Cell unit, main-gridless back-contact battery block, battery module and preparation method

Abstract

The present invention relates to the technical field of solar cells, and specifically provides a cell unit, a main-gridless back-contact cell block, a cell module and a preparation method. The same-polarity solder tapes and fine grids are electrically connected through a metal connection layer to achieve the unified connection of each positive fine grid and negative fine grid, thereby facilitating the series or parallel connection with the solder tapes of other cell units through the solder tapes. Moreover, the opposite-polarity solder tapes and fine grids are connected through an insulating adhesive layer and an adhesive layer. The insulating adhesive layer realizes the insulation isolation between the two, and the adhesive layer realizes the fixed connection, improving the fixed tensile force of the solder tapes; thus improving the structural stability of the entire cell unit, and simultaneously completing the fixed connection between the adhesive layer and the solder tapes while welding multiple cell units, greatly improving the production efficiency; at the same time, since the surface energy difference between the material of the insulating adhesive layer and the material of the adhesive layer is less than 20 mN / m, the tensile force of the solder tapes is effectively increased.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cells, and particularly relates to a cell unit, a main-gridless back-contact cell, a cell module and a preparation method thereof. Background Art

[0002] Existing back-contact cells with main grids adopt infrared string welding technology. After welding, the deformation of the cells is large (more than 2 mm), and external force is required for leveling. Moreover, the silver consumption of the products is very high, resulting in increased costs.

[0003] Existing main-gridless back-contact cells are initially bonded by methods such as film covering, tape sticking or dotting UV glue, and then welded by laminating with a laminator. The process welding efficiency of such cells is low, the process is complex, and the bonding stability also needs to be improved. Moreover, it is impossible to detect whether the products are in effective contact before lamination, and it can only be detected after lamination. However, if there is poor contact, repair cannot be carried out, resulting in increased battery costs.

[0004] It should be noted that this part of the content of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or well-known technology. Summary of the Invention

[0005] The purpose of the present invention is to provide a cell unit, a main-gridless back-contact cell, a cell module and a preparation method thereof, so as to solve the technical problems of low welding efficiency, complex process and unstable tensile performance of existing cells.

[0006] To achieve the above purpose, in the first aspect, the present invention provides a cell unit, including: a cell substrate, and a fine-grid electrode layer and a solder tape layer sequentially arranged on the back surface of the cell substrate;

[0007] The fine-grid electrode layer includes a plurality of positive fine grids and a plurality of negative fine grids arranged at intervals and alternately in the second direction; the solder tape layer includes a plurality of positive solder tapes and a plurality of negative solder tapes arranged at intervals and alternately in the first direction; the first direction is perpendicular to the second direction;

[0008] The area where the positive solder tape overlaps with the positive fine grid is connected through a metal connection layer, and the area where the positive solder tape overlaps with the negative fine grid is connected through an insulating glue layer and an adhesive layer, and the insulating glue layer is closer to the cell substrate than the adhesive layer;

[0009] The area where the negative solder tape overlaps with the negative fine grid is connected through a metal connection layer, and the area where the negative solder tape overlaps with the positive fine grid is connected through an insulating glue layer and an adhesive layer;

[0010] The surface energy difference between the insulating glue layer material and the adhesive layer material is less than 20 mN / m, and the surface energy of the insulating glue layer material is less than that of the adhesive layer material.

[0011] Optionally, the material of the metal connection layer is solder paste, the material of the insulating adhesive layer is one of epoxy-based insulating adhesives, silicone-based insulating adhesives, polyurethane-based insulating adhesives, and polyimide-based insulating adhesives, and the material of the bonding layer is a UV~thermal curing dual-curing adhesive or a two-component thermal curing adhesive.

[0012] Optionally, the dimensions of the bonding layer include: the dimension along the first direction is 0.2~0.5 mm, the dimension along the second direction is 0.6~3 mm, and the distance between adjacent positive and negative fine grids is 0.5 mm~0.8 mm.

[0013] In a second aspect, the present invention further provides a main-gridless back-contact battery block, including: m rows × n columns of battery cell units as described in the first aspect; wherein, n battery cell units are arranged along the first direction, and m battery cell units are arranged along the second direction;

[0014] The n battery cell units arranged along the first direction form a battery string, and a strip-shaped connection component is arranged between two adjacent battery strings arranged along the second direction. The strip-shaped connection component includes a plurality of first connection segments arranged at intervals along the first direction, and adjacent first connection segments are fixedly connected through a first insulating connector; the first connection segment is used to electrically connect the solder tapes of opposite polarities of two adjacent battery cell units along the second direction respectively.

[0015] Optionally, the first connection segment includes a first support bar and a plurality of first connection pieces fixed on the first support bar, and the first support bar is a long strip-shaped structure extending along the first direction;

[0016] The plurality of first connection pieces are arranged at intervals along the length direction of the first support bar, and the length direction of the first connection piece is perpendicular to the length direction of the first support bar, and is used to respectively butt the solder tapes of opposite polarities of two adjacent battery cell units along the second direction.

[0017] Optionally, two adjacent battery cell units along the second direction are overlapped, and the connection piece is a stepped structure or a flat plate structure.

[0018] Optionally, the first connection segment is an integral strip-shaped structure, and is used to respectively butt the solder tapes of opposite polarities of two adjacent battery cell units along the second direction.

[0019] In a third aspect, the present invention further provides a battery module, including two main-gridless back-contact battery blocks as described in the second aspect;

[0020] The two ownerless grid back contact battery blocks are the first battery block and the second battery block respectively; the first battery block and the second battery block are arranged side by side along the second direction, and the m-th rows of these two battery blocks are close to each other for splicing, and the 1st row to the m-th row of the first battery block and the second battery block are arranged in sequence from the end far away from each other to the end close to each other;

[0021] The solder tapes of every two adjacent cell units with opposite polarities in the 1st row of the first battery block and the 1st row of the second battery block are connected by a plurality of first busbars extending along the first direction;

[0022] The solder tapes of the cell units with the same polarity in the m-th row of the first battery block and the m-th row of the second battery block are connected by the same strip-shaped busbar assembly; the strip-shaped busbar assembly is located between the first battery block and the second battery block;

[0023] The strip-shaped busbar assembly includes a plurality of second busbars arranged along the second direction. Starting from the 2nd cell unit in the m-th row, the second busbars corresponding to every two cell units are connected by a conductive part or integrally formed, and the second busbars corresponding to the remaining adjacent cell units are fixedly connected by a second insulating connector, and the second busbars corresponding to the cell units in the 1st column and the n-th column are respectively led out as the entire positive electrode and negative electrode.

