Main-grid-free battery string and preparation method thereof

Abstract

According to the main-grid-free battery string and the preparation method thereof disclosed by the invention, direct contact between a grid line and a welding strip is avoided by arranging a conducting layer, so that tin-silver alloy formed by grid line silver paste and tin on the welding strip during welding of the welding strip is avoided, the over-welding problem is reduced, and electric connection between the special-shaped grid line and the welding strip is avoided by arranging an insulating layer. Furthermore, the height of the conductive layer is larger than that of the insulating layer, so that the welding strength and the electric connection between the welding strip and the conductive layer are ensured. Or the height of the conductive layer is smaller than the height of the insulating layer by adopting a specific preparation process, and meanwhile, electric contact between the welding strip and the conductive layer is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a busbar-free battery string and a preparation method thereof. Background Art

[0002] Photovoltaic welding strips, also known as welding strips, are often tinned copper strips or tin-coated copper strips and are an important component of photovoltaic modules. The welding strips are mainly used to connect the cells of photovoltaic modules, connecting the positive and negative electrodes of adjacent cells end to end to form a battery string. In the prior art, the welding strips are directly welded to the grid lines, generally directly welded to the main grid made of conductive silver paste. During the welding process, the tin on the welding strip melts and forms a tin-silver alloy with the silver paste of the grid line, thereby achieving a fixed connection between the welding strip and the grid line. However, over-welding and cold welding problems are prone to occur during the welding process. When the over-welding problem occurs, the silver paste of the grid line melts excessively, causing the area to turn black and the resistance to be too high. When the cold welding problem occurs, the welding strip fails to be welded to the grid line, resulting in the inability to achieve contact conduction in the area, thereby forming a short circuit. The above problems will reduce the photoelectric conversion efficiency and reliability of the main grid-free battery string. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a busbarless battery string, which avoids direct contact between the welding strip and the grid line while ensuring the welding tension and contact characteristics, thereby improving the photoelectric conversion efficiency and reliability of the busbarless battery string.

[0004] The technical problem to be solved by the present invention is to provide a busbarless battery string, which avoids direct contact between the welding strip and the grid line while ensuring the welding tension and contact characteristics, thereby improving the photoelectric conversion efficiency and reliability of the busbarless battery string.

[0005] In order to solve the above problems, the present invention provides a method for preparing a busbar-free battery string, comprising the following steps:

[0006] Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction;

[0007] Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction;

[0008] The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip;

[0009] A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip;

[0010] Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line;

[0011] Connecting adjacent back contact cells to obtain a busbar-free cell string;

[0012] The first conductive layer or the second conductive layer is made of one or more of copper paste, copper-silver paste, copper-aluminum paste, copper-nickel paste, copper-chromium paste, silver-aluminum paste, silver-nickel paste, silver-chromium paste, and conductive carbon paste.

[0013] In some embodiments, the height of the first conductive layer is greater than or equal to the height of the second insulating layer;

[0014] And / or, a height of the second conductive layer is greater than or equal to a height of the first insulating layer.

[0015] In some embodiments, the height of the first conductive layer is less than the height of the second insulating layer;

[0016] And / or, a height of the second conductive layer is smaller than a height of the first insulating layer.

[0017] In some embodiments, the height of the first insulating layer is 10 μm to 80 μm, and the height of the second insulating layer is 10 μm to 80 μm;

[0018] The height of the first conductive layer is 0 μm to 10 μm smaller than the height of the second insulating layer;

[0019] And / or, a height of the second conductive layer is smaller than a height of the first insulating layer by 0 μm to 10 μm.

[0020] In some embodiments, the distance between adjacent positive electrode grid lines is 0.5 mm to 5 mm;

[0021] And / or, the distance between adjacent negative electrode grid lines is 0.5 mm to 5 mm.

[0022] In some embodiments, the yield strength of the positive electrode welding strip is 30 MPa to 300 MPa;

[0023] And / or, the yield strength of the negative electrode welding strip is 30 MPa to 300 MPa.

[0024] In some embodiments, the viscosity of the slurry used for the first conductive layer is 100 Pa.s to 300 Pa.s;

[0025] And / or, the viscosity of the slurry used for the second conductive layer is 100 Pa.s to 300 Pa.s.

[0026] In some embodiments, the first conductive layer is printed on the positive grid line by screen printing, and the second conductive layer is printed on the negative grid line by screen printing. To solve the above problems, the present invention also provides a busbarless battery string, which is prepared by the preparation method of the busbarless battery string as described above.

