Pre-polishing additive suitable for BC battery and use method of pre-polishing additive

Abstract

The invention discloses a pre-polishing additive suitable for a BC battery and a use method thereof, and relates to the technical field of solar battery production and manufacturing, and the pre-polishing additive comprises the following components in percentage by mass: 0.1 wt%-5 wt% of an accelerant, 0.1 wt%-5 wt% of a complexing agent, 0.1 wt%-10 wt% of a defoaming agent, 0.1 wt%-3 wt% of a penetrating agent, 0.1 wt%-3 wt% of a pH regulator, 0.1 wt%-0.3 wt% of 2-hydrazinoethanol, 0.3 wt%-0.5 wt% of sodium cyclamate, 0.5 wt%-1 wt% of 2, 2 '-biquinoline-4, 4'-diketone, 0.5 wt%-1 wt% of a surfactant, 0.5 wt%-1 wt% of an antioxidant, 0.5 wt%-1 wt% of a corrosion inhibitor, and the balance of water. The cleaning agent is prepared from the following components in percentage by weight: 0.03 to 0.05 percent of disodium 4, 4 '-dicarboxylate, 0.15 to 0.3 percent of hyperbranched sulfonate surfactant and the balance of water. The additive has a remarkable polishing effect under the condition of low weight loss, the flatness of a polished surface is high, the suede uniformity is better, and diamond wire marks are fewer.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell production and manufacturing, and in particular to a pre-polishing additive suitable for BC cells and a method for using the same. Background Art

[0002] A back contact (BC) cell is a type of solar cell in which both the emitter electrode and the base electrode are located on the back of the cell. From the perspective of conversion efficiency, since there is no grid line blocking the front of the BC structure, the light-receiving area is increased and the utilization rate of incident light is improved, it basically has an absolute advantage in conversion efficiency. However, BC cells have high requirements for the passivation level of the front surface because it is necessary to ensure that the carriers have a long lifespan. Therefore, how to improve the passivation level of the front surface of the BC cell is a technical problem that technicians in this field are currently facing.

[0003] One of the effective measures to improve the passivation level of the front surface of BC cells is to optimize the flatness of the front surface of the original silicon wafer of BC cells by pre-polishing, reduce diamond wire marks, and improve the uniformity of the subsequent texturing pyramid. Polishing additives are needed in the pre-polishing process to improve the polishing effect and efficiency. However, the existing pre-polishing additives suitable for BC cells have more or less technical problems such as low flatness and reflectivity of the polished surface, and poor polishing effect under low weight loss.

[0004] In order to solve the above problems, the Chinese invention patent with the authorization announcement number CN114774004B discloses a silicon wafer polishing additive, a polishing liquid, and a preparation method and application thereof. The silicon wafer polishing additive includes a chelating agent, a catechin, and a surfactant. The invention overcomes the defect of the prior art that the polishing effect of silicon wafers in the chain alkali back polishing process is not ideal. By adding the additive in the invention during the chain alkali polishing process, the reaction rate of the chain alkali polishing process can be effectively improved, and the back polishing effect of the chain alkali polishing process can be improved. The back of the silicon wafer prepared after polishing is smoother, the tower base size is larger, and the reflectivity is higher, which is beneficial to the improvement of the efficiency of crystalline silicon cells. However, the flatness of the polishing surface of the additive used for BC cell front polishing needs to be further improved; the polishing effect under low weight loss needs to be further improved. Summary of the invention

[0005] The main purpose of the present invention is to provide a pre-polishing additive suitable for BC batteries, which has significant polishing effect under low weight loss, high polishing surface flatness, better velvet uniformity, and fewer diamond wire marks, and a method of using the same.

[0006] To achieve the above purpose, the present invention provides a pre-polishing additive suitable for BC batteries, including the following components calculated by mass percentage: accelerator 0.1wt%-5wt%, complexing agent 0.1wt%-5wt%, defoaming agent 0.1wt%-10wt%, penetrant 0.1wt%-3wt%, pH adjuster 0.1wt%-3wt%, 2-hydrazinoethanol 0.1wt%-0.3wt%, sodium cyclohexylaminosulfonate 0.3wt%-0.5wt%, 2,2'-biquinoline-4,4'-dicarboxylate disodium 0.03wt%-0.05wt%, hyperbranched sulfonate surfactant 0.15wt%-0.3wt%, and the balance is water.

