Low-silver conductive paste for back contact battery as well as preparation method and application of low-silver conductive paste

Abstract

The invention belongs to the technical field of conductive paste for a back contact battery, and particularly relates to low-silver conductive paste for a back contact battery and a preparation method and application thereof, and the low-silver conductive paste comprises silver powder, silver-coated copper powder, rosin, a metal ion capturing agent, epoxy resin and a solvent; based on the total mass of the low-silver conductive paste, the content of the silver powder is 10%-30%, the content of the silver-coated copper powder is 60%-80%, the content of the rosin is 0.1%-1%, the content of the metal ion trapping agent is 1%-5%, and the content of the epoxy resin is 2%-7%, the epoxy resin comprises bisphenol F epoxy resin, novolac epoxy resin and bisphenol A epoxy resin; the mass ratio of the bisphenol F type epoxy resin to the novolac epoxy resin to the bisphenol A type epoxy resin is 1: (0.5-1.5): (1.2-3). According to the invention, low-content silver powder is adopted, conductivity, cell conversion efficiency, stability, reliability and weatherability are improved, and the service life of the cell is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of conductive pastes for back contact batteries, and particularly relates to a low-silver conductive paste for back contact batteries, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of photovoltaic cells, conductive paste is a key material connecting the cell and the external circuit, and its performance directly affects the photoelectric conversion efficiency and reliability of the battery. Traditional photovoltaic cell conductive pastes mainly rely on silver powder as the conductive material. However, silver resources are limited and the price is expensive, resulting in high costs. In addition, silver powder is easily oxidized at high temperatures, affecting the conductive performance and battery stability. Therefore, developing conductive pastes with low silver content and high performance has become an important research direction in the industry.

[0003] In the prior art, some conductive pastes reduce the silver content by adding a small amount of silver powder and a large amount of silver-coated copper powder. However, the surface of silver-coated copper powder is easily oxidized, resulting in an increase in resistance and affecting the conductive performance. At the same time, the copper ions in the silver-coated copper powder will also corrode the cell, reducing the battery life. To solve these problems, some technical solutions attempt to improve the performance of the conductive paste by adding additives such as reducing agents and antioxidants, but the effects are often limited, and it is difficult to balance conductivity, stability, and cost.

[0004] In addition, it is difficult to obtain an ideal cross-linked network structure for the existing conductive pastes, resulting in insufficient adhesion and weather resistance of the conductive pastes. In some other solutions, during the preparation process, the mixing of silver powder, silver-coated copper powder, and resin is uneven, affecting the conductive performance and stability.

[0005] It should be noted that this part of the content of the present invention only provides the background technology related to the present invention, and does not necessarily constitute the prior art or well-known technology. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the existing conductive pastes that it is difficult to balance conductivity, stability, cost, and poor weather resistance. The present invention provides a low-silver conductive paste for back contact batteries, a preparation method thereof, and an application thereof. The present invention can improve the conductive performance, battery conversion efficiency, stability, reliability, weather resistance, and battery life while using low-content silver powder.

[0007] To achieve the above object, in a first aspect, the present invention provides a low-silver conductive paste for back-contact batteries, comprising silver powder, silver-coated copper powder, rosin, metal ion capturer, epoxy resin and solvent; based on the total mass of the low-silver conductive paste, the silver powder content accounts for 10%-30%, the silver-coated copper powder content accounts for 60%-80%, the rosin content accounts for 0.1%-1%, the metal ion capturer content accounts for 1%-5%, and the epoxy resin content accounts for 2%-7%. Among them, the epoxy resin includes bisphenol F epoxy resin, phenolic epoxy resin, and bisphenol A epoxy resin, and the mass ratio of bisphenol F epoxy resin, phenolic epoxy resin, and bisphenol A epoxy resin is 1:(0.5-1.5):(1.2-3).

