A graphene-modified silver paste and its application in RFID tags

Abstract

The present application discloses a graphene-modified silver paste and its application in RFID tags. The graphene-modified silver paste includes modified silver micropowder, modified graphene powder, adhesive, and solvent. The modified silver micropowder content is 20-30wt%, and the modified graphene powder content is 4-6wt%. The surface of the modified graphene powder is modified with tetraphenylporphyrin zinc, and the surface of the modified silver micropowder is modified with 4-mercaptopyridine. The present application can effectively solve the problem of two-phase separation and difficulty in uniform dispersion in the silver-graphene composite conductive system in the prior art; at the same time, the contact resistance between silver and graphene powder particles can be reduced, and the conductive performance of the slurry can be improved.

Description

Technical Field

[0001] The present application relates to the field of printed electronics, and in particular to a graphene-modified silver paste and its application in RFID tags. Background Art

[0002] In the manufacturing of RFID tags, the traditional aluminum foil etching process is gradually being replaced by printed electronics due to its complex processing flow, low material utilization rate, and difficulty in adapting to flexible production needs. Silver-based conductive paste, which is the core material of printed electronics, has a significant positive correlation between its conductivity and silver content. However, the excessive proportion of precious metal silver has led to a sharp increase in material costs, seriously restricting industrial applications. To overcome this dilemma, the industry generally adopts a technical route to reduce the silver content. However, when the silver content is reduced, the contact points of silver particles per unit area are insufficient, resulting in the inability to form a continuous conductive network after sintering. In recent years, the introduction of graphene to construct a composite conductive system and the use of its high specific surface area characteristics to increase contact sites have become an effective way to improve the conductive performance of low-silver pastes.

[0003] However, in practical applications, composite systems of graphene and silver micropowder face significant technical challenges. Specifically, when graphene and silver micropowder are directly mixed, the physical differences between the two lead to dispersed phase separation, seriously affecting the uniformity of printed films and product yield. To overcome these issues, existing technologies typically use amphiphilic surface modification to modify graphene and silver micropowder. While this improves the dispersibility of the conductive powder, the interfacial resistance between the powders is high, resulting in a decrease in the conductive properties of the slurry. Summary of the Invention

[0004] The present application provides a graphene-modified silver paste and its application in RFID tags, which can effectively solve the problem of two-phase separation and difficulty in uniform dispersion 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 conductive performance of the paste.

[0005] In the first aspect, the present application provides a graphene-modified silver paste, characterized in that it includes modified silver micropowder, modified graphene powder, an adhesive, and a solvent, wherein the content of the modified silver micropowder is 20 to 30 wt%, and the content of the modified graphene powder is 4 to 6 wt%; the surface of the modified graphene powder is modified with tetraphenylporphyrin zinc, and the surface of the modified silver micropowder is modified with 4-mercaptopyridine.

[0006] Traditional surface modification techniques for conductive powders (such as graphene and silver powders) using amphiphilic molecules (such as surfactants) create a significant electron transport barrier at the interface formed by weak interactions. Electrons must traverse this insulating layer when transferring between graphene and silver powder, resulting in significant contact resistance and a decrease in conductivity. While modification with strong chemical bonds can enhance interfacial bonding, it can disrupt the continuous π-electron cloud formed by graphene's intact sp²-hybridized carbon skeleton, damaging the intrinsic conductive structure that provides graphene with high conductivity and making it unsuitable for constructing a conductive network. This application simultaneously processes tetraphenylporphyrin zinc on the graphene surface (π-π bonding) and 4-mercaptopyridine on the silver particle surface (gold / sulfur bonding). Finally, the coordination between the pyridine on the silver particle surface and the zinc nuclei on the graphene surface is utilized to effectively disperse the two and construct an efficient conductive network, resulting in 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 and modifying graphene powder and tetraphenylporphyrin zinc solution, the concentration of the tetraphenylporphyrin zinc is 0.2-0.4wt%, and the concentration of the graphene powder is 0.5-2wt%.

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

[0009] In any of the above technical solutions, the modified silver micropowder is prepared by mixing and modifying 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 to 8 microns, and the number of layers is 1 to 20.

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

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

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

[0014] In any of the above technical solutions, the leveling agent is a silicone polyether leveling agent; illustratively, the leveling agent is BYK-333.

[0015] In any of the above technical solutions, the coupling agent is an epoxysilane coupling agent; illustratively, the coupling agent is 3-glycidyloxypropyltrimethoxysilane.

