A lithium secondary cell having incorporated therein a positive electrode or negative electrode active substance which is a compound sulfide having substantially the same crystal structure as stannous sulfide (SnS) or a lithium-containing compound sulfide comprising said compound sulfide and lithium contained therein, said compound sulfide comprising at least one transition metal selected from among copper (Cu), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni), tin and sulfur. This stabilizes the crystal structure of SnS serving as the active substance, giving the cell practically useful charge-discharge cycle characteristics.