Synergistic Pinning Effect in Layer-structured Oxide Cathode for Enhancing Stability towards Potassium-Ion Batteries

Abstract

Manganese based layer-structured transition-metal oxides are highly regarded as excellent cathode materials for potassium-ion batteries (KIBs) for their excellent industrial processing feasibility and high voltage platform. However, the energy density and cycling lifetime cannot simultaneously satisfy the basic requirements of the market for energy storage systems. One of the primary causes results from the complex structural transformation and transition metal migration during the potassium intercalation/deintercalation process. Constructing a low-strain host with minimal lattice volume change, maintaining the Mn^3+/Mn⁴⁺ valence state balance and suppressing the Jahn-Teller effect has emerged as an excellent approach to improving structural and electrochemical stability. A P3-K_0.5Mn_0.87Co_0.05Fe_0.05Li_0.03O₂ was synthesized and employed as cathode material. It effectively preserves the orbital and electronic integrity of octahedral center metal elements, mitigating the Jahn-Teller distortion caused by Mn³⁺ and stabilizing the lamellar structure by suppressing harmful phase transitions. Excellent rate performance over a wide voltage range of 1.5 to 4.0 V was exhibited. It has initial specific capacities of 107.1 and 100.87 mAh g^-1 at 20 and 50 mA g^-1, with capacity retentions of 82.3% and 99.2% after 100 cycles, respectively. Even at the high current densities of 200 mA g^-1 and 500 mA g^-1, the initial capacity retention reached 88.5% and 74.56% after 300 and 900 cycles, respectively.