CN110148716B - Structure and preparation method of multi-spherical stacked carbon-coated manganese dioxide composite material - Google Patents

Abstract

The invention relates to the structure of a multi-spherical stacked carbon-coated manganese dioxide composite material. The carbon-coated manganese dioxide has a submicron spherical shape, and is composed of nano-scale MnO ₂ , a graphitized carbon material coated on the surface of the manganese dioxide, Conductive materials and three-dimensional framework materials are formed by three-dimensional stacking of multi-spheres; manganese oxide precursor materials are any one or a mixture of α-MnO ₂ , β-MnO ₂ , and electrolytic manganese dioxide; conductive materials are activated carbon, acetylene black, graphite Any one of or mixing; carbon coating precursor is any one or mixing in glucose, sucrose, citric acid; three-dimensional skeleton material is any one or mixing in carbon nanotube, carbon fiber, graphene sheet; dispersion The agent is any one or a mixture of polyacrylic acid and sodium lauryl sulfate. The beneficial effects of the invention are as follows: the synthesis process of the invention is simple, and the requirements for equipment parameters are low; the invention can form an effective three-dimensional multi-spherical stacked carbon coating on the surface of manganese dioxide, thereby improving the electrical conductivity and electrochemical stability of the material. .

Description

Structure and preparation method of multi-spherical stacked carbon-coated manganese dioxide composite material

technical field

The invention belongs to the technical field of neutral zinc-manganese batteries, in particular to a structure and a preparation method of a multi-sphere stacked carbon-coated manganese dioxide composite material.

Background technique

With the increasing prominence of energy and environmental issues, the demand for clean energy and large-scale energy storage technologies continues to grow, which puts forward higher requirements for energy density and cycle stability of energy storage materials. Aqueous zinc ion battery is a new type of green and environmentally friendly battery energy storage system that has gradually emerged in recent years. It uses low-cost, high specific capacity metal zinc as the negative electrode of the battery, and the electrolyte is an aqueous solution of zinc ions, which is safe and non-toxic. Manganese dioxide has a unique three-dimensional pore structure and excellent electrochemical zinc storage properties, so it has broad application prospects in the field of aqueous zinc-ion batteries.

However, due to the poor conductivity of manganese dioxide material itself, the charge-discharge rate characteristics are poor when applied to zinc-ion batteries. In order to improve this deficiency, Sun et al. (Journal of the American Chemical Society, 2017, 139, 9775-9778) adopted The manganese dioxide composite material with carbon fiber cloth as the conductive substrate was prepared by electrodeposition method, and an aqueous zinc-ion battery was assembled. The specific capacity can reach 290mAh g ^-1 at a charge-discharge rate of 0.3C, and it is reversible at a large rate of 6.5C. The cycle can reach 10,000 cycles, and the Coulomb efficiency can reach 100%, but the preparation method is cumbersome, difficult to prepare in batches, and the cost of carbon fiber cloth is high, which limits the industrial application of the material. Wu et al. (Small, 2018, 1703850) used the hydrothermal method to prepare manganese dioxide by adding graphene oxide at the same time. By controlling the hydrothermal temperature and time, graphene-coated manganese dioxide nanowires were prepared. The conductivity of manganese material improves the electrochemical stability of the material. It is applied to the cathode material of zinc ion battery, the specific capacity can reach 382.2mAh g ^-1 , and the reversible cycle can reach 3000 cycles at a large rate of 3A g ^-1 , and the capacity retention rate is higher than 94%, but due to the need for a high-temperature and high-pressure hydrothermal environment during the preparation process, it is necessary to add graphene with a high price and cost, and the yield is low, which is still not suitable for batch synthesis. Liu Weiliang et al. (CN107706405 A) used conductive polymer materials with good electrical conductivity to improve the performance of manganese dioxide materials in aqueous zinc batteries. In the process of synthesizing manganese dioxide, the initiator was cross-linked to form a network, and through carbonization A nitrogen or nitrogen-sulfur-doped carbon-coated manganese dioxide composite material was prepared by the process, and a good application effect was achieved. However, since the carbon source used is pyrrole, aniline, thiophene and other toxic organics, it cannot achieve green environmental protection. However, the bulk density of the product is low and the cost is high, so there are still great obstacles in industrial application. Fu Yu et al. (CN 106684346 A) introduced a process method for preparing a carbon-coated lithium-ion battery positive electrode material by a spray granulation process, and good electrochemical results were obtained.

