According to one embodiment, provided is a secondary battery including a negative electrode, a positive electrode, a first composite layer joined to the negative electrode, a second composite layer joined to the positive electrode, and an aqueous electrolyte. The first composite layer includes a first principal surface on a reverse side with respect to a surface joined to the negative electrode. The second composite layer includes a second principal surface on a reverse side with respect to a surface joined to the positive electrode and facing the first principal surface. Each of the first composite layer and the second composite layer contains inorganic solid particles and a polymeric material. A peel strength σs between the first principal surface and second principal surface is 0.1 N/mm or less. The aqueous electrolyte includes water.