CN114613883A - Battery string interconnection method and battery string interconnection structure - Google Patents

Abstract

A method for interconnecting battery strings and a structure for interconnecting battery strings, wherein the method for interconnecting battery strings includes: providing a plurality of battery strings and arranging the plurality of dry battery strings in parallel, each battery string has a welding point on the back; providing conductive Foil connecting tape, the conductive foil connecting tape is placed on the back of several battery strings and opposite to the welding points; laser welding process is used to connect the conductive foil connecting tape and the several battery strings arranged side by side of the solder joints are welded together. The method for interconnecting the battery strings can reduce the series resistance, the parallel resistance and the shadow area, and solve the problem of thermal stress generated between the battery strings and the conductive foil connecting tape and the problem of the battery string cracking caused by welding.

Description

Battery string interconnection method and battery string interconnection structure

technical field

The invention relates to the field of solar cell manufacturing, in particular to a battery string interconnection method and a battery string interconnection structure.

Background technique

Solar cells are carriers of a new type of energy utilization. After the solar cells are prepared, they are usually connected in series to form a battery string, then multiple battery strings are welded together in parallel, and then a battery assembly is formed by laminating and assembling a junction box.

The battery string interconnection of traditional photovoltaic modules is to use a soldering iron to weld the bus bar and the battery string together. As the battery sheet tends to be thinned, the traditional welding method with soldering iron is easy to cause cracks or cracks, and it is difficult to meet the welding requirements of the thin film. In addition, during the welding process, thermal stress will be generated between the battery string and the bus bar. It is easy to cause warpage of the battery strings after welding, and at the same time, it will increase the series resistance, parallel resistance and shadow area between the battery strings.

Therefore, the existing method for interconnecting battery strings still needs to be improved.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the problems in the prior art that the series resistance, parallel resistance and shadow area between the battery strings are large after the battery strings are interconnected, and thermal stress is generated between the battery strings and the bus bars, and the battery strings are hidden due to welding. cracking problem.

In order to solve the above-mentioned technical problem, the present invention provides a method for interconnecting battery strings, including: providing a plurality of battery strings and arranging the battery strings side by side, each battery string has a plurality of rows of welding points on the back side, each row The arrangement direction of the welding points is perpendicular to the direction in which the battery strings are arranged side by side; a conductive foil connecting tape is provided, and the conductive foil connecting tape is placed on the back of the battery string and is opposite to at least one row of the welding points ; Using a laser welding process, the conductive foil connecting strips are welded together with the welding points of the plurality of battery strings arranged side by side.

Optionally, the thickness of the conductive foil connecting tape is 0.1mm-0.4mm.

Optionally, the conductive foil connecting tape includes metal foil.

Optionally, the metal foil is aluminum foil or copper foil.

Optionally, the component content of the aluminum foil is: the mass ratio of aluminum is 98.3%-99.25%, the mass ratio of silicon is 0.05%-0.3%, the mass ratio of iron is 0.7%-1.3%, and the mass ratio of copper is 0.7%-1.3%. The mass ratio of zinc is 0%-0.05%, and the mass ratio of zinc is 0%-0.05%.

Optionally, the hardness of the conductive foil connecting tape is smaller than the hardness of the welding point.

Optionally, the conductive foil connecting tape further includes: a conductive coating on the surface of the metal foil, and the conductive coating has a conductivity greater than that of the metal foil.

Optionally, the conductive coating includes a nano-conductive graphite layer, a carbon-doped silver layer or a tin-lead alloy layer.

Optionally, the electrical conductivity of the conductive foil connecting tape is 60%-70%.

Optionally, the reflectivity of the conductive foil connecting tape is 90%-99%.

Optionally, the parameters of the laser welding process include: the used laser wavelength is 0.75 μm-1000 μm, the laser welding temperature is 150°C-250°C, and the time is 10ms-900ms.

Optionally, the method further includes: before performing the laser welding process, applying pressure to a part of the surface of the conductive foil connecting tape.

Optionally, the pressing height of the pressing needle is 0.2 mm-1 mm.

