A Cation Chelation and Reassembly Route to Synthesize a P2-type Na0.67Ni0.26Mn0.67Mg0.07O2 Cathode Material for High-performance Sodium Storage

P2-type Na2/3Ni1/3Mn2/3O2 (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 Na0.67Ni0.26Mn0.67Mg0.07O2 (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.