Porous carbon material and preparation method thereof, lithium ion capacitor positive electrode and lithium ion capacitor

Abstract

The invention relates to the field of capacitor electrode materials, and discloses a porous carbon material and a preparation method thereof, a lithium ion capacitor positive electrode and a lithium ion capacitor, the specific surface area of the porous carbon material is 1500-3500m < 2 > / g, and the powder conductivity is not less than 50S / m; in an X-ray diffraction pattern of the porous carbon material, a characteristic peak of a (002) crystal face exists at 26 + / -0.5 degrees, and the half-peak width of the characteristic peak of the (002) crystal face is 0.4-1 degree. The porous carbon material is used as a positive electrode of a lithium ion capacitor, and has the characteristics of high specific capacity and good rate capability.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor electrode materials, and in particular to a porous carbon material and a preparation method thereof, a lithium ion capacitor positive electrode and a lithium ion capacitor. Background Art

[0002] As an important energy storage device, lithium-ion capacitors combine the advantages of lithium-ion batteries and double-layer supercapacitors, and can achieve high power density and high energy density at the same time. However, the matching problems between the positive and negative electrodes in terms of kinetics and specific capacity limit the further improvement of the performance of lithium-ion capacitors. The positive electrode material mainly stores energy by physical adsorption, and its specific capacity is much lower than that of the negative electrode material. In order to obtain a higher specific capacity, the positive electrode material of lithium-ion capacitors should have a developed pore structure and a high specific surface area. At present, in order to achieve an ideal specific surface area and pore structure, the preparation of materials mainly adopts two methods: (1) After the precursor is carbonized, it is further etched with potassium hydroxide, potassium bicarbonate, zinc chloride, etc. to form pores. This process has strong corrosiveness; (2) One-step pyrolysis of precursors containing alkali metals such as potassium and sodium. This process can achieve the preparation of high specific surface carbon materials without subsequent activation. For example, CN110182800A directly pyrolyzes and carbonizes ethylenediaminetetraacetic acid potassium salt at high temperature to prepare a carbon material with a specific surface area of ​​2702m 2 / g of activated carbon material. Although the carbon material prepared by the one-step pyrolysis process has a high specific surface area, the strong etching effect of alkali metals leads to a low degree of graphitization and poor conductivity of the material, which has a great impact on the rate performance of the material. In the reported results (Journal of Energy Chemistry 60(2021)209-221), when ethylenediaminetetraacetic acid potassium salt pyrolysis carbon is used as a lithium ion positive electrode, the specific capacity at high current density is low, and the rate performance needs to be further improved. Therefore, it is of great significance to effectively regulate the degree of graphitization and conductivity of high specific surface carbon materials, give play to the synergistic effect of the porous structure and graphitized structure in the material, and thus improve the specific capacity of the material at high current density for lithium ion capacitors to achieve high energy density and power density. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems of low specific capacity and poor rate performance of carbon positive electrode active materials of lithium ion capacitors in the prior art, and to provide a porous carbon material and a preparation method thereof, a lithium ion capacitor positive electrode and a lithium ion capacitor. The porous carbon material has the characteristics of good conductivity, high specific capacity and good rate performance.

[0004] In order to achieve the above object, the present invention provides a porous carbon material, wherein the specific surface area of ​​the porous carbon material is 1500-3500m 2 / g, the powder conductivity is not less than 50S / m; in the X-ray diffraction pattern of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26±0.5° and the half-peak width of the characteristic peak of the (002) crystal plane is 0.4-1°.

[0005] The second aspect of the present invention provides a method for preparing the porous carbon material, the method comprising:

[0006] (1) mixing an organic acid potassium salt, a transition metal salt and a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution to obtain a precursor material;

[0007] Wherein, the molar ratio of the organic acid potassium salt to the transition metal salt calculated as the metal element is 1:(0.1-0.5);

[0008] (2) calcining the precursor material under an inert atmosphere to obtain an intermediate product;

[0009] (3) The intermediate product is subjected to pickling treatment with an acid, followed by solid-liquid separation, washing and drying.

[0010] A third aspect of the present invention provides a positive electrode for a lithium ion capacitor, comprising a current collector and a positive electrode material composited on the current collector, wherein the positive electrode material comprises the above-mentioned porous carbon material.

[0011] A fourth aspect of the present invention provides a lithium ion capacitor, comprising the above-mentioned lithium ion capacitor positive electrode.

[0012] In order to obtain a higher specific capacity, the positive electrode material of a lithium ion capacitor should have a developed pore structure and a higher specific surface area. However, the existing high specific surface area carbon materials are usually amorphous carbon with poor conductivity, and it is difficult to balance the developed pore structure and the degree of graphitization. The porous carbon material provided by the present invention has a high specific surface area and a porous structure, as well as a graphitized structure and good conductivity. As a positive electrode for a lithium ion capacitor, the specific capacity of the carbon material in the present invention is better than that of a carbon material with the same specific surface area. At a low current density of 0.1A / g, the specific capacity exceeds 130mAh / g, and at a high current density of 10A / g, the highest specific capacity exceeds 95mAh / g.

