WO2015139049A1 - Procédés pour améliorer les performances de condensateurs à double couche électrochimique - Google Patents

Procédés pour améliorer les performances de condensateurs à double couche électrochimique Download PDF

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Publication number
WO2015139049A1
WO2015139049A1 PCT/US2015/020795 US2015020795W WO2015139049A1 WO 2015139049 A1 WO2015139049 A1 WO 2015139049A1 US 2015020795 W US2015020795 W US 2015020795W WO 2015139049 A1 WO2015139049 A1 WO 2015139049A1
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Prior art keywords
edlc
phosphonium
comprised
voltage
salts
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PCT/US2015/020795
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English (en)
Inventor
Wayne L. Gellett
Benjamin L. RUPERT
Leanne Beer
Steven Z. Shi
Shilpa A. Worlikar
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Esionic Corp.
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Priority claimed from PCT/US2014/029424 external-priority patent/WO2014144845A2/fr
Application filed by Esionic Corp. filed Critical Esionic Corp.
Publication of WO2015139049A1 publication Critical patent/WO2015139049A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/58—Liquid electrolytes
    • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Definitions

  • the invention broadly encompasses energy storage devices or systems and more specifically relates to methods of enhancing the performance of electrochemical double layer capacitors (EDLCs), or supercapacitors or ultracapacitors, and devices formed therefrom.
  • EDLCs electrochemical double layer capacitors
  • the invention relates generally to energy storage devices, such as EDLCs that use conventional ammonium based electrolytes or phosphonium-based electrolytes and methods for treating such devices to enhance their performance and operation.
  • Electrochemical double layer capacitor also called electrochemical capacitors or supercapacitors or ultracapacitors, are electrochemical cells that store energy by charge separation at an interface between an electrode and an electrolyte.
  • An EDLC is comprised of two porous electrodes, an electronically insulating separator that isolates the two electrodes from electrical contact with each other, and an electrolyte composition in contact with the two electrodes and the separator.
  • the electrode is characterized as comprised of highly porous active material that provides a high surface area.
  • the electrolyte composition is typically solution with salt dissolved in a solvent.
  • the pores of the electrode active material need to be filled with electrolyte in order to gain access to a large portion of the available surface area.
  • Charge and discharge processes in an EDLC involve only the movement of electronic charge through the solid electronic phase and ionic movement through the electrolyte solution phase. These characteristics enable EDLCs to store more energy than traditional capacitors and discharge this energy at higher rates than rechargeable batteries. In addition, the cycle life of an EDLC far exceeds that of battery systems. These advantages are achievable because neither rate-determining nor life-limiting phase transformations take place at the electrode/electrolyte interface in in an EDLC device.
  • EDLCs are attractive for potential applications in emerging technology areas that require electric power in the form of pulses. Examples of such applications include digital
  • a major advantage of an EDLC is that it can deliver electrical energy at high power. For example, after discharging an EDLC by powering an electrical device, the EDLC can be recharged in a matter of seconds, compared with the hours required to recharge a standard battery.
  • the EDLC can handle the peak power, and the battery can provide power for a sustained load between peaks. This allows manufacturers to use smaller, lighter, and cheaper batteries as they do not have to use oversized batteries that are needed to handle sudden surges in power demand.
  • Such a hybrid power system can improve overall power performance and extend battery cycle life.
  • EDLC electrostatic senor
  • the lifetime of an EDLC may be defined as the time when its capacitance decreases to 80% of the initial capacitance value or the ESR (equivalent series resistance) increases to 200% of the initial ESR value. It is of great challenge to achieve all these performance targets in a synergetic way. There are usually trade-offs among these targets. For example, increasing the operating voltage is an effective way to increase the energy density since the energy stored in a capacitor is given by 1 ⁇ 2 CV , where C is the capacitance and V is the cell voltage.
  • some embodiments of the present invention provide methods for treating an EDLC device after initial assembly to increase its operating voltage, thus energy density, and to increase its operating temperature and lifetime.
  • Other embodiments of the present invention provide a method for recovering or enhancing the performance of an EDLC that has been in operation thus extending its usage beyond its normal operating lifetime. Methods of the present invention make it possible to implement EDLC devices into broad applications that operate at temperatures and voltages much higher than are currently practical.
  • the invention broadly encompasses energy storage devices or systems and more specifically relates to methods of enhancing the performance of electrochemical double layer capacitors (EDLCs), or supercapacitors or ultracapacitors, and devices formed therefrom.
  • EDLCs electrochemical double layer capacitors
  • the invention relates generally to energy storage devices, such as EDLCs that use conventional ammonium based and/or phosphonium-based electrolytes and methods for treating such devices to enhance their performance and operation.
  • embodiments of the present invention provide a method for treating an EDLC to enhance its performance stability and hence increase its lifetime.
  • a method of treating an EDLC having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • methods of treating an EDLC are provided as an initial treatment.
  • the EDLC treatment is employed after initial assembly of the EDLC cell and when the EDLC is in a neutral state.
  • the EDLC once assembled has a designated positive electrode, a designated negative electrode and an electrolyte in contact with the positive electrode and the negative electrode. No voltage bias has yet been applied, and thus the EDLC is in a non-charged, neutral state.
  • a positive electrode is defined as the electrode that has a positive potential
  • a negative electrode is defined as the electrode that has a negative potential during normal operation of the EDLC.
  • positive cell voltage or “positive voltage” is defined as a positive bias that is applied to the EDLC so that the positive electrode has a positive potential and the negative electrode has a negative potential.
  • negative cell voltage or “negative voltage” is defined as a negative bias that is applied to the EDLC so that the positive electrode has a negative potential and the negative electrode has a positive potential; in this case the polarity of the positive electrode and the negative electrode is reversed.
  • a positive voltage E + is applied to the EDLC first.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is reversed by applying a negative voltage E " to the EDLC.
  • the polarity of the positive electrode and the negative electrode is reversed and a negative voltage E " is applied to the EDLC first.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is switched back by applying a positive voltage E + to the EDLC.
  • embodiments of the present invention provide a method for recovering or enhancing the performance of an EDLC that has been in operation thus extending its lifetime.
  • a method of treating an EDLC having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • methods of treating an EDLC are provided as a post treatment. In this instance, the EDLC treatment is employed after the EDLC is in a charged state and has been in operation.
  • the EDLC has been in operation for a time t and the EDLC is in a charged state at a positive nominal voltage E n , which is the rated operating voltage of the EDLC.
  • E n the rated operating voltage of the EDLC.
  • the EDLC is discharged to 0 volt first.
  • the polarity of the positive electrode and the negative electrode is reversed by applying a negative voltage E " to the EDLC.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is switched back by applying a positive voltage E + to the EDLC.
  • the polarity of the positive electrode and negative electrode is reversed periodically during operation of the EDLC.
  • the polarity is reversed at least every 100 hours during operation of the EDLC.
  • the polarity is reversed more frequently, for example, every other cycle during operation of the EDLC.
  • the EDLC has an initial capacitance and an operating capacitance, and the polarity of the positive and negative electrode is reversed before the operating capacitance reaches 80% of the initial capacitance.
  • electrochemical double layer capacitors EDLCs
  • EDLCs electrochemical double layer capacitors
  • the EDLCs are provided employing phosphonium-based electrolytes, such as phosphonium ionic liquids, salts, and compositions.
  • the EDLC employs electrolyte compositions comprised of phosphonium based cations with suitable anions.
  • electrolyte or “electrolyte solution” or “electrolyte composition” or “ionic electrolyte” or “ion conducting electrolyte” or “ion conducting composition” or “ionic composition” is used and is herein defined as any one or more of: (a) an ionic liquid, (b) a room temperature ionic liquid, (c) one or more salts dissolved in at least one solvent, and (d) one or more salts dissolved in at least one solvent together with at least one polymer to form a gel electrolyte.
  • the one or more salts are defined to include: (a) one or more salts that are a solid at a temperature of 100 °C and below, and (b) one or more salts that are a liquid at a temperature of 100 °C and below.
  • the EDLC is comprised of electrolyte compositions comprised of : one or more phosphonium ionic liquids, the one or more phosphonium ionic liquids comprising one or more phosphonium based cations of the general formula: and one or more anions, and wherein: R 1 , R 2 , R 3 and R 4 are each independently a substituent
  • R , R , R 3 and R 4 are each independently an alkyl group comprised of 1 to 6 carbon atoms, more usually 1 to 4 carbon atoms.
  • a phosphonium ionic liquid is comprised of one cation and one anion pair.
  • a phosphonium ionic liquid is comprised of one cation and multiple anions.
  • a phosphonium ionic liquid is comprised of one anion and multiple cations.
  • a phosphonium ionic liquid is comprised of multiple cations and multiple anions.
  • the EDLC is comprised of electrolyte compositions comprised of : one or more salts dissolved in a solvent, the one or more salts comprising one or more phosphonium based cations of the general formula:
  • R 1 , R 2 , R 3 and R 4 are each independently a substituent
  • R , R , R 3 and R 4 are each independently an alkyl group comprised of 1 to 6 carbon atoms, more usually 1 to 4 carbon atoms. Any one or more of the salts may be liquid or solid at a temperature of 100 °C and below.
  • a salt is comprised of one cation and one anion pair.
  • a salt is comprised of one cation and multiple anions.
  • a salt is comprised of one anion and multiple cations.
  • a salt is comprised of multiple cations and multiple anions.
  • the electrolyte is comprised of fluorine based compounds. In some embodiments, the electrolyte is comprised of a combination of phosphonium and fluorine based compounds.
  • the EDLC includes an electrolyte composition further comprising one or more conventional, non-phosphonium salts.
  • the electrolyte composition may be comprised of conventional salts, and wherein the phosphonium based ionic liquids or salts disclosed herein are additives.
  • electrolyte composition is comprised of phosphonium based ionic liquids or salts and one or more conventional salts, present at a mole (or molar) ratio in the range of 1 : 100 to 1 : 1, phosphonium based ionic liquid or salt: conventional salt.
  • the conventional salts include but are not limited to salts which are comprised of one or more cations selected from the group consisting of: tetraalkylammonium such as
  • the one or more conventional salts include but not limited to: tetraethylammonium tetrafluorborate (TEABF 4 ), triethylmethylammonium tetrafluoroborate (TEMABF 4 ), l-ethyl-3-methylimidazolium
  • EMIBF 4 tetrafluoroborate
  • E PBF 4 triethylmethylammonium trifluoromethanesulfonate
  • TEMACF3SO3 triethylmethylammonium trifluoromethanesulfonate
  • EMIIm triethylmethylammonium bis(trifluoromethanesulfonyl)imide
  • TEMAIm triethylmethylammonium bis(trifluoromethanesulfonyl)imide
  • the one or more conventional salts are lithium based salts including but not limited to: lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiC10 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesulfonate or lithium triflate (L1CF 3 SO 3 ), lithium
  • Li(CF3S0 2 ) 2 N or Lilm) bis(trifluoromethanesulfonyl)imide
  • Li(CF3S0 2 ) 2 N or Lilm bis(trifluoromethanesulfonyl)imide
  • Li(CF3CF 2 S0 2 ) 2 N or LiBETI bis(pentafluoromethanesulfonyl)imide
  • an EDLC comprising: a positive electrode, a negative electrode, a separator between said positive and negative electrode; and an electrolyte.
  • the electrolyte is comprised of an ionic liquid composition or one or more salts dissolved in a solvent, comprising: one or more phosphonium based cations of the general formula:
  • R 1 , R 2 , R 3 and R 4 are each independently a substituent group; and one or more anions.
  • the electrolyte is comprised of an ionic liquid having one or more
  • the ionic liquid composition exhibits thermodynamic stability up to 375 °C, a liquidus range greater than 400 °C, and ionic conductivity of at least 1 mS/cm, or at least 5 mS/cm, or at least 10 mS/cm at room temperature.
