TY - JOUR
T1 - Phase- and interlayer spacing-controlled cobalt hydroxides for high performance asymmetric supercapacitor applications
AU - Jana, Milan
AU - Sivakumar, Periyasamy
AU - Kota, Manikantan
AU - Jung, Min Gyu
AU - Park, Ho Seok
N1 - Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2019/5/15
Y1 - 2019/5/15
N2 - A facile and selective hydrothermal synthesis is performed to control the crystalline phases of cobalt hydroxides into α-Co(OH)2 and β-Co(OH)2: α-Co(OH)2, consisting of both octahedral and tetrahedral Co sites, is produced without ionic liquids, whereas β-Co(OH)2, containing octahedral Co sites, is synthesized in the presence of ionic liquids. The ionic liquids play significant role as co-solvent and template to tune the morphology of Co(OH)2. α-Co(OH)2 reveals flake-like structure, whereas β-Co(OH)2 exhibits nanorod-like network structure. The interlayer spacing of α-Co(OH)2 is 8.24 Å, which is larger than 4.63 Å of β-Co(OH)2 due to the expansion of interlayer by the precursor Cl─ anions. The presence of Cl─ anions hinders the insertion of hydroxide ion into α-Co(OH)2 interlayers, which shows the specific capacitance of 613 F g─1 less than 1066 F g─1 of β-Co(OH)2 at 2 A g─1. When the current density increases up to 20 A g─1, the capacitance retention of β-Co(OH)2 is 80%, greater than 70% of α-Co(OH)2. Configuring β-Co(OH)2 and reduced graphene oxide as positive and negative electrodes, asymmetric supercapacitor delivers the maximum energy and power densities of 20.05 W h kg─1 and 13.40 kW kg─1 with the capacitance retention of 93% over 10,000 cycles.
AB - A facile and selective hydrothermal synthesis is performed to control the crystalline phases of cobalt hydroxides into α-Co(OH)2 and β-Co(OH)2: α-Co(OH)2, consisting of both octahedral and tetrahedral Co sites, is produced without ionic liquids, whereas β-Co(OH)2, containing octahedral Co sites, is synthesized in the presence of ionic liquids. The ionic liquids play significant role as co-solvent and template to tune the morphology of Co(OH)2. α-Co(OH)2 reveals flake-like structure, whereas β-Co(OH)2 exhibits nanorod-like network structure. The interlayer spacing of α-Co(OH)2 is 8.24 Å, which is larger than 4.63 Å of β-Co(OH)2 due to the expansion of interlayer by the precursor Cl─ anions. The presence of Cl─ anions hinders the insertion of hydroxide ion into α-Co(OH)2 interlayers, which shows the specific capacitance of 613 F g─1 less than 1066 F g─1 of β-Co(OH)2 at 2 A g─1. When the current density increases up to 20 A g─1, the capacitance retention of β-Co(OH)2 is 80%, greater than 70% of α-Co(OH)2. Configuring β-Co(OH)2 and reduced graphene oxide as positive and negative electrodes, asymmetric supercapacitor delivers the maximum energy and power densities of 20.05 W h kg─1 and 13.40 kW kg─1 with the capacitance retention of 93% over 10,000 cycles.
KW - Asymmetric device
KW - Cobalt hydroxide
KW - Hybrid supercapacitors
KW - Ionic liquid
KW - Nanostructure
KW - Redox capacitor
UR - http://www.scopus.com/inward/record.url?scp=85062859054&partnerID=8YFLogxK
U2 - 10.1016/j.jpowsour.2019.03.019
DO - 10.1016/j.jpowsour.2019.03.019
M3 - Article
AN - SCOPUS:85062859054
SN - 0378-7753
VL - 422
SP - 9
EP - 17
JO - Journal of Power Sources
JF - Journal of Power Sources
ER -