Optionally, the pressing needle is a solid pressing needle, and the pressing position of the pressing needle corresponds to the conductive foil connecting tape between the welding points; or, the pressing needle is a hollow pressing needle, and the pressing needle is a hollow pressing needle. The pressed position of the needle corresponds to the welding point.

Optionally, after the laser welding process is performed, the method further includes: using an image sensor to collect at least the surface of the conductive foil connecting tape corresponding to the welding point, and judging the Check whether there is virtual welding between the welding point and the conductive foil connecting tape.

Optionally, the image sensor is placed obliquely with respect to the upper surface of the battery string, and the connection line from the center of the light-receiving surface of the image sensor to the detected soldering point is perpendicular to the extension of the conductive foil connection tape direction, the included angle between the connection line from the center of the light-receiving surface of the image sensor to the detected welding point and the back of the battery string is 30°-60°.

The present invention also provides a battery string interconnection structure, comprising: a plurality of battery strings, the battery strings are arranged side by side, the back of each battery string has a plurality of rows of welding points, and the arrangement direction of the welding points in each row is It is perpendicular to the direction in which the battery strings are arranged side by side; the conductive foil connecting tape is located on the back of the battery strings arranged side by side and is welded with at least one row of the welding points.

Optionally, the thickness of the conductive foil connecting tape is 0.1mm-0.4mm.

Optionally, the conductive foil connecting tape includes metal foil.

Optionally, the metal foil is aluminum foil or copper foil.

Optionally, the component content of the aluminum foil is: the mass ratio of aluminum is 98.3%-99.25%, the mass ratio of silicon is 0.05%-0.3%, the mass ratio of iron is 0.7%-1.3%, and the mass ratio of copper is 0.7%-1.3%. The mass ratio of zinc is 0%-0.05%, and the mass ratio of zinc is 0%-0.05%.

Optionally, the hardness of the conductive foil connecting tape is smaller than the hardness of the welding point.

Optionally, the conductive foil connecting tape further includes: a conductive coating on the surface of the metal foil, and the conductive coating has a conductivity greater than that of the metal foil.

Optionally, the conductive coating includes a nano-conductive graphite layer, a carbon-doped silver layer or a tin-lead alloy layer.

Optionally, the electrical conductivity of the conductive foil connecting tape is 60%-70%.

Optionally, the reflectivity of the conductive foil connecting tape is 90%-99%.

The technical solution of the present invention has the following advantages: in the method for interconnecting battery strings provided by the present invention, the back of each battery string has a plurality of rows of welding points, and the arrangement direction of the welding points in each row is arranged side by side with the battery strings The direction is vertical; the conductive foil connection tape is placed on the back of the battery string and opposite to at least one row of the welding points, and the conductive foil connection tape is connected to the battery strings arranged side by side by a laser welding process. The welding points are welded together, and the laser welding process heats the surface of the conductive foil connection strip by laser radiation. Since the thickness of the conductive foil connecting tape is relatively small, during the laser welding process, the heat on the surface of the conductive foil connecting tape is diffused to the back side through thermal conduction, so that the conductive foil connecting tape can be melted with the welding point. Uniform fusion, there is no protruding burr after the final fusion of the conductive foil connecting tape and the welding point, which can prevent the generation of leakage current, reduce the series resistance of the battery string and the parallel resistance of the entire battery string interconnection structure; at the same time, using the laser welding process, can To reduce the occurrence of virtual welding in the battery string interconnection structure, when a voltage is applied to the battery string interconnection structure, the near-infrared light intensity generated by each area of the battery slices in the battery string is consistent, and the formed near-infrared image has the same intensity. There are fewer dark spots, which reduces the shadow area of the battery string interconnection structure; the conductive foil connecting tape has good tensile strength or elongation, and has good thermal conduction characteristics, which can well withstand high temperature and cold. In extreme environments, performance will not be lost even in extreme environments, and there will be no deformation, melting or splitting, which can solve the problem of thermal stress between the battery string and the conductive foil connecting tape after welding and the cracking of the battery string caused by welding The problem.

