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.