XBC battery slurry based on copper alloy and preparation method thereof

Abstract

The invention provides xBC battery slurry based on copper alloy and a preparation method of the xBC battery slurry, and belongs to the field of battery slurry. The xBC battery slurry comprises the following chemical components: 30 to 50 parts of silver powder, 10 to 20 parts of silver coated copper, 1.5 to 5.5 parts of a glass material, 20 to 30 parts of an organic carrier, 0.5 to 1 part of a multi-walled carbon nanotube, 0.1 to 0.2 part of La2O3, 0.1 to 0.3 part of VO2 nanoparticles, and 1 to 3 parts of polyurethane-silver nanoparticle composite self-repairing microspheres. The silver powder, the silver-coated copper powder and the multi-walled carbon nanotubes jointly construct a three-dimensional conductive network, so that the conductivity of the paste is improved; through the combined action of the VO2 nanoparticles and the polyurethane-silver nanoparticle composite self-repairing microspheres, the intelligent temperature control and self-repairing functions of the battery are realized; and the cost of the slurry is reduced by using the silver-coated copper powder. Therefore, the dynamic self-repairing capability is improved on the basis of realizing low cost and high conductivity.

Description

Technical Field

[0001] The present application relates to the technical field of xBC battery pastes, and particularly relates to an xBC battery paste based on copper alloy and a preparation method thereof. Background Art

[0002] With the acceleration of the global energy transformation, photovoltaic technology continues to break through in the direction of high efficiency and low cost. As a new generation of high-efficiency battery technology, the xBC (cross back contact) battery has become a key development direction in the photovoltaic industry due to its advantages such as a full-back electrode design (no front shading), high conversion efficiency (≥26%), and low hot spot effect.

[0003] Currently, xBC batteries mainly rely on pure silver pastes or silver-aluminum mixed pastes, but there are the following core problems: (1) The silver content in pure silver pastes is as high as 85% - 90%, resulting in high raw material costs; (2) Although the silver-aluminum paste significantly reduces costs (silver content ≤ 50%), the oxidation tendency of aluminum leads to a sharp increase in contact resistance (sheet resistance > 80 mΩ / □). (3) The electrodes are prone to silver migration and copper oxidation (Cu → CuO / Cu2O) in a humid and hot environment, with an annual resistivity attenuation rate > 5%, and microcracks (< 10 μm) cannot self-heal, leading to the hot spot effect after long-term operation. Therefore, how to improve the dynamic self-healing ability on the basis of achieving low cost and high conductivity is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0004] The present application provides an xBC battery paste based on copper alloy and a preparation method thereof to solve the following technical problems: how to improve the dynamic self-healing ability on the basis of achieving low cost and high conductivity.

[0005] In the first aspect, the present application provides an xBC battery paste based on copper alloy. In terms of parts by mass, the xBC battery paste includes the following chemical components: 30 - 50 parts of silver powder, 10 - 20 parts of silver-coated copper, 1.5 - 5.5 parts of glass material, 20 - 30 parts of organic carrier, 0.5 - 1 part of multi-walled carbon nanotubes, 0.1 - 0.2 part of La2O3, 0.1 - 0.3 part of VO2 nanoparticles, and 1 - 3 parts of polyurethane-silver nanoparticle composite self-healing microspheres.

[0006] Optionally, in terms of parts by mass, the organic carrier includes the following chemical components: 50 - 70 parts of limonene, 10 - 30 parts of butyl carbitol acetate, 10 - 20 parts of pentaerythritol triacrylate, 1 - 3 parts of 2-hydroxy-2-methylpropiophenone, 2 - 5 parts of polydimethylsiloxane, 5 - 10 parts of polyurethane-modified acrylic resin, and 0.5 - 1 part of dispersant.

[0007] Optionally, in terms of mole percentage, the glass material is composed of the following components: P2O5: 5 - 10 mol%, Bi2O3: 25 - 35 mol%, Na2O: 5 - 8 mol%, ZnO: 5 - 8 mol%, B2O3: 18 - 22 mol%, SiO2: 5 - 8 mol%, Al2O3: 1 - 3 mol%, V2O5: 10 - 14 mol%, MoO3: 3 - 6 mol%, Ag2O: 0.5 - 1.5%, Li2O: 1 - 3%.

[0008] Optionally, the particle size of the polyurethane-silver nanoparticle composite self-healing microspheres is 1 - 5 μm, the shell thickness is 100 - 200 nm, and the core material loading rate is ≥85%.

[0009] Optionally, the particle size D50 of the silver powder is 1 - 5 μm, and it is flaky silver powder, and the ratio of the sheet diameter to the thickness is 10:1 - 20:1.

[0010] In a second aspect, the present application provides a method for preparing the xBC battery paste according to any one of the first aspects, and the method includes:

[0011] Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper and carbon nanotubes to obtain a conductive phase;

[0012] Vacuum stir and disperse glass powder and an organic carrier to obtain a carrier;

[0013] Mix the conductive phase with the carrier, and then add La2O3, VO2 and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery paste.

