WO2011154777A1 - Battery with over-pressure protection arrangement - Google Patents

Battery with over-pressure protection arrangement Download PDF

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Publication number
WO2011154777A1
WO2011154777A1 PCT/IB2010/052608 IB2010052608W WO2011154777A1 WO 2011154777 A1 WO2011154777 A1 WO 2011154777A1 IB 2010052608 W IB2010052608 W IB 2010052608W WO 2011154777 A1 WO2011154777 A1 WO 2011154777A1
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WO
WIPO (PCT)
Prior art keywords
battery
pressure
battery cell
conductive part
sensing surface
Prior art date
Application number
PCT/IB2010/052608
Other languages
French (fr)
Inventor
Pui Tsang Peter Ling
Original Assignee
Pui Tsang Peter Ling
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Pui Tsang Peter Ling filed Critical Pui Tsang Peter Ling
Priority to PCT/IB2010/052608 priority Critical patent/WO2011154777A1/en
Priority to CN201080068364.3A priority patent/CN103155211B/en
Publication of WO2011154777A1 publication Critical patent/WO2011154777A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/147—Lids or covers
    • H01M50/148—Lids or covers characterised by their shape
    • H01M50/152—Lids or covers characterised by their shape for cells having curved cross-section, e.g. round or elliptic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/147—Lids or covers
    • H01M50/166—Lids or covers characterised by the methods of assembling casings with lids
    • H01M50/167—Lids or covers characterised by the methods of assembling casings with lids by crimping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H01M50/533—Electrode connections inside a battery casing characterised by the shape of the leads or tabs
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H01M50/552—Terminals characterised by their shape
    • H01M50/559—Terminals adapted for cells having curved cross-section, e.g. round, elliptic or button cells
    • H01M50/56—Cup shaped terminals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • H01M50/578—Devices or arrangements for the interruption of current in response to pressure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2200/00—Safety devices for primary or secondary batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2200/00—Safety devices for primary or secondary batteries
    • H01M2200/20—Pressure-sensitive devices
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to batteries having over-pressure protection arrangements, and more particularly to rechargeable batteries, such as lithium ion rechargeable batteries, having over-pressure current interruption means or assembly.
  • This invention also relates to an over-pressure interruption arrangement for rechargeable batteries.
  • Batteries are a widely used form of stored energy source.
  • a typical battery comprises a positive electrode plate group and a negative electrode plate group which are connected respectively to a positive output terminal and a negative output terminal by their respective electrodes.
  • the pair of positive and negative electrode plate groups is contained within a battery cell and is immersed in electrolyte. Stored energy is released and converted into electrical energy during a conversion process when the output terminals of a battery are electrically connected. When a battery is being recharged, electrical energy will be converted into stored energy by a reversal prose. During these energy conversion processes, heat and gases are produced, and internal pressure of the battery cell may increase beyond a safety limit. To obviate safety risks, for example, to prevent explosion due to over-pressure, batteries with over-pressure protection are known.
  • Lithium rechargeable batteries are preferred for many consumer electronics, and are currently becoming more popular in power applications, such as power tools, powered bicycles, and electric vehicles, due to their high energy density, high battery voltage and long shelf life. However, it is well known that over-pressure protection is vital for maintaining safe usage of lithium rechargeable batteries.
  • Patent publications US 5,418,082 & US 4,943,497 describe sealed batteries having an over-pressure current interruption arrangement in which current connection between an electrode and a terminal is by a welded assembly. When the internal battery internal pressure reaches a predetermined threshold, a safety member operates to break the welded connection, thereby interrupting current connection of the battery.
  • Patent publication US 5,750,277 describes a sealed battery having another type of over-pressure current interrupting arrangement. In this arrangement, current connection between an electrode and a terminal is formed by a resilient conductive member urging against another conductive member. When the internal battery internal pressure reaches a predetermined threshold, a safety member is deformed and operates to break the current connection, thereby interrupting current connection of the battery.
  • Patent publication US 7, 186,477 describes a lithium rechargeable battery having an over-pressure protection header comprising essentially a rupture disc (31 ) which is riveted with an annular weld plate (33) to form the current connection. When the internal pressure of the battery exceeds a threshold, the rupture disc is popped up to break the current connection.
  • known over-pressure current interruption arrangements are not quite satisfactory. For example, in the welded type arrangement first mentioned above, a very high internal pressure is required to break the welded connection and therefore the current connection, since a large welded area is usually required to achieve a very low resistance.
  • the contact resistance can be variable and non-consistent during the life of a battery, and a battery incorporating such an arrangement would not perform well until a vibration test, which is required when a battery is to be put on the consumer market.
  • a very high internal pressure is required to pop up the rupture disc if the contact resistance between the rupture disc and the annular weld plate is to be low.
  • battery cell or battery comprising an over-pressure interruption assembly, the assembly providing electrical connection between a battery electrode and a corresponding battery terminal of the battery such that battery current could flow between the battery electrode and the corresponding battery terminal during normal working conditions, and being arranged to break the electrical connection when internal pressure of the battery reaches a predetermined pressure threshold
  • the over-pressure interruption assembly comprises a pressure sensing surface which is arranged to deform and break the electrical connection when the internal pressure of the battery reaches the predetermined pressure threshold; characterised in that the pressure sensing surface comprises a pattern of predefined mechanical weakness which is adapted to effect the electrical connection breaking deformation when over-pressure is detected.
  • An over-pressure interruption assembly comprising such mechanical weakness provides rapid electrical interruption when the internal battery pressure reaches a pre-determined level.
  • the pattern of predefined mechanical weakness may comprise weakness lines which are distributed on the pressure sensing surface.
  • the distributed weakness provides more sensitive and rapid response when the pre-determined threshold pressure is reached.
  • the pressure sensing surface may be configured such that the electrical connection breaking deformation will initially occur at, along or about the mechanical weakness. Such an arrangement provides added predictability when the deformation occurs.
  • the pattern of mechanical weakness may comprise weakness lines engraved on the pressure sensing surface.
