Abstract: A predoping technique considered as highly practicable is an electrochemical method in which predoping is performed by assembling a battery such that an active material (electrode) and lithium are brought into direct contact with each other or short-circuited therebetween via an electric circuit, and by filling an electrolytic solution in the battery. However, in this case, much time is required, and there are problems such as the handling and the thickness accuracy of an extremely thin lithium metal foil that is not greater than 30 ?m thick. By mixing a lithium-dopable material and lithium metal together in the presence of a solvent, such problems can be solved.