CN1757085A - Electric double-layer capacitor - Google Patents

Abstract

Present invention relates to an electric double-layer capacitor having positive and negative electrodes containing nonporous carbon as an electrode active material. In the nonporous carbon, multiple layers of graphene having an average interplanar spacing d002 of 0.350 to 0.380 nm have been grown well. The positive and negative electrodesare impregnated with an electrolyte solution. The nonporous carbon is obtained by activating easily graphitizable carbon, which in turn is obtained by calcining needle coke or pitch made infusible. The electrolyte solution is either a liquid electrolyte having a planar molecular structure or an electrolyte solution consisting of a liquid electrolyte dissolved in an organic solvent.

Description

Double-layer capacitor

Technical field:

The present invention relates to a kind of double-layer capacitor, it uses certain material with carbon element and liquid electrolyte, and wherein liquid electrolyte is by the cation that can present the planar molecule structure and anion with small ion Van der waals volumes BF for example ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Perhaps CF ₃SO ₃ ^-Form.

Background technology:

Can charge and the double-layer capacitor that discharges just is being expected to as can frequent charge and the electric energy storage device of discharge for example electric motor car, solar cell accessory power supply and wind energy accessory power supply with big electric current.Therefore, for have high-energy-density and can fast charging and discharging and double-layer capacitor with extraordinary durability be have demand (for example, referring to the situation of the 4th EV/HEV technical field situation seminar one current capacitor technology and the problem that is faced, " the situation seminar of international electric vehicle battery field ", executive committee, on November 8th, 1999).

In this double-layer capacitor, a pair of polarizing electrode relatively is placed in the electrolyte solution by division board, this has just formed positive and negative electrode.Its principle is that accumulation is on the electric double layer at the interface that is formed between each polarizing electrode and the electrolyte solution.Thought that the electric capacity of double-layer capacitor is that the area of general and polarizing electrode is proportional.Therefore, the active carbon (micro-pore diameter that just has is greater than about 2nm) that only has bigger serface in the past is used as the active material (for example patent disclosure No.2002-15958) of polarizing electrode.

On the contrary, the present inventor and other people have proposed to have good electric capacity and double-layer capacitor that can withstand voltage, it uses used traditionally electrolyte and the mentioned diverse material with carbon element of active carbon (for example, patent disclosure No..H11-317333,2000-77273 and 2002-25867) of feature and front.

Electrolytical research is also carried out.Jamaal Wilkes people such as (Wilkes) has announced that ethyl-methyl imidazoles (EMI) salt has outstanding thermal stability and macroion conductance as liquid electrolyte, it at room temperature is liquid (also being considered to room temperature fused salt or ionic liquid), and announce that EMI salt is liquid, even it also is stable (John S.Wilkes etc. in air, J.Chem.Soc., Chem.Commun., 1992, pp.965-7).In addition, card woods people such as (Carlin) has also announced 1-ethyl-3-methylimidazole (EMI) and 1, the AlCl of 2-dimethyl-3-propyl imidazole (DMPI) ₄ ^-And BF ₄ ^-Salt can be used as electrolyte, and further can move into/move out from graphite electrode in electrochemical mode, has so just formed simple battery (DIME battery) (Richard T.Carlin etc., J.Electrochem.Soc., Vol.141, No.7, pp.L73-L76 (1994)).

Then, a lot of trials have been carried out.In known technology, foregoing 1-ethyl-3-methylimidazole (EMI) is used as liquid electrolyte in the double-layer capacitor that uses active carbon, perhaps EMI is dissolved in and dredges in the proton-organic solvent and as electrolyte (patent disclosure No.2002-110472 and patent No.2945890).Another kind of known liquid electrolyte has a kind of quaternary ammonium salt structure (patent disclosure No.H11-297355).In further known liquid electrolyte, the substituted radical of imidazoles is replaced (patent disclosure No.2002-175948 and 2002-222740).

Summary of the invention

In these cases, need have higher voltage withstand capability and bigger electric capacity as the double-layer capacitor of energy reserve device, need more stable, and can fast charging and discharging, or the like, just have bigger energy density and bigger power density.Yet, the voltage of the DIME battery noted earlier 3V that only has an appointment, and its efficient is also lower.In addition, disclosed double-layer capacitor has only the voltage of 3.9V among the patent disclosure No.2002-110472, and its maximum capacitor density is about 19.3F/cm ³Aspect energy density and power density, this double-layer capacitor is not enough to satisfy the demand.In addition, the described double-layer capacitor of patent disclosure No.H11-317333 also needs further perfect.

Therefore, the present invention attempts to propose a kind ofly to have than the at present needed higher energy density and the double-layer capacitor of power density.After the mechanism that obtains these higher energy densities and power density had been discussed, we provided a kind of double-layer capacitor based on new mechanism.

Stablizing capacitance voltage and improving withstand voltage is important for improving energy density.Improving response speed in addition and reducing internal resistance also is important for improving energy density.

Among inventor and the patent disclosure No.2000-77273 that other people are quoted in front a kind of novel double-layer capacitor has been proposed.Especially, used the material with carbon element of our proposition as electrode active material.This capacitor uses the PF by propylene carbonate solvent and ethyl-methyl imidazoles (EMI) ₆The electrolyte solution that salting liquid is formed.The performance that is obtained is more superior than the active carbon type double-layer capacitor of prior art, and still, its electric capacity has only 25F/cm ³Therefore, this capacitor can not extensively adapt to various application.Through discussion and research afterwards, we find that successfully subject matter is present on the raw material of wood-charcoal material.Especially, as described in the execution mode of front institute referenced patents, the raw material of wood-charcoal material is through distillation and is activated.These treatment steps are suitable.Yet using palm shell charcoal is admissible as the plant charcoal of raw material and various essential loose structures.This has caused having many micropores and big to 750m ²The BET specific area of/g.It is found that its reason is that this material with carbon element is between the active carbon of prior art and a kind of so-called intermediate materials between the atresia charcoal.

Inventor and other people have showed a kind of double-layer capacitor in patent disclosure No.2002-25867.Particularly, by the charcoal of the graphite linings (multilayer graphite) of growth well that had of heat treatment and activation.More preferably, charcoal is to heat-treat having under the situation of hydrogen.The average interplanar distance d of this atresia charcoal ₀₀₂Be 0.360-0.380nm, and specific area is less than 270m ²/ g.Use is by the cation and the BF of alkyl quaternary ammonium salts ₄, PF ₆The electrolyte that perhaps similar anion is formed.This electrolyte dissolution is in by a kind of in acetonitrile, ethylene carbonate and the isobutyl carbonate third rare ester or solvent that its mixture is formed.The atresia charcoal is dissolved in the solvent, and concentration is used greater than 0.5mol/L and as electrolyte.This capacitor shows high-energy-density.This atresia charcoal does not almost have micropore, and the surface of formation electric double layer is very little in the starting stage.Yet, in the process of charging for the first time, electrolyte ion with solvent by electrochemical mode at the interlayer formation electric double layer of moving into.Like this, electrode is similar to the behavior of described activated carbon electrodes, has but kept high-energy-density.Kind electrode has these characteristics.

Then, the present inventor and other people have carried out conscientious discussion to obtain a kind of more double-layer capacitor of high-energy-density that has, and find can be by using the electrode of being made by this atresia charcoal and use a kind of liquid electrolyte obtain quite high energy density and power density as electrolyte, and this liquid electrolyte is by adopting for example BF of a kind of anion that can present the cation of planar molecule structure and have a small ion Van der waals volumes ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Perhaps CF ₃SO ₃ ^-Form.The discussion that its mechanism is will be with the characteristic of atresia charcoal detailed.So just finished double-layer capacitor of the present invention.

Double-layer capacitor according to the present invention has and comprises the positive and negative electrode of atresia charcoal as electrode active material, and the atresia charcoal has the multilayer graphite of fine growth, average interplanar distance d ₀₀₂Be 0.350-0.380nm.Positive and negative electrode is immersed in the electrolyte.This atresia charcoal obtains by activating easy graphitized carbon, and wherein easily graphitized charcoal is again by calcined petroleum coke or needle coke (just a kind of coal coke) or calcines the oil or the coal-based pitch acquisition of cannot not made moltenly.And electrolyte is by the cation that can present the planar molecule structure and anion with small ion Van der waals volumes BF for example ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Perhaps CF ₃SO ₃ ^-A kind of liquid electrolyte of forming.

About foregoing average interplanar distance d ₀₀₂, the initial preferred scope of considering to take 0.360-0.380nm, this is that electrolytical situation is same mode with adopting quaternary ammonium salt.Yet, find in the present invention when by the cation that can present the planar molecule structure and when having liquid electrolyte that the anion of small ion Van der waals volumes forms, if use average interplanar distance d as electrolyte ₀₀₂Atresia charcoal for about 0.350nm also can obtain preferred result.As a result, the preferred average interplanar distance d of atresia charcoal used in the present invention ₀₀₂Be 0.350-0.380nm.

Double-layer capacitor according to the present invention is to make up according to the description of front, and is feature with following character.Liquid electrolyte is dissolved in the organic solvent with the preparation electrolyte solution.This solution can be used as the electrolyte of this capacitor.This double-layer capacitor has and comprises the positive and negative electrode of atresia charcoal as electrode active material, and the atresia charcoal has the multilayer graphite of fine growth, average interplanar distance d ₀₀₂Be 0.350-0.380nm.Positive and negative electrode is immersed in the electrolyte.This atresia charcoal obtains by activating easy graphitized carbon, and easily graphitized charcoal can obtain by calcining needle coke or the pitch of cannot not made moltenly again.And electrolyte is a kind of by the cation that can present the planar molecule structure and anion with small ion Van der waals volumes BF for example ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Perhaps CF ₃SO ₃ ^-The mixture of the liquid electrolyte of forming with organic solvent.Preferably, this organic solvent can be select from the group of being made up of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxymethane, diethoxyethane, gamma-butyrolacton, acetonitrile and propionitrile a kind of or at least two kinds mixed solvent in them.Electrolytical concentration in the electrolyte solution need be greater than 0.5mol/L.Preferably, concentration will be higher than 1.0mol/L.

