Method for removing insulating glue on back surface of IBC battery piece

Abstract

The invention discloses a method for removing insulating glue on the back surface of an IBC battery piece, and the method comprises the following steps: (1) immersing the IBC battery piece with the insulating glue on the back surface into a nitric acid solution with the mass concentration of 30-50%, and carrying out the reaction at the temperature of 65-90 DEG C, so as to obtain an intermediate product; (2) carrying out ultrasonic treatment on the intermediate product prepared in the step (1) under the ultrasonic power of 500-1000W to prepare an ultrasonic battery piece; and (3) washing and drying the ultrasonic battery piece prepared in the step (2) to obtain a silicon wafer. The removal method has the advantages that the treatment process is simple, the treatment condition is mild, new impurities are not introduced, and the purity of the treated silicon wafer is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solar photovoltaic industry, and particularly relates to a method for removing back surface insulation glue of an interdigitated back contact (IBC) cell. BACKGROUND

[0002] The development of the solar photovoltaic industry is an important guarantee for promoting the transformation of the energy structure. With the increasingly serious environmental problems, China has accelerated the development of the solar photovoltaic industry by optimizing the industrial structure system. While constantly introducing protection policies, the industry scale is continuously expanding, the related technology system is increasingly perfect, and the industry supporting is more perfect.

[0003] A solar photovoltaic module mainly consists of cell pieces, back sheets, glass, ethylene-vinyl acetate copolymer (EVA), welding strips, busbars, frames, and silicone, etc. With the continuous innovation of industrial technology, the scale and types of waste photovoltaic modules are continuously expanding. Reasonable recycling of waste photovoltaic modules can reduce their adverse effects on the environment and promote the recycling of raw materials. Among them, the recycling of solar photovoltaic cell pieces needs to be processed according to the structural characteristics of the cell pieces, using different technologies to recover silver, aluminum and other metals, remove the coating, and finally purify the silicon pieces.

[0004] IBC cells can be combined with tunnel oxide passivated contact (TOPCon) cells and heterojunction with intrinsic thin-film (HJT) cells, and have good compatibility. The unique design of IBC cells makes the electrodes of the emitter region and the base region both located on the back surface, thereby realizing the effect of completely no grid line shielding on the front surface. This feature eliminates the light energy loss caused by traditional grid line shielding, ensures the maximization of the use of incident photons, and makes IBC cells have higher conversion efficiency. At the same time, this feature makes it particularly suitable for application in the field of building integrated photovoltaics (BIPV) and the relatively low price-sensitive household field. With further breakthroughs in related technologies, IBC cells are expected to become the mainstream of crystalline silicon cells. However, due to the uniqueness of the structure of IBC cells, special processes are needed for their recycling after being discarded or retired.

[0005] Patent document CN111822482A discloses a recycling method of photovoltaic cell pieces, which cleans the cell piece powder through a cleaning device to obtain pure silicon wafers; patent document CN208912062U discloses a recycling device for waste photovoltaic cell pieces, which is used for leaching silver in waste photovoltaic cell powder. Therefore, the recycling of the cell pieces in the prior art is mainly through the method of grinding the cell pieces into powder, but the impurity elements in the cell piece powder are complex, and the silicon cannot be purified, and only metals such as silver and aluminum can be extracted. Further, the prior art mainly aims at the purification and recycling of the cell pieces in the Aluminium Back Surface Field (BSF) cell and the Passivated Emitter and Rear Cell (PERC), and does not involve the recycling of IBC cell pieces with different cell structures, and even less involves the removal of the insulating glue on the back of the IBC cell pieces. In summary, there is no effective method to remove the insulating glue on the back of the IBC cell pieces. SUMMARY

[0006] To solve the problems existing in the prior art, the present application provides a method for removing the insulating glue on the back of an IBC cell piece. The present application uses the strong oxidizing property of nitric acid to oxidize the curing agent in the insulating glue, destroys the structure of the insulating glue, and reduces the adhesion of the insulating glue to the back of the cell piece, thereby removing the insulating glue remaining on the back of the IBC, and achieving the effect of purifying the silicon wafer. The present application has a simple treatment process, mild treatment conditions, does not introduce new impurities, and the silicon wafer after treatment has high purity.

