Back-contact battery and solder strip laying method thereof

Abstract

The present invention discloses a back-contact battery and a method for laying a welding strip thereof, and belongs to the technical field of solar cells. A back-contact battery of the present invention comprises a battery cell, and a plurality of positive grid lines and a plurality of negative grid lines are alternately arranged on the second surface of the battery cell, and the plurality of positive grid lines are connected by a positive welding strip, and the plurality of negative grid lines are connected by a negative welding strip, wherein the positive welding strip and the negative welding strip both comprise a connecting portion and a plurality of protrusions, and the distance between the protrusions of two adjacent positive welding strips is not greater than the distance between two adjacent positive grid lines on the battery cell, and the distance between the protrusions of two adjacent negative welding strips is not greater than the distance between two adjacent negative grid lines on the battery cell. The present application adopts a welding strip design comprising a connecting portion and a plurality of protrusions to eliminate the use of solder paste, and effectively reduces the cost of consumables. At the same time, the protrusion design can be just snapped into between adjacent insulating glues, which can play a role in fixing the welding strip and reduce the risk of welding strip deviation.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and more particularly to a back-contact type cell and a method for laying a soldering strip thereof. Background Art

[0002] At present, the back-contact battery has become an important development direction of photovoltaic cells due to its high efficiency characteristics, and its photovoltaic module finished products have also been effectively developed. Photovoltaic solar cells are devices that convert sunlight into electrical energy. In the actual working process, solar cells use the photovoltaic principle to generate carriers, and then use electrodes (i.e., grid lines) to lead out the carriers, thereby facilitating the effective use of electrical energy. In the interconnection process of its main grid-free battery, three materials, namely insulating glue, fixing glue, and solder paste, are required to assist welding, which has problems such as a large number of consumables, complicated processes, and high equipment investment costs.

[0003] Specifically, the welding process of the busbar-free back contact battery in the prior art is to print and dry the insulating glue at the overlap position of the solder strip at the fine grid line of the finished battery to isolate the grid lines of the opposite electrodes and prevent short circuits. Then, the solder paste is printed and dried at the fine grid line position of the same electrode (the overlap position of the solder strip), and the height of the solder paste must not be lower than the height of the insulating glue to play a role in flux. Then print the fixing glue (mostly UV curing glue) outside the insulating glue & solder paste, with a height not lower than the solder paste; then arrange the solder ribbon on the insulating glue & solder paste & fixing glue (perpendicular to the fine grid line), and fix the solder ribbon on the battery after ultraviolet light irradiation, and finally enter the laminator, and use the lamination temperature to alloy the solder ribbon, solder paste, and battery grid line to complete the welding. Considering the production cost, the above production sequence cannot be changed. The fixing glue is applied before the solder ribbon is laid, and only ordinary printing equipment is required. Although the requirements for battery welding equipment are relatively low, the colloid cannot completely cover the solder ribbon, but only contacts the bottom of the solder ribbon, and the wrapping area is small, which makes it difficult for the fixing glue to fix the solder ribbon to the battery well, that is, the tension is low. During lamination welding, the adhesive film flows and the risk of solder ribbon deviation increases, causing problems such as poor welding and short circuit.

[0004] In summary, the welding process in the prior art uses three materials, namely insulating glue, fixing glue and solder paste, to assist welding. In addition to the problems of large number of consumables, complicated process and high equipment investment cost, it also leads to the problem of insufficient tensile force caused by insufficient wrapping of the produced battery fixing glue, which may cause the solder strip to shift during lamination welding. Summary of the invention

[0005] The content of this application is used to introduce concepts in a brief form, which will be described in detail in the detailed implementation section below. The content of this application is not intended to identify the key features or essential features of the technical solution claimed for protection, nor is it intended to limit the scope of the technical solution claimed for protection.

[0006] Some embodiments of the present application propose a back-contact battery and a method for laying a solder strip therefor to solve the technical problems mentioned in the above background technology section.

