Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a high-performance composite positive electrode material, a preparation method and application thereof, and particularly aims to provide a transition metal oxide-based composite positive electrode material, a preparation method thereof and application thereof in a water-based zinc ion battery. The composite anode material obtained by the invention has good structural stability, and shows excellent specific capacity, rate capability and cycle performance. Has wide application prospect in the fields of energy storage, portable electronic equipment and the like.
The high performance in the high performance composite anode material of the invention refers to: the discharge specific capacity can reach 196mAh/g under the current density of 2A/g.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a composite positive electrode material comprising: with MnO2Carbon nanotube coated with a layer, pyrolytic carbon, and a coating layer dispersed in the organic compound having MnO2MnO between carbon nanotube and pyrolytic carbon of coating layer2Nanoparticles;
the MnO2The coating layer is at least positioned on the outer surface of the carbon nano tube.
In the composite positive electrode material of the invention, MnO2The coating layer may completely coat the carbon nanotubes, or may partially coat the carbon nanotubes, and preferably completely coat the carbon nanotubes.
The composite positive electrode material of the present invention contains MnO2Carbon nanotube, pyrolytic carbon and MnO of coating layer2The nanoparticles are preferably homogeneously dispersed in each other.
In the composite positive electrode material of the invention, MnO2The coating stabilizes the structure of the carbon nanotubes and is associated with MnO dispersed between the carbon nanotubes and the pyrolytic carbon2The nano particles have good interface binding property, and the embedding and removing capacity of zinc ions in the charge and discharge process is improved; pyrolytic carbon in carbon nanotubes and MnO2Plays a certain bridging role between the anode and the cathode, and greatly enhances the electronic conductivity of the composite anode material. The unique structure of the zinc oxideMn due to Jahn-Teller effect during ion-insertion phase transition2+The dissolution of ions in the circulation process has a significant inhibitory effect. The composite anode material disclosed by the invention has good structural stability, and shows excellent specific capacity, rate capability and cycle performance.
The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.
Preferably, MnO2The forming method of the coating layer is a method combining ultrasonic chemistry and microwave assistance.
Preferably, the carbon nanotubes are ordered carbon nanotubes. In the preferred technical scheme, the carbon nanotubes are distributed in an ordered form, and the array of the ordered carbon nanotubes is highly parallel, so that the carbon nanotubes can be regarded as one-dimensional quantum wires with good electrical conductivity and have good electrical conductivity.
Preferably, the MnO2The thickness of the coating layer is 1 to 15nm, for example, 1nm, 2nm, 3nm, 5nm, 8nm, 10nm, 12nm or 15nm, preferably 3 to 10 nm.
Preferably, the MnO2The nanoparticles have an average particle diameter of 20 to 300nm, for example, 20nm, 35nm, 50nm, 80nm, 100nm, 125nm, 155nm, 180nm, 200nm, 230nm, 260nm, 280nm or 300nm, preferably 30 to 260 nm. The MnO being2Nanoparticles dispersed in a matrix with MnO2If the particle size between the carbon nanotube and the pyrolytic carbon of the coating layer is less than 20nm, the components in the composite anode material are unevenly dispersed, and the material is easy to generate soft agglomeration, so that the electrochemical performance of the composite material is influenced; if the particle size is larger than 300nm, the structural integrity of the composite cathode material is lacked, the ion diffusion distance cannot be effectively shortened, and meanwhile, a more favorable path for ion permeation and transmission cannot be provided, and the improvement of the electrochemical performance of the electrode is not facilitated.
In the present invention, for the MnO2The crystal structure of the nanoparticle is not limited, and can be α -MnO2、β-MnO2Or gamma-MnO2Any one ofOr a combination of at least two.
In the present invention, for the MnO2The morphology of the nanoparticles is not limited and may include, for example, any one or a combination of at least two of nanoparticles, nanosheets, nanofibers, nanowires or nanorods, preferably any one or a combination of at least two of nanoparticles, nanowires or nanorods.
