WO2009145375A1

WO2009145375A1 - Rechargeable cell

Info

Publication number: WO2009145375A1
Application number: PCT/KR2008/003046
Authority: WO
Inventors: Dong Pil Park; Tae Hyuk Kang; Jin Hong Choi; Jung Joon Lee; Tae Woo Cho
Original assignee: Energreen Co., Ltd.
Priority date: 2008-05-29
Filing date: 2008-05-30
Publication date: 2009-12-03
Also published as: KR20090124113A

Abstract

The present invention relates to a rechargeable cell, more particularly to a rechargeable cell that allows easier heat release and provides increased recharge capacity. The rechargeable cell of the present invention may include: a casing, which is shaped as a hexahedron having two or more flat sides and is formed with its width greater than its thickness, and in which a hollow portion is formed; two or more cell units, which are arranged within the hollow portion of the casing and connected in parallel, and each of which has an anode collector and a cathode collector; and one or more partition that partition the hollow portion of the casing while enabling an electrolyte to pass between the two or more cell units.

Description

Description RECHARGEABLE CELL

Technical Field

[1] The present invention relates to a cell, more particularly to a rechargeable cell that allows easier heat release and provides increased recharge capacity. Background Art

[2] A cell is a device that generates a voltage and a current from chemical reactions, where the current is formed by the exchange of electrons at the end portions of conductive elements. The cell can be divided into the primary cell, which cannot be recharged once it is depleted, and the secondary cell, which can be recharged.

[3] Examples of rechargeable cells include lead-acid batteries, alkaline batteries, gas cells, lithium ion cells, nickel-cadmium cells, nickel metal hydride cells, polymer cells, etc.

[4] The lead-acid battery is a type that utilizes electrochemical reactions, with lead peroxide used for the anode and lead used for the cathode. Dilute sulfuric acid having a specific gravity of about 1.2 is used for the electrolyte. This is a battery in which the chemical reactions are reversible, so that the battery can be recharged. The lead-acid battery is widely used as a car battery, etc.

[5] The alkaline battery, which uses a strong alkaline solution as the electrolyte, with nickel hydroxide as the anode, and iron or cadmium used as the cathode, is light and has a long service life.

[6] The nickel-cadmium cell is an alkaline battery that uses a hydroxide of nickel for the anode and cadmium for the cathode. The nickel-cadmium cell used in safety lamps for mine shafts, lighting in train cars, power sources for communication systems, power supply for electric vehicles, starting systems for diesel engines, and other high-rate discharge applications.

[7] Nickel metal hydride cell is a rechargeable cell that uses nickel for the anode, a hydrogen storage alloy for the cathode, and an aqueous alkaline solution or water, etc., for the electrolyte. The nickel-hydrogen cell is widely used, as it can provide high capacity, small size, light weight, sufficiently withstand overcharging and overdis- charging, and can be recharged numerous times. Nickel metal hydride cell provides an energy density per unit volume close to twice that of the nickel-cadmium cell, and also provides a higher capacity and greater resistance to overcharging and overdischarging than does the nickel-cadmium cell. Furthermore, nickel metal hydride cell allows highspeed charging and discharging, enables smaller and lighter products, and provides a long service life of over 500 charge/discharge cycles. [8] These various types of rechargeable cell entail exothermic reactions during charging, but as the temperature is raised because of the exothermic reactions, the charge capacity is reduced and the number of charge/discharge cycles is lowered. As such, there is a need for a structure that can effectively release the heat generated during charging to the exterior.

[9] In nickel metal hydride cell, in particular, the hydrogen storage alloy that forms the active material in the cathode provides a lower hydrogen charging amount when the temperature is higher and the pressure is lower. Thus, when a rechargeable cell is being charged, the exothermic reactions cause the temperature to increase, while the increase in temperature causes the hydrogen charging amount of the hydrogen storage alloy to decrease.

[10] Consequently, by efficiently releasing the heat generated when charging a rechargeable cell, such as a nickel-hydrogen cell, etc., and thereby maintaining an adequate temperature level, the charge capacity can be increased. Disclosure of Invention Technical Problem

[11] The present invention has been conceived in consideration of the above, and an objective of the present invention is to provide a rechargeable cell that effectively releases the heat generated during charging and also greatly increases charge capacity. Technical Solution

[12] To achieve the above objective, a rechargeable cell according to a preferred embodiment of the present invention can include: a casing, which is shaped as a hexahedron having two or more flat sides and is formed with its width greater than its thickness, and in which a hollow portion is formed; two or more cell units, which are arranged within the hollow portion of the casing and connected in parallel, and each of which has an anode collector and a cathode collector; and one or more partition that partition the hollow portion of the casing while enabling an electrolyte to pass between the two or more cell units.

