Porous mesocarbon microbeads with graphitic shells: constructing a high-rate, high-capacity cathode for hybrid supercapacitor

140

Controlled micro/mesopores interconnected structures of three-dimensional (3D) carbon with high specific surface areas (SSA) are successfully prepared by carbonization and activation of biomass (raw rice brans) through KOH. The highest SSA of 2475 m2 g−1 with optimized pore volume of 1.21 cm3 g−1 (40% for mesopores) is achieved for KOH/RBC = 4 mass ratio, than others. The as-prepared 3D porous carbon-based electrode materials for supercapacitors exhibit high specific capacitance specifically at large current densities of 10 A g−1 and 100 A g−1 i.e., 265 F g−1 and 182 F g−1 in 6 M KOH electrolyte, respectively. Moreover, a high power density ca. 1223 W kg−1 (550 W L−1) and energy density 70 W h kg−1 (32 W h L−1) are achieved on the base of active material loading (~10 mg cm2) in the ionic liquid. The findings can open a new avenue to use abundant agricultural by-products as ideal materials with promising applications in high-performance energy-storage devices.

Section: Resultsmentioning

confidence: 80%

From Rice Bran to High Energy Density Supercapacitors: A New Route to Control Porous Structure of 3D Carbon

Hou

Cao

et al. 2014

140

“…Supercapacitors, an exclusive class of energy storage devices can look beyond the privileges of rechargeable batteries regarding instant power delivery and ability to sustain millions of charge-discharge cycles at higher current densities 1 , 2 . Unlike batteries, where, energy storage occurs by means of redox reactions; supercapacitors, particularly electrochemical double layer capacitors (EDLCs) store opposite charges at the interface of active layer/electrolyte only by physisorption, and their fast ion-exchange kinetics makes them specifically appealing to be used in high power applications such as hybrid electrical vehicles and power stations 3 . Integrating storage advantage with rate performances seems to be the solution to the recent demands in compact, multifunction portable electronic equipment.…”

Section: Introductionmentioning

confidence: 99%

High-performance flexible supercapacitors based on electrochemically tailored three-dimensional reduced graphene oxide networks

Purkait

Singh

Kumar

et al. 2018

333

150

A simple approach for growing porous electrochemically reduced graphene oxide (pErGO) networks on copper wire, modified with galvanostatically deposited copper foam is demonstrated. The as-prepared pErGO networks on the copper wire are directly used to fabricate solid-state supercapacitor. The pErGO-based supercapacitor can deliver a specific capacitance (Csp) as high as 81±3 F g−1 at 0.5 A g−1 with polyvinyl alcohol/H3PO4 gel electrolyte. The Csp per unit length and area are calculated as 40.5 mF cm−1 and 283.5 mF cm−2, respectively. The shape of the voltammogram retained up to high scan rate of 100 V s−1. The pErGO-based supercapacitor device exhibits noticeably high charge-discharge cycling stability, with 94.5% Csp retained even after 5000 cycles at 5 A g−1. Nominal change in the specific capacitance, as well as the shape of the voltammogram, is observed at different bending angles of the device even after 5000 cycles. The highest energy density of 11.25 W h kg−1 and the highest power density of 5 kW kg−1 are also achieved with this device. The wire-based supercapacitor is scalable and highly flexible, which can be assembled with/without a flexible substrate in different geometries and bending angles for illustrating promising use in smart textile and wearable device.

“…These two aspects ensure a much higher energy density. Secondly, when compared with LIB, the electric double-layer electrode promotes the power capability and cycling stability 32 . As a result, HSC has opened a new avenue for emerging energy-storage applications such as electric vehicles.…”

mentioning

confidence: 99%

Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs//Li4Ti5O12

Zuo

Wang

et al. 2015

107

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li4Ti5O12 (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3 V HSC device exhibits maximum volumetric energy density of ~4.38 mWh cm−3, much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5 V/100 mF supercapacitor (can be operated within 3 s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems.