Constructing FeSe2 nanorods supported on ketjenblack with superior cyclability for potassium-ion batteries

Abstract

Potassium ion batteries (PIBs) are attractive for the rapidly emerging large-scale energy storage market for intermittent renewable resources. The cost of PIBs can be substantially reduced by utilizing easily synthesized and long cycle-life active materials. This study introduces a one-step solid-state synthesis approach for the encapsulation of FeSe₂ nanorods within a ketjenblack (KB) carbon matrix, yielding an FeSe₂@C-3 composite. As an anode material for PIBs, it exhibits an excellent cycling performance (a high specific capacity of 286 mA h g⁻¹ after 3500 cycles at 1.0 A g⁻¹). Equally noteworthy is its superior rate performance, demonstrating a reversible specific capacity of 303 mA h g⁻¹ at a high-rate density of 2.0 A g⁻¹. Theoretical calculation confirms that the superior potassium storage performance of FeSe₂ is attributed to the low K⁺ intercalation energy. Additionally, the immobilization of FeSe₂ nanorods within the conductive KB network can preserve the electrical and structural integration of the whole electrode. Furthermore, when coupled with perylene-3,4,9,10-tetracarboxylic dianhydride as the cathode, the FeSe₂@C-3 full cell sustains a specific capacity of 107 mA h g⁻¹ at 0.1 A g⁻¹ and effectively powers 40 light-emitting diode light bulbs after 200 cycles. This study presents a cost-effective way to produce Fe-based anode materials and introduces a novel structural design strategy aimed at extending the cycle life.