Description of drawings

In order to illustrate the specific embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the specific embodiments or the prior art. Obviously, the accompanying drawings in the following description The drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

FIG. 1 is a flowchart of a method for interconnecting battery strings according to an embodiment of the present invention;

2 to 4 are schematic structural diagrams of a battery string interconnection process according to an embodiment of the present invention.

In the attached drawings:

1-battery string, 2-soldering point, 3-conductive foil connecting tape, 4-laser, 5-pressing pin, 6-image sensor.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation or a specific orientation. construction and operation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first", "second", and "third" are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

This embodiment provides a method for interconnecting battery strings. Referring to FIG. 1 , the method includes the following steps:

Step S1 : providing a plurality of battery strings and arranging the battery strings side by side, the back of each battery string has a plurality of rows of welding points, and the arrangement direction of the welding points in each row is arranged side by side with the battery strings. vertical direction;

Step S2: providing a conductive foil connection tape, and placing the conductive foil connection tape on the back of the battery string and opposite to at least one row of the welding points;

Step S3 : using a laser welding process to weld the conductive foil connecting tape and the welding points of the battery strings arranged side by side together.

In step S1 , referring to FIG. 2 , several battery strings 1 are provided, and the backsides of the battery strings 1 have welding points 2 , and the welding points 2 are on the backsides of the several battery strings 1 .

In one embodiment, each battery string 1 includes several battery slices connected in series. Cells can be of various types, including but not limited to Topcon, Perc or HJT, and can also be shingled. Taking HJT as an example, each cell includes: a semiconductor substrate layer, usually an N-type silicon wafer; a first intrinsic semiconductor layer on one side of the semiconductor substrate layer; a second intrinsic semiconductor layer on the other side of the semiconductor substrate layer ; The first doped semiconductor layer located on the side of the first intrinsic semiconductor layer away from the semiconductor substrate layer, usually an N-type doped semiconductor layer, forms a high-low junction with the N-type silicon wafer; the second intrinsic semiconductor layer is located away from the semiconductor substrate The second doped semiconductor layer on the bottom side, usually a P-type doped semiconductor layer, forms a PN junction with the N-type silicon wafer; the first transparent conductive film is located on the side of the first doped semiconductor layer away from the semiconductor substrate layer; A second transparent conductive film on the side of the second doped semiconductor layer away from the semiconductor substrate layer; a first gate line electrode located on the side of the first transparent conductive film away from the semiconductor substrate layer, the first gate line electrode includes a first main gate and a second gate line electrode. a thin grid; a second grid line electrode located on the side of the second transparent conductive film away from the semiconductor substrate layer, the second grid line electrode includes a second main grid and a second thin grid.

The main grid and the fine grid arranged on the cell are mainly used to derive the current formed by the PN junction (and the high and low junctions) by means of the transparent conductive film. The plurality of busbars are parallel to each other, the plurality of thin grids are parallel to each other, the number of the busbars is more than the number of the thin grids, and the arrangement directions of the busbars and the thin grids are perpendicular to each other. When the battery strings are connected to each other, the busbars of adjacent battery sheets are electrically connected to each other; a plurality of welding points are arranged in a direction perpendicular to the busbars. According to the arrangement of the solar cell facing the solar surface, in a specific embodiment, the welding point 2 is located between the adjacent first grids of each cell, or the welding point 2 is located in each cell between the adjacent second thin grids.

The solder joints 2 are produced by screen printing in the process stage of preparing the cell sheet. The paste used in the solder joint 2 can be silver paste with a mass ratio of silver of 65%-90%; the paste used in the solder joint 2 can also be a silver paste with a mass ratio of 15%-35%. Silver paste, the silver paste is doped with several particles, and the particles can be silver-coated nickel particles, silver-coated copper particles, or silver-coated aluminum particles; it can also be silver with a mass ratio of 50% -75% silver paste, the silver paste is doped with silver-coated glass particles, or it can be a nickel paste whose mass proportion of nickel is 60%-75%, and the nickel paste is doped with nickel-coated carbon particles.

