Enhancing electrochemical performance of high-entropy Co/Ni-free P2/O3 hybrid-phase layered metal oxide cathode for sodium-ion batteries

The high-entropy design strategy of the TM layer and the NTP capping strategy are conducive to the structural stabilization of the cathode material and improve its anion redox reversibility and cycling performance. [Display omitted] •NCFMMT@NTP cathode designed by high entropy design and surface cladding.•Improved voltage hysteresis in Co-Ni-free Fe-Mn-based modified materials.•NCFMMT@NTP has a composite phase structure and an elevated ion mobilization rate.•The redox reversibility of oxygen in the material rises at high voltages.•Both capacity degradation and structural damage of the material are suppressed. Sodium-ion batteries (SIBs) have currently garnered increasing attention due to their promising applications and potential advantages. Despite the cost and performance advantages, the Co/Ni-free Fe-Mn-based cathode materials tends to undergo a large phase transition in the sodium (de)intercalation layer, which will result in the material structure damage. In this work, high entropy P2/O3-Na0.75Cu0.1Fe0.2Mg0.2Mn0.4Ti0.1O2 (NCFMMT) materials were successfully prepared by employing NaTi2(PO4)3 (NTP) as the modification layer. It can be distinctly seen that the cyclic stability of NCFMMT@NTP has been significantly improved, and the first capacity at 0.2C reaches 165.32 mAh/g and the capacity can maintain 86.73 % after 100 cycles. Moreover, the voltage hysteresis after triggering anionic redox can be clearly ameliorated. Apparently, the high-entropy strategy not only can satisfactorily optimize the lattice structure and stability of the cathode material during sodium intercalation/de-intercalation process, but also can increase the ion mobilization rate and promote further electrochemical properties. Therefore, this study provides valuable exploration for the design and preparation of cobalt/nickel-free cathodes with excellent electrochemical performance.