10 hours to obtain a mixed solution;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 150 ℃, and the outlet temperature of spray drying is 190 ℃, so as to obtain the graphene modified silicon anode material.
Example 3
The embodiment provides a graphene modified silicon anode material and a preparation method thereof, wherein the graphene modified silicon anode material comprises graphene and silicon loaded on the surface of the graphene, and the preparation method comprises the following steps:
(1) Stirring nano silicon with the particle size D50 of 10nm in 20% HCl solution for 1h at room temperature, then drying in vacuum at 70 ℃ for 5h, putting the dried product into anhydrous toluene for ultrasonic treatment for 1h, adding APTES, reacting for 24h in nitrogen atmosphere at 80 ℃, centrifuging and washing with the anhydrous toluene to obtain nano Si-NH 2 ；
(2) The nano Si-NH of the step (1) 2 Ultrasonic dispersing with thionyl chloride, adding 0.5mL DMF catalyst, and adding into the mixtureSulfonated graphene with the number of layers of 2-4 layers and the particle size D50 of 1.2 mu m and nano Si-NH are added dropwise in nitrogen atmosphere at 60 DEG C 2 The mol ratio of the sulfonated graphene to the sulfonated graphene is 30:1, and the mixture is reacted for 20 hours to obtain a mixed solution;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 300 ℃, and the outlet temperature of spray drying is 110 ℃, so as to obtain the graphene modified silicon anode material.
Example 4
Removing nano Si-NH in the step (2) 2 And the molar ratio of sulfonated graphene was 10:1, the remainder were the same as in example 1.
Example 5
Removing nano Si-NH in the step (2) 2 And the molar ratio of sulfonated graphene was 32:1, the remainder were identical to example 1.
Example 6
The procedure of example 1 was followed except that the nanosilicon particle size D50 in step (1) was 5 nm.
Example 7
The procedure of example 1 was followed except that the nanosilicon particle diameter D50 in step (1) was 80nm.
Example 8
The procedure of example 1 was followed except that the sulfonated graphene in step (2) had a particle diameter D50 of 0.5. Mu.m.
Example 9
The procedure of example 1 was followed except that the sulfonated graphene in step (2) had a particle diameter D50 of 5. Mu.m.
Example 10
The procedure of example 1 was followed except that the number of layers of the sulfonated graphene in step (2) was 8 to 10.
Example 11
The procedure is as in example 1, except that the inlet temperature for spray drying in step (3) is 120 ℃.
Example 12
The procedure is as in example 1, except that the spray-drying inlet temperature in step (3) is 350 ℃.
Comparative example 1
The procedure of example 1 was followed except that step (1) was not performed, i.e., nano-silicon was directly used to react with sulfonated graphene in step (2).
Comparative example 2
The procedure of example 1 was followed except that the sulfonated graphene in step (2) was replaced with graphene.
Comparative example 3
Except that the operation of step (1) is not performed, and the nano Si-NH in step (2) is performed 2 The procedure of example 1 was repeated except that the silicone oil containing an amino group was used instead.
1. Preparation of pole piece and lithium ion battery
(1) Preparing a negative electrode plate: the graphene modified silicon anode material, graphite, a conductive agent SP and a binder PAA which are prepared in the examples and the comparative example are dissolved in a solvent according to the mass percentage of 8:88.5:0.5:3, the mixture is mixed to obtain slurry, the solid content of the slurry is controlled to be 55%, the slurry is coated on a copper foil current collector, and the anode piece is prepared by vacuum drying.
(2) Preparation of a lithium ion battery: the anode pole piece, the cathode pole piece and 1mol/L LiPF are used for preparing the anode pole piece and the cathode pole piece 6 And assembling the electrolyte of/EC+DMC+EMC (v/v=1:1:1) and Celgard2400 diaphragm into the soft-package lithium ion battery, wherein the active material in the positive electrode plate is NCM523, and the active material content is 94wt%.
2. Performance testing
(1) And (3) testing the expansion rate of the full-electrode negative electrode plate: the negative electrode sheets prepared by the materials in the examples and the comparative examples were subjected to expansion rate test, the battery was charged to 0.5C CC CV to 4.2V, the cut-off was 0.05C, then the thickness of the negative electrode sheet was measured by disassembling a caliper, and compared with the thickness of the negative electrode sheet before the battery was assembled, the full-charge expansion rate of the negative electrode was calculated, and the test results are shown in Table 1.
