CN114400312A - Low-expansion silicon-carbon composite negative electrode material and preparation method thereof - Google Patents
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- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 239000011868 silicon-carbon composite negative electrode material Substances 0.000 title claims abstract description 15
- 239000002131 composite material Substances 0.000 claims abstract description 33
- 239000011247 coating layer Substances 0.000 claims abstract description 29
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 claims abstract description 28
- 239000006258 conductive agent Substances 0.000 claims abstract description 24
- 239000007784 solid electrolyte Substances 0.000 claims abstract description 19
- 239000006087 Silane Coupling Agent Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 7
- 229920001940 conductive polymer Polymers 0.000 claims abstract description 6
- 229920005575 poly(amic acid) Polymers 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 14
- 239000004642 Polyimide Substances 0.000 claims description 13
- 229920001721 polyimide Polymers 0.000 claims description 13
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 238000010438 heat treatment Methods 0.000 claims description 12
- 239000011258 core-shell material Substances 0.000 claims description 9
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 8
- RJEIKIOYHOOKDL-UHFFFAOYSA-N [Li].[La] Chemical group [Li].[La] RJEIKIOYHOOKDL-UHFFFAOYSA-N 0.000 claims description 8
- 239000012528 membrane Substances 0.000 claims description 8
- 239000002121 nanofiber Substances 0.000 claims description 7
- 239000011870 silicon-carbon composite anode material Substances 0.000 claims description 7
- 238000002156 mixing Methods 0.000 claims description 6
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 6
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 claims description 6
- 238000010041 electrostatic spinning Methods 0.000 claims description 5
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 5
- 238000005507 spraying Methods 0.000 claims description 5
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical compound CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 claims description 4
- HXLAEGYMDGUSBD-UHFFFAOYSA-N 3-[diethoxy(methyl)silyl]propan-1-amine Chemical compound CCO[Si](C)(OCC)CCCN HXLAEGYMDGUSBD-UHFFFAOYSA-N 0.000 claims description 4
- SJECZPVISLOESU-UHFFFAOYSA-N 3-trimethoxysilylpropan-1-amine Chemical compound CO[Si](OC)(OC)CCCN SJECZPVISLOESU-UHFFFAOYSA-N 0.000 claims description 4
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 claims description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 4
- 239000002048 multi walled nanotube Substances 0.000 claims description 4
- 239000002109 single walled nanotube Substances 0.000 claims description 4
- 239000002134 carbon nanofiber Substances 0.000 claims description 3
- 239000003273 ketjen black Substances 0.000 claims description 3
- PHQOGHDTIVQXHL-UHFFFAOYSA-N n'-(3-trimethoxysilylpropyl)ethane-1,2-diamine Chemical compound CO[Si](OC)(OC)CCCNCCN PHQOGHDTIVQXHL-UHFFFAOYSA-N 0.000 claims description 3
- MQWFLKHKWJMCEN-UHFFFAOYSA-N n'-[3-[dimethoxy(methyl)silyl]propyl]ethane-1,2-diamine Chemical compound CO[Si](C)(OC)CCCNCCN MQWFLKHKWJMCEN-UHFFFAOYSA-N 0.000 claims description 3
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 claims description 2
- 239000003960 organic solvent Substances 0.000 claims 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 35
- 239000000126 substance Substances 0.000 abstract 1
- 239000002153 silicon-carbon composite material Substances 0.000 description 23
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- 238000012360 testing method Methods 0.000 description 16
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- 230000000052 comparative effect Effects 0.000 description 9
- 239000003575 carbonaceous material Substances 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 230000004907 flux Effects 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 239000011149 active material Substances 0.000 description 5
- 239000003792 electrolyte Substances 0.000 description 5
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- 239000002861 polymer material Substances 0.000 description 5
- 229910001290 LiPF6 Inorganic materials 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- 229920005570 flexible polymer Polymers 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000007773 negative electrode material Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229920000049 Carbon (fiber) Polymers 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013716 LiNi Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 229910021383 artificial graphite Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000004917 carbon fiber Substances 0.000 description 1
- 238000010000 carbonizing Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 239000007822 coupling agent Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
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- 150000002500 ions Chemical class 0.000 description 1
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
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- 239000002245 particle Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
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- 230000002195 synergetic effect Effects 0.000 description 1
- 238000001947 vapour-phase growth Methods 0.000 description 1
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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
- 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
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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
- 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
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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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
- H01M4/602—Polymers
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- General Chemical & Material Sciences (AREA)
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- Battery Electrode And Active Subsutance (AREA)
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Abstract
The invention provides a low-expansion silicon-carbon composite negative electrode material which comprises a silicon monoxide material core, a first coating layer and a second coating layer, wherein the first coating layer and the second coating layer are coated on the surface of the core, the first coating layer is composed of a conductive agent, a solid electrolyte and a silane coupling agent, and the second coating layer is composed of a conductive polymer composite material. The invention also provides a preparation method of the low-expansion silicon-carbon composite negative electrode material. The low-expansion silicon-carbon composite negative electrode material can effectively inhibit the expansion of the material and improve the structural stability of the material in the charge and discharge processes of the material; meanwhile, the first coating layer and the second coating layer are connected through chemical bonds, so that the structural stability of the materials is improved, and the cycle performance is improved.