[0014] Optionally, the method for preparing the polyurethane-silver nanoparticle composite self-healing microspheres includes:

[0015] Mix polytetrahydrofuran diol and isophorone diisocyanate, and react at 70°C for 2 h under nitrogen protection to generate a terminal isocyanate prepolymer;

[0016] Add dimethylolpropionic acid to the terminal isocyanate prepolymer to continue the reaction for 1 h to form a carboxylic acid group-modified polyurethane, then cool down to 40°C, and add acetone to adjust the viscosity to obtain a carboxylic acid-modified polyurethane;

[0017] Dissolve silver nitrate and polyvinylpyrrolidone in deionized water, then drop it into the carboxylic acid-modified polyurethane, stir for 30 min, then gradually add a 0.2 mol / L sodium borohydride solution, and carry out a reduction reaction at 45°C for 1 h to obtain a polyurethane-silver nanoparticle complex;

[0018] Dissolve the polyurethane-silver nanoparticle complex, toluene-2,4-diisocyanate, and Span-80 emulsifier in xylene to obtain an oil phase;

[0019] Dissolve gelatin and sodium dodecyl sulfate in deionized water to obtain an aqueous phase;

[0020] Pour the oil phase into the aqueous phase and shear- emulsify it at a high speed of 10,000 rpm for 10 min to form an emulsion;

[0021] Add ethylenediamine to the emulsion and react at 50 °C for 3 h to form a polyurea shell, and then perform centrifugal separation, washing and freeze-drying to obtain the polyurethane-silver nanoparticle composite self-healing microspheres.

[0022] Optionally, the molar ratio of the polytetrahydrofuran diol to the isophorone diisocyanate is 1:2.

[0023] Optionally, the mass of the dimethylolpropionic acid is 5% of the mass of the terminal isocyanate prepolymer.

[0024] Optionally, the mass ratio of the polyurethane-silver nanoparticle composite, the toluene-2,4-diisocyanate, the Span-80 emulsifier to the xylene is 50:10:2:100.

[0025] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0026] The present application provides an xBC battery paste based on a copper alloy. The xBC battery paste includes the following chemical components: 30-50 parts of silver powder, 10-20 parts of silver-coated copper, 1.5-5.5 parts of glass material, 20-30 parts of organic carrier, 0.5-1 part of multi-walled carbon nanotubes, 0.1-0.2 part of La2O3, 0.1-0.3 part of VO2 nanoparticles, and 1-3 parts of polyurethane-silver nanoparticle composite self-healing microspheres. A three-dimensional conductive network is jointly constructed by silver powder, silver-coated copper powder and multi-walled carbon nanotubes to improve the conductivity of the paste; through the combined action of VO2 nanoparticles and polyurethane-silver nanoparticle composite self-healing microspheres, the intelligent temperature control and self-healing functions of the battery are realized, and the reliability and durability of the battery are improved; the use of silver-coated copper powder reduces the cost of the paste while maintaining high conductivity, achieving a balance between performance and cost. Thus, on the basis of achieving low cost and high conductivity, the dynamic self-healing ability is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0028] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is a schematic flow chart of a preparation method of an xBC battery paste provided by an embodiment of the present application. Specific embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0031] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0032] In a first aspect, the present application provides an xBC battery paste based on a copper alloy. In parts by mass, the xBC battery paste includes the following chemical components: 30 - 50 parts of silver powder, 10 - 20 parts of silver-coated copper, 1.5 - 5.5 parts of glass material, 20 - 30 parts of organic carrier, 0.5 - 1 part of multi-walled carbon nanotubes, 0.1 - 0.2 part of La₂O₃, 0.1 - 0.3 part of VO₂ nanoparticles, and 1 - 3 parts of polyurethane-silver nanoparticle composite self-healing microspheres.

[0033] Silver powder (30 - 50 parts): As the main conductive phase, the silver powder provides high conductivity to ensure the efficient transmission of current inside the battery. The flaky structure of the silver powder helps to form a close packing, reduce porosity, and increase the packing density of the paste. At the same time, the silver powder and the silver-coated copper powder jointly construct a conductive network. The combination of the high conductivity of the silver powder and the cost-effectiveness of the silver-coated copper achieves a balance between performance and cost. The high-density packing of the silver powder helps to reduce the usage amount of the organic carrier, increase the solid content of the paste, and thus improve the energy density of the battery.

[0034] Silver-coated copper powder (10 - 20 parts): The silver-coated copper powder has a copper core coated with a silver layer, which not only maintains the low cost of copper but also has the high conductivity of silver. The silver layer can effectively prevent the oxidation of copper and improve the stability of the slurry. At the same time, it forms a gradient conductive network with silver powder. The silver-coated copper powder is filled between the silver powders, reducing the contact resistance. The presence of the silver layer enables the silver-coated copper powder to form a good interfacial bond with the silver powder, improving the overall conductivity.

[0035] Glass material (1.5 - 5.5 parts): The glass material melts during the sintering process, fills the pores in the slurry, and forms a dense conductive layer. The glass material can also act as a binder to enhance the bonding force between the slurry and the substrate. At the same time, it acts together with the silver powder and silver-coated copper powder to form a strong conductive network. The melting temperature of the glass material should match the sintering temperature to ensure the formation of a good conductive layer during the sintering of the slurry.

[0036] Organic carrier (20 - 30 parts): The organic carrier is the solvent and dispersant in the slurry, responsible for uniformly dispersing the conductive phases in the slurry. The organic carrier also plays a lubricating role, facilitating the printing and coating of the slurry. At the same time, it acts together with the dispersant to ensure the uniform dispersion of conductive phases such as silver powder and silver-coated copper powder in the slurry. The volatility of the organic carrier should be moderate to ensure that the slurry can be fully dried before sintering, avoiding bubbles and cracks during the sintering process.

[0037] Multi-walled carbon nanotubes (0.5 - 1 part): Multi-walled carbon nanotubes have excellent conductivity and mechanical strength and can be used as a reinforcing phase for the conductive network. The one-dimensional structure of the carbon nanotubes helps to form more conductive channels in the slurry. At the same time, it jointly constructs a three-dimensional conductive network with silver powder and silver-coated copper powder, improving the conductivity of the slurry. The reinforcing effect of the carbon nanotubes helps to improve the mechanical strength and wear resistance of the slurry.