Double-layer capacitor according to the present invention is to have the positive and negative electrode that comprises the electrode active material of being made by the atresia charcoal, and this atresia charcoal is made by the described graphite-like crystallite of patent disclosure No.2002-25867 charcoal, the average interplanar distance d of crystallite charcoal ₀₀₂Be about 0.360-0.380nm.This atresia charcoal enough not big to accept various electrolyte ions, solvent and N ₂The micropore of gas.The specific area that detects by the BET method is less than 270m ²/ g is preferably less than 100m ²/ g.This atresia charcoal is by activating a kind of activation atresia charcoal that easy graphitized carbon obtains, and wherein easily graphitized carbon is again by calcined petroleum coke, is referred to as the needle coke of coal or oil or coal-based pitch that calcining cannot not made moltenly and obtains.The charcoal of being calcined obtains by heat-treating or calcine at 650-850 ℃ of following commute graphitized carbon, and this charcoal has the needle coke of fine growth or do not melt the graphite microcrystal layer of pitch.The charcoal of being calcined is handled with aqueous caustic style such as KOH under 800-900 ℃.Use the hot steam to remove remaining alkali composition.If desired, at the reduction air-flow for example in the hydrogen, in the presence of the catalyst that transition metal Ni, Fe or Co are arranged or do not use under the situation of catalyst, charcoal is heat-treated to remove the active oxidized hydrogen (for example COOH, CHO and OH) at carbon surface.

Has little average interplanar distance d ₀₀₂Can be for the atresia charcoal of 0.350-0.360nm by replacing the charcoal raw material, the temperature that the raising charcoal heats in reduction air-flow such as hydrogen is perhaps carried out this heat treatment and is prepared under the situation of pressurization.

Use PULSED NMR spectrum analysis powdery carbon ¹H resonance is removed with the active oxidized hydrogen of whether observing at carbon surface.Found to be directly connected on the carbon skeleton and shown a short relaxation time component T ₂The number of the hydrogen of=20-50 μ sec (Gaussian).The hydrogen that discovery exists with chemical bond type adsorbed water form (for example COOH, CHO and OH) also shows a kind of medium relaxation time component T ₂The number of the hydrogen of=50-400 μ sec (Lorentz type).That the form with physical absorption water found simultaneously exists and show a kind of long relaxation time component T ₂The number of the hydrogen of=500-2000 μ sec or longer (Lorentz type).Can judge by the number that is present in the hydrogen in the charcoal with various different existences.By ¹Short relaxation time component T has been observed in H resonant impulse NMR spectrum analysis ₂=20-50 μ sec (Gaussian), medium relaxation time component T ₂=50-400 μ sec (Lorentz type) and long relaxation time component T ₂=500-2000 μ sec (Lorentz type).These relaxation time components have reflected the difference of the bonding state that remains in charcoal tissue hydrogen.In the relaxation time of these discoveries component, the long relaxation time component of expectation does not exist, and the ratio of medium relaxation time component and short relaxation time component was less than 1: 3.

Double-layer capacitor of the present invention has used a kind of electrolyte, and it is a kind of by the cation that can present the planar molecule structure with to have Van der waals volumes be 0.01-0.06nm ³The liquid electrolyte formed of the salt that constitutes of anion.This cation is to be made of the represented compound of following general formula:

[Chemical formula 1]

R wherein ¹And R ²Be respectively straight chained alkyl with 1-5 carbon atom, R ³Be hydrogen or straight chained alkyl with 1-5 carbon atom.Preferably, R ³Be that hydrogen and cation are 1,3-dialkylimidazolium, wherein R ¹And R ²It is the alkyl of from the group of forming by methyl, ethyl, n-pro-pyl and normal-butyl, selecting.Can select, cation is 1,2,3-trialkyl imidazol ion, wherein R ¹To R ³It is the alkyl of from the group of forming by methyl, ethyl, n-pro-pyl and normal-butyl, selecting.Preferably, has Van der waals volumes at 0.01-0.06nm ³Scope in anion be BF ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Perhaps CF ₃SO ₃ ^-

Different with the activated carbon electrodes of the capacitor of prior art, when this device of assembling or capacitor, in this atresia charcoal, there is not the interface of the electric double layer of any formation.In the initiation of charge process, when applied voltage had surpassed certain voltage threshold, electrolyte ion can be moved in the charcoal tissue altogether with solvent.Here it is, and solvent is moved into altogether.At this moment, formed the interface of electric double layer for the first time.Next, this interface is owing to the influence of hysteresis can be kept.As a result, this device is brought into play function effectively as double-layer capacitor.

Double-layer capacitor of the present invention has the working temperature of wide region, big electric capacity and high withstand voltage.Energy density is extra high.And internal resistance is smaller in discharge process.A kind of capacitor with good power density like this, just is provided.

The present invention relates to the theme that Japanese patent application No. No.2003-57305 (submission on March 4th, 2003) and Japanese patent application No. No.2003-424911 (submission on December 22nd, 2003) are comprised, its disclosed content is quoted as a reference in this integral body.

Brief Description Of Drawings

Fig. 1 is the figure of the external alive feature of electric capacity of explanation double-layer capacitor of the present invention.Feature when on behalf of the atresia charcoal, ■ i121 combine with liquid electrolyte among the figure.● the feature when on behalf of the atresia charcoal, i423 combine with the electrolyte solution of ammonium salt.Solid wire is represented capacitor C (F/cm ³).Dotted line is represented internal resistance value [resistance (Ω)].The order that the arrow representative detects among the figure.

Fig. 2 is the figure of the external alive feature of electric capacity of explanation double-layer capacitor of the present invention, and wherein capacitor has used the atresia charcoal that is different among Fig. 1.EMIBF is used in ■ i322 representative among the figure ₄Result during for electrolyte.★ i412 representative is used common active carbon to make electrode and is used EMIBF ₄Result during as electrolyte.Solid wire is represented electric capacity [C (F/cm ³)].Dotted line is represented internal resistance value [resistance (Ω)].The order that the arrow representative detects among the figure.

Fig. 3 is the energy density of explanation each double-layer capacitor discharge of the present invention and the graph of a relation of applied voltage.● the situation when on behalf of the atresia charcoal, i121 combine with liquid electrolyte.Situation when on behalf of the atresia charcoal, ▲ i423 combine with the electrolyte solution of ammonium salt.The situation that on behalf of active carbon, ■ i412 combine with liquid electrolyte.

Fig. 4 has illustrated the relation of solvent molal volume with the starting voltage of moving into.

Fig. 5 has illustrated that double-layer capacitor of the present invention is using EMIBF separately ₄During as liquid electrolyte, in the initiation of charge process of (first round), the feature that discharges and recharges.Situation when on behalf of applied voltage, (a) be 4.0V among the figure, the situation when (b) representing applied voltage to be 3.75V.

Fig. 6 has represented to illustrate the figure that discharges and recharges feature in the process of double-layer capacitor of the present invention initiation of charge (first round) under being set to the voltage of 4V, and this capacitor uses a kind of liquid electrolyte EMIBF ₄With organic solvent is the electrolyte solution that mixes at 1: 1 with volume ratio.Among the figure, (a) representing organic solvent is the situation of isobutyl carbonate third rare ester (PC), and (b) representing organic solvent is the situation of gamma-butyrolacton (GBL), and (c) representing organic solvent is the situation of ethylene carbonate (EC).

Fig. 7 has represented to illustrate the figure that discharges and recharges feature in the process of double-layer capacitor of the present invention initiation of charge (first round) under being set to the voltage of 3.5V, and this capacitor uses a kind of liquid electrolyte EMIBF ₄With organic solvent is that volume ratio is the electrolyte solution that mixes at 1: 1.Among the figure, (a) representing organic solvent is the situation of isobutyl carbonate third rare ester (PC), and (b) representing organic solvent is the situation of acetonitrile (AN).

Fig. 8 has represented to illustrate the chart of the turgor pressure that double-layer capacitor of the present invention detects.Among the figure, EMIBF is used in the A representative separately ₄Situation as liquid electrolyte.At first be set under the voltage of 3.75V capacitor to be carried out initiation of charge.Next repeat to discharge and recharge under the voltage of 3.3V being set to.EMIBF is used in the B representative separately ₄Situation as liquid electrolyte.Under the voltage of 3.3V capacitor is repeated to discharge and recharge being set to.Et is used in the C representative ₃MeNBF ₄Solution is as the situation of electrolyte solution.Under the voltage of 3.3V capacitor is repeated to discharge and recharge being set to.

Fig. 9 is the schematic diagram that is used for detecting the anchor clamps that exapnsion illustrated in fig. 8 presses, and this anchor clamps can limit the volume of electrode direction and detect the pressure that is produced.Among Fig. 9,1 represents screw mandrel, and 2 represent thrust bearing, and 3 represent aluminium block, 4 represent the output guide line of double-layer capacitor (EDLC) to charge and discharge device, and 5 represent EDLC, and 6 represent direct current 5.0V power supply, 7 represent register, and 8 represent deformation detector, and 9 represent vacuum packaging.

Figure 10 has illustrated electric capacity external alive feature under 50 ℃ of double-layer capacitor of the present invention, the wherein order of arrow representative detection.

Figure 11 has illustrated the cycle specificity of double-layer capacitor of the present invention.Among the figure, (A) represent applied voltage to be set to the situation of 4.0V, (B) represent applied voltage to be set to the situation of 3.5V.

The preferred forms of invention:

In order to make double-layer capacitor (EDLC) according to the present invention, need at first preparation to be used for the material with carbon element of capacitor.Polarizing electrode (carbon resistance rod) prepares from this material with carbon element.These electrodes use as positive and negative electrode, and are submerged in liquid electrolyte with planar molecule structure or a kind of by in the electrolyte solution that is dissolved in this liquid electrolyte in the organic solvent, have so just prepared capacitor.

Especially, when using liquid electrolyte, according to electric capacity that capacitor of the present invention produced just electric energy storage carry out according to following.There is not the interface of any formation electric double layer in double-layer capacitor when beginning.In the initiation of charge process, if applied voltage has surpassed certain threshold value, the ion of electrolyte itself can be moved in the charcoal tissue altogether with the ionic molecule of carrier.(cation and anion form the ion pair of liquid condition, and their mutual separately space orientation just can change.When taking place, by having the more cation decision limiting voltage of heavy ion volume when moving into altogether.) at this moment, formed the interface of electric double layer for the first time.Next, this interface is owing to the influence of hysteresis can be kept.This interface has formed electric double layer and has kept electric energy to certain voltage.When adding higher voltage, most electrolyte ion migrates into alone in the charcoal tissue, and this has kept electrochemical energy.Because this mechanism can reach high withstand voltage, high-energy-density and high power density.

Employed positive and negative electrode comprises the atresia charcoal as electrode active material among the present invention.This atresia charcoal is the atresia charcoal described in the patent disclosure No.2002-25867.Especially, the average interplanar distance d of the graphite-like crystallite of charcoal ₀₀₂Be about 0.350-0.380nm.The specific area that detects by the BET method is 270m ²/ g is preferably less than 100m ²/ g.What this atresia charcoal was enough not big can accept various electrolyte ions, solvent and N ₂The micropore of gas.This charcoal can obtain by following method.