Description
Technical Field
The invention belongs to the field of preparation of lithium ion battery materials, and particularly relates to a low-expansion silicon-carbon composite negative electrode material and a preparation method thereof.
Background
The silicon carbon material has the advantages of high first-stage energy density, wide material source and the like, and becomes a preferred material of a next-generation high-energy-density lithium ion battery, but the material has poor conductivity and low first-stage efficiency, and the material has large expansion in the charging and discharging processes, so that the cycle performance and the rate performance of the material are poor. One of the measures for improving the conductivity of the material is to improve the electron-withdrawing capability of the material by doping the surface of the material, for example, doping nitrogen atoms, thereby improving the conductivity of the material and improving the fast-charging performance of the material. Although the conductivity of the material is improved, the expansion of the material is still large, and the cycle performance of the battery and the battery grouping are influenced. The measures for reducing the expansion of the silicon-carbon material are various, such as the nanocrystallization of the material, porous silicon-carbon and the like, but the nano silicon-carbon has strong material activity, so that the problems of low initial efficiency, deviation of safety performance, deterioration of later performance of cycle performance, easy water jumping of a battery and the like are caused. On one hand, the silicon carbon material is coated with a layer of polymer material with good flexibility, so that the initial expansion and the cyclic expansion of the silicon carbon can be restrained in the charging and discharging processes; on the other hand, the polymer material can prevent the silicon carbon material from directly contacting with the electrolyte, reduce the side reaction and improve the cycle and storage performance of the silicon carbon material.
Disclosure of Invention
In order to improve the conductivity of the silicon carbon material and reduce the expansion of the silicon carbon material, the electronic ion conductivity of the material is improved by coating the first coating layer of the material with the electronic conductivity and the ionic conductivity on the surface of the silicon monoxide; and the second coating layer of the conductive polymer with strong flexibility improves the expansion and finally improves the cycle and rate capability of the silicon-carbon material.
The invention provides a low-expansion silicon-carbon composite negative electrode material which is in a core-shell structure, wherein a core of the core-shell structure is silicon monoxide, a shell of the core-shell structure is composed of a first coating layer arranged on the surface of the core and a second coating layer arranged on the surface of the first coating layer, the first coating layer is composed of a conductive agent, a solid electrolyte and a silane coupling agent, and the second coating layer is composed of a flexible conductive polymer composite material.
In a preferred embodiment of the invention, the thickness ratio of the core-shell structure is (5-20): (5-20) of the inner core, the first coating layer and the second coating layer = 100.
In a preferred embodiment of the present invention, the solid electrolyte is lanthanum lithium zirconate.
In a preferred embodiment of the present invention, the conductive agent is aminated graphene, aminated carbon nanotube or aminated porous carbon.
In a preferred embodiment of the present invention, the silane coupling agent is one of gamma-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, gamma-diethylenetriaminepropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldimethoxysilane and gamma-aminopropylmethyldiethoxysilane.
In a preferred embodiment of the present invention, the flexible conductive polymer composite is a polyimide nanofiber membrane containing a conductive agent. In a more preferred embodiment of the present invention, the conductive agent is a single-walled carbon nanotube, a multi-walled carbon nanotube, ketjen black, or a vapor grown carbon fiber.
