JP2012028016A - Connection structure of electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent connection state by reducing connection resistance.SOLUTION: A structure in which a connection plate 34 is connected to an aluminum-made electrode 32 including a pedestal 32a and a screw 32b formed integrally with the pedestal 32a and protruded onto the pedestal 32a is characterized in that the connection plate 34 is connected while held between a metallic nut 35 threadably engaging the screw 32b and the pedestal 32a, and fine projections 36 are arrayed and formed on a seating face 35a of the nut 35 which is opposed to the connection plate 34. The fine projections 36 grind a surface of the connection plate 34 and further dig into the surface and the nut 35 and connection plate 34 are electrically connected to each other with low contact resistance, thereby forming a current path shown by an arrow (b) in addition to a current path shown by an arrow (a).

Description

  The present invention relates to an electrode connection structure applied when, for example, a plurality of battery electrodes are connected via a connection plate.

  For example, in order to generate large electric power, a plurality of batteries (single cells) are connected in series to form an assembled battery, or a plurality of such assembled batteries are connected in parallel for use. ing.

  FIG. 9 shows a configuration described in Patent Document 1 as a conventional example of such an assembled battery. In this example, four batteries 11 are connected in series to form an assembled battery. Four batteries 11 are accommodated in a case 12, and a lid 13 is disposed on the opening side of the case 12, and the battery 11 is fixed in the case 12.

  Adjacent batteries 11 are connected in series via a metal connection plate 14 having a rectangular flat plate shape. Although not visible in the connection plate 14 in FIG. 9, through holes are formed at both ends.

  The battery 11 includes a positive electrode (electrode terminal) 15 and a negative electrode (electrode terminal) 16, and the electrodes 15 and 16 are plate-like joints having a flat upper surface in contact with the connection plate 14. There are provided portions 15a and 16a and rod-like connecting portions 15b and 16b protruding upward from the joint portions 15a and 16a. The rod-like connecting portions 15b and 16b are formed in a columnar shape, and a screw is formed on the outer surface.

  The electrodes 15 and 16 on the same end side of the adjacent batteries 11 are connected to the rod-like connection portions 15b and 16b after the rod-like connection portions 15b and 16b of the electrodes 15 and 16 are inserted into the through holes at both ends of the connection plate 14, respectively. This is done by screwing the nut 17 and tightening the nut 17. In FIG. 9, reference numeral 18 denotes a washer interposed between the connection plate 14 and the nut 17.

  FIG. 10 shows the electrode connection structure in Patent Document 1 on the electrode 15 side as an example, and the connection plate 14 is sandwiched and connected by a joint 15 a of the electrode 15 and a washer 18.

JP 2010-15760 A

  By the way, the constituent material of the electrode of the battery is generally selected according to the type of the battery. For example, in a lithium ion battery whose demand is increasing recently, aluminum (Al) is generally used for the positive electrode and copper is used for the negative electrode. (Cu) is used.

  However, Al used for the positive electrode has a problem that contact resistance is higher than Cu used for the negative electrode due to the influence of an oxide film of Al.

  FIG. 11 and FIG. 12 show the method and results when this problem was examined by experiment. As shown in FIG. 11, two experimental metal plates 21 are set on a jig 22, and the two metal plates 21 are screwed and fixed using M6 bolts 23 and nuts 24, and the jig is fixed. 22, the contact resistance between the two metal plates 21 was measured.

  The constituent material of the metal plate 21 is Al and Cu, that is, the Al and Cu metal plates 21 are brought into contact with each other, and the contact resistance when screwed and fixed and the two Cu metal plates 21 are brought into contact with each other. The contact resistance when the screw was fixed was measured by changing the tightening torque. In general, the electrode connection plate is made of Cu, the Cu plate is assumed to be a connection plate, and the Al plate is assumed to be an Al electrode surface in contact with the connection plate.

  As shown in FIG. 12, when the two metal plates 21 are made of Cu (in the case of Cu—Cu), the contact resistance is extremely low, but when one metal plate 21 is made of Al (in the case of Cu—Al). ), The contact resistance is nearly an order of magnitude higher than that of Cu-Cu, and it can be seen that the contact resistance hardly decreases despite increasing the tightening torque.

  Such a high contact resistance causes a deterioration in current efficiency and causes a situation in which heat generation increases.

  In view of the above-described problems, an object of the present invention is to provide an electrode that can be satisfactorily connected with a low connection resistance when connecting a connection plate to an aluminum electrode such as a positive electrode of a lithium ion battery. It is to provide a connection structure.

  According to the first aspect of the present invention, in the structure in which the connection plate is connected to the aluminum electrode including the pedestal and the screw integrally formed with the pedestal and protruding on the pedestal, the connection plate is screwed into the screw. The structure is such that the metal nut and the pedestal are sandwiched and connected, and the minute projections are arranged on the seating surface that contacts the connecting plate of the nut.

