CN103618094B - The preparation method of a kind of high-capacity lithium sulfur flow battery and electrode thereof - Google Patents

Abstract

The invention relates to the field of batteries and aims to provide a preparation method for a large-capacity lithium-sulfur flow battery and an electrode thereof. The preparation method of the high-power lithium-sulfur flow electrode comprises the following steps: preparing nickel foam with a carbon coating layer, preparing the nickel foam as the negative electrode of the lithium-sulfur flow battery, and preparing the nickel foam as the positive electrode of the lithium-sulfur flow battery ; The large-capacity lithium-sulfur flow battery includes a positive electrode plate carved with a flow path, a positive electrode, a separator, a negative electrode, a negative plate carved with a flow path, and a positive electrode liquid and a negative electrode liquid connected in sequence. The present invention utilizes Al with high specific capacity as the negative electrode active material, S as the positive electrode active material, carbon-coated nickel foam as the negative electrode, and nickel sulfide-coated nickel foam as the positive electrode, providing lithium-sulfur flow batteries with high activity and high strength. , low flow resistance electrodes, greatly improving the energy density and power density of lithium-sulfur flow batteries. The cost of the active material and the electrode material is low, the preparation process is simple and easy, and has broad application prospects.

Description

A kind of preparation method of large-capacity lithium-sulfur flow battery and electrode thereof

technical field

The invention relates to the field of batteries, in particular to a large-capacity lithium-sulfur flow battery and a method for preparing an electrode thereof.

Background technique

Sulfur is insoluble in water but soluble in non-polar solvents such as carbon disulfide, carbon tetrachloride, cyclohexane, etc. Crystal sulfur can form a ring consisting of eight atoms: S ₈ . S ₈ can form polysulfide ions such as S ₈ ^2- , S ₆ ^2- , and S ₄ ^2- after gaining electrons. These polysulfide ions can be dissolved in organic solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC ), ethyl methyl carbonate (EMC), dimethoxyethane (DME), 1,3-dioxolane (DOL), etc.

The flow battery is a kind of energy storage battery, the most representative one is the all-vanadium flow battery. It is composed of electrolyte solution, carbon material electrode, bipolar plate and ion exchange membrane and other components. The electrolyte is circulated between the stack and the storage tank through the fluid delivery equipment, and the mutual transformation of vanadium ions in different valence states and the storage and release of electric energy are completed during the charging/discharging process. The electrode reaction is: positive electrode: VO ₂ ⁺ +2H ⁺ +e=VO ²⁺ +H ₂ O, E ⁰ =1.00V; negative electrode: V ³⁺ +e=V ²⁺ , E ⁰ =-0.26V; Reaction VO ₂ ⁺ +V ²⁺ +2H ⁺ =VO ²⁺ +V ³⁺ +H ₂ O, E ⁰ =1.26V.

The all-vanadium redox flow battery has the following characteristics: 1. Large scale: the output power and energy storage capacity of the all-vanadium redox flow battery are independent of each other. By changing the amount of electrolyte in the storage tank, the demand for large-scale power storage and energy storage can be met; by adjusting the serial number and electrode area of single cells in the battery stack, the rated discharge power requirement can be met. 2. Long service life: Both positive and negative reactions of the battery are completed in the liquid phase, and the charging/discharging process only changes the state of vanadium ions in the solution. No external ions participate in the electrochemical reaction. The electrode only plays the role of transferring electrons. It does not participate in the electrochemical reaction itself. In theory, it can carry out unlimited charging and discharging cycles to any degree, which greatly prolongs the service life of the battery. 3. Low cost: In terms of the preparation of key battery materials, such as proton exchange membranes, conductive bipolar plates and other key battery materials. Large-scale, low-cost production through localization. The all-vanadium redox flow battery avoids the use of precious metal catalysts, and its cost is far lower than that of fuel cells and other chemical power sources. It is suitable for use in tens of kilowatts to several megawatts. 4. High efficiency: Since the active substances in the positive and negative half-cell electrolytes are stored in different storage tanks, the self-discharge consumption during the electrolytic wave storage process is completely avoided, and the energy efficiency of the optimized battery system is as high as 80%.

