Authors

Abstract

P2-type sodium-manganese-based layered cathodes, owing to their high capacity fromboth cationic and anionic redox, are a potential candidate for Na-ion batteries to replace Li-ion technology in certain applications. Still, the structure instability originates from irreversibleoxygen redox at high voltage remains a challenge. Here, a high sustainability cobalt-free P2-Na0.72Mn0.75Li0.24X0.01O2 (X= Ti/Si) cathode is developed. The outstanding capacity retention andvoltage retention after 150 cycles are obtained in Na half-cells. Our finding shows Ti locates onthe surface while Si diffuses to the bulk of the particles. Thus, Ti can act as protective layer thatalleviate side reactions in carbonate-based electrolyte. Meanwhile, Si can regulate the localelectronic structure and suppress oxygen redox activities. Notably, full-cells with hard carbon(~300-335 Whkg -1based on the cathode mass) deliver the capacity retention of 83% for P2-Na0.72Mn0.75Li0.24Si0.01O2 and 66% for P2-Na0.72Mn0.75Li0.24Ti0.01O2 after 500 cycles; thiselectrochemical stability is the best compared to other reported cathodes based on oxygen redoxat present. The superior cycle performance also stems from the ability to inhibit microcracking and planar gliding within the particles. Altogether, this finding offers new composition towardsdeveloping high performance low-cost cathodes for Na-ion batteries and highlights the unique roleof Ti/Si ions.