[0008] In some preferred embodiments of the present invention, the epoxy equivalent of the epoxy resin is 50-170 g / eq; and / or, the viscosity of the epoxy resin is 1000-50000 cps.

[0009] In some preferred embodiments of the present invention, the mass ratio of silver powder to silver-coated copper powder is 1:(4-7).

[0010] In some preferred embodiments of the present invention, the particle size of the silver powder is 50-500 nm, and the particle size of the silver-coated copper powder is 1-7 µm.

[0011] In some preferred embodiments of the present invention, the mass ratio of silver powder, silver-coated copper powder, and rosin is 1:(4-7):(0.05-0.3), and / or, the rosin includes hydrogenated rosin and / or polymerized rosin.

[0012] In some preferred embodiments of the present invention, the metal ion capturer includes at least one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, oxalic acid dihydrazide, polyethyleneimine, and sodium diethyldithiocarbamate.

[0013] In some preferred embodiments of the present invention, the mass ratio of silver powder, silver-coated copper powder, rosin, epoxy resin, and metal ion capturer is 1:(4-7):(0.03-0.3):(0.1-0.3):(0.02-0.15).

[0014] In some preferred embodiments of the present invention, the solvent mass content in the low-silver conductive paste accounts for 1.2%-8%, and / or, the solvent includes at least one of ethylene glycol butyl ether acetate, diethylene glycol hexyl ether, diethylene glycol butyl ether, alcohol ester twelve, and terpineol.

[0015] In some preferred embodiments of the present invention, the low-silver conductive paste further includes an anti-settling agent, a dispersant, and an ultraviolet absorber. Based on the total mass of the low-silver conductive paste, the anti-settling agent content accounts for 0.3%-2%, the dispersant content accounts for 0.1%-2%, and the ultraviolet absorber content accounts for 0.1%-3%.

[0016] In some preferred embodiments of the present invention, the anti-settling agent is at least one of polyamide wax, hydrogenated castor oil, and fumed silica, and / or the ultraviolet absorber is at least one of benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and phenyl salicylate.

[0017] In a second aspect, the present invention provides a method for preparing a low-silver conductive paste for a back-contact battery, which is used to prepare the low-silver conductive paste for a back-contact battery described in the first aspect. The preparation method includes the following steps: S1. Mix and disperse epoxy resin, rosin, and a solvent. S2. Introduce silver powder, silver-coated copper powder, a metal ion scavenger, and, optionally, additives including at least one of a dispersant, an anti-settling agent, and an ultraviolet absorber, and mix and disperse them.

[0018] In a third aspect, the present invention provides a back-contact battery, which includes a metal electrode. The metal electrode uses the low-silver conductive paste for a back-contact battery described in the first aspect, or the low-silver conductive paste prepared by the method for preparing a low-silver conductive paste for a back-contact battery described in the second aspect.

[0019] Beneficial effects: Through the above technical solutions, especially by using an appropriate amount of low-silver powder in combination with an appropriate amount of silver-coated copper powder, and in combination with a specific composition of rosin, a metal ion scavenger, and epoxy resin, the present invention can achieve the following effects. Rosin can remove the oxides on the surfaces of silver powder and silver-coated copper powder, and can form a low-temperature molten and reticulated intertwined structure during the curing of the conductive paste, significantly reducing the resistance and improving the conductivity of the battery. On the one hand, the metal ion scavenger prevents the surfaces of silver powder and silver-coated copper powder from being oxidized again and reduces the copper ions overflowing from the silver-coated copper powder, which helps to improve the stability and lifespan of the battery. On the other hand, it participates in the cross-linking reaction of epoxy resin as a curing agent, reducing the types and contents of additional substances introduced, lowering the cost, and preventing the contamination of battery wafers. At the same time, the formula of the present invention also obtains an appropriate epoxy equivalent by mixing three different proportions of epoxy resin, forming a dense cross-linked network, enhancing the physical barrier effect on metal particles, inhibiting oxidation diffusion, further improving the conversion efficiency, reliability, and weather resistance of the battery, extending the battery lifespan, and reducing the usage amount of silver powder, thereby reducing the cost. The low-silver conductive paste of the present invention can play an important role in improving the efficiency of photovoltaic cells and reducing costs, meeting the market demand for high-performance and low-cost photovoltaic cells.