[0013] The preparation method of the porous carbon material provided by the present invention uses an organic acid potassium salt as a raw material and a transition metal salt as an additive. After the coordination reaction, the transition metal can be evenly distributed in the precursor. After the precursor is subjected to high temperature and acid washing, a high specific surface multi-level porous carbon material is obtained. The process route is simple and easy to industrially scale up. In the preparation method of the present invention, due to the high proportion of organic acid potassium salt in the precursor, the carbon material retains the characteristics of high specific surface area through the pore-forming effect of gases such as carbon dioxide generated by in-situ activation of potassium atoms and pyrolysis; at the same time, thanks to the synergistic effect of potassium and transition metals, not only the degree of graphitization of the material is effectively improved, but also the pore structure of the material is further regulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a transmission electron microscope image of the carbon material prepared in Example 1;

[0015] Figure 2 is a transmission electron microscope image of the carbon material prepared in Comparative Example 1;

[0016] Figure 3 is a scanning electron microscope image of the carbon material prepared in Example 1;

[0017] Figure 4 is the nitrogen adsorption-desorption curve of the carbon material prepared in Example 1;

[0018] Figure 5 is the X-ray diffraction pattern of the carbon material prepared in Example 1;

[0019] Figure 6 is an X-ray diffraction pattern of the carbon material prepared in Comparative Example 1;

[0020] Figure 7 The porous carbon material prepared in Example 1 is used as the positive electrode rate performance of a lithium ion capacitor;

[0021] Figure 8 The porous carbon material prepared in Example 1 is used as the positive electrode rate performance of lithium ion capacitors;

[0022] Fig. 9 This is a power density-energy density diagram of a lithium ion capacitor composed of a porous carbon material prepared in Example 1 as a positive electrode and a nanocarbon cage negative electrode. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The first aspect of the present invention provides a porous carbon material, wherein the specific surface area of ​​the porous carbon material is 1500-3500m 2 / g, the powder conductivity is not less than 50S / m; in the X-ray diffraction pattern of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26±0.5° and the half-peak width of the characteristic peak of the (002) crystal plane is 0.4-1°.

[0025] It is well known to those skilled in the art that in order to obtain a higher specific capacity, the positive electrode material of a lithium ion capacitor should have a developed pore structure and a high specific surface area. However, the existing carbon materials with a high specific surface area are usually amorphous carbon, with a low degree of graphitization and poor conductivity. It is difficult to achieve both a developed pore structure and a high degree of graphitization and high conductivity. The porous carbon material provided by the present invention has a high specific surface area, a porous structure, and at the same time has a high degree of graphitization and conductivity.

[0026] In the X-ray diffraction pattern of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26±0.5°, indicating that the porous carbon material contains a graphite carbon structure. At the same time, the peak type of the characteristic peak of the (002) crystal plane is relatively sharp, indicating that the porous carbon material has a high degree of graphitization. In the X-ray diffraction pattern of the porous carbon material, the half-peak width of the (002) characteristic peak is 0.4-1°, more preferably 0.5-0.9°. In the above preferred case, the porous carbon material can take into account both high specific capacity and good rate performance.

[0027] In the present invention, the "half-width" of the characteristic peak in the X-ray diffraction pattern has the conventional definition in the art, which refers to the peak width at half the peak height of the characteristic peak, that is, the distance between the two points where a straight line parallel to the bottom of the peak passes through the midpoint of the peak height and intersects the two sides of the peak. The X-ray diffraction pattern of the porous carbon material can be directly read by analyzing the jade software.

[0028] The model of the XRD diffractometer used in the present invention is an XRD-6000 X-ray powder diffractometer (Shimadzu, Japan), and the XRD test conditions are: Cu target, Kα ray (wavelength λ=0.154nm), tube voltage of 40kV, tube current of 200mA, and scanning speed of 5°(2θ) / min.

[0029] According to the present invention, preferably, the porous carbon material has an obvious graphitized structure in its microscopic morphology. It can be seen from the transmission electron microscope (TEM) image of the porous carbon material that there are obvious carbon layer lattice stripes in the porous carbon material. By measuring the stripe spacing, it can be determined that it belongs to the graphite carbon structure, which further indicates that the porous carbon material contains a graphite carbon lattice structure.

[0030] According to the present invention, the porous carbon material has a rich pore structure. Preferably, the specific surface area of ​​the porous carbon material is 1800-3000m 2 / g, preferably 2000-2800m 2 / g, more preferably 2200-2600m 2 / g.

[0031] In a further preferred embodiment, the porous carbon material has a large number of microporous structures, and preferably, the micropore inner surface area of ​​the porous carbon material accounts for no less than 50% of the total specific surface area, preferably 60-85%. The porous carbon material having the above-mentioned preferred number of pores and pore distribution and the above-mentioned XRD crystallization characteristics has a higher specific capacity and better rate performance as a positive electrode material for lithium ion capacitors.