[0038] La2O3 (0.1 - 0.2 parts): As a rare earth oxide, La2O3 has excellent thermal stability and chemical stability. La2O3 can inhibit the oxidation and migration of copper and improve the stability of the slurry. At the same time, it acts together with the glass material to form a more stable conductive layer. The addition of La2O3 can also improve the high-temperature resistance of the slurry and extend the service life of the battery.

[0039] VO2 nanoparticles (0.1 - 0.3 parts): VO2 nanoparticles have reversible semiconductor-metal phase transition characteristics and can be used for intelligent temperature control. At a specific temperature, the resistivity of VO2 changes significantly, thereby regulating the heat distribution of the battery. At the same time, it acts together with the self-healing microspheres to achieve the intelligent temperature control and self-healing functions of the battery. The phase transition characteristics of VO2 help to dissipate heat in a timely manner when the battery overheats, preventing thermal runaway.

[0040] Polyurethane-silver nanoparticle composite self-healing microspheres (1 - 3 parts): The self-healing microspheres can release the repair agent when the battery is damaged to repair cracks and fractures. Polyurethane, as the shell material, has good elasticity and toughness and can absorb external impacts. Silver nanoparticles, as the repair agent, can reconstruct the conductive network and restore the battery's conductivity. At the same time, acting together with VO2 nanoparticles, it realizes the dual functions of intelligent temperature control and self-healing of the battery. The addition of self-healing microspheres improves the reliability and durability of the battery and extends its service life.

[0041] Thus, in this application, a three-dimensional conductive network is jointly constructed by silver powder, silver-coated copper powder, and multi-walled carbon nanotubes to improve the conductivity of the slurry. Through the combined action of glass materials and La2O3, a stable conductive layer is formed to improve the stability and high-temperature resistance of the slurry. Through the combined action of VO2 nanoparticles and polyurethane-silver nanoparticle composite self-healing microspheres, the intelligent temperature control and self-healing functions of the battery are realized, improving the reliability and durability of the battery. The use of silver-coated copper powder reduces the cost of the slurry while maintaining high conductivity, achieving a balance between performance and cost.

[0042] In some embodiments, by mass, the organic carrier includes the following chemical components: 50 - 70 parts of limonene, 10 - 30 parts of butyl carbitol acetate, 10 - 20 parts of pentaerythritol triacrylate, 1 - 3 parts of 2-hydroxy-2-methylpropiophenone, 2 - 5 parts of polydimethylsiloxane, 5 - 10 parts of polyurethane-modified acrylic resin, and 0.5 - 1 part of dispersant.

[0043] The functions of each component of the organic carrier are as follows:

[0044] Limonene (50 - 70 parts): As a natural terpene solvent, it replaces traditional toxic solvents (such as terpineol), reduces VOC emissions, and meets the RoHS standard. Its medium-boiling point characteristic balances the drying speed of the slurry, avoiding problems such as pinholes and cracks caused by too fast solvent evaporation during printing. It provides a low-polarity environment to promote the uniform dispersion of conductive phases such as silver powder and silver-coated copper (Zeta potential ≥ 30 mV) and prevent agglomeration.

[0045] Butyl carbitol acetate (10 - 30 parts): With a boiling point of 230 °C, it extends the open time of the slurry, ensures the fluidity of the slurry before drying after printing, and reduces printing defects. At the same time, it reduces the glass transition temperature (Tg) of the slurry, improves the flexibility of the uncured slurry, and adapts to the requirements of curved electrodes. In addition, the ester group (-COO-) enhances the wettability to silver powder and glass materials, with a contact angle ≤ 10°, reducing interfacial pores.

[0046] Pentaerythritol triacrylate (10 - 20 parts): It contains four acrylate functional groups and can quickly crosslink under UV irradiation (wavelength 365 nm) to form a three-dimensional network structure. The hardness of the cured film is ≥4H (pencil hardness), the wear resistance is improved, and the mechanical damage of the electrode during packaging is reduced. The curing shrinkage rate is ≤1%, reducing the thermal expansion difference with the silicon substrate and inhibiting interfacial stress cracks.

[0047] 2-Hydroxy-2-methylpropiophenone (1 - 3 parts): It absorbs ultraviolet light at 365 nm, decomposes to generate active free radicals, and triggers the polymerization of acrylate monomers. The decomposition temperature is ≥200 °C, which is suitable for the low-temperature sintering process and avoids the pollution of the electrode caused by the high-temperature decomposition of the residual initiator. At the same time, it cooperates with the photosensitive shell material of the self-healing microspheres to achieve light-triggered repair. The repair agent is released after 5 minutes of UV irradiation, accurately positioning the crack area. Combined with PDMS, it avoids the damage to the microcapsule structure caused by the heat release during curing.

[0048] Polydimethylsiloxane (PDMS, 2 - 5 parts): The thixotropic index (TI) is 1.5 - 2.0. It has a low viscosity during printing to ensure high resolution, and a high viscosity when standing still to inhibit sedimentation. The siloxane chain segment (-Si-O-) endows the cured film with elasticity, meeting the bending requirements of flexible batteries. The siloxane network is resistant to high temperature (>300 °C) and oxidation, improving the stability of the electrode in a humid and hot environment.

[0049] Polyurethane-modified acrylate resin (5 - 10 parts): The urethane group (-NHCOO-) forms hydrogen bonds with the microcapsule shell material (polyurea), increasing the interfacial bonding strength. The polyurethane chain segment (soft segment) and the acrylate chain segment (hard segment) form a microphase separation structure, increasing the elongation at break. It resists the erosion of acids, alkalis, and organic solvents, extending the service life of the electrode in a complex environment. At the same time, the repair agent (polyurethane-silver composite) has high compatibility with the resin matrix, and there are no defects at the interface after repair. In addition, the resin network can buffer the phase change stress of VO2, reducing the delamination of the electrode caused by thermal cycling.