  • the weakness lines provides a pattern along or above which deformation could occur.
  • the weakness lines may be distributed in a radial manner.
  • the radial distribution provides a more effective lateral contraction of he pressure sensing surface to effectuate disengagement.
  • the electrical connection may be effected by a tight mechanical engagement of conductive parts of the over-pressure interruption assembly, the conductive parts being disengaged from mechanical engagement when the pressure sensing surface is deformed due to over-pressure.
  • Such an arrangement is adapted to achieve a balance between low contact resistance and rapid disengagement to effectuate current interruption when the threshold pressure is reached.
  • the weakness may be arranged so that the effective footprint area of the pressure sensing surface is reduced by creasing, squeezing or crushing of the pressure sensing surface about the weakness upon deformation due to internal battery over- pressure, the reduction in effective footprint area brings about disengagement between the conductive parts. Such an arrangement facilitates rapid disengagement when the threshold pressure is reached.
  • the mechanical engagement may be by tight mechanical embracing, crimping or clasping of the conductive parts.
  • The provides a simple and effective engagement means.
  • the engagement strength of the mechanical engagement may be adapted to limit the contact resistance of the conductive parts at below a predetermined value suitable during normal battery operating conditions while permitting rapid disengagement of the engaged conductive parts when the battery internal pressure reaches the predefined threshold.
  • the weakness may be arranged to cause collapsing or crushing of the pressure sensing surface upon deformation, thereby breaking the electrical connection when battery over-pressure is detected.
  • the pressure sensing surface may be deformed into a rugged, creased, or partially crushed state to break the electrical connection when battery over-pressure is detected.
  • the deformation of the pressure sensing surface may be permanent, plastic or non- resilient.
  • the battery cell may comprise a sealed metallic can having a pressure bearing wall which is part of an output terminal of the battery cell, and the pressure sensing surface may form part of the pressure bearing wall of the metallic can.
  • the over-pressure interruption assembly may comprise a first conductive part which is in tight mechanical engagement with a second conductive part, the first conductive part comprising a pressure sensing surface, and the periphery of the pressure sensing surface being tightly embraced by the second conductive part to form the current connection.
  • the first and second conductive parts may be mechanically engaged by frictional, squeezing, compressive engagement, complementary engagement or teethed engagement.
  • the first conductive part may comprise a hollow boss or a hollow protrusion member which extends into a recess defined by a the second conductive part, the hollow boss or protrusion member being mechanically engaged along its outer side periphery by the inner periphery of the second conductive part which defines the recess to form the mechanical interlocking.
  • the end surface of the hollow protrusion member may be the pressure sensing surface.
  • the first conductive part may comprise a hollow plunger which protrudes into an aperture defined by the second conductive part, the mechanical engagement between the first and second conductive parts being formed between the outer side periphery of the hollow plunger and the inner periphery of the second conductive part.
  • the hollow plunger may be shrinkable or collapsible to reduce its effective lateral area, the plunger being moved out of mechanical engagement with the second conductive part when the hollow plunger so shrinks or so collapses.
  • the pressure sensing surface of the first conductive part may be adapted to be deformed to increase the volume of the sealed metallic can in response to an increase of battery internal pressure towards the predetermined threshold, the deformation being in a direction to break the mechanical engagement and the current connection.
  • the first conductive part may comprise a head portion protruding from a shoulder portion, the pressure sensing surface being formed on the end of the head portion; and the second conductive part may comprise a washer having an inner periphery and defining an aperture; and the head portion of the first conductive part may be in tight mechanical engagement with the inner periphery of the second conductive part, and an insulating spacer may be dispose intermediate the shoulder portion of the first conductive part and the washer of the second conductive part.
  • the head portion of the first conductive member may be arranged to contract laterally away from the periphery of the second conductive part to release from the mechanical engagement.
  • the first conductive part may be permanently attached to the battery terminal and the second conductive part is permanently attached to the battery electrode.
  • the first and second conductive parts may be separated by an insulating spacer.
  • Figure 1 is a partially cut-off view of a lithium rechargeable battery according to the present invention
  • Figure 2 is a partially exploded view of the battery of Figure 1 ,
  • Figures 3, 3A & 3B are respectively a top plan view, a bottom plan view and a longitudinal cross sectional view taken along line A-A of the top cap portion of the battery of Figure 1 ,
  • Figures 4 and 4A are respectively a top plan view & a longitudinal cross- sectional view of the insulating washer of the top cap portion Figure 1
  • Figures 5 and 5A are respectively a top plan view and a longitudinal cross- sectional view of the grip ring of the top cap portion Figure 1
  • Figure 6 is a perspective view of a cut top cap portion of Figure 1 when assembled with a washer and a grip ring
  • Figure 6A is a front plan view of the partially cut top cap portion of Figure 6
  • Figures 7A to 7C are schematic views showing transition of the rupture cup from a normal state to the collapsed state
  • Figure 8 is a perspective view of a partially cut battery incorporating a second embodiment of the current interrupting assembly of the present invention
  • Figure 9 is an exploded view of the battery of Figure 8
  • Figures 10A to 10C are schematic views showing transition of the battery of Figure 8 from a normal state to the collapsed state.
  • An exemplary lithium rechargeable battery cell 100 as an exemplary embodiment of a rechargeable battery shown in Figures 1 -7C comprises an electrode plate group 1 10 which is housed within a metallic can 1 12.
  • the metallic can 1 12 is made of aluminium sheet or aluminium alloy, comprises a peripheral wall interconnected by a top end portion 140 and a bottom end portion 160, and filled with a non-aqueous electrolyte.
  • the electrode plate group comprises a positive electrode plate 1 14 and a negative electrode plate 1 16 which are separated by an insulating separator 1 18.
  • the electrode plates 1 14, 1 16 and the separator 1 18 collectively form an electrode plate group of the battery 100.
