JP2016225261A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery capable of realizing quick operation of a CID in an overcharged state.SOLUTION: The lithium secondary battery comprises: an electrode body made by laminating a positive electrode sheet, a separator sheet and a negative electrode sheet in this order; a gas generating agent; a battery case housing the electrode body and the gas generating agent; and a current interruption mechanism operated by pressure rise in the battery case. In the secondary battery, a metal layer where lithium ions can circulate is placed in the separator sheet and the metal layer is electrically connected to a negative electrode.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lithium secondary battery.

  A lithium secondary battery that is lightweight and has a high energy density is preferably used as a high-output power source mounted on a vehicle such as an electric vehicle or a hybrid vehicle. As one aspect of such a secondary battery, a mechanism (current interruption mechanism: CID) that detects an overcharge state by a battery internal pressure or the like when an overcharge state occurs due to a malfunction of the charging device or the like (current interruption mechanism: CID). : Current Interrupt Device). In the secondary battery provided with the CID, a gas generating agent such as cyclohexylbenzene or biphenyl is included to control the amount and speed of increase of the internal pressure of the battery when the battery is overcharged, thereby improving the CID operating accuracy. Things have been done. As a prior art document disclosing a secondary battery including a CID and using a gas generating agent, for example, Patent Document 1 is cited. Patent Documents 2 and 3 are prior art documents related to a separator, and disclose that a metal layer is provided on the separator.

JP 2013-161731 A JP 2011-222215 A JP 2007-507850 A

The gas generating agent present in the secondary battery reacts on the positive electrode side when overcharged, and H ⁺ is generated at that time. This H ⁺ passes through the separator and moves to the negative electrode, where it is reduced to hydrogen gas (H ₂ ). The hydrogen gas thus generated raises the internal pressure in the battery, and the CID operates. In the gas generation process in such an overcharged state, the generation rate of hydrogen gas depends on the movement time between the positive and negative electrodes of H ⁺ . Therefore, depending on the thickness of the separator disposed between the positive and negative electrodes, it takes time to generate hydrogen gas, which may limit the high-precision operation of the CID.

  The present invention has been created in view of the above problems, and an object thereof is to provide a lithium secondary battery capable of realizing rapid operation of CID in an overcharged state.

  To achieve the above object, according to the present invention, an electrode body in which a positive electrode sheet, a separator sheet, and a negative electrode sheet are laminated in this order, a gas generating agent, a battery case containing the electrode body and the gas generating agent, and Provided is a lithium secondary battery including a current interrupting mechanism that is activated by an increase in pressure in the battery case. In this secondary battery, a metal layer capable of flowing lithium ions is disposed in the separator sheet, and the metal layer is electrically connected to the negative electrode. According to said structure, the operating speed of CID in an overcharge state improves.

It is a top view which shows typically the separator sheet which concerns on one Embodiment. It is explanatory drawing which shows typically the process of hydrogen gas generation. It is a schematic diagram which expand | deploys and shows the winding electrode body which concerns on one Embodiment. It is a schematic cross section of a lithium secondary battery according to an embodiment. It is a graph which shows the internal pressure change of the battery for a test in an overcharge test. It is a graph which shows the temperature change of the battery for a test in an overcharge test.

  Hereinafter, a preferred embodiment of a lithium secondary battery (sometimes abbreviated as a secondary battery) will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field. Also, the dimensional relationships (length, width, thickness, etc.) in the figure do not reflect actual dimensional relationships.

  FIG. 1 is a top view schematically showing a separator sheet according to an embodiment. As shown in FIG. 1, a separator sheet (sometimes abbreviated as a separator) 40 is a long (band-shaped) member including a porous resin layer 42 and a metal layer 44. A part of the metal layer 44 is sandwiched between the porous resin layers 42 and the other part is exposed to the outside of the porous resin layer 42. Here, in the metal layer 44, a portion sandwiched between the porous resin layers 42 is referred to as an inner layer portion 44a, and a portion exposed outside the porous resin layer 42 is referred to as an exposed portion 44b. The exposed portion 44 b is located in a predetermined region including one end of the metal layer 44 in the width direction, and extends in parallel to the length direction of the metal layer 44. The exposed portion 44b is a portion that comes into contact with a negative electrode to be described later, whereby the metal layer 44 is electrically connected to the negative electrode (specifically, the negative electrode current collector).