This atresia charcoal obtains by activating easy graphitized carbon.Oil or coal-based pitch that this graphitized charcoal cannot not made moltenly by the needle coke or the calcining of calcined petroleum coke base or coal coke base obtain.The pitch that uses these needle cokes and cannot not make moltenly carries out direct heat and handles, and then be divided into gas, oil and solid matter as raw material in 300-500 ℃ temperature range.This solid matter is original coke and it is ground into below the 120 μ m, so just obtained " raw material charcoal ".Under (for example in nitrogen environment) 650-850 ℃, preferably under 700-800 ℃ this " raw material charcoal " heat-treated 2-4 hour (The pre-heat treatment) in inert environments, this has just obtained the charcoal calcined.The charcoal that to be calcined and aqueous caustic style such as KOH are according to 1: 1.8-2.2, preferably approximately 1: 2 weight ratio is mixed.In inert environments, under (for example in nitrogen environment) 800-900 ℃, preferably under about 800 ℃, this mixture is heat-treated 2-4 hour once more, and use caustic alkali to activate.Next, remove the alkali that remains in above the charcoal according to the method that describes below.

Removing lixiviating can clean the alkali activation charcoal that is obtained and finish by following described method.For example, will greater than the carbon particle of 1 μ m from alkali activation charcoal, reclaim and the rustless post of packing in.To charge into the pressurized steam of 120-150 ℃, 10-100kgf (preferred 10-50kgf) in the post, be about 7 up to the pH value of the water of getting rid of, and generally kept 6-10 individual hour.After removing alkali and finishing, inert gas such as argon gas or nitrogen by pillar and carry out drying, have so just been obtained desirable raw material of wood-charcoal material.

In order to remove alkali more completely, can adopt following step, the soxhlet apparatus (Soxhlet extractor) that preferred use can be pressurizeed: (1) is with volatile acid (for example HCL or HNO ₃) the aqueous solution reflux, residual like this alkali extracts from raw material of wood-charcoal material powder by the acid hot water and steam that uses relative high concentration; (2) then, the aqueous solution of non-volatile alkali (for example NaOH or KOH) is refluxed, Can Yu acid is just washed away by water vapour and with the alkali neutralization like this, and (3) are again with the raw material of wood-charcoal material heating that obtains and dry.

If necessary, at 3H ₂+ N ₂Perhaps in the reducing environment of hydrogen, the mist that obtains by decomposing N H3 for example, can resulting to the front " atresia charcoal " further at 500-900 ℃ of following heat treatment 4-6 hour.Can select, in reducing environment, have transition metal for example the catalyst of Fe, Co or Ni or transistion metal compound exist down, charcoal is carried out 200-850 ℃ heat treatment 2-6 hour.Next, remove active oxidation hydrogen (for example COOH, CHO and OH), rather than be directly connected to the hydrogen of carbon skeleton.Can obtain the atresia charcoal that hydrogen embeds like this.

In the described in front method for preparing the atresia charcoal, comprise that the processing conditions of the temperature of activation process and the heat treatment temperature in reducing environment can influence the average interplanar distance d of the atresia charcoal that is obtained ₀₀₂For example, can obtain less average interplanar distance d by the temperature that improves processing ₀₀₂Charcoal.For example, temperature that can be by improving activation process obtains average interplanar distance d to about 900 ℃ or improve heat treatment temperature in the reduction air-flow to about 700-900 ℃ ₀₀₂Atresia charcoal for 0.350-0.360nm.A kind of effective method is under the pressure that improves, and heat-treats in the reduction air-flow.Use by the cation that can present the planar molecule structure in the present invention and have the liquid electrolyte that the anion of small ion Van der waals volumes is formed, use average interplanar distance d simultaneously ₀₀₂Charcoal for about 0.350nm.Yet this atresia charcoal does not have perfect graphite-structure.According to a feature of employed atresia charcoal in the double-layer capacitor of the present invention be also not the multilayer of complete graphited graphite obtained good growth, and average interplanar distance d ₀₀₂Be 0.350-0.380nm.

Heat-treat in reducing environment owing to foregoing, what remove is the hydrogen (for example COOH, CHO and OH) of active oxidation, rather than is directly connected to the hydrogen of carbon skeleton.Like this, will be easy to produce unpaired electronics or dangling bonds.Particularly the reaction site of these dangling bonds can be embedded by hydrogen.Therefore, if the atresia charcoal is kept in the air, charcoal unlikely and steam or the reaction of airborne oxygen, however can the oxidized hydrogen of regeneration activity.The quantity of the active oxidized hydrogen that remains in the atresia charcoal that is produced in this method is handled can be measured by the PULSED NMR spectrum analysis described in patent disclosure No.2002-25867.Briefly, if use the PULSED NMR spectrometer that the carbon of pulverulence is carried out ¹The H nuclear resounce is analyzed, and can observe decay signals on initial period improves the initial state decay curve of intensity.Decay curve is formed (as a rule) by two or 3 components with different relaxation times that overlap each other.One is to have hyphen to relaxation time T ₂Component for 10-50 μ sec.This can estimate according to the resonant line that shows Gaussian Profile.This component is made up of the hydrogen that directly is connected with carbon skeleton.In addition, a kind of T2 T that has is arranged ₂Be the medium relaxation time component of 50-400 μ sec, and show the Lorentz distribution.This represents the functional group of oxygen and hydrogen, for example COOH, CHO and OH.And, also have a kind of longer relaxation time T that has ₂Be the long relaxation time component of 500-2000 μ sec, it shows Lorentz and distributes.This water of representing physical absorption.Therefore, the quantity of active oxidation hydrogen can be found from the ratio of component with these relaxation times.

In these components, the water with the component represents physical absorption in long relaxation time can easily be removed, and is by the raw material of wood-charcoal material being higher than in a vacuum under 100 ℃ the temperature, or under reduced pressure, for example is lower than 10 ^-5Torr is heating and dry down.The raw material of wood-charcoal material can not contain this component fully.Yet, the component representative with medium relaxation time in carbon skeleton with the hetero-atom hydrogen that combines of O (oxygen) for example, it can not be removed by this heating under low pressure and dry technology.This component has only the foregoing heat treatment in reducing environment of use just can remove.

Therefore, having the atresia charcoal of the medium relaxation time component of lesser amt, is because mainly be connected to the hetero-atom hydrogen (active oxidation hydrogen) on the O (oxygen) for example in the carbon skeleton, that is to say the preferred T of the present invention ₂Medium relaxation time component (Lorentz type) and T for 50-400 μ sec ₃For the long relaxation time component (Lorentz type) of 500-2000 μ sec and to T ₂For the ratio of the short relaxation time component (Gaussian) of 10-50 μ sec less than 1: 3.Because the T of the water of represents physical absorption ₃For the long relaxation time component (Lorentz type) of 500-2000 μ sec come down to non-existent, therefore, if T ₂For the medium relaxation time component (Lorentz type) of 50-400 μ sec to T ₂For the ratio of the short relaxation time component (Gaussian) of 10-50 μ sec is less than 1: 3, preferably less than 1: 5, and if adopt the absorbent charcoal material of this charcoal as electrode, just can prevent the generation of gas and the formation of non-conductive film.Simultaneously, also can avoid the raising of internal resistance.Therefore, this material is stable.In these areas, this material with carbon element is that we are desirable.

About electrolyte solution used in the present invention, the liquid electrolyte with planar molecule structure is used as electrolyte by complete.Can select, this liquid electrolyte can be dissolved in the anhydrous organic solvent and as electrolyte solution and use.

Employed in the present invention liquid electrolyte is by the cation that can present the planar molecule structure and has Van der waals volumes at 0.01-0.06nm ³The salt that anion in the scope constitutes.Under the preferred room temperature is the salt of liquid.

The meaning is " can to present the cation of planar molecule structure ", when ion pair forms, has the cation that hinders the narrow gap of the raw material of wood-charcoal material shape of moving into, and can show a kind of constituent atoms arrangement molecular structure in one plane that allows.Simultaneously, " has Van der waals volumes at 0.01-0.06nm ³Anion in the scope " be meant anion with ionic radius enough littler than those cations.Just, the cation of the electrolyte molecule of being considered is significantly different on ion volume with anion.When forming ion pair, the cation that has than the heavy ion volume can form obstruction to the narrow gap of the raw material of wood-charcoal material of moving into.Yet if cation can show a kind of constituent atoms that allows at the molecular structure of arranging in one plane, this obstruction that the narrow gap of the raw material of wood-charcoal material of moving into is formed can alleviate to some extent.Especially, detect by the BET approach, the material with carbon element that uses among the present invention does not contain absorption N ₂Micropore.And the plane gap between the graphite linings is filled.Therefore, the cation that can present the planar molecule structure anion that can and have the small ion volume slit between the raw material of wood-charcoal bed of material of moving into altogether.

The cationic example that can present the planar molecule structure comprises the molecule of abundant flat configuration, for example heterocycle five-membered ring and the heterocycle hexatomic ring that replaced by straight chained alkyl, for example preferred fragrance ring structure.The cationic example of heterocycle hexatomic ring comprises pyridylium, pyrimidine cation and the pyrazine cation that is replaced by straight chained alkyl.The pentacyclic cationic example of heterocycle comprises glyoxaline cation, pyrazoles cation, 1,2,3 or 1,2,4-triazole cation (triazolium), thiadiazoles cation (thiazolium), different triazole cation (isothiazolium), oxazoline cation (oxazolium) and the isoxazoline cation (isoxazolium) that is replaced by straight chained alkyl.The preferred example of straight chained alkyl that replaces comprises the alkyl group with 1-5 carbon.Wherein, for example methyl group, ethyl group, n-pro-pyl group and normal-butyl group are that we are desirable to so-called non-big alkyl group (unbulky alkyl groups).Chemical formula 2 has been represented preferred cation.

[Chemical formula 2]

R wherein ¹And R ²The straight chained alkyl of hydrogen or 1-5 carbon is with in representative respectively, the straight chained alkyl of preferred 1-4 carbon, the straight chained alkyl of preferred especially 1-3 carbon, R ³And R ⁶The straight chained alkyl of representative band hydrogen or 1-5 carbon respectively is preferably with the straight chained alkyl of hydrogen or 1-4 carbon, especially preferably with the straight chained alkyl of hydrogen or 1-3 carbon.

