Abstract: One aspect of the present invention is an energy storage device satisfying the following formula 1, in which a flat electrode assembly obtained by winding a positive electrode and a negative electrode with a separator interposed therebetween and having two curved surface portions facing each other, and a case that houses the electrode assembly, and at least one of the positive electrode and the negative electrode includes an active material layer containing active material particles and a fibrous conductive agent. In the formula 1, X is a distance from a distal end of one of the curved surface portions to the inner surface of the case facing the distal end of the curved surface portion as viewed in the winding axis direction of the electrode assembly. R is a length of a periphery of the one curved surface portion as viewed in the winding axis direction of the electrode assembly. D is an average particle size D50 of the active material particles. A is a surface roughness Ra of the active material layer.

Abstract: A positive electrode for an energy storage device according to an aspect of the present invention includes a positive active material layer, the positive active material layer contains positive active material particles and a binder, the positive active material particles contain a nickel-containing lithium transition metal composite oxide that has an ?-NaFeO2-type crystal structure, the positive active material particles are at least one of: primary particles that are not substantially aggregated; and secondary particles that have primary particles aggregated, with the ratio of the median size to the average primary particle size being 5 or less, the product of the median size and BET specific surface area of the positive active material particles is 1.3 [?m m2/g] or more and 4.0 [?m m2/g] or less, and the binder has a weight average molecular weight of 500,000 or more.

Abstract: An energy storage device according to an aspect of the present invention includes an electrode assembly including a negative electrode and a positive electrode, the negative electrode includes a negative active material layer including a negative active material, the negative active material contains solid graphite, the negative active material layer has a BET specific surface area of 2.1 m2/g or less, and a pressure applied to the electrode assembly is 0.1 MPa or more.

Abstract: One aspect of the present invention is an energy storage device satisfying the following formula 1, in which a flat electrode assembly obtained by winding a positive electrode and a negative electrode with a separator interposed therebetween and having two curved surface portions facing each other, and a case that houses the electrode assembly, and at least one of the positive electrode and the negative electrode includes an active material layer containing active material particles and a fibrous conductive agent. In the formula 1, X is a distance from a distal end of one of the curved surface portions to the inner surface of the case facing the distal end of the curved surface portion as viewed in the winding axis direction of the electrode assembly. R is a length of a periphery of the one curved surface portion as viewed in the winding axis direction of the electrode assembly. D is an average particle size D50 of the active material particles. A is a surface roughness Ra of the active material layer.

Abstract: One aspect of the present invention is a positive electrode for an energy storage device including a positive active material layer, in which the positive active material layer includes a positive active material particle having a ratio of a secondary particle size to a primary particle size of 3 or less, and a fibrous conductive agent.

Abstract: A plate includes a current collector, an intermediate layer layered on the current collector, and an active material layer layered on the intermediate layer. The intermediate layer contains conductive particles and insulating particles. At least a portion of an end edge of the intermediate layer is not covered with the active material layer. The intermediate layer hays a higher mass content of the insulating particles in a region not covered with the active material layer than that in a region covered with the active material layer.

Abstract: A plate includes a current collector, an intermediate layer layered on the current collector, and an active material layer layered on the intermediate layer. The intermediate layer contains conductive particles and insulating particles. At least a portion of an end edge of the intermediate layer is not covered with the active material layer. The intermediate layer hays a higher mass content of the insulating particles in a region not covered with the active material layer than that in a region covered with the active material layer.

Abstract: An aspect of the present invention is an electrode for an energy storage device including a conductive substrate, an intermediate layer, and an active material layer in this order. In this electrode, the intermediate layer includes a conductive agent, an inorganic oxide, and a binder, and the content of the inorganic oxide in the intermediate layer is 30% by mass or more and 90% by mass or less.