Here, the advantage of disposing the metal layer 44 in the separator 40 will be described. When the secondary battery is overcharged, as shown to the left in FIG. 2, the gas generating agent in the secondary battery reacts with the surface of the positive electrode (positive electrode active material in particular), where H ⁺ Will occur. The H ⁺ passes through the separator and moves (diffuses) to the negative electrode (specifically, the negative electrode active material), where it is reduced to H ₂ . That is, hydrogen gas (H ₂ ) is generated. By this hydrogen gas, the internal pressure in the battery rises and the CID operates. According to the present invention, since the metal layer 44 is electrically connected to the negative electrode, H ⁺ generated by the reaction of the gas generating agent 100 on the positive electrode 10 side reaches the negative electrode 20 as shown on the right side of FIG. When reaching the earlier metal layer 44, it may become hydrogen gas. Therefore, as shown in the left side of FIG. 2, compared with the conventional structure in which H ⁺ has to move the entire positive and negative electrodes, reducing the time from the H ⁺ generated until hydrogen gas generation, rapid gas generation As a result, it is considered that the operating speed of the CID in the overcharged state is improved. This is advantageous also in terms of improving gas generation efficiency, and may bring advantages such as easy securing of the amount of gas necessary for CID operation. Note that the present invention is not limited to the above interpretation.

  The separator 40 of this embodiment will be described in more detail. Although not particularly illustrated, the porous resin layer 42 has two layers of a resin layer A and a resin layer B. The resin layer A and the resin layer B have the same rectangular shape (also referred to as a band shape), and are overlapped with the metal layer 44 interposed, with most of the metal layer 44 (main part) interposed therebetween. Yes. In the metal layer 44, the portion laminated with the resin layer A and the resin layer B is an inner layer portion 44a. In the region where the inner layer portion 44a exists, the separator 40 has a structure in which the metal layer 44 (inner layer portion 44a) is disposed between the resin layer A and the resin layer B. Further, at least one surface of the metal layer 44 that is not sandwiched between the resin layer A and the resin layer B (exposed portion 44b) is exposed to the outside. In the separator 40, the resin layer A and the resin layer B are bonded and fixed at the end opposite to the exposed portion 44 b side of the metal layer 44 in the width direction of the separator 40 by heat sealing or the like. In addition, the resin layer A and the resin layer B may be composed of independent sheet-like members, or may be formed by folding a single resin sheet.

  The separator may be formed of a member that insulates the positive electrode active material layer and the negative electrode active material layer and allows the electrolyte to move. As the separator material, various porous resin sheets (which may be a porous resin layer) can be used. Preferable examples of the porous resin sheet include a sheet mainly composed of a polyolefin such as polyethylene (PE) and polypropylene (PP), a thermoplastic resin such as polyester and polyamide. As a preferred example, a sheet having a single-layer structure or a multilayer structure (polyolefin-based sheet) mainly composed of one or more kinds of polyolefin-based resins can be given. The said porous resin sheet can contain additives, such as various plasticizers and antioxidant, as needed. The thickness of the porous resin sheet is suitably about 3 to 30 μm (preferably 5 to 25 μm, typically 8 to 15 μm). When the porous resin layer has a plurality of layers as in this embodiment, the thickness of each layer can be selected from the above range. In addition, the surface of the porous resin sheet may be provided with, for example, a heat-resistant layer containing an inorganic filler, or may be subjected to various surface treatments.

The metal layer has a shape that allows the flow of Li ⁺ and is typically porous. Note that whether or not the metal layer has a degree of porosity that allows the flow of Li ⁺ can be confirmed by evaluating the Gurley air permeability (JIS P8117) or the like. As a metal layer, the material excellent in electroconductivity is preferable and it is more preferable to use the same material as a negative electrode electrical power collector. As specific examples of the metal layer material, various metals such as copper, nickel, and titanium, and alloys thereof, and various alloys such as stainless steel can be preferably used. The thickness of the metal layer is determined by the balance between Li ⁺ flowability and conductivity, durability such as strength, and the like. The thickness is suitably less than about 10 μm, preferably less than 1 μm, more preferably 300 nm or less (for example, 100 nm or less, typically 70 nm or less). The thickness is preferably about 5 nm or more (for example, 10 nm or more, typically 30 nm or more). As a method for laminating and arranging the metal layer on the porous resin layer, various known and conventional methods can be adopted.

