Patent Description:
Along with technical development and increased demands on mobile devices, secondary batteries have been consumed more and more as energy sources. In the past, nickel cadmium batteries or hydrogen ion batteries have been used as secondary batteries, but recently, lithium ion batteries and lithium polymer batteries with a high energy density are widely used.

Among these secondary batteries, a lithium secondary battery using lithium transition metal oxide, lithium complex oxide or the like as a positive electrode active material and ensuring high output and capacity receives a great interest. Generally, a lithium secondary battery has a structure in which an electrode assembly composed of a positive electrode, a separator and a negative electrode is embedded in a sealed container together with an electrolyte.

Meanwhile, the lithium secondary battery includes a positive electrode, a negative electrode, and a separator and an electrolyte interposed therebetween. Depending on which material is used as a positive electrode active material and a negative electrode active material, the lithium secondary battery is classified into a lithium ion battery (LIB), a polymer lithium ion battery (PLIB) and so on. Typically, electrodes of these lithium secondary batteries are formed by applying a positive electrode active material or a negative electrode active material to a current collector such as aluminum or copper sheet, mesh, film, or foil, and then drying the same.

In the secondary battery module, cells accommodated in each cartridge by performing welding, bolting, riveting or the like between cell leads. In addition, when cells are arranged in series or in parallel in the secondary battery module, three members, namely the positive electrode lead made of aluminum, the negative electrode lead made of copper and the bus bar made of copper and disposed for sensing should be electrically connected by using the above method.

According to the prior art, there are various secondary battery modules, and the cartridges of the modules and bus bars for sensing are structured and located in different ways. For this reason, it is difficult to efficiently perform the connection work and the welding quality of the sensing structure is deteriorated. In addition, an unnecessary space of the secondary battery module should be provided for welding or the like, and resultantly energy density of the secondary battery module is lowered.

In addition, secondary battery modules used in energy storage devices or power storage devices have been developed for designing developing secondary battery modules as compact as possible in order to increase energy efficiency or density.

Meanwhile, in the configuration of a general secondary battery module, when welding (especially, laser welding) is performed to electrode leads (Al) (Cu) and bus bars (Cu) of cells, due to the different melting points of materials, generally, base materials are disposed in the order of an aluminum lead, a copper lead and bus bars, and then laser is irradiated from a cell lead for welding. However, if welding is performed in this order, the cell lead may be deformed first by the laser.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a method for welding electrode leads of a secondary battery module with an improved structure, in which when corresponding electrode leads of adjacent cells of a secondary battery module overlap with each other in contact, the lead made of a different material of a bus bar is partially cut, and the bus bar is located at the cut portion so that the bus bar is welded to a lead made of the same material. The present disclosure is also directed to providing a compact secondary battery module using the method.

In one aspect of the present disclosure, there is provided a compact secondary battery module according to claim <NUM>, comprising: a cartridge assembly having a plurality of cartridges stacked while accommodating cells, respectively, so that a plurality of lead overlapping portions where leads of adjacent cells overlap with each other are located at a cartridge sidewall with a predetermined pattern; and a sensing housing having a plurality of bus bars located and welded corresponding to the lead overlapping portions, respectively, the sensing housing being capable of being arranged at a side of the cartridge assembly, wherein a first lead of a cell of each lead overlapping portion is configured to have a shorter width than a second lead having a polarity opposite to the first lead as much as a predetermined width, and in a state where the sensing housing is coupled to the cartridge assembly, a corresponding bus bar comes into contact with the second lead substantially on the same line as the first lead so that a sum of the shorter width of the first lead and a length of the bus bar is substantially identical to a width of the second lead, and the second lead and the bus bar are made of the same material and are welded to each other.

Preferably, the secondary battery module may further comprise a barrier provided at a side of each cartridge to protect the cell during a welding work.

Preferably, the lead of each cell may be bent at a right angle at about <NUM> from a lead insulation portion in a state of being accommodated in the corresponding cartridge.

Preferably, the welding may be laser welding.

Preferably, in the laser welding, laser may be irradiated substantially perpendicular to the sensing housing.

Preferably, the bus bar and the second lead may be made of copper, and the first lead may be made of aluminum.

Preferably, the sensing housing may further include a battery management system (BMS) circuit board configured to manage voltage and/or temperature data of each cell detected by each bus bar.

Preferably, the sensing housing may be coupled to the cartridge assembly by means of snap-fitting or hooking.

Preferably, the secondary battery module may further comprise a sensing cover coupled to the sensing housing.

Preferably, the sensing cover may be coupled to the sensing housing by means of snap-fitting or hooking.

Preferably, two neighboring cartridges of the cartridge assembly may be coupled to each other by means of hooking.

Preferably, the cartridge assembly may further include an upper cover and a lower cover coupled to cartridges at both ends thereof by means of hooking.