  • the electrolyte is comprised of one or more salts having one or more phosphonium based cations, and one or more anions dissolved in a solvent, wherein the electrolyte composition exhibits ionic conductivity of at least at least 5 mS/cm, or at least 10 mS/cm, or at least 15 mS/cm, or at least 20 mS/cm, or at least 30 mS/cm, or at least 40 mS/cm, or at least 50 mS/cm, or at least 60 mS/cm at room temperature.
  • the electrolyte composition exhibits ionic conductivity of at least at least 5 mS/cm, or at least 10 mS/cm, or at least 15 mS/cm, or at least 20 mS/cm, or at least 30 mS/cm, or at least 40 mS/cm, or at least 50 mS/cm, or at least 60 mS/cm at
  • the phosphonium electrolyte exhibits reduced flammability as compared to conventional electrolytes, and thus improves the safety of EDLC operation.
  • the phosphonium ionic liquid or salt can be used as an additive to facilitate the formation of a solid electrolyte interphase (SEI) layer or electrode stabilization layer or electrode protective layer.
  • SEI solid electrolyte interphase
  • Such electrode protective layer may be formed during the treatment of EDLC performed according to the present invention. Without being bound by any particular theory, the inventors believe that the protective layer acts to widen the electrochemical stability window, suppress EDLC degradation or decomposition reactions and hence improve EDLC lifetime or cycle life.
  • FIG. 1 is cross-sectional view of an electrochemical double layer capacitor (EDLC) according to one embodiment of the present invention
  • FIGS. 2 A and 2B are cross-sectional views of bipolar electrode and multi-cell stack structures of an EDLC according to one embodiment of the present invention
  • FIG. 3 depicts one reaction scheme to form a phosphonium ionic liquid according to some embodiments of the present invention
  • FIG. 4 depicts another reaction scheme to form other embodiments of a phosphonium ionic liquid of the present invention
  • FIG. 5 depicts another reaction scheme to form a phosphonium ionic liquid according to other embodiments of the present invention.
  • FIG. 6 depicts another reaction scheme to form a phosphonium ionic liquid according to further embodiments of the present invention.
  • FIG. 7 is a thermogravimetric analysis (TGA) graph performed on exemplary
  • FIG. 8 A depicts a reaction scheme
  • FIGS. 8B and 8C illustrate thermogravimetric analysis (TGA) and evolved gas analysis (EGA) graphs, respectively, for exemplary embodiments of phosphonium ionic liquids prepared according to Example 2;
  • FIG. 9A and 9B are graphs illustrating thermogravimetric analysis (TGA) and evolved gas analysis (EGA), respectively, for exemplary embodiments of phosphonium ionic liquids prepared according to Example 3;
  • FIG. 10A depicts a reaction scheme
  • FIG. 10B shows the 1H NMR spectrum for exemplary embodiments of phosphonium ionic liquids prepared according to Example 4;
  • FIG. 11A is a reaction scheme
  • FIG. 1 IB is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium ionic liquids prepared according to Example 5;
  • FIG. 12 is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium ionic liquids prepared according to Example 6;
  • FIG. 13 is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium ionic liquids prepared according to Example 7;
  • FIG. 14A depicts a reaction scheme
  • FIG. 14B is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium ionic liquids prepared according to Example 8;
  • FIG. 15A and FIG. 15B show the 1H and 31 P NMR spectra respectively for exemplary embodiments of phosphonium salt prepared as described in Example 9;
  • FIG. 16 is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium salt prepared according to Example 9;
  • FIG. 17A and FIG. 17B show the 1H and 31 P NMR spectra respectively for exemplary embodiments of phosphonium salt prepared as described in Example 10;
  • FIG. 18 is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium salt prepared according to Example 10;
  • FIG. 19A and FIG. 19B show the 1H and 31 P NMR spectra respectively for exemplary embodiments of phosphonium salt prepared as described in Example 11 ;
  • FIG. 20 is a graph showing thermogravimetric analysis (TGA) results for exemplary embodiments of phosphonium salt prepared according to Example 11 ;
  • FIG. 21A and FIG. 21B are graphs showing differential scanning calorimetry (DSC) results for exemplary embodiments of phosphonium ionic liquids prepared according to Example
  • FIG. 22 depicts ionic conductivity as a function of ACN/salt volume ratio for phosphonium salt (CHsCHzCHzXCHsCHzXCHs ⁇ PQCN ⁇ in acetonitrile (ACN) as described in Example 14;
  • FIG. 23 depicts ionic conductivity as a function of PC/salt volume ratio for phosphonium salt (CH 3 CH2CH2)(CH3CH2)(CH 3 )2PC(CN)3 in propylene carbonate (PC) as described in Example 15;
  • FIG. 24 depicts ionic conductivity as a function of molar concentration of phosphonium salts compared to an ammonium salt in propylene carbonate as described in Examples 41-44;
  • FIG. 25 depicts vapor pressure as a function of temperature for acetonitrile, acetonitrile with 1.0 M ammonium salt, and acetonitrile with 1.0 M phosphonium salt as described in Example 45;
  • FIG. 26 shows the impact of phosphonium salt
  • FIG. 27 shows the impact of phosphonium salt (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 PCF 3 BF 3 on ionic conductivity of 1.0 M LiPF6 in EC:DEC 1 : 1 at different temperatures from 20 to 90 °C as described in Example 51 ;
  • FIG. 28 is cross sectional view of an EDLC coin cell according to one embodiment of the present invention as described in Example 52;
  • FIG. 29 shows the charge - discharge curve for a coin cell with 1.0 M phosphonium salt - (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 CF 3 BF 3 in propylene carbonate as described in Example 52;
  • FIG. 30A is cross sectional view of an EDLC pouch cell according to one embodiment of the present invention as described in Examples 53-56;
  • FIG. 30B illustrates the fabrication process of an EDLC pouch cell according to one embodiment of the present invention as described in Examples 53-56;
  • FIG. 31A shows the charge - discharge curve for a pouch cell with 1.0 M phosphonium salt - (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 CF 3 BF 3 in propylene carbonate as described in Examples 53-56;
  • FIG. 3 IB shows the resolved electrode potential at the positive and negative carbon electrodes measured with a silver reference electrode as described in Examples 53-56;
  • FIG. 32 is exploded view of an EDLC cylindrical cell according to one embodiment of the present invention as described in Example 57;
  • FIG. 33 shows the charge - discharge curve for a cylindrical cell with 1.0 M
  • FIG. 34 shows capacitance retention at 2.7 V and 70 °C for pouch cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate as described in Examples 58-60;
  • FIG. 35 shows capacitance retention at different temperatures for pouch cells withl .O M phosphonium salt compared to an ammonium salt in propylene carbonate as described in Example 61.
  • FIG. 36 is a graph that shows capacitance retention at 3.5 V and 85 °C for pouch cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate, as described in Examples 62-64.
  • FIG. 37 is a graph that shows cell ESR stability at 3.5 V and 85 °C for pouch cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate, as described in Examples 62-64.
  • FIG. 38 is a graph that shows capacitance retention at 3.0 V and 70°C for cylindrical cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate, as described in Examples 65-68.
  • FIG. 39 is a graph that shows cell ESR stability at 3.0 V and 70°C for pouch cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate, as described in Examples 65-68.
  • FIG. 40 is a graph that shows capacitance retention at 2.5 V and 85 °C for 150 F cylindrical cells with 1.0 M phosphonium salts compared to an ammonium salt in propylene carbonate, as described in Examples 69-72.
  • FIG. 41 is a graph that shows capacitance recovery at 2.5 V and 85 °C for 150 F cylindrical cells with 1.0 M phosphonium salts in propylene carbonate as described in Example 73.
  • the invention broadly encompasses energy storage devices or systems and more specifically relates to methods of enhancing the performance of electrochemical double layer capacitors (EDLCs), or supercapacitors or ultracapacitors, and devices formed therefrom.
  • EDLCs electrochemical double layer capacitors
  • the invention relates generally to energy storage devices, such as EDLCs that use conventional ammonium based and/or phosphonium-based electrolytes and methods for treating such devices to enhance their performance and operation.
  • the present invention provides a method for treating an EDLC to enhance its performance stability and hence increase its lifetime.
  • a method of treating an EDLC having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • a method of treating an EDLC is provided as an initial treatment. In this embodiment, the EDLC treatment is employed after initial assembly of the EDLC cell and when the EDLC is in a neutral state.
  • the present invention provides a method for recovering or enhancing the performance of an EDLC that has been in operation thus extending its lifetime.
  • a method of treating an EDLC having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • a method of treating an EDLC is provided as a post treatment. In this instance, the EDLC treatment is employed after the EDLC is in a charged state and has been in operation.
  • the EDLC devices include electrolytes comprised of phosphonium ionic liquids, salts, compositions.
  • the invention further encompasses methods of making such phosphonium ionic liquids, compositions and molecules, and devices and systems comprising the same.
  • embodiments of the present invention provide devices having an electrolyte comprised of phosphonium ionic liquid compositions or one or more salts dissolved in a solvent.
  • embodiments of the present invention provide an electrochemical double layer capacitor (EDLC) comprising an electrolyte comprised of phosphonium ionic liquid compositions or one or more salts dissolved in a solvent.
  • EDLC electrochemical double layer capacitor
  • electrolyte or “electrolyte solution” or “electrolyte composition” or “ionic electrolyte” or “ion conducting electrolyte” or “ion conducting composition” or “ionic composition” is used and is herein defined as any one or more of: (a) an ionic liquid, (b) a room temperature ionic liquid, (c) one or more salts dissolved in at least one solvent, and (d) one or more salts dissolved in at least one solvent together with at least one polymer to form a gel electrolyte.
  • the one or more salts are defined to include: (a) one or more salts that are a solid at a temperature of 100 °C and below, and (b) one or more salts that are a liquid at a temperature of 100 °C and below.
  • acyl refers to an organic acid group in which the OH of the carboxyl group is replaced by some other substituent (RCO-), such as described herein as “R” substituent groups. Examples include, but are not limited to, halo, acetyl, and benzoyl.
  • alkoxy group means an -O-alkyl group, wherein alkyl is as defined herein.
  • An alkoxy group can be unsubstituted or substituted with one, two or three suitable substituents.
  • the alkyl chain of an alkoxy group is from 1 to 6 carbon atoms in length, referred to herein, for example, as "(CI - C6) alkoxy.”
  • alkyl by itself or as part of another substituent, refers to a saturated or unsaturated, branched, straight-chain or cyclic monovalent hydrocarbon radical derived by the removal of one hydrogen atom from a single carbon atom of a parent alkane, alkene or alkyne. Also included within the definition of an alkyl group are cycloalkyl groups such as C5, C6 or other rings, and heterocyclic rings with nitrogen, oxygen, sulfur or phosphorus (heterocycloalkyl). Alkyl also includes heteroalkyl, with heteroatoms of sulfur, oxygen, nitrogen, phosphorous, and silicon finding particular use in certain embodiments. Alkyl groups can be optionally substituted with R groups, independently selected at each position as described below.
  • alkyl groups include, but are not limited to, (C1-C6) alkyl groups, such as methyl, ethyl, propyl, isopropyl, 2 -methyl- 1 -propyl, 2-methyl-2 -propyl, 2 -methyl- 1 -butyl, 3- methyl-1 -butyl, 2-methyl-3 -butyl, 2, 2 -dimethyl- 1 -propyl, 2-methyl-l-pentyl, 3-methyl-l-pentyl, 4-methyl-l-pentyl, 2-methyl-2-pentyl, 3-methyl-2-pentyl, 4-methyl-2-pentyl, 2,2-dimethyl-l- butyl, 3,3-dimethyl-l-butyl, 2-ethyl-l -butyl, butyl, isobutyl, t-butyl, pentyl, isopentyl, neopentyl, and hexyl,
  • alkyl is specifically intended to include groups having any degree or level of saturation, i.e., groups having exclusively carbon-carbon single bonds, groups having one or more carbon-carbon double bonds, groups having one or more carbon-carbon triple bonds and groups having mixtures of single, double and triple carbon-carbon bonds. Where a specific level of saturation is intended, the expressions “alkanyl,” “alkenyl,” and “alkynyl” are used.