The total thickness of the separator is not particularly limited, but is preferably 70 μm or less (for example, 60 μm or less, typically 50 μm or less) from the viewpoint of Li ⁺ permeability. From the viewpoint of strength, the total thickness is preferably about 5 μm or more (for example, 10 μm or more, typically 15 μm or more). As described above, the distance between the positive electrode and the negative electrode is defined by the thickness of the separator, and it is considered that the gas generation speed during overcharge decreases when the distance is long, but according to the present invention, regardless of the thickness of the separator, Rapid gas generation is possible in an overcharged state. Therefore, the effect of the present invention tends to be manifested preferably and remarkably in an embodiment using a thick separator.

  Next, an electrode body including a separator will be described. FIG. 3 is a diagram schematically showing a wound electrode body according to an embodiment, and shows a long sheet structure (electrode sheet) at a stage before constructing the wound electrode body 80. As shown in FIG. 3, the wound electrode body 80 includes a positive electrode sheet (sometimes abbreviated as a positive electrode) 10 and a negative electrode sheet (sometimes abbreviated as a negative electrode) 20. The positive electrode 10 includes a long positive electrode current collector 12 and a positive electrode active material layer 14 disposed on at least one surface (typically both surfaces) of the positive electrode current collector 12. The negative electrode 20 includes a long negative electrode current collector 22 and a negative electrode active material layer 24 disposed on at least one surface (typically both surfaces) of the negative electrode current collector 22.

  The separator 40 is disposed between the positive electrode 10 and the negative electrode 20. In FIG. 3, only one separator 40 is shown, but in the present embodiment, two separators are arranged in the wound electrode body 80. In other words, the wound electrode body 80 is composed of a laminate in which the positive electrode 10, the separator 40, the negative electrode 20, and another separator (not shown) are laminated in this order. The laminated body is formed into a wound body by being wound in the longitudinal direction, and further formed into a flat shape by crushing and ablating the wound body from the side surface direction. The porous resin layer 42 constituting the separator 40 has a width larger than the width of the laminated portion of the positive electrode active material layer 14 and the negative electrode active material layer 24. By arranging this so as to be sandwiched between the stacked portions of the positive electrode active material layer 14 and the negative electrode active material layer 24, the positive electrode active material layer 14 and the negative electrode active material layer 24 are prevented from contacting each other and causing an internal short circuit. . The electrode body is not limited to a wound electrode body. Depending on the shape and intended use of the battery, an appropriate shape and structure, such as a laminate mold, can be employed as appropriate. The wound electrode body is not limited to a flat shape, and may be cylindrical.

  The positive electrode active material layer 14 formed on the surface of the positive electrode current collector 12 and the surface of the negative electrode current collector 22 are formed at the center of the wound electrode body 80 in the width direction (direction orthogonal to the winding direction). The negative electrode active material layer 24 thus formed is overlapped and densely stacked. In addition, at one end in the width direction of the positive electrode 10, a portion where the positive electrode current collector 12 is exposed without forming the positive electrode active material layer 14 (positive electrode active material layer non-forming portion 16) is provided. This positive electrode active material layer non-forming portion 16 is in a state of protruding from the separator 40 and the negative electrode 20. That is, at one end in the width direction of the wound electrode body 80, a positive electrode current collector laminated portion 15 in which the positive electrode active material layer non-forming portion 16 of the positive electrode current collector 12 overlaps is formed. Further, similarly to the positive electrode 10 at the one end, the negative electrode current collector laminated portion in which the negative electrode active material layer non-formation portion 26 of the negative electrode current collector 12 is overlapped with the other end in the width direction of the wound electrode body 80. 25 is formed.

  The metal layer 44 included in the separator 40 is disposed so as to contact the negative electrode active material layer non-forming portion 26 of the negative electrode current collector 22 in the wound electrode body 80. As a result, the metal layer 44 is electrically connected to the negative electrode 20, and in combination with the arrangement in the separator 40, rapid gas generation is realized when the secondary battery including the wound electrode body 80 is overcharged. Is done.

