Electrolytic nickel stripping solution, preparation method thereof and application thereof in preparation of crystalline silicon solar cell

Abstract

The application provides an electrolytic nickel stripping liquid, a preparation method thereof and application in preparation of crystalline silicon solar cells. The electrolytic nickel stripping liquid comprises the following components in parts by mass: 50-150 parts of an oxidizing agent, 1-5 parts of an inhibitor, 10-20 parts of a buffer and 5-10 parts of a complexing agent; wherein the oxidizing agent comprises an acid compound, and the inhibitor comprises a nitrogen-containing compound. The electrolytic nickel stripping method specifically comprises the following steps: taking a nickel-plated layer of a silicon substrate which is in contact with the electrolytic nickel stripping liquid as an anode, taking a titanium mesh which is placed in the electrolytic nickel stripping liquid as a cathode, performing electrolytic nickel stripping, and obtaining a silicon substrate after the nickel-plated layer is stripped. The application adopts an environment-friendly electrolytic nickel stripping liquid and an electrolytic nickel stripping method, the nickel stripping speed is fast, the damage to the silicon substrate is small, and the adhesion of the metal plating layer of the crystalline silicon solar cell can be improved.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to an electrolytic nickel stripping solution, its preparation method, and its application in the preparation of crystalline silicon solar cells. Background Technology

[0002] In the manufacturing of crystalline silicon solar cells, silicon wafers are a widely used semiconductor material. The production process of crystalline silicon solar cells involves first plating nickel onto the silicon wafer surface, then annealing it to form a nickel-silicon alloy. Next, the annealed silicon substrate undergoes stripping to remove any defective nickel layers, leaving only the nickel-silicon alloy. Finally, electroplating continues to obtain the desired crystalline silicon solar cell. Removing the nickel plating from the silicon substrate is a crucial process step because if the nickel plating is not removed before proceeding to the next step, the adhesion of the entire metal plating layer will be compromised.

[0003] The existing nickel stripping method is mainly chemical stripping, which uses nitric acid with a concentration of 65-85% for treatment. This method has a fast nickel stripping speed and low cost, but the nickel stripping process generates toxic yellowish-brown nitrogen dioxide gas, which pollutes the environment and harms the health of operators; at the same time, it will damage the silicon substrate of crystalline silicon solar cells, resulting in a reduction in cell efficiency.

[0004] An existing technology discloses an environmentally friendly nickel stripping agent and its preparation and application methods. Each liter of solution in this nickel stripping agent contains: 30-150 g of sulfuric acid solution, 20-50 g of hydrogen peroxide solution, 4-10 g of nitric acid solution, 1-10 g of solvent promoter, 1-5 g of complexing agent, and 1-5 g of stabilizer, with pure water as the solvent. Although this nickel stripping agent reduces the amount of nitric acid solution used to some extent by using a sulfuric acid-hydrogen peroxide system, the use of nitric acid solution is still unavoidable. Furthermore, the application method of this nickel stripping agent is a chemical stripping method, which involves immersing the nickel-plated plate in the nickel stripping agent. This inevitably damages the silicon substrate of the crystalline silicon solar cell, causing a decrease in cell efficiency.

[0005] A prior art method and solution for removing nickel plating are disclosed. The solution is prepared by adding a strong acid, a strong oxidant, a complexing agent, a corrosion inhibitor, and a stabilizer to a preparation tank and stirring to ensure uniform mixing. The mass ratio of the strong acid, oxidant, complexing agent, corrosion inhibitor, and stabilizer is (40-60):(100-200):(20-60):(0.1-0.5):(10-20). The proportions and selection of the strong oxidant, complexing agent, corrosion inhibitor, and stabilizer in this formula limit its applicability to removing nickel plating from rack surfaces. Furthermore, the use of a high concentration of peroxide as the oxidant and the low content of the corrosion inhibitor make it unsuitable for removing nickel plating from silicon substrates in crystalline silicon solar cells, potentially damaging the silicon substrate and reducing cell efficiency.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One objective of this invention is to provide an electrolytic nickel stripping solution, comprising, by mass concentration: 50-150 g / L of oxidant, 1-5 g / L of corrosion inhibitor, 10-20 g / L of buffer, and 5-10 g / L of complexing agent; wherein the oxidant comprises an acidic compound, and the corrosion inhibitor comprises a nitrogen-containing compound. This invention, through the selection and proportioning of the components in the electrolytic nickel stripping solution, significantly improves the nickel stripping speed of the nickel plating layer on the silicon substrate surface and further reduces the damage to the silicon substrate caused by the nickel stripping solution.

[0008] The second objective of this invention is to provide a method for preparing the electrolytic nickel stripping solution, the method comprising the following steps: adding an oxidant to a portion of the water in the raw material and stirring for the first time; adding a buffer and stirring for the second time; adding a corrosion inhibitor and a complexing agent and stirring for the third time; and finally replenishing the remaining water in the remaining raw material to obtain the electrolytic nickel stripping solution.

