US 10,519,328 B2  34  33  TABLE 2  C: static capacitor measured at 120  Hz;  ESR: equivalent series resistance measured at 100 kHz;  DF: dissipation factor measured at 120 Hz.  Thermal stability test at 240°  C.  for 38 minutes  Functional component(s)  used  Capacitor  Polymerization Polymer  C (µF)  ESR (mQ)  DF  performance  Example  retardant  binder  (at 120 Hz)  (at 100 KHz)  (at 120 Hz) quality  5  No  No  518  42  0.100  downgraded  6  No  Yes  480  22  0.060  downgraded  7  Yes  No  564  50  0.100  downgraded  8  Yes  Yes  607  6  0.011  upgraded  Comparative B  EDOT/Fe(OTs)$_{3 }$ 774  21  2.92  failed in total  The results summarized in Tables 1 and 2 clearly dem› onstrated that the capacitor prepared by the conventional  oxidative polymerization method (as  in Comparative  Example B) based on the conventional composition (EDOT/  Fe(OTs )$_{3}$ )  had failed totally after been heated at 240°  C. for  38 minutes, having a DF value (2.92) that had already much  over 0.12 that is acceptable upper limit value of DF for a  commercial solid capacitor. All the capacitors prepared by  the newly invented cationic chain-growth polymerization  method (Examples 5-8) from the composition of the inven› tion (BEDOT plus acid catalyst) had all survived from the  thermal treatment at 240°  C. for 38 minutes. The results have  further indicated that the performance of the capacitors in  Examples 5-7 had actually already downgraded to some  extents (though still appeared within the acceptable range),  showing decreased capacitances together with increased  ESR and DF values. Clearly, only the capacitor in Example  8 (with the addition of both polymerization retardant and  polymer binder as the functional components) could com› pletely overcome such thermal heating treatment, without  suffering any degradation. Actually, the DF value of  Example 8 had been unexpectedly and significantly reduced  further from 0.016 to 0.011. The results herein clearly  confirmed that the composition and polymerization method  of this invention can render the solid capacitors with much  higher thermal stability than the conventional composition  and method. The results further indicated that best perfor› mance can be achieved when both polymerization retardant  and polymer binder are used as the functional components of  this invention.  An anode aluminum foil having an Al$_{2}$ 0 3  dielectric layer  formed at an electrochemical forming voltage of 50 V and  a cathode aluminum foil of high surface area prepared by an  electrochemical erosion were wounded together with an  interposed separator to form a solid electrolytic capacitor  element, as conventionally designed for a capacitor with a  rated voltage of 35 V and a rated capacitance of 220 µF.  After the electrochemical reforming treatment in an organic  acid solution to repair the damaged dielectric layer, the  capacitor element was dipped for 10 minutes in a compo› sition solution containing monomer (BEDOT; 1.5 M) and  various acid catalyst (as listed in Table 3; 0.15 equiv)  together with the functional components of both polymer› ization retardant (ether, 2 equiv) and polymer binder (poly  [styrene-co-(methyl methacrylate)]; PS-PMMA; 0.2 equiv).  Then, the polymerization was performed by heating the  dipped capacitor element at the elevated temperatures rang› ing from 60° C. to 190° C. for 30 min to drive the  polymerization to completion. After the preparation, the  resultant capacitors were all subjected to aging treatments to  reduce their leakage currents to below the value of -154 µA  (i.e., -0.02 CV). The capacitors were then subjected to  withstanding or breakdown voltage test, respectively, by  raising the applied voltage gradually until the breakdown of  the electrolyte had occurred or until 48 V (the voltage  slightly below the forming voltage of the anodic Al foil) was  reached. The results of the withstanding or breakdown  voltage for the respective electrolytes are summarized in  Table 3.  A wounded aluminum capacitor, as prepared by the same  method in Examples 8-11, was dipped with a monomer  solution of 3,4-ethylenedioxythiophene (EDOT; 30 wt %)  and then with an oxidant solution of iron(III) tosylate  (Fe(OTs)$_{3}$ ;  30 wt%; 2.5 equiv) for 10 minutes, respectively.  Then, the polymerization was performed by heating the  dipped capacitor element at the elevated temperatures rang› ing from 60° C. to 190° C. for 30 min to drive the  polymerization to completion. After the preparation, the  resultant capacitor was all subjected to aging treatments to  reduce its leakage current to -154 µA. The capacitors were  then subjected to the same withstanding or breakdown  voltage test, as in Examples 9-11, by raising the applied  voltage gradually until the breakdown of the electrolyte. The  breakdown voltage is listed in Table 3.  The results summarized in Table 3 clearly indicated that  the solid capacitor containing the conventional solid elec- Examples 9-11. Withstanding or Breakdown  Voltage Test I  Comparative Example C  TABLE 3  BEDOT: 2-bromo-3,4-ethylenedioxythiophene;  EDOT: 3,4-ethylenedioxythiophene;  DBSA: dedecylbenzenesulfonic acid;  DNNDSA: dinonylnaphthalenedisulfonic acid;  PSS: poly(styrenesulfonic acid);  Fe(OTs)s: iron(III) tosylate.  Withstanding or breakdown voltage tests  Withstanding or  Status of  Example  Composition used  breakdown voltage  capacitor  9  BEDOT/DBSA  ~41  V  breakdown  10  BEDOT/DNNDSA  >48  V  withstanding  11  BEDOT/PSS  >48  V  withstanding  Compara- EDOT/Fe(OTsh  <16  V  breakdown  live C 