JP4916263B2 - Power storage device - Google Patents

Description

  The present invention relates to an electricity storage device, and more particularly to an electricity storage device such as a secondary battery or an electrochemical capacitor.

  2. Description of the Related Art Conventionally, studies and development of secondary batteries such as lithium ion batteries, electrochemical capacitors such as electric double layer capacitors and hybrid capacitors have been underway as power storage devices mounted on hybrid vehicles and fuel cell vehicles.

  Such an electricity storage device generally includes a positive electrode, a negative electrode, a separator interposed between these electrodes, a cell tank containing an electrode and a separator and filled with an electrolyte so as to immerse them, and have. In each electrode, the energy stored by the electric double layer and / or the oxidation-reduction reaction is discharged, so that the storage device is charged and discharged.

However, when an organic electrolyte obtained by dissolving a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) in an organic solvent such as ethylene carbonate (C ₃ H ₄ O ₃ ) is used as the electrolyte, for example, There is a problem that hydrofluoric acid (HF) is generated in the discharge cycle, and the electric capacity and charge / discharge cycle characteristics of the negative electrode are deteriorated.

  Therefore, in order to solve the above-described problems, for example, Patent Document 1 uses a battery separator in which a thin film made of a compound having a Si—N bond is formed on one or both sides of a polyolefin microporous film. A battery is disclosed. In this battery, HF in the electrolytic solution can be captured by N—H groups contained in a thin film obtained from a compound having a Si—N bond, so that the negative electrode capacity and charge / discharge cycle characteristics are prevented from deteriorating. can do.

  Patent Document 2 discloses a negative electrode capable of inserting and extracting lithium, a positive electrode containing a positive electrode active material represented by the following general formula (1), and an aziridine having one or more aziridine rings. A lithium secondary battery comprising an electrolyte in which a compound is added to a non-aqueous electrolyte is disclosed.

Li _x Ni _1-yz Co _y M _z A ₂ (1)
(In the formula, M represents one or more elements of a transition metal or a lanthanoid metal selected from Al, Cr, Mn, Fe, Mg, La, Ce, Sr, and V, and A represents O, One or more elements selected from F, S and P, wherein x, y and z indicating the composition ratio are 1.0 ≦ x ≦ 1.1, 0.01 ≦ y ≦ 0.1, 0.01 ≦ z ≦ 0.5 is indicated.)
In this lithium secondary battery, even when HF is generated by impurities such as moisture contained in the positive electrode active material, HF is neutralized by the aziridine compound contained in the electrolyte. The deterioration of characteristics can be suppressed.
JP 2002-367484 A JP 2004-342504 A

  By the way, the above-mentioned electricity storage device stores energy by applying a voltage to each of the positive electrode and the negative electrode. The stored energy density (Wh / kg) is expressed by voltage (V) × electric capacity (Ah / kg), and by increasing the voltage, larger energy can be stored.

  However, for example, when the electrolytic solution is a lithium salt-containing organic solvent, when a high voltage is applied to the positive electrode, lithium fluoride (LiF) is generated from an acid derived from an anion contained in the organic solvent in the negative electrode. And this LiF coat | covers a negative electrode, and the fall of the electrical capacity and charging / discharging cycling characteristics of a negative electrode is produced. As a result, the energy density stored in the electricity storage device may decrease.

  On the other hand, in the battery described in Patent Document 1, although HF can be captured, the above-described thin film is formed by being applied to the surface of the separator, so that the thin film, more specifically, a compound having a Si-N bond. May come into contact with each electrode, thereby reducing the capacitance of each electrode.

  Moreover, in the lithium secondary battery described in Patent Document 2, although HF can be neutralized, for example, when activated carbon is used for the positive electrode, the polymer obtained by cleavage of the aziridine ring at the positive electrode is decomposed, In some cases, the pores of the activated carbon are blocked and the electric capacity of the positive electrode decreases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to store electricity that can suppress a decrease in electric capacity and charge / discharge cycle characteristics of the negative electrode when a high voltage is applied to the positive electrode. To provide a device.