[0007] As a first aspect of the present application, some embodiments of the present application provide a back-contact battery, comprising a battery cell, wherein a plurality of positive grid lines and a plurality of negative grid lines are alternately arranged on the second surface of the battery cell, the plurality of the positive grid lines are connected by a positive welding strip, the plurality of the negative grid lines are connected by a negative welding strip, the straight line where the length direction of the positive welding strip is located is perpendicular to the straight line where the length direction of the positive grid line is located, and the straight line where the length direction of the negative welding strip is located is perpendicular to the straight line where the length direction of the negative grid line is located; wherein both the positive welding strip and the negative welding strip comprise a connecting portion and a plurality of protruding portions, the plurality of protruding portions are equidistantly arranged on the same side of the connecting portion, the distance between the protruding portions of two adjacent positive welding strips is not greater than the distance between two adjacent positive grid lines on the battery cell, and the distance between the protruding portions of two adjacent negative welding strips is not greater than the distance between two adjacent negative grid lines on the battery cell.

[0008] Furthermore, insulating glue is coated on the negative electrode grid line between any two adjacent positive electrode grid lines in the length direction of the positive electrode welding strip on the battery cell; insulating glue is coated on the positive electrode grid line between any two adjacent negative electrode grid lines in the length direction of the negative electrode welding strip on the battery cell.

[0009] Furthermore, the height of the insulating glue ranges from 20 μm to 55 μm.

[0010] Furthermore, the height of the protrusion is greater than the height of the insulating glue.

[0011] Furthermore, the straight line of the battery cell perpendicular to the positive electrode grid line is defined as L1, the plane passing through L1 is defined as S, the point of the protrusion that is farthest from the connecting part and close to the insulating glue is defined as point A, the straight line passing through point A and tangent to the insulating glue is defined as L2, the point at which L2 first intersects the connecting part is defined as point B, and the area formed by the projections of point A, point B and L2 on S ranges from 400 square microns to 6600 square microns.

[0012] Furthermore, fixing glue is provided on the positive electrode welding strip and the negative electrode welding strip on the battery cell.

[0013] Furthermore, the fixing glue wraps the positive electrode welding strip and the negative electrode welding strip.

[0014] Furthermore, the viscosity coefficient of the fixing glue is 20000 mpa·s to 40000 mpa·s.

[0015] As the second aspect of the present application, some embodiments of the present application provide a back-contact battery string, which is composed of several of the above-mentioned back-contact batteries and also includes glass and a back plate, wherein the several back-contact batteries are connected by welding strips, the glass is arranged on the first side of the back-contact battery, and the back plate is arranged on the second side of the back-contact battery.

[0016] As a second aspect of the present application, some embodiments of the present application provide a method for laying a solder strip of a back-contact battery, the method for laying a solder strip of a back-contact battery is used to manufacture the above-mentioned back-contact battery, and the method for laying a solder strip of a back-contact battery comprises:

[0017] Printing and drying insulating glue at the negative electrode grid lines of the battery cell in a first vertical direction perpendicular to the positive electrode grid lines, and printing and drying insulating glue at the positive electrode grid lines of the battery cell in a second vertical direction perpendicular to the negative electrode grid lines;

[0018] Placing the positive electrode welding strip in the first vertical direction and / or placing the negative electrode welding strip in the second vertical direction;

[0019] A fixing glue is applied on the positive electrode welding strip and the negative electrode welding strip.

[0020] Furthermore, the method of placing the positive electrode welding strip in the first vertical direction and placing the negative electrode welding strip in the second vertical direction includes: placing the raised portion of the positive electrode welding strip between the insulating glue on two negative electrode grid lines and placing the raised portion of the negative electrode welding strip between the insulating glue on two positive electrode grid lines.

