Graphene modified silver paste and application thereof in RFID tag

Abstract

The invention discloses graphene modified silver paste and application of the graphene modified silver paste in an RFID tag. The graphene modified silver paste comprises modified silver micro powder, modified graphene powder, an adhesive and a solvent, the content of the modified silver micro powder is 20-30 wt%, and the content of the modified graphene powder is 4-6 wt%; the surface of the modified graphene powder is modified with zinc tetraphenylporphyrin, and the surface of the modified silver micro powder is modified with 4-mercaptopyridine. The problems of two-phase separation and difficulty in uniform dispersion in a silver-graphene composite conductive system in the prior art can be effectively solved; and meanwhile, the contact resistance between silver and graphene powder particles can be reduced, and the conductivity of the paste is improved.

Description

Technical Field

[0001] This application relates to the field of printing electronics, and particularly to a graphene-modified silver paste and its application in RFID tags. Background Art

[0002] In the field of manufacturing RFID tags, the traditional aluminum foil etching process has been gradually replaced by printed electronics technology due to its complex processing flow, low material utilization rate, and difficulty in meeting the requirements of flexible production. As the core material of printed electronics, silver-based conductive paste has a significant positive correlation between its conductivity and silver content. However, the high proportion of precious metal silver has led to a sharp rise in material costs, severely restricting industrial applications. To break through this dilemma, the industry generally adopts the technical route of reducing silver content. However, when the silver content is reduced, the lack of contact points of silver particles per unit area results in the inability to form a continuous conductive network after sintering. In recent years, introducing graphene to construct a composite conductive system and using its high specific surface area to increase contact sites has become an effective way to improve the conductivity of low-silver pastes.

[0003] However, in practical applications, the graphene-silver micropowder composite system faces severe technical challenges. Specifically, when graphene and silver micropowder are directly mixed, the phase separation of the dispersed phase occurs due to the physical property differences between the two, seriously affecting the uniformity of the printed film and the product yield. To overcome the above problems, in the prior art, surface modification of graphene and silver micropowder is usually based on amphiphilic molecular surface modification. Although it can improve the dispersibility of conductive powders, the interfacial resistance between the powders is large, resulting in a decrease in the conductivity of the paste. Summary of the Invention

[0004] This application provides a graphene-modified silver paste and its application in RFID tags, which can effectively solve the problems of two-phase separation and difficult uniform dispersion existing in the silver-graphene composite conductive system in the prior art; at the same time, it can reduce the contact resistance between silver and graphene powder particles and improve the conductivity of the paste.

[0005] In a first aspect, this application provides a graphene-modified silver paste, which is characterized by comprising modified silver micropowder, modified graphene powder, a binder, and a solvent. The content of the modified silver micropowder is 20-30 wt%, and the content of the modified graphene powder is 4-6 wt%; the surface of the modified graphene powder is modified with zinc tetraphenylporphyrin, and the surface of the modified silver micropowder is modified with 4-mercaptopyridine.

[0006] In the traditional technical route of surface modification of conductive powders (such as graphene powder and silver powder) with amphiphilic molecules (such as surfactants), there is a significant electron transport barrier at the interface formed by weak interactions. When electrons are transmitted between graphene and silver micropowders, they need to cross this insulating layer, resulting in a significant contact resistance and a decrease in conductivity. Although modification with strong chemical bonds can enhance the interfacial bonding, it may damage the continuous π electron cloud formed by the complete sp² hybrid carbon skeleton of graphene and damage the intrinsic conductive structure that is the source of the high conductivity of graphene. This is also not suitable for the construction of a conductive network. In this application, zinc tetraphenylporphyrin (π-π binding) is processed on the surface of graphene, and 4-mercaptopyridine (Au / S bonding) is processed on the surface of silver particles. Finally, the coordination of pyridine on the surface of silver particles with zinc nuclei on the surface of graphene is used to achieve the effective dispersion and the construction of a highly efficient conductive network of the two, obtaining an antenna structure with both high dispersibility and high conductivity.