(2) Capacity retention test: the lithium ion batteries prepared by adopting the materials in the examples and the comparative examples are placed on a LAND battery test system of the Wuhan Jinno electronic Co., ltd for testing, and the charge and discharge voltages are limited to 2.5V-4.2V.
The cyclic test process steps are as follows: charging 0.5C CC CV to 4.2V at 45deg.C, stopping at 0.05C, and standing for 10min; after the discharge of 1C DC to 2.5V and 900 weeks, the initial discharge capacity and 900 weeks discharge capacity of the battery were recorded, and the 900 weeks discharge capacity was divided by the initial discharge capacity to obtain a 900 weeks capacity retention rate, and the test results are shown in Table 1.
The multiplying power discharging process steps are as follows: charging 1C CC CV to 4.2V at 25deg.C, stopping at 0.05C, and standing for 10min; discharge was performed at 1C, 3C and 5C DC to 2.5V, respectively, and the discharge capacity was divided by the charge capacity to obtain capacity retention ratios of 1C/1C, 1C/3C and 1C/5C, respectively, and the test results are shown in Table 1.
TABLE 1
In summary, examples 1-12 show that the preparation method prepares the graphene modified silicon anode material by mixing the aminated nano silicon source with the sulfonated graphene and matching with a spray drying mode, and the amino group contained in the nano silicon source reacts with the sulfonic group of the graphene to generate sulfonamide, so that the graphene and the nano silicon are connected through covalent bonds, the compactness and uniformity of the graphene coating are improved, the volume expansion of the silicon is effectively reduced, and the rate capability and the cycle performance of the battery are improved.
As can be seen from a comparison of example 1 and examples 4-5, the nano Si-NH in the present invention 2 And the proportion of the sulfonated graphene can influence the comprehensive performance of the graphene modified silicon anode material; when nanometer Si-NH 2 When the content is low, the energy density of the battery is reduced, meanwhile, the graphene causes steric effect, so that the rate performance and the cycle performance are poor, and when the nano Si-NH is 2 When the content is higher, the sulfonated graphene is difficult to achieve a good coating effect on the silicon negative electrode, and the surface coating graphene is spread due to expansion of the silicon negative electrode, so that the rate performance and the cycle performance of the examples 4-5 are slightly poorer than those of the example 1.
As can be seen from the comparison of the example 1 and the examples 6-10, the size and the number of layers of the nano silicon and the sulfonated graphene in the invention can influence the comprehensive performance of the graphene modified silicon anode material; when the nano silicon is larger in size, the expansion of the silicon is excessive, and when the nano silicon is smaller in size, the nano silicon cannot be dispersed; when the graphene size is larger, the lithium ion transmission path is increased, when the graphene size is smaller, the specific surface area is larger, the dispersion is difficult, more active lithium is easy to consume, and when the number of graphene layers is larger, the lithium ion transmission path is increased, so that the rate performance and the cycle performance of the embodiment 1 are optimal.
As can be seen from a comparison of examples 1 and examples 11-12, the spray drying temperature in the present invention affects the overall performance of the graphene-modified silicon anode material; too low a spray temperature results in poor dispersion of the material and too high a spray temperature results in decomposition of the material.
As can be seen from comparison of the embodiment 1 and the comparative examples 1-2, in the invention, when the nano silicon source is not provided with amino groups or the graphene is not provided with sulfonic acid groups, the graphene and the nano silicon cannot be connected in a covalent bond, and cannot be combined with carboxyl groups and/or hydroxyl groups on the nano silicon to generate hydrogen bonds, so that the coating uniformity and compactness are poor, and therefore, the expansion rate of the pole piece of the comparative examples 1-2 is too high, and the capacity retention rate is also remarkably lower than that of the embodiment 1.
As is apparent from the comparison between example 1 and comparative example 3, the graphene-modified silicon anode material prepared by reacting the specific aminated nano silicon source with the sulfonated graphene in the present invention has the best performance, and when the amino silicone oil is used, the oxygen content in the amino silicone oil is high, the energy density of the battery is reduced, and the conductivity of the amino silicone oil is poorer, so that the rate performance and the cycle performance of comparative example 3 are poorer than those of example 1.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that fall within the technical scope of the present invention disclosed herein are within the scope of the present invention.

