Grids for lead-acid battery electrodes

Description

[0001] The invention relates to a grid for an electrode of a lead-acid battery, with a plurality of longitudinal ribs arranged at a distance from one another in the transverse direction and a plurality of transverse ribs each arranged between two adjacent longitudinal ribs and connected to these, which longitudinal and transverse ribs form a grid pattern with open areas for receiving an active mass, wherein the longitudinal ribs have a first, maximum width in the transverse direction at least in a section running in the longitudinal direction, which is designed to be optimized with regard to the receiving volume provided overall by the open areas for receiving the active mass.

[0002] Grids for an electrode in general, and grids for an electrode of a positive terminal plate of a lead-acid battery in particular, are well known from the prior art, which is why a separate written reference is not required here. Reference is therefore made, merely by way of example, to DE 696 22 312 T2 and DE 698 11 939 T2, which disclose such grids. DE 698 11 939 T2 relates to a stamped battery plate grid, whereas DE 696 22 312 T2 relates to a battery grid produced in a continuous casting process. Furthermore, corresponding technology is also already known from CN 106 654 284 A.

[0003] A generic grating has a plurality of longitudinal ribs. These extend in the longitudinal direction of the grating and are spaced apart from one another, leaving a gap in the transverse direction of the grating.

[0004] Furthermore, transverse ribs are provided which extend in the transverse direction and which are arranged between two adjacent longitudinal ribs and connected to them.

[0005] In combination, the longitudinal and transverse ribs form a grid pattern that has window-like, preferably rectangular, open areas that serve to accommodate an active mass.

[0006] In the final assembled state of an electrode, an active mass is introduced into the open areas provided by the grid, whereby the grid, including the active mass accommodated therein, is covered by an electrolyte-permeable separator.

[0007] The grid is made of an electrically conductive material, which in the case of a lead-acid battery is lead. A metal oxide such as MnO2, PbO2, NiOOH, HgO, and Ag2O can be used as the active material for a positive electrode, whereas the active material of a negative electrode is made of a metal such as Zn, Cd, Pb, and Sn. However, the invention is not limited to the aforementioned materials, but encompasses all materials capable of electrochemical action.

[0008] The aim is in principle to maximize the total volume provided by the open areas of the grid to accommodate the active mass, so that as much active mass as possible can be accommodated by the grid in relation to the passive mass of the grid material. For this reason, the longitudinal ribs must be designed to be as thin as possible in terms of their extension in the transverse direction. At the same time, however, a sufficient service life must be ensured and the desired current collection must be possible when used as intended. Generic grids therefore have longitudinal ribs which are optimized in terms of their geometric design in the transverse direction, i.e. longitudinal ribs which, at least in one section running in the longitudinal direction, have a first, maximum width in the transverse direction, which is optimized in terms of the total volume provided by the open areas to accommodate the active mass.This width is, for example, approximately 1.6 mm.

[0009] Although prior art grids have proven themselves in everyday practical use, there is still room for improvement. Corrosion, which occurs during intended use, causes the grids of a positive pole electrode to grow. As a result of such growth, the positive pole electrode expands, particularly in the longitudinal and transverse directions. The electrode can expand by 15% or more of its original length in the longitudinal and transverse directions. This, in turn, can lead to the active mass being torn away from the longitudinal and transverse ribs of the grid, which, under intended use, leads to a loss of battery capacity.

[0010] To counteract this problem, the longitudinal ribs of the grid can be reinforced, i.e., they can have a width in the transverse direction that exceeds the width optimized for a maximized receiving volume for the active mass. However, such a reinforcement of the longitudinal ribs has the disadvantage that the receiving volume provided by the grid for the active mass, also called the empty volume, is reduced, resulting in reduced capacity when used as intended. In this respect, two conflicting interests exist.

[0011] Based on the above-described state of the art, the TaskThe invention is to further develop a generic grating in such a way that, while simultaneously maximizing the receiving volume for receiving the active mass, a reduced grating growth is structurally ensured in the intended use.

[0012] To solve this Task The invention proposes a grid of the type mentioned at the outset, which is characterized by at least one further longitudinal rib which has a second, maximum width over its entire longitudinal extent in the transverse direction, which exceeds the first, maximum width of the other longitudinal ribs.

[0013] The grid according to the invention therefore has two types of longitudinal ribs. In accordance with the prior art, longitudinal ribs are provided which, at least in a longitudinally extending section, have a first, maximum width in the transverse direction, which is optimized with respect to the total receiving volume provided by the open areas for receiving the active mass. According to the invention, at least one further longitudinal rib is provided, wherein this longitudinal rib has a second, maximum width over its entire longitudinal extent in the transverse direction, which exceeds the first, maximum width of the other longitudinal ribs.

