Boosting the energy density of supercapacitors by encapsulating a multi-shelled zinc–cobalt-selenide hollow nanosphere cathode and a yolk–double shell cobalt–iron-selenide hollow nanosphere anode in a graphene network

A facile strategy is developed to construct graphene-encapsulated multi-shelled zinc–cobalt-selenide hollow nanospheres and graphene-encapsulated yolk–double shell cobalt–iron-selenide hollow nanospheres for asymmetric supercapacitors.