[0007] In any of the above technical solutions, the modified graphene powder is prepared by mixing graphene powder with a zinc tetraphenylporphyrin solution. The concentration of the zinc tetraphenylporphyrin is 0.2 - 0.4 wt%, and the concentration of the graphene powder is 0.5 - 2 wt%.

[0008] The concentration of the zinc tetraphenylporphyrin solution should be controlled at 0.2 - 0.4 wt%. Too high a concentration will cause multi-layer stacking of ZnTPP on the surface of graphene, reducing the conductivity, and too low a concentration will result in fewer active sites, reducing the subsequent binding efficiency.

[0009] In any of the above technical solutions, the modified silver micropowder is prepared by mixing silver micropowder with a 4-mercaptopyridine solution. The concentration of the 4-mercaptopyridine solution is 0.07 - 0.21 wt%, and the concentration of the silver micropowder is 5 - 15 wt%.

[0010] In any of the above technical solutions, the particle size of the modified graphene powder is 0.5 - 8 microns, and the number of layers is 1 - 20 layers.

[0011] In any of the above technical solutions, the particle size of the silver micropowder is 1 - 15 microns.

[0012] Based on the surface modification under the above conditions, the coverage rate of zinc tetraphenylporphyrin on the surface of the obtained modified graphene powder is about 90%; the growth of mercaptopyridine on the surface of the metal (silver micropowder) is a typical molecular self-assembly system, and the coverage rate of the obtained modified product (modified silver micropowder) is not less than 99%.

[0013] In any of the above technical solutions, the graphene-modified silver paste contains 20 - 30 wt% modified silver micropowder, 4 - 6 wt% modified graphene powder, 30 - 50 wt% binder, 20 - 30 wt% solvent, 2.5 - 3.5 wt% leveling agent, and 1.5 - 2.5 wt% coupling agent.

[0014] In any of the above technical solutions, the leveling agent is selected from organosilicon polyether leveling agents; for example, the leveling agent is BYK-333.

[0015] In any of the above technical solutions, the coupling agent is selected from epoxy group silane coupling agents; for example, the coupling agent is 3-glycidoxypropyltrimethoxysilane.

[0016] In any of the above technical solutions, the solvent is a mixture of diethylene glycol butyl ether acetate and turpentine with a mass ratio of 1-2:1-2.

[0017] In any of the above technical solutions, the preparation method of the graphene-modified silver paste is as follows: Mix the modified silver micropowder and the modified graphene powder according to the mass ratio to obtain a mixed powder. Mix the binder, solvent, leveling agent, and coupling agent according to the mass ratio to form an organic carrier, stir evenly, add the mixed powder in batches, and continue to stir evenly to form a thick paste. The thick paste is subjected to vacuum defoaming, grinding, and screening to obtain the graphene-modified silver paste.

[0018] In any of the above technical solutions, the graphene powder is obtained by centrifugal drying after high-energy exfoliation of expandable graphite in a mixed solvent of dihydrolevoglucosenone and triacetin with a mass ratio of 3-5:1.

[0019] In any of the above technical solutions, the high-energy exfoliation includes but is not limited to ultrasonic, air milling, ball milling, and shearing; preferably ultrasonic exfoliation.

[0020] In a second aspect, the present application provides an application of the graphene-modified silver paste in an RFID tag. The graphene-modified silver paste is printed on a substrate to form an antenna structure of the RFID tag.

