An electrochemical device includes electrode plates and a separation layer formed on a surface of an electrode plate. The separation layer includes a porous layer formed on the surface of the electrode plate. The porous layer includes nanofibers. It takes 15 seconds or less for an electrolytic solution to infiltrate into the separation layer. The separation layer exhibits functions of a separator. Therefore, the electrochemical device achieves at least a relatively high energy density without using a stand-alone separator.

An electrochemical device includes electrode plates and a separation layer formed on a surface of an electrode plate. The separation layer includes a porous layer formed on the surface of the electrode plate. The porous layer includes nanofibers. It takes 15 seconds or less for an electrolytic solution to infiltrate into the separation layer. The separation layer exhibits functions of a separator. Therefore, the electrochemical device achieves at least a relatively high energy density without using a stand-alone separator.

An electrochemical device includes an electrode plate and a separation layer on at least one surface of the electrode plate. The separation layer includes a nanofibrous porous substrate including nanofibers and polymer particles distributed in the nanofibrous porous substrate including nanofibers. A melting temperature of the polymer particles is 70° C. to 150° C.

An electrochemical device includes an electrode plate and a separation layer on at least one surface of the electrode plate. The separation layer includes a nanofibrous porous substrate including nanofibers and polymer particles distributed in the nanofibrous porous substrate including nanofibers. A melting temperature of the polymer particles is 70° C. to 150° C.

There is provided an LDH separator including a porous substrate and a layered double hydroxide (LDH)-like compound that fills up pores of the porous substrate. The LDH-like compound is a hydroxide and/or an oxide with a layered crystal structure, containing (i) Ti, Y, and optionally Al and/or Mg, and (ii) at least one additive element M selected from the group consisting of In, Bi, Ca, Sr, and Ba.

A separator structure for a secondary battery includes: a porous substrate; an intermediate layer on the porous substrate and including lithium fluoride (LiF) and a defluorinated polymer; and a lithium metal layer on the intermediate layer. An anode-separator assembly for a secondary battery includes an anode comprising an anode current collector and an anode active material layer on a surface of the anode current collector, and the separator structure. A secondary battery includes the anode-separator assembly, and a cathode on the porous substrate of the anode-separator assembly.

A separator structure for a secondary battery includes: a porous substrate; an intermediate layer on the porous substrate and including lithium fluoride (LiF) and a defluorinated polymer; and a lithium metal layer on the intermediate layer. An anode-separator assembly for a secondary battery includes an anode comprising an anode current collector and an anode active material layer on a surface of the anode current collector, and the separator structure. A secondary battery includes the anode-separator assembly, and a cathode on the porous substrate of the anode-separator assembly.

According to one embodiment, a separator is provided. The separator includes a composite membrane. The composite membrane includes a substrate layer, a first composite layer, and a second composite layer. The first composite layer is located on one surface of the substrate layer. The second composite layer is located on the other surface of the substrate layer. The composite membrane has a coefficient of air permeability of 1×10.sup.−14 m.sup.2 or less. The first composite layer has a first surface and a second surface. The first surface is in contact with the substrate layer. The second surface is located on an opposite side to the first surface. Denseness of a portion including the first surface is lower than denseness of a portion including the second surface in the first composite layer.

The present invention provides a nonaqueous electrolyte secondary battery porous layer which improves an initial battery characteristic immediately after initial charge and discharge of a nonaqueous electrolyte secondary battery. In the nonaqueous electrolyte secondary battery porous layer in accordance with an aspect of the present invention, a standard deviation of bursting strength is 0.6 or more and 11.0 or less.

The present invention provides a nonaqueous electrolyte secondary battery porous layer which improves an initial battery characteristic immediately after initial charge and discharge of a nonaqueous electrolyte secondary battery. In the nonaqueous electrolyte secondary battery porous layer in accordance with an aspect of the present invention, a standard deviation of bursting strength is 0.6 or more and 11.0 or less.