DE102013203190A1 - Protective device for electrochemical cells - Google Patents

Abstract

The invention relates to a protective device for at least one electrochemical cell (1), which comprises a housing (5). At least one protective element (10) is arranged therein, which forms an electrical connection between a terminal connection (18) and at least one electrode (20). The at least one protective element (10) comprises several sections (26, 28, 30). The section (26, 28, 30) in which a melting area is formed extends in the housing (5) of the electrochemical cell (1) essentially in a vertical orientation.

Description

The invention relates to a protective device for an electrochemical cell, which protects the electrochemical cell from damage, for example by charging, discharging or short circuit.

State of the art

DE 10 2008 063 136 A1 discloses a method and apparatus for protecting a lithium-ion battery under thermal and / or electrical overloading due to a malfunction, such as a short circuit or overcharge. The solution according to DE 10 2008 063 136 A1 can be used in a hybrid vehicle or an electric vehicle. Battery electronics monitor the operating status of the lithium-ion battery with regard to the current value, the voltage value, the temperature and the cell internal pressure. When stored limit values are exceeded, the lithium-ion battery is disconnected from the electrical system of the vehicle by means of a disconnecting device. The separating device is arranged between the lithium-ion battery and the electrical system, wherein the separating device can be designed as a relay, reversible fuse or pyrotechnic switch. The separator is integrated into a current path, whereby the current path is interrupted when activated and thus the current flow.

DE 10 2010 049 611 A1 discloses a battery module unit for vehicles, comprising a plurality of battery cells connected in series, which are separated in the event of a fault at predetermined breaking points by a safety device in sub-modules whose mains voltage is below a critical voltage. The safety device comprises a multiplicity of identical or differently designed separating means which are activated by a control unit, wherein a mechanical damage of at least one individual cell is detected directly or indirectly via indicative variables, for example by a crash or airbag sensor.

DE 10 2010 036 379 A1 relates to a high-voltage battery for hybrid or electric vehicles, comprising interconnected battery modules, wherein release means are provided, which are arranged in normal operation outside an electrical connection. As a result, no additional electrical resistance is displayed. An accident detected by accident sensors triggers activation of the release agent.

There is a need for a protective device for an electrochemical cell in which after a triggering subsequent reactions, such as evaporation of residual highly flammable electrolytes from an electrode ensemble of a battery cell or autoignition by a reaction of lithiated carbon with air are prevented.

Disclosure of the invention

According to the invention, a protective device for at least one electrochemical cell is proposed which comprises a housing in which at least one protective element is arranged. The at least one protective element forms an electrical connection between a terminal connection and at least one electrode or an electrode ensemble. The at least one protective element can have a first, a second and a third section, the second section lying between the first and third sections. The second section has a melting area. The at least one protective element is oriented vertically in such a way that the second section is under tensile stress in the installed state, since the electrodes or the electrode ensemble are suspended therefrom. The tensile stress is caused by the weight of the at least one electrode, so that a bias in the vertically arranged part of the at least one protective element prevails.

In one embodiment of the protective device according to the invention, the second portion has a second width, which is smaller than a width of the adjacent portions of the at least one protective element.

In a further embodiment, the protective element can have a constant thickness. Alternatively, the protective element may also be designed as a strip with a variable thickness. Furthermore, in the protective device according to the invention, at least one section can be provided with a jacket, which is preferably made of a plastic, in particular a thermoplastic, for example polyethylene, polypropylene, polyethylene terephthalate, polyfluoroalkylene, polyphenylsulfide or polyimide. The sheath may be formed as a plastic film, tape or Kunststoffumspritzung. The material of the sheath preferably has a lower melting temperature than the material from which the at least one protective element is made. In a preferred embodiment, the material of the sheath on an additive which causes a volume expansion of the material of 5% to 15%, preferably 10%, in a molten state. As an additive, a flame retardant is preferably used. The flame retardant may be a phosphate based or aluminum hydroxide based material.

In the protective device according to the invention, the melting region may be formed such that it is divided in the molten state into a first and a second end region. During melting, a free space is created between the first and second end region of the melting region, since the dead weight of the at least one electrode or the electrode assembly pulls one of the end regions away from the other end region due to gravity. The clearance preferably has a width that is insurmountable for an arc that can be generated with the electrical energy stored in the electrochemical cell. Preferably, the width of the free space is 1 mm to 2 mm, particularly preferably 1.4 mm to 1.5 mm.

When a short circuit occurs, an increased current density occurs in the tapered melting region, which leads to heat generation. The heat generation can melt the melting area itself and the sheath. The material from which the sheath is preferably made, is flowable in the molten state. Furthermore, after melting, the melting region may be enclosed at at least one end region of the sheathed and re-solidified material of the sheath.

