CN111554932A

CN111554932A - High-performance composite positive electrode material, preparation method and application thereof

Info

Publication number: CN111554932A
Application number: CN202010393705.XA
Authority: CN
Inventors: 谭强强; 徐宇兴
Original assignee: Institute of Process Engineering of CAS; Langfang Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS; Langfang Institute of Process Engineering of CAS
Priority date: 2020-05-11
Filing date: 2020-05-11
Publication date: 2020-08-18
Anticipated expiration: 2040-05-11
Also published as: CN111554932B

Abstract

A high-performance composite anode material, a preparation method and application thereof. The invention discloses a composite anode material, which comprises the following components in percentage by weight: at least the outer surface having MnO₂Carbon nanotubes coated with a layer, pyrolytic carbon, and a coating dispersed in a matrix having MnO₂MnO between carbon nanotube and pyrolytic carbon of coating layer₂Nanoparticles. 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.

Description

High-performance composite positive electrode material, preparation method and application thereof

Technical Field

The invention belongs to the technical field of zinc ion batteries, relates to a high-performance composite positive electrode material, a preparation method and application thereof, and particularly relates to a transition metal oxide-based composite positive electrode material, a preparation method thereof and application thereof in a water-system zinc ion battery.

Background

With the increasing prominence of environmental and energy problems, the development and use of new green energy and devices are receiving wide attention. The development of mobile electronic devices has brought higher demands on energy storage devices, and batteries with high electrochemical performance and low cost are the focus of research. Currently, many electrochemical energy storage devices, such as lead storage batteries, lithium ion batteries, and super capacitors, have limited their practical application in flexible electronic devices to some extent due to their inherent bulkiness, high price, low energy density, and other disadvantages.

In recent years, water-based zinc ion batteries are favored by researchers at home and abroad due to a plurality of advantages thereof and are considered as one of the most competitive substitutes for lithium ion batteries, wherein the water-based solid zinc ion batteries are expected to solve the inherent safety problems of organic electrolytes and rigid batteries, and have the characteristics of high energy and power density and the like, so that the water-based solid zinc ion batteries have great application potential in the field of equipment energy storage devices. The advantages of the zinc ion battery are mainly shown in the following aspects: (1) the content of metal zinc in the earth crust is higher; (2) the metal zinc has higher theoretical capacity; (3) the zinc metal is environment-friendly and non-toxic; (4) the metallic zinc is extremely stable in neutral and weakly acidic aqueous solutions.

The water system zinc ion battery mainly comprises four parts, namely a positive electrode, a negative electrode, a current collector, a diaphragm and electrolyte, wherein the positive electrode material is the most core factor influencing the electrochemical performance of the water system zinc ion battery. How to obtain the cathode material with better performance is a difficult problem for scientific researchers to overcome with great effort. To solve this problem, water-based zinc ion batteries have been the main direction of research and development.

At present, the available anode materials of the water-system zinc ion battery are limited, and the energy density of the water-system battery is low, which is a bottleneck link and a problem that the water-system zinc ion battery is restricted to be widely applied. The key to improving the energy density of the water-based zinc ion battery is to expand the electrochemical window of the water-based electrolyte. Currently, the main researches and developments on positive electrode materials of water-based zinc ion batteries include: control of material morphology, recombination between different substances, doping, etc. However, these materials all have disadvantages such as low theoretical capacity and poor cycle performance. Therefore, the research and industrialization of the anode material of the water-based zinc ion battery with higher theoretical capacity and high cycle stability are aimed.

