Electrochemical storage device and method for producing same

An electrochemical storage device which has electrode plates of different polarity which are alternately stacked on one another to form an electrode stack. Each of the electrode plates is formed from an electrode framework with a current-collecting lug arranged thereon. Identically polarized current-collecting lugs of an electrode stack are connected in an electrically conductive fashion to a terminal yoke. In order to ensure better welding, the terminal yoke has at the location of the current-collecting lugs a transverse slot into which the free end region of a current-collecting lug projects. The current-collecting lug is attached to the terminal yoke on the flat side that is remote from the electrode stack.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to an electrochemical storage device having 
electrode plates of different polarity alternately stacked on one another, 
each electrode plate being formed from an electrode framework having a 
current-collecting lug arranged thereon, the individual, identically 
polarized current-collecting lugs being connected in an electrically 
conductive fashion with their weld-on rims arranged on their free end 
region to a terminal yoke extending parallel to the electrode stack formed 
from the electrode plates and transverse to the flat side of the 
current-collecting lugs. The present invention also relates to a method 
for producing an electrochemical storage device which has a plurality of 
electrode plates formed in each case from an electrode framework having a 
current-collecting lug welded on the end, the individual, identically 
polarized current-collecting lugs being connected in an electrically 
conductive fashion with their weld-on rims arranged on their free ends to 
a terminal yoke. Each of the current-collecting lugs is connected at the 
end by in each case one electrode framework to an electrode plate, the 
electrode plates being stacked on one another with the intercalation of 
various parts such as separators, recombiners etc. transverse to their 
flat irons to form an electrode stack. The electrode stack is insulated on 
the outside and inserted into a housing. The current-collecting lugs 
respectively of the same polarity are connected with their weld-on rim 
arranged on the free end region to a terminal yoke assigned to this 
polarity and on which a terminal pillar is arranged. 
The fundamental electrochemical storage device of the above-described 
generic type has electrode plates of different polarity stacked on one 
another, each electrode plate being formed from a current-collecting lug 
having an electrode framework arranged on its one end region. The 
electrode plates are stacked on one another alternately to form an 
electrode stack, with separators being arranged between electrode plates 
of different polarity and recombiners being arranged between two 
successive electrode plates of the same, negative polarity, and electrode 
plates of the same polarity being connected to one another in an 
electrically conductive fashion via a terminal yoke. The 
current-collecting lugs are welded to the terminal yoke by electrical 
resistance welding along a weld-on rim arranged at their end region, for 
the purpose of electrically connecting the electrode plates of the same 
polarity. In order to simplify the welding, the weld-on rims of the 
current-collecting lugs are bent transverse to the flat side of the other 
current-collecting lug, preferably by an angle of approximately 
90.degree., the weld-on rim being provided with welding knobs in order to 
improve the welding result. In spite of these welding knobs, defective or 
poor welds keep recurring, which particularly in the case of high-quality 
electrochemical storage devices such as, for example, batteries for space, 
signify rejection. 
An object of the present invention is to improve a fundamental storage 
device of the initially described type to reduce rejections due to welding 
the current-collecting lugs to the terminal yoke. Furthermore, a method 
for producing it is to be developed. 
This and other objects are achieved by the present invention which provides 
an electrochemical storage device comprising electrode plates of different 
polarity alternately stacked on one another to form an electrode stack, 
each electrode plate including an electrode framework and a 
current-collecting lug arranged thereon, the current-collecting lugs 
having weld-on rims arranged on a free end region. A terminal yoke extends 
parallel to the electrode stack and transverse to a flat side of the 
current-collecting lugs, with individual identically polarized 
current-collecting lugs being connected in an electrically conductive 
fashion with their weld-on rims to the terminal yoke. The terminal yoke 
has a flat side remote from the electrode stack, and a transverse slot at 
a location of a current-collecting lug into which the free end region of 
the current-collecting lug at least projects. The current-collecting lug 
is attached to the terminal yoke in the region of the flat side of the 
terminal yoke. 
The above-stated objects are also achieved by an embodiment of the present 
invention which provides a method for producing an electrochemical storage 
device comprising forming a plurality of electrode plates by welding a 
plurality of current-collecting lugs respectively on an end of an 
electrode framework, stacking the electrode plates on one another with the 
intermediate positioning of elements transverse to flat sides of the 
electrode plates to form an electrode stack, and insulating outer regions 
of the electrode stack. The electrode stack is inserted into a housing. 
