CN113764195A - Lithium ion capacitor and preparation method thereof - Google Patents

Lithium ion capacitor and preparation method thereof Download PDF

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Publication number
CN113764195A
CN113764195A CN202111048891.4A CN202111048891A CN113764195A CN 113764195 A CN113764195 A CN 113764195A CN 202111048891 A CN202111048891 A CN 202111048891A CN 113764195 A CN113764195 A CN 113764195A
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magnesium oxide
pole piece
lithium ion
prepared
rod
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CN113764195B (en
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胡涵
覃海权
刘昭斌
邢涛
晁会霞
刘海燕
徐倩
韩嘉
李智
张奎同
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China University of Petroleum East China
Shandong Energy Group Co Ltd
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China University of Petroleum East China
Shandong Energy Group Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H01G11/06—Hybrid capacitors with one of the electrodes allowing ions to be reversibly doped thereinto, e.g. lithium ion capacitors [LIC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/50—Electrodes characterised by their material specially adapted for lithium-ion capacitors, e.g. for lithium-doping or for intercalation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • 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
    • Y02E60/13—Energy storage using capacitors

Abstract

The invention provides a lithium ion capacitor and a preparation method thereof, wherein the capacitor comprises a positive pole piece and a negative pole piece; the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material; the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template; the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure. The porous carbon material adopted in the positive and negative pole pieces has excellent lithium storage capacity and higher specific capacity, so that the lithium ion capacitor has higher energy density. Also has higher power density and excellent cycle stability.

Description

Lithium ion capacitor and preparation method thereof
Technical Field
The invention belongs to the technical field of capacitors, and particularly relates to a lithium ion capacitor and a preparation method thereof.
Background
In order to reduce the dependence on non-renewable energy, the development and utilization of new energy has become the direction of energy development in the future, and especially in recent years, people have achieved remarkable results in the development and utilization of wind energy, solar energy, water energy and other fields. However, due to the intermittent and fluctuating characteristics of new energy sources, the new energy sources are difficult to be directly incorporated into a power grid for use, and therefore, high-performance energy storage devices are urgently needed to be developed to store the energy. The lithium ion battery is widely applied to the fields of mobile phones, notebooks, electric automobiles and the like by virtue of the advantage of high energy density, but the development of the lithium ion battery in the field of quick charging is limited by low power density; in contrast, the super capacitor has high power density, but low energy density, and can only be used as an auxiliary device, so that the current market demand cannot be met only by the lithium ion battery and the super capacitor. Lithium ion hybrid capacitors (LICs) combine electrode materials and charge storage mechanisms of super capacitors and lithium ion batteries, are novel energy storage devices with high energy density, high power density and long cycle life, and are widely applied to important places such as energy recovery, aerospace, port equipment and the like at present.
The electrode material is used as a key component of the lithium ion capacitor and plays an important role in the performance of the device. Carbon materials are widely used in a variety of electrode materials by virtue of their advantages of high physicochemical compatibility, easily adjustable porosity, high conductivity, good stability, environmental friendliness, and the like. However, most carbon materials with excellent properties are still in the laboratory research phase at present, on the one hand because the precursors are derived from expensive polymer precursors, which inevitably increases the final cost of the product; in addition, the complicated process route and activation means make industrialization difficult. The petroleum asphalt is used as a low-added-value byproduct in petroleum products, the composition of the petroleum asphalt is mainly polycyclic aromatic hydrocarbon, and the carbon residue value is high, so the petroleum asphalt is used as a carbon material precursor and has great research value. The compounds are considered as basic subunits of graphene and derivatives thereof, and can form functional carbon materials after upgrading treatment, so that the compounds are expected to become the first choice of energy storage electrode active materials.
Among the numerous types of lithium ion capacitors, a dual carbon-based lithium ion capacitor is widely spotlighted by virtue of excellent electrochemical properties. Even if the positive electrode and the negative electrode are made of the same type of carbon material, the electrodes are required to be elaborately constructed due to different energy storage mechanisms. For the preparation of the negative electrode material, the electrode material with excellent electrochemical performance, such as two-dimensional carbon nanosheets, carbon nanofibers, carbon nanospheres, porous graphene and the like, needs to be obtained through structure regulation; for the preparation of the cathode active material, the cathode active material is usually subjected to further chemical activation to increase the specific surface area thereof on the basis of the preparation of the anode material, so that more reactive active sites can be provided to meet the requirements of the cathode material on high specific surface area and pore structure. However, the methods have limited adjustment degree on the pore structure, and in addition, the chemical activation method can etch most carbon materials to obviously reduce the carbon yield, so that some suitable methods need to be found for preparing the positive and negative carbon materials meeting the performance requirements.