[0024] Optionally, the second busbar includes a second support bar and a plurality of second connecting pieces fixed on the second support bar, and the second support bar is a strip-shaped structure extending along the first direction;

[0025] The plurality of second connecting pieces are arranged at intervals along the length direction of the second support bar, and the length direction of the second connecting piece is perpendicular to the length direction of the second support bar, and is used for connecting the solder tapes with the same polarity of the first battery block and the second battery block in parallel or connecting the solder tapes with different polarities in series.

[0026] In a fourth aspect, the present invention also provides a preparation method of a battery module for preparing the battery module as described in the second aspect, including:

[0027] S100, pre-prepare a solder paste layer at a preset position of the fine grid electrode layer on the back of the cell unit where the fine grid electrode layer and the insulating glue layer have been prepared; the fine grid electrode layer includes a plurality of positive fine grids and a plurality of negative fine grids arranged at intervals and alternately along the second direction;

[0028] S200, prepare an adhesive layer on the insulating glue layer of the cell unit and cure it into a mold;

[0029] S300, prefabricate the positive electrode welding tape and the negative electrode welding tape, place the positive electrode welding tape and the negative electrode welding tape alternately at preset positions on the fine grid electrode layer at intervals along the first direction, and make contact with the corresponding solder paste layer and adhesive layer; wherein, the second direction is perpendicular to the first direction;

[0030] S400, arrange the cell units obtained in S300 in the manner of m rows × n columns. Starting from the first row or the m-th row, sequentially connect the positive electrode welding tapes and the negative electrode welding tapes of adjacent two rows of cell units one by one through a strip-shaped connection component, so as to form a main-gridless back-contact battery block;

[0031] S500, arrange a plurality of first busbars outside the first row of the main-gridless back-contact battery block, and connect the welding tapes with different polarities or the welding tapes with the same polarity of every two adjacent cell units in the first row in series or in parallel through the first busbars;

[0032] S600, place the ends without the first busbars of two identical main-gridless back-contact battery blocks side by side, and perform series or parallel connection through a long-strip-shaped busbar component, and make the long-strip-shaped busbar component connect every two cell units in series starting from the second cell unit in the m-th row of each main-gridless back-contact battery block.

[0033] Optionally, in step S400, the first connection piece of the strip-shaped connection component is directly connected to the corresponding welding tape by soldering.

[0034] Optionally, in step S600, the second connection piece of the long-strip-shaped busbar component is directly connected to the corresponding welding tape by soldering.

[0035] The embodiments of the present invention have at least the following beneficial effects:

[0036] Through the above technical solution, the present invention electrically connects the solder tapes with the same polarity and the fine grids through the metal connection layer to achieve the unified connection of the positive and negative fine grids, so as to facilitate the series or parallel connection with the solder tapes of other cell units through the solder tapes. Moreover, the solder tapes with opposite polarities and the fine grids are connected through the insulating glue layer and the bonding layer. On the one hand, the insulating glue layer realizes the insulation isolation between the two, and on the other hand, the bonding glue layer realizes the fixed connection between the two, improving the fixed tensile force of the solder tape; thereby improving the structural stability of the entire cell unit. Compared with the prior art of dotting glue on the back of the battery or coating the glue layer on the solder tape, its defect is that after series soldering one by one, dotting glue and then curing, the welding efficiency is low, the process is more complex, and the tensile performance is unstable. However, in the present invention, the bonding glue layer is arranged on the insulating glue layer, and the fixed connection between the bonding glue layer and the solder tape can be completed while welding multiple cell units at the same time, greatly improving the production efficiency; at the same time, since the surface energy of the material of the insulating glue layer and the surface energy of the material of the bonding layer differ by less than 20 mN / m, and the surface energy of the material of the insulating glue layer is less than the surface energy of the material of the bonding layer, the tensile force of the solder tape can be effectively increased, which is beneficial to improving the stability of the cell.

[0037] After the series soldering connection of the second-direction battery string in the prior art, it is necessary to perform secondary rowing of the battery string for current collection, and the spacing between the cell units in the first direction cannot be too small, because the cell units on the battery string cannot be fixed in position only by the solder tapes. Therefore, during the secondary rowing or subsequent transfer process, the cell units may contact the electrodes of adjacent cell units, causing short circuits and other defects; while in the present invention, the solder tapes with the same polarity on the entire cell unit are connected in parallel by the strip connection component, and then series-parallel connection is made with the adjacent cell units in the second direction according to the component electrical connection design. At the same time, it plays the role of current conduction. When a single point or a single solder tape on the solder tape of the cell unit fails, the strip connection component can play the role of uniformly reinforcing the current collection of the cell unit, minimizing the loss caused by the failure of the solder joint. Through the connection method of the strip connection component, the typesetting can be directly completed during the welding process without secondary typesetting, which can effectively improve the production efficiency. And zero spacing or very small spacing can be set between the cell units, or even stack connection can be performed; the effective power generation area of the battery module can be increased, and the power density of the battery module can be improved.