[0020] Specifically, rosin is added in the present invention, which can remove the oxides on the surfaces of silver powder and silver-coated copper powder during the heating reaction, enabling the micro-nano silver powder to melt at a low temperature and fuse with the surrounding silver powder and silver-coated copper powder into a reticulated intertwined structure, effectively reducing the resistance and improving the electrical conductivity. A metal ion scavenger is also added, which functions as both a curing agent and a reducing agent. First, it acts as a curing agent for the cross-linking reaction of epoxy resin. By controlling its addition amount within an appropriate range so that it is greater than the content of the curing agent required for the cross-linking reaction, it can prevent the surfaces of the silver powder and silver-coated copper powder whose oxides have been removed by the reaction with rosin from being oxidized again after curing. It can also reduce the copper ions overflowing from the silver-coated copper powder. Three different components of epoxy resin with appropriate proportions are used in combination, which is conducive to the uniform contact between rosin and metal particles, improving the oxide removal efficiency, and at the same time not losing the adhesion to the substrate. The multi-benzene ring structure of phenolic epoxy resin is used to improve the weather resistance and increase the curing temperature to ensure that a cross-linking network is formed after rosin has fully reacted, avoiding the influence of unreacted rosin residues on the electrical conductivity.

[0021] In the preferred embodiment of the present invention, controlling the epoxy equivalent of the epoxy resin within an appropriate range can make the cured silver-copper paste film shrink more tightly, which is more conducive to the formation of a dense cross-linking network, resulting in better electrical conductivity. At the same time, the denser the film layer and the higher the cross-linking degree, the better the strength of the film layer and the better the weather resistance. It also enhances the physical barrier effect on metal particles, effectively inhibiting the oxidation diffusion, thereby further improving the electrical conductivity and weather resistance of the applied back contact battery.

[0022] The preparation method of the present invention ensures the full reaction of rosin with other components through a specific input sequence (preferably controlling an appropriate reaction temperature), avoiding the influence of the presence of oxides on the electrical conductivity. Detailed implementation mode

[0023] In the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature has a lower horizontal height than the second feature.

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0026] In a first aspect, the present invention provides a low-silver conductive paste for a back contact battery, comprising silver powder, silver-coated copper powder, rosin, a metal ion scavenger, an epoxy resin and a solvent; based on the total mass of the low-silver conductive paste, the silver powder content accounts for 10%-30%, the silver-coated copper powder content accounts for 60%-80%, the rosin content accounts for 0.1%-1%, the metal ion scavenger content accounts for 1%-5%, and the epoxy resin content accounts for 2%-7%.

[0027] In the present invention, the epoxy resin preferably includes bisphenol F epoxy resin, novolac epoxy resin, and bisphenol A epoxy resin. Bisphenol F epoxy resin, novolac epoxy resin, and bisphenol A epoxy resin are all commercially available products, which will not be described in detail here.

[0028] Preferably, in the present invention, the mass ratio of bisphenol F epoxy resin, novolac epoxy resin and bisphenol A epoxy resin is 1: (0.5-1.5): (1.2-3), preferably 1: (0.5-1.5): (1.2-1.8). The present invention adopts a suitable ratio of novolac epoxy resin, which can effectively improve the weather resistance by utilizing the polybenzene ring structure of novolac epoxy resin, increase the curing temperature, ensure that the rosin is fully reacted before forming a cross-linked network, and avoid the unreacted rosin residue affecting the conductivity; the use of a suitable ratio of bisphenol F epoxy resin is conducive to improving the chemical corrosion resistance of the silver-copper paste, thereby meeting the strict requirements of photovoltaic modules for high temperature and high humidity during use, and the use of a suitable ratio of bisphenol A epoxy resin is conducive to improving the adhesion of the silver-copper paste, thereby ensuring that the silver-copper paste will not fall off during long-term use after printing, thereby improving the stability, reliability and weather resistance of the battery and improving the battery life.