  • Alkanyl by itself or as part of another substituent, refers to a saturated branched, straight-chain or cyclic alkyl radical derived by the removal of one hydrogen atom from a single carbon atom of a parent alkane.
  • Heteroalkanyl is included as described above.
  • Alkenyl by itself or as part of another substituent, refers to an unsaturated branched, straight-chain or cyclic alkyl radical having at least one carbon-carbon double bond derived by the removal of one hydrogen atom from a single carbon atom of a parent alkene.
  • the group may be in either the cis or trans conformation about the double bond(s).
  • Suitable alkenyl groups include, but are not limited to (C2-C6) alkenyl groups, such as vinyl, allyl, butenyl, pentenyl, hexenyl, butadienyl, pentadienyl, hexadienyl, 2-ethylhexenyl, 2-propyl-2 -butenyl, 4-(2-methyl-3-butene)- pentenyl.
  • An alkenyl group can be unsubstituted or substituted with one or more independently selected R groups.
  • Alkynyl by itself or as part of another substituent, refers to an unsaturated branched, straight-chain or cyclic alkyl radical having at least one carbon-carbon triple bond derived by the removal of one hydrogen atom from a single carbon atom of a parent alkyne.
  • alkyl also included within the definition of “alkyl” is “substituted alkyl”. “Substituted” is usually designated herein as “R”, and refers to a group in which one or more hydrogen atoms are independently replaced with the same or different substituent(s).
  • R substituents can be independently selected from, but are not limited to, hydrogen, halogen, alkyl (including substituted alkyl (alkylthio, alkylamino, alkoxy, etc.), cycloalkyl, substituted cycloalkyl, cycloheteroalkyl, and substituted cycloheteroalkyl), aryl (including substituted aryl, heteroaryl or substituted heteroaryl), carbonyl, alcohol, amino, amido, nitro, ethers, esters, aldehydes, sulfonyl, sulfoxyl, carbamoyl, acyl, cyano, thiocyanato, silicon moieties, halogens, sulfur containing moieties, phosphorus containing moieties, etc.
  • R substituents include redox active moieties (ReAMs).
  • ReAMs redox active moieties
  • R and R together with the atoms to which they are bonded form a cycloalkyl (including cycloheteroalkyl) and/or cycloaryl (including cycloheteroaryl), which can also be further substituted as desired.
  • R is hydrogen when the position is unsubstituted. It should be noted that some positions may allow two or three substitution groups, R, R', and R", in which case the R, R, and R" groups may be either the same or different.
  • aryl or grammatical equivalents herein is meant an aromatic monocyclic or polycyclic hydrocarbon moiety generally containing 5 to 14 carbon atoms (although larger polycyclic rings structures may be made) and any carbocyclic ketone, imine, or thioketone derivative thereof, wherein the carbon atom with the free valence is a member of an aromatic ring.
  • Aromatic groups include arylene groups and aromatic groups with more than two atoms removed. For the purposes of this application aryl includes heteroaryl.
  • Heteroaryl means an aromatic group wherein 1 to 5 of the indicated carbon atoms are replaced by a heteroatom chosen from nitrogen, oxygen, sulfur, phosphorus, boron and silicon wherein the atom with the free valence is a member of an aromatic ring, and any heterocyclic ketone and thioketone derivative thereof.
  • heterocycle includes both single ring and multiple ring systems, e.g. thienyl, furyl, pyrrolyl, pyrimidinyl, indolyl, purinyl, quinolyl, isoquinolyl, thiazolyl, imidazolyl, naphthalene, phenanthroline, etc.
  • aryl is substituted aryl, with one or more substitution groups "R" as defined herein and outlined above and herein.
  • substitution groups "R” as defined herein and outlined above and herein.
  • perfluoroaryl refers to an aryl group where every hydrogen atom is replaced with a fluorine atom.
  • oxalyl is also included within the definition of aryl.
  • halogen refers to one of the electronegative elements of group VIIA of the periodic table (fluorine, chlorine, bromine, iodine, and astatine).
  • nitro refers to the -N0 2 group.
  • amino groups or grammatical equivalents herein is meant -NH2, -NHR and -NRR groups, with R and R independently being as defined herein.
  • pyridyl refers to an aryl group where one CH unit is replaced with a nitrogen atom.
  • cyano refers to the -CN group.
  • thiocyanato refers to the -SCN group.
  • sulfoxyl refers to a group of composition RS(O)- where R is a substitution group as defined herein, including alkyl, (cycloalkyl, perfluoroalkyl, etc.), or aryl (e.g., perfluoroaryl group). Examples include, but are not limited to methylsulfoxyl, phenylsulfoxyl, etc.
  • sulfonyl refers to a group of composition RS02- where R is a substituent group, as defined herein, with alkyl, aryl, (including cycloalkyl, perfluoroalkyl, or perfluoroaryl groups). Examples include, but are not limited to methylsulfonyl, phenylsulfonyl, p- toluenesulfonyl, etc.
  • carbamoyl refers to the group of composition R(R')NC(0)- where R and R' are as defined herein, examples include, but are not limited to N-ethylcarbamoyl, N,N- dimethylcarbamoyl, etc.
  • amido refers to the group of composition R 1 CONR 2 - where Ri and R 2 are substituents as defined herein. Examples include, but are not limited to acetamido, N- ethylbenzamido, etc.
  • a metal when a metal is designated, e.g., by "M” or “M n ", where n is an integer, it is recognized that the metal can be associated with a counter ion.
  • aryloxy group means an -O-aryl group, wherein aryl is as defined herein.
  • An aryloxy group can be unsubstituted or substituted with one or two suitable substituents.
  • the aryl ring of an aryloxy group is a monocyclic ring, wherein the ring comprises 6 carbon atoms, referred to herein as "(C6) aryloxy.”
  • benzyl means -CH2 -phenyl.
  • carbonyl is a divalent group of the formula -C(O)-.
  • electrochemical cell consists minimally of a working electrode, a counter electrode, and an electrolyte between the two electrodes.
  • An EDLC cell is a particular case of electrochemical cells.
  • electrode refers to any medium capable of transporting and storing charge.
  • Preferred electrodes are selected from the group consisting of carbon blacks, graphite, graphene; carbon-metal composites; polyaniline, polypyrrole, polythiophene; oxides, chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphides, or selenides of lithium, ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum, tungsten, or vanadium, and combinations thereof.
  • the electrodes can be manufactured to virtually any 2-dimensional or 3-dimensional shape.
  • positive electrode refers to the electrode in an EDLC cell that has a positive or plus potential
  • negative electrode refers to the electrode in an EDLC cell that has a negative or minus potential
  • positive cell voltage or “positive voltage” refers to a positive bias that is applied to the EDLC so that the positive electrode has a positive potential and the negative electrode has a negative potential.
  • negative cell voltage or “negative voltage” refers to a negative bias that is applied to the EDLC so that the positive electrode has a negative potential and the negative electrode has a positive potential; in this case the polarity of the positive electrode and the negative electrode is reversed.
  • linker is a molecule used to couple two different molecules, two subunits of a molecule, or a molecule to a substrate.
  • R groups include, but are not limited to, hydrogen, alkyl, alcohol, aryl, amino, amido, nitro, ethers, esters, aldehydes, sulfonyl, silicon moieties, halogens, cyano, acyl, sulfur containing moieties, phosphorus containing moieties, Sb, imido, carbamoyl, linkers, attachment moieties, ReAMs and other subunits. It should be noted that some positions may allow two substitution groups, R and R, in which case the R and R groups may be either the same or different, and it is generally preferred that one of the substitution groups be hydrogen.
  • An electrochemical double layer capacitor is basically the same as a battery in terms of general design, the difference being that the nature of charge storage in the electrode active material is capacitive; i.e., the charge and discharge processes involve only the movement of electronic charge through the solid electronic phase and ionic movement through the electrolyte solution phase. Compared to batteries, higher power densities and longer cycle life can be achieved because no rate-determining and life-limiting phase transformations take place at the electrode/electrolyte interface in an EDLC device.
  • the dominant EDLC technology has been based on double-layer type charging at high surface area carbon electrodes, where a capacitor is formed at the carbon/electrolyte interface by electronic charging of the carbon surface with counter-ions in the solution phase migrating to the carbon surface in order to counterbalance that charge.
  • Another technology is based on pseudocapacitance type charging at electrodes of conducting polymers and certain metal oxides.
  • Conducting polymers have been investigated for use in EDLCs. Higher energy densities can be achieved because charging occurs through the volume of the active polymer material rather than just at the outer surface.
  • Metal oxides also have been investigated for use in EDLCs. Charging in such active material has been reported to take place through the volume of the material and, as a result, the charge and energy densities observed are comparable with, or even higher than, those obtained for conducting polymers.
  • an EDLC device comprises a single cell.
  • FIG. 1 there is shown a schematic cross-sectional view of a single-cell EDLC 10, which includes a pair of electrodes 12, 12' bonded to current collector plates 14, 14', a separator film or membrane 16 sandwiched between the two electrodes, and an electrolyte solution 18 (not shown) which permeates and fills the pores of the separator and one or more of the electrodes.
  • the capacitor electrode can be fabricated into a bipolar arrangement 20 where two electrodes 22, 24 are attached on both sides of a "bipolar" current collector 26.
  • Multi-cell EDLCs can be fabricated by arranging a number of single cells into a bipolar stack in order to provide needed higher voltage (and power).
  • An exemplary multi-cell EDLC 30 is shown in FIG. 2B where the bipolar stack consists of four unit cells from 32 to 38. Each cell has a structure the same as that of the single cell 10 in FIG. 1.
  • each cell is separated from its neighboring cell with a single current collector plate that also acts as an ionic barrier between cells.
  • Such a design optimizes the current path through the cell, reduces ohmic losses between cells, and minimizes the weight of packaging due to current collection. The result is an efficient capacitor with higher energy and power densities.
  • the EDLCs are formed with electrode/separator/electrode assembly in planar or flat structures. In other embodiments, the EDLCs are formed with electrode/separator/electrode assembly in wound spiral structures such as cylindrical and prismatic structures.
  • the electrodes are made from high surface area micro- or nano- particles of active materials, which are held together by a binder material to form a porous structure.
  • active materials can be fabricated in other forms such as fibers, woven fibers, felts, foams, cloth, arogels, and mesobeads.
  • the active materials include but are not limited to: carbons such as carbon blacks, graphite, graphene; carbon-metal composites; conducting polymers such as polyaniline, polypyrrole, polythiophene; oxides, chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphides, or selenides of lithium, ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum, tungsten or vanadium, and combinations thereof.
  • carbons such as carbon blacks, graphite, graphene
  • carbon-metal composites such as conducting polymers such as polyaniline, polypyrrole, polythiophene
  • oxides chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphides, or selenides of lithium, ruthenium, tantalum
  • the electrode binder materials are selected from but not limited to one or more of the following: polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyacrylate, acrylate-type copolymer (ACM), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyamide, polyimide, polyurethane, polyvinyl ether (PVE), or combinations thereof.
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • SBR styrene-butadiene rubber
  • PAN polyacrylonitrile
  • ACM acrylate-type copolymer
  • CMC carboxymethyl cellulose
  • PAA polyacrylic acid
  • PVE polyamide
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • SBR st
  • the separator materials are selected from but not limited to one or more of the following: films or membranes of micro porous polyolefm such as polyethylene (PE) and polypropylene (PP), polyvinylidene fluoride (PVdF), PVdF coated polyolefm,
  • films or membranes of micro porous polyolefm such as polyethylene (PE) and polypropylene (PP), polyvinylidene fluoride (PVdF), PVdF coated polyolefm
  • PTFE polytetrafluoroethylene
  • polyvinyl chloride polyvinyl chloride
  • resorcinol formaldehyde polymer cellulose paper
  • non- woven polystyrene cloth acrylic resin fibers
  • non- woven polyester film non- woven polyester film
  • polycarbonate membrane polycarbonate membrane
  • fiberglass paper or combinations thereof.
