CN115020667B - Silicon-carbon composite anode material and preparation method and application thereof - Google Patents
Silicon-carbon composite anode material and preparation method and application thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 239000011870 silicon-carbon composite anode material Substances 0.000 title claims description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000010405 anode material Substances 0.000 claims abstract description 32
- 239000002131 composite material Substances 0.000 claims abstract description 31
- 239000004020 conductor Substances 0.000 claims abstract description 31
- 150000002500 ions Chemical class 0.000 claims abstract description 27
- 238000001694 spray drying Methods 0.000 claims abstract description 17
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 10
- 239000002105 nanoparticle Substances 0.000 claims abstract description 6
- 239000002135 nanosheet Substances 0.000 claims abstract description 6
- 238000005469 granulation Methods 0.000 claims abstract description 4
- 230000003179 granulation Effects 0.000 claims abstract description 4
- 238000005056 compaction Methods 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 26
- 239000000203 mixture Substances 0.000 claims description 24
- 239000000463 material Substances 0.000 claims description 21
- 229910021382 natural graphite Inorganic materials 0.000 claims description 19
- 230000001681 protective effect Effects 0.000 claims description 15
- 238000000034 method Methods 0.000 claims description 12
- 239000004576 sand Substances 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 10
- 229910052799 carbon Inorganic materials 0.000 claims description 9
- 239000010426 asphalt Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 229910003481 amorphous carbon Inorganic materials 0.000 claims description 5
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 2
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 2
- 229930006000 Sucrose Natural products 0.000 claims description 2
- 239000011258 core-shell material Substances 0.000 claims description 2
- 239000003822 epoxy resin Substances 0.000 claims description 2
- 239000005007 epoxy-phenolic resin Substances 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 229920001568 phenolic resin Polymers 0.000 claims description 2
- 229920000647 polyepoxide Polymers 0.000 claims description 2
- 239000005720 sucrose Substances 0.000 claims description 2
- 238000004873 anchoring Methods 0.000 claims 1
- 238000010000 carbonizing Methods 0.000 claims 1
- 238000000227 grinding Methods 0.000 claims 1
- 229910002804 graphite Inorganic materials 0.000 abstract description 26
- 239000010439 graphite Substances 0.000 abstract description 26
- 239000007773 negative electrode material Substances 0.000 abstract description 5
- 238000007599 discharging Methods 0.000 abstract description 3
- 239000002064 nanoplatelet Substances 0.000 abstract description 3
- 230000002776 aggregation Effects 0.000 abstract description 2
- 238000004220 aggregation Methods 0.000 abstract description 2
- 239000011868 silicon-carbon composite negative electrode material Substances 0.000 abstract description 2
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 50
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 28
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 20
- 229910052786 argon Inorganic materials 0.000 description 14
- 238000001816 cooling Methods 0.000 description 6
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- 239000013081 microcrystal Substances 0.000 description 6
- 229910052814 silicon oxide Inorganic materials 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- SKKMWRVAJNPLFY-UHFFFAOYSA-N azanylidynevanadium Chemical compound [V]#N SKKMWRVAJNPLFY-UHFFFAOYSA-N 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000010298 pulverizing process Methods 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 230000001351 cycling effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910004283 SiO 4 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005543 nano-size silicon particle Substances 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- 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
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention belongs to the technical field of negative electrode materials for lithium ion batteries, and particularly relates to a silicon-carbon composite negative electrode material, and a preparation method and application thereof. The invention sufficiently grinds the ion conductive material and the modified SiO into nano particles by sanding, graphite is peeled off to form graphite nano sheets, and the ion conductive material and the modified SiO nano particles are uniformly anchored in the graphite nano sheets. In this unique structure, the ion conducting material and the graphite nanoplatelets not only enhance electron conductivity, but also prevent aggregation of modified SiO during charging and discharging of the battery. The composite anode material with high tap density can be obtained through spray drying and mechanical compaction granulation, and the modified SiO, the ion conducting material and the graphite can be tightly connected, so that a good conducting network is formed inside the composite anode material.