  • Lithium transitional metal oxides for example, LiCo0 2 and LiMn0 4
  • the electrolyte is a non-aqueous electrolyte comprising, for example, LiBF 4 or LiPF 6 salts and solvent mixtures known to persons skilled in the art.
  • the electrode plate group is formed into a roll or coil form by wounding about one longitudinal end of the electrode plate group and is inserted into the battery housing in a close-fitted manner so that its transverse cross-section also follows the internal cross-sectional outline of the metallic can.
  • conductive electrode tabs 120, 122 respectively of the positive 1 14 and negative 1 16 electrode plates, protrude respectively from the upper and lower ends of the wound electrode plate group, and connect respectively with the top end portion 140 and the bottom end portion of the battery cell for making external electrical contact.
  • the free end of the positive electrode tab 120 is connected by welding to the underside of the top end portion 140 to form electrical connection between the positive electrode plate and the positive terminal of the battery, while the free end of the negative electrode tab 122 is connected, also by welding, to the upper surface of the bottom end portion 160 of the battery to form electrical connection between the negative electrode plate to the negative battery terminal.
  • the housing is filled with electrolyte after the bottom end portion 160 has been welded onto the lower rim of the peripheral wall, and the metallic can is then sealed by welding or crimping the top end portion 140 onto the top end of the peripheral wall. A good sealing ensures good preservation of electrolyte within the housing to ensure a long shelf and operation life of the battery.
  • the top end portion 140 comprises a rupture cup (or a rupture cap) 142, an insulating washer 144 and a grip ring 146 which are co- axially assembled.
  • the rupture cup 142 comprises a hollow protruding head portion 152 which extends axially towards the electrode plates and which is circumferentially surrounded by a shoulder portion 154.
  • the outer periphery of the shoulder portion is surrounded by a rim 154 and an upstanding circumferential fence which surrounds the rim, and extends axially in an opposite direction away from the free end of the head portion 152.
  • the rupture cup 142 When the top end portion 140 is attached onto the metallic housing to form the complete metallic can of the battery, the rupture cup 142 also defines the upper-most boundary of gaseous interior of the battery cell during battery operation. As a result, the outer surface of the rupture cup 142, which is the surface facing the electrode plates and electrolyte, is exposed to the gaseous environment inside the battery cell and is subject directly to battery internal pressure.
  • the assembly comprising the rupture cap 142, the insulating washer 144 and the grip ring 146 illustrates an embodiment of a over-pressure interruption assembly to be explained in more detail below.
  • the grip ring 146 is a rigid metal washer comprising a collar portion 156 which defines a central aperture 158 adapted for tight mechanical coupling with the head portion 152.
  • the central aperture of the grip ring is dimensioned slightly smaller than the cross-sectional dimension of the head portion 152, so that a tight mechanical grip can be formed between the grip ring 146 and the head portion 152 of the rupture cup, by way of riveting, when the head portion 152 is force- or press-fitted into the grip ring.
  • the insulating washer 144 is made of rubber or hard plastics and is disposed as an insulating spacer between the shoulder portion 154 of the rupture cup 142 and the collar portion 156 of the grip ring 146.
  • radial through-cuts are formed on the interior of the collar portion 156, that is, on the inner portion of the collar portion 156 which is immediately adjacent the central aperture.
  • the radial cuts are distributed and arranged so that the inner portion of the grip ring 146 is divided into equal portions of independently moveable teeth for independently "biting" into the peripheral wall of the head portion when the head portion 152 is force fitted into the grip ring 146.
  • the mechanical engagement strength (or the biting engagement) between the grip ring 146 and the head portion 152 of the rupture cup 142 is calculated or empirically adjusted so that the mechanical grip is tight enough to withstand a normal working internal pressure, while the "bite' depth is not too excessive to cause obstruction against detachment of the head portion 152 from the grip ring 146 when the head portion 152 is laterally collapsed upon reaching a threshold pressure.
  • the rupture cup 142 is integrally formed of a thin piece of metallic sheet by stamping the sheet into the shape of an inverted hat.
  • the hollow, protruding and cylindrical head (or boss) portion of the hat is disposed so that the head portion protrudes axially towards the battery interior to serve as a pressure sensing member, with the outer surface being the pressure sensing surface.
  • the hollow head portion also serves as an activation member to bring about battery current interruption when the internal pressure of the battery reaches a safety or a predetermined level.
  • each of the radial weakness lines starts from the centre of the head portion and extends transversely through the head portion to the edge of the shoulder portion 154.
  • the radial weakness lines are engraved alternately, and at an uniform angular separation of 45° in this instance, on the inner and outer surfaces of the head portion 152.
  • the alternately distributed weakness lines are designed to facilitate a foldable deformation of the head portion 152 about its center and along the weakness lines when a threshold pressure level has been reached. More specifically, the head portion 152 will undergo a transverse or radial shrinkage due to the threshold pressure, whereby the rupture cup 142 is electrically detached from the grip ring 146 to interrupt battery current,
  • the positive electrode tab 120 is connected to the positive battery terminal via the top end portion 140 of the battery. More specifically, the positive electrode tab 120 is connected to the grip ring 146, which is in turn connected to the rupture cup 142 and the positive terminal by mechanical engagement as described above. Therefore, a normal battery current connection will be maintained for as long as the positive electrode tab 120 is connected to the positive battery terminal. On the other hand, the battery current connection will be interrupted when the mechanical engagement between the grip ring 146 and the rupture cup 142 is broken due to over-pressure induced deformation of the rupture cup 142 which will lead to decoupling between the grip ring 146 and the rupture cup in the manner described below.
  • the threshold pressure is set to be around 7-9 bar.
  • the pressure required to release the mechanical engagement is above 10 bars without the weakness.
  • FIG. 8 A second embodiment of a lithium rechargeable battery 200 of this invention is shown in Figures 8 and 9, in which like, similar or equivalent parts are designated with a numeral of the equivalent part of the first embodiment plus 100.
  • the top end portion 240 is insulated from the metallic can 212 by means of an insulating cap 288 for connection to the positive battery terminal.