[0038] In the prior art, after secondary rowing, it is necessary to fix the position of the battery string with tape before lamination, otherwise the cell units may shift during the movement, causing defects; while in the present invention, the strip connection component simultaneously completes the layout and fixation of the entire battery module during the welding of the solder tape, that is, the strip connection component is used as a metal conductor and can also fix the cell units and the battery string, eliminating the processes of battery string rowing and tape fixation, and further improving the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a schematic structural diagram of a battery cell unit provided by an embodiment of the present invention;

[0041] Figure 2 Provided by an embodiment of the present invention Figure 1 It is a schematic cross-sectional view of the overlapping area between the positive electrode welding strip and the positive electrode fine grid and the negative electrode fine grid in [the content not clearly defined];

[0042] Figure 3 It is a schematic structural diagram of a battery block provided by an embodiment of the present invention;

[0043] Figure 4 It is a schematic structural diagram of a battery string of a battery block provided by an embodiment of the present invention;

[0044] Figure 5 It is a schematic structural diagram of the connection of the battery strings of a battery block along the second direction provided by an embodiment of the present invention;

[0045] Figure 6 It is a schematic structural diagram of a strip-shaped connection component between the battery strings of a battery block provided by an embodiment of the present invention;

[0046] Figure 7 It is a schematic partial method diagram of the connection between the first connection segments provided by an embodiment of the present invention;

[0047] Figure 8 It is a schematic connection diagram of the first connection piece and the welding strip of a battery cell unit provided by an embodiment of the present invention;

[0048] Figure 9 It is a schematic connection diagram of the first connection piece and the welding strip of another battery cell unit provided by an embodiment of the present invention;

[0049] Figure 10 It is a schematic connection diagram of another first connection segment and the corresponding welding strip provided by an embodiment of the present invention;

[0050] Figure 11 It is a schematic structural diagram of a battery module provided by an embodiment of the present invention;

[0051] Figure 12 It is a schematic structural diagram of a long strip-shaped current collecting component of a battery module provided by an embodiment of the present invention;

[0052] Figure 13 Schematic diagram of the second bus bar of the strip-shaped bus bar assembly of the cell module provided by the embodiment of the present invention;

[0053] Figure 14 Flow chart of a preparation method of a battery module provided by the embodiment of the present invention.

[0054] Description of reference numerals:

[0055] 100~Cell unit; 100a~Cell string; 110~Cell substrate; 121~Positive electrode solder tape; 122~Negative electrode solder tape; 131~Metal connection layer; 132~Insulating adhesive layer; 133~Adhesive layer; 140~Positive electrode fine grid; 150~Negative electrode fine grid; 200~Strip-shaped connection assembly; 210~First connection section; 211~First support bar; 212~First connection piece; 220~First insulating connector; 231~Cushion layer; 300~Battery block; 400~Strip-shaped bus bar assembly; 410~Second bus bar; 411~Second support bar; 412~Second connection piece; 420~Second insulating connector; 430~Conductive member. Detailed implementation manners

[0056] In the present invention, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0057] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0058] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Among them, the terms "optional" and "optional" all mean that they may be included or not included (or may be present or not).

[0059] The first aspect, such as Figure 1 and Figure 2 As shown, an embodiment of the present invention provides a battery cell unit 100, including: a battery substrate 110, and a fine grid electrode layer and a welding strip layer sequentially arranged on the back side of the battery substrate 110.

[0060] Specifically, the fine grid electrode layer includes a plurality of positive fine grids 140 and a plurality of negative fine grids 150 arranged alternately at intervals along the second direction, that is, a negative fine grid 150 is provided between any two adjacent positive fine grids 140, or a positive fine grid 140 is provided between any two adjacent negative fine grids 150. The welding strip layer includes a plurality of positive welding strips 121 and a plurality of negative welding strips 122 arranged alternately at intervals along the first direction, that is, a negative welding strip 122 is provided between any two adjacent positive welding strips 121, or a positive welding strip 121 is provided between any two adjacent negative welding strips 122, and all the positive fine grids 140 are connected by the same positive welding strip 121, and all the negative fine grids 150 are connected by the same negative welding strip 122. Optionally, the first direction is Figure 1 The horizontal direction in the second direction is Figure 1 In the vertical direction, namely, the positive electrode fine grid 140 and the negative electrode fine grid 150.

[0061] Furthermore, the overlapping area of the positive electrode welding strip 121 and the positive electrode fine grid 140 is connected by the metal connecting layer 131, and the overlapping area of the positive electrode welding strip 121 and the negative electrode fine grid 150 is connected by the insulating glue layer 132 and the adhesive layer 133. The insulating glue layer 132 is closer to the battery substrate 110 than the adhesive layer 133, that is, all the positive electrode fine grids 140 are electrically connected through the positive electrode welding strip 121, and the overlapping area of the positive electrode welding strip 121 and the negative electrode fine grid 150 of opposite polarity is isolated by the insulating glue layer 132 and fixed by the adhesive layer 133.

[0062] Similarly, the area where the negative electrode solder ribbon 122 overlaps with the negative electrode fine grid 150 is connected through the metal connection layer 131, and the area where the negative electrode solder ribbon 122 overlaps with the positive electrode fine grid 140 is also connected through the insulating adhesive layer 132 and the bonding layer 133. That is, all the negative electrode fine grids 150 are electrically connected through the negative electrode solder ribbon 122. The area where the negative electrode solder ribbon 122 overlaps with the positive electrode fine grid 140 of the opposite polarity is isolated by the insulating adhesive layer 132 and fixed by the bonding layer 133.

[0063] It should be noted that the surface energy difference between the material of the insulating adhesive layer 132 and the material of the bonding layer 133 is less than 20 mN / m, and the surface energy of the material of the insulating adhesive layer 132 is less than that of the material of the bonding layer 133, which is beneficial to improving the adhesive force between the adhesive and the solder ribbon and the insulating adhesive, thereby improving the solder ribbon tensile force. Among them, the surface energy difference between the two materials is less than 20 mN / m (millinewton per meter), indicating that their polarities are similar. Similar polarities mean having similar properties in terms of surface energy or molecular polarity, which helps the interaction between them and the enhancement of adhesive performance. Usually, it is to establish good intermolecular forces between the adhesive and the material surface, thereby promoting a firm bond.