In these cations, preferred pyridylium and glyoxaline cation.The special example of compound comprises the picoline cation, the ethylpyridine cation, the n-pro-pyl pyridylium, the normal-butyl pyridylium, 1,3-methylimidazole cation, 1,3-diethyl glyoxaline cation, 1,3-di glyoxaline cation, 1,3-di-n-butyl glyoxaline cation, 1-ethyl-3-methylimidazole cation, 1-methyl-3-n-pro-pyl glyoxaline cation, 1-normal-butyl-3-methylimidazole cation, 1-ethyl-3-n-pro-pyl glyoxaline cation, 1-ethyl-3-normal-butyl glyoxaline cation, 1-n-pro-pyl-3-normal-butyl glyoxaline cation, 1-normal-butyl-3-n-pro-pyl glyoxaline cation, 1,2-dimethyl-3-n-pro-pyl glyoxaline cation and 1,3-dimethyl-2-n-pro-pyl glyoxaline cation.

Simultaneously, about anion, preferred Van der waals volumes is at 0.01-0.06nm ³Anion in the scope.Each Van der waals volumes can become the model of ion that key forms to calculate under given bond distance and bond angle situation by atom.These Van der waals volumes are at 0.01-0.06nm ³In the anion in the scope, since electrolyte electrochemical stability and their size, BF ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-, CF ₃SO ₃ ^-, AlCl ₄ ^-And SbF ₆ ^-Be preferred.Preferred especially BF ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-And CF ₃SO ₃ ^-

Electrolyte used in the present invention is made up of the salt of foregoing cation and anionic compound.Selection has wide gesture window (potential window), low viscosity, macroion conductivity and is liquid and stable electrolyte under the temperature of wide region.Such liquid electrolyte compound more preferred example comprises: 1-ethyl-3-methylimidazole ⁺BF ₄ ^-, 1-ethyl-3-methylimidazole ⁺PF ₆ ^-, 1-methyl-3-n-pro-pyl imidazoles ⁺BF ₄ ^-, 1-methyl-3-n-pro-pyl imidazoles ⁺PF ₆ ^-, 1,2-dimethyl-3-n-pro-pyl imidazoles ⁺BF ₄ ^-, 1,2-dimethyl-3-n-pro-pyl imidazoles ⁺FP ₆ ^-, 1,3-dimethyl-2-n-pro-pyl imidazoles ⁺BF ₄ ^-, and 1,3-dimethyl-2-n-pro-pyl imidazoles ⁺PF ₆ ^-Especially, preferred 1-ethyl-3-methylimidazole ⁺BF ₄ ^-With 1-ethyl-3-methylimidazole ⁺PF ₆ ^-,, have macroion conductivity and relative low viscosity because they are liquid under the temperature than relative broad range.

Because foregoing liquid electrolyte at room temperature is liquid, so they can directly use (being so-called pure electrolyte solution) as electrolyte solution., it need be dissolved in the organic solvent than higher and at room temperature be under the situation of solid at electrolytical fusing point, use so that electrolyte can be used as electrolyte solution.In addition, even at room temperature be that the electrolyte of liquid also can be dissolved in the organic solvent and uses.With an organic solvent, can find that its energy density is with an organic solvent lower slightly than not.Yet viscosity also can reduce.Especially, the electrolyte of Shi Yonging can prevent the internal resistance that improves owing to viscosity significantly at low temperatures.

Employed organic solvent need be selected according to the solubility of liquid electrolyte and with the reactivity of electrode.Usually representative examples of organic is: isobutyl carbonate third rare ester, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxymethane, diethoxyethane, gamma-butyrolacton, acetonitrile and propionitrile.These solvents can use separately or can it two kinds or more ofly use as mixed solvent.

According to double-layer capacitor of the present invention, taken place to move into altogether in the charcoal tissue, so solvent is to interrelate with the starting voltage of describing later of moving into solvent.From this view point, can think when the solvent molecule that uses has less molal volume, can easier moving into.Therefore, when independent use solvent, wish to use littler molal volume.In addition, if when using mixed solvent, wish to use the solvent that keeps littler molal volume.From these viewpoints, can show when separately with an organic solvent the time, preferably use isobutyl carbonate third rare ester.The example of preferred mixed solvent comprises the combination of acetonitrile and ethylene carbonate and the combination of acetonitrile and isobutyl carbonate third rare ester.

Various types of double-layer capacitors, for example the box type and button-type, can use described atresia charcoal and liquid electrolyte, use with prior art double-layer capacitor method therefor similar methods and assemble.

Can use the active carbon similar methods to make electrode with prior art.For example, when making the electrode of sheet, will make the granular size of about 5-100 μ m by the atresia charcoal that aforesaid method obtains.Then, for example, add carbon black as the conductivity of conductive filler with auxiliary powdered carbon.For example add cement, polytetrafluoroethylene (PTFE).These article are rubbed together and pressed and grind in flakes.Except that adding carbon black, can also use graphite powder to lead and give agent (conductivity imparting agent) as electricity.Except PTFE, can also use polyvinylidene fluoride (PVDF), polyethylene (PE) and polypropylene (PP) as cement.At this moment, the mixture weight ratio of atresia charcoal, conductive filler (carbon black) and cement is typically about 10: 1-0.5: 0.5-0.25.

In order to make each electrode, be necessary to make atresia carbon particle and carbon black evenly to distribute and with density fully uniformly attached on the PTFE fiber.Therefore, need fully rub up.Usually, be necessary from the horizontal and vertical stone roller of pressing.Detect the degree of drying of the weight of the electrode that obtains with the explanation electrode.Calculate the density of electrode by the apparent volume and weight of carbon resistance rod.When the density of electrode the time, obtained the electric capacity and the internal resistance result of expectation at 0.8-1.2g/cm3.

The density of electrode mainly comes from the density of used atresia charcoal.Even use identical atresia charcoal, if by suppressing the raising electrode density, electrolyte or electrolyte solution linked hole also can get clogged.This will improve internal resistance widely.This just is difficult to use this device as double-layer capacitor.

The electrode that this mode is obtained overlaps by a division board, and this has formed positive and negative electrode.Like this, electrode can be immersed in liquid electrolyte or by liquid electrolyte being dissolved in the electrolyte that electrolyte solution prepared in the organic solvent forms.By this method, assembled double-layer capacitor.

In the process of assembling, if employed liquid electrolyte is not dissolved in the organic solvent, number of assembling steps can obtain simplifying, because liquid electrolyte vapour pressure at room temperature is almost nil, even at high temperature (for example 150 ℃) are also quite low, electrolyte just can bear vacuumize like this.

Especially, in double-layer capacitor of the present invention, being present in intrasystem water can influence electric property negatively.Usually, the material that is used for assembling can contain the adsorbed water of residual amount.Therefore, in the process of assembling, material can be heated to the immovable high temperature of quality of materials.Like this, this material is by vacuumize.Yet this dehydration method can not be used to have the organic solvent of high relatively vapour pressure.Dehydration is to use highly pure active aluminium oxide or active silica to carry out.On the other hand, if use liquid electrolyte, this consideration is unnecessary.Carbon resistance rod, division board and collector electrode are inserted in the container, then, liquid electrolyte are injected in the container.When temperature surpass 100 ℃, container carried out vacuum soak into processing thereafter.Like this, water and other volatile organic solvents can be evaporated.Liquid electrolyte can be impregnated into each corner of capacitor.At this moment, if polyethylene, polypropylene, low-density pitch (pertroleum wax) or similar material are added to the top, when being heated to when surpassing institute and add melting point substance, because the density that institute adds material is lower than the density of liquid electrolyte and can mix with electrolyte, therefore container is understood sealed when temperature returns to room temperature.

The double-layer capacitor that this mode is assembled adds the voltage (usually, being about 3.5-3.75V) than the specified high 10-20% of voltage, and then to its charging.The ion of liquid electrolyte can be moved in the charcoal tissue altogether with liquid electrolyte.Under the situation that organic solvent exists, equally also can move into.Next, formed electric double layer.Except the situation of the electrolyte solution that adds organic solvent, can liquid electrolyte self ion mainly be moved in the charcoal tissue by adding higher voltage.Its result has obtained quite high energy density.

Double-layer capacitor of the present invention is described in further detail below.

Fig. 1 has illustrated the external alive feature of the electric capacity of double-layer capacitor of the present invention.Make the carbon resistance rod of each use according to following introduction.Under 700 ℃, (raw material charcoal B) heat-treated 4 hours to this needle coke from petroleum coke, with preparation " charcoal of being calcined ".The KOH of this charcoal of being calcined and twice handled 4 hours down at 800 ℃, and cleaned to pH=7 with hot water and steam.Next, use soxhlet apparatus, utilize aqueous hydrochloric acid solution to extract alkali.The residue water cleans back heating and vacuumize.Next under the situation that has metal Ni catalyst to exist, residue carries out 500 ℃ heat treatment 4 hours in hydrogen, to remove metal Ni catalyst.Like this, just prepared atresia charcoal [B704804S+504H].And with 10: 1: 0.5 (atresia charcoals: carbon black: PTFE) weight ratio adding carbon black and PTFE.Sheet is rubbed together and made to material.Kind electrode has the diameter of 20mm, the about 0.2mm of thickness, electrode density 1.06g/cm ³The electrolyte solution vacuum is soaked in the electrode.The aluminium foil that uses surface roughening is as collector electrode.The CTW-GA55-CTW that use is made up of the glass fibre GA-55 that is pressed on the cardboard is as division board.The electrode vacuum packaging is put into the polyethylene bag of lamination by division board, made testing battery like this.

For describe resulting every kind of atresia charcoal according to the front, raw material or charcoal have been described.The front two numeral provides the temperature of The pre-heat treatment.Processing time is in the 3rd bit digital explanation.The time of activation processing the 4th and five digit number in illustrate.Processing time illustrates in the 6th bit digital.Add six numerals altogether and represented the condition of The pre-heat treatment and activation respectively.To having used soxhlet apparatus to remove every kind of charcoal of alkali, added at the end " S ".To every kind of atresia charcoal that carries out hydrogenation by after-baking, add mark "+" six numeral backs.Similar, front two digitized representation after-baking temperature, the next digitized representation processing time, or 3 numerals provide together.Adding mark " H " representative handles in hydrogen stream.Like this, provide labelling method.As mentioned above, prepared atresia charcoal has been described the atresia charcoal according to the method preparation of foregoing Mk system with [B704804S+504H].Kind with the corresponding to atresia charcoal of these marks is provided in the back.

The d of the atresia charcoal [B704804S+504H] that is obtained ₀₀₂Be 0.360nm.Specific area is about 60m ²/ g.Medium relaxation time component to the ratio (being designated hereinafter simply as " relaxation ratio of component ") of short relaxation time component less than 0.05.