Traditional lithium-ion flow batteries are mainly composed of battery reactors, positive electrode suspension storage tanks, negative electrode suspension storage tanks, liquid pumps, and sealed pipelines. The positive electrode suspension storage tanks contain positive electrode active material particles, conductive agents, and electrolytes. The mixture, the negative electrode suspension storage tank holds the mixture of negative electrode active material particles, conductive agent and electrolyte. The battery reactor is the core of the lithium-ion flow battery, and its structure mainly includes: positive electrode current collector, positive electrode reaction chamber, porous diaphragm, negative electrode reaction chamber, negative electrode current collector and casing. When the lithium-ion flow battery is working, a liquid pump is used to circulate the suspension. The suspension flows continuously or intermittently between the suspension storage tank and the battery reactor through the sealed pipe under the drive of the liquid pump or other power. The flow rate can be adjusted according to the suspension. The liquid concentration and the ambient temperature are adjusted.

Usually, there is an electronically non-conductive porous diaphragm between the positive electrode reaction chamber and the negative electrode reaction chamber, which separates the positive electrode active material particles in the positive electrode suspension and the negative electrode active material particles in the negative electrode suspension from each other, avoiding direct contact between the positive and negative electrode active material particles. The contact causes a short circuit inside the battery. The positive electrode suspension in the positive electrode reaction chamber and the negative electrode suspension in the negative electrode reaction chamber can perform lithium ion exchange and transport through the electrolyte in the porous diaphragm. When the battery is discharged, the lithium ions inside the negative electrode active material particles in the negative electrode reaction chamber are deintercalated, enter the electrolyte, and reach the positive electrode reaction chamber through the porous diaphragm, and are embedded in the positive electrode active material particles; at the same time, the negative electrode reaction The electrons inside the negative electrode active material particles in the cavity flow into the negative electrode current collector, and flow into the external circuit of the battery through the negative electrode tab of the negative electrode current collector. Inside the active material particles. The battery charging process is the opposite. The traditional negative electrode active material is graphite powder, and the positive electrode active material is lithium cobalt oxide "New Technology of Electrical Engineering and Energy, Volume 31, Issue 3".

CN102324550 proposes a design and preparation method of a semi-liquid flow lithium-sulfur battery, which is characterized in that: the semi-liquid flow lithium-sulfur battery is made of lithium particles or Si-based materials, lithium titanate and Sn-based materials and electrolyte The mixed solution is the cathode, and the mixed solution of elemental sulfur, elemental sulfur compound, sulfur-based compound, inorganic sulfur, organic sulfur and the electrolyte solution is the anode.

Sodium in traditional sodium-sulfur batteries is in the liquid state of metal, so there are major problems: 1. High working temperature; 2. It is not suitable for intermittent work. too big. The all-vanadium redox flow battery has low working voltage and low energy density. Traditional lithium ion flow batteries use graphite as the active material, but the lithium intercalation capacity of graphite can only reach 372mAhg ^-1 , and the energy density is relatively low. The semi-liquid flow lithium-sulfur battery proposed by CN102324550 does not use a collector, but forms a cathode and an anode in a metal box or metal tube, so the reaction area is small, and it is difficult to provide high current and high power output.

Contents of the invention

The main purpose of the present invention is to overcome the deficiencies in the prior art and provide a low-cost lithium-sulfur flow battery and its electrode preparation method with high capacity, high power, high efficiency, long life and no pollution, which work at room temperature. In order to solve the problems of the technologies described above, the solution of the present invention is:

A preparation method for a high-power lithium-sulfur liquid flow electrode is provided, which specifically includes the following steps:

Step A: Take the carbon source material and heat it to 100-150°C to a liquid state, then immerse the foamed nickel into the liquid carbon source material, then connect a rheostat box and a power supply in series at both ends of the foamed nickel, and self-heat when energized (the The principle and effect are the same as electric heating wire heating), and the rheostat box is used to control the temperature of nickel foam by controlling the current; when the temperature of nickel foam reaches the carbonization temperature of the carbon source material, the carbon source material is carbonized on the inner surface of the nickel foam Forming a carbon coating layer; the carbon source material is a polymer with a molecular weight of less than or equal to 10,000 (such as polyethylene glycol and polyacrylic acid with a molecular weight of less than or equal to 10,000), higher fatty alcohols (monohydric alcohols of C6-C26) or higher Fatty acids (monocarboxylic acids from C6 to C26);

