JP2015088268A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device which is superior in safety when being overcharged.SOLUTION: A power storage device comprises: a housing body having an internal space; a positive electrode, a negative electrode, and an electrolyte which are housed in the internal space of the housing body; and a current interrupt device mechanism for cutting off a current path according to the rise in internal pressure in the internal space. The positive electrode includes an inorganic oxide which reacts at a potential higher than an end-of-charge potential of the positive electrode at an end of a normal charging operation to generate an oxygen gas, and has a transition metal.

Description

  The present invention relates to a power storage device excellent in safety during overcharge.

  Safety has become an important issue as the size of batteries increases. There is a current interrupt device (CID) as a safety mechanism. The current interrupting mechanism is a mechanism that increases the internal pressure using gas generated in the battery during overcharge or the like and interrupts the circuit by the pressure. In order to operate this CID, it is necessary to generate gas at the time of overcharge, and therefore it is important to select a gas generating agent that generates an appropriate amount of gas at an appropriate voltage.

  Conventionally, an overcharge additive has been added to an electrolyte or an electrode. However, these overcharge additives cause deterioration over time. For this reason, it is difficult to generate a prescribed amount of gas at the time of overcharging over the entire battery life.

For example, Patent Document 1 discloses that the positive electrode includes an inorganic compound having PO ₄ , and Patent Documents 2 and 3 include a carbonate inorganic compound, an oxalic acid inorganic compound, or a nitrate inorganic compound as a positive electrode mixture. Proposed to include. Patent Document 4 proposes that a gas generating resin be included in the positive electrode. Patent Document 5 proposes adding a monomer additive that can be polymerized at a battery voltage equal to or higher than the maximum operating charging voltage to the liquid electrolyte. Patent Document 6 proposes that a dicarboxylic acid be accommodated in a hollow portion formed in an electrode terminal.

JP 2008-243659 A JP 2008-277106 A JP 2009-217946 A JP 2010-009942 A Japanese Patent Laid-Open No. 09-171840 JP-A-10-270011

  This invention is made | formed in view of this situation, and makes it a subject to provide the electrical storage apparatus excellent in the safety | security at the time of an overcharge.

  A power storage device according to the present invention includes a housing body having an internal space, a positive electrode, a negative electrode, and an electrolyte housed in the internal space of the housing body, and a current that blocks a current path according to an increase in internal pressure of the internal space. The positive electrode includes an inorganic oxide having a transition metal and reacting at a potential higher than the charge end potential of the positive electrode at the end of normal charge and generating a gas. It is characterized by.

  According to the power storage device of the present invention, the positive electrode contains an inorganic oxide that decomposes at a potential higher than the charge end potential of the positive electrode at the end of normal charge to generate gas. For this reason, gas is generated from the inorganic oxide contained in the positive electrode when the positive electrode becomes higher than the end-of-charge potential during overcharge. The internal pressure of the container is increased by the generation of gas, the current path is interrupted by the current interrupt mechanism, and the operation of the power storage device can be stopped.

It is a model figure of the charge curve of the lithium transition metal oxide of a reverse fluorite structure. FIG. 3 is an explanatory cross-sectional view of a current interrupt mechanism of Example 1.

  A power storage device according to an embodiment of the present invention will be described in detail.

  A power storage device according to the present invention includes a housing body having an internal space, a positive electrode, a negative electrode, and an electrolyte housed in the internal space of the housing body, and a current blocking mechanism that blocks a current path according to an increase in internal pressure of the internal space. Have.

  The positive electrode of the power storage device includes an inorganic oxide that reacts at a potential higher than the charge end potential of the positive electrode at the end of normal charge to generate gas. The inorganic oxide has a transition metal. The transition metal contained in the inorganic oxide is oxidized during charging to increase the valence. Along with this, gas is released from the inorganic oxide. When the gas is released, the internal pressure of the internal space of the container increases. When added to the positive electrode, the inorganic oxide becomes a gas generating agent that generates gas at a constant voltage. The current interruption mechanism operates in response to an increase in internal pressure in the internal space, and interrupts the current path.

