Stable electrochemical properties of trace titanium doping layered P3-type K0.5Mn0.92Ti0.08O2 cathode material for potassium ion batteries

Abstract

The wide application of potassium ion batteries (PIBs) urgently requires the development of ideal cathode materials with low cost, good reaction kinetics and structural stability. Here, a titanium-doped K_0.5Mn_0.92Ti_0.08O₂ cathode material for potassium ion batteries is developed by doping modification strategy using a high-temperature solid-state method. The structure and performance structure-activity relationship of binary K_0.5Mn_1-xTi_xO₂ cathode materials doped with non-electrochemically active element Ti⁴⁺ are studied experimentally and theoretically. With the introduction of Ti⁴⁺, when the doping amount is <10 mol%, the doped solid solution is hexagonal P3 phase, and the transition metal layer spacing increases. The non-equivalent doping affects the relative content of Mn³⁺/Mn⁴⁺, smoothes the redox peak in the electrochemical process, reduces the doping formation energy, and improves the structural stability. The ex-situ XRD fine structure study of the electrochemical process shows that the structural change of the material during the discharge process is suppressed after doping. The best Ti-doped cathode material K_0.5Mn_0.92Ti_0.08O₂ has an initial discharge capacity of 126.9 mAh·g⁻¹ at a current density of 20 mA·g⁻¹, and the capacity retention rate is 53.7 % after 100 cycles. This work provides a feasible strategy for the construction of stable electrode materials for PIBs.