A graphene battery negative electrode material and preparation method thereof

Abstract

The invention relates to a graphene battery negative electrode material and a preparation method thereof, belonging to the technical field of battery negative electrode materials. The method comprises the following steps: adding an auxiliary agent and an alkylsiloxane to a polytetrafluoroethylene emulsion, stirring to obtain a binder; adding three-dimensional graphene, barium sulfate, an organic additive and lead powder to an ethanol aqueous solution, stirring, adding a binder, continuing to stir, obtaining a slurry, spray drying, and obtaining a powder; dispersing fibers in deionized water to obtain a dispersion, adding the dispersion and the powder to a paste machine, stirring, adding a 45-51wt% sulfuric acid solution, continuing to stir, and obtaining a lead paste; coating the lead paste on a lead-acid battery grid, and drying to obtain a graphene battery negative electrode material; in the invention, three-dimensional graphene is selected as a conductive agent, combined with a homemade binder, active substances and carbon powder are closely combined and evenly distributed, and excellent mechanical properties and electrochemical properties are given to the negative electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery negative electrode materials, and in particular, relates to a graphene battery negative electrode material and a preparation method thereof. Background Art

[0002] Lead-acid batteries are secondary batteries with the longest research history, the most mature production process, and the highest recycling rate among existing chemical power sources. However, with the gradual industrialization of hybrid vehicles and pure electric vehicles, the performance requirements for lead-acid batteries are becoming increasingly higher, among which the demand for high-performance negative electrode materials is particularly prominent.

[0003] The existing means of improving negative electrode materials are often to fill in additives, such as binders, conductive agents, nucleating agents and expanders. For example, a lead paste for negative electrode of a lead-acid battery and a preparation method thereof are disclosed in Chinese patent CN113540424B, which uses polytetrafluoroethylene and polytetrafluoroethylene-acrylic acid copolymer as binders to reduce the shedding of negative electrode active substances during battery cycling and improve the cycle life of lead-acid batteries. The binder can achieve a certain improvement effect, but due to the lack of active groups in the molecular chains of polytetrafluoroethylene and polytetrafluoroethylene-acrylic acid copolymer and the single type (carboxyl group), although the paste can stably bond the active substances, the paste has poor bonding properties with the negative electrode grid, and the overall shedding of the lead paste is likely to occur during the battery cycling, which has limited effect on improving the cycle life of the lead-acid battery. Summary of the invention

[0004] In order to solve the technical problems mentioned in the background technology, the present invention provides a graphene battery negative electrode material and a preparation method thereof.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a graphene battery negative electrode material comprises the following steps:

[0007] Step 1: Add three-dimensional graphene, barium sulfate, organic additives and lead powder to an ethanol aqueous solution, stir for 10-15 minutes, then add a binder, continue stirring for 10-15 minutes to obtain a slurry, and spray dry the slurry to obtain a powder;

[0008] Step 2: Disperse the fiber in deionized water to obtain a dispersion, add the dispersion and the above powder into a paste making machine, stir for 10-15 minutes, add 45-51wt% sulfuric acid solution, continue stirring for 5-7 minutes, and obtain a lead paste;

[0009] Step 3: Apply the lead paste on the lead-acid battery grid with a coating thickness of 1 mm to 3.0 mm, and then dry it in an oven at 50 to 70° C. for 24 to 45 hours to obtain a graphene battery negative electrode material.

[0010] The mass ratio of three-dimensional graphene, barium sulfate, organic additive, adhesive, lead powder and ethanol aqueous solution is 0.5-1.5: 0.8-1.2: 0.2-1: 2-5: 100: 250-270, and the ethanol aqueous solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 10-20: 1;

[0011] Furthermore, the amount of fiber added is 0.1-0.2% of the mass of the lead powder, the fiber is polyester fiber or acrylic fiber, the amount of deionized water is 9-11% of the mass of the lead powder, and the amount of sulfuric acid solution is 8-9% of the mass of the lead powder.