[0021] In summary, the present application has the following beneficial effects: The present invention addresses the interface optimization problem in a heterogeneous material composite system (graphene and silver micropowder), and proposes a two-way surface modification technology based on molecular engineering. Zinc tetraphenylporphyrin (ZnTPP) is used to modify the surface of graphene, and a stable molecular adsorption layer is constructed on the surface of graphene through π-π interaction of the macrocyclic conjugated system. The steric hindrance effect of its structure can effectively inhibit the secondary aggregation of nanosheets. Synchronously, a molecular protection layer of 4-mercaptopyridine (4-Mpy) is constructed on the surface of silver micropowder to achieve surface functionalization by the specific binding of mercapto-silver. The repulsion between the ZnTPP metal cores on the surface of graphene and the lone pair electrons of pyridine on the surface of silver micropowder can prevent the aggregation of graphene-graphene or silver micropowder-silver micropowder, while the coordination between pyridine and the zinc metal core can strengthen the interaction between graphene and silver micropowder and improve the uniformity of their dispersion. Through the coordination bonding (bond energy 0.3-0.5 eV) between the pyridyl terminal and the zinc metal center of porphyrin, a heterogeneous interface connection with strong interaction is established, breaking through the transmission barrier problem caused by modification through molecular van der Waals forces (bond energy ~0.01 eV). This synergistic modification strategy can not only achieve the uniform dispersion of the graphene-silver system, but also construct an efficient electron transport channel at the atomic scale, and finally form a composite slurry with an efficient conductive network structure, which is successfully applied to the precision printing and manufacturing of radio frequency identification tags. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of the RFID tag of this application.

[0023] Figure 2 It is an atomic force microscope image (3 microns) of graphene micropowder covered with zinc tetraphenylporphyrin in Example 1.

[0024] Figure 3 It is an atomic force microscope image (0.8 microns) of graphene micropowder covered with zinc tetraphenylporphyrin in Example 1.

[0025] Figure 4 It is an SEM image of the slurry printed antenna structure in Example 1.

[0026] Figure 5 It is an SEM image of the slurry printed antenna structure in Comparative Example 5.

[0027] Figure 6 It is an SEM image of the slurry printed antenna structure in Comparative Example 6.

[0028] Figure 7 It is the read spectrum diagram of the RFID tag in Example 1.

[0029] Description of the Reference Numerals: 1. Chip; 2. Antenna; 3. Substrate. Detailed Embodiments

[0030] Example 1. A graphene-modified silver paste is prepared according to the following steps: Step 1: Expandable graphite is ultrasonically exfoliated in a mixed solvent of dihydrolevoglucosenone / glycerol triacetate with a mass ratio of 4:1 for 8 hours and then centrifuged and dried to obtain graphene powder (particle size 0.5 - 8 microns, number of layers 1 - 20). Take the graphene powder and add it to DMF solvent, stir for 5 minutes, then add zinc tetraphenylporphyrin to obtain a mixed solution with a zinc tetraphenylporphyrin content of 0.3 wt% and a graphene content of 1 wt%. After stirring for 30 minutes, centrifuge at 3000 rpm, remove the supernatant, and rinse twice with N-hexane to remove physically adsorbed ZnTPP, obtaining modified graphene powder with a ZnTPP coverage rate of approximately 90% (see Figure 1 , Figure 2 the AFM images).

[0031] Step 2: Add silver microplate powder to a 0.14 wt% 4-mercaptopyridine ethanol solution to obtain a mixed solution with a silver differential content of 10 wt%. Continuously stir at 200 rpm for 5 hours to form a self-assembled monolayer on the surface of the silver microplates. After stirring, wait for the silver micropowder to precipitate, remove the supernatant, and rinse twice with ethanol to remove physically adsorbed 4-mercaptopyridine, obtaining modified silver micropowder.

[0032] Step 3: Take 25 g of modified silver micropowder and 5 g of modified graphene powder and mix them by stirring to obtain a mixed powder. Mix 40 g of LR9100 TPU resin, 25 g of a mixed solvent of diethylene glycol butyl ether acetate and turpentine (mass ratio 1:1), BYK-333 leveling agent, and 3-glycidoxypropyltrimethoxysilane to form an organic carrier, and stir at 500 rpm for 50 minutes. Increase the stirring speed to 1500 rpm and add the mixed powder to the organic carrier in 5 portions at intervals of 5 minutes. After mixing, continue to stir at 1500 rpm for 3 hours to form a crude paste.

