CN108199032B - Preparation of carbon-coated nano hollow bismuth simple substance and application of alkaline battery - Google Patents

Abstract

The invention relates to the preparation of carbon-coated nanometer hollow bismuth element and research on its application in alkaline batteries, and belongs to the technical field of alkaline batteries. Although nano-metal bismuth has good electrical conductivity and electrochemical properties, it has poor structural stability in the electrolyte environment. In order to improve its stability and cycle efficiency, we proposed an effective method to confine nano-hollow bismuth in a carbon microreactor. The method is as follows: First, hollow bismuth ammonium fluoride (NH ₄ Bi ₃ F ₁₀ ) precursor; then, the carbon coating of the precursor is realized by polymerizing dopamine molecules at room temperature; finally, the obtained product is carbonized at low temperature to obtain the carbon-coated nano-hollow bismuth element. When applied to alkaline batteries, the composite can exhibit superior rate performance and cycle durability. The preparation process involved is very simple, it is easy to realize large-scale production, the product has stable structure and properties, and has practical prospect and commercial value.

Description

Preparation of carbon-coated hollow bismuth nanomaterials and their application in alkaline batteries

technical field

The invention belongs to the technical field of alkaline batteries, and in particular relates to a preparation method and application of a negative electrode material for an alkaline battery.

Background technique

With the increasingly serious problems of fossil energy depletion and environmental degradation, the development and utilization of green energy (including wind energy, tidal energy and solar energy, etc.) have become particularly important. Although these energy sources can be converted into electricity and are sustainable, their utilization is often limited by external factors such as time, place, and weather. In order to facilitate the needs of daily life, developing a battery system to collect the converted electrical energy is the most effective strategy at present. In recent years, lithium batteries have dominated the field of rechargeable energy storage. However, the current lithium battery is facing many serious problems. In addition to the lack of lithium and other mineral resources, it also includes battery explosion, waste battery pollution and safe recycling. The root of the problem is related to the highly toxic and flammable organic electrolyte. Therefore, the development of safe and high-performance batteries is an important trend in today's development.

Compared with lithium batteries, the electrolyte of alkaline batteries is an ordinary aqueous solution, which is cheap and low in toxicity. At present, many types of rechargeable and dischargeable alkaline battery systems (including nickel-hydrogen, nickel-iron, nickel-bismuth batteries, etc.) have been proposed. It is worth emphasizing that new bismuth-based alkaline batteries are receiving widespread attention from the global scientific research community. For example, Liu Jinping's research group from Wuhan University of Technology recently directly grown bismuth oxide nanofilms on titanium electrodes and used them in alkalis. field of battery energy storage. But unfortunately, almost all developed bismuth-based anode materials are oxides or hydroxides with poor conductivity, which will directly affect the fast charge-discharge characteristics of batteries. In comparison, metal bismuth has better electrical conductivity and electrochemical reactivity, and the theoretical specific capacity is much higher than other bismuth oxides/hydroxides. However, the metal bismuth element is easily corroded and oxidized in the electrolyte environment, and its chemical structure stability is poor, which has become a fatal problem for the further application and development of this material.

In order to improve its stability and realize the bismuth-based alkaline battery with fast charge-discharge point function, we propose an effective synthesis method for confining nano-hollow bismuth in a carbon microreactor. A nanometer hollow bismuth ammonium fluoride (NH ₄ Bi ₃ F ₁₀ ) precursor was synthesized; then, the precursor was coated by dopamine molecular polymerization at room temperature; finally, the obtained product was subjected to low-temperature carbonization treatment to obtain carbon Coated nanometer hollow bismuth element. On the one hand, the hollow metal bismuth nanostructure provides a larger specific surface area, which enables the electrode to fully contact the electrolyte and accelerates the electrochemical reaction rate of the system; on the other hand, the hollow metal bismuth and the carbon shell form better synergistic effect. The inner metal bismuth has excellent electrical conductivity and electrochemical activity, while the outer carbon layer enhances the chemical structure stability of the bismuth core and effectively inhibits the fragmentation and agglomeration of the active material. It is worth emphasizing that the preparation method and conditions are very simple, it is easy to realize large-scale production, and the product has stable structure and properties, and has practical prospects and commercial value.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to: (1) provide a preparation method of carbon-coated metal nano hollow bismuth; (2) provide a cobalt/nickel-bismuth high power density rechargeable and dischargeable alkaline full battery.