[0064] The cell unit 100 provided by the embodiment of the present invention uses solder ribbons of the same polarity and fine grids to be electrically connected through the metal connection layer 131 to achieve the unified connection of each positive electrode fine grid 140 and negative electrode fine grid 150, so as to facilitate the series connection with the solder ribbons of other cell units 100 through the solder ribbon. And the solder ribbons of opposite polarities and the fine grids are connected through the insulating adhesive layer 132 and the bonding layer 133. On the one hand, the insulating adhesive layer 132 realizes the insulation isolation between them, and on the other hand, the bonding adhesive layer realizes the fixed connection between them, improving the structural stability of the entire cell unit 100. Compared with the prior art, in the method of dispensing glue on the back of the battery or coating the glue layer on the solder ribbon, its defect is that after string welding one by one, then dispensing glue and curing, the string welding efficiency is low, the process is more complex, and the solder ribbon tensile performance is unstable. While in the present invention, the bonding adhesive layer is arranged on the insulating adhesive layer 132, and the fixed connection between the bonding adhesive layer and the solder ribbon can be completed while welding multiple cell units 100 at the same time, greatly improving the production efficiency; at the same time, since the surface energy difference between the material of the insulating adhesive layer 132 and the material of the bonding layer 133 is less than 20 mN / m, and the surface energy of the material of the insulating adhesive layer 132 is less than that of the material of the bonding layer 133, the adhesive force between the adhesive and the solder ribbon and the insulating adhesive can be improved, and the solder ribbon tensile force can be further improved.

[0065] Optionally, the material of the metal connection layer 131 is solder paste, the material of the insulating adhesive layer 132 is one of epoxy resin-based insulating glue, silicone-based insulating glue, polyurethane-based insulating glue, and polyimide-based insulating glue, and the material of the bonding layer 133 is UV~thermal curing dual-curing adhesive or two-component thermal curing adhesive.

[0066] The specific characteristics of the materials of the adhesive layer 133 are described as follows: For the UV-thermal dual-curing adhesive, this material effectively combines UV curing and thermal curing, enabling the adhesive to have different curing characteristics at different stages. It not only ensures rapid curing and processing performance in the initial stage but also directly bonds with the welding through subsequent heat treatment and undergoes an irreversible cross-linking reaction to form a final stable structure, which will not melt even during subsequent high-temperature lamination processes. This effectively improves the production yield and conversion efficiency.

[0067] For the two-component thermal-curing adhesive, different cross-linking reactions are triggered by different curing temperatures to achieve primary low-temperature curing. It not only ensures rapid curing and processing performance in the initial stage but also directly bonds with the welding through subsequent secondary heat treatment and undergoes an irreversible cross-linking reaction to form a final stable structure.

[0068] Optionally, the size of the adhesive layer 133 includes: the size in the first direction is 0.2 - 0.5 mm, the size in the second direction is 0.6 - 3 mm, and the distance between adjacent positive fine grids 140 and negative fine grids 150 is 0.5 mm - 0.8 mm.

[0069] Optionally, the thickness of the insulating adhesive layer 132 is 10 - 30 μm, and the size is (0.4 - 0.6) mm × (3.5 - 4.5) mm; the thickness of the adhesive layer 133 is 10 - 40 μm, and the size is (0.2 - 0.5) mm × (0.6 - 3) mm; the size of the solder paste layer is (0.1 - 0.5 mm) × (0.5 - 2) mm, and the thickness is 20 - 50 μm.

[0070] Optionally, the infrared series soldering process conditions are: 150°C - 180°C, 1.8 - 2.5 seconds; the UV curing energy of the adhesive layer 133 is 1000 - 4000 mj; the low-temperature curing temperature of the adhesive layer 133 is: 50 - 80°C, and the time is 3 - 8 min.

[0071] For the cell unit 100 provided by the embodiment of the present invention, by setting the laminated insulation connection structure of the insulating adhesive layer 132 and the adhesive layer 133, during infrared series soldering, the adhesive layer 133 mainly plays the role of bonding between the solder tape and the cell. The adhesive used in the adhesive layer 133 is in a cured state at low temperature. Thus, even if the adhesive layer 133 shows a hot melting phenomenon due to high temperature, it will still be in a solidified state after the soldering temperature drops. When solidifying, the solder tape and the cell are bonded together by the adhesive, and there will be no secondary hot melting phenomenon.

[0072] In the second aspect, as Figures 3 - 6As shown in the figure, an embodiment of the present invention further provides a main-gridless back-contact battery block, including: m rows × n columns of battery cell units 100 as described in the first aspect; wherein, n battery cell units 100 are arranged along the first direction, and m battery cell units 100 are arranged along the second direction, and the first direction is perpendicular to the second direction (the first direction is the horizontal direction, and the second direction is the vertical direction). For the specific structure of the battery cell unit 100, reference can be made to the content of the foregoing embodiment, which will not be repeated here.

[0073] Specifically, the n battery cell units 100 arranged along the first direction form a battery string 100a, and a strip-shaped connection component 200 is arranged between two adjacent battery strings 100a arranged along the second direction. The strip-shaped connection component 200 is used to electrically connect the battery cell units 100 adjacent along the second direction to achieve the series connection of the battery cell units 100.

[0074] Further, the strip-shaped connection component 200 includes a plurality of first connection segments 210 arranged at intervals along the first direction, and adjacent first connection segments 210 are fixedly connected through a first insulating connector 220; the first connection segment 210 is used to electrically connect the solder tapes of opposite polarities of two adjacent battery cell units 100 along the second direction, thereby realizing the series connection of the battery cell units 100.

[0075] Optionally, as Figure 7 shown, the first connection segment 210 includes a first support bar 211 and a plurality of first connection pieces 212 fixed on the first support bar 211. The first support bar 211 is a long strip-shaped structure extending along the first direction and serves as the installation base for the first connection pieces 212.

[0076] The plurality of first connection pieces 212 are arranged at intervals along the length direction of the first support bar 211. The length direction of the first connection piece 212 is perpendicular to the length direction of the first support bar 211 and is used to respectively butt the solder tapes of opposite polarities of two adjacent battery cell units 100 along the second direction. Optionally, the first connection piece 212 and the first support bar 211 can be connected by welding or integrally formed into an integral structure.

[0077] As Figure 7As shown, the first set of horizontally (or in the horizontal direction) six cell units 100 in the first row form the first set of horizontally connected cell strings 100a, and the second set of horizontally (or in the horizontal direction) six cell units 100 in the second row form the second set of horizontally connected cell strings 100a. They are connected together by the first connecting piece 212 of the first connecting section 210. Then, the second set of horizontally connected cell strings 100a and the third set of horizontally connected cell strings 100a are connected together through the first connecting section 210, and this connection continues until the eleventh set of horizontally connected cell strings 100a. After forming a battery block 300, it is then connected in parallel and converged with the second battery block 300. Through the above arrangement and connection method, the positions of the cell pieces are directly fixed, making the operation simpler. The two cell units 100 in the horizontal direction of the first connecting section 210 are not electrically connected, so the adjacent two first connecting sections 210 are insulated and connected through the first insulating connecting piece 220.

