Realizing a single-phase reaction and K+/vacancy disordering in P2-K0.56Na0.11Li0.12Ni0.22Mn0.66O2 by lithium substitution for potassium-ion batteries

Abstract

Rechargeable potassium-ion batteries (PIBs) have shown great potential as an alternative to lithium-ion batteries (LIBs) owing to the abundant and available potassium reserves. However, their applications are hindered by unsatisfactory cycling stability of cathode materials. Herein, through electrochemical ion-exchange of the Na_0.85Li_0.12Ni_0.22Mn_0.66O₂ compound, we reported P2-K_0.56Na_0.11Li_0.12Ni_0.22Mn_0.66O₂ (P2-KNaLNM) as a potential high-performance cathode for PIBs. The presence of Li plays a key role in suppressing the K⁺/vacancy ordering within transition metal slabs. Therefore, P2-KNaLNM underwent a simple single-phase reaction during intercalation/extraction of K⁺ ions. Consequently, P2-KNaLNM delivers a reversible capacity of 90.2 mA h g⁻¹ and good capacity retention of 89.6% over 150 cycles at 0.2C between 1.5 and 4.6 V (vs. K⁺/K). Furthermore, a satisfactory capacity retention of 91.5% after 300 cycles is achieved at 0.5C because of the excellent K⁺ kinetics during the charge and discharge process. This work provides a feasible way to develop a promising cathode candidate for PIBs.