To achieve the above object, the present invention provides the following technical solutions:

1. The preparation of carbon-coated nano hollow bismuth element and its application in alkaline batteries, including the following steps:

(1) Material synthesis: Using bismuth salt and fluorine salt as raw materials, making them react in a reaction solvent, and adopting a room temperature liquid phase method and low temperature carbonization treatment to obtain a carbon-coated nano-hollow bismuth composite negative electrode material;

(2) Preparation of electrode sheet: Add the negative electrode material, conductive agent and binder to the solvent, stir at room temperature to obtain a black viscous slurry, apply it on the current collector electrode, and dry it to obtain carbon Electrode coated with nano hollow bismuth element;

(3) Electrode activation and performance testing: The carbon-coated nano-hollow bismuth element prepared in (2) was activated by cyclic voltammetry; Discharge and cycle performance testing;

(4) Full battery assembly and testing: the carbon-coated CoNi ₃ O ₄ nanoarray thin-film positive electrode was used as the positive electrode, and the carbon-coated metal nano-hollow bismuth element activated in step (3) was used as the negative electrode, 6 mol/ L sodium hydroxide solution is used as the electrolyte, and cellulose filter paper is used as the diaphragm material. The positive electrode, the diaphragm, and the negative electrode are stacked in sequence, and after injecting the electrolyte, they are thermoplastically encapsulated in a transparent polyethylene film, that is, the alkaline cobalt is completed. / Assembly of nickel-bismuth full cells; then performance testing of full cells.

Further, the bismuth salt in the step (1) is bismuth nitrate pentahydrate, the fluoride salt is ammonium fluoride, and the reaction solvent is ethylene glycol.

Further, the conductive agent in the step (2) is carbon black; the adhesive in the step (2) is polyvinylidene fluoride (PVdF); the solvent in the step (2) is N-methyl methacrylate pyrrolidone; the collector electrode in the step (2) is nickel foam.

Further, in the step (2), the mass ratio of the negative electrode material, the conductive agent and the binder is 8:1:1.

Further, the drying treatment in the step (2) is to stand for 10 hours under the baking condition of 120 ^° C.

Further, the electrode activation in the step (3) includes the following steps: immersing the carbon-coated nano hollow bismuth element electrode prepared in the step (2) into a 6 mol/L sodium hydroxide solution, using Ag/AgCl as a parameter The specific electrode, the platinum wire electrode as the counter electrode, was subjected to 100-200 cycles of cyclic voltammetry scanning on the electrochemical workstation at a rate of 50 mV/s.

Further, the preparation method of the carbon-coated CoNi ₃ O ₄ nanoarray thin film cathode sheet in the step (4) is as follows: 0.7 g Ni(NO ₃ ) ₂ ·6H ₂ O, 0.4 g Co(NO ₃ ) ₂ · 6H ₂ O, 0.2 g NH ₄ F and 0.75 g CO(NH ₂ ) ₂ were ultrasonically dispersed in 50 mL of distilled water; then, the above mixture was transferred into a 100 mL reactor liner, and a stainless steel sheet (size : 40 × 25 × 0.5 mm) immersed in the solution, sealed the reactor and reacted at a constant temperature of 120 ^o C for 4 hours; after the reactor was cooled, take out the stainless steel sheet and rinse it with distilled water for three times, and soak it in 0.1 g dopamine (DA) molecule solution; after immersion at room temperature for 6 hours, the stainless steel sheet was taken out and the surface was rinsed with distilled water, and then the sample was placed in a quartz tube furnace in an argon atmosphere and heated at 600 ^o C for 1 hour.

Further, the mass ratio of the negative electrode sheet to the positive electrode sheet in the full battery test in the step (4) is 7:10.

2. The beneficial effects of the present invention are as follows: the present invention discloses an effective and low-cost novel preparation method of carbon-coated metal nano-hollow bismuth and its application in alkaline batteries. When applied to alkaline batteries, the composite can exhibit superior rate performance and cycle durability. The preparation process involved is very simple, it is easy to realize large-scale production, the product has stable structure and properties, and has practical prospects and commercial value.

Description of drawings

In order to make the purpose, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings for description:

1 is a scanning electron microscope (a) and an X-ray diffraction (XRD) spectrum (b) of the negative electrode material used in Example 1;

Fig. 2 is the discharge curve diagram of different current densities of the negative electrode material used in Example 2;

Figure 3 is a specific capacity diagram (a) and a cycle life diagram (b) of the negative electrode material used in Example 2 under different current densities;

Fig. 4 is the discharge curve diagram of different current densities of the full battery of Example 2;

FIG. 5 is the specific capacity diagram (a) and cycle life diagram (b) of the full battery of Example 2 under different current densities.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Example 1 Synthesis of carbon-coated metal nano-hollow bismuth anode material

(1) Synthesis of ammonium bismuth fluoride (NH ₄ Bi ₃ F ₁₀ ) precursor: Take 0.2 g Bi(NO ₃ ) ₃ ·6H ₂ O and 0.6 g NH ₄ F respectively in 25 mL of ethylene glycol and centrifuge Dissolve by vortexing in the tube. The above two solutions were mixed evenly, placed at room temperature for 12 hours, filtered and washed, and dried at 60 ^o C for 8 hours to obtain the NH ₄ Bi ₃ F ₁₀ precursor material.

