Layered P2/P3-intergrowth cathode materials with biphasic interlocking towards stable potassium (de)intercalation

Abstract

Potassium layered oxide cathodes usually deliver diverse prismatic-coordinated structural chemistry, enabling to explore thermodynamic-stable P2/P3 biphasic structures to tailor the electrochemical properties for potassium-ion batteries (PIBs). However, their intrinsic thermodynamic phase preference and complex electrochemical reaction mechanism in terms of phase evolution, charge compensation and stress response remain unclear. With this perspective, a P2/P3 biphasic cathode material-K_xLi_0.03Mg_0.03Ti_0.07Ni_0.1Mn_0.77O₂ with a specific phase proportion (P2: P3 = 35.2%: 64.8%) is designed under the guidance of first principles calculation. Benefiting from the interfacial interlocking effect at the phase boundary, the sliding of TM layers is well inhibited. Moreover, the different orientation of P2 and P3 crystalline domain serves to mitigate long range Jahn-Teller ordering of MnO₆ octahedron, lattice mismatch and mechanical stress. Consequently, the P2/P3 biphasic cathode exhibits a high capacity of 110.8 mA h g⁻¹ at 0.2 C and good cycling stability of 82.0% after 150 cycles at 1 C. This work provides insightful guidelines to develop stable biphasic cathode materials through thermodynamic phase modulation for high-performance PIBs.