  The gas that can be generated from the inorganic oxide is preferably oxygen gas.

  Carbon dioxide gas generated by reaction of oxygen or oxygen gas with the electrolyte has a larger molecule than hydrogen. It is difficult to pass through a metal thin film such as a diaphragm that may be used for a current interruption mechanism, and the current interruption mechanism can be reliably operated at the time of overcharging without wasting inorganic oxides unnecessarily. When the gas generated from the inorganic oxide is hydrogen gas, the hydrogen gas passes through the metal thin film, the inorganic oxide is consumed at the time of overcharge, and the internal pressure cannot be increased, and the current interrupting mechanism is activated. There is a possibility that it cannot be made.

Here, “the charge end potential of the positive electrode at the end of normal charge” refers to the end potential of the positive electrode (Li / Li ⁺ is a reference potential) when the charge is stopped during normal use of the power storage device. Hereinafter, it is sometimes simply referred to as “charging end potential”. The power storage device is designed to be charged to such a high potential that the positive electrode can reversibly charge and discharge. The power storage device is not limited to being charged to full charge, but may be designed to terminate charging at a lower potential. In either case, the positive electrode potential (Li / Li ⁺ is a reference potential) when charging is terminated is referred to as “positive electrode termination potential”.

The inorganic oxide reacts at a potential higher than the charge end potential of the positive electrode at the end of normal charge to generate oxygen. For example, when the charge end potential of the positive electrode is 4.3 V (Li / Li ⁺ is a reference potential), the inorganic oxide can react at 4.3 V or more (Li / Li ⁺ is a reference potential) to generate oxygen. .

  The inorganic oxide has a transition metal and oxygen. The inorganic oxide is represented by MxOy (M: one or more elements having at least a transition metal, x, y: an integer of 1 or more) (formula 1). The inorganic oxide may be an inorganic oxide represented by, for example, LizMxOy (M: one or more elements having at least a transition metal, x, y, and z are integers above) (formula 2). . In Formula 2, x is preferably 1 or more and 3 or less, y is preferably 1 or more and 10 or less, and more preferably 3 or more and 8 or less. z is preferably 1 or more and 8 or less, and more preferably 3 or more and 8 or less, and 4 or more and 6 or less.

The inorganic oxide is preferably made of a lithium transition metal oxide having lithium, a transition metal, and oxygen and having an inverted fluorite structure. Such a lithium transition metal oxide has a large amount of oxygen gas released by decomposition. The inorganic oxide is preferably composed of one or more selected from the group consisting of Li ₆ MnO ₄ , Li ₆ CoO ₄ , and Li ₅ FeO ₄ . These generate a large amount of oxygen.

For example, Li ₆ MnO ₄ having a reverse fluorite structure releases oxygen gas at 4.5 V (Li / Li ⁺ reference potential), and the amount of oxygen at that time is 1.5 mol per mol of Li ₆ MnO _4. Very many. In addition, since the lithium transition metal oxide is an oxide, it is resistant to deterioration over time, the decomposition voltage is constant, the current interrupting mechanism can be reliably operated at the target potential, and an excessive increase in internal pressure is appropriately achieved. Can be prevented.

  A lithium transition metal oxide having a reverse fluorite structure has a maximum lithium amount of 6 mol per mole, and can be used not only as a gas generating agent during overcharging but also as a pre-doping agent. For example, a lithium transition metal oxide having a reverse fluorite structure is incorporated into the positive electrode together with the positive electrode active material, and this is charged, and the negative electrode active material is predoped with lithium. At the time of pre-doping charging, an amount of oxygen and lithium corresponding to the charging capacity of the lithium transition metal oxide is released from the lithium transition metal oxide.

  FIG. 1 is a model diagram of a charging curve of a lithium transition metal oxide having a reverse fluorite structure. As shown in FIG. 1, when a lithium transition metal oxide having a reverse fluorite structure is charged for the first time, the amount of oxygen released in the initial stage increases as the potential increases. When the potential becomes constant, the amount of released oxygen becomes almost constant. The end of charging at the time of pre-doping may be any time before the lithium transition metal oxide having a reverse fluorite structure is fully charged, for example, during the potential increase or when the potential increase becomes moderate .

