MnOx (at) C composite material and preparation method of positive plate of zinc ion battery using MnOx (at) C composite material

Abstract

The invention discloses a preparation method of a MnOX-C composite material, which specifically comprises the following steps: mixing leather scraps with an activating agent, carbonizing, dispersing the obtained porous carbon material in water, adding diluted hydrochloric acid to adjust the pH value to be neutral, heating, stirring, washing, centrifuging and drying; mixing the obtained material with potassium permanganate, adding deionized water, reacting in a microwave reactor, centrifuging, drying, calcining the alpha-MnO / porous carbon material, mixing the obtained MnO / C composite material with potassium permanganate, adding deionized water, reacting in the microwave reactor, centrifuging, washing, and drying. The invention also discloses a method for preparing a positive plate of a zinc ion battery by adopting the MnOX-C composite material. The composite material has high specific capacity and excellent rate performance, and electrochemical active sites and ion diffusion efficiency are remarkably improved due to the fact that the activated carbon substrate prepared from recovered chrome tanned leather waste is compounded with the high-dispersion manganese oxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of electrochemical energy storage materials, and specifically relates to a preparation method of MnO X @C composite material, and also relates to a preparation method of a positive electrode sheet for a zinc-ion battery. Background Art

[0002] Due to its high safety, low cost and environmental friendliness, zinc-ion batteries have become a research hotspot for next-generation energy storage devices. However, the low electrical conductivity and poor cycle stability of the positive electrode material limit its practical application. In the prior art, manganese-based oxides are considered to be ideal positive electrode materials for aqueous zinc-ion batteries due to their high theoretical capacity, rich resources, low cost and environmental friendliness.

[0003] However, its practical application faces significant challenges: firstly, the intrinsic conductivity of manganese oxides is poor, resulting in high polarization and low rate performance; secondly, the insertion / extraction of Zn² + is accompanied by severe volume expansion, leading to material pulverization and capacity attenuation; in addition, manganese oxides are prone to disproportionation reactions in the electrolyte, resulting in the dissolution and loss of active substances. Although existing improvement strategies have partially alleviated the above problems, there are still limitations such as unsustainable carbon sources, insufficient interfacial binding force and complex processes.

[0004] In the research of positive electrode materials for zinc-ion batteries, carbon-based materials have become an important carrier for improving electrode performance due to their high electrical conductivity, chemical stability and rich pore structure. Traditional carbon sources mostly rely on fossil fuel derivatives (such as asphalt, phenolic resin) or expensive materials such as carbon nanotubes and graphene, which are not only costly but also difficult to meet the requirements of green manufacturing. In recent years, biomass carbon materials have gradually become a research hotspot due to their wide sources, strong renewable ability and environmental friendliness.

[0005] As a biomass resource rich in collagen and organic fibers, leather waste has the following unique advantages: (1) Natural porous structure: The collagen fibers in leather form a rich porous structure after high-temperature carbonization, with a specific surface area of 200-400 m² / g, providing sufficient space for the loading of active substances, while promoting the infiltration of electrolyte and ion transport. (2) High conductivity: The graphitized carbon skeleton formed after leather carbonization has excellent conductivity (the conductivity can reach 10² S / cm), which can effectively reduce the internal resistance of the electrode and improve the rate performance of the battery. (3) Green and sustainable: The resource utilization of leather waste not only reduces the cost of carbon source but also reduces environmental pollution. (4) Surface active groups: The surface of leather after carbonization is rich in oxygen-containing functional groups (such as -OH, -COOH), and these active groups can form strong interfacial bonding with active substances, inhibiting volume expansion and material shedding during charge and discharge. In view of this, using leather porous carbon materials as the substrate of manganese oxide can achieve strong coupling of carbon-manganese oxide. This preparation method is low-cost, green and efficient, and is of great significance for promoting the practical application of manganese-based cathode materials. Summary of the Invention

[0006] The first object of the present invention is to provide a preparation method of MnO X @C composite material, which has a high specific capacity and cycle stability as the positive electrode sheet of a zinc-ion battery.

