A method for preparing positive electrode active material for high-power and high-energy-density battery capacitors

Abstract

The present invention discloses a method for preparing a positive electrode active material for a high-power and high-specific energy battery-type capacitor, belonging to the technical field of battery-type capacitors. The positive electrode active material is firstly obtained by oxidation-reduction and hydrothermal reduction methods to obtain a heteroatom-doped graphene compound, and then a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material is prepared by high-speed dispersion and mechanical mixing methods. The positive electrode active material for a battery-type capacitor of the present invention has the advantages of a large electrolyte storage capacity and low internal resistance of the prepared electrode sheet, thereby ensuring that the battery-type capacitor has both high specific energy and specific power, and has excellent cycle stability of 100% DOD at high potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery-type capacitors, and in particular relates to a method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor. Background Art

[0002] With the rapid development of the new energy market in recent years, the requirements for energy density and power density of energy storage devices have become increasingly higher. Traditional secondary batteries have high energy density but low power density, which cannot meet the power requirements of emerging markets. Traditional capacitors have low energy density and cannot meet the energy density requirements. In this situation, battery-type capacitors, which combine the advantages of two types of electric energy, have become an effective solution to balance these requirements.

[0003] A battery-type capacitor is essentially an energy storage device that incorporates a certain amount of activated carbon or other high-surface-area capacitive carbon material into the positive electrode of a lithium-ion battery. In other words, the positive electrode is primarily a lithium-ion battery's positive electrode material with some capacitive carbon material added, while the negative electrode is the same as the lithium-ion battery's negative electrode. Although adding a small amount of capacitive carbon to the positive electrode of a lithium-ion battery will reduce some of the battery's capacity, it can significantly improve the battery's power density and cycle performance without significantly reducing its energy density.

[0004] Battery-type capacitors have become a development direction for achieving high power density in energy storage devices. Based on the research of common lithium-ion battery cathode materials such as LFP, LMO, LCO, ternary materials, and lithium vanadium phosphate [Li3V2(PO4)3, LVP], composite cathodes suitable for battery-type capacitors are being continuously developed.

[0005] Patent CN102969162A discloses a method for preparing a capacitor positive electrode sheet. The method involves coating a lithium-ion battery positive electrode material and activated carbon onto a current collector. While this method is simple to operate and provides good slurry foil coating, the double coating increases the tortuosity of the electrode sheet, increasing the lithium ion conduction path, and does not significantly improve the power performance of the capacitor.

[0006] PASQUIER et al. first attempted to use a composite of LCO and activated carbon as the positive electrode material for a capacitive battery. This battery can be fully charged within 3 minutes (20C), and its cycle life is only one to two orders of magnitude lower than that of a supercapacitor, reaching more than 10,000 cycles, with an energy density of 40Wh / kg. Similar methods have made significant progress in cycle life within a narrow voltage range. However, due to the simple mechanical mixing of the composite materials and the mismatch between the positive electrode material and the activated carbon material particles, the positive electrode slurry is difficult to disperse and the slurry uniformity cannot be guaranteed, resulting in a low limit pulse power of the capacitor.

[0007] The research team studied battery-type capacitors with AC / NCM and graphite, with the highest specific energy of 36.2Wh / kg and specific power of 2.38kW / kg. Although the system has been cycled for 500 cycles within a narrow voltage range (3.2-4.0V), the specific power and specific energy are low, and the combination of AC and NCM has not achieved the optimal effect. Based on the above analysis, as an important component of battery-type capacitors, electrodes are the key factor that determines their performance. On the basis of ensuring a high specific surface area porous carbon positive electrode material and a negative electrode material with high rate characteristics, it is not difficult to obtain a battery-type capacitor with both high specific energy and high specific power. Supercapacitors in the traditional sense have a high self-discharge rate and poor shelf performance; the rate performance of lithium-ion batteries is restricted by the intrinsic transmission characteristics of the positive electrode / electrolyte / negative electrode material combination system, and the 100% DOD cycle performance is poor. Therefore, in addition to the high specific power and high specific energy characteristics, the continuous high capacity output capability of the battery-type capacitor with both characteristics is also the focus of the present invention. After analyzing numerous patents and papers on battery-type capacitor research, we found that there are many research results with lifespans exceeding thousands of times, but most of them are based on non-100% DOD charge and discharge cycles. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention proposes a method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor.

