High-capacitance MXene anode based on Zn-ion pre-intercalation strategy for degradable micro Zn-ion hybrid supercapacitors

Degradable energy storage systems (ESSs) have been proposed to tackle increasing electronic waste such as heavy metals and toxic organic electrolytes. However, ensuring ESS degradability and cycle life at the same time is a paradox challenge. Here we reported a degradable micro Zn-ion hybrid supercapacitor (DMZHSC) based on MXene/ZnCl2 anode and MnO2-MWCNTs cathode. Considering the problem of the lower capacitance of MXene, the ZnCl2 modification strategy of pre-intercalating Zn2+ into the layer of MXene was used by osmotic pressure, opening more active sites for the subsequent Zn2+ intercalation. During this process, Cl- will replace part of the -F terminals on the surface of MXene. Benefited from above modification, the MXene/ZnCl2 anode shown a very high capacitance up to 529.1 F g−1 at 1.00 mV s−1, which is 32.2% higher than pure MXene (400.3 F g−1 at 1.00 mV s−1). More importantly, the assembled DMZHSCs not only possesses excellent flexibility but also can degrades within 2.0 h after mild external stimulation in PBS buffer. This work not only provides a new method for MXene modification but also provides a new idea for the construction of environmentally friendly new capacitors.