The number of welding points 2 on each battery sheet in the battery string 1 can be appropriately increased or decreased according to actual needs.

Continuing to refer to FIG. 2 , a plurality of the battery strings 1 are arranged side by side. Specifically, a plurality of the battery strings 1 are placed on a substrate to be arranged side by side, and the back of the battery is facing upward. The substrate may be a high light transmittance glass substrate.

In step S2 , with continued reference to FIG. 2 , conductive foil connection tapes are provided, and the conductive foil connection tapes are placed on the backs of several battery strings 1 and disposed opposite to the welding points 2 .

In one embodiment, the thickness of the conductive foil connecting tape 3 is 0.1 mm-0.4 mm, for example, 0.3 mm; if the thickness of the conductive foil connecting tape 3 is less than 0.1 mm, the thickness of the conductive foil connecting tape 3 is too high. If the thickness of the conductive foil connection tape 3 is greater than 0.4mm, the thickness of the conductive foil connection tape 3 is too large, which will lead to the use of laser During the welding process, the laser cannot penetrate through the conductive foil connecting tape 3 , so that it is difficult to obtain a good welding effect between the conductive foil connecting tape 3 and the welding point.

Before welding the conductive foil connection strip 3 to the solder joint 2, the conductive foil connection strip 3 is preferably subjected to annealing treatment, and the annealing treatment of the conductive foil connection strip 3 can eliminate and improve the interior of the conductive foil connection strip 3 Legacy of tissue defects and internal stress. The conductive foil connecting tape 3 includes metal foil, the metal foil has good tensile strength or elongation, and has good thermal conduction properties, and can well withstand extreme environments of high temperature and cold, even in extreme environments. There is no loss of performance, no deformation, melting or splitting, thus ensuring the quality of the battery components.

The metal foil is aluminum foil or copper foil. In this embodiment, the metal foil is an aluminum foil, and the aluminum foil has the advantages of an oxide protective film, a soft texture, favorable for bonding, a relatively mature manufacturing technology, and a relatively low price.

In this embodiment, the component content of the aluminum foil is as follows: the mass ratio of aluminum is 98.3%-99.25%, the mass ratio of silicon is 0.05%-0.3%, and the mass ratio of iron is 0.7%-1.3%, The mass ratio of copper is 0%-0.05%, and the mass ratio of zinc is 0%-0.05%. The component content of the aluminum foil can increase the electrical conductivity of the aluminum foil, and can also increase the toughness of the aluminum foil to prevent the aluminum foil from wrinkling.

In other embodiments, the component content of the aluminum foil can also be other values.

In another embodiment, the conductive foil connecting tape 3 further includes: a conductive coating on the surface of the metal foil, the conductive coating has a conductivity greater than that of the metal foil; the conductive coating comprises nanometer Conductive graphite layers, carbon-doped silver layers or tin-lead alloy layers.

In one embodiment, the tin-lead alloy includes 60% tin and 40% lead (Sn ₆₀ Pb ₄₀ ).

Specifically, the nano-conductive graphite layer, carbon-doped silver layer or tin-lead alloy layer is evenly and delicately coated on the surface of the metal foil, the conductive coating can provide excellent static conductivity, collect active The micro-current of the substance can greatly reduce the contact resistance between the material and the current collector, and can improve the adhesion between the metal foil and the welding point, and can reduce the amount of binder used in the conductive coating. , the binder can play the role of auxiliary lubrication.

The hardness of the conductive foil connecting strip 3 is smaller than the hardness of the welding point 2 , so that the conductive foil connecting strip 3 and the welding point 2 can be easily welded together during the welding process.

In one embodiment, the conductivity of the conductive foil connecting tape 3 is 60%-70%.

In one embodiment, the reflectivity of the conductive foil connecting tape 3 is 90%-99%, the conductive foil connecting tape 3 can reflect 90%-99% of light and infrared rays, and can enhance light in the battery string The reflection in 1 increases the optical path of the light and thus achieves the effect of increasing the power of the battery string.

