Publication: Analyzing various parameters on supercapacitor performance
Abstract
Elektrokimyasal özellikleri iyileştirilmiş geçiş metal oksitleri yüksek performanslı elektrot üretimi için önem taşımaktadır. Bu sebeple, bu çalışmada, asıl amacımız nikel-kobalt oksitten (NCO) üretilen elektroların iletkenliğini ve aktif yüzey alanını artırarak kütle ve elektron transferini kolaylaştırmaktır. Bu amaç doğrultusunda, NCO ve NCO-indirgenmiş grafen oksit (NCO-RGO) hibritleri, nikel-köpüğü sübstratı üzerine kolay, tek aşamalı ve ilk kez gerçekleştirilen elektrodeposizyon yöntemi kullanılarak elde edilmiştir. NCO-RGO hibritleri, eş zamanlı gerçekleşen elektrodepozisyon ve indirgeme işlemleri sonucu hazırlanmıştır. Elde edilen hibritlerin elektrot yüzeyi üzerindeki kütlesinin RGO etkisi ile azaldığı belirlenmiştir. Ayrıca, NCO-RGO hibritleri nikel- köpüğü üzerine yüklenirken herhangi bir bağlayıcı malzeme kullanılmamıştır. Bu sayede bağlayıcı kaynaklı direnç ortadan kaldırılmış ve iletkenliğin düşmesi engellenmiştir. Kaplama kat sayısının belirlenmesinin ardından, eşit mol sayıda nikel ve kobalt içeren öncüler ile hazırlanmış elektrolit içerisinde GO miktarı optimizasyonu yapılmıştır. Son olarak, NCO-RGO hibritleri, en iyi performansı saptayabilmek adına farklı nikel-kobalt mol oranlarında sentezlenmiştir. Elektrokimyasal ölçümler göstermiştir ki elde edilen elektrotların spesifik kapasitans ve şarj/ deşarj çevrim dayanıklılığı yapıdaki RGO varlığı ile kayda değer ölçüde artmıştır. 0.25 mg GO içeren elektrolitten üretilen NCO-RGO hibrit elektrotu NCO elektrot ile kıyaslandığında mükemmel çevrim ömrü yanı sıra oldukça yüksek spesifik kapasitans sergilemiştir. Ek olarak, yapıda belli oranda nikel içeriğinin artışı ile spesifik kapasitansın arttığı belirlenmiştir. Tüm hazırlanan ürünler karşılaştırıldığında, NCO-RGO hibritleri 1 A/ g akım yoğunluğunda en yüksek spesifik kapasitans 1916.5 F/ g ve 10 A/ g gibi yüksek akım yoğunluğunda 3000 şarj/ deşarj çevrim sonucu 95.6% kapasite korunumu elde edilmiştir. NCO-RGO hibritleri güç yoğunluğu değeri 235 W/ kg da yüksek enerji yoğunluğu olarak 53.90 Wh/ kg değeri elde edilmiş ve enerji yoğunluğu değeri, yüksek güç yoğunluğunda (7500 W/ kg) 41.20 Wh/ kg olarak belirlenmiştir. Bu sonuçlar, bu malzemelerin dayanaklığının yüksek olduğunu göstermiştir. Sonuç olarak, oldukça iyi elektrokimyasal özelliklere sahip NCO-RGO malzemesi, gelecekte süperkapasitör uygulamalarında kullanılmak üzere kolay ve bağlayıcı içermeyen elektrot yapımı için umut vaat etmektedir.