[0032] According to some preferred embodiments of the present invention, the total adsorption pore volume of the porous carbon material is 1-2 cm 3 / g, preferably 1.1-1.5cm 3 / g.

[0033] In the present invention, the pore structure properties of the sample are measured by a Quantachrome AS-6B analyzer, and the specific surface area and total adsorption pore volume of the material are obtained by the Brunauer-Emmett-Taller (BET) method.

[0034] According to some preferred embodiments of the present invention, the powder conductivity of the porous carbon material is 50-500 S / m, preferably 50-300 S / m. In the above preferred case, it is beneficial to obtain excellent rate performance.

[0035] In the present invention, the electrical conductivity of the porous carbon material is calculated by testing the powder resistivity of Ningbo Ruikewei FT-301 using a four-terminal measurement method under a pressure of 10 MPa.

[0036] The present invention has no particular limitation on the elemental composition of the porous carbon material. In addition to the C element, the porous carbon material may also contain various doping elements such as N element that are known to those skilled in the art and can be applied to carbon materials. The present invention has no particular requirements on the content of each element in the porous carbon material. Preferably, the porous carbon material does not contain potassium and transition metal elements.

[0037] The second aspect of the present invention provides a method for preparing the porous carbon material, the method comprising:

[0038] (1) mixing an organic acid potassium salt, a transition metal salt and a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution to obtain a precursor material;

[0039] Wherein, the molar ratio of the organic acid potassium salt to the transition metal salt calculated as the metal element is 1:(0.1-0.5);

[0040] (2) calcining the precursor material under an inert atmosphere to obtain an intermediate product;

[0041] (3) The intermediate product is subjected to pickling treatment with an acid, followed by solid-liquid separation, washing and drying.

[0042] In the present invention, organic acid potassium salt is used as raw material and transition metal salt is used as additive. After coordination reaction, transition metal can be evenly distributed in the precursor. After high temperature and acid washing, the precursor is obtained to obtain a high specific surface multi-level porous carbon material. The process route is simple and easy to industrially scale up.

[0043] In the preparation method of the present invention, the molar ratio of the organic acid potassium salt to the transition metal salt in terms of metal elements is 1: (0.1-0.5), and the pore-forming effect of gases such as carbon dioxide generated by in-situ activation of potassium atoms and pyrolysis, at the same time, thanks to the synergistic effect of the organic acid potassium salt and the transition metal, not only the degree of graphitization of the material is effectively improved, but also the pore structure of the material is further regulated. Preferably, in terms of metal elements, the molar ratio of the organic acid potassium salt to the transition metal salt in terms of metal elements is 1: (0.1-0.3), for example, it can be a specific molar ratio of 1: 0.1, 1: 0.15, 1: 0.2, 1: 0.25, 1: 0.3 or a range between the two. Controlling the molar ratio of the organic acid potassium salt to the transition metal salt within the above preferred range is conducive to achieving a high specific area while having a high degree of graphitization.

[0044] The present invention has a wide range of selection for the specific type of the organic acid potassium salt, and can use the potassium salt of a monoprotic acid or a polyprotic acid conventional in the art, for example, it can be at least one of dipotassium ethylenediaminetetraacetate, tripotassium ethylenediaminetetraacetate and potassium tartrate, preferably dipotassium ethylenediaminetetraacetate. The organic acid potassium salt can be a hydrate of an organic acid potassium salt, which is well known to those skilled in the art.

[0045] The present invention has a wide selection range for the transition metal. Preferably, the transition metal is selected from at least one of nickel, cobalt and manganese, and more preferably nickel. In the above preferred case, the synergistic effect of the organic acid potassium salt and nickel can be further exerted to further optimize the graphitization degree and pore structure of the porous carbon material, thereby improving the specific capacity and rate performance of the porous carbon material.

[0046] In the present invention, the transition metal salt may be an organic metal salt and / or an inorganic metal salt conventionally used in the art, for example, may be at least one of acetate, oxalate and basic carbonate of a transition metal.

[0047] According to a particularly preferred embodiment of the present invention, the organic acid potassium salt is dipotassium ethylenediaminetetraacetate, and the transition metal salt is nickel acetate. The above preferred embodiment is advantageous for having more microporous structures and a higher degree of graphitization, further improving the specific capacity and rate performance of the porous carbon material.

[0048] In the present invention, there is no particular limitation on the method for forming the homogeneous solution, for example, the homogeneous solution can be formed by heating, preferably by heating and stirring. The present invention has no particular requirements for the conditions of heating and stirring, as long as the homogeneous solution can be formed. Preferably, the heating temperature is 80-110° C. and the heating time is 2-4 hours.

[0049] The present invention has no particular limitation on the type of the solvent, as long as a homogeneous solution can be formed. For example, the solvent can be water, ethanol, etc., preferably water. The amount of the solvent used is also not particularly limited, as long as a homogeneous solution can be formed. The solvent in the homogeneous solution can be removed by direct evaporation. The evaporation temperature and process can adopt the existing technology known to those skilled in the art. For example, the homogeneous solution can be fully dried in an oven to remove the solvent.