[0009] This is achieved specifically through the following technical solutions:

[0010] The first object of the present invention is to provide a method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor, comprising the following steps:

[0011] 1) Preparation of heteroatom-doped graphene oxide compound: Concentrated sulfuric acid is added to a conical flask, which is placed in an ice-water bath. Solid sodium nitrate is added under mechanical stirring. After the sodium nitrate solid is completely dissolved, graphite is added and stirred continuously. Potassium permanganate is then slowly added in multiple portions for reaction, and then heated in a water bath. Deionized water is slowly added to the mixture, and the mixture is stirred in a high-temperature water bath. Deionized water is then slowly added, followed by slow addition of hydrogen peroxide for reaction, followed by addition of dilute hydrochloric acid solution, and the mixture is allowed to stand for 12 hours. The mixture is then washed with water until neutral and dried to obtain heteroatom-doped graphene oxide.

[0012] 2) Preparation of heteroatom-doped graphene compound: deionized water is added to heteroatom-doped graphene oxide, followed by intermittent ultrasonic treatment, and then transferred to a hydrothermal reactor for hydrothermal reaction, and finally washed with water until neutral, and dried to obtain the heteroatom-doped graphene compound;

[0013] 3) Preparation of composite cathode material: The heteroatom-doped graphene compound is planetarily dispersed and mixed with activated carbon and lithium cobalt oxide, and then transferred to a vacuum stirring pot and mechanically stirred for 4-8 hours to finally obtain a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite cathode material.

[0014] Furthermore, the mass ratio of the added volume of concentrated sulfuric acid in step 1) to sodium nitrate is (46-50):1.

[0015] Furthermore, the mass ratio of the amount of graphite added in step 1) to sodium nitrate is (1-2.5):1.

[0016] Furthermore, the mass ratio of the amount of potassium permanganate added in step 1) to the graphite is (3-4):1.

[0017] Furthermore, the volume ratio of the hydrogen peroxide solution to deionized water in step 1) is 1:(4-4.5).

[0018] Furthermore, the amount of deionized water added in step 2) is 1 / 2 of the volume of the beaker.

[0019] Furthermore, the intermittent ultrasound interval in step 2) is 20s.

[0020] Furthermore, the mass ratio of the heteroatom-doped graphene, activated carbon, and lithium cobalt oxide in step 2) is (1-1.6): (5-20): (79.4-94).

[0021] Furthermore, the particle size of the activated carbon in step 3) is 6-8 μm, and the particle size of the lithium cobaltate is 6 μm.

[0022] Furthermore, the rotation speed of the planetary dispersion mixing in step 3) is 200-300 rppm / min; the revolution speed of the mechanical stirring is 30-50 rppm / min, and the dispersion speed is 20-30 rppm / min.

[0023] A second object of the present invention is to provide an application of a positive electrode active material for a high-power and high-energy-density battery-type capacitor prepared by the aforementioned preparation method in the manufacture of a battery-type capacitor, wherein the application method comprises the following steps:

[0024] 1) Positive electrode sheet preparation: The positive electrode active material, conductive agent, and binder are mixed in N-2 methylpyrrolidone (NMP) solvent, coated on aluminum foil, and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode sheet active material is 45-60 μm. The mass ratio of the positive electrode active material, conductive agent, and binder is 92.5:4.5:3, and the conductive agent is composed of SP and CNTs in a mass ratio of 2:1. The thickness of the aluminum foil is 14 μm, and the amount of NMP used is 2.5 times the mass of the positive electrode active material.

[0025] 2) Negative electrode sheet preparation: The negative electrode material is hard carbon. Hard carbon, acetylene black, and polyvinylidene fluoride are mixed in an NMP solvent at a mass ratio of 90:5:5 to form a uniform slurry, which is then coated on copper foil and dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the resulting positive electrode active material is 40-45 μm. The particle size of the hard carbon is 3 μm, the thickness of the copper foil is 6 μm, and the amount of NMP used is 1.5 times the mass of the negative electrode material.

[0026] 3) Assembly: Cut the positive and negative electrodes into 56×54 mm square electrodes, prepare the diaphragm, electrolyte, tabs, and casing, and assemble them into a soft-package battery-type capacitor in a dry room with a humidity of less than 10%.

