Cu-doped MOF-derived α-Fe 2 O 3 coatings on carbon fiber fabric as Li-ion and Na-ion battery anodes for potential structural batteries

Multifunctional composite materials have emerged as the most promising way to develop materials that can simultaneously store energy and serve structural roles. However, although carbon fiber is a suitable substrate due to its excellent mechanical properties and electrical conductivity, its low specific capacity limits its performance. To address this, coatings constituted by Transition Metal Oxides (TMOs) have been proposed to enhance the specific capacity. Unfortunately, these materials suffer from some drawbacks as a low rate capability and limited cyclability. To mitigate these issues, strategies such as surface coating of carbon fibers with TMOs derived from metal-organic frameworks (MOFs) are being explored. In this study, a simple and cost-effective doping process has been carried out to improve the electrochemical performance of carbon fiber as a Li-ion anode. This was achieved by depositing MOF-derived alpha-Fe2O3 on carbon fiber, followed by Cu2+ doping. The doping with Cu2+ has not only improved the rate capability but also increased the specific capacity by 18 % at a current density of 25 mA/g, reaching 383 mAh/g. Furthermore, Cu2+ doped alpha-Fe2O3 on carbon fiber has been successfully characterized for Na-ion applications, demonstrating a specific capacity of 150 mAh/g at 5 mA/g.