CN100521009C - Purifying technique for super-capacitor electrolyte - Google Patents

Abstract

This invention discloses a purifying technology for an electrolyte used in a liquid electrolyte of a super level capacitor, which resolves a being purified electrolyte in a solvent with high solubility to it, then puts said solution and the electrolyte in a solvent with difficult solubility to it and mixes them in a certain proportion and separates the deposited subjects from the solution by filter to be dried and a purified electrolyte is got.

Description

Purifying technique for super-capacitor electrolyte

Technical field

The present invention relates to the electrolytical impurity elimination purifying technique that uses in the electrolyte of electrochemical devices such as ultracapacitor.

Background technology

Ultracapacitor is very a kind of rapidly model electrochemical energy storage device of development in recent years, it has the capacity more much higher than traditional electrolytic capacitor, have again than outstanding high current charge-discharge ability of power type accumulator battery and much longer cycle life, be considered to a kind of novel electrical source of power.Large capacity version or high-power type ultracapacitor can be used for electrical source of power, the startup power supply of automobile, perhaps fuel cell and ultracapacitor mixed type, lithium ion battery and ultracapacitor hybrid electric vehicles, the ultracapacitor of miniaturization can be applicable to be used in the electronic instrument information storage of anti-power failure, the supper bass compensation of acoustics circuit and the purposes such as energy storage of small-sized solar device, is a kind of very promising new-type element.

The electrolyte of ultracapacitor can be water electrolyte, organic electrolyte and polymer dielectric etc.Water electrolyte has advantages such as conductivity height, fail safe are good, with low cost, but has obvious defects, and is low as the operating voltage of capacitor, is no more than 1.0V usually.The electrolyte of water electrolyte is commonly used dilute sulfuric acid or potassium hydroxide solution, has stronger corrosivity, and the sealing that damages device easily is airtight.Organic electrolyte uses in the stronger organic solvent of polarity the high ammonium salt of dissolving conductivity, lithium salts etc. to make usually, has the operating voltage advantage of higher.The present conductivity of polymer-type electrolyte is also lower, uses to be subjected to certain restriction.

Energy computing formula according to capacitor

$E=\frac{1}{2}{\mathrm{CU}}^2$

In the formula, E is the energy of capacitor storage, and C is the capacitance of capacitor, and U is an operating voltage.As can be seen, the energy of capacitor storage and operating voltage square is directly proportional.Improve the operating voltage of capacitor, can improve the energy density of capacitor rapidly.Therefore, the organic electrolyte of ultracapacitor more and more obtains developer's attention, and the trend that progressively replaces water electrolyte is arranged.

Electrolytic salt is one of important material in the organic electrolyte, and on the one hand, the necessary redox of sustaining electrode under high voltage of electrolyte must have higher electric conductivity simultaneously.The conductivity of electrolyte directly has influence on the equivalent series resistance (ESR) of ultracapacitor, and then has influence on its power density.On the other hand, owing to be operated under the higher voltage, the trace impurity in the electrolyte often has significant effects to the performance and the life-span of capacitor.Therefore, preparing high-purity high conductivity electrolyte, is the important prerequisite that guarantees the electrolytic solution for super capacitor performance.It is big must to have in solvent solubility for the electrolyte that uses, and conductivity height, Undec characteristics under high operating voltage, kinds such as tetrafluoroborate, trifluoromethyl sulfonic acid, hexafluorophosphate, fluoroalkyl sulfimide salt, perchlorate are arranged by the anion branch, alkyl quaternary ammonium salts, heterocyclic aromatic compounds salt and lithium salts etc. such as tetraethyl quaternary ammonium salt, methyl triethyl group quaternary ammonium salt, tetrabutyl quaternary ammonium salt are arranged by the cation branch.The organic quaternary ammonium salt of tetrafluoro boric acid is to use more ultracapacitor electrolysis matter at present, it is big that it has in solvent solubility, conductivity, stable electrochemical property, plurality of advantages such as cost is lower, its exemplary are tetraethyl ammonium tetrafluoroborate (TEATFB) and methyltriethylammonitetrafluoroborate tetrafluoroborate (MTEATFB).

