TWI692786B - Hybrid capacitor - Google Patents

Abstract

A hybrid capacitor is directed to a stacked hybrid capacitor that is able to maintain a discharge capacity retention rate of at least 80% or more for at least 1000 hours or more in a constant current-constant voltage continuous discharge test at 3.5 V and 60℃, and includes: a positive electrode including graphite as a positive electrode active material; and a current collector located on a side of the positive electrode and made of aluminum material. The aluminum material is coated with an amorphous carbon film having a thickness ranging from 60 nm and 300 nm. A surface of a negative electrode and an outer periphery of the surface of the negative electrode exist in an outer periphery of a surface of the positive electrode.

Description

Hybrid capacitor

The invention relates to a hybrid capacitor.

This application claims priority based on Japanese Patent Application No. 2017-139521 filed in Japan on July 18, 2017, the contents of which are incorporated herein by reference.

Conventionally, as a technique for storing electrical energy, an electric double layer capacitor (for example, refer to Patent Document 1) or a secondary battery is known. Electric double layer capacitors (EDLC: Electric double layer capacitor) are far superior to secondary batteries in life, safety, and output density. However, electrical double-layer capacitors have a lower energy density (volume energy density) than secondary batteries.

Here, the energy (E) stored in the electric double-layer capacitor is represented by E=1/2×C×V ² using the capacitance (C) and applied voltage (V) of the capacitor, and the energy system and the capacitance and application The square of the voltage is proportional to. Therefore, in order to improve the energy density of the electric double layer capacitor, a technique of increasing the electrostatic capacity or applied voltage of the electric double layer capacitor has been proposed.

As a technique for increasing the electrostatic capacity of an electric double layer capacitor, a technique of increasing the specific surface area of activated carbon constituting the electrode of the electric double layer capacitor is known. Today, the known activated carbon has a specific surface area of 1000 m ² /g to 2500 m ² /g. An electric double-layer capacitor using such activated carbon as an electrode uses an organic electrolytic solution in which a quaternary ammonium salt is dissolved in an organic solvent, an aqueous electrolytic solution such as sulfuric acid, or the like as an electrolytic solution.

The wide range of voltages that can be used with organic electrolytes can increase the applied voltage, so the energy density can be increased.

As a person who uses the principle of an electric double layer capacitor to increase the applied voltage of the electric double layer capacitor, a lithium ion capacitor is known. The use of graphite or carbon that can insert and extract lithium ions in the negative electrode, and the use of activated carbon equivalent to the electrode material of the electric double layer capacitor that can absorb and desorb electrolyte ions in the positive electrode are called lithium ion capacitors. In addition, the use of activated carbon equivalent to the electrode material of the electric double layer capacitor for any one of the positive electrode and the negative electrode, and the use of metal oxides and conductive polymers as the electrode for Faraday reaction on the other electrode is called a hybrid capacitor. (Hybrid capacitor). Regarding lithium ion capacitors, the negative electrode of the electrode constituting the electric double layer capacitor is composed of graphite or carbon black of the negative electrode material of the lithium ion secondary battery, and lithium ion is embedded in the graphite or carbon black. Lithium-ion capacitors are characterized by more general electric double-layer capacitors, that is, those whose poles are composed of activated carbon, have a larger applied voltage.

However, when graphite is used as an electrode, it is a problem that propylene carbonate cannot be used as an electrolyte. When graphite is used for the electrode, propylene carbonate is electrolyzed, and the decomposition product of propylene carbonate adheres to the graphite surface, which reduces the reversibility of lithium ions. Propylene carbonate is a solvent that can operate at low temperatures. When propylene carbonate is used as an electric double layer capacitor, the electric double layer capacitor can also operate at -40°C. Therefore, in lithium ion capacitors, hard carbon that is not easily decomposed by propylene carbonate is used for the electrode system. However, compared to graphite, hard carbon has a lower capacity per unit volume of electrode, and the voltage is lower than graphite (which becomes an expensive potential). Therefore, lithium ion capacitors have problems such as lower energy density.

When emphasis is placed on low-temperature characteristics, it is difficult to use high-capacity graphite as the negative electrode for lithium-ion capacitors, and it will be difficult to further increase the energy density. In addition, in the lithium ion capacitor, since the copper foil is used for the current collector in the same way as the negative electrode of the lithium ion secondary battery, when overdischarge of 2 V or less is performed, copper will be eluted to cause a short circuit, and there is a problem that the discharge capacity decreases . Therefore, compared with an electric double layer capacitor capable of discharging to 0V, the use method of the lithium ion capacitor has a problem of being limited.

In the case of a new concept capacitor, graphite has been used as a positive electrode active material instead of activated carbon, and a reaction has been developed in which a desorbed electrolyte ion is inserted between graphite layers (for example, refer to Patent Document 2). Patent Document 2 describes that in a conventional electric double-layer capacitor using activated carbon as a positive electrode active material, if a voltage exceeding 2.5 V is applied to the positive electrode, the electrolyte will decompose to generate gas. On the other hand, the positive electrode active material uses graphite The electric double layer capacitor does not decompose the electrolyte even at a charging voltage of 3.5V, and can operate at a higher voltage than conventional electric double layer capacitors using activated carbon as the positive electrode active material. Regarding cycle characteristics or low-temperature characteristics, the output characteristics are also equal to or higher than those of conventional electric double-layer capacitors. The specific surface area of graphite is several hundredths of the specific surface area of activated carbon. The difference in the decomposition of the electrolyte results from such a huge specific surface area.

In a new concept capacitor using graphite as a positive electrode active material, its practical application is hindered due to insufficient durability, but it has been found that a technique using an aluminum material covered with an amorphous carbon film as a current collector (see Patent Document 3), can improve the high temperature durability to a practical level. This new concept capacitor is a capacitor that uses a reaction that desorbs electrolyte ions between graphite layers on the positive electrode, and strictly speaking this is not an electric double layer capacitor, but in Patent Document 3, it is in a broad sense It is called an electric double layer capacitor.

Here, the durability test is generally performed by an accelerated test (high temperature durability test, charge-discharge cycle test) to increase the temperature. This test can be performed in accordance with the method of "durability (high temperature continuous rated voltage application) test" described in JIS D 1401:2009. If the temperature is increased from room temperature by 10°C, the rate of deterioration will be approximately doubled. The high temperature durability test is, for example, a test maintained at a constant temperature bath at 60° C. (continuous charging) at a predetermined voltage (3 V or more in the present invention) for 2000 hours, and then returned to room temperature for charging and discharging, and a test for measuring the discharge capacity at this time. After the high-temperature durability test, it is preferable that the discharge capacity retention rate with respect to the initial discharge capacity be 80% or more.