[0007] Preferably, the accelerator is one or a combination of two or more of nitroimidazole, nitrophenol, nitrobenzenesulfonic acid, and nitrobenzoic acid.

[0008] Preferably, the complexing agent is one or a combination of two or more of diethanolamine, tetrasodium iminodisuccinate, disodium ethylenediaminetetraacetate, citric acid, and sodium citrate.

[0009] Preferably, the defoaming agent is one or a combination of two or more of cellulose, starch and maltose.

[0010] Preferably, the penetrant is one of acetic acid, sodium acetate, sodium chloride, potassium chloride, or a combination of two or more thereof.

[0011] Preferably, the pH adjuster is one or a combination of two or more of malic acid, tartaric acid, acetic acid, sodium acetate, potassium hydroxide and sodium hydroxide.

[0012] Furthermore, there is no special requirement for the source of the hyperbranched sulfonate surfactant. In one embodiment of the present invention, the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP-1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0013] Another object of the present invention is to provide a method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0014] Preferably, the volume ratio of the pre-polishing additive suitable for BC batteries in step S2 to the total volume of the polishing liquid is 0.1-2%.

[0015] Preferably, the alkali solution in step S2 is sodium hydroxide or potassium hydroxide solution; the mass percentage concentration of the alkali solution is 2-4wt%.

[0016] Preferably, the polishing treatment in step S3 is performed at a temperature of 60 to 80° C. and for a time of 50 to 300 seconds.

[0017] Preferably, in the polishing process in step S3, the silicon wafer is placed vertically in a basket in a tank containing the polishing liquid.

[0018] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The method for using the pre-polishing additive for BC batteries disclosed in the present invention is simple to operate, has low labor intensity, does not require special equipment and instruments, requires little capital investment, has low energy consumption, has little impact on the environment, and is suitable for continuous large-scale production.

[0019] (2) The pre-polishing additive for BC cells disclosed in the present invention comprises the following components calculated by mass percentage: accelerator 0.1wt%-5wt%, complexing agent 0.1wt%-5wt%, defoaming agent 0.1wt%-10wt%, penetrant 0.1wt%-3wt%, pH regulator 0.1wt%-3wt%, 2-hydrazineethanol 0.1wt%-0.3wt%, sodium cyclohexylaminosulfonate 0.3wt%-0.5wt%, disodium 2,2'-biquinoline-4,4'-dicarboxylate 0.03wt%-0.05wt%, hyperbranched sulfonate surfactant 0.15wt%-0.3wt%, and the balance is water; through the mutual coordination and joint action of the components, the polishing effect of the prepared additive under low weight loss is significant. After alkaline polishing, the polishing surface has higher flatness, better velvet uniformity, and fewer diamond wire marks, thereby effectively removing the damaged layer and dead knot of the original silicon wafer, improving the passivation contact level, and improving the conversion efficiency of the solar cell.

[0020] (3) The pre-polishing additive for BC batteries disclosed in the present invention, the free radicals generated by the decomposition of the accelerator in an alkaline environment, accelerate the reaction of the inorganic base with silicon, enhance the polishing ability of the polishing liquid, can better remove the damaged layer and dead knots, reduce diamond wire marks, improve the overall flatness and the uniformity of the velvet surface, and achieve the purpose of improving the passivation level of the front surface of the battery; the complexing agent can complex the polishing liquid and the metal ions remaining in the silicon wafer cutting, reduce the composite center formed by metal doping; the penetrant increases the contact between the polishing liquid and the silicon wafer, making the reaction faster and more uniform; the degassing agent can more quickly remove the bubbles generated on the surface of the silicon wafer, improving Appearance, improve reflectivity; pH ​​adjuster can adjust the pH value of additives to make them more stable and safe; 2-hydrazineethanol, sodium cyclohexylaminosulfonate, disodium 2,2'-biquinoline-4,4'-dicarboxylate and hyperbranched sulfonate surfactant are added to the composition of the pre-polishing additive, and cooperate with other components in the composition to further improve the polishing effect under low weight loss, so that after alkaline polishing, the polishing surface has higher flatness, better velvet uniformity, and fewer diamond wire marks, thereby effectively removing the damaged layer and dead knot of the original silicon wafer, improving the passivation contact level, and improving the conversion efficiency of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a SEM picture of the silicon wafer surface after pre-polishing using the pre-polishing additive suitable for BC batteries according to Example 1 of the present invention.