The transition metal oxide is rich in reserves, so the transition metal oxide is low in price, and the characteristic is very favorable for being applied to the anode material of the water-system zinc ion battery and industrial production. An article "Polyaniline-intercalated manganese dioxide nanoparticles as high-performance catalyst material for an aqueous zinc-ion base", published in Nature Commun, 2018,9:2906, intercalates Polyaniline (PANI) as an object material in a host material of nano-layered MnO through an interface reaction method₂MnO is expanded₂The expanded layer structure is effectively strengthened while the zinc storage channel is used, so that the zinc ion storage performance and the structural stability of the material are effectively improved. The zinc ion battery taking the material as the positive electrode has excellent rate performance and cycle life. Particularly, the high-efficiency active material can still keep good circulation stability when the utilization rate of the active material is up to 90 percent (-280 mAh/g). The invention patent (patent application No. 201910547663.8) discloses MnO for aqueous zinc ion battery₂Nanofiber material, preparation method thereof, MnO₂The nanofiber material is mainly prepared by one-step hydrothermal synthesis reaction, and the specific steps are as follows: firstly, pouring a hydrochloric acid solution into a reaction kettle, carrying out ultrasonic treatment to remove residual impurities in the reaction kettle, and then washing the reaction kettle to be neutral by using deionized water to obtain a clean reaction kettle serving as a container for hydrothermal reaction; respectively placing manganese sulfate monohydrate and potassium permanganate in a beaker, respectively adding deionized water, stirring, and then dropwise adding a potassium permanganate solution into a manganese sulfate solution to obtain a precursor solution; pouring the precursor solution into a treated reaction kettle, carrying out hydrothermal reaction, cooling to room temperature, collecting a product in the hydrothermal reaction kettle, filtering, washing and drying to obtain a product MnO₂A nanofiber material. The MnO thus obtained₂The nanofiber material shows high specific capacity of 297.7mAh/g at a current density of 154mA/g, and is used as an electrode material of a water-based zinc ion battery. However, the zinc ion cathode material prepared by the method has poor conductivity, and Mn is caused by Jahn-Teller effect in the zinc ion intercalation phase transition process²⁺The ions are dissolved in the circulation process, so that the positive electrode material is circulatedThe life is limited.

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;

(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.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

Example 1

The present embodiment provides a composite positive electrode material, including: at least the outer surface having MnO₂Carbon nanotubes coated with a coating layer (coating layer thickness 3nm), pyrolytic carbon, and dispersed in a solution containing MnO₂MnO between carbon nanotube and pyrolytic carbon of coating layer₂Nanoparticles;

the composite anode material comprises 4% of carbon nano tube and MnO in percentage by mass based on 100% of the composite anode material₂Coating layer and MnO₂The mass percentage of the total amount of the nano particles is 95 percent, and the mass percentage of the pyrolytic carbon is 1 percent.

The preparation method of the composite cathode material comprises the following steps:

(1) preparation of MnO coated on the outer surface₂Ordered carbon nanotubes of nanomaterials

Soaking an anodic alumina template (AAO template) with holes at two ends in polypyrrole solution (with the mass concentration of 0.01mg/L), wherein the mass ratio of the AAO template to the polypyrrole is 100:20, then washing the AAO template by using ethanol, drying the AAO template in vacuum at 120 ℃ for 1h, and carrying out heat treatment on the AAO template after vacuum drying at 1000 ℃ in argon atmosphere for 1h to obtain the ordered carbon nanotube containing the AAO template. Dissolving the product in 10% sodium hydroxide solution, washing with distilled water until the material is neutral (pH 7), and fully drying at 125 deg.C under vacuum condition to obtain ordered carbon nanotube.

(2) Preparation of a catalyst having MnO₂Coated carbon nanotube

(A) Dispersing the ordered carbon nano tube in deionized water, and carrying out ultrasonic treatment for 30min under the power of 100W to obtain a dispersion liquid;

(B) adding potassium permanganate into the dispersion liquid obtained in the step (A), stirring at the rotating speed of 300 revolutions per minute for 30min, and then carrying out ultrasonic treatment at the power of 100W for 20min to obtain a mixture;

(C) performing microwave reaction on the mixture in the step (B) for 10min under the power of 1000W, performing suction filtration after cooling, and performing freeze drying for 15h to obtain the product with MnO₂Ordered carbon nanotubes of coating layer, MnO₂The coating layer is at least positioned on the outer surface of the carbon nano tube.

(3) Will have MnO₂Ordered carbon nanotube and MnO of coating layer₂Dispersing nanoparticles (average particle diameter of 30nm) and citric acid in mixed solution of water and ethylene glycol (volume ratio of ethylene glycol to water is 0.1:1), and performing ultrasonic treatment at 50W power for 5 hrA suspension is obtained.

And (3) carrying out microwave treatment on the suspension for 0.5h at 600 ℃ in an argon atmosphere to obtain the high-performance composite cathode material.

Example 2

The present embodiment provides a composite positive electrode material, including: at least the outer surface having MnO₂Carbon nanotubes with coating (coating thickness 5nm), pyrolytic carbon, and dispersed in a solution containing MnO₂MnO between carbon nanotube and pyrolytic carbon of coating layer₂Nanoparticles;

the mass percentage of the carbon nano tube is 2 percent and MnO is calculated by 100 percent of the mass of the composite anode material₂Coating layer and MnO₂The mass percentage of the total amount of the nano particles is 96 percent, and the mass percentage of the pyrolytic carbon is 2 percent.