  • the EDLCs are provided employing conventional ammonium based electrolytes. In other embodiments, the EDLCs are provided employing phosphonium- based electrolytes, such as phosphonium ionic liquids, salts, and compositions. In some embodiments, the electrolyte is comprised of fluorine based compounds. In some embodiments, the electrolyte is comprised of a combination of phosphonium and fluorine based compounds.
  • the electrolyte is comprised of an ionic liquid composition or one or more ionic liquids or salts dissolved in a solvent, comprising: one or more phosphonium based cations of the general formula:
  • R 1 , R 2 , R 3 and R 4 are each independently a substituent group, such as but not limited to an alkyl group as described below.
  • R 1 , R 2 , R 3 and R 4 are each independently an alkyl group comprised of 1 to 6 carbon atoms, more usually 1 to 4 carbon atoms.
  • Any one or more of the salts may be liquid or solid at a temperature of 100 °C and below.
  • a salt is comprised of one cation and one anion pair.
  • a salt is comprised of one cation and multiple anions.
  • a salt is comprised of one anion and multiple cations.
  • a salt is comprised of multiple cations and multiple anions.
  • the electrolyte is comprised of an ionic liquid having one or more phosphonium based cations, and one or more anions, wherein the ionic liquid composition exhibits thermodynamic stability up to 375 °C, a liquidus range greater than 400 °C, and ionic conductivity of at least 1 mS/cm, or at least 5 mS/cm, or at least 10 mS/cm at room temperature.
  • the electrolyte is comprised of one or more salts having one or more phosphonium based cations, and one or more anions dissolved in a solvent, wherein the electrolyte composition exhibits ionic conductivity of at least at least 5 mS/cm, or at least 10 mS/cm, or at least 15 mS/cm, or at least 20 mS/cm, or at least 30 mS/cm, or at least 40 mS/cm, or at least 50 mS/cm, or at least 60 mS/cm at room temperature.
  • the electrolyte composition further comprises one or more conventional, non-phosphonium salts.
  • the electrolyte composition may be comprised of conventional salts, and wherein the phosphonium based ionic liquids or salts disclosed herein are additives.
  • electrolyte composition is comprised of phosphonium based ionic liquids or salts and one or more conventional salts, present at a mole (or molar) ratio in the range of 1 : 100 to 1 : 1, phosphonium based ionic liquid or salt: conventional salt.
  • the conventional salts include but are not limited to salts which are comprised of one or more cations selected from the group consisting of: tetraalkylammonium such as
  • the one or more conventional salts include but not limited to: tetraethylammonium tetrafluorborate (TEABF 4 ), triethylmethylammonium tetrafluoroborate (TEMABF 4 ), l-ethyl-3-methylimidazolium
  • EMIBF 4 tetrafluoroborate
  • EMPF 4 triethylm.ethylamm.omum. trifluoromethanesuifonate
  • TEM ACF 3 S0 3 1 -ethyl-3- methylimidazolium bis(trifluoromethanesulfonyl)imide
  • EMIIm triethylmethylammonium bis(trifluoromethanesulfonyl)imide
  • TEM Aim 1 -ethyl-3-methylimidazolium
  • the one or more conventional salts are lithium based salts including but not limited to: lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (L1BF 4 ), lithium perchlorate (LiC10 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesuifonate or lithium triflate (LiCF 3 S0 3 ), lithium
  • Li(CF3CF 2 S0 2 ) 2 N or LiBETI bis(pentafluoromethanesulfonyl)imide
  • the electrolyte composition is further comprised of, but not limited to one or more of the following solvents: acetonitrile, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) or methyl ethyl carbonate (MEC), methyl propionate (MP), fluoroethylene carbonate (FEC), fluorobenzene (FB), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), phenylethylene carbonate (PhEC), propylmethyl carbonate (PMC), diethoxyethane (DEE), dimethoxyethane (DME), tetrahydrofuran (THF), ⁇ -butyrolactone (GBL), and ⁇ -valerolactone (GVL).
  • solvents acetonitrile, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate
  • the phosphonium electrolyte composition disclosed herein is in contact with the separator and the porous electrodes and may be applied onto the porous electrodes and separator prior to the cell assembly by any suitable means, such as by soaking, spray, screen printing, and the like.
  • the phosphonium electrolyte composition disclosed herein may be applied onto the porous electrodes and separator after the cell assembly by any suitable means, such as by using a vacuum injection apparatus.
  • the phosphonium electrolyte composition disclosed herein may be formed into a polymer gel electrolyte film or membrane. Alternatively, the polymer gel electrolyte may be applied onto the electrodes directly.
  • both of such free-standing gel electrolyte films or gel electrolyte coated electrodes are particularly suitable for high volume and high throughput manufacturing process, such as roll-to-roll winding process.
  • Another advantage of such electrolyte film can function not only as the electrolyte but also as a separator.
  • Such electrolyte films may also be used as an electrolyte delivery vehicle to precisely control the amount and distribution of the electrolyte solution thus improving cell assembly consistency and increasing product yield.
  • the electrolyte film is comprised of a membrane as described in co-pending Patent Application Serial No. 12/027,924 filed on February 7, 2008, the entire disclosure of which is hereby incorporated by reference.
  • the current collectors are selected from but not limited to one or more of the following: plates or foils or films of aluminum, carbon coated aluminum, stainless steel, carbon coated stainless steel, gold, platinum, silver, highly conductive metal or carbon doped plastics, or combinations thereof.
  • both electrodes 12, 12' of a single-cell EDLC 10 can be fabricated with the same type of active material, to provide a symmetric electrode configuration.
  • an EDLC may have an asymmetric electrode configuration, in which each electrode is formed of a different type of active material.
  • a symmetric EDLC the preferred embodiment, is easier to fabricate than an asymmetric EDLC.
  • the symmetric EDLC also allows the polarity of the two electrodes to be reversed, a possible advantage for continuous high performance during long-term charge cycling.
  • an asymmetric EDLC may be selected where the choice of electrode material is determined by cost and performance.
  • an EDLC device comprises a pair of porous electrodes made of activated carbon bonded to aluminum current collectors, a NK cellulose separator sandwiched between the two electrodes, and a phosphonium electrolyte disclosed herein which permeates and fills the pores of the separator and the electrodes.
  • an EDLC is made as a stack of cell components. Electrode active materials of activated carbon particles and binders are adhered to one side of a current collector to form a single-sided electrode or on both sides of a "bipolar" current collector to form a bipolar or double-sided electrode as illustrated in FIGS. 2A and 2B.
  • a multi-cell stack is made by positioning a first NK cellulose separator on top of the a first single-sided electrode, a first bipolar electrode on top of the first separator, a second separator on top of the first bipolar electrode, a second bipolar electrode on top of the second separator, a third separator on top of the second bipolar electrode, a third bipolar electrode on top of the third separator, a fourth separator on top of the third bipolar electrode, and a second single-sided electrode on top of the fourth separator to form a 4-cell stack.
  • An EDLC that includes many more cells can be made first forming muti-cell modules as described above. The modules are then stacked one on top of another until a desired number of modules has been reached.
  • the electrode/separator/electrode assembly is sealed partially around the edges. A sufficient amount of a phosphonium electrolyte disclosed herein is added to the assembly to fill the pores of the separator and the electrodes before the edges are sealed completely.
  • a spiral-wound EDLC is formed. Electrode active materials of activated carbon particles and binders are adhered to both sides of a current collector to form a double-sided electrode similar to the structure as illustrated in FIGS. 2A and 2B.
  • An electrode/separator stack or assembly is made by positioning a first electrode on top of a first Celgard® polypropylene/polyethylene separator, a second separator on top of the first r electrode, and a second electrode on top of the second separator. The stack is wound into a tight cell core of either a round spiral to form a cylindrical structure or a flattened spiral to form a prismatic structure. The stack is then either partially sealed at the edges or placed into a can. A sufficient amount of any of the electrolytes described herein is added to the pores of the separator and the electrodes of the stack before final sealing.
  • an EDLC device may be built using the
  • the conducting polymer may be chosen from any of the classes of conducting organic materials, including polyanilines, polypyrroles, and polythiophenes. Of particular interest are polythiophenes such as poly(3-(4-fluorophenyl)thiophene) (PFPT), which are known to have good stability to electrochemical cycling, and can be processed readily.
  • PFPT poly(3-(4-fluorophenyl)thiophene)
  • an EDLC device may be built using the phosphonium electrolyte composition disclosed herein, a cathode (positive electrode) made of high surface area activated carbon and an anode (negative electrode) made of lithium ion intercalated graphite.
  • the EDLC formed is an asymmetric hybrid capacitor, called lithium ion capacitor (LIC).
  • ESR cell equivalent series resistance
  • a phosphonium electrolyte composition disclosed herein replaces a conventional electrolyte or when a phosphonium salt is used as an additive with a conventional electrolyte, the ionic conductivity is significantly increased; and the performance stability of the EDLC device is greatly improved, as can be seen in the Examples below.
  • the phosphonium ionic liquid [00128] In another exemplary embodiment, the phosphonium ionic liquid
  • the phosphonium ionic liquid [00129] In another exemplary embodiment, the phosphonium ionic liquid
  • various phosphonium salts are dissolved in acetonitrile (ACN) solvent at 1.0 M concentration.
  • ACN acetonitrile
  • the resulting electrolytes exhibit ionic conductivity at room temperature greater than about 28 mS/cm, or greater than about 34 mS/cm, or greater than about 41 mS/cm, or greater than about 55 mS/cm, or greater than about 61 mS/cm.
  • a phosphonium salt (CH 3 CH 2 CH2)(CH 3 CH2)(CH 3 ) 2 PC(CN)3 is added at 10 w%.
  • the ionic conductivity of the electrolyte is increased by 109% at -30 °C, and about 25% at +20 °C and +60 °C with the addition of the phosphonium additive.
  • ionic conductivity of the conventional electrolyte solution increased by at least 25% as a result of the phosphonium additive.
  • a conventional electrolyte solution of 1.0 M LiPF 6 in a mixed solvent of EC (ethylene carbonate), DEC (diethyl carbonate) and EMC 1.0 M LiPF 6 in a mixed solvent of EC (ethylene carbonate), DEC (diethyl carbonate) and EMC
  • a phosphonium salt (CHsCHzCHzXCHsCHzXCHs ⁇ PCFsBFs is added at 10 w%.
  • the ionic conductivity of the electrolyte is increased by 36% at 20 °C, 26% at 60° C, and 38% at 90 °C with the addition of the phosphonium additive.
  • ionic conductivity of the conventional electrolyte solution is increased by at least 25%> as a result of the phosphonium additive.
  • the separator is the largest single source of cell ESR. Therefore a suitable separator needs to have high ionic conductivity when soaked with electrolyte and has minimum thickness.
  • the separator is less than about 100 ⁇ thick. In another embodiment, the separator is less than about 50 ⁇ thick. In another embodiment, the separator is less than about 30 ⁇ thick. In yet another embodiment, the separator is less than about 10 ⁇ thick.
  • novel phosphonium electrolyte compositions either as replacements or using phosphonium salts as additives in conventional electrolytes, disclosed herein is that they exhibit wider electrochemical voltage stability window compared to the conventional electrolytes.
  • various phosphonium salts are dissolved in acetonitrile (ACN) solvent to form electrolyte solutions at 1.0 M concentration.
  • ACN acetonitrile
  • the electrochemical voltage window is determined in cells with a Pt working electrode and a Pt counter electrode and an Ag/Ag+ reference electrode.
  • the stable voltage window is between about - 3.0 V and +2.4 V.
  • the voltage window is between about -3.2 V and +2.4 V.
  • the voltage window is between about -2.4 V and +2.5 V.
  • the voltage window is between about -1.9 V and +3.0 V.
  • single-cell EDLCs are comprised of two carbon electrodes, a cellulose separator sandwiched between the two electrodes, and an electrolyte solution of various phosphonium salts dissolved in a solvent of propylene carbonate (PC) at 1.0 M concentration.