(2) Synthesis of carbon-coated metal nano-hollow bismuth anode material: take 0.4 g of NH ₄ Bi ₃ F ₁₀ into a solution containing 0.1 g of dopamine molecules and stir at room temperature for 6 hours, centrifuge and rinse with absolute ethanol for many times, and then at 60 The samples were dried at ^oC for 8 hours to obtain gray NH ₄ Bi ₃ F ₁₀ @PDA nanopowders. Next, carbon-coated metal nano-hollow bismuth material was obtained by carbonizing at a low temperature of 400 ^° C for 30 minutes in an argon atmosphere. The example results can be seen in Figure 1.

Figure 1(a) shows the microscopic morphology of the obtained product. The surface sample is in the shape of hollow nanospheres with an average size of about 70 nm. Figure 1(b) is the X-ray diffraction (XRD) phase analysis result of the product. It can be seen from the figure that the diffraction peak of the prepared sample is consistent with the standard card peak, indicating that the sample prepared by this method is a metal bismuth material.

Embodiment 2 Making and testing method of alkaline full battery with carbon-coated metal nano-hollow bismuth as negative electrode

(1) Production of negative electrode pole piece: after mixing the negative electrode material, the conductive agent and the binder in a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone solvent and stir for 12 hours to obtain a black viscous slurry material. Apply the slurry evenly on the foam nickel current collector electrode with a scraper, and vacuum dry at 120 ^o C for 12 hours to obtain a negative electrode piece.

(2) Activation and testing of electrode sheet: The electrode sheet prepared in step (2) was used as the working electrode, Ag/AgCl and platinum wire were the reference electrode and counter electrode, respectively, and 6 mol/L sodium hydroxide solution was used for electrolysis. The electrode prepared in step (2) was cyclically scanned for 100-200 cycles on the electrochemical workstation at a scan rate of 50 mV/s. After the activation, the electrode sheets were subjected to cyclic voltammetry tests and constant current charge-discharge tests at different rates. The results of the examples are shown in FIGS. 2 and 3 .

(3) Full battery assembly and testing: the carbon-coated CoNi ₃ O ₄ nanoarray thin film cathode was used as the working battery, the carbon-coated metal nano-hollow bismuth was used as the negative electrode, and the 6 mol/L sodium hydroxide solution was used for the electrolysis liquid, and cellulose filter paper is used as the membrane material. The positive electrode, the separator and the negative electrode are stacked in sequence, and the electrolyte is injected and then thermoplastically encapsulated in a transparent polyethylene film to complete the assembly of the full battery. After the full battery was activated by cyclic voltammetry for several cycles, cyclic voltammetry tests and constant current charge-discharge tests at different rates were carried out on an electrochemical workstation. The results of the examples are shown in Figures 4 and 5 .

FIG. 2 is the constant current discharge curve of the prepared carbon-coated metal nano-hollow bismuth negative electrode material under different current densities. It can be seen that when the discharge current density is changed from 1 A/g to 32 A/g, the charge-discharge platform of the battery does not change greatly, indicating the excellent electrochemical kinetic properties of the material system.

Figure 3(a) shows the specific capacity of the electrode at different current densities. At a discharge current density of 1 A/g, the electrode specific capacity is as high as 110 mAh/g; even when the current density reaches 32 A/g, its capacity can still be maintained at 83 mAh/g, which proves the carbon-coated metal nano-hollow bismuth Superior rate performance. Figure 3(b) is the cycle life diagram of the electrode. After 10,000 cycles of charge and discharge at a current density of 0.5 A/g, the specific capacity has almost no major attenuation, and the capacity retention rate can reach 96%, which fully confirms The carbon-coated metal nano-hollow bismuth has excellent cycling performance.

Figure 4 shows the constant current discharge curves of the prepared cobalt/nickel-bismuth full cells at different current densities. It can be seen that at the discharge current density of 0.5 A/g, the main discharge platform of the full cell is 0.9 V; even when the current density is increased by more than 30 times (to 16 A/g), the main discharge platform of the full cell remains. can be maintained at around 0.8 V.

