JP6550732B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery, and more particularly to a secondary battery that has improved safety by including a short-circuit mechanism. Furthermore, the present invention relates to an electrically powered vehicle, a storage facility and the like provided with the secondary battery.

  With the rapid market expansion of notebook computers, mobile phones, and electric vehicles, various secondary batteries are being developed. When the secondary battery is used, the secondary battery generates heat due to overcharging or the like, and there is a possibility that leakage of electrolyte vapor due to temperature rise, rapid increase in volume of the battery, or the like may occur. In order to suppress such a thermal runaway of the secondary battery, secondary batteries having various safety mechanisms are known.

  In Patent Document 1, an expansion case due to an increase in internal pressure of an outer case, which accommodates a power generation element inside and which becomes one electrode terminal, the other electrode terminal disposed in the outer case via an insulating member, and A secondary battery including an outer case and a short-circuit mechanism for short-circuiting the other electrode terminal is described.

  Patent Document 2 discloses a composite safety element including a voltage reaction heating element and a temperature sensitive element, where the voltage reaction heating element is connected in parallel between the positive electrode terminal and the negative electrode terminal of the battery, and the PTC element or bimetal. It is described that a temperature sensitive element such as is connected in series to the positive electrode terminal or the negative electrode terminal of the battery.

  In Patent Document 3, the bimetal is connected in series to the positive electrode of the secondary battery and the positive electrode of the external electrode at normal temperature, and when the temperature rises, the bimetal connected to the positive electrode of the external electrode is connected to the negative electrode of the external electrode, A protection circuit for a secondary battery is disclosed that blocks the flow of current from the external electrode by shorting the positive electrode and the negative electrode of the secondary battery.

  Patent Document 4 discloses a battery short-circuit element connected between a positive electrode terminal and a negative electrode terminal of a battery, and the battery short-circuit element includes a first electric conductor, a second electric conductor, and a short-circuit layer therebetween, Has a structure in which an insulator film is sandwiched between two low melting point alloy layers. It is described that when the battery generates heat, the low melting point alloy layer melts and flows into the opening of the insulator film, thereby electrically shorting the first electrical conductor and the second electrical conductor.

JP 2004-319463 A Patent No. 4494461 Patent No. 5372495 gazette JP, 2013-098132, A

  However, the secondary batteries described in Patent Documents 1 to 4 are not necessarily safe because the entire battery has already generated heat when the protection mechanism is activated by detecting thermal runaway of the battery. Therefore, development of a secondary battery that can quickly detect thermal runaway of the battery and has high safety has been demanded.

  The present invention relates to the following matters.

The first battery element,
A second battery element electrically connected in parallel with the first battery element, having a positive electrode, a negative electrode and a separator disposed therebetween;
Equipped with
A secondary battery characterized in that an average thermal decomposition temperature of a positive electrode active material constituting a positive electrode of the second battery element is lower than an average thermal decomposition temperature of a positive electrode active material constituting a positive electrode of the first battery element. .

  ADVANTAGE OF THE INVENTION According to this invention, the secondary battery provided with the safety mechanism when it will be in an excessively high temperature state can be provided.

It is the schematic which shows an example of the structure of a film-clad battery. It is sectional drawing which shows an example of the structure of a film exterior battery. It is a figure which shows an example of the laminated structure of a battery element. It is a figure which shows the structure of the secondary battery of one Embodiment of this invention. It is a figure which shows an example of the structure of a protection cell. It is a figure which shows the structure of the secondary battery of one Embodiment of this invention. It is a figure which shows an example of the laminated structure of the composite battery element which is one Embodiment of this invention. It is a figure which shows an example of the laminated structure of the composite battery element which is one Embodiment of this invention.

  The secondary battery of the present embodiment includes a first battery element and a second battery element electrically connected in parallel thereto. The first battery element and the second battery element each have at least a positive electrode. The second battery element has a positive electrode, a negative electrode, and a separator disposed therebetween, and the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the second battery element is the positive electrode of the first battery element Lower than the average thermal decomposition temperature of the positive electrode active material. The first battery element has at least a positive electrode, and preferably includes a structure having a positive electrode, a negative electrode and a separator disposed therebetween.

  The secondary battery of the present embodiment may be in any form such as a cylindrical type, a flat wound rectangular type, a laminated rectangular type, a coin type, a flat wound laminated type, and a laminated laminated type. From the viewpoint of properties, it is preferably a laminated laminate type. The laminate type secondary battery is preferably a film-clad battery in which the battery element is accommodated in the film package together with the electrolytic solution. Hereinafter, in the description of the present embodiment, the form of the secondary battery is described as being a film-clad battery, but the present invention is not limited to this.