  • Operation of the CIA is similar to that of the first embodiment and is self-explanatory with reference to Figures 10A to 10C.
  • the pressure sensing surface of the rupture cup 142 will begin to undergo creased or folded deformation at or about the weakness, resulting in reduction of the footprint of the head portion 152 of the rupture cup to facilitate decoupling from the grip ring 146.
  • the assembly of the top end portion 140, 240 comprising the rupture cup 142, 242 and the grip-ring 146, 246 is arranged to form a current interruption assembly ("CIA") which provides a normal current connection path between the positive battery terminal and the positive electrode during normal battery operation, and the current connection path is calculated to be broken when the internal battery pressure rises to a predetermined threshold.
  • the CIA comprises first and second conductive parts which are mechanically engaged to form a current connection between the electrode and the output terminal. The mechanical engagement is adapted so that the contact resistance between the first and second conductive parts is low for low heat dissipation at the rated operating current and the strength of mechanical engagement is arranged to withstand a normal internal pressure during normal operation of the battery.
  • rupture cup 142, 242 and the grip ring 146, 246 are respectively connected to a battery terminal and an electrode plate, it would be understood that the connection can be reversed, so that the rupture cup 142, 242 and the grip ring 146, 246 are respectively connected to an electrode plate and a battery terminal.
  • the rupture cup 142, 242 is connected to the positive battery terminal, it could be connected to the negative battery terminal without loss of generality.
  • the weakness is in the form of radial lines engraved on the rupture cup, it will be appreciated that other forms of mechanical weakness, for example, distributed recesses or indentation, could be used.
  • a grip ring has a smooth circular inner periphery, its inner periphery can be teethed or serrated to enhance a firmer, yet resilient, grip.
  • the outer periphery of the protruding head may be made complementary to the inner periphery of the lock ring for an even better grip.
  • a 45° angular interval has been selected as an example of the angular separation between adjacent weakness lines, it should be appreciated that other angular separation could be used, although an angular separation of at least 45° is preferred.
  • the embodiment above is a lithium battery
  • the CIA design can be used on other types of batteries, especially rechargeable batteries, without loss of generality.
  • cylindrical batteries are described above, it would be appreciated that teh present application can be applied on other configuration of batteries, for example, oval and prismatic batteries.
  • other appropriate electrode plate and electrolyte materials from time to time known to persons skilled in the art can be used.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Connection Of Batteries Or Terminals (AREA)

Abstract

A battery comprises an over-pressure interruption assembly having a pressure sensing surface which is arranged to deform and break electrical connection when the internal pressure of the battery reaches a predetermined pressure threshold. The pressure sensing surface comprises a pattern of predefined mechanical weakness which is adapted to effect the electrical connection breaking deformation when over-pressure is detected. The assembly has a low contact resistance during normal battery operation conditions while permitting rapid current interruption when the internal pressure of the battery reaches or exceeds the predetermined pressure threshold.

Description

BATTERY WITH OVER-PRESSURE PROTECTION ARRANGEMENT
Field of the Invention
The present invention relates to batteries having over-pressure protection arrangements, and more particularly to rechargeable batteries, such as lithium ion rechargeable batteries, having over-pressure current interruption means or assembly. This invention also relates to an over-pressure interruption arrangement for rechargeable batteries.
Background of Invention
Batteries are a widely used form of stored energy source. A typical battery comprises a positive electrode plate group and a negative electrode plate group which are connected respectively to a positive output terminal and a negative output terminal by their respective electrodes. The pair of positive and negative electrode plate groups is contained within a battery cell and is immersed in electrolyte. Stored energy is released and converted into electrical energy during a conversion process when the output terminals of a battery are electrically connected. When a battery is being recharged, electrical energy will be converted into stored energy by a reversal prose. During these energy conversion processes, heat and gases are produced, and internal pressure of the battery cell may increase beyond a safety limit. To obviate safety risks, for example, to prevent explosion due to over-pressure, batteries with over-pressure protection are known.
Lithium rechargeable batteries are preferred for many consumer electronics, and are currently becoming more popular in power applications, such as power tools, powered bicycles, and electric vehicles, due to their high energy density, high battery voltage and long shelf life. However, it is well known that over-pressure protection is vital for maintaining safe usage of lithium rechargeable batteries.
Patent publications US 5,418,082 & US 4,943,497 describe sealed batteries having an over-pressure current interruption arrangement in which current connection between an electrode and a terminal is by a welded assembly. When the internal battery internal pressure reaches a predetermined threshold, a safety member operates to break the welded connection, thereby interrupting current connection of the battery. Patent publication US 5,750,277 describes a sealed battery having another type of over-pressure current interrupting arrangement. In this arrangement, current connection between an electrode and a terminal is formed by a resilient conductive member urging against another conductive member. When the internal battery internal pressure reaches a predetermined threshold, a safety member is deformed and operates to break the current connection, thereby interrupting current connection of the battery.
Patent publication US 7, 186,477 describes a lithium rechargeable battery having an over-pressure protection header comprising essentially a rupture disc (31 ) which is riveted with an annular weld plate (33) to form the current connection. When the internal pressure of the battery exceeds a threshold, the rupture disc is popped up to break the current connection. However, known over-pressure current interruption arrangements are not quite satisfactory. For example, in the welded type arrangement first mentioned above, a very high internal pressure is required to break the welded connection and therefore the current connection, since a large welded area is usually required to achieve a very low resistance. In the spring urged arrangement, the contact resistance can be variable and non-consistent during the life of a battery, and a battery incorporating such an arrangement would not perform well until a vibration test, which is required when a battery is to be put on the consumer market. In the riveted type arrangement of US 7,186,477, a very high internal pressure is required to pop up the rupture disc if the contact resistance between the rupture disc and the annular weld plate is to be low.