In a specific embodiment, the electrical conductivity of the aluminum foil used is 64.94%, the reflectivity is 98%, the density is 2.7g/cm ³ , the melting point is 660°C, the resistivity is 26.5nΩm, and the thermal conductivity is 235W/( m·K).

The density of the aluminum foil used in this example is 2.7g/cm ³ , which is smaller than the density of copper: 8.96g/cm ³ and the density of iron: 7.86g/cm ³ . Conductive foil connection tapes are lighter in mass. Before placing the conductive foil connecting tapes 3 on the backs of the plurality of battery strings 1 and opposite to the welding points 2 , straighten the conductive foil connecting tapes 3 and cut them to a specified length.

In this embodiment, the laser welding equipment is preferably a multi-function machine, which can be compatible with different materials, integrate the straightening and cutting functions of the conductive foil connecting tapes of different thicknesses, lengths and widths, and can record the usage of the conductive foil connecting tapes at the same time. and alarm function. Of course, in other embodiments, other laser welding equipment may also be used.

In step S3, the parameters of the laser welding process include: the wavelength of the laser 4 used is 0.75 μm-1000 μm, the laser welding temperature is 150°C-250°C, and the time is 10ms-900ms. The laser 4 is suitable for heating the conductive foil connecting tape 3, so that the conductive foil connecting tape 3 and the welding point 2 are welded together. In one embodiment, the instrument for emitting the laser 4 includes an infrared laser machine.

Specifically, the laser system automatically determines and fine-tunes the laser focus, so that the welding point 2 is in the focal plane of the scanning laser system, and a single one kilowatt infrared continuous wave laser is used to weld the conductive foil connecting strip 3 to the welding point 2. , so that the conductive foil connecting strip 3 and the soldering point 2 form a metal-metal interface, which can improve the conductivity.

The method for interconnecting battery strings further includes: before performing the laser welding process, pressing a portion of the conductive foil connecting tape 3 with a pressing pin 5, and the pressing pin 5 is mainly suitable for fixing the conductive foil connecting tape. 3. The shape of the pressing pin 5 can be adjusted according to the size of the soldering point 2 and the width of the conductive foil connecting tape 3. The pressing pin 5 is made of a heat-resistant material with a non-hard texture.

In one embodiment, the pressing height of the pressing needle 5 is 0.2 mm-1 mm, and the pressing height is that after the conductive foil connecting tape 3 is pressed by the pressing needle 5 relative to the conductive foil connecting tape 3 The height when pressed by the pressing needle 5, the pressing height here is the pressing height of the conductive foil connecting tape 3 relative to the conductive foil connecting tape 3 in the initial state. If the pressing height of the pressing pin 5 is less than 0.2 mm, the conductive foil connecting tape 3 and the soldering point 2 cannot be well fixed; if the pressing height of the pressing pin 5 is greater than 1 mm, it is possible The battery string 1 is crushed by pressure.

In one embodiment, the pressing needle 5 is a solid pressing needle, and the pressing position of the pressing needle 5 is corresponding to the conductive foil connecting tape 3 between the welding points 2 , and the laser 4 directly irradiates the The position of the conductive foil connection strip 3 between several of the solder joints 2 .

In this embodiment, referring to FIG. 3 and FIG. 4 in combination, the pressing needle 5 is a hollow pressing needle, and the pressing position of the pressing needle 5 corresponds to the welding point 2 . The hollow pressing needle includes a hollow area surrounded by a barrel area and a barrel area, the cross-sectional shape of the barrel area is a circular ring, the cross-sectional shape of the hollow area is a circle, and the barrel area and the hollow area are concentric nested. When the laser welding process is adopted, the laser 4 is irradiated on the conductive foil connecting tape corresponding to the position of the welding point 2 through the hollow area.

