Background
The storage and conversion of energy has become an important issue that restricts the sustainable development of the world economy. Among the various technologies at present, lithium ion batteries have conquered the portable electronic market due to their advantages of high working voltage, high capacity, small self-discharge, long cycle life, etc., and have become the first choice of power sources for electric vehicles and large-scale energy storage systems. One of the key technologies of lithium ion batteries is the negative electrode material. The main negative electrode materials studied more at present are: carbon-based materials, metal oxides, alloys, elemental non-metals, organic compounds, and the like. The carbon material includes graphite, graphene, carbon nanotube and biomass carbon.
The biomass carbon prepared from the biomass material has the characteristics of light weight, rich pore structure, large specific surface area, good structural stability, excellent conductivity and the like, and the commonly used biomass waste material has the advantages of environmental protection, waste recycling and the like, and is widely applied to the advanced scientific and technological fields of lithium ion batteries, super capacitors, sodium ion batteries and the like. However, a single biomass carbon material has disadvantages of low capacity, poor rate capability, and easy occurrence of volume expansion during a cycle. The conventional solutions to the above problems include material nanocrystallization, porous active materials, and nanocomposites, and the third approach is the most extensive in research.
Recently, iron-based materials have shown very good performance in lithium batteries, such as Fe3C has many advantages, such as high theoretical capacity, no toxicity, rich content, corrosion resistance, low price, etc. However, to our knowledge, Fe3C-based materials are generally used as high-performance magnets and catalysts, and additionally, carbides are rarely used in lithium ion batteries for two reasons, one being volume expansion and contraction during cycling and the other being pure carbides with low electrical conductivity. In order to solve the above-mentioned troublesome problems, many methods have been proposed to improve the structural stability of the electrode material. This problem can be partially addressed by fabricating nanostructured electrode materials of different morphologies, including nanoparticles, nanosheets, nanowires, nanorods, nanotubes, and hollow nanostructures, because nanostructured materials can better accommodate the strain during lithium intercalation and deintercalation than materials of micron order. Another approach is to incorporate a carbonaceous precursor into the active material to synthesize a mixed nanostructure material. It is clear that the carbon in the mixture material has several functions: as conductive additives to promote electron transport in poorly conductive materials, as elastic buffer supports to promote electrodesAnd (4) stability. The concept of producing sustainable materials in an energy efficient process is important in order to enable large scale applications.
Disclosure of Invention
The invention aims to provide a preparation process of an iron carbide/carbon ultrathin nano sheet-shaped composite electrode material for a lithium ion battery, which overcomes the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation process of an iron carbide/carbon ultrathin nano sheet-shaped composite electrode material for a lithium ion battery comprises the following steps:
1) cleaning biomass waste with alcohol, then carrying out vacuum drying, crushing into powder, and sieving to obtain powder A;
2) adding an acid solution into the powder A, and stirring to obtain a mixture B;
3) transferring the mixture B into a hydrothermal induction kettle, adding carbon cloth as an induction source, moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 150-180 ℃ from room temperature at an induction frequency of 300-600 KHz, preserving heat for 20-50 min, cooling to room temperature, taking out the carbon cloth, scraping the obtained product, washing with deionized water and ethanol, performing suction filtration, and drying to obtain powder C;
4) preparing an iron source solution with the Fe mass concentration of 0.1-0.4%, adding powdery C into the iron source solution, and heating and stirring to obtain D;
5) heating the D to 600-900 ℃ at a heating rate of 3-10 ℃/min in a protective atmosphere, preserving heat for 1-3 h, cooling to room temperature, washing, filtering and drying the obtained product by deionized water and ethanol to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
Further, the biomass waste in the step 1) is paper-making waste residue, waste newspaper, waste disposable chopsticks or waste paper shells.
Further, in the step 1), the vacuum drying temperature is 70-130 ℃, and the time is 6-12 hours; and crushing the mixture into powder, and sieving the powder with a 200-500-mesh sieve to obtain powder A.