[0078] Optionally, as Figure 8 shown, two adjacent cell units 100 along the second direction are overlapped. The first connecting piece 212 is a stepped structure. This kind of first connecting piece 212 requires special processing, but no additional cushion layer 231 needs to be added to form good contact and electrical connection.

[0079] Optionally, as Figure 9 shown, two adjacent cell units 100 along the second direction are overlapped, and the first connecting piece 212 is a flat plate structure. The first connecting piece 212 does not require special processing, but a cushion layer 231 needs to be set to adjust the connection position of the first connecting piece 212.

[0080] Optionally, as Figure 10 shown, the first connecting section 210 is a whole strip structure. The width of the whole strip structure is relatively wide, and no connecting piece needs to be set. The solder tapes of opposite polarities of two adjacent cell units 100 along the second direction are respectively connected to the corresponding whole strip structure, so as to realize the series connection of these two cell units ( Figure 10 in which the positive electrode solder tape 121 of one cell unit 100 and the negative electrode solder tape 122 of another cell unit 100 are connected through the first connecting section 210 of the strip-shaped connecting component 200), which can avoid the alignment connection between the connecting piece and the corresponding solder tape and make the operation more convenient.

[0081] In the third aspect, as Figure 11 shown, the embodiment of the present invention further provides a battery module, including two main-gridless back-contact battery blocks as in the second aspect.

[0082] For ease of description, the two ownerless grid back-contact battery blocks are respectively named the first battery block (the upper battery block 300 in the figure) and the second battery block (the lower battery block 300 in the figure), that is, the first battery block is in the upper position in the figure, and the second battery block is in the lower position in the figure; the first battery block and the second battery block are arranged side by side along the second direction, and the m-th rows of these two battery blocks 300 are spliced close to each other. The first rows to the m-th rows of the first battery block and the second battery block are arranged in sequence from the ends far from each other to the ends close to each other, that is, the second battery block is formed by rotating the first battery block by 180 degrees.

[0083] Specifically, the solder tapes with opposite polarities of every two adjacent cell units 100 in the first row of the first battery block and the first row of the second battery block are connected by a plurality of first busbars extending along the first direction; the solder tapes with the same polarity of the cell units 100 in the m-th row of the first battery block and the cell units 100 in the m-th row of the second battery block are connected by the same long-strip busbar assembly 400; the long-strip busbar assembly 400 is located between the first battery block and the second battery block and serves as the lead-out structure for the solder tapes with the same polarity.

[0084] Specifically, as Figure 12 shown, the long-strip busbar assembly 400 includes a plurality of second busbars 410 arranged along the first direction ( Figure 12 schematically shows Figure 11 the 1st to the 3rd second busbars 410 from left to right, a total of 3 second busbars 410). Starting from the 2nd cell unit 100 in the m-th row, the second busbars 410 corresponding to every two cell units 100 are connected by a conductive member 430 or integrally formed ( Figure 12 the 2nd second busbar 410 and the 3rd second busbar 410 in Figure 12 are connected by a conductive member 430), and the second busbars 410 corresponding to the remaining adjacent cell units 100 are fixedly connected by a second insulating connector 420 ( Figure 12 the 1st second busbar 410 and the 2nd second busbar 410 in Figure 12 are connected by a second insulating connector 420), and the second busbars 410 corresponding to the cell units 100 in the 1st column and the nth column are respectively used as the positive and negative electrodes of the whole to be led out.

[0085] Taking Figure 11 as an example, Figure 11 each battery block 300 in Figure 11 includes 11 horizontal battery strings 100a, and these 11 horizontal battery strings 100a are arranged in sequence along the second direction. Each battery string 100a includes 6 cell units 100 arranged along the first direction. Among them, the battery string 100a in the first row of the first battery block is located at Figure 11 the uppermost part of Figure 11 , and the battery string 100a in the first row of the second battery block is located at Figure 11At the bottom. The m-th (m = 11) row of battery strings 100a of the first battery block and the m-th (m = 11) row of battery strings 100a of the second battery block are located Figure 11 at the middle position, and they are connected in parallel through a long strip-shaped busbar assembly 400.

[0086] Optionally, continue to refer to Figure 13 , the second busbar 410 includes a second support bar 411 and a plurality of second connection pieces 412 fixed on the second support bar 411. The second support bar 411 is a long strip-shaped structure extending along the first direction.

[0087] The plurality of second connection pieces 412 are arranged at intervals along the length direction of the second support bar 411. The length direction of the second connection piece 412 is perpendicular to the length direction of the second support bar 411, and is used to connect the solder tapes of the same polarity of the first battery block and the second battery block in parallel or connect the solder tapes of different polarities in series.

[0088] In a fourth aspect, as Figure 14 shown, the embodiment of the present invention further provides a preparation method for a battery module, which is used to prepare the battery module as in the third aspect. The preparation method includes the following steps:

[0089] S100, pre-prepare a solder paste layer at a preset position of the fine grid electrode layer on the back of the battery cell 100 that has been prepared with a fine grid electrode layer and an insulating adhesive layer 132; the fine grid electrode layer includes a plurality of positive fine grids 140 and a plurality of negative fine grids 150 that are alternately arranged at intervals along the second direction.

[0090] S200, prepare an adhesive layer 133 on the insulating adhesive layer 132 of the battery cell 100 and cure it into a mold.

[0091] S300, prefabricate a positive solder tape 121 and a negative solder tape 122, and alternately place the positive solder tape 121 and the negative solder tape 122 at intervals along the first direction at the preset positions on the fine grid electrode layer, and contact the corresponding solder paste layer and the adhesive layer 133; wherein, the second direction is perpendicular to the first direction.

[0092] S400, arrange the battery cells 100 obtained in S300 in an m-row × n-column manner. Starting from the first row or the m-th row, sequentially connect the positive solder tapes 121 and the negative solder tapes 122 of adjacent two rows of battery cells 100 one by one through the strip-shaped connection assembly 200, so as to form a main-gridless back-contact battery block.