[0014] Under normal use, corrosion cannot be avoided. As a result of this corrosion, lead oxide forms on the grid ribs, including the longitudinal ribs. Lead oxide has a much larger molar volume than lead, from which the grid ribs are made. This additional volume with regard to the lead oxide leads to shear and tensile stresses, particularly in the longitudinal ribs. As a result of this force, the grid grows, i.e. it expands over time. Such expansion is disadvantageous for several reasons. Firstly, the open areas provided by the grid, which accommodate the active mass provided by the grid, increase in size. This can lead to contact between the active mass and individual grid ribs being severed, which disadvantageously reduces the capacity of a battery equipped with such a grid.

[0015] Furthermore, corrosion-induced grid growth can adversely lead to individual longitudinal or transverse ribs breaking through the separator covering the grid, which can then lead to undesirable short circuits.

[0016] The inventive design is capable of preventing such undesired lattice growth, or at least limiting it to a range below 5% relative to the original geometric configuration of the lattice. Not all longitudinal ribs are reinforced, i.e., deviated from the width optimized to maximize the capacity for the active mass, but only at least one longitudinal rib.

[0017] As has been shown, undesired lattice growth can be effectively prevented simply by reinforcing not every longitudinal rib of the lattice, but only some, or at least one. This takes into account the conflicting interests of, on the one hand, minimizing lattice growth by means of a reinforced longitudinal rib, and, on the other hand, maximizing the receiving volume for the active mass by means of a width design of the remaining longitudinal ribs adapted to this. The result of the design according to the invention is a lattice which, due to the at least one additional longitudinal rib, has reduced lattice growth in the intended use compared to the prior art, but which at the same time also provides a maximized empty volume for receiving the active mass.

[0018] According to a further feature of the invention, the second maximum width exceeds the first maximum width by 20% to 35%, preferably by 25% to 30%, even more preferably by 27.5%. Such width ratios provide a further optimized design with respect to reduced lattice growth on the one hand and maximizing the receiving volume for accommodating the active mass on the other.

[0019] According to a further feature of the invention, the first maximum width is 1.4 mm to 1.8 mm, preferably 1.5 mm to 1.7 mm, even more preferably 1.6 mm. The first maximum width is to be designed with a view to maximizing the volume for the active mass, maximizing service life, and optimizing current collection. For this reason, the invention proposes the width dimensions listed above. According to a particular embodiment of the invention, the first maximum width is 1.62 mm.

[0020] According to a further feature of the invention, the second, maximum width is 1.8 mm to 2.2 mm, preferably 1.9 mm to 2.1 mm, even more preferably 2.0 mm. The second, maximum width is to be designed differently than the first, maximum width in such a way that such a reinforcement of the grid is achieved that, during intended use, undesired grid growth does not occur, and the grid growth is limited to at least 5% based on the original geometric dimensions. This can be achieved with the width dimensions listed above, wherein, according to a particularly preferred embodiment, a second, maximum width of 2.06 mm is given.

[0021] According to a further feature of the invention, not just one further longitudinal rib, but a plurality of further longitudinal ribs with a second, maximum width in the transverse direction is provided. The exact number of further longitudinal ribs depends in particular on the extent of the grid in the transverse direction and the forces expected to be applied to the grid during intended use, which lead to its expansion. For given dimensions for the second, maximum width, the total number of further longitudinal ribs to be provided must be selected such that the forces applied to the grid during intended use can be compensated to the extent that grid growth is limited to less than 5%.

[0022] According to a further feature of the invention, in this context, it is provided that in the transverse direction of the grid every third to fifth, preferably every fourth longitudinal rib is a further longitudinal rib with a second, maximum width in the transverse direction. Accordingly, a grid according to the invention preferably has three longitudinal ribs arranged one behind the other in the transverse direction, followed by a further longitudinal rib, i.e. a longitudinal rib with a second, maximum width in the transverse direction. It has been shown that with such a sequence of longitudinal ribs, an optimized result is achieved in terms of reduced growth during intended use and absorption capacity for active mass.

[0023] According to a further feature of the invention, it is provided that the longitudinal ribs in a second section running in the longitudinal direction have a width in the transverse direction which corresponds to the second, maximum width of the further longitudinal rib.

