▎ 摘　　要

Cobalt phosphate Co-3(PO4)(2) and Cobalt phosphate/graphene foam composites Co-3(PO4)(2)/GF were synthesized via a co-precipitation technique. Co-3(PO4)(2)/GF composite was synthesized from Co-3(PO4)(2) with addition of different graphene foam (GF) mass loading to optimize the appropriate amount of GF which effectively synergized its properties with those of the phosphate materials. The structural, morphological and chemical bonding nature of the synthesized products were characterized extensively using various microscopy and spectroscopy techniques to confirm the successful integration of conductive GF with Co-3(PO4)(2) grains. The electrochemical properties of the prepared materials were tested in 1 M KOH electrolyte by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). Co-3(PO4)(2)/20 mg GF composite exhibited a remarkable gravimetric capacity of 57 mAh g(-1) higher than Co-3(PO4)(2) (21 mAh g(-1)) at 0.5 A g(-1) in a half-cell configuration. An asymmetric device was fabricated using Co-3(PO4)(2)/20 mg GF as a positive electrode) with biomass-derived activated carbon from pepper seed (ppAC) as negative electrode, which delivered a specific energy of 52 Wh kg(-1) with an equivalent power of 847 W kg(-1) at 1 A g(-1). The asymmetric device exhibited a capacity retention of 80% over 10 000 cycles at 10 A g(-1). The study demonstrates an adoption of a facile route for obtaining composite materials and interfaced with biomass-derived porous structures for assembly of a stable asymmetric device. (C) 2019 Elsevier B.V. All rights reserved.