[Prior Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2011-046584

Patent Document 2: Japanese Patent Laid-Open No. 2010-040180

Patent Literature 3: International Publication No. 2017/216960

In the case of a conventional lithium-ion battery, on the surfaces of the positive electrode and the negative electrode facing each other in the stacking direction of the electrodes, the area of the positive electrode is smaller than the area of the negative electrode, that is, the outer contours of the surface of the positive electrode and the surface of the positive electrode are designed on the negative electrode Within the outer contour of the surface. This is to prevent lithium ions from being precipitated due to the electric field concentration on the outer peripheral contour of the surface of the negative electrode when lithium ions move from the positive electrode to the negative electrode during charging, thereby preventing the battery from short-circuiting.

On the other hand, in the case of electric double-layer capacitors, activated carbon is used for the positive electrode and the negative electrode, and unlike lithium-ion batteries, lithium ions are precipitated on the outer peripheral profile (outer peripheral side). Therefore, by designing the area of the positive electrode and the negative electrode to be the same, the capacity of the positive electrode and the negative electrode can be maximized.

However, when the positive electrode is smaller than the negative electrode, the electric field is concentrated on the outer peripheral contour of the surface of the positive electrode. Even when an aluminum material covered with an amorphous carbon film is used as a current collector, since the outer peripheral contour (outer side) of the surface of the positive electrode is not coated with the amorphous carbon film, the exposed aluminum material is directly affected by the electric field There is a problem of corrosion and high-temperature durability deterioration. When graphite is used as a positive electrode active material, since the charging voltage is charged at a high voltage of 3.0 V or more, it is particularly susceptible to the influence of an electric field.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a hybrid capacitor that can suppress corrosion of a current collector and improve high-temperature durability.

In order to solve the above-mentioned problems, the present invention provides the following means.

(1): An aspect of the present invention relates to a hybrid capacitor, which can maintain a discharge capacity retention rate of 80% or more for 1000 hours or more in a continuous charging test at a constant current and a constant voltage of 60°C and 3.5V, and has A stacked hybrid capacitor with a structure in which a positive electrode and a negative electrode are stacked in one direction through a separator, wherein: the positive electrode contains graphite as a positive electrode active material; the positive electrode side current collector is made of aluminum; the aluminum material is passed through Crystalline carbon film coating; the thickness of the amorphous carbon film is 60 nm or more and 300 nm or less; and the positive electrode and the negative electrode are on opposite surfaces of the stack in the direction of the stack, the surface of the negative electrode and the The outer peripheral contour of the surface of the negative electrode exists within the outer peripheral contour of the surface of the positive electrode.

(2): Another aspect of the present invention relates to a hybrid capacitor, which can maintain a discharge capacity retention rate of 80% or more for 1000 hours or more in a continuous charging test at a constant current and constant voltage of 60°C and 3.5V. A wound hybrid capacitor having a structure in which a positive electrode and a negative electrode are stacked in a direction through a separator and further wound, wherein: the positive electrode contains graphite as a positive electrode active material; the positive electrode side current collector is made of aluminum; The aluminum material is coated with an amorphous carbon film; the thickness of the amorphous carbon film is 60 nm or more and 300 nm or less; and the positive electrode and the negative electrode are on opposite surfaces of each other in the stacking direction, The outer contour of the surface of the negative electrode and the surface of the negative electrode exists within the outer contour of the surface of the positive electrode.

In the hybrid capacitor of the present invention, the area of the negative electrode is smaller than the area of the positive electrode, and on the surfaces of the positive electrode and the negative electrode opposed to each other in the stacking direction, the outer circumference having the surface of the negative electrode and the surface of the negative electrode The profile exists within the outer peripheral contour of the surface of the positive electrode. Therefore, in the hybrid capacitor of the present invention, the electric field is not concentrated on the outer peripheral contour (outer peripheral side) of the surface of the positive electrode during its operation. Even when an aluminum material covered with an amorphous carbon film is used as a current collector, the aluminum material exposed at the outer peripheral contour of the surface will not be directly affected by the electric field. Therefore, corrosion of the aluminum material can be suppressed, and high-temperature durability can be improved.

10‧‧‧Positive

10a‧‧‧The surface opposite to the negative electrode

10b‧‧‧Outer contour of the surface of the positive electrode

11‧‧‧Aluminum foil (collector)

12‧‧‧Amorphous carbon film

13‧‧‧ Positive active material layer

20‧‧‧Negative

20a‧‧‧Surface opposite to the positive electrode

20b‧‧‧Outer outline of the surface of the negative electrode

21‧‧‧Aluminum foil (collector)

23‧‧‧Anode active material layer

D, D1, D2‧‧‧Stacking direction

30‧‧‧Partition

100‧‧‧Hybrid capacitor

101‧‧‧Housing

102‧‧‧Positive

102a‧‧‧Positive lead

103‧‧‧Negative

103a‧‧‧Negative lead

104‧‧‧Partition

105‧‧‧washer

106‧‧‧Seal plate

FIG. 1A: A schematic perspective view schematically showing the configuration of a hybrid capacitor according to an embodiment of the present invention.

FIG. 1B: A schematic plan view schematically showing the configuration of a hybrid capacitor according to an embodiment of the present invention.

Fig. 2: A schematic perspective view schematically showing the configuration of a hybrid capacitor according to another embodiment of the present invention.

Fig. 3: Shows the discharge characteristics of the hybrid capacitors of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 6 of the present invention (discharge capacity retention rate when a constant current and constant voltage continuous charging test at 60°C is performed) Chart.

Fig. 4: Shows the charging characteristics of the hybrid capacitor in Example 1 of the present invention before the start of the continuous charging test at a constant current and constant voltage of 60°C and after conducting 1053 hours for measuring the discharge capacity retention rate in the charge and discharge test chart.

Fig. 5: shows the charging characteristics of the hybrid capacitor of Comparative Example 3 of the present invention before the continuous charging test at a constant current and constant voltage of 60°C and 450 hours after the start of the charging test for measuring the discharge capacity retention rate chart.

Hereinafter, the structure of the hybrid capacitor to which the present invention is applied will be described using drawings. In the drawings used in the following description, for easy understanding of the features, there are cases where the feature parts are enlarged for convenience, and the dimensional ratio of each component is not always the same as the actual one. In addition, the materials, dimensions, etc. exemplified in the following description are only examples, and the present invention is not limited thereto, and can be implemented by appropriately changing within the scope of exerting effects.