Further, in the step 2), 1-4 g of powdery A is added into every 30-60 mL of acid solution, wherein the acid solution is sulfuric acid solution or nitric acid solution, and the concentration of the acid solution is 1-4 mol/L.
Further, the stirring mode in the step 2) is specifically as follows: stirring for 10-40 min at a frequency of 20-50 KHz and a rotating speed of 200-500 r/min by adopting an ultrasonic-magnetic two-in-one stirring method.
Further, the length, the width and the height of the carbon cloth in the step 3) are respectively 3cm, 2cm and 0.5 cm; in the step 3), the drying temperature is 80 ℃ and the drying time is 6 h.
Further, in the step 4), the iron source is one of ferrous chloride, ferrous chloride tetrahydrate, ferric chloride, ferric perchlorate, ferrous sulfate, ferric sulfate, ferrous nitrate, ferric nitrate, ferrous fluoride, ferric fluoride, ferrous bromide, ferric bromide, ferrous iodide and ferric iodide.
Further, 1g of powdery C is added into every 30-60 mL of the iron source solution in the step 4).
Further, the heating and stirring in the step 4) are specifically as follows: stirring for 1-4 h at the temperature of 50-80 ℃ and the rotating speed of 60-90 r/min.
Further, the drying in the step 5) specifically comprises the following steps: and (3) drying for 6-9 h in vacuum at the temperature of 60-90 ℃.
Compared with the prior art, the invention has the following beneficial technical effects:
1. the invention selects the biomass waste as the biomass carbon source, changes waste into valuable, is environment-friendly, and has extremely high resource advantage and cost advantage.
2. The preparation process of the lithium ion battery cathode material provided by the invention is simple, the conditions are mild and controllable, the production cost is low, the repeatability is high, and the industrial production is easy to realize.
3. The lithium ion battery cathode material synthesized by the invention has an ultrathin nano flaky structure, can effectively cope with volume expansion in a circulation process, and shortens an ion diffusion distance; the specific surface area is large, so that the contact area between the electrolyte and the electrolyte is effectively increased, ion adsorption/desorption is facilitated, and the adsorption capacity is improved; the composite biomass carbon material is beneficial to accelerating the electron transmission speed and improving the conductivity.
4. The composite electrode material prepared by the invention can obviously prolong the cycle life of a battery when being applied to a lithium ion battery, and has high capacity, excellent cycle stability, thermal stability, chemical stability and mechanical flexibility.
Detailed Description
Embodiments of the invention are described in further detail below:
the invention adopts biomass carbon as a raw material, and provides Fe with an ultrathin nano flaky structure3A preparation process of a C/C composite electrode material. The process has the advantages of wide raw material source and low cost; the synthesized product has excellent electrochemical performance when applied to a lithium ion battery; and the whole process flow is simple and controllable, and the repeatability is good. The composite electrode material can form a sample with a porous communicated three-dimensional carbon nano structure after hydrothermal induction and carbonization treatment. The composite electrode material is simple in preparation process, environment-friendly in raw materials, wide in source, capable of changing waste into valuable, and has great cost advantage, and has excellent electrochemical performance when being applied to lithium ion batteries.
The method specifically comprises the following steps:
1. cleaning the biomass waste papermaking waste residues, waste newspapers, waste disposable chopsticks, waste paper shells and the like with alcohol for three times, drying in vacuum at the temperature of 70-130 ℃ for 6-12 h, crushing into powder by using a crusher, and sieving with a 200-500-mesh sieve to obtain powder A;
2. weighing 1-4 g A, adding 30-60 ml of acid solution (sulfuric acid or nitric acid) with the concentration of 1-4 mol/L into A, and stirring for 10-40 min by adopting an ultrasonic-magnetic two-in-one stirring method at the frequency of 20-50 KHz and the rotating speed of 200-500 r/min to obtain a mixture B.