[0050] Dispersant (0.5 - 1 part, such as BYK-9076): The phosphate group (-PO3 2- ) anchors on the surface of the conductive phase (silver powder, silver-coated copper), and the electrostatic repulsion inhibits agglomeration. It reduces the surface tension of the slurry and improves the wettability to the substrate (such as SiNx passivation layer).

[0051] In some embodiments, the glass material consists of the following components in mole percentages: P2O5: 5 - 10 mol%, Bi2O3: 25 - 35 mol%, Na2O: 5 - 8 mol%, ZnO: 5 - 8 mol%, B2O3: 18 - 22 mol%, SiO2: 5 - 8 mol%, Al2O3: 1 - 3 mol%, V2O5: 10 - 14 mol%, MoO3: 3 - 6 mol%, Ag2O: 0.5 - 1.5%, Li2O: 1 - 3%.

[0052] The functions of each component of the glass material are as follows:

[0053] P2O5 (5 - 10 mol%): P2O5 forms a [PO4] tetrahedral structure, enhancing the short-range order of the glass, reducing the high-temperature viscosity, and improving the leveling property of the paste during printing. At the same time, P2O5 and B2O3 cooperate to inhibit the migration of alkaline ions (such as Na + ), reducing the risk of electrode corrosion.

[0054] Bi2O3 (25 - 35 mol%): Bi2O3 can significantly reduce the glass softening point, adapting to the low-temperature sintering process of xBC batteries. At the same time, the Bi 3+ ions of Bi2O3 and the V 5+ of V2O5 form an electron transition path, enhancing the weak conductivity of the glass and reducing the silver-silicon contact resistance.

[0055] Na2O (5 - 8 mol%): Na2O breaks the glass network (such as B - O - B bonds), reducing the melting viscosity and improving the printing adaptability of the paste. At the same time, it balances the charge distribution after the introduction of Li + and inhibits the tendency of crystallization.

[0056] ZnO (5 - 8 mol%): Zn 2+ acts as an intermediate to fill the network gaps, enhancing the hydrolysis resistance of the glass. It cooperates with Al2O3 to enhance the interfacial bonding force between the glass and the silver layer, reducing cracks after sintering.

[0057] B2O3 (18 - 22 mol%): Forms a mixed structure of [BO3] triangles and [BO4] tetrahedrons, optimizing the thermal expansion coefficient (4 - 6×10 -6 / °C) to match the silicon-based substrate. At the same time, it reduces the glass transition temperature, adapting to the fine grid printing process.

[0058] SiO2 (5 - 8 mol%): Improves the high-temperature stability of the glass through [SiO4] tetrahedrons, tolerating fluctuations in the sintering temperature. It inhibits the crystallization of components such as Bi2O3 and V2O5 during cooling, ensuring the uniformity of the paste.

[0059] Al2O3 (1 - 3 mol%): Al 3+Partially replace Si 4+ Enter the network, enhance the structural density, and reduce the porosity of the glass. Form a protective layer in an acidic slurry environment to prevent component dissolution.

[0060] V2O5 (10 - 14 mol%): V 5+ / V 4+ The variable valence provides an electron hopping channel and reduces the volume resistivity. At the same time, it corrodes the silicon-based silicon nitride layer (SiN x ) synergistically with MoO3 to form a micron-scale rough surface and improve the electrode adhesion.

[0061] MoO3 (3 - 6 mol%): Mo 6+ Forms a covalent bond network with V 5+ to enhance the glass conductivity continuity. MoO3 reacts with Ag to form Ag2MoO4, reducing the agglomeration of silver particles during high-temperature sintering.

[0062] Ag2O (0.5 - 1.5%): Ag + Is reduced to nano-silver particles during the sintering process, filling the gaps between silver powders and reducing the contact resistance. At the same time, it can reduce the usage of main silver powder and lower the cost of the slurry.

[0063] Li2O (1 - 3%): Li + Has high ionic mobility, further reduces the glass viscosity, and adapts to high-speed printing. Synergistically optimizes the thermal expansion coefficient with Na2O to reduce the warping of the electrode after sintering.

[0064] Thus, through the conductive optimization of the Bi-V-Mo system, the enhancement of the B-Si-Al network stability, and the Ag-Li process adaptability design of this glass material, the core requirements of xBC battery slurry in conductivity (low contact resistance), adhesion (interface anchoring), and cost control (less silverization) are achieved. At the same time, it adapts to the ultra-fine grid printing and low-temperature sintering processes, providing key material support for the mass production of high-efficiency xBC batteries.

[0065] In some embodiments, the particle size of the polyurethane-silver nanoparticle composite self-healing microspheres is 1 - 5 μm, the shell thickness is 100 - 200 nm, and the core material loading rate is ≥85%.

[0066] In some embodiments, the D50 of the silver powder is 1 - 5 μm, and it is flaky silver powder, and the ratio of the sheet diameter to the thickness is 10:1 - 20:1.

[0067] Figure 1 It is a schematic flow chart of a preparation method of an xBC battery slurry provided by an embodiment of this application.

[0068] Second aspect, as Figure 1As shown, the present application provides a preparation method of the xBC battery paste according to any one of the first aspects, and the method includes:

[0069] S1. Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper and carbon nanotubes to obtain a conductive phase;

[0070] S2. Vacuum stir and disperse glass powder and an organic carrier to obtain a carrier;

[0071] S3. Mix the conductive phase with the carrier, and then add La2O3, VO2 and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery paste.

