BACKGROUND
1. Field
[0001] Aspects of embodiments of the present invention relate to a battery pack.

2. Description of the Related Art
[0002] Secondary batteries are chargeable/dischargeable batteries  unlike primary batteries that are unable to be charged. Such secondary batteries have been widely used in small high-tech electronic devices  such as mobile phones  personal digital assistants (PDAs)  laptop computers  and the like  and in energy storing systems.
[0003] Secondary batteries may be a type of single battery or a plurality of batteries that are electrically connected to one another according to types of external electronic devices in which the secondary batteries are used. For example  small devices  such as mobile phones  are operable with output and capacity of one battery for a certain amount of time  whereas medium or large devices  such as laptop computers  portable digital versatile disc (DVD) players  small personal computers (PCs)  and the like  use a plurality of batteries due to large output and capacity.
[0004] Battery packs including a protection circuit or the like connected to a plurality of battery cells which may be connected in series and/or in parallel  are used. In order to ensure for such battery packs to have sufficient output and capacity when they are manufactured  electrical connection between the plurality of battery cells has to be stably performed. In addition  as the demand for smaller and thinner external electronic devices increases  there is a need for battery packs that are smaller and thinner.

SUMMARY
[0005] According to an aspect of embodiments of the present invention  a battery pack includes a lead plate  or lead electrode  which may be used in a small space and easily and stably connected at connecting portions  and an overall size of the battery pack may thereby be reduced.
[0006] According to an embodiment of the present invention  a battery pack includes: a battery cell; a protection circuit module electrically connected to the battery cell; a case accommodating the battery cell; and a lead electrode electrically connected between the protection circuit module and the battery cell  the lead electrode including a plurality of end connecting portions  each connected to the battery cell or the protection circuit module  and a body portion connecting the plurality of end connecting portions and having a thickness greater than a thickness of the end connecting portions.
[0007] A width of an end connecting portion of the plurality of end connecting portions may be greater than a width of the body portion. In one embodiment  the end connecting portion of the plurality of end connecting portions is connected to the protection circuit module.
[0008] The body portion may include first and second overlapping metallic layers. In one embodiment  an end connecting portion of the plurality of end connecting portions includes a connecting portion of the first metallic layer that extends beyond and is not overlapped with the second metallic layer. In one embodiment  the first and second metallic layers are integrated together by at least one of welding or a conductive adhesive.
[0009] The battery cell may include an electrode tab at a first side thereof  and an end connecting portion of the plurality of end connecting portions may be connected to the electrode tab. In one embodiment  the battery cell further includes a terrace portion at the first side  and a width of the body portion is less than or equal to a width of the terrace portion.
[0010] An end connecting portion of the plurality of end connecting portions and the body portion may be bent with respect to each other.
[0011] A width of the body portion may be less than or equal to a thickness of the battery cell.
[0012] The lead electrode may further include an insulating material surrounding the body portion  and at least a portion of each of the end connecting portions may be exposed outside the insulating material.
[0013] The battery pack may further include an auxiliary lead tab electrically connected between an end connecting portion of the plurality of end connecting portions and the battery cell. In one embodiment  the auxiliary lead tab has a hole formed therein  and the case includes a protrusion engaged in the hole to fix a position of the auxiliary lead tab relative to the case. In one embodiment  the battery pack further includes a temperature cutoff (TCO) electrically connected between the end connecting portion of the plurality of end connecting portions and the auxiliary lead tab.
[0014] An end connecting portion of the plurality of end connecting portions may have a hole formed therein  and the case may include a protrusion engaged in the hole to fix a position of the end connecting portion of the plurality of end connecting portions relative to the case.
[0015] According to another embodiment of the present invention  a lead electrode for a battery pack includes: a plurality of end connecting portions; and a body portion connecting the plurality of end connecting portions and having a thickness greater than a thickness of the end connecting portions.
[0016] A width of an end connecting portion of the plurality of end connecting portions may be greater than a width of the body portion.
[0017] The body portion may include first and second overlapping metallic layers. In one embodiment  the first and second metallic layers are integrated together by at least one of welding or a conductive adhesive.
[0018] The lead electrode may further include an insulating material surrounding the body portion  at least a portion of each of the end connecting portions being exposed outside the insulating material.

BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The accompanying drawings  together with the specification  illustrate some exemplary embodiments of the present invention  and  together with the description  serve to explain aspects and principles of the present invention.
[0020] FIG. 1A is an exploded perspective view schematically illustrating a lead plate according to an embodiment of the present invention;
[0021] FIG. 1B is a perspective view of the lead plate of FIG. 1A;
[0022] FIG. 1C is a perspective view of the lead plate of FIG. 1A that is coated with an insulating material;
[0023] FIG. 2A is an exploded perspective view schematically illustrating a lead plate according to another embodiment of the present invention;
[0024] FIG. 2B is a perspective view of the lead plate of FIG. 2A;
[0025] FIG. 2C is a perspective view of the lead plate of FIG. 2A that is coated with an insulating material;
[0026] FIG. 3A is an exploded perspective view schematically illustrating a lead plate according to another embodiment of the present invention;
[0027] FIG. 3B is a perspective view of the lead plate of FIG. 3A;
[0028] FIG. 3C is a perspective view of the lead plate of FIG. 3A that is coated with an insulating material;
[0029] FIG. 4 is an exploded perspective view schematically illustrating a battery pack according to an embodiment of the present invention;
[0030] FIG. 5A is a perspective view of a lead plate  a temperature cutoff (TCO)  and auxiliary lead tabs of the battery pack of FIG. 4;
[0031] FIG. 5B is an exploded perspective view of the lead plate  the temperature cutoff (TCO)  and the auxiliary lead tabs of FIG. 5A;
[0032] FIG. 6 is a perspective view of another lead plate of the battery pack of FIG. 4;
[0033] FIG. 7 is a partially exploded perspective view of a portion of the battery pack of FIG. 4;
[0034] FIG. 8 is an exploded perspective view schematically illustrating a battery pack according to another embodiment of the present invention;
[0035] FIG. 9 is a perspective view of a lead plate of the battery pack of FIG. 8; and
[0036] FIG. 10 is a perspective view of another lead plate of the battery pack of FIG. 8.

