A unique porous architecture built by ultrathin wrinkled NiCoO2/rGO/NiCoO2 sandwich nanosheets for pseudocapacitance and Li ion storage

Abstract

Hierarchical porous architectures assembled by ultrathin mesoporous nanosheets are attractive for electrochemical energy storage. Herein, we present a facile and scalable strategy where two ultrathin mesoporous NiCoO₂ sheets (∼2 nm) are anchored on both sides of a rGO sheet to form an ultrathin sandwich nanosheet (∼6 nm) using a chemical co-precipitation method. The sandwich nanosheets are randomly wrinkled, thus the framework built up by such sheets is porous and has a high specific surface area. The high quality rGO endows the composite with excellent conductivity. And the firm adhesion between the NiCoO₂ sheet and flexible rGO also guarantees the integration of the electrode during electrochemical cycling. The electrochemical tests on the electrode made by such ultrathin sandwich nanosheets validate that the strategy is effective to obtain high performance electrodes for supercapacitors and lithium ion batteries. As an electrode of a lithium ion battery, it shows excellent cycling performance with a specific capacity close to 998 mA h g⁻¹ at a current density of 0.1 A g⁻¹; and as an electrode of a supercapacitor, capacitance retention of 87.6% is achieved over 2000 cycles at a constant current density of 20 A g⁻¹.