In a preferred embodiment of the protective device according to the invention, the portion of the at least one protective element, which has the melting region, is arranged vertically oriented in the housing. In the intact state of the second section is acted upon by the weight of the at least one electrode or at least one electrode ensemble with a tensile stress. The bias voltage is generated by the weight of the at least one electrode or the electrode ensemble. In a further embodiment, the at least one protective element has a bending region, which may be formed in the first section of the at least one protective element as an arc section, for example as a 90 ° arc. Alternatively, the bending region may be formed in the third section of the at least one protective element.

Advantages of the invention

The protective device proposed according to the invention provides a possibility of protecting an electrochemical cell against electrical damage after a short circuit, for example as a result of an accident. When a short circuit occurs, the circuit in the electrochemical cell is interrupted. Upon melting of the melting region in the second section, the dead weight of the at least one electrode or of the at least one electrode ensemble produces a lowering movement of the electrode ensemble or of the at least one electrode, whereby a free space is created between the mutually opposite ends of the molten melting region. By the solution proposed according to the invention, the weight of the internals, i. the at least one electrode or the at least one electrode ensemble exploited for the separation of the electrical connection. The protective device according to the invention can be attached in an advantageous manner at each point of a battery. The protective device according to the invention is maintenance-free and can also be installed in places in a battery that are difficult to access. By activating the protective device according to the invention, chemical reactions in the cell interior in which gas evolution or inflammation can occur are avoided. The protective device according to the invention increases the safety when operating an electrochemical cell and avoids damage caused by a short circuit, which can occur, for example, in an accident.

Furthermore, the proposed protective device is simple and inexpensive to produce and can be used in a variety of types of electrochemical cells. The installation of the protective device can be carried out with minimal effort into a manufacturing process, e.g. a battery manufacturing, integrated. Furthermore, the taper of the at least one protective element in the second section ensures easy manufacturability. At least one end region of the melting region is fused in the molten state by the molten material of the sheath and thereby electrically insulated. As a result, a rapid and reliable inclusion of at least one end region of the molten melting region is possible, whereby the reliability of an electrochemical cell is further increased.

If the second portion of the at least one protective element is arranged vertically, the tensile stress of the melting region by the at least one electrode or the at least one electrode ensemble causes the electrode-side end of the at least one protective element to lower in a molten state of the melting region due to its own weight. The lowering of the electrode-side end region of the melting region of the at least one protective element creates a clearance between the end regions. The increased clearance ensures increased safety against the occurrence of an arc, which can be caused by the electrical energy stored in the electrochemical cell. Ignition of electrolytes or gases in the electrochemical cell is prevented. The operation of the invention proposed The protective device is inherently safe, so that the risk of spontaneous ignition of electrolytes or gases in the electrochemical cell due to a short circuit in an accident is further minimized.

Furthermore, in the proposed protective device, the sheath leaks simultaneously with the melting region when a short circuit occurs. The flow of the material of the molten shell ensures inclusion of the end portions of the molten melting portion and prevents arcing between the separated end portions of the at least one protective member. The melting and deliquescence of the material of the casing is triggered directly by melting the melting region of the at least one protective element. Furthermore, a volume expansion of 5% to 15% of the material of the shell in the molten state ensures a continuous and reliable enclosure of the end regions of the melting region and creates an electrical insulation of the at least one electrode or of the at least one electrode assembly. Overall, the protection device according to the invention improves the safety in the operation of an electrochemical cell and simplifies its use in safety-critical applications, such as e.g. Motor vehicles.

Brief description of the drawings

Further aspects and advantages of the invention will now be described in more detail with reference to the accompanying figures.

Hereby shows:

1 in schematic form a fuse according to the prior art;

2 an electrochemical cell;

3 schematically a protective element of a first embodiment of the protective device according to the invention;

4 shows a side view of the protective device according to the invention proposed arranged between a battery terminal and an electrode ensemble,

5 a protective element with a sheath;

6 a protective element with a sheath in a molten state of the melting region of the protective device according to the invention and

7 a side view of in 6 illustrated plan view of the inventively proposed protective element.

1 shows a protective element according to the prior art. The protective element 10 has a strip shape with extensions 17 . 19 on. The first extension 17 provides an electrical connection to a terminal connection 18 an electrochemical cell 1 ago. The second extension 19 connects the protective element 10 with an electrode 20 , In addition, the protective element points 10 a branch on, which has a first and a second branched cross-section 12 . 14 includes. Between the first and second branched cross section 12 . 14 of the protective element 10 is a recess 16 intended.

Embodiments of the invention

In 2 is schematically an electrochemical cell 1 shown a housing 5 has and with terminal connections 18 is provided. The protective device according to the invention is located inside the housing 5 ,

3 schematically shows the structure of a first embodiment of the at least one protective element 10 which is used in the protective device proposed according to the invention.

