Mechanism influence on the coexistence of two anions on redox kinetics and volume effect of CoPSe as anode material for potassium-ion batteries and potassium-ion hybrid capacitors

Ternary metal phosphorus chalcogenides (TMPSe) with two anions of P and Se are promising anode material for potassium-ion battery (PIBs) and potassium-ion hybrid capacitors (PIHCs). The electrical structure and physicochemical properties can be further modified by the coexistence of two anions. However, only few studies have been performed on TMPSe as anode material for batteries. Further, no reviews have attempted to discuss the combined effects of reaction intermediates and doping on the electrochemical properties for PIBs and PIHC. Herein, ternary cobalt phosphoselenide (CoPSe) are in-situ grown in amorphous N-doped carbon nanofibers (denoted as CoPSe@N-CNFs nanotube) via electrospinning technique, followed by synchronous gaseous phosphorization and selenization. Compared with CoSe2, CoPSe@N-CNFs nanotubes, as anode electrode material for PIBs, have significant advantages, such as lower mechanical stress, shorter ion diffusion distance, faster interfacial ion migration, and full exposure of K+ storage site. Furthermore, simulation result indicate that the CoPSe electrode outperforms the CoSe2 electrode in terms of volume expansion buffering during the charge and discharge process. As a result, CoPSe@N-CNFs offers a significant long cycle durability of over 400 cycles at 0.1 A g(-1). Meanwhile, the CoPSe@N-CNFs-based PIHCs achieve the good cycling stability during 2000 cycles at 1.0 A g(-1). Moreover, the root cause of the enhanced performance and phase transformation mechanism of the CoPSe@N-CNFs are revealed through in-situ EIS, ex-situ HRTEM, SAED, and theoretical calculations. Our work proposes an effective strategy to address the volume expansion and kinetic retardation of MSe2 that are often present in PIBs and PIHCs systems.