Dual storage mechanism of Bi2O3/Co3O4/MWCNT composite as an anode for lithium-ion battery and lithium-ion capacitor

Bismuth oxide(Bi₂O₃) and cobalt oxide(Co₃O₄) are promising owing to their unique properties, high storage capacity, low cost, and eco-friendliness, making them ideal for lithium-ion batteries(LIBs) and lithium-ion capacitors(LICs) anodes. This study presents the synthesis and thorough characterization of Bi₂O₃/Co₃O₄ and Bi₂O₃/Co₃O₄/MWCNT composites as potential LIB and LIC anode materials. The materials are synthesized using a hydrothermal process succeeded by annealing. Structural, morphological, and compositional studies were analyzed. Various tests evaluated electrochemical performance, including cyclic voltammetry(CV), confirming a dual storage mechanism like alloying and conversion reaction involved for better energy storage. Specific discharge capacities of 834 mAh/g and 1184 mAh/g were recorded for Bi₂O₃/Co₃O₄ and Bi₂O₃/Co₃O₄/MWCNT composite electrodes at a current density of 100 mA/g, respectively. The composite material exhibited notably enhanced rate capability, with 31 % and 51 % discharge capacities for Bi₂O₃/Co₃O₄ and Bi₂O₃/Co₃O₄/MWCNT, respectively. The cyclic stability assessment revealed that Bi₂O₃/Co₃O₄ and Bi₂O₃/Co₃O₄/MWCNT maintained a high coulombic efficiency of around 99 % over 250 charge–discharge cycles at a high current density of 1 A/g. The capacity retention was approximately 253 mAh/g for Bi₂O₃/Co₃O₄ and 439 mAh/g for the Bi₂O₃/Co₃O₄/MWCNT composite, indicating excellent cyclic stability and minimal energy loss during cycling. Moreover, the LICs assembly of Bi₂O₃/Co₃O₄/MWCNT//CB was investigated, revealing a power density of 200 W kg⁻¹ alongside an energy density of 8.64 Wh kg⁻¹. The cyclic stability assessment over 10,000 cycles exhibits a capacity retention of approximately 45 % under a high current density of 2 A/g.