The at least one protective element 10 is essentially strip-shaped and has a first extension 19 up to at least one electrode 20 or an electrode ensemble leads. Furthermore, a second extension 17 on at least one protective element 10 trained, leading to a terminal connection 18 leads.

At least one protective element 10 is a second section 28 formed between a first section 26 and a third section 30 lies. The second section 28 of the at least one protective element 10 has a second, reduced width 34 on. The first paragraph 26 has a first width 32 , the third section 30 a third width 36 on, with the latitudes 32 . 36 can essentially correspond to each other. The second width 34 of the second section 28 is less than the first width 32 of the first section 26 and the third width 36 of the third section 30 , The first width 32 of the first section 26 goes continuously into the second width 34 of the second section 28 above. Further, the second width goes 34 of the second section 28 continuously in the third width 36 of the third section 30 above. The second section 28 forms between the first section 26 and the third section 30 a cross-sectional taper in at least one protective element 10 , The second section 28 of the at least one protective element 10 is preferably in the vertical direction in the housing 5 oriented and stands by the weight of the at least one electrode 20 or the at least one electrode ensemble under tensile stress. If a short circuit occurs in the in 3 not shown electrochemical cell 1 occurs in the second section 28 a high current density, which leads to heat generation. The heat generation leads to a melting of the melting range 22 ,

In 4 is a protective element 10 illustrated according to another embodiment of the invention proposed protective device.

The at least one protective element 10 is with the terminal connection 18 connected. Furthermore, this is at least one protective element 10 with at least one electrode 20 or an electrode ensemble 20 connected. In addition, this is at least one protective element 10 formed strip-shaped, and has over its entire length a substantially constant thickness 38 on. The at least one protective element 10 includes a first, a second and a third section 26 . 28 . 30 , In the second section 28 has the at least one protective element 10 the reduced, second width 34 each smaller than the first width 32 in the first part 26 and the third width 36 in the third section 30 , The second section 28 in which the melting range 22 lies, (see illustration according to 3 ), stands by the weight of the electrode 20 or the electrode ensemble 20 under tension. In the second section 28 of the at least one protective element 10 lies the cross-sectional taper. In the event of a short circuit in the electrochemical cell 10 occurs in the melting range 22 an increased current density, which leads to a heat generation. The occurring heat generation in the melting range 22 causes the material of the at least one protective element 10 in the melting range 22 melts. Further, go out 4 that in the first section 26 a bending area 24 of the at least one protective element 10 may be formed - indicated here by dashed lines. The bending area 24 is designed as a 90 ° arc. The at least one protective element 10 can also have a bending area 24 in the third section 30 show what's in 4 also indicated by dashed lines.

In 5 is a protective element 10 according to the proposed protective device, which in a first and second section 26 . 28 provided with a jacket made of thermoplastic material.

The at least one protective element 10 includes the first, second and third sections 26 . 28 . 30 , each of the first, second and third width 32 . 34 . 36 exhibit. The first, second and third sections 26 . 28 . 30 are in the illustration according to 5 arranged vertically. Here is the second width 34 of the second section 28 less than the first width 32 in the first part 26 and the third width 36 in the third section 30 , The at least one protective element 10 is with the terminal connection 18 on the one hand and the electrode 20 , or an electrode ensemble 20 on the other hand electrically connected. In the second section 28 is the melting range 22 formed by the weight of the electrode 20 is under tensile stress, and in the case of a short circuit of the electrochemical cell 1 an increased current density occurs. The increased current density leads to heat generation, which is a melting of the melting range 22 causes. The jacket 40 made of thermoplastic encloses the second and third sections 28 . 30 of the at least one protective element 10 , When heating the protective element 10 in the melting range 22 there is an immediate heat input into the sheath 40 , When the melting range melts 22 melts the jacket 40 in the vicinity of the melting area 22 also. The material of the casing 40 is fluid in the molten state. This in 5 illustrated protective element 10 is in an intact state.

Out 6 goes a protective element 10 the protective device according to the invention in the plan view, which is in the molten state.