  First, an example of a basic configuration of a film-clad battery will be described with reference to FIGS. 1 and 2. Although the secondary battery of the present invention has the first battery element and the second battery element, the contents described as "battery element" in the following description are the first battery element and the second battery element. It applies to any of the battery elements.

  As shown in FIG. 1 and FIG. 2, the film-clad battery 50 is connected to the battery element 20, the film case 10 housing the same, and the positive electrode drawn to the outside of the film case 10 while being connected to the battery element 20. A tab 21 and a negative electrode tab 25 (hereinafter simply referred to as “electrode tabs”) are provided.

  The battery element 20 is formed by alternately laminating a plurality of positive electrodes and a plurality of negative electrodes made of metal foils coated with electrode materials on both sides with a separator interposed therebetween. Although the overall external shape of the battery element 20 is not particularly limited, in this example, it is a flat and substantially rectangular parallelepiped. Also, the electrode material may be applied to only one side of the metal foil. The number of positive electrodes and negative electrodes may be singular.

  Although detailed illustration is omitted, each of the positive electrode and the negative electrode has an extended portion that partially protrudes from a part of the outer periphery. The extension part of the positive electrode and the extension part of the negative electrode are alternately arranged so as not to interfere with each other when the positive electrode and the negative electrode are stacked. The extensions of all the negative electrodes are collected together and connected with the negative electrode tab, and likewise, with regard to the positive electrodes, the extensions of all the positive electrodes are collected together and connected with the positive electrode tab. The connection between the electrode tab and the extension may be made by welding.

  FIG. 3 shows one embodiment of the battery element 20. The battery element 20 has a structure in which a plurality of negative electrodes 31 and a plurality of positive electrodes 32 are arranged to face each other with a separator 33 interposed therebetween. The negative electrode 31 and the positive electrode 32 have portions where the active material layer is not formed in order to connect to the negative electrode tab 25 and the positive electrode tab 26, respectively.

  Next, the configuration of the secondary battery of the present embodiment will be described. In the present specification, the secondary battery in which the first battery element and the electrolytic solution are contained in the outer package is referred to as the “main cell”, and the second battery element and the electrolytic solution are contained in the outer package. The secondary battery is referred to as "protective cell".

  In the present embodiment, the main body cell and the protection cell may constitute independent secondary batteries, or the protection cell may be built in the main body cell. Alternatively, the first battery element and the second battery element may be accommodated in the same package together with a common electrolyte to constitute one secondary battery. In addition, the secondary battery of this embodiment should just have at least 1 1st battery element and 2nd battery element, and may have either one or both.

  As will be described in detail later, in the present embodiment, the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the second battery element is the average heat of the positive electrode active material constituting the positive electrode of the first battery element. Since the temperature is lower than the decomposition temperature, when the temperature of the secondary battery is excessively increased, the positive electrode active material in the second battery element is pyrolyzed earlier than the positive electrode active material in the first battery element, and the release occurs at that time Due to the heat generated, the temperature in the second battery element further rises to cause thermal runaway. The progress of thermal runaway causes the separator in the second battery element to melt and shrink, and the positive electrode and the negative electrode in the second battery element are shorted. The short-circuit between the positive electrode and the negative electrode in the second battery element occurs before the thermal runaway reaction of the first battery element occurs, and the battery tab discharges due to a short circuit between the electrode tabs in the first battery element. Is consumed. In other words, in the present embodiment, the positive electrode and the negative electrode in the second battery element are short-circuited, thereby preventing the heat generation and short circuit of the entire secondary battery including the first battery element, and the high safety of the second battery element. A secondary battery can be provided.

  One embodiment of the secondary battery of the present invention is shown in FIG. 4A. In FIG. 4A, a protection cell or a second battery element 42 is electrically connected in parallel between the positive electrode tab 43 and the negative electrode tab 44 of the first battery element 41. Reference numeral 42 may be a protective cell in which the second battery element and the electrolytic solution are accommodated in the outer package, or may be only the second battery element not including the outer package.

  An example of the structure of 42 when 42 of FIG. 4A is a protection cell is shown to FIG. 4B. In the protective cell, the second battery element having the positive electrode 421, the negative electrode 423, and the separator 422 disposed therebetween is accommodated in the package 426 together with the electrolytic solution. A positive electrode tab 424 and a negative electrode tab 425 are drawn out of the exterior body 426.

  When 42 in FIG. 4A is a protective cell, the electrolyte contained in the protective cell 42 and the first battery element are housed in the exterior body 46 in a separated state, and the protective cell is contained in the main cell. It has a built-in configuration.