In a dual carbon-based lithium ion capacitor, an additional prelithiation process is required to replenish lithium ions due to the lack of a lithium source in both the positive and negative electrode materials. By carrying out pre-lithiation treatment on the electrode, lithium consumption of the cathode in the first charging and discharging process can be compensated, and the cycle stability of the device is improved; meanwhile, the voltage operation window can be widened, and the energy density of the device can be improved. The currently mainstream prelithiation techniques mainly include: electrochemical pre-intercalation, external short-circuit pre-intercalation, internal short-circuit pre-intercalation, etc. The electrochemical pre-lithium intercalation is only suitable for laboratory research, and the external and internal pre-lithium intercalation has the problems of non-uniform lithium intercalation, strict requirements on lithium intercalation environment and the like, so that the industrial popularization and application cannot be carried out at present. Therefore, the development of a simpler, safer and more effective lithium pre-intercalation method for realizing the pre-intercalation of the electrode material is urgently needed.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a lithium ion capacitor having a higher energy density and a method for manufacturing the same.
The invention provides a lithium ion capacitor, which comprises a positive pole piece and a negative pole piece;
the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material;
the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template;
the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure.
Preferably, the magnesium oxide template with the hierarchical porous structure in the positive active material is mainly mesoporous; the particle size distribution of the mesopores is 2-24 nm, and the pore diameter is mainly concentrated at 3 nm.
Preferably, the petroleum asphalt-based rod-shaped porous carbon material prepared by the rod-shaped magnesium oxide template is prepared by the following method:
mixing a rod-shaped magnesium oxide template and petroleum asphalt in a mass ratio of 2: 0.95-1.05, and uniformly mixing to obtain a mixture;
and calcining the mixture at 700-900 ℃ for 110-130 min under the nitrogen atmosphere, and pickling, washing and drying a calcined product to obtain the rod-like porous carbon material.
Preferably, the rod-shaped magnesium oxide template is prepared according to the following method:
mixing Na2CO3The solution was slowly added to MgCl2And (3) uniformly stirring in the solution, standing, filtering, washing with water, drying and calcining to obtain the rod-shaped magnesium oxide template.
Preferably, the petroleum asphalt-based graded porous carbon material prepared by the graded porous structure magnesium oxide template is prepared by the following method:
ultrasonically dispersing petroleum asphalt in n-heptane, and filtering with a microporous filter membrane to obtain filtrate;
mixing the filtrate with a graded porous magnesium oxide template according to a mass ratio of 2: 0.95-1.05, heating and stirring at 90 ℃ until n-heptane is evaporated to dryness, then calcining for 110-130 min at 700-900 ℃ in a nitrogen atmosphere, and acid-washing, washing and drying a calcined product to obtain the petroleum asphalt-based hierarchical porous carbon material.
Preferably, the magnesium oxide template with the hierarchical porous structure is prepared according to the following method:
dissolving the rod-shaped magnesium oxide, standing, filtering, drying, and calcining in the air to obtain the magnesium oxide template with the hierarchical porous structure.
The invention provides a preparation method of the lithium ion capacitor in the technical scheme, which comprises the following steps:
mixing a negative active material, conductive carbon black and polyvinylidene fluoride, adding N-methyl pyrrolidone to adjust viscosity, and coating the mixture on a copper foil current collector to obtain a negative pole piece; pre-lithiating the negative pole piece in an aromatic lithium compound to obtain a pre-lithiated negative pole piece;
mixing the positive active material, conductive carbon black and sodium alginate, adding water to adjust viscosity, and coating the mixture on an aluminum foil current collector to obtain a positive pole piece;
and assembling the pre-lithiated negative pole piece and the positive pole piece to obtain the lithium ion capacitor.
Preferably, the electrolyte adopted by the assembly is LiPF6The concentration of the electrolyte is 1mol/L, and the solvent in the electrolyte is EC and DMC in a volume ratio of 1: 1; the additive in the electrolyte is FEC, and the mass fraction of the additive is 2%; assembled batteryThe separator had a pore size of 0.064 μm and a thickness of 25 μm.
The invention provides a lithium ion capacitor, which comprises a positive pole piece and a negative pole piece; the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material; the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template; the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure. The porous carbon material adopted in the positive and negative pole pieces has excellent lithium storage capacity and higher specific capacity, so that the lithium ion capacitor has higher energy density. Also has higher power density and excellent cycle stability.
Drawings
FIG. 1 is SEM images of templates prepared in preparative example 1 and preparative example 2;
FIG. 2 is an SEM image of a rod-like porous carbon material prepared in example 1 of the present invention;
FIG. 3 is an SEM photograph of a commercial magnesium oxide template in comparative example 1;
fig. 4 is an SEM image of the porous carbon prepared in comparative example 1 of the present invention;
FIG. 5 is an SEM photograph of a rod-like porous carbon material prepared in example 4 of the present invention;
fig. 6 is an SEM image of the porous carbon prepared in comparative example 3 of the present invention;
FIG. 7 shows the preparation process of naphthalene lithium reagent and the prelithiation of the electrode plate.