1-ethyl-3-methylimidazole BF is used in ■ i121 representative among Fig. 1 ₄ ^-Salt (EMIBF ₄) be the situation of electrolyte solution.● the BF with the triethyl group ammonium methyl is used in the i423 representative ₄Salt (Et ₃MeNBF ₄) situation when the volume ratio that is dissolved in acetonitrile (AN) and isobutyl carbonate third rare ester (PC) is the electrolyte solution of the 1.5mol/L that obtained in 1: 1 the mixed solvent.Electric current with 10mA between two electrodes detects.It is carried out increasing according to per step the mode repeated charge of (or minimizing) 0.5V from 0.5V to 4V, the charging interval, per step increased by 500 seconds since 500 seconds.(positive and negative electrode is whenever done the electric capacity of unit volume, F/cm to electric capacity under each voltage ³) calculate (representing) by the feature of discharge with solid line.Similar, also calculated internal resistance (being represented by dotted lines).Notice that the value of internal resistance has directly been represented the actual value of prepared battery.This value is not corrected fully.The order that the arrow representative detects among the figure.

Can when using,, can after surpassing given voltage, produce electric capacity as seen from the figure if progressively improve the voltage that is added as the disclosed ammonium salt of patent disclosure No.2001-25867.After applied voltage surpassed 3.0V, advancing the speed with respect to the electric capacity of voltage increase can very fast decline.And electric capacity can have decline a little when 3.5-4.0V.In 3.75V, electric capacity almost reaches capacity.Simultaneously, during this, internal resistance also improves fast, even and voltage reduce, internal resistance can not recover original state yet.On the contrary, impedance has improved.Obviously, this means irreversible reaction has taken place in this process.When electrolyte by tetraethyl ammonium BF ₄Salt (Et ₄NBF ₄) when replacing, phenomenon can change a little.

Yet, when the electrolyte that uses is EMIBF ₄The time, with respect to improving voltage, the speed that electric capacity improves can't change, and reaches 4.0V up to voltage.Consequently, the maximum capacitor of increase has surpassed 50F/cm widely ³.

Equally, when applied voltage when maximum applied voltage progressively reduces, the influence of hysteresis can appear.Can find to have obtained such characteristic, the performance that is had when promptly keeping electric capacity much larger than raising voltage.If use EMIBF ₄, the shown influence near the 3.5V applied voltage time of the influence of its characteristic and hysteresis and the disclosed use ammonium salt of patent disclosure No.2001-25867 is similar.Can see 3.5 and 4.0V between almost do not have the influence of hysteresis to occur, and shown identical voltage-capacitance characteristic (V-C characteristic).

Fig. 2 has also shown the V-C characteristic similar to Fig. 1.■ i322 is by under the situation of using different atresia charcoals among the figure, and detection V-C characteristic obtains.Particularly, use petroleum asphalt based charcoal (raw material charcoal A) through after cannot not being treated as moltenly, as the prepared atresia charcoal of raw material charcoal [A704804+504H].Prepare electrode with similar method.Use EMIBF ₄As electrode.The d of atresia charcoal [A704804+504H] that use ₀₀₂Be 0.360nm.Specific area approximately is 100m ²/ g.The relaxation ratio of component is less than 0.17.★ i412 shows in order to compare the common active carbon manufacturing electrode of use and to use EMIBF ₄V-C characteristic during as electrolyte.The order that the arrow representative detects among the figure.Under the situation of active carbon, if applied voltage greater than 3.5V, internal resistance also can improve fast, electric capacity just less improves.Therefore, in testing process, maximum applied voltage is set to 3.5V.Active carbon is the charcoal with steam activation.Its specific area is 1015m ²/ g, the maximum magnitude of micropore are about 0.74nm.Use the method identical to detect specific area, use Sorptie1750 and BET1-point method with the atresia charcoal.As adsorbed gas, the temperature of heating furnace is arranged on 110 ℃ with nitrogen, and relative pressure is 0.05-1.35.

As can be seen from Figure 2, under the situation of activated carbon electrodes, do not demonstrate hysteresis, and electric capacity also is little.

Fig. 3 has illustrated the relation between applied voltage and the energy reserve.Because energy reserve is with square raising of voltage, it is important therefore adopting high operating voltage.Yet, when improving voltage, probably electrochemical reaction can take place, and also can shorten the life-span.Among Fig. 1, voltage is mapped with electric capacity.Among Fig. 3, do not use unit of capacity F/cm ³, and be to use discharge energy Wsec/cm ³Applied voltage is mapped.As a reference, the situation that has also shown the charcoal of except active carbon is used as active material, making with aforementioned similarity method.Fig. 3 has shown use Et ₃MeNBF ₄The situation of AN/PC solution, its result is significantly different with the apparent capacity characteristic of acquisition.Just, when the voltage that adds above 3.5V, internal resistance increases significantly.Discharge energy reduction as a result, (▲ i423).The present invention uses EMIBF as can be seen ₄● the discharge energy that i121 has, be to use about twice as the double-layer capacitor ▲ i423 of the disclosed use ammonium salt of patent disclosure No.2001-25867, be to use prior art active carbon and EMIBF ₄About 4 times of ■ i412.Can know from Fig. 3 has how many deposits and discharge energy can remain on the double-layer capacitor of the present invention, wherein to using EMIBF ₄The activated carbon electrodes situation of prior art under " deposit and discharge energy " and " the laying in and discharge energy " when using no pore carbon electrode directly compare.

The present inventor and other people have found this phenomenon and have carried out following discussion, to consider the mechanism of preparation capacitor.

In order to confirm patent disclosure No.2001-25867 disclosed " electrochemistry of ion and solvent is moved into ", detected 1-ethyl-3-methylimidazole (EMI ⁺) dilution is the starting voltage of moving under the solvent situation of different molal volumes.The molal volume of every kind of solvent is " molecular weight/density ".1-ethyl-3-methylimidazole (EMI ⁺) molal volume can pass through EMIBF ₄Molecular weight divided by this density of liquid (1.28g/cm ³) obtain, drawn the molal volume of salt self, and according to EMI ⁺Ion and BF ₄ ^-Ion is respectively 118A ³And 48A ³The ratio of the Van der waals volumes of (U.S. Patent No. 5,827,602) is determined volume.EMIBF ₄Under the situation of not dissociating, molal volume is (198/1.28)=154.7.The EMI that dissociates ⁺The molal volume of ion is 154.7 * [118/ (118+48)]=110.0.

In order to experimentize, to use and pass through EMIBF ₄The electrolyte solution that is dissolved in isobutyl carbonate third rare ester (PC), gamma-butyrolacton (GBL), ethylene carbonate (EC) and acetonitrile (AN) acquisition according to identical volume ratio prepares battery.Carrying out charge/discharge detects.From the initiation of charge feature, find to move into starting voltage.Employed atresia charcoal is to use the prepared atresia charcoal [B704804S+504H] of needle coke (raw material charcoal B) of deriving and obtaining from the petroleum coke of original raw material of wood-charcoal material.d ₀₀₂Be 0.360nm, specific area is about 60m ²/ g, the relaxation ratio of component is less than 0.05.

Fig. 4 has shown the result of starting voltage to the mapping of solvent molal volume that move into.As can be seen from the figure each move into starting voltage and solvent molal volume are proportional.Can think, at the EMIBF that does not contain solvent ₄Situation under, cation 1-ethyl-3-methylimidazole (EMI ⁺) own to solvent, ionophore just.

Alkyl ammonium cation (Et for example ₄N ⁺And Et ₃MeN ⁺) and EMI ⁺The huge difference of being introduced below existing between the cation.The former shows three-dimensional structure, and wherein alkyl is positioned a regular tetrahedron of formation around the N atom.On the contrary, about EMI ⁺Ion has been found that importantly the imidazoles five-membered ring forms a plane.The alkyl location planar.Whole molecule exists with plane form.

When ion is sucked the lamellar spacing of multilayer graphite-structure by the Coulomb force, obviously, has the EMI of planar molecule structure ⁺The alkyl ammonium cation of cation ratio three-dimensional structure is Et for example ₄N ⁺And Et3MeN ⁺Want much superior.Therefore, seem EMI ⁺Cation can not migrate into has in the past become possibility in the areolar, and has produced additional capacitor.When the influencing of hysteresis occurring, if the supposition solvent rests on interlayer and causes this influence, so ion can 3.5-4.0V the time move into separately.Therefore, estimate almost not have the influence of hysteresis to occur.

Introduce the feature that discharges and recharges of double-layer capacitor of the present invention below.

Fig. 5 shows, only uses EMIBF ₄The charge-discharge characteristic of battery.Detect charge-discharge characteristic according to following introduction, under stable electric current, charge.When electric charge was assembled on each capacitor, voltage can be enhanced.It is monitored, under stable electric current, charge.When reaching predetermined voltage, keep this voltage.Like this, just entered the voltage stabilizing charge mode, electric current also just descends (this is called as trickle charge).After having crossed preset time, enter the current stabilization pattern again, and discharge.When discharge was carried out, the electric charge that gathers began to reduce, and voltage descends.Finally, continuing discharge is 0V up to voltage.(a) among Fig. 5 shown the situation when applied voltage is 4.0V.(b) shown the result of first round when applied voltage is 3.75V.(a) in the situation, be atresia charcoal [A704804+504H] as the atresia charcoal of electrode, it is to use petroleum asphalt charcoal (raw material charcoal A) through after cannot not being treated as moltenly, and is prepared as the raw material charcoal.Its d ₀₀₂Be 0.360nm, specific area approximately is 100m ²/ g, the relaxation ratio of component is less than 0.17.(b) in the situation, charcoal is atresia charcoal [B704804S+504H], and it is to use needle coke (raw material charcoal B) as raw material preparing, and needle coke is from the petroleum coke acquisition of deriving.Its d ₀₀₂Be 0.360nm, specific area is about 60m ²/ g, the relaxation ratio of component is less than 0.05.

Fig. 6 has shown when using the characteristic that discharges and recharges under the situation of liquid electrolyte as electrolyte solution.In electrolyte solution, EMIBF ₄Mix by 1: 1 volume ratio with organic solvent, setting voltage is 4.0V.Among the figure, (a) representing organic solvent is the situation of isobutyl carbonate third rare ester (PC), and (b) representing organic solvent is the situation of gamma-butyrolacton (GBL), and (c) representing organic solvent is the situation of ethylene carbonate (EC).The atresia charcoal that uses in the electrode is atresia charcoal [A704804+504H], and it is to use petroleum asphalt charcoal (raw material charcoal A) through after cannot not being treated as moltenly, and is prepared as the raw material charcoal.Its d ₀₀₂Be 0.360nm, specific area approximately is 100m ²/ g, the relaxation ratio of component is less than 0.17.

EMIBF among Fig. 7 ₄The electrolyte solution that mixes by 1: 1 volume ratio with organic solvent is as liquid electrolyte, and its method with Fig. 6 is the same.In this case, voltage is set at 3.5V.Among the figure, (a) representing organic solvent is the situation of isobutyl carbonate third rare ester (PC), and (b) representing organic solvent is the situation of acetonitrile (AN).The atresia charcoal that uses in the electrode is the same with the situation of Fig. 6.

