Abstract: A charging method includes: in a case of charging a lithium ion secondary battery having a positive electrode, a negative electrode, and an electrolyte housed in an exterior body, calculating a value obtained by second-order differentiation of a charging current in constant-voltage charging with respect to a charging electric quantity or time during charging; and, during charging with an environmental temperature of T1 immediately before start of charging, in a case where a change in a sign of the value calculated by second-order differentiation from positive to negative or from negative to positive is observed, if an ambient temperature immediately before start of next and subsequent charging is T2 or lower, making the whole or a part of a current in a constant-current charging current section lower than an initial setting.

Abstract: Provided is a separator including a first layer of a porous substance and a second layer that is provided on at least one face of the first layer and that includes a resin material and particles. The second layer has an agglomeration network structure of the particles.

Abstract: A separator includes a substrate layer and a porous surface layer that is provided on at least one major surface of the substrate layer and contains a first particle, a second particle, and a resin material. The surface layer includes a first region configured by the first particle and a second region configured by the second particle and the resin material.

Abstract: A separator includes a substrate layer and a porous surface layer that is provided on at least one major surface of the substrate layer and contains a first particle, a second particle, and a resin material. The surface layer includes a first region configured by the first particle and a second region configured by the second particle and the resin material.

Abstract: Provided is a separator including a first layer of a porous substance and a second layer that is provided on at least one face of the first layer and that includes a resin material and particles. The second layer has an agglomeration network structure of the particles.

Abstract: A separator includes a substrate layer and a porous surface layer that is provided on at least one major surface of the substrate layer and contains a first particle, a second particle, and a resin material. The surface layer includes a first region configured by the first particle and a second region configured by the second particle and the resin material.

Abstract: A separator includes a substrate layer that is porous, and a surface layer that is provided on at least one main face of the substrate layer and that has an uneven shape. The surface layer includes first particles that are for forming convexities of the uneven shape and that are a main component of the convexities, second particles that have a smaller average particle size than the first particles, cover at least a part of a surface of the first particles, and cover at least a part of a surface of the substrate layer that is exposed between the first particles, and a resin material.

Abstract: A retardation element includes an alignment film and a retardation layer in contact with a surface of the alignment film, and the retardation layer is formed by applying a paint containing a liquid crystal monomer and a non-liquid crystal monomer on the surface of the alignment film and then polymerizing the paint while the liquid crystal monomer is placed in an alignment state.

Abstract: A separator has: a substrate including a porous film; and a surface layer which is provided on at least one surface of the substrate, which includes a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, and which has a plurality of minute pores.

Abstract: A retardation element includes an alignment film and a retardation layer in contact with a surface of the alignment film, and the retardation layer is formed by applying a paint containing a liquid crystal monomer and a non-liquid crystal monomer on the surface of the alignment film and then polymerizing the paint while the liquid crystal monomer is placed in an alignment state.

Abstract: A shrink resistant microporous membrane includes a base material composed of a porous membrane, and a surface layer that is formed on at least one surface of the base material, and contains a heat resistant resin, a ceramic, and a clay mineral.