[0021] Furthermore, the method of applying the fixing glue on the positive electrode welding strip and the negative electrode welding strip comprises: spraying or printing the fixing glue on the positive electrode welding strip and the negative electrode welding strip and drying them.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] This application adopts a solder strip design including a connecting portion and a plurality of raised portions to eliminate the use of solder paste, effectively reducing the cost of consumables. At the same time, the raised portion design can be just snapped into the adjacent insulating adhesives in the vertical direction, which can play a role in fixing the solder strip and reduce the risk of solder strip deviation. Second, the fixing adhesive is applied after the solder strip is laid. The colloid can wrap the top and side of the solder strip, and then bond with the battery, which is enough to fix the solder strip and the battery well together, basically avoiding the risk of solder strip deviation in laminated welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting a part of this application are used to provide a further understanding of this application, so that other features, purposes and advantages of this application become more obvious. The illustrative embodiment drawings and their descriptions of this application are used to explain this application and do not constitute an improper limitation on this application.

[0025] In addition, throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and that the components and elements are not necessarily drawn to scale.

[0026] Figure 1 is a schematic structural diagram of a back-contact battery according to an embodiment of the present application;

[0027] Figure 2 is a schematic structural diagram of a back-contact battery welding strip according to an embodiment of the present application;

[0028] Figure 3 is a schematic diagram of the gap structure between the protrusion and the insulating adhesive of a back-contact battery according to an embodiment of the present application;

[0029] Figure 4 It is a schematic diagram of the structure in which the fixing glue of the back-contact battery is coated on the welding strip according to an embodiment of the present application;

[0030] Explanation of the symbols in the schematic diagram:

[0031] 100, battery cell; 110, positive electrode grid line; 120, negative electrode grid line;

[0032] 200, positive electrode welding strip;

[0033] 300, negative electrode welding strip;

[0034] 400, raised portion;

[0035] 500, connecting part;

[0036] 600, insulation glue;

[0037] 700. Fixing glue. DETAILED DESCRIPTION

[0038] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to provide a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0039] It should also be noted that, for ease of description, only the parts related to the invention are shown in the drawings. In the absence of conflict, the embodiments and features in the embodiments of the present disclosure can be combined with each other.

[0040] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0041] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0042] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only used for illustrative purposes and are not used to limit the scope of these messages or information.

[0043] The present disclosure will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0044] Back-contact cells refer to busbar-free cells, i.e., both positive and negative electrodes are arranged on the non-light-receiving surface of the cell 100. Since there is no grid line blocking the front of the cell 100, the solar energy collected by the cell 100 per unit area is increased, and the short-circuit current of the cell 100 is improved. The positive grid lines 110 and negative grid lines 120 of busbar-free solar cells in the prior art are evenly arranged on the non-light-receiving surface of the cell, and the carriers on the positive grid lines 110 and the negative grid lines 120 are smoothly led out. In order to prevent interconnection short circuits between the positive grid lines 110 and the negative grid lines 120, insulating glue 600 is printed on the opposite-sex electrodes, and solder paste is printed on the same-sex electrodes to achieve interconnection welding of the welding strips.

[0045] Specifically, the conventional method for preparing a main-grid-free back-contact battery string includes the following steps: first, insulating glue printing and drying, solder paste printing and memory drying, fixing glue printing, solder tape laying and fixing (fixing glue fixing, heat curing or UV curing), lamination welding and other processes are performed on the battery surface. The main disadvantages are as follows: first, there are many processes, which will cause problems such as increased process defect rate and increased cost; second, after the solder paste is dried, not only the surface is smooth, but also the top is in an arc shape. When the solder tape is laid on it, it is easy to slip and deviate; third, the fixing glue is often applied before the solder tape is laid, and only ordinary printing equipment is required. Although the requirements for battery welding equipment are relatively low, the colloid cannot completely cover the solder tape, but only contacts the bottom of the solder tape, and the wrapping area is small, which makes it difficult for the fixing glue to fix the solder tape to the battery well, that is, the tension is low. During lamination welding, the glue film flows and the risk of solder tape deviation increases, causing frequent problems such as poor welding and short circuit.

