A battery cell cutting damage repair liquid and repair method and application

Abstract

The present invention discloses a cell cutting damage repairing liquid, a repairing method and an application. The cell cutting damage repairing liquid provided by the present invention is obtained by dissolving a silicate compound in a fluosilicic acid aqueous solution. The repairing liquid obtained above is applied to the cut edge of the cell, and then annealed, so that the silicate compound attached to the cut edge of the cell is thermally decomposed to produce a SiO2 film attached to the cut edge of the cell to form a passivation film, thereby repairing the damage to the cut edge of the cell, thereby achieving the effect of improving the efficiency of the cell.

Description

Technical Field

[0001] The present invention relates to the technical field of battery cell cutting damage repair, and in particular to a battery cell cutting damage repair liquid, a repair method and an application thereof. Background Art

[0002] In recent years, the size of silicon wafers has been increasing, from 125mm to 156mm, 166mm, 182mm, and now 210mm; the power of battery modules has also increased rapidly with the increase in the size of silicon wafers, and the cost has been continuously reduced. However, as the size of silicon wafers increases, the current of single-chip batteries continues to increase, and the loss of a single string of battery modules is also increasing. Today's battery modules often use a method of splitting large-size cells into two, three, or even six to reduce the current of the battery module, reduce the internal loss of the battery module, and thus increase the power of the battery module.

[0003] The current mainstream cell slicing process is laser non-destructive cutting, which is based on a laser thermal stress controlled fracture technology that uses laser to quickly heat the cell cutting position, followed by cooling the heated position with pure water, thereby inducing thermal stress to break the cell. New edges are generated at the cell cutting position, and a large number of hanging bonds are generated on the new edge surface to form a composite center. At the same time, the cutting edge will also cause many defects and lattice distortion, ultimately leading to a significant decrease in cell efficiency. At present, it has been measured that laser cutting has an efficiency loss of about 0.2% / cut for TOPCon cells, and cutting damage has seriously affected the efficiency of cells and battery components. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a battery cell cutting damage repair liquid and a repair method and application.

[0005] The present invention solves the technical problem by adopting the following technical solutions.

[0006] The invention provides a battery cell cutting damage repairing liquid, which is obtained by dissolving a silicic acid compound in a fluorosilicic acid aqueous solution.

[0007] In some embodiments, the silicic acid compound comprises at least one of monomeric silicic acid, dimeric silicic acid, oligomeric silicic acid and sub-colloidal polymeric silicic acid, preferably monomeric silicic acid, and the purity of the monomeric silicic acid is ≥99.99%.

[0008] In some embodiments, the fluosilicic acid is analytically pure fluosilicic acid, and the mass concentration of the fluosilicic acid aqueous solution is 20% to 40%, preferably 25% to 35%.

[0009] In some embodiments, the temperature of the aqueous solution of fluosilicic acid is 40±2°C.

[0010] In some embodiments, the cell cutting damage repair solution is obtained by adding a silicic acid compound to a fluorosilicic acid aqueous solution until saturated, and the temperature of the saturated solution is 30°C to 45°C, preferably 35 to 40°C.

[0011] The present invention also provides a method for repairing cell cutting damage, which comprises: applying the above-mentioned cell cutting damage repairing liquid to the cell cutting edge, and then annealing the cell to form a passivation film on the cell cutting edge to complete the cell cutting edge damage repair.

[0012] In some embodiments, the steps are included: laser cutting the battery cell, placing all the cut battery strips horizontally with their front sides facing upward, stacking them neatly so that the cut edge sides of the battery strips form cut surfaces on the same vertical plane, and pressing the neatly stacked battery strips tightly; then applying a repair liquid to the cut surfaces; placing the battery strips coated with the repair liquid in an annealing furnace for annealing to complete the repair of the cut edge damage of the battery cell.

[0013] In some embodiments, a polyethylene soft brush is used to pick up the repair liquid and evenly apply it to the cut surface of the battery strip.

[0014] In some embodiments, the annealing temperature is 150° C. to 400° C., preferably 200° C. to 250° C., and the annealing time is 3 min to 6 min, preferably 4 min to 5 min.