Detailed Description
The invention provides a lithium ion capacitor, which comprises a positive pole piece and a negative pole piece;
the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material;
the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template;
the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure.
The lithium ion capacitor provided by the invention comprises a positive pole piece, wherein the positive pole piece comprises a positive active material, and the positive active material is a petroleum asphalt-based hierarchical porous carbon material prepared by a magnesium oxide template with a hierarchical porous structure.
The magnesium oxide template with the hierarchical porous structure in the positive active material is mainly mesoporous; the particle size distribution of the mesopores is 2-24 nm, and the pore diameter is mainly concentrated at 3 nm.
In the invention, the petroleum asphalt-based graded porous carbon material prepared by the graded porous structure magnesium oxide template is prepared by the following method:
ultrasonically dispersing petroleum asphalt in n-heptane, and filtering with a microporous filter membrane to obtain filtrate;
mixing the filtrate with a graded porous magnesium oxide template according to a mass ratio of 2: 0.95-1.05, heating and stirring at 90 ℃ until n-heptane is evaporated to dryness, then calcining for 110-130 min at 700-900 ℃ in a nitrogen atmosphere, and acid-washing, washing and drying a calcined product to obtain the petroleum asphalt-based hierarchical porous carbon material.
The invention ultrasonically disperses the petroleum asphalt in n-heptane, and the filtrate is obtained by filtering with a microporous filter membrane. In the invention, the filtration membrane adopted by the microporous filtration is an organic filtration membrane, the manufacturer is a new inferior purification device manufacturer in Shanghai, and the aperture is 0.22 μm. The adopted n-heptane is analytically pure, the power of the ultrasonic wave is 400W, and the frequency of the ultrasonic wave is 40 KHz.
After the filtrate is obtained, the filtrate and the graded porous magnesium oxide template are preferably mixed according to the mass ratio of 2:1, and heating and stirring at 90 ℃ until n-heptane is evaporated to dryness to obtain the porous carbon precursor. And calcining for 120min at 700-900 ℃ under the nitrogen atmosphere, and pickling, washing and drying a calcined product to obtain the petroleum asphalt-based hierarchical porous carbon material. The pickling temperature is 60 ℃, and the pickling time is 5 hours; the drying temperature is 60 ℃ and the drying time is 12 h.
In the invention, the graded porous magnesium oxide template is prepared according to the following method:
dissolving the rod-shaped magnesium oxide, standing, filtering, drying, and calcining in the air to obtain the magnesium oxide template with the hierarchical porous structure.
In the invention, the hierarchical porous magnesium oxide template is mainly of a mesoporous leading structure, the pore size range is 2-24 nm, and the pore size is mainly concentrated at 3 nm.
In the specific embodiment, rod-shaped magnesium oxide is dissolved in water, and the mass ratio of the rod-shaped magnesium oxide to the water is 1g:200 mL; the dissolution was carried out under stirring at a rate of 100rpm for a period of 30 min. The drying temperature is 100 ℃, and the drying time is 12 h. The calcining temperature is 550 ℃, the heating rate is 5 ℃/min, and the calcining time is 3 h.
In the present invention, the rod-shaped magnesium oxide is preferably prepared by the following method:
mixing Na2CO3The solution was slowly added to MgCl2And (3) uniformly stirring in the solution, standing, filtering, washing with water, drying and calcining to obtain the rod-shaped magnesium oxide.
In a specific embodiment, the preparation steps of the rod-shaped magnesium oxide are as follows:
mixing Na2CO3And MgCl2·6H2Preparing O into a solution with the concentration of 1 mol/L; 100ml of Na are respectively taken2CO3Solution and MgCl2Solution of Na2CO3The solution was slowly added to MgCl2And (3) uniformly stirring the mixture in the solution, standing the mixture for 6 hours until the reaction is finished, filtering the mixture to collect a filter cake, washing the filter cake for 3 to 5 times by using deionized water, drying the filter cake in a forced air drying oven, and calcining the filter cake in the air to obtain the rod-shaped magnesium oxide.
The lithium ion capacitor provided by the invention comprises a negative pole piece; the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template;
in the invention, the petroleum asphalt-based rod-shaped porous carbon material prepared by the rod-shaped magnesium oxide template is prepared by the following method:
mixing a rod-shaped magnesium oxide template and petroleum asphalt in a mass ratio of 2: 0.95-1.05, and uniformly mixing to obtain a mixture;
and calcining the mixture at 700-900 ℃ for 110-130 min under the nitrogen atmosphere, and pickling, washing and drying a calcined product to obtain the rod-like porous carbon material.