[First Implementation Type]

The hybrid capacitor of the first embodiment of the present invention is a hybrid capacitor capable of maintaining a discharge capacity retention rate of 80% or more for 1000 hours or more in a continuous charging test at a constant current and constant voltage of 60°C and 3.5V. The two electrodes between which the separator is inserted and opposed to each other, and the electrolyte filling the space between the two electrodes are contained in a sealed container. Of the two electrodes, one is positive and the other is negative. The positive electrode and the negative electrode are each formed by forming a positive electrode active material layer and a negative electrode active material layer on the corresponding current collectors. The positive electrode contains graphite as a positive electrode active material, and the positive electrode-side current collector is made of an aluminum material that is coated with an amorphous carbon thin film, and the thickness of the amorphous carbon thin film is 60 nm or more and 300 nm or less. The facing surfaces are substantially parallel to each other between the opposing surfaces of the positive electrode and the negative electrode. In this embodiment, a stacked hybrid capacitor has a positive electrode and a negative electrode stacked in one direction through a separator, and the positive electrode and the negative electrode are on opposite surfaces of each other in the stacking direction, and the surface of the negative electrode The structure in which the outer peripheral contour of the surface of the negative electrode exists within the outer peripheral contour of the surface of the positive electrode is exemplified.

The positive electrode is formed by forming a positive electrode active material layer on a current collector (collector on the positive electrode side).

The positive electrode active material layer can be formed by applying a paste-like positive electrode material containing a binder and a conductive material in a required amount on a positive electrode-side current collector and drying it.

As the binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propadiene rubber, styrene butadiene, acrylic, olefin, carboxymethyl cellulose (CMC) is a single system or a mixed system of two or more.

The conductive material is not particularly limited as long as the conductivity of the positive electrode active material can be made good, and a well-known conductive material can be used. For example, carbon black, carbon fiber (including carbon nanotubes (CNT), VGCF (registered trademark), etc., not limited to carbon nanotubes) and the like can be used.

For the positive electrode side current collector, an aluminum material with improved corrosion resistance can be used, for example, an aluminum material coated with an amorphous carbon thin film can be used. The aluminum material may be coated with only the amorphous carbon film, or a conductive carbon layer may be provided between the amorphous carbon film and the positive electrode active material.

For the aluminum material of the base material, the aluminum material used for general current collector applications can be used.

The shape of aluminum material can be made into foil, sheet, film, net and other types. Aluminum foil is preferably used as the current collector.

In addition, the aluminum material may be etched aluminum as described below in addition to those having a flat surface.

When the aluminum material is a foil, sheet, or film, its thickness is not particularly limited, but when the battery itself has the same size, the thinner the more active materials that can be enclosed in the battery case, but due to the reduced strength, it is more Choose the appropriate thickness. The actual thickness is preferably 10 μm to 40 μm , more preferably 15 μm to 30 μm . When the thickness is less than 10 μm , the aluminum material may be cracked or cracked in the step of roughening the surface of the aluminum material or in other manufacturing steps.

Etched aluminum can also be used for aluminum coated with amorphous carbon film.

Etching aluminum is a roughening process by etching. For etching, a method of immersion in an acid solution such as hydrochloric acid (chemical etching) or a method of electrolysis (electrochemical etching) using aluminum as an anode in an acid solution such as hydrochloric acid can be used. For electrochemical etching, since the current waveform during electrolysis, the composition of the solution, the temperature, etc. will make the etching shape different, it can be selected from the viewpoint of capacitor performance.

The aluminum material can be used for any one with or without a passivation layer on the surface. When a passivation film of a natural oxide film is formed on the surface of the aluminum material, an amorphous carbon passivation layer may be provided on the natural oxide film, or, for example, the natural oxide layer may be removed by argon sputtering.

The natural oxide film on aluminum is a passivation film, which has the advantage that it is not easily eroded by the electrolyte. On the other hand, it is also related to the increase in the resistance of the current collector. Therefore, from the viewpoint of reducing the resistance of the current collector, there is no natural Oxide film is better.

In this specification, the amorphous carbon thin film refers to an amorphous carbon film or a hydrogenated carbon film, including a diamond-like carbon (DLC) film, a carbon hard film, an amorphous carbon (aC) film, and hydrogenated amorphous carbon (aC:H) film, etc. As a method for forming an amorphous carbon thin film, a well-known method such as a plasma CVD method using a hydrocarbon gas, a sputtering evaporation method, an ion plating method, and a vacuum arc evaporation method can be used. In addition, the amorphous carbon thin film preferably has a degree of conductivity as a current collector.

Among the exemplified materials of the amorphous carbon thin film, the diamond-like carbon is a material having an amorphous structure in which both diamond bonds (SP ³ ) and graphite bonds (SP ² ) are mixed, and has high chemical resistance. However, when used as a thin film of a current collector, the conductivity is low, so in order to improve the conductivity, it is preferable to dope with boron or nitrogen.

The thickness of the amorphous carbon thin film is preferably 60 nm or more and 300 nm or less. The thickness of the amorphous carbon thin film is too thin if it is less than 60 nm, so that the coating effect of the amorphous carbon thin film becomes small, and the corrosion of the current collector in the constant current and constant voltage continuous charging test cannot be sufficiently suppressed. If it becomes too thick beyond 300 nm, the amorphous carbon thin film becomes a resistor and the resistance with the active material layer increases, so an appropriate thickness should be selected appropriately. The thickness of the amorphous carbon thin film is preferably 80 nm or more and 300 nm or less, and more preferably 120 nm or more and 300 nm or less. When the amorphous carbon film is formed by the plasma CVD method using hydrocarbon-based gas, the thickness of the amorphous carbon film can be controlled by the energy injected into the aluminum material, specifically by applying voltage, application time, and temperature control.

The positive electrode active material used in the hybrid capacitor of this embodiment includes graphite. As graphite, either artificial graphite or natural graphite can be used. In addition, natural graphite is known to have scales and soils. Natural graphite is obtained by crushing and repeatedly mining the raw ore, which is called a beneficiation method. In addition, artificial graphite is manufactured, for example, by a graphitization step of firing a carbon material at a high temperature. More specifically, for example, a binder such as pitch can be added to the raw coke to form, and the primary firing can be performed by heating to about 1300°C, and then the primary firing product can be impregnated with asphalt resin, and then carried out at a high temperature close to 3000°C. It is prepared by secondary firing. In addition, a coating of graphite particles coated with carbon can also be used.

The crystal structure of graphite can be roughly divided into a hexagonal crystal with a layer structure composed of ABAB and a rhombohedral crystal with a layer structure composed of ABCABC. These conditions depend on whether the structures are in a single or mixed state, but any crystal structure or mixed state can be used.

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‧

)股份公司製KS-6(商品名)之石墨的菱面體晶的比率為26%，大阪氣體化學股份有限公司製之人造石墨的介穩相球狀碳(MCMB)，菱面體晶的比率為0%。 For example, Irisite graphite and carbon Japan (

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‧

) The ratio of rhombohedral crystals of graphite of KS-6 (trade name) made by the joint-stock company is 26%. The metastable phase spherical carbon (MCMB) of artificial graphite manufactured by Osaka Gas Chemical Co., Ltd. The ratio is 0%.