[0007] Specifically, the present application provides a method for removing the insulating glue on the back of an IBC cell piece, which comprises the following steps:

[0008] (1) immersing the IBC cell piece with only insulating glue on the back into a nitric acid solution with a mass concentration of 30% to 50%, and reacting at a temperature of 65 to 90°C to obtain an intermediate product;

[0009] (2) placing the intermediate product obtained in step (1) under ultrasonic waves at an ultrasonic power of 500 to 1000 W to obtain an ultrasonic cell piece;

[0010] (3) washing and drying the ultrasonic cell piece obtained in step (2) to obtain a silicon wafer.

[0011] In one or more embodiments, in step (1), the reaction time is 15 to 60 min.

[0012] In one or more embodiments, in step (1), the reaction temperature is 80 to 90°C.

[0013] In one or more embodiments, in step (2), the ultrasonic time is 2-10 minutes.

[0014] In one or more embodiments, in step (3), the ultrasonic cell sheet prepared in step (2) is washed with water.

[0015] In one or more embodiments, in step (3), the ultrasonic cell sheet prepared in step (2) is washed with water.

[0016] In one or more embodiments, the method further comprises, before step (1), removing the grid lines and film layer on the surface of the IBC cell sheet to obtain an IBC cell sheet with only insulating glue on the back surface.

[0017] In one or more embodiments, the method further comprises filtering the remaining solution after the reaction of step (1) and step (2) to obtain a filtrate and insulating glue particles.

[0018] In one or more embodiments, the method further comprises washing, drying and recovering the insulating glue particles.

[0019] In one or more embodiments, the method further comprises recovering the filtrate.

[0020] The present application provides a device for removing insulating glue on the back surface of an IBC cell, which comprises a reaction system, an ultrasonic system, a washing system and a drying system; wherein the reaction system is used for reacting an IBC cell sheet with only insulating glue on the back surface with a nitric acid solution to prepare an intermediate product; the ultrasonic system is used for ultrasonic treatment of the intermediate product to obtain an ultrasonic cell sheet; the washing system and the drying system are used for washing and drying the ultrasonic cell sheet to obtain a silicon sheet. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The process flow chart of the method for removing insulating glue on the back surface of an IBC cell sheet according to some embodiments of the present application.

[0022] Figure 2 The photo of an IBC cell sheet with only insulating glue on the back surface according to Example 1 of the present application.

[0023] Figure 3 The photo of the insulating glue on the back surface of an IBC cell sheet after removal according to Example 1 of the present application. DETAILED DESCRIPTION

[0024] To enable persons skilled in the art to understand the features and effects of the present application, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific words used in the text are of the usual meaning understood by those skilled in the art of the present application, and in case of conflict, the definition in the specification shall prevail.

[0025] Theories or mechanisms described and disclosed herein, whether or not correct, should not be construed as limiting the scope of the present application, i.e., the present application can be practiced without regard to any particular theory or mechanism.

[0026] In the present application, the terms "comprising", "including", "containing", and the like, are inclusive, in the sense of "having at least", and should be construed as specifying the presence of stated features, integers, steps, or components, but not precluding the presence or addition of one or more other features, integers, steps, components, or groups thereof.

[0027] In the present application, all features, numerical values, amounts, contents and concentrations defined in the form of numerical value range or percentage range are for the sake of brevity and convenience. Therefore, the description of numerical value range or percentage range should be considered as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0028] In the present application, unless otherwise specified, the percentage refers to mass percentage, and the ratio refers to mass ratio.

[0029] In the present application, when describing embodiments or examples, it should be understood that they are not intended to limit the present application to these embodiments or examples. On the contrary, all alternatives, modifications and equivalents of the described methods and materials that are within the scope of the present application are included in the scope of the claims.

[0030] In the present application, for the sake of brevity, all possible combinations of the technical features in each embodiment or example are not described. Therefore, as long as the combinations of the technical features do not contradict each other, the technical features in each embodiment or example can be combined in any manner, and all possible combinations should be considered as being within the scope of the present application.

[0031] The present application provides a method for removing the back surface insulation glue of IBC battery piece, which has the following steps:

[0032] (1) immerging the IBC battery piece with only insulation glue on the back surface into a nitric acid solution with a mass concentration of 30% to 50% and reacting at a temperature of 65 to 90°C to obtain an intermediate product;

[0033] (2) placing the intermediate product obtained in step (1) under ultrasonic wave with an ultrasonic power of 500 to 1000 W to obtain an ultrasonic battery piece;

[0034] (3) washing and drying the ultrasonic battery piece obtained in step (2) to obtain a silicon piece.

