The problem of Li-metal battery The uniformity of the deposit may become poor, leading to dendrite formation and short circuits Since the passivation reaction is highly exothermic, the cell may overheat and in extreme cases, given the low melting point of lithium, thermal runaway may occur Li polymer battery Li-ion battery Careful design of the electrolyte system to optimize the formation of the passivating layer, in particular by use of polymer electrolytes Replacement of the lithium metal negative by a second insertion host, usually based on graphitic carbon.