In the present invention, the MnO2The nanoparticles may comprise any one or a combination of at least two of hollow, solid or porous structures, preferably any one or a combination of two of solid or porous structures.
Preferably, the carbon nanotubes are present in an amount of (0.1 to 10)%, for example, 0.2%, 0.5%, 1%, 3%, 5%, 7%, 10%, etc., preferably (0.5 to 5)%, based on 100% by mass of the composite positive electrode material, preferably MnO is present in an amount of (0.1 to 10)%, based on 100% by mass of the composite positive electrode material2Coating layer and MnO2The total amount of nanoparticles is (75-99.8)%, for example, 75%, 80%, 86%, 90%, 95%, 97%, or 98%, preferably (80-95)%.
Preferably, the pyrolytic carbon is present in an amount of (0.1-15)%, for example, 0.1%, 0.5%, 1%, 5%, 10%, 13%, 15%, etc., preferably (1-10)%, based on 100% by mass of the composite positive electrode material.
Preferably, the mass ratio of the carbon nanotubes to the pyrolytic carbon is 3/7-4/6, such as 3/7, 3.5/6.5, 4/6, or the like.
In a second aspect, the present invention provides a method for preparing a composite positive electrode material according to the first aspect, the method comprising:
(1) preparation of a catalyst having MnO Using carbon nanotubes and manganese salt2Coated carbon nanotubes, said MnO2The coating layer is at least positioned on the outer surface of the carbon nano tube;
(2) will have MnO2Carbon nanotube and MnO of coating layer2Dispersing the nano material and an organic carbon source in a water-alcohol solution, and performing ultrasonic treatment to obtain a suspension;
(3) and (3) performing microwave treatment on the suspension obtained in the step (2) in an inert atmosphere to obtain the composite cathode material.
The composite anode material prepared by the method combining ultrasonic chemistry and microwave treatment can greatly improve the content of MnO2Carbon nanotube and MnO of coating layer2The nano particles and the pyrolytic carbon are mutually and uniformly distributed, and in the microwave treatment process at a certain temperature, the pyrolytic carbon is not only in the ordered carbon nano tube and MnO2The nano particles are uniformly dispersed between the two, and MnO is arranged on the outer surface of the carbon nano tube2Coating layer, so that MnO is generated when microwave is applied at a certain temperature2The nanoparticles can be bound to MnO2The coating layer carries out effective interface combination, thereby enhancing MnO2The binding force between the nano particles and the surface of the ordered carbon nano tube improves the embedding and removing capacity of zinc ions in the charging and discharging process; simultaneously, pyrolytic carbon in ordered carbon nanotubes and MnO2The nano materials play a certain bridging role, and the electronic conductivity of the composite anode material is greatly enhanced. The obtained composite anode material has good structural stability, and shows excellent specific capacity, rate capability and cycle performance.
As a preferred technical scheme of the method, the carbon nano tubes in the step (1) are ordered carbon nano tubes;
preferably, the preparation method of the ordered carbon nanotube comprises the following steps:
(a) dipping an anodic alumina template (AAO template) with holes at two ends in a carbon-containing polymer solution, then cleaning the AAO template by using ethanol, drying, and then carrying out heat treatment in an argon atmosphere to obtain an ordered carbon nanotube containing the AAO template;
(b) and (b) dissolving the product obtained in the step (a) in a sodium hydroxide solution with the mass percentage of 5-10%, washing until the material is neutral (namely, the pH value is 7), and fully drying to obtain the ordered carbon nanotube.
Preferably, the mass ratio of the anodized aluminum template to the carbon-containing polymer in the step (a) is 100 (1-20), such as 100:5, 100:10, 100:15 or 100: 20.
Preferably, the carbon-containing polymer solution of step (a) has a mass concentration of 0.01-1mg/L, such as 0.05mg/L, 0.1mg/L, 0.5mg/L, or 0.7mg/L, etc.
