CN113683082B - Graphene quantum dot composite material and application thereof - Google Patents

Graphene quantum dot composite material and application thereof Download PDF

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CN113683082B
CN113683082B CN202110927160.0A CN202110927160A CN113683082B CN 113683082 B CN113683082 B CN 113683082B CN 202110927160 A CN202110927160 A CN 202110927160A CN 113683082 B CN113683082 B CN 113683082B
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graphene quantum
quantum dot
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lead
carbon source
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CN113683082A (en
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何可立
铁绍龙
何幸华
吴嘉豪
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Zhaoqing Zhongteneng Technology Investment Co ltd
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Abstract

The invention discloses a graphene quantum dot composite material and application thereof, wherein the composite material is prepared by uniformly mixing a carbon source and solid carrier particles, and reacting for at least 30min at 45-80 ℃; then heating to 180-220 ℃ to continue the reaction, or carrying out microwave treatment to continue the reaction. The graphene quantum dot composite material is an in-situ synthesized nano composite material, the size distribution of the quantum dots is uniform, the uniformity is better, and the performance is more stable and controllable. GQDs in the graphene quantum dot composite material has larger specific surface area and excellent conductivity, so that the contact area of an electrode material and electrolyte can be increased, the electronic conductivity of the material is improved, the active site of reaction is improved, the reaction dynamics characteristic is improved, the electrochemical performance of the material in a lead-acid battery is improved, and the long service life of the lead-acid battery secondary battery is realized.

Description

Graphene quantum dot composite material and application thereof
Technical Field
The invention relates to a novel functional material, in particular to a graphene quantum dot composite material and application thereof.
Background
With the advanced development of economy, society and science and technology, people have increased environmental requirements, and environmental pollution brought by application in power, electric power and other aspects in various fields is increasingly emphasized, so that clean energy enters various just-needed scenes, the contradiction between economic growth and resource environment is well solved, and positive contribution is made to sustainable development of human society and economy. The lead-acid battery with application development history in the last 150 years is invented by the people of france in 1859, so that various technologies such as coating plates for replacing lead plates, gel for replacing mobile dilute sulfuric acid and the like are injected, the product types, the electrical properties of the product, the cycle life, the convenience, the environmental protection safety and the like are improved and developed, the lead-acid battery is particularly superior to a lithium battery in aspects of high and low temperature environment, and a lead-acid battery recovery system is established and well operated in the global scope, and lead pollution is effectively avoided, so that the lead-acid battery is used as a lead-acid battery for starting, a lead-acid battery for power, a lead-acid battery for a fixed valve-controlled sealing type, a lead-acid battery for miner lamp or street lamp, or a lead-acid battery for a communication base station, or an extreme scene application and the like, and is widely applied in various fields including traffic (various motor vehicles), communication, electric power, military, navigation and aviation.
The lead-acid storage battery is low in cost, but short in cycle life, and is widely used for cycle charge and discharge for about 300-500 times in practical application. Due to the electrode material passing through during use or charge-discharge cyclesDegree of sulfation (PbSO) 4 Size-enlarging activity decreases) leads to a significant decrease in capacity, a decrease in cycle performance, leading to a service life of the lead-acid battery in the range of 1-1.5 years. In order to prolong the service life of the lead-acid battery, researchers at home and abroad adopt various methods, such as adding various additives into electrode materials, such as titanium dioxide, white carbon black, various active carbon, acetylene black, graphene, bismuth oxide, sulfate and the like, or changing the structural aspect into a lead-carbon battery structure or compounding. These additives contribute more or less well to the dynamic life of the battery, but still bring about other negative effects such as still severe sulfation, aggravated partial self-discharge, significant decrease of absolute capacity (of lead-carbon batteries), high costs, etc., for example, graphene as reported in the literature has the effect of improving cycle life, rate stability, but results in an excessively low overall cost performance compared to the expensive cost of graphene. Therefore, how to crack lead-acid batteries with short life at acceptable cost, especially the serious degradation of performance due to sulfation of electrode materials, is one of the important challenges worth solving.