[0050] In some embodiments of the present invention, preferably, the inert atmosphere is provided by at least one of nitrogen, argon, neon and helium, preferably a nitrogen atmosphere and / or an argon atmosphere.

[0051] The inventors of the present invention have found in their research that controlling the gradient temperature rise during calcination can help fully exert the in-situ activation effect of the organic acid potassium salt and the catalytic effect of the nickel atoms, thereby facilitating the acquisition of a porous carbon material having both a high specific surface area and a high degree of graphitization.

[0052] According to some preferred embodiments of the present invention, the calcination conditions include: first, heating to 400-600°C at a heating rate of 1-4°C / min, preferably 2-3°C / min, and keeping warm for 0-120min, preferably 0-60min; then heating to 700-900°C, preferably 700-800°C, at a heating rate of 5-10°C / min, preferably 5-8°C / min, and calcining for 60-240min, preferably 60-120min. The above preferred embodiments are advantageous in ensuring a high degree of graphitization while increasing the proportion of microporous structures in the material, and further improving the specific capacity and rate performance of porous carbon materials.

[0053] According to the present invention, in step (3), the potassium element and transition metal elements in the intermediate product are removed by the acid washing treatment.

[0054] The present invention has a wide range of choices for the type of acid. The pickling treatment can be carried out using various conventional inorganic acids and / or organic acids in the art, preferably at least one of hydrochloric acid, sulfuric acid and acetic acid, more preferably hydrochloric acid.

[0055] Preferably, the acid is provided by an aqueous acid solution, and the concentration of the aqueous acid solution is, for example, 1-3 mol / L.

[0056] The present invention has no special requirements for the conditions of the pickling treatment, which is based on the removal of potassium and transition metal elements in the intermediate product, and those skilled in the art can adjust according to actual needs. The present invention also has no special requirements for the amount of the acid, which is also based on the removal of potassium and transition metal elements in the intermediate product.

[0057] According to some preferred embodiments of the present invention, the conditions for the pickling treatment include: a temperature of 60-120° C., preferably 90-105° C.; and a contact time of 2-12 h, preferably 4-8 h.

[0058] According to the present invention, the washing is used to remove the acid remaining on the porous carbon material caused by the pickling process. Therefore, various water washing methods that can make the pickling product neutral are applicable to the present invention.

[0059] In some embodiments of the present invention, drying is used to remove water from the porous carbon material. Drying can be performed under normal pressure or reduced pressure. Drying conditions may include: a temperature of 100-120° C. and a time of 6-10 hours.

[0060] Another aspect of the present invention provides a method for preparing a porous carbon material, comprising:

[0061] (1) mixing an organic acid potassium salt, a transition metal salt and a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution to obtain a precursor material; the organic acid potassium salt is dipotassium ethylenediaminetetraacetate, and the transition metal salt is nickel acetate; wherein the molar ratio of the organic acid potassium salt to the transition metal salt is 1:(0.1-0.3);

[0062] (2) calcining the precursor material under inert atmosphere to obtain an intermediate product; the calcining conditions include: firstly heating to 500°C at a heating rate of 2-3°C / min, and keeping the temperature for 0-60min; then heating to 700-800°C at a heating rate of 5-8°C / min, and calcining for 60-120min;

[0063] (3) washing the intermediate product with an acid, and then performing solid-liquid separation, washing and drying to obtain a porous carbon material;

[0064] The specific surface area of ​​the porous carbon material is 2000-3500m 2 / g, the powder conductivity is 50-300S / m; in the X-ray diffraction spectrum of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26±0.5° and the half-peak width of the characteristic peak of the (002) crystal plane is 0.4-1°.

[0065] A third aspect of the present invention provides a positive electrode for a lithium ion capacitor, comprising a current collector and a positive electrode material composited on the current collector, wherein the positive electrode material comprises the porous carbon material described in the first aspect.

[0066] The porous carbon material provided by the present invention has both a high specific surface area and a high degree of graphitization, so that the specific capacity of the positive electrode of the lithium ion capacitor composed of the porous carbon material is better than that of the carbon material with the same specific surface area. At a low current density of 0.1A / g, the specific capacity reaches 130mAh / g, and at a high current density of 10A / g, the maximum specific capacity exceeds 95mAh / g.

[0067] The present invention has no particular limitation on the composition of the positive electrode material, as long as it contains the porous carbon material, which is used to provide positive electrode active material. The positive electrode material may also contain any conventional additives or auxiliary agents in the art.

[0068] According to some preferred embodiments of the present invention, the positive electrode material further includes a conductive agent and a binder. The present invention does not particularly limit the amount of the conductive agent and the binder, and those skilled in the art can select them according to actual needs. Preferably, in the positive electrode material, the mass ratio of the porous carbon material, the conductive agent and the binder is (6-9): (0.5-3): (0.5-3), for example, it can be 9:0.5:0.5, 8:1:1, 8:1.5:0.5, 7:2:1 and any value in the range formed by any two of these values, preferably 8:1:1.

