Three-dimensional thiophene-diketopyrrolopyrrole-based molecules/graphene aerogel as high-performance anode material for lithium-ion batteries

Abstract

Herein, 3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (TDPP) and di-tert-butyl 2,2'-(1,4-dioxo-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-2,5(1H,4H)-diyl)diacetate (TDPPA) were synthesized, which were then loaded in graphene aerogels. The as-prepared thiophene-diketopyrrolopyrrole-based molecules/reduced graphene oxide composites for lithium-ion battery (LIB) anode composites consist of DPPs nanorods on a graphene network. In relation to the DPPs part, embedding DPPs nanorods into graphene aerogels can effectively reduce the dissolution of DPPs in the electrolyte. It can serve to prevent electrode rupture and improve electron transport and lithium-ion diffusion rate, by partially connecting DPPs nanorods through graphene. The composite not only has a high reversible capacity, but also shows excellent cycling stability and performance, due to the densely distributed graphene nanosheets forming a three-dimensional conductive network. The TDPP₆₀ electrode exhibits high reversible capacity and excellent performance, showing an initial discharge capacity of 835 mA h g^-1 at a current density of 100 mA g^-1. Even at a current density of 1000 mA g^-1, after 500 cycles, it still demonstrates a discharge capacity of 303 mA h g^-1 with a capacity retention of 80.7%.

Scheme 1. Molecular structures of the TDPP and TDPPA.

Fig. 1. Schematic illustration of the fabrication process for the DPPs.

Fig. 2. SEM image of (a) TDPP₆₀ surface. (b) TDPPA₆₀ surface.

Fig. 3. (a) The FT-IR spectra and (b) the XRD patterns of TDPP₆₀, TDPPA₆₀ and RGO.

Fig. 4. CV curves of the DPPs at a scan rate of 0.1 mV s⁻¹ (a) TDPP₆₀, (b) TDPPA₆₀, and galvanostatic charge/discharge profiles at a constant current of 100 mA g⁻¹ (c) TDPP₆₀, (d) TDPPA₆₀.

Fig. 5. (a) TDPP/RGO and (b) TDPPA/RGO cycling performance for the electrodes conducted at a current density of 1000 mA g⁻¹ between 0.01 V to 3.0 V over 2000 cycles.

Fig. 6. (a) Rate capability of TDPP₆₀, and (b) TDPPA₆₀ with the current density increased from 100 to 1000 mA g⁻¹ in a stepwise manner.

Fig. 7. Electrochemical impedance spectra of different samples at a range from 100 kHz to 10 mHz. (a) TDPPs and (b) TDPPAs.

Fig. 8. The ex situ FT-IR patterns for the DPPs electrodes obtained at different cycling states. (a) TDPP₆₀ and (b) TDPPA₈₀.

Fig. 9. XPS spectra of the surface for the TDPPA60 electrodes (a and d) as-prepared, (b and e) after 3rd-cycle lithiation process, (c and f) after 3rd-cycle delithiation process.

Fig. 10. SEM images for the DPPs electrodes (a, c and e) TDPP₆₀ and (b, d and f) TDPPA₆₀ at a current density of 1000 mA g⁻¹. (a and b) 200 cycles, (c and d) 500 cycles, (2000) cycles.