To the first section 26 and the third section 30 close each a first and second end 28.1 . 28.2 of the second section 28 at. The top view according 6 it can be seen that the third section 30 in the direction of the arrow 18 with a terminal connection, not shown here 18 is connected while through the arrow 20 implied that the first section 26 (compare illustration according to 4 ) with at least one electrode 20 or an electrode ensemble 20 electrically connected. Im in 6 illustrated molten state of the melting region 22 arises from the previously intact second section 28 a first end area 28 and a second end area 28.2 , Due to the reference numerals 46 indicated lowering movement in the vertical direction down the at least one electrode 20 or the at least one electrode ensemble 20 , arises between the opposite ends of the end portions 28.1 and 28.2 a free space 42 , The larger a clear width 44 between the opposite metallic ends of the end portions 28.1 and 28.2 is, the more secure electrical isolation is achieved. In addition it comes - as in 6 indicated - at a warming within the melting range 22 by the cross-sectional taper according to the second width 34 by heat conduction into the sheath 40 made of thermoplastic material for their Melting. Once the second section 28 is melted and it is the formation of a free space 42 between the end areas 28.1 and 28.2 comes, is at least the first end region by flowing of the thermoplastic material 28 completely encapsulated by this and thus electrically against the second end region 28.2 isolated. The bigger the clear width 44 within the open space 42 between the two end areas 28.1 and 28.2 is, the more secure electrical isolation can be achieved.

Immediately after the melting range 22 and the sheath 40 are melted from thermoplastic material, the plastic material of the sheath flows 40 and covers at least the first end portions 28.1 of the second section 28 and forms an electrical insulation. By melting the melting area 22 the current flow through the at least one protective element 10 interrupted. As a result, the heat generation in the melting area 22 prevented, so that a cooling and thus a solidification of the materials of the at least one protective element 10 and the sheath 40 entry

The representation according to 7 is a side view of in 6 illustrated plan view of the invention proposed protective element 10 refer to.

Out 7 shows that the example strip-shaped protective element 10 essentially a constant thickness 38 having. 6 moreover shows that the sheath 40 made of thermoplastic material, which can be found in the in 6 and 7 illustrated embodiment on the outside of the third section 30 by corresponding heat input around the first end region 28.1 flows and this electrically from the second end 28.2 separates. The bigger the clear width 44 between the opposite end portions 28.1 and 28.2 is, the safer electrical isolation is achieved. By reference 46 is the lowering movement of the at least one electrode 20 or an electrode ensemble 20 indicated. The greater its weight, the safer electrical separation can be achieved by forming a correspondingly enlarged free space 52 upon occurrence of a short circuit after melting of the melting range 21 between the end areas 28.1 and 28.2 be achieved.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008063136 A1 [0002, 0002]
• DE 102010049611 A1 [0003]
• DE 102010036379 A1 [0004]

Claims (11)

Protective device for at least one electrochemical cell ( 1 ), comprising a housing ( 5 ), in which at least one protective element ( 10 ), which has a terminal connection ( 18 ) and at least one electrode ( 20 ) or an electrode ensemble ( 20 ) electrically connects and a melting area ( 22 ), characterized in that the protective element ( 10 ) several sections ( 26 . 28 . 30 ) and a section ( 26 . 28 . 30 ), which has a melting range ( 22 ), in the housing ( 5 ) in a vertical orientation. Protective device according to claim 1, characterized in that the at least one protective element ( 10 ) a constant thickness ( 38 ) having. Protective device according to claim 1 or 2, characterized in that the melting region ( 22 ) in the second section ( 28 ) and a second width ( 34 ) which is smaller than a width ( 32 . 36 ) of the adjacent first and third sections ( 26 . 30 ) of the at least one protective element ( 10 ). Protective device according to one of Claims 1 to 3, characterized in that at least one of the sections ( 26 . 28 . 30 ) with a sheath ( 40 ) is provided. Protective device according to claim 4, characterized in that the sheath ( 40 ) made of a thermoplastic material, in particular polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyfluoroalkylene or polyphenylsulfide. Protective device according to claim 4 or 5, characterized in that the sheath ( 40 ) is designed as a plastic film, tape or Kunststoffumspritzung. Protective device according to one of claims 4 to 6, characterized in that the material of the sheath ( 40 ) has a lower melting temperature than the material of the at least one protective element ( 10 ). Protective device according to one of claims 1 to 7, characterized in that the melting region ( 22 ) in the molten state a first end region ( 28.1 ) and a second end region ( 28.2 ) and between the end regions ( 28.1 . 28.2 ) a free space ( 42 ) arises. Protective device according to claim 8, characterized in that the free space ( 42 ) a width ( 44 ), which, for one through the electrochemical cell ( 1 ) is insurmountable, and preferably 1 mm to 2 mm, more preferably 1.4 mm to 1.5 mm. Protective device according to claim 8 or 9, characterized in that the sheath ( 40 ) in a molten state of the melting range ( 22 ) the at least one end region ( 28.1 . 28.2 ) includes electrically insulating. Protective device according to one of Claims 1 to 10, characterized in that the second section ( 28 ) vertically in the housing ( 5 ) is arranged and in the intact state of the protective element ( 10 ) through the at least one electrode ( 20 ) or the at least one electrode ensemble ( 20 ) is subjected to a tensile stress.

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