Step B: Put the nickel foam with carbon coating prepared in step A in a muffle furnace, and under the protection of an inert gas, calcinate at 800-1000°C for 5-10 hours, at the nickel interface of the foamed nickel Ni ₃ C is formed, and the resulting nickel foam is used as the negative electrode of the lithium-sulfur flow battery;

Step C: Dissolve colloidal sulfur in water to form a colloidal solution, and then apply the colloidal solution to the nickel foam so that the mass ratio of Ni to S is 100-1000:1, dry it in the shade and place it in a vacuum quartz tube and heat it to 900°C to react After 6 hours, the foamed nickel was coated with nickel sulfide, and the prepared foamed nickel was used as the positive electrode of the lithium-sulfur flow battery.

As a further improvement, in step A, polyethylene glycol and polyacrylic acid with molecular weight less than or equal to 10000 are used for polymers with molecular weight less than or equal to 10000, stearyl alcohol C ₁₈ H ₃₇ OH is used for higher fatty alcohols, stearic acid is used for higher fatty acids Acid C ₁₇ H ₃₅ COOH.

As a further improvement, the thickness of the foamed nickel-carbon coating layer formed in the step A is 0.1-1 micron.

As a further improvement, the inert gas in the step B is argon or nitrogen.

A large-capacity lithium-sulfur flow battery prepared based on the prepared lithium-sulfur flow electrode is provided, and the large-capacity lithium-sulfur flow battery includes a positive plate with a flow path, a positive electrode, a diaphragm, a negative electrode and a negative electrode with a flow path connected in sequence. The negative electrode plate of the flow path, and the positive electrode liquid and the negative electrode liquid; the diaphragm is a microporous polypropylene film for separating the positive electrode and the negative electrode, the positive electrode adopts the positive electrode prepared in step C, and the negative electrode adopts the negative electrode obtained in step B The positive electrode plate is provided with a positive electrode liquid inlet pipe and a positive electrode liquid outlet pipe, and the positive electrode liquid flows through the positive electrode liquid inlet pipe, the flow path on the positive electrode plate and the positive electrode liquid outlet pipe, and penetrates into the positive electrode to undergo an electrochemical reaction; There are negative electrode liquid inlet pipe and negative electrode liquid outlet pipe, the negative electrode liquid flows through the negative electrode liquid inlet pipe, the flow path on the negative electrode plate and the negative electrode liquid outlet pipe, and penetrates into the negative electrode to undergo electrochemical reaction;

The positive electrode solution refers to the suspension formed by lithium sulfide powder mixed in the electrolyte, and the negative electrode solution refers to the suspension formed by aluminum powder mixed in the electrolyte; the solute of the electrolyte is LiPF ₆ , and the solvent of the electrolyte is ethylene carbonate A mixture of ester (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and carbon disulfide; the concentration of LiPF ₆ is 1 mol/L, ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate , The volume ratio of carbon disulfide is 1:1:1:1, and the carbon disulfide here can be replaced by carbon tetrachloride or cyclohexane.

As a further improvement, in the high-capacity lithium-sulfur flow battery, a positive electrode sealing ring is also provided between the positive electrode and the diaphragm, and a negative electrode sealing ring is also provided between the diaphragm and the negative electrode. Both the positive electrode sealing ring and the negative electrode sealing ring are made of fluorine. Seals made of rubber.

As a further improvement, the lithium sulfide powder in the catholyte solution is 1-50 microns.

As a further improvement, the aluminum powder in the negative electrolyte is 1-50 microns.

A control method based on the above-mentioned large-capacity lithium-sulfur flow battery is provided. When charging a large-capacity lithium-sulfur flow battery, firstly, the positive electrode side is catalyzed by nickel sulfide, and lithium sulfide undergoes electrochemical oxidation to form S ₈ : 8Li ₂ S=16Li ⁺ +S ₈ +16e, S ₈ dissolves in the electrolyte, Li ⁺ passes through the separator to the negative electrode, and forms LiC ₆ on the carbon layer of the negative electrode: C ₆ +Li ⁺ +e=LiC ₆ , then Li ⁺ Under the catalysis of LiC ₆ on the negative electrode, an electrochemical reduction reaction occurs to form AlLi alloy powder: Al+Li ⁺ +e=AlLi, and AlLi is further charged to obtain Li ₉ Al ₄ : 4AlLi+5Li ⁺ +5e=Li ₉ Al ₄ ; When the large-capacity lithium-sulfur flow battery is being discharged, the reverse reaction of the above reaction occurs at the positive and negative electrodes respectively to realize power generation. The battery reaction is: 16Li ₉ Al ₄ +9S ₈ =64Al+72Li ₂ S.