[0027] Beneficial effects:

[0028] 1) Planetary high-speed dispersion mixing is performed before traditional mechanical mixing, and a low-speed dispersion step is added during mechanical mixing to fully and evenly disperse the graphene and activated carbon particles between the lithium cobalt oxide particles, which is convenient for subsequent slurrying.

[0029] 2) The high particle matching degree of lithium cobalt oxide and activated carbon improves the dispersion uniformity of the composite positive electrode slurry, improves the thickness and weight uniformity of the positive electrode sheet, and ensures good heat dissipation performance of the battery-type capacitor during high current charging and discharging.

[0030] 3) The addition of activated carbon improves the conductivity of the electrode, reduces the electrode density, and changes the porosity around the LCO particles. In addition, the presence of activated carbon "dilutes" the LCO particles in the electrode, which can effectively avoid the depletion of lithium salts in the positive electrode area and helps the electrode obtain lithium salts from the electrolyte close to the active material particles, thereby improving the rate performance of the electrode.

[0031] 4) In the composite electrode, at the beginning of the charging process, since the activated carbon responds faster than LCO, when its potential is higher than LCO, electrons will transfer from LCO to the activated carbon. From a microscopic point of view, this is equivalent to the activated carbon charging the LCO. During the discharge process, when the potential of the activated carbon is lower than that of the LCO, electrons will transfer from the activated carbon to the LCO, i.e., recharging occurs. In this way, during the rapid charge and discharge process, the activated carbon can buffer the impact of high current on LCO through its rapid response, slow down the decay rate of LCO, establish a fast electron transfer channel between the two components, and cooperate with the double-layer charging process and Faraday reaction, thereby producing excellent rate performance and cycle performance. Especially during pulse discharge, the synergistic effect of this cross-charging will increase the contribution to the total current, improving the capacitor's ultimate pulse power performance while reducing the impact damage of high current on the electrode.

[0032] 5) The introduction of a small amount of heteroatom-doped graphene, in conjunction with the conductive network constructed by activated carbon, improves the material's conductivity, resulting in superior rate and cycling performance. The porous structure of activated carbon can adsorb and retain electrolyte, thereby shortening the ion transport distance and facilitating the extraction and insertion of lithium ions into active sites.

[0033] In summary, the positive electrode active material for the battery-type capacitor of the present invention has the advantages of large electrolyte storage capacity and low internal resistance of the electrode sheet, ensuring that the battery-type capacitor has high specific energy and specific power at the same time, and has excellent cycle stability of 100% DOD at high potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 XRD pattern of the positive electrode active material prepared in Example 1 of the present invention;

[0035] Figure 2 This is a SEM image of the positive electrode active material prepared in Example 1 of the present invention;

[0036] Figure 3 This is a SEM image of the positive electrode active material prepared in Comparative Example 1 of the present invention;

[0037] Figure 4 This is the 1C rate charge and discharge curve of the battery-type capacitor prepared in Comparative Example 2 of the present invention;

[0038] Figure 5 This is a 1000 pulse discharge curve of a battery-type capacitor prepared in Comparative Example 2 of the present invention;

[0039] Figure 6 The capacity retention rate of the battery-type capacitor prepared in Comparative Example 2 of the present invention is 1000 times of 10C charging, 20C discharging, 100% DOD cycle. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention are further described in detail below, but the present invention is not limited to these embodiments. Any improvement or replacement based on the basic spirit of the present embodiment still falls within the scope of protection required by the claims of the present invention.

[0041] Example 1

[0042] A method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor comprises the following steps:

[0043] 1) Add 50 ml of concentrated sulfuric acid to a 250 ml conical flask, place the conical flask in an ice-water bath at a temperature of ≤5°C, add 1.2 g of sodium nitrate solid under low-speed stirring, and add 2 g of graphite while stirring continuously after the sodium nitrate solid is completely dissolved; then slowly add 6.2 g of potassium permanganate in three portions, react for 1 hour, move to a 35°C water bath, and stir and react for 2 hours; slowly add deionized water equivalent to the volume of concentrated sulfuric acid to the mixture, move to a 90°C water bath, and stir and react for 30 minutes; slowly add deionized water equivalent to the volume of concentrated sulfuric acid, then slowly add 28 ml of hydrogen peroxide, then react for 15 minutes, add an appropriate amount of dilute hydrochloric acid solution, and let it stand for 12 hours; then wash with deionized water until neutral, and dry at 80°C to obtain heteroatom-doped graphene oxide;