Therefore, it would be advantageous if an improved over-pressure current interruption arrangement for a sealed battery mitigating at least some of the shortcomings of known arrangements could be provided. Summary of Invention
According to the invention, there is provided battery cell or battery comprising an over-pressure interruption assembly, the assembly providing electrical connection between a battery electrode and a corresponding battery terminal of the battery such that battery current could flow between the battery electrode and the corresponding battery terminal during normal working conditions, and being arranged to break the electrical connection when internal pressure of the battery reaches a predetermined pressure threshold, wherein the over-pressure interruption assembly comprises a pressure sensing surface which is arranged to deform and break the electrical connection when the internal pressure of the battery reaches the predetermined pressure threshold; characterised in that the pressure sensing surface comprises a pattern of predefined mechanical weakness which is adapted to effect the electrical connection breaking deformation when over-pressure is detected. An over-pressure interruption assembly comprising such mechanical weakness provides rapid electrical interruption when the internal battery pressure reaches a pre-determined level.
The pattern of predefined mechanical weakness may comprise weakness lines which are distributed on the pressure sensing surface. The distributed weakness provides more sensitive and rapid response when the pre-determined threshold pressure is reached.
The pressure sensing surface may be configured such that the electrical connection breaking deformation will initially occur at, along or about the mechanical weakness. Such an arrangement provides added predictability when the deformation occurs.
The pattern of mechanical weakness may comprise weakness lines engraved on the pressure sensing surface. The weakness lines provides a pattern along or above which deformation could occur.
For example, the weakness lines may be distributed in a radial manner. The radial distribution provides a more effective lateral contraction of he pressure sensing surface to effectuate disengagement. The electrical connection may be effected by a tight mechanical engagement of conductive parts of the over-pressure interruption assembly, the conductive parts being disengaged from mechanical engagement when the pressure sensing surface is deformed due to over-pressure. Such an arrangement is adapted to achieve a balance between low contact resistance and rapid disengagement to effectuate current interruption when the threshold pressure is reached.
The weakness may be arranged so that the effective footprint area of the pressure sensing surface is reduced by creasing, squeezing or crushing of the pressure sensing surface about the weakness upon deformation due to internal battery over- pressure, the reduction in effective footprint area brings about disengagement between the conductive parts. Such an arrangement facilitates rapid disengagement when the threshold pressure is reached.
The mechanical engagement may be by tight mechanical embracing, crimping or clasping of the conductive parts. The provides a simple and effective engagement means.
The engagement strength of the mechanical engagement may be adapted to limit the contact resistance of the conductive parts at below a predetermined value suitable during normal battery operating conditions while permitting rapid disengagement of the engaged conductive parts when the battery internal pressure reaches the predefined threshold. The weakness may be arranged to cause collapsing or crushing of the pressure sensing surface upon deformation, thereby breaking the electrical connection when battery over-pressure is detected.
The pressure sensing surface may be deformed into a rugged, creased, or partially crushed state to break the electrical connection when battery over-pressure is detected.
The deformation of the pressure sensing surface may be permanent, plastic or non- resilient.
The battery cell may comprise a sealed metallic can having a pressure bearing wall which is part of an output terminal of the battery cell, and the pressure sensing surface may form part of the pressure bearing wall of the metallic can.
The over-pressure interruption assembly may comprise a first conductive part which is in tight mechanical engagement with a second conductive part, the first conductive part comprising a pressure sensing surface, and the periphery of the pressure sensing surface being tightly embraced by the second conductive part to form the current connection.
The first and second conductive parts may be mechanically engaged by frictional, squeezing, compressive engagement, complementary engagement or teethed engagement. The first conductive part may comprise a hollow boss or a hollow protrusion member which extends into a recess defined by a the second conductive part, the hollow boss or protrusion member being mechanically engaged along its outer side periphery by the inner periphery of the second conductive part which defines the recess to form the mechanical interlocking.
The end surface of the hollow protrusion member may be the pressure sensing surface.
The first conductive part may comprise a hollow plunger which protrudes into an aperture defined by the second conductive part, the mechanical engagement between the first and second conductive parts being formed between the outer side periphery of the hollow plunger and the inner periphery of the second conductive part. The hollow plunger may be shrinkable or collapsible to reduce its effective lateral area, the plunger being moved out of mechanical engagement with the second conductive part when the hollow plunger so shrinks or so collapses.
The pressure sensing surface of the first conductive part may be adapted to be deformed to increase the volume of the sealed metallic can in response to an increase of battery internal pressure towards the predetermined threshold, the deformation being in a direction to break the mechanical engagement and the current connection.
The first conductive part may comprise a head portion protruding from a shoulder portion, the pressure sensing surface being formed on the end of the head portion; and the second conductive part may comprise a washer having an inner periphery and defining an aperture; and the head portion of the first conductive part may be in tight mechanical engagement with the inner periphery of the second conductive part, and an insulating spacer may be dispose intermediate the shoulder portion of the first conductive part and the washer of the second conductive part.
The head portion of the first conductive member may be arranged to contract laterally away from the periphery of the second conductive part to release from the mechanical engagement.
The first conductive part may be permanently attached to the battery terminal and the second conductive part is permanently attached to the battery electrode.
The first and second conductive parts may be separated by an insulating spacer. Brief Description of Figures
Exemplary embodiments of the present invention will be described below by way of example and with reference to the following Figures, in which:
Figure 1 is a partially cut-off view of a lithium rechargeable battery according to the present invention, Figure 2 is a partially exploded view of the battery of Figure 1 ,
Figures 3, 3A & 3B are respectively a top plan view, a bottom plan view and a longitudinal cross sectional view taken along line A-A of the top cap portion of the battery of Figure 1 ,
Figures 4 and 4A are respectively a top plan view & a longitudinal cross- sectional view of the insulating washer of the top cap portion Figure 1 , Figures 5 and 5A are respectively a top plan view and a longitudinal cross- sectional view of the grip ring of the top cap portion Figure 1 ,
Figure 6 is a perspective view of a cut top cap portion of Figure 1 when assembled with a washer and a grip ring, Figure 6A is a front plan view of the partially cut top cap portion of Figure 6,
Figures 7A to 7C are schematic views showing transition of the rupture cup from a normal state to the collapsed state,
Figure 8 is a perspective view of a partially cut battery incorporating a second embodiment of the current interrupting assembly of the present invention, and Figure 9 is an exploded view of the battery of Figure 8, and
Figures 10A to 10C are schematic views showing transition of the battery of Figure 8 from a normal state to the collapsed state.
