Method for preparing positive electrode of hydrogen fuel cell by using waste manganese-based sodium-ion battery

Abstract

The invention relates to the technical field of positive electrodes of hydrogen fuel cells, in particular to a method for preparing a positive electrode of a hydrogen fuel cell by using a waste manganese-based sodium-ion battery, which comprises the following steps: placing the waste manganese-based sodium-ion battery in a NaCl solution for discharging to obtain an electroless manganese-based sodium-ion battery; the method comprises the following steps of: crushing the waste carbon into manganese-based sodium-ion battery slag, blowing the slag to obtain manganese-based sodium-ion battery slag without a diaphragm and a plastic skin, soaking the manganese-based sodium-ion battery slag into an organic solvent, completely separating the waste carbon of the negative electrode from a current collector under the assistance of ultrasonic waves to obtain a clear solution, and preparing graphene oxide from the waste carbon of the negative electrode by utilizing a Hummers method; adjusting the pH value of the clarified solution, filtering to obtain sodium carbonate filter residues and manganese ion-containing filtrate, mixing graphene oxide and the filtrate, stirring, heating and drying to obtain the manganese-doped graphene catalyst, and applying the manganese-doped graphene catalyst to the positive electrode of the hydrogen fuel cell. The method can realize controllable full recovery of positive and negative electrode waste materials; selected materials are cheap and easy to control; and the prepared manganese-doped graphene catalyst has a good application effect.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen fuel cell positive electrodes, and in particular to a method for preparing a hydrogen fuel cell positive electrode by utilizing waste manganese-based sodium ion batteries. Background Art

[0002] Sodium-ion batteries have obvious advantages such as high sodium abundance, uniform distribution, and low price. At the same time, because sodium-ion batteries have high specific capacity and extremely high safety, and their structure is highly similar to that of lithium-ion batteries, the production of sodium-ion batteries can basically follow the mature manufacturing route of lithium-ion batteries, thereby effectively reducing production costs. It has become a general trend for them to replace lead-acid batteries and low-end lithium-ion batteries and provide energy for low-speed mobile tools. However, this also means that a large number of retired sodium-ion batteries will be produced in the near future. Sodium-ion batteries are rich in carbon materials and heavy metal elements. Taking the most typical Prussian white sodium-ion battery as an example, its positive electrode contains a large amount of heavy metal manganese. Improper treatment will lead to serious environmental pollution and waste of resources. Therefore, it is very urgent to develop technical solutions for the recycling and functional utilization of sodium-ion batteries.

[0003] In addition, the value of manganese-containing waste in the positive electrode and waste carbon in the negative electrode of sodium-ion batteries is relatively low, resulting in low cost-effectiveness of recycling and weak willingness of enterprises to recycle. If these materials are not handled properly, it will lead to resource waste and environmental pollution. Therefore, using waste manganese-based sodium-ion batteries as raw materials to develop universal and reliable recycling and resource utilization technologies can alleviate and avoid environmental pollution problems while bringing rich economic benefits. As a new type of high-performance energy storage device, the smooth operation of hydrogen fuel cells is inseparable from the role of efficient catalytic positive electrodes, and properly treated Mn-doped graphene is an ideal positive electrode catalyst that can effectively promote the oxygen reduction process in fuel cells, thereby promoting the improvement of fuel cell performance.

[0004] In view of the above situation, using waste manganese-based sodium-ion batteries as raw materials, developing universal and reliable recycling and resource utilization technologies to prepare low-value and toxic waste into Mn-doped graphene for hydrogen fuel cells can bring economic benefits while alleviating and avoiding environmental pollution caused by waste sodium-ion batteries. Summary of the invention

[0005] In view of the above problems, a method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries is provided. The toxic heavy metal ions Mn contained in the positive electrode of the sodium ion battery and the negative electrode waste carbon are prepared into Mn-doped graphene through the preparation method, and the graphene is applied in the positive electrode of the hydrogen fuel cell.