Compared with prior art, the beneficial effect of the present invention is:

The present invention utilizes Al with high specific capacity as the negative electrode active material, S as the positive electrode active material, carbon-coated nickel foam as the negative electrode, and nickel sulfide-coated nickel foam as the positive electrode, providing lithium-sulfur flow batteries with high activity and high strength. , low flow resistance electrodes, which greatly improve the energy density and power density of lithium-sulfur flow batteries, and can be widely used in wind power, solar power, tidal power and other large unsteady power plants to play the role of power regulation, It can also be applied to steady-state power plants to balance peak and valley power consumption, improve power generation efficiency, and reduce power generation costs. The source of the active substance is abundant, the cost is low, pollution-free and easy to prepare. The cost of electrode materials is low, and the preparation process is simple and easy, which is conducive to large-scale production, can effectively reduce the cost of flow batteries, and has broad application prospects.

Description of drawings

FIG. 1 is an assembly diagram of a large-capacity lithium-sulfur flow battery of the present invention.

Fig. 2 is the charging and discharging performance chart of the battery in the embodiment.

The reference signs in the figure are: 1 positive plate; 2 positive electrode; 3 positive electrode sealing ring; 4 diaphragm; 5 negative electrode sealing ring; 6 negative electrode; 7 negative electrode plate; Introduction tube; 11 Negative electrode liquid outlet tube; 12 Charging curve; 13 Discharging curve.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

A preparation method of a high-power lithium-sulfur liquid flow electrode, specifically comprising the following steps:

Step A: Take the carbon source material and heat it to 100-150°C to a liquid state, then immerse the foamed nickel into the liquid carbon source material, then connect a rheostat box and a power supply in series at both ends of the foamed nickel, and self-heat when the power is turned on. The principle and effect are equivalent to the heating of the electric heating wire, and the rheostat box is used to control the temperature of the nickel foam by controlling the magnitude of the current. When the temperature of the nickel foam reaches the carbonization temperature of the carbon source material, the carbon source material is carbonized on the inner surface of the nickel foam to form a 0.1-1 micron thick carbon coating layer. The carbon source material is a polymer with a molecular weight of less than or equal to 10,000 (polyethylene glycol, polyacrylic acid with a molecular weight of Carboxylic acid), polymers with a molecular weight less than or equal to 10,000 use polyethylene glycol, polyacrylic acid, higher fatty alcohols, and higher fatty acids.

Step B: Place the nickel foam with carbon coating prepared in step A in a muffle furnace, and under the protection of argon or nitrogen, calcinate at 800-1000° C. for 5-10 hours. Ni ₃ C is formed at the interface, and the prepared nickel foam is used as the negative electrode of the lithium-sulfur flow battery.

Step C: Dissolve colloidal sulfur in water to form a colloidal solution, and then apply the colloidal solution to the nickel foam so that the mass ratio of Ni to S is 100-1000:1, dry it in the shade and place it in a vacuum quartz tube and heat it to 900°C to react After 6 hours, the foamed nickel was coated with nickel sulfide, and the prepared foamed nickel was used as the positive electrode of the lithium-sulfur flow battery.

