Patent ID: 7592095

Claim:
A lithium secondary battery comprising an anode including an anode active material capable of performing reversible storage and release of lithium ions, a cathode including a cathode active material capable of performing reversible storage and release of lithium ions, a porous separator interposed between the anode and cathode, and an electrolyte containing a lithium salt, wherein the electrolyte and/or electrode include a controlled-release capsule containing a release material inside a microporous cell, such that the release material essentially required in relation to the operation of the battery can be controllably released, wherein the microporous cell of the controlled-release capsule is composed of an electrolyte-insoluble material which is at least one selected from the group consisting of polyethylene, polypropylene, polystyrene, nylon, polycaprolactone, polyethylene terephthalate, polyurethane, gelatin, chitosan, and cellulose; wherein the size of the controlled-release capsule is less than 5 μm within the range of being smaller than the size of pores of the separator, wherein a material identical to the release material contained in the controlled-release capsule is contained in the electrolyte and/or electrode, in addition to the controlled-release capsule; wherein the release material is a material necessary for formation and restoration of a solid electrolyte interface (SEI) layer, and is at least one selected from the group consisting of vinylene carbonate (VC), vinylene ethylene carbonate, fluoro-ethylene carbonate, succinic anhydride, lactide, caprolactam, ethylene sulfite, propane sultone (PS), propene sultone, vinyl sulfone, and halogen-substituted compounds thereof; and wherein the release material is released in a rate of 1 to 10000 μg/day.