FeSe2 nanoparticle embedded in 3D honeycomb-like N-doped carbon architectures coupled with electrolytes engineering boost superior potassium ion storage

Potassium ion batteries (KIB) have been considered as helpful alternative energy storage devices owing to the low-cost and abundant potassium sources. However, it is a critical challenge to explore suitable anode materials and electrolytes for adapting large radius and high activity of K ions. In this study, a novel FeSe 2 nanoparticle embedded in 3D honeycomb-like N-doped carbon architectures (FeSe 2 -NC) is synthesized through a simple solid-state strategy. Such unique architecture structure can not only provide a high-way for electron and K + transport, but also effectively alleviate volume variation during long-term K + intercalation/deintercalation process. Hence, FeSe 2 -NC as anode materials for KIB display a high discharge capacity of 460 mAh g −1 at 100 mA g −1 and excellent long-term cycling stability even at a high current density of 2 A g −1 . Beyond the electrochemical performance, it is found that storage K + of FeSe 2 -NC represents a conversion mechanism during discharge/charge in KIB. Furthermore, regulating the electrolyte salts via replacing potassium bis(fluorosulfonyl)imide (KFSI) electrolyte with potassium hexafluorophosphate (KPF 6 ) electrolyte can form a more uniform and robust solid electrolyte interphase film, which be responsible for the enhanced electrochemical performance. Therefore, it is helpful to understand the fundamentals of FeSe 2 -NC and promote the practical application of KIB.