In the present invention, the rod-shaped magnesium oxide template and the petroleum asphalt are preferably in a mass ratio of 2: 1. The calcination product acid washing is preferably performed with 1mol/L hydrochloric acid.
In the invention, the rod-shaped magnesium oxide template is prepared according to the following method:
mixing Na2CO3The solution was slowly added to MgCl2And (3) uniformly stirring in the solution, standing, filtering, washing with water, drying and calcining to obtain the rod-shaped magnesium oxide template.
The invention provides a preparation method of the lithium ion capacitor in the technical scheme, which comprises the following steps:
mixing a negative active material, conductive carbon black and polyvinylidene fluoride, adding N-methyl pyrrolidone to adjust viscosity, and coating the mixture on a copper foil current collector to obtain a negative pole piece; pre-lithiating the negative pole piece in an aromatic lithium compound to obtain a pre-lithiated negative pole piece;
mixing the positive active material, conductive carbon black and sodium alginate, adding water to adjust viscosity, and coating the mixture on an aluminum foil current collector to obtain a positive pole piece;
and assembling the pre-lithiated negative pole piece and the positive pole piece to obtain the lithium ion capacitor.
In the present invention, the aromatic lithium compound is preferably prepared according to the following method:
in a glove box filled with inert atmosphere, naphthalene is dissolved in ethylene glycol dimethyl ether, and metal lithium sheets are added and completely dissolved to obtain the aromatic lithium compound. In the present invention, the molar ratio of naphthalene to lithium flakes is preferably 1: 1. Theoretically 1 mole of lithium reacts with 1 mole of naphthalene to produce 1 mole of lithium naphthalene.
The method comprises the steps of preferably soaking a negative pole piece in an aromatic lithium compound under an inert atmosphere, taking out the negative pole piece after reacting for a period of time, then cleaning the negative pole piece in an ethylene glycol dimethyl ether solution, and drying in vacuum to obtain the pre-lithiated negative pole piece.
In a specific embodiment of the present invention, the concentration of lithium naphthalene in the prelithiation reagent is 0.5 mol/L. The volume of the reagent taken each time during pre-lithiation is 4mL, the mass of the negative pole piece is 0.8-1 mg, the diameter of the pole piece is 12mm, the thickness of the pole piece is 12 micrometers, and the soaking time is 1-20 min; the temperature for drying the pole piece was 40 ℃.
In the invention, the electrolyte adopted by assembling the pre-lithiated negative pole piece and the positive pole piece is LiPF6The concentration of the electrolyte is 1mol/L, and the solvent in the electrolyte is EC and DMC in a volume ratio of 1: 1; the additive in the electrolyte is FEC, and the mass fraction of the additive is 2%; the aperture of the battery separator used for assembly was 0.064 μm, and the thickness was 25 μm.
Compared with the prior art, the lithium ion capacitor provided by the invention has the following advantages:
1. the raw material used in the invention is the hard petroleum asphalt which is a byproduct in the petroleum refining process, compared with the raw materials of the active carbon and the graphite which are industrially prepared, the price is low, the source is wide, the yield is high, the high carbon content enables the yield of the prepared porous carbon product to be high, and the carbon precursor is a carbon precursor with high added value;
2. the preparation method of the material used in the invention is simple to operate, the used chemical reagent is low in price, and the prepared template material can be recycled, so that the production cost is greatly reduced, and the method has an objective large-scale application prospect.
3. Compared with graphite of a negative electrode of a commercial lithium ion battery/capacitor and activated carbon of a positive electrode of a commercial super capacitor/lithium ion capacitor, the porous carbon material prepared by the method has more excellent lithium storage capacity and higher specific capacity, and can greatly improve the energy density, power density and cycle stability of the commercial lithium ion battery and the super capacitor.
4. The cathode obtained by chemical pre-lithiation has excellent electrochemical performance, has higher efficiency and simpler method compared with the conventional electrochemical pre-lithiation method, and has more uniform lithium intercalation and safer process compared with the metallic lithium powder pre-lithiation method.
5. The one-dimensional porous carbon micron rod and the three-dimensional hierarchical porous carbon prepared by the invention can be respectively used as active materials of a cathode and an anode of a lithium ion capacitor, and show ultrahigh specific capacity and excellent cycling stability; the lithium ion capacitor assembled by the two materials has higher energy density and power density than a commercial lithium ion capacitor, and has good long-cycle stability; the anode and cathode prepared by the method have simple processes, save the activation process compared with the conventional preparation method, greatly reduce the production cost and have great popularization and application values.
In order to further illustrate the present invention, the following will describe a lithium ion capacitor and a method for manufacturing the same in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention.