  When 42 of FIG. 4A is only the second battery element, the first battery element 41 and the second battery element 42 are housed together with the common electrolyte in the outer package 46, and one secondary Configure the battery.

  Alternatively, as another aspect of the present embodiment, the second battery element and the first battery element separately constitute an independent protective cell and a main body cell in both the electrolyte solution and the outer package, and these cells constitute electricity. Alternatively, they may be connected in parallel.

  In one embodiment of the present invention, as shown in FIG. 5, the resistor 53 is electrically connected to the second battery element or the protective cell 52 between the electrode tabs of the first battery element or the main cell 51. Alternatively, they may be connected in series. By connecting a resistor having an appropriate resistance value, it is possible to discharge at a safe current value when a short circuit occurs in the protective cell, and it is possible to further enhance the safety of the secondary battery.

  Further, as another embodiment of the present invention, a composite battery element in which a first battery element and a second battery element are stacked and these battery elements are electrically connected in parallel is provided. The composite battery element may be accommodated in the outer package to form a secondary battery. The first battery element and the second battery element are preferably laminated via an insulator. A schematic cross-sectional view of an example of the laminated structure of this composite battery element is shown in FIGS. 6A and 6B.

  The composite battery element of FIG. 6A includes a first battery element 71, a second battery element 72, and an insulator 73 disposed therebetween. The first battery element 71 is formed by alternately stacking a plurality of negative electrodes 61 and a plurality of positive electrodes 63 with the separator 62 interposed therebetween. The second battery element 72 is formed by stacking the positive electrode 64 and the negative electrode 66 with the separator 65 interposed therebetween. The positive electrode current collector 82 is welded and electrically connected to each other at an end portion not covered with the positive electrode active material of each of the positive electrodes 63 and 64, and a positive electrode tab 83 is welded to the welded portion. The negative electrode current collector 81 is welded and electrically connected to each other at an end portion not covered with the negative electrode active material of each of the negative electrodes 61 and 66, and a negative electrode tab 84 is welded to the welded portion. Further, a resistor 67 is connected in series with the positive electrode 64 of the second battery element. In FIG. 6A, the electrodes of the second battery element are shown smaller than the electrodes of the first battery element, but the size of the electrodes is not particularly limited. Further, the number of positive electrodes, negative electrodes, and separators included in the first battery element 71 and the number of positive electrodes, negative electrodes, and separators included in the second battery element 72 are not limited and may be one each. There may be more than one.

  Another aspect of the composite battery element in this embodiment is shown in FIG. 6B. In the composite battery element of FIG. 6B, the negative electrode 68 is part of the first battery element and is also part of the second battery element. The second battery element 72 is composed of a negative electrode 68, a positive electrode 64, and a separator 69 disposed therebetween, and the size (area of the electrode) of the positive electrode 64 is smaller than that of the negative electrode 68. Other configurations are the same as those in FIG. 6A.

  Although the number of the first battery element and the second battery element included in the composite battery element is not particularly limited, as shown in FIGS. 6A and 6B, at least one outermost layer of the composite battery element is the second battery element. Is preferred. Alternatively, as another aspect of the composite battery element, a second battery element may be disposed between the two first battery elements via an insulator.

  The insulator 73 disposed between the first battery element and the second battery element is preferably a high-temperature resistant material that does not melt even if the second battery element is thermally runaway. Moreover, it is preferable that the insulator 73 has a size capable of preventing a short circuit between the positive electrode and the negative electrode on both sides of the insulator. The insulator 73 may be a nonporous insulator film, or may be a porous separator used in a first battery element or a second battery element described later. When the insulator is a non-porous film, it is possible to prevent the occurrence of a short circuit between the first battery element and the second battery element when the second battery element is thermally runaway due to overcharging or the like. This is preferable. On the other hand, when the first battery element and the second battery element are stacked via the separator, even during normal use of the secondary battery, even between the second battery element and the first battery element This is preferable in that lithium ions can be moved.

  Next, each element which comprises a 1st battery element and a 2nd battery element is demonstrated. Of the elements constituting the first battery element and the elements constituting the second battery element, the average thermal decomposition temperature of the positive electrode active material contained in the positive electrode is different from each other, but the other elements are the same. It may be different.

<Positive electrode>
The positive electrode preferably has a positive electrode current collector made of a metal foil and a positive electrode active material coated on both sides of the positive electrode current collector. The positive electrode active material is bound by the positive electrode binder so as to cover the positive electrode current collector. The positive electrode current collector is formed to have an extension connected to the positive electrode terminal, and the positive electrode active material is not coated on the extension.