3. And transferring the mixture B into a hydrothermal induction kettle, and adding carbon cloth with the length, width and height of 3cm, 2cm and 0.5cm as an induction source. Moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 150-180 ℃ from room temperature at an induction frequency of 300-600 KHz, preserving the temperature for 20-50 min, cooling to room temperature, taking out carbon cloth, scraping the obtained product, washing with deionized water and ethanol, performing suction filtration, and drying in an oven at 80 ℃ for 6h to obtain powdery C;
4. preparing 30-60 mL of an iron source solution (the iron source is one or a mixture of more of ferrous chloride, ferrous chloride tetrahydrate, ferric chloride, ferric perchlorate, ferrous sulfate, ferric sulfate, ferrous nitrate, ferric nitrate, ferrous fluoride, ferric fluoride, ferrous bromide, ferric bromide, ferrous iodide, ferric iodide and other inorganic iron salts) with the Fe mass concentration of 0.1-0.4 wt%, adding 1g of powdery C, and stirring for 1-4 hours at the rotating speed of 60-90 r/min by adopting an oil bath rotary evaporator at the temperature of 50-80 ℃ to obtain D.
5. And D, moving the D into a tubular furnace into which argon is introduced, heating to 600-900 ℃ at a heating rate of 3-10 ℃/min, preserving the heat for 1-3 h, and cooling to room temperature. Washing and filtering the obtained product with deionized water and ethanol, and drying in a vacuum oven at 60-90 ℃ for 6-9 h to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
The present invention is described in further detail below with reference to examples:
example 1
1. Cleaning the biomass waste papermaking waste residue with alcohol for three times, drying the biomass waste papermaking waste residue for 6 hours in vacuum at 70 ℃, crushing the biomass waste papermaking waste residue into powder by using a crusher, and sieving the powder with a 200-mesh sieve to obtain powder A;
2. weighing 1g A, adding 30ml of sulfuric acid solution with the concentration of 1mol/L into A, and stirring for 10min at the frequency of 20 KHz and the rotating speed of 200r/min by adopting an ultrasonic-magnetic two-in-one stirring method to obtain a mixture B.
3. And transferring the mixture B into a hydrothermal induction kettle, and adding carbon cloth with the length, width and height of 3cm, 2cm and 0.5cm as an induction source. Moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 150 ℃ from room temperature at an induction frequency of 300KHz, preserving heat for 20min, cooling to room temperature, taking out carbon cloth, scraping the obtained product, washing with deionized water and ethanol, performing suction filtration, and drying in an oven at 80 ℃ for 6h to obtain powdery C;
4. preparing 30mL of ferrous chloride solution with the Fe mass concentration of 0.1 wt%, adding 1g of powdery C, and stirring for 1h at the rotating speed of 60r/min at the temperature of 50 ℃ by adopting an oil bath rotary evaporator to obtain D.
5. And D is moved to a tubular furnace filled with argon, the temperature is raised to 600 ℃ at the heating rate of 3 ℃/min, the temperature is kept for 1h, and the temperature is cooled to the room temperature. Washing and filtering the obtained product with deionized water and ethanol, and drying in a vacuum oven at 60 ℃ for 6h to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
Example 2
1. Cleaning biomass waste newspaper with alcohol for three times, vacuum-drying at 90 ℃ for 8h, crushing into powder by a crusher, and sieving with a 300-mesh sieve to obtain powder A;
2. weighing 2g A, adding 30-60 ml of nitric acid solution with the concentration of 2mol/L into A, and stirring for 20min by adopting an ultrasonic-magnetic two-in-one stirring method at the frequency of 30 KHz and the rotating speed of 300r/min to obtain a mixture B.
3. And transferring the mixture B into a hydrothermal induction kettle, and adding carbon cloth with the length, width and height of 3cm, 2cm and 0.5cm as an induction source. Moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 160 ℃ from room temperature at an induction frequency of 400KHz, preserving heat for 30min, cooling to room temperature, taking out carbon cloth, scraping the obtained product, washing with deionized water and ethanol, performing suction filtration, and drying in an oven at 80 ℃ for 6h to obtain powdery C;
4. preparing 40mL of ferrous perchlorate solution with the Fe mass concentration of 0.2 wt%, adding 1g of powdery C, and stirring for 2h at the rotating speed of 70r/min at the temperature of 60 ℃ by adopting an oil bath rotary evaporator to obtain D.