Preferably, the carbon-containing polymer solution of step (a) is one of polypyrrole, polyacrylonitrile, polystyrene, polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), polystyrene-polyacrylonitrile block copolymer, or a combination of at least two thereof.
Preferably, the solvent of step (a) is one of n-hexane, n-octane, cyclohexane, diethyl ether and tetrahydrofuran.
Preferably, the drying of step (a) is: vacuum drying at 60-120 deg.C (such as 60 deg.C, 80 deg.C, 100 deg.C or 110 deg.C) for 1-12 hr (such as 1 hr, 3 hr, 5 hr, 8 hr or 10 hr).
Preferably, the temperature of the heat treatment in the step (a) is 500-1000 ℃, and the heat treatment time is 1-5 h. Such as 500 ℃, 650 ℃, 800 ℃, 900 ℃, 1000 ℃ or the like; for example, 1h, 2h, 3h, 5h, etc.
Preferably, the washing in step (b) is performed with distilled water.
Preferably, the drying of step (b) is: drying at 55-125 deg.C under vacuum, such as 55 deg.C, 65 deg.C, 80 deg.C, 100 deg.C or 115 deg.C.
As a preferred embodiment of the method of the present invention, the step (1) of preparing a catalyst having MnO2The method of coating the carbon nano tube is a method combining ultrasonic chemistry and microwave assistance.
Preferably, step (1) is conducted with MnO2The method for coating the carbon nano tube comprises the following steps:
(A) dispersing carbon nanotubes in deionized water, and performing ultrasonic treatment at 50-300W for 10-60min to obtain a dispersion liquid;
(B) adding potassium permanganate into the dispersion liquid in the step (A), stirring at the rotating speed of 100-;
(C) performing microwave reaction on the mixture obtained in the step (B) for 5-30min under the power of 1000-3000W, and drying to obtain the product with MnO2Coating layerThe MnO of2The coating layer is at least positioned on the outer surface of the carbon nano tube.
In the preferred technical scheme, the power of the ultrasound in the step (A) is 50W, 100W, 125W, 150W, 200W or 280W, etc. The ultrasound time is 10min, 25min, 30min, 40min or 60 min.
The stirring speed in the step (B) is, for example, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm or the like. The stirring time is 15min, 20min, 30min or 40 min. The power of the ultrasound is 100W, 120W, 150W, 180W, 200W or the like. The ultrasound time is 10min, 20min or 30min, etc.
The microwave reaction in step (C) has a power of, for example, 1000W, 1250W, 1500W, 1800W, 2000W, 2500W, 3000W, or the like. The microwave reaction time may be, for example, 5min, 15min, 20min, 25min, or 30 min.
Preferably, the addition of potassium permanganate in step (B) is carried out slowly.
Preferably, after the reaction in step (C) is completed, before drying, the reaction is cooled to room temperature and filtered with suction.
Preferably, the drying in step (C) is freeze drying for 20-40h, such as 20h, 24h, 30h, 32h, 36h or 40h, etc.
Preferably, the organic carbon source in step (2) is any one or a combination of at least two of citric acid, sucrose, glucose, succinic acid, lactic acid or acetic acid, and the combination is typically but not limited to: a combination of citric acid and lactic acid, a combination of citric acid and acetic acid, a combination of sucrose and glucose, a combination of sucrose and lactic acid, a combination of glucose and succinic acid, a combination of citric acid, sucrose and acetic acid, a combination of sucrose, glucose, lactic acid, succinic acid and acetic acid, and the like.
Preferably, the hydroalcoholic solution in step (2) is: an aqueous solution of any one or a mixture of at least two of ethanol, methanol, ethylene glycol, glycerol or isopropanol.
Preferably, in the hydroalcoholic solution in step (2), the volume ratio of alcohol to water is (0.1-0.5): 1, for example, 0.1:1, 0.2:1, 0.3:1, 0.4:1, or 0.5: 1.
