Rational design of double-sandwich-like C@Co,CoO/Co2SiO4/rGO architectures boost electrochemical performances of Co2SiO4 for energy storage devices

Abstract

• A double-sandwich-like C@Co,CoO/Co 2 SiO 4 /rGO structure with enhanced performance is prepared. • The intimal rGO plays the role of supporting structure and conductive core for Co 2 SiO 4 . • The outer layer C@Co,CoO acts as the protective and conductive carapace for the whole electrode. • C@Co,CoO/Co 2 SiO 4 /rGO achieves the specific capacitance of 360F·g −1 at 0.5 A·g −1 in − 0.4 V ∼ 0.5 V. • C@Co,CoO/Co 2 SiO 4 /rGO delivers super long lifespan with 88 % after 15,000 cycles. The research on developing cobalt silicate (Co 2 SiO 4 )-based materials with high energy and power densities for energy storage devices has sprung up in the field of transition metal silicates (TMSs)-type supercapacitors (SCs). However, the electrochemical performances of the reported Co 2 SiO 4 -based materials are not enough desirable owing to the poor conductivity and narrow voltage ranges originated from the intrinsic shortcomings of Co 2 SiO 4 . Herein, we design a double-sandwich-like composite, C@Co,CoO/Co 2 SiO 4 /rGO/Co 2 SiO 4 /C@Co,CoO (denoted as C@Co,CoO/Co 2 SiO 4 /rGO) architecture, to improve the electrochemical performance of Co 2 SiO 4 , where, reduced graphene oxide (rGO) is inside, both sides of rGO are coated by Co 2 SiO 4 , and carbon@cobalt/cobalt oxide (C@Co,CoO) are formed on the surface of Co 2 SiO 4 . This integrated construction can not only avert the sluggish mass/electron transfer progress caused by the conventional Co 2 SiO 4 , C@Co,CoO and rGO multi-phase mixture system, but also improve the cycle stability by protecting Co 2 SiO 4 from the dissolution and structural collapse during the electrochemical process. As expected, the double-sandwich-like C@Co,CoO/Co 2 SiO 4 /rGO displays promising electrochemical performances. At 0.5 A·g −1 , it achieves the specific capacitance of 360 F·g −1 (324 C·g −1 ) in the potential interval of − 0.4 V ∼ 0.5 V, and super long lifespan with 88 % after 15,000 cycles. Moreover, the hybrid supercapacitor (HSC) device C@Co,CoO/Co 2 SiO 4 /rGO//AC displays the capacitance with 687 mF·cm −2 at 1 mA·cm −2 , energy density with 1.373 Wh·m −2 at 1.5 W·m −2 , and even shows practical application for lightening the LED bulb. This work provides an idea for the preparation of the integrated double-sandwich-like carbon/TMSs/carbon architecture to boost the electrochemical performance of TMSs.