Structural stability of P2-Na 0.67 Fe 0.5 Mn 0.5 O 2 by Mg doping

As a cathode material for sodium-ion batteries (SIBs), P2-Na 0.67 Fe 0.5 Mn 0.5 O 2 has the advantages of high capacity and high working voltage. However, the irreversible phase transition of P2-O2 causes the electrochemical performances to rapidly decline with cycling. The phase stability and therefore cycle stability could be effectively improved by cation doping. The precursor Fe 0.5 Mn 0.5 CO 3 is prepared by coprecipitation method. The initial discharge-specific capacity of P2-Na 0.67 Fe 0.5 Mn 0.5 O 2 in the voltage range of 2–4.3 V is 164 mAh·g −1 , and its capacity retention rate after 100 cycles is 48.6%. Mg doping can improve the cycling stability and rate capability, while slightly reducing the initial capacity. The capacity retention is improved from 48.6 to 75.3% with Mg doping.