In order to achieve the above object, an electricity storage device of the present invention is interposed between a positive electrode, a negative electrode, an electrolytic solution containing an organic solvent containing a lithium salt containing halogen as an anion, and the positive electrode and the negative electrode. A capture member that captures a negative electrode activity inhibitor derived from an anion contained in the electrolytic solution, and the positive electrode has a potential of 4.23 V vs. Li / Li ⁺ or der is, the a positive electrode polarizable electrode, the negative electrode is an electrode made of reversibly occluding and releasing material capable of lithium ion, characterized in that said capture member is a lithium metal It is said.

In addition, the electricity storage device of the present invention is interposed between the positive electrode, the negative electrode, an electrolytic solution including an organic solvent containing a lithium salt containing halogen as an anion, and the positive electrode and the negative electrode, and is included in the electrolytic solution. A capture member that captures a negative electrode activity-inhibiting substance derived from an anion; and a separator interposed between the positive electrode and the capture member and between the negative electrode and the capture member . It is an electrode, the negative electrode is an electrode made of a material capable of reversibly occluding and releasing lithium ions, and the capturing member is lithium metal .

  In the electricity storage device of the present invention, even when a high voltage is applied to the positive electrode to generate a negative electrode activity inhibiting substance derived from an anion contained in the electrolytic solution, the negative electrode activity inhibiting substance is captured by the capturing member. Therefore, in the negative electrode, it is possible to suppress the generation of a negative electrode activity inhibiting substance that hinders charging and discharging, and it is possible to suppress a decrease in electric capacity and charge / discharge cycle characteristics of the negative electrode. As a result, a high voltage can be applied to the positive electrode, and the energy density of the electricity storage device can be improved.

  FIG. 1 is a schematic configuration diagram of a hybrid capacitor showing an embodiment of an electricity storage device of the present invention.

  In FIG. 1, the hybrid capacitor 1 includes a positive electrode 2, a negative electrode 3 disposed opposite to the positive electrode 2 with a space therebetween, and a separator 4 interposed between the positive electrode 2 and the negative electrode 3 (more specifically, , A separator 4a disposed on the positive electrode 2 side and a separator 4b disposed on the negative electrode 3 side), a lithium foil 5 as a capturing member interposed between the separator 4a and the separator 4b, a positive electrode 2, a negative electrode 3, A separator 4 and a lithium foil 5 are accommodated, and a cell tank 7 filled with an electrolytic solution 6 is provided so as to immerse them. The hybrid capacitor 1 is a battery cell that is employed on a laboratory scale, and industrially, the hybrid capacitor 1 is appropriately scaled up by a known technique.

  The positive electrode 2 is formed by, for example, forming a mixture containing activated carbon, a conductive agent and a binder into an electrode shape and then drying the mixture.

  The activated carbon can be obtained, for example, by subjecting the activated carbon raw material to activation treatment.

  The activated carbon raw material is not particularly limited. For example, pitch-based raw materials such as petroleum pitch, coal-based pitch, and mesophase pitch, coke-based raw materials obtained by heat-treating these pitch-based materials, palms, wood flour Plant-based raw materials such as, phenol-based resins, vinyl chloride-based resins, resorcinol-based resins, polyacrylonitrile, polybutyral, polyacetal, polyethylene, polycarbonate, polyvinyl acetate, and the like, and carbides thereof, preferably, Examples thereof include pitch-based raw materials, coke-based raw materials, and synthetic resin-based raw materials (in particular, vinyl chloride-based and polyacrylonitrile), which are graphitizable carbon (soft carbon).

As the activation treatment, for example, alkaline activation treatment using potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), cesium hydroxide (CsOH), rubidium hydroxide (RbOH) or the like as an activator. Chemical activation treatment using zinc chloride (ZnCl ₂ ), phosphoric acid (H ₃ PO ₄ ) or the like as an activator, gas activation treatment using carbon dioxide (CO ₂ ), air or the like as an activator, and water vapor (H ₂ A steam activation treatment using O) as an activator, and the like, preferably an alkali activation treatment, and more preferably an alkali activation treatment using potassium hydroxide (KOH) as an activator. Such activation treatment is performed, for example, by firing the activated carbon raw material in a nitrogen atmosphere at, for example, 600 to 1000 ° C. when performing the above-described KOH activation treatment.

  Examples of the conductive agent include carbon black, ketjen black, and acetylene black. Moreover, the mixture ratio of a electrically conductive agent is 0 to 20 weight% in a mixture, for example. That is, the conductive agent may or may not be blended.

  Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, fluoroolefin copolymer crosslinked polymer, fluoroolefin vinyl ether copolymer crosslinked polymer, carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylic acid. Moreover, the mixture ratio of a binder is 2 to 10 weight% in a mixture, for example.

  And in order to shape | mold the positive electrode 2 in an electrode shape, for example, the mixture which mix | blended the above-mentioned activated carbon, a electrically conductive agent, and a binder is pressed and rolled using a roll press, for example, The electrode sheet obtained by this is used. After punching into an electrode shape, it is dried and pressed onto a metal foil to be a current collector.

  Examples of the metal foil include aluminum foil, copper foil, stainless steel foil, and nickel foil.

  Since the positive electrode 2 obtained in this way is a polarizable electrode mainly composed of activated carbon, in addition to power storage by adsorption of anions and cations on the positive electrode 2 and the negative electrode 3 respectively, that is, power storage by an electric double layer, oxidation It can also have electricity storage by reduction reaction.

  The negative electrode 3 is an electrode that reversibly stores and releases lithium ions, and is formed of an electrode material that can reversibly store and release lithium ions. Such an electrode material is not particularly limited. For example, a non-graphitizable carbon material (hard carbon) or graphite is used. The negative electrode 3 is formed by, for example, forming a mixture containing hard carbon or graphite, a conductive agent and a binder into an electrode shape and then drying it.

  Hard carbon is a general thermosetting resin such as phenol resin, melamine resin, urea resin, furan resin, epoxy resin, alkyd resin, unsaturated polyester resin, diallyl phthalate resin, furfural resin, silicone resin, xylene resin, It can be obtained by firing a urethane resin or the like.

  Examples of graphite include pyrolytic products of condensed polycyclic hydrocarbon compounds such as natural graphite, artificial graphite, graphitized mesophase carbon microspheres, graphitized mesophase carbon fiber, graphite whisker, graphitized carbon fiber, pitch, and coke. A graphite-type carbon material is mentioned. Such a graphite-based carbon material is preferably a powder having an average particle diameter of 25 μm or less.

  The blending ratio of hard carbon or graphite is, for example, 80 to 98% by weight in the mixture.

  Examples of the conductive agent include the above-described conductive agents. Moreover, the mixture ratio of a electrically conductive agent is 0 to 20 weight% in a mixture, for example. That is, the conductive agent may or may not be blended.

  Examples of the binder include the above-described binders. Moreover, the mixture ratio of a binder is 2 to 10 weight% in a mixture, for example.

  In order to form the negative electrode 3 into an electrode shape, for example, a mixture containing the above hard carbon or graphite, a conductive agent and a binder is stirred and mixed in a solvent, and the mixture is mixed on a metal foil serving as a current collector. After coating, it is dried, punched into an electrode shape, and then dried.

  Examples of the solvent include N-methylpyrrolidone, dimethylformamide, toluene, xylene, isophorone, methyl ethyl ketone, ethyl acetate, methyl acetate, ethyl acetate, dimethyl phthalate, ethanol, methanol, butanol, water, and the like.

  Examples of the metal foil include the above-described metal foil.

  The separator 4 is made of an insulating material such as glass fiber, silica or alumina fiber, ceramic fiber, whisker or other inorganic fiber, for example, natural fiber such as cellulose, for example, organic fiber such as polyolefin or polyester. Can be mentioned. Moreover, the separator 4 is shape | molded, for example in plate shape.

  As the lithium foil 5, a known lithium foil can be used, and for example, it is formed in a circular shape or a square shape.

  Further, the surface area of the lithium foil 5 is preferably substantially the same as the surface areas of the positive electrode 2 and the negative electrode 3 or a wider area. When the surface area of the lithium foil 5 is such an area, a negative electrode activity inhibiting substance (for example, HF) described later can be efficiently captured. Furthermore, the thickness is 0.01-0.1 mm, for example, Preferably, it is 0.01-0.05 mm.

  The lithium foil 5 has a plurality of holes in the thickness direction. By forming such a hole, the electrolytic solution 6 can pass between the separator 4a and the separator 4b, and can be charged and discharged.