As shown in Figure 1, the large-capacity lithium-sulfur flow battery prepared by using the prepared lithium-sulfur flow electrode includes a positive plate 1 with a flow path engraved on it, a positive electrode 2, a positive electrode sealing ring 3, a separator 4, and a negative electrode connected in sequence. A sealing ring 5, a negative electrode 6, a negative electrode plate 7 engraved with a flow path, and a positive electrode liquid and a negative electrode liquid. The separator 4 is a microporous polypropylene film used to separate the positive electrode 2 from the negative electrode 6. The positive electrode 2 is the positive electrode prepared in step C, and the negative electrode 6 is the negative electrode prepared in step B. The positive electrode plate 1 is provided with a positive electrode liquid inlet pipe 8 and a positive electrode liquid outlet pipe 9, and the catholyte liquid flows through the positive electrode liquid inlet pipe 8, the flow path on the positive electrode plate 1, and the positive electrode liquid outlet pipe 9, and penetrates into the positive electrode 2 to generate an electrochemical reaction. reaction. The negative electrode plate 7 is provided with a negative electrode liquid inlet pipe 10 and a negative electrode liquid outlet pipe 11, and the negative electrode liquid flows through the negative electrode liquid inlet pipe 10, the flow path on the negative electrode plate 7 and the negative electrode liquid outlet pipe 11, and penetrates into the negative electrode 6 to generate an electrochemical reaction. reaction.

The catholyte refers to the suspension formed by mixing lithium sulfide powder of 1-50 microns in the electrolyte, and the negative electrode refers to the suspension formed by mixing the aluminum powder of 1-50 microns in the electrolyte. The capacity of the flow battery depends on the content of lithium sulfide in the catholyte and aluminum in the anode. The solute of the electrolyte is LiPF ₆ , and the solvent of the electrolyte is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and carbon disulfide; the concentration of LiPF ₆ is 1 mol/ liter, the volume ratio of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and carbon disulfide is 1:1:1:1, and the carbon disulfide here can be replaced by carbon tetrachloride or cyclohexane.

When charging the above-mentioned large-capacity lithium-sulfur flow battery, firstly, under the catalysis of nickel sulfide on the positive electrode side, lithium sulfide undergoes electrochemical oxidation to form S ₈ : 8Li ₂ S=16Li ⁺ +S ₈ +16e, S ₈ dissolves in electrolyte, Li ⁺ passes through the separator to the negative electrode, and forms LiC ₆ on the carbon layer of the negative electrode: C ₆ +Li ⁺ +e=LiC ₆ , and then Li ⁺ undergoes electrochemical reduction reaction under the catalysis of LiC ₆ on the negative electrode to form AlLi alloy powder: Al+Li ⁺ +e=AlLi, AlLi is further charged to obtain Li ₉ Al ₄ : 4AlLi+5Li ⁺ +5e=Li ₉ Al ₄ ; Reverse reactions of the above reactions occur respectively to realize power generation, and the battery reaction is: 16Li ₉ Al ₄ +9S ₈ =64Al+72Li ₂ S.

Li ₉ Al ₄ has a very high theoretical specific capacity, as high as 2234mAhg ^-1 , and the specific capacity of sulfur is as high as 1675mAhg ^-1 , which is much higher than the capacity of lithium cobalt oxide batteries widely used in commerce, generally less than 150mAhg ^-1 , so , a lithium-sulfur flow battery with high specific capacity can be obtained by using S and Al as the active materials of the positive electrode 2 and the negative electrode 6 respectively.

The following examples can enable those skilled in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

Taking advantage of the characteristic that sulfur is soluble in ethanol and slightly soluble in water, first dissolve sulfur in ethanol, then drop the ethanol solution of sulfur into water, stir while dripping, to obtain sulfur sol, and obtain colloidal sulfur after drying. Generally high purity, mainly used in medicine. The base material used for foamed nickel is porous open-cell foam plastic. The conductive layer can be prepared by three methods: electroless nickel plating, vacuum nickel plating and dipping conductive glue (palladium sol, submicron graphite emulsion, etc.). Thick nickel can be electroplated in the common sulfate nickel plating electrolyte, and after burning, reduction and annealing processes, a three-dimensional network foam nickel material with excellent performance can be obtained. It is the best choice for manufacturing cadmium-nickel batteries and hydrogen-nickel batteries. One of the best electrode materials. Both colloidal sulfur and nickel foam are commercially available.

Embodiment 1: electric heating carbonization

Heat polyethylene glycol with a molecular weight of 10,000 to 100°C to melt it, and immerse foamed nickel with a porosity of 95% in it. The two ends of the foamed nickel are connected to a 220V power supply for heating, and the current density is controlled at 0.1 to 1Acm ^-2 . The nickel foam is carbonized at a temperature of 250-350°C to form a carbon coating. In the early stage of carbonization, a higher current density can be used. When the temperature of nickel foam exceeds 350°C, the current density can be reduced to adjust the carbonization temperature to within the range of 250-350°C.