The preparation method of fluoboric acid quaternary ammonium salt can be divided into several classes, comprises that mainly hydrofluoboric acid and quaternary ammonium type halogen acid salt, borofluoride and quaternary ammonium salt carry out ion-exchange reactions, and the reaction of the carbonate of quaternary ammonium and fluoboric acid etc.Product by these method preparations can not be directly used in the application of capacitor occasion usually, must carry out purification step to reduce impurity content.In ultracapacitor, because operating voltage is higher, the content of impurity requires to be lower than 10ppm usually, and general commercially available prod can not reach this requirement, the anionic content of its metal impurities or impurity is generally tens to hundreds of PPM, must carry out purifying and just can be used for the electrolytic solution for super capacitor use.

Yet the purifying of high purity product is often very difficult, can not introduce new impurity, must reduce the content of impurity in the existing product again, and aspects such as reagent, equipment have been proposed many restrictions.For example, traditional method of removing free chlorine, can use chemical reagent such as adding silver salt, sodium methoxide, or by means such as antichlor absorption, ion-exchange absorption, but for the electrolysis salt of chlorinity at tens PPM, it is undesirable that above method all can not be suitable for or reduce the effect of chlorinity, the requirement that does not reach high-purity product.

Summary of the invention

At the problems referred to above, the invention provides a kind of can preparing and meet the needed electrolytical purifying technique of ultracapacitor.

Main technical principle of the present invention is: will need the electrolyte P of purifying to be dissolved in making highly concentrated solution (comprising saturated solution) in the high solvent orange 2 A of its dissolubility, then with solution and another kind of electrolyte P therein the solvent B of indissoluble mix, utilize the solubility of electrolyte in mixed solvent to reduce and cause supersaturation to be separated out, low content compositions such as impurity are stayed in the solution owing to can not reach supersaturation in mixed solvent, like this can be by filtering to isolate the higher electrolyte P of purity.

The technical solution used in the present invention is: will need the electrolyte P of purifying to be dissolved in the solvent orange 2 A of Yi Rong, wherein electrolyte P is at 100 minimum 20 grams that are not less than of solubility that restrain in the solvent orange 2 As, then electrolyte P is dissolved in the resulting solution of solvent orange 2 A and electrolyte P therein the solvent B of indissoluble mix by a certain percentage, wherein electrolyte P is at 100 the highest 5 grams that are not more than of solubility that restrain among the solvent B, by filtering the sediment of separating out is isolated, again with the electrolyte P that just obtains after this drying precipitate through edulcoration purification.

The further technical scheme of the present invention is: described electrolyte P is the fluoboric acid quaternary ammonium salt, and its structural formula is:

In the formula, R ₁, R ₂, R ₃, R ₄Can be identical or different; Range of choice is that hydrogen atom, carbon number are that 1 to 12 alkyl, carbon number are the alkyl that 1 to 12 fluorine or chlorine partly or entirely replaces.Can have for example: the tetramethyl ammonium tetrafluoroborate, tetraethyl ammonium tetrafluoroborate (TEATFB, tetraethylammoniumtetrafluoroborate), four n-pro-pyl ammonium tetrafluoroborates, the tetra isopropyl ammonium tetrafluoroborate, tetrabutyl ammonium tetrafluoroborate, methyltriethylammonitetrafluoroborate tetrafluoroborate (MTEATFB, methyltriethyl ammonium tetrafluoroborate), dimethyl diethyl ammonium tetrafluoroborate, trimethyl ethyl ammonium tetrafluoroborate, methyl triisopropyl ammonium tetrafluoroborate, dimethyl diisopropyl ammonium tetrafluoroborate, the trimethyl isopropyl ammonium tetrafluoroborate, ethyl triisopropyl ammonium tetrafluoroborate etc.

