New P2 - Na_0.70Mn_0.60Ni_0.30Co_0.10O₂Layered Oxide as Electrode Material for Na-Ion Batteries

Abstract

Sodium layered oxide, Na0.70Mn0.60Ni0.30Co0.10O2, with a P2-type structure was synthesized by a co-precipitation method and characterized as positive electrode of sodium batteries. The P2-NaxMn0.60Ni0.30Co0.10O2 electrode delivered a high specific capacity of 185 mAh/g in the 1.5–4.3 V range at 1st cycle at C/20 rate; however, rapid capacity decay is observed. In the 1.7–4.0 V range the capacity is equal to 125 mAh/g with a fading considerably reduced. The rate capability is reasonably good. According to the electrochemical profile, a potential plateau around 4.2 V vs. Na+/Na, meaning a bi-phasic domain, and several voltage drops that could be related to single phase domains in a narrow sodium content range are observed. Even if the capacity decreases when the battery is cycled above 4.0 V, there is no irreversible structural change.