[0009] A third objective of this invention is to provide an application of the aforementioned electrolytic nickel stripping solution in the fabrication of crystalline silicon solar cells. This invention proposes an electrolytic nickel stripping solution, which, when applied to crystalline silicon solar cells, can improve the adhesion of the entire metal coating.

[0010] The fourth objective of this invention is to provide a method for removing nickel plating from a silicon substrate in solar cells. This method specifically includes the following steps: using the nickel plating on the silicon substrate in contact with the electrolytic nickel stripping solution as the anode, and a titanium mesh placed in the electrolytic nickel stripping solution as the cathode, electrolytic nickel stripping is performed to obtain the silicon substrate after the nickel plating layer has been removed. Based on the selection and proportioning of each component in the electrolytic nickel stripping solution, this invention employs an electrochemical nickel stripping method to assist in nickel stripping, further improving the speed of nickel stripping. It can completely remove the substandard nickel plating layer from the surface of the crystalline silicon cell in one step, allowing for further plating of other metals. This significantly improves the adhesion of the entire metal plating layer and avoids damage to the silicon substrate of the crystalline silicon solar cell, thus helping to maintain the cell's efficiency.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In a first aspect, the present invention provides an electrolytic nickel stripping solution, wherein the electrolytic nickel stripping solution comprises the following components in parts by mass: Oxidizing agent 50-150 parts, corrosion inhibitor 1-5 parts, buffer 10-20 parts, complexing agent 5-10 parts.

[0012] The oxidant includes concentrated sulfuric acid, and the corrosion inhibitor includes nitrogen-containing compounds.

[0013] In this invention, by selecting and proportioning the components in the electrolytic nickel stripping solution, the nickel stripping speed of the nickel plating layer on the silicon substrate surface is significantly improved, and the damage of the nickel stripping solution to the silicon substrate is further reduced.

[0014] In the electrolytic nickel stripping solution, the content of oxidant is 50 to 150 parts, for example, it can be 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, 100 parts, 110 parts, 120 parts, 130 parts, 140 parts, 150 parts, etc.

[0015] In the electrolytic nickel stripping solution, the content of corrosion inhibitor is 1 to 5 parts, for example, it can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0016] In the electrolytic nickel stripping solution, the content of the buffer is 10 to 20 parts, for example, it can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc.

[0017] In the electrolytic nickel stripping solution, the content of the complexing agent is 5 to 10 parts, for example, it can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, 10 parts, etc.

[0018] The water content in the electrolytic nickel stripping solution is 800-1200 parts, for example, it can be 800 parts, 820 parts, 840 parts, 860 parts, 880 parts, 890 parts, 900 parts, 910 parts, 920 parts, 930 parts, 940 parts, 950 parts, 960 parts, 970 parts, 980 parts, 990 parts, 995 parts, 1000 parts, 1005 parts, 1010 parts, 1020 parts, 1030 parts, 1040 parts, 1050 parts, 1180 parts, 1100 parts, 1120 parts, 1150 parts, 1180 parts, 1200 parts, etc.

[0019] Preferably, the electrolytic nickel stripping solution comprises the following components by mass concentration: Oxidizing agent 50~150 g / L, corrosion inhibitor 1~5 g / L, buffer 10~20 g / L, complexing agent 5~10 g / L; In the electrolytic nickel stripping solution, the concentration of the oxidant is 50~150 g / L, for example, it can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, etc.

[0020] In the electrolytic nickel stripping solution, the concentration of the corrosion inhibitor is 1~5 g / L, for example, it can be 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc.

[0021] In the electrolytic nickel stripping solution, the concentration of the buffer is 10~20 g / L, for example, it can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 20 g / L, etc.

[0022] In the electrolytic nickel stripping solution, the concentration of the ligand is 5~10 g / L, for example, it can be 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, 10 g / L, etc.

[0023] Preferably, the concentrated sulfuric acid is a sulfuric acid solution with a mass fraction of 70% or more, such as 70%, 75%, 80%, 85%, 90%, 95%, 98%, etc., and preferably a 98% sulfuric acid solution.

[0024] Preferably, the oxidant further includes phosphoric acid and / or oxalic acid.

[0025] This invention avoids the use of high-concentration nitric acid solution, thus avoiding environmental pollution and having minimal impact on the health of operators. It is an environmentally friendly method for removing electroplated nickel layers and is suitable for large-scale production in the field of crystalline silicon solar cells.

[0026] Preferably, the oxidant is a mixture of concentrated sulfuric acid and phosphoric acid.

[0027] Preferably, the mass ratio of concentrated sulfuric acid to phosphoric acid is (3~5):1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc.

[0028] Preferably, the nitrogen-containing compound includes any one or a combination of at least two of thiourea, hexamethylenetetramine, or ethylenediamine.