[0006] In order to solve the problems of the prior art, the present invention provides a method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries, and the preparation method comprises the following steps:

[0007] Step S1: placing the waste manganese-based sodium ion battery in a NaCl solution for discharge to obtain an electroless manganese-based sodium ion battery; Step S2: crushing the electroless manganese-based sodium ion battery to obtain a manganese-based sodium ion battery slag; Step S3: blowing the manganese-based sodium ion battery slag to obtain a manganese-based sodium ion battery slag free of a diaphragm and a plastic skin; Step S4: immersing the manganese-based sodium ion battery slag free of a diaphragm and a plastic skin in an organic solvent, and completely separating the negative electrode waste carbon from the current collector under the assistance of ultrasound , obtaining a clarified solution; step S5: preparing graphene oxide from the negative electrode waste carbon in step S4 by Hummers method; step S6: adjusting the pH value of the clarified solution in step S4, filtering to obtain sodium carbonate residue and a filtrate containing manganese ions; step S7: mixing, heating and drying the graphene oxide in step S5 and the filtrate in step S6 under stirring conditions to obtain a manganese-doped graphene catalyst; step S8: using the manganese-doped graphene catalyst in step S7 for the positive electrode of a hydrogen fuel cell.

[0008] Preferably, the concentration of the NaCl solution in step S1 is 1M or 1.25M or 1.5M.

[0009] Preferably, the crushing process in step S2 is crushing by a crusher, manual crushing or frozen crushing.

[0010] Preferably, the blowing process in step S3 is a high-speed airflow field, a medium-speed airflow field, or a low-speed airflow field.

[0011] Preferably, the organic solvent in step S4 is N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0012] Preferably, the waste carbon concentration used in the Hummers method in step S5 is 1.0 g / L, 1.5 g / L or 2.0 g / L.

[0013] Preferably, the pH value in step S6 is in the range of 11±0.5.

[0014] Preferably, in step S6, the pH value of the clear solution is adjusted by using concentrated ammonia water, sodium hydroxide or sodium bicarbonate.

[0015] Preferably, in step S7, the concentration of graphene oxide in the filtrate is 1.2 g / L or 1.4 g / L or 1.6 g / L.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The present invention makes full use of the positive and negative electrode waste materials of waste sodium ion batteries, converts them into high-efficiency catalysts as a whole, and realizes the controllable full recovery of the positive and negative electrode waste materials.

[0018] 2. The solvent, dispersant and precipitant used in the preparation of the present invention are cheap and easy to obtain, the processing conditions are easy to control, the equipment is simple and easy to operate, and the preparation process has good continuity, which provides the possibility for large-scale production.

[0019] 3. The manganese-doped graphene catalyst prepared by the present invention has high discharge voltage, high discharge capacity and good cycle performance when applied to hydrogen fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The present invention is a preparation flow chart of a method for preparing a positive electrode of a hydrogen fuel cell by utilizing waste manganese-based sodium ion batteries.

[0021] Figure 2 This is a scanning electron microscope image of a manganese-doped graphene catalyst.

[0022] Figure 3 This is a transmission electron microscopy image of a manganese-doped graphene catalyst.

[0023] Figure 4 This is the X-ray diffraction pattern of manganese-doped graphene catalyst. DETAILED DESCRIPTION

[0024] In order to further understand the features, technical means, specific objectives and functions of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0025] Reference Figure 1-Figure 4 :A method for preparing a positive electrode for a hydrogen fuel cell using waste manganese-based sodium ion batteries, the preparation method comprising the following steps:

[0026] Step S1: placing the waste manganese-based sodium ion battery in a NaCl solution for discharge to obtain an electroless manganese-based sodium ion battery;

[0027] Step S2: crushing the electroless manganese-based sodium ion battery to obtain manganese-based sodium ion battery slag;

[0028] Step S3: blowing the manganese-based sodium ion battery slag to obtain a manganese-based sodium ion battery slag free of a diaphragm and a plastic skin;