[0029] In some preferred embodiments of the present invention, the epoxy equivalent of the epoxy resin is 50-170 g / eq, preferably 50-150 g / eq. This preferred solution is more conducive to forming a dense cross-linked network, enhancing the physical barrier effect on metal particles, and effectively inhibiting oxidation diffusion, thereby further improving the conductivity and weather resistance of the back contact battery.

[0030] In some preferred embodiments of the present invention, the viscosity of the epoxy resin is 1000 - 50000 cps, preferably 21000 - 50000 cps. Using an epoxy resin with a suitable viscosity is more conducive to the processing of the silver copper paste and also helps to improve the long-term printability of the silver copper paste.

[0031] In some preferred embodiments of the present invention, the mass ratio of silver powder to silver-coated copper powder is 1:(4 - 7). Using a low content of silver powder and a relatively high content of silver-coated copper powder is more conducive to reducing the cost of the silver copper paste.

[0032] In some preferred embodiments of the present invention, the particle size of the silver powder is 50 - 500 nm.

[0033] Preferably, in the present invention, the particle size of the silver-coated copper powder is 1 - 7 µm.

[0034] The present invention uses a suitable nano-scale silver powder in combination with a suitable range of micron-scale silver-coated copper powder. The nano-scale silver powder can well fill the voids formed by the accumulation of micron-scale silver copper powder, which can effectively improve the conductivity of the silver copper paste. The micron-scale silver-coated copper powder has good conductivity.

[0035] In some preferred embodiments of the present invention, the mass ratio of silver powder, silver-coated copper powder, and rosin is 1:(4 - 7):(0.05 - 0.3). The present invention uses a low content of silver powder, a relatively high content of silver-coated copper powder, and a suitable amount of rosin. During the curing process after the printing of the silver copper paste, rosin can remove the oxides on the surfaces of the silver powder and silver-coated copper powder, thereby improving the conductivity of the silver copper paste.

[0036] In some preferred embodiments of the present invention, the rosin includes hydrogenated rosin and / or polymerized rosin.

[0037] In some preferred embodiments of the present invention, the metal ion capturer includes at least one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, oxalic diacylhydrazide, polyethyleneimine, and sodium diethyldithiocarbamate. Further preferably, the metal ion capturer includes at least one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, oxalic diacylhydrazide, and sodium diethyldithiocarbamate, which is more conducive to enhancing the stability, reliability, and weather resistance of the battery.

[0038] In some preferred embodiments of the present invention, the mass ratio of silver powder, silver-coated copper powder, rosin, epoxy resin, and metal ion capturer is 1:(4 - 7):(0.03 - 0.3):(0.1 - 0.3):(0.02 - 0.15), preferably 1:(4 - 7):(0.03 - 0.3):(0.1 - 0.3):(0.05 - 0.15). By using the key components with such appropriate mass ratios, the conductivity of the silver-copper paste is improved, and it also has good printability and processability. At the same time, it takes into account the improvement of battery conversion efficiency and the stability, reliability, and weather resistance of the battery.

[0039] In the present invention, by using an appropriate ratio of epoxy resin and metal ion capturer, the content of the metal ion capturer can be made greater than the content of the curing agent required for the cross-linking reaction (calculated according to the equivalent of epoxy in the epoxy resin), so that after curing, it can effectively prevent the surfaces of the silver powder and silver-coated copper powder whose oxides have been removed by the reaction with rosin from being oxidized again, and can also effectively reduce the copper ions overflowing from the silver-coated copper powder.

[0040] In some preferred embodiments of the present invention, the mass content of the solvent in the low-silver conductive paste accounts for 1.2% - 8%, preferably 2% - 8%.