[0007] The second object of the present invention is to provide MnO X @C composite material.

[0008] The third object of the present invention is to provide a method for preparing a positive electrode sheet of a zinc-ion battery using MnO X @C composite material.

[0009] The technical solution adopted by the present invention is that the preparation method of MnO X @C composite material is specifically implemented according to the following steps: Step 1: Crush, wash and dry the leather material to obtain pretreated leather scraps; Step 2: Mix the leather scraps with an activator and carry out carbonization in an inert gas atmosphere to obtain porous carbon materials; Step 3: Disperse the obtained porous carbon materials in water, adjust the pH to neutral with a dilute hydrochloric acid solution, heat and stir, then wash several times with water and ethanol in sequence, centrifuge and dry; Step 4: Mix the material obtained in Step 3 with potassium permanganate, add deionized water, react in a microwave reactor, centrifuge and dry to obtain α-MnO2 / porous carbon materials; calcine the α-MnO2 / porous carbon materials under an inert gas to obtain MnO / C composite materials; Step 5: Mix the MnO / C composite material with potassium permanganate, add deionized water, react in a microwave reactor, centrifuge, wash, and dry to obtain MnO X @C composite material.

[0010] The characteristics of the present invention also lie in that In Step 2, the carbonization temperature is 400 - 800 °C, the carbonization time is 1 - 3 h; the mass ratio of leather scraps to the activator is 1:0.5 - 2; the activator is potassium hydroxide or zinc chloride.

[0011] In Step 3, the stirring temperature is 60 - 100 °C, the stirring time is 2 - 4 h; the concentration of the dilute hydrochloric acid solution is 0.1 - 1 mol / L.

[0012] In Step 4, the reaction temperature is 150 - 180 °C, the reaction time is 10 - 15 h; the calcination temperature is 600 - 800 °C, and the calcination time is 2 h.

[0013] In Step 5, the reaction temperature is 160 °C, and the reaction time is 4 - 8 h. The second technical solution adopted by the present invention is that the MnO X @C composite material is prepared by the preparation method of the MnO X @C composite material.

[0014] The third technical solution adopted by the present invention is a method for preparing a zinc ion battery positive electrode sheet using the MnO X @C composite material, specifically: Mix the MnO X @C composite material with conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone evenly to obtain a slurry, coat the slurry on a current collector, and dry to obtain a zinc ion battery positive electrode sheet.

[0015] The beneficial effects of the present invention are: (1) This material has a high specific capacity and excellent rate performance. Because the activated carbon substrate prepared by recycling chrome-tanned leather waste is combined with highly dispersed manganese oxides, the electrochemical active sites and ion diffusion efficiency are significantly improved; (2) This material exhibits good cycle stability. The carbon substrate provides structural support and a conductive network, effectively alleviating the volume change and structural collapse of manganese oxides during charge and discharge. In addition, this preparation method is low-cost and environmentally friendly. By using leather waste as a raw material, not only the production cost is reduced, but also waste resource utilization is realized, reducing environmental pollution.

[0016] (3)The electrode material of the present invention is tested for charge and discharge at a constant temperature of 25 °C and an electrolyte of 2M ZnSO4 within a voltage range of 0.8 - 1.8V at a current density of 0.1A / g. The initial discharge specific capacity is ≥400 mAh / g, and the specific capacity remains 95.2% after 150 charge-discharge cycles under the same conditions. Description of the Drawings

