Electric vehicles(EVs)and grid storage for renewable energies will require batter-ies in tens of millions of tons,and thus they need to be sustainable.EVs call also for batteries with higher energy density than currently available,and this value is intrinsically limited by the properties of the transition metal oxide(TMO)cath-odes[1].There are two possible strate-gies to overcome these limitations:i)in-crease the operating voltage in the ＞4.4 V range;and ii)attempt to use more than one electron per transition metal[2].The first strategy faces problems of electrolyte stability limit and oxygen evolution,and thus safety hazards.The second is limited to vanadium and nickel,but using only 1.3 electrons for the former,and the latter must be diluted in 300％manganese lat-tice.Cobalt,used today,nickel and vana-dium are metals for which shortages are foreseen with the expansion of the bat-tery market.There have been countless research efforts over the past 30 years,but,to date,the current TMO cathode has practically reached its limit in terms of its theoretical specific capacity and volt-age performance.