Describedly to the high solvent orange 2 A of electrolyte P dissolubility be: the solubility of electrolyte P in 100 gram solvent orange 2 As is minimum should to be not less than 20 grams.The solvent orange 2 A that can select has: nitrile is the solvent of the high polarity of a kind of low viscosity, electrolyte dissolution can obtain higher concentration therein, comprise that optionally carbon number is 1 to 4 alkyl nitrile, the aromatic radical nitrile, carbon number is 1～4 a dintrile etc., for instance, acetonitrile, propionitrile, butyronitrile, malononitrile, succinonitrile, benzene acetonitrile, phthalonitrile etc. are arranged, preferably use acetonitrile.In addition, the polarity carbonic ester also can be used to dissolve the fluoboric acid quaternary ammonium salt, and optionally carbonic ester has propene carbonate (PC), ethylene carbonate (EC), butyrolactone (GBL) etc., preferably uses propene carbonate.The concentration of the electrolyte solution that is mixed with should be high as much as possible, separates out electrolyte to guarantee to be easy to reach supersaturation in the blend step of back, and can reduce the consumption of solvent.As a rule, can consider to use saturated solution.

The described electrolyte P solvent B of indissoluble therein is: the solubility of electrolyte P in 100 gram solvent B is the highest should to be not more than 5 grams.The solvent B that can select has: most solvents nonpolarity or low pole are all less to the solubility of electrolytic salt, as aliphatic hydrocarbon, aromatic hydrocarbon, carboxylate, linear carbonate, alcohols etc., such as having: n-hexane, benzene,toluene,xylene, carbon ester dimethyl ester, diethyl carbonate, methyl ethyl carbonate, acetate acetate, ethanol etc.In addition, in order to reach the higher effect of separating out, solvent B should have certain effect of dissolving each other with solvent orange 2 A, if dissolve each other fully then effect is better, can select according to solvent cost and drying condition, preferred dimethyl carbonate and diethyl carbonate.

Electrolyte dissolution forms highly concentrated solution in solvent orange 2 A after, with the insoluble solvent B of electrolyte is mixed, can make mixed solvent that electrolytical solvability is descended rapidly, electrolyte supersaturation and separate out solid in solution, wherein impurity anion such as the impurity component of being carried secretly such as small amount of impurities metal ion, halogen is because content is lower, in mixed solvent, still do not reach capacity, be retained in the liquid phase, thereby realize electrolyte ingredient and separate impurities.This process meeting loss part electrolyte by regulating the ratio of solvent orange 2 A and solvent B, can reduce this a part of loss.Obviously, in mixed solvent, the ratio of solvent orange 2 A is more little, and electrolytical solubility is also just more little in mixed solvent, and its meltage also should be more little.Therefore, select the ratio of appropriate solvent A and solvent B most important for reducing solvent consumption and electrolytical loss, the ratio that can select is, the mass ratio of solvent orange 2 A and solvent B be 1:100 between the 10:1, be preferably 1:20～2:1.

Electrolyte filters after separating out in solvent, and usually because the surface of solids of separating out is long-pending bigger, the surface is all kinds of impurity of absorption easily, can use solvent that it is carried out drip washing.The purpose of drip washing is to dissolve the various impurity of surface adsorption, but little to the electrolyte dissolution degree that will filter.The solvent that can select has carbon number to be lower than 8 all kinds of alkyl alcohols, carboxylic acid esters, linear carbonate class, as propylene glycol, isopropyl alcohol, ethyl propionate, butyl propionate, dimethyl carbonate, carbonic acid first propyl ester etc., preferably use dimethyl carbonate or diethyl carbonate.The solvent that is applied should can be divided into one or many and carry out with heavy about 10%～30% being advisable of solids.Apply at every turn and should make solvent and solid behind the solvent evenly moistening 3～10 minutes, can stir solid in case of necessity and evenly soak helping, carry out the solvent that negative pressure leaching is fully removed drip washing then.