[0035] Due to the particularity of the IBC battery structure, special processes are required for recycling after abandonment or retirement. The removal method of the back surface insulating glue of the IBC battery piece in the application can remove the back surface insulating glue of the IBC battery piece and obtain purified silicon pieces. In the application, the recycled silicon pieces can be used to produce new silicon pieces; the recycled silicon pieces can be modified by doping elements such as phosphorus and germanium and applied to thermoelectric components; the theoretical capacity of the silicon anode is 4200 mAh / g, which is considered to be the best energy storage material to replace graphite (372 mAh / g), and the recycled silicon pieces can be nano-sized by ball milling and doped with materials such as graphite to prepare battery electrodes.

[0036] In step (1), the reaction time can be 15-60 min, for example, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min.

[0037] In step (1), the reaction temperature can be 65-90℃, preferably 80-90℃, for example, 80℃, 82℃, 84℃, 86℃, 88℃, or 90℃. In the application, if the reaction temperature is too low, the insulating glue on the back surface of the IBC battery piece cannot be completely removed, and if the reaction temperature is too high, the insulating glue on the back surface of the IBC battery piece cannot be completely removed, and the nitric acid solution will boil, causing serious volatilization of the nitric acid. Controlling the reaction temperature within the above range, the removal treatment conditions are mild, the insulating glue on the back surface of the IBC battery piece is completely removed, the solvent is not easy to volatilize, and the environmental pollution is small.

[0038] In step (1), the mass concentration of the nitric acid solution can be 30%-50%, for example, 30%, 35%, 40%, 45%, or 50%. In the application, nitric acid is selected to remove the insulating glue on the back surface of the IBC battery piece, without introducing new impurities, and the purity of the treated silicon piece is high. In the application, if the mass concentration of the nitric acid solution is too low, the insulating glue on the back surface of the IBC battery piece cannot be completely removed, and if the mass concentration of the nitric acid solution is too high, the insulating glue on the back surface of the IBC battery piece cannot be completely removed, and the insulating glue is soft and sticky, adhering to the surface of the battery piece. Controlling the mass concentration of the nitric acid solution within the above range is conducive to the complete removal of the insulating glue on the back surface of the IBC battery piece and the recycling of the insulating glue particles.

[0039] In step (2), the ultrasonic power can be 500-1000 W, for example, 500 W, 600 W, 700 W, 800 W, 900 W, or 1000 W. Controlling the ultrasonic power within the above range can achieve good removal effect of the insulating glue on the back surface of the IBC battery piece.

[0040] In step (2), the ultrasonic time can be 2-10 min, for example, 2 min, 4 min, 6 min, 8 min, or 10 min.

[0041] In step (3), the ultrasonic cell prepared in step (2) can be washed with water, preferably deionized water.

[0042] The removal method of the present application further comprises removing the grid lines and film layers on the surface of the IBC cell to obtain an IBC cell with only insulating glue on the back surface. In the present application, the functional layers of the IBC cell include, in sequence, a silicon nitride film layer on the front surface, a passivation layer on the front surface, an IBC cell, an aluminum grid line on the back surface, a silver grid line on the back surface, insulating glue on the back surface, a silicon nitride film layer on the back surface, and a passivation layer on the back surface. In some embodiments, the aluminum grid line on the back surface can be removed by alkali, and the silver grid line on the back surface can be cleaned by acid. After the aluminum grid line on the back surface and the silver grid line on the back surface are removed, the silicon nitride film layers on the front and back surfaces can be cleaned by acid, and the passivation layers on the front and back surfaces can be cleaned by alkali, so as to remove the grid lines and film layers on the surface of the IBC cell and obtain an IBC cell with only insulating glue on the back surface.

[0043] The removal method of the present application further comprises filtering the remaining solution after the reaction in step (1) and step (2) to obtain a filtrate and insulating glue particles.

[0044] The removal method of the present application further comprises washing, drying, and recycling the insulating glue particles.

[0045] The removal method of the present application further comprises recycling the filtrate.