[0046] like Figures 1 to 4 As shown, a back-contact battery of one embodiment of the present application comprises a battery cell 100, a plurality of positive grid lines 110 and a plurality of negative grid lines 120 are alternately arranged on the second surface of the battery cell 100, a plurality of the positive grid lines 110 are connected by a positive welding strip 200, a plurality of the negative grid lines 120 are connected by a negative welding strip 300, a straight line where the length direction of the positive welding strip 200 is located is perpendicular to a straight line where the length direction of the positive grid lines 110 is located, and a straight line where the length direction of the negative welding strip 300 is located is perpendicular to a straight line where the length direction of the negative grid lines 120 is located. 0; wherein the positive electrode welding strip 200 and the negative electrode welding strip 300 both include a connecting portion 500 and a plurality of raised portions 400, and the plurality of raised portions 400 are equidistantly arranged on the same side of the connecting portion 500, and the distance between the raised portions 400 of two adjacent positive electrode welding strips 200 is not greater than the distance between the two adjacent positive electrode grid lines 110 on the battery cell 100, and the distance between the raised portions 400 of two adjacent negative electrode welding strips 300 is not greater than the distance between the two adjacent negative electrode grid lines 120 on the battery cell 100.

[0047] Specifically, the cell 100 has a light-facing surface and a backlight surface, the light-facing surface is defined as the first surface, the backlight surface is defined as the second surface, and a plurality of grid lines are provided on the backlight surface, namely, positive grid lines 110 and negative grid lines 120, the positive grid lines 110 and the negative grid lines 120 are alternately arranged on the second surface, and at the same time, the positive grid lines 110 and the negative grid lines 120 are arranged roughly in parallel. The cell 100 has a first linear direction and a second linear direction in two dimensions, wherein the first linear direction and the second linear direction are perpendicular. In order to better guide the carriers, in the first linear direction of the cell 100, the positive grid lines 110 are connected by the positive electrode welding strips 200, and the negative grid lines 120 are connected by the negative electrode welding strips 300.

[0048] More specifically, the positive electrode welding strip 200 and the negative electrode welding strip 300 both include a connecting portion 500 and a plurality of raised portions 400. The raised portions 400 are arranged on the same side of the connecting portion 500. The distances between the raised portions 400 and the raised portions 400 are substantially equal. The function of the raised portions 400 is to contact the grid lines and thereby extract the current in the grid lines. Therefore, in order to ensure that the raised portions 400 can fully contact the grid lines, the distance between two adjacent raised portions 400 needs to be less than or equal to the distance between two grid lines of the same polarity. That is, the distance between the protrusions 400 of two adjacent positive electrode welding strips 200 is not greater than the distance between the two adjacent positive electrode grid lines 110 on the battery cell 100, and the distance between the protrusions 400 of two adjacent negative electrode welding strips 300 is not greater than the distance between the two adjacent negative electrode grid lines 120 on the battery cell 100, wherein the height range of the protrusion 400 is 0.2 mm to 0.355 mm, and the distance range between the two protrusions is 0.2 mm to 1.2 mm.

[0049] In a specific embodiment, an insulating glue 600 is applied on the negative electrode grid line 120 between any two adjacent positive electrode grid lines 110 in the length direction of the positive electrode welding strip 200 on the battery cell 100; and an insulating glue 600 is applied on the positive electrode grid line 110 between any two adjacent negative electrode grid lines 120 in the length direction of the negative electrode welding strip 300 on the battery cell 100.

[0050] In order to prevent the occurrence of short circuit, when the welding strip is overlapped on the grid line of the same pole, an insulating glue 600 needs to be applied on the grid line between the two protrusions 400. The insulating glue 600 is generally applied before overlapping the welding strip, and the coating method includes but is not limited to printing. The height range of the insulating glue 600 is 20μm to 55μm. Within this height range, the insulating glue 600 is not too high to cause the protrusion 400 of the welding strip to fail to contact the grid line, nor is it too low to play an insulating role.