  The structure of the positive electrode active material becomes unstable when lithium is extracted from the crystal lattice as charging of the battery proceeds, the thermal decomposition temperature decreases, and the thermal decomposition temperature decreases as the lithium extraction amount increases. When the temperature of the positive electrode active material from which lithium has been extracted is raised, it decomposes while releasing oxygen at a predetermined temperature (thermal decomposition temperature).

  In the present embodiment, the average thermal decomposition temperature T2 of the positive electrode active material constituting the positive electrode of the second battery element is lower than the average thermal decomposition temperature T1 of the positive electrode active material constituting the positive electrode of the first battery element (that is, T2 <T1). As a result, when the temperature of the secondary battery rises due to overcharging or high temperature storage, etc., the positive electrode active material in the second battery element is pyrolyzed earlier than the positive electrode active material of the first battery element. The heat released further raises the temperature in the second battery element to cause thermal runaway. The progress of thermal runaway causes the separator in the second battery element to melt and shrink, and the positive electrode and the negative electrode in the second battery element are shorted. The short-circuit between the positive electrode and the negative electrode in the second battery element occurs before the thermal runaway reaction of the first battery element occurs, and the battery tab discharges due to a short circuit between the electrode tabs in the first battery element. Is consumed. That is, in the present embodiment, the positive electrode and the negative electrode in the second battery element are short-circuited to prevent the heat generation and short circuit of the first battery element and the entire secondary battery, and the secondary battery is highly safe. A battery can be provided.

here,
The average thermal decomposition temperature T1 of the positive electrode active material constituting the positive electrode of the first battery element is represented by the following formula (1):
T1 = (s ₁ p ₁ + s ₂ p ₂ +... + S _{r pr} ) / (p ₁ + p ₂ +... + P _r ) Equation (1)
[In the formula (1), T 1 represents the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the first battery element, s _r represents the r th positive electrode active material constituting the positive electrode of the first battery element The thermal decomposition temperature, _pr is the content (mol) of the r-th positive electrode active material constituting the positive electrode of the first battery element, r is the number of types of positive electrode active material constituting the positive electrode of the first battery element Represents a positive integer. ]
Can be determined by
The average thermal decomposition temperature T2 of the positive electrode active material constituting the positive electrode of the second battery element is represented by the following formula (2):
T2 = (t ₁ m ₁ + t ₂ m ₂ +... + T _n m _n ) / (m ₁ + m ₂ +... + M _n ) Formula (2)
[In the formula (2), T2 is the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the second battery element, t _n is the nth positive electrode active material constituting the positive electrode of the second battery element The thermal decomposition temperature, m _n is the content (mol) of the nth positive electrode active material constituting the positive electrode of the second battery element, n is the number of types of positive electrode active materials constituting the positive electrode of the second battery element Yes, it represents a positive integer. ]
It can be determined by

  In the present specification, the thermal decomposition temperature of the positive electrode active material is a fully charged state in a range where a lithium ion secondary battery having a positive electrode containing the positive electrode active material and a negative electrode of metal lithium is generally used. The temperature refers to the temperature at which oxygen in the positive electrode active material begins to be released and released (oxygen desorption initiation temperature) when preferably charged to 4.2 V. In general, the pyrolysis temperature can be measured using DSC (differential scanning calorimetry) or ARC (accelerating rate calorimeter).

  In this embodiment, T2 <T1 is sufficient, but from the viewpoint of safety, the temperature difference (T1-T2) between T1 and T2 is preferably 5 ° C. or more, and more preferably 10 ° C. or more. preferable.

  In the present embodiment, as for the type and content of the positive electrode active material, as described above, the average thermal decomposition temperature T2 of the positive electrode active material constituting the positive electrode of the second battery element constitutes the positive electrode of the first battery element. It can be selected to be lower than the average thermal decomposition temperature T1 of the positive electrode active material.

As the positive electrode active material, layered structures such as LiMnO ₂ , LixMn ₂ O ₄ (0 <x <2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0 <x <2), etc. Lithium manganate or lithium manganate having a spinel structure, LiCoO ₂ , LiNiO ₂ or some of these transition metals replaced with another metal, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ etc. Lithium transition metal oxides in which the number of specific transition metals does not exceed half, lithium in excess of the stoichiometric composition in these lithium transition metal oxides, those having an olivine structure such as LiFePO ₄ , and the like are listed. Be In addition, these metal oxides were partially substituted with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Materials can also be used. In particular, Li _α Ni _β Co _γ Al _δ O ₂ (1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0.2) or Li _α Ni _β Co _γ Mn _δ O ₂ (1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6, γ ≦ 0.2) is preferable. The positive electrode active materials can be used alone or in combination of two or more.