Description of Reference Numerals Indicating Some Elements in the Drawings
[0037]
10  20  30: lead plate 11  21  31: first metallic layer
12  22  32: second metallic layer 10a  20a  30a: body portion
10b  20b  30b: electrode connecting portion
10c  20c  30c: terminal connecting portion
S: insulating material 400  500: battery pack
410  510: battery cells 420  520: protection circuit module
431  531: lower case 432  532: upper case
440  540: first lead plate 442: TCO
444: auxiliary lead tabs 450  550: second lead plate
460  560: third lead plate 570: fourth lead plate
580: fifth lead plate

DETAILED DESCRIPTION
[0038] The present invention will be described more fully hereinafter with reference to the accompanying drawings  in which some exemplary embodiments of the invention are shown and described. However  as those skilled in the art would realize  the described embodiments may be modified in various different ways  all without departing from the spirit or scope of the present invention. Accordingly  the drawings and description are to be regarded as illustrative in nature and not restrictive. The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of other embodiments. Like reference numerals designate like elements throughout the specification. As used herein  the singular forms "a " "an " and "the" are intended to include the plural forms as well  unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" as used herein specify the presence of stated features  integers  steps  operations  members  components  and/or groups thereof  but do not preclude the presence or addition of one or more other features  integers  steps  operations  members  components  and/or groups thereof. It will be understood that  although the terms first  second  third  etc. may be used herein to describe various elements  components  regions  layers  and/or sections  these elements  components  regions  layers  and/or sections should not be limited by these terms. These terms are only used to distinguish one element  component  region  layer  or section from another element  component  region  layer  or section. It will be understood that when an element  such as a layer  a region  or a substrate  is referred to as being "on " "connected to " or "coupled to" another element  it may be directly on  connected or coupled to the other element or one or more intervening elements may be present.
[0039] FIG. 1A is an exploded perspective view schematically illustrating a lead plate 10 according to an embodiment of the present invention; FIG. 1B is a perspective view of the lead plate 10 illustrated in FIG. 1A; and FIG. 1C is a perspective view of the lead plate 10 illustrated in FIG. 1A that is coated with an insulating material.
[0040] The lead plate 10  or lead electrode  is a medium that electrically connects elements of a battery pack. The lead plate 10 may electrically connect a plurality of battery cells or a battery cell and a protection circuit module. Alternatively  the plurality of battery cells and the protection circuit module may be concurrently (e.g.  simultaneously) electrically connected to one another by the lead plate 10  as described below.
[0041] Referring to FIG. 1A  the lead plate 10 may include at least two metallic layers. In one embodiment  the lead plate 10 includes a first metallic layer 11 and a second metallic layer 12. The first and second metallic layers 11 and 12 are formed of a conductive material such that a current flows through the first and second metallic layers 11 and 12. The conductive material  in one embodiment  may be nickel (Ni)  iron (Fe)  aluminum (Al)  copper (Cu)  or an alloy thereof. The first metallic layer 11 and the second metallic layer 12 may be integrated with each other by welding  such as spot welding  ultrasonic welding  laser welding  soldering  or the like. In one embodiment  the first and second metallic layers 11 and 12 may include the same material so as to improve an adhesion property thereof (e.g.  by welding). In another embodiment  the first metallic layer 11 and the second metallic layer 12 may be integrated with each other by using a conductive adhesive.
[0042] The first metallic layer 11 may include a first body portion 11a and a terminal connecting portion 11c that extends in a direction from the first body portion 11a. The first body portion 11a may be approximately T-shaped  and a width of the first body portion 11a is smaller than a width of the terminal connecting portion 11c.
[0043] The second metallic layer 12 may include a second body portion 12a that may be approximately T-shaped so as to overlap with the first body portion 11a. Ends of the second body portion 12a are shorter than corresponding ends of the first body portion 11a  and  thus  when the first and second metallic layers 11 and 12 overlap with each other  the ends of the first body portion 11a constitute electrode connecting portions 11b that do not overlap with the second metallic layer 12 and are exposed to the outside. The electrode connecting portions 11b may be electrically connected to electrodes of the battery cell by welding.
[0044] When the first and second metallic layers 11 and 12 overlap with each other  a portion of the first metallic layer 11 that does not overlap with the second metallic layer 12 may also be the terminal connecting portion 11c as well as the ends of the first body portion 11a. The terminal connecting portion 11c extends in a direction from the first body portion 11a and has a greater width than that of the first body portion 11a. The terminal connecting portion 11c may be electrically connected to terminals of the protection circuit module by welding.
[0045] Referring to FIG. 1B  the first and second metallic layers 11 and 12 overlap with each other and are integrated with each other such that the lead plate 10 is formed. The first body portion 11a and the second body portion 12a overlap with each other such that a body portion 10a of the lead plate 10 is formed  and ends of the first body portion 11a that do not overlap with the second body portion 12a  that is  the electrode connecting portions 11b and the terminal connecting portion 11c of the first body portion 11a  constitute electrode connecting portions 10b and a terminal connecting portion 10c of the lead plate 10  respectively. The body portion 10a of the lead plate 10 is formed as two metallic layers  whereas each of the electrode connecting portions 10b and the terminal connecting portion 10c of the lead plate 10 is formed as one metallic layer.
[0046] Each of the electrode connecting portions 10b and the terminal connecting portion 10c of the lead plate 10 is formed as one metallic layer  and  thus  the electrode connecting portions 10b and the terminal connecting portion 10c may be easily welded. If each of the electrode connecting portions 10b and the terminal connecting portion 10c is formed as two metallic layers  welding of the metallic layers that constitute the electrode connecting portions 10b or the terminal connecting portion 10c and welding of elements to be welded to the metallic layers  such as electrodes of the battery cell or terminals of the protection circuit module  have to be performed. Thus  the number of welding processes increases  and an adhesive force therebetween is lowered compared to an adhesive force of the electrode connecting portions 10b and the terminal connecting portion 10c  each of which is formed as one metallic layer.
[0047] The body portion 10a of the lead plate 10 is formed by overlapping two metallic layers with each other and  thus  the body portion 10a has an increased thickness  and a width of the lead plate 10 may be reduced compared to a width of a lead plate formed as one metallic layer. That is  the body portion 10a of the lead plate 10 includes at least two metallic layers such that the width of the lead plate 10 may be reduced while preventing or reducing an increase in resistance of the lead plate 10. On the other hand  since the terminal connecting portion 10c is formed as one metallic layer  resistance of the terminal connecting portion 10c may be increased compared to resistance of the body portion 10a of the lead plate 10 (that is if the terminal connecting portion 10c is of the same width as that of the body portion 10a). In order to prevent or reduce such an increase in resistance of the terminal connecting portion 10c  a width Wc of the terminal connecting portion 10c  in one embodiment  is greater than a width Wa of the body portion 10a.