Among Fig. 5-7, under the current stabilization of 10mA, discharge and recharge detection.Because the diameter of each electrode is 20mm, so current density is 3.18mA/cm ²Voltage and current is to map from charging beginning back institute elapsed time.Simultaneously, shown after keeping given voltage (trickle charge) that the voltage that internal resistance begins along with discharge descends and increases.

Fig. 5-7 has illustrated:, applied voltage is being separately positioned under two kinds of situations of 4.0V and 3.75V when using liquid electrolyte as electrolyte when independent, voltage can be brought up to about 2.7V-2.9V rapidly.Then, voltage improves with the speed that relaxes but almost reaches given voltage linearly.Also the decline of voltage when the discharge beginning is less (Fig. 5) as can be seen.

On the other hand, when the electrolyte solution that uses by being dissolved in liquid electrolyte in the organic solvent when forming, its feature can change according to applied voltage.Under any circumstance, the starting voltage of moving into is all than the little 2.0-2.4V of the situation of only using liquid electrolyte, and this is because used the organic solvent with little molal volume.As can be seen, when applied voltage was set in 4.0V, the raising speed of voltage became near the applied voltage of 3.3-3.5V and has more relaxed.After 4.0V charged, voltage began and can descend fast and internal resistance increase (Fig. 6) discharge.Simultaneously, if applied voltage is set at 3.5V, previously described phenomenon just can not take place.According to observations, the feature that discharges and recharges and similar (Fig. 7) shown in Fig. 5.

Following introduction can be explained this phenomenon.If with an organic solvent, can be when the 3.5V that is everlasting is above take place and the moving into altogether of solvent molecule.At the voltage of higher 3.5-4.0V, EMI ⁺Move into separately.Just, lyate ion and electrolyte ion (EMI ⁺) appear in the narrow zone jointly, and have only electrolyte ion (EMI ⁺) be absorbed in the space of narrower graphite layers.As a result, only stayed solvent molecule.So just interrupt the conductive capability of ion and caused big internal resistance in the discharge process.Next, caused voltage decline.

When using liquid electrolyte, if having only electrolyte ion (EMI ⁺) be absorbed in the space of narrower graphite layers residual electrolyte ion (EMI ⁺) just still exist.Therefore, prevented that the ionic conduction ability is interrupted.Next, in discharge process, there is not big internal resistance to occur as can be seen.

The double-layer capacitor of patent disclosure No.2002-25867 has shown such characteristic, i.e. volumetric expansion when applied voltage.If exert pressure from the outside with opposing because electrode expands caused pressure, and the volumetric expansion of electrode suppressed fully, the electric capacity that is generated between the electrode does not have different with the permission electric capacity that its free wxpansion generated so.Yet, when applying in the instrument, when the fixed distance between the gatherer, if, can produce the result who more expects owing to after the atresia charcoal can be because applied voltage expands diminishes to gatherer applied pressure (hereinafter referred to as turgor pressure).Next, discussion is about the turgor pressure of double-layer capacitor of the present invention.

Fig. 8 represents to use the curve chart of the testing result of the turgor pressure in the battery that different atresia charcoals makes.EMIBF is used in A and B representative separately among the figure ₄Result as liquid electrolyte.1.0mol/LEt is used in the C representative among the figure ₃MeNBF ₄(acetonitrile and isobutyl carbonate propyl ester are according to the mixed solvent of 1: 1 volume ratio) solution is as the result of electrolyte solution.

Use is atresia charcoal [B704804S+504H] as the atresia charcoal of electrode, and it is to use needle coke (raw material charcoal B) prepared as original raw material of wood-charcoal material, and needle coke is by the petroleum coke acquisition of deriving.d ₀₀₂Be 0.360nm, specific area is 60m ²/ g, the relaxation ratio of component is less than 0.05.

Then, about the battery of each manufacturing, the volume in electrode direction is limited as shown in Figure 9.Use a kind of anchor clamps that can monitor force to measure the pressure (patent disclosure No.H11-317333) that is produced.The curve representation of Fig. 8 the result who detects.Among the figure, A carries out initiation of charge under the 3.7V voltage of setting, then under the situation that repeats to discharge and recharge under the 3.3V voltage of setting, by the record of the change in voltage that a kind of straingauge produced.Situation when B and C represent also to repeat to discharge and recharge under the 3.3V voltage of setting.In addition, as shown in FIG., without limits the time, the numerical value of turgor pressure and volumetric expansion can be learnt from the variation of voltage.

Fig. 8 shows, uses liquid electrolyte EMIBF among the application ₄The expansion-pressure ratio of battery use asymmetric ammonium salt Et ₃MeNBF ₄Shi Yaoxiao about 30%.According to the consideration, this may be because the difference of the molecular structure between the cation.Be the molecular structure that EMI cation among the application has the plane, and ammonium salt Et ₃The MeN cation then has three-dimensional structure.

If raising electric capacity, when the carbon resistance rod volumetric expansion, the electric capacity of unit volume can be cancelled, and therefore, when making actual device, the method for needs use restricted volume is suppressed at the volumetric expansion on the direction of an electric field.For example, lamellar electrode roll is got up to put into cylindrical chamber, its expansion be therefrom mind-set outward for direction.Therefore, the page or leaf sheet is placed in the polymer film cylinder with high-tensile strength intensity, for example fluorocarbon or polyimides.Under the situation of overlapping plane electrode, the page or leaf sheet is sandwiched between the compression plate with high rigidity.Then, the page or leaf sheet is put in the bag shaped polymer sheet with high-tensile strength intensity similarly, for example fluorocarbon, polyimides or polyamide, this has just suppressed volumetric expansion.Can select, by the page or leaf sheet being put in the aluminum alloy container with high rigidity, carry out initiation of charge, closed container also can reach this purpose then.

Next, the temperature characterisitic of the double-layer capacitor electric capacity of invention is discussed.The result is illustrated among Figure 10.Figure 10 is the V-C characteristic that the electric capacity of double-layer capacitor (cell preparation No.j533) shows under 50 ℃.Capacitor uses atresia charcoal [A704804+504H] (to have d ₀₀₂Be 0.360nm, specific area approximately is 100m ²/ g, the relaxation ratio of component is less than 0.17), it is to use petroleum asphalt charcoal (raw material charcoal A) through after cannot not being treated as moltenly, and is prepared as the raw material charcoal.Capacitor uses EMIEMIBF ₄As electrolyte.

As can be seen from Figure 10, when improving working temperature, compare under electric capacity and the room temperature and have raising (Fig. 2, cell preparation No.i332).

Can think that when the working temperature of battery improved, the internal resistance meeting reduction of electric capacity and electric capacity increased.On the other hand, also know, therefore also accelerated the inefficacy of battery owing to improve impurity and electrolyte electrochemical reaction in the working temperature meeting activation system.Yet, in double-layer capacitor of the present invention, the quick decline in the execution mode that the tenth electric capacity of taking turns can not suffer to introduce later.Simultaneously, the also less inefficacy of battery.Therefore, battery is metastable.

Generally know, use the double-layer capacitor of prior art active carbon, increase hardly if the working temperature of battery improves electric capacity, but shorten the life-span soon, its reason is as follows.It is almost impossible removing remaining functional group fully, so may react under high working voltage between electrolyte and the solvent.This also can be promoted along with the raising of temperature.On the contrary, in the atresia charcoal, can significantly reduce remaining functional group.Therefore, for double-layer capacitor of the present invention, if improve working temperature, the shortening in life-span can not take place.A main feature of double-layer capacitor of the present invention is exactly the working temperature with wide region.

As described previously, double-layer capacitor of the present invention provides a kind of to have the working temperature of high withstand voltage, wide region and has big electric capacity, this ascribes two mechanism to: the one, because electrolyte ion and electrochemical reaction form electric double layer, other is using separately under the situation of liquid electrolyte, by adding stable high pressure electrolyte ion self major part is moved in the charcoal tissue.When the solution of liquid electrolyte is used as electrolyte solution, if use capacitor being no more than under the voltage of 3.5V, then obtained to have than double-layer capacitor that uses active carbon and the device that the described double-layer capacitor of patent disclosure No.2002-25867 has bigger electric capacity.

Embodiment:

Below by execution mode the present invention is described in further detail.

Embodiment 1-18 and Comparative Examples 1-5

The method of describing according to patent disclosure No.2002-25867 prepares the atresia charcoal.Except foregoing method, what can also select is, use transition metal for example Ni as the catalyst (patent disclosure No.2002-362912) of hydrogenation process.Then, to the atresia charcoal of each acquisition, use XRD to detect average interplanar distance d ₀₀₂, detect specific area by the method for BET, detect the relaxation time component by the PULSED NMR spectrum analysis, simultaneously, use these atresia charcoals to make double-layer capacitor according to the methods below.

Use is by the cation that can present the planar molecule structure and have liquid electrolyte that the anion of small ion Van der waals volumes forms as electrolyte, has average interplanar distance d ₀₀₂Be 0.350-0.360nm, and up-to-date to be found to be useful atresia charcoal mainly be to prepare by the temperature that improves hydrogenation.Just, use petroleum asphalt charcoal (raw material charcoal A), prepare a kind of used atresia charcoal through after cannot not being treated as moltenly.Hydrogenation temperature is brought up to 700 ℃ [A704804+704H] from 500.Use petroleum asphalt charcoal (raw material charcoal A) through after cannot not being treated as moltenly, prepare the atresia charcoal of another kind of type.At 700 ℃ and 90kg/cm ²The pressurized hydrogen condition under, charcoal is carried out hydrogenation treatment [A704804+704 (90) H] (for the atresia charcoal of hydrogenation under the condition of pressurization, operating pressure (kg/cm ²) force value in bracket (), represent, with the explanation hydrogenation be the pressurization condition under carry out.)。The needle coke (raw material charcoal C) that use obtains from the difference source prepares other type, and needle coke is to derive from petroleum coke.The temperature of hydrogenation is 700 ℃ [C704804+704H].The average interplanar distance d of these atresia charcoals ₀₀₂Be to use XRD to detect, their specific area and relaxation time component are listed in table 1.Use powder sample and copper target line (Cuk α line) in air, to carry out XRD and detect (use the copper target, activation voltage is 30kV).

[table 1]

The atresia charcoal	d 002(nm)	Specific area (m 2/g)	Relaxation component ratio
				A704804+704H	0.355	About 46	0.10
A704804+704(90)H	0.354	About 40	0.05 below
				C704804+704H	0.356	About 60	0.20

Average interplanar distance d ₀₀₂Change according to heat treated temperature in hydrogen stream (reduction air-flow).Improve heat treated temperature and can reduce spacing.When temperature range below 800 ℃ the time, the amount of variation is less than 0.05nm.

