A solid-state secondary lithium battery with excellent charge and discharge cycle characteristics, using a negative electrode active material which shows discontinuous change of potential caused by the lithium ion insertion and extraction reactions, wherein the amount of the lithium ion inserted, until discontinuous change of potential of the negative elctrode takes place, is equal to or smaller than the maximum amount of extraction of lithium ions within the range where lithium ions are inserted and extracted into or from the lithium transition metal oxide reversibly, and a battery assembly using these batteries.