  • the EDLC can be charged and discharged from 0 V to 3.9 V.
  • the EDLC can be charged and discharged from 0 V to 3.6 V.
  • the EDLC can be charged and discharged from 0 V to 3.3 V.
  • the EDLC can be operated between - 3.9 V and +3.9 V, or between -3.6 V and +3.6 V, or between -3.3 V to +3.3 V.
  • phosphonium electrolyte compositions disclosed herein either as replacements or using phosphonium salts as additives in a conventional electrolyte of an EDLC is that they exhibit reduced vapor pressure and therefore flammability as compared to conventional electrolytes, and thus improve the safety of EDLC operation.
  • conventional electrolytes which contain conventional, non- phosphonium salts
  • the phosphonium salt and the conventional salt are present in the electrolyte at a mole ratio in the range of 1/100 to 1/1, phosphonium salt/conventional salt.
  • salts include, but are not limited to: tetraethylammonium tetrafluorborate (TEABF 4 ), triethylmethylammonium tetrafluoroborate (TEMABF 4 ), triethyimethylammonium trifluoromethanesulfonate (TEMACF3SO3), l-ethyl-3- methylimidazolium tetrafluoroborate (EMIBF 4 ), l-ethyl-3-methylimidazolium
  • EMIPFe hexafluorophosphate
  • an electrolyte was formed by dissolving phosphonium salt- in a solvent of acetonitrile (ACN) to 1.0 M concentration.
  • ACN acetonitrile
  • the vapor pressure of ACN was lowered by about 39% at 25 °C, and by 38% at 105 °C.
  • the significant suppression in vapor pressure by phosphonium salt is an advantage in reducing the flammability of the electrolyte solution, thus improving the safety of device operation.
  • the phosphonium salt (CHsCF ⁇ CF ⁇ XCHsCF ⁇ XCHsXPQCNX was added to the standard electrolyte solution at 20 w%.
  • the fire self-extinguishing time was reduced by 53% with the addition of the phosphonium additive to the conventional electrolyte. This is an indication that the safety and reliability of energy storage devices can be substantially improved by using the phosphonium salt as an additive in the conventional electrolytes.
  • a further important advantage of the EDLCs formed according to the present invention compared to the prior art is their wide temperature range.
  • the EDLCs made with the novel phosphonium electrolytes disclosed herein can be operated in a temperature range between about -50°C and +120°C, or between about -40 °C and +105 °C, or between -20 °C and +85 °C, or between -10 °C and +65 °C.
  • the EDLCs are designed to operate at different voltage and temperature combinations.
  • the EDLC can be operated at 2.5 V and 120 °C.
  • the EDLC can be operated or at 2.7 V and 105 °C.
  • the EDLC can be operated or at 2.8 V and 85 °C.
  • the EDLC can be operated at 3.0 V and 70 °C.
  • the EDLC can be operated at 3.5 V at 60 °C.
  • EDLCs of higher operating voltage thus higher energy density, higher operating temperature, and longer lifetime are needed.
  • Some embodiments of the present invention provide methods for treating an EDLC device after initial assembly to increase its operating voltage, operating temperature and lifetime. Other embodiments of the present invention provide a method for recovering or enhancing the performance of an EDLC that has been in operation thus extending its usage beyond its normal operating lifetime. Methods of the present invention make it possible to implement EDLC devices into broad applications that operate at temperatures and voltages much higher than are currently practical.
  • embodiments of the present invention provide a method for treating an EDLC to enhance its performance stability and hence increase its lifetime.
  • a method of treating an EDLC having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • methods of treating an EDLC are provided as an initial treatment.
  • the EDLC treatment is employed after initial assembly of the EDLC cell and when the EDLC is in a neutral state.
  • the EDLC once assembled has a designated positive electrode, a designated negative electrode and an electrolyte in contact with the positive electrode and the negative electrode. No voltage bias has yet been applied, and thus the EDLC is in a non-charged, neutral state.
  • a positive electrode is defined as the electrode that has a positive potential
  • a negative electrode is defined as the electrode that has a negative potential during normal operation of the EDLC.
  • positive cell voltage or “positive voltage” is defined as a positive bias that is applied to the EDLC so that the positive electrode has a positive potential and the negative electrode has a negative potential.
  • negative cell voltage or “negative voltage” is defined as a negative bias that is applied to the EDLC so that the positive electrode has a negative potential and the negative electrode has a positive potential; in this case the polarity of the positive electrode and the negative electrode is reversed.
  • a positive voltage E + is applied to the EDLC first.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is reversed by applying a negative voltage E " to the EDLC.
  • the polarity of the positive electrode and the negative electrode is reversed and a negative voltage E " is applied to the EDLC first.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is switched back by applying a positive voltage E + to the EDLC.
  • the EDLC has a nominal voltage E n .
  • the nominal voltage is the rated voltage, generally defined as the typical operating voltage of the EDLC. In some embodiments, the nominal voltage is in the range of about 2.5 to 3.5 V.
  • the initial treatment is performed by applying the positive voltage at a value 0.05 to 0.20 V more positive than the nominal voltage of the EDLC.
  • , where ⁇ -0.8 to + 0.2 V and
  • the initial treatment is performed by applying the negative voltage which absolute value is 0.05 to 0.80 V lower than the nominal voltage of the EDLC.
  • the positive voltage is applied to the EDLC at a constant voltage E + for a time t + in the range of about 1 to 16 hours.
  • the negative voltage is applied to the EDLC at a constant voltage E " for a time f in the range of about 0.25 to 4 hours.
  • voltage may be applied at a constant rate.
  • the voltage may be applied by ramping over time.
  • the voltage may be applied in a pulse-like manner.
  • the positive voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E + at a ramping rate in the range of 1 to 10 mV/s.
  • the negative voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E " at a ramping rate in the range of 1 to 10 mV/s.
  • the sequence by which voltage is applied may be selected.
  • the positive voltage treatment is applied first and then followed by the negative voltage treatment.
  • the negative voltage treatment is applied first and then followed by the positive voltage treatment.
  • a method of treating an electrochemical double layer capacitor (EDLC) having a positive electrode, a negative electrode, and an electrolyte in contact with the positive electrode and the negative electrode is provided.
  • a treatment voltage El is applied to the EDLC.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is reversed by applying a reversed polarity voltage E2 to the EDLC.
  • the treatment voltage El is a positive voltage E + and the reversed polarity voltage E2 is a negative voltage E " .
  • the treatment voltage El is a negative voltage E " and the reversed polarity voltage E2 is a positive voltage E + .
  • the initial treatment is performed by applying the positive voltage at a value 0.05 to 0.20 V more positive than the nominal voltage of the EDLC.
  • , where ⁇ -0.8 to + 0.2 V and
  • the initial treatment is performed by applying the negative voltage which absolute value is 0.05 to 0.80 V lower than the nominal voltage of the EDLC.
  • the positive voltage is applied to the EDLC at a constant voltage E + for a time t + in the range of about 1 to 16 hours.
  • the negative voltage is applied to the EDLC at a constant voltage E " for a time t " in the range of about 0.25 to 4 hours.
  • the positive voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E + at a ramping rate in the range of 1 to 10 mV/s.
  • the negative voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E " at a ramping rate in the range of 1 to lO mV/s.
  • embodiments of the present invention provide a method for recovering or enhancing the performance of an EDLC that has been in operation for a time ⁇ .
  • a "post treatment” is applied, meaning that the EDLC is treated according to the present invention after the EDLC is in a charged state and has been in operation.
  • a method of treating an EDLC cell having a positive electrode and a negative electrode and an electrolyte in contact with the electrodes is provided, characterized in that: the polarity of the positive electrode and the negative electrode is reversed.
  • the polarity of the electrodes is simply switched without changing the absolute value of the cell voltage.
  • the value of the cell voltage is changed by the post treatment.
  • the EDLC has been in operation for a time ⁇ and the EDLC is in a positive voltage state at its nominal voltage E n , which is the rated operating voltage of the EDLC.
  • E n nominal voltage of the EDLC.
  • the EDLC is discharged to 0 volt first.
  • the polarity of the positive electrode and the negative electrode is reversed by applying a negative voltage E " to the EDLC.
  • the EDLC is discharged to 0 volt.
  • the polarity of the positive electrode and the negative electrode is switched back by applying a positive voltage E + to the EDLC.
  • the initial treatment is performed by applying the positive voltage at a value 0.05 to 0.20 V more positive than the nominal voltage of the EDLC.
  • , where ⁇ -0.8 to + 0.2 V and
  • the initial treatment is performed by applying the negative voltage which absolute value is 0.05 to 0.80 V lower than the nominal voltage of the EDLC.
  • the post treatment voltages may be applied in a variety of ways.
  • the negative voltage is applied to the EDLC at a constant voltage E " for a time f in the range of about 0.1 to 2.0 hours; and the positive voltage is applied to the EDLC at a constant voltage E + for a time t + is in the range of about 0.1 to 2.0 hours.
  • the negative voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E " at a ramping rate in the range of 1 to 10 mV/s; and the positive voltage is applied to the EDLC by ramping the voltage from 0 volt to a final voltage E + at a ramping rate in the range of 1 to 10 mV/s.
  • Post treatment may be applied at any desired time in order to recover performance of the EDLC.
  • the negative voltage treatment and the positive voltage treatment are applied after the EDLC is in operation for time ⁇ .
  • the EDLC has an initial capacitance and an operating capacitance. Over time, the operating capacitance declines in relation to the initial capacitance of the EDLC.
  • time ⁇ is defined with respect to the value of the operation capacitance as a percentage of the initial capacitance. In one example, time ⁇ is defined to be the time at which the operating capacitance of the EDLC cell reaches 80% of the initial capacitance. Time ⁇ can be any other desired value, and 80% is disclosed solely as one exemplary value. In some embodiments and the polarity of the positive and negative electrode is reversed when the operating capacitance of the EDLC reaches x percent of the initial capacitance, where x is: x ⁇ 80%. In another embodiment, time ⁇ is defined as a desired number of hours. For example, in some embodiments ⁇ is in the range of 50 - 2000 hours.
  • the post treatment may be performed on the EDLC multiple times in order to provide continued performance recovery.
  • the polarity of the positive electrode and the negative electrode may be reversed periodically during operation of the EDLC cell.
  • the steps of the negative voltage treatment and the positive voltage treatment are repeated n times, where n is an integer.
  • the polarity is reversed at least every 200 hours during operation of the EDLC cell.
  • the polarity is reversed at least every 100 hours during operation of the EDLC cell.
  • the polarity is reversed at least every 50 hours during operation of the EDLC cell.
  • the polarity is reversed more frequently, for example, every other cycle during operation of the EDLC.
  • the above approaches to energy storage may be combined with batteries to form a capacitor-battery hybrid energy storage system comprising an array of batteries and EDLCs.
  • embodiments of the EDLC devices provided by the present invention employ one or more electrolytes or electrolyte compositions.
  • the electrolyte is comprised of conventional ammonium based compositions.
  • the electrolyte is comprised of fluorine based compounds.
  • the electrolyte composition is comprised of one or more phosphonium salts and one or more ammonium salts dissolved in a solvent.
  • the electrolyte is comprised of phosphonium-based ionic liquids, salts, and compositions.
  • the electrolyte is comprised of a combination of phosphonium and fluorine based compounds. In some embodiments, such electrolytes are found to exhibit desirable properties and in particular a combination of at least two or more of: high thermodynamic stability, low volatility, wide liquidus range, high ionic conductivity, and wide electrochemical stability window.
  • EDLCs having electrolytes comprised of phosphonium-based ionic liquids of the present invention comprise phosphonium cations of selected molecular weights and substitution patterns, coupled with selected anion(s), to form ionic liquids with tunable combinations of thermodynamic stability, ionic conductivity, liquidus range, and low volatility properties.
  • ionic liquid herein is meant a salt that is in the liquid state at and below 100 °C.
  • Room temperature ionic liquid is further defined herein in that it is in the liquid state at and below room temperature.