[0072] In some embodiments, the preparation method of the polyurethane-silver nanoparticle composite self-healing microspheres includes:

[0073] Mix polytetrahydrofuran diol and isophorone diisocyanate, and react at 70 °C for 2 h under nitrogen protection to generate an isocyanate-terminated prepolymer;

[0074] Add dimethylolpropionic acid to the isocyanate-terminated prepolymer to continue the reaction for 1 h to form a carboxylic acid group-modified polyurethane, then cool down to 40 °C, and add acetone to adjust the viscosity to obtain a carboxylic acid-modified polyurethane;

[0075] Dissolve silver nitrate and polyvinylpyrrolidone in deionized water and then drop them into the carboxylic acid-modified polyurethane, stir for 30 min, then gradually add a 0.2 mol / L sodium borohydride solution, and carry out a reduction reaction at 45 °C for 1 h to obtain a polyurethane-silver nanoparticle composite;

[0076] Dissolve the polyurethane-silver nanoparticle composite, toluene-2,4-diisocyanate, and Span-80 emulsifier in xylene to obtain an oil phase;

[0077] Dissolve gelatin and sodium dodecyl sulfate in deionized water to obtain an aqueous phase;

[0078] Pour the oil phase into the aqueous phase, and carry out high-speed shear emulsification at 10000 rpm for 10 min to form an emulsion;

[0079] Add ethylenediamine to the emulsion, react at 50 °C for 3 h to form a polyurea shell, and then carry out centrifugal separation, washing and freeze-drying to obtain the polyurethane-silver nanoparticle composite self-healing microspheres.

[0080] In some embodiments, the molar ratio of the polytetrahydrofuran diol to the isophorone diisocyanate is 1:2.

[0081] In some embodiments, the mass of the dimethylolpropionic acid is 5% of the mass of the isocyanate-terminated prepolymer.

[0082] In some embodiments, the mass ratio of the polyurethane-silver nanoparticle composite, the toluene-2,4-diisocyanate, the Span-80 emulsifier, and the xylene is 50:10:2:100.

[0083] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0084] Example 1

[0085] This example provides an xBC battery paste based on a copper alloy. In parts by mass, the xBC battery paste includes the following chemical components: 40 parts of silver powder, 15 parts of silver-coated copper (Tenghui Kecai Model 1040), 3 parts of glass material, 25 parts of organic carrier, 0.8 part of multi-walled carbon nanotubes (CAS No.: 308068-56-6), 0.2 part of La2O3, 0.1 part of VO2 nanoparticles (Model: SS-V50, CAS: 12036-21-4), and 2 parts of polyurethane-silver nanoparticle composite self-healing microspheres.

[0086] Among them, in parts by mass, the organic carrier includes the following chemical components: 60 parts of limonene, 20 parts of butyl carbitol acetate, 25 parts of pentaerythritol triacrylate, 2 parts of 2-hydroxy-2-methylpropiophenone, 3 parts of polydimethylsiloxane, 8 parts of polyurethane-modified acrylic resin, and 0.8 part of dispersant.

[0087] In terms of molar percentage, the glass material consists of the following components: P2O5: 10 mol%, Bi2O3: 30 mol%, Na2O: 6 mol%, ZnO: 6 mol%, B2O3: 20 mol%, SiO2: 7 mol%, Al2O3: 2 mol%, V2O5: 12 mol%, MoO3: 4 mol%, Ag2O: 1%, Li2O: 2%.

[0088] The particle size of the polyurethane-silver nanoparticle composite self-healing microspheres is 1 - 5 μm, the shell thickness is 100 - 200 nm, and the core material loading rate is 90%.

[0089] The particle size D50 of the silver powder is 1 - 5 μm, and it is flaky silver powder, and the ratio of the sheet diameter to the thickness is 10:1 - 20:1.

[0090] Based on the above xBC battery paste, this embodiment also provides a preparation method of the xBC battery paste described in any one of the above, and the method includes:

[0091] S11. Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper, and carbon nanotubes to obtain a conductive phase;

[0092] S21. Vacuum stir and disperse glass powder and an organic carrier to obtain a carrier;

[0093] S31. Mix the conductive phase and the carrier, and then add La2O3, VO2, and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery paste.

[0094] Among them, the preparation method of the microcapsule repair agent of the self-healing polymer carrier includes the following steps:

[0095] (1) Prepare a polyurethane-silver nanoparticle composite repair agent:

[0096] a. Mix polytetrahydrofuran diol (PTMG) and isophorone diisocyanate (IPDI) in a molar ratio of 1:2, and react at 70 °C for 2 hours under nitrogen protection to generate an isocyanate-terminated prepolymer;

[0097] b. Add 5% of its mass of dimethylolpropionic acid (DMPA) to the prepolymer in step a, and continue to react for 1 hour to form a carboxylic acid group-modified polyurethane;

[0098] c. Cool down to 40 °C, and add acetone to adjust the viscosity to 1000 mPa·s;

[0099] d. Dissolve silver nitrate (0.1 mol / L) and polyvinylpyrrolidone (0.5 wt%) in deionized water, then drop them into the polyurethane in step c, stir for 30 minutes, and gradually add 0.2 mol / L sodium borohydride solution (Ag + :BH4 - = 1:5), and carry out a reduction reaction at 45 °C for 1 hour to obtain a polyurethane-silver nanoparticle composite with a silver content of 10-15 wt%;

[0100] (2) Microencapsulation process:

[0101] a. Prepare an oil phase: Dissolve 50 g of the composite obtained in step (1), 10 g of toluene-2,4-diisocyanate (TDI), and 2 g of Span-80 emulsifier in 100 mL of xylene;

[0102] b. Prepare an aqueous phase: Dissolve 5 g of gelatin and 1 g of sodium dodecyl sulfate (SDS) in 200 mL of deionized water;

[0103] c. Pour the oil phase into the water phase and shear emulsify at a high speed of 10000 rpm for 10 minutes to form a W / O emulsion with a droplet size of 1 - 5 μm;

[0104] d. Add 5 g of ethylenediamine to the emulsion and react at 50 °C for 3 hours to form a polyurea shell;

[0105] e. Centrifuge, wash and freeze-dry to obtain a polyurethane-silver nanoparticle composite repair agent.