Description
Technical Field
The invention belongs to the technical field of negative electrode materials for lithium ion batteries, and particularly relates to a silicon-carbon composite negative electrode material, and a preparation method and application thereof.
Background
Lithium ion batteries have become a current world research hot spot due to the advantages of large specific capacity, long service life, high safety, portability and the like, and are widely applied to various electronic devices, electric automobiles and portable energy storage devices. Silicon oxide is used as a novel negative electrode material for a lithium ion secondary battery, has higher specific capacity (2000 mAh/g) than graphite, but has poor conductivity, large volume expansion, easy pulverization, falling off and the like in the charge and discharge process, and seriously influences the service life of the negative electrode material. In particular, lithium ions of the silicon oxide material can react with silicon oxide to generate Li in the first charge and discharge process 2 O and Li 2 SiO 4 Eliminating medicineConsuming more active lithium, resulting in low first week coulomb efficiency<70％)。
To solve a series of problems caused by poor conductivity and volume expansion of silicon oxide, those skilled in the art modify it by various methods including nanocrystallization, surface coating with carbon, compounding with graphite, and the like. These methods can improve cycle performance and first-week coulombic efficiency to some extent, but there are still many problems such as poor cycle performance and first-week coulombic efficiency, low tap density, or difficulty in industrialization. Therefore, how to effectively relieve the volume expansion, ensure the cycling stability of the battery, obtain the silicon oxide negative electrode material with high first cycle coulomb efficiency, better cycling performance and high tap density, and is still a technical hot spot to be solved in the current lithium ion battery field.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the silicon-carbon composite anode material, and the preparation method and application thereof, and the use of the silicon-carbon composite anode material can effectively improve the first-week coulomb efficiency of a battery and relieve the problem of the volume expansion of silicon oxide, so that the lithium ion battery assembled by the silicon-carbon composite anode material has better cycle performance.
Specifically, the invention provides the following technical scheme:
a method for preparing a silicon-carbon composite anode material, comprising the following steps:
(1) Performing heat treatment on SiO under inert protective atmosphere to obtain modified SiO;
(2) Mixing the modified SiO, the ion conductive material and the natural graphite in the step (1), and spray-drying to obtain a mixture;
(3) Mixing the mixture obtained in the step (2) with an organic carbon source, compacting and granulating to obtain a block material;
(4) And (3) carrying out high-temperature heat treatment on the block material in the step (3) under an inert protective atmosphere, and crushing to obtain the silicon-carbon composite anode material.
According to the invention, in the step (1), the heat treatment method comprises the following steps: the SiO is maintained in an inert atmosphere (e.g., argon) at a temperature of 800-1200 ℃ (e.g., 950-1150 ℃) for a period of time (e.g., 1-10 hours) to obtain a modified SiO. The rate of temperature rise is, for example, 2 to 10 ℃/min or 2 to 5 ℃/min.
According to the invention, in step (1), the SiO has a median particle diameter D 50 It is 3mm to 15mm, preferably 5mm to 10mm, for example 6mm, 8mm, 10mm.
According to the present invention, in step (2), the modified SiO and the ion conductive material of step (1) are mixed with water, and then put into a sand mill to sand for a period of time (e.g., 1 to 15 hours or 3 to 10 hours), and then natural graphite is added to sand for a period of time (e.g., 1 to 15 hours or 1 to 10 hours). And then spray drying is carried out to obtain the modified SiO/ion conducting material/graphite mixture. The rotational speed of the sand mill is, for example, 1800rmp to 2500rmp.
According to the invention, in the step (2), the natural graphite is spherical natural graphite, and the purity is more than or equal to 99.0%.
According to the invention, in step (2), the ion-conducting material is selected from VN, li 3 N, coN, niN.
According to the invention, in the step (2), the mass ratio of the modified SiO, the ion conducting material and the natural graphite is 100 (3-12): 60-120, preferably 100 (5-10): 70-100, for example 100 (5, 6, 7, 8, 9, 10): 70, 75, 80, 85, 90, 95, 100.
According to the invention, in the step (2), the temperature of a feed inlet of the spray drying is 120-150 ℃, and the temperature of a discharge outlet is 80-95 ℃.