[0012] Further, the binder is prepared by the following steps:

[0013] Add auxiliary agent and alkyl siloxane to polytetrafluoroethylene emulsion, stir at a speed of 10-20 r / min for 30-50 minutes to obtain a binder.

[0014] The solid content of the polytetrafluoroethylene emulsion is preferably 60%, the molecular weight of the polytetrafluoroethylene is in the range of 8000-20000, preferably 8000-10000, and the dosage of the auxiliary agent and the alkyl siloxane is 2.5-5% of the solid content of the polytetrafluoroethylene emulsion.

[0015] Furthermore, the alkylsiloxane is one or more of tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane in any proportion.

[0016] Further, the adjuvant is prepared by the following steps:

[0017] Add allyl catechol and siloxane containing silicon-hydrogen bonds to toluene, stir evenly, slowly heat to 30-50°C under nitrogen atmosphere, add chloroplatinic acid isopropanol solution, heat to 70°C, stir to react for 2-4h, and after the reaction is completed, remove toluene by rotary evaporation to obtain an auxiliary agent;

[0018] The siloxane containing silicon-hydrogen bonds is one of trimethoxysilane, triethoxysilane, dimethoxymethylsilane and diethoxymethylsilane; the molar ratio of allyl catechol to the siloxane containing silicon-hydrogen bonds is 1:1.2-1.5; the amount of toluene used is 3-5 times the sum of the masses of allyl catechol and the siloxane; the amount of chloroplatinic acid in the chloroplatinic acid isopropanol solution is 0.01-0.05% of the mass of allyl catechol, the mass of isopropanol is 1000 times the mass of chloroplatinic acid, and allyl catechol and siloxane are used as substrates, and the auxiliary agent is obtained through a silylation reaction under the action of a catalyst.

[0019] Furthermore, the organic additive is composed of sodium lignin sulfonate and humic acid in a mass ratio of 1:1.

[0020] Furthermore, the air inlet temperature is controlled at 180-250°C during spray drying.

[0021] A graphene battery negative electrode material is prepared by the above preparation method.

[0022] Beneficial effects of the present invention:

[0023] 1. The present invention uses three-dimensional graphene to replace conventional carbon powder as a conductive additive, and adds a binder at the end of the powder preparation process. The purpose is to utilize the porous structure of the three-dimensional graphene to embed the lead powder in the gaps of the three-dimensional graphene, so that the active substance and the carbon powder are tightly combined and evenly distributed. Subsequently, the binder is connected through hydrogen bonding, coordination, and condensation reactions, so that the raw material distribution is more uniform, which is conducive to forming a dense and continuous conductive network.

[0024] 2. The present invention adopts a hybrid binder, specifically a hybrid liquid composed of polytetrafluoroethylene, an auxiliary agent and an alkyl siloxane. The three form a cross-linked network in the negative electrode lead paste, wherein polytetrafluoroethylene has strong hydrophobicity and poor wettability to the electrolyte, and plays the role of an oxygen recombination channel in the negative electrode material. The introduction of auxiliary agents and alkyl siloxanes can produce silanols by hydrolysis, and silanols then react with the hydroxyl groups on the surface of the grid metal to form Me-OS i chemical bonds through condensation reactions. The catechol groups in the auxiliary agent form strong coordination and chelating capabilities with the grid metal, and the adhesion between the lead paste and the grid is improved through chemical linkage and coordination.

[0025] 3. The introduction of the auxiliary agent and alkyl siloxane in the present invention can not only improve the adhesion between the lead paste and the grid, but also undergo a condensation reaction after hydrolysis to produce a S iOS i structure, which has good hydrophobic properties, enhances the barrier properties to the electrolyte, and improves the cycle life of the battery. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] Preparation of three-dimensional graphene:

[0029] 40 mg of graphene oxide was added to 20 mL of deionized water, and after ultrasonic dispersion for 20 min, 80 mg of L-cysteine ​​was added, followed by 600 μL of 25 wt% ammonia water. The mixture was placed in a flask, reacted at 95° C. for 4 h, filtered, and freeze-dried to obtain three-dimensional graphene.

