Enhancing the Structure Stability and Sodium Storage Performance of P2-Na2/3Ni1/3Mn2/3O2 via Ti-doped

Sodium-ion batteries (SIBs) are considered promising alternative electrochemical energy storage technologies due to the abundant element reserves and low cost of sodium. P2-type layered Na2/3Ni1/3Mn2/3O2 is a neoteric and fascinating cathode material for SIBs due to its stable structures and high operating voltage. However, the internal structure leads to multiple phase transitions and sluggish Na+ ion diffusion, resulting in rapid capacity decay and poor rate performance. Herein, we find that titanium-doped Na2/3Ni1/3Mn2/3O2 cathode exhibits a robust layer-structured framework with frustrated Na+ migration barriers below 0.149 eV. Benefiting from the large Ti-O bond energy and the created O-Ti-O configurations, the new cathode materials can not only stabilize the P2-type layered structure during a wide voltage range of 1.5‒4.3 V, but also lead to the rapid Na+ transport dynamics. Moreover, the excess Ti dopants occupies into Na sites, serving as “immovable pillars”, have virtually adverse effects of blocking working sodium ions diffusion and reducing the rechargeable capacity. These findings reveal an important strategy for the design of layered cathode materials that are vital for sodium-ion batteries.