[0015] The present invention also provides a use of the above-mentioned battery cell cutting damage repairing liquid in repairing battery cell cutting damage.

[0016] The present invention has the following beneficial effects:

[0017] The present invention provides a cell cutting damage repair liquid, a repair method and an application. The cell cutting damage repair liquid provided by the present invention is obtained by dissolving a silicate compound in a fluosilicic acid aqueous solution. Dissolving a silicate compound in a fluosilicic acid aqueous solution can increase the amount of silicate compound dissolved. When using the above-mentioned repair liquid to repair the damage on the cell cutting edge, the above-mentioned repair liquid is applied to the cell cutting edge to form a silicate compound film, and then annealed to decompose the silicate compound attached to the cell cutting edge by heat to generate a SiO2 film. The film can repair the hanging structure and defects on the cell cutting edge, thereby achieving the effect of improving the efficiency of the cell. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0019] The following is a detailed description of a battery cell cutting damage repair liquid, a repair method and an application provided in an embodiment of the present invention.

[0020] In a first aspect, an embodiment of the present invention provides a battery cell cutting damage repair liquid, wherein the battery cell cutting damage repair liquid is obtained by dissolving a silicic acid compound in a fluorosilicic acid aqueous solution.

[0021] An embodiment of the present invention provides a cell cutting damage repair liquid, which is obtained by dissolving a silicic acid compound in a fluorosilicic acid aqueous solution, and the amount of the silicic acid compound dissolved in the fluorosilicic acid aqueous solution can be increased. When repairing the cell cutting damage later, the above-mentioned repair liquid is applied to the cut edge of the cell, and then annealing is performed. Annealing can cause the silicic acid compound attached to the cut edge of the cell to decompose under heat to produce SiO2, which passivates the cut edge of the cell and forms a passivation film, thereby repairing the cell cutting damage and the dangling bonds produced, thereby achieving the purpose of improving the efficiency of the cell.

[0022] In some optional embodiments, the silicate compound includes at least one of monomeric silicate, dimerized silicate, oligomeric silicate and subcolloidal polymerized silicate, preferably monomeric silicate, and the purity of monomeric silicate is ≥99.99%. The cell cutting damage repairing liquid obtained by dissolving the silicate compound of the above composition in a fluorosilicic acid aqueous solution can effectively repair the cell cutting edge damage.

[0023] In some optional embodiments, the fluosilicic acid is analytically pure fluosilicic acid, and the mass concentration of the fluosilicic acid aqueous solution is 20% to 40%, preferably 25% to 35%.

[0024] Exemplarily, the mass concentration of the aqueous solution of fluosilicic acid can be 20%, 22%, 25%, 27%, 29%, 30%, 32%, 34%, 35%, 37%, 39%, 40% and any other value between 20% and 40%.

[0025] In some optional embodiments, the temperature of the hydrofluorosilicic acid aqueous solution is 40±2°C.

[0026] Illustratively, the temperature of the hydrofluorosilicic acid aqueous solution may be 38°C, 39°C, 40°C, 41°C, 42°C, and any other value between 38°C and 42°C.

[0027] The embodiment of the present invention provides a battery cell cutting damage repair liquid, which is obtained by adding a silicic acid compound to a fluosilicic acid aqueous solution. Since the solubility of the silicic acid compound is low, in order to increase the amount of the silicic acid compound dissolved in the fluosilicic acid aqueous solution. The solution provided in the embodiment of the present invention is beneficial to further increase the amount of the silicic acid compound dissolved in the fluosilicic acid aqueous solution by controlling the appropriate mass concentration and temperature of the fluosilicic acid aqueous solution. Since the stability of the silicic acid compound is poor, the appropriate mass concentration and temperature are beneficial to improving the solubility and stability of the silicic acid compound in the fluosilicic acid aqueous solution.

[0028] In some optional embodiments, the cell cutting damage repair solution is obtained by adding a silicic acid compound to a fluorosilicic acid aqueous solution until saturated, and the temperature of the saturated solution is 30°C to 45°C, preferably 35 to 40°C.