[0069] The present invention has no particular requirements for the type of the conductive agent, and any conductive agent known in the art that can be used for lithium ion capacitors can be used, such as at least one of acetylene black, Ketjen black, Super-P, graphene and carbon nanotubes, preferably acetylene black.

[0070] The present invention has no particular limitation on the type of the adhesive. Preferably, the adhesive is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber emulsion and acrylonitrile copolymer, preferably polyvinylidene fluoride.

[0071] In the present invention, the current collector may be any current collector known to those skilled in the art, such as stainless steel mesh, nickel foam, aluminum foil, and the like.

[0072] A fourth aspect of the present invention provides a lithium ion capacitor, comprising the lithium ion capacitor positive electrode described in the third aspect.

[0073] The present invention has no particular limitation on the structure and composition of the lithium ion capacitor, as long as it includes the above-mentioned lithium ion capacitor positive electrode, and other components can be conventionally selected in the art.

[0074] According to some preferred embodiments of the present invention, the lithium ion capacitor comprises a positive electrode, a negative electrode, a separator and an electrolyte, and the positive electrode is the positive electrode of the lithium ion capacitor described in the third aspect.

[0075] Preferably, the negative electrode comprises a negative electrode current collector and a negative electrode material composited on the negative electrode current collector, wherein the negative electrode material comprises a pre-lithiated nanocarbon cage and an optional conductive agent and a binder. The conductive agent and the binder are the same as defined above, and the conductive agent and the binder used in the negative electrode and the positive electrode may be the same or different, and the present invention has no particular limitation on this.

[0076] Wherein, preferably, the nanocarbon cage is prepared according to the method disclosed in CN115966714A. The porous carbon material provided in the present invention is used as a positive electrode, and the pre-lithiated nanocarbon cage is used as a negative electrode, which has an excellent positive and negative electrode matching effect, and the composed lithium ion capacitor has a high energy density. The pre-lithiation can be carried out by conventional methods in the field. For example, the nanocarbon cage can be pulped to prepare a negative electrode, and then the obtained negative electrode is pre-lithiated by an electrochemical method to obtain a pre-lithiated nanocarbon cage negative electrode. The present invention has no special requirements for the electrochemical pre-lithiation method, and it can be carried out in a conventional manner in the field.

[0077] The present invention has no particular limitation on the composition of the diaphragm, and conventional lithium ion capacitor diaphragm materials in the art may be used, such as Celgard 2400 diaphragm.

[0078] The present invention has no special requirements for the composition of the electrolyte, and any conventional non-aqueous electrolyte in the art can be applied to the present invention.

[0079] The present invention will be described in detail below through examples.

[0080] The model of the high-resolution transmission electron microscope (HRTEM) used in the present invention is JEM-2100 (HRTEM) (Japan Electron Co., Ltd.), and the test conditions of the high-resolution transmission electron microscope are: the acceleration voltage is 200 kV.

[0081] In the present invention, the pore structure properties of the sample are measured by a Quantachrome AS-6B analyzer, and the specific surface area and total adsorption pore volume of the material are obtained by the Brunauer-Emmett-Taller (BET) method.

[0082] The model of the XRD diffractometer used in the present invention is an XRD-6000 X-ray powder diffractometer (Shimadzu, Japan), and the XRD test conditions are: Cu target, Kα ray (wavelength λ=0.154nm), tube voltage of 40kV, tube current of 200mA, and scanning speed of 5°(2θ) / min.

[0083] In the present invention, the electrical conductivity of the porous carbon material is calculated by testing the powder resistivity of Ningbo Ruikewei FT-301 using a four-terminal measurement method under a pressure of 10 MPa.

[0084] In the present invention, the cathode performance of the high specific surface porous carbon material is obtained by testing with the Wuhan Blue Electricity Testing System in the voltage range of 2-4.3V and at different current densities.

[0085] Example 1

[0086] (1) 10 g of ethylenediaminetetraacetic acid dipotassium dihydrate and 0.615 g of nickel acetate tetrahydrate (the molar ratio of ethylenediaminetetraacetic acid dipotassium hydrate to nickel acetate tetrahydrate calculated as nickel element is 1:0.1) are added to 200 mL of deionized water, heated and stirred at 105° C. for 4 h, and then placed in an oven to be fully dried.

[0087] (2) The dried precursor material was fully ground and transferred to a ceramic crucible, which was then placed in a tubular calcining furnace. Under the protection of nitrogen, the temperature was increased to 500°C at a rate of 3°C / min, then increased to 700°C at a rate of 5°C / min, calcined at a constant temperature for 2h, and finally naturally cooled to room temperature to obtain a black intermediate product.

[0088] (3) Add the intermediate product to 50 mL of deionized water, stir evenly, and then add excess concentrated hydrochloric acid (concentration is 3 mol / L). Then heat to 105°C and heat and stir for 8 hours. After cooling to room temperature, filter and wash with water until neutral. Put it in an oven and dry it overnight to finally obtain porous carbon material A1.