  In addition, if the lithium foil 5 is a lithium metal, it will not restrict | limit to foil especially, For example, lithium powder and paste-form lithium can also be used.

  In this embodiment, the lithium foil 5 is interposed between the two separators 4a and 4b, but the lithium foil 5 is interposed between the positive electrode 2 and the negative electrode 3, and the lithium foil 5 and the positive electrode 2 are interposed. And the configuration in which the lithium foil 5 and the negative electrode 3 are separated from each other by the separator 4, that is, the lithium foil 5 and the positive electrode 2 and the lithium foil 5 and the negative electrode 3 are not in contact with each other. If so, for example, a configuration in which the lithium foil 5 is provided inside one separator 4 may be employed. In other words, any configuration may be used as long as the lithium foil 5 and the positive electrode 2 and the lithium foil 5 and the negative electrode 3 can be prevented from contacting and short-circuiting.

  The electrolytic solution 6 is made of an organic solvent containing a lithium salt containing halogen as an anion, and is prepared by dissolving the lithium salt in the organic solvent.

Examples of the lithium salt containing halogen as an anion include LiClO ₄ , LiCF ₃ SO ₃ , LiC (SO ₂ CF ₃ ) ₃ , LiC ₄ F ₉ SO ₃ , LiC ₈ F ₁₇ SO ₃ , LiB [C ₆ H ₃ ( _{CF 3) 2 -3,5] 4,} LiB (C 6 F 5) 4, LiB [C 6 H 4 (CF 3) -4] 4, LiBF 4, LiPF 6, LiAsF 6, LiSbF 6, LiCF 3 CO ₂ , LiN (CF ₃ SO ₂ ) _{2 and the} like. In the above formula, [C ₆ H ₃ (CF ₃ ) ₂ -3, 5] is the 3rd and 5th positions of the phenyl group, and [C ₆ H ₄ (CF ₃ ) -4] is the 4th position of the phenyl group. Each of which is substituted with —CF ₃ .

  Examples of the organic solvent include propylene carbonate, propylene carbonate derivatives, ethylene carbonate, ethylene carbonate derivatives, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, 1,3-dioxolane, dimethyl sulfoxide, sulfolane, and formamide. , Dimethylformamide, dimethylacetamide, dioxolane, phosphoric acid triester, maleic anhydride, succinic anhydride, phthalic anhydride, 1,3-propane sultone, 4,5-dihydropyran derivative, nitrobenzene, 1,3-dioxane, 1 , 4-dioxane, 3-methyl-2-oxazolidinone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydride Furan derivatives, sydnone compounds, acetonitrile, nitromethane, alkoxy ethane, and toluene. These can be used alone or in combination of two or more.

  The electrolytic solution 6 is prepared so that the concentration of the lithium salt in the organic solvent is, for example, 0.5 to 5 mol / L, preferably 1 to 3 mol / L. Moreover, it prepares so that the moisture content in the electrolyte solution 6 may be 50 ppm or less, for example, Preferably, it may be 10 ppm or less so that a high withstand voltage may be obtained.

In this hybrid capacitor 1, the potential of the positive electrode 2 is 4.23 V vs. Lithium foil 5 captures a negative electrode activity inhibiting substance that is equal to or higher than Li / Li ⁺ and derived from an anion contained in the lithium salt in electrolytic solution 6.

The potential of the positive electrode 2 is 4.23 V vs. In order to make it Li / Li ⁺ or more, for example, when hard carbon is used for the negative electrode 3, the cell voltage is applied at 3V or more.

At this time, for example, when LiPF ₆ is used as the lithium salt and ethylene carbonate is used as the organic solvent, PF ₆ ⁻ and H ⁺ generated by decomposition of residual water in the positive electrode 2 and the organic solvent in the positive electrode 2 Hydrofluoric acid (HF) as a negative electrode activity inhibiting substance that appears to have been generated by this reaction is captured in the lithium foil 5. Therefore, LiF is not generated in the negative electrode 3. That is, in the negative electrode 3, the production | generation of LiF which obstructs charging / discharging can be suppressed, and the fall of the electrical capacity and charging / discharging cycling characteristics of the negative electrode 3 can be suppressed.

