The invention relates to novel materials of the formula: A1-δM1VM2WM3XM4YM5ZO2 wherein A is one or more alkali metals comprising sodium and/or potassium either alone or in a mixture with lithium as a minor constituent; M1 is nickel in oxidation state +2; M2 comprises a metal in oxidation state +4 selected from one or more of manganese, titanium and zirconium; M3 comprises a metal in oxidation state +2, selected from one or more of magnesium, calcium, copper, zinc and cobalt; M4 comprises a metal in oxidation state +4, selected from one or more of titanium, manganese and zirconium; M5 comprises a metal in oxidation state +3, selected from one or more of aluminum, iron, cobalt, molybdenum, chromium, vanadium, scandium and yttrium; wherein 0≦δ≦0.1 V is in the range 0