[0029] An embodiment of the present invention provides a battery cell cutting damage repair liquid, which is obtained by adding a silicic acid compound to a fluosilicic acid aqueous solution until saturation. Adding the silicic acid compound to the fluosilicic acid aqueous solution until saturation can increase the amount of the silicic acid compound dissolved in the fluosilicic acid aqueous solution to a greater extent, which is beneficial to the subsequent repair of the battery cell cutting damage.

[0030] It should be noted that in the present invention, the silicate compound is added to the fluosilicic acid aqueous solution until saturation. The method for judging the saturated solution is: hydrogen peroxide is added to the saturated solution. The solution that has not reached saturation is colorless when hydrogen peroxide is added. After saturation, the addition of hydrogen peroxide shows yellow. By adding hydrogen peroxide during the addition of the silicate compound for testing, the end point of saturation can be accurately judged. If the silicate compound continues to be added after saturation, the silicate compound will precipitate, resulting in waste.

[0031] Illustratively, the temperature of the saturated solution may be 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, 40°C, 42°C, 44°C, 45°C, and any other value between 30°C and 45°C.

[0032] In a second aspect, an embodiment of the present invention further provides a method for repairing cell cutting damage, which comprises: applying the above-mentioned cell cutting damage repair liquid to the cell cutting edge, and then annealing the cell to form a passivation film on the cell cutting edge to complete the cell cutting edge damage repair.

[0033] In some optional embodiments, the following steps are included: laser cutting the battery cell, placing all the cut battery strips horizontally with their front sides facing upward, stacking them neatly so that the cut edge sides of the battery strips form cutting surfaces on the same vertical plane, and pressing the neatly stacked battery strips tightly to reduce the penetration of repair liquid into the gaps between the battery cells; then applying repair liquid to the cut surfaces; placing the battery strips coated with the repair liquid in an annealing furnace for annealing to complete the repair of the damage to the cut edges of the battery cells.

[0034] It is worth noting that if the battery cell is cut into two, the battery strip after cutting has only one cutting edge. If the battery cell is cut into three or more, the middle battery strip after cutting has two cutting edges, and the battery strips on both sides have only one cutting edge. During the stacking process, the battery strips with only one cutting edge can be stacked neatly so that the cutting edge sides of the battery strips are in the same vertical plane, forming a cutting surface on one side, or the battery strips with two cutting edges can be stacked neatly so that the cutting edge sides of the battery strips are in the same vertical plane, forming cutting surfaces on both sides, and then applying repair liquid to the cutting surfaces formed by the stacking; the battery strips coated with the repair liquid are placed in an annealing furnace for annealing to complete the repair of the damage to the cutting edges of the battery cells.

[0035] In some optional embodiments, a polyethylene soft brush is used to pick up a small amount of repair liquid and evenly apply it to the cut edge of the battery strip. The polyethylene soft brush will not damage the cut surface of the battery sheet.

[0036] In some optional embodiments, the annealing temperature is 150° C. to 400° C., preferably 200° C. to 250° C., and the annealing time is 3 min to 6 min, preferably 4 min to 5 min.

[0037] The above-mentioned annealing temperature and annealing time are suitable and beneficial for forming a SiO2 film on the cut edge of the battery strip. If the temperature is lower than 150°C, the decomposition of the silicate compound is insufficient. If the temperature is higher than 400°C, some silicate compounds will be volatilized and lost, which is not conducive to forming a passivation film after the decomposition of the silicate compound to repair the damage on the cut edge of the battery cell.

[0038] For example, the annealing temperature may be 150° C., 200° C., 250° C., 300° C., 350° C., 400° C. and any other value between 150° C. and 400° C. The annealing time may be 3 min., 4 min., 5 min., 6 min. and any other value between 3 min and 6 min.

[0039] In a third aspect, an embodiment of the present invention provides a use of the above-mentioned battery cell cutting damage repairing liquid in repairing battery cell cutting damage.

[0040] The present invention will be further described below in conjunction with the embodiments.

