NOVELTY - The unit (100) has an exterior body (107) enveloping a positive electrode (101), a negative electrode (102), and an envelope (103). A first wiring is electrically connected to the positive electrode and extends from inside the exterior body. A second wiring is electrically connected to the negative electrode and extends from inside the exterior body, where one of the positive electrode and the negative electrode is in the envelope, where the exterior body, the positive electrode, the negative electrode and the envelope have flexibility.    USE - Power storage unit e.g. cylindrical/coin-type power storage unit and secondary battery such as lithium-ion secondary battery, lithium-ion capacitor, and air battery, for use in an electronic device (claimed). Uses include but are not limited to portable information terminal e.g. mobile phone, smartphone and laptop computer, portable music player, digital camera, medical equipment, next-generation clean energy vehicle e.g. hybrid electric vehicle (HEV), electric vehicle (EV), and plug-in hybrid electric vehicle (PHEV).    ADVANTAGE - The unit forms coating film on the surface of negative electrode active material layer, thus preventing decrease in the capacity of the power storage unit by using the coating film. The unit improves safety against liquid leakage when a gelled high-molecular material is used as the solvent for electrolyte solution. The unit facilitates depression or projection formed on surface of the exterior body to reduce influence of a strain caused by application of external force to the power storage unit to an acceptable level, thus providing power storage unit having high reliability. The unit removes lithium deposited on the surface of the negative electrode active material layer, thus preventing occurrence of a short circuit between the positive electrode and the negative electrode, and preventing a function of the power storage unit from being degraded, and hence increasing reliability of the power storage unit.    DETAILED DESCRIPTION - The envelope comprises an insulating material e.g. porous insulator, polypropylene and polyethylene.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a power storage unit.    Power storage unit (100)    Positive electrode (101)    Negative electrode (102)    Envelope (103)    Positive electrode lead (104)    Negative electrode lead (105)    Exterior body (107)