Energy storage device

An energy storage device, comprising:

• a positive electrode;
• a negative electrode;
• and
• an insulating layer arranged between the positive and negative electrodes to electrically insulate the positive and negative electrodes,
• wherein the negative electrode includes a composite layer containing active material particles,
• the composite layer of the negative electrode, and the positive electrode are arranged to face each other across the insulating layer,
• the insulating layer contains electrically insulating particles, and is made porous by a gap between the electrically insulating particles,
• the composite layer of the negative electrode is made porous by a gap between the active material particles,
• the following relational expression (1) is satisfied:
• −0.8≦Log B−Log A≦1.0
• in which in a distribution of pores in the composite layer, a pore peak diameter is represented by A (μm), and in a distribution of pores in the insulating layer, a pore peak diameter is represented by B (μm), and
• the pore peak diameter of the composite layer is 0.5 μm or more and 1.5 μm or less.