[0044] 2) The heteroatom-doped graphene oxide prepared above was placed in a beaker, 100 ml of deionized water was added, and the aqueous solution was placed in a high-power ultrasonic device and intermittently ultrasonicated for 1 hour; then the solution was transferred to a 150 ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours; finally, the solution was washed with deionized water until neutral, and then fully dried in a forced air drying oven at 80° C. to obtain a heteroatom-doped graphene compound;

[0045] 3) Weighing 2 g of the heteroatom-doped graphene compound, 10 g of activated carbon, and 188 g of lithium cobalt oxide, and performing planetary dispersion mixing at a speed of 300 rppm / min, then transferring the mixture to a vacuum stirring pot and mechanically stirring for 8 h at a revolution speed of 50 rppm / min and a dispersion speed of 30 rppm / min, finally obtaining a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material. Figure 1 and Figure 2 They are the XRD pattern and SEM pattern of the composite positive electrode material.

[0046] Example 2

[0047] A method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor comprises the following steps:

[0048] 1) Add 50 ml of concentrated sulfuric acid to a 250 ml conical flask, place the conical flask in an ice-water bath at a temperature of ≤5°C, add 1.2 g of sodium nitrate solid under low-speed stirring, and add 2 g of graphite while stirring continuously after the sodium nitrate solid is completely dissolved; then slowly add 6.2 g of potassium permanganate in three portions, react for 1 hour, move to a 35°C water bath, and stir and react for 2 hours; slowly add deionized water equivalent to the volume of concentrated sulfuric acid to the mixture, move to a 90°C water bath, and stir and react for 30 minutes; slowly add deionized water equivalent to the volume of concentrated sulfuric acid, then slowly add 28 ml of hydrogen peroxide, then react for 15 minutes, add an appropriate amount of dilute hydrochloric acid solution, and let it stand for 12 hours; then wash with deionized water until neutral, and dry at 80°C to obtain heteroatom-doped graphene oxide;

[0049] 2) The heteroatom-doped graphene oxide prepared above was placed in a beaker, 100 ml of deionized water was added, and the aqueous solution was placed in a high-power ultrasonic device and intermittently ultrasonicated for 1 hour; then the solution was transferred to a 150 ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours; finally, the solution was washed with deionized water until neutral, and then fully dried in a forced air drying oven at 80° C. to obtain a heteroatom-doped graphene compound;

[0050] 3) Weigh 2 g of the heteroatom-doped graphene compound, 10 g of activated carbon, and 188 g of lithium cobalt oxide, and mix them together at a planetary dispersion speed of 300 rppm / min. Then transfer them to a vacuum stirring pot and mechanically stir them for 8 h under the conditions of revolution 50 rppm / min and dispersion 0 rppm / min to obtain a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material.

[0051] Example 3

[0052] A method for preparing a positive electrode active material for a high-power and high-specific-energy battery-type capacitor comprises the following steps:

[0053] 1) Add 50 ml of concentrated sulfuric acid to a 250 ml conical flask, place the conical flask in an ice-water bath at a temperature of ≤5°C, add 1.2 g of sodium nitrate solid under low-speed stirring, and add 2 g of graphite while stirring continuously after the sodium nitrate solid is completely dissolved; then slowly add 6.2 g of potassium permanganate in three portions, react for 1 hour, move to a 35°C water bath, and stir and react for 2 hours; slowly add deionized water equivalent to the volume of concentrated sulfuric acid to the mixture, move to a 90°C water bath, and stir and react for 30 minutes; slowly add deionized water equivalent to the volume of concentrated sulfuric acid, then slowly add 28 ml of hydrogen peroxide, then react for 15 minutes, add an appropriate amount of dilute hydrochloric acid solution, and let it stand for 12 hours; then wash with deionized water until neutral, and dry at 80°C to obtain heteroatom-doped graphene oxide;

[0054] 2) The heteroatom-doped graphene oxide prepared above was placed in a beaker, 100 ml of deionized water was added, and the aqueous solution was placed in a high-power ultrasonic device and intermittently ultrasonicated for 1 hour; then the solution was transferred to a 150 ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours; finally, the solution was washed with deionized water until neutral, and then fully dried in a forced air drying oven at 80° C. to obtain a heteroatom-doped graphene compound;

[0055] 3) Weigh 2 g of the heteroatom-doped graphene compound, 10 g of activated carbon, and 188 g of lithium cobalt oxide and add them together into a vacuum stirring pot. After mechanical stirring for 8 h under the conditions of revolution 50 rppm / min and dispersion 30 rppm / min, a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material is finally obtained.