[0033] Step 4: Place the crude paste in a vacuum oven (>30 Pa, 25 °C, 30 minutes) to remove air bubbles, pass it through a three-roll mill three times, and then pass it through a 350-mesh sieve to obtain the graphene-modified silver paste.

[0034] Example 2. A graphene-modified silver paste, which is different from Example 1 in that the concentration of zinc tetraphenylporphyrin in Step 1 is adjusted to 0.85 wt%, and the others are the same as in Example 1.

[0035] Example 3. A graphene-modified silver paste, which is different from Example 1 in that the concentration of zinc tetraphenylporphyrin in Step 1 is adjusted to 0.085 wt%, and the others are the same as in Example 1.

[0036] Example 4. A graphene-modified silver paste, which is different from Example 1 in that in Step 3, the amounts of modified silver micropowder and modified graphene powder are 24 g and 6 g respectively (mixed in a mass ratio of 4:1), and the others are the same as in Example 1.

[0037] Comparative Example 1. A silver paste, which is different from Example 1 in that in Step 3, 25 g of silver micropowder (silver content 25%) is used to replace the mixed powder of 25 g of modified silver micropowder and 5 g of modified graphene, and the amount of LR9100 TPU resin is increased to 45 g, and the others are the same as in Example 1.

[0038] Comparative Example 2. A silver paste, which is different from Example 1 in that in Step 3, 40 g of silver micropowder (silver content 40%) is used to replace the mixed powder of 25 g of modified silver micropowder and 5 g of modified graphene, and the amount of LR9100 TPU resin is reduced to 30 g, and the others are the same as in Example 1.

[0039] Comparative Example 3. A graphene-modified silver paste, which is different from Example 1 in that in Step 3, unmodified silver micropowder of equal amount is used to replace the modified silver micropowder, and the others are the same as in Example 1.

[0040] Comparative Example 4. A graphene-modified silver paste, which is different from Example 1 in that in Step 3, unmodified graphene powder of equal amount (particle size 0.5 - 8 microns, number of layers 1 - 20) is used to replace the modified graphene powder, and the others are the same as in Example 1.

[0041] Comparative Example 5. A graphene-modified silver paste, which is different from Example 1 in that in Step 3, unmodified silver micropowder of equal amount is used to replace the modified silver micropowder, and unmodified graphene powder of equal amount is used to replace the modified graphene powder, and the others are the same as in Example 1.

[0042] Comparative Example 6. A graphene-modified silver paste, which is different from Example 1 in that in Step 3, unmodified silver micropowder of equal amount is used to replace the modified silver micropowder, and PVP-modified graphene powder of equal amount (PVP is K30, addition amount is 0.8% of the mass of graphene) is used to replace the modified graphene powder, and the others are the same as in Example 1.

[0043] Performance detection test: Using the conductive pastes of each example, print the antenna structure shown in Figure 1 on copper paper through a 260-mesh screen printing (the printing is in the first direction, and the antenna structure is designed according to the conductivity of the paste and the impedance characteristics of the chip), and pass through a pressure roller at 6 MPa and 165 °C. The N×P-U9 chip is coupled with the antenna by the flip chip bonding method. After connecting the chip and the antenna through a conductive adhesive (DELOMONOPO× AC268 of DELO), complete the label processing by hot pressing at 140 °C for 15 s.

[0044] 1. Conductivity analysis: Test method: In step 7, the screen printing structure is changed from the antenna structure to a 1 cm × 1 cm square. The substrate is art paper. After printing, it is dried at 120 °C for 30 minutes and rolled with a 160 MPa roller. The sheet resistance of the square printed matter is measured using a four-probe sheet resistance meter (DWR1C, Shanghai Instrumentation). The four probes are placed on the diagonal of the square, and the corresponding sheet resistance value is read. The thickness of the printed film is measured using a film thickness gauge (Shen Da Wei Ai Rui Pu SW6300-A), and the sheet resistance is converted into conductivity (conductivity = 1 / (sheet resistance × film thickness)).