[0030] Example 2

[0031] The adhesive is made by the following steps:

[0032] 15 g of auxiliary agent and 15 g of tetramethoxysilane were added to 1 kg of polytetrafluoroethylene emulsion, and the mixture was stirred at a speed of 10 r / min for 30 min to obtain a binder. The solid content of the polytetrafluoroethylene emulsion was 60%, and the molecular weight of the polytetrafluoroethylene was in the range of 8000-10000.

[0033] The auxiliary agent is prepared by the following steps:

[0034] 0.1 mol of allyl catechol and 0.12 mol of trimethoxysilane are added to toluene, stirred evenly, and then slowly heated to 30°C under a nitrogen atmosphere, and chloroplatinic acid isopropanol solution is added, heated to 70°C, stirred for reaction for 2 hours, and toluene is removed by rotary evaporation to obtain an auxiliary agent. The amount of toluene is 3 times the total mass of allyl catechol and siloxane; the amount of chloroplatinic acid in the chloroplatinic acid isopropanol solution is 0.01% of the mass of allyl catechol, and the mass of isopropanol is 1000 times the mass of chloroplatinic acid.

[0035] Example 3

[0036] The adhesive is made by the following steps:

[0037] 30 g of auxiliary agent and 30 g of alkyl siloxane were added to 1 kg of polytetrafluoroethylene emulsion, and the mixture was stirred at a speed of 20 r / min for 50 min to obtain a binder. The solid content of the polytetrafluoroethylene emulsion was 60%, and the molecular weight of the polytetrafluoroethylene was in the range of 8000-10000.

[0038] The alkylsiloxane is composed of tetramethoxysilane, tetraethoxysilane and phenyltrimethoxysilane in a mass ratio of 1:1:1.

[0039] The auxiliary agent is prepared by the following steps:

[0040] 0.1 mol of allyl catechol and 0.15 mol of dimethoxymethylsilane are added to toluene, stirred evenly, and then slowly heated to 50°C under a nitrogen atmosphere, and chloroplatinic acid isopropanol solution is added, heated to 70°C, stirred for reaction for 4 hours, and toluene is removed by rotary evaporation to obtain an auxiliary agent; the amount of toluene is 5 times the mass of allyl catechol and siloxane; the amount of chloroplatinic acid in the chloroplatinic acid isopropanol solution is 0.05% of the mass of allyl catechol, and the mass of isopropanol is 1000 times the mass of chloroplatinic acid.

[0041] Example 4

[0042] A method for preparing a graphene battery negative electrode material comprises the following steps:

[0043] Step 1: add 0.5 g of three-dimensional graphene, 0.8 g of barium sulfate, 0.2 g of organic additive and 100 g of lead powder to 250 g of ethanol aqueous solution, stir for 10 min, add 2 g of adhesive of Example 2, continue stirring for 10 min to obtain slurry, spray dry the slurry to obtain powder, and the ethanol aqueous solution is prepared by anhydrous ethanol and deionized water in a volume ratio of 10:1;

[0044] Step 2, dispersing the fiber in deionized water to obtain a dispersion, adding the dispersion and the above-mentioned powder into a paste making machine, stirring for 10 minutes, adding a 45wt% sulfuric acid solution, and continuing to stir for 5 minutes to obtain a lead paste, wherein the amount of fiber added is 0.1% of the mass of the lead powder, the fiber is polyester fiber, the amount of deionized water used is 9% of the mass of the lead powder, and the amount of sulfuric acid solution used is 8% of the mass of the lead powder;

[0045] Step 3: Apply the lead paste on the lead-acid battery grid with a coating thickness of 1 mm, and then dry it in an oven at 50° C. for 24 hours to obtain a graphene battery negative electrode material.

[0046] The organic additive is composed of sodium lignin sulfonate and humic acid in a mass ratio of 1:1, and the air inlet temperature is controlled at 180°C during spray drying.