According to the invention, in step (3), the compacting and granulating pressure is 20-50 MPa, such as 20MPa, 30MPa, 40MPa and 50MPa, and the pressure maintaining time is 10-30 minutes. The compacting granulation is carried out, for example, in a hydraulic press.
According to the invention, in the step (3), the mass ratio of the organic carbon source to the mixture of the step (2) is (8-25): 100, for example, 8:100, 9:100, 10:100, 12:100, 15:100, 16:100, 18:100, 20:100, 22:100, 25:100.
According to the invention, in the step (3), the organic carbon source is at least one selected from asphalt, epoxy resin, phenolic resin and sucrose. Wherein the softening point of the asphalt is 120-250 ℃.
According to the invention, in the step (4), the block material of the step (3) is kept for a period of time (for example, 1-10 hours, or 1-5 hours) in an inert atmosphere (for example, argon) at a temperature of 650-1000 ℃, cooled to room temperature, and then crushed to obtain the composite anode material. The temperature is, for example, 750 to 850 ℃ (e.g., 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃, 800 ℃, 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃). The rate of the temperature rise is, for example, 2 to 10 ℃/min.
According to the present invention, in the step (4), the pulverization may be performed using various conventional fine powder pulverizing apparatuses in the art, preferably to the average particle diameter D of the composite anode material 50 From 10 μm to 20 μm, such as 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.
According to the invention, the method comprises the following steps:
(1) Placing SiO in a box furnace, introducing argon protective atmosphere, and heating to 950-1150 ℃ at a heating rate of 2-5 ℃/min for 2-5 h of high-temperature heat treatment, so that Si microcrystals are uniformly dispersed in the SiO to obtain modified SiO;
(2) Adding the modified SiO and the ion conductive material in the step (1) into deionized water, uniformly stirring, putting into a sand mill, sanding for 5-10 hours, adding natural graphite, sanding for 1-4 hours, and then spray drying to obtain a modified SiO/ion conductive material/graphite mixture;
(3) Uniformly mixing the mixture obtained in the step (2) with an organic carbon source, and compacting and granulating in a hydraulic press to obtain a block material;
(4) Placing the block material in the step (3) into a box furnace, introducing argon protective atmosphere, heating to 700-850 ℃ at a heating rate of 2-10 ℃/min, performing high-temperature heat treatment for 1-5 h, cooling to room temperature, and then crushing to obtain the composite anode material.
The invention also provides the composite anode material prepared by the method.
According to the invention, the first-week discharge capacity of the composite anode material is more than or equal to 800mAh/g, the first-week charge-discharge efficiency is more than or equal to 80%, and the 300-week circulation capacity retention rate is more than or equal to 91%.
According to the invention, the composite anode material has a core-shell structure, wherein the core is a mixture of modified SiO/ion conductive material/graphite, and the shell is amorphous carbon.
According to the invention, in the modified SiO/ion conducting material/graphite mixture, the median particle diameter D of the modified SiO 50 150nm to 250nm, preferably 180nm to 220nm; median particle diameter D of graphite 50 150nm to 250nm, preferably 180nm to 220nm; median particle diameter D of ion-conducting material 50 10nm to 30nm, preferably 15nm to 20nm.
According to the invention, the ion-conducting material and the modified SiO are anchored in the nanoplatelets of graphite.
According to the invention, the amorphous carbon content is 1-5 wt%, the modified SiO content is 45-55 wt%, the ion conductive material content is 2-6 wt%, and the graphite content is 40-45 wt%.
According to the invention, the amorphous carbon content in the composite anode material is 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, the modified SiO content is 45wt%, 46wt%, 47wt%, 48wt%, 49wt%, 50wt%, 51wt%, 52wt%, 53wt%, 54wt%, and 55wt%, the ion conductive material content is 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, and the graphite content is 40wt%, 41wt%, 42wt%, 43wt%, 44wt%, 45wt%.
According to the invention, the modified SiO is a mixture of nano-silicon, silica and silicon dioxide.
The invention also provides application of the composite anode material in a lithium ion battery, and the composite anode material is preferably used as the anode material of the lithium ion battery.