  • electrolyte or “electrolyte solution” or “electrolyte composition” or “ionic electrolyte” or “ion conducting electrolyte” or “ion conducting electrolyte” or “ion conducting electrolyte” or “ion conducting
  • composition or "ionic composition” is used and is herein defined as any one or more of: (a) an ionic liquid, (b) a room temperature ionic liquid, (c) one or more salts dissolved in at least one solvent, and (d) one or more salts dissolved in at least one solvent together with at least one polymer to form a gel electrolyte. Additionally, the one or more salts are defined to include: (a) one or more salts that are a solid at a temperature of 100 °C and below, and (b) one or more salts that are a liquid at a temperature of 100 °C and below.
  • EDLCs are provided having electrolytes comprised of phosphonium ionic liquids and phosphonium electrolytes that exhibit thermodynamic stability up to temperatures of approximately 400 °C, and more usually up to temperatures of approximately 375 °C. Exhibiting thermal stability up to a temperature this high is a significant development, and allows use of the phosphonium ionic liquids of the present invention in a wide range of applications.
  • Embodiments of phosphonium ionic liquids and phosphonium electrolytes of the present invention further exhibit ionic conductivity of at least of at least 1 mS/cm, or at least 5 mS/cm, or at least 10 mS/cm, or at least 15 mS/cm, or at least 20 mS/cm, or at least 30 mS/cm, or at least 40 mS/cm, or at least 50 mS/cm, or at least 60 mS/cm at room temperature.
  • Embodiments of phosphonium ionic liquids and phosphonium electrolytes of the present invention exhibit volatilities that are about 20 % lower compared to their nitrogen-based analogs.
  • EDLCs having electrolytes comprised of phosphonium ionic liquids and phosphonium electrolytes are comprised of cations having molecular weight of up to 500 Daltons.
  • phosphonium ionic liquids and phosphonium electrolytes are comprised of cations having molecular weight in the range of 200 to 500 Daltons for ionic liquids at the lower thermal stability ranges.
  • EDLCs having electrolytes comprised of phosphonium-based ionic liquids of the present invention are comprised of phosphonium based cations of the general formula: wherein: R 1 , R 2 , R 3 and R 4 are each independently a substituent group. In some embodiments, wherein the cations are comprises of open chains.
  • R R in an aromatic, heterocyclic moiety.
  • R or R are comprised of phenyl or substituted alkylphenyl.
  • R and R are the same and are comprised of tetramethylene (phospholane) or
  • R and R are the same and are comprised of
  • R and R are the same and are comprised of
  • R , R and R are the same and are comprised of phospholane, phosphorinane or phosphole.
  • At least one, more, of or all of R 1 , R 2 , R 3 and R 4 are selected such that each does not contain functional groups that would react with the redox active molecules
  • R , R , R and R 4 do not contain halides, metals or O, N, P, or Sb.
  • the alkyl group comprises from 1 to 7 carbon atoms. In other embodiments the total carbon atoms from all alkyl groups is 12 or less. In yet other
  • the alkyl groups are each independently comprised of 1 to 6 carbon atoms, more typically, from 1 to 5 carbon atoms.
  • EDLCs having electrolytes comprised of phosphonium-based electrolytes of the present invention are comprised of: one or more salts dissolved in a solvent, the one or more salts comprising one or more phosphonium based cations of the general formula: and one or more anions, and wherein: R 1 , R 2 , R 3 and R 4 are each independently a substituent
  • R , R , R 3 and R 4 are each independently an alkyl group comprised of 1 to 6 carbon atoms, more usually 1 to 4 carbon atoms.
  • one or more of the hydrogen atoms in one or more of the R groups are substituted by fluorine.
  • Any one or more of the salts may be liquid or solid at a temperature of 100 °C and below.
  • a salt is comprised of one cation and one anion.
  • a salt is comprised of one cation and multiple anions.
  • a salt is comprised of one anion and multiple cations.
  • a salt is comprised of multiple cations and multiple anions.
  • suitable solvents include, but are not limited to, one or more of the following: acetonitrile, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) or methyl ethyl carbonate (MEC), methyl propionate (MP), , fluoroethylene carbonate (FEC), fluorobenzene (FB), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), phenylethylene carbonate (PhEC), propylmethyl carbonate (PMC), diethoxyethane (DEE), dimethoxyethane (DME), tetrahydrofuran (THF), ⁇ - butyrolactone (GBL), and ⁇ -valerolactone (GVL).
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • phosphonium cations are comprised of the following formula:
  • Another exemplary provides phosphonium cations comprised of the following formula:
  • examples of suitable phosphonium cations include but are not limited to: di-n-propyl ethyl phosphonium; n-butyl n-propyl ethyl phosphonium; n-hexyl n-butyl ethyl phosphonium; and the like.
  • examples of suitable phosphonium cations include but are not limited to: ethyl phospholane; n-propyl phospholane; n-butyl phospholane; n-hexyl phopholane; and phenyl phospholane.
  • examples of suitable phosphonium cations include but are not limited to: ethyl phosphole; n-propyl phosphole; n-butyl phosphole; n-hexyl phophole; and phenyl phosphole.
  • examples of suitable - phosphonium cations include but are not limited to: 1 -ethyl phosphacyclohexane; n-propyl phosphacyclohexane; n-butyl
  • Phosphonium ionic liquids or salts of the present invention are comprised of cations and anions. As will be appreciated by those of skill in the art, there are a large variety of possible cation and anion combinations. Phosphonium ionic liquids or salts of the present invention comprise cations as described above with anions that are generally selected from compounds that are easily ion exchanged with reagents or solvents of the general formula:
  • C + is a cation and A + is an anion.
  • C + is preferably Li + , K + , Na + , NH 4 + or Ag + .
  • C+ is preferably Ag + .
  • the anion is bis- perfluoromethyl sulfonyl imide.
  • suitable anions include, but are not limited to, any one or more of: N0 3 ⁇ , 0 3 SCF 3 " , N(S0 2 CF 3 ) 2 ⁇ , PF 6 " , 0 3 SC 6 H 4 CH 3 ⁇ , 0 3 SCF 2 CF 2 CF 3 ⁇ , 0 3 SCH 3 -, ⁇ , C(CN) 3 -, O 3 SCF 3 , N(S0 2 ) 2 CF 3 , CF 3 BF 3 " , O 3 SCF 2 CF 2 CF 3 , S0 4 2" , O 2 CCF 3 , " 0 2 CCF 2 CF 2 CF 3 , or " N(CN) 2 .
  • phosphonium ionic liquids or salts of the present invention are comprised of a single cation-anion pair.
  • two or more phosphonium ionic liquids or salts may be used to form common binaries, mixed binaries, common ternaries, mixed ternaries, and the like.
  • Composition ranges for binaries, ternaries, etc. include from 1 ppm, up to 999,999 ppm for each component cation and each component anion.
  • phosphonium electrolytes are comprised of one or more salts dissolved in a solvent, and the salts may be liquid or solid at a temperature of 100 °C.
  • a salt is comprised of a single cation-anion pair.
  • a salt is comprised of a one cation and multiple anions.
  • a salt is comprised of one anion and multiple cations.
  • a salt is comprised of multiple cations and multiple anions.
  • Electrolyte compositions according to some embodiments of the present invention are further described in co-pending United States Patent application serial number 13/706,207 (attorney docket no. 057472-058), filed concurrently herewith, the entire disclosure of which is hereby incorporated by reference.
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Tables 1 A and IB, below.
  • phosphonium electrolytes are comprised of cation and anion combinations shown in Tables 1C, ID, IE, and IF below. For clarity, signs of charge have been omitted in the formulas.
  • Table 1 A illustrates examples of anion binaries with a common cation: Table 1
  • Table IB illustrates examples of cation and anion combinations:
  • phosphonium electrolytes are comprised of salts having cations as shown in Tables lC-1 to lC-3 below:
  • phosphonium electrolytes are comprised of salts having anions as shown in Tables lD-1 to 1D-4 below: Table lD-1:
  • phosphonium electrolyte compositions are comprised of salts having cation and anion combinations as shown in Tables ⁇ -lto 1E-4 below:
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of: one or more cations of the formula:
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, wherein the salt is comprised of: one or more cations of the formula:
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, wherein the salt is comprised of: one or more cations of the formula:
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of one or more anions selected from the group consisting of:
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of: a cation of the formula: (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CFl 3 ) 2 P + and an anion of any one or more of the formula: BF 4 " , PF 6 " , CF 3 BF 3 " , (-OCOCOO-)BF 2 ⁇ , (- OCOCOO-)(CF 3 ) 2 B ⁇ , (-OCOCOO-) 2 B ⁇ , CF 3 S0 3 ⁇ , C(CN) 3 " , (CF 3 S0 2 ) 2 N ⁇ or combinations thereof
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (CH 3 )(CH 3 CH 2 ) 3 P + and an anion of any one or more of the formula BF 4 " , PF 6 " , CF 3 BF 3 ⁇ ,(-OCOCOO-)BF 2 ⁇ , (- OCOCOO-)(CF 3 ) 2 B ⁇ , (-OCOCOO-) 2 B ⁇ , CF 3 S0 3 ⁇ , C(CN) 3 " , (CF 3 S0 2 ) 2 N ⁇ or combinations thereof
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (CH 3 CH 2 CH 2 )(CH 3 CH 2 ) 3 P + and an anion of any one or more of the formula BF 4 " , PF 6 " , CF 3 BF 3 " , (-OCOCOO-)BF 2 " , (-OCOCOO- )(CF 3 ) 2 B “ , (-OCOCOO-) 2 B “ , CF 3 S0 3 " , C(CN) 3 " , (CF 3 S0 2 ) 2 N " or combinations thereof.
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (CH 3 CH 2 CH 2 )3(CH 3 )P + and an anion of any one or more of the formula BF 4 ⁇ , PF 6 " , CF 3 BF 3 " , (-OCOCOO-)BF 2 ⁇ , (- OCOCOO-)(CF 3 ) 2 B " , (-OCOCOO-) 2 B ⁇ , CF 3 SO 3 " , C(CN) 3 " , (CF 3 S0 2 ) 2 N ⁇ or combinations thereof
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (CH 3 CH 2 CH 2 )3(CH 3 CH 2 )P + and an anion of any one or more of the formula BF 4 " , PF 6 " , CF 3 BF 3 " , (-OCOCOO-)BF 2 ⁇ , (-OCOCOO- )(CF 3 ) 2 B “ , (-OCOCOO-) 2 B ⁇ , CF 3 SO 3 " , C(CN) 3 " , (CF 3 S0 2 ) 2 N " or combinations thereof
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (C ⁇ CF ⁇ C ⁇ C ⁇ CF ⁇ ) (CH 3 )P + and an anion of any one or more of the formula BF 4 " , PF 6 " , CF 3 BF 3 " , (- OCOCOO-)BF 2 ⁇ , (-OCOCOO-)(CF 3 ) 2 B “ , (-OCOCOO-) 2 B “ , CF 3 SO 3 " , C(CN) 3 " , (CF 3 S0 2 ) 2 N “ or combinations thereof.
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of : a cation of the formula (CH 3 CH 2 ) 4 P + and an anion of any one or more of the formula BF 4 " , PF 6 " , CF 3 BF 3 " , (-OCOCOO-)BF 2 ⁇ , (- OCOCOO-)(CF 3 ) 2 B “ , (-OCOCOO-) 2 B ⁇ , CF 3 SO 3 " , C(CN) 3 " , (CF 3 S0 2 ) 2 N ⁇ or combinations thereof
  • the phosphonium electrolyte is comprised of a salt dissolved in a solvent, where the salt is comprised of: a cation of the formula 1 :3: 1 mole ratio of
  • the anions are comprised of a mixture of BF 4 " and CF 3 BF 3 " at a concentration of [BF 4 ⁇ ] : [CF 3 BF 3 ] mole ratio in the range of 100/ 1 to 1 / 1.
