“…[1][2][3][4][5][6][7] Among the various materials studied, sodium layered oxides (NaxMO2, M = transition metal) represent a promising family [8][9][10] . The most promising candidates are based on the Mn and / or Fe elements, which are the less expensive ones among the 3d elements: Nax(Mn,Fe)O2 [11][12][13][14][15][16][17][18][19] , Nax(Mn,Ni)O2 [20][21] , Nax(Mn,Mg)O2 [22][23][24] , Nax(Mn,Ni, Fe)O2 [25][26][27] , Nax(Mn,Co)O2 [28][29][30][31] Nax(Mn,Ni, Co)O2 [32][33][34][35][36][37][38][39] ,Nax(Li,Ni,Mn)O2 [39][40] .…”