The invention has the beneficial effects that:
according to the invention, the ion conductive material and the modified SiO are sufficiently ground into nano particles through sanding, graphite is peeled off to form graphite nano sheets, and further, the ion conductive material and the modified SiO nano particles are uniformly anchored in the graphite nano sheets. In this unique structure, the ion conducting material and the graphite nanoplatelets not only enhance electron conductivity, but also prevent aggregation of modified SiO during charging and discharging of the battery. The composite anode material with high tap density can be obtained through spray drying and mechanical compaction granulation, and the modified SiO, the ion conducting material and the graphite can be tightly connected, so that a good conductive network is formed inside the composite anode material, and when the ion conducting material with high strength and good conductivity is combined with the graphite, a synergistic effect is achieved, the defect that the anode structure is easy to be damaged in the repeated charging and discharging process is overcome, and the cycle performance of the composite anode material is further improved.
Detailed Description
The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
Example 1
(1) 100g of SiO (D) 50 6 mm) is placed in a box furnace, argon protective atmosphere is introduced, and the temperature is raised to 950 ℃ at 5 ℃ per minute for high-temperature heat treatment for 5 hours, so that Si microcrystals are uniformly dispersed in SiO, and modified SiO is obtained;
(2) Adding 100g of modified SiO and 5g of NiN in the step (1) into deionized water, uniformly stirring, putting into a sand mill, sanding for 7 hours, adding 70g of natural graphite, sanding for 3 hours, and then spray drying to obtain the modified SiO/NiN/graphite mixture. The temperature of the feed inlet of the spray drying equipment is 130 ℃ and the temperature of the discharge outlet is 90 ℃.
(3) Uniformly mixing the mixture obtained in the step (2) and asphalt (with the softening point of 150 ℃) according to the mass ratio of 100:20, and then compacting and granulating at high pressure by a 30MPa hydraulic press, and maintaining the pressure for 25 minutes to obtain the block material.
(4) Will step by stepPlacing the block material in the step (3) in a box furnace, introducing argon protective atmosphere, heating to 750 ℃ at 4 ℃/min, performing high-temperature heat treatment for 2 hours, cooling to room temperature, and then crushing to obtain a composite anode material (D) 50 15 μm).
Example 2
(1) 100g of SiO (D) 50 8 mm) is placed in a box furnace, argon protective atmosphere is introduced, the temperature is increased to 1050 ℃ at 3 ℃/min, and high-temperature heat treatment is carried out for 4 hours, so that Si microcrystals are uniformly dispersed in SiO, and modified SiO is obtained;
(2) 100g of modified SiO and 7g of Li from step (1) 3 Adding N into deionized water, stirring, sanding in a sand mill for 6 hours, adding 80g of natural graphite, sanding for 4 hours, and spray drying to obtain modified SiO/Li 3 N/graphite mixture. The temperature of the feed inlet of the spray drying equipment is 120 ℃, and the temperature of the discharge outlet is 92 ℃.
(3) Uniformly mixing the mixture obtained in the step (2) and asphalt (with the softening point of 220 ℃) according to the mass ratio of 100:16, and then compacting and granulating at high pressure by a 40MPa hydraulic press, and maintaining the pressure for 20 minutes to obtain the block material.
(4) Placing the block material in the step (3) in a box furnace, introducing argon protective atmosphere, heating to 800 ℃ at 3 ℃/min, performing high-temperature heat treatment for 2 hours, cooling to room temperature, and then crushing to obtain a composite anode material (D) 50 12 μm).
Example 3
(1) 100g of SiO (D) 50 10 mm) is placed in a box furnace, argon protective atmosphere is introduced, and the temperature is raised to 1000 ℃ at 4 ℃ per minute for high-temperature heat treatment for 4 hours, so that Si microcrystals are uniformly dispersed in SiO, and modified SiO is obtained;
(2) Adding 100g of modified SiO and 10g of VN (vanadium nitride) in the step (1) into deionized water, stirring uniformly, putting into a sand mill, sanding for 6 hours, adding 100g of natural graphite, sanding for 4 hours, and then spray drying to obtain the modified SiO/VN/graphite mixture. The temperature of the feed inlet of the spray drying equipment is 120 ℃, and the temperature of the discharge outlet is 95 ℃.
