A cylindrical single-piece lithium-ion battery of 400 Ah includes: a cylindrical battery enclosure (1), a battery mandrel (3), a plurality of tabs (4), a wiring terminal (6), a positive and negative electrode cover (11); a positive electrode sheet, said battery positive electrode is composed of LiFePO4, conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP; a negative electrode sheet, the battery negative electrode is composed of lithium titanate, conductive carbon-black, graphite, adhesive such as PVDF, and solvent such as NMP. The cylindrical lithium-ion battery made by the invention has a capacity of 400 Ah which is the one reportedly having the largest capacity in the world presently.