  A radical material or the like can also be used as the positive electrode active material.

Since LiMO ₂ (M is a transition metal) having a layered rock salt structure has a lower thermal decomposition temperature than a compound having a spinel structure with high crystal structure stability, in this embodiment, the positive electrode of the second battery element is It is preferable to include a compound having a layered rock salt structure as a positive electrode active material. In addition, since the compound having a layered rock salt structure has a high thermal runaway rate, the second battery element includes it to sense an excess heat generation of the secondary battery more quickly and ensure safety of the entire secondary battery. Can be secured. As a positive electrode active material having a layered rock salt structure included in the positive electrode of the second battery element, specifically, lithium nickelate (LiNiO ₂ ); a part of Ni of LiNiO ₂ with another metal (preferably Co, Al) A positive electrode active material substituted by at least one element selected from the group consisting of Mn, Mg, Zr, Ti and Zn, more preferably at least one element selected from Co, Al and Mn; lithium cobaltate (LiCoO 2) ₂ ); Part of Co of LiCoO ₂ is at least one element selected from the group consisting of other elements (preferably Ni, Al, Mn, Mg, Zr, Ti and Zn), more preferably Ni, Al and Mn And at least one element selected from the group consisting of As a preferable embodiment of a positive electrode active material in which a part of nickel of lithium nickelate is substituted by another element, or a positive electrode active material in which a part of cobalt of lithium cobaltate is substituted by another element, Li _α Ni _β Co _γ Al _δ O ₂ (1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, 0 <γ ≦ 0.2, δ> 0) and Li _α Ni _β Co _γ Mn _δ O ₂ (1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6, 0 <γ ≦ 0.2, δ> 0), and more specifically, LiNi _0.8 Co _0.15 Al _{0. 05} O ₂ and LiNi _0.6 Co _0.2 Mn _0.2 O _{2 and the} like can be mentioned. Among these, it is particularly preferable that LiCoO ₂ is included. Among the positive electrode active materials contained in the positive electrode of the second battery element according to an embodiment of the present invention, it is preferable to contain 10 mol% or more of LiCoO ₂ , more preferably 20 mol% or more, and 50 mol% or more More preferably, it may contain 100 mol%.

  In the present embodiment, the elements constituting the positive electrode other than the positive electrode active material may be the same or different between the first battery element and the second battery element.

  As the positive electrode binder, the same negative electrode binder can be used. The amount of the positive electrode binder to be used is preferably 2 to 15 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoint of "sufficient binding ability" and "high energy" in a trade-off relationship. .

  As the positive electrode current collector, for example, aluminum, nickel, silver, or an alloy thereof can be used. Examples of the shape of the positive electrode current collector include a foil, a flat plate, and a mesh. As the positive electrode current collector, an aluminum foil can be suitably used.

  A conductive auxiliary material may be added to the coating layer of the positive electrode active material for the purpose of reducing impedance. Examples of the conductive auxiliary material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.

<Negative electrode>
The negative electrode preferably has a negative electrode current collector made of a metal foil and a negative electrode active material coated on both sides of the negative electrode current collector. The negative electrode active material is bound by the negative electrode binder so as to cover the negative electrode current collector. The negative electrode current collector is formed to have an extension connected to the negative electrode terminal, and the negative electrode active material is not coated on the extension.

  The negative electrode active material in the present embodiment is not particularly limited. For example, a carbon material capable of absorbing and desorbing lithium ions, a metal capable of alloying with lithium, and a metal oxide capable of absorbing and desorbing lithium ions Is mentioned.

  As a carbon material, carbon, amorphous carbon, diamond-like carbon, a carbon nanotube, or these composites etc. are mentioned, for example. Here, carbon having high crystallinity has high electrical conductivity, and is excellent in adhesion to a negative electrode current collector made of a metal such as copper and voltage flatness. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.

  A negative electrode containing a metal or metal oxide is preferable in that it can improve energy density and increase the capacity per unit weight or unit volume of the battery.

  Examples of the metal include Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, an alloy of two or more of these, and the like. Moreover, you may use these metals or alloys in mixture of 2 or more types. Also, these metals or alloys may contain one or more nonmetallic elements.

  Examples of the metal oxide include silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, or a composite thereof. In this embodiment, it is preferable that tin oxide or silicon oxide is included as a negative electrode active material, and it is more preferable that silicon oxide is included. This is because silicon oxide is relatively stable and hardly causes a reaction with other compounds. In addition, one or two or more elements selected from nitrogen, boron and sulfur can be added to the metal oxide, for example, 0.1 to 5% by mass. By this, the electrical conductivity of the metal oxide can be improved.

