ISSN:
1572-8838
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
,
Elektrotechnik, Elektronik, Nachrichtentechnik
Notizen:
Abstract Natural graphite flakes (80 wt%), with polypropylene (20 wt%) as a binder, constitute a practical and non-expensive graphite electrode of high crystallinity ‘CPP’. Galvanostatic cycling of these electrodes with current densities in the range 0.3–30 mA cm−2 (charging time 5–120 min) has been investigated in aqueous acids (12, 20 and 36 mol dm−3 HF, 6 and 12 mol dm−3 H2SO4, 4 mol dm−3 HClO4). The anion of the acid is anodically intercalated and cathodically de-intercalated. In spite of the high water concentrations, quantitative current efficiencies have been obtained. From variation of the rest times after charging, a corrosion current density of less than 0.03 mA cm−2 (j ch=3 mA cm−2) has been derived. The overvoltage during charge and discharge is typically about 0.1 V. The potential at the start of the charging process coincides with the intercalation potential defined previously. A strong electrode formation effect is observed upon cycling. The electrode is initially smooth and non-porous; it acquires a high surface roughness after a few cycles, which is then stable. The initial charging curves increase witht 1/2, while the charging curve after electrode formation is linear. Both clearly indicate a linear relationship between surface concentration of intercalated anions and potential. This agrees with our previous finding of linear dependence with respect to acid concentration in the solution.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00614976
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