Compared with the activated carbon used in the conventional EDLC, the graphite used in the present embodiment has a different display mechanism of electrostatic capacity. In the case of activated carbon, with a large specific surface area, electrolyte ions are adsorbed and desorbed on the surface to generate electrostatic capacity. On the other hand, in the case of graphite, the electrostatic capacity is exhibited by intercalation and deintercalation (intercalation-deintercalation) of anions which are electrolyte ions between graphite layers. Due to this difference, in Patent Document 3, the hybrid capacitor using graphite according to the present embodiment is broadly referred to as an electric double-layer capacitor, but is different from EDLC using activated carbon having an electric double layer.

Since the current collector of this embodiment has an amorphous carbon film on the surface of the aluminum material, that is, on the surface of the positive electrode and the negative electrode opposite to each other, the aluminum material is prevented from contacting the electrolyte and current collection can be prevented The body is corroded by the electrolyte during high-voltage charging. Moreover, when the current collector is stamped to the size of the electrode, there is no amorphous carbon film in its cross section, and the aluminum material is exposed.

The negative electrode is formed by forming a negative electrode active material layer on a current collector (negative electrode-side current collector).

The negative electrode active material layer can be formed by applying a slurry-like negative electrode material mainly containing a negative electrode active material, a binder, and a conductive material in an amount as required to the negative electrode current collector and drying it.

As the negative electrode active material, a material capable of adsorbing and desorbing or intercalating (intercalating-extracting) cations of electrolyte ions can be used. For example, carbonaceous materials such as activated carbon, graphite, hard carbon, and soft carbon, and lithium titanate can be used. , Where lithium titanate is a lower electrode potential material than carbonaceous materials.

The negative electrode-side current collector can use a well-known one, and an aluminum material coated with an amorphous carbon film, a conductive carbon layer is an aluminum material provided between the amorphous carbon film and the negative electrode active material, etched aluminum, And ethnic groups made of aluminum. Preferably, when using an aluminum material coated with an amorphous carbon film on the negative electrode side, or an aluminum material provided with a conductive carbon layer between the amorphous carbon film and the negative electrode active material, the high voltage When the hybrid capacitor is operated, high-temperature durability can be improved.

As the binder, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propadiene rubber, styrene butadiene, acrylic, olefin, carboxymethyl cellulose (CMC) is a single system or a mixed system of two or more.

The conductive material is not particularly limited as long as the conductivity of the negative electrode active material layer can be made good, and a well-known conductive material can be used. For example, carbon black, carbon fiber (including carbon nanotubes (CNT), VGCF (registered trademark), etc., not limited to carbon nanotubes) and the like can be used.

As the electrolyte, an organic electrolyte using an organic solvent can be used. The electrolyte contains electrolyte ions that can be adsorbed and desorbed from the electrode. The type of electrolyte ions is preferably the one with the smallest ion diameter. Specifically, an ammonium salt or a phosphorus salt, or an ionic liquid, a lithium salt, or the like can be used.

As the ammonium salt, tetraethylammonium (TEA) salt, triethylammonium (TEMA) salt, etc. can be used. As the phosphorus salt, a spiro compound having two five-membered rings can be used.

The type of ionic liquid is not particularly limited, and considering the ease of movement of electrolyte ions, a material with a viscosity as low as possible or a high conductivity (conductivity) is preferable. Specific examples of the cation constituting the ionic liquid include imidazolium ion and pyridinium ion. Examples of the imidazolium ion include 1-ethyl-3-methylimidazolium (EMIm) ion and 1-methyl-1-propylpyrrolidinium (1-methyl-1- propyl-pyrrolizinium) (MPPy) ion, 1-methyl-1-propyl-piperizinium (MPPi) ion, etc. In addition, lithium tetrafluoroborate LiBF ₄ , lithium hexafluorophosphate LiPF ₆ and the like can be used as the lithium salt.

Examples of the pyridinium ion include 1-ethylpyridium ion, 1-buthylpyridnium ion, and the like.

Examples of the anion constituting the ionic liquid include BF ₄ ion, PF ₆ ion, [(CF ₃ SO ₂ ) ₂ N] ion, FSI (bis(fluorosulfonyl)imide; bis(fluorosulfonyl)imide) ion, TFSI( Bis(trifluoromethanesulfonyl)imide; bis(trifluorosulfonyl)imide) ions, etc.

The solvent can be acetonitrile, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl sulfone, ethyl isopropyl ash, ethyl carbonate, fluoroethylene carbonate, γ butyrolactone , Cyclobutane, N,N-dimethylformamide, or dimethyl sulfoxide, alone or in a mixed solvent.

The separator is preferably a cellulose-based paper-like separator, a glass fiber separator, or a microporous membrane such as polyethylene or polypropylene for reasons such as preventing short circuit of the positive electrode and the negative electrode, or ensuring storage stability of the electrolyte.

FIG. 1A is a perspective view showing an example of the arrangement of the hybrid capacitor of this embodiment. FIG. 1B shows the positional relationship between the positive electrode 10, the negative electrode 20, and the separator 30 in FIG. 1A, which is a plan view from the D2 side in the stacking direction D of the three to the D1 direction.

In FIGS. 1A and 1B, the positive electrode 10 and the negative electrode 20 are arranged so that the positive electrode active material layer 13 and the negative electrode active material layer 23 face each other. The positive electrode 10 is formed by sequentially stacking an aluminum foil 11, an amorphous carbon thin film 12, and a positive electrode active material layer 13 made of graphite in the direction of the negative electrode 20 (i.e., direction D2). The negative electrode 20 exemplifies a structure in which an aluminum foil 21 and a negative electrode active material layer 23 made of activated carbon are sequentially stacked in the direction of the positive electrode 10 (that is, the direction D1). The separator 30 is interposed between the positive electrode 10 and the negative electrode 20, and although not shown here, the electrolyte is filled therein. Furthermore, an amorphous carbon thin film can be formed between the aluminum foil 21 of the negative electrode 20 and the negative electrode active material layer 23.

In addition, in FIGS. 1A and 1B, disc-shaped positive and negative electrodes are shown, but the shapes of the positive and negative electrodes are determined according to the shape of the battery. For example, when used as an electrode for a button battery, a disc-shaped electrode as shown in FIGS. 1A and 1B is used; when used as an electrode for a cylindrical battery, a rectangular battery, or a laminated battery, a square plate-type electrode can be used.