When the carbon source material is replaced by polyethylene glycol with a molecular weight of 400, since it is liquid at room temperature, it can be carbonized by electricity without heating. Similarly, C ₆ fatty alcohols such as 2-hexanol C ₆ H ₁₃ OH, and fatty acids such as n-hexanoic acid C ₅ H ₁₁ COOH are liquid at room temperature and can be carbonized without heating. As for hexacosic acid or hexacosic acid, such as cerotic acid CH ₃ (CH ₂ ) ₂₄ COOH, it needs to be heated to 100°C for melting before it can be energized and carbonized.

Example 2: Negative Electrode Preparation

Polyacrylic acid with a molecular weight of 5000 is heated to 120°C to melt it, and nickel foam with a porosity of 95% is immersed in it. Both ends of the nickel foam are connected to a 220V power supply for heating, and the current density is controlled at 0.1 to 1Acm ^-2 to control the The temperature is 250-350°C for carbonization to form a carbon coating layer. In the early stage of carbonization, a higher current density can be used. When the temperature of nickel foam exceeds 350°C, the current density can be reduced to adjust the carbonization temperature to within the range of 250-350°C. When the carbon layer reaches a thickness of 0.1 micron, take it out and place it in a muffle Under the protection of nitrogen, the furnace is calcined at 800°C for 10 hours to form Ni ₃ C at the interface between the carbon layer and the nickel, increase the binding force between the carbon layer and the nickel foam, and obtain the negative electrode of the lithium-sulfur flow battery.

Example 3: Positive Electrode Preparation

Dissolve colloidal sulfur in water to form a colloidal solution and coat it on nickel foam with a porosity of 95%, the mass ratio of Ni to S is 100:1, dry it in the shade, place it in a vacuum quartz tube and heat it to 900°C, and react for 6 hours to obtain nickel sulfide Coated nickel foam, as the positive electrode of lithium-sulfur flow battery.

Embodiment 4: Composition of lithium-sulfur flow battery

Stearyl alcohol, namely C ₁₈ higher alcohol C ₁₈ H ₃₇ OH, is heated to 150°C for melting, and nickel foam with a porosity of 95% is immersed in it, and the two ends of the foam nickel are connected to a 220V power supply for heating, and the current density is controlled at 0.1-1Acm ^-2 , the temperature of nickel foam is controlled to be 250-350°C for carbonization to form a carbon coating layer. In the early stage of carbonization, a higher current density can be used. When the temperature of nickel foam exceeds 350°C, the current density can be reduced to adjust the carbonization temperature to within the range of 250-350°C. When the carbon layer reaches a thickness of 0.5 microns, take it out and place it in a muffle The negative electrode was obtained by calcining at 900° C. for 8 hours in a furnace under the protection of argon.

Dissolve colloidal sulfur in water to form a colloidal solution and coat it on nickel foam with a porosity of 95%, the mass ratio of Ni and S is 500:1, dry it in the shade, place it in a vacuum quartz tube and heat it to 900°C, and react for 6 hours to obtain nickel sulfide Coated with nickel foam, as the positive electrode.

The positive electrode 2 and the negative electrode 6 are separated by a microporous polypropylene film, and the positive electrode plate 1 engraved with the flow path, the positive electrode 2, the separator 4, the negative electrode 6, and the negative electrode plate 7 engraved with the flow path are combined to form a battery, as shown in Figure 1 . The electrolyte uses LiPF ₆ as the solute, the concentration of LiPF ₆ is 1 mole/liter, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), carbon disulfide (or carbon tetrachloride, ring Hexane) as the solvent, the volume ratio of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and carbon disulfide (or carbon tetrachloride, cyclohexane) is 1:1:1:1.

Example 5: Lithium-sulfur flow battery power generation

Stearic acid, that is, C ₁₈ higher fatty acid C ₁₇ H ₃₅ COOH, is heated to 150°C for melting, and nickel foam with a porosity of 95% is immersed in it, and the two ends of the nickel foam are connected to a 220V power supply for heating, and the current density is controlled at 0.1-1Acm ^-2 , the temperature of nickel foam is controlled to be 250-350°C for carbonization to form a carbon coating layer. In the early stage of carbonization, a higher current density can be used. When the temperature of nickel foam exceeds 350°C, the current density can be reduced to adjust the carbonization temperature to within the range of 250-350°C. When the carbon layer reaches a thickness of 1 micron, take it out and place it in a muffle Under the protection of argon, calcined at 1000° C. for 5 hours in a furnace to obtain a negative electrode.