Detailed Description of the Embodiments
An exemplary lithium rechargeable battery cell 100 as an exemplary embodiment of a rechargeable battery shown in Figures 1 -7C comprises an electrode plate group 1 10 which is housed within a metallic can 1 12. The metallic can 1 12 is made of aluminium sheet or aluminium alloy, comprises a peripheral wall interconnected by a top end portion 140 and a bottom end portion 160, and filled with a non-aqueous electrolyte. The electrode plate group comprises a positive electrode plate 1 14 and a negative electrode plate 1 16 which are separated by an insulating separator 1 18. The electrode plates 1 14, 1 16 and the separator 1 18 collectively form an electrode plate group of the battery 100. Lithium transitional metal oxides, for example, LiCo02 and LiMn04, are suitable materials for use as the cathode or positive electrode material, while many carbonaceous compounds, for example, coke and non-graphitizing hard carbon, are suitable for use as the anode or negative terminal materials. The electrolyte is a non-aqueous electrolyte comprising, for example, LiBF4 or LiPF6 salts and solvent mixtures known to persons skilled in the art.
The electrode plate group is formed into a roll or coil form by wounding about one longitudinal end of the electrode plate group and is inserted into the battery housing in a close-fitted manner so that its transverse cross-section also follows the internal cross-sectional outline of the metallic can. As shown more particularly in Figure 2, conductive electrode tabs 120, 122, respectively of the positive 1 14 and negative 1 16 electrode plates, protrude respectively from the upper and lower ends of the wound electrode plate group, and connect respectively with the top end portion 140 and the bottom end portion of the battery cell for making external electrical contact. More particularly, the free end of the positive electrode tab 120 is connected by welding to the underside of the top end portion 140 to form electrical connection between the positive electrode plate and the positive terminal of the battery, while the free end of the negative electrode tab 122 is connected, also by welding, to the upper surface of the bottom end portion 160 of the battery to form electrical connection between the negative electrode plate to the negative battery terminal. The housing is filled with electrolyte after the bottom end portion 160 has been welded onto the lower rim of the peripheral wall, and the metallic can is then sealed by welding or crimping the top end portion 140 onto the top end of the peripheral wall. A good sealing ensures good preservation of electrolyte within the housing to ensure a long shelf and operation life of the battery.
Referring to Figures 1 to 6, the top end portion 140 comprises a rupture cup (or a rupture cap) 142, an insulating washer 144 and a grip ring 146 which are co- axially assembled. The rupture cup 142 comprises a hollow protruding head portion 152 which extends axially towards the electrode plates and which is circumferentially surrounded by a shoulder portion 154. The outer periphery of the shoulder portion is surrounded by a rim 154 and an upstanding circumferential fence which surrounds the rim, and extends axially in an opposite direction away from the free end of the head portion 152. When the top end portion 140 is attached onto the metallic housing to form the complete metallic can of the battery, the rupture cup 142 also defines the upper-most boundary of gaseous interior of the battery cell during battery operation. As a result, the outer surface of the rupture cup 142, which is the surface facing the electrode plates and electrolyte, is exposed to the gaseous environment inside the battery cell and is subject directly to battery internal pressure. The assembly comprising the rupture cap 142, the insulating washer 144 and the grip ring 146 illustrates an embodiment of a over-pressure interruption assembly to be explained in more detail below.
The grip ring 146 is a rigid metal washer comprising a collar portion 156 which defines a central aperture 158 adapted for tight mechanical coupling with the head portion 152. The central aperture of the grip ring is dimensioned slightly smaller than the cross-sectional dimension of the head portion 152, so that a tight mechanical grip can be formed between the grip ring 146 and the head portion 152 of the rupture cup, by way of riveting, when the head portion 152 is force- or press-fitted into the grip ring. The insulating washer 144 is made of rubber or hard plastics and is disposed as an insulating spacer between the shoulder portion 154 of the rupture cup 142 and the collar portion 156 of the grip ring 146. To strengthen the mechanical engagement between the head portion 152 and the collar portion 156, whereby contact reliability can be increased and contact resistance lowered, radial through-cuts are formed on the interior of the collar portion 156, that is, on the inner portion of the collar portion 156 which is immediately adjacent the central aperture. The radial cuts are distributed and arranged so that the inner portion of the grip ring 146 is divided into equal portions of independently moveable teeth for independently "biting" into the peripheral wall of the head portion when the head portion 152 is force fitted into the grip ring 146. In general, the mechanical engagement strength (or the biting engagement) between the grip ring 146 and the head portion 152 of the rupture cup 142 is calculated or empirically adjusted so that the mechanical grip is tight enough to withstand a normal working internal pressure, while the "bite' depth is not too excessive to cause obstruction against detachment of the head portion 152 from the grip ring 146 when the head portion 152 is laterally collapsed upon reaching a threshold pressure.