After if precipitation is separated out after filtration, the impurity content that obtains of drying meets the requirements, and can omit this step of drip washing, but in most cases, drip washing helps obtaining lower impurity content.

Wherein still there is a spot of solvent composition in electrolyte through behind the suction filtration, can remove by the method for drying, and the technology that can also repeat the present invention relates to is carried out further purifying.Generally, use the electrolytic salt of this method preparation, common one to twice purifying can make impurity content be less than the 10ppm rank.Dry mode is a lot, can select forced air drying, vacuumize, infrared drying, hot N for use with appointed condition according to actual needs ₂Drying etc.In most cases, vacuumize is a kind of suitable means, can avoid excessive temperature to cause the rotten or decomposition of electrolyte, can reach drying effect more completely again.

Execution mode

The invention will be further described below by specific embodiment.But the present invention is not limited in these embodiment.

Embodiment 1

Get TEATFB crude product (purity 98.9%) 9.0g, chlorinity is 40ppm, adds acetonitrile therein and is made into saturated solution.Add 170g dimethyl carbonate (purity 〉=99%) in the beaker of a 250ml, the acetonitrile saturated solution of TEATFB is slowly added and continuous the stirring, the adularescent solid is separated out.Add finish after, filter with the sand mold funnel, and divide with the 15ml dimethyl carbonate and to carry out drip washing three times, carry out vacuumize at 130 ℃ behind the suction filtration.Dry post analysis purity is 99.5%, and chlorinity is 7ppm.

Embodiment 2

Get MTEATFB (purity 99.2%) 10.0g, chlorinity is 50ppm, adds acetonitrile therein and is made into saturated solution.Add 200g diethyl carbonate (purity 〉=99%) in the beaker of 250ml, the acetonitrile saturated solution of MTEATFB is slowly added and continuous the stirring, the adularescent solid is separated out.Mix finish after, filter with the sand mold funnel, and divide with the 15ml diethyl carbonate and to carry out drip washing three times, suction filtration finishes and then carried out vacuumize 24 hours at 110 ℃.Dry post analysis purity is 99.8%, and chlorinity is 8ppm.

Claims (6)

1, purifying technique for super-capacitor electrolyte, it is characterized in that: will need the electrolyte P of purifying to be dissolved in the solvent orange 2 A of Yi Rong, wherein electrolyte P is at 100 minimum 20 grams that are not less than of solubility that restrain in the solvent orange 2 As, then electrolyte P is dissolved in the resulting solution of solvent orange 2 A and electrolyte P therein the solvent B of indissoluble mix by a certain percentage, wherein electrolyte P is at 100 the highest 5 grams that are not more than of solubility that restrain among the solvent B, by filtering the sediment of separating out is isolated, again with the electrolyte P that just obtains after this drying precipitate through edulcoration purification.

2, purifying process as claimed in claim 1 is characterized in that: described electrolyte P is the fluoboric acid quaternary ammonium salt, and its structural formula is:

In the formula, R ₁, R ₂, R ₃, R ₄Can be identical or different; Range of choice is that hydrogen atom, carbon number are that 1 to 12 alkyl, carbon number are the alkyl that 1 to 12 fluorine or chlorine partly or entirely replaces.

3 purifying process as claimed in claim 1 or 2 is characterized in that: the mass ratio of described solvent orange 2 A and solvent B is 1: 100 to 10: 1.

4, purifying process as claimed in claim 3 is characterized in that: the mass ratio of described solvent orange 2 A and solvent B is 1: 20 to 2: 1.

5, purifying process as claimed in claim 1 or 2, it is characterized in that: behind the sediment that filtration obtains separating out, again with electrolyte P therein solubility less than the solvents of 5 grams this sediment is carried out drip washing, and then carry out drying, obtain more highly purified electrolyte P.

6, purifying process as claimed in claim 5 is characterized in that: be used for the weight of solvent of drip washing by 10%～30% of the sedimentary weight of drip washing.