[0045] Table 1. Test results of conductivity

[0046] Comparing Examples 1 - 3, it can be seen that the conductivity of Example 1 is higher than that of Examples 2 and 3. This shows that too high or too low ZnTPP concentration during the graphene treatment will affect the conductivity of the slurry. Specifically, when the concentration is too high, ZnTPP will form multiple layers of molecules on the surface of graphene, reducing the system conductivity; while when the concentration is too low, due to insufficient active sites, the subsequent binding of graphene and silver particles is not sufficient.

[0047] The conductivity of Comparative Example 1 is significantly lower than that of other examples (about 1 / 10 of Example 1). This is because the silver powder content is low, so the average distance between silver particles is large, resulting in a reduction in the particle contact area and poor continuity of the conductive network. When the silver content is significantly increased (Comparative Example 2), the average distance between silver particles decreases, and the continuity of the conductive network is greatly improved. Although the conductivity of Comparative Example 2 is higher than that of Example 1, the silver content is 1.6 times that of Example 1, and the cost is significantly higher than this example. Example 5 is a direct mixture of graphene and silver powder. Since the specific surface area of few-layer graphene (100 - 500 m 2 / g) is much larger than that of silver microflakes (0.1 - 0.2 m 2 / g), it can greatly increase the contact area between conductive particles and improve the quality of the conductive network. Therefore, the conductivity of Example 5 is significantly higher than that of Example 1. However, since there is no linking molecule between graphene and silver microflakes in Example 5, the dispersibility is poor and the interaction force is weak. Therefore, the conductivity is significantly lower than that of other similar formulations with linking molecules (Examples 1 - 3 and Comparative Example 6).

[0048] The conductivity of Comparative Example 3 is close to that of Comparative Example 5, indicating that the modification of the graphene surface by ZnTPP cannot directly enhance the coupling between graphene and silver particles. The conductivity of Comparative Example 4 is slightly higher than that of Comparative Example 5 because there is a weak coupling between the lone pair electrons of the pyridine group on the surface of the modified silver particles and the graphene surface, which can play a bridging role. However, its interfacial barrier is much higher than the coordination effect between the double-modified materials in the examples, so the conductivity is about 65% lower than that of Example 1. The PVP modified on the graphene surface in Comparative Example 6 can play a role in connecting silver microplates, so the conductivity is higher than that of Comparative Example 3. However, due to the van der Waals force being much weaker than the coordination bond (the gap is about 30 times), its conductivity is more than 60% lower than that of Example 1.

[0049] Finally, the conductivity of Example 4 is lower than that of Example 1 because the proportion of graphene in the conductive network increases while the proportion of silver decreases. Since the conductivity of few-layer graphene is much lower than that of silver, the overall conductivity decreases. However, it is worth noting that although Example 4 has a lower silver content, its conductivity is higher than that of Comparative Example 1 and Comparative Example 5, indicating that the coordination effect strategy of the present invention can construct a more efficient conductive network with a lower silver content.

[0050] 2. Homogeneity analysis: Test method: In Step 7, the screen-printed structure is changed from the antenna structure to a 1 cm × 1 cm square, the substrate is copperplate paper, printed 10 times, dried at 120 °C for 30 minutes after printing, and a pressure roller of 160 MPa.

[0051] Since the working principles of Examples 1-4 are similar, only the homogeneity of Example 1 and each comparative example is compared in this test. The sheet resistance of the square printed product is measured using a four-probe sheet resistance meter (DWR1C, Shanghai Instrumentation), and the coefficient of variation CV = standard deviation / mean × 100% is calculated. The lower the CV value, the better the homogeneity of the slurry.