[0041] In some preferred embodiments of the present invention, the solvent includes at least one of ethylene glycol butyl ether acetate, diethylene glycol hexyl ether, diethylene glycol butyl ether, alcohol ester twelve, and terpineol.

[0042] In some preferred embodiments of the present invention, the low-silver conductive paste further includes at least one of an anti-settling agent, a dispersant, and an ultraviolet absorber.

[0043] Further preferably, based on the total mass of the low-silver conductive paste, the content of the anti-settling agent accounts for 0.3% - 2%, the content of the dispersant accounts for 0.1% - 2%, and the content of the ultraviolet absorber accounts for 0.1% - 3%.

[0044] In some preferred embodiments of the present invention, the anti-settling agent is at least one of polyamide wax, hydrogenated castor oil, and fumed silica.

[0045] In some preferred embodiments of the present invention, the ultraviolet absorber is at least one of benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and phenyl salicylate.

[0046] In the present invention, the dispersant can refer to the corresponding dispersant types in the prior art in this field. For example, the dispersant can be at least one of BYK-163 and BYK-111 of BYK.

[0047] In a second aspect, the present invention provides a method for preparing a low-silver conductive paste for a back-contact battery. The preparation method includes the following steps: S1. Mix and disperse epoxy resin, rosin and solvent; S2. Introduce silver powder, silver-coated copper powder and metal ion capturer and mix and disperse them.

[0048] Further preferably, an auxiliary agent is also added in S2, and the auxiliary agent includes at least one of a dispersant, an anti-settling agent and an ultraviolet absorber.

[0049] For the mixing and dispersion in S1 - S2 of the present invention, any existing method beneficial to dispersion can be adopted and can be used in the present invention, which will not be elaborated herein.

[0050] The preparation method of the present invention can prepare the low-silver conductive paste for back-contact battery described in the first aspect, and the obtained conductive paste has the same composition and performance as the low-silver conductive paste for back-contact battery in the first aspect, which will not be elaborated herein.

[0051] In the third aspect, the present invention provides a back-contact battery, which includes a metal electrode, and the metal electrode uses the low-silver conductive paste for back-contact battery described in the first aspect, or the low-silver conductive paste prepared by the preparation method of the low-silver conductive paste for back-contact battery described in the second aspect.

[0052] The low-silver conductive paste of the present invention can be used in back-contact batteries with any passivation structure in the prior art, such as back-contact batteries with heterojunction passivation or combined passivation, and can be used in the present invention. The low-silver conductive paste is used as a metal electrode in the back-contact battery, and can significantly improve the conductive performance, battery conversion efficiency, stability, reliability and weather resistance.

[0053] The embodiments of the present invention will be described in detail below. They are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0054] Example 1 A conductive paste has the following composition: based on the total mass of the conductive paste, the content of silver powder (average particle size is 350nm ± 10nm) accounts for 15%, the content of silver-coated copper powder (average particle size is 3μm ± 0.5μm) accounts for 70%, the content of hydrogenated rosin accounts for 0.5%, the content of ethylenediaminetetramethylenephosphonic acid accounts for 2%, the content of epoxy resin accounts for 5%, the content of polyamide wax accounts for 1%, the content of BYK-16 accounts for 1.2%, the content of benzotriazole accounts for 1%, and the balance is ethylene glycol monobutyl ether acetate. The components contained in the epoxy resin are: bisphenol F-type epoxy resin, phenolic epoxy resin, bisphenol A-type epoxy resin, and the mass ratio of bisphenol F-type epoxy resin, phenolic epoxy resin, and bisphenol A-type epoxy resin is 1:1:2. The epoxy equivalent of the epoxy resin is 120g / eq, and the viscosity of the epoxy resin is 20000cps. After calculation, the mass ratio of silver powder, silver-coated copper powder, rosin, epoxy resin, and metal ion capturer is 1:5:0.03:0.3:0.13.

