RESUMEN
The study presents a novel, one-pot, and scalable solid-state reaction scheme to prepare bismuth sulphide (Bi2S3)-reduced graphene oxide (rGO) nanocomposites using bismuth oxide (Bi2O3), thiourea (TU), and graphene oxide (GO) as starting materials for energy storage applications. The impact of GO loading concentration on the electrochemical performance of the nanocomposites was investigated. The reaction follows a diffusion substitution pathway, gradually transforming Bi2O3 powder into Bi2S3 nanostrips, concurrently converting GO into rGO. Enhanced specific capacitances were observed across all nanocomposite samples, with the Bi2S3@0.2rGO exhibiting the highest specific capacitance of 705 F g-1 at a current density of 1 A g-1 and maintaining a capacitance retention of 82% after 1000 cycles. The superior specific capacitance is attributed to the excellent homogeneity and synergistic relation between rGO and Bi2S3 nanostrips. This methodology holds promise for extending the synthesis of other chalcogenides-rGO nanocomposites.
RESUMEN
A 3D framework with Nasicon structured polyanionic Na3V2(PO4)3 (NVP) has been emphasized as a leading cathode material for sodium-ion batteries (SIBs) due to its high working voltage plateau, structural stability, and good rate performance. Herein, pristine NVP and MWCNT@NVP composite synthesized via a facile solid-state method are examined and compared as cathode materials for Na-ion batteries. The morphological study confirms the uniform distribution of MWCNTs in the pristine NVP structure. Impedance spectroscopy clearly confirms more diffusion of Na ions for the MWCNT@NVP composite as compared to pristine NVP, considering its diffusion coefficient which directly implies on an increase in specific capacity. MWCNT@NVP (FNV-2) showed specific discharge capacity 110 mAhg-1 at 0.1C current rate which is almost stable at higher current rates with marginal fading. However, the pristine NVP shows capacity loss at a higher current rate. It is noteworthy that the MWCNT@NVP composite shows stable performance with marginal specific capacity fading (1%) compared to pristine (15%). This is because of the mechanical integrity and stability afforded to the composite by the intertwined MWCNT framework in the MWCNT@NVP composite matrix against electrode degradation during the electrochemical reaction. More significantly, even at a higher current rate, that is, at 10 C, the composite recorded a very stable and excellent Columbic efficiency of 97% with a reversible specific capacity of 94 mAhg-1 after 2000 cycles. An enhanced electrochemical performance, that is, rate capability and cycling stability, demonstrates the high potential of the MWCNT@NVP composite for Na-ion storage. Moreover, a sodium-ion full cell with hard carbon demonstrated a reversible capacity of 103 mAhg-1 at C/20 current rate, which clearly demonstrates that MWCNT@NVP is a promising cathode material for sodium-ion batteries.