The weld-on rims of the current-collecting lugs are plugged into 
transverse slots of the terminal yoke. In an electrically conductive 
manner, the individual, identically polarized current-collecting lugs are 
connected to a terminal yoke assigned to this polarity, the 
current-collecting lugs being connected to said terminal yoke by weld-on 
rims of free ends of the current-collecting lugs to the terminal yoke, the 
terminal yoke having webs between the transverse slots, and a terminal 
pillar. The step of connecting the current-collecting lugs to the terminal 
yoke includes electrical resistance welding the weld-on rims of the 
current-collecting lugs to the webs of the terminal yoke. 
Due to the design according to the invention of the current-collecting lug 
and the terminal yoke, the weld of the terminal yoke with the weld-on rims 
of the current-collecting lug, which weld is easy to produce, has a high 
strength and low contact resistances, these properties being ensured even 
in the case of high vibration loads on the electrochemical storage device. 
A further advantage is that, with a welded connection of the terminal yoke 
and the current-collecting lug as against a screwed connection, a 
plurality of components are spared and thus the mass of the storage device 
is reduced, the overall height of the storage device is reduced and the 
contact resistance between the current-collecting lug and terminal yoke is 
lower. On the production side, there is the further advantage that the 
production of the storage device according to the invention can be 
automated since, inter alia, the welding zones are easily accessible after 
the assembly of the cell stack. The result is that, despite the higher 
quality of the electrochemical storage device and despite reduced 
rejection during production, there is a reduction in cost during 
production of the electrochemical storage device and a shorter production 
time. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
In the following description, an embodiment of a terminal yoke 1 (FIGS. 1 
and 2) will first be described, then an embodiment of an associated 
current-collecting lug 2 (FIGS. 3 to 5), and finally two arrangements of 
the terminal yoke 1 and a plurality of current-collecting lugs 2 stacked 
on one another to form an electrode stack 5 (see FIGS. 8 and 9). These 
common arrangements are subdivided into an arrangement of positive 
polarity (FIG. 8) and into an arrangement of negative polarity (FIG. 9). 
Due to the mutual dependencies in the configuration of the terminal yoke 1 
and the current-collecting lug 2, it will be impossible to avoid referring 
back to or anticipating the respective other element. 
The side view of a terminal yoke 1 is represented in FIG. 1 and the plan 
thereof in FIG. 2. The terminal yoke 1, which for reasons of cost is 
produced from nickelized steel in the illustrated embodiment, has a 
plurality of webs 10 which are spaced apart from one another by transverse 
slots 3, 3' open at the edge side and are arranged on a solid middle part 
of the terminal yoke 1. The webs 10 are at an approximately right angle 
relative to the longitudinal center line 8 of the solid middle part of the 
terminal yoke 1. The webs 10 are aligned on both sides of the solid middle 
part and project outwards. For the sake of better comprehension, the 
terminal pillar of the terminal yoke 1, which is appropriately welded on 
the solid middle part, is additionally illustrated by dashes. 
It is advantageous for the purpose of a simple and unambiguous arrangement 
of current-collecting lugs 2 of one polarity if the transverse slots 3 
arranged along one side of the terminal yoke 1 are longer than the 
transverse slots 3' arranged along the other side of the terminal yoke 1. 
So as to have available an adequate area for the later welding of the 
current-collecting lugs 2 to the webs 10 of the terminal yoke 1, the width 
of the webs 10 situated between two adjacent transverse slots 3, 3' 
corresponds to 10 to 25 times the thickness of the current-collecting lugs 
2. 
Moreover, the transverse slots 3, 3' on the flat side 6 of the terminal 
yoke 1 facing the electrode stack 5 are chamfered, thus facilitating the 
insertion of an upper end region 4 of a current-collecting lug 2 of an 
electrode stack 5. The mass of the terminal yoke 1 is simultaneously 
reduced by means of this measure. 
In certain embodiments, the terminal yoke 1 has transverse slots only on 
one side. This allows the current-collecting lugs 2 to be inserted at the 
edge side. It is appropriate in this unillustrated embodiment for the webs 
10 to be chamfered at the edge side in a way which facilitates lateral 
insertion. 
FIG. 3 shows a current-collecting lug 2 corresponding to the terminal yoke 
1 according to FIGS. 1 and 2. On its free, upper end region 4, the 
current-collecting lug 2 has two lug tongues 9, 9' which during later 
assembly are assigned to the opposite transverse slots 3, 3' of the 
terminal yoke 1. The weld-on rim 7 of the current-collecting lug 2 is 
provided with welding knobs arranged on the lug tongues 9, 9'. So that the 
weld-on rims 7 of the current-collecting lugs 2 do not project in the 
region of the transverse slots 3, 3', the extent of the weld-on rims 7 
corresponds to the external dimension of the terminal yoke 1 measured in 
the direction and at the level of the transverse slots 3, 3'. The welding 
knobs are constructed as solid-walled material protuberances 13. As 
represented in FIGS. 4 and 5, the material protuberances 13 have a cutout 
from the rims of which there project sheet metal tongues which are aligned 
transverse to the flat side of the weld-on rim 7, which flat side is to be 
welded on, and which form a toothed crown. 