[0048] Referring to FIG. 1C  the lead plate 10 excluding a portion for electrical connection may be surrounded or coated by an insulating material "S " thereby preventing or substantially preventing a short circuit between peripheral devices. For example  the insulating material "S" may surround the lead plate 10 excluding the electrode connecting portions 10b and the terminal connecting portion 10c of the lead plate 10. The insulating material "S" may include a suitable material  such as polyimide (PI). In one embodiment  a length of the terminal connecting portion 10c is long such that the insulating material "S" may surround the remaining regions of the terminal connecting portion 10c while an end of the terminal connecting portion 10c is exposed to the outside (i.e. an end of the terminal connecting portion 10c is not surrounded or coated by the insulating material "S").
[0049] According to another embodiment of the present invention  the length of the terminal connecting portion 10c may be short  similar to the electrode connecting portions 10b. In this case  the terminal connecting portion 10c may not be surrounded by the insulating material "S" and may be exposed to the outside  as in the electrode connecting portions 10b  and the width Wc of the terminal connecting portion 10c may not be greater than the width Wa of the body portion 10a.
[0050] FIG. 2A is an exploded perspective view schematically illustrating a lead plate 20 according to another embodiment of the present invention; FIG. 2B is a perspective view of the lead plate 20 illustrated in FIG. 2A; and FIG. 2C is a perspective view of the lead plate 20 illustrated in FIG. 2A that is coated with an insulating material.
[0051] Referring to FIG. 2A  the lead plate 20  or lead electrode  may be formed by integrating a first metallic layer 21 and a second metallic layer 22 with each other  such as by welding or by using a conductive adhesive. In one embodiment  the first metallic layer 21 and the second metallic layer 22 may be formed of the same metallic material so as to improve an adhesion property thereof (e.g.  by welding).
[0052] The first metallic layer 21 may include a first body portion 21a and a terminal connecting portion 21c that extends in a direction from the first body portion 21a. The first body portion 21a may be approximately I-shaped  and the terminal connecting portion 21c may be L-shaped.
[0053] The second metallic layer 22  in one embodiment  includes a second body portion 22a that may be approximately I-shaped so as to overlap with the first body portion 21a  and the second body portion 22a is shorter than the first body portion 21a such that  when the first and second metallic layers 21 and 22 overlap with each other  ends of the first body portion 21a may constitute electrode connecting portions 21b that are not overlapped with the second metallic layer 22 and are exposed to the outside.
[0054] Referring to FIG. 2B  in one embodiment  the lead plate 20 is formed by overlapping the first and second metallic layers 21 and 22 with each other and includes a body portion 20a that is formed as two metallic layers  and electrode connecting portions 20b and a terminal connecting portion 20c  each of which is formed as one metallic layer. The electrode connecting portions 20b may extend from both ends of the body portion 20a and may be electrically connected to the electrodes of the battery cell  and the terminal connecting portion 20c may extend from a side of the body portion 20a and may be electrically connected to the terminals of the protection circuit module.
[0055] In one embodiment  the body portion 20a of the lead plate 20 is formed by overlapping two metallic layers with each other and thus has an increased thickness  and a width of the lead plate 20 may be reduced compared to a width of a lead plate formed as one metallic layer. That is  the body portion 20a of the lead plate 20 includes at least two metallic layers such that the width of the lead plate 20 may be reduced while preventing or reducing an increase in resistance of the lead plate 20. On the other hand  since the terminal connecting portion 20c is formed as one metallic layer  resistance of the terminal connecting portion 20c may be increased compared to resistance of the body portion 20a of the lead plate 20 (i.e. if the terminal connecting portion 20c is of same width as that of the body portion 20a). In order to prevent or reduce such an increase in resistance of the terminal connecting portion 20c  a width Wc of the terminal connecting portion 20c  in one embodiment  is greater than a width Wa of the body portion 20a.
[0056] Referring to an enlarged portion of FIG. 2B  the terminal connecting portion 20c and the body portion 20a may be bent approximately perpendicular to each other. Accordingly  even though a plurality of battery cells and a protection circuit module may be arranged in various shapes  the lead plate 20 may be positioned in a proper position.
[0057] Referring to FIG. 2C  the lead plate 20 excluding a portion for electrical connection may be surrounded or coated by an insulating material "S" so as to prevent or substantially prevent a short circuit between peripheral devices. In one embodiment  the terminal connecting portion 20c extends to a length  and the remaining regions of the lead plate 20 excluding the end of the terminal connecting portion 20c may be surrounded by the insulating material "S" (that is an end of the terminal connecting portion 20c is not surrounded or coated by the insulating material "S").
[0058] FIG. 3A is an exploded perspective view schematically illustrating a lead plate 30 according to another embodiment of the present invention; FIG. 3B is a perspective view of the lead plate 30 illustrated in FIG. 3A; and FIG. 3C is a perspective view of the lead plate 30 illustrated in FIG. 3A that is coated with an insulating material.
[0059] Referring to FIG. 3A  the lead plate 30  or lead electrode  may be formed by integrating a first metallic layer 31 and a second metallic layer 32 with each other  such as by welding or by using a conductive adhesive. In one embodiment  the first metallic layer 31 and the second metallic layer 32 may be formed of the same metallic material so as to improve an adhesion property thereof (e.g.  by welding).
[0060] The first metallic layer 31 may include a first body portion 31a  electrode connecting portions 31b that extend in a direction from the first body portion 31a  and a terminal connecting portion 31c that extends from a side of the first body portion 31a. The first body portion 31a  in one embodiment  may be approximately I-shaped  and the terminal connecting portion 31c may be L-shaped. The second metallic layer 32 includes a second body portion 32a that may be approximately I-shaped so as to overlap with the first body portion 31a.
[0061] In one embodiment  the lead plate 30 is formed by overlapping the first and second metallic layers 31 and 32 with each other  and the terminal connecting portion 31c and the electrode connecting portions 31b of the first metallic layer 31 are not overlapped with the second metallic layer 32.
[0062] Referring to FIG. 3B  in one embodiment  the lead plate 30 is formed by overlapping the first and second metallic layers 31 and 32 with each other and includes a body portion 30a that is formed as two metallic layers  and electrode connecting portions 30b and a terminal connecting portion 30c  each of which is formed as one metallic layer. The electrode connecting portions 30b may protrude in a direction from the body portion 30a and may be electrically connected to the electrodes of the battery cell. The terminal connecting portion 30c may extend from a side of the body portion 30a and may be electrically connected to the terminals of the protection circuit module.