[0029] Preferably, the corrosion inhibitor comprises a mixture of thiourea and hexamethylenetetramine.

[0030] Preferably, the mass ratio of thiourea to hexamethylenetetramine is (1~2):1, for example, it can be 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, etc.

[0031] Preferably, the buffer comprises any one or a combination of at least two of boric acid, sodium borate, acetic acid, sodium acetate, or ammonium acetate, and more preferably a combination of any one or a combination of at least two of boric acid, sodium acetate, or ammonium acetate.

[0032] Preferably, the ligand comprises any one or a combination of at least two of lactic acid, citric acid, malic acid, succinic acid, glycine, tartaric acid, ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, or aminotrimethylphosphonic acid.

[0033] Preferably, the electrolytic nickel stripping solution further includes 0.05 to 5 parts of additives by weight, such as 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0034] Preferably, the electrolytic nickel stripping solution further includes 0.05~5 g / L of additives, for example, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc., based on mass concentration.

[0035] Preferably, the additives include any one or a combination of at least two of surfactants, plating accelerators, or cosolvents.

[0036] Preferably, the electrolytic nickel stripping solution further includes 0.05 to 5 parts of surfactant by mass, for example, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0037] Preferably, the electrolytic nickel stripping solution further includes 0.05 to 5 parts of a stripping accelerator by weight, for example, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0038] Preferably, the electrolytic nickel stripping solution further includes 0.05 to 5 parts of flux by weight, for example, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, etc.

[0039] Preferably, the electrolytic nickel stripping solution further includes a surfactant at a concentration of 0.05 to 5 g / L, such as 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc.

[0040] Preferably, the electrolytic nickel stripping solution further includes 0.05~5 g / L of a stripping accelerator, for example, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc., based on mass concentration.

[0041] Preferably, the electrolytic nickel stripping solution further includes a flux of 0.05~5 g / L, for example, 0.05 g / L, 0.1 g / L, 0.5 g / L, 1 g / L, 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, etc., based on mass concentration.

[0042] Preferably, the surfactant includes nonionic surfactants and / or anionic surfactants, and more preferably, it is a compound surfactant consisting of a combination of nonionic surfactants and anionic surfactants.

[0043] Preferably, the nonionic surfactant includes any one or a combination of at least two of Tween, polyethylene glycol, or alkyl polyoxyethylene ether.

[0044] Preferably, the Tween includes any one or a combination of at least two of Tween 20, Tween 40, Tween 60, Tween 65 or Tween 80.

[0045] Preferably, the polyethylene glycol includes any one or a combination of at least two of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 or polyethylene glycol 800.

[0046] Preferably, the alkyl polyoxyethylene ether includes any one or a combination of at least two of dodecyl polyoxyethylene ether, tetradecyl polyoxyethylene ether, or hexadecyl polyoxyethylene ether.

[0047] Preferably, the anionic surfactant comprises any one or a combination of at least two of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, sodium dodecyl sulfate, or sodium dodecylbenzenesulfonate.

[0048] Preferably, the plating accelerator comprises any one or a combination of at least two of potassium thiocyanate, sodium thiocyanate, or ammonium thiocyanate.

[0049] Preferably, the cosolvent comprises any one or a combination of at least two of 1,2-propanediol, glycerol, monoethanolamine, diethanolamine, or triethanolamine.

[0050] In a second aspect, the present invention provides a method for preparing an electrolytic nickel stripping solution as described in the first aspect, the method comprising the following steps: An oxidant is added to a portion of the water in the raw material and stirred for the first time; a buffer is added and stirred for the second time; a corrosion inhibitor and a complexing agent are added and stirred for the third time; finally, the remaining water in the remaining raw material is added to obtain the electrolytic nickel stripping solution.

[0051] Preferably, the amount of water added is 40-60% (v / v) of the total volume of water in the raw material, for example, it can be 40% (v / v), 42% (v / v), 44% (v / v), 46% (v / v), 48% (v / v), 50% (v / v), 52% (v / v), 54% (v / v), 56% (v / v), 58% (v / v), 60% (v / v), etc.

[0052] Preferably, the first stirring speed is 30~60 rpm, for example, 30 rpm, 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, etc., and the time is 5~10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0053] Preferably, the second stirring speed is 60~100 rpm, for example, 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, etc., and the time is 10~20 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, etc.

[0054] Preferably, the third stirring speed is 100~200 rpm, for example, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, etc., and the time is 3~6 min, for example, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, etc.

[0055] Preferably, the speed of the fourth stirring is 100~200 rpm, for example, 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, etc., and the time is 4~8 min, for example, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, etc.

[0056] Thirdly, the present invention provides an application of the electrolytic nickel stripping solution according to the first aspect in the preparation of crystalline silicon solar cells.

