Mitigating the P2–O2 phase transition-induced structural instability in P2-Nax[Ni1/3Mn2/3]O2 Na-ion battery cathodes: to dope or not to dope, that is the question

Na 2/3 [Ni 1/3 Mn 2/3 ]O 2 (NNMO) Na-ion battery cathodes cycle well between 2 and 4 V (a) but suffer from severe decay when cycled above 4 V (b) due to P2–O2 transition. Doping strategies used to overcome this issue are discussed in this article.