[13] The partition may be shaped as a hexahedron that has a sufficient width to prevent short circuiting between adjacent cell units, and a lower end of the partition may be separated from a lower end of the casing so as to form a passageway.

[14] A guide indentation and a guide protrusion may be formed in correspondence to each other at a point of contact between the casing and the partition.

[15] The guide indentation and the guide protrusion may form a dovetail structure.

[16] The partition may include a hollow portion inside, which may be open in its upper and lower portions.

[17] The casing may include an opening, while the opening may be sealed by a first cap, the anode collectors and the cathode collectors of the cell units may penetrate through the first cap, the anode collectors of the two or more cell units may be connected by one or more anode connector, and the cathode collectors of the two or more cell units may be connected by one or more cathode connector.

[18] The anode connector and the cathode connector may include two or more connecting portions, which may be electrically connected to each of the anode collectors and the cathode collectors, and one or more joining portion, which may join the connecting portions.

[19] The joining portion may be folded in a direction perpendicular to the connecting portion, and a cut portion may partially be formed in a lower end of the joining portion.

[20] The first cap may further include a vent that connects to the hollow portion of the casing.

[21] The vent may include: a side wall, which may extend upwards from an upper surface of the first cap, and which may be open in its upper and lower portions; a horizontal wall, which may be formed in a horizontal direction inside the side wall, and in which a first hole may be formed that connects to the hollow portion of the casing; a vent cap, which may be detachably coupled to an inner perimeter at an upper portion of the side wall, and in an upper surface of which a second hole may be formed; a valve, which may be installed on the first hole such that the valve is able to move upwards and downwards; and an elastic element, which may force the valve downwards.

[22] A sealing ring may be installed at a point of contact between the valve and the first hole.

[23] A second cap may be fitted onto an upper portion of the first cap, where the second cap may cover the first cap and the anode and cathode connectors.

[24] A holding indentation may be formed in an inner surface of the second cap to hold the joining portion of the connector.

[25] An assembly indentation and an assembly protrusion may be formed in correspondence to each other at a point of coupling between the second cap and the first cap.

Advantageous Effects

[26] According to the present invention, by forming the casing with wide flat walls, the high levels of heat generated during charging can be effectively released to the exterior, to thereby prevent reductions in hydrogen charging amount in the hydrogen storage alloy forming the active material of the cathode.

[27] Also, the present invention can include two or more cell units arranged within the casing, where the two or more cell units can be connected in parallel, to increase the charge capacity of the cell. [28] Furthermore, with the present invention, two or more cell units can be made to share the electrolyte and the casing, making it possible to readily implement high capacities for the cell. Brief Description of Drawings

[29] Figure 1 is a perspective view of a rechargeable cell according to an embodiment of the present invention.

[30] Figure 2 is an exploded perspective view of a rechargeable cell according to an embodiment of the present invention.

[31] Figure 3 is a lower perspective view of a second cap based on the present invention.

[32] Figure 4 is a plan view of a casing based on the present invention.

[33] Figure 5 is a front cross-sectional view of a casing based on the present invention.

[34] Figure 6 is a front cross-sectional view of a rechargeable cell based on the present invention.

[35] Figure 7 is a magnified cross-sectional view of portion A in Figure 6.

[36] Figure 8 is an illustration of another embodiment of the present invention.

[37]

Mode for the Invention

[38] A preferred embodiment of the present invention will be described below in more detail with reference to the accompanying drawings.

[39] Figure 1 through Figure 7 illustrate a rechargeable cell according to an embodiment of the present invention.

[40] As shown in the illustrations, a rechargeable cell 10 based on the present invention may include a casing 100, and two or more cell units 21, 22 installed inside the casing 100.

[41] The cell 10 based on the present invention may include two or more opposing flat sides, and may preferably be shaped as a hexahedron.

[42] As illustrated in Figure 4 and Figure 5, the casing 100 may include a pair of opposing first flat walls 101, 102, a pair of opposing second flat walls 103, 104, a closed end 105, and an opening 106 facing the closed end.

[43] Referring to Figure 3 and Figure 4, the thickness (t) of the casing 100 may be defined by the distance between the pair of first flat walls 101, 102, and the width (w) of the casing 100 may be defined by the distance between the pair of second flat walls 103, 104, while the height (h) of the casing 100 may be defined by the length of the first and second flat walls 101, 102, 103, 104 along the vertical direction. The casing 100 may be formed with the width (w) greater than the thickness (t). As a result, the first flat walls 101, 102 may be greater in area than the second flat walls 103, 104. In particular, a ratio (t/w) of the thickness (t) to the width (w) of 1/10 or higher may be preferred. Thus, the casing 100 may be formed with the first flat walls 101, 102 having large areas facing each other, so that the area for releasing the heat generated during the charging of the cell 10 can be increased, and the efficiency of heat release can be increased accordingly.