[0089] The TEM image of the porous carbon material A1 is as follows Figure 1 As shown, it can be seen that there are obvious carbon layer lattice stripes in the porous carbon material. By measuring the stripe spacing, it can be determined that it belongs to the graphite carbon structure, which further indicates that the porous carbon material contains a graphite carbon lattice structure.

[0090] The SEM image of the porous carbon material A1 is as follows Figure 3As shown in FIG. 1 , it can be seen that the carbon material has a blocky morphology and a large number of pore structures. The nitrogen adsorption-desorption isotherm of the porous carbon material A1 is shown in FIG. Figure 4 As shown, the pore structure characteristics of the porous carbon material A1 calculated by the isothermal adsorption curve are shown in Table 1.

[0091] The porous carbon material A1 was subjected to an X-ray diffraction test, such as Figure 5 As shown, in the X-ray diffraction pattern of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26.5°, and the half-peak width of the (002) characteristic peak is 0.532°.

[0092] The conductivity of the porous carbon material A1 was tested by the four-terminal measurement method using Ningbo Ruikewei FT-301 powder resistivity tester under a pressure of 10 MPa, as shown in Table 1.

[0093] Example 2

[0094] (1) 10 g of ethylenediaminetetraacetic acid dipotassium dihydrate and 1.845 g of nickel acetate tetrahydrate (the molar ratio of ethylenediaminetetraacetic acid dipotassium hydrate to nickel acetate tetrahydrate calculated as nickel element is 1:0.3) are added to 200 mL of deionized water, heated and stirred at 105° C. for 4 h, and then placed in an oven to be fully dried.

[0095] (2) The dried precursor material was fully ground and transferred to a ceramic crucible, which was then placed in a tubular calcining furnace. Under the protection of nitrogen, the temperature was increased to 500°C at a rate of 3°C / min, then increased to 800°C at a rate of 5°C / min, calcined at a constant temperature for 2h, and finally naturally cooled to room temperature to obtain a black intermediate product.

[0096] (3) Add the intermediate product to 50 mL of deionized water, stir evenly, and then add excess concentrated hydrochloric acid (concentration is 3 mol / L). Then heat to 105°C and heat and stir for 8 hours. Cool to room temperature and filter, wash with water until neutral. Put in an oven and dry overnight to finally obtain porous carbon material A2.

[0097] TEM image of porous carbon material A2 and Figure 1 Similar, with a distinct graphite carbon lattice structure.

[0098] The physical and chemical properties of A2 are shown in Table 1. In the X-ray diffraction spectrum of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26.5°, and the half-peak width of the (002) characteristic peak is 0.78°.

[0099] Example 3

[0100] The method of Example 1 is followed, except that the amount of nickel acetate tetrahydrate used is 3.075 g (the molar ratio of dipotassium ethylenediaminetetraacetate hydrate to nickel acetate tetrahydrate calculated as nickel element is 1:0.5).

[0101] Finally, a porous carbon material A3 was obtained. The physical and chemical properties of A3 are shown in Table 1. In the X-ray diffraction spectrum of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26.5°, and the half-peak width of the (002) characteristic peak is 0.91°.

[0102] Example 4

[0103] (1) 15 g of dipotassium ethylenediaminetetraacetate hydrate and 0.54 g of basic nickel carbonate (commercially available, nickel content 40 wt%) (the molar ratio of dipotassium ethylenediaminetetraacetate hydrate to basic nickel carbonate calculated as nickel element is 1:0.1) were added to 200 mL of deionized water, heated and stirred at 105° C. for 4 h, and then placed in an oven to be fully dried.

[0104] (2) The dried precursor material was fully ground and transferred to a ceramic crucible, which was then placed in a tubular calcining furnace. Under the protection of nitrogen, the temperature was increased to 500°C at a rate of 3°C / min, then increased to 700°C at a rate of 5°C / min, calcined at a constant temperature for 2h, and finally naturally cooled to room temperature to obtain a black intermediate product.

[0105] (3) Add the intermediate product to 50 mL of deionized water, stir evenly, and then add excess concentrated hydrochloric acid (concentration is 3 mol / L). Then heat to 105°C and heat and stir for 8 hours. After cooling to room temperature, filter and wash with water until neutral. Put it in an oven and dry it overnight to finally obtain porous carbon material A4.

[0106] The physical and chemical properties of A4 are shown in Table 1. In the X-ray diffraction spectrum of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26.5°, and the half-peak width of the (002) characteristic peak is 0.55°.

[0107] Example 5

[0108] The method of Example 1 is followed, except that the calcination conditions are: heating to 700° C. at a heating rate of 5° C. / min and calcining at a constant temperature for 2 h.

[0109] Finally, a porous carbon material A5 was obtained, and the physical and chemical properties of A5 are shown in Table 1. In the X-ray diffraction spectrum of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26.5°, and the half-peak width of the (002) characteristic peak is 0.55°.