[0055] The conductive paste is prepared by the following method: S1. Mix and disperse epoxy resin, rosin and solvent; S2. Introduce silver powder, silver-coated copper powder, metal ion capturer, dispersant, anti-settling agent and ultraviolet absorber and mix and disperse them.

[0056] Example 2 It is carried out with reference to Example 1, except that the amount of bisphenol A epoxy resin is adjusted so that the mass ratio of bisphenol F epoxy resin to bisphenol A epoxy resin is 1:1.3, the epoxy equivalent of the epoxy resin is 70 g / eq, and the viscosity of the epoxy resin is 28000 cps; the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0057] Example 3 It is carried out with reference to Example 1, except that the amount of phenolic epoxy resin is adjusted so that the mass ratio of bisphenol F epoxy resin to phenolic epoxy resin is 1:1.5, the epoxy equivalent of the epoxy resin is 140 g / eq, and the viscosity of the epoxy resin is 25000 cps; the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0058] Example 4 It is carried out with reference to Example 1, except that the amount of rosin is adjusted so that the mass ratio of silver powder to rosin is 1:0.2, the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0059] Example 5 It is carried out with reference to Example 1, except that the amount of metal ion capturer is adjusted so that the mass ratio of silver powder to metal ion capturer is 1:0.02, the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0060] Example 6 It is carried out with reference to Example 1, except that the metal ion capturer is adjusted to polyethyleneimine and the amount remains unchanged.

[0061] Comparative Example 1 It is carried out with reference to Example 1, except that rosin is not added, the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0062] Comparative Example 2 It is carried out with reference to Example 1, except that the amount of metal ion capturer is adjusted to 0.3%, so that the mass ratio of silver powder to metal ion capturer is 1:0.02, the amounts of components other than silver powder remain unchanged, and the silver powder is made up to 100%.

[0063] Comparative Example 3 Performed with reference to Example 1, except that bisphenol F type epoxy resin was not added.

[0064] Comparative Example 4 Performed with reference to Example 1, except that bisphenol A type epoxy resin was not added.

[0065] Test Example The low-silver conductive pastes obtained in the above Examples and Comparative Examples were used as metal electrodes to prepare back-contact cells with the same structure. The back-contact cells were in a finger-cross structure, and the two semiconductors contained therein were both heterojunction structures of intrinsic amorphous silicon and corresponding doped amorphous silicon. It also included metal electrodes and a conductive film layer laid on the outer surfaces of the two semiconductors. Isolation grooves were opened on the part of the conductive film layer located in the interval area where the two semiconductors were superimposed; the metal electrodes were arranged on the outer surfaces of the respective corresponding conductive film layers of the two semiconductor regions. And the performance of the obtained back-contact cells was tested, and the results are shown in Table 1. Among them, the resistivity was obtained by testing according to GB / T 351-2019 and was used to characterize the conductivity. The battery conversion efficiency was determined according to the IEC 61215 standard.

[0066] Power attenuation rate of the module before and after the high-temperature and high-humidity DH1000H test (test conditions: temperature 85°C ± 5°C, humidity 85% ± 5%RH, lasting 1000 h): The battery conversion efficiencies of the back-contact cells before and after the high-temperature and high-humidity DH1000H test were C 0 、C 1 , respectively. The power attenuation rate of the module = (C 0 -C 1 ) / C 0 ×%. The power attenuation rate of the module < 2% was considered qualified and was used to characterize the stability, reliability and weather resistance of the battery.

[0067] Table 1

[0068] From the above results, it can be seen that compared with the Comparative Examples, by adopting the embodiment scheme of the present invention, while using low-content silver powder, high electrical conductivity can be ensured, a high battery conversion efficiency can be obtained, and the stability, reliability and weather resistance of the battery can be greatly improved, and the battery life can be extended.