[44] The casing 100 may include a hollow portion 107, which may be bounded by the pair of first flat walls 101, 102, the pair of second flat walls 103, 104, the closed end 105, and the opening 106.

[45] Two or more cell units 21, 22 may be arranged in the hollow portion 107 of the casing 100, where the cell units 21, 22 may be connected in parallel to increase charge capacity.

[46] Each of the cell units 21, 22 may include a plurality of anode plates 21a, 22a, a plurality of cathode plates 21b, 22b, and a plurality of separators 21c, 22c between the anode plates 21a, 22a and cathode plates 21b, 22b, etc.

[47] Leads 21d, 22d may be equipped at the upper ends of the plurality of anode plates

21a, 22a, with each lead 2 Id, 22d connected to an anode collector 2 Ip, 22p, and through-holes 2 Ig, 22g may be formed in the upper portions of the anode collectors 21p, 22p.

[48] Leads 21e, 22e may be equipped at the upper ends of the plurality of cathode plates

21b, 22b, with each lead 21e, 22e connected to a cathode collector 21n, 22n, and through-holes 2 If, 22f may be formed in the upper portions of the cathode collectors 21n, 22n.

[49] One or more partition 110 may be installed in the hollow portion 107 of the casing

100, where the partition 110 may partition the internal space of the hollow portion 107 into a number of regions corresponding to the number of cell units 21, 22. For example, in cases where there are two cell units, such as in Figure 3 and Figure 4, there may be one partition 110 installed to partition the hollow portion 107 into two regions, and in cases where there are three or more cell units, there may be two or more partitions 110 installed to partition the hollow portion 107 into three or more regions.

[50] The partition 110 may be made of an insulating material, and as each cell unit 21, 22 is installed in a partitioned region of the hollow portion 107, the two or more cell units 21, 22 may be partitioned from one another.

[51] In particular, the partition 110 may be shaped as an elongated hexahedron that extends along a longitudinal direction of the casing 100, and may include a pair of first surfaces 111, 112, which may be placed in contact with the inner surfaces of the first flat walls 101, 102, and a pair of second surfaces 113, 114, which may be placed in contact with the inner surfaces of the second flat walls 103, 104.

[52] The thickness (tl) of the partition 110 may be defined by the distance between the pair of first surfaces 111, 112, and the width (wl) of the partition 110 may be defined by the distance between the pair of second surfaces 113, 114. The width (wl) of the partition 110 may preferably be of a minimum length that can prevent short circuiting between adjacent cell units 21, 22.

[53] The first surfaces 111, 112 of the partition 110 may closely adhere to and be guided by the first flat walls 101, 102, and for this purpose, guide protrusions 101a, 102a can extend along a longitudinal direction on the inner surfaces of the first flat walls 101, 102, while guide indentations I l ia, 112a can be formed respectively in the first surfaces 111, 112 of the partition 110. Thus, as the components can be assembled in predetermined positions with the guide indentations I l ia, 112a of the partition 110 following the guide protrusions 101a, 102a, the two or more cell units 21, 22 can be partitioned with greater precision.

[54] Also, in order to allow precise assembly of the partition 110 and to prevent the partition 110 from becoming separated, etc., the guide protrusions 101a, 102a and guide indentations I l ia, 112a can be formed as dovetail structures.

[55] A stopper 109 may be formed at a lower portion on an inside surface of each first flat wall 101, 102, specifically, at a lower portion of the guide protrusion 101a, 102a, and as the stoppers 109 separate the lower end of the partition 110 from the closed end 105 of the casing 100 by a particular gap, a passageway 29 may be formed between adjacent cell units 21, 22, so that the two or more cell units 21, 22 may share the electrolyte within a single casing 100, to not only implement a large capacity for the cell but also utilize the electrolyte efficiently.

[56] The passageway 29 may preferably form a minimum amount of space that enables the electrolyte to pass between the two or more cell units 21, 22 while preventing short circuiting between the two or more cell units 21, 22.