[0110] Comparative Example 1

[0111] Take 10g of dipotassium ethylenediaminetetraacetic acid hydrate and place it in a tubular calcining furnace. Under the protection of nitrogen, heat it to 700℃ at a heating rate of 5℃ / min, calcine it at a constant temperature for 2h, and finally cool it naturally to room temperature. After acid washing and drying, the porous carbon material DA1 is obtained. The physical and chemical properties of DA1 are shown in Table 1.

[0112] The TEM image of the porous carbon material DA1 is as follows Figure 2 As shown, it can be seen that the material has no obvious carbon layer structure; the porous carbon material DA1 was subjected to X-ray diffraction test, as shown Figure 6 As shown, the X-ray diffraction pattern of the porous carbon material has obvious characteristics of amorphous carbon and presents a broad bun peak.

[0113] Comparative Example 2

[0114] (1) 10 g of potassium citrate monohydrate and 0.767 g of nickel acetate tetrahydrate (molar ratio of 1:0.1) were added to 100 mL of deionized water, heated and stirred at 105° C. for 4 h, and then placed in an oven to be fully dried.

[0115] (2) The dried precursor material was fully ground and transferred to a ceramic crucible, which was then placed in a tubular calcining furnace. Under the protection of nitrogen, the temperature was increased to 500°C at a rate of 3°C / min, then increased to 700°C at a rate of 5°C / min, calcined at a constant temperature for 2h, and finally naturally cooled to room temperature to obtain a black intermediate product.

[0116] (3) Add the intermediate product to 50 mL of deionized water, stir evenly, and then add excess concentrated hydrochloric acid (concentration is 3 mol / L). Then heat to 105°C and heat and stir for 8 hours. After cooling to room temperature, filter and wash with water until neutral. Put it in an oven and dry it overnight to finally obtain the porous carbon material DA2.

[0117] The physical and chemical properties of DA2 are shown in Table 1.

[0118] Table 1

[0119]

[0120] Test Case

[0121] The porous carbon material, acetylene black and polyvinylidene fluoride prepared in the above embodiments and comparative examples are mixed in a ratio of 8:1:1 by mass percentage, an appropriate amount of N-methylpyrrolidone is added, and the mixture is fully mixed using a homogenizer. The slurry is then scraped onto an aluminum foil current collector and dried at 80°C in a vacuum oven to obtain a capacitor positive electrode. A 2032-type button cell was made in a glove box using a metal lithium sheet as the counter electrode. The diaphragm used was an ordinary celgard2400 diaphragm, and the electrolyte used was LiPF6 / EC:DEC:EMC (1:1:1 Vol%). The prepared half-cell was left to stand for 3 hours, and then its performance was tested using a blue electricity test system with a voltage range of 2-4.3V. The specific capacity at different current densities is shown in Table 2.

[0122] The rate cycling performance of the button cell assembled with the porous carbon material A1 prepared in Example 1 is as follows: Figure 7 As shown, the rate cycling performance of the button cell assembled with the porous carbon material DA1 prepared in Comparative Example 1 is as follows Figure 8 As shown, it can be seen that it not only has a very high specific capacity at low current density, but also exhibits a high capacity retention rate at high current density, which is closely related to its high specific surface area, pore structure and degree of graphitization.

[0123] Table 2

[0124] sample Specific capacity at 0.1A / g (mAh / g) Specific capacity at 5A / g (mAh / g) Specific capacity at 10A / g (mAh / g) A1 130.2 106.5 95.4 A2 120.6 92 81.2 A3 114 86.3 77.2 A4 118.5 84.1 70.5 A5 122.2 86.5 73.7 DA1 117.5 83.1 66.5 DA2 67.2 52.9 43.5

[0125] Application Examples

[0126] The positive electrode assembled with the porous carbon material A1 prepared in Example 1 of the test example is the positive electrode, and the pre-lithiated nanocarbon cage is the negative electrode. The nanocarbon cage is prepared according to Example 1 of CN115966714A, and the nanocarbon cage is mixed with acetylene black and polyvinylidene fluoride in a mass percentage of 8:1:1, and an appropriate amount of N-methylpyrrolidone is added, and the mixture is fully mixed using a homogenizer. Then the slurry is scraped onto the copper foil current collector and dried at 80°C in a vacuum oven to obtain the capacitor negative electrode. Using a metal lithium sheet as the counter electrode, a 2032-type button battery is made in a glove box, the diaphragm uses an ordinary celgard2400 diaphragm, and the electrolyte uses LiPF6 / EC:DEC:EMC (1:1:1 Vol%). The prepared half-cell is left to stand for 3 hours, and then charged and discharged 5 times at a current density of 0.1A / g through a blue electric test system to complete the electrochemical pre-lithiation. The battery is disassembled in the glove box to obtain a pre-lithiated nanocarbon cage negative electrode.

[0127] The porous carbon A1 positive electrode and the pre-lithiated nanocarbon cage negative electrode were used to make a 2032-type button capacitor in a glove box. The diaphragm used was a common celgard2400 diaphragm, and the electrolyte used was LiPF6 / EC:DEC:EMC (1:1:1 Vol%). The prepared lithium ion capacitor was left to stand for 3 hours, and then its performance was tested by the blue electric test system with a voltage range of 0-4V.

