Abstract
Biomass is treated as the most promising carbon source for supercapacitor electrodes. However, ash in biomass especially Si component is always identified as an adverse substance, which is moved by acid pickling in advance. Factually, SiO2 in biomass can be converted into transition metal silicate (TMS). In this work, NaH2PO2 and Co(NO3)2 are newly used in sequence to form mesopores and micropores on the rice husks which can be regarded as one carbon-silicon compound material. SiO2 in rice husks is converted to TMSs reacting with Co(NO3)2, and carbon is catalyzed to graphitize by the Co element. The remaining CoO derived from Co(NO3)2 forms a heterostructure with Co2SiO4. The pore design criteria for electrode materials with redox reactions are proposed based on COMSOL simulation results, which include mesopores playing a decisive role in ion diffusion, the pore size should be gradually reduced, and the specific capacitance is significantly increased when the porosity is greater than 0.8. The electrode material prepared that Co2SiO4/CoO is anchored on carbon with hierarchical pores has outstanding performance: 246.60 F·g−1 at 0.5 A·g−1 for specific capacitance and good cycle capability (88.06% after 10,000 cycles). For the mr10-500-C/CoSi/CoO-900//AC device, it has excellent energy density (37.500 Wh·kg−1 at 1350 W·kg−1).
Published Version
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