As shown in FIG. 1A, for the arrangement of the two electrodes, the surface 20a of the negative electrode 20 opposite to the positive electrode 10 (which may be referred to as "negative electrode surface", "surface 20a of the negative electrode 20" in this specification) and the positive electrode 10 The surfaces 10a on the opposite side of the negative electrode 20 (which may be referred to as "positive electrode surface" in this specification, "the surface 10a of the positive electrode 10") are substantially parallel to each other, and are each substantially perpendicular to the lamination direction D. As shown in FIG. 1B, when the positive electrode 10 and the negative electrode 20 are viewed in the direction D1 from the D2 side of the negative electrode 20, the entire negative electrode 20 is disposed inside the outer peripheral contour 10 b of the surface 10 a of the positive electrode 10. The area of the negative electrode 20 with respect to the surface 20 a of the positive electrode 10 is smaller than the area of the positive electrode 10 with respect to the surface 10 a of the negative electrode 20.

Therefore, in the same plan view, the outer peripheral contour 20b with respect to the surface 20a of the negative electrode 20 does not contact the outer peripheral contour 10b of the surface 10a of the positive electrode 10 and does not intersect.

As described above, in the hybrid capacitor according to the present embodiment, the area of the negative electrode 20 is smaller than the area of the positive electrode 10, and the plan view of the negative electrode 20 from the D2 side in the stacking direction D of the two electrodes to the D1 direction The entire surface 20 a exists within the outer peripheral contour 10 b of the surface 10 a of the positive electrode 10. That is, in the same plan view, there is a structure in which the surface 20a of the negative electrode and the peripheral contour 20b are located within the peripheral contour 10b of the surface 10a of the positive electrode 10. Therefore, in the hybrid capacitor of the present embodiment, the electric field is not concentrated on the outer peripheral contour (outer peripheral side) 10b of the surface 10a of the positive electrode 10 during operation, and the aluminum foil exposed in the outer peripheral contour 10b is not directly affected Due to the influence of the electric field, the corrosion of the aluminum foil can be suppressed, and the high-temperature durability can be improved.

In this plan view, since the outer peripheral contour 10b of the surface 10a of the positive electrode 10 is far from the outer peripheral contour 20b of the surface 20a of the negative electrode 20, the influence of the surrounding electric field is less affected, so the above effect can be enhanced. Therefore, in this plan view, the area of the negative electrode is preferably smaller than the area of the positive electrode.

In this embodiment, the graphite positive electrode using an aluminum foil coated with an amorphous carbon film is not limited to a hybrid capacitor. The graphite positive electrode can also be used as an electrode of a lithium ion capacitor, for example, by using a material alloyed with lithium such as hard carbon, soft carbon, graphite, lithium metal, tin or silicon, or lithium titanate as a negative electrode.

In addition, the aluminum foil coated with amorphous carbon used in the present embodiment exhibits the above-mentioned effects even when activated carbon is used as a positive electrode active material, making it possible to generate a higher voltage than before. However, because the specific surface area of activated carbon is higher than that of graphite by two to three digits. Therefore, it can be considered that the electrode reaction area becomes larger, the decomposition of the electrolytic solution, the decomposition of the activated carbon itself, or the decomposition of the functional group on the surface of the activated carbon, etc., which may be considered to have the influence of the gas generation caused by the increase in the internal pressure of the gas. Therefore, the effect of this embodiment cannot be obtained only by the combination of activated carbon and aluminum foil coated with amorphous carbon.

[Second Embodiment Type]

FIG. 2 is a longitudinal cross-sectional view schematically showing the configuration of the hybrid capacitor 100 according to the second embodiment of the present invention. The hybrid capacitor 100 is a wound type hybrid capacitor 100 in which a positive electrode 102 and a negative electrode 103 are stacked through a separator 104 in a cylindrical case 101 and further has a wound structure. Here, the state in which a part (the part surrounded by the dotted line) in the wound structure of the positive electrode, the negative electrode, and the separator is unwound is shown.

The housing 101 has an opening at one end, and this opening is sealed by a sealing plate 106, which has a gasket 105 at its peripheral portion. The positive electrode 102 and the negative electrode 103 are each connected to a positive electrode lead 102a and a negative electrode lead 103a for connection to external terminals.

The configuration of the hybrid capacitor 100 of this embodiment is the same as the configuration of the hybrid capacitor of the first embodiment except that the positive electrode 102 and the negative electrode 103 have a wound structure. That is, the positive electrode 102 contains graphite as a positive electrode active material, the current collector on the positive electrode 102 side is an aluminum material, the aluminum material is coated with an amorphous carbon thin film, and the thickness of the amorphous carbon thin film is 60 nm or more and 300 nm or less. Also, on the surfaces of the positive electrode 102 and the negative electrode 103 which are opposite to each other in the stacking direction, the outer peripheral contours of the surface of the negative electrode 103 and the surface of the negative electrode 103 exist within the outer peripheral contour of the surface of the positive electrode 102.

Similarly, in the hybrid capacitor of the present embodiment, in a state where the winding structure is unwound (unfolded), on the surface of the positive electrode and the negative electrode in the stacking direction of the positive electrode and the negative electrode, due to the surface of the negative electrode and the negative electrode The outer peripheral contour of the surface of the electrode is within the outer peripheral contour of the surface of the positive electrode, so it has the same effect as the hybrid capacitor of the first embodiment.

[Example]

The effect of the present invention will be made clearer by the following examples. It should be noted that the present invention is not limited to the following embodiments, but can be implemented by appropriate changes within the scope of exerting effects.

[Example 1]

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)股份公司製石墨(商品名：KS-6)作為正極活性物質、乙炔黑、聚偏二氟乙烯以重量百分比濃度為80：10：10wt%的比率秤量後，以N-甲基吡咯酮溶解混合而得的漿料，將該漿料使用刮刀塗布於被覆有類鑽碳(DLC)的鋁箔(20μm)上，將其作為正極。 Irisite graphite and carbon Japan (

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) Graphite (trade name: KS-6) made by the joint-stock company is used as the positive electrode active material, acetylene black, and polyvinylidene fluoride at a weight percentage concentration of 80:10:10wt%, and then dissolved in N-methylpyrrolidone The slurry obtained by mixing was applied to a diamond-like carbon (DLC)-coated aluminum foil (20 μm) using a doctor blade to make it a positive electrode.

The aluminum foil coated with DLC (hereinafter sometimes referred to as "DLC-coated aluminum foil") is a positive electrode-side current collector, and is equivalent to an aluminum material covered with an amorphous carbon thin film. The manufacturing method of DLC coated aluminum foil is to remove the natural oxide film on the surface of the aluminum foil by argon sputtering on the aluminum foil with a purity of 99.99%, and then discharge it in the mixed gas of methane, acetylene and nitrogen near the aluminum surface to generate plasma , By applying a negative pulse voltage to the aluminum material to generate a DLC film. Here, the thickness of the DLC film on the DLC-coated aluminum foil was measured with a probe-type surface shape measuring instrument DektakXT manufactured by BRUKER, and the result was 135 nm.