As represented in FIGS. 6 and 7, in certain embodiments, the welding knob 
are tongues 17 spaced apart from one another by cutouts 11 or by material 
recesses 12, the material recesses 12 being deeper than the degree of 
sinking when the weld-on rim 7 is welded onto the terminal yoke 1. 
It is desired that the weld-on rim 7 provided with welding knobs 13 be 
plugged in through the transverse slot 3, 3' of the terminal yoke 1 
assigned to it as far as over the flat side 6 remote from the electrode 
stack 5. For this purpose, the clear width of the transverse slots 3, 3' 
measured parallel to the surface normal of a plugged-in current-collecting 
lug 2 corresponds at least to the thickness of the current-collecting lug 
2 plus the height of the welding knobs above the current-collecting lug 2. 
In particular, this clear width of the transverse slots is 7 to 18 times 
the thickness of the current-collecting lugs 2, the current-collecting 
lugs 2 having a thickness of between 0.1 mm and 1.0 mm. 
FIGS. 8 and 9 represent an electrochemical storage device without a storage 
device housing, the representation in accordance with FIG. 8 relating to 
mounting the positive electrode plates 18, and FIG. 9 to the mounting of 
the negative electrode plates 15 on the respectively associated terminal 
yoke 1. 
The electrochemical storage device represented in FIGS. 8 and 9 has an 
electrode stack 5 which is formed from electrode plates 15 of different 
polarity alternately stacked on one another, each electrode plate 15 
having an electrode framework with a current-collecting lug 2 welded 
thereon. The individual, identically polarized current-collecting lugs 2 
of the electrode stack 5 are connected in an electrically conductive 
fashion to a terminal yoke 1 by electrical resistance welding of their 
weld-on rims 7, which are arranged on the respective free end region 4 of 
each individual current-collecting lug 2, the terminal yoke 1 extending 
parallel to the electrode stack 5 and transverse to the flat side 14 of 
the current-collecting lugs 2. 
The lug tongues 9, 9' of the current-collecting lugs 2 of the positive 
electrode plates 15 are plugged through the transverse slots 3, 3' of the 
positive terminal yoke 1, the positive current-collecting lugs 2 being 
aligned approximately parallel to the flat side of the associated 
electrode frameworks and at right angles to the terminal yoke 1 and to the 
electrode stack 5. The reason why this is advantageous is because, in the 
region where the current-collecting lug 2 is welded on, the electrode 
frameworks, especially a fiber structure design, then experience no load 
or only a slight load due to a shear stress. For this purpose, it is 
appropriate to apply the current-collecting lugs 2, which are plugged into 
the transverse slots 3, 3' and project upwards essentially vertically from 
the electrode stack 5, with their upper end region 4 on the left-hand or 
on the right-hand side of the webs 10. 
By contrast, the lug tongues 9, 9' of juxtaposed current-collecting lugs 2, 
which are spaced apart from one another only by an interposed recombiner 
19, of the negative electrode plates are led together at their free end 
region 4 on the terminal yoke side and plugged, mostly in pairs, through a 
transverse slot 3, 3' of tho negative terminal yoke 1 assigned to them. It 
is common to both the positive and negative electrode connections that the 
respective weld-on rims 7 of the respective current-collecting lugs 2, 
which are provided with welding knobs, project over the flat side 6 of the 
associated terminal yoke 1 which faces away from tho electrode stack 5, 
and that the current-collecting lugs 2 are welded by electrical resistance 
welding on the flat side 6, remote from the electrode stack 5, of the 
respectively assigned terminal yoke 1. 
In certain embodiments, the terminal yokes 1 are provided with one of the 
webs 10 being thicker than the adjacent webs 10 and against which a 
current-collecting lug 2 bears against the left-hand rim and the next 
current-collecting lug 2 of the same polarity bears against the right-hand 
rim. Thus, no weld-on rim 7 projects from the terminal yoke 1 after the 
current-collecting lugs 2 have been bent over onto the flat side 6 of the 
webs 10 remote from the electrode stack 5. 
