TECHNOLOGY FOCUS - ELECTRONICS - Preferred Method: The method further comprises adding further liquid medium to the kneaded material and kneading before shaping the kneaded material into a sheet form. In the method, 11/89-19/81 of the liquid medium by mass relative to the total mass of the (A1), (B1), (C1), (D1) and (E1) is added to obtain the liquid-added mixture.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: In the method: the amount of the carbon fibers (C1) is 10-70 mass% in the total amount 100 mass% of the carbon fibers (B1) and the carbon fibers (C1); the amount of the active material (A1) to be contained in the electrode is 85-95 mass% by mass relative to the mass of the electrode; the amount of the carbon fibers (B1) is 0.5-20 parts by mass relative to 100 parts by mass of the active material (A1); the amount of the carbon fibers (C1) is 0.1-10 parts by mass relative to 100 parts by mass of the active material (A1); the amount of the carbon black (D1) is 10-100 parts by mass relative to 100 parts by mass of the active material (A1); and the amount of the binder (E1) is 3-5 mass% relative to the mass of the electrode. The carbon fibers (C1) have a fiber diameter of 9-15 nm. The carbon fibers (B1) have a fiber diameter of 70-200 nm. EXAMPLE - Into a planetary mixer, 90 parts by mass of the positive electrode active material (a) (a powder of lithium iron phosphate), 1.8 parts by mass of the carbon fibers (b) having a mean fiber diameter of 180 nm and the mean fiber length of 7 mu m, 0.2 part by mass of the carbon fibers (c) having a mean fiber diameter of 12 nm and a fiber diameter range of 5-40 nm, 3 parts by mass of the carbon black (d), and 5 parts by mass of the binder (e) (a powder of polyvinylidene fluoride), were introduced, and dry process mixing was performed for 5 minutes at a revolution of 15 rpm. N-methylpyrrolidone was added to the dry process mixture to adjust the solid content concentration to be 87 mass%. This was kneaded with a planetary mixer for 30 minutes at a revolution of 45 rpm while applying shear stress. To the resulting kneaded product, N-methylpyrrolidone was further added and kneaded to prepare a slurry having the optimal viscosity for coating. The resulting slurry was applied to an aluminum foil in an amount of 12 mg/cm2 using a C-type coater, and dried at 80-120 degrees C. The resulting laminated sheet was punched out in the predetermined size, and the electrode density was adjusted to 2.1 g/cm3 by flat press to obtain a positive electrode.