Soaking an anodic alumina template (AAO template) with holes at two ends in polypyrrole solution (with the mass concentration of 0.5mg/L), wherein the mass ratio of the AAO template to the polypyrrole is 100:10, then washing the AAO template by using ethanol, drying the AAO template in vacuum at 80 ℃ for 3h, and carrying out heat treatment on the AAO template after vacuum drying at 800 ℃ for 5h in argon atmosphere to obtain the ordered carbon nanotube containing the AAO template. Dissolving the product in 10% sodium hydroxide solution, washing with distilled water until the material is neutral (pH 7), and fully drying at 75 deg.C under vacuum condition to obtain ordered carbon nanotube.

(2) Preparation of a catalyst having MnO₂Coated carbon nanotube

(A) Dispersing the ordered carbon nano tube in deionized water, and carrying out ultrasonic treatment for 40min under the power of 200W to obtain a dispersion liquid;

(B) adding potassium permanganate into the dispersion liquid obtained in the step (A), stirring at the rotating speed of 450 rpm for 15min, and then carrying out ultrasonic treatment at the power of 150W for 10min to obtain a mixture;

(C) performing microwave reaction on the mixture in the step (B) for 15min under 2000W power, and coolingFiltering, freezing and drying for 25h to obtain the product with MnO₂Ordered carbon nanotubes of coating layer, MnO₂The coating layer is at least positioned on the outer surface of the carbon nano tube.

(3) Will have MnO₂Ordered carbon nanotube and MnO of coating layer₂Dispersing nanoparticles (average particle diameter of 60nm) and acetic acid in a mixed solution of water and ethylene glycol (volume ratio of ethylene glycol to water is 0.5:1), and performing ultrasonic treatment at 80W power for 4h to obtain a suspension.

And (3) carrying out microwave treatment on the suspension for 4h at 400 ℃ in a combined atmosphere of argon and helium (the volume ratio of argon to helium is 6:4) to obtain the high-performance composite cathode material.

Example 3

The present embodiment provides a composite positive electrode material, including: at least the outer surface having MnO₂Carbon nanotubes coated with a coating layer (coating layer thickness 10nm), pyrolytic carbon, and dispersed in a solution containing MnO₂MnO between carbon nanotube and pyrolytic carbon of coating layer₂Nanoparticles;

the composite anode material comprises 3% of carbon nano tube and MnO in percentage by mass based on 100% of the composite anode material₂Coating layer and MnO₂The mass percentage of the total amount of the nano particles is 90 percent, and the mass percentage of the pyrolytic carbon is 7 percent.

(1) preparation of ordered carbon nanotubes

Soaking an anodic alumina template (AAO template) with holes at two ends in polypyrrole solution (with the mass concentration of 0.1mg/L), wherein the mass ratio of the AAO template to the polypyrrole is 100:5, then washing the AAO template by using ethanol, drying the AAO template in vacuum at 70 ℃ for 8h, and carrying out heat treatment on the AAO template after vacuum drying at 650 ℃ for 3.5h in argon atmosphere to obtain the ordered carbon nanotube containing the AAO template. Dissolving the product in 10% sodium hydroxide solution, washing with distilled water until the material is neutral (pH 7), and fully drying at 90 ℃ under vacuum condition to obtain the ordered carbon nanotube.

(2) Preparation of a coating having MnO on the outer surface₂Of a coatingCarbon nanotube

(A) Dispersing the ordered carbon nano tube in deionized water, and carrying out ultrasonic treatment for 10min under the power of 300W to obtain a dispersion liquid;

(B) adding potassium permanganate into the dispersion liquid obtained in the step (A), stirring at the rotating speed of 500 rpm for 20min, and then carrying out ultrasonic treatment at the power of 170W for 25min to obtain a mixture;

(C) performing microwave reaction on the mixture in the step (B) for 5min under 3000W, cooling, performing suction filtration, and freeze-drying for 35h to obtain the product with MnO₂Ordered carbon nanotubes of coating layer, MnO₂The coating layer is at least positioned on the outer surface of the carbon nano tube.

(3) Will have MnO₂Ordered carbon nanotube and MnO of coating layer₂The nano particles (average particle size 100nm) and sucrose are dispersed in a mixed solution of water and ethylene glycol (the volume ratio of the ethylene glycol to the water is 0.5:1), and a suspension is obtained after ultrasonic treatment for 3 hours under 260W power.

