Provided is a lithium ion secondary battery including Li.sub.4Ti.sub.5O.sub.12 particles in a negative electrode active material layer and having both high heat generation suppressing performance during overcharging, and high storage stability in a high SOC region. The lithium ion secondary battery herein disclosed includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode has a positive electrode active material layer. The positive electrode active material layer includes Li.sub.3PO.sub.4 as a secondary material. The negative electrode has a negative electrode active material layer. The negative electrode active material layer includes Li.sub.4Ti.sub.5O.sub.12 as a secondary material. The Li.sub.3PO.sub.4 content in the positive electrode active material layer is 0.5 mass % or more and 5.0 mass % or less. The Li.sub.4Ti.sub.5O.sub.12 content in the negative electrode active material layer is 0.5 mass % or more and 5.0 mass % or less.

Provided is a lithium ion secondary battery including Li.sub.4Ti.sub.5O.sub.12 particles in a negative electrode active material layer and having both high heat generation suppressing performance during overcharging, and high storage stability in a high SOC region. The lithium ion secondary battery herein disclosed includes a positive electrode, a negative electrode, and a nonaqueous electrolyte. The positive electrode has a positive electrode active material layer. The positive electrode active material layer includes Li.sub.3PO.sub.4 as a secondary material. The negative electrode has a negative electrode active material layer. The negative electrode active material layer includes Li.sub.4Ti.sub.5O.sub.12 as a secondary material. The Li.sub.3PO.sub.4 content in the positive electrode active material layer is 0.5 mass % or more and 5.0 mass % or less. The Li.sub.4Ti.sub.5O.sub.12 content in the negative electrode active material layer is 0.5 mass % or more and 5.0 mass % or less.

A method of preparing an electrochemical electrode which is partially or totally covered with a film that is obtained by spreading an aqueous solution comprising a water-soluble binder over the electrode and subsequently drying same. The production cost of the electrodes thus obtained is reduced and the surface porosity thereof is associated with desirable resistance values.

A method of preparing an electrochemical electrode which is partially or totally covered with a film that is obtained by spreading an aqueous solution comprising a water-soluble binder over the electrode and subsequently drying same. The production cost of the electrodes thus obtained is reduced and the surface porosity thereof is associated with desirable resistance values.

Graphene is formed with a practically uniform thickness on an uneven object. The object is immersed in a graphene oxide solution, and then taken out of the solution and dried; alternatively, the object and an electrode are immersed therein and voltage is applied between the electrode and the object used as an anode. Graphene oxide is negatively charged, and thus is drawn to and deposited on a surface of the object, with a practically uniform thickness. After that, the object is heated in vacuum or a reducing atmosphere, so that the graphene oxide is reduced to be graphene. In this manner, a graphene layer with a practically uniform thickness can be formed even on a surface of the uneven object.

Graphene is formed with a practically uniform thickness on an uneven object. The object is immersed in a graphene oxide solution, and then taken out of the solution and dried; alternatively, the object and an electrode are immersed therein and voltage is applied between the electrode and the object used as an anode. Graphene oxide is negatively charged, and thus is drawn to and deposited on a surface of the object, with a practically uniform thickness. After that, the object is heated in vacuum or a reducing atmosphere, so that the graphene oxide is reduced to be graphene. In this manner, a graphene layer with a practically uniform thickness can be formed even on a surface of the uneven object.

Materials and methods for preparing electrode film mixtures and electrode films including reduced damage bulk active materials are provided. In a first aspect, a method for preparing an electrode film mixture for an energy storage device is provided, comprising providing an initial binder mixture comprising a first binder and a first active material, processing the initial binder mixture under high shear to form a secondary binder mixture, and nondestructively mixing the secondary binder mixture with a second portion of active materials to form an electrode film mixture.

Materials and methods for preparing electrode film mixtures and electrode films including reduced damage bulk active materials are provided. In a first aspect, a method for preparing an electrode film mixture for an energy storage device is provided, comprising providing an initial binder mixture comprising a first binder and a first active material, processing the initial binder mixture under high shear to form a secondary binder mixture, and nondestructively mixing the secondary binder mixture with a second portion of active materials to form an electrode film mixture.

A composite for use as an electrode, the composition comprising a uniformly distributed spontaneously formed segregated network of carbon nanotubes, metallic nanowires or a combination thereof, and a particulate active material, and in which the composite is free of carbon black and has no additional polymeric binder.

A negative electrode active material particle with little deterioration is provided. Alternatively, a novel negative electrode active material particle is provided. Alternatively, a power storage device with little deterioration is provided. Alternatively, a highly safe power storage device is provided. Alternatively, a novel power storage device is provided. The electrode includes an active material and a conductive additive; the active material contains a metal or a compound including one or more elements selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, and indium; the conductive additive contains a graphene compound; and the graphene compound contains fluorine.