Graphene Quantum Dots (GQDs) refer to an emerging carbonaceous fluorescent material with graphene sheets with a size of less than 100nm and a number of sheets of less than 10. Generally, graphene quantum dots include a general term for carbonaceous fluorescent materials and derivatives thereof with similar structures and similar performances to those of graphene quantum dots, graphene oxide quantum dots and partially reduced graphene oxide quantum dots.
The preparation of the graphene quantum dots comprises a top-down method and a bottom-up method.
Synthesis from top to bottom
The top-down method is to etch large-size substances into nano-size graphene quantum dots by a physical or chemical method, and has preparation paths of solvothermal method, electrochemistry, chemical stripping and the like.
The solvothermal method is one of many methods for preparing graphene quantum dots, and the process can be divided into three steps: firstly, reducing graphene oxide into graphene nano sheets at a high temperature in a vacuum state; oxidizing and cutting graphene nano sheets in concentrated sulfuric acid and concentrated nitric acid; and finally, reducing the oxidized graphene nano sheet in a solvothermal environment to form the graphene quantum dots.
The process of the process for preparing the graphene quantum dots by the electrochemical method can be summarized into three stages: the first stage is an induction period in which graphite is exfoliated to form graphene, and the color of the electrolyte starts to change from colorless to yellow to dark brown; the second stage is that graphite of the anode expands obviously; the third stage is that the graphite flakes have been exfoliated from the anode, forming a black solution with the electrolyte. In the second and third stages, a sediment was found at the bottom of the beaker. There is an interaction of water with anions in the ionic liquid in the electrochemical reaction, so the shape and size distribution of the product can be adjusted by changing the ratio of water to ionic liquid. The size of the quantum dot prepared by the electrolyte with large ion concentration is larger than that prepared by the electrolyte with small ion concentration.
The chemical stripping carbon fiber rule is to strip a carbon source layer by layer through chemical reaction to prepare the graphene quantum dot. Peng et al used resin-based carbon fibers as a carbon source, and then peeled off graphite stacked in the fibers by acid treatment. Graphene quantum dots can be obtained in one step, however, the particle sizes of the graphene quantum dots are not uniform.
Bottom-up synthesis
The bottom-up measure is to prepare graphene quantum dots by using smaller constructional units as precursors through a series of interaction forces, and the graphene quantum dots mainly have preparation paths of a solution chemical method, an ultrasonic wave method, a microwave method and the like.
The solution chemical method is mainly used for preparing the graphene quantum dots by a solution phase chemical method of aryl oxidative condensation. The synthesis process is to gradually condense and react small molecule (3-iodine-4 bromoaniline or other benzene derivatives) polymer to prepare a polyphenyl dendritic precursor, prepare graphene through oxidation reaction, and finally prepare the graphene quantum dot through etching.
The microwave rule uses saccharides (e.g., glucose, fructose, etc.) as carbon sources, because the saccharides can form c=c after dehydration, so that they can constitute the basic framework units of graphene quantum dots. The hydrogen and oxygen elements in the hydroxyl and carboxyl groups are dehydrated and removed in a hydrothermal environment, and the residual functional groups are still bonded on the surface of the graphene quantum dot and exist as a passivation layer, so that the graphene quantum dot has good water solubility and fluorescence property.
The existing graphene quantum dot synthesis process is generally complex in operation, needs strong acid, strong oxidant and the like, is relatively complex in synthesis process and takes a long time. Complex purification treatment is required after synthesis, so that the cost is high, and the application range is severely limited.
Disclosure of Invention
The invention aims to overcome at least one defect of the prior art and provides a graphene quantum dot composite material and application thereof.
The technical scheme adopted by the invention is as follows:
in a first aspect of the invention, there is provided:
a preparation method of the graphene quantum dot composite material comprises the following steps:
uniformly mixing a carbon source and solid carrier particles, and reacting at 45-80 ℃ for at least 30 min; the solid support particles are selected from lead acid battery acceptable additives;
heating to 180-220 ℃ to continue the reaction, or carrying out microwave treatment to continue the reaction, thus obtaining the graphene quantum dot composite material.