[0041] A method for repairing cell cutting damage comprises the following steps:

[0042] Prepare the cell cutting damage repair solution: Use high-purity silicic acid powder (purity ≥ 99.99%), add it to the analytical pure fluorosilicic acid aqueous solution, the fluorosilicic acid concentration is 20% to 40%, preferably 25% to 35%, until saturation. The saturated solution is maintained at 30℃ to 45℃, preferably 35℃ to 40℃, to prevent the precipitation of silicic acid, and magnetic stirring is used to ensure the uniform concentration of the solution.

[0043] Repair the damage on the cut edge of the battery cell: laser cut the battery cell, place all the cut battery strips horizontally with the front side facing up, stack them neatly so that the cut edge sides of the battery strips form the cut surface on the same vertical plane, and press the neatly stacked battery strips tightly; then apply repair fluid to the cut surface; put the battery strips coated with the repair fluid into the annealing furnace for annealing to complete the repair of the damage on the cut edge of the battery cell.

[0044] Among them: use a soft brush made of polyethylene to dip the repair liquid and evenly apply it on the cut surface of the battery strip; put the battery strip coated with the repair liquid into an annealing furnace for annealing, the annealing temperature is 150℃~400℃, preferably 200℃~250℃, the annealing time is 3min~6min, preferably 4min-5min, during the annealing process, the components in the repair liquid decompose and volatilize, SiO2 generated by dehydration of silicic acid adheres to the cut edge of the battery cell to form a passivation film, the cut edge of the battery cell is repaired, and the efficiency of the battery cell is improved.

[0045] The annealed battery strips are tested for efficiency and classified into different grades, and battery strips of the same power are assembled into modules according to the module manufacturing process.

[0046] Example 1

[0047] A method for repairing cell cutting damage comprises the following steps:

[0048] 1. Prepare the cell cutting damage repair solution: Take 250 ml of analytical pure fluorosilicic acid (H2SiF6) solution with a concentration of 30%, keep the solution temperature at 40±2°C, then add high-purity silicic acid powder (>99.9%) to the pure fluorosilicic acid aqueous solution until saturated, and use magnetic force to stir slowly while adding to maintain the uniformity of the solution concentration.

[0049] 2. Prepare the battery slices: Use laser cutting technology to cut the TOPCon battery slice into three parts, stack the same battery slices together and align them, keep the cut edges on the same vertical plane to form a cutting surface, and press the aligned battery slices tightly to reduce the infiltration of the repair liquid into the gaps between the battery slices;

[0050] 3. Apply silica film: Use a soft brush made of polyethylene to apply a small amount of repair liquid evenly on the cut surface to form a layer of silica film on the cut surface;

[0051] 4. Annealing: Place the small battery strips coated with silica film into the annealing furnace and anneal at 250℃ for 5 minutes, so that the silica in the silica film attached to the cut edge of the battery cell is decomposed into SiO2 and H2O, and the water and fluoride are extracted by the exhaust system of the annealing furnace due to the heat. The SiO2 produced by the decomposition of silica forms a passivation film on the cut edge of the battery cell, repairing the damage on the cut edge of the battery cell and the dangling bonds produced, so as to achieve the purpose of improving the efficiency of the battery cell.

[0052] 5. Efficiency test: The passivated battery strips are tested using a SunsVoc test instrument to obtain efficiency data of the battery strips.

[0053] Example 2

[0054] The steps are basically the same as those in Example 1, except that the annealing is performed at 300° C. for 4 minutes.

[0055] Example 3

[0056] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 40%, and annealing is performed at 200° C. for 3 minutes.

[0057] Example 4

[0058] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 40%, and annealing is performed at 300° C. for 4 minutes.

[0059] Example 5

[0060] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 20%, and annealing is performed at 200° C. for 3 minutes.

[0061] Comparative Example 1

[0062] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 10%, and annealing is performed at 200° C. for 3 minutes.

[0063] Comparative Example 2

[0064] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 10%, and annealing is performed at 300° C. for 5 minutes.

[0065] Comparative Example 3

[0066] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 30%, and annealing is performed at 100° C. for 5 minutes.