Referring to FIG. 4 , the method for interconnecting battery strings further includes: after the laser welding process is performed, further includes: using an image sensor 6 to at least capture the surface of the conductive foil connection tape corresponding to the welding point, The degree of warpage of the surface of the conductive foil connecting strip 3 determines whether there is a virtual welding between the welding point 2 and the conductive foil connecting strip 3; It is easy to obtain a complete picture of the surface of the conductive foil connection tape 3 on the solder joint 2 . The connection line from the center of the light-receiving surface of the image sensor 6 to the detected soldering point 2 is perpendicular to the extending direction of the conductive foil connecting tape 3, and the center of the light-receiving surface of the image sensor 6 to the detected The angle between the connection line of the welding point 2 and the back of the battery string 1 is 30°-60°; the angle is the level of the laser beam emitted by the image sensor 6 and the conductive foil connecting tape 3 acute angle between.

If there is a virtual welding, the laser welding process is used to re-weld the welding point 2 and the conductive foil connecting strip 3; if there is no virtual welding, the welding is completed.

It should be noted that, in one embodiment, a part of the conductive foil connection tape of the battery string interconnection structure is used as a positive electrode, and a part of the conductive foil connection tape of the battery string interconnection structure is used as a negative electrode, and the battery string interconnection structure also includes: The first lead, one end of the first lead is connected to the positive electrode; the second lead, one end of the second lead is connected to the negative electrode; the back of the battery string interconnection structure also has a number of jumpers, for example: connected perpendicular to the conductive foil A first jumper and a second jumper are arranged in the direction of the tape, and a third jumper is arranged in a direction parallel to the conductive foil connecting tape; the battery string interconnection structure further includes: a first diode, a second diode tube and a third diode; the other end of the first lead is connected to the anode of the first diode, the cathode of the first diode is connected to one end of the first jumper, the first The other end of the jumper is connected to the third jumper, the cathode of the first diode is also connected to the anode of the second diode, and the cathode of the second diode is connected to the second jumper one end of the second jumper, the other end of the second jumper is connected to the anode of the third diode, and the cathode of the third diode is connected to the other end of the second lead.

The projections of the soldering point 2 and the jumper on the semiconductor substrate layer are arranged at intervals.

This embodiment also provides a battery string interconnection structure, referring to FIG. 2 , including:

A plurality of battery strings 1, the battery strings 1 are arranged side by side, the back of each battery string 1 has a plurality of rows of welding points 2, and the arrangement direction of the welding points 2 in each row is side by side with the battery string 1 The direction of the cloth is vertical;

The conductive foil connecting strips 3 are located on the back of the battery strings 1 arranged side by side and are welded together with at least one row of the welding points 2 .

In one embodiment, each battery string 1 includes several series-connected battery slices, and each battery slice includes: a semiconductor substrate layer; a first intrinsic semiconductor layer on one side of the semiconductor substrate layer; and a first intrinsic semiconductor layer on the other side of the semiconductor substrate layer The second intrinsic semiconductor layer; the first doped semiconductor layer located on the side of the first intrinsic semiconductor layer away from the semiconductor substrate layer; the second intrinsic semiconductor layer located on the side of the second intrinsic semiconductor layer away from the semiconductor substrate layer and away from the semiconductor substrate layer Doped semiconductor layer; first transparent conductive film on the side of the first doped semiconductor layer away from the semiconductor substrate layer; second transparent conductive film on the side of the second doped semiconductor layer away from the semiconductor substrate layer; on the first transparent conductive film The first gate line electrode on the side of the film away from the semiconductor substrate layer, the first gate line electrode includes a first main gate and a first fine gate; the second gate line electrode on the side of the second transparent conductive film away from the semiconductor substrate layer, the first gate line electrode is located on the side of the second transparent conductive film away from the semiconductor substrate layer. The two grid line electrodes include a second bus grid and a second fine grid.

In a specific embodiment, the welding point 2 is located between adjacent first thin grids, or the welding point 2 is located between adjacent second thin grids.

The solder joints 2 are produced by screen printing in the process stage of preparing the cell sheet. The paste used in the solder joint 2 can be silver paste with a mass ratio of silver of 65%-90%; the paste used in the solder joint 2 can also be a silver paste with a mass ratio of 15%-35%. Silver paste, the silver paste is doped with several particles, and the particles can be silver-coated nickel particles, silver-coated copper particles, or silver-coated aluminum particles; it can also be silver with a mass ratio of 50% -75% silver paste, the silver paste is doped with silver-coated glass particles, or it can be a nickel paste whose mass proportion of nickel is 60%-75%, and the nickel paste is doped with nickel-coated carbon particles.

