Secondary batteries and battery packs

Abstract

This invention relates to a secondary battery and a battery pack. It provides a long-life secondary battery and a battery pack. According to one embodiment, a secondary battery comprising an electrode group and an electrolyte is provided. The electrode group has a structure comprising at least one electrode, including a current collector and active material containing layers respectively disposed on its two main surfaces, formed by lamination or winding. The active material containing layers include either at least one positive electrode active material containing layer or at least one negative electrode active material containing layer. In a portion of the electrode containing the positive electrode active material containing layer, the outermost positive electrode portion located at the outermost edge of the electrode group contains a compound selected from the group consisting of sulfur, boron, phosphorus, and fluorine at a higher concentration than the aforementioned compound in the inner positive electrode portion located further inside the electrode group than the outermost positive electrode portion.

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