[0016] In any of the above technical solutions, the solvent is a mixture of diethylene glycol butyl ether acetate and turpentine in 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:

[0018] Mixing modified silver micropowder and modified graphene powder according to a mass ratio to obtain a mixed powder;

[0019] Mix the adhesive, solvent, leveling agent and coupling agent in a certain mass ratio to form an organic carrier, stir evenly, add the mixed powder in batches, continue stirring evenly to form a coarse slurry;

[0020] The crude slurry is vacuum defoamed, ground and screened to obtain graphene-modified silver slurry.

[0021] In any of the above technical solutions, the graphene powder is obtained by high-energy exfoliation of expandable graphite in a mixed solvent of dihydro-levulinone and triacetin with a mass ratio of 3 to 5:1, followed by centrifugal drying.

[0022] In any of the above technical solutions, the high-energy peeling includes but is not limited to ultrasound, air milling, ball milling, and shearing; preferably, ultrasonic peeling.

[0023] In a second aspect, the present application provides an application of graphene-modified silver paste in an RFID tag, wherein the graphene-modified silver paste is printed on a substrate to form an antenna structure of the RFID tag.

[0024] In summary, this application has the following beneficial effects:

[0025] This invention addresses the interface optimization problem in heterogeneous material composite systems (graphene and silver micropowder) by proposing a bidirectional surface modification technology based on molecular engineering. Graphene is surface-modified with zinc tetraphenylporphyrin (ZnTPP). Through the π-π interaction of the macrocyclic conjugated system, a stable molecular adsorption layer is constructed on the graphene surface. This structural steric hindrance effectively inhibits secondary aggregation of nanosheets. Simultaneously, a 4-mercaptopyridine (4-Mpy) molecular protective layer is constructed on the silver micropowder surface, achieving surface functionalization through the specific binding of mercapto groups with silver. The mutual repulsion between the ZnTPP metal core on the graphene surface and the lone electron pairs of the 4-Mpy pyridine on the silver micropowder surface prevents graphene-graphene or silver micropowder-silver micropowder aggregation. The coordination of the pyridine with the zinc metal core strengthens the interaction between graphene and silver micropowder, improving the uniformity of their dispersion. Through the coordinated bonding of the pyridyl termini with the porphyrin zinc metal center (bond energy 0.3-0.5 eV), a strongly interacting heterojunction is established, overcoming the transport barrier typically associated with modification through molecular van der Waals forces (bond energy ~0.01 eV). This synergistic modification strategy not only achieves uniform dispersion of the graphene-silver system but also constructs efficient electron transport channels at the atomic scale, ultimately forming a composite paste with a highly efficient conductive network structure, which has been successfully applied to the precision printing of radio frequency identification tags. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural diagram of the RFID tag of this application.

[0027] Figure 2 This is an atomic force microscope image (3 microns) of the graphene powder covered with tetraphenylporphyrin zinc in Example 1.

[0028] Figure 3 This is an atomic force microscope image (0.8 μm) of the graphene powder covered with tetraphenylporphyrin zinc in Example 1.

[0029] Figure 4 This is an SEM image of the paste-printed antenna structure of Example 1.

[0030] Figure 5 This is the SEM image of the paste-printed antenna structure of Comparative Example 5.

[0031] Figure 6 This is the SEM image of the paste-printed antenna structure of Comparative Example 6.

[0032] Figure 7 This is the RFID tag reading spectrum diagram of Example 1.

[0033] Description of reference numerals:

[0034] 1. Chip; 2. Antenna; 3. Substrate. DETAILED DESCRIPTION

[0035] Example 1, a graphene-modified silver paste, is prepared according to the following steps:

[0036] Step 1: Ultrasonic exfoliation of expandable graphite in a 4:1 dihydro-levulinone / triacetin mixed solvent for 8 hours followed by centrifugal drying yields graphene powder (particle size 0.5-8 μm, 1-20 layers). The graphene powder is then added to DMF and stirred for 5 minutes. Zinc tetraphenylporphyrin is then added to yield a mixture containing 0.3 wt% zinc tetraphenylporphyrin and 1 wt% graphene. After stirring for 30 minutes, the mixture is centrifuged at 3000 rpm, the supernatant removed, and rinsed twice with N-hexane to remove physically adsorbed ZnTPP, yielding modified graphene powder with approximately 90% ZnTPP coverage (see [1]). Figure 1 、 Figure 2 AFM images of the

[0037] Step 2: Add the silver microflake powder to a 0.14wt% 4-mercaptopyridine ethanol solution to obtain a mixture with a 10wt% silver content. Stir continuously at 200 rpm for 5 hours to form a self-assembled monolayer on the surface of the silver microflakes. After stirring, wait for the silver micropowder to settle. Remove the supernatant and rinse twice with ethanol to remove physically adsorbed 4-mercaptopyridine, obtaining modified silver micropowder.