  At the time of charging, the charging is stopped to the extent that a part of oxygen contained in the lithium transition metal oxide having a reverse fluorite structure remains. The lithium transition metal oxide having a reverse fluorite structure releases oxygen during charging. The battery including the positive electrode after completion of the dope is filled with carbon dioxide gas generated by reaction of oxygen or oxygen gas with the electrolyte. Therefore, a part of the sealed battery is opened, degassed, and sealed again. In a power storage device incorporating a pre-doped positive electrode, a potential lower than the charge end potential during pre-doping is preferably the charge end potential. Accordingly, in the new power storage device, oxygen is not released from the lithium transition metal oxide having a reverse fluorite structure at a potential equal to or lower than the set end-of-charge potential. Oxygen is released from the lithium transition metal oxide having an inverted fluorite structure when the potential becomes higher than the set end-of-charge potential, such as overcharge. Eventually, when the internal space of the container of the power storage device becomes equal to or higher than a predetermined internal pressure, the current path is interrupted by the operation of the current interrupt mechanism.

An inorganic oxide generates a gas component such as oxygen by an oxidative decomposition reaction when the potential becomes a predetermined value or more. The potential at which oxygen generation starts (Li / Li ⁺ reference potential) is referred to as gas generation start potential. The inorganic oxide has a transition metal. The oxidation potential of the transition metal varies depending on the type. Inorganic oxides have different oxidative decomposition potentials and gas generation start potentials depending on the type of transition metal. That is, the operating potential of the current interrupt mechanism can be set finely by changing the type of transition metal contained in the inorganic oxide.

  Depending on the type of inorganic oxide, there are some which can generate oxygen slightly even when the positive electrode has a potential lower than the end-of-charge potential. Such a gas generation start potential of the inorganic oxide refers to a start potential when oxygen is actively generated to such an extent that the internal pressure of the internal space of the container can be increased.

Examples of the inorganic oxide having a gas generation start potential of 4.0 V or more and less than 4.5 V (Li / Li ⁺ reference potential) include Li ₅ FeO ₄ (4.0 V) and Li ₆ CoO ₄ (4.3 V). It is done.

Examples of the inorganic oxide having a gas generation start potential of 4.5 V or more (Li / Li ⁺ reference potential) include Li ₆ MnO ₄ (4.5 V) and Li ₂ MnO ₃ (4.6 V). The potential in parentheses after the above substance name indicates the gas generation start potential (Li / Li ⁺ reference potential) of the substance.

The inorganic oxide can generate oxygen as long as the potential is equal to or higher than the gas generation start potential. For example, Li ₆ CoO ₄ having a gas generation start potential of 4.3 V can generate gas when the voltage is 4.3 V or higher.

  The gas generation start potential of the inorganic oxide is preferably higher than the charge end potential. The gas generation start potential of the inorganic oxide is preferably higher than the end-of-charge potential by 0.1 V or more, more preferably 0.2 V or more, and further preferably 0.5 V or more. In this case, it is possible to suppress a problem that gas is generated in the vicinity of the end-of-charge potential due to the increased activity of the inorganic oxide at high temperatures.

  The current interruption mechanism is configured such that when the battery internal pressure rises due to overcharging, the charging current is interrupted and no more electric quantity flows into the battery. The operating voltage of the current interrupt mechanism is preferably higher than the gas generation start potential. If the operating voltage of the current interrupting mechanism is lower than the gas generation start potential, the current interrupting mechanism operates at the normal internal pressure before the gas is generated from the inorganic oxide, or even during normal use. There is a risk that the shut-off mechanism will be activated.

  Examples of the power storage device of the present invention include a secondary battery and a capacitor. In particular, the power storage device of the present invention is preferably a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor. In particular, the power storage device of the present invention is preferably a lithium ion secondary battery. The power storage device of the present invention is characterized by the electrolytic solution and the separator, and the other constituent elements constituting the power storage device may be known ones suitable for each power storage device.