[0106] Example 2

[0107] This example provides an xBC battery paste based on copper alloy. In parts by mass, the xBC battery paste includes the following chemical components: 30 parts of silver powder, 20 parts of silver-coated copper, 1.5 parts of glass material, 30 parts of organic carrier, 0.5 part of multi-walled carbon nanotubes, 0.2 part of La2O3, 0.3 part of VO2 nanoparticles, and 3 parts of polyurethane-silver nanoparticle composite self-healing microspheres.

[0108] Among them, in parts by mass, the organic carrier includes the following chemical components: 70 parts of limonene, 10 parts of butyl carbitol acetate, 10 parts of pentaerythritol triacrylate, 3 parts of 2-hydroxy-2-methylpropiophenone, 5 parts of polydimethylsiloxane, 10 parts of polyurethane-modified acrylic resin, and 1 part of dispersant.

[0109] In terms of mole percentage, the glass material is composed of the following components: P2O5: 10 mol%, Bi2O3: 25 mol%, Na2O: 8 mol%, ZnO: 8 mol%, B2O3: 22 mol%, SiO2: 5 mol%, Al2O3: 3 mol%, V2O5: 10 mol%, MoO3: 6 mol%, Ag2O: 1%, Li2O: 2%.

[0110] The particle size of the polyurethane-silver nanoparticle composite self-healing microspheres is 1 - 5 μm, the shell thickness is 100 - 200 nm, and the core material loading rate is 90%.

[0111] The particle size D50 of the silver powder is 1 - 5 μm, and it is flaky silver powder with a ratio of flake diameter to thickness of 10:1 - 20:1.

[0112] Based on the above xBC battery paste, this example also provides a preparation method of the xBC battery paste described in any one of the above, and the method includes:

[0113] S11. Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper and carbon nanotubes to obtain a conductive phase;

[0114] S21. Vacuum stir and disperse glass powder and organic carrier to obtain a carrier;

[0115] S31. Mix the conductive phase with the carrier, and then add La2O3, VO2 and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery slurry.

[0116] Among them, the preparation method of the microcapsule repair agent of the self-healing polymer carrier includes the following steps:

[0117] (1) Prepare polyurethane-silver nanoparticle composite repair agent:

[0118] a. Mix polytetrahydrofuran diol (PTMG) and isophorone diisocyanate (IPDI) in a molar ratio of 1:2, and react at 70 °C for 2 hours under nitrogen protection to generate an isocyanate-terminated prepolymer.

[0119] b. Add 5% of its mass of dimethylolpropionic acid (DMPA) to the prepolymer in step a, and continue to react for 1 hour to form a carboxylic acid group-modified polyurethane.

[0120] c. Cool down to 40 °C, and add acetone to adjust the viscosity to 1000 mPa·s.

[0121] d. Dissolve silver nitrate (0.1 mol / L) and polyvinylpyrrolidone (0.5 wt%) in deionized water and then drop it into the polyurethane in step c, stir for 30 minutes, and gradually add 0.2 mol / L sodium borohydride solution (Ag + :BH4 - = 1:5), and carry out a reduction reaction at 45 °C for 1 hour to obtain a polyurethane-silver nanoparticle composite with a silver content of 10-15 wt%.

[0122] (2) Microencapsulation process:

[0123] a. Prepare the oil phase: Dissolve 50 g of the composite obtained in step (1), 10 g of toluene-2,4-diisocyanate (TDI), and 2 g of Span-80 emulsifier in 100 mL of xylene.

[0124] b. Prepare the water phase: Dissolve 5 g of gelatin and 1 g of sodium dodecyl sulfate (SDS) in 200 mL of deionized water.

[0125] c. Pour the oil phase into the water phase, and carry out high-speed shear emulsification at 10000 rpm for 10 minutes to form a W / O emulsion with a droplet size of 1-5 μm.

[0126] d. Add 5 g of ethylenediamine to the emulsion, and react at 50 °C for 3 hours to generate a polyurea shell.

[0127] e. Centrifuge, wash and freeze-dry to obtain the polyurethane-silver nanoparticle composite repair agent.

[0128] Example 3

[0129] This example provides an xBC battery paste based on copper alloy. By mass, the xBC battery paste includes the following chemical components: 50 parts of silver powder, 10 parts of silver-coated copper, 5.5 parts of glass material, 20 parts of organic carrier, 0.5 part of multi-walled carbon nanotubes, 0.1 part of La2O3, 0.3 part of VO2 nanoparticles, and 1 part of polyurethane-silver nanoparticle composite self-healing microspheres.

[0130] Among them, by mass, the organic carrier includes the following chemical components: 50 parts of limonene, 30 parts of butyl carbitol acetate, 10 parts of pentaerythritol triacrylate, 1 - 3 parts of 2-hydroxy-2-methylpropiophenone, 5 parts of polydimethylsiloxane, 5 parts of polyurethane-modified acrylate resin, and 0.5 part of dispersant.

[0131] By mole percentage, the glass material is composed of the following components: P2O5: 5 mol%, Bi2O3: 35 mol%, Na2O: 5 mol%, ZnO: 8 mol%, B2O3: 18 mol%, SiO2: 8 mol%, Al2O3: 1 mol%, V2O5: 14 mol%, MoO3: 3 mol%, Ag2O: 0.5%, Li2O: 2.5%.

[0132] The particle size of the polyurethane-silver nanoparticle composite self-healing microspheres is 1 - 5 μm, the shell thickness is 100 - 200 nm, and the core material loading rate is 90%.

[0133] The particle size D50 of the silver powder is 1 - 5 μm, and it is flaky silver powder, and the ratio of sheet diameter to thickness is 10:1 - 20:1.