In another aspect of the present disclosure, there is also provided a method for manufacturing a compact secondary battery module according to claim <NUM>, comprising: (a) preparing a plurality of cells having leads which have opposite polarities and are bent in opposite directions so that a first lead is formed to have a shorter width than a second lead as much as a predetermined width; (b) forming a cartridge assembly by stacking a plurality of cartridges accommodating cells, respectively, so that lead overlapping portions where leads of adjacent cells with opposite polarities overlap with each other are formed at a cartridge sidewall with a predetermined pattern; (c) disposing a sensing housing having a plurality of bus bars respectively installed corresponding to the lead overlapping portions at a side of the cartridge assembly so that a corresponding bus bar comes into contact with the second lead substantially on the same line as the first lead so that a sum of the shorter width of the first lead and a length of the bus bar is substantially identical to a width of the second lead, wherein the second lead and the bus bar are made of the same material; and (d) welding the second lead and the bus bar of each lead overlapping portion.

Preferably, in the step (b), a cartridge having a barrier at each sidewall where the first lead and the second lead are disposed may be used.

Preferably, in the step (a), each lead may be bent at a right angle at about <NUM> from a lead insulation portion of the cell in a state of being accommodated in the corresponding cartridge.

Preferably, the step (d) may use a laser welder.

Preferably, a laser irradiation direction of the laser welder may be substantially perpendicular to the sensing housing.

In another aspect of the present disclosure, there is also provided a compact secondary battery module, manufactured by the above method.

In another aspect of the present disclosure, there is also provided a secondary battery packing, in the compact secondary battery modules as described above are coupled.

The method for welding electrode terminals of a secondary battery module and the compact secondary battery module using the same according to embodiments of the present disclosure give the following effects.

First, a bending length of the lead of the cell is minimized, and while assembling a structure to which the bus bar is attached is assembled to a side of the cartridge assembly, a lead of the cell made of the same material as the bus bar may be welded to the bus bar so that the materials of the same kind are welded, thereby improving the welding quality of the sensing structure.

Second, an unnecessary space is minimized in the module configuration, so that the module may be compactly constructed to improve the energy efficiency.

Third, since the aluminum lead made of the same material as the bus bar may be cut off, the material cost of the lead may be reduced.

Fourth, it is possible to prevent the damage of the lead by irradiating laser to the bus bar first in a welding irradiation direction, in the order of the welding base material between the cell leads and the bus bar.

<FIG> is a perspective view showing a secondary battery module according to an embodiment of the present disclosure, and <FIG> is an exploded perspective view showing the secondary battery module according to an embodiment of the present disclosure.

Referring to <FIG> and <FIG>, a compact secondary battery module <NUM> according to an embodiment of the present disclosure includes a cartridge assembly <NUM> in which a plurality of cartridges <NUM> accommodating cells <NUM>, respectively, are stacked, and a sensing housing <NUM> coupled to a side of the cartridge assembly <NUM> by means of, for example, one-touch, snap-fitting, hooking or the like.

The cartridge assembly <NUM> is prepared by stacking a plurality of cartridges <NUM> which are made by injection-molding plastic and respectively have an accommodation portion capable of accommodating the cell <NUM>. The cartridges <NUM> may be coupled to each other by means of snap-fitting or hooking. As shown in <FIG>, in the cartridge assembly <NUM>, a plurality of lead overlapping portions <NUM> where leads <NUM>, <NUM> having opposite polarities of neighboring cells <NUM>, for example a first lead <NUM> made of aluminum and having a first polarity and a second lead <NUM> made of copper and having a second polarity opposite to the first polarity, overlap with each other are located at the sidewall of each cartridge <NUM> with a predetermined pattern.

In addition, the cartridge assembly <NUM> has an upper cover <NUM> and a lower cover <NUM>, coupled to the cartridges <NUM> at both ends by means of, for example, hooking. The upper cover <NUM> and the lower cover <NUM> are injection-molded to have substantially the same shape as the individual cartridge <NUM> of the cartridge assembly <NUM>, respectively. It will be understood by those skilled in the art that the upper cover <NUM> and the lower cover <NUM> have a function of protecting the cell <NUM> accommodated in the cartridges <NUM> at both ends and have a function and structure to finish and surround the appearance of the secondary battery module <NUM>.

<FIG> is a partial perspective view showing a sensing housing available for the secondary battery module according to an embodiment of the present disclosure, <FIG> is a partial perspective view showing a cartridge assembly available for the secondary battery module according to an embodiment of the present disclosure, and <FIG> is an enlarged view showing a portion A of <FIG>.