[0057] Fourthly, the present invention provides a method for removing a nickel plating layer from a silicon substrate of a solar cell, the method specifically including the following steps: Using the nickel-plated layer on the silicon substrate in contact with the electrolytic nickel stripping solution as the anode and a titanium mesh placed in the electrolytic nickel stripping solution as the cathode, electrolytic nickel stripping is performed to obtain the silicon substrate after the nickel plating layer has been removed.

[0058] Preferably, the nickel plating layer is a nickel-silicon alloy layer formed by annealing a nickel-plated silicon substrate.

[0059] More specifically, the nickel plating layer is prepared by the following steps: providing a silicon substrate for solar cells, electroplating a nickel plating layer on the silicon substrate using a nickel plating solution, and annealing the nickel-plated silicon substrate in an annealing furnace to form a nickel-silicon alloy.

[0060] Preferably, the thickness of the nickel plating layer is 0.3~1.0 μm, for example, it can be 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, etc.

[0061] Preferably, the annealing temperature is 250~400℃, for example, it can be 250℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc., and the annealing time is 60~180 s, for example, it can be 60 s, 80 s, 100 s, 120 s, 140 s, 160 s, 180 s, etc.

[0062] Preferably, the electrolytic nickel stripping temperature is 20~60℃, for example, it can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, etc.

[0063] Preferably, the current density at the anode of the electrolytic nickel stripping process is 1~3 A / dm³. 2 For example, it could be 1 A / dm 2 1.2A / dm 2 1.4 A / dm 2 1.6 A / dm 2 1.8 A / dm 2 2 A / dm 2 2.2 A / dm 2 2.4 A / dm 2 2.6 A / dm 2 2.8 A / dm 2 3 A / dm 2 wait.

[0064] Preferably, the cutoff voltage for the electrolytic nickel stripping is 3~6 V, for example, it can be 3 V, 3.5 V, 4 V, 4.5 V, 5 V, 5.5 V, 6 V, etc.

[0065] Compared with the prior art, the present invention has the following beneficial effects: (1) The electrolytic nickel stripping solution described in this invention does not use the industry's traditional high-concentration nitric acid solution, does not pollute the environment, has little impact on the health of operators, and is an environmentally friendly method for removing electroplated nickel layers, which is suitable for large-scale production in the field of crystalline silicon cells.

[0066] (2) The electrolytic nickel stripping solution of the present invention has a fast nickel stripping speed and can remove the unqualified nickel plating layer on the surface of the crystalline silicon battery in one go. After plating other metals, the adhesion of the entire metal plating layer is greatly improved. Detailed Implementation

[0067] Unless otherwise defined herein, the scientific and technical terms used in conjunction with this invention shall have the meanings commonly understood by one of ordinary skill in the art. The meaning and scope of terms shall be clear; however, in any case of potential ambiguity, the definitions provided herein shall prevail over any dictionary or foreign definitions. In this application, unless otherwise stated, the use of "or" means "and / or". Furthermore, the use of the term "comprising" and other forms is non-limiting.

[0068] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] The present invention will be further illustrated by the following examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0070] Example 1 This embodiment provides an electrolytic nickel stripping solution, which comprises the following components by mass concentration:

[0071] The electrolytic nickel stripping solution is prepared by the following method: (a) Add oxidant to half of the water in the raw material and stir for the first time; wherein, the stirring speed for the first time is 45 rpm and the time is 7 min; (b) Add the buffer and stir a second time; the second stirring speed is 80 rpm and the time is 15 min; (c) Add corrosion inhibitor, complexing agent, surfactant, stripping accelerator and cosolvent and stir for a third time; wherein, the stirring speed for the third time is 150 rpm and the time is 4 min; (d) Finally, add half of the remaining water to the remaining raw materials and stir for the fourth time. The stirring speed for the fourth time is 150 rpm and the time is 5 min; thus, the electrolytic nickel stripping solution is obtained.

[0072] Example 2 This embodiment provides an electrolytic nickel stripping solution, which comprises the following components by mass concentration:

[0073] The electrolytic nickel stripping solution is prepared by the following method: (a) Take 1 / 2 of the water in the raw material and add oxidant for the first stirring; wherein, the stirring speed for the first stirring is 30 rpm and the time is 10 min; (b) Add the buffer and stir a second time; the stirring speed for the second time is 60 rpm and the time is 20 min; (c) Add corrosion inhibitor, complexing agent, surfactant, stripping accelerator and cosolvent and stir for a third time; wherein, the stirring speed for the third time is 100 rpm and the time is 6 min; (d) Finally, add half of the remaining water to the remaining raw materials and stir for the fourth time. The stirring speed for the fourth time is 100 rpm and the time is 8 min; to obtain the electrolytic nickel stripping solution.

