Fabrication of a Mo-Doped Strontium Cobaltite Perovskite Hybrid Supercapacitor Cell with High Energy Density and Excellent Cycling Life.

Abstract

Enriched with oxygen vacancies, Mo-doped strontium cobaltite (SrCo0.9 Mo0.1 O3-δ , SCM) is synthesized as an oxygen anion-intercalated charge-storage material through the sol-gel method. The supplemented oxygen vacancies, good electrical conductivity, and high ion diffusion coefficient bestow the SCM electrode with excellent specific capacitance (1223.34 F g-1 ) and specific capacity (168.88 mAh g-1 ) at 1 A g-1 . The decisive constant (b-value) deduced for the charge storage mechanism (low scan-rate region) is nearly 0.8, indicating a highly capacitive process. In the high scan-rate region, however, the b-value is almost 0.5, and a linear pattern of charge (q) versus the inverse of the square root of the scan rate (v-1/2 ) is obtained. The results reveal O2- diffusion as the rate-limiting factor for charge storage. Furthermore, a hybrid cell (SCM∥LRGONR) is fabricated by using lacey, reduced graphene oxide nanoribbon (LRGONR) as the negative electrode, which exhibits a high energy density (74.8 Wh kg-1 at a power density of 734.5 W kg-1 ). With a charging time of only 20.7 s, the cell sustains a very high energy density (33 Wh kg-1 ) with a high power delivery rate (6600 W kg-1 ). The excellent cycling stability (165.1 % activated specific capacitance retention and 97.6 % of the maximum value attained) after 10 000 charge-discharge cycles, demonstrates SCM is a potential electrode material for supercapacitors.