Referring to <FIG>, the sensing housing <NUM> is provided with a plurality of bus bars <NUM> corresponding to the lead overlapping portions <NUM>, respectively. Each bus bar <NUM> may be made of, for example, copper. In addition, the sensing housing <NUM> may be injection-molded in an approximately rectangular shape by, for example, insulating plastic, and a plurality of accommodation holes <NUM> capable of respectively accommodating the bus bars <NUM> are formed therethrough in a predetermined pattern. At an approximate center of the sensing housing <NUM>, a BMS circuit board <NUM> functioning to collect voltage and/or temperature data of each cell <NUM> sensed by the corresponding bus bar <NUM>, balancing the corresponding cell <NUM> by means of the collected data, and transferring the data to another controller (not shown) of the module is installed. The BMS circuit board <NUM> is electrically connected to one end of each bus bar <NUM>.

The first lead <NUM> and the second lead <NUM> extend and bend from a side of each cell <NUM> by a predetermined length and have a predetermined width, respectively. The first lead <NUM> of each cell <NUM> is bent by <NUM> degrees upwards on the drawing, and the second lead <NUM> is bent <NUM> degrees downwards on the drawing. As shown in <FIG>, a width W1 of the first lead <NUM> is shorter than a width W2 of the second lead <NUM>, and thus the sum of the width W1 of the first lead <NUM> and a length Lb of the bus bar <NUM>, explained later, is substantially identical to the width W2 of the second lead <NUM>.

In <FIG>, the reference sign <NUM> represents a pair of data communication ports for exchanging data between BMS circuit board <NUM>, when a plurality of secondary battery modules <NUM> are coupled, and the reference sign <NUM> represents a temperature data port for receiving a signal of a temperature sensor (not shown) for measuring an internal temperature of the secondary battery module <NUM>. The reference sign <NUM> respectively represents a positive electrode terminal and a negative electrode terminal of the secondary battery module <NUM>.

As described above, the first lead <NUM> of the cell <NUM> of each lead overlapping portion <NUM> is configured to have a shorter width than the second lead <NUM> having a polarity opposite to the first lead <NUM> as much as a predetermined width, and when the sensing housing <NUM> is coupled to the cartridge assembly <NUM>, the second lead <NUM> and the bus bar <NUM> may be welded by means of, for example, laser welding in a state where each corresponding bus bar <NUM> come into contact with the second lead <NUM> substantially on the same line as the first lead <NUM>. According to a modified embodiment, it would be understood by those skilled in the art that the first lead <NUM>, the second lead <NUM>, and the bus bars <NUM> corresponding thereto may also be coupled together by ultrasonic welding.

<FIG> is a cross-sectioned view showing a curved portion of a secondary battery module according to an embodiment of the present disclosure, and <FIG> is a schematic diagram for illustrating a welding process between a bus bar of the sensing housing and each cell lead, when the secondary battery module according to an embodiment of the present disclosure is assembled.

Referring to <FIG> and <FIG>, the sensing housing <NUM> is coupled to a side of the cartridge assembly <NUM> in a state where the first lead <NUM> and the second lead <NUM> of the cells <NUM> adjacent to the respective lead overlapping portions <NUM> overlap with each other in contact, thereby configuring the secondary battery module <NUM>. In this case, the bus bar <NUM>, the first lead <NUM> and the second lead <NUM> are positioned in order in a direction from the outside of the module <NUM>, namely from a side where laser welding is performed, toward the cartridge assembly. In this arrangement, when welding is performed between the leads <NUM>, <NUM> and between the bus bar <NUM> and the leads <NUM>, <NUM> in this deployed state, particularly when laser is irradiated in a direction substantially perpendicular to the sensing housing <NUM>, each cartridge <NUM> has a barrier <NUM> on a side thereof in order to protect the cells <NUM> accommodated in each cartridge <NUM>. It will be fully understood by those skilled in the art that the barrier <NUM> serves as a blocking wall to prevent a laser (not shown) emitting from a laser device (not shown) from being directly irradiated onto the cell <NUM>.

According to an embodiment of the present disclosure, in order to configure the secondary battery module in a compact design to enhance energy efficiency to the maximum, the leads <NUM>, <NUM> of each cell <NUM> may be bent at a right angle at a point of about <NUM> to <NUM> from a lead insulating unit <NUM> in state of being accommodated in the corresponding cartridge.

Referring to <FIG> which is an exploded perspective view showing the secondary battery module according to an embodiment of the present disclosure a the present disclosure, which is net yet completely assembled, and <FIG> which is a perspective view in a completely assembled state, in a state where the sensing housing <NUM> is coupled to the cartridge assembly <NUM>, a sensing cover <NUM> is coupled to the sensing housing <NUM> to protect the BMS circuit board <NUM> and bus bar <NUM>. The sensing cover <NUM> may be coupled to the sensing housing <NUM> by means of snap-fitting or hooking.

A method for welding electrode leads of a secondary battery module according to another embodiment of the present disclosure will be described.