[0074] Example 3 This embodiment provides an electrolytic nickel stripping solution, which comprises the following components by mass concentration:

[0075] The electrolytic nickel stripping solution is prepared by the following method: (a) Add oxidant to half of the water in the raw material and stir for the first time; wherein, the stirring speed for the first time is 60 rpm and the time is 5 min; (b) Add the buffer and stir a second time; the second stirring speed is 100 rpm and the time is 10 min; (c) Add corrosion inhibitor, complexing agent, surfactant, stripping accelerator and cosolvent and stir for a third time; wherein the stirring speed for the third time is 200 rpm and the time is 3 min; (d) Finally, add half of the remaining water to the remaining raw materials and stir for the fourth time. The stirring speed for the fourth time is 200 rpm and the time is 4 min; to obtain the electrolytic nickel stripping solution.

[0076] Example 4 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the oxidant does not contain phosphoric acid, and the concentrated sulfuric acid content is increased to 100 g / L. The content of other components and the preparation method are completely consistent with Example 1.

[0077] Example 5 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the corrosion inhibitor does not contain thiourea, and the content of hexamethylenetetramine is increased to 2.5 g / L. The content of other components and the preparation method are completely consistent with Example 1.

[0078] Example 6 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the oxidant does not contain hexamethylenetetramine, and the thiourea content is increased to 2.5 g / L. The content of other components and the preparation method are completely consistent with Example 1.

[0079] Example 7 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the buffer boric acid is replaced with acetic acid of the same concentration of 15 g / L. The content of other components and the preparation method are completely the same as in Example 1.

[0080] Example 8 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the surfactant is replaced with 2 g / L Tween 40, while the content of other components and the preparation method are completely the same as in Example 1.

[0081] Example 9 This embodiment provides an electrolytic nickel stripping solution, which differs from Embodiment 1 only in that the electrolytic nickel stripping solution is prepared by the following method: After adding oxidant, corrosion inhibitor, buffer, complexing agent, surfactant, stripping accelerator and co-solvent to the water in the raw material, the temperature is raised to 40°C and stirred at 600 rpm for 2 hours to obtain the electrolytic nickel stripping solution.

[0082] Comparative Example 1 This comparative example provides an electrolytic nickel stripping solution, which differs from Example 1 only in that concentrated sulfuric acid in the oxidant is replaced with 80 g / L hydrogen peroxide (30 vol%). The content of other components and the preparation method are completely the same as in Example 1.

[0083] Comparative Example 2 This comparative example provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the corrosion inhibitor is 2.5 g / L sodium polyphosphate, while the content of other components and the preparation method are completely the same as in Example 1.

[0084] Comparative Example 3 This comparative example provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the buffer boric acid is not added, the content of the ligand lactic acid is increased to 22 g / L, and the content of other components and the preparation method are completely consistent with Example 1.

[0085] Comparative Example 4 This comparative example provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the complexing agent lactic acid is not added, the content of the buffer boric acid is increased to 22 g / L, and the content of other components and the preparation method are completely consistent with Example 1.

[0086] Comparative Example 5 This embodiment provides an electrolytic nickel stripping solution, which differs from Example 1 only in that the oxidant does not contain concentrated sulfuric acid, and the phosphoric acid content is increased to 100 g / L. The content of other components and the preparation method are completely consistent with Example 1.

[0087] Application Example 1 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The method specifically includes the following steps: S1. Provide a silicon substrate for solar cells, and electroplate a 0.5 μm nickel layer on the silicon substrate using a nickel plating solution. Place the nickel-plated silicon substrate in an annealing furnace and anneal it at 300°C for 120 s to form a nickel-silicon alloy.

[0088] S2. Make full contact between the annealed nickel plating layer on the silicon substrate and the nickel stripping solution as the anode, and put the titanium mesh into the nickel stripping solution as the cathode to form an electrolytic nickel stripping system; set the electrolytic current and cut-off voltage, turn on the power supply to perform electrolytic stripping; after the nickel plating layer on the silicon substrate is completely removed, take out the silicon substrate, clean it with deionized water and dry it, and proceed to the next electroplating operation. The nickel stripping solution is the electrolytic nickel stripping solution provided in Example 1, the electrolytic nickel stripping temperature is 30°C, and the anode current density is 2 A / dm³. 2 The cutoff voltage is 4 V.

[0089] Application Example 2 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The method specifically includes the following steps: S1. Provide a silicon substrate for solar cells, and electroplate a 0.5 μm nickel layer on the silicon substrate using a nickel plating solution. Place the nickel-plated silicon substrate in an annealing furnace and anneal it at 300°C for 120 s to form a nickel-silicon alloy.

[0090] S2. Make full contact between the annealed nickel plating layer on the silicon substrate and the nickel stripping solution as the anode, and put the titanium mesh into the nickel stripping solution as the cathode to form an electrolytic nickel stripping system; set the electrolytic current and cut-off voltage, turn on the power supply to perform electrolytic stripping; after the nickel plating layer on the silicon substrate is completely removed, take out the silicon substrate, clean it with deionized water and dry it, and proceed to the next electroplating operation. The nickel stripping solution is the electrolytic nickel stripping solution provided in Example 2, the electrolytic nickel stripping temperature is 20°C, and the anode current density is 3 A / dm³. 2 The cutoff voltage is 6 V.

