Insights into magnesium and titanium co-doping to stabilize the O3-type NaCrO2 cathode material for sodium-ion batteries

The development of high-performance cathode materials is critical to the practical application of sodium-ion batteries (SIBs). O3-type NaCrO 2 (NCO) is one of the most competitive cathodes, but it suffers from rapid capacity decay caused by severe irreversible structural evolution. An Mg-Ti co-doped Na 0.99 Cr 0.95 Mg 0.02 Ti 0.03 O 2 (NCO-MT) cathode material is designed and synthesized via a facile solid-state reaction to enhance the cyclability of NCO. A capacity retention of 71.6% after 2500 cycles with the capacity fade rate of 0.011% per cycle is achieved for NCO-MT at 5 C, which is attributed to the highly reversible crystal structure during cycling. Our findings offer a novel insight into the high-performance O3-type layered cathode materials for SIBs and are beneficial to promote the development of high-rate SIBs.