[0052] Table 2. Test results of homogeneity (CV)

[0053] As can be seen from Table 2, Comparative Example 2 has the best uniformity because, as a pure silver paste, it does not involve the problem of graphene dispersibility. Although the uniformity of Example 1 is inferior to that of Comparative Example 2, it is better than other examples. This shows that in the present invention, the surface modification of silver particles and graphene can inhibit the aggregation between silver particles or graphene, and at the same time strengthen the interaction between graphene and silver particles, thereby achieving a highly uniform dispersion. Although Comparative Example 1 is also a pure silver paste, due to the low silver content, there are a large number of defects in the conductive network of the printed product. Since the number and position of the defects generated are not fixed in each printing, its CV value is not only higher than that of Comparative Example 2, but also slightly higher than that of Example 1. The CV values of Comparative Examples 3 and 5 are the largest, far higher than other examples, because there is a lack of interaction between the above-mentioned graphene powder (or ZnTPP-modified graphene powder) and silver powder, the dispersibility is poor, and the uniformity of the paste is significantly insufficient. The CV values of Comparative Examples 4 and 6 are significantly better than that of Comparative Example 5 because both PVP and 4-Mpy can act as bridging molecules to improve the dispersibility of graphene in silver powder, but their uniformity is still inferior to the graphene-silver particle double-modified coordination connection strategy of Example 1. SEM images ( Figure 5 ) further show that there is obvious aggregation of graphene and silver microplates in the printed product of Comparative Example 5. The dispersibility of Comparative Example 4 is better than that of Comparative Example 5, but a small amount of PVP clusters can be observed, while the dispersion of silver microplates and graphene in Example 1 is the best.

[0054] 3. Tensile resistance test: In Step 7, the screen-printed structure is changed from an antenna structure to a 1 cm × 1 cm square, and the substrate is thermoplastic polyurethane elastomer (TPU). After printing, it is dried at 120 °C for 30 minutes. The sheet resistance (R) of the square printed product is measured using a 4-probe sheet resistance meter (DWR1C, Shanghai Instrumentation). After the TPU is stretched 5 times by 20% in both the transverse and longitudinal directions (the edge length of the printed square structure is stretched from 1 cm to 1.2 cm), the sheet resistance of the printed product is measured again, and the attenuation rate is calculated as = ((1 / R before stretching - 1 / R after stretching) / (1 / R before stretching)) × 100%. The lower the performance attenuation rate, the better the tensile resistance of the paste.

[0055] This application mainly tests Example 1 and each comparative example, and the test results are shown in Table 3.

[0056] Table 3. Tensile resistance performance test results

[0057] As can be seen from Table 3, the performance attenuation of Comparative Example 1 is the most serious after stretching. Since the silver in it is pure silver and the conductive network has brittleness problems, it is easily damaged during stretching. Moreover, the silver content in Comparative Example 1 is relatively low, and the conductive network is relatively sparse, and it is completely damaged under multiple stretches. Therefore, the sheet resistance after stretching is greater than 2 MΩ, and the conductive ability is completely lost. In Comparative Example 2, the silver content is relatively high and the network is denser. Therefore, the conductive path still exists under multiple stretches, but it is also severely damaged, and the performance attenuation reaches more than 90%. Graphene has excellent flexibility. Thanks to its high specific surface area and sheet structure, it can disperse stress, inhibit crack propagation and provide redundant conductive networks. Therefore, the performance attenuation of Comparative Example 5 is lower than that of Comparative Example 1 and Comparative Example 2. However, due to the uneven dispersion of graphene, its attenuation is still as high as nearly 70%. Comparative Example 3 is similar to Comparative Example 5, with an attenuation of about 70%. The tensile resistance performance of Comparative Example 4 is better than that of Comparative Example 3 and Comparative Example 5 because the bridging effect of 4-MPy improves the dispersion uniformity of graphene / silver to a certain extent, and the performance attenuation is about 40%. Comparative Example 6 shows the best tensile resistance performance. On the one hand, because the graphene is better dispersed, and on the other hand, because PVP, as a polymer, can provide a certain degree of tensile resistance for the material. And Example 1 benefits from the more effective dispersion of graphene. Although the performance attenuation after stretching is slightly higher than that of Comparative Example 6 (the gap is about 6%), it is much lower than that of other examples, indicating the application potential of the present invention in the field of flexible printed products.