[0027] The implementation of the present invention has the following beneficial effects:

[0028] The present invention avoids direct contact between the grid line and the welding strip by providing a conductive layer, thereby avoiding the formation of tin-silver alloy between the grid line silver paste and the tin on the welding strip during welding of the welding strip, reducing the problem of over-welding, and avoiding electrical connection between the special-shaped grid line and the welding strip by providing an insulating layer. Furthermore, the height of the conductive layer is greater than the height of the insulating layer to ensure the welding strength and electrical connection between the welding strip and the conductive layer. Alternatively, by adopting a specific preparation process, the height of the conductive layer is less than the height of the insulating layer, and electrical contact between the welding strip and the conductive layer is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of a busbar-free battery string provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "upper", "lower", "back surface", "front surface", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0032] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0033] In the present invention, “preferred” is only used to describe an implementation method or example with better effects, and it should be understood that it does not constitute a limitation on the protection scope of the present invention.

[0034] In the present invention, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0035] The present invention provides a main grid-free battery string, such as Figure 1 As shown, the following steps are included:

[0036] Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction;

[0037] Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction;

[0038] The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip;

[0039] A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip;

[0040] Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line;

[0041] Connecting adjacent back contact cells to obtain a busbar-free cell string;

[0042] The first conductive layer or the second conductive layer is made of one or more of copper paste, copper-silver paste, copper-aluminum paste, copper-nickel paste, copper-chromium paste, silver-aluminum paste, silver-nickel paste, silver-chromium paste, and conductive carbon paste.

[0043] It should be noted that the present invention avoids direct contact between the gate wire and the soldering strip by providing a conductive layer, thereby avoiding the formation of tin-silver alloy between the gate wire silver paste and the tin on the soldering strip during soldering, reducing the over-soldering problem, and avoiding electrical connection between the special-shaped gate wire and the soldering strip by providing an insulating layer.

[0044] Furthermore, the present invention arranges a conductive layer and an insulating layer on the gate line at intervals. In order to ensure the welding strength and stable electrical connection between the welding strip and the gate line, in some embodiments, the height of the first conductive layer is greater than or equal to the height of the second insulating layer; and / or, the height of the second conductive layer is greater than or equal to the height of the first insulating layer. In the above embodiment, the height of the conductive layer is greater than the height of the insulating layer, ensuring that the conductive layer can contact the welding strip. Preferably, the height of the first conductive layer is 0μm to 2μm higher than the height of the second insulating layer; and / or, the height of the second conductive layer is 0μm to 2μm higher than the height of the first insulating layer.

[0045] More preferably, in some embodiments, the height of the first conductive layer is less than the height of the second insulating layer; and / or, the height of the second conductive layer is less than the height of the first insulating layer. In some embodiments, the height of the first insulating layer is 10μm to 80μm, and the height of the second insulating layer is 10μm to 80μm; exemplary heights of the first insulating layer or the second insulating layer are 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, but not limited thereto. The height of the first conductive layer is 0μm to 10μm less than the height of the second insulating layer; and / or, the height of the second conductive layer is 0μm to 10μm less than the height of the first insulating layer. Preferably, the height of the first conductive layer is 5μm to 10μm less than the height of the second insulating layer; and / or, the height of the second conductive layer is 5μm to 10μm less than the height of the first insulating layer.

[0046] In the above embodiment, the amount of conductive layer material can be reduced and the cost can be reduced. However, after the welding tape is laid, the welding tape first contacts the insulating layer with a higher height, and then contacts the conductive layer. In this way, there is a problem that the welding tape and the conductive layer cannot contact each other. Moreover, the slurry used for the first conductive layer or the second conductive layer does not melt during the welding process and still maintains the original morphology. Therefore, it is impossible to achieve a seamless connection between the welding tape and the conductive layer by increasing the height of the welding point.

[0047] In order to solve the above problems, the present invention adopts a specific preparation process to achieve that the height of the conductive layer is less than the height of the insulating layer, and at the same time, electrical contact between the welding strip and the conductive layer is achieved, and the welding tension is relatively high, which significantly improves the reliability of the photovoltaic module.

[0048] First, the present invention controls the degree of curvature of the positive electrode welding strip or the negative electrode welding strip after laying by controlling the distance between the adjacent positive electrode grid lines or the adjacent negative electrode grid lines, so as to achieve good electrical contact performance and welding tension between the welding strip and the conductive layer. In some embodiments, the distance between the adjacent positive electrode grid lines is 0.5mm to 5mm; and / or, the distance between the adjacent negative electrode grid lines is 0.5mm to 5mm. If the distance between the adjacent positive electrode grid lines or the adjacent negative electrode grid lines is too large, the degree of curvature of the positive electrode welding strip or the negative electrode welding strip after laying will be too large, causing the welding strip to be in a bent state for a long time, affecting the life of the component; if the distance between the adjacent positive electrode grid lines or the adjacent negative electrode grid lines is too small, the degree of curvature of the positive electrode welding strip or the negative electrode welding strip after laying will be too small, resulting in the inability of direct contact between the welding strip and the conductive layer.