(Secondary battery)
The positive electrode of the secondary battery has an inorganic oxide that reacts at a potential higher than the normally usable maximum operating potential of the positive electrode to generate gas, and a positive electrode active material that can occlude and release cations. The positive electrode is preferably composed of a positive electrode active material and a current collector coated with the positive electrode active material.

  Here, the positive electrode includes a positive electrode active material that can occlude and release cations and the inorganic oxide.

As the positive electrode active material, the layered compound Li _a Ni _b Co _c Mn _{d De} O _f (0.2 ≦ a ≦ 1.2, b + c + d + e = 1, 0 ≦ e <1, D is Li, Fe, Cr, At least one element selected from Cu, Zn, Ca, Mg, S, Si, Na, K, Al, Zr, Ti, P, Ga, Ge, V, Mo, Nb, W, La, 1.7 ≦ f ≦ 2.1) and Li ₂ MnO ₃ . Further, as a positive electrode active material, a solid solution composed of a spinel such as LiMn ₂ O ₄ and Li ₂ Mn ₂ O ₄ and a mixture of a spinel and a layered compound, LiMPO ₄ , LiMVO _4, or Li ₂ MSiO ₄ (M in the formula) Are selected from at least one of Co, Ni, Mn, and Fe). Furthermore, as the positive electrode active material, tavorite compound (the M a transition metal) LiMPO ₄ F, such as LiFePO ₄ F represented by, Limbo ₃ such LiFeBO ₃ (M is a transition metal) include borate-based compound represented by be able to. Any metal oxide used as the positive electrode active material may have the above composition formula as a basic composition, and a metal element contained in the basic composition may be substituted with another metal element. Further, as the positive electrode active material, a positive electrode active material that does not contain lithium ions contributing to charge / discharge, for example, sulfur alone (S), a compound in which sulfur and carbon are combined, a metal sulfide such as TiS ₂ , V ₂ O, etc. ₅ , oxides such as MnO ₂ , polyaniline and anthraquinone, compounds containing these aromatics in the chemical structure, conjugated materials such as conjugated diacetic acid organic materials, and other known materials can also be used. Further, a compound having a stable radical such as nitroxide, nitronyl nitroxide, galvinoxyl, phenoxyl, etc. may be adopted as the positive electrode active material. When using a positive electrode active material that does not contain lithium, it is necessary to add ions to the positive electrode and / or the negative electrode in advance by a known method. Here, in order to add the ion, a metal or a compound containing the ion may be used.

  The inorganic oxide can react at a potential higher than the normal charge end potential of the positive electrode to release a gas. The normally usable maximum operating potential of the positive electrode is often the normally usable maximum operating potential of the positive electrode active material. For this reason, the inorganic oxide is preferably decomposed at a potential higher than the maximum usable operating potential of the positive electrode active material.

  The maximum operating potential of the positive electrode active material varies depending on the type of the positive electrode active material.

Examples of the positive electrode active material having a maximum operating potential of 3.5 V or more and less than 4.0 V (Li / Li ⁺ reference potential) include LiFePO ₄ .

Examples of the positive electrode active material having a maximum operating potential of 4.0 V or more and less than 4.5 V (Li / Li ⁺ reference potential) include LiCoO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , and LiNi _1/2. Mn _1/2 O _{2 and the} like can be mentioned.

Examples of the positive electrode active material having a maximum operating potential of 4.5 V or more (Li / Li ⁺ reference potential) include LiNi _1/2 Mn _3/2 O ₄ and LiCoPO ₄ .

  Examples of the combination of the positive electrode active material and the inorganic oxide contained in the positive electrode include those shown in Table 1, but are not limited thereto.

The positive electrode active material preferably includes LiMeO ₂ (Me: one or more selected from transition metals and includes at least Ni), and the inorganic oxide preferably includes Li ₆ MnO ₄ . The positive electrode active material preferably includes LiCoO ₂ and the inorganic oxide preferably includes Li ₆ CoO ₄ . The positive electrode active material preferably has LiFePO ₄ , and the inorganic oxide preferably has Li ₅ FeO ₄ .