And (3) carrying out microwave treatment on the suspension for 2.5h at 500 ℃ in an argon atmosphere to obtain the high-performance composite cathode material.

Example 4

The present embodiment provides a composite positive electrode material, including: at least the outer surface having MnO₂Carbon nanotubes with coating layer (coating layer thickness 12nm), pyrolytic carbon, and dispersed in a solution containing MnO₂MnO between carbon nanotube and pyrolytic carbon of coating layer₂Nanoparticles;

the composite anode material comprises 3% of carbon nano tube and MnO in percentage by mass based on 100% of the composite anode material₂Coating layer and MnO₂The mass percentage of the total amount of the nano particles is 92%, and the mass percentage of the pyrolytic carbon is 5%.

Soaking an anodic alumina template (AAO template) with holes at two ends in polypyrrole solution (the mass concentration is 1mg/L), wherein the mass ratio of the AAO template to the polypyrrole is 100:15, then washing the AAO template by using ethanol, drying the AAO template in vacuum at 90 ℃ for 5h, and carrying out heat treatment on the AAO template after vacuum drying at 700 ℃ for 4h in argon atmosphere to obtain the ordered carbon nanotube containing the AAO template. Dissolving the product in 10% sodium hydroxide solution, washing with distilled water until the material is neutral (pH 7), and fully drying at 75 deg.C under vacuum condition to obtain ordered carbon nanotube.

(2) Preparation of a catalyst having MnO₂Coated carbon nanotube

(A) Dispersing the ordered carbon nanotubes in deionized water, and carrying out ultrasonic treatment for 60min under the power of 130W to obtain a dispersion liquid;

(B) adding potassium permanganate into the dispersion liquid obtained in the step (A), stirring at the rotating speed of 300 revolutions per minute for 40min, and then carrying out ultrasonic treatment at the power of 100W for 20min to obtain a mixture;

(C) performing microwave reaction on the mixture in the step (B) for 30min at 2250W, cooling, performing suction filtration, and freeze-drying for 24h to obtain the product with MnO₂Ordered carbon nanotubes of coating layer, MnO₂The coating layer is at least positioned on the outer surface of the carbon nano tube.

(3) Will have MnO₂Ordered carbon nanotube and MnO of coating layer₂The nano particles (with the average particle size of 200nm), succinic acid and glucose (the mass ratio of the succinic acid to the glucose is 1:1) are dispersed in a mixed solution of water and glycol (the volume ratio of the glycol to the water is 0.35:1), and the suspension is obtained after ultrasonic treatment for 3.5h under the power of 120W.

And (3) carrying out microwave treatment on the suspension for 6h at 300 ℃ in a combined atmosphere of argon and neon (the volume ratio of argon to neon is 7:3) to obtain the high-performance composite cathode material.

Example 5

Except that in step (3), MnO is added₂The method and conditions were the same as in example 1 except that the average particle diameter of the nanoparticles was adjusted to 15 nm.

Example 6

Except that in step (3), MnO is added₂The method and conditions were the same as in example 4 except that the average particle diameter of the nanoparticles was adjusted to 350 nm.

Example 7

The method and conditions were the same as in example 1 except that the prepared ordered carbon nanotubes were replaced with ordinary carbon nanotubes.

Example 8

The procedure and conditions were the same as in example 1 except that the mixed solution of water and ethylene glycol in step (3) (the volume ratio of ethylene glycol to water was 0.1:1) was replaced with water.

Comparative example 1

Except for direct use without MnO₂The coated ordered carbon nanotubes were directly subjected to the step (3), and other methods and conditions were the same as in example 1.

Comparative example 2

Except that MnO is directly used without carrying out steps (1) to (2)₂Nanoparticles and citric acid were used as starting materials, and other methods and conditions were the same as in example 1.

Comparative example 3

Except that no MnO is added in step (3)₂Nanoparticles, other methods and conditions were the same as in example 1.

Comparative example 4

The procedure and conditions were the same as in example 1 except that citric acid was not added in step (3).

Electrochemical performance test of composite positive electrode material

Uniformly mixing the composite positive electrode material, the PVDF adhesive and the acetylene black according to the ratio of 80:10:10, preparing the mixture into a paste by using water, uniformly coating the paste on a zinc foil, and drying the zinc foil in a vacuum oven at 80 ℃ for 12 hours to obtain the positive electrode. A2016 type button zinc ion battery is assembled by using a zinc foil as a negative electrode, using a zinc sulfate aqueous solution as an electrolyte and using a glass fiber diaphragm as a diaphragm, the first discharge specific capacity, the discharge specific capacity after circulation of 150 circles and the discharge specific capacity under the current density of 2A/g are tested within a voltage range of 1.0-1.8V, and the electrochemical performance of the composite positive electrode material in each embodiment and comparative example is tested and shown in Table 1.