In some examples, the solid support is selected from Na 2 SO 4 、TiO 2 、BaSO 4 、SiO 2 Activated carbon and PbSO 4 、NiSO 4 、Bi 2 O 3 NiO, glass fiber, talcum powder and CaSiO 3 At least one of them.
In some examples, the carbon source is selected from carbon sources having a molecular weight of no greater than 1000.
In some examples, the carbon source is selected from a sulfur and/or nitrogen containing carbon source, or a C6 or greater carbon source containing a carboxyl group.
In some examples, the sulfur-containing carbon source is selected from the group consisting of thioaromatic alcohols or acids, thiophene derivatives, thioamides, thioureas.
In some examples, the nitrogen-containing carbon source is selected from the group consisting of pyridine, bipyridine derivatives, para-aniline, quinine, and derivatives thereof.
In some examples, the above C6 carboxyl group containing carbon source is selected from citric acid and its derivatives, salicylic acid and its derivatives, benzoic acid and its derivatives.
In some examples, the carbon source includes at least one carbon source that contains sulfur and/or nitrogen, and one or more carbon sources that contain carboxyl groups.
In some examples, the molar ratio of the sulfur and/or nitrogen containing carbon source to the carboxyl group containing carbon source above C6 is (2-3): 1.
in some examples, the sulfur and/or nitrogen containing carbon source is thiourea and the carboxyl containing carbon source above C6 is citric acid.
In some examples, the carbon source is dissolved in a solvent and then mixed with the solid support particles.
In some examples, the carbon source is used in an amount of 0.001 to 0.1 mass of the solid support.
In some examples, the 180-220 ℃ reaction time is not less than 60 minutes, preferably 120-240 minutes.
In some examples, the microwave treatment is for a period of time ranging from 5 to 20 minutes; the preferred microwave power is 600-800W/g carbon source.
In a second aspect of the invention, there is provided:
use of a graphene quantum dot composite material in the preparation of a lead acid battery additive, the graphene quantum dot composite material being as described in the first aspect of the invention.
In a third aspect of the invention, there is provided:
an electrode material for a lead acid battery, which is mixed with the graphene quantum dot composite material according to the first aspect of the present invention.
The electrode material is a positive electrode material or a negative electrode material.
In a fourth aspect of the invention, there is provided:
a lead-acid battery is prepared by mixing the graphene quantum dot composite material according to the first aspect of the invention into an electrode material.
The beneficial effects of the invention are as follows:
according to some examples of the invention, the graphene quantum dot composite material is an in-situ synthesized nanocomposite, the size of the quantum dots is uniformly distributed, the uniformity is better, and the performance is more stable and controllable. GQDs in the graphene quantum dot composite material has larger specific surface area and excellent conductivity, so that the contact area of an electrode material and electrolyte can be increased, the electronic conductivity of the material is improved, the active site of reaction is improved, the reaction dynamics characteristic is improved, the electrochemical performance of the material in a lead-acid battery is improved, and the long service life of the lead-acid battery secondary battery is realized.
According to some examples of the invention, the synthesis process of the graphene quantum dots is simple, strong acid, strong oxidant and the like are not needed, the solvent used in the synthesis process can be completely and simply recycled for secondary use, complex purification operation is omitted, the synthesis cost of the graphene quantum dot composite material is low, the synthesis process is environment-friendly, and industrial production is easy to realize.
In some examples of the invention, the synthesis time of the graphene quantum dot composite material can be shortened to within 1 h.
According to some examples of the invention, the graphene quantum dot composite material can be simply and conveniently added into a lead-acid battery, the service life of the lead-acid battery is obviously prolonged, and the cycle life of the obtained lead-acid battery exceeds 2000 times and the highest value reaches 12000 times under a 1C multiplying power partial charge mode (High-Rate Partial State of Charge, HRPSC). Compared with the graphene powder, the cost of the graphene quantum dot composite material added with some examples of the invention can be reduced to less than one thousandth.