[0056] Application Example 1

[0057] A method for preparing a battery-type capacitor comprises the following steps:

[0058] 1) The positive electrode active material prepared in Example 1, a conductive agent, and a polyvinylidene fluoride (PVDF) binder were mixed in an N-2-methylpyrrolidone (NMP) solvent, coated on aluminum foil, and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode active material was 52 μm. The mass ratio of the positive electrode active material, the conductive agent, and the binder was 92.5:4.5:3, and the conductive agent was composed of SP and CNTs in a mass ratio of 2:1. The amount of NMP used was 2.5 times the mass of the positive electrode active material.

[0059] 2) A negative electrode active material, hard carbon, a conductive agent, acetylene black, and a binder, polyvinylidene fluoride, were mixed in an NMP solvent at a mass ratio of 90:5:5 to form a uniform slurry, which was then coated on a copper foil and dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the resulting positive electrode active material was 42 μm. The hard carbon had a particle size of 3 μm, the copper foil had a thickness of 6 μm, and the amount of NMP used was 1.5 times the mass of the negative electrode active material.

[0060] 3) Cut the positive and negative electrodes into 56×54 mm square electrodes respectively, prepare the diaphragm, electrolyte, tabs, and casing, and assemble them into a soft-package battery-type capacitor in a dry room with a humidity of less than 10%.

[0061] Application Example 2

[0062] A method for preparing a battery-type capacitor comprises the following steps:

[0063] On the basis of Application Example 1, the positive electrode active material prepared in Example 1 was replaced with the positive electrode active material prepared in Example 2.

[0064] Application Example 3

[0065] A method for preparing a battery-type capacitor comprises the following steps:

[0066] On the basis of Application Example 1, the positive electrode active material prepared in Example 1 was replaced with the positive electrode active material prepared in Example 3.

[0067] Comparative Example 1

[0068] A method for preparing a positive electrode active material for a battery-type capacitor comprises the following steps

[0069] 50 ml of concentrated sulfuric acid was added to a 250 ml conical flask, and the conical flask was placed in an ice-water bath (below 5 ° C). 1.2 g of sodium nitrate solid was added under mechanical stirring (low speed). After the sodium nitrate solid was completely dissolved, 2 g of graphite was added and stirred continuously; then 6.2 g of potassium permanganate was slowly added in three times, and after reacting for 1 hour, the mixture was moved to a 35 ° C water bath and stirred for 2 hours; deionized water equivalent to the volume of concentrated sulfuric acid was slowly added to the mixture, and the mixture was moved to a 90 ° C water bath and stirred for 30 minutes; deionized water equivalent to the volume of concentrated sulfuric acid was slowly added, and then 28 ml of hydrogen peroxide was slowly added, and then the mixture was reacted for 15 minutes. An appropriate amount of dilute hydrochloric acid solution was added and the mixture was allowed to stand for 12 hours; then the mixture was washed with deionized water until neutral, and dried at 80 ° C to obtain heteroatom-doped graphene oxide; the above-mentioned preparation was prepared. The obtained heteroatom-doped graphene oxide was placed in a beaker, 100 ml of deionized water was added, and the aqueous solution was placed in a high-power ultrasonic device, intermittently ultrasonicated for 1 hour, and then transferred to a 150 ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours, and finally washed with deionized water until neutral, and then fully dried in a blast drying oven at 80 ° C to obtain a heteroatom-doped graphene compound; finally, 2 g of the heteroatom-doped graphene compound and 198 g of lithium cobalt oxide were weighed together for planetary dispersion mixing (speed of 300 rppm / min), and then transferred to a vacuum stirring pot for mechanical stirring for 8 hours (revolution 50 rppm / min, dispersion 30 rppm / min), and finally a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material was obtained. Figure 3 is a SEM image of the composite material prepared in this example.