[0049] Next, the present invention lays welding tape on the gate wires at the above-mentioned specific spacing distances. After the welding tape is laid, it will bend to a certain extent. Welding tapes with different yield strengths have different bending degrees under the same conditions, in order to achieve good electrical contact performance and welding tension between the welding tape and the conductive layer. In some embodiments, the yield strength of the positive electrode welding tape is 30Mpa to 300Mpa; and / or, the yield strength of the negative electrode welding tape is 30Mpa to 300Mpa. If the yield strength of the welding tape is too high, it will increase the brittleness of the welding tape and reduce its reliability and durability under complex stress conditions. If the yield strength of the welding tape is too low, the gap between the welding tape and the gate wire is large after laying, and good electrical contact performance and welding tension cannot be guaranteed.

[0050] In addition, in some embodiments, the viscosity of the slurry used in the first conductive layer is 100Pa.s to 300Pa.s; and / or, the viscosity of the slurry used in the second conductive layer is 100Pa.s to 300Pa.s. When the viscosity of the slurry used in the first conductive layer or the second conductive layer is too high, the tensile strength during printing will increase, resulting in a reduction in the amount of slurry actually coated on the grid line, thereby affecting the height of the pattern after printing, and too high a viscosity will also increase the printing resistance, making the edges of the pattern after printing blurred or irregular in shape, affecting the printing accuracy and uniformity. When the viscosity of the slurry used in the first conductive layer or the second conductive layer is too low, the fluidity is too strong, and it may not be accurately deposited on the preset position of the grid line, resulting in insufficient height or blurred shape of the pattern after printing.

[0051] In some embodiments, the first conductive layer is printed on the positive electrode grid line by screen printing, and the second conductive layer is printed on the negative electrode grid line by screen printing.

[0052] In order to solve the above problems, the present invention further provides a busbar-free battery string, which is prepared by the method for preparing the busbar-free battery string as described above.

[0053] The present invention is further described below with reference to specific embodiments.

[0054] Example 1

[0055] This embodiment provides a method for preparing a busbar-free battery string, comprising the following steps:

[0056] Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction;

[0057] Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction;

[0058] The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip;

[0059] A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip;

[0060] Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line;

[0061] Connecting adjacent back contact cells to obtain a busbar-free cell string;

[0062] The first conductive layer or the second conductive layer is made of one or more of copper paste, copper-silver paste, copper-aluminum paste, copper-nickel paste, copper-chromium paste, silver-aluminum paste, silver-nickel paste, silver-chromium paste, and conductive carbon paste.

[0063] The height of the first conductive layer is 2 μm higher than the height of the second insulating layer, and the height of the second conductive layer is 2 μm higher than the height of the first insulating layer.

[0064] Example 2

[0065] This embodiment provides a method for preparing a busbar-free battery string, comprising the following steps:

[0066] Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction;

[0067] Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction;

[0068] The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip;

[0069] A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip;

[0070] Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line;

[0071] Connecting adjacent back contact cells to obtain a busbar-free cell string;

[0072] The first conductive layer or the second conductive layer is made of copper paste.

[0073] A height of the first conductive layer is smaller than a height of the second insulating layer, and a height of the second conductive layer is smaller than a height of the first insulating layer.

[0074] The height of the first insulating layer is 70 μm, and the height of the second insulating layer is 70 μm;

[0075] The height of the first conductive layer is 10 μm smaller than the height of the second insulating layer, and the height of the second conductive layer is 10 μm smaller than the height of the first insulating layer.

[0076] The distance between adjacent positive electrode grid lines is 4.5 mm, and the distance between adjacent negative electrode grid lines is 4.5 mm.

[0077] The yield strength of the positive electrode welding strip is 150 MPa, and the yield strength of the negative electrode welding strip is 150 MPa.

[0078] The viscosity of the slurry used for the first conductive layer is 180 Pa.s, and the viscosity of the slurry used for the second conductive layer is 180 Pa.s.

[0079] The first conductive layer is printed on the positive electrode grid line by screen printing, and the second conductive layer is printed on the negative electrode grid line by screen printing.

[0080] Example 3

[0081] This embodiment provides a method for preparing a busbar-free battery string, comprising the following steps:

[0082] Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction;

[0083] Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction;

[0084] The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip;

[0085] A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip;

[0086] Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line;

[0087] Connecting adjacent back contact cells to obtain a busbar-free cell string;

[0088] The first conductive layer or the second conductive layer is made of copper-silver paste.