[0093] S500, arrange a plurality of first busbars on the outside of the first row of the main-gridless back-contact battery block, and connect the solder tapes of different polarities or the solder tapes of the same polarity of every two adjacent battery cells 100 in the first row in series or in parallel through the first busbars.

[0094] For S600, the ends of two identical main-gridless back-contact battery blocks without the first bus bar are placed side by side, and are connected in series or in parallel through a strip-shaped bus bar assembly 400, and the strip-shaped bus bar assembly 400 makes every two cell units 100 starting from the second cell unit 100 in the m-th row of their respective main-gridless back-contact battery blocks connected in series.

[0095] Optionally, in step S400, the first connecting piece 212 of the strip-shaped connecting assembly 200 is directly connected to the corresponding solder tape by soldering.

[0096] Optionally, in step S600, the second connecting piece of the strip-shaped bus bar assembly 400 is directly connected to the corresponding solder tape by soldering.

[0097] Compared with the prior art in which glue is applied to the back of the battery or the glue layer is coated on the solder tape, the defect is that it is first welded and then the glue is applied and cured, the process is more complex and the tensile performance is unstable. In the present invention, the adhesive glue layer is arranged on the insulating glue layer 132, and the fixed connection between the adhesive glue layer and the solder tape can be completed simultaneously during the series soldering process; and when the solder tape is in series soldering; at the same time, since the surface energy difference between the material of the insulating glue layer 132 and the material of the adhesive layer 133 is less than 20 mN / m, and the surface energy of the material of the insulating glue layer 132 is less than the surface energy of the material of the adhesive layer 133, the tensile force of the solder tape can be effectively increased.

[0098] After the series soldering connection of the second-direction battery string 100a in the prior art, the battery string 100a needs to be re-arranged for bus bar connection, and the spacing between the cell units 100 in the first direction cannot be too small, because the cells on the battery string 100a are only connected by solder tapes and cannot be fixed in position. Therefore, during the re-arrangement or subsequent transfer process, the cell unit 100 may contact the electrodes of the adjacent cell unit 100, causing short circuits and other defects. In the present invention, the strip-shaped connecting assembly 200 parallel-welds the solder tapes of the same polarity on the entire cell unit 100, and then makes series-parallel connections with the adjacent cell units 100 in the second direction according to the component electrical connection design, which plays the role of current conduction at the same time. When a single point or a single solder tape of the solder tapes on the cell unit 100 fails, the strip-shaped connecting assembly 200 can play the role of evenly reinforcing the current collection of the cell unit 100, minimizing the loss caused by the failure of the solder joint of the electrode. Through the connection method of the strip-shaped connecting assembly 200, the typesetting can be directly completed during the welding process without the need for secondary typesetting, which can effectively improve the production efficiency, and the spacing between the cell units 100 can be set to zero or very small, and even stack connection can be performed; the effective power generation area can be increased and the battery power density can be improved.

[0099] In the prior art, after the secondary film arrangement, it is necessary to fix the position of the battery string 100a with tape before lamination. Otherwise, the battery cell unit 100 may shift during the movement, resulting in defects. However, in the present invention, the strip-shaped connecting component 200 simultaneously completes the layout and fixation of the entire battery module during the soldering of the solder tape. That is, the strip-shaped connecting component 200 is used as a metal conductor and can also fix the battery cell unit 100 and the battery string 100a, eliminating the processes of arranging the battery string 100a and fixing it with tape, and further improving the production efficiency.

[0100] It should be noted that the secondary film arrangement means that conventional battery cells need to first arrange the longitudinal battery strings for the first film arrangement and series welding, and then perform the secondary film arrangement according to the battery module layout (i.e., arrange the battery strings according to the layout) and then perform welding and current collection as shown in the following figure. The present invention can perform unified welding after the first film arrangement, or in other words, when the battery units are arranged and welded according to the battery module layout, the layout is also fixed, and there is no need for secondary film arrangement like the conventional packaging method.

[0101] Embodiment 1

[0102] The battery cell unit 100 provided by the embodiment of the present invention includes: a battery substrate 110, and a fine grid electrode layer and a solder tape layer sequentially arranged on the back surface of the battery substrate 110;

[0103] The fine grid electrode layer includes a plurality of positive fine grids 140 and a plurality of negative fine grids 150 arranged at intervals and alternately in the second direction; the solder tape layer includes a plurality of positive solder tapes 121 and a plurality of negative solder tapes 122 arranged at intervals and alternately in the first direction; the first direction is the horizontal direction, and the second direction is the vertical direction.

[0104] The area where the positive solder tape 121 overlaps with the positive fine grid 140 is connected through a metal connection layer 131, and the area where the positive solder tape 121 overlaps with the negative fine grid 150 is connected through an insulating glue layer 132 and an adhesive layer 133, and the insulating glue layer 132 is closer to the battery substrate 110 than the adhesive layer 133;

[0105] The area where the negative solder tape 122 overlaps with the negative fine grid 150 is connected through a metal connection layer 131, and the area where the negative solder tape 122 overlaps with the positive fine grid 140 is connected through an insulating glue layer 132 and an adhesive layer 133;

[0106] The surface energy difference between the material of the insulating adhesive layer 132 and the material of the bonding layer 133 is about 15 mN / m, and the surface energy of the material of the insulating adhesive layer 132 is less than that of the material of the bonding layer 133. This can effectively ensure the adhesion force between the bonding layer 133, the insulating adhesive layer 132 and the solder tape, effectively improve the tensile force of the solder tape, further ensure the stability of the solder tape welding, and thus improve the battery efficiency and production yield. It should be noted that the surface energy of the materials in the embodiments of the present invention is measured by the contact angle measurement method, and the specific measurement method refers to the European standard EN828:2013.

[0107] In addition, the thickness of the insulating adhesive layer 132 is 20 μm, the thickness of the bonding layer 133 is 30 μm, the size of the insulating adhesive layer 132 is 0.4 mm × 4 mm, and the size of the bonding layer 133 is 0.3 mm × 1.5 mm. Embodiment 1 is the optimal setting, thereby ensuring the effects of firm bonding, light transmittance, battery efficiency, etc.