[0070] This comparative example also provides a method for preparing a battery-type capacitor, comprising the following steps:

[0071] 1) A positive electrode active material, a conductive agent, and a polyvinylidene fluoride (PVDF) binder were mixed in an N-2-methylpyrrolidone (NMP) solvent, coated on aluminum foil, and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode active material was 52 μm. The mass ratio of the positive electrode active material, the conductive agent, and the binder was 92.5:4.5:3, and the conductive agent was composed of SP and CNTs in a mass ratio of 2:1. The amount of NMP used was 2.5 times that of the positive electrode active material.

[0072] 2) A negative electrode active material, hard carbon, a conductive agent, acetylene black, and a binder, polyvinylidene fluoride, were mixed in an NMP solvent at a mass ratio of 90:5:5 to form a uniform slurry, which was then coated on a copper foil and dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the resulting positive electrode active material was 42 μm. The hard carbon had a particle size of 3 μm, the copper foil had a thickness of 6 μm, and the amount of NMP used was 1.5 times the mass of the negative electrode active material.

[0073] 3) Cut the positive and negative electrodes into 56×54 mm square electrodes respectively, prepare the diaphragm, electrolyte, tabs, and casing, and assemble them into a soft-package battery-type capacitor in a dry room with a humidity of less than 10%.

[0074] Comparative Example 2

[0075] A method for preparing a positive electrode active material for a battery-type capacitor comprises the following steps:

[0076] 50 ml of concentrated sulfuric acid was added to a 250 ml conical flask, and the conical flask was placed in an ice-water bath (below 5 ° C). 1.2 g of sodium nitrate solid was added under mechanical stirring (low speed). After the sodium nitrate solid was completely dissolved, 2 g of graphite was added and stirred continuously. Then 6.2 g of potassium permanganate was slowly added in three times. After reacting for 1 hour, the mixture was moved to a 35 ° C water bath and stirred for 2 hours. Deionized water equivalent to the volume of concentrated sulfuric acid was slowly added to the mixture, and the mixture was moved to a 90 ° C water bath and stirred for 30 minutes. Deionized water equivalent to the volume of concentrated sulfuric acid was slowly added, and then 28 ml of hydrogen peroxide was slowly added, and then the mixture was reacted for 15 minutes. An appropriate amount of dilute hydrochloric acid solution was added and the mixture was allowed to stand for 12 hours. The mixture was then washed with deionized water until neutral and dried at 80 ° C to obtain heteroatom-doped graphene oxide. The heteroatom-doped graphene oxide prepared above was obtained. The heteroatom-doped graphene oxide was placed in a beaker, 100 ml of deionized water was added, the aqueous solution was placed in a high-power ultrasonic device, intermittently ultrasonicated for 1 hour, and then transferred to a 150 ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours, and finally washed with deionized water until neutral, and then fully dried in a blast drying oven at 80 ° C to obtain a heteroatom-doped graphene compound; finally, 2 g of the heteroatom-doped graphene compound, 20 g of activated carbon and 178 g of lithium cobalt oxide were weighed together for planetary dispersion mixing (speed of 300 rppm / min), and then transferred to a vacuum stirring pot and mechanically stirred for 8 hours (revolution 50 rppm / min, dispersion 30 rppm / min) to finally obtain a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material.

[0077] This comparative example also provides a method for preparing a battery-type capacitor, comprising the following steps:

[0078] 1) A positive electrode active material, a conductive agent, and a polyvinylidene fluoride (PVDF) binder were mixed in an N-2-methylpyrrolidone (NMP) solvent, coated on aluminum foil, and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode active material was 52 μm. The mass ratio of the positive electrode active material, the conductive agent, and the binder was 92.5:4.5:3, and the conductive agent was composed of SP and CNTs in a mass ratio of 2:1. The amount of NMP used was 2.5 times that of the positive electrode active material.

[0079] 2) A negative electrode active material, hard carbon, a conductive agent, acetylene black, and a binder, polyvinylidene fluoride, were mixed in an NMP solvent at a mass ratio of 90:5:5 to form a uniform slurry, which was then coated on a copper foil and dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the resulting positive electrode active material was 42 μm. The hard carbon had a particle size of 3 μm, the copper foil had a thickness of 6 μm, and the amount of NMP used was 1.5 times the mass of the negative electrode active material.

[0080] 3) Cut the positive and negative electrodes into 56×54mm square electrodes respectively, and prepare the diaphragm, electrolyte, tabs, and shell. Assemble them into soft-package battery-type capacitors in a dry room with a humidity of less than 10%. Figure 4 This is the 1C rate capacity test curve of the comparative example. Figure 5 This is the 2000A pulse discharge curve of the comparative example, Figure 6 This is the performance of the comparative example.

