A Cation Chelation and Reassembly Route to Synthesize a P2‐type Na_0.67Ni_0.26Mn_0.67Mg_0.07O₂ Cathode Material for High‐performance Sodium Storage

Abstract P2‐type Na_2/3Ni_1/3Mn_2/3O₂ (Na‐NM) is an appealing cathode candidate for sodium‐ion batteries (SIBs) but still suffers a fast capacity decay. Mg doping on the Ni‐site in Na‐NM cathode is an effective way to maintain structural stability, but how to achieve the uniform Mg dopant distribution is still a problem. Here, we report a facile cation chelation and reassembly route to prepare one‐dimensional Na_0.67Ni_0.26Mn_0.67Mg_0.07O₂ (Na‐NMM) cathode material with uniform element distribution. When evaluated as a cathode material for SIBs, the lower cut‐off voltage could be set to 1.35 V so that an extra reversible capacity of 61 mAh g⁻¹ is contributed from the Mn⁴⁺/Mn³⁺ couple between 2 and 1.35 V, and a total reversible capacity of 173 mAh g⁻¹ is achieved between 4.25 and 1.35 V at 0.1 C. Moreover, the Na‐NMM cathode shows good cycling performance with a reversible capacity of 83 mAh g⁻¹ after 100 cycles at 1 C.