  When the positive electrode mixture is 100% by mass, the content of the inorganic oxide in the positive electrode mixture is preferably 1% by mass to 30% by mass, and more preferably 2% by mass to 20% by mass. % Or less is preferable. In this case, it is possible to generate oxygen that can increase the internal pressure of the battery during excessive charging while maintaining the battery capacity high.

  The positive electrode preferably includes a positive electrode mixture having a positive electrode active material and the inorganic oxide, and a current collector having a surface coated with the positive electrode mixture. The positive electrode mixture includes a positive electrode active material and, if necessary, a binder and / or a conductive aid. The positive electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used. For example, silver, copper, gold, aluminum, tungsten, cobalt, zinc, nickel, iron, platinum, tin , Indium, titanium, ruthenium, tantalum, chromium, molybdenum, and metal materials such as stainless steel. The current collector may be covered with a known protective layer. What collected the surface of the electrical power collector by the well-known method may be used as an electrical power collector.

  The current collector can take the form of a foil, a sheet, a film, a linear shape, a rod shape, a mesh, or the like. Therefore, for example, a metal foil such as a copper foil, a nickel foil, an aluminum foil, and a stainless steel foil can be suitably used as the current collector. When the current collector is in the form of foil, sheet or film, the thickness is preferably in the range of 1 μm to 100 μm.

  The positive electrode mixture may contain a conductive additive. The conductive assistant is added to increase the conductivity of the electrode. Examples of the conductive aid include carbon black, graphite, acetylene black (AB), ketjen black (KB), and vapor grown carbon fiber (VGCF), which are carbonaceous fine particles. . These conductive assistants can be added to the positive electrode mixture alone or in combination of two or more. Although there is no restriction | limiting in particular about the usage-amount of a conductive support agent, For example, it can be set as 1-30 mass parts with respect to 100 mass parts of positive electrode active materials.

  The positive electrode mixture may contain a binder. The binder serves to bind the active material and the conductive additive to the surface of the current collector. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to. The blending ratio of the binder in the positive electrode mixture is preferably a mass ratio of active material: binder = 1: 0.005 to 1: 0.3. This is because when the amount of the binder is too small, the moldability of the electrode is lowered, and when the amount of the binder is too large, the energy density of the electrode is lowered.

  In order to form a layer made of a positive electrode mixture on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. The active material may be applied to the surface of the current collector. Specifically, an active material layer-forming composition containing an active material and, if necessary, a binder and a conductive aid is prepared, and an appropriate solvent is added to the composition to make a paste, and then the collection is performed. After applying to the surface of the electric body, it is dried. Examples of the solvent include N-methyl-2-pyrrolidone, methanol, methyl isobutyl ketone, and water. In order to increase the electrode density, the dried product may be compressed.

  The negative electrode has a current collector and a negative electrode mixture bonded to the surface of the current collector. The negative electrode mixture has a negative electrode active material. The negative electrode mixture preferably contains a conductive additive or / and a binder in addition to the negative electrode active material. The conductive auxiliary agent and / or binder that may be contained in the negative electrode mixture may be the same as the conductive auxiliary agent and / or binder that may be contained in the positive electrode mixture.