[0128] The relationship between energy density and power density of lithium-ion capacitors is shown in the figure below: Fig. 9 As shown, at a power density of 200 W / kg, the energy density of the capacitor reaches 212 Wh / kg, and at a high power density of 20 kW / kg, the capacitor can still maintain an energy density of 114 Wh / kg. The results fully demonstrate the excellent electrochemical performance of the porous carbon material electrode in the present invention.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A porous carbon material, characterized in that: The specific surface area of ​​the porous carbon material is 1500-3500m 2 / g, the powder conductivity is not less than 50S / m; in the X-ray diffraction pattern of the porous carbon material, there is a characteristic peak of the (002) crystal plane at 26±0.5° and the half-peak width of the characteristic peak of the (002) crystal plane is 0.4-1°.

2. The porous carbon material according to claim 1, wherein The specific surface area of ​​the porous carbon material is 1800-3000m 2 / g, preferably 2000-2800m 2 / g; Preferably, the powder conductivity of the porous carbon material is 50-500 S / m, preferably 50-300 S / m; Preferably, in the X-ray diffraction pattern of the porous carbon material, the half-peak width of the characteristic peak of the (002) crystal plane is 0.5-0.9°; Preferably, according to TEM characterization analysis, the porous carbon material contains a graphite carbon lattice structure.

3. The porous carbon material according to claim 1 or 2, wherein: The proportion of the micropore inner surface area of ​​the porous carbon material to the total specific surface area is not less than 50%, preferably 60-85%; Preferably, the total adsorption pore volume of the porous carbon material is 1-2 cm 3 / g, preferably 1.1-1.5cm 3 / g; Preferably, the average pore diameter of the porous carbon material is 1-5 nm, preferably 2-3 nm.

4. The method for preparing the porous carbon material according to any one of claims 1 to 3, characterized in that: The preparation method comprises: (1) mixing an organic acid potassium salt, a transition metal salt and a solvent to form a homogeneous solution, and then removing the solvent from the homogeneous solution to obtain a precursor material; Wherein, the molar ratio of the organic acid potassium salt to the transition metal salt calculated as the metal element is 1:(0.1-0.5); (2) calcining the precursor material under an inert atmosphere to obtain an intermediate product; (3) The intermediate product is subjected to pickling treatment with an acid, followed by solid-liquid separation, washing and drying.

5. The preparation method according to claim 4, wherein: The molar ratio of the organic acid potassium salt to the transition metal salt calculated as the metal element is 1:(0.1-0.3); Preferably, the organic acid potassium salt is selected from at least one of dipotassium ethylenediaminetetraacetate, tripotassium ethylenediaminetetraacetate and potassium tartrate, preferably dipotassium ethylenediaminetetraacetate; Preferably, the transition metal is selected from at least one of nickel, cobalt and manganese; Preferably, the transition metal salt is selected from at least one of acetate, oxalate and basic carbonate of a transition metal.

6. The preparation method according to claim 4 or 5, wherein: The calcination conditions include: firstly heating to 400-600°C at a heating rate of 1-4°C / min, preferably 2-3°C / min, and keeping warm for 0-120min, preferably 0-60min; then heating to 700-900°C, preferably 700-800°C, at a heating rate of 5-10°C / min, preferably 5-8°C / min, and calcining for 60-240min, preferably 60-120min.

7. The preparation method according to any one of claims 4 to 6, wherein: In step (3), the potassium element and transition metal elements in the intermediate product are removed by the acid washing treatment; Preferably, in step (3), the acid is selected from an inorganic acid and / or an organic acid, preferably at least one of hydrochloric acid, sulfuric acid and acetic acid, preferably hydrochloric acid; Preferably, the acid is provided by an aqueous solution of the acid, and the concentration of the aqueous solution of the acid is 1-3 mol / L; Preferably, the conditions of the pickling treatment include: a temperature of 60-120° C., preferably 90-105° C.; and a contact time of 2-12 h, preferably 4-8 h.

8. A positive electrode for a lithium ion capacitor, comprising a current collector and a positive electrode material composited on the current collector, wherein: The positive electrode material comprises the porous carbon material according to any one of claims 1 to 3.

9. The positive electrode for a lithium ion capacitor according to claim 8, wherein: The positive electrode material also includes a conductive agent and a binder; Preferably, in the positive electrode material, the mass ratio of the porous carbon material, the conductive agent and the binder is (6-9): (0.5-3): (0.5-3); Preferably, the conductive agent is selected from at least one of acetylene black, Ketjen black, Super-P, graphene and carbon nanotubes, preferably acetylene black; Preferably, the binder is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl alcohol, styrene-butadiene rubber emulsion and acrylonitrile copolymer, preferably polyvinylidene fluoride.

10. A lithium ion capacitor, comprising the lithium ion capacitor positive electrode according to claim 8 or 9.

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