[0017] Figure 1 is the scanning electron microscope image (one) of the MnO X @C composite material prepared in Example 1 of the present invention; Figure 2 is the scanning electron microscope image (two) of the MnO X @C composite material prepared in Example 1 of the present invention; Figure 3 is the distribution map of C element in the MnO X @C composite material prepared in Example 1 of the present invention; Figure 4 is the distribution map of Mn element in the MnO X @C composite material prepared in Example 1 of the present invention; Figure 5 is the distribution map of O element in the MnO X @C composite material prepared in Example 1 of the present invention; Figure 6 is the physical picture of the positive electrode sheet prepared in Example 2 of the present invention; Figure 7 is the XRD pattern of the MnO X @C composite material prepared in Example 3 of the present invention and the standard card; Figure 8 is the cyclic voltammetry test pattern of the MnO X @C composite material prepared in Example 1 of the present invention when used as the positive electrode sheet of a zinc-ion battery; Figure 9 is the MnO prepared in Example 1 of the present invention X @C composite material when used as the positive electrode sheet of a zinc-ion battery, at 0.1Ag -1 discharge specific capacity cycle pattern at a current density; Figure 10 is the XPS spectrum of Mn element in the MnO X @C composite material prepared in Example 3 of the present invention.

[0018] Figure 11 is the charge-discharge pattern after assembling the electrode sheets prepared from the MnO / C composite material and the MnO X @C composite material prepared in Example 3 of the present invention (current is 0.1 A g -1 ). Detailed implementation mode

[0019] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation modes.

[0020] The MnO X @C composite material preparation method is specifically implemented according to the following steps: Step 1: Crush, wash and dry the leather material to obtain pretreated leather scraps; Step 2: Mix the leather scraps with an activator and carry out carbonization in an inert gas atmosphere to obtain a porous carbon material; The carbonization temperature is 400 - 800 °C, and the carbonization time is 1 - 3 h; The mass ratio of leather scraps to activator is 1:0.5 - 2; the activator is potassium hydroxide or zinc chloride; Step 3: Disperse the obtained porous carbon material in water, adjust the pH to neutral with a dilute hydrochloric acid solution, and heat and stir at 60 - 100 °C for 2 - 4 h, then wash several times with water and ethanol in sequence, centrifuge, and dry; The concentration of the dilute hydrochloric acid solution is 0.1 - 1 mol / L; Step 4: Mix the material obtained in Step 3 with potassium permanganate at a mass ratio of 1:1 - 3, add deionized water as the solvent, react in a microwave reactor, centrifuge, and dry to obtain α-MnO2 / porous carbon material; calcine the α-MnO2 / porous carbon material under an inert gas to obtain the MnO / C composite material; The reaction temperature is 150 - 180 °C, the reaction time is 10 - 15 h; the calcination temperature is 600 - 800 °C, and the calcination time is 2 h; Step 5: Mix the MnO / C composite material with potassium permanganate at a mass ratio of 1:3 - 6, add deionized water, react in a microwave reactor, centrifuge, wash, and dry to obtain the MnO X @C composite material.

[0021] The reaction temperature is 160 °C, and the reaction time is 4 - 8 h.

[0022] In the method of the present invention, leather biomass porous carbon is used as the matrix, and microwave heating is used to deposit and grow multivalent manganese oxides on the carbon matrix. The carbon skeleton is used to improve the conductivity of metal oxides, and the structure of the modified manganese oxides is more stable. Under the synergy of the double-layer adsorption of porous carbon and the insertion and extraction of Zn 2+ ions by manganese oxides, the energy storage characteristics of zinc ion batteries are optimized, and the specific capacity and stability of zinc ion batteries are improved.

[0023] The present invention adopts MnO XMethod for preparing a zinc-ion battery positive electrode sheet using a MnO@C composite material, specifically: mixing the above-mentioned MnO@C composite material with conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone to obtain a slurry, coating the slurry on a current collector, and drying to obtain a zinc-ion battery positive electrode sheet. X

[0024] The zinc-ion battery includes the above-mentioned zinc-ion battery positive electrode sheet, a battery negative electrode sheet, and an electrolyte containing a zinc salt.