As the negative electrode active material, a material that can occlude and release metal ions such as lithium ions can be used. Therefore, there is no particular limitation as long as it is a simple substance, alloy, or compound that can occlude and release metal ions such as lithium ions. For example, as a negative electrode active material, Li, group 14 elements such as carbon, silicon, germanium and tin, group 13 elements such as aluminum and indium, group 12 elements such as zinc and cadmium, group 15 elements such as antimony and bismuth, magnesium , Alkaline earth metals such as calcium, and group 11 elements such as silver and gold may be employed alone. When silicon or the like is used for the negative electrode active material, a silicon atom reacts with a plurality of lithiums, so that it becomes a high-capacity active material. However, there is a problem that volume expansion and contraction due to insertion and extraction of lithium becomes significant. In order to reduce the fear, it is also preferable to employ an alloy or compound in which another element such as a transition metal is combined with a simple substance such as silicon as the negative electrode active material. Specific examples of the alloy or compound include tin-based materials such as Ag-Sn alloy, Cu-Sn alloy, Co-Sn alloy, carbon-based materials such as various graphites, SiOx (0 which disproportionates to silicon simple substance and silicon dioxide). .3 ≦ x ≦ 1.6), silicon simple substance, or a composite of a silicon-based material and a carbon-based material. Further, the anode active _{material, Nb 2 O 5, TiO 2} , Li 4 Ti 5 O 12, WO 2, MoO 2, Fe oxides, such as 2 _{O 3, or, Li 3-x M x N} (M = A nitride represented by (Co, Ni, Cu) may be employed. One or more of these materials can be used as the negative electrode active material.

  The negative electrode has a current collector and a negative electrode mixture bonded to the surface of the current collector. As the negative electrode current collector, for example, the one described for the positive electrode current collector can be adopted.

  The negative electrode mixture contains a negative electrode active material and, if necessary, a binder and / or a conductive aid. The negative electrode current collector is not particularly limited as long as it is a metal that can withstand a voltage suitable for the active material to be used, and for example, the one described for the positive electrode current collector can be adopted. As the negative electrode binder and the conductive additive, those described for the positive electrode can be adopted.

  A separator is used in the non-aqueous secondary battery as necessary. The separator separates the positive electrode and the negative electrode and allows metal ions such as lithium ions to pass while preventing a short circuit of current due to contact between the two electrodes.

  A separator is sandwiched between the positive electrode and the negative electrode as necessary to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting between the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal that communicate with the outside using a current collecting lead or the like, an electrolytic solution may be added to the electrode body to form a power storage device. . In addition, the power storage device of the present invention only needs to be charged and discharged within a voltage range suitable for the type of active material included in the electrode.

(Electric double layer capacitor)
An electric double layer capacitor has a structure in which a positive electrode and a negative electrode are arranged facing each other with a separator interposed between them, placed in a container, and filled with an electrolytic solution. An electric double layer capacitor can store electric charge between electrodes by applying a voltage between the electrodes. The electric double layer is a phenomenon in which positive charges and negative charges face each other at very short intervals at the interface between the electrode and the electrolyte.

  The positive electrode and the negative electrode of the electric double layer capacitor are obtained by arranging a conductor having a large surface area on a current collector. Examples of the conductor having a large surface area include activated carbon and polyacene compounds. The positive electrode contains an inorganic oxide as in the lithium ion secondary battery. Each electrode may contain a binder in order to bind such a conductor having a large surface area, and may further contain a conductive additive. Other components can be the same as those described for the lithium ion secondary battery.

(Lithium ion capacitor)
The lithium ion capacitor is a combination of a negative electrode of a lithium ion secondary battery and a positive electrode of an electric double layer capacitor. The positive electrode of the lithium ion capacitor is charged and discharged by forming an electric double layer, and the negative electrode is charged and discharged by a lithium chemical reaction.

  The description of the positive electrode is the same as the description of the electric double layer capacitor, and the description of the negative electrode is the same as the description of the lithium ion secondary battery.

  The container of the power storage device of the present invention contains a positive electrode, a negative electrode, a separator, and an electrolytic solution. Examples of the container include a bag-like laminate film, a rigid case, and a rigid cylinder.

  The shape of the power storage device of the present invention is not particularly limited, and various shapes such as a cylindrical shape, a square shape, a coin shape, and a laminate shape can be employed.