(3) Uniformly mixing the mixture obtained in the step (2) and asphalt (with the softening point of 200 ℃) according to the mass ratio of 100:15, and then compacting and granulating at high pressure by a 50MPa hydraulic press, and maintaining the pressure for 10 minutes to obtain the block material.
(4) Placing the block material in the step (3) in a box furnace, introducing argon protective atmosphere, heating to 820 ℃ at 5 ℃/min, performing high-temperature heat treatment for 1h, cooling to room temperature, and then crushing to obtain a composite anode material (D) 50 18 μm).
Example 4
(1) 100g of SiO (D) 50 6 mm) is placed in a box furnace, argon protective atmosphere is introduced, and the temperature is raised to 950 ℃ at 5 ℃ per minute for high-temperature heat treatment for 5 hours, so that Si microcrystals are uniformly dispersed in SiO, and modified SiO is obtained;
(2) Adding the modified SiO and 5g NiN in the step (1) into deionized water, uniformly stirring, putting into a sand mill, sanding for 5 hours, adding 90g of natural graphite, sanding for 4 hours, and then spray drying to obtain the modified SiO/NiN/graphite mixture. The temperature of the feed inlet of the spray drying equipment is 120 ℃ and the temperature of the discharge outlet is 90 ℃.
(3) Uniformly mixing the mixture obtained in the step (2) and asphalt (with the softening point of 180 ℃) according to the mass ratio of 100:17, then compacting and granulating at high pressure by a 30MPa hydraulic press, and maintaining the pressure for 16 minutes to obtain the block material.
(4) Placing the block material in the step (3) in a box furnace, introducing argon protective atmosphere, heating to 820 ℃ at 5 ℃/min, performing high-temperature heat treatment for 2 hours, cooling to room temperature, and then crushing to obtain a composite anode material (D) 50 13 μm).
Comparative example 1
(1) 100g of SiO (D) 50 6 mm) is placed in a box furnace, argon protective atmosphere is introduced, and the temperature is raised to 950 ℃ at 5 ℃ per minute for high-temperature heat treatment for 5 hours, so that Si microcrystals are uniformly dispersed in SiO, and modified SiO is obtained;
(2) Adding the modified SiO obtained in the step (1) into deionized water, uniformly stirring, putting into a sand mill, sanding for 7 hours, adding 70g of natural graphite, sanding for 3 hours, and then spray drying to obtain the modified SiO/graphite mixture. The temperature of the feed inlet of the spray drying equipment is 130 ℃ and the temperature of the discharge outlet is 90 ℃.
(3) Uniformly mixing the mixture obtained in the step (2) and asphalt (with the softening point of 150 ℃) according to the mass ratio of 100:20, and then compacting and granulating at high pressure by a 30MPa hydraulic press, and maintaining the pressure for 25 minutes to obtain the block material.
(4) Placing the block material in the step (3) in a box furnace, introducing argon protective atmosphere, heating to 750 ℃ at 4 ℃/min, performing high-temperature heat treatment for 2 hours, cooling to room temperature, and then crushing to obtain a composite anode material (D) 50 15 μm).
Physical and chemical indexes of the composite anode materials of the above examples 1 to 4 and comparative example 1 were tested, and the following are specific: testing the median particle diameter of the sample by using a laser particle sizer; the tap density was measured using a Quantachrome Auto Tap tap density meter.
Electrochemical performance test:
half-electric test method: the composite anode materials prepared in examples 1 to 4 and comparative example 1 were uniformly mixed with conductive carbon black (SP) carboxymethylcellulose (CMC) Styrene Butadiene Rubber (SBR) =95:1:1.5:2.5 (mass ratio), coated on copper foil, and the coated electrode sheet was dried in a vacuum oven at 120 ℃ for 12 hours. Simulated battery assembly was performed in an argon-protected Braun glove box with electrolyte 1M-LiPF 6 +EC: DEC: DMC (volume ratio: 1:1:1), metal lithium sheet as counter electrode, and simulation battery test was conducted in a 5V, 10mA New Wei battery test cabinet, with charge-discharge voltage of 0.01-1.5V, charge-discharge rate of 0.1C, and the first week discharge capacity and first week charge-discharge efficiency obtained by the test are shown in Table 1.