[0091] Application Example 3 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The method specifically includes the following steps: S1. Provide a silicon substrate for solar cells, and electroplate a 0.5 μm nickel layer on the silicon substrate using a nickel plating solution. Place the nickel-plated silicon substrate in an annealing furnace and anneal it at 300°C for 120 s to form a nickel-silicon alloy.

[0092] S2. Make full contact between the annealed nickel plating layer on the silicon substrate and the nickel stripping solution as the anode, and put the titanium mesh into the nickel stripping solution as the cathode to form an electrolytic nickel stripping system; set the electrolytic current and cut-off voltage, turn on the power supply to perform electrolytic stripping; after the nickel plating layer on the silicon substrate is completely removed, take out the silicon substrate, clean it with deionized water and dry it, and proceed to the next electroplating operation. The nickel stripping solution is the electrolytic nickel stripping solution provided in Example 3, the electrolytic nickel stripping temperature is 60°C, and the anode current density is 1 A / dm³. 2 The cutoff voltage is 3 V.

[0093] Application Example 4 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 4. The other steps are completely consistent with Application Example 1.

[0094] Application Example 5 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 5. The other steps are completely consistent with Application Example 1.

[0095] Application Example 6 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 6. The other steps are completely consistent with Application Example 1.

[0096] Application Example 7 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 7. The other steps are completely consistent with Application Example 1.

[0097] Application Example 8 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 8. The other steps are completely consistent with Application Example 1.

[0098] Application Example 9 This application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Example 9. The other steps are completely consistent with Application Example 1.

[0099] Comparative Application Example 1 This comparative application example provides a method for stripping nickel plating on a silicon substrate for solar cells. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Comparative Example 1. The other steps are completely consistent with Application Example 1.

[0100] Comparative Application Example 2 This comparative application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Comparative Example 2. The other steps are completely consistent with Application Example 1.

[0101] Comparative Application Example 3 This comparative application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Comparative Example 3. The other steps are completely consistent with Application Example 1.

[0102] Comparative Application Example 4 This comparative application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Comparative Example 4. The other steps are completely consistent with Application Example 1.

[0103] Comparative Application Example 5 This comparative application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The only difference from Application Example 1 is that the nickel stripping solution is the electrolytic nickel stripping solution provided in Comparative Example 5. The other steps are completely consistent with Application Example 5.

[0104] Comparative Application Example 6 This comparative application example provides a method for removing nickel plating from a silicon substrate in a solar cell. The method specifically includes the following steps: S1. Provide a silicon substrate for solar cells, and electroplate a 0.5 μm nickel layer on the silicon substrate using a nickel plating solution. Place the nickel-plated silicon substrate in an annealing furnace and anneal it at 300°C for 120 s to form a nickel-silicon alloy.

[0105] S2. Place the annealed silicon substrate in the nickel stripping solution provided in Example 1, immerse it at 40°C for 10 min for chemical nickel stripping, remove the silicon substrate, clean it with deionized water and dry it, and proceed to the next electroplating operation.

[0106] Test case Test samples: Silicon substrates of solar cells after deplating provided in Examples 1-9, and silicon substrates of solar cells after deplating provided in Comparative Examples 1-6; Test method: (1) Nickel stripping speed: Turn on the power to perform electrolytic stripping. After the nickel plating on the silicon substrate is completely removed (the residual amount of nickel plating is 0%), take out the silicon substrate; record the time consumed in the nickel stripping process as the nickel stripping time. t (Unit: s), and according to the formula v= Nickel plating thickness / t， Calculate the nickel stripping rate v (Unit: μm / s), the nickel stripping time for each group was tested in parallel 5 times, and the average value was recorded; (2) Residual condition of nickel plating layer: observed using a microscope; (3) Corrosion at the edge of the silicon substrate: Observed using a microscope.

[0107] The test results are shown in Table 1 below: Table 1

[0108] As shown in Table 1, using the electrolytic nickel stripping solution described in this invention, combined with the electrolytic stripping method, results in rapid nickel stripping speeds, all exceeding 0.005 μm / s. Furthermore, it can completely remove substandard nickel plating from the surface of crystalline silicon solar cells in a single pass, leaving no residue. Moreover, the electrolytic nickel stripping solution does not damage the silver grid lines at the edge of the silicon substrate of the crystalline silicon solar cell. This demonstrates that this invention employs an environmentally friendly electrolytic nickel stripping solution, achieving rapid nickel stripping with minimal damage to the substrate, thereby improving the adhesion of the metal plating layer on crystalline silicon solar cells.

