Hollow Porous CoO@Reduced Graphene Oxide Self-Supporting Flexible Membrane for High Performance Lithium-Ion Storage

Abstract

We report an environment-friendly preparation method of rGO-based flexible self-supporting membrane electrodes, combining Co-MOF with graphene oxide and quickly preparing a hollow CoO@rGO flexible self-supporting membrane composite with a porous structure. This unique hollow porous structure can shorten the ion transport path and provide more active sites for lithium ions. The high conductivity of reduced graphene oxide further facilitates the rapid charge transfer and provides sufficient buffer space for the hollow Co-MOF nanocubes during the charging process. We evaluated its electrochemical performance in a coin cell, which showed good rate capability and cycling stability. The CoO@rGO flexible electrode maintains a high specific capacity of 1103 mAh g^-1 after 600 cycles at 1.0 A g^-1. The high capacity of prepared material is attributed to the synergistic effect of the hollow porous structure and the 3D reduced graphene oxide network. This would be considered a promising new strategy for synthesizing hollow porous-structured rGO-based self-supported flexible electrodes.

Keywords: CoO@rGO; MOF; flexible electrodes; graphene; hollow structure; lithium-ion batteries; ultrafast integration.

Scheme 1

Schematic illustration for the synthesis and construction of the Co-MOF@rGO flexible film.

Figure 1

(a) Digital images of CoO@rGO films; SEM images of (b,c) Co-MOF@GO composites, (d–g) etched Co-MOF@rGO composites, (h,i) CoO@rGO flexible film.

Figure 2

(a–c) TEM image of Co-MOF@rGO, (d) HRTEM images of EDX mapping of hollow Co-MOF@rGO flexible films, (e–i) are the elemental mapping of C, Co, O, S and N, respectively.

Figure 3

(a) XRD patterns; (b) TG curve; (c) Raman spectra; (d) FT-IR spectra of the CoO@rGO flexible film.

Figure 4

Nitrogen adsorption–desorption isotherms of (a) Co-MOF@rGO before etching and (b) Co-MOF@rGO after etching; (c) XPS survey spectrum and corresponding (d) C 1s, (e) Co 2p, and (f) O 1s XPS spectra of the CoO@rGO flexible film.

Figure 5

Electrochemical properties of the CoO@rGO flexible film for LIBs: (a) discharge/charge curves at a current density of 1 A g⁻¹; (b) rate properties; (c) CV curve at different sweep speeds; (d) fitting curves of the b-values; (e) the capacitive contribution to charge storage at a scan rate of 0.2 mV s⁻¹; (f) the capacitive and diffusion contributions at different scan rates; (g) cycling properties at 1.0 A g⁻¹.