A novel zinc-ion hybrid supercapacitor for long-life and low-cost energy storage applications

The development of multivalent cation based rechargeable devices have attracted increased interest because that one mole of multivalent ion can contribute double (for M2+) or triple (for M3+) electrons than monovalent ion (M+). Recently, multivalent cation based battery systems (e.g. Mg2+ and Al3+ batteries) have been widely investigated, however, less attention were paid on multivalent cation based supercapacitors and especially hybrid supercapacitors. Herein, we demonstrate a Zn-ion based hybrid supercapacitor (Zn-HSC) through directly designing Zn foil as both anode and current collector, and bio-carbon derived porous material as the cathode. The bivalent nature and high abundance of zinc can enable the Zn-HSC to achieve high energy density with low cost. After optimization, this Zn-HSC demonstrated superior electrochemical performances such as high discharge capacitance (170 F g−1 at 0.1 A g−1), good rate performance (~ 85% capacitance retention at 2 A g−1), high energy density (52.7 Wh kg−1 at 1725 W kg−1 based on the weight of active materials), and excellent cycling stability with 91% capacitance retention after 20,000 cycles at 2 A g−1.