P3-type layered K0.6Cr0.6Ti0.4O2 for potassium storage applications

Abstract

P3-type K_0.6Cr_0.6Ti_0.4O₂ is synthesized via a solid-state method and is tested as a positive electrode for potassium-ion batteries. It operates at a higher potential of E_ave. = 3.14 V vs. K/K⁺, while delivering a reversible capacity superior to 40 mA h g⁻¹ in a K cell. Excellent reversibility as an electrode material is achieved with a 3.9 V cutoff based on solid-state redox reaction of Cr ions. An in situ X-ray diffraction study reveals a reversible phase transition during K⁺ ion extraction/insertion. Furthermore, the excellent cyclability for 500 cycles at a rate of 40 mA g⁻¹ coupled with good rate capability demonstrates its advantage as the host structure for potassium ion storage applications.