[0024] According to this particular embodiment, which is capable of protection in its own right, the longitudinal ribs not only have a first section in which they have a first, maximum width in the transverse direction, but also a second section in which they have a width in the transverse direction that corresponds to the second, maximum width of the further longitudinal ribs. The further longitudinal ribs are thus of the same width across their entire longitudinal extent, with the remaining longitudinal ribs each having sections with different width configurations.

[0025] The second sections of the longitudinal ribs are preferably located on the current pickup side, as this is where the most severe corrosion phenomena occur during normal use. This design measure further minimizes the grating growth that occurs during normal use.

[0026] According to a further feature of the invention, the longitudinal ribs, in a third section running longitudinally between the second and first sections, have a width in the transverse direction which, starting from the second maximum width, tapers continuously down to a third maximum width. Accordingly, the longitudinal ribs have a section at one end, preferably on the downstream side, in which the longitudinal ribs have a second maximum width in the transverse direction. Starting from this width dimension, the width configuration of the longitudinal ribs preferably decreases continuously until a third maximum width is reached, which is greater than the first maximum width. From this point, the width dimension in the longitudinal direction of the longitudinal rib decreases further, preferably abruptly, down to the first maximum width. A continuous taper is also possible here.

[0027] According to the preferred embodiment of the invention, the width dimension of a longitudinal rib decreases continuously from the second maximum width until reaching a third maximum width, wherein the third maximum width exceeds the first maximum width. The transition to the first maximum width is then abrupt, starting from the third maximum width, i.e., not continuous like the transition from the second maximum width to the third maximum width.

[0028] This particularly proposed width profile of the longitudinal ribs also contributes to an optimization with regard to reduced lattice growth in the intended use and maximized absorption capacity for the active mass.

[0029] According to a further feature of the invention, the longitudinal ribs and the further longitudinal rib extend between a first frame web and a second frame web, to which they are each integrally connected, the second frame web carrying a current collector vane. Overall, a preferably one-piece grid is thus formed which comprises all the longitudinal ribs, transverse ribs, frame webs and the current collector vane. According to a further feature of the invention, the second sections of the longitudinal ribs adjoin the second frame web and the first sections of the longitudinal ribs adjoin the first frame web. In this case, one of the longitudinal ribs tapers in the longitudinal extension of the grid from top to bottom, i.e. starting from the second frame web in the direction of the first frame web. In contrast, the further longitudinal ribs each have the second, maximum width over their entire longitudinal extension in the transverse direction and therefore do not taper.

[0030] According to a further feature of the invention, the grid is manufactured in a continuous casting process. To ensure demoldability in this case, both the longitudinal ribs and the further longitudinal ribs each have a trapezoidal cross-section.

[0031] The use of a continuous casting process is particularly preferred because longitudinal ribs with different geometric dimensions are provided. With regard to this geometric design, a continuous casting process is particularly simple and cost-effective to use.

[0032] Alternatively, the grid can also be produced by punching, in which case the longitudinal ribs and the additional longitudinal ribs preferably each have a rectangular cross-section. Due to the lack of necessary demoldability, a trapezoidal cross-section design can be omitted during punching, which also simplifies the punching process.

[0033] Further features and advantages of the invention will become apparent from the following description with reference to the figures. Fig. 1 shows a schematic perspective view of a grid according to the invention; Fig. 2 shows a schematic plan view from the front of the grid according to the invention according to Figure 1 ; Fig. 3 in schematic plan view from the front the grid according to the invention according to Figure 1 with section planes drawn in; Fig. 4; the grid according to the invention in a section along the section line AA according to Figure 3; Fig. 5 the grid according to the invention in a section along the section line BB according to Figure 3 ; Fig. 6 the grid according to the invention in a section along the section line CC according to Figure 3 ; Fig. 7 in a schematic side view the grid according to the invention according to Figure 3 and Fig. 8 the grid according to the invention in a detailed view according to section Z according to Figure 7 .

[0034] Figure 1 shows a schematic perspective view of a grid 1 according to the invention for an electrode, in particular of a lead-acid battery.

[0035] The grid 1 has, in a manner known per se, a first frame web 7 and a second frame web 8, between which longitudinal ribs 2 and 4 extend. These longitudinal ribs 2 and 4 are arranged at a distance from one another in the transverse direction 6.

[0036] The grid 1 further comprises a plurality of transverse ribs 3 arranged between two adjacent longitudinal ribs 2 and 4 and connected thereto.

[0037] The longitudinal and transverse ribs 2 and 4 and 3 form a grid pattern with open areas 10, which areas 10 serve to accommodate an active mass.