(1) preparation carbon resistance rod

To comprise and make the average interplanar distance d that obtains in this way ₀₀₂For the atresia charcoal of 0.350-0.360nm is recovered in the aluminium box, heating and 200 ℃ of following vacuumizes to 0.1Torr 2-4 hour.Then, charcoal is gone in the mortar, add, the Denka Black carbon black that Ltd. obtains and from Mitsui-DuPont Fluorochemicals Co., the PTFE cement that Ltd. provides from Denki Kagaku Kogyo Co..Rub together with material mixing and with sledge mill.An embodiment of charcoal, carbon black and PTFE cement weight ratio is 10: 0.5: 0.25.Then, the carbon plate of rubbing that shows viscosity is wrapped in the aluminium foil up to they are rolled into sheet.Then they are installed on the hot cylinder, remove aluminium foil.Finally obtained the plate like form of class.

Then use the punching press anchor clamps with every described above size that is cut into diameter as 20mm, thickness reaches 0.2mm, and as the test carbon resistance rod.Measure thickness and quality and install and use the device of molded carbon resistance rod.The density of these electrodes is all at 0.8-1.1g/cm ³Scope in.Resulting carbon resistance rod is placed on dish respectively to be gone up to soak into.The heating, vacuum drying instrument that electrode is packed into and directly linked to each other with glove box with glass fibre GA-100 or GA-55.The heating and 250 ℃ of following vacuumize to 5 * 10 ^-7About 24 hours of Torr.Then it being transferred to vacuum soaks in the vessel.With this vessel pump to 0.1Torr.Then, open the electrolyte injection valve, inject by the electrolyte of activated aluminum post or the electrolyte solution of forming by the liquid electrolyte that is dissolved in given organic solvent.The amount of injecting enough make each carbon resistance rod fully covered (use a kind of in advance with cardboard division board (CTW-GA55-CTW) compressed together, this cardboard can become brown when reaching 250 ℃.Therefore, in this case, carbon resistance rod is at 120-150 ℃, 5 * 10 ^-7Vacuumize is about 24 hours under the Torr, is kept in the glove box then.Employed these and their operation similarly carried out).By electrode being carried out visual observations at the window that forms near vessel top.Variation by fluid level in the electrolyte solution bottle is confirmed.

After adding infiltration electrolyte or electrolyte solution, open valve it is pumped once more from vessel inside.At this moment, can observe gas exhales as bubble from inside or other positions of charcoal.

After about 3-5 minute, stopped bubble.Then, open the valve decompression.Open the lid of vessel, take out carbon resistance rod and contain the division board (GA-100, GA-55 or CTW-GA55-CTW) of electrolyte solution, and through the following steps it is assembled into battery.

About employed liquid electrolyte EMIBF ₄, in glove box, open aluminum composite membrane packaged products and dustless operation that Stella ChemifaCorporation company makes.The organic solvent that uses intensive drying and further purify.

(2) Zhuan Zhi assembling (testing battery)

The aluminium collector electrode of the surface roughening that preparation is partly obtained by pre-envelope extractor electrode and contain the laminate bag of aluminium.Collector electrode, carbon resistance rod, CTW, GA55 or GA100CTW, carbon resistance rod and collector electrode are in the same place according to this order stack.What can select is to be in the same place according to this order stack with collector electrode according to collector electrode, carbon resistance rod, CTW-GA55-CTW electrolyte solution division board, carbon resistance rod.With anchor clamps these components are clutched and inserted in the laminate bag that contains aluminium.

Then,, from glove box, take out, and use anchor clamps to carry out vacuum packaging its clamping.The gas that produces when using overvoltage in order to store has been reserved a block space in advance in polymer pouches.

As a kind of method of apparatus for assembling, foregoing electrode and division board be placed in the container that vacuum soaks into assemble.Except this method, can also make the assembling of carrying out device (testing battery) in the following method.Especially, electrode, division board and the collector electrode of use preceding method drying assemble and put into the laminate bag that contains aluminium of a prepared beforehand.After extractor electrode partly sealed, inject liquid electrolyte or electrolyte solution from the other end of bag, and bag is placed in the evacuated vellel.Its integral body is reduced pressure, so that liquid arrives all parts of the every nook and cranny of electrode.Then, device takes out from vessel.The other end to bag in glove box seals.This method is called " liquid injecting method " and adds that letter " i " represents.With adding that letter " j " rather than " i " represent the device (testing battery) of coming of new.

Carry out charge-discharge test with the testing battery that obtains.Test comprises the electrology characteristic of electric capacity.

Detect by following method.

(a) program mode continuous detecting

Use the detection method of auto-programming formula, wherein discharge and recharge under the stabling current of 10mA, and improve applied voltage in the mode of per step increase 0.5V, trickle charge time in per step increases by 500 seconds.When surpassing maximum applied voltage 4.0V or 3.75V, carry out the same step that discharges and recharges and reduce voltage and time simultaneously.

(b) initiation of charge and Road test

A kind of method of automatic detection.As initiation of charge, first round charging is to carry out under 10mA up to 4.0V (perhaps, under some situation up to 3.75V).Be provided with the trickle charge time longer (about 5000 seconds or longer).Then, under 10mA, discharge up to 0V.After initiation of charge was finished, charging was same as or is lower than initial voltage slightly up to voltage under 10mA.Through after the suitable trickle charge, under 10mA, discharge with 0V (perhaps 0.5-0.8V, just in fact the storage power more than 90% is all bled off).Order according to this step repeats specific number of times.

Fig. 1,2 and 10 electric capacity that show are the results who detects by method (a) to discharging and recharging the applied voltage mapping among applied voltage mapping and Fig. 3.The result of move into starting voltage and Figure 11 cycle detection of Fig. 4 detects by method (b).Detected temperatures mainly is at room temperature, but has some detections to carry out under 50 ℃.

Use is from the numerical value of total discharging current 50% of beginning to discharge, by Q=(1/2) * CV ²Calculate electric capacity, and be converted to the dry weight and the volume of positive and negative electrode.Internal resistance in the discharge process is a fixed value to for example employed electrode of detection battery.This as a reference.

Simultaneously, has the device that uses no pore carbon electrode with similar method preparation.The solution that uses alkylammonium salt is as electrolyte solution (reference examples 1-3).Active carbon is used in preparation, and (its specific area is 1015m ²The maximum magnitude of/g and micropore is 0.74nm.) rather than atresia charcoal and the device that uses liquid electrolyte example in contrast.Rong petroleum asphalt does not use as the raw material charcoal, and uses water vapour to activate (reference examples 4).Use water vapour that petroleum asphalt is activated.Further, use the solution of alkylammonium salt to be used to utilize above-mentioned Preparation of Activated Carbon electrolyte of electrodes solution as electrolyte solution.This is example 5 in contrast.Gained the results are shown in table 2.When producing device (detection pond), some devices (detection pond) are by making in carbon resistance rod and the division board insertion vacuum soaking vessel.Other device (testing battery) is made by " liquid injecting method ".These two kinds of devices for example come down on the electric capacity identical at detected electrology characteristic.Therefore, only enumerated the result of the device (testing battery) that uses simple " liquid injecting method " making in the table.

[table 2]

	The raw material of wood-charcoal material	Electrolyte solution
				Electrolyte	Solvent
		Embodiment
1	A704804+504H		EMI·BF 4	Do not have
		Embodiment 2			B704804S+504H 1	EMI·BF 4	Do not have
Embodiment 3	B704804+504H 2		EMI·BF 4	Do not have
		Embodiment 4			B704804+504H 3	EMI·BF 4	Do not have
Embodiment 5	B704804+504H 1		EMI·BF 4	Do not have
		Embodiment 6			A704804+504H	EMI·BF 4	Do not have
Embodiment 7	B704804S+504H 1		EMI·BF 4	PC
		Embodiment 8			B704804S+504H 1	EMI·BF 4	GBL
Embodiment 9	B704804S+504H 1		EMI·BF 4	EC
		Embodiment 10			B704804S+504H 1	EMI·BF 4	PC
Embodiment 11	B704804S+504H 1		EMI·BF 4	AN
		Embodiment 12			A704804+504H	EMI·BF 4	Do not have
Embodiment 13	A704804+704H		EMI·BF 4	Do not have
		Embodiment 14			C704804+704H	EMI·BF 4	Do not have
Embodiment 15	C704804+704H		EMI·BF 4	Do not have
		Embodiment 16			A704804+704H	EMI·BF 4	Do not have
Embodiment 17	C704804+704H		EMI·BF 4	Do not have
		Embodiment 18			A704804+504H	EMI·BF 4	Do not have
Comparative Examples 1	A704804+504H		Et 4N·BF 4	AN+EC 5
		Comparative Examples 2			A704804+504H	Et 3MeN·BF 4	AN+EC 5
Comparative Examples 3	B704804S+504H 1		Et 3MeN·BF 4	AN+EC 5
		Comparative Examples 4			Active carbon 4	EMI·BF 4	Do not have
Comparative Examples 5	Active carbon 4		Et 4N·BF 4	AN+EC 5

[table 2 is continuous]

	The first round
					Electric capacity F/g	Electric capacity F/cm 3	Applied voltage V	Internal resistance Ω
	Embodiment
1		55.7	52.3	4.0	9.9
	Embodiment 2					46.4	41.3	4.0	12.8
Embodiment 3		57.6	46.1	4.0	11.9
	Embodiment 4					55.9	46.4	4.0	14.3
Embodiment 5		39.4	31.2	3.75	26.6
	Embodiment 6					46.7	42.2	4.0	-
Embodiment 7		79.5 *	71.0 *	4.0	132
	Embodiment 8					28.5 *	25.2 *	4.0	107
Embodiment 9		67.1 *	57.8 *	4.0	140
	Embodiment 10					51.2	46.2	3.5	5.8
Embodiment 11		43.3	42.9	3.5	4.5
	Embodiment 12					65.4	55.4	4.0	-
Embodiment 13		59.7	59.6	4.0	-
	Embodiment 14					54.6	44.0	4.0	-
Embodiment 15		52.6	40.9	4.0	-
	Embodiment 16					68.1	71.5	4.0	-
Embodiment 17		49.4	41.7	4.0	-
	Embodiment 18					57.8	50.1	4.0	-
Comparative Examples 1		38.5	34.5	3.75	10.3
	Comparative Examples 2					39.1	38.0	3.75	10.4
Comparative Examples 3		38.4	30.6	4.0	42.3
	Comparative Examples 4					31.3	17.7	3.5	7.0
Comparative Examples 5		23.2	17.0	3.75	40.6