The rupture cup 142 is integrally formed of a thin piece of metallic sheet by stamping the sheet into the shape of an inverted hat. The hollow, protruding and cylindrical head (or boss) portion of the hat is disposed so that the head portion protrudes axially towards the battery interior to serve as a pressure sensing member, with the outer surface being the pressure sensing surface. In addition, the hollow head portion also serves as an activation member to bring about battery current interruption when the internal pressure of the battery reaches a safety or a predetermined level. To enable the head portion 152 to be swiftly decoupled from the grip ring when the battery internal pressure reaches a predetermined level, distributed weakness is formed on the head portion 152 of the rupture cup 142, as shown more particularly in Figures 3-3A, in which solid lines represent weakness lines formed on the inner surface of the head portion 152 and dotted lines represent weakness lines formed on the outer surface of the head portion which faces the battery interior. Specifically, each of the radial weakness lines starts from the centre of the head portion and extends transversely through the head portion to the edge of the shoulder portion 154. The radial weakness lines are engraved alternately, and at an uniform angular separation of 45° in this instance, on the inner and outer surfaces of the head portion 152. The alternately distributed weakness lines are designed to facilitate a foldable deformation of the head portion 152 about its center and along the weakness lines when a threshold pressure level has been reached. More specifically, the head portion 152 will undergo a transverse or radial shrinkage due to the threshold pressure, whereby the rupture cup 142 is electrically detached from the grip ring 146 to interrupt battery current,
As shown in Figures 1 & 7A, the positive electrode tab 120 is connected to the positive battery terminal via the top end portion 140 of the battery. More specifically, the positive electrode tab 120 is connected to the grip ring 146, which is in turn connected to the rupture cup 142 and the positive terminal by mechanical engagement as described above. Therefore, a normal battery current connection will be maintained for as long as the positive electrode tab 120 is connected to the positive battery terminal. On the other hand, the battery current connection will be interrupted when the mechanical engagement between the grip ring 146 and the rupture cup 142 is broken due to over-pressure induced deformation of the rupture cup 142 which will lead to decoupling between the grip ring 146 and the rupture cup in the manner described below.
Operation of the current interruption assembly of this battery will be described with reference to Figures 7A to 7C. When the battery with the assembled top end portion 140 is operating at a normal operating pressure, the state of the current interrupting assembly is that of Figure 7A. However, when the internal pressure of the battery rises, for example, due to over-charging, over-discharging, or over-heating due to whatever reasons, the pressure acting on the outer surface of the rupture cup 142 also rises. When the internal battery rises to a predetermined threshold value, the rupture cup 142 will begin to deform, and more particularly, will deform at or about the distributed weakness lines. Due to the alternate disposition of the weakness lines on the inner and outer surfaces of the rupture cup 142, creases or folds will be formed when the pressure sensing surfaces of the rupture cup 142 is deformed due to an increase in internal pressure, as shown in Figures 7B and 7C. Due to the radial and alternately distributed weakness lines, portions of the end surface of the head portion 152 adjacent a weakness line on the outer surface of the head portion 152 will be folded towards weakness lines on the inner surface of the head portion 152, thereby also pushing the weakness lines on the inner surface upwards towards the positive terminal. When the pressure sensing surface of the head portion 152 is sufficiently deformed, the transverse shrinkage of the head portion 152 will be sufficient to free the header portion 152 from the mechanical locking by the grip ring 146. As a result, the mechanical engagement and electrical connection will be released, thereby resulting in interruption of current of the battery. For this exemplary lithium battery of 2200 mAh, the threshold pressure is set to be around 7-9 bar. As a comparison, the pressure required to release the mechanical engagement is above 10 bars without the weakness.
A second embodiment of a lithium rechargeable battery 200 of this invention is shown in Figures 8 and 9, in which like, similar or equivalent parts are designated with a numeral of the equivalent part of the first embodiment plus 100. In this embodiment, the top end portion 240 is insulated from the metallic can 212 by means of an insulating cap 288 for connection to the positive battery terminal. Operation of the CIA is similar to that of the first embodiment and is self-explanatory with reference to Figures 10A to 10C. In summary, when the internal battery pressure rises to a predetermined threshold, the pressure sensing surface of the rupture cup 142 will begin to undergo creased or folded deformation at or about the weakness, resulting in reduction of the footprint of the head portion 152 of the rupture cup to facilitate decoupling from the grip ring 146. In the above embodiments, the assembly of the top end portion 140, 240 comprising the rupture cup 142, 242 and the grip-ring 146, 246 is arranged to form a current interruption assembly ("CIA") which provides a normal current connection path between the positive battery terminal and the positive electrode during normal battery operation, and the current connection path is calculated to be broken when the internal battery pressure rises to a predetermined threshold. Generally, the CIA comprises first and second conductive parts which are mechanically engaged to form a current connection between the electrode and the output terminal. The mechanical engagement is adapted so that the contact resistance between the first and second conductive parts is low for low heat dissipation at the rated operating current and the strength of mechanical engagement is arranged to withstand a normal internal pressure during normal operation of the battery.
While the rupture cup 142, 242 and the grip ring 146, 246 are respectively connected to a battery terminal and an electrode plate, it would be understood that the connection can be reversed, so that the rupture cup 142, 242 and the grip ring 146, 246 are respectively connected to an electrode plate and a battery terminal. Moreover, although the rupture cup 142, 242 is connected to the positive battery terminal, it could be connected to the negative battery terminal without loss of generality.
Although the weakness is in the form of radial lines engraved on the rupture cup, it will be appreciated that other forms of mechanical weakness, for example, distributed recesses or indentation, could be used. Furthermore, while a grip ring has a smooth circular inner periphery, its inner periphery can be teethed or serrated to enhance a firmer, yet resilient, grip. Similarly, the outer periphery of the protruding head may be made complementary to the inner periphery of the lock ring for an even better grip. Also, although a 45° angular interval has been selected as an example of the angular separation between adjacent weakness lines, it should be appreciated that other angular separation could be used, although an angular separation of at least 45° is preferred.
Moreover, while the embodiment above is a lithium battery, it will be appreciated that the CIA design can be used on other types of batteries, especially rechargeable batteries, without loss of generality. In addition, while cylindrical batteries are described above, it would be appreciated that teh present application can be applied on other configuration of batteries, for example, oval and prismatic batteries. Furthermore, it will be appreciated that even for lithium rechargeable batteries, other appropriate electrode plate and electrolyte materials from time to time known to persons skilled in the art can be used.