[0022] Figure 2 This is a SEM picture of the silicon wafer surface after pre-polishing using the pre-polishing additive suitable for BC batteries according to Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art may think of other obvious variations.

[0024] Example 1: A pre-polishing additive suitable for BC batteries, comprising the following components calculated by mass percentage: 0.1wt% accelerator, 0.1wt% complexing agent, 0.1wt% defoaming agent, 0.1wt% penetrant, 0.1wt% pH adjuster, 0.1wt% 2-hydrazinoethanol, 0.3wt% sodium cyclohexylaminosulfonate, 0.03wt% disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.15wt% hyperbranched sulfonate surfactant, and the balance is water.

[0025] The promoter is nitroimidazole; the complexing agent is diethanolamine; the defoaming agent is cellulose; the penetrant is acetic acid; the pH regulator is malic acid; the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP-1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0026] A method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0027] The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 0.1% of the total volume of the polishing liquid; the alkali solution in step S2 is sodium hydroxide solution; the mass percentage concentration of the alkali solution is 2wt%; the temperature of the polishing treatment in step S3 is 60°C and the time is 50s; the placement method of the silicon wafer during the polishing treatment in step S3 is to place it vertically in a basket in a trough containing the polishing liquid.

[0028] Example 2: A pre-polishing additive suitable for BC batteries, comprising the following components calculated by mass percentage: 1.5wt% accelerator, 1.5wt% complexing agent, 2wt% defoaming agent, 1wt% penetrant, 1wt% pH adjuster, 0.15wt% 2-hydrazinoethanol, 0.35wt% sodium cyclohexylaminosulfonate, 0.035wt% disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.18wt% hyperbranched sulfonate surfactant, and the balance is water.

[0029] The promoter is nitrophenol; the complexing agent is tetrasodium iminodisuccinate; the defoaming agent is starch; the penetrant is sodium acetate; the pH adjuster is tartaric acid; the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP-1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0030] A method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0031] The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 0.5% of the total volume of the polishing liquid; the alkali solution in step S2 is a potassium hydroxide solution; the mass percentage concentration of the alkali solution is 2.5wt%; the temperature of the polishing treatment in step S3 is 65°C and the time is 130s; the placement of the silicon wafer during the polishing treatment in step S3 is to place it vertically in a basket in a trough containing the polishing liquid.

[0032] Example 3: A pre-polishing additive suitable for BC batteries, comprising the following components calculated by mass percentage: 3wt% accelerator, 3wt% complexing agent, 4wt% defoaming agent, 1.5wt% penetrant, 1.5wt% pH adjuster, 0.2wt% 2-hydrazinoethanol, 0.4wt% sodium cyclohexylaminosulfonate, 0.04wt% disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.23wt% hyperbranched sulfonate surfactant, and the balance is water.

[0033] The promoter is nitrobenzene sulfonic acid; the complexing agent is disodium ethylenediaminetetraacetic acid; the defoaming agent is maltose; the permeabilizing agent is sodium chloride; the pH regulator is acetic acid; the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP-1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0034] A method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0035] The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 1.2% of the total volume of the polishing liquid; the alkali solution in step S2 is a potassium hydroxide solution; the mass percentage concentration of the alkali solution is 3wt%; the temperature of the polishing treatment in step S3 is 70°C and the time is 200s; the placement of the silicon wafer during the polishing treatment in step S3 is to place it vertically in a basket in a trough containing the polishing liquid.