Next, each component which comprises the electrode body of a secondary battery is demonstrated. As the positive electrode current collector constituting the positive electrode, for example, a foil-like material made of aluminum or an alloy containing aluminum as a main component can be used. The thickness of the positive electrode current collector is not particularly limited, and can be, for example, 5 to 30 μm. The positive electrode active material layer includes a positive electrode active material as a main component (a component included in excess of 50% by weight; the same shall apply hereinafter). The positive electrode active material is not particularly limited, and for example, one or more of a lithium transition metal composite oxide having a spinel structure or a layered structure, a polyanion type (for example, olivine type) lithium transition metal compound, or the like may be used. In a preferred embodiment, a lithium transition metal composite oxide (eg, LiNiCoMnO ₂ ) containing Li and at least one transition metal element (preferably at least one of Ni, Co, and Mn) is used as the positive electrode active material. . In addition to the positive electrode active material, the positive electrode active material layer includes various additives as necessary (for example, conductive materials such as carbon black, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), etc. A binder, a thickener and the like.

As the negative electrode current collector constituting the negative electrode, for example, a foil-like one made of copper or an alloy containing copper as a main component can be used. The thickness of the negative electrode current collector is not particularly limited, and can be, for example, 5 to 30 μm. The negative electrode active material layer contains, as a main component, one or more negative electrode active materials capable of inserting and extracting Li ^{+ serving} as a charge carrier. There is no restriction | limiting in particular in a composition and shape of a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite carbon (graphite) and amorphous carbon. A particulate carbon material (carbon particles) containing a graphite structure (layered structure) at least partially is preferably used. Of these, the use of a carbon material mainly composed of natural graphite is preferred. The natural graphite may be obtained by spheroidizing flaky graphite. In particular, a carbonaceous powder in which amorphous carbon is coated on the surface of graphite is preferable. The average particle diameter of the negative electrode active material particles is not particularly limited, but is preferably about 5 to 30 μm. In the present specification, the average particle diameter is a median diameter (average particle diameter D ₅₀ : 50% volume average particle diameter) that can be derived from the particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering / diffraction method. Adopted. In addition to the negative electrode active material, the negative electrode active material layer may contain one or more of binders, thickeners, and other additives as necessary. As the binder and the thickener, for example, those that can be contained in the positive electrode active material layer can be preferably used.

  Next, a secondary battery including the wound electrode body will be described. FIG. 4 is a schematic cross-sectional view of a secondary battery according to an embodiment. As shown in FIG. 4, the secondary battery 1 includes a rectangular battery case 50 and a wound electrode body 80 accommodated in the battery case 50. A non-aqueous electrolyte (non-aqueous electrolyte) 90 is also accommodated in the battery case 50. The non-aqueous electrolyte 90 is impregnated in the wound electrode body 80. The battery case 50 includes a flat box-shaped case main body 52 having an opening on the upper surface, and a lid 54 that closes the opening. The opening of the case body 52 is sealed by the lid 54 after the wound electrode body 80 is accommodated in the case body 52 from the opening. Thus, the inside of the battery case 50 is sealed, so that the secondary battery 1 becomes a sealed battery.