Preferably, the power of the ultrasonic treatment in the step (2) is 50-300W, such as 50W, 60W, 75W, 80W, 100W, 125W, 150W, 170W, 200W, 220W, 240W, 260W, 280W, 300W, etc., preferably 80-260W.
Preferably, the time of the ultrasonic treatment in the step (2) is 0.5-5h, such as 0.5h, 1h, 1.5h, 2h, 3h, 4h or 5h, etc., preferably 1-3 h.
Preferably, the mass concentration of the organic carbon source in the hydroalcoholic solution in the step (2) is 0.01-3%, such as 0.01%, 0.05%, 1%, 1.5%, 2%, 2.3%, 2.7%, 3%, or the like.
Preferably, the inert atmosphere in step (3) includes an atmosphere of any one of helium, neon, argon, krypton, xenon, radon or nitrogen or a combined atmosphere of at least two gases, preferably an argon atmosphere, or a combination of argon and any one of helium, neon, argon, krypton, xenon, radon or nitrogen or a combined atmosphere of at least two gases, and the volume ratio of argon in the combined atmosphere is more than 50%.
Because the argon has certain reducibility and the reducibility is not too strong, the argon can partially reduce MnO2The formation of oxides of manganese in various valence states has a beneficial effect on increasing the capacity of the material.
Preferably, the temperature of the microwave treatment in the step (3) is 300-.
Preferably, the microwave treatment time in step (3) is 0.5-6h, such as 0.5h, 1h, 3h, 5h or 6h, etc., preferably 0.5-4h, and more preferably 1-2 h.
As a further preferred technical solution of the method of the present invention, the method comprises the steps of:
(1) preparation of a catalyst having MnO2Coating carbon nanotube:
(A) dispersing the ordered carbon nano tube in deionized water, and carrying out ultrasonic treatment for 10-60min under the power of 50-300W to obtain a dispersion liquid;
(B) adding potassium permanganate into the dispersion liquid in the step (A), stirring at the rotating speed of 100-;
(C) performing microwave reaction on the mixture obtained in the step (B) for 5-30min under the power of 1000-3000W, cooling, performing suction filtration, and freeze-drying for 20-40h to obtain the product with MnO2Coated carbon nanotubes, said MnO2The coating layer is at least positioned on the outer surface of the carbon nano tube;
(2) will have MnO2Carbon nanotube and MnO of coating layer2Dispersing the nano material and the organic carbon source in a water-alcohol solution to ensure that the mass concentration of the organic carbon source in the water-alcohol solution is 0.01-3%, and performing ultrasonic treatment to obtain a suspension, wherein the power of the ultrasonic treatment is 50-300W and the time is 0.5-5 h;
(3) performing microwave treatment on the suspension obtained in the step (2) for 0.5-6h at the temperature of 600 ℃ in an inert atmosphere to obtain a composite anode material;
wherein the organic carbon source in the step (2) is any one or a combination of at least two of citric acid, sucrose, glucose, succinic acid, lactic acid and acetic acid, and the volume ratio of alcohol to water in the hydroalcoholic solution is (0.1-0.5) to 1;
the inert atmosphere is argon atmosphere, or the combination of argon and any one of helium, neon, krypton, xenon, radon and nitrogen or the combination atmosphere of at least two gases, and the volume ratio of argon in the combination atmosphere is more than 50%.
In a third aspect, the present invention provides a zinc ion battery comprising the composite positive electrode material of the first aspect.
Preferably, the zinc ion battery is an aqueous zinc ion battery.
The invention also provides a preparation method of the zinc ion battery, which takes the composite anode material of the first aspect as the anode of the zinc ion battery, zinc powder, zinc foil or zinc-based alloy as the cathode, zinc sulfate aqueous solution as electrolyte and a glass fiber diaphragm as the diaphragm.