[0036] Example 4: A pre-polishing additive suitable for BC batteries, comprising the following components calculated by mass percentage: 4wt% accelerator, 4wt% complexing agent, 9wt% defoaming agent, 2.5wt% penetrant, 2.5wt% pH adjuster, 0.25wt% 2-hydrazinoethanol, 0.45wt% sodium cyclohexylaminosulfonate, 0.045wt% disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.28wt% hyperbranched sulfonate surfactant, and the balance is water.

[0037] The accelerator is a mixture of nitroimidazole, nitrophenol, nitrobenzenesulfonic acid and nitrobenzoic acid in a mass ratio of 1:2:3:2; the complexing agent is a mixture of diethanolamine, tetrasodium iminodisuccinate, disodium ethylenediaminetetraacetic acid, citric acid and sodium citrate in a mass ratio of 1:1:1:2:1; the defoaming agent is a mixture of cellulose, starch and maltose in a mass ratio of 1:1:1; the penetrant is a mixture of acetic acid, sodium acetate, sodium chloride and potassium chloride in a mass ratio of 1:3:5:3; the pH adjuster is a mixture of malic acid, tartaric acid, acetic acid, sodium acetate, potassium hydroxide and sodium hydroxide in a mass ratio of 1:1:1:1:2:1; the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP~1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0038] A method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0039] The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 1.8% of the total volume of the polishing liquid; the alkali solution in step S2 is sodium hydroxide solution; the mass percentage concentration of the alkali solution is 3.5wt%; the temperature of the polishing treatment in step S3 is 75°C and the time is 260s; the placement method of the silicon wafer during the polishing treatment in step S3 is to place it vertically in a basket in a trough containing the polishing liquid.

[0040] Example 5: A pre-polishing additive suitable for BC batteries, comprising the following components calculated by mass percentage: 5wt% accelerator, 5wt% complexing agent, 10wt% defoaming agent, 3wt% penetrant, 3wt% pH adjuster, 0.3wt% 2-hydrazinoethanol, 0.5wt% sodium cyclohexylaminosulfonate, 0.05wt% disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.3wt% hyperbranched sulfonate surfactant, and the balance is water.

[0041] The promoter is nitrobenzoic acid; the complexing agent is sodium citrate; the defoaming agent is maltose; the osmotic agent is potassium chloride; the pH regulator is sodium acetate; the hyperbranched sulfonate surfactant is prepared according to the preparation method of the hyperbranched sulfonate surfactant SHBP-1 in Example 1 of the Chinese invention patent with authorization announcement number CN102690641B.

[0042] A method for using a pre-polishing additive for BC batteries, comprising the following steps: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

[0043] The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 2% of the total volume of the polishing liquid; the alkali solution in step S2 is a potassium hydroxide solution; the mass percentage concentration of the alkali solution is 4wt%; the temperature of the polishing treatment in step S3 is 80°C and the time is 300s; the placement method of the silicon wafer during the polishing treatment in step S3 is to place it vertically in a basket in a trough containing the polishing liquid.

[0044] Comparative Example 1 The present invention provides a pre-polishing additive suitable for BC batteries and a method of using the same, which is similar to Example 1, except that 2-hydrazinoethanol and sodium cyclohexylaminosulfonate are not added.

[0045] Comparative Example 2 The present invention provides a pre-polishing additive suitable for BC batteries and a method of using the same, which is similar to Example 1, except that no disodium 2,2'-biquinoline-4,4'-dicarboxylate and hyperbranched sulfonate surfactant are added.

[0046] The pre-polishing additives suitable for BC batteries involved in the above Examples 1-5 and Comparative Examples 1-2 were subjected to relevant performance tests. The test results are shown in Table 1. The testing method is as follows: a reflectivity testing system is used to measure the integrated reflectivity in the wavelength range of 300-1100nm; a weight loss balance is used to weigh the weight loss of the silicon wafer before and after polishing; the flatness (Sq value) is obtained by Zeta microscope testing, and the smaller the value, the better the flatness.

