Phase-transition-free rivets for layered oxide potassium cathodes

As a cathode material for potassium-ion batteries (PIBs), manganese-based layered oxides have attracted widespread attention due to their low cost, ease of synthesis, and high performance. However, the Jahn–Teller effect caused by Mn³⁺ and the irreversible phase transformation of the structure leads to poor cycle stability, limiting the development of layered oxides in PIBs. Herein, we demonstrate the use of phase-transition-free CaTiO₃ as rivets in K_0.5Mn_0.9Ti_0.1O₂ by a simple solid-state method. As verified by the in situ X-ray diffraction, the CaTiO₃ rivets effectively prevent the slippage of the transition metal layer during charge and discharge, inhibiting structural degradation. As a result, the obtained K_0.5Mn_0.9Ti_0.1O₂-0.02CaTiO₃ shows excellent cycling stability and rate performance, with high capacities of 119.3 and 70.1 mAh·g⁻¹ at 20 and 1000 mA·g⁻¹, respectively. At 200 mA·g⁻¹, the capacity retention remains 94.7% after more than 300 cycles. This work represents a new avenue for designing and optimizing layered cathode materials for PIBs and other batteries.