  The power storage device of the present invention may be mounted on a vehicle. The vehicle may be a vehicle that uses electric energy from the power storage device for all or part of its power source, and may be, for example, an electric vehicle, a hybrid vehicle, or the like. When a lithium ion secondary battery is mounted on a vehicle, a plurality of lithium ion secondary batteries may be connected in series to form an assembled battery. Examples of devices equipped with the power storage device include various home appliances driven by batteries such as personal computers and portable communication devices, office devices, and industrial devices in addition to vehicles. Furthermore, the power storage device of the present invention includes wind power generation, solar power generation, hydroelectric power generation and other power system power storage devices and power smoothing devices, power for power sources such as ships and / or power supply sources for auxiliary equipment, aircraft, spacecrafts, etc. Power source for power and / or auxiliary equipment, auxiliary power source for vehicles not using electricity as a power source, power source for mobile home robots, power source for system backup, power source for uninterruptible power supply, for electric vehicles You may use for the electrical storage apparatus which stores temporarily the electric power required for charge in a charging station.

Example 1
As shown in FIG. 1, the power storage device of this example is a lithium ion secondary battery. The power storage device includes a container, a positive electrode, a negative electrode, an electrolytic solution, a separator, and a current interruption mechanism.

  The positive electrode, the negative electrode, the separator, and the electrolytic solution are accommodated in an internal space formed inside the container. The positive electrode and the negative electrode are laminated via a separator.

The positive electrode is composed of a positive electrode mixture and a current collector coated with the positive electrode mixture. The positive electrode mixture includes a positive electrode active material and an inorganic oxide. The positive electrode active material is made of LiNi _1/5 Mn _1/3 Co _1/3 O ₂ having a layered structure. The inorganic oxide is made of Li ₆ MnO ₄ . The positive electrode used was not charged for the first time.

The content of Li ₆ MnO ₄ is 5% by mass, and the content of LiNi _1/3 Mn _1/3 Co _1/3 O ₂ is 90% by mass when the entire positive electrode mixture is 100% by mass. The current collector is made of an aluminum foil having a thickness of 20 μm. The gas generation start potential of Li ₆ MnO ₄ is 4.5 V (Li / Li ⁺ reference potential).

  The negative electrode is composed of a negative electrode mixture and a current collector coated with the negative electrode mixture. The negative electrode mixture has graphite as a negative electrode active material. The current collector is made of a copper foil having a thickness of 20 μm.

The electrolytic solution is composed of a mixed solvent composed of ethylene carbonate (EC) and diethyl carbonate (DEC) and LiPF ₆ as a lithium salt. The concentration of LiPF ₆ in the electrolytic solution is 1 mol / L.

  The separator is made of a polypropylene film. The container is made of an aluminum laminate film.

  The positive electrode and the negative electrode are each connected to an external terminal via a connection member.

  As shown in FIG. 2, the current interrupt mechanism 1 is provided on a connection member 23 that connects between the positive electrode 21 and the external terminal 22. The connection member 23 is fixed to the insulating gasket 4 held on the inner surface of the container 3. The current interruption mechanism 1 includes support members 11 a and 11 b, a metal diaphragm 12, and an interposition member 13. The connecting member 23 is divided in the middle, and support members 11a and 11b are fixed to the cut end portions 23a and 23b, respectively. Between the support members 11a and 11b, the diaphragm 12 and the interposition member 13 are arranged in parallel at positions close to or in contact with each other. The peripheral edges of the diaphragm 12 and the interposition member 13 are fixed to the support members 11 and 11b.

  The interposition member 13 is provided with a notch 13a on the side facing the diaphragm 12, and the thickness of the interposition member 13 is thin at the notch 13a. When oxygen is generated by oxidative decomposition of the inorganic oxide and the internal pressure rises to a predetermined value or more, the diaphragm 12 expands. The expanded diaphragm 12 presses the interposition member 13, and the interposition member 13 is broken at the notch 13a. The connection member 23 that is a current path is disconnected.

The end-of-charge potential of the power storage device of this example is 4.3 V (Li / Li ⁺ reference potential).

In the power storage device of this example, when the charging potential rises to a predetermined value or more due to overcharging, Li ₆ MnO ₄ is oxidized and decomposed to generate oxygen gas. When the internal pressure of the power storage device rises to a predetermined value or more, the diaphragm 12 of the current interrupt mechanism 1 presses the interposition member 13 to break the interposition member 13 and disconnect the connection member 23. Thereby, charging is stopped.