[0067] Comparative Example 4

[0068] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 30%, and annealing is performed at 500° C. for 5 minutes.

[0069] Comparative Example 5

[0070] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 50%, and annealing is performed at 300° C. for 3 minutes.

[0071] Comparative Example 6

[0072] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 30%, and annealing is performed at 250° C. for 1 min.

[0073] Comparative Example 7

[0074] The steps are basically the same as those in Example 1, except that the mass concentration of the hydrofluorosilicic acid aqueous solution is 10%, and annealing is performed at 120° C. for 2 minutes.

[0075] Table 1 below shows the experimental results of repairing the cut edges of the battery cells using the repairing liquids of the examples and comparative examples:

[0076] Table 1

[0077]

[0078] Note: Uoc (Open Circuit Voltage), pFF (pseudo fill factor), pEff (effective power).

[0079] Through experimental verification, it can be seen from Table 1 that the performance of the battery strips repaired with the repair solution provided in Examples 1-5 is good, especially the repair solution prepared by adding saturated silica powder at a 30% fluorosilicic acid concentration in Example 1 achieves the best repair effect after annealing at 250°C for 5 minutes. The Uoc and pFF of the battery strips are optimal and the efficiency is the highest, indicating that the method of Example 1 has the best passivation effect on the cut edge of the battery strip. In Comparative Examples 1-7, the performance of the battery strips decreases when the concentration of the fluorosilicic acid aqueous solution or the annealing conditions are changed.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A battery cell cutting damage repair liquid, characterized in that: The cell cutting damage repair liquid is obtained by dissolving a silicic acid compound in a fluosilicic acid aqueous solution, wherein the mass concentration of the fluosilicic acid aqueous solution is 20% to 40% and the temperature is 40±2°C.

2. The cell cutting damage repair liquid according to claim 1, characterized in that: The silicic acid compound includes at least one of monomeric silicic acid, dimeric silicic acid, oligomeric silicic acid and sub-colloidal polymeric silicic acid.

3. The cell cutting damage repairing liquid according to claim 1, characterized in that: The silicic acid compound is monomeric silicic acid, and the purity of the monomeric silicic acid is ≥99.99%.

4. The cell cutting damage repairing liquid according to claim 1, characterized in that: The fluorosilicic acid is analytical pure fluorosilicic acid, and the mass concentration of the fluorosilicic acid aqueous solution is 25% to 35%.

5. The cell cutting damage repairing liquid according to claim 1, characterized in that: The cell cutting damage repair solution is obtained by adding a silicic acid compound into a fluorosilicic acid aqueous solution until saturated, and the temperature of the saturated solution is 30° C. to 45° C.

6. The cell cutting damage repairing liquid according to claim 5, characterized in that: The temperature of the saturated solution is 35-40°C.

7. A method for repairing battery cell cutting damage, characterized in that: It includes: The cell cutting damage repair liquid according to any one of claims 1 to 6 is applied to the cut edge of the cell, and then the cell is annealed to form a passivation film on the cut edge of the cell, thereby completing the cell cutting edge damage repair.

8. The repair method according to claim 7, characterized in that: The following steps are involved: The battery cells are laser cut, and the cut battery strips are placed horizontally with the front side facing upwards, and are neatly stacked so that the cut edge sides of the battery strips form cut surfaces on the same vertical plane, and the neatly stacked battery strips are pressed tightly; then a repair liquid is applied to the cut surfaces; the battery strips coated with the repair liquid are placed in an annealing furnace for annealing to complete the repair of the cut edge damage of the battery cells.

9. The repair method according to claim 8, characterized in that: Use a polyethylene soft brush to dip the repair fluid and apply it evenly on the cut surface of the battery strip.

10. The repair method according to claim 8, characterized in that: The annealing temperature is 150℃~400℃, and the annealing time is 3min~6min.

11. The repair method according to claim 10, characterized in that: The annealing temperature is 200℃~250℃, and the annealing time is 4min-5min.

12. Use of the cell cutting damage repairing liquid according to any one of claims 1 to 6 in repairing cell cutting edge damage.

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