  According to a second aspect of the invention, in the first aspect of the invention, a groove for discharging scraped scraps is formed on a seating surface on which microprojections are arranged.

  According to a third aspect of the invention, in the first or second aspect of the invention, tin plating is performed on the fine protrusions.

  In the invention of claim 4, in the invention of any one of claims 1 to 3, the inside of the nut is made of copper.

  In this invention, the connection plate is structured to be sandwiched and connected by the electrode pedestal and a nut having a microprojection on the seat surface, and at that time, the microprojection of the nut scrapes and bites the surface of the connection plate. It has become.

  Therefore, according to the present invention, the nut and the connection plate conduct well with extremely low contact resistance, that is, a good current path is formed between the screw of the electrode and the connection plate via the nut. It has become. Due to the influence of the aluminum oxide film, the contact resistance between the electrode pedestal and the connection plate becomes high, and even if the contact resistance is unstable, the presence of the current path through the nut makes it The electrode and the connection plate are well connected with a low connection resistance.

The perspective view which shows one Example of the connection structure of the electrode by this invention. The principal part enlarged view of FIG. A is a bottom view of the nut in FIG. 2, and B is a perspective view thereof. The figure for demonstrating a current pathway. A graph showing the relationship between load and wiping amount and contact resistance, A is a combination of a stainless steel projection and an aluminum plate, and B is a combination of a tin projection and an aluminum plate. The figure which shows the other example of a shape of a nut seat surface, A is a bottom view, B is a perspective view. The figure which shows the structural example of the nut which has copper inside, A is a perspective view, B is sectional drawing. The figure which shows the other structural example of the nut which has copper inside, A is a perspective view, B is sectional drawing. The perspective view which shows the example of a conventional structure of an assembled battery. The figure which shows the connection structure of the electrode in FIG. The figure for demonstrating the method of the measurement experiment of contact resistance. The graph which shows the relationship between the tightening torque of a screw, and contact resistance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of an electrode connection structure according to the present invention, and FIG. 2 shows an enlarged main portion thereof. In this example, the electrodes of two assembled batteries are connected via a connection plate.

  Although the assembled battery 31 is illustrated in a simplified manner in FIG. 1, the assembled battery 31 includes a plurality of batteries inside and includes a pair of electrodes 32 and 33 on the outside. The electrode 32 is a positive electrode and the electrode 33 is a negative electrode. In this example, the two assembled batteries 31 are connected in parallel, that is, the electrodes 32 forming the positive electrode and the electrodes 33 forming the negative electrode are connected to each other via the connection plate 34. In FIG. 1, the connection plate 34 on the electrode 33 side is hidden and cannot be seen.

  The electrode 32 includes a pedestal 32a and a screw 32b formed integrally with the pedestal 32a and protruding on the pedestal 32a, and the electrode 33 has the same configuration.

  The electrodes 32 are connected to each other by inserting screws 32b of the electrodes 32 into through holes (not visible in FIG. 2) formed at both ends of the connection plate 34, and screwing nuts 35 into the screws 32b. Then, the nut 35 is tightened, whereby the connection plate 34 is sandwiched and connected between the nut 35 and the base 32a of the electrode 32 as shown in FIG. Connection between the electrodes 33 is performed in the same manner.

  FIG. 3 shows the details of the nut 35 used for the above-mentioned connection, and the nut 35 has a large number of minute protrusions 36 formed on the contact surface with the connection plate 34, that is, the seat surface 35a. The In this example, the microprotrusions 36 have a quadrangular pyramid shape and are arranged vertically and horizontally. The nut 35 is made of metal, and is formed of, for example, stainless steel.

  Since the nut 35 has a large number of minute protrusions 36 on the seat surface 35a as described above, the minute protrusion 36 actively scrapes the surface of the connection plate 34 when the nut 35 is screwed into the screw 32b of the electrode 32 and tightened. In this example, the nut 35 and the connection plate 34 are electrically connected with extremely low contact resistance.

  FIG. 4 shows a current path in the connection structure as described above. When the connection plate 34 is pressed against the pedestal 32a of the electrode 32, the arrow a flowing from the pedestal 32a to the connection plate 34 through the contact surface. In this example, a current path indicated by an arrow b flowing from the screw 32b of the electrode 32 through the nut 35 to the connection plate 34 is configured.

  Therefore, even if the electrode 32 is made of aluminum (Al), the contact resistance between the pedestal 32a of the electrode 32 and the connection plate 34 is increased due to the influence of the Al oxide film, and the contact resistance is not stable, Since there is a good current path (arrow b) through the nut 35, in this example, the Al electrode 32 and the connection plate 34 can be satisfactorily connected with a low connection resistance.

  In the case where the electrodes 32 made of Al are connected to each other via the connection plate 34, the connection plate 34 is preferably made of Al since there is a risk of corrosion due to a galvanic potential if the connection plate 34 is made of a different metal. In some cases, an Al oxide film also exists on the surface of the connection plate 34. Therefore, in the current path indicated by the arrow a, the contact resistance between the connection plate 34 and the base 32a may be further increased.