It can be seen from the above research results that looking for a carbon-coated manganese dioxide composite electrode material with simple and feasible preparation process, green environmental protection, excellent electrical conductivity and stable electrochemical performance, will be the practical application of this material in aqueous zinc-ion batteries. Application has a driving effect.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the deficiencies in the prior art, provide a liquid-phase reaction method and add a multi-sphere stacked carbon coating precursor to carry out spray granulation process flow, and prepare a carbon coating with excellent crystalline properties and high electrical conductivity. Manganese dioxide-coated composite electrode material and its application in the cathode material of neutral zinc-manganese battery. The method has the characteristics of simple preparation process, low cost, green and pollution-free, and can be synthesized in batches. The multi-spherical stacked carbon-coated manganese dioxide product has a micro-scale spherical morphology, which is formed by stacking nano-scale _MnO and graphitized carbon materials coated on its surface. It has excellent electrical conductivity and electrochemical stability. As a cathode material for neutral zinc-manganese batteries, it can significantly improve the specific capacity and rate performance of the full battery, and has broad application prospects.

The structure of the multi-spherical stacked carbon-coated manganese dioxide composite material, the carbon-coated manganese dioxide has a sub-micron spherical morphology, and is composed of nano-scale MnO ₂ , graphitized carbon materials coated on the surface of manganese dioxide, conductive materials and Three-dimensional framework materials and other multi-sphere three-dimensional stacking; manganese oxide precursor materials are any one or a mixture of α-MnO ₂ , β-MnO ₂ , and electrolytic manganese dioxide; conductive materials are any of activated carbon, acetylene black, and graphite. One or a mixture; the carbon-coated precursor is any one or a mixture of glucose, sucrose, maltose, and citric acid; the three-dimensional skeleton material is any one or a mixture of carbon nanotubes, carbon fibers, and graphene sheets; a dispersant Any one or a mixture of polyacrylic acid and sodium lauryl sulfate; the pore-forming agent is any one of benzoic acid and PMMA or their mixture; the solid content in the slurry is 10-60wt%; an inert gas atmosphere nitrogen or argon.

Preferably, the manganese oxide precursor material is α-MnO ₂ .

As a preference: the conductive material is a mixture of acetylene black and activated carbon.

As a preference: the carbon coating precursor is sucrose.

Preferably, the three-dimensional framework material is carbon nanotubes.

The preparation method of multi-spherical stacked carbon-coated manganese dioxide composite material comprises the following steps:

Step 1: Combine the manganese oxide precursor material with the conductive material, the carbon-coated precursor, the three-dimensional framework material and the dispersant according to (50-90): (1-15): (1-15): (1-10): The mass ratio of (1-10) is mixed, dispersed in deionized water under the condition of ball milling to form a mixed dispersion solution, the ball milling speed is 150-300 rev/min, and the mass ratio of the total weight of the solid material to the deionization is 1: (2 -5);

Step 2: Add a certain proportion of pore-forming agent to the dispersant, and continue to stir for 2-12 hours to form a uniform slurry. The mass ratio of manganese oxide precursor material to pore-forming agent is 1: (0.01-0.1) ;

Step 3: Pass the slurry obtained in step 2 into the spray granulation equipment, and spray granulation at a spray temperature of 100-130 ° C and an air inlet pressure of 0.2-0.8 MPa; then collect the materials after spray granulation ;

Step 4: The material obtained in Step 3 is placed in a tube furnace, and heat treated in an inert gas atmosphere at 300-1000° C. for 2-24 hours to obtain a multi-spherical stacked carbon-coated manganese dioxide material with excellent crystallization properties.

The beneficial effects of the invention are as follows: the synthesis process of the invention is simple, and the requirements for equipment parameters are low. The invention can form an effective three-dimensional multi-spherical stacked carbon coating on the surface of manganese dioxide, thereby improving the electrical conductivity and electrochemical stability of the material. The process of the present invention can realize batch synthesis of materials. The preparation method of the invention has low cost, and the product multi-spherical stacked carbon-coated manganese dioxide composite material has excellent electrochemical performance when applied to a neutral zinc-manganese battery.

Description of drawings

FIG. 1 is an XRD pattern of the multi-spherical stacked carbon-coated manganese dioxide composite material prepared in Example 1. FIG.

FIG. 2a is an SEM image of the multi-spherical stacked carbon-coated manganese dioxide composite prepared in Example 1 at a magnification of 850 times.

FIG. 2b is an SEM image of the multi-spherical stacked carbon-coated manganese dioxide composite prepared in Example 1 at a magnification of 8000 times.

3 is a CV curve diagram of the assembled full battery of Example 1 with multi-sphere stacked carbon-coated manganese dioxide composite material as the positive electrode material and metallic zinc as the negative electrode material at a scan rate of 0.5mV s ⁻¹ .