[0108] In addition, the embodiments of the present invention provide a battery module prepared by using the battery cell unit 100. In this battery module, the battery cell units 100 of the battery block 300 are arranged in a 11-row × 6-column manner, and the number of battery cell units 100 is 66 (i.e., the specific numbers of m and n). The 6 battery cell units 100 in each row are welded and fixedly connected to the 6 battery cell units 100 in the next row through the strip-shaped connection assembly 200; the battery cell units 100 in each row are connected in series with the adjacent battery cell units 100 in the next row.

[0109] In addition, n battery cell units 100 arranged along the first direction form a battery string 100a. A strip-shaped connection assembly 200 is provided between two adjacent battery strings 100a arranged along the second direction. The multiple first connection pieces 212 of the strip-shaped connection assembly 200 directly connect the corresponding solder tapes of the adjacent battery cell units 100 along the second direction, and the first connection piece 212 overlaps with the corresponding solder tape for lapping.

[0110] Embodiment 2

[0111] Referring to the battery cell unit 100 of Embodiment 1, the difference is that the surface energy difference between the material of the insulating adhesive layer 132 and the material of the bonding layer 133 is about 19.5 mN / m.

[0112] Embodiment 3

[0113] Referring to the battery cell unit 100 of Embodiment 1, the difference is that the thicknesses of the bonding layer 133 and the insulating adhesive layer 132 are 40 μm and 30 μm respectively.

[0114] Embodiment 4

[0115] Referring to the cell unit 100 of Embodiment 1, the difference is that the sizes between the bonding layer 133 and the insulating adhesive layer 132 are 0.2 mm × 1.0 mm and 0.35 mm × 3 mm respectively.

[0116] Embodiment 5

[0117] Referring to the cell unit module 100 of Embodiment 1, the difference is that the cells of adjacent cell strings 100a do not adopt an overlapping connection method, and the spacing between cell units 100 in the first direction is 0.5 mm.

[0118] Embodiment 6

[0119] Referring to the cell module of Embodiment 1, the difference is that the number of cell units 100 is 6 × 3 × 2 = 36 (i.e., m = 6 and n = 3).

[0120] Embodiment 7

[0121] Referring to the cell module of Embodiment 5, the difference is that the first connection segment 210 is a whole strip-shaped structure, which is used to butt the solder tapes of opposite polarities of two adjacent cell units in the second direction respectively.

[0122] Comparative Example 1

[0123] Referring to the cell unit 100 of Embodiment 1, the difference is that the cell unit 100 does not set the solder tape first. Instead, 11 cell units 100 in the first column in the vertical direction are directly connected in series welding to form a cell string 100a in the second direction, and then the cell strings 100a in the second column to the sixth column are successively connected in series welding; then the bonding adhesive layer and the solder tape are cured and connected, and then the cells are re-arranged in a 6 × 11 layout to form the battery block 300 arrangement. The spacing between cell units 100 in the first direction is 2 mm, and then the cell strings 100a are subjected to bus bar welding and tape fixing to prevent the displacement and short circuit defects of the cell units 100.

[0124] Comparative Example 2

[0125] Referring to the cell unit 100 of Comparative Example 1, the difference is that the bonding layer 133 is not set on the cell unit 100. After the cell string 100a is formed by series welding, glue is applied or coated on the upper surface of the solder tape and then cured and connected, and then the second re-arrangement is carried out; the bonding adhesive is a thermosetting bonding adhesive.

[0126] Comparative Example 3

[0127] Referring to the cell unit 100 of Embodiment 1, the difference is that the thickness of the insulating adhesive layer 132 is 10 μm, the thickness of the bonding layer 133 is 15 μm, the size of the bonding layer 133 is 0.3 mm × 1.5 mm, and the size of the insulating adhesive layer 132 is 0.3 mm × 1.5 mm.

[0128] Comparative Example 4

[0129] Referring to the cell unit 100 of Example 1, the difference is that the surface energy of the insulating adhesive layer 132 material is about 25 mN / m different from the surface energy of the bonding layer 133 material.

[0130] Comparative Example 5

[0131] Referring to the cell unit 100 of Example 1, the difference is that the surface energy of the insulating adhesive layer 132 material is less than the surface energy of the bonding layer 133 material.

[0132] Test Example

[0133] The cell performance obtained from the above examples and comparative examples was tested to obtain the relevant data in Table 1 below. (Taking Example 1 as the reference 1 for comparison) Specifically as follows:

[0134] Table 1 Statistical Table of Performance Indicators of Different Examples and Comparative Examples

[0135]

[0136] From the above results, it can be seen that compared with the comparative examples, adopting the embodiment scheme of the present invention can simplify the production process, effectively improve the tensile force of the welding tape and reduce the pulling of the connecting welding tape when moving the typeset battery blocks during the production process, which is beneficial to effectively improving the reliability of the welding of the welding tape, and then improving the production yield, production efficiency and battery power density. Further, according to Example 1 and Examples 2 to 5, by adopting the preferred adhesive layer and the thickness and size settings of the insulating adhesive layer 132 and the lap joint connection scheme of the present invention, the matching of various performances can be further synergistically optimized, which is more conducive to simultaneously obtaining the best production yield, production efficiency and battery power density. Further, according to Example 1 and Example 6, the preferred scheme of the present invention is applicable to battery cell modules of different plate types. Further, according to Example 5 and Example 7, the preferred scheme of the present invention can be applied to strip connection component structures of different shapes. Further, according to Example 1 and Example 3, the thickness of the bonding layer 133 and the insulating adhesive layer 132 in the preferred scheme of the present invention is beneficial to taking into account the material cost and ensuring the bonding force.