[0046] The recycling of the insulating glue particles and the filtrate is beneficial for the reuse of resources.

[0047] Figure 1 The process flow chart of the removal method of the insulating glue on the back surface of the IBC cell in some embodiments of the present application is shown in FIG. 1. The method comprises the following steps:

[0048] (1) removing the grid lines and film layers on the surface of the IBC cell to obtain an IBC cell with only insulating glue on the back surface;

[0049] (2) immersing the IBC cell with only insulating glue on the back surface in a nitric acid solution with a mass concentration of 30% to 50% and reacting at a temperature of 65 to 90°C to obtain an intermediate product;

[0050] (3) placing the intermediate product prepared in step (2) under ultrasonic waves with an ultrasonic power of 500 to 1000 W to obtain an ultrasonic cell;

[0051] (4) washing and drying the ultrasonic cell prepared in step (3) to obtain a pure silicon wafer;

[0052] (5) filtering the remaining solution after the reaction in step (2) and step (3) to obtain a filtrate and insulating glue particles, and recycling the filtrate;

[0053] (6) The insulating adhesive particles obtained in step (5) are washed with deionized water, and then dried and recovered.

[0054] The application provides a device for removing insulating adhesive on the back of an IBC battery, which comprises a reaction system, an ultrasonic system, a washing system and a drying system; the reaction system is used for preparing an intermediate product by reacting an IBC battery piece with insulating adhesive on the back and nitric acid solution; the ultrasonic system is used for ultrasonic treatment of the intermediate product to obtain an ultrasonic battery piece; and the washing system and the drying system are used for washing and drying the ultrasonic battery piece.

[0055] A silicon wafer is obtained.

[0056] Compared with the prior art, the application has the following beneficial effects:

[0057] 1) The application can remove the insulating adhesive on the back of an IBC battery piece;

[0058] 2) The removal method of the application does not introduce new impurities, and the purity of the silicon wafer after treatment is high;

[0059] 3) The battery piece treated by the removal method of the application can be a complete whole piece or a broken piece;

[0060] 4) The removal method of the application has a simple treatment process and mild treatment conditions.

[0061] The application will be described below in the form of specific examples. It should be understood that these examples are merely illustrative and are not intended to limit the scope of the application. The methods, reagents and materials used in the examples are conventional in the art unless otherwise specified. The raw material compounds in the examples can be purchased through commercial channels.

[0062] Example 1

[0063] This example removes the insulating adhesive on the back of an IBC battery piece by the following steps:

[0064] Step 1: Remove the grid lines and film layer on the surface of the IBC battery piece to provide an IBC battery piece with only insulating adhesive remaining on the back, as shown in Figure 2 .

[0065] Step 2: Put the IBC battery piece with only insulating adhesive on the back obtained in step 1 into nitric acid to react, and ensure full contact between the nitric acid and the back of the battery piece to ensure sufficient reaction, to obtain an intermediate product, wherein the concentration of the nitric acid is 40%, the reaction temperature is 80°C, and the reaction time is 20 min;

[0066] Step 3: Take out the intermediate product prepared in step 2 and put it into an ultrasonic device for ultrasonic treatment to obtain an ultrasonic battery piece, wherein the ultrasonic power is 900 W, and the ultrasonic treatment time is 5 min.

[0067] Step 4: The ultrasonic cell piece prepared in step 3 is taken out, and deionized water is used to clean the ultrasonic cell piece to remove residual acid solution, and then dried to obtain a pure silicon piece, as shown in Figure 3

[0068] Step 5: The remaining solution after the reaction in step 2 and step 3 is filtered to obtain a filtrate and insulating glue particles, and the filtrate is recovered.

[0069] Step 6: The insulating glue particles prepared in step 5 are cleaned with deionized water, and then dried and recovered.

[0070] Example 2

[0071] The other steps of this example are the same as those of example 1, except that the reaction temperature in step 2 is replaced by 65°C instead of 80°C, and the reaction time is replaced by 40 min instead of 20 min.

[0072] Example 3

[0073] The other steps of this example are the same as those of example 1, except that the reaction temperature in step 2 is replaced by 90°C instead of 80°C, and the reaction time is replaced by 10 min instead of 20 min.