4 is a voltage-specific capacity curve diagram of the assembled full battery at a rate of 0.2C, using the multi-ball stacked carbon-coated manganese dioxide composite material as the positive electrode material and metallic zinc as the negative electrode material of Example 1.

Fig. 5 is the rate performance curve diagram of the assembled full battery with multi-ball stacked carbon-coated manganese dioxide composite material as the positive electrode material and metallic zinc as the negative electrode material of Example 1 (the upper curve represents the Coulomb efficiency, and the lower curve represents the discharge Specific capacity).

Fig. 6 is the cycle-specific capacity curve diagram of the assembled full battery at the rate of 8C with the multi-ball stacked carbon-coated manganese dioxide composite material as the positive electrode material and the metal zinc as the negative electrode material of Example 1 (the upper curve represents the Coulomb efficiency , the lower curve represents the discharge specific capacity).

FIG. 7 is a SEM image of the multi-spherical stacked carbon-coated manganese dioxide composite material prepared in Example 2. FIG.

Detailed ways

The present invention will be further described below in conjunction with the embodiments. The following examples are illustrative only to aid in the understanding of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Example 1:

Step 1: Mix the electrolytic MnO ₂ material with graphite, carbon nanotubes, sucrose, and polyacrylic acid in a mass ratio of 80:5:10:2.5:2.5 (total solid content is 100 g), and disperse it in 300 ml under the condition of ball milling. Dispersion solution is formed in ionized water.

Step 2: Add 2 grams of benzoic acid to the above dispersant, and continue stirring for 12 hours to form a uniform slurry.

Step 3: spray and granulate the slurry obtained in step 2, set the spray pressure to 0.4MPa, and set the material inlet temperature to 120°C. The spray granulated material was subsequently collected.

Step 4: The material obtained in Step 3 is placed in a tube furnace, and heat-treated in a nitrogen atmosphere at 800° C. for 24 hours to obtain a multi-sphere stacked carbon-coated manganese dioxide composite material with excellent crystalline properties. Figure 1 is the XRD pattern of the prepared carbon-coated manganese dioxide composite material. It can be seen from the figure that the peak shape of the spectrum is sharp, indicating that the product has good crystalline properties, and the diffraction peak at 26 degrees corresponds to the peak position of carbon, Indicates the formation of an effective carbon coating. Figure 2 shows the SEM images of the multi-spherical stacked carbon-coated manganese dioxide composite material under different magnifications. It can be seen from the figure that the product has a micro-scale spherical morphology, which is composed of nano-manganese dioxide and surface-coated carbon layers. It is formed by stacking cross-links and has good electron transport properties.

In order to further study the performance of the material when it is used as a cathode material for neutral zinc-manganese batteries, the prepared carbon-coated manganese dioxide composite material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a ratio of 7:2:1 , adding an appropriate amount of methyl pyrrolidone (NMP), ball milling and mixing evenly, and then coating the slurry on stainless steel by casting to obtain a positive pole piece. The positive electrode piece is cut into a certain size as the positive electrode, and the zinc battery is assembled with metal zinc as the negative electrode and a zinc sulfate solution with a concentration of 2M as the electrolyte. Figure 3 shows the CV curves of the assembled full battery at a scan rate of 0.5mV s ^-1 using carbon-coated manganese dioxide composite material as the positive electrode material and metal zinc as the negative electrode material. It can be seen from the figure that the material has good The redox activity, with two pairs of oxidation and reduction peaks, respectively, confirms that the material has good electrochemical activity in water-zinc batteries. Figure 4 shows the voltage-specific capacity curve of the battery assembled into a full battery. It can be seen from the figure that the charge-discharge specific capacity of the material is about 245mAh g ^-1 at a rate of 0.2C, and the charge-discharge platform is good. Figure 5 is the rate performance diagram of the full battery. It can be seen from the figure that the material has excellent rate performance, and its specific capacity can still be maintained at 100mAh g ^-1 at a large rate of 8C. Figure 6 shows the cycle-specific capacity curve of the full battery at a high rate of 8C. It can be seen from the figure that the material has excellent cycle stability, and the reversible cycle can reach more than 1500 cycles.

Example 2:

Step 1: Mix α-MnO ₂ material with acetylene black, glucose, carbon fiber, and sodium lauryl sulfate in a mass ratio of 75:10:10:2.5:2.5 (total solid content is 100 g), under ball milling conditions Disperse in 300 ml of deionized water to form a slurry.

Step 2: Add 4 grams of PMMA to the above dispersant, and continue to stir for 6 hours to form a uniform slurry.

Step 3: spray and granulate the slurry obtained in step 2, set the spray pressure to 0.3MPa, and set the material inlet temperature to 110°C. The spray granulated material was subsequently collected.