Listing of Numerals:
100 battery 44 insulating washer
1 12 housing 146 grip ring
1 14 positive electrode plate 148 rim surrounding shoulder portion
1 16 negative electrode plate 152 head portion of rupture cup
1 18 insulating separator 154 shoulder portion of rupture cup
120 positive tab 156 collar of grip ring
122 negative tab 158 aperture of grip ring
140 top end portion 160 bottom end portion
142 rupture cup 288 insulating cap

Claims

CLAIMS:
A battery cell comprising an over-pressure interruption assembly, the assembly providing electrical connection between a battery electrode and a corresponding battery terminal of the battery such that battery current could flow between the battery electrode and the corresponding battery terminal during normal working conditions, and being arranged to break the electrical connection when internal pressure of the battery reaches a predetermined pressure threshold, wherein the over-pressure interruption assembly comprises a pressure sensing surface which is arranged to deform and break the electrical connection when the internal pressure of the battery reaches the predetermined pressure threshold; characterised in that the pressure sensing surface comprises a pattern of predefined mechanical weakness which is adapted to effect the electrical connection breaking deformation when overpressure is detected.
A battery cell according to Claim 1 , wherein the pattern of predefined mechanical weakness comprises weakness lines which are distributed on the pressure sensing surface.
A battery cell according to Claims 1 or 2, wherein the pressure sensing surface is configured such that the electrical connection breaking deformation will initially occur at, along or about the mechanical weakness.
4. A battery cell according to any of the preceding Claims, wherein the pattern of mechanical weakness comprises weakness lines engraved on the pressure sensing surface.
5. A battery cell according to Claim 4, wherein the weakness lines are distributed in a radial manner.
6. A battery cell according to any of the preceding Claims, wherein the electrical connection is effected by a tight mechanical engagement of conductive parts of the over-pressure interruption assembly, the conductive parts being disengaged from mechanical engagement when the pressure sensing surface is deformed due to over-pressure.
7. A battery cell according to Claim 6, wherein the weakness is arranged so that the effective footprint area of the pressure sensing surface is reduced by creasing, squeezing or crushing of the pressure sensing surface about the weakness upon deformation due to internal battery over-pressure, the reduction in effective footprint area brings about disengagement between the conductive parts.
8. A battery cell according to Claims 6 or 7, wherein the mechanical engagement is by tight mechanical embracing, crimping or clasping of the conductive parts.
9. A battery according to any of Claims 6 to 8, wherein the engagement strength of the mechanical engagement is adapted to limit the contact resistance of the conductive parts at below a predetermined value suitable during normal battery operating conditions while permitting rapid disengagement of the engaged conductive parts when the battery internal pressure reaches the predefined threshold.
10. A battery cell according to any of the preceding Claims, wherein the weakness is arranged to cause collapsing or crushing of the pressure sensing surface upon deformation, thereby breaking the electrical connection when battery over-pressure is detected.
1 1 . A battery cell according to any of the preceding Claims, wherein the pressure sensing surface is deformed into a rugged, creased, or partially crushed state to break the electrical connection when battery over-pressure is detected.
12. A battery cell according to any of the preceding Claims, wherein the deformation of the pressure sensing surface is permanent, plastic or non- resilient.
13. A battery cell according to any of the preceding Claims, wherein the battery cell comprises a sealed metallic can having a pressure bearing wall which is part of an output terminal of the battery cell, and wherein the pressure sensing surface forms part of the pressure bearing wall of the metallic can.
14. A battery cell according to any of the preceding Claims, wherein the overpressure interruption assembly comprises a first conductive part which is in tight mechanical engagement with a second conductive part, the first conductive part comprising a pressure sensing surface, and the periphery of the pressure sensing surface being tightly embraced by the second conductive part to form the current connection.
15. A battery according to Claim 14, wherein the first and second conductive parts are mechanically engaged by frictional, squeezing, compressive engagement, complementary engagement or teethed engagement.
16. A battery cell according to Claims 14 or 15, wherein the first conductive part comprises a hollow boss or a hollow protrusion member which extends into a recess defined by a the second conductive part, the hollow boss or protrusion member being mechanically engaged along its outer side periphery by the inner periphery of the second conductive part which defines the recess to form the mechanical interlocking.
17. A battery cell according to Claims 16, wherein the end surface of the hollow protrusion member is the pressure sensing surface.
18. A battery cell according to any of Claims 14 to 17, wherein the first conductive part comprises a hollow plunger which protrudes into an aperture defined by the second conductive part, the mechanical engagement between the first and second conductive parts being formed between the outer side periphery of the hollow plunger and the inner periphery of the second conductive part.
19. A battery according to Claims 18, wherein the hollow plunger is shrinkable or collapsible to reduce its effective lateral area, the plunger being moved out of mechanical engagement with the second conductive part when the hollow plunger so shrinks or so collapses.
20. A battery cell according to Claim 19, wherein the pressure sensing surface of the first conductive part is adapted to be deformed to increase the volume of the sealed metallic can in response to an increase of battery internal pressure towards the predetermined threshold, the deformation being in a direction to break the mechanical engagement and the current connection.
21 . A battery cell according to any of Claims 14-20, wherein the first conductive part comprises a head portion protruding from a shoulder portion, the pressure sensing surface being formed on the end of the head portion; and the second conductive part comprises a washer having an inner periphery and defining an aperture; and wherein the head portion of the first conductive part is in tight mechanical engagement with the inner periphery of the second conductive part, and an insulating spacer is dispose intermediate the shoulder portion of the first conductive part and the washer of the second conductive part.
22. A battery cell according to Claim 21 , wherein the head portion of the first conductive member is arranged to contract laterally away from the periphery of the second conductive part to release from the mechanical engagement.
23. A battery according to any of Claims 14-22, wherein the first conductive part is permanently attached to the battery terminal and the second conductive part is permanently attached to the battery electrode.
24. A battery according to any of Claims 14-23, wherein the first and second conductive parts are separated by an insulating spacer.
25. A battery comprising a plurality of cells of battery according to any of the preceding claims. 26. A battery cell or battery cell substantially as described herein with reference to the Figures.
PCT/IB2010/052608 2010-06-11 2010-06-11 Battery with over-pressure protection arrangement WO2011154777A1 (en)

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