[0063] In one embodiment  the body portion 30a of the lead plate 30 is formed by overlapping two metallic layers with each other and thus has an increased thickness  and a width of the lead plate 30 may be reduced compared to a width of a lead plate formed as one metallic layer. That is  the body portion 30a of the lead plate 30 includes at least two metallic layers such that the width of the lead plate 30 may be reduced while preventing or reducing an increase in resistance of the lead plate 30. On the other hand  since the terminal connecting portion 30c is formed as one metallic layer  resistance of the terminal connecting portion 30c may be increased compared to resistance of the body portion 30a of the lead plate 30 (i.e. if the terminal connecting portion 30c is of same width as that of the body portion 30a). In order to prevent or reduce such an increase in resistance of the terminal connecting portion 30c  a width Wc of the terminal connecting portion 30c  in one embodiment  is greater than a width Wa of the body portion 30a.
[0064] Referring to an enlarged portion of FIG. 3B  the electrode connecting portions 30b may be bent toward the body portion 30a of the lead plate 30. Accordingly  even though a plurality of battery cells and a protection circuit module may be arranged in various shapes  the lead plate 30 may be positioned in a proper position.
[0065] For example  in one embodiment  the electrode connecting portions 30b may be bent toward the body portion 30a so as to be approximately parallel to the body portion 30a of the lead plate 30. In one embodiment  a width Wb of the electrode connecting portion 30b may be the same as or less than the width Wa of the body portion 30a such that the bent electrode connecting portions 30b do not protrude in a widthwise direction of the body portion 30a.
[0066] Referring to FIG. 3C  the lead plate 30 excluding a portion for electrical connection may be surrounded or coated by an insulating material "S" so as to prevent or substantially prevent a short circuit between peripheral devices. In one embodiment  the terminal connecting portion 30c extends to a length  and the remaining regions of the lead plate 30 excluding the end of the terminal connecting portion 30c may be surrounded by the insulating material "S" ((i.e. an end of the terminal connecting portion 30c is not surrounded or coated by the insulating material "S").
[0067] The lead plates 10  20  and 30 described above with respect to FIGS. 1A through 1C  FIGS. 2A through 2C  and FIGS. 3A through 3C  respectively  may include at least two metallic layers so as to increase thicknesses of the body portions 10a  20a  and 30a and to reduce widths thereof. An increase in resistance of the terminal connecting portions 10c  20c  and 30c may be prevented or substantially prevented while the widths of the body portions 10a  20a  and 30a may be reduced  such that electrodes of the battery cell or the battery cell and the protection circuit module may be electrically connected to each other in a narrow space.
[0068] In addition  each of the electrode connecting portions 10b  20b  and 30b and the terminal connecting portions 10c  20c  and 30c to be welded is formed as a one metallic layer such that the electrode connecting portions 10b  20b  and 30b may be easily electrically connected to the electrodes of the battery cell by welding  and the terminal connecting portions 10c  20c  and 30c may be easily connected to the terminals of the protection circuit module by welding.
[0069] In one embodiment  the widths of the terminal connecting portions 10c  20c  30c  each of which is formed as one metallic layer  are greater than the widths of the body portions 10a  20a  and 30a each of which are formed as two metallic layer such that resistance may be prevented or substantially prevented from being increased when currents that have flowed through the body portions 10a  20a  and 30a flow through the terminal connecting portions 10c  20c  and 30c.
[0070] A battery pack using lead plates  or lead electrodes  according to embodiments of the present invention is described below.
[0071] FIG. 4 is an exploded perspective view schematically illustrating a battery pack 400 according to an embodiment of the present invention.
[0072] Referring to FIG. 4  the battery pack 400 includes a plurality of battery cells 410  a protection circuit module 420  a lower case 431 and an upper case 432  and a first lead plate 440  a second lead plate 450  and a third lead plate 460 that electrically connect the plurality of battery cells 410 and the protection circuit module 420 to each other.
[0073] The battery cells 410  in one embodiment  may be polymer cells. For example  the battery cells 410 may be manufactured by accommodating an electrode assembly in which a positive electrode plate (not shown) and a negative electrode plate (not shown) are alternately stacked by interposing a separator (not shown) between the positive electrode plate and the negative electrode plate  thereby separating the positive electrode plate and the negative electrode plate from each other. The electrode assembly may be wound in the form of a jelly roll  and accommodated in a pouch in which an electrolyte is accommodated. Electrode tabs 411 including a positive electrode tab 411a and a negative electrode tab 411b that are electrically connected to the positive electrode plate and the negative electrode plate  respectively  may be taken out from a side of the battery cell 410.
[0074] The protection circuit module 420 may prevent or substantially prevent occurrence of overheating and explosion due to overcharge  overdischarge or overcurrent of the plurality of battery cells 410. The protection circuit module 420 may include a safety element including a passive element  such as a resistor or capacitor  or an active element  such as a field effect transistor  or direct circuits.
[0075] The protection circuit module 420 may include terminals 422 to be electrically connected to the plurality of battery cells 410. The protection circuit module 420 may include connectors (not shown) to be electrically connected to an external electronic device.
[0076] The lower case 431 and the upper case 432 face each other and accommodate the plurality of battery cells 410 and the protection circuit module 420. An accommodation space  in which the plurality of battery cells 410 and the protection circuit module 420 are accommodated  is defined by the lower case 431  and the lower case 431 may include a barrier "B" that prevents or substantially prevents a short circuit between peripheral devices.
[0077] The lower case 431 and the upper case 432 may include an electrically insulating material. For example  the lower case 431 and the upper case 432 may be formed of an injection-molded material of insulating resin  such as a plastic. In one embodiment  the lower case 431 and the upper case 432 may be manufactured of an insulating film having rigidity (e.g.  predetermined rigidity). In one embodiment  the lower case 431 and the upper caser 432 may include a thin metal material of which an outer surface is coated with an insulating film.
[0078] The first through third lead plates 440  450  and 460 may electrically connect the plurality of battery cells 410 and may concurrently (e.g.  simultaneously) connect the battery cells 410 and the protection circuit module 420. For example  the first lead plate 440 may be electrically connected to positive electrodes of battery cells 410 (e.g.  three battery cells 410) disposed at the left side of the battery pack 400  and the second lead plate 450 may be electrically connected to negative electrodes of battery cells 410 (e.g.  three battery cells 410) disposed at the right side of the battery pack 400  thereby constituting large current terminals of the battery pack 400. The third lead plate 460 may be electrically connected to negative electrodes of battery cells 410 (e.g.  three battery cells 410) disposed at the left side of the battery pack 400 and to positive electrodes of battery cells 410 (e.g.  three battery cells 410) disposed at the right side of the battery pack 400  thereby connecting battery cells 410 (e.g.  six battery cells 410) in series.
[0079] In one embodiment  the battery pack 400 illustrated in FIG. 4 includes six battery cells 410. However  the illustrated embodiment is merely one example of the present invention  and the battery pack 400 is not limited to the structure and number of battery cells 410 illustrated in FIG. 4.