  • the anions are comprised of a mixture of PF 6 " and CF 3 BF 3 " at a concentration of [PF 6 ⁇ ] :[CF 3 BF 3 ⁇ ] mole ratio in the range of 100/1 to 1/1.
  • the anions are comprised of a mixture of PF 6 " and BF 4 " at a concentration of [PF 6 ⁇ ]:[BF 4 ⁇ ] mole ratio in the range of 100/1 to 1/1.
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 2 below: Table 2
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 3 below:
  • phosphonium ionic liquid compositions are comprised of the cation and anion combinations as shown in Table 4 below:
  • phosphonium ionic liquid compositions are comprised of the cation and anion combinations as shown in Table 5 below:
  • phosphonium ionic liquid compositions are comprised of the cation and anion combinations as shown in Table 6 below:
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 7 below: Table 7
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 8 below:
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 9 below:
  • phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 10 below: Table 10
  • Additional preferred embodiments include phosphonium ionic liquid compositions are comprised of cation and anion combinations as shown in Table 11 below:
  • Another preferred exemplary embodiment includes phosphonium ionic liquid compositions comprised of cation and anion combinations as shown in Table 13 below: Table 13
  • compositions include but are not limited to: di-n-propyl ethyl methyl phosphonium bis- (trifluoromethyl sulfonyl) imide; n-butyl n-propyl ethyl methyl phosphonium bis-(trifluoromethyl sulfonyl) imide; n-hexly n-butyl ethyl methyl phosphonium bis-(trifluoromethyl sulfonyl) imide; and the like.
  • Suitable phosphonium ionic liquid compositions further include but are not limited to: 1 -ethyl- 1 -methyl phospholanium bis-(trifluoromethyl sulfonyl) imide; n- propyl methyl phospholanium bis-(trifluoromethyl sulfonyl) imide; n-butyl methyl
  • phospholanium bis-(trifluoromethyl sulfonyl) imide n-hexyl methyl phopholanium bis- (trifluoromethyl sulfonyl) imide; and phenyl methyl phospholanium bis-(trifluoromethyl sulfonyl) imide.
  • examples of suitable phosphonium ionic liquid compositions include but are not limited to: 1 -ethyl- 1 -methyl phospholanium bis-(trifluoromethyl sulfonyl) imide; n-propyl methyl phospholanium bis-(trifluoromethyl sulfonyl) imide; n-butyl methyl phospholanium bis-(trifluoromethyl sulfonyl imide; n-hexyl methyl phopholanium bis- (trifluoromethyl sulfonyl) imide; and phenyl methyl phospholanium bis-(trifluoromethyl sulfonyl) imide.
  • suitable phosphonium ionic liquid compositions include but are not limited to: 1 -ethyl- 1 -methyl phosphacyclohexane bis-(trifluoromethyl sulfonyl) imide; n-propyl methyl phosphacyclohexane bis-(trifluoromethyl sulfonyl) imide; n- butyl methyl phosphacyclohexane bis-(trifluoromethyl sulfonyl) imide; n-hexyl methyl phosphacyclohexane bis-(trifluoromethyl sulfonyl) imide; and phenyl methyl
  • Phosphonium ionic liquids of the present invention may also form a eutectic from one or more solids, or from a solid and a liquid, according to some embodiments.
  • the term "ionic liquid” is further defined to include ionic liquid that are eutectics from ionic solids, or from an ionic liquid and an ionic solid, such as binaries, ternaries, and the like.
  • phosphonium ionic liquids were prepared by either metathesis reactions of the appropriately substituted phosphonium salt with the appropriately substituted metal salt, or by reaction of appropriately substituted phosphine precursors with an appropriately substituted anion precursor.
  • FIGs. 3 to 6 illustrate reaction schemes to make four exemplary embodiments of phosphonium ionic liquids of the present invention.
  • Phosphonium ionic liquids were prepared. AgS0 3 CF 3 was charged into a 50 ml round bottom (Rb) flask and assembled to a 3 cm swivel frit. The flask was evacuated and brought into a glove box. In the glove box, di-n-propyl ethyl methyl phosphonium iodide was added and the flask re-assembled, brought to the vacuum line, evacuated, and anhydrous THF was vacuum transferred in. The flask was allowed to warm to room temperature and was then heated to 40 °C for 2 hours. This resulted in the formation of a light green bead-like solid. This solid was removed by filtration.
  • TGA Thermogravimetric Analysis
  • EVA evolved gas analysis
  • di-n-propyl ethyl methyl phosphonium iodide was added to a 100 ml Rb flask in a glove box, and then brought out of the fume hood and dissolved in 70 ml MeOH. Next, Ag0 2 CCF 2 CF 2 CF 3 was added, immediately giving a yellow colored slurry. After stirring for 3 hours the solids were moved by filtration, the bulk MeOH removed by rotary evaporation and the remaining residue dried under high vacuum. This gave a yellow, gel-like slushy material.
  • a ternary phosphonium ionic liquid composition comprising 1 :3: 1 mole ratio of (CH3CH 2 CH 2 )(CH3)3PCF3BF3/(CH3CH 2 CH 2 )(CH3CH 2 )(CH 3 ) 2 P CF3BF3
  • phosphonium salt (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 PC(CN)3 was prepared.
  • This salt exhibits a low viscosity of 19.5 cP at 25 °C, melting point of -10.9 °C, onset decomposition temperature of 396.1 °C, liquid range of 407 °C, ionic conductivity of 13.9 mS/cm, and electrochemical voltage window of -1.5 5o +1.5 V when measured in an electrochemical cell with a Pt working electrode and a Pt counter electrode and an Ag/Ag + reference electrode.
  • Table 14 The results are summarized in Table 14 below.
  • phosphonium salt (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 PC(CN) 3 was prepared.
  • the salt was dissolved in a solvent of acetonitrile (ACN) with ACN/salt volume ratios ranging from 0 to 4.
  • ACN acetonitrile
  • the ionic conductivities of the resulting electrolyte solution were measured at room temperature and the results are shown in FIG. 22. As FIG. 22 shows, the ionic conductivity increases with the increase of ACN/salt ratio from 13.9 mS/cm at zero ratio (neat ionic liquid) to a peak value of 75 mS/cm at ratios between 1.5 and 2.0.
  • phosphonium salt (CH 3 CH 2 CH 2 )(CH 3 CH 2 )(CH 3 ) 2 PC(CN) 3 was prepared.
  • the salt was dissolved in a solvent of propylene carbonate (PC) with PC/salt volume ratios ranging from 0 to 2.3.
  • PC propylene carbonate
  • the ionic conductivities of the resulting electrolyte solution were measured at room temperature and the results are shown in FIG. 23. As FIG. 23 shows, the ionic conductivity increases with the increase of PC/salt ratio from 13.9 mS/cm at zero ratio (neat ionic liquid) to a peak value of 22 mS/cm at ratios between 0.75 and 1.25.
  • the electrolytes exhibited ionic conductivity at room temperature greater than about 28 mS/cm, or greater than about 34 mS/cm, or greater than about 41 mS/cm, or greater than about 55 mS/cm, or greater than about 61 mS/cm.
  • the Echem window was between about -3.2 V and +2.4 V.
  • the Echem window was between about -3.0 V and +2.4 V.
  • the Echem window was between about -2.0 V and +2.4 V.
  • phosphonium salt was used as an additive in a lithium battery conventional electrolyte solution.
  • the phosphonium salt was provided by Novolyte Technologies (part of BASF Group).
  • phosphonium salt was used as an additive in a lithium battery standard electrolyte solution.
  • the phosphonium salt (CF ⁇ CHzCHzXCF ⁇ CHzXCF ⁇ PQCN ⁇ was added to the standard electrolyte solution at 10 w%.
  • the ionic conductivities of both the standard electrolyte solution and the solution with phosphonium additive were measured at different temperatures from -30 to 60 °C. As illustrated in FIG. 26, the phosphonium additive improves the ionic conductivity of the electrolyte solution in a broad temperature range. At -30°C, the ionic conductivity is increased by 109% as a result of the phosphonium additive. At +20°C, the ionic conductivity is increased by 23% as a result of the phosphonium additive. At +60°C, the ionic conductivity is increased by about 25%> as a result of the phosphonium additive. In general, ionic conductivity of the standard electrolyte solution increased by at least 25% as a result of the phosphonium additive
  • phosphonium salt was used as an additive in a lithium battery standard electrolyte solution.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethylmethyl carbonate
  • the phosphonium additive were measured at different temperatures from 20 to 90 °C. As illustrated in FIG. 27, the phosphonium additive improves the ionic conductivity of the electrolyte solution in a broad temperature range. At 20°C, the ionic conductivity is increased by about 36%> as a result of the phosphonium additive. At 60°C, the ionic conductivity is increased by about 26% as a result of the phosphonium additive. At 90°C, the ionic conductivity is increased by about 38% as a result of the phosphonium additive. In general, ionic conductivity of the standard electrolyte solution increased by at least 25% as a result of the phosphonium additive.
  • a coin cell is comprised of two disk- shaped carbon electrodes of 14 mm diameter, a separator of 19 mm diameter sandwiched between the two electrodes, and an impregnating electrolyte solution.
  • two carbon electrodes of 100 ⁇ thickness were prepared from activated carbon (Kuraray YP-50F, 1500 - 1800 m /g), mixed with a binder and each bounded to a 30 ⁇ thick aluminum current collector.
  • the separator was prepared from 35 ⁇ NK cellulose separator (TF40-35).
  • Both the carbon electrodes and the separator were impregnated with an electrolyte solution containing 1.0 M phosphonium salt in either acetonitrile or propylene carbonate.
  • the assembly was placed into a 2032 coin cell case and sealed by applying appropriate pressure using a crimper.
  • the finished cell had a diameter of 20 mm and a thickness of 3.2 mm.
  • the entire assembly process was carried out in a nitrogen- filled glove box.
  • the finished cell was
  • FIG. 29 shows the charge - discharge curve for such a coin cell with 1.0 M
  • the cell was first charged from 0 V to 2.5 V then discharged to 1.0 V at 10 mA.
  • the cell capacitance was determined to be 0.55 F.
  • a pouch cell is comprised of two carbon electrodes of 15 mm x 15 mm, a separate of 20 mm x 20 mm
  • the pouch cell includes a third electrode - a reference electrode such as a silver electrode so that the potential at each carbon electrode can be determined.
  • a third electrode - a reference electrode such as a silver electrode so that the potential at each carbon electrode can be determined.
  • two carbon electrodes of 100 ⁇ thickness were prepared from activated carbon (Kuraray YP- 50F, 1500 - 1800 m /g), mixed with a binder and each bounded to a 30 ⁇ thick aluminum current collector.
  • the separator was prepared from 35 ⁇ NKK cellulose separator (TF40-35). Both the carbon electrodes and the separator were impregnated with an electrolyte solution containing 1.0 M phosphonium salt in either acetonitrile or propylene carbonate.
  • FIG. 31 A shows the charge - discharge curve for a pouch cell with 1.0 M
  • FIG. 3 IB shows the resolved electrode potential at the positive and negative carbon electrodes measured with a silver reference electrode.
  • the pouch cell could be fully charged to high voltages up to 3.9 V.
  • Table 19 The results are summarized in Table 19 below.
  • the EDLC can be charged and discharged from 0 V to 3.9 V.
  • the EDLC can be charged and discharged from 0 V to 3.6 V.
  • the EDLC can be charged and discharged from 0 V to 3.3 V.
  • a cylindrical cell is comprised of a first separator strip of 6 cm x 50 cm, a first carbon electrode strip of 5.8 cm x 50 cm placed on top of the first separator, a second separator strip of 6 cm x 50 cm placed on top of the first carbon electrode, and a second carbon electrode strip of 5.8 cm x 50 cm placed on top of the second separator.
  • the electrode/separator assembly was wound in a jellyroll fashion into a tight cell core.
  • carbon electrodes of 100 ⁇ thickness were prepared from activated carbon (Kuraray YP-50F, 1500 - 1800 m /g) mixed with a binder and bounded to both sides of a 30 ⁇ thick aluminum current collector resulting in a double-sided electrode structure.