The invention also provides a preparation method of the low-expansion silicon-carbon composite negative electrode material, which comprises the following steps:
(1) preparation of composite material B:
mixing a solid electrolyte, a conductive agent A, a silane coupling agent and an organic flux to obtain a coating solution A, then adding silicon monoxide into the coating solution A, and preparing a composite material B coated with the solid electrolyte on the surface through a hydrothermal reaction, wherein the mass ratio of the components is solid electrolyte, conductive agent A, silane coupling agent, organic flux and silicon monoxide = (1-5): 100-500): 30-50;
(2) preparation of composite material D:
preparing an N-methyl pyrrolidone solution of 0.5-2 wt% of polyamic acid, adding a conductive agent B and a composite material B, preparing a solution, spraying the solution on a light plate through electrostatic spinning, crushing, and heating in a nitrogen atmosphere to convert the polyamic acid into polyimide, thereby obtaining a low-expansion silicon-carbon composite negative electrode material with a polyimide nanofiber membrane as a shell, namely a composite material D, wherein the mass ratio of the components is polyamic acid to the conductive agent B to the composite material B = (10-30): 1-5): 100.
in a preferred embodiment of the present invention, the solid electrolyte in step (1) is lanthanum lithium zirconate.
In a preferred embodiment of the present invention, the conductive agent a in step (1) is aminated graphene, aminated carbon nanotube or aminated porous carbon.
In a preferred embodiment of the present invention, the silane coupling agent in step (1) is one of gamma-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, gamma-diethylenetriaminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldimethoxysilane and gamma-aminopropylmethyldiethoxysilane.
In a preferred embodiment of the present invention, the organic flux in step (1) is one of N-methylpyrrolidone, carbon tetrachloride, butanediol and cyclohexane.
In a preferred embodiment of the present invention, the heating temperature in the step (2) is 150 to 250 ℃ and the heating time is 1 to 6 hours.
In a preferred embodiment of the present invention, the conductive agent B in step (2) is a single-walled carbon nanotube, a multi-walled carbon nanotube, ketjen black, or a vapor grown carbon fiber.
The invention has the beneficial effects that:
1) the surface of the inner core silicon monoxide is coated with a first coating layer consisting of a conductive agent, a solid electrolyte and a silane coupling agent, the quick charging performance of the material is improved by utilizing the characteristic of high ionic conductivity of the solid electrolyte, the electronic conductivity of the conductive agent is improved, the electronic conductivity of the conductive agent and the network structure formed by the inner core silicon monoxide and the shell by the silane coupling agent are improved, the rate and the cycle performance of the material are improved by exerting the synergistic effect of the conductive agent, the solid electrolyte and the silane coupling agent, and the expansion of the material is reduced;
2) the outermost layer is coated with a layer of flexible polymer material, so that the expansion of silicon in the charging and discharging process is restrained, the SEI (solid electrolyte interphase) damage on the silicon surface is prevented, and the cycle performance of the silicon surface is improved; on the other hand, the flexible polymer is in a fibrous structure, has the characteristics of high flexibility, strong binding force and high electronic conductivity, and further reduces the internal resistance of the material and improves the cycle performance of the material.
Drawings
The invention may be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, in which:
fig. 1 is an SEM image of a low expansion silicon carbon composite anode material prepared in example 1.
Detailed Description
Example 1
1) Preparation of composite material B:
uniformly mixing 3g of lanthanum lithium zirconate, 3g of aminated graphene, 3g of gamma-aminopropyltrimethoxysilane and 500ml of N-methylpyrrolidone to obtain a coating solution A, then adding 20g of silicon monoxide into the coating solution A, and reacting for 6 hours at 150 ℃ and 3Mpa through hydrothermal reaction to prepare a composite material B with the surface coated with a solid electrolyte;
2) preparation of composite material D:
adding 20g of polyamic acid into 2000ml of N-methyl pyrrolidone to prepare a 1% polyamic acid solution, then adding 3g of single-walled carbon nanotube and 100g of composite material B, preparing a solution with the concentration of 6.1wt%, then spraying the solution onto a light plate through electrostatic spinning, then crushing, heating in a nitrogen atmosphere to convert the polyamic acid into polyimide, and keeping the heating temperature at 200 ℃ for 3 hours to obtain a silicon-carbon composite anode material with a polyimide nanofiber membrane as an outer shell, namely the composite material D, wherein the thicknesses of the inner core, the first coating layer and the second coating layer are respectively 10 mu m, 1 mu m and 1 mu m.
