Coin-cell Supercapacitors Based on CVD Grown and Vertically Aligned Carbon Nanofibers (VACNFs)

Com­plete super­ca­pac­i­tors (SCs) com­pris­ing ver­ti­cal­ly aligned car­bon nanofibers (VAC­N­Fs) as elec­trode mate­ri­als have been assem­bled as coin-cells. The VAC­N­Fs were grown direct­ly onto the cur­rent col­lec­tor by direct cur­rent plas­ma enhanced chem­i­cal vapor depo­si­tion (DC-PECVD), there­by pro­vid­ing excel­lent con­tact with the cur­rent col­lec­tor, but also elim­i­nat­ing the need of any binder. The ver­ti­cal align­ment facil­i­tates fast ion trans­port and the elec­trolyte to access the entire sur­face of the CNFs. The mor­phol­o­gy of the VAC­N­Fs was eval­u­at­ed by scan­ning elec­tron microscopy (SEM), while the per­for­mance was assessed by sev­er­al meth­ods: cyclic voltam­me­try (CV), elec­tro­chem­i­cal imped­ance spec­troscopy (EIS) and device relat­ed cycling by gal­vano­s­ta­t­ic charge/​discharge. The capac­i­tance, 3.64 mF/​cm², is >15 times high­er than the capac­i­tance of a coin-cell with­out CNFs and the cyclic per­for­mance shows these proof-of-con­cept SCs to retain >80% of the capac­i­tance after 2000 full charge/​discharge cycles. The direct growth of VAC­N­Fs as elec­trodes at the cur­rent col­lec­tor opens path­ways for SC pro­duc­tion using exist­ing coin-cell bat­tery pro­duc­tion technology.