Illustratively, a zinc ion battery positive electrode was prepared as follows:
uniformly mixing the composite cathode material, the adhesive PVDF and the acetylene black according to the mass ratio of 80:10:10, preparing the mixture into a paste with water, uniformly coating the paste on a zinc foil, and drying the zinc foil in a vacuum oven at 80 ℃ for 12 hours.
Compared with the prior art, the invention has the following beneficial effects:
(1) in the composite positive electrode material of the invention, MnO2The coating stabilizes the structure of the carbon nanotubes and is associated with MnO dispersed between the carbon nanotubes and the pyrolytic carbon2The nano particles have good interface binding property, and the embedding and removing capacity of zinc ions in the charge and discharge process is improved; pyrolytic carbon in carbon nanotubes and MnO2Plays a certain bridging role between the anode and the cathode, and greatly enhances the electronic conductivity of the composite anode material. The unique structure is used for Mn caused by Jahn-Teller effect in the process of zinc ion intercalation phase transition2+The dissolution of ions in the circulation process has a significant inhibitory effect. The composite anode material disclosed by the invention has good structural stability, and shows excellent specific capacity, rate capability and cycle performance.
(2) The composite anode material prepared by the method combining ultrasonic chemistry and microwave treatment can greatly improve the content of MnO2Carbon nanotube and MnO of coating layer2The nano particles and the pyrolytic carbon are mutually and uniformly distributed, and in the microwave treatment process at a certain temperature, the pyrolytic carbon is not only in the ordered carbon nano tube and MnO2The nano particles are uniformly dispersed between the two, and MnO is arranged on the outer surface of the carbon nano tube2Coating layer, so that MnO is generated when microwave is applied at a certain temperature2The nanoparticles can be bound to MnO2The coating layer carries out effective interface combination, thereby enhancing MnO2The binding force between the nano particles and the surface of the ordered carbon nano tube improves the embedding and removing capacity of zinc ions in the charging and discharging process; simultaneously, pyrolytic carbon in ordered carbon nanotubes and MnO2The nano materials play a certain bridging role, and the electronic conductivity of the composite anode material is greatly enhanced. The obtained composite anode material has good structural stability, and shows excellent specific capacity, rate capability and cycle performance.
(3) Compared with the traditional pyrolysis method, the microwave pyrolysis method is adopted to prepare the composite cathode material, the composite cathode material has unique heat and mass transfer rules and better heating uniformity, and the microwave treatment method can better realize MnO2The interface between them enhances the effect. Moreover, the temperature regulation and control, the pyrolysis process and the control of the expected final product are easier to operate and realize, the pyrolysis time is short, the comprehensive energy consumption is low, the cost can be effectively reduced, the method is more suitable for industrial production, and the method has wide market application prospect.
(4) Surface coated MnO2Ordered carbon nanotube and MnO2The nano particles and the amorphous organic pyrolytic carbon are uniformly distributed among the nano particles, the amorphous organic pyrolytic carbon and the amorphous organic pyrolytic carbon to form the composite anode material. On one hand, the synergistic effect of the three can be effectively exerted, the conductivity of the material is improved, the resistance of the material is reduced, and the problems of agglomeration, volume expansion, manganese ion dissolution and the like of manganese oxide particles in the heat treatment and charge-discharge cycle processes are also inhibited. On the other hand, the conductive network formed together obviously improves the mechanical stability and the total conductivity of the composite cathode material, and greatly promotes the diffusion rate of Zn ions during circulation. Wherein the surface is coated with MnO2The ordered carbon nano tube provides an additional transmission channel, is beneficial to the transfer of ions/electrons, and can effectively improve the specific capacity and the comprehensive electrochemical performance of the composite cathode material.
(5) The microwave treatment is preferably carried out in an inert atmosphere with certain reducibility, and argon has certain reducibility and does not have too strong reducibility, so that MnO can be partially reduced2The formation of oxides of manganese in various valence states has a beneficial effect on increasing the capacity of the material.