Phase-junction engineering boosts the performance of CoSe2 for efficient sodium/potassium storage

Sodium ion batteries (SIBs) and potassium ion batteries (PIBs) are the most promising alternative candidates to lithium ion batteries (LIBS), owing to their natural abundance and low cost. Herein, a unique cubic/orthorhombic-CoSe2 phase-junction (c/o-CoSe2) anchored on SiC nanowires (NWs) (denoted as c/o-CoSe2@SiC) is developed. The electron coupling effect of phase-junction interface promotes the diffusion of Na+/K+. Meanwhile, SiC NWs play a pivotal role in stabilizing the active materials, improving the cycling stability and providing fast transport pathways for electrons. Thus, c/o-CoSe2@SiC exhibits a sodium storage performance of 413 mA h g(-1) after 300 cycles at 0.2 A g(-1) with an 86.66% capacity retention rate and 300 mA h g(-1) after 1000 cycles at 1 A g(-1), as well as a potassium storage performance of 190 mA h g(-1) after 500 cycles at 1.0 A g(-1). Moreover, the electrochemical reaction mechanism and the structural reversibility of c/o-CoSe2@SiC are also revealed by operando Raman, operando powder X-ray diffraction (PXRD) and ex situ high resolution transmission electron microscopy (HRTEM) characterization. And theoretical calculations revealed the redistribution of charge and the strongest adsorption of Na+ from the electrolyte at the phase-junction of c/o-CoSe2. Phase-junction engineering could provide a new strategy for developing high-performance SIBs and PIBs.