Some examples of the invention, graphene quantum dots contain S, which in use is firmly combined with Pb in the lead-acid electrode material matrix, the battery reaction sites are fixed and uniform, and part of sulfur is converted into nano PbSO 4 As seed crystal in cell reaction, plays a role in refining PbSO 4 Acting as a medicine. The performance of the lead acid battery can be further improved.
Drawings
FIG. 1 is S prepared in example 1iO 2 TEM image of graphene quantum dot composite.
FIG. 2 is a SiO produced in example 1 2 Raman spectra of GQDs in graphene quantum dot composites.
FIG. 3 shows examples 1, 2 and 3, respectively, for SiO application 2 Graphene quantum dot composite material and TiO (titanium dioxide) 2 Graphene quantum dot composite and comparative example (blank: no a/graphene quantum dot composite added) 1C rate HRPSoC cycle curve comparison graph of lead-acid battery.
FIG. 4 is a fluorescence spectrum of 365nm ultraviolet excitation after 100 times dilution of the graphene quantum dot composite material aqueous solution prepared in example 3
FIG. 5 is Na prepared in example 3 2 SO 4 Raman spectra of GQDs in graphene quantum dot composites.
FIG. 6 is a cycle of the lead acid battery magnification corresponding to examples 4 to 6, respectively corresponding to Na addition 2 SO 4 /GQDs、BaSO 4 GQDs, activated carbon/GQD lead-acid battery rate cycle curve made of electrode material.
FIG. 7 is a cycle of lead acid battery rates corresponding to examples 7-10, respectively corresponding to the addition of PbSO 4 / GQDs、NiSO 4 /GQDs、Bi 2 O 3 GQDs, niO/GQDs are included in the rate cycling curves of lead-acid batteries made of electrode materials.
FIG. 8 is a cycle chart of the magnification of lead-acid batteries corresponding to examples 11 to 13, corresponding to the addition of glass fibers/GQDs, talc/GQDs, caSiO, respectively 3 GQDs (electrolyte is further added with 0.1% of SiO prepared in example 1) 2 Graphene quantum dot composite) is added into a multiplying power circulation curve of a lead-acid battery made of a negative electrode material.
Fig. 9 and 10 are HRPSoC curves for different lead acid batteries.
Fig. 11 is a 1C cycle curve for different lead acid batteries.
Detailed Description
A preparation method of the graphene quantum dot composite material comprises the following steps:
uniformly mixing a carbon source and solid carrier particles, and reacting at 45-80 ℃ for at least 30 min; the solid support particles are selected from lead acid battery acceptable additives;
heating to 180-220 ℃ to continue the reaction, or carrying out microwave treatment to continue the reaction, thus obtaining the graphene quantum dot composite material.
The solid carrier has no special requirement and is acceptable for lead-acid batteries. In some examples, the solid support is selected from Na 2 SO 4 、TiO 2 、BaSO 4 、SiO 2 Activated carbon and PbSO 4 、NiSO 4 、Bi 2 O 3 NiO, glass fiber, talcum powder and CaSiO 3 At least one of them. The particular type of solid support may be selected accordingly, depending upon the particular performance of the lead acid battery.
In some examples, the carbon source is selected from carbon sources having a molecular weight of no greater than 1000.
In some examples, the carbon source is selected from a sulfur and/or nitrogen containing carbon source, or a C6 or greater carbon source containing a carboxyl group.
In some examples, the sulfur-containing carbon source is selected from the group consisting of thioaromatic alcohols or acids, thiophene derivatives, thioamides, thioureas.
In some examples, the nitrogen-containing carbon source is selected from the group consisting of pyridine, bipyridine derivatives, para-aniline, quinine, and derivatives thereof.
In some examples, the above C6 carboxyl group containing carbon source is selected from citric acid and its derivatives, salicylic acid and its derivatives, benzoic acid and its derivatives.