[0038] Furthermore, a current collector vane 9 is provided, which is arranged on the upper, second frame web 8 in the longitudinal direction 5.

[0039] Figure 2 shows the grid 1 according to the invention in a plan view from the front, wherein this view shows in particular that the transverse ribs 3 are arranged offset in the longitudinal direction 5 from longitudinal rib 2 or 4 to longitudinal rib 2 or 4. This results in a likewise offset pattern of the open areas 10.

[0040] According to the invention, the longitudinal ribs 2, on the one hand, and the further longitudinal ribs 4, on the other hand, are designed differently in their width configuration in the transverse direction 6. With respect to the width extension in the transverse direction 6, the longitudinal ribs 2 therefore represent a first longitudinal rib type and the second longitudinal ribs 4 represent a second longitudinal rib type.

[0041] The different design of the longitudinal ribs 2 and 4 results in particular from a synopsis of the Figures 3 to 8 .

[0042] As initially Figure 3 As can be seen, in the transverse direction 6 every fourth longitudinal rib is designed as a further longitudinal rib 4. All other longitudinal ribs are longitudinal ribs of the first type, ie longitudinal ribs 2. Accordingly, a further longitudinal rib 4 is followed by three longitudinal ribs 2, followed by a further longitudinal rib 4, followed in turn by three longitudinal ribs 2, etc.

[0043] The longitudinal ribs 2 each have a first section A1, to which the first frame web 7 is connected. In the area of ​​this first section A1, the longitudinal ribs 2 each have a first, maximum width B1 in the transverse direction 6, as can be seen in particular from the sectional view according to Figure 6 This first, maximum width B1 is optimized with respect to the total receiving volume provided by the open areas 10 of the grid 1 for receiving the active mass. In the illustrated embodiment, this first, maximum width B1 is 1.62 mm.

[0044] In contrast to the longitudinal ribs 2, the further longitudinal ribs 4 have a second, maximum width B2 over their entire longitudinal extent in the transverse direction 6, which exceeds the first, maximum width B1 of the longitudinal ribs 2. In the exemplary embodiment shown, this second, maximum width B2 is 2.06 mm, as can be seen from a summary of the sectional views according to the Figures 4, 5 and 6 results.

[0045] The reinforced design of the additional longitudinal ribs 4 compared to the design of the longitudinal ribs 2 has the positive effect of minimizing the grid growth that occurs due to unavoidable corrosion during the intended use of a grid for a battery electrode. The reinforced longitudinal ribs 4 are able to compensate for the forces that occur during corrosion, which in particular counteracts a longitudinal expansion of the grid 1 in the longitudinal direction 5.

[0046] The longitudinal ribs 2 are optimized with respect to their width in the transverse direction 6 to provide a maximized receiving volume for accommodating the active mass. In combination, the longitudinal ribs 2 on the one hand and the further longitudinal ribs 4 on the other hand provide a grid 1 that ensures minimized grid growth during intended use while simultaneously providing a maximized receiving volume for accommodating the active mass.

[0047] According to the Figures 3 to 8 In the preferred embodiment shown, the longitudinal ribs 2 each have a width configuration in the transverse direction 6 that changes in the longitudinal direction 5. Thus, in addition to the previously described section A1, the two further sections A2 and A3 are also provided. Section A2 of the longitudinal ribs 2 adjoins the second frame web 8. The third section A3 represents a transition section between the two sections A1 and A2.

[0048] As can be seen particularly from the sectional view according to Figure 4 As a result, the longitudinal ribs 2 in section A2 have a width in the transverse direction 6 that corresponds to the second, maximum width B2. Accordingly, the longitudinal ribs 2 in their second section A2 on the pantograph vane side have a width in the transverse direction 6 that is preferably 2.06 mm. In the region of the second section A2, the longitudinal ribs 2 and the further longitudinal ribs 4 are therefore of the same width in the transverse direction 6.

[0049] Starting from the second section A2, the longitudinal ribs 2 taper in width in the transverse direction 6, continuously until they reach the cross-sectional view according to Figure 5 reach a third, maximum width B3, which is smaller in dimension than the second, maximum width B2, but larger than the first, maximum width B1.

[0050] Starting from this width extension according to width B3, the width of the longitudinal ribs 2 tapers abruptly in the transverse direction 6 to the Figure 6 shown first, maximum width B1. Accordingly, with regard to the longitudinal ribs 2, a continuous, conically tapered width taper from width B2 to width B3 is provided, followed by a sudden width reduction to the first, maximum width B1.