In one embodiment, the thickness of the conductive foil connecting tape 3 is 0.1 mm-0.4 mm, for example, 0.3 mm; if the thickness of the conductive foil connecting tape 3 is less than 0.1 mm, the thickness of the conductive foil connecting tape 3 is too high. If the thickness of the conductive foil connection tape 3 is greater than 0.4mm, the thickness of the conductive foil connection tape 3 is too large, which will lead to the use of laser During the welding process, the laser cannot pass through the conductive foil connecting tape 3 , so that the conductive foil connecting tape 3 and the welding point 2 are not easily welded.

The conductive foil connecting tape 3 is in an annealed state, and the annealing of the conductive foil connecting tape 3 can eliminate and improve the tissue defects and internal stress left in the previous process, and the conductive foil connecting tape 3 includes metal foil, so The metal foil has good tensile strength or elongation, and has good thermal conductivity, can well withstand extreme environments of high temperature and cold, and will not lose performance even in extreme environments, and will not deform, melt or split situation.

The metal foil is aluminum foil or copper foil. In this embodiment, the metal foil is aluminum foil. The aluminum foil has the advantages of an oxide protective film, soft texture, good bonding, mature manufacturing technology, and relatively low price.

In this embodiment, the component content of the aluminum foil is as follows: the mass ratio of aluminum is 98.3%-99.25%, the mass ratio of silicon is 0.05%-0.3%, and the mass ratio of iron is 0.7%-1.3%, The mass ratio of copper is 0%-0.05%, and the mass ratio of zinc is 0%-0.05%. The component content of the aluminum foil can increase the electrical conductivity of the aluminum foil, and can also increase the toughness of the aluminum foil to prevent the aluminum foil from wrinkling.

In other embodiments, the component content of the aluminum foil can also be other values.

In another embodiment, the conductive foil connecting tape 3 further includes: a conductive coating on the surface of the metal foil, the conductive coating has a conductivity greater than that of the metal foil; the conductive coating comprises nanometer Conductive graphite layers, carbon-doped silver layers, or alloys with tin-lead, eg, comprising 60% tin and 40% lead (Sn ₆₀ Pb ₄₀ ).

Specifically, the nano-conductive graphite layer, carbon-doped silver layer or tin-lead alloy is evenly and delicately coated on the surface of the metal foil, the conductive coating can provide excellent static conductivity and collect active substances. Therefore, the contact resistance between the material and the current collector can be greatly reduced, the adhesion between the two can be improved, and the amount of binder used can be reduced.

The hardness of the conductive foil connecting strip 3 is smaller than the hardness of the welding point 2 , so that the conductive foil connecting strip 3 and the welding point 2 can be easily welded together during the welding process.

In one embodiment, the conductivity of the conductive foil connecting tape 3 is 60%-70%.

In one embodiment, the reflectivity of the conductive foil connecting tape 3 is 90%-99%. The conductive foil connecting tape 3 can reflect 90%-99% of light and infrared rays, and can enhance the reflection of light in the battery string 1 and increase the optical path of the light, thus achieving the effect of increasing the power of the battery string.

In a specific embodiment, the electrical conductivity of the aluminum foil used is 64.94%, the reflectivity is 98%, the density is 2.7g/cm ³ , the melting point is 660°C, the resistivity is 26.5nΩm, and the thermal conductivity is 235W/( m·K).

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. There is no need and cannot be exhaustive of all implementations here. And the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (10)

1. A method of cell string interconnection, comprising:

providing a plurality of battery strings and arranging the battery strings side by side, wherein the back of each battery string is provided with a plurality of rows of welding points, and the arrangement direction of each row of welding points is vertical to the direction in which the battery strings are arranged side by side;

providing a conductive foil connecting strip, placing the conductive foil connecting strip on the back of the battery string and opposite to at least one row of the welding points;

and welding the conductive foil connecting band and the welding points of the plurality of battery strings which are arranged side by side together by adopting a laser welding process.