  On the other hand, in the current path indicated by the arrow b, the surface of the connecting plate 34 is shaved by the minute protrusions 36 of the nut 35, that is, the Al oxide film is shaved, so that a low contact resistance can be obtained. A good conduction state of the connection plate 34 can be ensured.

  Such an effect can be obtained by directly fastening the connecting plate 34 with the nut 35 having the minute projections 36 on the seating surface 35a. For example, the nut 17 is connected via the conventional washer 18 as shown in FIG. It cannot be obtained with a mounting (tightening) structure.

  In the above-described example, the nut 35 has the quadrangular pyramid-shaped microprojections 36 on the seating surface 35a. The height of the microprojections 36 is, for example, 0.02 mm or more, and the arrangement pitch is, for example, 0.02 mm or more. The shape of the minute protrusions 36 is not limited to a quadrangular pyramid, and may be a cone, for example, or may be another shape as long as the tip is sharp. In the above-described example, the minute protrusions 36 are arranged on the entire seating surface 35a of the nut 35. However, the minute protrusions 36 are not necessarily formed on the entire seating surface 35a, and only on a part of the seating surface 35a. The minute protrusion 36 may be formed. The number of the fine protrusions 36 is at least 10 or more.

  It is preferable to use press working for the formation of the fine protrusions 36 in terms of cost. Note that the minute protrusions 36 can be formed by cutting, etching, laser processing, or the like.

  The nut 35 is not limited to stainless steel, and may be made of iron. Further, tin (Sn) plating may be performed on the minute protrusions 36.

  FIG. 5 shows the results of an experiment conducted to examine the effect of applying Sn plating on the microprojections 36. A stainless steel probe having a tip of R0.1 and an Sn plate are formed on an Al plate. Each probe was pressed, and the relationship between the load and the contact resistance and the relationship between the wiping amount and the contact resistance when wiping was performed with a load of 10 N were examined. FIG. 5A shows the case where the probe is made of stainless steel, and FIG. 5B shows the case where the probe is made of Sn.

  From FIGS. 5A and 5B, it can be seen that the contact resistance can be greatly reduced by applying Sn plating to the fine protrusions 36 made of stainless steel.

  FIG. 6 shows another example of the shape of the seating surface of the nut used for connecting the connection plate 34 to the electrode 32. In this example, the nut 41 is formed on the seating surface 41a in addition to the minute protrusions 42, and scraped scraps are discharged. A groove 43 is provided. In this example, a large number of grooves 43 are formed in a spiral shape, and the spiral is formed in a direction that does not oppose the rotational direction when the nut 41 is tightened. The depth of the groove 43 is, for example, 0.02 mm or more, and the width is, for example, 0.02 mm or more.

  If such a groove 43 is formed, the scrap can be efficiently discharged, and thus an increase in contact resistance due to the presence of the scrap can be prevented. The grooves 43 are not limited to a spiral shape but may be formed in a radial shape.

  7 and 8 show a structure for reducing the resistance value of the nut itself constituting the current path and improving the conductivity, and the nut has copper (Cu) inside.

  The nut 50 shown in FIG. 7 has a box body 51 and a plate-like lid 52, each having a U-shaped cross section cut in the radial direction, formed of stainless steel, and has Cu 53 in the box body 51. A nut 53 is formed by putting Cu 53 in the box 51 and covering with a lid 52. The lid 52 and the box 51 are joined and integrated by welding. The minute protrusion 54 is formed on the outer surface of the lid 52.

  On the other hand, the nut 60 shown in FIG. 8 has a structure in which Cu 63 is put in a box body 61 having a U-shaped cross section cut in the radial direction, and a cap 62 is covered. The box body 61 and the cap 62 are made of stainless steel. The micro protrusion 64 is formed on the cap 62.

  Thus, if the nut by which the inside is comprised with Cu is used, the electroconductivity of a nut can be improved.

31 assembled battery 32, 33 electrode 32a pedestal 32b screw 34 connection plate 35 nut 36 minute projection 41 nut 42 minute projection 43 groove 50, 60 nut

Claims (4)

A structure in which a connecting plate is connected to an electrode made of aluminum comprising a pedestal and a screw formed integrally with the pedestal and protruding on the pedestal,
The connection plate is structured to be sandwiched and connected by a metal nut screwed to the screw and the pedestal,
An electrode connection structure, wherein micro projections are arranged on a seating surface of the nut facing the connection plate. The electrode connection structure according to claim 1,
An electrode connection structure, wherein a groove for discharging scraps is formed on a seating surface on which the minute protrusions are arranged. The electrode connection structure according to claim 1 or 2,
An electrode connection structure, wherein the fine protrusions are tin-plated. In the electrode connection structure according to any one of claims 1 to 3,
An electrode connection structure, wherein the inside of the nut is made of copper.

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