[0074] Example 4

[0075] The other steps of this example are the same as those of example 1, except that the concentration of nitric acid in step 2 is replaced by 30% instead of 40%, the ultrasonic power in step 3 is replaced by 1000W instead of 900W, and the ultrasonic time is replaced by 8 min instead of 5 min.

[0076] Example 5

[0077] The other steps of this example are the same as those of example 1, except that the concentration of nitric acid in step 2 is replaced by 50% instead of 40%, and the ultrasonic power in step 3 is replaced by 700W instead of 900W.

[0078] Example 6

[0079] The other steps of this example are the same as those of example 1, except that the reaction time in step 2 is replaced by 15 min instead of 20 min, and the ultrasonic time in step 3 is replaced by 10 min instead of 5 min.

[0080] Example 7

[0081] The other steps of this example are the same as those of example 1, except that the reaction time in step 2 is 60 min, and the ultrasonic power in step 3 is 500W.

[0082] Comparative Example 1

[0083] ​The other steps of this comparative example are the same as Example 1, the only difference is that the ultrasonic power in step 3 is replaced from 900 W to 400 W, and the ultrasonic time is replaced from 5 min to 12 min.

[0084] Comparative Example 2

[0085] The other steps of this comparative example are the same as Example 1, the only difference is that the nitric acid concentration in step 2 is replaced from 40% to 25%, the reaction temperature is replaced from 80°C to 60°C, and the reaction time is replaced from 20 min to 90 min.

[0086] Comparative Example 3

[0087] The other steps of this comparative example are the same as Example 1, the only difference is that the reaction temperature in step 2 is replaced from 80°C to 95°C.

[0088] Comparative Example 4

[0089] The other steps of this comparative example are the same as Example 1, the only difference is that the reaction temperature in step 2 is replaced from 80°C to 60°C.

[0090] Comparative Example 5

[0091] The other steps of this comparative example are the same as Example 1, the only difference is that the nitric acid concentration in step 2 is replaced from 40% to 25%.

[0092] Comparative Example 6

[0093] The other steps of this comparative example are the same as Example 1, the only difference is that the nitric acid concentration in step 2 is replaced from 40% to 55%.

[0094] Table 1: Removal effect of IBC cell backside insulation glue under the removal conditions of Examples 1-7 and Comparative Examples 1-3 and the purity of silicon prepared

[0095]

[0096]

Claims

1. A method for removing back surface insulation paste of an IBC cell, characterized in that, The removal method includes the following steps: (1) Immerse the IBC battery cell with only insulating adhesive on the back into a nitric acid solution with a mass concentration of 30% to 50% and react it at a temperature of 65 to 90°C to obtain an intermediate product; (2) The intermediate product obtained in step (1) is subjected to ultrasonication at an ultrasonic power of 500-1000W to obtain an ultrasonic battery cell. (3) The ultrasonic cell obtained in step (2) is washed and dried to obtain a silicon wafer.

2. The removal method of claim 1, wherein, In step (1), the reaction time is 15 to 60 minutes.

3. The removal method of claim 1, wherein, In step (1), the reaction temperature is 80-90℃.

4. The removal method of claim 1, wherein, In step (2), the ultrasound time is 2 to 10 minutes.

5. The removal method of claim 1 wherein, In step (3), the ultrasonic cell obtained in step (2) is washed with water.

6. The removal method as described in claim 1, characterized in that, The method further includes: before performing step (1), the grid lines and film layer on the surface of the IBC cell are removed to obtain an IBC cell with only insulating adhesive on the back.

7. The removal method as described in claim 1, characterized in that, The method further includes filtering the remaining solution after the reactions in steps (1) and (2) to obtain filtrate and insulating adhesive particles.

8. The removal method as described in claim 7, characterized in that, The method further includes washing, drying, and recycling the insulating adhesive particles.

9. The removal method as described in claim 7, characterized in that, The method further includes: recovering the filtrate.

10. A device for removing insulating adhesive from the back of an IBC battery, characterized in that, The removal device includes a reaction system, an ultrasonic system, a washing system, and a drying system; wherein, the reaction system is used to react IBC solar cells with only insulating adhesive on the back with nitric acid solution to prepare intermediate products; the ultrasonic system is used to ultrasonicate the intermediate products to obtain ultrasonic solar cells; the washing system and the drying system are used to wash and dry the ultrasonic solar cells to obtain silicon wafers.

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