[0051] The grid 1 is preferably produced in a continuous casting process. For the purpose of demoulding, both the longitudinal ribs 2 and 4 as well as the transverse ribs 3 are trapezoidal in cross-section, as the Figures 4, 5 and 6 with regard to the longitudinal ribs 2 and 4 and Figure 8 with regard to the transverse ribs 3.

[0052] As the Figures 4, 5 and 6Furthermore, "maximum width" in the sense of the invention means the cross-sectional point at which a longitudinal rib 2 or 4 has the largest dimension in the transverse direction 6. In the case of a trapezoidal cross-section, this cross-sectional point is, for example, with reference to the plane of the drawing according to Fig. 4 formed on the upper edge of a longitudinal rib 2 or 4, wherein in Fig. 4 the second, maximum width B2 is shown. In a rectangular cross-section, the width of a longitudinal strut 2 or 4 in the transverse direction 6 is constant, i.e., unlike a trapezoidal cross-section, it does not taper, so that in a rectangular cross-section, the given width in the transverse direction 6 is equal to the maximum width. Reference symbol

[0053] 1Grid 2Longitudinal rib 3Transverse rib 4Further longitudinal rib 5Longitudinal direction 6Transverse direction 7First frame web 8Second frame web 9Current collector vane 10Open areas

Claims

1. Grid for an electrode of a lead-acid battery, the grid comprising a plurality of longitudinal ribs (2) arranged at a distance from each other in the transverse direction (6) and a plurality of transverse ribs (3), each arranged between two adjacent longitudinal ribs (2) and connected thereto, which longitudinal and transverse ribs (2, 3) form a grid pattern with open areas (10) for receiving an active mass, wherein the longitudinal ribs (2) have a first, maximum width (B1) in the transverse direction (6) at least in a section (A1) extending in the longitudinal direction (5), which first, maximum width is designed in an optimized manner with regard to the total receiving volume provided by the open areas (10) for receiving the active mass, characterized in that at least one further longitudinal rib (4) is provided, which has a second, maximum width (B2) in the transverse direction (6) over its entire longitudinal extent, which second, maximum width exceeds the first, maximum width (B1) of the other longitudinal ribs (2).

2. Grid according to claim 1, characterized in that the second, maximum width (B2) exceeds the first, maximum width (B1) by 20% to 35%, preferably by 25% to 30%, even more preferably by 27.5%.

3. Grid according to any one of the preceding claims, characterized in that the first, maximum width (B1) is 1.4 to 1.8 mm, preferably 1.5 to 1.7 mm, even more preferably 1.6 mm.

4. Grid according to any one of the preceding claims, characterized in that the second, maximum width (B2) is 1.8 mm to 2.2 mm, preferably 1.9 mm to 2.1 mm, even more preferably 2.0 mm.

5. Grid according to any one of the preceding claims, characterized in that a plurality of further longitudinal ribs (4) having a second, maximum width (B2) in the transverse direction (6) is provided.

6. Grid according to claim 5, characterized in that every third to fifth, preferably every fourth longitudinal rib in the transverse direction (6) is a further longitudinal rib (4) having a second, maximum width (B2) in the transverse direction (6).

7. Grid according to any one of the preceding claims, characterized in that the longitudinal ribs (2) have, in a second section (A2) extending in the longitudinal direction (5), a width in the transverse direction (6) that corresponds to the second, maximum width (B2) of the further longitudinal rib (4).

8. Grid according to claim 7, characterized in that the longitudinal ribs (2) have in a third section (A3), which extends in the longitudinal direction (5) between the second and the first section (A2, A1), a width in the transverse direction (6) that continuously narrows from the second, maximus width (B2) to a third, maximum width (B3).

9. Grid according to any one of the preceding claims, characterized in that the longitudinal ribs (2) and the further longitudinal rib (4) extend between a first frame web (7) and a second frame web (8) to which they are integrally connected, wherein the second frame web (8) carries a current collector lug (9).

10. Grid according to claim 9, characterized in that the second section (A2) of the longitudinal ribs (2) merge into the second frame web (8) and the first sections (A1) of the longitudinal ribs (2) merge into the first frame web (7).

11. Grid according to any one of the preceding claims, characterized in that the gird is produced in a continuous casting process.

12. Grid according to claim 11, characterized in that the longitudinal ribs (2) as well as the further longitudinal rib (4) each have a trapezoidal cross-section.

13. Grid according to any one of the preceding claims 1 to 10, characterized in that the longitudinal ribs (2) as well as the further longitudinal rib (4) each have a rectangular cross-section.