[0025] Example 1 First, 5 g of leather was crushed and mixed with 7.5 g of KOH, carbonized at 500 °C for 2 hours, the activator and its by-products in the product were removed by boiling in 0.5 mol / L hydrochloric acid, and washed with ethanol and water to obtain a porous carbon matrix. 1 g of the porous carbon matrix was mixed with 3 g of KMnO4, 40 mL of water was added, and microwave reaction was carried out at 150 °C for 10 hours to generate α-MnO2 / C composite material. Then, it was calcined at 700 °C for 2 hours in a nitrogen atmosphere to obtain MnO / C. 0.3 g of MnO / C was mixed with 1.5 g of KMnO4, and microwave reaction was carried out at 160 °C for 6 hours to obtain MnO@C composite material. X

[0026] Figure 1 and Figure 2 Figure 18 is a scanning electron microscope image of the MnOx@C composite material prepared in Example 1 of the present invention. It can be seen that MnO has been successfully deposited on the porous carbon substrate. It is observed that the MnO nanoflowers are in a flaky structure and relatively dense. MnOx nanoflowers are formed on the surface of the porous carbon, which are composed of multiple nanosheets, with distinct morphological levels, significantly increasing the specific surface area, providing more electrochemically active sites, and facilitating the adsorption and reaction of Zn. 2+ At the same time, the gap between the flaky units of the nanoflowers forms a porous structure, which promotes electrolyte penetration and ion diffusion, reduces the transport resistance, and improves the rate performance. And the CV curve shows good rate performance, and the peak current increases with the increase of the sweep rate, indicating high ion diffusion efficiency. The open structure of the nanoflowers improves the wettability of the electrolyte and reduces the interfacial resistance, which is particularly important for high rate performance.

[0027] From Figures 3 - 5 it can be seen that the distributions of C, Mn, and O elements are relatively uniform, in line with the chemical composition of the material.

[0028] Example 2 The spherical nanoflower-like MnO / C composite material obtained in Example 1 was used to make an electrode according to the following method: Weigh the MnOx@C composite material, acetylene black, and polytetrafluoroethylene at a mass ratio of 70:20:10, grind them evenly and coat them on a titanium foil, and then dry them in a vacuum dryer at 100 °C for 10 hours to make a positive electrode sheet.Figure 6 (for the front and back sides of the positive electrode sheet), using metallic zinc foil as the negative electrode, 2 mol / L ZnSO4 + 0.2 mol / L MnSO4 as the electrolyte, a commercial glass fiber as the separator, and assembling a button cell using a CR2032 battery case. Figure 9 are the long-term cycling curves of the corresponding battery within the voltage range of 0.8 - 1.8 V at a current density of 0.1 A / g. It can be found that this composite electrode material has excellent cycling stability, and the specific capacity is 381.7 mAh / g after 150 cycles. -1 From Figure 8 the cyclic voltammetry curves, it can be seen that at a scan rate of 1 - 5 mV / s, the material exhibits distinct redox peaks, and the peak current increases linearly with the increase of the scan rate, indicating excellent rate performance.

[0029] Example 3 Take 5 g of leather shavings after crushing, carbonize at 500 °C for 2 hours, wash with ethanol and water and dry to obtain a porous carbon matrix. Take 0.5 g of the carbon matrix and mix it with 3 g of KMnO4, add 40 mL of water, and react under microwave at 150 °C for 10 hours to generate an α-MnO2 / C composite material. Then calcine at 700 °C for 2 hours in a nitrogen atmosphere to obtain MnO / C. Take 0.2 g of MnO / C and mix it with 0.8 g of KMnO4, add 40 mL of water, and react under microwave at 160 °C for 6 hours to obtain the final material. Figure 7 The XRD patterns and standard cards in Figure 10 show that MnO and amorphous carbon exist in the sample. And

[0030] Example 4 Prepare a positive electrode sheet from the MnOx@C composite material prepared in Example 3 according to the method of Example 2, assemble it into a button cell. At a current density of 0.1 A / g, -1 its reversible capacity reaches 395 mAh / g. -1 In addition, prepare a positive electrode sheet from the MnO / C composite material using the method of Example 2 and assemble it into a battery. Figure 11 is the charge-discharge comparison diagram of the battery assembled with the MnO / C composite material and the battery assembled with the MnOx@C composite material. It can be seen that the secondary microwave heating significantly improves its specific capacity and structural stability.