[0080] FIG. 5A is a perspective view of the first lead plate 440  a temperature cutoff (TCO)  and auxiliary lead tabs of the battery pack 400 illustrated in FIG. 4; and FIG. 5B is an exploded perspective view of the first lead plate 440  the TCO  and the auxiliary lead tabs of FIG. 5A.
[0081] Referring to FIGS. 5A and 5B  in one embodiment  the first lead plate 440  or lead electrode  is formed by integrating two metallic layers with each other such that a body portion 440a  electrode connecting portions 440b  and a terminal connecting portion 440c of the first lead plate 440 are formed. In one embodiment  the body portion 440a of the first lead plate 440 may be formed as two metallic layers  and each of the electrode connecting portions 440b and the terminal connecting portion 440c may be formed as one metallic layer. The first lead plate 440  excluding a portion for electrical connection (e.g. excluding a portion which is to be electrically connected such as by welding)  may be surrounded or coated by an insulating material "S." A structure of the first lead plate 440 may be the same or similar to that described above with respect to FIGS. 1A through 1C  and  thus  further description thereof will not be provided here.
[0082] The first lead plate 440  in one embodiment  includes electrode connecting portions 440b (e.g.  three electrode connecting portions 440b) so as to be electrically connected to positive electrodes of battery cells 410 (e.g.  three battery cells 410). In one embodiment  auxiliary lead tabs 444 may be further provided to electrically connect the electrode connecting portions 440b to the positive electrodes of the battery cells 410.
[0083] In one embodiment  the auxiliary lead tabs 444 may be formed of a single metallic layer of which one side is electrically connected to the electrode connecting portions 440b  and the other side is directly welded to the positive electrode tab 411a that is a positive electrode of the battery cell 410.
[0084] In one embodiment  a temperature cutoff (TCO) 442 may be connected between one side of the auxiliary lead tabs 444 and the electrode connecting portions 440b. The TCO 442 may be connected to one side of the auxiliary lead tabs 444 and the electrode connecting portions 440b  such as by welding. The TCO 442 may serve as a fuse that cuts off a current when a temperature of the battery cells 410 exceeds a reference temperature.
[0085] In one embodiment  a hole "h" is formed in each of the auxiliary lead tabs 444. The hole may be of any suitable shape. For example  the hole "h" may have a circular shape  a "*" shape  a "+" shape  or a combined shape thereof. When the hole "h" of the auxiliary lead tab 444 is engaged with a protrusion (not shown) formed in the lower case 431  one side of the auxiliary lead tab 444 may be welded to the positive electrode tab 411a of the battery cell 410.
[0086] In one embodiment  the auxiliary lead tab 444 and the first lead plate 440 are mechanically connected to each other  such as by welding  and  thus  a position of the first lead plate 440 may be fixed. Thus  even when an external vibration is transferred to the battery pack 400  an electrical connection between the first lead plate 440 and the battery cells 410 may be stably maintained.
[0087] The first lead plate 440 includes the terminal connecting portion 440c so as to electrically connect the battery cells 410 and the protection circuit module 420. The terminal connecting portion 440c extends from a side of the first lead plate 440  and an end of the terminal connecting portion 440c that is not surrounded or coated by the insulating material "S" may be electrically connected to the protection circuit module 420  such as by welding.
[0088] As described above  the first lead plate 440 is electrically connected to the TCO 442 and the auxiliary lead tabs 444. In one embodiment  such a structure may apply to the second lead plate 450 such that the second lead plate 450 is electrically connected to the negative electrode tab 411b that is a negative electrode of the battery cells 410 disposed at a side (e.g.  the right side) of the battery pack 400. The second lead plate 450 may have a same or similar structure as that of the first lead plate 440 described above and shown in FIGS. 5A and 5B  and  thus  further description thereof will not be provided here.
[0089] FIG. 6 is a perspective view of the third lead plate 460 of the battery pack 400 illustrated in FIG. 4.
[0090] Referring to FIG. 6  in one embodiment  the third lead plate 460  or lead electrode  is formed by integrating two metallic layers with each other such that a body portion 460a  electrode connecting portions 460b  and a terminal connecting portion 460c of the third lead plate 460 are formed. In one embodiment  the body portion 460a of the third lead plate 460 may be formed as two metallic layers  and each of the electrode connecting portions 460b and the terminal connecting portion 460c may be formed as one metallic layer. In one embodiment  the third lead plate 460  excluding a portion for electrical connection (i.e. excluding a portion to which is to be electrically connected such as by welding)  may be surrounded or coated by an insulating material "S."
[0091] Referring to FIGS. 4 and 6  some of the electrode connecting portions 460b of the third lead plate 460 are electrically connected to positive electrodes of the battery cells 410  and the other electrode connecting portions 460b of the third lead plate 460 are electrically connected to negative electrodes of the battery cells 410. For example  electrode connecting portions 460b (e.g.  three electrode connecting portions 460b) disposed at the left side of the battery pack 400 may be welded to negative electrodes of battery cells 410 (e.g.  three battery cells 410)  and the other electrode connecting portions 460b (e.g.  three electrode connecting portions 460b) disposed at the right side of the battery pack 400 may be welded to positive electrodes of the battery cells 410 (e.g.  three remaining battery cells 410).
[0092] In one embodiment  a hole "h" is formed in at least one of the electrode connecting portions 460b and may be engaged with a protrusion (not shown) formed in the lower case 431. The hole "h" may have a circular shape  a "*" shape  a "+" shape  or a combined shape thereof. By engaging the hole "h" and the protrusion (not shown) with each other  a position of the third lead plate 460 may be fixed. Thus  even when an external vibration is transferred to the battery pack 400  an electrical connection between the third lead plate 460 and the battery cells 410 may be stably maintained.
[0093] The terminal connecting portion 460c of the third lead plate 460 extends from the body portion 460a in a direction and  in one embodiment  has a greater width than a width of the body portion 460a. An end of the terminal connecting portion 460c may be electrically connected to the protection circuit module 420  such as by welding.
[0094] FIG. 7 is a partially exploded perspective view of a portion of the battery pack 400 illustrated in FIG. 4.
[0095] Referring to FIG. 7  the plurality of battery cells 410 are accommodated in the lower case 431. According to one embodiment  two of the battery cells 410 that are electrically connected to each other by the first lead plate 440  are accommodated in the lower case 431 such that the electrode tab 411 is directed rightward  and the other one battery cell (not shown) that is electrically connected to the first lead plate 440 may be accommodated in the lower case 431 such that the electrode tab 411 is directed backward. A terrace portion 413 may be disposed at a side of the battery cell 410  such as at a side from which the electrode tab 411 is taken out.
[0096] The battery cells 410 may be electrically connected to each other by the first lead plate 440. For example  the auxiliary lead tabs 444 that are electrically connected to the electrode connecting portions 440b of the first lead plate 440 may be welded to the electrode tab 411 of the battery cells 410 such that the plurality of battery cells 410 are electrically connected to each other. In one embodiment  the TCO 442 may be disposed between the auxiliary lead tab 444 and the electrode connecting portion 440b  as described above.
