Abstract: A cathode for a lithium ion secondary battery of the present invention is provided with a current collector and an active material layer formed on a surface of the current collector. The active material layer has holes in its surface and has an active material density of 68 to 83% relative to a true density of an active material included in the active material layer. The thickness of the active material layer is 150 to 1000 ?m. Hence, the amount of the active material included in the cathode is increased. When the cathode is used in the battery, transfer of an electron and insertion/release of lithium ion take place deep in the thickness direction from the surface and in the surface of the active material layer. Hence, the active material deep in the thickness direction from the surface of the active material layer is effectively utilized.

Abstract: A cathode for lithium ion secondary battery of the present invention includes a cathode including a current collector and active material supported on the current collector. The current collector is made of porous metal. The cathode has holes in its surface, and active material density is 50 to 80% of true density of the active material. Because the cathode is thick and supported with the active material densely and the holes are formed in its surface, transfer of an electron and insertion/release of lithium ion take place in the cathode surface and deep in the cathode in the lithium ion secondary battery. Therefore, the lithium ion released from the active material can migrate in the electrolyte solution in the holes, so that the active material present deep in the cathode is effectively utilized, and thus, the lithium ion secondary battery has high capacity and can promptly charge/discharge.

Abstract: An electrode for a lithium ion secondary cell includes a conductive auxiliary agent, a binder and an active material. The conductive auxiliary agent includes carbon black and carbon nanofibers. The carbon nanofibers are configured to electrically crosslink the active material and the carbon black so that the carbon nanofibers coat part or all of a surface of the active material to be secured by a binder. In addition, by defining the entire surface of the active material as 100%, 10 to 100% of the surface of the active material is coated with the carbon nanofibers. By bonding the carbon black to the carbon nanofibers with which the surface of the active material is coated, the active material and the carbon black are electrically crosslinked.

Abstract: An electrode of a lithium-ion secondary battery includes: an electrode film that contains a conductive auxiliary agent, a binder and an active material; and an electrode foil, on a surface of which the electrode film is formed. The conductive auxiliary agent is carbon nano-fibers and the carbon nano-fibers are contained in the range of 0.1 to 3.0% by mass relative to 100% by mass of the electrode film. Further, when using an organic solvent as a solvent, 1.0 to 8.0% by mass of the binder excluding the organic solvent is contained. The active material is made of a mixed powder of a coarse particle powder having an average particle size of 1 to 20 ?m and a fine particle powder having an average particle size of ? to 1/10 of an average particle size of the coarse particle powder, and the porosity of the electrode film is 10 to 30%.