Next, the activated carbon (trade name: MSP-20), acetylene black, and polyvinylidene fluoride produced by Kansai Thermochemical Co., Ltd. were weighed at a ratio of 80:10:10 weight percent concentration (wt%), and N- The slurry obtained by dissolving and mixing methylpyrrolidone was applied to an etched aluminum foil (20 μm) manufactured by Nippon Electric Equipment Industry Co., Ltd. using a doctor blade, and this was used as a negative electrode.

Next, each of the positive electrode and the negative electrode was punched into a disk shape having a diameter of 16 mm and a diameter of 14 mm, and vacuum dried at 150° C. for 24 hours, and then moved to an argon glove box. These paper separators manufactured by Japan High Paper Industry Co., Ltd. were laminated and 0.1 mL of electrolyte was added (wherein the electrolyte used 1M TEA-BF ₄ (tetraethylammonium tetrafluoroborate) as the electrolyte, and SL +DMS (Sulfolane + dimethyl sulfide) as a solvent), making a 2032 button-type battery in an argon glove box.

[Example 2]

A 2032 type button battery similar to Example 1 was produced except that artificial graphite (MCMB6-10) manufactured by Osaka Gas Chemical Co., Ltd. was used as the positive electrode active material.

[Example 3]

The preparation was the same as in Example 1, except that lithium titanate Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, and 1M lithium tetrafluoroborate LiBF ₄ electrolyte and propylene carbonate (PC) solvent were used as electrolytes. 2032 type button battery.

Furthermore, when an aluminum foil with a DLC film thickness of 0 nm (without a DLC film) is used as the positive electrode-side current collector, this is not an embodiment of the present invention.

[Comparative Example 1]

The activated carbon (trade name: MSP-20) of the negative electrode active material in Example 1 is also used as the positive electrode active material (that is, the activated carbon is used not only for the positive electrode active material but also for the negative electrode active material). Except for this, a 2032 type button battery similar to Example 1 was produced.

[Comparative Example 2]

In Example 1, the etched aluminum foil (thickness 20 μm) manufactured by Japan Accumulator Industry Co., Ltd. used as the negative electrode side current collector is also used as the positive electrode active material (that is, the etched aluminum foil is not only used for the positive electrode side current collector, It is also used for the negative electrode current collector). Except for this, a 2032 type button battery similar to Example 1 was produced.

[Comparative Example 3]

The positive electrode and the negative electrode obtained using the same procedure as in Example 1 were each punched into a disk shape having a diameter of 14 mm and a diameter of 16 mm. In addition, the aforementioned positive and negative electrodes were used, and a 2032 type button battery was manufactured by the same order as in Example 1.

[Comparative Example 6]

The positive electrode and the negative electrode obtained using the same procedure as in Example 1 were each punched into a disk shape with a diameter of 16 mm. In addition, the aforementioned positive and negative electrodes were used, and a 2032 type button battery was manufactured by the same order as in Example 1.

[Comparative Example 7]

The positive electrode and the negative electrode obtained using the same procedure as in Example 3 were each punched into a disk shape having a diameter of 14 mm and a diameter of 16 mm. In addition, the aforementioned positive and negative electrodes were used, and a 2032 type button battery was manufactured by the same order as in Example 1.

(Test 1) <Evaluation (Energy, Discharge Capacity)>

For the fabricated batteries of Example 1, Example 2, Example 3, and Comparative Example 1, a charge and discharge test device BTS2004 manufactured by Nagano Co., Ltd. was used, and the current density was 0.4 mA/cm ^{2 in a} constant temperature bath at 20°C. Charge and discharge in the range of 0 to 3.5V. As a result, the energy (Wh) was calculated from the obtained discharge capacity and average discharge voltage, and the results are shown in Table 1. Table 1 shows the values of the energy and discharge capacity of Examples 1 to 3 after being standardized with Comparative Example 1, respectively. At this time, the result of Comparative Example 1 was normalized to 100.

In addition, the upper limit of the applied voltage can be applied to 3.5 V in Examples 1, 2 and 3 using graphite as the active material, but it is measured to 2.5 V in Comparative Example 1 using activated carbon in the positive electrode.

Compared to Comparative Example 1 using activated carbon as the positive electrode active material, the energy (product of the discharge capacity and the average discharge voltage) of Examples 1 and 2 using graphite as the positive electrode active material became 3.2 times and 3.0 times, respectively High energy. This is presumably because graphite can intercalate and desorb electrolyte ions between layers (between layers), so that the discharge capacity can be increased compared to activated carbon that adsorbs and desorbs electrolyte ions only on the surface of fine pores. Regarding the actual discharge capacity, the capacity of Example 1 can be increased by 2.3 times and Example 2 by 2.15 times compared to the battery of Comparative Example 1. In addition, when graphite is used as the positive electrode active material, compared with the use of activated carbon as the positive electrode active material, the voltage can be increased and the main reason for the energy increase.

In addition, in Example 3 except that graphite was used as the positive electrode active material and lithium titanate was used as the negative electrode active material, the energy became 4.6 times that of Comparative Example 1 using activated carbon as the positive electrode active material and the negative electrode active material. , The discharge capacity becomes 2.75 times. Although the point of using graphite as the positive electrode active material is the same, compared with Example 1 using activated carbon as the negative electrode active material, the discharge potential of Example 3 using lithium titanate as the negative electrode active material is flatter. Therefore, the average voltage becomes higher, and high energy can be achieved. In addition, since the discharge capacity has a greater effect than activated carbon, the capacity can be increased.

The difference between Example 1 and Example 2 is that only the type of graphite of the positive electrode active material is different, but the energy and discharge capacity are different as shown in Table 1.

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)股份公司製石墨(商品名：KS-6)含有菱面體晶26%(因此，六方晶為76%)，相對於此，大阪氣體化學股份有限公司製之介穩相球狀碳(MCMB)並不含菱面體晶。 Iris graphite and carbon Japan (

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) Graphite (trade name: KS-6) made by a joint-stock company contains 26% rhombohedral crystals (hence, hexagonal crystals are 76%). In contrast, metastable phase spherical carbon (MCMB) made by Osaka Gas Chemical Co., Ltd. ) Does not contain rhombohedral crystals.

The rhombohedral crystal is a layer structure composed of ABCABC, and the hexagonal crystal is a layer structure composed of ABAB. It is speculated that the difference in crystal structure will also affect the above properties. In other words, rhombohedral crystals are larger than hexagonal crystals due to structural changes caused by ion insertion, which is a factor affecting the difficulty of ion insertion.

