A flexible battery, comprising: a first substrate; a second substrate; a glue frame, being sandwiched between the first substrate and the second substrate in an orthogonal direction to form an enclosed space; an electrochemical reaction element, disposed in the enclosed space and the electrochemical reaction element including: a first active material layer, disposed adjacent to the first substrate and electrically connected to the first substrate; a second active material layer, disposed adjacent to the second substrate and electrically connected to the second substrate; an intermediate layer, being sandwiched between the first active material layer and the second active material layer for electrically isolating the first active material layer and the second active material layer; a first interface, located between the first active material layer and the intermediate layer; and a second interface, located between the second active material layer and the intermediate layer; characterized in that: one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes a first adhesive, and the first adhesive includes at least one first linear polymer and at least one first cross-linked polymer, wherein the first adhesive contains 0.05 to 70 percent by weight of the first cross-linked polymer; wherein when one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes the first adhesive, one of the remaining includes at least one second adhesive, wherein the second adhesive includes at least one second linear polymer and at least one second cross-linked polymer; and wherein the first adhesive and the second adhesive are different. a first substrate; a second substrate; a glue frame, being sandwiched between the first substrate and the second substrate in an orthogonal direction to form an enclosed space; an electrochemical reaction element, disposed in the enclosed space and the electrochemical reaction element including: a first active material layer, disposed adjacent to the first substrate and electrically connected to the first substrate; a second active material layer, disposed adjacent to the second substrate and electrically connected to the second substrate; an intermediate layer, being sandwiched between the first active material layer and the second active material layer for electrically isolating the first active material layer and the second active material layer; a first interface, located between the first active material layer and the intermediate layer; and a second interface, located between the second active material layer and the intermediate layer; a first active material layer, disposed adjacent to the first substrate and electrically connected to the first substrate; a second active material layer, disposed adjacent to the second substrate and electrically connected to the second substrate; an intermediate layer, being sandwiched between the first active material layer and the second active material layer for electrically isolating the first active material layer and the second active material layer; a first interface, located between the first active material layer and the intermediate layer; and a second interface, located between the second active material layer and the intermediate layer; characterized in that: one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes a first adhesive, and the first adhesive includes at least one first linear polymer and at least one first cross-linked polymer, wherein the first adhesive contains 0.05 to 70 percent by weight of the first cross-linked polymer; wherein when one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes the first adhesive, one of the remaining includes at least one second adhesive, wherein the second adhesive includes at least one second linear polymer and at least one second cross-linked polymer; and wherein the first adhesive and the second adhesive are different. one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes a first adhesive, and the first adhesive includes at least one first linear polymer and at least one first cross-linked polymer, wherein the first adhesive contains 0.05 to 70 percent by weight of the first cross-linked polymer; wherein when one of the first active material layer, the second active material layer, the intermediate layer, the first interface and the second interface includes the first adhesive, one of the remaining includes at least one second adhesive, wherein the second adhesive includes at least one second linear polymer and at least one second cross-linked polymer; and wherein the first adhesive and the second adhesive are different.