[57] The partition 110 can include a hollow portion 115, which can be open at its upper and lower portions, so that a part of the electrolyte may be stored in the hollow portion 115. This surplus electrolyte stored in the hollow portion 115 of the partition 110 can partially supplement the electrolyte that is consumed when the cell units 21, 22 are charged or discharged, and since the surplus electrolyte stored in the hollow portion 115 does not participate in the reactions and hence maintains a relatively low temperature, the surplus electrolyte can be utilized as a coolant for reducing the high levels of heat generated in each cell unit 21, 22.

[58] The opening 106 can be arranged at an upper portion of the casing 100, and a first cap 120 can be fitted onto the upper portion of the casing 100 to seal the opening 106, where the first cap 120 can seal the upper surface of the casing 100 after it is preliminarily assembled by way of assembly indentations and assembly protrusions.

[59] The first cap 120 may include a plurality of through-holes 121, through which the anode collectors 21p, 22p and cathode collectors 21n, 22n of the respective cell units 21, 22 may pass. In one side of the first cap 120 may be formed a vent 125, through which certain amounts of gas may be exhausted to the exterior when there is an excessive amount of gas generated in the cell units 21, 22.

[60] The vent 125 may include a side wall 125a extending upwards from an upper surface of the first cap 120, a horizontal wall 125b formed inside the side wall 125a along a horizontal direction, and a vent cap 125c detachably coupled to the inner perimeter at an upper portion of the side wall 125 a.

[61] The upper and lower portions of the side wall 125a may be open, and the vent cap

125c may be detachably coupled to the inner perimeter of an upper portion of the side wall 125a by way of a screw fit, etc. The horizontal wall 125b may include a first hole 125d that connects to the hollow portion 107 of the casing 100, and a valve 125e may be installed in the first hole 125d such that the valve 125e is able to move upwards and downwards. Also, the vent cap 125c may include a second hole 125h, and an elastic element 125f may be positioned between the valve 125e and the vent cap 125c such that the valve 125e is forced downwards by the elastic element 125f. A sealing ring 125g may be installed, at the portion where the valve 125e and the first hole 125d contact each other, to ensure a tight seal.

[62] With the composition described above, the vent 125 can prevent the cell from exploding, etc., in cases where an excessive amount of gas is generated in the cell units 21, 22 within the casing 100, as the valve 125e may move upwards to open the first hole 125d, if the pressure of the gas exceeds the elastic force of the elastic element 125f, allowing some of the gas to be exhausted to the exterior through the first hole 125d and second hole 125h.

[63] The anode collectors 21p, 22p and cathode collectors 21n, 22n protruding from the respective cell units 21, 22 may be connected in parallel by way of one or more anode connectors 31 and one or more cathode connectors 32. An anode connector 31 may interconnect the anode collector 2 Ip, 22p of each cell unit 21, 22, while a cathode connector 32 may interconnect the cathode collector 2 In, 22n of each cell unit 21, 22, to thereby connect adjacent cell units 21, 22 in parallel. As such, with respect to energy density in the cell 10 according to the present invention, two or more cell units 21, 22 can be connected in parallel to increase charge capacity.

[64] Each connector 31, 32 may include two or more connecting portions 31a, 32a, which may be coupled to the anode collectors 21p, 22p or cathode collectors 21n, 22n of the respective cell units 21, 22 by way of fasteners 51, 52 made from a conductive material, and one or more joining portion 31b, 32b, which may traverse between and join the connecting portions 31a, 32a.

[65] Through-holes 3 If, 32f may be formed in the connecting portions 31a, 32a, and the fasteners 51, 52 may pass through these through-holes 3 If, 32f to be fastened to the through-holes 21g, 22g, 21f, 22f of the anode collectors 21p, 22p and cathode collectors 2 In, 22n.

[66] The joining portions 31b, 32b may be folded in a direction orthogonal to the connecting portions 31a, 32a. The joining portions 31b, 32b may preferably be designed to have an optimum allowable area that permits a maximum flow of electric current. Rendering the joining portions 31b, 32b with such an allowable area can make it easier to charge and discharge high currents.

[67] A cut portion 31c, 32c may partially be formed at a lower end of a joining portion

31b, 32b, to prevent the joining portion 31b, 32b from contacting the conductive fastener 51, 52.

[68] A second cap 130 may be fitted on an upper portion of the first cap 120, where the second cap 130 may cover the upper surface of the first cap 120, the anode and cathode connectors 31, 32, the side wall 125a of the vent 125, etc.

[69] The second cap 130 may include first flat walls 131, 132 that correspond with the first flat walls 111, 112 of the casing 110, second flat walls 133, 134 that correspond with the second flat walls 113, 114 of the casing 110, a closed end 135, and an opening 136 opposite the closed end 135.