[0109] Among them, since Application Examples 1 to 3 respectively use the nickel stripping solution (optimal composition and ratio) provided in Examples 1 to 3 for electrolytic stripping, the nickel stripping speed can reach more than 0.009 μm / s; and the unqualified nickel plating layer on the surface of the crystalline silicon cell can be completely removed in one go, with no nickel plating layer residue; and the silver grid lines at the edge of the silicon substrate will not be corroded.

[0110] A comparison of Application Examples 1 and 4 shows that without phosphoric acid, the nickel stripping time is longer and the speed is slower, and there is some corrosion at the edge of the silicon substrate, which may be related to the excessive acidity of the oxidant. This indicates that the combination of phosphoric acid and concentrated sulfuric acid has a synergistic effect, which can increase the nickel stripping speed while reducing the probability of corrosion.

[0111] The comparison between Application Examples 1 and 5-6 shows that while using only one corrosion inhibitor can achieve the corrosion inhibition effect and reduce the probability of corrosion, the nickel stripping rate is reduced. This indicates that the combination of thiourea and hexamethylenetetramine has a synergistic effect, which can improve the nickel stripping rate while ensuring the corrosion inhibition effect.

[0112] As can be seen from the comparison between Application Example 1 and Application Example 7, under the premise of equal concentration, not only is the buffering effect of boric acid better than that of acetic acid, but the addition of boric acid can also promote the speed of nickel stripping.

[0113] A comparison of Application Example 1 and Application Example 8 shows that using only one surfactant is not conducive to solution dispersion and improving the rate of nickel stripping.

[0114] A comparison of Examples 1 and 9 shows that without adding the components step-by-step and controlling the order and speed of addition of the corresponding raw materials during the preparation process, it is difficult to mix the components evenly. Even with the speed increased to 600 rpm, it would still take at least 2 hours to obtain a nickel stripping solution with a clarity similar to that of Example 1. Furthermore, the nickel stripping speed of Application Example 9 is only 0.0050 μm / s, indicating that even though Example 9 obtained a nickel stripping solution with an appearance similar to Example 1, it is difficult to further increase the nickel stripping speed due to the poor dispersion stability of its components.

[0115] As can be seen from the comparison between Application Example 1 and Comparative Application Example 1, using a non-acidic oxidant, such as hydrogen peroxide, not only significantly reduces the nickel stripping speed, but also leaves a large amount of nickel layer residue.

[0116] As can be seen from the comparison between Application Example 1 and Comparative Application Example 2, other types of corrosion inhibitors cannot achieve the desired corrosion inhibition effect, and some areas at the edges are corroded.

[0117] As can be seen from the comparison between Application Example 1 and Comparative Application Example 3, if boric acid is not added as a buffer and lactic acid is used as a complexing agent instead, the nickel stripping time will increase significantly and the nickel stripping speed will be slower.

[0118] As can be seen from the comparison between Application Example 1 and Comparative Application Example 4, even without adding the coordinating agent lactic acid, using boric acid as a substitute will still increase the nickel stripping time and decrease the nickel stripping speed.

[0119] As can be seen from the comparison between Application Example 1 and Comparative Application Example 5, without the addition of concentrated sulfuric acid, it is difficult to completely remove the nickel layer by relying solely on the acidity of phosphoric acid, and even if the nickel stripping time is extended, a small amount of nickel will still remain.

[0120] As can be seen from the comparison between Application Example 1 and Comparative Application Example 6, if the nickel stripping solution of this application is directly used in the immersion chemical stripping method instead of electrolytic stripping, a small amount of nickel will still remain even if the stripping time is extended; and since the battery cell is nickel-plated on one side and the other side is silver grid lines obtained by printing silver paste and sintering, when the time is extended, it is found that all the silver grid lines at the edge of the silicon substrate are corroded.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolytic nickel stripping solution, characterized in that, The electrolytic nickel stripping solution comprises the following components by mass parts: Oxidizing agent 50-150 parts, corrosion inhibitor 1-5 parts, buffer 10-20 parts, complexing agent 5-10 parts and water 800-1200 parts; The oxidant is a mixture of concentrated sulfuric acid and phosphoric acid, and the corrosion inhibitor includes nitrogen-containing compounds; the nitrogen-containing compounds are thiourea and hexamethylenetetramine.

2. The electrolytic nickel stripping solution according to claim 1, characterized in that, The electrolytic nickel stripping solution comprises the following components by mass concentration: Oxidizing agent 50~150 g / L, corrosion inhibitor 1~5 g / L, buffer 10~20 g / L, complexing agent 5~10 g / L.

3. The electrolytic nickel stripping solution according to claim 1, characterized in that, The concentrated sulfuric acid is a sulfuric acid solution with a mass fraction of 70% or higher.

4. The electrolytic nickel stripping solution according to claim 1, characterized in that, The concentrated sulfuric acid is a 98% sulfuric acid solution.

5. The electrolytic nickel stripping solution according to claim 1, characterized in that, The mass ratio of concentrated sulfuric acid to phosphoric acid is (3~5):

1.