Preparatory example 1
The preparation steps of the rod-shaped magnesium oxide template are as follows:
step (1) adding Na2CO3And MgCl2·6H2Preparing O into a solution with the concentration of 1 mol/L;
step (2) taking 100ml of Na respectively2CO3Solution and MgCl2Solution of Na2CO3The solution was slowly added to MgCl2Stirring the solution uniformly, standing the solution for 6 hours, filtering the solution after the reaction is finished, collecting a filter cake, washing the filter cake for 3 to 5 times by using deionized water, and drying the filter cake in a forced air drying oven;
and (3) heating the collected product to 550 ℃ at the speed of 5 ℃/min in the air, and calcining for 2h to obtain the rod-shaped magnesium oxide template.
Preparatory example 2
The preparation steps of the hierarchical porous structure magnesium oxide template are as follows:
taking 2g of the rod-shaped magnesium oxide template prepared in the preparation example 1, adding the rod-shaped magnesium oxide template into 400ml of deionized water, uniformly stirring, standing at room temperature for reaction for a period of time, then filtering, and drying a filter cake in a forced air drying oven;
and (3) heating the collected product to 550 ℃ at the speed of 5 ℃/min in the air, and calcining for 2h to obtain the magnesium oxide template with the hierarchical porous structure.
Fig. 1 is SEM images of templates prepared in preparative example 1 and preparative example 2, in which a is an SEM image of a rod-shaped porous magnesium oxide template prepared in preparative example 1; b is an SEM image of the graded porous magnesium oxide prepared in preparative example 2; as seen in fig. 1: the magnesium oxide after reaction in water exhibits a hierarchical structure of rod and sheet combinations.
Example 1
2g of hard asphalt and 4g of a rod-shaped magnesium oxide template were thoroughly mixed in a 250mL agate mill and then transferred to a nitrogen-filled tube furnace to be calcined at a high temperature of 800 ℃ for 2 hours, with the temperature rise rate set at 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1 mol/hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. And after the acid washing is finished, washing and filtering the sample until the pH value of the washing filtrate is 7, then transferring the sample into a vacuum oven, and drying at the temperature of 60 ℃ for 12 hours to obtain a final product which is named as PCMs-A-800.
FIG. 2 is an SEM image of a rod-like porous carbon material prepared in example 1 of the present invention; as can be seen from fig. 2: the carbon material can still well maintain the shape of the rodlike magnesium oxide template after the template is removed, which shows that the material has excellent structural stability.
Example 2
2g of hard pitch and 4g of a rod-shaped magnesium oxide template were thoroughly mixed in a 250mL agate mill and then transferred to a nitrogen-filled tube furnace to be calcined at a high temperature of 700 ℃ for 2h, with the temperature rise rate set at 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1 mol/hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. After the acid washing is finished, washing and filtering the sample until the pH value of the washing filtrate is 7, then transferring the sample into a vacuum oven, and drying at the temperature of 60 ℃ for 12h to obtain a final product which is named as PCMs-A-700.
Example 3
2g of hard asphalt and 4g of a rod-shaped magnesium oxide template were thoroughly and uniformly mixed in a 250mL agate mortar, and then transferred to a nitrogen-filled tube furnace to be calcined at a high temperature of 900 ℃ for 2 hours, with the temperature rise rate set at 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1 mol/hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. After the acid washing is finished, washing and filtering the sample until the pH value of the washing filtrate is 7, then transferring the sample into a vacuum oven, and drying at the temperature of 60 ℃ for 12h to obtain a final product which is named as PCMs-A-900.
Comparative example 1
2g of hard pitch and 4g of a commercial magnesium oxide template (see the structure shown in FIG. 3) were thoroughly mixed in a 250mL agate mortar and then transferred to a nitrogen-filled tube furnace to be calcined at a high temperature of 800 ℃ for 2 hours with the temperature rise rate set at 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1mol/L hydrochloric acid solution for 5 hours at the pickling temperature of 50 ℃. And after the acid washing is finished, washing and filtering the sample until the pH value of the washing filtrate is 7, then transferring the sample into a vacuum oven, and drying at the temperature of 60 ℃ for 12 hours to obtain a final product which is named as PCNs-A-2.
Fig. 4 is an SEM image of the porous carbon material prepared in comparative example 1 of the present invention, and it can be seen that the material has a bulk structure as a whole and is stacked relatively closely.
Comparative example 2
Carrying out hydrothermal treatment on commercial magnesium oxide powder at 100 ℃ for 12h, calcining the commercial magnesium oxide powder in air at 550 ℃ for 180min to obtain a hexagonal porous magnesium oxide template, fully and uniformly mixing 2g of hard asphalt and 4g of flaky magnesium oxide template in an agate mortar, and then transferring the mixture to a nitrogen-filled tubular furnace to calcine the mixture for 2h at 800 ℃, wherein the temperature rise speed is set to be 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1mol/L hydrochloric acid solution for 5 hours at the pickling temperature of 50 ℃. After the acid washing is finished, the sample is washed and filtered until the pH value of the washing filtrate is 7, and then the sample is transferred to a vacuum oven and dried for 12 hours at the temperature of 60 ℃ to obtain the final product which is named as HCMs-A-2.