The carbon sources are widely available, and the graphene quantum dots are dehydrated and degrouped on the surface of the solid carrier to form a uniform dispersion system in situ in the subsequent heating process by performing surface chemical adsorption with the solid carrier in solid-solid mixture or solvent, so that the agglomeration of GQDs is effectively prevented.
In some examples, the carbon source includes at least one carbon source that contains sulfur and/or nitrogen, and one or more carbon sources that contain carboxyl groups.
In some examples, the molar ratio of the sulfur and/or nitrogen containing carbon source to the carboxyl group containing carbon source above C6 is (2-3): 1.
in some examples, the sulfur and/or nitrogen containing carbon source is thiourea and the carboxyl containing carbon source above C6 is citric acid.
In some examples, the carbon source is dissolved in a solvent and then mixed with the solid support particles.
In some examples, the carbon source is used in an amount of 0.001 to 0.1 mass of the solid support.
In some examples, the 180-220 ℃ reaction time is not less than 60 minutes, preferably 120-240 minutes.
In some examples, the microwave treatment is for a period of time ranging from 5 to 20 minutes; the preferred microwave power is 600-800W/g carbon source.
The principle of the invention is as follows: the micro-molecular organic matter (such as thiourea and citric acid contain amino and carboxyl) and the solid carrier are subjected to surface chemisorption in solid-solid mixture or solvent, and graphene quantum dots are dehydrated and degrouped on the surface of the solid carrier in situ to form a uniform dispersion system in the subsequent heating process, so that agglomeration of GQDs is effectively prevented.
According to the invention, the graphene quantum dot composite material is applied to a lead-acid battery as one of the components in the electrode material, and because the graphene quantum dots are uniformly distributed in the graphene quantum dot/solid carrier composite material (which is attributed to the fact that the solid carrier plays an in-situ catalytic role in subsequent dehydration and degranulation reaction between carbon source functional groups in subsequent echelon heating), the dispersion performance is good, the electrochemical performance of the graphene quantum dot/solid carrier composite material is greatly improved when the graphene quantum dot/solid carrier composite material is applied to a scene such as a battery, and the like due to the electrostatic adsorption effect of GQDs generated in situ and a matrix, the solid carrier prevents the GQDs from mutually agglomerating, the graphene quantum dot/solid carrier composite material is smaller than 10nm in size and large in specific surface area, has good conductivity and can provide more reactive sites, plays heterogeneous crystal nuclei and electron transfer roles when the graphene quantum dot/solid carrier composite material is applied to a charge-discharge scene of the lead-acid battery, such as acceleration refined lead sulfate formation during discharge, polarization and dendrite generation are reduced, and electron transfer are favorable, so that the dynamic characteristics of discharge/charge reaction are improved, rate performance is improved, and capacity is slowed down. All these excellent properties are difficult to achieve by adding GQDs alone (because of the tendency to agglomerate with sizes less than 5 nm).
The present invention will be described in further detail with reference to examples and drawings, but embodiments of the present invention are not limited thereto.
For convenience of description, the lead-acid battery fabrication, formation and test parameters in the following examples are briefly summarized as follows:
(1) Full battery assembly: the prepared solid carrier/graphene quantum dot composite material is added into a negative electrode material PbO according to a certain proportion, blank examples correspond to untreated PbO negative electrode materials and pastes, the formula and the process are similar to those reported in published lead-acid battery manufacturing documents, for example, the negative electrode materials are respectively mixed with an expanding agent, polytetrafluoroethylene emulsion, sodium sulfate and deionized water according to the general mass ratio of the positive electrode material and the negative electrode material of a lead-acid battery, the paste is mixed, a plate is coated, a baking plate and the like, sulfuric acid (1.25-1.3M) is taken as an electrolyte solution, and the lead-acid full battery is assembled.
(2) And (3) formation: the formation is carried out in a four-charge and three-discharge mode which is common to lead-acid batteries.