[0137] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A battery module, characterized in that, It includes two main-gridless back-contact battery blocks; The main-gridless back-contact battery block includes: m rows × n columns of cell units; wherein, n cell units are arranged along the first direction, and m cell units are arranged along the second direction; the cell unit includes: a cell substrate, and a fine-grid electrode layer and a solder strip layer sequentially arranged on the back surface of the cell substrate; the fine-grid electrode layer includes a plurality of positive fine grids and a plurality of negative fine grids arranged at intervals and alternately along the second direction; the solder strip layer includes a plurality of positive solder strips and a plurality of negative solder strips arranged at intervals and alternately along the first direction; the first direction is perpendicular to the second direction; The n cell units arranged along the first direction form a battery string, and a strip-shaped connection component is arranged between two adjacent battery strings arranged along the second direction. The strip-shaped connection component includes a plurality of first connection segments arranged at intervals along the first direction, and adjacent first connection segments are fixedly connected through a first insulating connector; the first connection segment is used to electrically connect the solder strips with opposite polarities of two adjacent cell units along the second direction; the first connection segment includes a first support bar and a plurality of first connection pieces fixed on the first support bar. The first support bar is a long strip-shaped structure extending along the first direction; the plurality of first connection pieces are arranged at intervals along the length direction of the first support bar, and the length direction of the first connection piece is perpendicular to the length direction of the first support bar, and is used to respectively butt the solder strips with opposite polarities of two adjacent cell units along the second direction; The two main-gridless back-contact battery blocks are respectively a first battery block and a second battery block; the first battery block and the second battery block are arranged side by side along the second direction, and the m-th rows of these two battery blocks are close to each other for splicing, and the 1st row to the m-th row of the first battery block and the second battery block are sequentially arranged from the end far from each other to the end close to each other; The solder strips with opposite polarities of every two adjacent cell units in the 1st row of the first battery block and the 1st row of the second battery block are connected through a plurality of first busbars extending along the first direction; The solder strips with the same polarity of the cell units in the m-th row of the first battery block and the m-th row of the second battery block are connected through the same long strip-shaped busbar assembly; the long strip-shaped busbar assembly is located between the first battery block and the second battery block; The long strip-shaped busbar assembly includes a plurality of second busbars arranged along the second direction. Starting from the 2nd cell unit in the m-th row, the second busbars corresponding to every two cell units are connected by a conductive part or integrally formed, and the second busbars corresponding to the remaining adjacent cell units are fixedly connected through a second insulating connector, and the second busbars corresponding to the 1st column and the n-th column cell units are respectively used as the positive and negative leads of the whole; 2. The battery module according to claim 1, characterized in that, The second busbar includes a second support bar and a plurality of second connection pieces fixed on the second support bar. The second support bar is a long strip-shaped structure extending along the first direction; A plurality of the second connecting pieces are arranged at intervals along the length direction of the second support bar, and the length direction of the second connecting piece is perpendicular to the length direction of the second support bar, and is used for connecting the solder tapes with the same polarity of the first battery block and the second battery block in parallel or connecting the solder tapes with different polarities in series.

3. The battery module according to claim 1, characterized in that For the main-gridless back-contact battery block, two adjacent cell units along the second direction are overlapped, and the connecting piece is a stepped structure or a flat structure.

4. The battery module according to claim 1, wherein, For the main-gridless back-contact battery block, the first connecting section is a whole strip-shaped structure and is used for respectively butting the solder tapes with opposite polarities of two adjacent cell units along the second direction.

5. The battery module according to any one of claims 1 to 4, characterized in that, For the cell unit, the area where the positive solder tape overlaps with the positive fine grid is connected through a metal connection layer, and the area where the positive solder tape overlaps with the negative fine grid is connected through an insulating glue layer and an adhesive layer, and the insulating glue layer is closer to the battery substrate than the adhesive layer; The area where the negative solder tape overlaps with the negative fine grid is connected through a metal connection layer, and the area where the negative solder tape overlaps with the positive fine grid is connected through an insulating glue layer and an adhesive layer; The surface energy difference between the insulating glue layer material and the adhesive layer material is less than 20 mN / m, and the surface energy of the insulating glue layer material is less than the surface energy of the adhesive layer material.

6. The battery module according to claim 5, characterized in that, For the cell unit, the material of the metal connection layer is solder paste, the material of the insulating glue layer is one of epoxy resin-based insulating glue, silicone-based insulating glue, polyurethane-based insulating glue, and polyimide-based insulating glue, and the material of the adhesive layer is UV~thermal curing dual-curing adhesive or two-component thermal curing adhesive.

7. The battery module according to claim 6, wherein, For the cell unit, the size of the adhesive layer includes: the size along the first direction is 0.2~0.5 mm, the size along the second direction is 0.6~3 mm, and the distance between adjacent positive fine grids and negative fine grids is 0.5 mm~0.8 mm.

8. A method for preparing a battery module, which is used to prepare the battery module as described in claim 6, characterized in that, Including: S100, pre-preparing a solder paste layer at a preset position of the fine grid electrode layer on the back of the cell unit where the fine grid electrode layer and the insulating glue layer have been prepared; the fine grid electrode layer includes a plurality of positive fine grids and a plurality of negative fine grids arranged at intervals and alternately along the second direction; S200, preparing an adhesive layer on the insulating glue layer of the cell unit and curing and forming; S300, prefabricating a positive solder tape and a negative solder tape, placing the positive solder tape and the negative solder tape at intervals and alternately along the first direction at the preset positions on the fine grid electrode layer, and contacting the corresponding solder paste layer and adhesive layer; wherein, the second direction is perpendicular to the first direction; S400, arranging the cell units obtained in S300 in the manner of m rows × n columns, starting from the first row or the mth row, and sequentially connecting the positive solder tapes and the negative solder tapes of two adjacent rows of cell units one by one through a strip-shaped connecting component, so as to form a main-gridless back-contact battery block; S500, arranging a plurality of first busbars outside the first row of the main-gridless back-contact battery block, and connecting the solder tapes with different polarities or the solder tapes with the same polarity of every two adjacent cell units in the first row in series through the first busbars; In S600, one ends of two identical back-contact cells without main busbars are placed side by side, and are connected in series or parallel through a strip-shaped busbar assembly, and the strip-shaped busbar assembly connects every two cell units in series starting from the second cell unit in the m-th row of each back-contact cell without a main busbar.

9. A method for preparing a battery module according to claim 8, characterized in that, Including: In step S400, the first connecting piece of the strip-shaped connecting assembly is directly connected to the corresponding solder tape by soldering.

10. A method for preparing a battery module according to claim 8, wherein, Including: In step S600, the second connecting piece of the strip-shaped busbar assembly is directly connected to the corresponding solder tape by soldering.

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