Dissolve colloidal sulfur in water to form a colloidal solution and coat it on nickel foam with a porosity of 95%, the mass ratio of Ni to S is 1000:1, dry it in the shade, place it in a vacuum quartz tube and heat it to 900°C, and react for 6 hours to obtain nickel sulfide Coated with nickel foam, as the positive electrode.

The positive electrode 2 and the negative electrode 6 are separated by a microporous polypropylene film, and the positive electrode plate 1 engraved with a flow path, the positive electrode 2, the separator 4, the negative electrode 6, and the negative electrode plate 7 engraved with a flow path are combined to form a battery. The electrolyte uses LiPF ₆ as the solute, a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and carbon tetrachloride as the solvent, and the concentration of LiPF ₆ is 1 mol/liter , The volume ratio of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and carbon tetrachloride is 1:1:1:1. Mix 150 grams of lithium sulfide powder of 1-50 microns into 500 ml of electrolyte to form a suspension as anode solution, and mix 150 grams of aluminum powder of 1-50 microns into 500 ml of electrolyte to form a suspension as anode solution. The positive electrode solution and the negative electrode solution are sent to the positive electrode 2 and the negative electrode 6 through the catholyte solution and the negative electrode solution inlet pipes on the positive electrode plate 1 and the negative electrode plate 7 respectively by a peristaltic pump. When charging, on the positive electrode side, under the catalytic action of nickel sulfide, lithium sulfide undergoes electrochemical oxidation to form S ₈ :

8Li ₂ S=16Li ⁺ +S ₈ +16e

S ₈ dissolves in the electrolyte, Li ⁺ passes through the separator 4 to the negative electrode 6, and LiC _{6 is formed on the carbon layer of the negative electrode 6} :

C ₆ +Li ⁺ =LiC ₆ +e

Then Li ⁺ undergoes an electrochemical reduction reaction under the catalysis of LiC ₆ on the negative electrode 6 to form AlLi alloy powder:

Al+Li ⁺ +e=AlLi

AlLi is further charged to Li ₉ Al ₄ :

4AlLi+5Li ⁺ +5e=Li ₉ Al ₄

When the lithium-sulfur flow battery is discharged, the reverse reaction of the above reaction occurs at the positive electrode 2 and the negative electrode 6 respectively. The charging and discharging performance of the battery is shown in Figure 2. The battery capacity is determined by the amount of positive and negative active materials added.

Finally, it should be noted that what is listed above are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many modifications are possible. All deformations that can be directly derived or associated by those skilled in the art from the content disclosed in the present invention should be considered as the protection scope of the present invention.

Claims (9)

1. a preparation method for high power lithium sulphur Flow-through electrode, is characterized in that, specifically comprises the following steps:

Steps A: get carbon source material and be heated to 100 ~ 150 DEG C to liquid, immerse in liquid carbon source material by nickel foam again, then variable rheostat and power supply in the series connection of nickel foam two ends, namely energising is carried out from heating, variable rheostat is used for by controlling size of current, and then controls the temperature of nickel foam; When nickel foam temperature reaches the carburizing temperature of carbon source material, carbon source material forms carbon coating layer in the inner surface generation carbonization of nickel foam; Described carbon source material is polymer, higher aliphatic or the higher fatty acids that molecular weight is less than or equal to 10000;

Step B: the nickel foam with carbon coating layer obtained in steps A is placed in Muffle furnace, under inert gas shielding, calcines 5 ~ 10 hours, forms Ni in the nickel interface of nickel foam at 800 ~ 1000 DEG C ₃c, obtained nickel foam is namely as the negative pole of lithium sulphur flow battery;

Step C: by formation colloidal solution soluble in water for colloid sulphur, then colloidal solution is coated nickel foam, the mass ratio of Ni and S is made to be 100 ~ 1000:1, dry in the shade to be placed in vitreosil pipe and be heated to 900 DEG C, react after 6 hours, nickel foam is coated with nickel sulfide, and obtained nickel foam is namely as the positive pole of lithium sulphur flow battery.

