Highly-stable P2–Na0.67MnO2 electrode enabled by lattice tailoring and surface engineering

One of the key challenges of sodium ion batteries is to develop sustainable, low-cost and high capacity cathodes, and this is the reason that layered sodium manganese oxides have attracted so much attention. However, the undesired phase transitions and poor electrolyte-electrode interfacial stability facilitate their capacity decay and limit their practical applications. Herein, we design a novel Al2O3@Na0.67Zn0.1Mn0.9O2 electrode to mitigate these problems, by taking the advantages of both structural stabilization and surface passivation via Zn2+ substitution and Al2O3 atomic layered deposition (ALD) coating, respectively. Long-range and local structural analyses during charging/discharging processes indicate that P2–P2’ phase transformation can be suppressed by substituting proper amount of Mn3+ Jahn-Teller centers with Zn2+, whereas excessive Zn2+ leads to P2-OP4 structure transition at low sodium contents and facilitates the electrode degradations. Furthermore, the homogeneous and robust cathode electrolyte interphase (CEI) layers formed on the Al2O3-coated electrodes effectively hinder the organic electrolytes from further decomposition. Therefore, our synergetic strategy of Zn2+ substitution and ALD surface engineering remarkably boosts the cycling performance of P2–Na0.67MnO2 and provides some new insights into the designing of highly stable cathode electrodes for sustainable sodium ion batteries.