[0134] Based on the above xBC battery paste, this example also provides a preparation method of the xBC battery paste described in any one of the above, and the method includes:

[0135] S11. Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper, and carbon nanotubes to obtain a conductive phase;

[0136] S21. Vacuum stir and disperse glass powder and organic carrier to obtain a carrier;

[0137] S31. Mix the conductive phase and the carrier, and then add La2O3, VO2, and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery paste.

[0138] Among them, the preparation method of the microcapsule repair agent of the self-healing polymer carrier includes the following steps:

[0139] (1) Prepare a polyurethane-silver nanoparticle composite repair agent:

[0140] a. Mix polytetrahydrofuran diol (PTMG) and isophorone diisocyanate (IPDI) in a molar ratio of 1:2, and react at 70 °C for 2 hours under nitrogen protection to form an isocyanate-terminated prepolymer;

[0141] b. Add 5% (by mass) of dimethylolpropionic acid (DMPA) to the prepolymer in step a, and continue to react for 1 hour to form a carboxylic acid group-modified polyurethane;

[0142] c. Cool down to 40 °C, and add acetone to adjust the viscosity to 1000 mPa·s;

[0143] d. Dissolve silver nitrate (0.1 mol / L) and polyvinylpyrrolidone (0.5 wt%) in deionized water, then drop it into the polyurethane in step c, stir for 30 minutes, and gradually add 0.2 mol / L sodium borohydride solution (Ag + :BH4 - = 1:5), and carry out a reduction reaction at 45 °C for 1 hour to obtain a polyurethane-silver nanoparticle composite with a silver content of 10-15 wt%;

[0144] (2) Microencapsulation process:

[0145] a. Prepare the oil phase: Dissolve 50 g of the composite obtained in step (1), 10 g of toluene-2,4-diisocyanate (TDI), and 2 g of Span-80 emulsifier in 100 mL of xylene;

[0146] b. Prepare the water phase: Dissolve 5 g of gelatin and 1 g of sodium dodecyl sulfate (SDS) in 200 mL of deionized water;

[0147] c. Pour the oil phase into the water phase, and carry out high-speed shear emulsification at 10000 rpm for 10 minutes to form a W / O emulsion with a droplet size of 1-5 μm;

[0148] d. Add 5 g of ethylenediamine to the emulsion, and react at 50 °C for 3 hours to form a polyurea shell;

[0149] e. Carry out centrifugal separation, washing, and freeze-drying to obtain a polyurethane-silver nanoparticle composite repair agent.

[0150] Comparative Example 1

[0151] Based on what is disclosed in Example 1, this comparative example is modified as follows:

[0152] Do not add multi-walled carbon nanotubes to the xBC battery slurry.

[0153] Comparative Example 2

[0154] Based on what is disclosed in Example 1, this comparative example is modified as follows:

[0155] Do not add La2O3 to the xBC battery paste.

[0156] Comparative Example 3

[0157] Based on the disclosure of Example 1, this comparative example is modified as follows:

[0158] Do not add VO2 nanoparticles to the xBC battery paste

[0159] Comparative Example 4

[0160] Based on the disclosure of Example 1, this comparative example is modified as follows:

[0161] Do not add polyurethane-silver nanoparticle composite self-healing microspheres to the xBC battery paste.

[0162] Comparative Example 5

[0163] Based on the disclosure of Example 1, this comparative example is modified as follows:

[0164] Do not add silver-coated copper to the xBC battery paste.

[0165] The xBC battery pastes obtained in Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to performance measurements, and the results are shown in Table 1. The performance measurement methods are as follows:

[0166] Sheet resistance: Four-probe method, using a four-probe tester (Loresta-GXMCP-T700) to measure the surface resistance of the electrode after sintering.

[0167] Bending stability (ΔR): Dynamic bending test (radius of curvature 5 mm, change rate of resistance after 1000 cycles).

[0168] Self-healing efficiency (%): Manually create a 10-μm-wide crack, trigger repair with UV (365 nm, 500 mJ / cm 2 ) or at 80 °C, and measure the resistance recovery rate.

[0169] High-temperature stability (ΔR): Change rate of resistance after aging for 1000 hours in an 85 °C / 85% RH environment.

[0170] Hot spot effect (°C): Simulate local shading (50% light blocking), and record the maximum temperature rise with an infrared thermal imager.

[0171] Table 1 Performance of xBC battery pastes in Examples 1 to 3 and Comparative Examples 1 to 5

[0172]

[0173] As can be seen from Table 1, the sheet resistance of the xBC battery paste obtained in Examples 1 to 3 is 32 to 36 mΩ / □, the bending ΔR is 3.5 to 5.5%, the self-healing efficiency ≥ 90%, the high-temperature ΔR ≤ 3.0%, and the hot spot temperature rise ≤ 10°C.

[0174] In Comparative Example 1, there is no multi-walled carbon nanotube, the sheet resistance increases, the bending ΔR increases, and the hot spot temperature rise increases. The multi-walled carbon nanotubes construct a three-dimensional conductive network in the examples, penetrate the gaps between silver particles, and reduce the percolation threshold (decrease in conductivity); the one-dimensional structure of the carbon nanotubes enhances flexibility, and when missing, the silver particles are prone to breakage during bending (decrease in mechanical strength); the absence of the thermal conductivity of the carbon nanotubes (3000 W / m·K) results in the inability to diffuse local heat (increase in hot spot temperature rise).

[0175] In Comparative Example 2, there is no La2O3, the high-temperature ΔR increases, and the bending ΔR increases. La2O3 inhibits the oxidation of copper nuclei and forms a stable LaAlO3 phase in the examples. After the absence, copper oxidation intensifies (decrease in conductivity); the coordination bond between La 3+ and the carboxylated carbon nanotubes is missing, and the carbon nanotubes agglomerate (decrease in dispersibility).