Since the lug tongues 9, 9' of a current-collecting lug 2 are spaced apart 
from one another by a cutout, it is appropriate for the cutout to be 
designed in such a way that when the lug tongues 9, 9' are plugged into 
the assigned transverse slots 3, 3', the cutout forms a stop limiting the 
plug-in depth of the current-collecting lug 2, and that the width of the 
cutout corresponds approximately to the width of the solid middle part of 
the terminal yoke 1 plus an extra amount facilitating the plugging-in. 
The number of the transverse slots 3, 3' assigned to the individual 
current-collecting lugs 2 is two smaller than the total number of the 
positive electrode plates 15, as a result of which the outer positive 
current-collecting lugs 2 can in each case be applied to the free outside 
surface of the outer webs 10 which is assigned to them and is easily 
accessible. It is appropriate, furthermore, to dimension the extent of the 
terminal yoke 1 in this direction in such a way that the ends 16, 16' of 
the terminal yoke 1 do not project over the boundaries of the electrode 
stack 5, as a result of which the electrode stack 5 can be effectively 
pressed into the storage device housing. A projection which corresponds to 
twice to fifteen times the thickness of the current-collecting lug 2 has 
proved to be a satisfactory dimension in this regard. In the present 
embodiment, the terminal yokes 1 are plugged onto the current-collecting 
lugs 2 either before or after the insertion of the electrode stack 5 into 
the storage device housing, and then welded on. 
The production of an electrochemical storage device according to the 
invention is described below and represented in principle in FIGS. 10 and 
11. After the electrode frameworks with the current-collecting lugs 2 are 
welded to electrode plates 15 and completely prepared for assembly, the 
electrode plates 15 are stacked on one another with the intermediate 
positioning of various parts, such as separators 18, recombiners 19 etc. 
transverse to the flat irons of the electrode plate 15 to form an 
electrode stack 5. The electrode stack 5 is insulated on the outside by 
means of the stack insulation 20. 
The free end regions 4 of the current-collecting lugs 2 are plugged into 
the transverse slots 3, 3' of the terminal yoke 1 which corresponds to 
their polarity, in such a way that the weld-on rims 7 of the 
current-collecting lugs 2 project over the flat side 6 of the webs 10 or 
of the terminal yoke 1 remote from the electrode stack 5. Subsequently, 
the weld-on rims 7 are bent in the direction of the flat side 6, onto 
which welding is to take place, of the terminal yoke 1 onto the webs 10 
and firmly welded thereon. 
So that no weld-on rim 7 projects after the current-collecting lug 2 has 
been welded on the flat side 6 of the webs 10 remote from the electrode 
stack 7, it is expedient for the weld-on rim 7 of at least one 
current-collecting lug 2 situated at the end in the electrode stack 5 to 
be bent over in the direction of a web 10 which is already overlapped by 
another weld-on rim 7. 
For the purpose of realizing good results when welding, the weld on rims 7 
are provided with solid walled welding knobs, which are provided in the 
region of the weld-on rim 7 by penetration of the current-collecting lugs 
2, the penetrated sheet metal tongues forming the sides of the welding 
knobs. The sheet metal tongues are at an angle of between 75.degree. and 
105.degree., in particular approximately 90.degree., to the flat side 14 
of the current-collecting lug 2 which is to be welded on. Their inside 
diameter is between 0.5 mm and 2.0 mm and the mutual spacing of the 
individual welding knobs from one another is between 1.3 and 5 times their 
outside diameter. 
As may be seen, in particular, from FIG. 10, before the welding current 
flows the pushed out sheet metal tongues of a material protuberance 13 are 
generally situated approximately in the middle of the webs 10 on the flat 
side 6 of the terminal yoke 1 on which welding is no take place. When the 
welding current is flowing, the material of the sheet metal tongues melts, 
and the weld-on rim 7 is applied to make Contact with the flat side 6 be 
welded and is welded thereto (see FIG. 11). Another possibility for 
providing welding knobs is to punch out cutouts 11 in the weld-on rims 7 
and thereby to expose tongues 17 spaced apart from one another. 
A further design of the welded connection between the terminal yoke 1 and 
the weld-on rim 7 of a current-collecting lug 2 is described in FIG. 12. 
This exemplary embodiment differs from the preceding ones that in this 
case the flat side 6 of the terminal yoke 1 remote from the electrode 
stack 5 is provided with welding knobs 21. The result is once again to 
simplify the welding. 
In the type of welding presented here, it is particular advantage that the 
current-collecting lugs can be welded to the terminal yoke 1 independently 
of the progress of the assembly of the electrode stack 5. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.