[0081] Comparative Example 3

[0082] A method for preparing a positive electrode active material for a battery-type capacitor comprises the following steps:

[0083] Add 50ml of concentrated sulfuric acid to a 250ml Erlenmeyer flask, place the flask in an ice-water bath (below 5°C), add 1.2g of solid sodium nitrate while mechanically stirring (low speed), and after the sodium nitrate solid is completely dissolved, add 2g of graphite while stirring continuously. Then, slowly add 6.2g of potassium permanganate in three portions. After reacting for 1 hour, transfer to a 35°C water bath and stir for 2 hours. Slowly add deionized water equivalent to the volume of concentrated sulfuric acid to the mixture, transfer to a 90°C water bath and stir for 30 minutes. Slowly add deionized water equivalent to the volume of concentrated sulfuric acid, then slowly add 28ml of hydrogen peroxide, react for 15 minutes, add an appropriate amount of dilute hydrochloric acid solution, and let it stand for 12 hours. Then, wash with deionized water until neutral and dry at 80°C to obtain heteroatom-doped graphene oxide. Take the heteroatom-doped graphene oxide prepared above and place it in a beaker. Add 100ml of deionized water. Place the aqueous solution in a high-power ultrasonic device and sonicate intermittently for 1 hour. Then transfer it to a 150ml polytetrafluoroethylene-lined hydrothermal reactor for hydrothermal reaction for 20 hours. Finally, wash it with deionized water until neutral, and then fully dry it in a blast drying oven at 80°C to obtain a heteroatom-doped graphene compound. Finally, weigh 2g of the heteroatom-doped graphene compound, 40g of activated carbon and 158g of lithium cobalt oxide and mix them together in a planetary dispersion (speed of 300rppm / min), then transfer it to a vacuum stirring pot and mechanically stir it for 8h (revolution 50rppm / min, dispersion 30rppm / min), and finally obtain a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material.

[0084] This comparative example also provides a method for preparing a battery-type capacitor, comprising the following steps:

[0085] 1) A positive electrode active material, a conductive agent, and a polyvinylidene fluoride (PVDF) binder were mixed in an N-2-methylpyrrolidone (NMP) solvent, coated on aluminum foil, and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode active material was 52 μm. The mass ratio of the positive electrode active material, the conductive agent, and the binder was 92.5:4.5:3, and the conductive agent was composed of SP and CNTs in a mass ratio of 2:1. The amount of NMP used was 2.5 times that of the positive electrode active material.

[0086] 2) A negative electrode active material, hard carbon, a conductive agent, acetylene black, and a binder, polyvinylidene fluoride, were mixed in an NMP solvent at a mass ratio of 90:5:5 to form a uniform slurry, which was then coated on a copper foil and dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the resulting positive electrode active material was 42 μm. The hard carbon had a particle size of 3 μm, the copper foil had a thickness of 6 μm, and the amount of NMP used was 1.5 times the mass of the negative electrode active material.

[0087] 3) Cut the positive and negative electrodes into 56×54 mm square electrodes respectively, prepare the diaphragm, electrolyte, tabs, and casing, and assemble them into a soft-package battery-type capacitor in a dry room with a humidity of less than 10%.

[0088] Experimental Example 1 Electrochemical Performance Test

[0089] To test the performance of the composite positive electrode sheet and battery-type capacitor of the present invention, the assembled soft-pack battery-type capacitors of the above examples and comparative examples were used. Capacity testing (2.5-4.4V) was conducted at a 1C rate, cycle testing (100% DOD 2.2-4.4V) was conducted at a 10C charge / 20C discharge rate, and full-cell power performance testing (2.5-4.2V) was conducted at a 1000A discharge rate.

[0090]

[0091] As can be seen from Table 1, the battery-type capacitor prepared by combining planetary dispersed mixing with mechanical mixing has better specific energy, specific power and cycle performance. On this basis, the composite positive electrode material composed of a suitable material mass ratio can ensure that the battery-type capacitor has both high specific energy and specific power while maintaining excellent 10C / 20C100% DOD cycle performance.