Lithium storage performance of the porous carbons prepared in examples 1 to 3 and comparative examples 1 to 2 as a negative electrode, the results are shown in table 1:
TABLE 1 lithium storage Performance test results for porous carbons prepared in examples 1-3 and comparative examples 1-2
Figure BDA0003252102800000101
As can be seen from table 1: the HCMs-800 prepared in example 1 have better electrochemical properties and more excellent electrochemical properties than the porous carbon prepared from commercial graphite and some other ways.
Example 4
Dissolving 2g of hard asphalt in 50mL of n-heptane solution for ultrasonic dispersion, filtering by a microporous membrane, collecting filtrate and 4g of magnesium oxide template with a hierarchical porous structure, fully and uniformly mixing, heating, stirring and evaporating a sample in an oil bath kettle at 90 ℃, and then transferring the sample to a nitrogen-filled tube furnace for calcination at the high temperature of 800 ℃ for 2 hours, wherein the temperature rise speed is set to be 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1mol/L hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. After the acid washing is finished, the sample is washed and filtered until the pH value of the washing filtrate is 7, and then the sample is transferred to a vacuum oven and dried for 12 hours at the temperature of 60 ℃ to obtain a final product which is named as HPCs-C-800.
Fig. 5 is a morphology view of the graded porous carbon material prepared in example 4 of the present invention, in which a and b are SEM images of the graded porous carbon material, and c and d are HRTEM images of the graded porous carbon material. As seen from a and b in fig. 5: the carbon material can still well maintain the shape of the magnesium oxide template after the template is removed, which shows that the material has excellent structural stability, the material has a hierarchical porous structure, and the hierarchical structure can provide more charge storage sites. To investigate the structure of the porous carbon in detail, we used a high-power transmission electron microscope (HRTEM) to explore its interior, as shown in fig. 5 c, from which we can see a number of macroporous networks composed of curved ultrathin carbon nanosheets, roughly estimated at about tens of nanometers in thickness, and from fig. 5 d it can be seen that the porous laminar carbon layer is composed of highly disordered nanocrystals, and these lattice layer spacings are roughly around 0.407 nm.
Example 5
Dissolving 2g of hard asphalt in 50mL of n-heptane solution for ultrasonic dispersion, filtering by a microporous membrane, collecting filtrate and 4g of magnesium oxide template with a hierarchical porous structure, fully and uniformly mixing, heating, stirring and evaporating a sample in an oil bath kettle at 90 ℃, and then transferring the sample to a nitrogen-filled tube furnace for calcination at high temperature of 700 ℃ for 2h, wherein the temperature rise speed is set to be 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1mol/L hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. After the acid washing is finished, the sample is washed and filtered until the pH value of the washing filtrate is 7, and then the sample is transferred to a vacuum oven and dried for 12 hours at the temperature of 60 ℃ to obtain a final product which is named as HPCs-C-700.
Example 6
Dissolving 2g of hard asphalt in 50mL of n-heptane solution for ultrasonic dispersion, filtering by a microporous membrane, collecting filtrate and 4g of magnesium oxide template with a hierarchical porous structure, fully and uniformly mixing, heating, stirring and evaporating a sample in an oil bath kettle at 90 ℃, and then transferring the sample to a nitrogen-filled tube furnace for calcining for 2 hours at high temperature of 900 ℃, wherein the temperature rise speed is set to be 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, and pickling the sample in 1mol/L hydrochloric acid solution for 5 hours at the pickling temperature of 60 ℃. And after the acid washing is finished, washing and filtering the sample until the pH value of the washing filtrate is 7, then transferring the sample into a vacuum oven, and drying at the temperature of 60 ℃ for 12 hours to obtain a final product which is named as HPCs-C-900.
Comparative example 3
1g of the porous carbon nanomaterial prepared in [ comparative example 1 ] and 3g of KOH were weighed, mixed uniformly in a 250mL agate mortar, and then transferred to a nitrogen-filled tube furnace to be calcined at a high temperature of 800 ℃ for 2 hours, with the temperature rise rate set at 5 ℃/min. And (3) taking out the sample after the furnace body is cooled to room temperature, washing and filtering the sample in deionized water until the pH value of the washing filtrate reaches 7, transferring the sample into a vacuum oven, and drying the sample at the temperature of 60 ℃ for 12 hours to obtain a final product named as PCNs-C-3.