[0069] Furthermore, according to Example 1 and Examples 2-6, it can be seen that by adopting the preferred scheme of the present invention, it is more conducive to taking into account high battery conversion efficiency and low power attenuation.

[0070] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A low-silver conductive paste for back contact batteries, characterized in that: It includes silver powder, silver-coated copper powder, rosin, metal ion scavenger, epoxy resin and solvent; based on the total mass of the low-silver conductive paste, the silver powder content accounts for 10%-30%, the silver-coated copper powder content accounts for 60%-80%, the rosin content accounts for 0.1%-1%, the metal ion scavenger content accounts for 1%-5%, and the epoxy resin content accounts for 2%-7%, wherein the epoxy resin includes bisphenol F epoxy resin, novolac epoxy resin, and bisphenol A epoxy resin, and the mass ratio of bisphenol F epoxy resin, novolac epoxy resin, and bisphenol A epoxy resin is 1: (0.5-1.5): (1.2-3).

2. The low-silver conductive paste for back contact battery according to claim 1, characterized in that: The epoxy equivalent of the epoxy resin is 50-170 g / eq; and / or the viscosity of the epoxy resin is 1000-50000 cps.

3. The low-silver conductive paste for back contact battery according to claim 1, characterized in that: The mass ratio of silver powder to silver-coated copper powder is 1:(4-7); and / or, The particle size of silver powder is 50-500nm, and the particle size of silver-coated copper powder is 1-7µm.

4. The low-silver conductive paste for back contact battery according to claim 1, characterized in that: The mass ratio of silver powder, silver-coated copper powder and rosin is 1:(4-7):(0.05-0.3), and / or the rosin includes hydrogenated rosin and / or polymerized rosin.

5. The low-silver conductive paste for back contact battery according to any one of claims 1 to 4, characterized in that: The metal ion capture agent includes at least one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, oxalic acid dihydrazide, polyethyleneimine, and sodium diethyldithiocarbamate; and / or, The mass ratio of silver powder, silver-coated copper powder, rosin, epoxy resin and metal ion scavenger is 1: (4-7): (0.03-0.3): (0.1-0.3): (0.02-0.15).

6. The low-silver conductive paste for back contact battery according to claim 1, characterized in that: The mass content of the solvent in the low-silver conductive paste is 1.2%-8%, and / or the solvent includes at least one of ethylene glycol butyl ether acetate, diethylene glycol hexyl ether, diethylene glycol butyl ether, alcohol ester dodecanol, and pinene alcohol.

7. The low-silver conductive paste for back contact battery according to claim 1, characterized in that: The low-silver conductive paste also includes an anti-settling agent, a dispersant, and a UV absorber. Based on the total mass of the low-silver conductive paste, the anti-settling agent content accounts for 0.3%-2%, the dispersant content accounts for 0.1%-2%, and the UV absorber content accounts for 0.1%-3%.

8. The low-silver conductive paste for back contact battery according to claim 7, characterized in that: The anti-settling agent is at least one of polyamide wax, hydrogenated castor oil, and fumed silica, and / or the ultraviolet absorber is at least one of benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and phenyl salicylate.

9. A method for preparing a low-silver conductive paste for a back contact battery, characterized in that: The method is used to prepare a low-silver conductive paste for a back contact battery according to any one of claims 1 to 8, and the preparation method comprises the following steps: S1, mixing and dispersing epoxy resin, rosin and solvent; S2. Silver powder, silver-coated copper powder, metal ion scavenger, and auxiliary agents which may or may not be added as required are introduced for mixing and dispersion, wherein the auxiliary agent comprises at least one of a dispersant, an anti-settling agent, and an ultraviolet absorber.

10. A back contact battery, characterized in that: It comprises a metal electrode, which is made of the low-silver conductive paste for a back contact battery as described in any one of claims 1 to 8, or the low-silver conductive paste prepared by the preparation method of the low-silver conductive paste for a back contact battery as described in claim 9.

Images