[0097] The first lead plate 440 may be disposed on the terrace portion 413 of each of the battery cells 410. In one embodiment  a width of the first lead plate 440  for example  a width Wa of the body portion 440a is the same as or less than a width Wt of the terrace portion 413. In one embodiment  two metallic layers overlap with each other such that the width Wa of the body portion 440a of the first lead plate 440 may be small while preventing or reducing an increase in resistance of the first lead plate 440. Thus  the first lead plate 440 may be disposed in a narrow space of the terrace portion 413.
[0098] When the first lead plate 440 is disposed on the terrace portion 413  the auxiliary lead tabs 444 that are connected to the first lead plate 440 may be disposed on the electrode tab 411  and one end of the auxiliary lead tab 444 may be welded to the positive electrode tab 411a.
[0099] In one embodiment  a through hole "H" may be formed in the lower case 431 so as to facilitate welding of the auxiliary lead tabs 444 and the electrode tab 411. Upper and lower portions of a region in which the end of the auxiliary lead tab 444 and the positive electrode tab 411a overlap with each other may be welded by using a welding rod (not shown). In this case  the welding rod that is disposed in the lower portion of the region may contact the electrode tab 411 via the through hole "H " and the welding rod that is disposed in the upper portion of the region may contact the end of the auxiliary lead tab 444.
[00100] In one embodiment  a hole "h" may be formed in the auxiliary lead tab 444. For example  the hole "h" may be formed in the auxiliary lead tab 444  and a protrusion "p" may be formed in the lower case 431 that corresponds to the hole "h." When the hole "h"  formed in the auxiliary lead tab 444  is engaged with the protrusion "p " a position of the auxiliary lead tab 444 may be fixed  and the auxiliary lead tabs 444 and the positive electrode tab 411a may be easily welded to each other. In addition  when the position of the auxiliary lead tabs 444 is fixed  a position of the first lead plate 440 that is connected to the auxiliary lead tabs 444 may also be fixed.
[00101] In one embodiment  a region including battery cells 410 (e.g.  three battery cells 410) that are electrically connected to one another by the first lead plate 440 has been described. However  the present invention is not limited thereto. For example  the through hole "H" that is formed in the lower case 431  as described above with reference to FIG. 7  may be formed in a position that corresponds to the electrode tab 411 of the battery cell 410 illustrated in FIG. 7.
[00102] In one embodiment  the hole "h" may be formed in the auxiliary lead tabs 444 connected to the second lead plate 450 and in the electrode connecting portion 460b of the third lead plate 460  and the protrusion "p" corresponding to the hole "h" may be formed in the lower case 431  as described above.
[00103] FIG. 8 is an exploded perspective view schematically illustrating a battery pack 500 according to another embodiment of the present invention.
[00104] Referring to FIG. 8  the battery pack 500 includes a plurality of battery cells 510  a protection circuit module 520  a lower case 531 and an upper case 532  and a plurality of lead plates 540  550  560  570  and 580 that electrically connect the plurality of battery cells 510 and the protection circuit module 520.
[00105] The battery cells 510  in one embodiment  may be polymer cells. For example  the battery cells 510 may be manufactured by accommodating an electrode assembly in which a positive electrode plate (not shown) and a negative electrode plate (not shown) are alternately stacked by interposing a separator (not shown) between the positive electrode plate and the negative electrode plate  thereby separating the positive electrode plate and the negative electrode plate from each other  and the electrode assembly may be wound in the form of a jelly roll  and accommodated in a polygonal can in which an electrolyte is accommodated.
[00106] Electrode terminals 511 are formed on sides of the battery cells 510 and have a protrusion shape. The electrode terminals 511 may be electrically connected to the negative electrode plate of the electrode assembly and thus may constitute negative electrodes. In one embodiment  the can that accommodates the electrode assembly may be electrically connected to the positive electrode plate of the electrode assembly and thus may serve as positive electrodes. Although not shown  in order to prevent or substantially prevent a short circuit between peripheral devices  an outer surface of the can except for a side opposite to a side on which the electrode terminal 511 that is a negative electrode is disposed  may be insulated from peripheral devices (that is a side of the can opposite to a side on which the negative electrode terminal is disposed is not insulated and remains exposed to outside for electrical connection).
[00107] The protection circuit module 520 may prevent or substantially prevent occurrence of overheating and explosion due to overcharge  overdischarge or overcurrent of the plurality of battery cells 510. The protection circuit module 520 may include a safety element including a passive element  such as a resistor or capacitor  or an active element  such as a field effect transistor  or direct circuits.
[00108] The protection circuit module 520 may include terminals 522 to be electrically connected to the plurality of battery cells 510. The protection circuit module 520 may include connectors (not shown) to be electrically connected to an external electronic device.
[00109] The lower case 531 and the upper case 532 face each other and accommodate the plurality of battery cells 510 and the protection circuit module 520. An accommodation space  in which the plurality of battery cells 510 and the protection circuit module 520 are accommodated  is defined by the lower case 531  and the lower case 531 may include barriers (not shown) that prevent or substantially prevent a short circuit between peripheral devices.
[00110] The lower case 531 and the upper case 532 may include an electrically insulating material. For example  the lower case 531 and the upper case 532 may be formed of an injection-molded material of insulating resin  such as a plastic. In one embodiment  the lower case 531 and the upper case 532 may be manufactured of an insulating film having rigidity (e.g.  predetermined rigidity). In one embodiment  the lower case 531 and the upper caser 532 may include a thin metal material of which an outer surface is coated with an insulating film.
[00111] The plurality of lead plates 540  550  560  570  and 580 may electrically connect the plurality of battery cells 510 and may concurrently (e.g.  simultaneously) connect the battery cells 510 and the protection circuit module 520. In one embodiment  the battery cells 510 include an embedded fuse (not shown) and do not include the TCO 422 as in the first and second lead plates 440 and 450 of the battery pack 400 illustrated in FIGS. 4 through 7  and the auxiliary lead tabs 444 may not be provided.
[00112] The battery pack 500 according to one embodiment in which two parallel-connected battery cells 510 are connected in series is described below. However  the described embodiment is merely one example  and the battery pack 500 illustrated in FIG. 8 is not limited to the above-described structure.
[00113] FIG. 9 is a perspective view of a first lead plate 540 of the battery pack 500 illustrated in FIG. 8.
[00114] Referring to FIG. 9  in one embodiment  the first lead plate 540  or lead electrode  is formed by integrating two metallic layers with each other such that a body portion 540a  electrode connecting portions 540b  and a terminal connecting portion 540c of the first lead plate 540 are formed. In one embodiment  the body portion 540a of the first lead plate 540 may be formed as two metallic layers  and each of the electrode connecting portions 540b and the terminal connecting portion 540c may be formed as one metallic layer. In one embodiment  the first lead plate 540 excluding a portion for electrical connection (i.e. excluding a portion which is to be electrically connected such as by welding) may be surrounded or coated by an insulating material "S." The first lead plate 540 may have a same or similar structure as that of the lead plate 20 described above with respect to FIGS. 2A and 2B  and  thus  further description thereof will not be provided here.