[0038] Step 3: Mix 25g of modified silver micropowder with 5g of modified graphene powder and stir to obtain a mixed powder. Mix 40g of LR9100 TPU resin, 25g of a mixed solvent of diethylene glycol butyl acetate and turpentine (mass ratio 1:1), BYK-333 leveling agent, and 3-glycidyloxypropyltrimethoxysilane to form an organic vehicle and stir at 500rpm for 50 minutes. Increase the stirring speed to 1500rpm and add the mixed powder to the organic vehicle in five portions, with 5-minute intervals between each addition. After mixing, continue stirring at 1500rpm for 3 hours to form a coarse slurry.

[0039] Step 4: Place the crude slurry in a vacuum oven (>30Pa, 25°C, 30 minutes) to remove bubbles, pass through a three-roll mill three times, and then pass through a 350-mesh sieve to obtain graphene-modified silver paste.

[0040] Example 2, a graphene-modified silver paste, differs from Example 1 in that the concentration of tetraphenylporphyrin zinc in step 1 is adjusted to 0.85 wt %, and the rest is the same as Example 1.

[0041] Example 3, a graphene-modified silver paste, differs from Example 1 in that the concentration of tetraphenylporphyrin zinc in step 1 is adjusted to 0.085 wt %, and the rest is the same as Example 1.

[0042] Example 4, a graphene-modified silver paste, differs from Example 1 in that the amounts of modified silver micropowder and modified graphene powder used in step 3 are 24 g and 6 g, respectively (mixed in a 4:1 mass ratio), and the rest are the same as Example 1.

[0043] Comparative Example 1, a silver paste, differs from Example 1 in that in step 3, 25 g of silver micropowder (silver content 25%) is used instead of 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. Other conditions are the same as in Example 1.

[0044] Comparative Example 2, a silver paste, differs from Example 1 in that in step 3, 40 g of silver micropowder (silver content 40%) is used instead of 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. Other conditions are the same as in Example 1.

[0045] Comparative Example 3, a graphene-modified silver paste, differs from Example 1 in that in step 3, the modified silver powder is replaced by an equal amount of unmodified silver powder, and the rest is the same as Example 1.

[0046] Comparative Example 4, a graphene-modified silver paste, differs from Example 1 in that in step 3, an equal amount of unmodified graphene powder (particle size 0.5 to 8 μm, number of layers 1 to 20) is used to replace the modified graphene powder, and the rest is the same as Example 1.

[0047] Comparative Example 5, a graphene-modified silver paste, differs from Example 1 in that in step 3, the modified silver powder is replaced by an equal amount of unmodified silver powder, and the modified graphene powder is replaced by an equal amount of unmodified graphene powder, and the rest is the same as Example 1.

[0048] Comparative Example 6, a graphene-modified silver paste, differs from Example 1 in that in step 3, the modified silver powder is replaced with an equal amount of unmodified silver powder, and the modified graphene powder is replaced with an equal amount of PVP-modified graphene powder (PVP is K30, and the addition amount is 0.8% of the mass of the graphene). Other steps are the same as in Example 1.

[0049] Performance test: Use each conductive paste to print on coated paper by 260 mesh screen printing. Figure 1 The antenna structure shown (printed in the first orientation, designed based on the paste conductivity and chip impedance characteristics) is then subjected to a roller press at 6MPa and 165°C. The N×P-U9 chip is flip-chip bonded to the antenna. The chip and antenna are connected using conductive adhesive (DELOMONOPO× AC268), and then hot-pressed at 140°C for 15 seconds to complete the label process.

[0050] 1. Conductivity analysis:

[0051] Test method: In step 7, the screen-printed structure was changed from an antenna structure to a 1cm×1cm square. The substrate was coated paper. After printing, the printed material was dried at 120°C for 30 minutes and then subjected to a roller pressure of 160 MPa. The square resistance of the printed material was measured using a four-probe square resistance meter (DWR1C, Shanghai Instruments). The four probes were placed on the diagonals of the square and the corresponding square resistance values ​​were read. The printed film thickness was measured using a film thickness meter (Shendawei ARIPU SW6300-A), and the square resistance was converted to conductivity (conductivity = 1 / (square resistance × film thickness)).