  A positive electrode terminal 70 and a negative electrode terminal 72 are provided on the upper surface (lid 54) of the battery case 50. The positive electrode terminal 70 is electrically connected to a positive electrode current collector plate 74 attached to one end in the width direction of the positive electrode 10, and the negative electrode terminal 72 is connected to a negative electrode current collector plate 76 attached to one end in the width direction of the negative electrode 20. Electrically connected. A CID 30 is provided in the battery case 50. The CID 30 is provided between the positive electrode terminal 70 and the wound electrode body 80, and electrically connects a conductive path from the positive electrode terminal 70 to the positive electrode 10 when the internal pressure of the battery case 50 increases and reaches a predetermined pressure. It is configured to divide. Specifically, the CID 30 includes a deformed metal plate 32 and a connection metal plate 34 joined to the deformed metal plate 32. The deformed metal plate 32 has an arch-shaped curved portion 33 having a central portion curved downward. The peripheral portion of the curved portion 33 is connected to the positive electrode terminal 70 via the current collecting lead terminal 35. Further, a part (tip) of the curved portion 33 of the deformed metal plate 32 is joined to the upper surface of the connection metal plate 34 at a joint point 36. A positive electrode current collector plate 74 is joined to the lower surface (back surface) of the connection metal plate 34, and the positive electrode current collector plate 74 is connected to the positive electrode 10 of the wound electrode body 80. The CID 30 also includes an insulating case 38 formed of plastic. The insulating case 38 is provided so as to surround the deformed metal plate 32. An opening for fitting the curved portion 33 of the deformed metal plate 32 is formed in the insulating case 38, and the curved portion 33 of the deformed metal plate 32 is fitted into the opening to seal the opening. doing. As a result, since the inside of the insulating case 38 is kept in a sealed state, the internal pressure of the battery case 50 does not act above the sealed curved portion 33. On the other hand, the internal pressure of the battery case 50 acts on the lower surface of the curved portion 33 outside the insulating case 38. In the CID 30 having such a structure, when the internal pressure of the battery case 50 increases due to the overcharge current, the internal pressure acts to push up the curved portion 33 curved downward of the deformed metal plate 32. This action (force) increases as the internal pressure of the battery case 50 increases. When the internal pressure of the battery case 50 exceeds the set pressure, the curved portion 33 is inverted upside down. By the inversion of the curved portion 33, the connection between the deformed metal plate 32 and the connection metal plate 34 is cut off, the conductive path is electrically cut off, and the current is cut off. The CID is not limited to the above structure, and is not limited to one based on mechanical deformation. For example, it may be a CID provided with an external circuit that detects the internal pressure of the battery case with a sensor and interrupts the charging current when the internal pressure detected by the sensor exceeds a set pressure.

The nonaqueous electrolyte is typically an electrolytic solution having a composition in which a supporting salt is contained in a suitable nonaqueous solvent. The non-aqueous solvent is not particularly limited, and for example, one or more of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). Can be used. Of these, a mixed solvent of EC, DMC and EMC is preferable. Examples of the supporting salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiI and the like. One type or two or more types of lithium compounds (lithium salts) can be used. The concentration of the supporting salt is not particularly limited, but is approximately 0.1 mol / L to 5 mol / L (for example, 0.5 mol / L to 3 mol / L, typically 0.8 mol / L to 1.5 mol / L). Concentration.

The secondary battery includes a gas generating agent. Here, the gas generating agent is an additive that generates gas when a predetermined battery voltage is exceeded, and typically reacts when the battery is overcharged (specifically, a positive electrode). Refers to a compound that decomposes on the side) to generate H ⁺ and generate gas derived from this H ⁺ . The gas generant is typically included in the non-aqueous electrolyte. In that case, the gas generating agent is preferably a compound that can be dissolved or dispersed in the non-aqueous electrolyte. Further, the gas generating agent is not oxidized at the operating voltage of the battery, but it is desirable that the gas generating agent reacts (oxidizes) prior to the oxidative decomposition of the nonaqueous solvent of the nonaqueous electrolyte when the battery is overcharged. Therefore, the oxidation potential (oxidation start potential) of the gas generating agent is preferably higher than the upper limit potential of the positive electrode corresponding to the maximum value of the operating voltage, but the oxidation potential (oxidation start potential) of the nonaqueous solvent of the nonaqueous electrolyte. Lower than. A suitable range of the oxidation potential of the gas generating agent is 4.3 V or higher (typically 4.4 V or higher), and 4.8 V or lower (typically 4.6 V or lower). Preferable examples of the gas generating agent include alkylbenzenes, cycloalkylbenzenes, biphenyls, terphenyls, diphenyl ethers, and dibenzofurans. Of these, cycloalkylbenzenes (for example, cyclohexylbenzene (CHB)) and biphenyls (for example, biphenyl (BP)) are preferable. The amount (addition amount) of the gas generating agent is preferably about 0.1 to 10% by weight (for example, 0.5 to 7% by weight, typically 1 to 5% by weight) in the non-aqueous electrolyte. .

  Said secondary battery can implement | achieve the rapid action | operation of CID in an overcharge state, and is excellent in practicality. Therefore, taking advantage of this feature, it can be preferably used as a drive power source for vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles. According to the present invention, there is provided a vehicle equipped with the secondary battery (which may be in the form of an assembled battery in which a plurality of batteries are connected).