  Further, the negative electrode active material can be used by mixing a plurality of materials without using a single material. For example, the same kind of materials such as graphite and amorphous carbon may be mixed, or different kinds of materials such as graphite and silicon may be mixed.

  The binder for the negative electrode is not particularly limited, and examples thereof include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, and styrene-butadiene copolymer. Rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, polyacrylic acid, or the like can be used. The amount of the binder for the negative electrode to be used is 0.5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoint of "sufficient binding ability" and "high energy" in a trade-off relationship. Is preferred.

  As the negative electrode current collector, aluminum, nickel, stainless steel, chromium, copper, silver, and their alloys are preferable from the viewpoint of electrochemical stability. Examples of the shape include foil, flat plate, and mesh.

<Separator>
The separator may be a web or sheet made of an organic material, for example, a woven fabric of polyamide, polyimide, cellulose or the like, a non-woven fabric, a polyolefin type such as polyethylene or polypropylene, a porous polymer membrane such as polyamide, polyimide, porous polyvinylidene fluoride membrane Alternatively, an ion conductive polymer electrolyte membrane or the like can be used. These can be used alone or in combination.

In addition, as the separator, a separator made of an inorganic material such as ceramic or glass can also be used. Nonwoven separators made of ceramic short fibers such as alumina, alumina-silica, potassium titanate and the like as inorganic separators; Fabrics, non-woven fabrics, base materials made of paper or porous films, heat-resistant nitrogen-containing aromatic polymers and ceramic powders A heat-resistant layer is provided on part of the surface, and the heat-resistant layer is a porous thin film layer containing a ceramic powder, a porous thin film layer of a heat-resistant resin, or a ceramic powder and a heat-resistant layer Thin film layer separator comprising a composite of a hydrophobic resin; a separator comprising a porous film layer in which secondary particles obtained by sintering or dissolving / recrystallizing a part of primary particles of ceramic material are bound by a binder A substrate layer made of a polyolefin porous membrane, and a heat-resistant insulating layer formed on one or both sides of the substrate layer. Insulating layer, the separator comprises an oxidation-resistant ceramic particles and heat-resistant resin; wherein a porous membrane ceramic material and the binder is formed by combining, as the ceramic material, silica (SiO _2), alumina (Al ₂ O ₃ ), Zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), nitride of silicon (Si), hydroxide of aluminum (Al), alkoxide of zirconium (Zr), or ketone of titanium (Ti) A separator using a compound; and a polymer base and a ceramic of Al ₂ O ₃ , MgO, TiO ₂ , Al (OH) ₃ , Mg (OH) ₂ , Ti (OH) ₄ formed on the polymer base The separator etc. which contain a containing coating layer are mentioned. In the present embodiment, it may be preferable that the first battery element includes a high melting point heat-resistant separator.

  In the present embodiment, the separator included in the first battery element and the separator included in the second battery element may be the same or different, but the separator included in the second battery element When the melting point is lower than the melting point of the separator included in the first battery element, when the temperature of the secondary battery is excessively increased, the second battery element can be short-circuited quickly, which may be preferable.

  Next, an electrolytic solution, an exterior body, a resistor, and the like that constitute the secondary battery of this embodiment together with the battery element will be described.

<Electrolyte solution>
As the electrolytic solution used in the present embodiment, a non-aqueous electrolytic solution containing a lithium salt (supporting salt) and a non-aqueous solvent that dissolves the supporting salt can be used.

  As the non-aqueous solvent, an aprotic organic solvent such as a carbonic acid ester (chain or cyclic carbonate), a carboxylic acid ester (chain or cyclic carboxylic acid ester), or a phosphoric acid ester can be used.

  As a carbonate solvent, cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), vinylene carbonate (VC), etc .; dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), chain carbonates such as dipropyl carbonate (DPC); and propylene carbonate derivatives.

  Examples of carboxylic acid ester solvents include aliphatic carboxylic acid esters such as methyl formate, methyl acetate and ethyl propionate; and lactones such as γ-butyrolactone.

  Among these, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), dipropyl carbonate Carbonates (cyclic or linear carbonates) such as (DPC) are preferred.

  Examples of phosphoric acid esters include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, trioctyl phosphate, triphenyl phosphate and the like.