[0052] Table 1. Conductivity test results

[0053]

[0054] Comparing Examples 1-3, Example 1 exhibits higher conductivity than Examples 2 and 3. This suggests that either excessively high or low ZnTPP concentrations can affect the slurry's conductivity during graphene processing. At high concentrations, ZnTPP forms multiple layers on the graphene surface, reducing the system's conductivity. At low concentrations, however, insufficient active sites prevent subsequent bonding between the graphene and silver particles.

[0055] The conductivity of Comparative Example 1 is significantly lower than that of the other examples (about 1 / 10 of that of Example 1). This is because the silver powder content is low, so the average distance between silver particles is larger, resulting in a reduced contact area between particles 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 mixing of graphene and silver powder. Due to the specific surface area of ​​few-layer graphene (100-500 m 2 / g) is much larger than silver micro-sheets (0.1-0.2 m 2 / g), which 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 are no linking molecules between the graphene and silver microsheets in Example 5, the dispersion is poor and the interaction force is weak. Therefore, the conductivity is significantly lower than that of other similar formulas with the addition of linking molecules (Examples 1-3 and Comparative Example 6).

[0056] 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 improved compared to Comparative Example 5. This is because the lone electron pairs of the pyridine groups on the surface of the modified silver particles are weakly coupled to the graphene surface, which can act as a bridge. However, the interfacial barrier is much higher than the coordination effect between the two modified materials in Example 1, so the conductivity is about 65% lower than that of Example 1. In Comparative Example 6, the PVP modified on the graphene surface can serve to connect the silver microsheets, so the conductivity is higher than that of Comparative Example 3. However, because the van der Waals interaction is much weaker than the coordination bond interaction (the difference is about 30 times), its conductivity is more than 60% lower than that of Example 1.

[0057] Finally, Example 4 has a lower conductivity than Example 1. This is because the specific gravity of graphene in the conductive network increases while the specific gravity 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 despite the lower silver content, Example 4 has a higher conductivity than Comparative Examples 1 and 5, demonstrating that the coordination strategy of the present invention can build a more efficient conductive network with a lower silver content.

[0058] 2. Homogeneity analysis:

[0059] Test method: In step 7, the silk screen structure was changed from the antenna structure to a 1cm×1cm square, the substrate was coated paper, and it was printed 10 times. After printing, it was dried at 120℃ for 30 minutes and pressed with a 160MPa roller.

[0060] Because Examples 1-4 operate on similar principles, this test only compares the uniformity of Example 1 with the comparative examples. A four-probe square resistance meter (DWR1C, Shanghai Instruments) was used to measure the square resistance of the printed materials. The coefficient of variation (CV) was calculated as: standard deviation / mean × 100%. A lower CV value indicates better slurry uniformity.

[0061] Table 2. Uniformity (CV) test results

[0062]

[0063] 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 that of the other examples. This shows that in the present invention, the surface modification of silver particles and graphene can inhibit the agglomeration between silver particles or graphene, while strengthening the interaction between graphene and silver particles, thereby achieving high uniformity 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 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, much higher than those of the other examples. This is because the above-mentioned graphene powder (or ZnTPP modified graphene powder) and silver powder lack interaction, the dispersibility is poor, and the slurry uniformity is obviously insufficient. The CV values ​​of Comparative Examples 4 and 6 are significantly better than those of Comparative Example 5. This is because both PVP and 4-Mpy can act as bridging molecules to improve the dispersion of graphene in silver powder. However, their uniformity is still inferior to the graphene-silver particle dual-modification coordination connection strategy of Example 1. SEM images ( Figure 5 ) further shows that there is obvious agglomeration of graphene and silver microflakes in the print of Comparative Example 5, the dispersion 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 microflakes and graphene in Example 1 is the best.

[0064] 3. Tensile test:

[0065] In step 7, the screen-printed structure was changed from an antenna structure to a 1cm×1cm square. The substrate was thermoplastic polyurethane (TPU). After printing, the printed square was dried at 120°C for 30 minutes. The square resistance (R) of the printed square was measured using a four-probe square resistance meter (DWR1C, Shanghai Instruments). The TPU was stretched 20% in both the horizontal and vertical directions (the edge length of the printed square structure was stretched from 1cm to 1.2cm) five times. The printed square resistance was then measured again, and the attenuation was calculated as ((1 / R before stretching - 1 / R after stretching) / (1 / R before stretching)) × 100%. The lower the performance attenuation, the better the stretch resistance of the slurry.

[0066] This application mainly tests Example 1 and various comparative examples, and the test results are shown in Table 3.