2. the preparation method of a kind of high power lithium sulphur Flow-through electrode according to claim 1, it is characterized in that, in steps A, the polymer that molecular weight is less than or equal to 10000 adopts molecular weight to be not more than polyethylene glycol or the polyacrylic acid of 10000, and higher aliphatic adopts octadecyl alcolol C ₁₈h ₃₇oH, higher fatty acids adopts stearic acid C ₁₇h ₃₅cOOH.

3. the preparation method of a kind of high power lithium sulphur Flow-through electrode according to claim 1, is characterized in that, the thickness of the nickel foam carbon coating layer formed in described steps A is 0.1 ~ 1 micron.

4. the preparation method of a kind of high power lithium sulphur Flow-through electrode according to claim 1, is characterized in that, the inert gas in described step B adopts argon gas or nitrogen.

5. based on high-capacity lithium sulfur flow battery prepared by the lithium sulphur Flow-through electrode obtained by claim 1, it is characterized in that, described high-capacity lithium sulfur flow battery comprises the positive plate being carved with stream, positive pole, barrier film, the negative pole that connect successively and is carved with the negative plate of stream, and positive pole liquid and negative electrode solution; Described barrier film is microporous polypropylene film, and for separating positive pole and negative pole, positive pole adopts positive pole obtained in step C, and negative pole adopts negative pole obtained in step B; Positive plate is provided with positive pole liquid ingress pipe and positive pole liquid delivery line, and positive pole liquid is flowed by the stream on positive pole liquid ingress pipe, positive plate and positive pole liquid delivery line, and infiltrates positive pole generation electrochemical reaction; Negative plate is provided with negative pole liquid ingress pipe and negative pole liquid delivery line, and negative electrode solution is flowed by the stream on negative pole liquid ingress pipe, negative plate and negative pole liquid delivery line, and infiltrates negative pole generation electrochemical reaction;

Positive pole liquid refers in electrolyte the suspension-turbid liquid being mixed with lithium sulfide powder and being formed, and negative electrode solution refers in electrolyte the suspension-turbid liquid being mixed with aluminium powder and being formed; The solute of electrolyte is LiPF ₆, the solvent of electrolyte is the mixture of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate and carbon disulfide; Wherein LiPF ₆concentration be 1 mol/L, the volume ratio of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, carbon disulfide is 1:1:1:1, and carbon disulfide here can replace to carbon tetrachloride or cyclohexane.

6. a kind of high-capacity lithium sulfur flow battery according to claim 5, it is characterized in that, in described high-capacity lithium sulfur flow battery, positive pole sealing ring is also provided with between positive pole and barrier film, also be provided with negative pole sealing ring between barrier film and negative pole, positive pole sealing ring and negative pole sealing ring are all the sealing rings that fluorubber is made.

7. a kind of high-capacity lithium sulfur flow battery according to claim 5, is characterized in that, the lithium sulfide powder in described positive pole liquid is 1 ~ 50 micron.

8. a kind of high-capacity lithium sulfur flow battery according to claim 5, is characterized in that, the aluminium powder in described negative electrode solution is 1 ~ 50 micron.

9. based on the control method of high-capacity lithium sulfur flow battery according to claim 5, it is characterized in that, when charging to high-capacity lithium sulfur flow battery, first side of the positive electrode is under the catalytic action of nickel sulfide, and lithium sulfide generation electrochemical oxidation forms S ₈: 8Li ₂s=16Li ⁺+ S ₈+ 16e, S ₈be dissolved in electrolyte, Li ⁺then arrive negative pole through barrier film, form LiC at the carbon-coating of negative pole ₆: C ₆+ Li ⁺+ e=LiC ₆, then Li ⁺liC on negative pole ₆catalytic action under there is electrochemical reducting reaction and form AlLi alloy powder: Al+Li ⁺+ e=AlLi, AlLi charge further and obtain Li ₉al ₄: 4AlLi+5Li ⁺+ 5e=Li ₉al ₄; When discharging to high-capacity lithium sulfur flow battery, the back reaction of above-mentioned reaction occurs respectively at positive pole and negative pole, realize generating, its cell reaction is: 16Li ₉al ₄+ 9S ₈=64Al+72Li ₂s.