  Other solvents that can be contained in the non-aqueous electrolyte include, for example, ethylene sulfite (ES), propane sultone (PS), butane sultone (BS), dioxathilane-2,2-dioxide (DD), and sulfolene. , 3-Methylsulfolene, sulfolane (SL), succinic anhydride (SUCAH), propionic anhydride, acetic anhydride, acetic anhydride, maleic anhydride, diallyl carbonate (DAC), dimethyl 2,5-dioxahexanenoate, 2,5 -Dioxahexanoate dimethylate, furan, 2,5-dimethyl furan, diphenyl disulfide (DPS), dimethoxyethane (DME), dimethoxymethane (DMM), diethoxyethane (DEE), ethoxymethoxyethane, chloroethylene carbonate , Dimethyl ether, methyl ether Ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl butyl ether, diethyl ether, phenyl methyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), tetrahydropyran (THP), 1,4-dioxane (DIOX), 1,3-dioxolane (DOL), methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl difluoroacetate, methyl propionate, ethyl propionate, propyl propionate, methyl formate Ethylformate, Ethylbutyrate, Isopropylbutyrate, Methylisobutyrate, Methylcyanoacetate, Vinyl Acetate, Dipheny Disulfide, dimethyl sulfide, diethyl sulfide, adiponitrile, valeronitrile, glutaronitrile, malononitrile, succinonitrile, pimeronitrile, suberonitrile, isobutyronitrile, biphenyl, thiophene, methyl ethyl ketone, fluorobenzene, hexafluorobenzene, carbonate electrolyte, glyme , Ether, acetonitrile, propiononitrile, γ-butyrolactone, γ-valerolactone, dimethyl sulfoxide (DMSO) ionic liquid, phosphazene, methyl formate, methyl acetate, ethyl propionate and other aliphatic carboxylic acid esters, or these compounds In which a part of the hydrogen atoms are substituted with fluorine atoms.

  The non-aqueous solvents can be used alone or in combination of two or more.

As the supporting salt in the present embodiment, LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN ( Lithium salts usable for ordinary lithium ion batteries such as CF ₃ SO ₂ ) ₂ can be used. The supporting salts can be used alone or in combination of two or more.

<Exterior body>
The exterior body can be appropriately selected as long as it is stable to the electrolytic solution and has a sufficient water vapor barrier property. For example, in the case of a laminated laminate type secondary battery, it is preferable to use a laminate film of aluminum and resin as the outer package. The exterior body may be constituted by a single member or may be constituted by combining a plurality of members.

  In the present embodiment, as shown in FIG. 1, the film case 10 may be configured of a first film 11 and a second film 12 disposed to face the first film 11. The outline shape of the film case 10 is not particularly limited, but may be square, and in this example is rectangular. Both the films 11 and 12 are heat-welded to each other around the battery element 20 and joined. Thus, the peripheral portion of the film case 10 is a thermally welded portion 15. A positive electrode tab 21 and a negative electrode tab 25 are drawn from one side of the short side of the heat-welded portion 15.

<Resistor>
In the present embodiment, as described above, a resistor may be connected in series with the second battery element to ensure safety when the second battery element is shorted. Although it does not specifically limit as a resistor, A thing with high heat dissipation is preferable, and a shunt resistor, a cement resistor, etc. are mentioned. Also, the resistance value of the resistor can be determined according to the capacitance of the main cell. For example, when the main cell is at 4.2 V and 5 Ah and the energy of the main cell is dissipated in about 15 minutes after the short circuit of the second battery element, the resistance value of the resistor can be about 210 mΩ.

  In the secondary battery of the present invention, the discharge capacity of the second battery element is preferably low capacity, for example, preferably 1 Ah or less, more preferably 0.5 Ah or less, and preferably 0.01 Ah or more. When the discharge capacity of the second battery element is 1 Ah or less, the amount of heat released when the second battery element is short-circuited can be suppressed within a safe range. In addition, it is preferable that the discharge capacity of the second battery element is 0.01 Ah or more, because the second battery element can be more reliably short-circuited.

  As an embodiment of the method for producing a secondary battery of the present invention, an embodiment in which 42 is a protective cell in FIG. 4A will be described.

  First, a 1st battery element and a 2nd battery element are each manufactured. In each battery element, the positive electrode and the negative electrode are alternately stacked with a separator interposed therebetween. The positive electrode and the negative electrode may be single or plural. The average thermal decomposition temperature of the positive electrode active material contained in the second battery element is lower than the average thermal decomposition temperature of the positive electrode active material contained in the first battery element.

  The protective cell 42 is manufactured by enclosing the second battery element and the electrolytic solution in the exterior body. Subsequently, the protective cell 42 is connected between the positive electrode tab 43 and the negative electrode tab 44 of the first battery element so as to be electrically in parallel with the first battery element 41. The resistors may be connected in electrical series with the protective cell 42. Subsequently, the secondary battery can be manufactured by enclosing the first battery element electrically connected in parallel and the protective cell 42 together with the electrolytic solution in the exterior body 46.