6. The electrolytic nickel stripping solution according to claim 1, characterized in that, The mass ratio of thiourea to hexamethylenetetramine is (1~2):

1.

7. The electrolytic nickel stripping solution according to claim 1, characterized in that, The buffer includes any one or a combination of at least two of boric acid, sodium borate, acetic acid, sodium acetate, or ammonium acetate.

8. The electrolytic nickel stripping solution according to claim 1, characterized in that, The buffer is any one or a combination of at least two of boric acid, sodium acetate, or ammonium acetate.

9. The electrolytic nickel stripping solution according to claim 1, characterized in that, The ligand includes any one or a combination of at least two of the following: lactic acid, citric acid, malic acid, succinic acid, glycine, tartaric acid, ethylenediaminetetraacetic acid, hydroxyethylidene diphosphonic acid, or aminotrimethylphosphonic acid.

10. The electrolytic nickel stripping solution according to claim 1, characterized in that, The electrolytic nickel stripping solution also includes 0.05 to 5 parts of additives by weight.

11. The electrolytic nickel stripping solution according to claim 1, characterized in that, The electrolytic nickel stripping solution also contains 0.05~5 g / L of additives based on mass concentration.

12. The electrolytic nickel stripping solution according to claim 10, characterized in that, The additives include any one or a combination of at least two of surfactants, plating accelerators, or cosolvents.

13. The electrolytic nickel stripping solution according to claim 12, characterized in that, The surfactants include nonionic surfactants and / or anionic surfactants.

14. The electrolytic nickel stripping solution according to claim 12, characterized in that, The surfactant is a compound surfactant consisting of a nonionic surfactant and anionic surfactant.

15. The electrolytic nickel stripping solution according to claim 13, characterized in that, The nonionic surfactant includes any one or a combination of at least two of Tween, polyethylene glycol, or alkyl polyoxyethylene ether.

16. The electrolytic nickel stripping solution according to claim 15, characterized in that, The Tween includes any one or a combination of at least two of Tween 20, Tween 40, Tween 60, Tween 65, or Tween 80.

17. The electrolytic nickel stripping solution according to claim 15, characterized in that, The polyethylene glycol includes any one or a combination of at least two of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600 or polyethylene glycol 800.

18. The electrolytic nickel stripping solution according to claim 15, characterized in that, The alkyl polyoxyethylene ether includes any one or a combination of at least two of dodecyl polyoxyethylene ether, tetradecyl polyoxyethylene ether, or hexadecyl polyoxyethylene ether.

19. The electrolytic nickel stripping solution according to claim 13, characterized in that, The anionic surfactant includes any one or a combination of at least two of dodecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, sodium dodecyl sulfate, or sodium dodecylbenzenesulfonate.

20. The electrolytic nickel stripping solution according to claim 12, characterized in that, The plating accelerator includes any one or a combination of at least two of potassium thiocyanate, sodium thiocyanate, or ammonium thiocyanate.

21. The electrolytic nickel stripping solution according to claim 12, characterized in that, The cosolvent includes any one or a combination of at least two of 1,2-propanediol, glycerol, monoethanolamine, diethanolamine, or triethanolamine.

22. A method for preparing an electrolytic nickel stripping solution according to any one of claims 1 to 21, characterized in that, The preparation method includes the following steps: An oxidant is added to a portion of the water in the raw material and stirred for the first time; a buffer is added and stirred for the second time; a corrosion inhibitor and a complexing agent are added and stirred for the third time; finally, the remaining water in the remaining raw material is added and stirred for the fourth time to obtain the electrolytic nickel stripping solution.

23. The application of an electrolytic nickel stripping solution according to any one of claims 1 to 21 in the preparation of crystalline silicon solar cells.

24. A method for removing a nickel plating layer from a silicon substrate in a solar cell, characterized in that, The plating removal method specifically includes the following steps: Using a nickel-plated silicon substrate in contact with the electrolytic nickel stripping solution as described in any one of claims 1 to 21 as the anode, and a titanium mesh placed in the electrolytic nickel stripping solution as described in any one of claims 1 to 21 as the cathode, electrolytic nickel stripping is performed to obtain a silicon substrate after the nickel plating layer has been removed.

25. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 24, characterized in that, The nickel plating layer is a nickel-silicon alloy layer formed by annealing a nickel-plated silicon substrate.

26. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 24, characterized in that, The thickness of the nickel plating layer is 0.3~1.0 μm.

27. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 25, characterized in that, The annealing temperature is 250~400℃, and the annealing time is 60~180 s.

28. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 24, characterized in that, The electrolytic nickel stripping temperature is 20~60℃.

29. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 24, characterized in that, The current density at the anode of the electrolytic nickel stripping process is 1~3 A / dm³. 2 .

30. The method for removing the nickel plating layer from a silicon substrate in a solar cell according to claim 24, characterized in that, The cutoff voltage for the electrolytic nickel stripping is 3~6 V.

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