Example 2
1) Preparation of composite material B:
mixing 1g of lanthanum lithium zirconate, 1g of aminated carbon nanotube, 5g of 3-aminopropyltriethoxysilane and 100ml of carbon tetrachloride organic flux to obtain coating liquid A, then adding 30g of silicon monoxide into the coating liquid A, carrying out hydrothermal reaction, and reacting at 150 ℃ and 3Mpa for 6 hours to prepare a composite material B with the surface coated with solid electrolyte;
2) preparation of composite material D:
adding 10g of polyamic acid into 2000ml of N-methyl pyrrolidone to prepare a 0.5% polyamic acid solution, then adding 5g of multi-walled carbon nanotubes and 100g of composite material B, preparing a solution with the concentration of 5.75wt%, then spraying the solution on a light plate through electrostatic spinning, then crushing, heating in a nitrogen atmosphere to convert the polyamic acid into polyimide, and keeping the heating temperature at 150 ℃ for 6 hours to obtain a silicon-carbon composite anode material with a polyimide nanofiber membrane as an outer shell, namely the composite material D, wherein the thicknesses of the inner core, the first coating layer and the second coating layer are respectively 12 mu m, 0.6 mu m and 0.6 mu m.
Example 3
1) Preparation of composite material B:
uniformly mixing 5g of lanthanum lithium zirconate, 5g of aminated porous carbon, 1g of gamma-aminopropyl methyl diethoxy silane and 500ml of cyclohexane organic flux to obtain coating liquid A, then adding 50g of silicon monoxide into the coating liquid A, carrying out hydrothermal reaction, and reacting at the temperature of 150 ℃ and the pressure of 3MPa for 6 hours to prepare a composite material B with the surface coated with solid electrolyte;
2) preparation of composite material D:
adding 30g of polyamic acid into 1500ml of N-methyl pyrrolidone to prepare a 2% polyamic acid solution, then adding 5g of vapor phase growth carbon fiber and 100g of composite material B, preparing a solution with the concentration of 9wt%, then spraying the solution onto a light plate through electrostatic spinning, then crushing, heating in a nitrogen atmosphere to convert the polyamic acid into polyimide, and keeping the heating temperature at 250 ℃ for 1 hour to obtain a silicon-carbon composite negative electrode material with a polyimide nanofiber membrane as an outer shell, thereby obtaining a composite material D, wherein the thicknesses of the inner core, the first coating layer and the second coating layer are respectively 9 mu m, 1.8 mu m and 1.8 mu m.
Comparative example
And (3) uniformly mixing 500ml of cyclohexane organic flux with 50g of silicon monoxide, then carrying out spray drying, and then carbonizing at 800 ℃ for 6 hours in a nitrogen atmosphere to obtain the silicon-carbon composite material.
Test example 1
SEM tests were performed on the silicon carbon composite of example 1. The test results are shown in fig. 1. As shown in FIG. 1, the silicon-carbon composite material has a particle size of 5 to 15 μm and a fibrous structure on the surface.
Test example 2
The physicochemical properties (powder conductivity, tap density) of the silicon-carbon composites of examples 1 to 3 and the silicon-carbon composites of the comparative examples were measured according to the method of the national standard GBT-245332009 graphite-based negative electrode material for lithium ion batteries, and the test results are shown in table 1.
As can be seen from table 1, compared with the comparative example, the powder conductivity of the silicon-carbon composite material of the present invention is significantly improved, because the example material is doped with graphene, the electronic conductivity of the material is improved, and meanwhile, the coupling agent can form a composite material with high density, so as to improve the tap density of the material.
Test example 3
The silicon-carbon composite materials of the embodiments 1-3 and the silicon-carbon composite materials in the comparative examples are respectively used as active materials to prepare the pole piece, and the specific preparation method comprises the following steps: adding 9g of active substance, 0.5g of conductive agent SP and 0.5g of binder LA133 into 220mL of deionized water, and uniformly stirring to obtain slurry; and coating the slurry on a copper foil current collector to obtain the pole piece.