2. The method of cell string interconnection of claim 1, wherein the conductive foil connecting strip has a thickness of 0.1mm to 0.4 mm;

preferably, the conductive foil connecting tape comprises a metal foil;

preferably, the metal foil is an aluminum foil or a copper foil;

preferably, the aluminum foil comprises the following components in percentage by weight: 98.3-99.25% of aluminum, 0.05-0.3% of silicon, 0.7-1.3% of iron, 0-0.05% of copper and 0-0.05% of zinc;

preferably, the hardness of the conductive foil connecting tape is smaller than the hardness of the welding point.

3. The method of cell string interconnection of claim 2, wherein the conductive foil connection tape further comprises: the conductive coating is positioned on the surface of the metal foil, and the conductive capacity of the conductive coating is greater than that of the metal foil;

preferably, the conductive coating comprises a nano conductive graphite layer, a carbon-doped silver layer or a tin-lead alloy layer;

preferably, the conductivity of the conductive foil connecting band is 60% -70%;

preferably, the reflectivity of the conductive foil connecting strip is 90% -99%.

4. The method of claim 1, wherein the parameters of the laser welding process comprise: the laser wavelength is 0.75-1000 um, the laser welding temperature is 150-250 deg.C, and the time is 10-900 ms.

5. The method of interconnecting battery strings according to any of claims 1-4, further comprising: before the laser welding process is carried out, a pressing pin is adopted to press part of the surface of the conductive foil connecting band;

preferably, the pressing height of the pressing pin is 0.2mm-1 mm.

6. The method of claim 5, wherein the pressing pins are solid pressing pins, and the pressing positions of the pressing pins correspond to the conductive foil connecting bands between the welding points; or the pressing needle is a hollow pressing needle, and the pressing position of the pressing needle corresponds to the welding point.

7. The method of interconnecting battery strings according to any of claims 1-4, further comprising, after performing the laser welding process: adopting an image sensor to at least collect the surface of the conductive foil connecting band corresponding to the welding point, and judging whether a cold joint exists between the welding point and the conductive foil connecting band according to the warping degree of the surface of the conductive foil connecting band;

preferably, the image sensor is obliquely arranged relative to the upper surface of the battery string, a connecting line from the center of the light receiving surface of the image sensor to the detected welding point is perpendicular to the extending direction of the conductive foil connecting band, and an included angle between the connecting line from the center of the light receiving surface of the image sensor to the detected welding point and the back surface of the battery string is 30-60 degrees.

8. A battery string interconnection structure, comprising:

the battery pack comprises a plurality of battery strings, a plurality of battery strings and a plurality of welding points, wherein the battery strings are arranged side by side, the back of each battery string is provided with a plurality of rows of welding points, and the arrangement direction of each row of welding points is vertical to the direction in which the battery strings are arranged side by side;

and the conductive foil connecting band is positioned on the back surfaces of the battery strings which are arranged side by side and is welded with the welding points in at least one row.

9. The battery string interconnection structure of claim 8, wherein the conductive foil connecting strap has a thickness of 0.1mm to 0.4 mm;

preferably, the conductive foil connecting tape comprises a metal foil;

preferably, the metal foil is an aluminum foil or a copper foil;

preferably, the aluminum foil comprises the following components in percentage by weight: 98.3-99.25% of aluminum, 0.05-0.3% of silicon, 0.7-1.3% of iron, 0-0.05% of copper and 0-0.05% of zinc;

preferably, the hardness of the conductive foil connecting tape is smaller than that of the welding point.

10. The battery string interconnection structure of claim 9, wherein the conductive foil connection strap further comprises: the conductive coating is positioned on the surface of the metal foil, and the conductive capacity of the conductive coating is greater than that of the metal foil;

preferably, the conductive coating comprises a nano conductive graphite layer, a carbon-doped silver layer or a tin-lead alloy layer;

preferably, the conductivity of the conductive foil connecting strip is 60% -70%;

preferably, the reflectivity of the conductive foil connecting strip is 90% -99%.

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