(3) And (3) charge and discharge testing: carrying out rate cycle test on a lead-acid battery prepared by adding the solid carrier/graphene quantum dot composite material of each embodiment and a lead-acid battery prepared by the blank anode material PbO under 1C, wherein the test parameters are as follows: cut-off voltage is 1.75-2.2V; the charge and discharge are performed at a constant current, and the charge and discharge are terminated when the initial capacity is reduced to 80% or less.
Example 1
Graphene quantum dot/SiO of the embodiment 2 The preparation method of the composite material comprises the following specific preparation steps:
adding thiourea and citric acid in a molar ratio of 3:1 into white carbon black SiO under stirring condition 2 In the xylene dispersion liquid of (1), the mass of thiourea and citric acid is SiO 2 1% of mass; stirring for 30min, reacting at 80 ℃ for 1h, then refluxing and heating at 180 ℃ for 1h, cooling, centrifuging and drying to obtain the graphene quantum dot/SiO 2 Composite materials, i.e. GQDs/SiO 2 Can be directly usedThe additive is used as a lead-acid battery additive, and the additive amount is 1% of the mass percentage of the negative electrode material.
The application of SiO for example 1 is given in FIG. 3 2 1C rate HRPSC cycle graph corresponding to lead-acid battery made of graphene quantum dot composite material. Fig. 3 shows that the life span is more than 6000 times, which is more than 10 times that of comparative example PbO (500 times) (see fig. 11).
Example 2
Graphene quantum dot/TiO used in this example 2 The preparation method of the composite material comprises the following specific preparation steps:
adding benzothiazole and benzoic acid in a molar ratio of 2:1 into TiO under stirring 2 The mass of the benzothiazole and the citric acid in the solid powder is TiO 2 0.5% of the mass. Grinding for 30min, reacting at 60deg.C for 1 hr, heating at 200deg.C for 1 hr, and cooling to obtain graphene quantum dot/TiO 2 Composite materials, i.e. GQDs/TiO 2 Can be used as an electrode material additive of a lead-acid battery. The addition amount is 0.5 percent of the mass percentage of the cathode material.
Application example 2 graphene Quantum dot/TiO is shown in FIG. 4 2 The composite material and the lead-acid battery prepared by the additive amount of 0.5 percent of the mass percentage of the negative electrode material are 1C rate HRPSC cycle curve graphs. As can be seen from FIG. 4, the lifetime is more than 5000 times, 10 times that of comparative example PbO.
Example 3
Na used in this example 2 SO 4 The preparation method of the graphene quantum dot composite material comprises the following specific preparation steps:
under stirring, 5g of the total mass, corresponding to a molar ratio of 3:1, of thiosalicylic acid to (citric acid+aniline, molar ratio 1:1) were added to Na 2 SO 4 In the solid powder, the mass of the thiosalicylic acid and (citric acid+aniline, molar ratio 1:1) is Na 2 SO 4 10% of the mass. Grinding for 30min, placing into 800W microwave oven, heating for reaction at low fire for 4min, heating at medium fire for 5min, and cooling to obtain graphene quantum dot/Na 2 SO 4 Composite materials, i.e. GQDs/Na 2 SO 4 Can be used as the anode material of lead-acid battery to be addedThe addition ratio of the agent is 0.55%.
FIG. 5 is a fluorescence spectrum of 365nm ultraviolet excitation after 100 times dilution of the aqueous solution of the graphene quantum dot composite material prepared in example 3.
FIG. 6 is Na prepared in example 3 2 SO 4 Raman spectrum of graphene quantum dot composite material.
Fig. 7 shows a 1C rate HRPSoC cycle graph of the lead-acid battery prepared by adding the graphene quantum dot composite material of example 3 to the negative electrode material PbO by 0.55% by mass. As can be seen in FIG. 7, the lifetime is up to 4000 times that of comparative example PbO.