[0029] Step S4: soaking the manganese-based sodium ion battery slag material without a separator and a plastic skin in an organic solvent, and completely separating the negative electrode waste carbon from the current collector under the assistance of ultrasound to obtain a clarified solution;

[0030] Step S5: preparing graphene oxide from the negative electrode waste carbon in step S4 using the Hummers method;

[0031] Step S6: adjusting the pH value of the clarified solution in step S4, filtering to obtain a sodium carbonate residue and a filtrate containing manganese ions;

[0032] Step S7: mixing, heating and drying the graphene oxide in step S5 and the filtrate in step S6 under stirring conditions to obtain a manganese-doped graphene catalyst;

[0033] Step S8: Using the manganese-doped graphene catalyst in step S7 as a positive electrode of a hydrogen fuel cell.

[0034] Reference Figure 1 : The concentration of the NaCl solution in step S1 is 1M or 1.25M or 1.5M.

[0035] Reference Figure 1 : The crushing process in step S2 is crusher crushing, manual crushing or frozen crushing.

[0036] Reference Figure 1 : The blowing process in step S3 is a high-speed airflow field, a medium-speed airflow field, or a low-speed airflow field.

[0037] Reference Figure 1 : The organic solvent in step S4 is N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0038] Reference Figure 1 : The waste carbon concentration used in the Hummers method in step S5 is 1.0 g / L, 1.5 g / L or 2.0 g / L.

[0039] Reference Figure 1 : The range of pH value in step S6 is 11±0.5.

[0040] Reference Figure 1 : In step S6, the pH value of the clarified solution is adjusted by using concentrated ammonia water, sodium hydroxide or sodium bicarbonate.

[0041] Reference Figure 1 : The concentration of graphene oxide in the filtrate in step S7 is 1.2 g / L or 1.4 g / L or 1.6 g / L.

[0042] Working principle: Physical methods are used to crush waste manganese-based sodium ion batteries into powder residues. By virtue of the differences in mass between the internal positive electrode active material, negative electrode waste carbon, diaphragm, plastic skin, current collector, steel shell and other components, the light component diaphragm and plastic skin are separated from the heavy component positive and negative electrode materials and current collector, steel shell in the air flow field. The solid component is further separated from the liquid component by the difference in solubility of organic solution to inorganic and organic matter. At the same time, by virtue of the difference in density of each component, the low-density waste carbon, medium-density active material, high-density steel shell and aluminum current collector are separated by buoyancy. Sodium and manganese elements are separated under the action of precipitant. After the waste carbon is converted into graphene by Hummers method, the specific surface area of ​​carbon is significantly increased. By virtue of the large surface area of ​​graphene and the good electrostatic adsorption of metal ions, heavy metal manganese is adsorbed on the surface of graphene, and manganese is embedded in the surface and inside of the graphene carbon layer at high temperature to form a manganese-doped graphene catalyst.

[0043] Embodiment 1:

[0044] A method for preparing a fuel cell cathode using waste manganese-based sodium ion batteries comprises the following steps:

[0045] (1) Soaking the used manganese-based sodium ion batteries in 1.0 M NaCl salt water, and then drying the batteries for later use;

[0046] (2) Using a crusher to crush the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a high-speed air flow field, and immersing the obtained waste in N,N-dimethylformamide, filtering the mixed waste after ultrasonic treatment for 30 minutes, separating the upper waste carbon, the middle positive electrode active material and the lower steel shell and the current collector, and preparing the upper waste carbon into graphene using a 1.0 g / L Hummers method; immersing the positive electrode active material in malic acid and stirring for 12 hours, adjusting the pH value to 11.0 using concentrated ammonia water, filtering and separating the filtrate and the manganese ion-containing residue; stirring the graphene and the manganese ion-containing filtrate at a concentration of 5 mg / mL, and heating and drying at 100°C for 18 hours;

[0047] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0048] Comparative Example 1:

[0049] (1) Soaking the used manganese-based sodium ion batteries in 1.0 M NaCl salt water, and then drying the batteries for later use;