The pole piece using the silicon-carbon composite material of example 1 as an active material is labeled a, the pole piece using the silicon-carbon composite material of example 2 as an active material is labeled B, the pole piece using the silicon-carbon composite material of example 3 as an active material is labeled C, and the pole piece using the silicon-carbon composite material of comparative example as an active material is labeled D.
And then, the prepared pole piece is used as a positive electrode, and the pole piece, a lithium piece, electrolyte and a diaphragm are assembled into a button cell in a glove box with the oxygen and water contents lower than 0.1 ppm. Wherein the membrane is celegard 2400; the electrolyte is LiPF6Solution of (2), LiPF6Is 1.2mol/L, and the solvent is a mixed solution of Ethylene Carbonate (EC) and diethyl carbonate (DMC) (weight ratio is 1: 1). The button cells are labeled A-1, B-1, C-1, and D-1, respectively. And then testing the performance of the button cell by adopting a blue light tester under the following test conditions: and (3) carrying out charge and discharge at a multiplying power of 0.1C, wherein the voltage range is 0.05-2V, the cycle is stopped after 3 weeks, and then the full-electricity expansion of the negative pole piece is tested, and the test results are shown in table 2.
As can be seen from table 2, the first efficiency of the silicon carbon composite material of the present invention is significantly improved compared to the comparative example, the surface of the silicon carbon composite material is coated with lanthanum lithium zirconate to reduce the irreversible capacity of the silicon carbon composite material and improve the first efficiency of the silicon carbon composite material, and the polymer material in the outer shell of the silicon carbon composite material in the embodiment constrains the expansion of the material during the charging and discharging processes.
Test example 4
The silicon-carbon composite materials of examples 1 to 3 and the comparative example were doped with 80% artificial graphite as a negative electrode material and a positive electrode ternary material (LiNi)1/3Co1/3Mn1/3O2) The electrolyte and the diaphragm are assembled into the 5Ah soft package battery. Wherein the diaphragm is celegard 2400, and the electrolyte is LiPF6Solution (solvent is mixed solution of EC and DEC with volume ratio of 1:1, LiPF6The concentration of (1.3 mol/L). And marking the prepared soft package batteries as A-2, B-2, C-2 and D-2 respectively.
The following performance tests were performed on the pouch cells:
(1) dissecting and testing the thickness D1 of the negative pole piece of the soft package battery A-2-D-2 with constant volume, then circulating each soft package battery for 100 times (1C/1C @25 +/-3 ℃ @ 2.5-4.2V), fully charging the soft package battery, dissecting again to test the thickness D2 of the negative pole piece after circulation, and then calculating the expansion rate (the expansion rate is equal to the expansion rate of the negative pole piece after circulation)
) The test results are shown in Table 3.
As can be seen from table 3, the expansion rate of the negative electrode plate of the soft-package lithium ion battery using the silicon-carbon composite material of the present invention is significantly lower than that of the comparative example. The reason is that the silicon-carbon composite material has high compactness, and the expansion rate of the material is reduced by the expansion of the polyimide bound silicon-carbon on the outer layer of the silicon-carbon composite material.
(2) And (3) carrying out cycle performance test and rate test on the soft package batteries A-2-D-2 under the following test conditions: the charge-discharge voltage range is 2.5-4.2V, the temperature is 25 +/-3.0 ℃, and the charge-discharge multiplying power is 0.5C/1.0C. And (3) rate testing: the material was tested for constant current ratio at 2C and the results are shown in table 4.
As can be seen from table 4, the cycle performance of the soft-package lithium ion battery prepared by using the silicon-carbon composite material of the present invention is superior to that of the comparative example at each stage of the cycle, because the outer shell of the silicon-carbon composite material of the present invention has a polymer material for reducing the expansion, and improving the cycle performance; meanwhile, the lanthanum lithium zirconate in the middle layer has the characteristic of high lithium ion conductivity, and the quick charging performance of the material is improved.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. The low-expansion silicon-carbon composite negative electrode material is of a core-shell structure, the core of the core-shell structure is silicon monoxide, the shell of the core-shell structure is composed of a first coating layer arranged on the surface of the core and a second coating layer arranged on the surface of the first coating layer, the first coating layer is composed of a conductive agent, a solid electrolyte and a silane coupling agent, and the second coating layer is composed of a flexible conductive polymer composite material.