[00115] Referring to FIGS. 8 and 9  a width of the body portion 540a of the first lead plate 540 may be the same as or less than a thickness of the battery cell 510. As described above  in one embodiment  two metal layers overlap with each other such that the width of the body portion 540a of the first lead plate 540 may be small while preventing or reducing an increase in resistance of the first lead plate 540. Thus  the body portion 540a of the first lead plate 540 may be disposed along sides of the battery cells 510 having small thicknesses.
[00116] The electrode connecting portions 540b of the first lead plate 540 may be welded to electrodes of the battery cells 510  such as to the positive electrodes of battery cells 510 (e.g.  two battery cells 510) that are disposed at the front left side of the battery pack 500. In one embodiment  each of the electrode connecting portions 540b is formed as one metallic layer  and  thus  the electrode connecting portions 540b may be easily welded.
[00117] In one embodiment  the terminal connecting portion 540c of the first lead plate 540 may be welded to the terminals 522 of the protection circuit module 520 and may be bent approximately perpendicular to the body portion 540a so as to be parallel to a top surface of the battery cell 510. If the terminal connecting portion 540c is formed as two metallic layers  the overall thickness of the battery pack 500 is increased by the thickness of the terminal connecting portion 540c that passes through a top surface of the battery cell 510. However  since the terminal connecting portion 540c illustrated in FIG. 9 is formed as one metallic layer  the overall thickness of the battery pack 500 may be reduced or minimized.
[00118] The first lead plate 540  in one embodiment  may be welded to positive electrodes of battery cells 510 (e.g.  two battery cells 510) that are disposed at the front left side of the battery pack 500  thereby constituting a positive electrode of a large current terminal. The second lead plate 550 is disposed adjacent to the first lead plate 540 and may be welded to positive electrodes of battery cells 510 (e.g.  two battery cells 510) that are disposed at the back left side of the battery pack 500  thereby constituting a positive electrode of a large current terminal. The second lead plate 550 may have a same or similar structure as that of the first lead plate 540  and  thus  further detailed description thereof will not be provided here.
[00119] FIG. 10 is a perspective view of a third lead plate 560 of the battery pack 500 illustrated in FIG. 8.
[00120] Referring to FIG. 10  in one embodiment  the third lead plate 560  or lead electrode  is formed by integrating two metallic layers with each other such that a body portion 560a  electrode connecting portions 560b  and a terminal connecting portion 560c of the third lead plate 560 are formed. In one embodiment  the body portion 560a of the third lead plate 560 may be formed as two metallic layers  and each of the electrode connecting portions 560b and the terminal connecting portion 560c may be formed as one metallic layer. The third lead plate 560 excluding a portion for electrical connection (i.e. excluding a portion which is to be electrically connected such as by welding) may be surrounded or coated by an insulating material "S."
[00121] In one embodiment  the electrode connecting portions 560b of the third lead plate 560 to be welded to electrodes of the battery cell 510 and may be bent toward the body portion 560a so as to be approximately parallel to the body portion 560a. In one embodiment  a width of the electrode connecting portion 560b may be the same as or less than a width of the body portion 560a such that the bent electrode connecting portions 560b do not protrude in a widthwise direction of the body portion 560a  as described above with reference to FIGS. 3A and 3B.
[00122] Referring to FIGS. 8 and 10  the width of the body portion 560a of the third lead plate 560 may be the same as or less than the thickness of the battery cell 510. As described above  in one embodiment  two metal layers overlap with each other such that the width of the body portion 560a of the third lead plate 560 may be small while preventing or substantially preventing an increase in resistance of the third lead plate 560. Thus  the body portion 560a of the third lead plate 560 may be disposed along sides of the battery cells 510 having small thicknesses.
[00123] In one embodiment  the terminal connecting portion 560c of the third lead plate 560 may be welded to the terminals 522 of the protection circuit module 520 and may be bent approximately perpendicular to the body portion 560a so as to be parallel to a top surface of the battery cell 510. The terminal connecting portion 560c  in one embodiment  is formed as one metallic layer  and  thus  the overall thickness of the battery pack 500 may be reduced or minimized.
[00124] The width of the terminal connecting portion 560c may be greater than that of the body portion 560a so as to prevent or substantially prevent resistance of the third lead plate 560 from being increased when a current that has flowed through the body portion 560a of the third lead plate 560 flows through the terminal connecting portion 560c  as described above.
[00125] In one embodiment  the third lead plate 560 electrically connects battery cells 510 (e.g.  four battery cells 510) that are disposed in a rear or back side direction of the battery pack 500 to one another  and the fourth lead plate 570 is disposed symmetrically or substantially symmetrically to the third lead plate 560 and electrically connects battery cells 510 (e.g.  four battery cells 510) that are disposed in a front direction of the battery pack 500 to one another. The fifth lead plate 580 electrically connects battery cells 510 (e.g.  four battery cells 510) that are disposed in a side-to-side manner in the right side direction of the battery pack 500 to one another. The structures of the fourth lead plate 570 and the fifth lead plate 580 may be the same or similar to the structure of the third lead plate 560 and  thus  further detailed description thereof will not be provided here.
[00126] In one embodiment  the first and second lead plates 540 and 550 have the structure or a similar structure to that of the lead plate 20 illustrated in FIGS. 2A through 2C. However  the present invention is not limited thereto. For example  the first and second lead plates 540 and 550 may have a structure in which the electrode connecting portions 540b protrude not from both ends  but from sides of the body portion 540a and may be bent  as in the third through fifth lead plates 560  570  and 580. That is  the first and second lead plates 540 and 550 may have the structure or a similar structure to that of the lead plate 30 illustrated in FIGS. 3A through 3C.
[00127] The battery packs 400 and 500 described herein with respect to FIGS. 4 and 8 include a lead plate including a body portion that  in one embodiment  is formed as two metallic layers and has a small width and thus may use a narrow space efficiently. In addition  since  in one embodiment  each of the electrode connecting portions and the terminal connecting portion is formed as one metallic layer  the electrode connecting portions and the terminal connecting portion may be easily welded.
[00128] A width of the terminal connecting portion formed as one metallic layer may be large such that an increase in resistance of the terminal connecting portion may be prevented or reduced  and since the thickness of the terminal connecting portion is small  the overall thickness of the battery pack may be reduced or minimized.
[00129] While the present invention has been described in connection with certain exemplary embodiments  it is to be understood that the invention is not limited to the disclosed embodiments  but  on the contrary  is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims  and equivalents thereof. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments.