[0047] Table 1

[0048] As can be seen from Table 1, the pre-polishing additive suitable for BC batteries disclosed in the embodiments of the present invention and the method of using the same have a more excellent pre-polishing effect at low weight loss compared with the comparative products, and can more thoroughly remove the damaged layer and dead knots of the original silicon wafer, and the flatness is also better; the addition of 2-hydrazinoethanol, sodium cyclohexylaminosulfonate, disodium 2,2'-biquinoline-4,4'-dicarboxylate and hyperbranched sulfonate surfactants are beneficial to improving the above properties.

[0049] At the same time, taking Example 1 and Comparative Example 1 as examples, the SEM images of the silicon wafer surface after pre-polishing using the additives and methods of use in each example are shown respectively. Figure 1 and Figure 2 ,Compare Figure 1 and Figure 2 It can be seen that Figure 1 The suede uniformity is significantly better than Figure 2 It can be seen that the silicon wafer pre-polished with the additive prepared in the embodiment of this case has better velvet uniformity and fewer diamond line marks.

[0050] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A pre-polishing additive suitable for BC batteries, characterized in that: The invention comprises the following components calculated by mass percentage: 0.1wt%-5wt% of an accelerator, 0.1wt%-5wt% of a complexing agent, 0.1wt%-10wt% of a defoaming agent, 0.1wt%-3wt% of a penetrant, 0.1wt%-3wt% of a pH regulator, 0.1wt%-0.3wt% of 2-hydrazinoethanol, 0.3wt%-0.5wt% of sodium cyclohexylaminosulfonate, 0.03wt%-0.05wt% of disodium 2,2'-biquinoline-4,4'-dicarboxylate, 0.15wt%-0.3wt% of a hyperbranched sulfonate surfactant, and the balance is water.

2. The pre-polishing additive for BC batteries according to claim 1, characterized in that: The accelerator is one of nitroimidazole, nitrophenol, nitrobenzenesulfonic acid and nitrobenzoic acid or a combination of two or more thereof.

3. The pre-polishing additive for BC batteries according to claim 1, characterized in that: The complexing agent is one of diethanolamine, tetrasodium iminodisuccinate, disodium ethylenediaminetetraacetate, citric acid, sodium citrate, or a combination of two or more thereof.

4. The pre-polishing additive for BC batteries according to claim 1, characterized in that: The defoaming agent is one of cellulose, starch and maltose or a combination of two or more thereof.

5. The pre-polishing additive for BC batteries according to claim 1, characterized in that: The penetrant is one of acetic acid, sodium acetate, sodium chloride, and potassium chloride, or a combination of two or more thereof.

6. The pre-polishing additive for BC batteries according to claim 1, characterized in that: The pH adjuster is one of malic acid, tartaric acid, acetic acid, sodium acetate, potassium hydroxide, and sodium hydroxide, or a combination of two or more thereof.

7. A method for using the pre-polishing additive for BC batteries according to any one of claims 1 to 6, characterized in that: The steps include: Step S1, after uniformly mixing the components of the pre-polishing additive suitable for BC batteries, the mixture is allowed to stand until the foam completely disappears, thereby obtaining the pre-polishing additive suitable for BC batteries; Step S2, adding the pre-polishing additive suitable for BC batteries prepared in step S1 into the alkaline solution and stirring well to obtain a polishing solution; Step S3, polishing the silicon wafer using the polishing liquid prepared in step S2, followed by sequentially ionized water cleaning, post-cleaning, deionized water cleaning, acid cleaning, deionized water cleaning, and finally drying.

8. The method for using the pre-polishing additive for BC batteries according to claim 7, characterized in that: The volume usage of the pre-polishing additive suitable for BC batteries in step S2 accounts for 0.1-2% of the total volume of the polishing liquid.

9. The method for using the pre-polishing additive for BC batteries according to claim 7, characterized in that: The alkali solution in step S2 is sodium hydroxide or potassium hydroxide solution; the mass percentage concentration of the alkali solution is 2-4wt%.

10. The method for using the pre-polishing additive for BC batteries according to claim 7, characterized in that: The polishing temperature in step S3 is 60-80° C. and the time is 50s-300s. During the polishing process in step S3, the silicon wafer is placed vertically in a basket in a tank containing the polishing liquid.

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