[table 2 is continuous]

	The tenth takes turns				Cell preparation No.
						Electric capacity F/g	Electric capacity F/cm 3	Applied voltage V	Internal resistance Ω
	Embodiment
1		41.3	38.7	3.5	6.2	i322
	Embodiment
2		38.3	34.1	3.5	7.8	i613
	Embodiment
3		48.2	38.6	3.5	12.6	i731
	Embodiment
4		44.9	37.2	3.5	13.8	i721
	Embodiment
5		33.6	26.9	3.3	19.9	i521
	Embodiment 6						36.9	33.9	3.5	5.7	i612
Embodiment 7		39.4	35.2	3.5	23.6	i622
	Embodiment
8		35.5	31.3	3.5	20.8	i513
	Embodiment 9						42.0	36.2	3.5	16.9	i531
Embodiment
	10	42.0	37.9	3.5	7.4	i623
Embodiment 11							39.0	39.4	3.5	3.7	i633
	Embodiment 12	42.5	36.0	3.5	3.4	j533 6
Embodiment 13							36.3	34.5	3.5	4.6	j233 6
	Embodiment 14	43.6	35.2	3.5	3.0	j222 6
Embodiment 15							41.1	31.9	3.5	4.3	j223
	Embodiment 16	36.2	37.7	3.5	5.8	j013 6
Embodiment 17							39.3	33.2	4.0	15.0	j711
	Embodiment 18	48.8	42.4	4.0	11.5	j611
Comparative Examples 1							35.2	31.6	3.3	5.9	i221
	Comparative Examples 2	33.9	33.0	3.3	8.8	i233
Comparative Examples 3							31.8	25.3	3.5	41.8	i423
	Comparative Examples 4	24.0	13.6	3.3	6.5	i412
Comparative Examples 5							21.8	16.0	13.0	19.7	-

Annotate sample:

1-3: the petroleum coke based raw material charcoal B of different lot numbers

4: specific area is 1015m ²The porous charcoal of/g

5: having electrolyte concentration is the mixed solvent of the equal volume component (1: 1) of 1.0mol/L

6: 50 ℃ of battery testing temperature

In electrolyte one row in the table, with EMIBF ₄Be dissolved under the situation that obtains electrolyte solution in the organic solvent, then use EMIBF ₄Mixture with the organic solvent equal volume.The represented raw-material charcoal kind of atresia charcoal of A is a petroleum asphalt raw material of wood-charcoal material.The charcoal kind of the raw material that B is represented is meant the needle coke of deriving and from petroleum coke.3 kinds of raw material charcoals that use has different product batch numbers prepare raw material charcoal B.These raw material charcoals B is labeled as 1-3.Simultaneously, the kind of the represented raw material charcoal of C is the needle coke of deriving and from the petroleum coke in difference source.

According to table 2, use to have average interplanar distance d ₀₀₂For the device of the atresia charcoal of 0.350-0.380nm has than bigger electric capacity of Comparative Examples and littler internal resistance.Also applied voltage can be up to 4.0V as can be seen.In addition, can see, show same stability under itself and the room temperature if probe temperature is set to 50 ℃.

On behalf of electrolyte solution, the embodiment 7-9 in the table contain the situation of organic solvent.First round charging is carried out under 4.0V voltage.Under these situations, in the first round, 107-140 Ω is brought up in internal resistance widely, and therefore, the selftest result by the resulting electric capacity of aforesaid computational methods (adds in Fig. 2 ^*) come down to nonsensical.Yet, when then when 3.5V repeats to discharge and recharge, the value of the tenth electric capacity of taking turns and the value that obtains by other embodiment be can compare (embodiment the 10, the 11st, in the 3.5V repeated charge, the electrolyte solution that has been to use solvent of its usefulness, and other uses the embodiment of liquid electrolyte separately).Like this, as can be seen,, but in follow-up discharging and recharging, do not have the problem generation even double-layer capacitor of the present invention can be because overvoltage have temporary transient internal resistance to increase.

And, do not have in the system of solvent in use as can be seen, under the situation that at applied voltage is 4.0V, carry out the first round, then voltage is set at 3.5V, and take turns under the situation about identifying at the voltage that adds 4.0V and to the tenth, can show the identical electric capacity of essence.

The cycle specificity of the double-layer capacitor that is obtained then, is discussed.As embodiment, use atresia charcoal [B704804+504H] manufacturing installation.This device is used different applied voltages and repeated charge 100 times.Among Figure 11, changes in capacitance is mapped to cycle-index.Among the figure, (A) represent applied voltage to be set to the situation of 4.0V, (B) represent applied voltage to be set to the situation of 3.5V.As can be seen from Figure 11, when applied voltage was set at 4.0V, electric capacity can some reduction along with the increase of cycle-index, but when applied voltage 3.5V quite stable.Therefore, device has good cycle specificity.

From result and the description that is provided, double-layer capacitor of the present invention can be summarised in the table 3.In the table, withstand voltage is to recommend the applied voltage of use, and it can use and give full play of the performance of double-layer capacitor of the present invention safely.

[table 3]

	The electrode carbon material	Electrolyte solution		Electric capacity (F/cm 3)	Withstand voltage (V)	Discharge energy density (Wh/L)
							Electrolyte	Solvent
		Invention	The atresia charcoal						EMI·BF 4	Do not have (pure)	46	4	115
The atresia charcoal	EMI·BF 4			AN, PC, EC or analog	38	3.3	57
			The prior art example					The atresia charcoal	Et 3MeN·BF 4	AN+EC	32	3.3	48
Porous activated carbon	Et 3MeN·BF 4	AN+EC		15	2.7	15
							Porous activated carbon	EMI·BF 4	Do not have (pure)	14	3.3	21

Can be as seen from Figure 3, double-layer capacitor of the present invention has the discharge energy density bigger than prior art.

Result based on the embodiment that introduces has previously carried out comprehensive introduction to double-layer capacitor of the present invention.In the double-layer capacitor with the electrode that comprises that atresia carbon activity material combines with liquid electrolyte of the present invention, electrolyte ion forms electric double layer to reach certain applied voltage.Under very high applied voltage, most of electrolyte ion self can be moved into separately in the charcoal tissue.Like this, electrochemical energy is stored with this electrochemical behavior.Therefore, provide a kind of device based on new mechanism.

Under the operating voltage 3.3V at the double-layer capacitor of prior art, double-layer capacitor of the present invention has than prior art and uses quaternary ammonium salt solution as high about 1.2 times of the electric capacity of the device of electrolyte solution.Because device can be operated, therefore can reach big 2.4 times energy density under higher voltage.Just, double-layer capacitor of the present invention has big electric capacity and high withstand voltage.Its energy density is quite high.And the internal resistance in the discharge process is little.Therefore, provide device with good power density.Further, though double-layer capacitor of the present invention be metastable and also show higher electric capacity removing under the high-temperature of remaining functional group, the device that reaches high-energy-density is provided.

When use is dissolved in the electrolyte solution of the liquid electrolyte in the organic solvent, if used applied voltage is 4.0V, beginning and can raise in discharge owing to the former thereby internal resistance of mechanism.As long as use the applied voltage of 3.5V, take place with regard to not having problem.Provide and had the electric capacity higher, the device of just higher energy density and the power density of Geng Gao than the device of routine.If two electrodes are added voltage above 3.5V, and internal resistance increases in the process of discharge, then can form electric double layer once more in the process that next round is charged in this device.So in discharge process, device can be returned to original low internal resistance state.That is to say, this means that this device has the buffer capacity that opposing surpasses the applied voltage of rated voltage.A kind of double-layer capacitor with high reliability and fail safe based on new mechanism is provided.

Claims (10)

1. double-layer capacitor comprises:

Positive and negative electrode, it comprises the atresia charcoal as electrode active material, this atresia charcoal have grow well, average interplanar distance d ₀₀₂Multilayer graphite for 0.350-0.380nm; With

Be used for soaking the electrolyte of positive and negative electrode;

Wherein said atresia charcoal obtains by activating easy graphitized carbon, and easily graphitized carbon is to obtain by the pitch of calcining needle coke or cannot not made moltenly; With

Wherein said electrolyte is the liquid electrolyte with planar molecule structure.

2. double-layer capacitor comprises:

Positive and negative electrode, it comprises the atresia charcoal as electrode active material, this atresia charcoal have grow well, average interplanar distance d ₀₀₂Multilayer graphite for 0.350-0.380nm; With

Be used for soaking the electrolyte solution of positive and negative electrode;

Wherein said atresia charcoal obtains by activating easy graphitized carbon, and wherein easily graphitized carbon obtains by the pitch of calcining needle coke or cannot not made moltenly; With

Wherein said electrolyte solution is the electrolyte solution that liquid electrolyte mixes with organic solvent, and described liquid electrolyte has the molecular structure on plane.

3. the double-layer capacitor described in the claim 2, wherein organic solvent can be select from the group of being made up of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxymethane, diethoxyethane, gamma-butyrolacton, acetonitrile and propionitrile a kind of or at least two kinds mixed solvent in them.

4. claim 2 or 3 described double-layer capacitors, wherein electrolyte solution has the electrolyte of concentration greater than 0.5mol/L.

5. any one described double-layer capacitor of claim 1-4, the salt formed by cation and anion of liquid electrolyte wherein, wherein cation is to be made of the represented compound of following general formula:

[Chemical formula 1]

R wherein ¹And R ²Be respectively straight chained alkyl with 1-5 carbon atom, R ³Be hydrogen or the straight chained alkyl with 1-5 carbon atom, anion has at 0.01-0.06nm ³Van der waals volumes in the scope.

6. the described double-layer capacitor of claim 5, wherein cation is 1,3-dialkylimidazolium or 1,2,3-trialkyl imidazoles.

7. any one described double-layer capacitor in the claim 5 and 6, wherein anion is BF ₄ ^-, PF ₆ ^-, AsF ₆ ^-, ClO ₄ ^-Or CF ₃SO ₃ ^-

8. any one described double-layer capacitor of claim 1-7 wherein uses the PULSED NMR spectrum analysis to pass through ¹H resonance can be observed the T of the hydrogen of representing the different bonding states of charcoal tissue that remain in the atresia charcoal ₂Be the short relaxation time component of 20-50 μ sec (Gaussian), T ₂Medium relaxation time component and T for 50-400 μ sec (Lorentz type) ₂Be the long relaxation time component of 500-2000 μ sec (Lorentz type), and the ratio of medium relaxation time component and short relaxation time component was less than 1: 3.

9. any one described double-layer capacitor among the claim 1-8, wherein the atresia charcoal has less than 270m ²The specific area of/g.

10. the double-layer capacitor described in the claim 9, wherein specific area is less than 100m ²/ g.

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