  Next, some examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Example>
A long positive electrode sheet having a positive electrode active material layer formed on both surfaces of an aluminum foil (thickness 15 μm) as a positive electrode current collector was produced. The formed positive electrode active material layer contains LiNiCoMnO ₂ as a positive electrode active material, acetylene black as a conductive material, and PVDF as a binder in a mixing ratio of 94: 3: 3. Moreover, the elongate negative electrode sheet in which the negative electrode active material layer was formed on both surfaces of the copper foil (thickness 10 micrometers) as a negative electrode collector was produced. The formed negative electrode active material layer contains spheroidized graphite as a negative electrode active material, CMC as a thickener, and SBR as a binder in a mixing ratio of 98: 1: 1.

  A single-layer PE sheet (thickness 10 μm) is prepared as a porous resin sheet, and a copper foil (thickness 50 nm) is sandwiched between the PE sheets so as to have the structure shown in FIG. A long metal layer-containing separator sheet disposed inside was prepared. In this metal layer-containing separator, the metal layer has an inner layer portion sandwiched between resin layers (PE layers) and an exposed portion exposed from the resin layer. The resin layer sandwiching the metal layer was bonded and fixed by heat sealing or the like at the end of the separator opposite to the exposed portion in the width direction of the separator.

The negative electrode sheet is sandwiched between the metal layer-containing separators, the positive electrode sheets are stacked and wound to produce a wound body, and further, the rolled body is pressed from the side direction to be ablated. A wound electrode body having a shape was produced. In this wound electrode body, the metal layer exposed from the separator is in contact with the negative electrode active material layer non-formation part of the negative electrode current collector along the winding direction of the wound electrode body. For the wound electrode body, the electrode terminals are welded to the ends of the positive and negative electrode current collectors, respectively, and after the wound electrode body is accommodated in the rectangular battery case, a non-aqueous electrolyte is injected and the inside of the battery case is filled. Sealed. As a non-aqueous electrolyte, a mixed solvent of EC, DMC, and EMC contains LiPF ₆ as a supporting salt at a concentration of about 1 mol / L, and further contains CHB at a concentration of 4%. I used something. Thus, a square lithium secondary battery (battery capacity: 30 Ah) was produced. In this prismatic lithium secondary battery, a CID as shown in FIG. 4 is provided between the positive electrode current collector and the positive electrode terminal.

<Comparative example>
A lithium secondary battery was fabricated in the same manner as in the example except that the metal layer was not disposed and the thickness of the separator was 20 μm.

[Overcharge test]
The prismatic lithium secondary batteries according to Examples and Comparative Examples were used as test batteries. For each test battery, an overcharge test was performed under the conditions of a starting SOC (State of Charge) of 100% and a charging current value of 60 A in an environment of 25 ° C. The internal pressure [MPa] and temperature [° C.] of the test battery during the overcharge test were measured. The results are shown in FIGS.

  As shown in FIGS. 5 and 6, in the secondary battery according to the example, the increase in internal pressure proceeded faster than the comparative example, and the operation of CID could be reduced by about 10% based on the SOC. As a result, the temperature rise stopped and the safety valve did not open. On the other hand, in the secondary battery according to the comparative example, the SOC at which the CID operates is about 155%. Further, the temperature rise did not stop even after the circuit was shut off by CID, and the safety valve was opened. It will be understood by those skilled in the art that these results support the effects of the present invention described herein.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The present invention may include various modifications and alterations of the specific examples described above.

DESCRIPTION OF SYMBOLS 1 Lithium secondary battery 10 Positive electrode sheet 20 Negative electrode sheet 30 Current interruption | blocking mechanism (CID)
40 Separator sheet 42 Porous resin layer 44 Metal layer 50 Battery case 80 Winding electrode body 100 Gas generating agent

Claims (1)

An electrode body in which a positive electrode sheet, a separator sheet, and a negative electrode sheet are laminated in this order, a gas generating agent, a battery case containing the electrode body and the gas generating agent, and a current that operates due to an increase in pressure in the battery case A shut-off mechanism,
A lithium secondary battery in which a metal layer capable of flowing lithium ions is disposed in the separator sheet, and the metal layer is electrically connected to the negative electrode.

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