Transition metal oxides with enhanced electrochemical performance are points of interest in the fabrication of high efficient electrodes for supercapacitors. Therefore, in this study, our main purpose is to increase the conductivity and the effective surface area of the electrode composed of nickel-cobalt oxide (NCO) which enables to ease the mass diffusion and electron transport. With this aim, the nanosheets of NCO and NCO-reduced graphene oxide (NCO-RGO) hybrids were produced on nickel-foam substrate by a using facile one-step electrodeposition technique which was first performed. The hybrids of NCO-RGO were simultaneously prepared by the electrodeposition and reduction of GO and NCO, leading to a decrease in the total mass of active material on the electrode surface. The NCO-RGO hybrids were further deposited on the nickel-foam without using any binder; thus, it was avoided to decay in conductivity owing to the resistance of binder. After the optimizing of the number of coating layers, the optimization of GO amounts in the electrolyte comprised of equal moles of nickel and cobalt precursors was employed. Finally, NCO-RGO hybrids were fabricated at different nickel and cobalt molar ratios to determine the best performance. Electrochemical measurements confirmed that the specific capacitance and cycling stability of as-obtained electrodes were remarkably enhanced in the presence of RGO in the structure. The NCO-RGO hybrid which was fabricated from the electrolyte solution involving 0.25 mg of GO, exhibited a quite high specific capacitance as well as extraordinary cycling stability compared to NCO. Furthermore, the results indicated that with the increase in nickel content up to a certain rate, the specific capacitance was considerably increased. Out of all the prepared samples, the NCO-RGO hybrids possessed the highest specific capacitance of 1916.5 F/ g at 1 A/ g with extraordinary retention of 95.6% at a high current density of 10 A/ g even after 3000 charge/ discharge cycles. Additionally, NCO-RGO hybrids exhibited a high energy density of 53.90 Wh/ kg at the power density of 235 W/ kg and remained 41.20 Wh/ kg at a high power density of 7500 W/ kg, implying the attractive rate capability of these materials. As a result of this study, the NCO-RGO nanosheets having remarkable electrochemical performance have a potential as a promising facile and binder-free electrode for supercapacitor applications in the future.
Transition metal oxides with enhanced electrochemical performance are points of interest in the fabrication of high efficient electrodes for supercapacitors. Therefore, in this study, our main purpose is to increase the conductivity and the effective surface area of the electrode composed of nickel-cobalt oxide (NCO) which enables to ease the mass diffusion and electron transport. With this aim, the nanosheets of NCO and NCO-reduced graphene oxide (NCO-RGO) hybrids were produced on nickel-foam substrate by a using facile one-step electrodeposition technique which was first performed. The hybrids of NCO-RGO were simultaneously prepared by the electrodeposition and reduction of GO and NCO, leading to a decrease in the total mass of active material on the electrode surface. The NCO-RGO hybrids were further deposited on the nickel-foam without using any binder; thus, it was avoided to decay in conductivity owing to the resistance of binder. After the optimizing of the number of coating layers, the optimization of GO amounts in the electrolyte comprised of equal moles of nickel and cobalt precursors was employed. Finally, NCO-RGO hybrids were fabricated at different nickel and cobalt molar ratios to determine the best performance. Electrochemical measurements confirmed that the specific capacitance and cycling stability of as-obtained electrodes were remarkably enhanced in the presence of RGO in the structure. The NCO-RGO hybrid which was fabricated from the electrolyte solution involving 0.25 mg of GO, exhibited a quite high specific capacitance as well as extraordinary cycling stability compared to NCO. Furthermore, the results indicated that with the increase in nickel content up to a certain rate, the specific capacitance was considerably increased. Out of all the prepared samples, the NCO-RGO hybrids possessed the highest specific capacitance of 1916.5 F/ g at 1 A/ g with extraordinary retention of 95.6% at a high current density of 10 A/ g even after 3000 charge/ discharge cycles. Additionally, NCO-RGO hybrids exhibited a high energy density of 53.90 Wh/ kg at the power density of 235 W/ kg and remained 41.20 Wh/ kg at a high power density of 7500 W/ kg, implying the attractive rate capability of these materials. As a result of this study, the NCO-RGO nanosheets having remarkable electrochemical performance have a potential as a promising facile and binder-free electrode for supercapacitor applications in the future.