2. The low-expansion silicon-carbon composite negative electrode material is characterized in that the thickness ratio of the core-shell structure to the core-shell structure is (5-20): (100).
3. The low expansion silicon carbon composite anode material according to claim 1, wherein the solid electrolyte is lanthanum lithium zirconate.
4. The low-expansion silicon-carbon composite anode material as claimed in claim 1, wherein the conductive agent is aminated graphene, aminated carbon nanotube or aminated porous carbon.
5. The low-expansion silicon-carbon composite negative electrode material as claimed in claim 1, wherein the silane coupling agent is one of gamma-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, gamma-diethylenetriaminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldimethoxysilane and gamma-aminopropylmethyldiethoxysilane.
6. The low-expansion silicon-carbon composite anode material as claimed in claim 1, wherein the flexible conductive polymer composite material is a polyimide nanofiber membrane containing a conductive agent.
7. The low expansion silicon carbon composite anode material as claimed in claim 6, wherein the conductive agent is single-walled carbon nanotube, multi-walled carbon nanotube, Ketjen black or vapor grown carbon fiber.
8. The preparation method of the low-expansion silicon-carbon composite negative electrode material is characterized by comprising the following steps of:
(1) preparation of composite material B:
mixing a solid electrolyte, a conductive agent A, a silane coupling agent and an organic solvent to obtain a coating solution A, then adding silicon monoxide into the coating solution A, and preparing a composite material B coated with the solid electrolyte on the surface through hydrothermal reaction, wherein the mass ratio of the components is solid electrolyte, conductive agent A, silane coupling agent, organic solvent and silicon monoxide = (1-5): 100-500): 30-50;
(2) preparation of composite material D:
preparing 0.5-2 wt% of N-methyl pyrrolidone solution of polyamic acid, adding a conductive agent B and the composite material B, preparing the solution, spraying the solution on a light plate through electrostatic spinning, crushing, and heating in a nitrogen atmosphere to convert the polyamic acid into polyimide, thereby obtaining the low-expansion silicon-carbon composite negative electrode material with the polyimide nanofiber membrane as the shell, namely the composite material D, wherein the mass ratio of the components is polyamic acid to the conductive agent B to the composite material B = (10-30): 1-5): 100.
9. The production method according to claim 8, wherein the organic solvent in step (1) is one of N-methylpyrrolidone, carbon tetrachloride, butanediol, and cyclohexane.
10. The method according to claim 8, wherein the heating temperature in the step (2) is 150 to 250 ℃ and the heating time is 1 to 6 hours.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114920242A (en) * | 2022-05-23 | 2022-08-19 | 格龙新材料科技(常州)有限公司 | Preparation method of high-capacity graphite composite material |
| CN115020710A (en) * | 2022-07-11 | 2022-09-06 | 陕西君和聚源科技有限公司 | Low-expansion silicon-based composite negative electrode material, preparation method thereof and lithium ion battery |
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| CN113745489A (en) * | 2021-09-15 | 2021-12-03 | 河北坤天新能源科技有限公司 | Low-expansion silicon-carbon composite negative electrode material and preparation method thereof |
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| CN113745489A (en) * | 2021-09-15 | 2021-12-03 | 河北坤天新能源科技有限公司 | Low-expansion silicon-carbon composite negative electrode material and preparation method thereof |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114920242A (en) * | 2022-05-23 | 2022-08-19 | 格龙新材料科技(常州)有限公司 | Preparation method of high-capacity graphite composite material |
| CN114920242B (en) * | 2022-05-23 | 2023-05-05 | 格龙新材料科技(常州)有限公司 | Preparation method of high-capacity graphite composite material |
| CN115020710A (en) * | 2022-07-11 | 2022-09-06 | 陕西君和聚源科技有限公司 | Low-expansion silicon-based composite negative electrode material, preparation method thereof and lithium ion battery |
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