5. And D is moved into a tube furnace filled with argon, the temperature is raised to 70 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 2h, and the temperature is cooled to the room temperature. Washing and filtering the obtained product with deionized water and ethanol, and drying in a vacuum oven at 70 ℃ for 7h to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
Example 3
1. Cleaning the waste disposable chopsticks of the biomass waste with alcohol for three times, drying the waste disposable chopsticks in vacuum at the temperature of 110 ℃ for 10 hours, crushing the waste disposable chopsticks into powder by a crusher, and sieving the powder with a 400-mesh sieve to obtain powder A;
2. weighing 3g A, adding 50ml of sulfuric acid solution with the concentration of 3mol/L into A, and stirring for 30min by adopting an ultrasonic-magnetic two-in-one stirring method at the frequency of 40 KHz and the rotating speed of 400r/min to obtain a mixture B.
3. And transferring the mixture B into a hydrothermal induction kettle, and adding carbon cloth with the length, width and height of 3cm, 2cm and 0.5cm as an induction source. Moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 170 ℃ from room temperature at the induction frequency of 500KHz, preserving the heat for 40min, cooling to room temperature, taking out carbon cloth, scraping the obtained product, washing with deionized water and ethanol, filtering, and drying in an oven at 80 ℃ for 6h to obtain powdery C;
4. preparing 50mL of ferrous nitrate solution with the Fe mass concentration of 0.3 wt%, adding 1g of powdery C, and stirring for 3h at the temperature of 70 ℃ and the rotating speed of 80r/min by adopting an oil bath rotary evaporator to obtain D.
5. And D is moved into a tube furnace filled with argon, the temperature is raised to 800 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 2h, and the temperature is cooled to the room temperature. Washing and filtering the obtained product with deionized water and ethanol, and drying in a vacuum oven at 80 ℃ for 8h to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
Example 4
1. Cleaning waste paper shells of biomass wastes with alcohol for three times, drying in vacuum at 130 ℃ for 12h, crushing into powder by a crusher, and sieving with a 500-mesh sieve to obtain powder A;
2. weighing 4g A, adding 60ml of nitric acid solution with the concentration of 4mol/L into A, and stirring for 40min by adopting an ultrasonic-magnetic two-in-one stirring method at the frequency of 50KHz and the rotating speed of 500r/min to obtain a mixture B.
3. And transferring the mixture B into a hydrothermal induction kettle, and adding carbon cloth with the length, width and height of 3cm, 2cm and 0.5cm as an induction source. Moving the hydrothermal induction kettle into hydrothermal induction heating equipment, heating the hydrothermal induction kettle to 180 ℃ from room temperature at an induction frequency of 600KHz, preserving heat for 50min, cooling to room temperature, taking out carbon cloth, scraping the obtained product, washing with deionized water and ethanol, performing suction filtration, and drying in an oven at 80 ℃ for 6h to obtain powdery C;
4. preparing 60mL of ferrous bromide solution with the Fe mass concentration of 0.4 wt%, adding 1g of powdery C, and stirring for 4 hours at the rotating speed of 90r/min at the temperature of 80 ℃ by adopting an oil bath rotary evaporator to obtain D.
5. And D is moved into a tube furnace filled with argon, the temperature is raised to 900 ℃ at the heating rate of 10 ℃/min, the temperature is kept for 3h, and the temperature is cooled to the room temperature. Washing and filtering the obtained product with deionized water and ethanol, and drying in a vacuum oven at 90 ℃ for 9h to obtain Fe3C/C ultrathin nanometer sheet-shaped composite electrode material.
As can be seen from the SEM image of FIG. 1, Fe prepared in example 33The C/C composite material has an ultrathin nano flaky morphology structure, and is beneficial to shortening the diffusion path of lithium ions. As can be seen from the cycle performance graph of FIG. 2, the sample of example 3 was applied to a lithium ion battery at 50mAg-1The capacity can reach 1005mAhg at the current density-1The capacity retention rate after 120 cycles is more than 95%, and the high-capacity lithium ion battery has high capacity and excellent cycle stability.