[0089] A height of the first conductive layer is smaller than a height of the second insulating layer, and a height of the second conductive layer is smaller than a height of the first insulating layer.

[0090] The height of the first insulating layer is 50 μm, and the height of the second insulating layer is 50 μm;

[0091] The height of the first conductive layer is 5 μm smaller than the height of the second insulating layer, and the height of the second conductive layer is 5 μm smaller than the height of the first insulating layer.

[0092] The distance between adjacent positive electrode grid lines is 3.5 mm, and the distance between adjacent negative electrode grid lines is 3.5 mm.

[0093] The yield strength of the positive electrode welding strip is 210 MPa, and the yield strength of the negative electrode welding strip is 210 MPa.

[0094] The viscosity of the slurry used for the first conductive layer is 200 Pa.s, and the viscosity of the slurry used for the second conductive layer is 200 Pa.s.

[0095] The first conductive layer is printed on the positive electrode grid line by screen printing, and the second conductive layer is printed on the negative electrode grid line by screen printing.

[0096] In the description of this specification, the description with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0097] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a busbar-free battery string, characterized in that: The following steps are involved: Providing a plurality of busbar-free batteries, preparing a plurality of positive electrode grid lines and a plurality of negative electrode grid lines on the back of the busbar-free batteries, wherein the plurality of positive electrode grid lines and the plurality of negative electrode grid lines are alternately arranged in parallel along a second direction; Laying a positive electrode welding strip at the position of the first conductive layer, laying a negative electrode welding strip at the position of the second conductive layer, the positive electrode welding strip and the negative electrode grid lines are alternately arranged in parallel along a first direction, and the first direction is perpendicular to the second direction; The first conductive layer is printed at the position where the positive electrode grid line intersects with the positive electrode welding strip, and the second conductive layer is printed at the position where the negative electrode grid line contacts and intersects with the negative electrode welding strip; A first insulating layer is provided at a position where the positive electrode grid line intersects with the negative electrode welding strip, and a second insulating layer is provided at a position where the negative electrode grid line intersects with the positive electrode welding strip; Directly welding the positive electrode welding strip to the first conductive layer so that the positive electrode welding strip is electrically connected to the positive electrode grid line, and directly welding the negative electrode welding strip to the second conductive layer so that the negative electrode welding strip is electrically connected to the negative electrode grid line; Connecting adjacent back contact cells to obtain a busbar-free cell string; The first conductive layer or the second conductive layer is made of one or more of copper paste, copper-silver paste, copper-aluminum paste, copper-nickel paste, copper-chromium paste, silver-aluminum paste, silver-nickel paste, silver-chromium paste, and conductive carbon paste.

2. The method for preparing a busbar-free battery string according to claim 1, characterized in that: The height of the first conductive layer is greater than or equal to the height of the second insulating layer; And / or, a height of the second conductive layer is greater than or equal to a height of the first insulating layer.

3. The method for preparing a busbar-free battery string according to claim 1, characterized in that: The height of the first conductive layer is smaller than the height of the second insulating layer; And / or, a height of the second conductive layer is smaller than a height of the first insulating layer.

4. The method for preparing a busbar-free battery string according to claim 3, characterized in that: The height of the first insulating layer is 10 μm to 80 μm, and the height of the second insulating layer is 10 μm to 80 μm; The height of the first conductive layer is 0 μm to 10 μm smaller than the height of the second insulating layer; And / or, a height of the second conductive layer is smaller than a height of the first insulating layer by 0 μm to 10 μm.

5. The method for preparing a busbar-free battery string according to claim 4, characterized in that: The distance between adjacent positive grid lines is 0.5 mm to 5 mm; And / or, the distance between adjacent negative electrode grid lines is 0.5 mm to 5 mm.

6. The method for preparing a busbar-free battery string according to claim 4, characterized in that: The yield strength of the positive electrode welding strip is 30Mpa to 300Mpa; And / or, the yield strength of the negative electrode welding strip is 30 MPa to 300 MPa.

7. The method for preparing a busbar-free battery string according to claim 4, characterized in that: The viscosity of the slurry used in the first conductive layer is 100 Pa.s to 300 Pa.s; And / or, the viscosity of the slurry used for the second conductive layer is 100 Pa.s to 300 Pa.s.

8. The method for preparing a busbar-free battery string according to claim 1, characterized in that: The first conductive layer is printed on the positive electrode grid line by screen printing, and the second conductive layer is printed on the negative electrode grid line by screen printing.

9. A busbarless battery string, characterized in that: The battery is prepared by the method for preparing a busbar-free battery string as described in any one of claims 1 to 8.

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