[0047] Example 5

[0048] A method for preparing a graphene battery negative electrode material comprises the following steps:

[0049] Step 1: add 1.0 g of three-dimensional graphene, 1.0 g of barium sulfate, 0.5 g of an organic additive and 100 g of lead powder to 260 g of an ethanol aqueous solution, stir for 13 min, then add 4 g of the adhesive of Example 3, continue stirring for 13 min to obtain a slurry, spray dry the slurry to obtain a powder, and the ethanol aqueous solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 15:1;

[0050] Step 2, dispersing the fiber in deionized water to obtain a dispersion, adding the dispersion and the above-mentioned powder into a paste making machine, stirring for 13 minutes, adding a 48wt% sulfuric acid solution, and continuing to stir for 6 minutes to obtain a lead paste, wherein the amount of fiber added is 0.1% of the mass of the lead powder, the fiber is acrylic fiber, the amount of deionized water used is 10% of the mass of the lead powder, and the amount of sulfuric acid solution used is 8% of the mass of the lead powder;

[0051] Step 3: Apply the lead paste on the lead-acid battery grid with a coating thickness of 2 mm, and then dry it in an oven at 60° C. for 35 hours to obtain a graphene battery negative electrode material.

[0052] The organic additive is composed of sodium lignin sulfonate and humic acid in a mass ratio of 1:1, and the air inlet temperature is controlled at 200°C during spray drying.

[0053] Example 6

[0054] A method for preparing a graphene battery negative electrode material comprises the following steps:

[0055] Step 1: add 1.5 g of three-dimensional graphene, 1.2 g of barium sulfate, 1 g of an organic additive and 100 g of lead powder to 270 g of an ethanol aqueous solution, stir for 15 min, then add 5 g of the adhesive of Example 2, continue stirring for 15 min to obtain a slurry, spray dry the slurry to obtain a powder, and the ethanol aqueous solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 20:1;

[0056] Step 2, dispersing the fiber in deionized water to obtain a dispersion, adding the dispersion and the above-mentioned powder into a paste making machine, stirring for 15 minutes, adding a 51wt% sulfuric acid solution, and continuing to stir for 7 minutes to obtain a lead paste, wherein the amount of fiber added is 0.2% of the mass of the lead powder, the fiber is polyester fiber or acrylic fiber, the amount of deionized water used is 11% of the mass of the lead powder, and the amount of sulfuric acid solution used is 9% of the mass of the lead powder;

[0057] Step 3: Apply the lead paste on the lead-acid battery grid with a coating thickness of 3.0 mm, and then dry it in an oven at 70° C. for 45 hours to obtain a graphene battery negative electrode material.

[0058] The organic additive is composed of sodium lignin sulfonate and humic acid in a mass ratio of 1:1, and the air inlet temperature is controlled at 250°C during spray drying.

[0059] Comparative Example 1

[0060] The binder in Example 4 is replaced by a polytetrafluoroethylene emulsion with a solid content of 60%, and the molecular weight of the polytetrafluoroethylene is in the range of 8000-10000. The remaining raw materials and preparation are the same as in Example 4.

[0061] Comparative Example 2

[0062] The binder in Example 4 is replaced with the oxygen composite channel forming agent described in Example 4 of Patent Publication No. CN113540424B, which is composed of polytetrafluoroethylene and tetrafluoroethylene-acrylic acid copolymer in a mass ratio of 3:1. The remaining raw materials and preparation are the same as in Example 4.

[0063] The negative electrode materials prepared in Examples 4-6 and Comparative Examples 1-2 were tested:

[0064] (I) Mechanical properties: Weigh each group of materials and record m1, then place them at a height of 1m with the plate surface parallel to the ground, and then let them fall freely to observe the degree of damage to the plate. Next, hang the plate surface perpendicular to the ground at a height of 1m, cut the thin rope at the same height, let them fall freely, and observe the degree of damage to the plate. After the plates have been dropped twice, gently wipe off the floating powder on the surface, weigh them again and record m2, and calculate the mass loss (m1-m2). The test results are shown in Table 1.