Figure 5(a) shows the specific capacity of the battery calculated according to Figure 4. At current densities of 0.5, 1, 2, 4, 8, and 16 A/g, the charge-discharge specific capacities of the material are 80, 72, 63, and 80, respectively. 57, 48, and 36.5 mAh/g, reflecting the rate capability of the cobalt/nickel-bismuth full cell. Figure 5(b) is the cycle life diagram of the full battery at 0.5 A/g ^/ current density. After 2000 charge-discharge cycle tests, the capacity retention rate of the full battery can still reach 88%, which fully reflects its large capacity. practical application potential.

Claims (8)

1. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material is characterized by comprising the following steps of: (1) material synthesis: bismuth salt and fluorine salt are used as raw materials and are reacted in a reaction solvent, and a room temperature liquid phase method and low temperature carbonization treatment are adopted to obtain the carbon-coated nano hollow bismuth composite negative electrode material; (2) preparing an electrode slice: adding a negative electrode material, a conductive agent and an adhesive into a solvent, stirring at room temperature to obtain black viscous slurry, and coating the black viscous slurry on a current collectorPerforming electrode treatment, and drying to obtain a carbon-coated nano hollow bismuth simple substance electrode slice; (3) electrode activation and performance detection: activating the carbon-coated nano hollow bismuth elemental electrode prepared in the step (2) by using a cyclic voltammetry scanning method; after activation is finished, constant current charging and discharging with different multiplying powers and cycle performance detection are carried out on the electrode slice; (4) assembling and testing the full battery: coating carbon with CoNi₃O₄The nano-array film positive plate is used as a positive electrode, the activated carbon-coated metal nano hollow bismuth simple substance electrode in the step (3) is used as a negative electrode, 6mol/L sodium hydroxide solution is used as electrolyte, and cellulose filter paper is used as a diaphragm material; and stacking the positive electrode, the diaphragm and the negative electrode in sequence, injecting electrolyte, then encapsulating the electrolyte in a transparent polyethylene film in a thermoplastic manner, namely completing the assembly of the alkaline cobalt/nickel-bismuth full battery, and then carrying out performance detection on the full battery.

2. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material as claimed in claim 1, wherein the bismuth salt in the step (1) is bismuth nitrate pentahydrate, the fluorine salt is ammonium fluoride, and the reaction solvent is ethylene glycol.

3. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material as claimed in claim 1, wherein the conductive agent in the step (2) is carbon black; the adhesive in the step (2) is polyvinylidene fluoride (PVdF); the solvent in the step (2) is N-methyl pyrrolidone; the current collector electrode in the step (2) is foamed nickel.

4. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material as claimed in claim 1, wherein the mass ratio of the anode material, the conductive agent and the binder in the step (2) is 8:1: 1.

5. the preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material according to claim 1, characterized by comprising the following steps(2) Middle drying treatment at 120^oAnd C, standing for 10 hours under the baking condition.

6. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material as claimed in claim 1, wherein the activation of the electrode sheet in the step (3) comprises the following steps: and (3) immersing the electrode slice of the carbon-coated nano hollow bismuth simple substance prepared in the step (2) into 6mol/L sodium hydroxide solution, taking Ag/AgCl as a reference electrode, taking a platinum wire electrode as a counter electrode, and carrying out 100-loop 200-loop cyclic voltammetry scanning process on the electrode slice at the rate of 50 mV/s on an electrochemical workstation.

7. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material as claimed in claim 1, wherein the carbon-coated CoNi in the step (4)₃O₄The preparation method of the nano-array film positive plate comprises the following steps: 0.7 g of Ni (NO)₃)₂·6H₂O、0.4 g Co(NO₃)₂·6H₂O、0.2 g NH₄F and 0.75 g CO (NH)₂)₂Ultrasonically dispersing in 50 mL of distilled water; then, the mixture was transferred to a 100 mL reactor liner, a stainless steel sheet 40X 25X 0.5 mm in size was dipped in the solution, the reactor was sealed and the contents were heated to 120 deg.C^oC, reacting for 4 hours under the constant temperature condition; after the reaction kettle is cooled, taking out the stainless steel sheet, washing the stainless steel sheet with distilled water for three times, and soaking the stainless steel sheet in a solution containing 0.1 g of Dopamine (DA) molecules; after immersing at room temperature for 6 hours, the stainless steel sheet was taken out and the surface thereof was rinsed with distilled water, and then the sample was placed in a quartz tube furnace 600 in an argon atmosphere^oC was heated for 1 hour.

8. The preparation method of the alkaline battery containing the carbon-coated nano hollow bismuth composite anode material according to claim 1, wherein the mass ratio of the anode plate to the cathode plate in the full battery test in the step (4) is 7: 10.

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