[0092] According to Comparative Example 2, as the amount of activated carbon increases, the energy density will decrease, but the power density and cycle performance will increase. This is because the activated carbon has a low specific capacity, which will sacrifice some specific energy but improve the power performance and cycle stability of the capacitor.

Claims

1. A method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor, characterized in that: The steps include: 1) Preparation of heteroatom-doped graphene oxide compound: Concentrated sulfuric acid is added to a conical flask, which is placed in an ice-water bath. Solid sodium nitrate is added under mechanical stirring. After the sodium nitrate solid is completely dissolved, graphite is added and stirred continuously. Potassium permanganate is then slowly added in multiple portions for reaction, and then heated in a water bath. Deionized water is slowly added to the mixture, and the mixture is stirred in a high-temperature water bath. Deionized water is then slowly added, followed by slow addition of hydrogen peroxide for reaction, followed by addition of dilute hydrochloric acid solution, and the mixture is allowed to stand for 12 hours. The mixture is then washed with water until neutral and dried to obtain heteroatom-doped graphene oxide. 2) Preparation of heteroatom-doped graphene compound: deionized water is added to heteroatom-doped graphene oxide, followed by intermittent ultrasonic treatment, and then transferred to a hydrothermal reactor for hydrothermal reaction, and finally washed with water until neutral, and dried to obtain the heteroatom-doped graphene compound; 3) Preparation of composite positive electrode material: The heteroatom-doped graphene compound is planetarily dispersed and mixed with activated carbon and lithium cobalt oxide, and then transferred to a vacuum stirring pot and mechanically stirred for 4-8 hours to finally obtain a heteroatom-doped graphene / activated carbon / lithium cobalt oxide composite positive electrode material; the planetary dispersion mixing speed described in step 3) is 200-300 rppm / min; the orbital speed of the mechanical stirring is 30-50 rppm / min, and the dispersion speed is 20-30 rppm / min; the mass ratio of the heteroatom-doped graphene, activated carbon, and lithium cobalt oxide is (1-1.6): (5-20): (79.4-94).

2. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The volume mass ratio of concentrated sulfuric acid to sodium nitrate in step 1) is V concentrated sulfuric acid: m sodium nitrate = 50:1.

2.

3. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The mass ratio of graphite to sodium nitrate in step 1) is (1-2.5):

1.

4. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The mass ratio of potassium permanganate to graphite in step 1) is (3-4):

1.

5. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The volume ratio of the total amount of hydrogen peroxide used in step 1) to the total amount of deionized water used is 28:

100.

6. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The total time of the intermittent ultrasonic treatment in step 2) is 1 h, and the intermittent time is 20 s.

7. The method for preparing a positive electrode active material for a high-power and high-energy-density battery capacitor according to claim 1, wherein: The activated carbon particle size described in step 3) is 6-8 μm, and the particle size of lithium cobaltate is 6 μm.

8. Use of the positive electrode active material for high-power and high-energy-density battery capacitors prepared by the preparation method according to any one of claims 1 to 7 in the manufacture of battery capacitors, characterized in that: The application method comprises the following steps: 1) preparing a positive electrode sheet: mixing a positive electrode active material, a conductive agent and a binder in an N-2 methylpyrrolidone (NMP) solvent, coating the mixture on an aluminum foil, and then drying the mixture in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode sheet active material is 45-60 μm; wherein the mass ratio of the positive electrode active material, the conductive agent and the binder is 92.5:4.5:3, and the conductive agent is composed of SP and CNTs in a mass ratio of 2:1; the thickness of the aluminum foil is 14 μm, and the amount of NMP used is 2.5 times the mass of the positive electrode active material; 2) preparing a negative electrode sheet: the negative electrode material is Hard carbon, hard carbon, acetylene black and polyvinylidene fluoride are mixed in an NMP solvent in a mass ratio of 90:5:5 to form a uniform slurry, which is then coated on a copper foil and then dried in a vacuum drying oven at 120°C for 24 hours. The thickness of the obtained positive electrode active material is 40-45 μm; wherein the particle size of the hard carbon is 3 μm, the thickness of the copper foil is 6 μm, and the amount of NMP used is 1.5 times the mass of the negative electrode material; 3) Assembly: The positive and negative electrode sheets are respectively cut into 11 56×54 mm square electrodes, and the diaphragm, electrolyte, tabs, and casing are prepared, and assembled into soft-package battery-type capacitors in a drying room with a humidity of less than 10%.

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