[0050] (2) Using a crusher to crush the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a high-speed air flow field, and immersing the obtained waste in N-methylpyrrolidone, filtering the mixed waste after ultrasonic treatment for 30 minutes, separating the upper waste carbon, the middle positive electrode active material and the lower steel shell and the current collector, and preparing the upper waste carbon into graphene using a 1.0 g / L Hummers method; immersing the positive electrode active material in citric acid and stirring for 12 hours, adjusting the pH value to 11.0 using concentrated ammonia water, filtering and separating the filtrate and the manganese ion-containing residue; stirring the graphene and the manganese ion-containing filtrate at a concentration of 5 mg / mL, and heating and drying at 100°C for 18 hours;

[0051] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0052] The comparison results show that due to the better solubility of N-methylpyrrolidone in the electrolyte, the purity of the active substances and waste carbon in the subsequent waste is higher. The manganese-doped graphene prepared in Comparative Example 1 has higher purity; a larger specific surface area of ​​287m2 / g; better migration and anchoring effects of Mn atoms; and assembled into a fuel cell, it has a higher discharge capacity at a current density of 100mA / g.

[0053] Embodiment 2:

[0054] (1) Soak the waste manganese-based sodium ion batteries in 1.25 M NaCl salt water, and then dry the batteries for later use;

[0055] (2) Using freeze crushing to crush the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a high-speed air flow field, and immersing the obtained waste in N-methylpyrrolidone. After ultrasonic treatment for 30 minutes, the mixed waste is filtered to separate the upper waste carbon, the middle positive electrode active material and the lower steel shell and the current collector, and the upper waste carbon is prepared into graphene using a 1.5 g / L Hummers method; the positive electrode active material is immersed in malic acid and stirred for 12 hours, and the pH value is adjusted to 11.0 using concentrated ammonia water, and the filtrate and the manganese ion-containing residue are separated by filtering; the graphene and the manganese ion-containing filtrate are evenly stirred at a concentration of 5 mg / mL, and heated and dried at 100°C for 18 hours;

[0056] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0057] Comparative Example 2:

[0058] (1) Soak the waste manganese-based sodium ion batteries in 1.25 M NaCl salt water, and then dry the batteries for later use;

[0059] (2) Using freeze crushing to crush the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a medium-speed air flow field, and immersing the obtained waste in N-methylpyrrolidone. After ultrasonic treatment for 60 minutes, the mixed waste is filtered to separate the upper waste carbon, the middle positive electrode active material and the lower steel shell and the current collector, and the upper waste carbon is prepared into graphene using a 1.5 g / L Hummers method; the positive electrode active material is immersed in malic acid and stirred for 12 hours, and the pH value is adjusted to 11.0 using concentrated ammonia water, and the filtrate and the manganese ion-containing residue are filtered and separated; the graphene and the manganese ion-containing filtrate are evenly stirred at a concentration of 5 mg / mL, and heated and dried at 100°C for 18 hours;

[0060] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0061] The comparison results show that the medium-speed air flow field can satisfy the separation of different components in the waste and reduce the loss of powder residue; at the same time, due to the increase in ultrasonic time, the positive and negative electrode materials fall off from the collector more completely, the waste prepared in Comparative Example 1 is of higher quality, and more manganese-doped graphene can be prepared; the fuel cell assembled has a higher discharge capacity at a current density of 100mA / g.