[0065] (II) Electrochemical performance: The grids used in the factory were coated with the lead paste obtained in Example 4, assuming that the amount of active material in the positive plate was three times that of the negative plate (the calculation method of the active material was: the mass of the grid after the paste was dried minus the mass of the empty grid), to obtain the corresponding positive electrode materials of each group, thereby ensuring that the quality of the battery performance was completely determined by the negative plate. The obtained positive and negative plates were used to prepare lead-acid batteries. After 300 cycles, the water loss of the lead-acid batteries was detected. The test results are shown in Table 1.

[0066] Table 1

[0067]

[0068]

[0069] It can be seen from Table 1 that, compared with Comparative Examples 1-2, the negative electrode materials prepared in Examples 4-6 have higher mechanical strength, stronger adhesion between the lead paste and the grid, and can reduce the shedding of active materials, reduce battery water loss, and improve battery cycle life.

[0070] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0071] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a graphene battery negative electrode material, characterized in that: The following steps are involved: Step 1, adding an auxiliary agent and an alkyl siloxane to a polytetrafluoroethylene emulsion, and stirring to obtain a binder; Step 2: adding three-dimensional graphene, barium sulfate, organic additives and lead powder into an ethanol aqueous solution, stirring, adding a binder, continuing to stir to obtain a slurry, and spray drying to obtain a powder; Step 3, dispersing the fibers in deionized water to obtain a dispersion, adding the dispersion and the above-mentioned powder into a paste making machine, stirring, adding 45-51wt% sulfuric acid solution, and continuing to stir to obtain a lead paste; Step 4: Apply the lead paste on the lead-acid battery grid with a coating thickness of 1 mm to 3.0 mm, and then dry it in an oven at 50-70° C. for 24-45 hours to obtain a graphene battery negative electrode material; The adjuvant is prepared by the following steps: Add allyl catechol and siloxane containing silicon-hydrogen bonds to toluene, stir evenly, slowly heat to 30-50°C under nitrogen atmosphere, add chloroplatinic acid isopropanol solution, heat to 70°C, stir to react for 2-4h, and remove toluene by rotary evaporation to obtain an auxiliary agent; The siloxane containing a silicon-hydrogen bond is one of trimethoxysilane, triethoxysilane, dimethoxymethylsilane and diethoxymethylsilane; The molar ratio of allyl catechol to siloxane containing silicon-hydrogen bonds is 1:1.2-1.5; the amount of toluene used is 3-5 times the total mass of allyl catechol and siloxane; the amount of chloroplatinic acid in the chloroplatinic acid isopropanol solution is 0.01-0.05% of the mass of allyl catechol.

2. The method for preparing a graphene battery negative electrode material according to claim 1, characterized in that: The mass ratio of three-dimensional graphene, barium sulfate, organic additive, adhesive, lead powder and ethanol aqueous solution is 0.5-1.5:0.8-1.2:0.2-1:2-5:100:250-270, and the ethanol aqueous solution is prepared by mixing anhydrous ethanol and deionized water in a volume ratio of 10-20:

1.

3. The method for preparing a graphene battery negative electrode material according to claim 1, characterized in that: The added amount of fiber is 0.1-0.2% of the mass of the lead powder, the fiber is polyester fiber or acrylic fiber, the amount of deionized water is 9-11% of the mass of the lead powder, and the amount of sulfuric acid solution is 8-9% of the mass of the lead powder.

4. The method for preparing a graphene battery negative electrode material according to claim 1, characterized in that: The solid content of polytetrafluoroethylene emulsion is 60%.

5. The method for preparing a graphene battery negative electrode material according to claim 1, characterized in that: The dosage of the auxiliary agent and the alkyl siloxane is 2.5-5% of the solid content of the polytetrafluoroethylene emulsion.

6. The method for preparing a graphene battery negative electrode material according to claim 1, characterized in that: The alkylsiloxane is one or more of tetramethoxysilane, tetraethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane in any proportion.

7. A graphene battery negative electrode material, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 6.

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