Highly bonded T -Nb 2 O 5 /rGO nanohybrids for 4 V quasi-solid state asymmetric supercapacitors with improved electrochemical performance

Yuzhi Jiao, Haitao Zhang, Hailang Zhang, Ao Liu, Yanxia Liu, Suojiang Zhang

Index: 10.1007/s12274-018-2049-1

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Abstract

T-Nb2O5/reduced graphene oxide nanohybrids were fabricated via the hydrothermal attachment of Nb2O5 nanowires to dispersed graphene oxide nanosheets followed by a high-temperature phase transformation. Electrochemical measurements showed that the nanohybrid anodes possessed enhanced reversible capacity and superior cycling stability compared to those of a pristine T-Nb2O5 nanowire electrode. Owing to the strong bonds between graphene nanosheets and T-Nb2O5 nanowires,the nanohybrids achieved an initial capacity of 227 mAh·g−1. Additionally, non-aqueous asymmetric supercapacitors (ASCs) were fabricated with the synthesized nanohybrids as the anode and activated carbon as the cathode. The 3 V Li-ion ASC with a LiPF6-based organic electrolyte achieved an energy density of 45.1 Wh·kg−1 at 715.2 W·kg−1. The working potential could be further enhanced to 4 V when a polymer ionogel separator (PVDF-HFP/LiTFSI/EMIMBF4) and formulated ionic liquid electrolyte were employed. Such a quasi-solid state ASC could operate at 60 °C and delivered a maximum energy density of 70 Wh·kg−1 at 1 kW·kg−1.