[0051] like Figure 3As shown, more specifically, the height of the protrusion 400 needs to be greater than the height of the insulating glue 600, that is, when the protrusion 400 contacts the grid line, there is still a certain gap between the highest point of the insulating glue 600 and the connecting portion 500 of the welding strip. The straight line perpendicular to the positive grid line 110 of the battery cell 100 is defined as L1, the plane passing through L1 is defined as S, the point of the protrusion 400 farthest from the connecting portion 500 and close to the insulating glue 600 is defined as point A, the straight line passing through point A and tangent to the insulating glue 600 is defined as L2, and the point where L2 first intersects with the connecting portion 500 is defined as point B. The area composed of the projections of point A, point B and L2 on S is in the range of 400 square microns to 6600 square microns. A fixing glue 700 is provided on both the positive welding strip 200 and the negative welding strip 300 on the battery cell 100. The fixing glue 700 wraps the positive electrode welding strip 200 and the negative electrode welding strip 300. The viscosity coefficient of the fixing glue 700 is 20000 mpa·s to 40000 mpa·s.

[0052] Specifically, the distance between the protrusions ranges from 0.2mm to 1.2mm, and the height of the protrusion ranges from 0.02mm to 0.055mm. Since the insulating glue is semi-arc-shaped as a whole, the straight line at point A and tangent to the insulating glue 600 is L2, and the point where L2 first intersects with the connecting portion 500 is point B, and point B is approximately 1 / 5 of the protrusion. Therefore, the area composed of the projections of point A, point B and L2 on S ranges from 400 square microns to 6600 square microns. The size of the area formed by the projection of point A, point B and L2 on S indicates the size of the gap between the insulating glue 600 and the two adjacent protrusions 400. Due to the existence of the gap, in the subsequent production steps, when the fixing glue 700 needs to be applied to the protrusions 400 and the grid lines, part of the fixing glue 700 can enter from the gap between the insulating glue 600 and the connecting part 500 of the solder strip, which greatly increases the bonding force between the solder strip and the battery, and avoids the displacement of the solder strip during the subsequent lamination welding process. The viscosity coefficient of the fixing glue 700 is limited to 20000mpa·s to 40000mpa·s, and the fixing glue 700 can automatically flow into the gap to increase its adhesion.

[0053] An embodiment of the present application provides a method for laying a solder strip of a back-contact battery, the method for laying a solder strip of a back-contact battery being used to manufacture the above-mentioned back-contact battery, and the method for laying a solder strip of a back-contact battery comprising:

[0054] Step 1: printing and drying insulating glue 600 at the negative electrode grid lines 120 of the battery cell 100 in a first vertical direction perpendicular to the positive electrode grid lines 110 and printing and drying insulating glue 600 at the positive electrode grid lines 110 of the battery cell 100 in a second vertical direction perpendicular to the negative electrode grid lines 120;

[0055] Step 2: placing the positive electrode welding strip 200 in the first vertical direction and / or placing the negative electrode welding strip 300 in the second vertical direction;

[0056] Step three: applying a fixing glue 700 on the positive electrode welding strip 200 and the negative electrode welding strip 300 .

[0057] Among them, the method of placing the positive electrode welding strip 200 in the first vertical direction and placing the negative electrode welding strip 300 in the second vertical direction includes: placing the raised portion 400 of the positive electrode welding strip 200 between the insulating glue 600 on the two negative electrode grid lines 120 and placing the raised portion 400 of the negative electrode welding strip 300 between the insulating glue 600 on the two positive electrode grid lines 110.

[0058] The method of applying the fixing glue 700 on the positive electrode welding strip 200 and the negative electrode welding strip 300 includes: spraying or printing the fixing glue 700 on the positive electrode welding strip 200 and the negative electrode welding strip 300 and drying. The length of the fixing glue 700 in the direction of the grid line length needs to be greater than the length of the welding strip in this direction, and the length of the fixing glue 700 in the direction perpendicular to the grid line is not less than 0.2 mm, and then the welding strip is fixed on the battery cell 100 by heating or ultraviolet light irradiation. Since the fixing glue 700 is applied after the welding strip is laid, it can fully wrap the upper surface and side of the welding strip and can be firmly combined with the battery.

