期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 968, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2023.172175
关键词
Titanium dioxide; Lithium iron phosphate; Carbonization; Hybrid supercapacitor; PAN -b; PFPA copolymer
Hybrid supercapacitors, functioning as both batteries and supercapacitors, have limitations in large-scale applications due to low conductivity and electrical stability. A carbon coating over mixed-phase titanium dioxide, formed by introducing carbon-rich polyacrylonitrile block copolymer, improves the performance and cycling stability of the hybrid supercapacitors.
Hybrid supercapacitors can function as both batteries and supercapacitors owing to their high specific energy and capacitive power, respectively. Transition metal oxide-based electrodes exhibit a high theoretical specific capacitance, but their large-scale application in charge storage devices is limited by their low conductivity and electrical stability. To address this problem, we introduced a highly conductive carbon coating over mixed-phase titanium dioxide (C/TiO2) using a novel carbon-rich polyacrylonitrile block copolymer containing an active pentafluorophenyl acrylate ester block (PAN-b-PFPA). The LiFePO4 (LFP) positrode and C/TiO2 negatrode assembled hybrid LFPC/TiO2 @ 800 supercapacitor exhibited a high specific capacitance of 227 F/g (current density of 1 A/g), power density of 500 W/kg, and energy density of 32 W h/kg. Importantly, higher specific capacitance (-84%) and Coulombic efficiency (-96%) were maintained over 5000 charge-discharge cycles. The improved performance of hybrid LFPC/TiO2 @ 800 supercapacitor is attributable to (1) selectively mixed anatase-rutile TiO2 phases that led to additional Ti3+ oxidation state formation, (2) firm porous carbon coating resulting from the surface anchoring of PAN-b-PFPA copolymer, and (3) fluorine/sulfur impurities from pyrolysis residues. The carbon coating of transition metal oxides from the pyrolysis of PAN-b-PFPA copolymers can facilitate the large-scale development of energy storage materials.
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