That is, in the conventional hybrid capacitor, for example, the high voltage (for example, cell voltage: 4 V or more, positive electrode potential: 4.23 V vs. Li / Li ⁺ or more) is applied to FIG. As shown in the figure obtained by photographing the surface state with a scanning electron microscope (SEM), foreign substances are deposited on the surface of the negative electrode 3 (the negative electrode surface in FIG. 2 is subjected to X-ray photoelectron spectroscopy (XPS) and Fourier transform). When structural analysis was performed using conversion infrared spectroscopy (FT-IR), the foreign material was LiF.)

On the other hand, in the hybrid capacitor 1 in this embodiment, since HF is captured by the lithium foil 5, a high voltage (for example, cell voltage: 4 V or more, positive electrode potential: 4.23 V vs. Li / Li ⁺ or more) is shown in FIG. As shown in the SEM image of the state of the surface of the negative electrode 3 after being charged and discharged, it is possible to suppress the deposition of LiF on the surface of the negative electrode 3 even when charging and discharging are performed at a high voltage. (The structure of the negative electrode surface in FIG. 3 was analyzed using XPS and FT-IR. LiF was not detected, and normal SEI film components (for example, lithium carbonate, lithium alkyl carbonate, etc.) were detected. ).

As a result, as shown in FIG. 4, the potential of the positive electrode 2 is 4.23 V vs. so that the change in electric capacity of the negative electrode in the charge / discharge cycle is shown. (In FIG. ^{4, 4.23V vs.Li/Li +, 4.42V vs.Li/Li} + and 4.68V vs.Li/Li ⁺⁾ Li / Li ⁺ or more hybrid capacitor in the electrical capacity of the negative electrode and The charge / discharge cycle characteristics are degraded.

On the other hand, the potential of the positive electrode 2 is 4.23 V vs. In the hybrid capacitor 1 (FIG. 4 even Li / Li ⁺ or according to the present embodiment to provide a lithium foil 5, the potential of the positive electrode 2 is a 4.90V vs.Li/Li ^+, provided the lithium foil 5 In the negative electrode 3, the deposition of LiF that hinders charging and discharging can be suppressed in the negative electrode 3, and the decrease in the electric capacity and charging / discharging cycle characteristics of the negative electrode 3 can be suppressed.

Thus, in a conventional hybrid capacitor, when a cell voltage of 4 V or higher is applied (positive electrode potential: 4.23 V vs. Li / Li ⁺ or higher), the generation of LiF is accelerated (see FIG. 4), and the negative electrode capacity is increased. Since the voltage drops drastically, the hybrid capacitor 1 according to the present embodiment is useful when a high voltage of 4 V or higher is applied (positive electrode potential: 4.23 V vs. Li / Li ⁺ ). That is, the cell voltage can be increased, and the hybrid capacitor 1 having an excellent energy density can be obtained.

  The measurement sample in FIG. 4 is as follows.

Cathode 2: Activated carbon (RP-15 manufactured by Kuraray Chemical Co., Ltd .: PTFE (polytetrafluoroethylene))
Negative electrode 3: Hard carbon (Carbotron PS (F) manufactured by Kureha Co., Ltd. Binder: PVdF (polyvinylidene fluoride))
Electrolyte 6: 1 mol / L LiPF ₆ / ethylene carbonate + diethylene carbonate FIG. 5 is a schematic configuration diagram of a button-type hybrid capacitor showing a second embodiment of the electricity storage device of the present invention. In FIG. 5, parts corresponding to those shown in FIG. 1 are denoted by the same reference numerals as in FIG.

  In FIG. 5, the button-type hybrid capacitor 8 is a capacitor having a configuration different from that of the hybrid capacitor 1, and a positive electrode case 9 that also serves as a positive electrode terminal, and a negative electrode that also serves as a negative electrode terminal that is disposed to face the positive electrode case 9 in the vertical direction. Case 10 is provided.

  The positive electrode case 9 is, for example, a case having a substantially concave shape on the lower side, and is formed of, for example, a conductive and corrosion-resistant metal having a thickness of 0.2 to 0.4 mm, such as SUS304.

  The negative electrode case 10 is, for example, a case that can accommodate the positive electrode case 9 and has a substantially concave shape on the upper side. For example, the negative electrode case 10 is formed of the same material as the above-described positive electrode case 9 having a thickness of 0.2 to 0.4 mm. Yes.

  Between the positive electrode case 9 and the negative electrode case 10, the positive electrode 2 in contact with the positive electrode case 9, the negative electrode 3 in contact with the negative electrode case 10, which is opposed to the positive electrode 2 with a space therebetween, and the positive electrode 2 and the negative electrode 3. The upper separator 4a and the lower separator 4b impregnated with the electrolytic solution 6 and the lithium foil 5 interposed between the separator 4a and the separator 4b are interposed. Thereby, charging / discharging can be performed between the positive electrode 2 and the negative electrode 3.

  An insulating gasket 14 is filled in a gap 13 between the peripheral edge 11 of the positive electrode case 9 and the peripheral edge 12 of the negative electrode case 10. Thereby, it can prevent that the positive electrode case 9 and the negative electrode case 10 contact, and can prevent that the positive electrode 2 and the negative electrode 3 short-circuit.

  In the button-type hybrid capacitor 8, as in the hybrid capacitor 1, the negative electrode activity inhibitor derived from the anion contained in the lithium salt in the electrolytic solution 6 is captured by the lithium foil 5. 3 can be prevented from lowering the electric capacity and charge / discharge cycle characteristics.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various change is possible within the range of a claim description. For example, the hybrid capacitor 1 can be changed to an electric double layer capacitor or a lithium ion battery.

  For example, in the case of an electric double layer capacitor, for example, activated carbon, which is the same material as that of the positive electrode 2, is used as the negative electrode material instead of the material used for the negative electrode 3 described above.

On the other hand, in the case of a lithium ion battery, as the positive electrode material, various oxides and sulfides are used instead of the material (activated carbon) used for the positive electrode 2 described above. For example, manganese dioxide (MnO ₂ ), Lithium manganese composite oxide (eg, LiMn ₂ O ₄ , LiMnO _2, etc.), lithium nickel composite oxide (eg, LiNiO _2, etc.), lithium cobalt composite oxide (eg, LiCoO _2, etc.), lithium nickel cobalt composite oxide Lithium manganese cobalt composite oxide and vanadium oxide (for example, V ₂ O ₅ etc.) are used. Organic materials such as conductive polymer materials and disulfide polymer materials can also be used.

Next, although this invention is demonstrated based on an Example and a comparative example, this invention is not limited by the following Example.
Example 1
(Positive electrode) Activated carbon (RP-15 manufactured by Kuraray Chemical Co., Ltd.): Carbon black: PTFE (polytetrafluoroethylene) is mixed at a mixing weight ratio of 85: 5: 10, and is pressed and rolled using a roll press. Thus, an electrode sheet having a thickness of 200 μm was obtained. This electrode sheet was punched into a size of φ10 and further vacuum-dried at 100 ° C. for 12 hours to produce a positive electrode.
(Negative electrode) Hard carbon (Carbotron PS (F) manufactured by Kureha Co., Ltd.): PVdF (polyvinylidene fluoride) was mixed at a blending weight ratio of 9: 1 and sufficiently stirred in NMP (1-methyl-2-pyrrolidone). Thereafter, the film was applied to an aluminum foil to a thickness of about 30 μm, dried, then punched out to a size of φ10, and further vacuum dried at 100 ° C. for 12 hours to produce a negative electrode.
(Separator) A 400 μm thick ceramic filter (GB-100R manufactured by ADVANTEC) was punched into φ24 to produce a separator.
(Electrolytic Solution) An electrolytic solution was prepared by preparing 1 mol / L LiPF ₆ / ethylene carbonate + diethylene carbonate solvent (1: 1 volume ratio).
(Lithium foil) A 30 μm-thick lithium foil (Honjo Metal Co., Ltd.) 10 mm × 10 mm was perforated and used as a test lithium foil.

A test cell was assembled using one positive electrode, one negative electrode, two separators, 1.5 cc of electrolyte and one lithium foil, and a voltage range of 2.2 to 4.4 V (current density: 1 mA / cm). ^The charge / discharge test was conducted in ² ). The charge / discharge curve is shown in FIG. The monopolar potential was measured based on the Li reference electrode.