According to the results shown in Table 1, from the viewpoint of energy and discharge capacity, the graphite of the positive electrode active material preferably contains rhombohedral crystals.

(Test 2) <Evaluation (Discharge Capacity Improvement Rate)>

For the fabricated batteries of Example 1, Example 3, Comparative Example 1, Comparative Example 3, and Comparative Example 7, a charge and discharge test device (manufactured by Nagano Corporation, BTS2004) was used, and the charging current was 0.4 The continuous charging test (constant current and constant voltage continuous charging test) was conducted for 2000 hours at mA/cm ² and a voltage of 3.5V. Specifically, the charging was stopped within a predetermined time during the charging period, and after the battery was transferred to a constant temperature bath at 25°C, the charging was performed five times at a current density of 0.4 mA/cm ² and a voltage of 0 V to 3.5 V as in Test 1. Discharge test to obtain discharge capacity. After that, return to the thermostat at 60°C and restart the continuous charging test, and perform the test until the sum of the continuous charging test time reaches 2000 hours.

The resulting discharge capacity improvement rate is shown in Table 2. The discharge capacity improvement rate is defined as the life of the charging time when the discharge capacity maintenance rate after the constant current constant voltage continuous charging test becomes less than 80% relative to the discharge capacity before the start of the constant current constant voltage continuous charging test, and will be compared respectively The life time in Example 1, Comparative Example 3 or Comparative Example 7 is normalized to 100. That is, Comparative Example 1 (when activated carbon is used not only as a positive electrode active material but also as a negative electrode active material), or Comparative Example 3 (when the diameters of the positive electrode and the negative electrode are opposite to those of Example 1) or Comparative Example 7 (positive electrode and negative electrode) The diameter is the reverse of Example 1, and lithium titanate is used as the negative electrode active material) is standardized to 100.

Table 2

Except that the area of the positive electrode is larger than the area of the negative electrode (see FIGS. 1A and 1B), graphite 1 is used as the positive electrode active material, and DLC-coated aluminum foil is used as the positive electrode side current collector in Example 1, after 2000 hours The discharge capacity maintenance rate after the constant current and voltage continuous charging test was 88%.

In addition, in addition to the area of the positive electrode being larger than the area of the negative electrode (see FIGS. 1A and 1B), graphite is used as the positive electrode active material, and in addition to using DLC-coated aluminum foil as the positive electrode side current collector, titanic acid is further used In Example 3 in which lithium was used as the negative electrode active material, the discharge capacity retention rate after a 2000-hour constant current and voltage continuous charging test was 81%.

The hybrid capacitor of the present invention can meet the specification of a discharge capacity retention rate of 80% or more after a continuous charging test at a voltage of 3 V or more (especially a high voltage of 3.5 V or more) and a constant current and constant voltage of 2000 hours at 60° C. .

On the other hand, in Comparative Example 3 in which the area of the positive electrode is smaller than the area of the negative electrode, or in addition to Comparative Example 7 in which the area of the positive electrode is smaller than the area of the negative electrode and lithium titanate is used as the negative electrode active material The discharge capacity maintenance rate in less than 400 hours has reached below 80%.

As shown in Table 2, different negative electrode active materials were used, but in either Example 1 or Example 3 using graphite as the positive electrode active material, in both cases, compared with the use of activated carbon as the positive electrode active material Compared with Example 1, the durability can be greatly improved.

Furthermore, as compared with Comparative Example 3 in which the area of the positive electrode is smaller than the area of the negative electrode, as shown in FIGS. 1A and 1B, the discharge capacity retention rate of Example 1 in which the area of the positive electrode is larger than the area of the negative electrode is as high as 1.65 times. In addition, in the case of using an electrolytic solution or negative electrode active material different from Example 1 or Comparative Example 3, that is, Example 3 and Comparative Example 7 using lithium titanate as the negative electrode active material, the area relative to the positive electrode is smaller than that of the negative electrode In Comparative Example 7, the area of the positive electrode shown in FIGS. 1A and 1B is larger than the area of the negative electrode in Example 3, and the discharge capacity retention rate is as high as 1.4 times.

These results indicate that, regardless of the structure of the electrode material, the concentration of the electric field on the outer peripheral contour (outer peripheral side) 10b of the positive electrode surface is prevented due to the electrode arrangement shown in FIGS. 1A and 1B, showing that the peripheral surface can be suppressed Corrosion of aluminum foil of contour 10b.

(Test 3)

Except for the batteries of Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 6, the same continuous charging test (constant current and constant voltage continuous charging test) as in Test 2 was performed.

The results are shown in the graph in Figure 3. In this figure, the discharge capacity before the start of the test is 100, and after the start of the test, the discharge capacity after each charging time is displayed in a ratio to the discharge capacity of 100. The horizontal axis of the graph indicates that the constant current and voltage at 60°C are continuous. Charging time (h), the vertical axis of the graph represents the discharge capacity retention rate (%).

In Comparative Example 2 using an etched aluminum foil as a current collector, the discharge capacity of 400 hours or more could not be maintained. On the other hand, Example 1 and Comparative Example 3 using DLC-coated aluminum foil as a current collector showed a high discharge capacity retention rate of 70% or more after 1000 hours. This is considered to be because the DLC film prevents the electrolyte from directly contacting the aluminum foil, and can suppress the corrosion of the electrolyte on the aluminum foil.

In addition, when Example 1 and Comparative Example 3 are compared with Comparative Example 6, Example 1 shows a higher discharge capacity retention rate. This difference is considered to be due to the size relationship and positional relationship between the areas of the positive and negative electrodes. In Comparative Example 3, the electric field is concentrated on the outer peripheral profile (outer peripheral side) of the positive electrode surface, and the aluminum of the cross-sectional portion not coated with DLC is susceptible to corrosion. Due to this effect, the discharge capacity retention rate is lower than in Example 1. Also in Comparative Example 6, although it is not as good as Comparative Example 3, it is considered that the same phenomenon will occur. In contrast, in Example 1, since the electric field is concentrated on the outer peripheral profile (outer peripheral side) of the negative electrode surface, the corrosion of aluminum in the cross-sectional portion where the DLC is not coated on the positive electrode side is suppressed, so compared to the comparative example 3 and Comparative Example 6, the discharge capacity retention rate is high.

As described above, when the area of the positive electrode is larger than the area of the negative electrode, that is, the surfaces of the positive electrode and the negative electrode facing each other in the stacking direction, the outer surface contour of the negative electrode surface and the surface exists within the peripheral contour of the positive electrode surface In the continuous charging test of constant current and constant voltage of ℃ and 3.5V, the 80% discharge capacity maintenance rate can be maintained for more than 1000 hours.