Step 4: The material obtained in Step 3 is placed in a tube furnace, and heat treated in an argon atmosphere at 600 ° C for 12 hours to obtain a multi-spherical stacked carbon-coated manganese dioxide composite material with excellent crystalline properties. The diagram is shown in Figure 7.

When this material is applied to the cathode material of zinc battery, its specific capacity can reach 256mAh g ^-1 , and it has excellent rate performance and cycle stability.

Example 3:

Step 1: Mix β-MnO ₂ material with acetylene black, citric acid, carbon nanotubes, and polyacrylic acid in a mass ratio of 70:15:10:2.5:2.5 (total solid content is 100 g), and disperse under ball milling conditions A slurry was formed in 300 ml of deionized water.

Step 2: Add 5 grams of benzoic acid to the above dispersant, and continue stirring for 6 hours to form a uniform slurry.

Step 3: spray and granulate the slurry obtained in step 2, set the spray pressure to 0.25MPa, and set the material inlet temperature to 105°C. The spray granulated material was subsequently collected.

Step 4: The material obtained in Step 3 is placed in a tube furnace, and heat-treated under an argon atmosphere at 750° C. for 24 hours to obtain a carbon-coated manganese dioxide composite material with excellent crystalline properties.

When this material is applied to the cathode material of neutral zinc-manganese battery, its specific capacity can reach 235mAh g ^-1 , and it has excellent rate performance and cycle stability.

Example 4:

Step 1: Mix the electrolytic MnO ₂ material with graphite, citric acid, graphene sheets, and polyacrylic acid in a mass ratio of 60:15:10:7.5:7.5 (total solid content is 100 g), and disperse in 250 ml under ball milling conditions A slurry is formed in deionized water.

Step 2: Add 3 grams of benzoic acid to the above dispersant, and continue stirring for 12 hours to form a uniform slurry.

Step 3: spray and granulate the slurry obtained in step 2, set the spray pressure to 0.3MPa, and set the material inlet temperature to 95°C. The spray granulated material was subsequently collected.

Step 4: The material obtained in Step 3 is placed in a tube furnace and heat-treated in an argon atmosphere at 550° C. for 24 hours to obtain a carbon-coated manganese dioxide composite material with excellent crystalline properties.

When this material is applied to the cathode material of neutral zinc-manganese battery, its specific capacity can reach 240mAh g ^-1 , and it has excellent rate performance and cycle stability.

Claims (1)

1. A process for preparing the multi-sphere deposited carbon-coated manganese dioxide composite material with submicron spherical shape is prepared from nano-class MnO ₂ The graphitized carbon material, the conductive material and the three-dimensional framework material coated on the surface of the manganese dioxide are formed by three-dimensional stacking; the manganese oxide precursor material is alpha-MnO ₂ 、β- MnO ₂ And electrolytic manganese dioxide; the conductive material is any one or mixture of active carbon, acetylene black and graphite; the carbon-coated precursor is any one or mixture of glucose, sucrose, maltose and citric acid; the three-dimensional framework material is any one or mixture of carbon nano tubes, carbon fibers and graphene sheets; the dispersant is any one or mixture of polyacrylic acid and sodium dodecyl sulfate; the pore-forming agent is any one of benzoic acid and PMMA or the mixture of the benzoic acid and the PMMA; the solid content in the slurry is 10-60wt%; the inert gas atmosphere is nitrogen or argon, and is characterized by comprising the following steps:

the method comprises the following steps: mixing a manganese oxide precursor material with a conductive material, a carbon-coated precursor, a three-dimensional framework material and a dispersing agent according to the proportion of (50-90): (1-15): (1-15): (1-10): (1-10), dispersing in deionized water under a ball milling condition to form a mixed dispersion solution, wherein the ball milling rotating speed is 150-300 r/min, and the mass ratio of the total weight of the solid material to the deionized water is 1: (2-5);

step two: adding a pore-forming agent in a certain proportion into the dispersing agent, and continuously stirring for 2-12 hours to form uniform slurry, wherein the mass ratio of the manganese oxide precursor material to the pore-forming agent is 1: (0.01-0.1);

step three: introducing the slurry obtained in the step two into spray granulation equipment, and performing spray granulation at the spray temperature of 100-130 ℃ and the air inlet pressure of 0.2-0.8 MPa; subsequently collecting the material after spray granulation;

step four: and (4) placing the material obtained in the third step into a tubular furnace, and carrying out heat treatment for 2-24 hours at the temperature of 300-1000 ℃ in an inert gas atmosphere to obtain the multi-sphere stacking carbon-coated manganese dioxide material with crystallization performance.

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