La-doped V2O5·nH2O@OAB and flexible Fe2O3@rGO as binder-free thin film electrodes for asymmetric supercapacitors.

• The binder-free thin film electrodes were synthesized by sol-gel method. • The host material could be firmly riveted on the rGO or OAB surface. • The La-VOH@OAB exhibited an excellent rate capability (81.1% retention). • The assembled ASC devices showed an ultrahigh energy density of 56.3 Wh kg−1. In this work, multilayer networks lanthanum-doped V 2 O 5 · n H 2 O@OAB (noted as La-VOH@OAB) binder-free thin film positive electrode has been first successfully synthesized via a simple and economical sol-gel and drop-coating methods. Benefiting from its unique architecture and the favorable synergetic contributions for rare earth metal ions of La3+ and hydrophilic carbon of OAB, after the condition optimization, the 20%La-VOH@OAB-4 exhibits an excellent electrochemical performance with an ultrahigh specific capacitance of 612 F g−1 at a current density of 1 A g−1, good rate capability (81.1%, the current density increases tenfold) and outstanding cycling stability (90.4% capacitance retention over 2000 cycles). In addition, flexible Fe 2 O 3 @rGO binder-free thin film negative electrode prepared with the similarly facile strategy demonstrates a high specific capacitance of 366 F g−1 due to Fe 2 O 3 nanoparticles tightly anchored on the rGO surface. The assembled 20%La-VOH@OAB-4//Fe 2 O 3 @rGO ASCs device within a voltage window of 1.7 V delivers a relatively high specific energy density of 56.3 Wh kg−1 at a power density of 849.9 W kg−1 with exceptional cycling stability (81.3% capacitance retention after 5000 cycles), moreover, two ASCs devices in parallel can light up a red LED for 3 min, demonstrating its potential in practical applications. This work provides a certain reference for the fabrication of environmentally friendly thin film electrodes for developing high efficient energy storage systems. [ABSTRACT FROM AUTHOR]