In the power storage device of Example 1, the amount of gas inside the battery after charging was measured by the Archimedes method. Specifically, the current interrupting device was removed from the power storage device of Example 1 used for measurement. For this power storage device, the power storage device was initially charged under a charge condition of 4.6 V (Li / Li ⁺ reference potential). As the charging potential increased, the laminate film as the container expanded. The volume increase of the entire power storage device was measured. The increase in volume is due to the generation of oxygen gas generated during charging or carbon dioxide gas generated by the reaction of oxygen gas with the electrolyte. Volume increase is equal to gas generation. The amount of gas generated during charging was 52 ml. Further, when the composition of the generated gas was analyzed, it was found that 62% oxygen gas and 36% carbon dioxide gas were contained. From this, when the potential at the time of charging rises to an excess potential equal to or higher than the gas generation start potential (4.5 V (Li / Li ⁺ reference potential)), Li ₆ MnO ₄ was oxidized and decomposed to generate gas. I understood.

(Example 2)
The power storage device of Example 2 differs from Example 1 in that the content of the inorganic oxide (Li ₆ MnO ₄ ) included in the positive electrode is 10% by mass. Others are the same as in the first embodiment.

For the power storage device of Example 2, as in Example 1, the amount of gas generated when initially charged to 4.6 V (Li / Li ⁺ reference potential) was measured. The amount of gas generated was 108 ml.

(Example 3)
In the power storage device of Example 3, the inorganic oxide included in the positive electrode is made of Li ₆ CoO ₄ . The content of Li ₆ CoO ₄ is 5% by mass when the total amount of the positive electrode mixture is 100% by mass. The gas generation start potential of Li ₆ CoO ₄ is 4.3 V (Li / Li ⁺ reference potential).

The end-of-charge potential of the power storage device of this example is 4.2 V (Li / Li ⁺ reference potential).

  For the power storage device of Example 3, as in Example 1, the amount of gas generated when initially charged was measured. The amount of gas generated was 59 ml.

(Comparative Example 1)
In the power storage device of Comparative Example 1, the positive electrode contains no inorganic oxide. Others are the same as in the first embodiment.

  For the power storage device of Comparative Example 1, as with Example 1, the amount of gas generated when initially charged was measured. The amount of gas generated was 3 ml. Little gas was generated.

Claims (9)

An electricity storage comprising: a housing body having an internal space; a positive electrode, a negative electrode, and an electrolyte housed in the internal space of the housing body; and a current interrupting mechanism that interrupts a current path according to an increase in internal pressure of the internal space. A device,
The positive electrode includes an inorganic oxide having a transition metal while reacting at a potential higher than a charge end potential of the positive electrode at the end of normal charge to generate gas.   The power storage device according to claim 1, wherein the gas that can be generated from the inorganic oxide is oxygen gas. The inorganic _{oxides, Li 6 MnO 4, Li 6} CoO 4, and the power storage device according to claim 1 or 2 comprising one or more selected from the group consisting of _Li 5 FeO _4.   The electrical storage according to any one of claims 1 to 3, wherein the positive electrode includes a positive electrode mixture having a positive electrode active material and the inorganic oxide, and a current collector having a surface coated with the positive electrode mixture. apparatus.   The power storage device according to claim 4, wherein the content of the inorganic oxide in the positive electrode mixture is 1% by mass or more and 30% by mass or less when the positive electrode mixture is 100% by mass. The positive active material is LiMeO ₂ (Me:. Be one or more selected from transition metals, including at least Ni) have the inorganic oxide according to claim 4 or 5 having a _Li 6 MnO ₄ Power storage device. The power storage device according to claim ₄ , wherein the positive electrode active material includes LiCoO ₂ and the inorganic oxide includes Li ₆ CoO ₄ . The power storage device according to claim ₄ , wherein the positive electrode active material includes LiFePO ₄ , and the inorganic oxide includes Li ₅ FeO ₄ .   The power storage device according to claim 1, wherein the power storage device is a lithium ion secondary battery.

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