| In this paper,simple solvothermal,sol-gel,and carbonization methods were used to prepare core-shell Ni-Ce O2@PANI nanospheres,double-shell Ce O2@C hollow spheres,yolk-shell Si O2@Ti O2@C spheres,and radial mesochannels Si O2/S@PANI.The morphologies and structures of the prepared materials are controllable.Through a series of characterization tests,the conjecture of the experimental mechanism is obtained.These materials are used in supercapacitors,lithium-ion batteries,and lithium-sulfur batteries,respectively.Preparation of core-shell Ni-Ce O2@PANI composites:First,we utilized a facile and template-free glycol solvothermal method to synthesize Ni-Ce O2 nanospheres.Then,ammonium persulfate was added as oxidant,and aniline monomer was polymerized on the surface of Ni-Ce O2 through chemical oxidation polymerization.The core-shell structure of Ni-Ce O2@PANI can play the role of protecting the inner shell of the outer shell.Ni-Ce O2 possesses a uniform spherical nanostructure with a diameter of approximately 100 nm and and PANI is approximately 20 nm.It is used as the electrode material of supercapacitors.When the current density is 1 A g-1,the specific capacitance is 866 F g-1 and the energy density is 120.3 Wh kg-1,and the initial capacitance retention is 85.6%after 10000 cycles.Preparation of double-shell Ce O2@C hollow spheres:First,PVP was used as a soft template,ethylene glycol was used as a solvent,and resorcinol and formaldehyde?RF?was used as a carbon source.After calcination,Ce O2@C composite material can be obtained.This double-shelled structure,in which the Ce O2 hollow nanospheres are uniformly dispersed inside the carbon nanoshells,can simultaneously act as a conductive framework and a protective buffer layer to restrain volume variations.The fabricated nanospheres exhibit remarkable electrochemical performance as anodes for lithium-ion batteries,displaying a high reversible capability(1309.1 m A h g-1 at 100 m A g-1),stable cycling life(903.6m A h g-1 after 300 cycles at 100 m A g-1),and excellent rate capacities(761.6 m A h g-1at 1000 m A g-1).Si O2@Ti O2@C nanospheres were prepared by the sol-gel method and carbon coating,and the hierarchical Si O2@Ti O2@C nanospheres were obtained by further changing the etching time.The Si O2@Ti O2@C with 30 nm void space between yolk and shell exhibits a high discharge capacity of?1195.4 m A h g-1 at the current density of 0.1 A g-1 after 300 cycles and?701.1 m A h g-1 at 1 A g-1 for over 800 cycles.These results suggest that the unique structure can accommodate the volume expansion of yolk,provide a unique buffering space for the charge/discharge processes,improve the structure stability of the electrode material during repeated Li+intercalation/deintercalation,and enhance the cycling stability.The Si O2/S@PANI composite with radial meso-channels was designed and synthesized by in situ chemical oxidative polymerization of aniline on Si O2/S surface.The composite was used as the cathode for lithium–sulfur batteries.The Si O2 nanospheres with radial meso-channels provided sufficient internal space to accommodate the volume expansion for sulfur and possessed strong adsorption capability for lithium polysulfides?Li PSs?.Additionally,the thin PANI coating serving as conductive frameworks generated sufficient electrical conduction paths and effectively prevented the outward diffusion of Li PSs,leading to long-term stability.Benefitting from the composites'unique structural and compositional advantages,we obtained an initial specific capacity of 1008.6 m A h g-1at 0.2 C and an outstanding cycling stability at 1 C rate over 1000 cycles with a capacity decay of 0.04%per cycle. |
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