[0062] Embodiment 3:

[0063] (1) Soak the waste manganese-based sodium ion batteries in 1.5 M NaCl salt water, and then dry the batteries for later use;

[0064] (2) Mechanically crushing the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a medium-speed air flow field, and immersing the obtained waste in N,N-dimethylformamide. After ultrasonic treatment for 60 minutes, filtering the mixed waste to separate the upper waste carbon, the middle positive electrode active material, and the lower steel shell and the current collector, and preparing the upper waste carbon into graphene using a 2.0 g / L Hummers method; immersing the positive electrode active material in citric acid and stirring for 12 hours, adjusting the pH value to 11.5 with concentrated ammonia water, filtering and separating the filtrate and the manganese ion-containing residue; stirring the graphene and the manganese ion-containing filtrate at a concentration of 5 mg / mL, and heating and drying at 120°C for 24 hours;

[0065] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0066] Comparative Example 3:

[0067] (1) Soak the waste manganese-based sodium ion batteries in 1.5 M NaCl salt water, and then dry the batteries for later use;

[0068] (2) Mechanically crushing the waste manganese-based sodium ion battery into powder residue, separating the diaphragm and the plastic skin in a low-speed air flow field, and immersing the obtained waste in dimethyl sulfoxide. After ultrasonic treatment for 60 minutes, filtering the mixed waste to separate the upper waste carbon, the middle positive electrode active material, and the lower steel shell and the current collector, and preparing the upper waste carbon into graphene using a 2.0 g / L Hummers method; immersing the positive electrode active material in citric acid and stirring for 12 hours, adjusting the pH value to 11.5 using ammonium bicarbonate, filtering and separating the filtrate and the manganese ion-containing residue; stirring the graphene and the manganese ion-containing filtrate at a concentration of 5 mg / mL, and heating and drying at 120°C for 24 hours;

[0069] (3) Assembling manganese-doped graphene as a catalytic material to form a hydrogen fuel cell;

[0070] The comparison results show that the low-speed air flow field is not enough to provide sufficient power to separate the lightweight diaphragm and plastic skin from the mixed powder residue, and dimethyl sulfoxide has a better dissolving ability for the electrolyte.

[0071] The above embodiments only express one or several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a positive electrode for a hydrogen fuel cell using waste manganese-based sodium ion batteries, characterized in that: The preparation method comprises the following steps: Step S1: placing the waste manganese-based sodium ion battery in a NaCl solution for discharge to obtain an electroless manganese-based sodium ion battery; Step S2: crushing the electroless manganese-based sodium ion battery to obtain manganese-based sodium ion battery slag; Step S3: blowing the manganese-based sodium ion battery slag to obtain a manganese-based sodium ion battery slag free of a diaphragm and a plastic skin; Step S4: soaking the manganese-based sodium ion battery slag material without a separator and a plastic skin in an organic solvent, and completely separating the negative electrode waste carbon from the current collector under the assistance of ultrasound to obtain a clarified solution; Step S5: preparing graphene oxide from the negative electrode waste carbon in step S4 using the Hummers method; Step S6: adjusting the pH value of the clarified solution in step S4, filtering to obtain a sodium carbonate residue and a filtrate containing manganese ions; Step S7: mixing, heating and drying the graphene oxide in step S5 and the filtrate in step S6 under stirring conditions to obtain a manganese-doped graphene catalyst; Step S8: Using the manganese-doped graphene catalyst in step S7 as a positive electrode of a hydrogen fuel cell.

2. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The concentration of the NaCl solution in step S1 is 1M, 1.25M or 1.5M.

3. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The crushing process in step S2 is crushing by a crusher, manual crushing or frozen crushing.

4. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The blowing process in step S3 is a high-speed airflow field, a medium-speed airflow field, or a low-speed airflow field.

5. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The organic solvent in step S4 is N-methylpyrrolidone (NMP) or dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

6. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The waste carbon concentration used in the Hummers method in step S5 is 1.0 g / L, 1.5 g / L or 2.0 g / L.

7. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: The pH value in step S6 is in the range of 11±0.

5.

8. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: In step S6, the pH value of the clear solution is adjusted by using concentrated ammonia water, sodium hydroxide or sodium bicarbonate.

9. The method for preparing a positive electrode of a hydrogen fuel cell using waste manganese-based sodium ion batteries according to claim 1, characterized in that: In step S7, the concentration of graphene oxide in the filtrate is 1.2 g / L, 1.4 g / L or 1.6 g / L.

Images