The full battery test method comprises the following steps: the composite anode materials prepared in examples 1 to 4 and comparative example 1 were used as anodes, and lithium cobaltate was used as a cathode, 1M-LiPF 6 The +EC:DEC:DMC (volume ratio 1:1:1) solution was used as an electrolyte to assemble a full cell, charge and discharge was performed at normal temperature at a rate of 0.1C, the voltage range was 3.0 to 4.2V, and the cycle properties obtained by the test are shown in Table 1.
TABLE 1 electrochemical Performance test results
As can be seen from Table 1, the composite anode material prepared by the invention has the characteristics of higher capacity, high first-week charge-discharge efficiency and good cycle performance. Comparative example 1 was free of addition of ion conductive material, and the material had good first-week charge-discharge efficiency, but had poor cycle performance.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A method for preparing a silicon-carbon composite anode material, comprising the following steps:
(1) Maintaining SiO at 800-1200 ℃ for 1-10 hours in an inert atmosphere to obtain modified SiO;
(2) Mixing the modified SiO and the ion conductive material in the step (1) with water, putting the mixture into a sand mill, sanding for 1-15 hours, adding natural graphite, sanding for 1-15 hours, and spray drying to obtain a modified SiO/ion conductive material/natural graphite mixture; the rotating speed of the sand mill is 1800rpm-2500rpm; grinding the ion conductive material and the modified SiO into nano particles by sanding, stripping natural graphite to obtain natural graphite nano sheets, and anchoring the ion conductive material and the modified SiO nano particles in the natural graphite nano sheets;
(3) Mixing the mixture obtained in the step (2) with an organic carbon source, compacting and granulating to obtain a block material;
(4) Carbonizing the organic carbon source in the block material in the step (3) through high-temperature heat treatment under an inert protective atmosphere, and crushing to obtain the silicon-carbon composite anode material;
in step (1), the SiO has a median particle diameter D 50 3mm to 15mm;
in step (2), the ion-conducting material is selected from VN, li 3 N, coN, niN;
in the step (2), the mass ratio of the modified SiO to the ion conducting material to the natural graphite is 100 (3-12) (60-120);
in the silicon-carbon composite anode material, the median diameter D of modified SiO 50 150nm to 250nm。
2. The preparation method of claim 1, wherein in the step (1), the heating rate is 2-10 ℃/min.
3. The preparation method according to claim 1, wherein in the step (3), the compacting and granulating pressure is 20-50 mpa, and the dwell time is 10-30 minutes; the compaction granulation is carried out in a hydraulic press;
and/or in the step (3), the mass ratio of the organic carbon source to the mixture is (8-25) 100;
and/or the organic carbon source is selected from at least one of asphalt, epoxy resin, phenolic resin and sucrose.
4. The preparation method of claim 1, wherein in the step (4), the block material of the step (3) is kept for 1-10 hours in an inert atmosphere at 650-1000 ℃, cooled to room temperature, and then crushed to obtain the silicon-carbon composite anode material.
5. The composite anode material prepared by the method of any one of claims 1-4.
6. The composite anode material of claim 5, wherein the composite anode material has a first cycle discharge capacity of greater than or equal to 800mAh/g, a first cycle charge-discharge efficiency of greater than or equal to 80%, and a 300 cycle capacity retention of greater than or equal to 91%.
7. The composite anode material of claim 5 or 6, wherein the composite anode material has a core-shell structure, wherein the core is a mixture of modified SiO/ion conductive material/natural graphite and the shell is amorphous carbon.
8. The composite anode material according to claim 7, wherein the content of amorphous carbon in the composite anode material is 1-5wt%, the content of modified SiO is 45-55wt%, the content of ion conductive material is 2-6wt%, and the content of natural graphite is 40-45wt%.
9. Use of the composite anode material of any one of claims 5-8 in a lithium ion battery.
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