[0059] Specifically, in step one, the insulating glue 600 is printed and dried. In order to ensure that the negative electrode grid lines 120 in the first vertical direction perpendicular to the positive electrode grid lines 110 can be fully covered by the insulating glue 600, the height range of the insulating glue 600 on the negative electrode grid lines 120 is: 20μm to 55μm. The width range of the insulating glue 600 is: 0.2mm to 1.2mm. Similarly, in order to ensure that the positive electrode grid lines 110 in the first vertical direction perpendicular to the negative electrode grid lines 120 can be fully covered by the insulating glue 600, the height range of the insulating glue 600 on the positive electrode grid lines 110 is: 20μm to 55μm. The width range of the insulating glue 600 is: 0.2mm to 1.2mm. The height and width of the insulating glue 600 in step one will also provide a good installation environment for subsequent steps.

[0060] Specifically, in step two, since the insulating glue 600 printed in step one is at the corresponding position, and at the same time, the positive electrode welding strip 200 and the negative electrode welding strip 300 used in step two are the welding strips with a connecting portion 500 and a plurality of protrusions 400 as mentioned above, and the protrusions 400 are arranged on the same side of the connecting portion 500, and the distances between the protrusions 400 and the protrusions 400 are roughly equal, therefore, the protrusions 400 can be just stuck between the two insulating glues 600, and the insulating glue 600 and the protrusions 400 cooperate to position the welding strip, so that the welding strip is not easy to shift when the subsequent process steps are carried out on the battery cell 100.

[0061] Further, in step three, since the height of the protrusion 400 needs to be greater than the height of the insulating glue 600, that is, when the protrusion 400 contacts the grid line, there is still a certain gap between the highest point of the insulating glue 600 and the connecting portion 500 of the welding strip. The straight line perpendicular to the positive grid line 110 of the battery cell 100 is defined as L1, the plane passing through L1 is defined as S, the point of the protrusion 400 farthest from the connecting portion 500 close to the insulating glue 600 is defined as point A, the straight line passing through point A and tangent to the insulating glue 600 is defined as L2, and the point where L2 first intersects with the connecting portion 500 is defined as point B. The area composed of the projections of point A, point B and L2 on S is in the range of 400 square microns to 6600 square microns. A fixing glue 700 is provided on both the positive welding strip 200 and the negative welding strip 300 on the battery cell 100. The fixing glue 700 wraps the positive electrode welding strip 200 and the negative electrode welding strip 300. The viscosity coefficient of the fixing glue 700 is 20000 mpa·s to 40000 mpa·s.

[0062] The size of the area formed by the projection of point A, point B and L2 on S indicates the size of the gap between the insulating glue 600 and the two adjacent protrusions 400. Due to the existence of this gap, in the subsequent production steps, when the fixing glue 700 is applied to the protrusion 400 and the grid line, part of the fixing glue 700 can enter from the gap between the insulating glue 600 and the connecting part 500 of the welding strip, which greatly increases the bonding force between the welding strip and the battery, and avoids the displacement of the welding strip during the subsequent lamination welding process. The viscosity coefficient of the fixing glue 700 is limited to 20000mpa·s to 40000mpa·s, and the fixing glue 700 can automatically flow into the gap to increase its adhesion. Therefore, the method of first laying the welding strip and then applying the fixing glue 700 can effectively improve the bonding force between the welding strip and the battery and avoid the displacement of the welding strip during the lamination welding process. Finally, the battery strings are laid out according to the component circuit design, and after laying glass, film, backplane and other packaging materials, they enter the laminator for low-temperature welding and packaging.

[0063] The above descriptions are only some preferred embodiments of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) and the technical solutions formed.