TABLE 1 electrochemical Properties of composite cathode materials corresponding to examples and comparative examples

As can be seen from a comparison of example 5 with example 1, MnO₂The particle size of the nano particles is too small, so that the components in the composite anode material are not uniformly dispersed, and the material is easy to generate soft agglomeration, thereby influencing the electrochemical performance of the composite material.

By comparing example 6 with example 4, MnO was recognized₂The excessive particle size of the nanoparticles can cause the structural lack of integrity of the composite cathode material, the ion diffusion distance cannot be effectively shortened, meanwhile, a more favorable path cannot be provided for ion permeation and transmission, and the improvement of the electrochemical performance of the electrode is not facilitated.

As can be seen from the comparison between example 7 and example 1, the ordered carbon nanotubes have excellent conductivity due to the highly parallel arrays, and are more favorable for improving the electrochemical properties of the material compared with the common carbon nanotubes.

As can be seen by comparing example 8 with example 1, the dispersion will have MnO dispersed therein before the microwave treatment under inert atmosphere₂Ordered carbon nanotube and MnO of coating layer₂After the nano particles (with the average particle size of 200nm), the succinic acid and the glucose are completely replaced by water in a mixed solution of water and glycol (the volume ratio of the glycol to the water is 0.35:1), the whole dispersion effect becomes poor, uneven dispersion exists, and even an agglomeration phenomenon is generated, so that a composite positive electrode material with good performance cannot be obtained during subsequent microwave treatment, the electrochemical performance is seriously influenced, the first discharge specific capacity under the current density of 260mA/g is reduced from 242mAh/g to 235mAh/g, the capacity retention rate after 150 times of circulation is reduced from 98% to 93%, the specific capacity under the high rate (the current density of 2A/g) is reduced from 196mAh/g to 188mAh/g, the reduction amplitude is up to 4%, and the service performance of the zinc ion battery is seriously influenced.

As can be seen from comparison of comparative example 1 with example 1, the use of a catalyst having no MnO₂The ordered carbon nanotube of the coating layer is used for preparing the composite anode material, and the composite anode material can be influencedThe effect of reducing MnO in the microwave treatment under the continuous inert atmosphere₂The interface contact performance of the nano particles and the ordered carbon nano tubes further influences the de-intercalation effect of ions in the charging and discharging process, and greatly reduces the specific capacity, cycle and rate capability of the composite cathode material. The first discharge specific capacity under the current density of 260mA/g is reduced from 242mAh/g to 228mAh/g, the capacity retention rate after circulation for 150 times is reduced from 98% to 92.1%, and the specific capacity under high multiplying power (2A/g current density) is reduced from 196mAh/g to 179 mAh/g.

As is clear from comparison of comparative example 2 with example 1, MnO was not added to the surface₂The ordered carbon nanotube of the coating layer can reduce the ion transmission rate and the electrical conductivity of the composite anode material in the charging and discharging process, and further influences the specific capacity and the rate capability of the composite anode material. The first discharge specific capacity under the current density of 260mA/g is only 181.3mAh/g, and the specific capacity under high multiplying power (2A/g current density) is only 168 mAh/g.

By comparing comparative example 3 with example 1, it can be seen that MnO was not added in the preparation of the composite positive electrode material₂The nano particles can not effectively protect the structural integrity of the composite cathode material, and can not effectively shorten the ion diffusion distance, thereby influencing the electrochemical performance, the first discharge specific capacity under the current density of 260mA/g is only 165mAh/g, and the specific capacity under the high multiplying power (the current density of 2A/g) is only 132 mAh/g.

Compared with the example 1, the comparative example 4 shows that the organic pyrolytic carbon cannot be converted without adding citric acid, the electronic conductivity of the composite cathode material cannot be effectively enhanced, and the effect of inhibiting manganese ions from being dissolved in electrolyte cannot be achieved in the charging and discharging processes, so that the specific capacity of the composite cathode material is reduced, the first discharge specific capacity under the current density of 260mA/g is only 227mAh/g, and the specific capacity under the high rate (the current density of 2A/g) is only 186 mAh/g.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A composite positive electrode material, characterized in that it comprises: 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;

2. The composite positive electrode material according to claim 1, wherein MnO is₂The forming method of the coating layer is a method combining ultrasonic chemistry and microwave assistance.