Fig. 6 is an SEM image of the porous carbon prepared in comparative example 3; it can be seen that many pore structures are generated on the surface of the porous carbon material prepared by KOH activation, and the pore structures are beneficial to the transmission of electrolyte, so that the charge storage performance is enhanced.
The results of the capacitive performance test of the graded porous carbon prepared in examples 4 to 6 and comparative example 3 as a positive electrode are shown in table 2:
table 2 results of performance test of the hierarchical porous carbons prepared in examples 4 to 6 and comparative example 3
Figure BDA0003252102800000121
As seen from table 2: the HPCs-C-800 prepared in example 4 has the best electrochemical performance, and has more excellent electrochemical performance compared with the electrochemical performance of the commercial activated carbon positive electrode and porous carbon prepared in other ways.
Example 7
The negative electrode piece prepared in example 1 was directly immersed in 4mL of naphthalene lithium reagent and kept for 10 min. Taking out the electrode slice, cleaning the surface of the electrode slice in glycol dimethyl ether solution, drying the residual liquid on the surface in inert gas and naming the residual liquid as PCMs-N10-800.
FIG. 7 is a process flow for preparing naphthalene lithium reagent and prelithiation of the pole pieces; naphthalene and lithium are dissolved in glycol dimethyl ether solution to prepare an organic naphthalene lithium reagent and serve as a prelithiation reagent, and obvious change on the surface of a pole piece can be found after the pole piece is subjected to prelithiation treatment.
Example 8
The negative electrode piece prepared in example 2 was directly immersed in 4mL of naphthalene lithium reagent and kept for 10 min. Taking out the electrode slice, cleaning the surface of the electrode slice in glycol dimethyl ether solution, drying the residual liquid on the surface in inert gas and naming the residual liquid as PCMs-N10-700.
Example 9
The negative electrode piece prepared in example 3 was directly immersed in 4mL of naphthalene lithium reagent and kept for 10 min. Taking out the electrode slice, cleaning the surface of the electrode slice in glycol dimethyl ether solution, drying the residual liquid on the surface in inert gas and naming the residual liquid as PCMs-N10-900.
Comparative example 4
And assembling the prepared cathode electrode plate into a 2032R-type button cell, taking a lithium plate as a counter electrode, performing pre-lithiation treatment on a Xinwei electrochemical test system, and circulating for about 10 circles under the voltage interval of 0.01-3V and the current density of 0.1Ag < -1 >, thereby completing the pre-lithium intercalation process and recording as PCMs-L-800.
Comparative example 5
The negative electrode sheet prepared in example 1 was directly immersed in a biphenyl prelithiation reagent of 4mL and 0.5mol/L for 10min, respectively. Taking out the electrode slice, cleaning the surface of the electrode slice in glycol dimethyl ether solution, and drying the residual liquid on the surface in inert gas and marking as PCMs-B10-800.
Comparative example 6
4mL of 0.5mol/L p-methylbiphenyl prelithiation reagent was taken, and the negative electrode sheet prepared in example 1 was directly immersed in the solution for 10min each. Taking out the electrode slice, cleaning the surface of the electrode slice in glycol dimethyl ether solution, and drying the residual liquid on the surface in inert gas and marking as PCMs-P10-800.
The results of the chemical prelithiation test of the rod-like porous carbon anodes prepared in examples 7 to 9 and comparative examples 4 to 6 are shown in table 3:
table 3 test results for negative electrode prelithiation
Figure BDA0003252102800000131
Figure BDA0003252102800000141
It can be seen from table 3 that the initial coulombic efficiency of the negative electrode can be greatly improved by pre-lithiating the negative electrode by the chemical pre-lithiation method, time is greatly saved, the pre-lithiation process is simplified, and the pre-lithiated PCMs-N10-800 in the comprehensive comparative example 7 have the best performance.
By analyzing the electrochemical properties of the above various positive and negative electrodes, a lithium ion capacitor was finally assembled by selecting the most functional HCMs-C-800 of example 4 as the positive electrode and the prelithiated PCMs-N10-800 of example 7 as the negative electrode.
Example 10
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 7 and the positive electrode tab was the tab prepared in example 4. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 11
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 7 and the positive electrode tab was the tab prepared in example 4. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:1, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 12
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 7 and the positive electrode tab was the tab prepared in example 4. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:3, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
TABLE 4 electrochemical Performance test results for lithium ion capacitors prepared in examples 10-12
Figure BDA0003252102800000151
Optimizing the electrochemical performance of the device by adjusting the mass ratio of the anode to the cathode, and finding that when the mass ratio of the anode to the cathode is 2: the lithium ion capacitor constructed at 1 had the best electrochemical performance, and the results are shown in example 10.