We claim:
1. A battery pack comprising:
a battery cell;
a protection circuit module electrically connected to the battery cell;
a case accommodating the battery cell; and
a lead electrode electrically connected between the protection circuit module and the battery cell  the lead electrode comprising:
a plurality of end connecting portions  each connected to the battery cell or the protection circuit module; and
a body portion connecting the plurality of end connecting portions and having a thickness greater than a thickness of the end connecting portions.

2. The battery pack of claim 1  wherein a width of an end connecting portion of the plurality of end connecting portions is greater than a width of the body portion.

3. The battery pack of claim 2  wherein the end connecting portion of the plurality of end connecting portions is connected to the protection circuit module.

4. The battery pack of claim 1  wherein the body portion comprises first and second overlapping metallic layers.

5. The battery pack of claim 4  wherein an end connecting portion of the plurality of end connecting portions comprises a connecting portion of the first metallic layer that extends beyond and is not overlapped with the second metallic layer.

6. The battery pack of claim 4  wherein the first and second metallic layers are integrated together by at least one of welding or a conductive adhesive.

7. The battery pack of claim 1 
wherein the battery cell comprises an electrode tab at a first side thereof  and
wherein an end connecting portion of the plurality of end connecting portions is connected to the electrode tab.

8. The battery pack of claim 7 
wherein the battery cell further comprises a terrace portion at the first side  and
wherein a width of the body portion is less than or equal to a width of the terrace portion.

9. The battery pack of claim 1  wherein an end connecting portion of the plurality of end connecting portions and the body portion are bent with respect to each other.

10. The battery pack of claim 1  wherein a width of the body portion is less than or equal to a thickness of the battery cell.

11. The battery pack of claim 1 
wherein the lead electrode further comprises an insulating material surrounding the body portion  and
wherein at least a portion of each of the end connecting portions is exposed outside the insulating material.

12. The battery pack of claim 1  further comprising an auxiliary lead tab electrically connected between an end connecting portion of the plurality of end connecting portions and the battery cell.

13. The battery pack of claim 12 
wherein the auxiliary lead tab has a hole formed therein  and
wherein the case comprises a protrusion engaged in the hole to fix a position of the auxiliary lead tab relative to the case.

14. The battery pack of claim 12  further comprising a temperature cutoff (TCO) electrically connected between the end connecting portion of the plurality of end connecting portions and the auxiliary lead tab.

15. The battery pack of claim 1 
wherein an end connecting portion of the plurality of end connecting portions has a hole formed therein  and
wherein the case comprises a protrusion engaged in the hole to fix a position of the end connecting portion of the plurality of end connecting portions relative to the case.

16. A lead electrode for a battery pack  the lead electrode comprising:
a plurality of end connecting portions; and
a body portion connecting the plurality of end connecting portions and having a thickness greater than a thickness of the end connecting portions.

17. The lead electrode of claim 16  wherein a width of an end connecting portion of the plurality of end connecting portions is greater than a width of the body portion.

18. The lead electrode of claim 16  wherein the body portion comprises first and second overlapping metallic layers.

19. The lead electrode of claim 18  wherein the first and second metallic layers are integrated together by at least one of welding or a conductive adhesive.

20. The lead electrode of claim 16  further comprising an insulating material surrounding the body portion  at least a portion of each of the end connecting portions being exposed outside the insulating material.