Claims

1. A back-contact battery, characterized in that: A battery cell is included, wherein a plurality of positive grid lines and a plurality of negative grid lines are alternately arranged on the second surface of the battery cell, the plurality of positive grid lines are connected by a positive welding strip, the plurality of negative grid lines are connected by a negative welding strip, the straight line where the length direction of the positive welding strip is located is perpendicular to the straight line where the length direction of the positive grid line is located, and the straight line where the length direction of the negative welding strip is located is perpendicular to the straight line where the length direction of the negative grid line is located; Wherein, the positive electrode welding strip and the negative electrode welding strip both include a connecting portion and a plurality of protrusions, and the plurality of protrusions are equidistantly arranged on the same side of the connecting portion, and the distance between the protrusions of two adjacent positive electrode welding strips is not greater than the distance between two adjacent positive electrode grid lines on the battery cell, and the distance between the protrusions of two adjacent negative electrode welding strips is not greater than the distance between two adjacent negative electrode grid lines on the battery cell.

2. The back-contact battery according to claim 1, characterized in that: Insulating glue is applied on the negative electrode grid line between any two adjacent positive electrode grid lines in the length direction of the positive electrode welding strip on the battery cell; insulating glue is applied on the positive electrode grid line between any two adjacent negative electrode grid lines in the length direction of the negative electrode welding strip on the battery cell.

3. The back-contact battery according to claim 2, characterized in that: The height of the insulating glue ranges from 20 to 55 μm.

4. The back-contact battery according to claim 3, characterized in that: The height of the protrusion is greater than the height of the insulating glue.

5. The back-contact battery according to claim 4, characterized in that: The straight line of the battery cell perpendicular to the positive electrode grid line is defined as L1, the plane passing through L1 is defined as S, the point of the protrusion that is farthest from the connecting part and close to the insulating glue is defined as point A, the straight line passing through point A and tangent to the insulating glue is defined as L2, the point where L2 first intersects the connecting part is defined as point B, and the area formed by the projections of point A, point B and L2 on S ranges from 400 square microns to 6600 square microns.

6. The back-contact battery according to claim 1 or 5, characterized in that: Fixing glue is provided on the positive electrode welding strip and the negative electrode welding strip on the battery sheet.

7. The back-contact battery according to claim 6, characterized in that: The fixing glue wraps the positive electrode welding strip and the negative electrode welding strip.

8. The back-contact battery according to claim 7, characterized in that: The viscosity coefficient of the fixing glue is 20000 mpa·s to 40000 mpa·s.

9. A back-contact battery string, characterized in that: It is composed of a plurality of back-contact batteries as described in any one of claims 1 to 8, and also includes glass and a back plate, wherein the plurality of back-contact batteries are connected by welding strips, the glass is arranged on the first side of the back-contact battery, and the back plate is arranged on the second side of the back-contact battery.

10. A method for laying a solder strip of a back-contact battery, characterized in that: The method for laying a solder strip of a back-contact battery is used to manufacture a back-contact battery as claimed in any one of claims 1 to 8, and the method for laying a solder strip of a back-contact battery comprises: Printing and drying insulating glue at the negative electrode grid lines of the battery cell in a first vertical direction perpendicular to the positive electrode grid lines, and printing and drying insulating glue at the positive electrode grid lines of the battery cell in a second vertical direction perpendicular to the negative electrode grid lines; Placing the positive electrode welding strip in the first vertical direction and / or placing the negative electrode welding strip in the second vertical direction; A fixing glue is applied on the positive electrode welding strip and the negative electrode welding strip.

11. The method for laying a solder strip of a back-contact battery according to claim 10, characterized in that: The method of placing the positive electrode welding strip in the first vertical direction and the negative electrode welding strip in the second vertical direction includes: placing the raised portion of the positive electrode welding strip between the insulating glue on two negative electrode grid lines and placing the raised portion of the negative electrode welding strip between the insulating glue on two positive electrode grid lines.

12. The method for laying a solder strip of a back-contact battery according to claim 11, characterized in that: The method for applying the fixing glue on the positive electrode welding strip and the negative electrode welding strip comprises: spraying or printing the fixing glue on the positive electrode welding strip and the negative electrode welding strip and drying them.

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