[0031] Example 5 Take 5 g of leather scraps after crushing and mix them with 10 g of ZnCl2. Carbonize at 500 °C for 2 hours, wash with ethanol and water multiple times, and dry to obtain a porous carbon matrix. Take 0.5 g of the carbon matrix and mix it with 3 g of KMnO4, add 40 mL of water, and react under microwave at 150 °C for 10 hours to generate an α-MnO2 / C composite material. Then, calcine at 700 °C for 2 hours under a nitrogen atmosphere to obtain MnO / C. Take 0.2 g of MnO / C and mix it with 0.6 g of KMnO4, add 40 mL of water, and react under microwave at 160 °C for 6 hours to obtain the final material.

[0032] Example 6 Prepare an electrode from the MnOx@C composite material prepared in Example 5 according to the method of Example 2, assemble it into a button cell, and at a current density of 0.1 A g -1 , its reversible capacity is 387 mAh g -1 . At a rate of 0.3 A g-1, the discharge capacity of the battery is close to 300 mAh g -1 .

[0033] Using the method of the present invention, a MnO X @C composite material with high specific capacity and capacity retention rate is prepared by in-situ growth of manganese oxide with leather biomass precursor through multi-step carbonization. Through the processes of potassium permanganate oxidation and high-temperature carbonization, the uniform composite of manganese oxide and carbon matrix is realized. The composite material of the present invention significantly improves the ion diffusion rate and inhibits volume expansion. When used as the positive electrode of a button zinc-ion battery, it has a high specific capacity and good capacity retention rate. In addition, the process of the present invention is green and efficient, and the raw material cost is low, improving the charge storage ability of the zinc-ion battery.

Claims

1. MnO X @C A method for preparing a composite material, characterized in that: Follow the steps below to implement it: Step 1: crushing, cleaning and drying the leather material to obtain pre-treated leather scraps; Step 2: Mix the leather scraps with an activator and carbonize them in an inert gas atmosphere to obtain a porous carbon material; Step 3: Disperse the obtained porous carbon material in water, adjust the pH to neutral with a dilute hydrochloric acid solution, heat and stir, then wash with water and ethanol several times, centrifuge, and dry; Step 4: Mix the material obtained in step 3 with potassium permanganate, add deionized water, react in a microwave reactor, centrifuge, and dry to obtain an α-MnO2 / porous carbon material; calcine the α-MnO2 / porous carbon material under an inert gas to obtain a MnO / C composite material; Step 5: Mix the MnO / C composite material with potassium permanganate, add deionized water, react in a microwave reactor, centrifuge, wash, and dry to obtain MnO X @CComposite materials.

2. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In the step 2, the carbonization temperature is 400-800° C., the carbonization time is 1-3 hours, the mass ratio of leather scraps to activator is 1:0.5-2, and the activator is potassium hydroxide or zinc chloride.

3. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In step 3, the stirring temperature is 60-100° C., and the stirring time is 2-4 hours; the concentration of the dilute hydrochloric acid solution is 0.1-1 mol / L.

4. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In step 4, the reaction temperature is 150-180° C., and the reaction time is 10-15 hours; the calcination temperature is 600-800° C., and the calcination time is 2 hours.

5. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In step 4, the mass ratio of the material to potassium permanganate is 1:1-3.

6. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In step 5, the reaction temperature is 160° C. and the reaction time is 4 to 8 hours.

7. MnO as claimed in claim 1 X @C A method for preparing a composite material, characterized in that: In the step 5, the mass ratio of the MnO / C composite material to potassium permanganate is 1:3-6.

8. MnO according to any one of claims 1 to 7 X @C Composite material preparation method prepared MnO X @CComposite materials.

9. Using MnO as described in any one of claims 1 to 7 X A method for preparing a positive electrode sheet for a zinc ion battery using a composite material, characterized in that: Specifically: MnO X The @C composite material is uniformly mixed with conductive carbon black, polyvinylidene fluoride and N-methylpyrrolidone to obtain a slurry, and the slurry is coated on a current collector and dried to obtain a positive electrode sheet of a zinc ion battery.

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