  The lithium ion secondary battery of the present invention can also be used in an electric vehicle such as an electric car, a hybrid car, an electric bike, and an electric assist bicycle.

  The lithium ion secondary battery of the present invention can also be used for a storage system. The storage system is connected, for example, between a commercial power supply supplied to a general household and a load such as a home appliance, and is used as a backup power supply or auxiliary power at the time of a power failure or the like. Furthermore, it is also used for large-scale power storage to stabilize power output with large time fluctuation due to renewable energy, such as solar power generation.

  The battery according to the present invention can be used, for example, in any industrial field requiring a power source, and in the industrial field related to transport, storage and supply of electrical energy. Specifically, power supplies for mobile devices such as mobile phones and laptops; power supplies for moving and transporting media such as trains, satellites and submarines, including electric vehicles such as electric cars, hybrid cars, electric bikes and electric assist bicycles Backup power supply such as UPS; storage equipment for storing electric power generated by solar power generation, wind power generation, etc .;

DESCRIPTION OF SYMBOLS 10 film exterior body 11, 12 film 15 heat sealing part 20 battery element 21 positive electrode tab 25 negative electrode tab 31 negative electrode 32 positive electrode 33 separator 41 first battery element 42 protection cell or second battery element 43 positive electrode tab 44 negative electrode tab DESCRIPTION OF SYMBOLS 46 exterior body 421 positive electrode 422 separator 423 negative electrode 424 positive electrode tab 425 negative electrode tab 426 exterior body 51 1st battery element or main cell 52 2nd battery element or cell for protection 53 resistor 54 positive electrode tab 55 negative electrode tab 61 negative electrode 62 separator 63 positive electrode 64 positive electrode 65 separator 66 negative electrode 67 resistor 68 negative electrode 69 separator 71 first battery element 72 second battery element 73 insulator 81 negative electrode current collector 82 positive electrode current collector 83 positive electrode tab 84 negative electrode tab

Claims (10)

The first battery element,
A second battery element electrically connected in parallel with the first battery element;
Equipped with a,
The second battery element includes a positive electrode, a negative electrode, and a separator disposed therebetween.
Average thermal decomposition temperature of the positive electrode active material constituting the positive electrode before Symbol second battery element, rather low than the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the first battery element,
The separator is a separator that melts and shrinks;
When the temperature of the second battery element rises and the separator melts and contracts, the positive electrode and the negative electrode in the second battery element are lower than the average thermal decomposition temperature of the positive electrode active material in the first battery element A secondary battery characterized by shorting at a temperature . Furthermore, the secondary battery according to the resistor is connected to the second battery element and electrically in series to claim 1 you characterized. The second battery element is housed in an outer package together with an electrolyte to constitute a cell;
The secondary battery according to claim 1, wherein the first battery element and the electrolyte solution in the cell are isolated.   The secondary battery according to claim 1 or 2, wherein the first battery element and the second battery element are stacked to form a composite battery element and housed in a package together. .   The secondary battery according to claim 4, wherein the first battery element and the second battery element are laminated via an insulator to form a composite battery element. The secondary battery according to claim 4 or 5 wherein at least one of the outermost layer of double engagement battery element is characterized in that said second battery element. The positive electrode of the second battery element is a compound in which part of Ni in LiNiO ₂ and LiNiO ₂ is replaced with at least one element selected from the group consisting of Co, Al, Mn, Mg, Zr, Ti and Zn, At least one selected from the group consisting of LiCoO ₂ and a compound in which a part of Co of LiCoO ₂ is replaced with at least one element selected from the group consisting of Ni, Al, Mn, Mg, Zr, Ti and Zn The secondary battery according to any one of claims 1 to 6, comprising a positive electrode active material.   The electric vehicle which has a secondary battery as described in any one of Claims 1-7.   A power storage facility having the secondary battery according to any one of claims 1 to 7. Manufacturing a first battery element;
Manufacturing a second battery element having a positive electrode, a negative electrode and a separator disposed therebetween;
Possess a step of electrically connecting in parallel with said second battery element and the first battery element,
The average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the second battery element is lower than the average thermal decomposition temperature of the positive electrode active material constituting the positive electrode of the first battery element ,
The separator is a melt-shrinkable separator,
When the temperature of the second battery element rises and the separator melts and contracts, the positive electrode and the negative electrode in the second battery element are lower than the average thermal decomposition temperature of the positive electrode active material in the first battery element A method of manufacturing a secondary battery, characterized by short-circuiting at a temperature .

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