[70] Each of the first flat walls 131, 132 can be formed with a relatively low thickness to form a holding indentation 131a, 132a, in which the joining portion 31b of the anode connector 31 or the joining portion 32b of the cathode connector 32 described above may be held. By thus having the holding indentations 131a, 132a of the second cap 130 hold the joining portions 31b, 32b of the connectors 31 , 32, the degree of freedom can be increased in designing the allowable areas for the joining portions 31b, 32b.

[71] In the closed end 135 of the second cap 130, a first through-hole 135a may be included, through which the upper end of the vent 125 may pass, and two or more second through-holes 135b may be included, through which the anode terminal 41 and cathode terminal 42 may be pass. The anode terminal 41 and cathode terminal 42 may be electrically connected to the anode connector 31 and cathode connector 32.

[72] The second cap 130 may have one or more assembly protrusions 137 on a bottom edge of the first and second flat walls 131, 132, 133, 134, while the first cap 120 may have one or more assembly indentations 127 at an edge of its upper surface. This can further facilitate the assembly of the second cap 130 and first cap 120.

[73] While the embodiment shown in Figure 1 through Figure 7 illustrates only two cell units 21, 22, the present invention is not thus limited, and four cell units 21, 22, 23, 24 can be installed in the casing 100, as in the illustration of Figure 8. Furthermore, the number of cell units 21, 22 can be varied, with certain embodiments utilizing, for example, three, five, six, or seven cell units.

[74] If the number of cell units 21, 22 is changed to three, four, five, etc., the number of connecting portions 31a, 32a of the connectors 31, 32 may also be changed accordingly, to three, four, five, etc. [75]

Claims

[1] A rechargeable cell comprising: a casing shaped as a hexahedron having two or more flat sides, the casing having a width thereof formed greater than a thickness thereof, the casing having a hollow portion formed therein; two or more cell units arranged within the hollow portion of the casing and connected in parallel, the cell units each having an anode collector and a cathode collector; and one or more partition partitioning the hollow portion of the casing and enabling an electrolyte to pass between the two or more cell units.

[2] The rechargeable cell of claim 1, wherein the partition is shaped as a hexahedron having a sufficient width to prevent short circuiting between adjacent cell units, the partition having a lower end thereof separated from a lower end of the casing so as to form a passageway.

[3] The rechargeable cell of claim 1, wherein a guide indentation and a guide protrusion are formed in correspondence to each other at a point of contact between the casing and the partition.

[4] The rechargeable cell of claim 3, wherein the guide indentation and the guide protrusion form a dovetail structure.

[5] The rechargeable cell of claim 1, wherein the partition has a hollow portion therein, the hollow portion opened in an upper portion thereof and in a lower portion thereof.

[6] The rechargeable cell of claim 1, wherein the casing has an opening formed therein, the opening sealed by a first cap, the anode collectors and the cathode collectors of the cell units penetrate through the first cap, the anode collectors of the two or more cell units are connected by one or more anode connector, and the cathode collectors of the two or more cell units are connected by one or more cathode connector.

[7] The rechargeable cell of claim 6, wherein the anode connector and the cathode connector comprise: two or more connecting portions electrically connected to each of the anode collectors and the cathode collectors, and one or more joining portion joining the connecting portions.

[8] The rechargeable cell of claim 7, wherein the joining portion is folded in a direction perpendicular to the connecting portion, and the joining portion has a cut portion partially formed in a lower end thereof.

[9] The rechargeable cell of claim 6, wherein the first cap further comprises a vent connecting to the hollow portion of the casing.

[10] The rechargeable cell of claim 6, wherein the vent comprises: a side wall extending upwards from an upper surface of the first cap, the side wall opened in an upper portion thereof and in a lower portion thereof; a horizontal wall formed in a horizontal direction inside the side wall, the horizontal wall having a first hole formed therein connecting to the hollow portion of the casing; a vent cap detachably coupled to an inner perimeter at an upper portion of the side wall, the vent cap having a second hole formed in an upper surface thereof; a valve installed on the first hole such that the valve is movable upwards and downwards; and an elastic element forcing the valve downwards.

[11] The rechargeable cell of claim 10, wherein a sealing ring is installed at a point of contact between the valve and the first hole.

[12] The rechargeable cell of claim 8, wherein a second cap is fitted onto an upper portion of the first cap, the second cap covering the first cap and the anode and cathode connectors.

[13] The rechargeable cell of claim 12, wherein the second cap has a holding indentation formed in an inner surface thereof, the holding indentation holding the joining portion of the connector. [14] The rechargeable cell of claim 12, wherein an assembly indentation and an assembly protrusion are formed in correspondence to each other at a point of coupling between the second cap and the first cap.