[0058] 4. Performance of radio frequency identification tags: Test method: The tag is designed by CST based on the conductivity, thickness of the printed paste and the impedance of the chip. The reading distance of the tag is tested by the Voyantic Tagformance UHF test system. The distance between the tag and the transmitting antenna is 1 meter. The test environment is at a temperature of 25 °C and a humidity of 60%. The reading transmit power is 1 watt. The forward and reverse tag powers are read and converted into the forward and reverse reading distances through the built-in algorithm.

[0059] Since the reading distance of the tag depends on the antenna / chip impedance matching, it is of little practical significance to directly compare each example. The reading distance of the tag in this work can reach more than 9 meters at 915 MHz (the results are shown in Figure 7 ) and is comparable to that of commercial aluminum foil etching / high silver content pure silver paste printed similar tags, which can meet the application requirements of passive ultra-high frequency RFID tags.

[0060] This specific embodiment is only an explanation of the present application and does not limit the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A graphene-modified silver paste, characterized in that, It includes modified silver micropowder, modified graphene powder, binder, and solvent. The content of the modified silver micropowder is 20 - 30 wt%, and the content of the modified graphene powder is 4 - 6 wt%. The surface of the modified graphene powder is modified with zinc tetraphenylporphyrin, and the surface of the modified silver micropowder is modified with 4-mercaptopyridine.

2. The graphene-modified silver paste according to claim 1, wherein The modified graphene powder is prepared by mixing graphene powder and zinc tetraphenylporphyrin in a solution for modification. The concentration of zinc tetraphenylporphyrin in the solution is 0.2 - 0.4 wt%, and the concentration of the graphene powder is 0.5 - 2 wt%.

3. The graphene-modified silver paste according to claim 1, wherein, The modified silver micropowder is prepared by mixing silver micropowder and 4-mercaptopyridine in a solution for modification. The concentration of the 4-mercaptopyridine solution in the solution is 0.07 - 0.21 wt%, and the concentration of the silver micropowder is 5 - 15 wt%.

4. The graphene-modified silver paste according to claim 1, wherein, The particle size of the modified graphene powder is 0.5 - 8 microns.

5. The graphene-modified silver paste according to claim 1, wherein, The particle size of the silver micropowder is 1 - 15 microns.

6. The graphene-modified silver paste according to claim 1, wherein, The graphene-modified silver paste contains 20 - 30 wt% modified silver micropowder, 4 - 6 wt% modified graphene powder, 30 - 50 wt% binder, 20 - 30 wt% solvent, 2.5 - 3.5 wt% leveling agent, and 1.5 - 2.5 wt% coupling agent.

7. The graphene-modified silver paste according to claim 1, wherein The solvent uses a mixture of diethylene glycol butyl ether acetate and turpentine with a mass ratio of 1 - 2:1 - 2.

8. The graphene-modified silver paste according to claim 6, wherein The preparation method is as follows: Mix the modified silver micropowder and the modified graphene powder according to the mass ratio to obtain a mixed powder. Mix the binder, solvent, leveling agent, and coupling agent according to the mass ratio to form an organic carrier, stir evenly, add the mixed powder in batches, and continue to stir evenly to form a crude paste. The crude paste is subjected to vacuum defoaming, grinding, and screening to obtain the graphene-modified silver paste.

9. The graphene-modified silver paste according to claim 1, wherein The graphene powder is obtained by centrifugal drying after high-energy exfoliation of expandable graphite in a mixed solvent of dihydrolevoglucosenone and triacetin with a mass ratio of 3 - 5:

1.

10. The application of the graphene-modified silver paste according to any one of claims 1 to 9 in an RFID tag, characterized in that, Print the graphene-modified silver paste on a substrate to form the antenna structure of the RFID tag.

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