Synergetic Lattice and Surface Engineering: Stable High-Voltage Cycle Performance in P3-Type Layered Manganese Oxide

Abstract

A synergetic strategy on lattice and surface is implemented using a NaTi2(PO4)3 (NTP) ionic conductor for the P3-type Na0.67[Zn0.3Mn0.7]O2 (NZMO) cathode material; specifically, the stabilization of the oxide lattice through Ti incorporation and the reinforcement of the surface stability with P-containing moieties. This dual functionality enhances electrode performances in terms of long-term capacity retention and charge transfer. More importantly, the presence of the NTP layer contributes to the interfacial stability under high voltage conditions, which is associated with lattice oxygen redox occurring in the highly oxidized Nax[Zn0.3Mn0.7]O2 O/P phase, triggered by Zn migration from the transition metal layer to the Na layer. The enhanced electrode performance is likely attributed to enhanced surface stability, increased ionic conductivity, and the stabilization of the anionic O2-/(O2)n- redox progress at high voltage. The NTP layer suppresses surface reactions with the electrolyte by scavenging HF and H2O, while the introduced Ti contributes to the stabilization of the c-axis variations. Additionally, ab initio molecular dynamics simulations suggest that the NTP layer acts as a protective barrier against electrolyte degradation, preventing HF-induced metal ion dissolution and ensuring long-term stability. These results demonstrate the effectiveness of NTP coatings in enhancing the performance of cathode materials for sodium-ion batteries.