Claims (19)

1. The preparation method of the graphene modified silicon anode material is characterized by comprising the following steps of:
mixing an aminated nano silicon source with sulfonated graphene, and performing spray drying to obtain a graphene modified silicon anode material;
in the process of mixing the aminated silicon source and the sulfonated graphene, a third solvent and a catalyst are also added, wherein the third solvent comprises thionyl chloride, the catalyst comprises N, N-dimethylformamide, the temperature of mixing the aminated silicon source and the sulfonated graphene is 60-100 ℃, the time of mixing the aminated silicon source and the sulfonated graphene is 12-36 hours, and the process of mixing the aminated silicon source and the sulfonated graphene is carried out in the atmosphere of nitrogen;
the inlet temperature of the spray drying is 150-300 ℃, and the outlet temperature of the spray drying is 110-190 ℃.
2. The method according to claim 1, wherein the molar ratio of the aminated nanosilicon source to the sulfonated graphene is (1-30): 1.
3. The method according to claim 2, wherein the molar ratio of the aminated nanosilicon source to the sulfonated graphene is (20-30): 1.
4. The method of claim 1, wherein the aminated nanosilicon source is aminated nanosilicon.
5. The preparation method according to claim 4, wherein the aminated nano-silicon is prepared as follows:
stirring the nano silicon in an acid solution, drying, mixing with a first solvent and a second solvent, and heating to obtain the aminated nano silicon.
6. The method according to claim 5, wherein the nano-silicon has a particle diameter D50 of 5 to 80nm.
7. The method according to claim 6, wherein the nano-silicon has a particle diameter D50 of 28 to 32nm.
8. The method of claim 5, wherein the acid solution comprises HCl solution.
9. The method of claim 5, wherein the first solvent comprises toluene.
10. The method of claim 5, wherein the second solvent comprises 3-aminopropyl triethoxysilane.
11. The method according to claim 5, wherein the molar ratio of the nanosilicon to the second solvent is 1 (0.2 to 5).
12. The method according to claim 5, wherein the heating is performed at 80 to 120℃for 6 to 24 hours.
13. The method of claim 5, wherein the gas in the heated atmosphere comprises nitrogen.
14. The method according to claim 1, wherein the sulfonated graphene has a particle size D50 of 1.2 to 4 μm.
15. The preparation method of claim 1, wherein the number of layers of the sulfonated graphene is less than 5.
16. The preparation method of claim 15, wherein the number of layers of the sulfonated graphene is 2-4.
17. The preparation method according to claim 1, characterized in that the preparation method comprises:
(1) Stirring nano silicon with the particle size D50 of 5-80 nm in an acid solution, drying at 60-80 ℃, mixing with a first solvent and a second solvent, and heating at 80-120 ℃ for 6-24 hours to obtain aminated nano silicon;
(2) Performing ultrasonic dispersion on the aminated nano silicon and a third solvent in the step (1), adding 0.5-2 mL of catalyst, dropwise adding sulfonated graphene with the particle size D50 of 1.2-4 mu m in a nitrogen atmosphere at the temperature of 60-100 ℃, mixing for 12-36 h to obtain a mixed solution, wherein the molar ratio of the aminated nano silicon to the sulfonated graphene is (20-30): 1;
(3) And (3) carrying out spray drying on the mixed solution obtained in the step (2), wherein the inlet temperature of spray drying is 150-300 ℃, and the outlet temperature of spray drying is 110-190 ℃, so as to obtain the graphene modified silicon anode material.
18. The graphene-modified silicon anode material is characterized in that the graphene-modified silicon anode material is prepared by the preparation method according to any one of claims 1-17, and comprises graphene and silicon loaded on the surface of the graphene.
19. A lithium ion battery, characterized in that the negative electrode of the lithium ion battery comprises the graphene-modified silicon negative electrode material according to claim 18.
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CN105206802A (en) * 2015-08-24 2015-12-30 苏州高通新材料科技有限公司 Lithium-rich sulfonated graphene-nanometer SiOx negative electrode material and preparation method and application thereof
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