First, a plurality of cells <NUM> in which a width W1 of the first lead <NUM> is shorter than a width W2 of the second lead <NUM> (for example, as much as a length Lb of each bus bar <NUM>, and leads <NUM>, <NUM> with opposite polarities are bent in opposite directions. Here, it could be fully understood that the width W1 of the first lead <NUM> may be shorter than the width W2 of the second lead <NUM> when the leads are initially manufactured, or the first lead <NUM> and the second lead <NUM> may be manufactured to have the same width and then the first lead <NUM> of each cell <NUM> may be cut by a predetermined length so that the first lead <NUM> have the width W1. In addition, in a state where the cell <NUM> is accommodated in the corresponding cartridge <NUM>, the leads <NUM>, <NUM> of the cell may be bent at a point of approximately <NUM> to <NUM>, preferably <NUM>, from the lead insulation portion <NUM> at a right angle, thereby maximizing the energy efficiency.

Subsequently, a plurality of cartridges <NUM> respectively accommodating the cells <NUM> are stacked to form the cartridge assembly <NUM> so that the leads <NUM>, <NUM> of the neighboring cells <NUM> with opposite polarities overlap with each other and thus the lead overlapping portions <NUM> are positioned in a predetermined pattern on the sidewall of the cartridges <NUM>. Each cartridge <NUM> of the cartridge assembly <NUM> may include an accommodation portion capable of accommodating the cell <NUM>, and may also have a hook or a slot so that a pair of adjacent cartridges <NUM> may be coupled to each other by means of snap-fitting or hooking, as being easily understood by those skilled in the art. In addition, at both sides of the cartridge assembly <NUM>, the upper cover <NUM> and the lower cover <NUM> which may accommodate and protect the cell <NUM> are coupled to each other by means of, for example, snap-fitting or hooking. In addition, the cartridge <NUM> at which the first lead <NUM> and the second lead <NUM> are placed may employ a cartridge having a barrier <NUM> at a side thereof so that the cell <NUM> may be protected against the laser during the laser welding operation described below.

Next, the sensing housing <NUM> having a plurality of bus bars <NUM> respectively installed corresponding to respective lead overlapping portions <NUM> is coupled to a side of the cartridge assembly <NUM> by means of snap-fitting or hooking so that the corresponding bus bar <NUM> may come into contact with the second lead <NUM> substantially on the same line as the first lead <NUM>. In this case, as described above, the bus bars <NUM> are arranged in the sensor housing <NUM> in advance with a predetermined pattern. Here, the first lead <NUM> is made of aluminum, and the second lead <NUM> and the bus bar <NUM> are made of copper.

Finally, the second lead <NUM> and the bus bar <NUM> of each lead overlapping portion <NUM> are welded. In this stage, a welding system having a plurality of welding points may be used, and also an individual laser welder may be used to perform point welding several times. In addition, it would be fully understood by those skilled in the art that a separate laser welder or welding point may be used between the first lead <NUM> and the second lead <NUM>. Moreover, the laser welder may irradiate laser in a direction substantially perpendicular to the sensing housing <NUM>.

The secondary battery modules <NUM> according to the above embodiments may electrically connected to each other in series or in parallel and are accommodated in a predetermined case to provide a compact secondary battery pack for a power storage device for a home photovoltaic (PV) solar energy panel.

The foregoing description is merely illustrative of the technical features of the present disclosure, and various modifications and variations can be made by those having ordinary skill in the art without departing from the essential characteristics of the present disclosure. Therefore, the embodiments disclosed herein are not intended to limit but to illustrate the technical features of the present disclosure, and the scope of the technical features of the present disclosure is not limited by these embodiments. The scope of the present disclosure should be construed according to the appended claims.

Claim 1:
A compact secondary battery module (<NUM>), comprising:
a cartridge assembly (<NUM>) having a plurality of cartridges (<NUM>) stacked while accommodating cells (<NUM>), respectively, so that a plurality of lead overlapping portions (<NUM>) where leads (<NUM>, <NUM>) of adjacent cells overlap with each other are located at a cartridge sidewall with a predetermined pattern; and
a sensing housing (<NUM>) having a plurality of bus bars (<NUM>) located and welded corresponding to the lead overlapping portions, respectively, the sensing housing being capable of being arranged at a side of the cartridge assembly,
characterized in that a first lead (<NUM>) of a cell of each lead overlapping portion is configured to have a shorter width (W1) than a second lead (<NUM>) having a polarity opposite to the first lead as much as a predetermined width, and in a state where the sensing housing is coupled to the cartridge assembly, a corresponding bus bar comes into contact with the second lead substantially on the same line as the first lead so that a sum of the shorter width of the first lead and a length (Lb) of the bus bar is substantially identical to a width (W2) of the second lead, and the second lead and the bus bar are made of the same material and are welded to each other.