Cathode materials and cathodes for sodium and sodium-ion cells and batteries include sodium, lithium and transition metal oxide cathode materials. An example cathode is the composition Na.sub.xLi.sub.yNi.sub.zMn.sub.uM.sub.vO.sub.w, with M being one or more metal cation, x+y.gtoreq.0.9, (x+y)/(z+u+v)>1, (z+u+v)>1, 0.ltoreq.z.ltoreq.0.9, 0.ltoreq.u.ltoreq.0.9, 0.ltoreq.v.ltoreq.0.9, x+y+z+u+v is less than w, and the value of w depends on the proportions and average oxidation states of the metallic elements. The combined positive charge of the metallic elements is balanced by the number of oxygen anions, w. W is less than or equal to 2, i.e., Na.sub.xLi.sub.yNi.sub.zMn.sub.uMvO.sub.2-a, and desirably equal to or slightly less than 2. M is one or more metal cations selected preferably from one or more divalent, trivalent, tetravalent, pentavalent or hexavalent cations, such as Mg.sup.2+, Cu.sup.2+, Co.sup.3+, B.sup.3+, Fe.sup.3+, Al.sup.3+, Ti.sup.4+, Zr.sup.4+, V.sup.5+, and Cr.sup.6+ etc. Synthesis methods are provided.
STATEMENT OF GOVERNMENT INTEREST
 This invention was made with government support under Award Number DE-SC0001294 from U.S. Department of Energy, Office of Basic Energy Sciences. The government has certain rights in the invention.