[0176] In Comparative Example 3, there is no VO2, the hot spot temperature rise increases, and the self-healing efficiency decreases. The semiconductor-metal phase transition (68°C) of VO2 regulates the local resistance in the examples. After the absence, the hot spot cannot be self-regulated (increase in temperature rise); the absence of the photothermal effect of VO2, and the self-healing microspheres only rely on UV triggering, and the thermal trigger response is delayed (decrease in repair efficiency).

[0177] In Comparative Example 4, there is no self-healing microsphere, the self-healing efficiency drops to 0, and the bending ΔR increases. The self-healing microspheres repair cracks by releasing polyurethane-silver nanoparticles in the examples. After the absence, they cannot be dynamically repaired (irreversible increase in resistance); the stress buffering effect of the microspheres is missing, and the crack propagation accelerates during bending (decrease in mechanical stability).

[0178] In Comparative Example 5, there is no silver-coated copper, and the sheet resistance increases. Silver-coated copper replaces pure silver in the examples to reduce costs. After the absence, the conductive network is discontinuous (increase in sheet resistance).

[0179] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and the individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0180] In addition, in the description of the specification of this application, terms such as "include" and "comprise" mean "include but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0181] The above are only specific implementation manners of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. An xBC battery paste based on copper alloy, characterized in that, The xBC battery paste, in parts by mass, comprises the following chemical components: 30-50 parts of silver powder, 10-20 parts of silver-coated copper, 1.5-5.5 parts of glass material, 20-30 parts of organic carrier, 0.5-1 part of multi-walled carbon nanotubes, 0.1-0.2 part of La2O3, 0.1-0.3 part of VO2 nanoparticles, and 1-3 parts of polyurethane-silver nanoparticle composite self-healing microspheres.

2. The xBC battery paste according to claim 1, wherein The organic carrier, in parts by mass, comprises the following chemical components: 50-70 parts of limonene, 10-30 parts of butyl carbitol acetate, 10-20 parts of pentaerythritol triacrylate, 1-3 parts of 2-hydroxy-2-methylpropiophenone, 2-5 parts of polydimethylsiloxane, 5-10 parts of polyurethane-modified acrylate resin, and 0.5-1 part of dispersant.

3. The xBC battery paste according to claim 1, wherein The glass material, in mole percentages, consists of the following components: P2O5: 5-10 mol%, Bi2O3: 25-35 mol%, Na2O: 5-8 mol%, ZnO: 5-8 mol%, B2O3: 18-22 mol%, SiO2: 5-8 mol%, Al2O3: 1-3 mol%, V2O5: 10-14 mol%, MoO3: 3-6 mol%, Ag2O: 0.5-1.5%, Li2O: 1-3%.

4. The xBC battery paste according to claim 1, wherein The polyurethane-silver nanoparticle composite self-healing microspheres have a particle size of 1-5 μm, a shell thickness of 100-200 nm, and a core material loading rate ≥ 85%.

5. The xBC battery paste according to claim 1, wherein The silver powder has a D50 particle size of 1-5 μm and is flaky silver powder with a flake diameter to thickness ratio of 10:1-20:

1.

6. The preparation method of the xBC battery paste according to any one of claims 1 to 5, characterized in that, The method comprises: Under nitrogen protection, ball-mill and mix silver powder, silver-coated copper, and carbon nanotubes to obtain a conductive phase; Vacuum stir and disperse glass powder and the organic carrier to obtain a carrier; Mix the conductive phase with the carrier, and then add La2O3, VO2, and polyurethane-silver nanoparticle composite self-healing microspheres to obtain the xBC battery paste.

7. The preparation method of the xBC battery paste according to claim 6, characterized in that, The preparation method of the polyurethane-silver nanoparticle composite self-healing microspheres comprises: Mix polytetrahydrofuran diol and isophorone diisocyanate, and react at 70 °C for 2 h under nitrogen protection to form a terminal isocyanate prepolymer; Add dimethylolpropionic acid to the terminal isocyanate prepolymer and continue to react for 1 h to form a carboxylic acid group-modified polyurethane. Then cool to 40 °C and add acetone to adjust the viscosity to obtain a carboxylic acid-modified polyurethane; Dissolve silver nitrate and polyvinylpyrrolidone in deionized water and drop it into the carboxylic acid-modified polyurethane, stir for 30 min, then gradually add a 0.2 mol / L sodium borohydride solution and perform a reduction reaction at 45 °C for 1 h to obtain a polyurethane-silver nanoparticle composite; Dissolve the polyurethane-silver nanoparticle composite, toluene-2,4-diisocyanate, and Span-80 emulsifier in xylene to obtain an oil phase; Dissolve gelatin and sodium dodecyl sulfate in deionized water to obtain an aqueous phase; Pour the oil phase into the aqueous phase and perform high-speed shear emulsification at 10000 rpm for 10 min to form an emulsion; Ethylenediamine was added to the emulsion and reacted at 50 °C for 3 h to form a polyurea shell, followed by centrifugal separation, washing and freeze-drying to obtain the polyurethane-silver nanoparticle composite self-healing microspheres.

8. The preparation method of the xBC battery paste according to claim 7, wherein, The molar ratio of the polytetrahydrofuran diol to the isophorone diisocyanate is 1:

2.

9. The preparation method of the xBC battery paste according to claim 7, characterized in that, The mass of the dimethylolpropionic acid is 5% of the mass of the terminal isocyanate prepolymer.

10. The preparation method of the xBC battery paste according to claim 7, wherein, The mass ratio of the polyurethane-silver nanoparticle composite, the toluene-2,4-diisocyanate, the Span-80 emulsifier to the xylene is 50:10:2:100.

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