Example 13
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 8, and the positive electrode tab was the tab prepared in example 4. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 14
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 9, and the positive electrode tab was the tab prepared in example 4. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 15
This example provides a lithium ion capacitor, the negative electrode tab was the tab prepared in example 7, and the positive electrode tab was the tab prepared in example 5. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 16
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 8, and the positive electrode tab was the tab prepared in example 5. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 17
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 9, and the positive electrode tab was the tab prepared in example 5. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 18
This example provides a lithium ion capacitor, the negative electrode tab was the tab prepared in example 7, and the positive electrode tab was the tab prepared in example 6. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 19
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 8, and the positive electrode tab was the tab prepared in example 6. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
Example 20
This example provides a lithium ion capacitor, where the negative electrode tab was the tab prepared in example 9, and the positive electrode tab was the tab prepared in example 6. And the mass ratio of the negative electrode plate to the positive electrode plate is 1:2, and the positive electrode plate and the negative electrode plate are assembled into a complete lithium ion capacitor.
From the above embodiments, the invention provides a lithium ion capacitor, which includes a positive electrode plate and a negative electrode plate; the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material; the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template; the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure. The porous carbon material adopted in the positive and negative pole pieces has excellent lithium storage capacity and higher specific capacity, so that the lithium ion capacitor has higher energy density. Also has higher power density and excellent cycle stability.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A lithium ion capacitor comprises a positive pole piece and a negative pole piece;
the negative pole piece comprises a negative active material; the positive pole piece comprises a positive active material;
the negative active material is a petroleum asphalt-based rod-shaped porous carbon material prepared by a rod-shaped magnesium oxide template;
the positive active material is a petroleum asphalt-based graded porous carbon material prepared from a magnesium oxide template with a graded porous structure.
2. The lithium ion capacitor according to claim 1, wherein the magnesium oxide template having a hierarchical porous structure in the positive electrode active material is mainly mesoporous; the particle size distribution of the mesopores is 2-24 nm, and the pore diameter is mainly concentrated at 3 nm.
3. The lithium ion capacitor according to claim 1, wherein the petroleum asphalt-based rod-shaped porous carbon material prepared from the rod-shaped magnesium oxide template is prepared by the following method:
mixing a rod-shaped magnesium oxide template and petroleum asphalt in a mass ratio of 2: 0.95-1.05, and uniformly mixing to obtain a mixture;
and calcining the mixture at 700-900 ℃ for 110-130 min under the nitrogen atmosphere, and pickling, washing and drying a calcined product to obtain the rod-like porous carbon material.
4. The lithium ion capacitor of claim 3, wherein the rod-shaped magnesium oxide template is prepared by the following method:
mixing Na2CO3The solution was slowly added to MgCl2And (3) uniformly stirring in the solution, standing, filtering, washing with water, drying and calcining to obtain the rod-shaped magnesium oxide template.
5. The lithium ion capacitor according to claim 1, wherein the petroleum asphalt-based hierarchical porous carbon material prepared from the hierarchical porous structure magnesium oxide template is prepared according to the following method:
ultrasonically dispersing petroleum asphalt in n-heptane, and filtering with a microporous filter membrane to obtain filtrate;
mixing the filtrate with a graded porous magnesium oxide template according to a mass ratio of 2: 0.95-1.05, heating and stirring at 90 ℃ until n-heptane is evaporated to dryness, then calcining for 110-130 min at 700-900 ℃ in a nitrogen atmosphere, and acid-washing, washing and drying a calcined product to obtain the petroleum asphalt-based hierarchical porous carbon material.
6. The lithium ion capacitor according to claim 5, wherein the hierarchical porous structure magnesium oxide template is prepared by the following method:
dissolving the rod-shaped magnesium oxide, standing, filtering, drying, and calcining in the air to obtain the magnesium oxide template with the hierarchical porous structure.
7. A preparation method of the lithium ion capacitor of any one of claims 1 to 6, comprising the following steps:
mixing a negative active material, conductive carbon black and polyvinylidene fluoride, adding N-methyl pyrrolidone to adjust viscosity, and coating the mixture on a copper foil current collector to obtain a negative pole piece; pre-lithiating the negative pole piece in an aromatic lithium compound to obtain a pre-lithiated negative pole piece;
mixing the positive active material, conductive carbon black and sodium alginate, adding water to adjust viscosity, and coating the mixture on an aluminum foil current collector to obtain a positive pole piece;
and assembling the pre-lithiated negative pole piece and the positive pole piece to obtain the lithium ion capacitor.
8. The method according to claim 7, wherein the electrolyte used for the assembly is LiPF6The concentration of the electrolyte is 1mol/L, and the solvent in the electrolyte is EC and DMC in a volume ratio of 1: 1; the additive in the electrolyte is FEC, and the mass fraction of the additive is 2%; the aperture of the battery separator used for assembly was 0.064 μm, and the thickness was 25 μm.
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