Comparative Example 1
A test cell was assembled using one positive electrode, one negative electrode, one separator, and 1 cc of the electrolyte used in Example 1, and a voltage range of 2.2 to 4.4 V (current density: 1 mA / cm ² ). A charge / discharge test was conducted. The charge / discharge curve is shown in FIG. The monopolar potential was measured based on the Li reference electrode.

Discussion FIG. 8 shows the change in electric capacity of the negative electrode in the charge / discharge cycle of Example 1 and Comparative Example 1, and FIG. 9 shows the change in Coulomb efficiency in the charge / discharge cycle of Example 1 and Comparative Example 1.

In Comparative Example 1, the positive electrode potential was 4.23 V vs. Li / Li ⁺ or higher, and no lithium foil is provided. Therefore, LiF is deposited on the surface of the negative electrode, and as shown in FIG. 8, the electric capacity of the negative electrode decreases with the progress of the charge / discharge cycle. For example, the electric capacity of about 21 mAh (first cycle) is reduced to about 14 mAh (10th cycle), and the electric capacity of the entire test cell is reduced due to the lower electric capacity of the negative electrode. (See FIG. 7). That is, the charge / discharge cycle characteristics are deteriorated. In addition, the Coulomb efficiency (ratio of discharge capacity to charge capacity) is a low value (see FIG. 9), and charging / discharging is not performed efficiently.

On the other hand, in Example 1, the positive electrode potential was 4.23 V vs. Although it is more than Li / Li ⁺ , since HF is trapped in the lithium foil, an average capacitance of about 21 to 22 mAh is developed in the charge / discharge cycle (see FIG. 8). Therefore, the electric capacity as a whole test cell does not decrease and shows excellent charge / discharge cycle characteristics (see FIG. 6). Furthermore, the coulomb efficiency is also high (see FIG. 9).

  As a result, a high voltage (for example, 4 V or more) can be applied to the positive electrode as long as it is a hybrid capacitor that can suppress the precipitation of LiF, which is a cause of capacity reduction, in the negative electrode as in Example 1. That is, the cell voltage can be increased, and a hybrid capacitor having an excellent energy density can be obtained.

It is a schematic block diagram of the hybrid capacitor which shows one Embodiment of the electrical storage device of this invention. It is the figure which image | photographed the state of the surface of the negative electrode after charging / discharging by applying a high voltage with respect to the hybrid capacitor which does not provide lithium foil between separators. It is the figure which image | photographed the state of the surface of the negative electrode after charging / discharging by applying a high voltage with respect to the hybrid capacitor which provided lithium foil between the separators. It is a figure which shows the change of the electrical capacity of the negative electrode in a charging / discharging cycle. It is a schematic block diagram of the button type hybrid capacitor which shows 2nd Embodiment of the electrical storage device of this invention. 2 is a charge / discharge curve of Example 1. FIG. 3 is a charge / discharge curve of Comparative Example 1. It is a figure which shows the change of the electrical capacity of the negative electrode in the charging / discharging cycle of Example 1 and Comparative Example 1. It is a figure which shows the change of the Coulomb efficiency in the charging / discharging cycle of Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hybrid capacitor 2 Positive electrode 3 Negative electrode 5 Lithium foil 6 Electrolyte 8 Button type hybrid capacitor

Claims (2)

A positive electrode;
A negative electrode,
An electrolytic solution comprising an organic solvent containing a lithium salt containing halogen as an anion;
A capturing member that is interposed between the positive electrode and the negative electrode and captures a negative electrode activity inhibitor derived from an anion contained in the electrolyte solution,
The potential of the positive electrode is 4.23 V vs. Li / Li ⁺ or more der is,
The positive electrode is a polarizable electrode;
The negative electrode is an electrode made of a material capable of reversibly occluding and releasing lithium ions,
The electric storage device, wherein the capturing member is lithium metal . A positive electrode;
A negative electrode,
An electrolytic solution comprising an organic solvent containing a lithium salt containing halogen as an anion;
A capture member that is interposed between the positive electrode and the negative electrode and captures a negative electrode activity inhibitor derived from an anion contained in the electrolyte;
A separator interposed between the positive electrode and the capture member and between the negative electrode and the capture member ,
The positive electrode is a polarizable electrode;
The negative electrode is an electrode made of a material capable of reversibly occluding and releasing lithium ions,
The electric storage device, wherein the capturing member is lithium metal .