Example 4
BaSO used in this example 4 The preparation method of the GQDs composite material comprises the following specific preparation steps:
adding thiophene and ethyl citrate in a molar ratio of 3:1 into BaSO under stirring 4 In the solid powder, the mass of thiourea and the mass of the ethyl citrate are Na 2 SO 4 5% of the mass. Grinding for 30min, heating in an oven at 80deg.C for 1 hr, heating in an oven at 200deg.C for 1 hr, and cooling to obtain BaSO 4 GQDs composites, i.e., can be used as lead acid battery electrode material additives. The mass percent is 0.55 percent to the anode material PbO.
FIG. 8 shows the addition of example 4 BaSO 4 1C rate HRPSC cycle graph of lead acid batteries made of GQDs composites. As can be seen in FIG. 8, the lifetime is up to 3000 times, 6 times that of comparative example PbO.
Examples 5 to 12 activated carbon/GQD, pbSO 4 /GQDs、NiSO 4 /GQDs、Bi 2 O 3 GQDs, niO/GQDs, glass fibers/GQDs, talc/GQDs, caSiO 3 GQDs (electrolyte of example 12 is further added with 0.1% of SiO prepared in example 1) 2 Graphene quantum dot composite) nanocomposite preparation method was the same as in example 1. The additives were added to the negative electrode material in amounts of 0.2%, 10%, 0.1%, 0.3%, 0.25%, 5%, 3% and 1%, respectively, to prepare lead-acid batteries. The HRPSO performance of the obtained battery is summarized in FIGS. 9 and 10, respectively, and the results show that the battery performance is shown in the tableAll of them are significantly better than the comparative examples.
Comparative example
Negative electrode PbO and positive electrode PbO 2 As a control for the blank negative electrode positive electrode material, commercial battery grade products used in example 1 were each used. Lead acid batteries were made using the same process and subjected to the same test.
Fig. 11 (blank) shows the charge-discharge curve cycle number of about 500 times when the battery is operated in the 1C charge mode (HRPSoC), and for comparison, the battery performance of the added PbO/GQDs is also shown in fig. 11.
From fig. 3 to 11 and the above detection data, it can be seen that the a/graphene quantum dot composite material obtained by the preparation method of the present invention is used for lead-acid batteries, and can obtain stable and long-life rate cycle performance, which is significantly better than that of blank or comparative example. This is related to the close loading of the GQDs on the a surface (facilitating uniform dispersion of the GQDs in the electrode material or electrolyte), discontinuous distribution of the GQDs, and excellent conductivity. In contrast, the comparative examples are due to sulfation, pbSO, during battery operation 4 The size is increased, the effective contact area of the active substance and the electrolyte is greatly reduced, the polarization of the material is obvious, the material utilization rate is low, and the electrochemical reaction is not facilitated.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.

Claims (4)

1. A preparation method of a graphene quantum dot composite material comprises the following steps:
uniformly mixing a carbon source and solid carrier particles, and reacting at 45-80 ℃ for at least 30 min; the solid carrier particles are selected from additives acceptable by lead-acid batteries, the carbon source is used in an amount of 0.001-0.1 of the mass of the solid carrier, and the solid carrier is selected from Na 2 SO 4 、TiO 2 、BaSO 4 、SiO 2 Activated carbon and PbSO 4 、NiSO 4 、Bi 2 O 3 NiO, glass fiber, talcum powder and CaSiO 3 At least one of the carbon sources is a mixture of (2-3): 1 thiourea and citric acid;
heating to 180-220 ℃ to continue the reaction, or carrying out microwave treatment to continue the reaction, wherein the microwave power is 600-800W/g carbon source, and obtaining the graphene quantum dot composite material.
2. The method of manufacturing according to claim 1, characterized in that: and after the carbon source is dissolved in the solvent, the carbon source is uniformly mixed with the solid carrier particles.
3. The preparation method according to claim 1 or 2, characterized in that:
the reaction time at 180-220 ℃ is not shorter than 60 min;
the microwave treatment time is 5-20 min.
4. A method of preparation according to claim 3, characterized in that: the reaction time of 180-220 ℃ is 120-240 min.
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