[0067] Table 3. Tensile resistance test results

[0068]

[0069] As can be seen from Table 3, Comparative Example 1 suffers the most severe performance degradation after stretching. The silver content in Comparative Example 1 is low, and the conductive network is relatively thin, which is completely destroyed after multiple stretching. Therefore, the square resistance after stretching is greater than 2MΩ, and the conductive ability is completely lost. Comparative Example 2, on the other hand, has a higher silver content and a denser network. Therefore, the conductive path still exists after multiple stretching, but it is also severely damaged, with performance degradation reaching over 90%. Graphene has excellent flexibility, thanks to its high specific surface area and lamellar structure, which can disperse stress, inhibit crack propagation, and provide conductive network redundancy. Therefore, the performance degradation of Comparative Example 5 is lower than that of Comparative Example 1 and Comparative Example 2, but due to the uneven dispersion of graphene, its degradation is still as high as nearly 70%. Comparative Example 3 is similar to Comparative Example 5, with a degradation of approximately 70%. Comparative Example 4 performs better in tensile resistance than Comparative Examples 3 and 5 because the 4-MPy bridging effect improves the uniformity of graphene / silver dispersion to a certain extent, with a performance degradation of approximately 40%. Comparative Example 6 performed best in terms of stretch resistance, partly due to better graphene dispersion and partly because PVP, as a polymer, provides a certain degree of stretch resistance. Thanks to more effective graphene dispersion, Example 1 exhibited slightly higher post-stretch performance degradation than Comparative Example 6 (by approximately 6%), but significantly lower than the other examples, demonstrating the potential application of this invention in the field of flexible printed products.

[0070] 4. RFID tag performance:

[0071] Test Method: Tags are designed by CST based on printed paste conductivity, thickness, and chip impedance. Tag read distance is tested using a Voyantic Tagformance UHF test system. The tag is 1 meter away from the transmitting antenna in an environment with a temperature of 25°C and a humidity of 60%. The transmit power is 1 watt. The forward and reverse tag power is read and converted to forward and reverse read distances using a built-in algorithm.

[0072] Since the tag reading distance depends on the antenna / chip impedance matching, direct comparison of each case lacks practical significance. The tag in this work can reach a reading distance of more than 9 meters at 915MHz (see the results). Figure 7 ), which is comparable to commercial aluminum foil etching / high silver and pure silver paste printing tags of the same type, and can meet the application requirements of passive UHF RFID tags.

[0073] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, 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: The invention comprises modified silver micropowder, modified graphene powder, an adhesive and a solvent, wherein the content of the modified silver micropowder is 20-30wt%, and the content of the modified graphene powder is 4-6wt%. The surface of the modified graphene powder is modified with tetraphenylporphyrin zinc, and the surface of the modified silver micropowder is modified with 4-mercaptopyridine.

2. The graphene-modified silver paste according to claim 1, characterized in that The modified graphene powder is prepared by mixing and modifying graphene powder and tetraphenylporphyrin zinc in a solution, wherein the concentration of the tetraphenylporphyrin zinc 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, characterized in that The modified silver micropowder is prepared by mixing and modifying silver micropowder and 4-mercaptopyridine in a solution. 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, characterized in that The particle size of the modified graphene powder is 0.5 to 8 microns.

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

6. The graphene-modified silver paste according to claim 1, characterized in that The graphene-modified silver paste comprises 20-30 wt% of modified silver powder, 4-6 wt% of modified graphene powder, 30-50 wt% of adhesive, 20-30 wt% of solvent, 2.5-3.5 wt% of leveling agent, and 1.5-2.5 wt% of coupling agent.

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

8. The graphene-modified silver paste according to claim 6, characterized in that: The preparation method is as follows: Mixing modified silver micropowder and modified graphene powder according to a mass ratio to obtain a mixed powder; Mix the adhesive, solvent, leveling agent and coupling agent in a certain mass ratio to form an organic carrier, stir evenly, add the mixed powder in batches, continue stirring evenly to form a coarse slurry; The crude slurry is vacuum defoamed, ground and screened to obtain graphene-modified silver slurry.

9. The graphene-modified silver paste according to claim 1, characterized in that: The graphene powder is obtained by high-energy stripping of expandable graphite in a mixed solvent of dihydro-levulinone and triacetin with a mass ratio of 3 to 5:1, followed by centrifugal drying.

10. Use of the graphene-modified silver paste in RFID tags according to any one of claims 1 to 9, characterized in that: The graphene-modified silver paste is printed on the substrate to form the antenna structure of the RFID tag.

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