(Test 4)

The graph of FIG. 4 shows the charging voltage curve before the start of the constant current and constant voltage continuous charging test and the charging voltage curve that was conducted for 1053 hours at the start of the constant current and constant voltage continuous charging test when the battery of Example 1 was used. The horizontal axis of the graph represents the charging capacity (%), and the vertical axis of the graph represents the battery voltage (V).

(Test 5)

The graph in FIG. 5 shows the charging voltage curve before the start of the constant current and constant voltage continuous charging test and the charging voltage curve that was conducted for 450 hours at the start of the constant current and constant voltage continuous charging test when the battery of Comparative Example 1 was used. The horizontal and vertical axes of the graph are the same as the graph in Figure 4 respectively.

In the battery of Comparative Example 3, the voltage fluctuated greatly during 450 hours of constant-voltage charging, but in the battery of Example 1, no special change was observed even after 1053 hours. This difference is considered to be due to the size relationship and positional relationship between the areas of the positive and negative electrodes. In other words, in Comparative Example 3, the electric field is concentrated on the outer peripheral profile (outer peripheral side) of the positive electrode surface, and aluminum in the cross-sectional portion of the uncoated DLC is susceptible to corrosion. As a result, stable constant voltage charging characteristics cannot be obtained. In contrast to this, in Example 1, since the electric field is concentrated on the outer peripheral profile (outer peripheral side surface) of the negative electrode surface, corrosion of aluminum in the cross-sectional portion where the DLC is not coated on the positive electrode side is suppressed. As a result, stable constant voltage charging characteristics can be obtained.

As described in Patent Document 3, in a capacitor using graphite as a positive electrode active material, when a conventional etched aluminum is used as a current collector in a high-temperature constant current and constant voltage continuous charging test, the current collector in the positive electrode is higher than that in the negative electrode. It is more likely to corrode, so it is known that the aluminum foil coated with DLC can be used as the current collector on the positive electrode side to improve the durability to a practical level. From this point of view, it has been found that the concentration of electrolyte can be avoided in the cross section of the current collector on the positive electrode side, and it can also be an effective means to improve high-temperature durability.

[Example 4]

The battery was prepared by the same procedure as in Example 1, and a constant current and voltage continuous charging test was performed at 70°C. The conditions other than the temperature in the constant temperature bath are the same as in Example 1.

[Example 5]

The battery was prepared by the same procedure as in Example 1, and a constant current and voltage continuous charging test was performed at 80°C. The conditions other than the temperature in the constant temperature bath are the same as in Example 1.

[Comparative Example 4]

The battery was prepared by the same procedure as in Comparative Example 3, and a constant current and constant voltage continuous charging test was performed at 70°C. The conditions other than the temperature in the thermostat are the same as in Comparative Example 3.

[Comparative Example 5]

The battery was prepared by the same procedure as in Comparative Example 3, and a constant current and constant voltage continuous charging test was conducted at 80°C. The conditions other than the temperature in the thermostat are the same as in Comparative Example 3.

(Test 6) Evaluation (discharge capacity improvement rate: at high temperature)

The temperature (ambient temperature) in the constant temperature and constant voltage continuous charging test in Test 2 was changed to 70°C in Example 4 and Comparative Example 4, and 80°C in Example 5 and Comparative Example 5. The results are as follows Table 3 shows. The discharge capacity improvement rate of Example 4 is normalized to 100 by the results of Comparative Example 4, and the discharge capacity improvement rate of Example 5 is normalized to 100 by the results of Comparative Example 5.

The discharge capacity retention rate of Example 4 at 70°C was 1.83 times that of Comparative Example 4. In addition, the discharge capacity retention rate of Example 5 at 80°C was 2.4 times that of Comparative Example 5. Compared to Example 1, which has a higher discharge capacity improvement rate (1.65 times) than Comparative Example 3, which has an ambient temperature of 60° C. for a constant current and constant voltage continuous charging test, neither Example 4 nor Example 5 With higher magnification.

Due to the increase in ambient temperature, in Comparative Examples 4 and 5, there was more corroded aluminum on the outer peripheral contour (outer peripheral side) of the electrode surface affected by the electric field concentration, while in Examples 4 and 5 In Example 5, the corrosion of aluminum was suppressed. As a result, the difference between the discharge capacity maintenance rates of the two increases.

This result shows that the electrode structure of the area size of the positive electrode and the negative electrode is opposite to that of the present invention, and the electrode structure of the present invention is excellent in durability at higher temperatures.

10‧‧‧Positive

10a‧‧‧The surface opposite to the negative electrode

11‧‧‧Aluminum foil (collector)

12‧‧‧Amorphous carbon film

13‧‧‧ Positive active material layer

20‧‧‧Negative

20a‧‧‧Surface opposite to the positive electrode

21‧‧‧Aluminum foil (collector)

23‧‧‧Anode active material layer

D, D1, D2‧‧‧Stacking direction

30‧‧‧Partition

Claims (2)

A hybrid capacitor that can maintain a discharge capacity retention rate of more than 80% for more than 1000 hours in a continuous charging test at a constant current and a constant voltage of 60°C and 3.5V and has a positive electrode and a negative electrode stacked in one direction through a separator A stacked hybrid capacitor of the structure includes: the positive electrode including graphite as a positive electrode active material; a positive electrode side current collector made of aluminum material; and an electrolytic solution containing electrolyte ions; wherein the aluminum The material system is coated with only an amorphous carbon film; the thickness of the amorphous carbon film is 60 nm or more and 300 nm or less; the positive electrode and the negative electrode are on opposite surfaces of each other in the stacking direction, the The surface of the negative electrode and the outer peripheral contour of the surface of the negative electrode exist within the outer peripheral contour of the surface of the positive electrode; and the electrostatic capacity is exhibited by the intercalation and deintercalation of the anions of the electrolyte ions between the layers of the graphite. A hybrid capacitor, which can maintain a discharge capacity retention rate of more than 80% for more than 1000 hours in a continuous charging test at a constant current and constant voltage of 60°C and 3.5V, and has a positive electrode and a negative electrode stacked through a separator and further wound A wound hybrid capacitor of the structure, the hybrid capacitor includes: the positive electrode, including graphite as a positive electrode active material; a positive electrode side current collector, made of aluminum; and an electrolytic solution, containing electrolyte ions; The aluminum material system is only coated with an amorphous carbon film; The thickness of the amorphous carbon thin film is 60 nm or more and 300 nm or less; when the wound structure is unwound, the positive electrode and the negative electrode are on opposite surfaces of each other in the stacking direction, and the negative electrode The outer contours of the surface of the surface and the surface of the negative electrode exist within the outer peripheral contour of the surface of the positive electrode; and the electrostatic capacity is exhibited by intercalation and deintercalation of anions for the electrolyte ions between the layers of the graphite.

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