  • the separator was prepared from 35 ⁇ NK cellulose separator (TF40-35).
  • the jellyroll core was placed into an 18650 cylindrical cell case.
  • An electrolyte solution containing 1.0 M phosphonium salt in either acetonitrile or propylene carbonate was added using a vacuum injection apparatus to ensure that the electrolyte permeated and completely filled the porosity of the separators and carbon electrodes.
  • FIG. 33 shows the charge - discharge curve for such a cylindrical cell with an electrolyte solution of 1M (CHsCF ⁇ CF ⁇ XCHsCF ⁇ XCHsXPCFsBFs in propylene carbonate.
  • the cell was first charged from 1.0 V to 2.5 V, held at 2.5 V for 300 sec, and then discharged to 2.5 V at 600 mA.
  • the cell capacitance was determined to be 132 F.
  • the EDLCs made with the novel phosphonium electrolytes disclosed herein can be operated in a temperature range between -40 °C and +80 °C. It is expected that the EDLCs made with the phosphonium electrolytes disclosed herein can be operated in a temperature range between about -50 °C and +120 °C.
  • the initial treatment dramatically improved the EDLC lifetime at high voltage and high temperature for the cells with phosphonium salts.
  • the lifetime was increased to over 1200 hours for cells with phosphonium salts, in contrast the control cell with ammonium salt failed after 50 hours due to bulging.
  • the lifetime for cells with phosphonium salts without the initial treatment was in a range below 200 hours.
  • FIG. 37 shows the ESR stability at 3.5 V and 85°C for the pouch cells.
  • the initial treatment also dramatically improves the ESR stability for the cells with phosphonium salts.
  • the cell with ammonium salt failed after 50 hours due to bulging.
  • the initial treatment dramatically improved the EDLC lifetime at high voltage and high temperature for the cells with phosphonium salts.
  • the lifetime was increased to over 500 hours for cells with phosphonium salts, in contrast the control cell with ammonium salt failed after 50 hours due to bulging.
  • FIG. 39 shows the ESR stability at 3.0 V and 70°C for the cylindrical cells.
  • the initial treatment also dramatically improves the ESR stability for the cells with phosphonium salts.
  • the cell with ammonium salt failed after 50 hours due to bulging.
  • accelerated stress testing was performed at 2.5 V and 85 °C for 150 F cylindrical cells containing 1.0 M phosphonium salts in propylene carbonate compared to an ammonium salt as control.
  • initial treatments were performed on the cylindrical cells by the following protocol: -2.7 V applied for 2 hours; discharged to 0 V; +2.6 V applied for 12 hours; discharged to 0 V.
  • the stress test was performed by holding the cell voltage at 2.5 V and temperature at 85 °C for up to 1600 hours.
  • the cell performance stability was measured as retention of the initial capacitance. The results are shown in FIG. 40.
  • the numerical values of the lifetime at 80% capacitance retention are shown in Table 23.
  • accelerated stress testing was performed at 2.5 V and 85 °C for 150 F cylindrical cells containing 1.0 M (CH 3 CH 2 CH 2 XCH 3 CH 2 ) 3 PCF 3 BF 3 in propylene carbonate.
  • initial treatments were performed on the cylindrical cells by the following protocol: -2.7 V applied for 2 hours; discharged to 0 V; +2.6 V applied for 12 hours; discharged to 0 V.
  • the stress test was performed by holding the cell voltage at 2.5 V and temperature at 85 °C for up to 1000 hours. After aging at 2.5 V and 85 °C for about 600 hours, the cells capacitance had fallen to about 80% for both Cell 1 and Cell 2.
  • a post treatment was then performed on Cell 2 by the following protocol: discharged to 0 V; -2.7 V applied for 2 hours; discharged to 0 V; +2.6 V applied for 2 hours; discharged to 0 V.
  • the capacitance retention of Cell 2 was increased to about 90% - 10% recovery compared to Cell 1 which received no treatment.
  • the capacitance retention of Cell 2 stayed at about 90% for 100 hours and then returned to the same baseline as Cell 1.
  • Repeat of the post treatment on Cell 2 at about 700 hour resulted in similar capacitance recovery for even longer time. Based on these results, continued performance recovery can be achieved by repeated post treatment every 100 hours.
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH 3 CH 2 ) 4 NBF 4 in acetonitrile.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt:(CH 3 CH 2 ) 4 NBF 4 for a total salt concentration of 1.0 M in acetonitrile.
  • Accelerated stress testing was performed at 3.3 V and 70 °C for 25 F cylindrical cells. After cell assembly, initial treatments were performed on the cylindrical cells by the following protocol: - 2.7 V applied for 2 hours; discharged to 0V; +3.4 V applied for 12 hours; discharged to 0V.
  • the stress test was performed by holding the cell voltage at 3.3 V and temperature at 70 °C for up to 215 hours for the ammonium salt control cell and 473 hours for the cell with phosphonium additive.
  • the cell performance stability was measured as retention of the initial capacitance. The results are shown in Table 24. As shown, the initial treatment dramatically improved the EDLC capacitance retention thus lifetime at high voltage and high temperature.
  • the phosphonium additive further increased the capacitance retention by about 26% compared to the ammonium salt control.
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH 3 CH 2 ) 4 NBF 4 in acetonitrile.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt:(CH 3 CH 2 ) 4 NBF 4 for a total salt concentration of 1.0 M in acetonitrile.
  • Accelerated stress test was performed at 3.0 V and 70 °C for 25 F cylindrical cells. After cell assembly, initial treatments were performed on the cell with phosphonium additive by the following protocol: -2.5 V applied for 2 hours; discharged to 0 V; +3.1 V applied for 12 hours; discharged to 0 V.
  • the stress test was performed by holding the cell voltage at 3.0 V and temperature at 70 °C for up to 1752 hours.
  • the cell performance stability was measured as retention of the initial capacitance.
  • the result of lifetime at 80% capacitance retention is shown in Table 25.
  • the result illustrates once again that the initial treatment dramatically improves the EDLC lifetime at high voltage and high temperature for the cells with phosphonium salt.
  • the lifetime was increased to over 1500 hours for the cell with phosphonium salt, in contrast the control cell with ammonium salt failed after 288 hours.
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH 3 CH 2 ) 4 NBF 4 in acetonitrile.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt:(CH 3 CH 2 ) 4 NBF 4 for a total salt concentration of 1.0 M in acetonitrile.
  • Accelerated stress test was performed at 3.0 V and 70 °C for 25 F cylindrical cells. After cell assembly, initial treatments were performed on the cell with phosphonium additive by the following protocol: -2.7 V applied for 2 hours; discharged to 0 V; +3.1 V applied for 12 hours; discharged to 0 V.
  • the stress test was performed by holding the cell voltage at 3.0 V and temperature at 70 °C for up to 860 hours.
  • the cell performance stability was measured as retention of the initial capacitance.
  • the result of lifetime at 80% capacitance retention is shown in Table 26. The lifetime was increased to 860 hours for the cell with phosphonium salt, in contrast the control cell with ammonium salt failed after 288 hours.
  • accelerated stress test was performed at 3.3 V and 70 °C for 50 F cylindrical cells containing 1.0 M phosphonium salt in acetonitrile compared to (CH 3 CH 2 ) 4 NBF 4 as control.
  • initial treatments were performed on the cell with the phosphonium salt by the following protocol: -2.7 V applied for 2 hours; discharged to 0 V; +3.4 V applied for 12 hours; discharged to 0 V.
  • the stress test was performed by holding the cell voltage at 3.3 V and temperature at 70 °C for up to 480 hours.
  • the cell performance stability was measured as retention of the initial capacitance.
  • the result of lifetime at 80% capacitance retention is shown in Table 27. The lifetime was increased to 480 hours for the cell with phosphonium salt, in contrast the control cell with ammonium salt failed after 134 hours.
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH 3 CH 2 )3(CH 3 )NBF 4 in propylene carbonate.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt:
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH 3 CH 2 )3(CH 3 )NBF 4 in propylene carbonate.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt: (CH 3 CH 2 )3(CH 3 )NBF 4 for a total salt concentration of 1.0 M in propylene carbonate (about 5 wt% of phosphonium salt).
  • the phosphonium salt was added to the
  • ammonium salts (CH 3 CH 2 )3(CH 3 )NCF 3 BF 3 , (CH 3 CH 2 )3(CH 3 )NS0 3 CF 3 and (CH 3 CH 2 )3(CH 3 )N(CF 3 S0 2 ) 2 N were prepared by ion exchange reactions of
  • triethylmethylammonium chloride with potassium trifluoro(trifluoromethyl)borate, potassium trifluoromethanesulfonate, and lithium bis(triflouromethane)sulfonamide respectively.
  • ammonium salts were tested as additive in a conventional electrolyte solution of
  • phosphonium salt was used as additive in a conventional electrolyte solution of (CH CH 2 ) (CH )NBF 4 in propylene carbonate.
  • the phosphonium salt was added to the conventional electrolyte solution at a mole ratio of 1 :3, phosphonium salt:
  • Ammonium salt control (CH 3 CH 2 ) 3 (CH 3 )NBF 4 35
  • phosphonium salts as electrolytes or as additives to conventional ammonium based electrolytes provide an advantage and may be preferred
  • embodiments of the present invention also include ammonium based electrolytes. Further it is found that ammonium based electrolytes subject to the initial treatment and/or post treatment steps as taught by the embodiments described herein perform better than ammonium based electrolytes not subject to the disclosed treatments.

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Abstract

L'invention concerne de manière générale des dispositifs ou systèmes de stockage d'énergie et concerne plus particulièrement des procédés permettant d'améliorer les performances de condensateurs à double couche électrochimique (EDLC), ou de supercondensateurs ou d'ultracondensateurs, ainsi que des dispositifs formés à partir de ces derniers. Selon certains modes de réalisation, l'invention se rapporte de manière générale à des dispositifs de stockage d'énergie tels que des EDLC qui utilisent des électrolytes à base de phosphonium et à des procédés de traitement de tels dispositifs afin d'améliorer leurs performances et leur fonctionnement. Des modes de réalisation de l'invention se rapportent en outre à des électrolytes à base d'ammonium et à des électrolytes à base de phosphonium classiques composés de liquides ioniques au phosphonium, de sels et de compositions employés dans de tels EDLC.
PCT/US2015/020795 2014-03-14 2015-03-16 Procédés pour améliorer les performances de condensateurs à double couche électrochimique WO2015139049A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US201461953567P 2014-03-14 2014-03-14
PCT/US2014/029424 WO2014144845A2 (fr) 2013-03-15 2014-03-14 Procédés d'amélioration des performances d'un condensateur double-couche électrochimique (edlc) et dispositifs edlc formés à partir de ceux-ci
US61/953,567 2014-03-14
USPCT/US2014/029424 2014-03-14

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002142369A (ja) * 2000-11-07 2002-05-17 Meidensha Corp 電気二重層キャパシタのセル電圧均等化方法
JP2003009412A (ja) * 2001-06-27 2003-01-10 Meidensha Corp 積層型電気二重層キャパシタ用極性反転装置
US20090268376A1 (en) * 2006-07-21 2009-10-29 Add Power Technologies Limited Electrolytes and capacitors
US20130095351A1 (en) * 2008-07-14 2013-04-18 Wayne L. Gellett Electrolyte Compositions And Electrochemical Double Layer Capacitors Formed There From

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002142369A (ja) * 2000-11-07 2002-05-17 Meidensha Corp 電気二重層キャパシタのセル電圧均等化方法
JP2003009412A (ja) * 2001-06-27 2003-01-10 Meidensha Corp 積層型電気二重層キャパシタ用極性反転装置
US20090268376A1 (en) * 2006-07-21 2009-10-29 Add Power Technologies Limited Electrolytes and capacitors
US20130095351A1 (en) * 2008-07-14 2013-04-18 Wayne L. Gellett Electrolyte Compositions And Electrochemical Double Layer Capacitors Formed There From

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