Abstract
Given the rapid miniaturization of technology, it is of interest to produce viable on-chip micro-electrochemical energy storage systems. In this study, interdigitated asymmetric microsupercapacitors were fabricated using photolithography, lift-off and electrodeposition methods. Manganese oxide (MnOx) and reduced graphene oxide (rGO) comprised the pseudocapacitive and the double layer component, respectively. Symmetric MnOx//MnOx, rGO//rGO as well as asymmetric rGO//MnOx microsupercapacitors with three different MnOx thicknesses were constructed and characterized in aqueous media. The asymmetric microsupercapacitor with the intermediate MnOx film thickness displayed the optimal energy-power trade-off superior to that of both the symmetric and well as the other asymmetric configurations. The optimal microsupercapacitor exhibited a high stack energy density of 1.02 mWh·cm−3 and a maximal power density of 3.44 W·cm−3. The high energy-power trade-off of the device is attributed to the synergistic effects of utilizing double layer and pseudocapacitive charge storage mechanisms along with in-plane interdigital microelectrode design within one optimized micro-device.
Highlights
With the technological impetus of going “micro”, it is imperative to create small-scale energy devices that can effectively power such miniaturized devices
For spectroscopic characterization on the electrochemically deposited Manganese oxide (MnOx) and the electrophoretically reduced graphene oxide (rGO) films, Fourier Transform Infrared (FTIR) studies were carried out using a JASCO FTIR-4100 (JASCO, Easton, MD, USA) equipped with an attenuated total reflectance (ATR) accessory The top and the cross sectional views of the symmetric and asymmetric microsupercapacitors were investigated using scanning electron microscopy (SEM) with a JEOL SEM 6330 (JEOL, Peabody, MA, USA) in the secondary electron imaging (SEI) mode
The broad absorption peak centered around 3374 cm−1 in the graphene oxide (GO) powder is the characteristic infrared (IR) band position from the OH stretching vibrations [37,38], whereas the peaks at 1727, 1624, 1377, 1234, and 1083 cm−1 are attributed to C=O stretching [38], aromatic C=C stretching [39], carboxyl [40], Micromachines 2018, 9, x FOR PEER REVIEW
Summary
With the technological impetus of going “micro”, it is imperative to create small-scale energy devices that can effectively power such miniaturized devices. Pseudocapacitive materials exhibit larger specific capacitances, whereas double layer type materials exhibit better rate handling capability and superior cycle longevity [2]. Quite akin to their larger variants, miniaturized electrochemical energy storage (EES) systems can be connected externally for peak power and energy delivery; it is desirable for the generation micro-power devices to be single standalone systems that can provide with simultaneous supply of high energy and high power. One of the strategies for achieving the latter is the asymmetric or hybrid supercapacitor design Such systems typically combine a redox-type electrode along with a counter double layer capacitive electrode in one cohesive system and benefit from the larger capacity of the redox material and the superior kinetics and cycle life of the double layer material. Each eloercgtarnoidc erecsoidmuepsr.iTsehde t1y8pificanlgweirdst,hreosfuthlteinggoldinfiangtoertsalwoafs 31600fiμnmgewrsithfoarnainstienrgdliegitdael vgiacpeoafn1d00a total finger aμrmeaaonfd0a.3le1n6g8thcmof28,8w00hμerme.aEsatchheeelefcfetrcotdiveecofomoptrpisreindt1a8rfeiangoefrst,hreesdueltvinicgein(ina ctolutadl ionfg36fifninggeerrsgafoprs) was ~0.66 cma(ins2ic.nlugUdlenindlgeesvfsiincoegteahrnedgraawptsio)stewalamfsine~gn0e.t6ri6oarncemead2o.,fUt0hn.3lee1s6es8leocctmhtre2o,rwwchihseeemremaiecsnathtlieopneaefrfdea,cmttihveeeteefloresocttwproreicnrheteamnreiocaramol fpatahlrieazmdeedevteiwcresith the finger awreeareinnotrhmisalwizeodrkw.ith the finger area in this work
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