3. The composite positive electrode material according to claim 1 or 2, wherein the carbon nanotubes are ordered carbon nanotubes;

preferably, the MnO₂The thickness of the coating layer is 1-15nm, preferably 3-10 nm;

preferably, the MnO₂The average particle diameter of the nano particles is 20-300nm, preferably 30-260 nm;

preferably, the MnO₂The crystal structure of the nano particle comprises α -MnO₂、β-MnO₂Or gamma-MnO₂Any one or a combination of at least two of;

preferably, the MnO₂The morphology of the nanoparticle comprises any one or a combination of at least two of nanoparticle, nano-sheet, nano-fiber, nanowire or nanorod, preferably any one or a combination of at least two of nanoparticle, nanowire or nanorod;

preferably, the MnO₂The nano particles comprise any one or the combination of at least two of a hollow structure, a solid structure or a porous structure, preferably any one or the combination of two of the solid structure or the porous structure;

preferably, the mass percentage of the carbon nanotubes is (0.1-10)%, preferably (0.5-5)%, based on 100% of the mass of the composite cathode material;

preferably, MnO is 100% of the mass of the composite positive electrode material₂Coating layer and MnO₂The mass percentage of the total amount of the nano particles is (75-99.8)%, preferably (80-95)%;

preferably, the mass percentage of the pyrolytic carbon is (0.1-15)%, preferably (1-10)%, based on 100% of the mass of the composite cathode material;

preferably, the mass ratio of the carbon nanotubes to the pyrolytic carbon is 3/7-4/6.

4. A method for producing a composite positive electrode material according to any one of claims 1 to 3, characterized in that the method comprises:

(3) and (3) carrying out microwave treatment on the suspension obtained in the step (2) in an inert atmosphere to obtain the composite cathode material.

5. The method of claim 4, wherein the carbon nanotubes of step (1) are ordered carbon nanotubes;

(a) dipping the anodic alumina 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) 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, and fully drying to obtain the ordered carbon nano tube;

preferably, the mass ratio of the anodic alumina template to the carbon-containing polymer in the step (a) is 100 (1-20);

preferably, the mass concentration of the carbon-containing polymer solution in the step (a) is 0.01-1 mg/L;

preferably, the carbon-containing polymer solution of step (a) is one or a combination of at least two of polypyrrole, polyacrylonitrile, polystyrene, polyvinylpyrrolidone, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), polystyrene-polyacrylonitrile block copolymer;

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 for 1-12 h;

preferably, the temperature of the heat treatment in the step (a) is 500-1000 ℃, and the heat treatment time is 1-5 h;

preferably, said washing of step (b) is performed with distilled water;

preferably, the drying of step (b) is: drying at 55-125 deg.C under vacuum.

6. The method of claim 4 or 5, wherein step (1) produces a composition having MnO₂The method of the carbon nano tube of the coating layer is a method combining ultrasonic chemistry and microwave assistance;

(C) the mixture in the step (B) is subjected to microwave reaction for 5-30min under the power of 1000-3000W, and is dried 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.

7. The method according to any one of claims 4 to 6, wherein 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;

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 the step (2), the volume ratio of alcohol to water is (0.1-0.5): 1;

preferably, the power of the ultrasonic treatment in the step (2) is 50-300W, preferably 80-260W;

preferably, the time of the ultrasonic treatment in the step (2) is 0.5-5h, 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%.

8. The method according to any one of claims 4 to 7, wherein the inert atmosphere in step (3) comprises 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, krypton, xenon, radon, nitrogen or a combination of at least two gases, wherein the volume ratio of argon in the combined atmosphere is more than 50%;

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, preferably 0.5-4h, and more preferably 1-2 h.

9. Method according to any of claims 4-8, characterized in that the method comprises the steps of:

(1) preparation of a composition havingMnO₂Coating carbon nanotube:

the inert atmosphere is argon atmosphere, or the combination of argon and any one of helium, neon, argon, krypton, xenon, radon and nitrogen or the combination atmosphere of at least two gases, and the volume of argon in the combination atmosphere accounts for more than 50%.

10. A zinc-ion battery comprising the composite positive electrode material according to any one of claims 1 to 3;

preferably, the zinc ion battery is an aqueous zinc ion battery.