Patent ID: 8101295
Filing Date: 2012-01-24
Classification: H01M,Y02E,Y02P,Y02T

Abstract:
1. A lithium secondary battery comprising: a wound electrode assembly comprising: a positive electrode having a positive electrode active material layer containing a positive electrode active material capable of intercalating and deintercalating lithium; a negative electrode having a negative electrode current collector and a negative electrode active material layer formed on both sides of the negative electrode current collector, the negative electrode active material layer containing a negative electrode active material having a filling density of 2.0 g/cc or less and being capable of alloying with lithium; a separator disposed between the positive and negative electrodes and having a penetration resistance of 500 g or greater; and a cylindrical hollow space disposed at a winding axis of the wound electrode assembly and in the vicinity thereof; and a columnar center pin disposed in the hollow space and having a diameter of from 75% to 95% of the diameter of the hollow space, wherein the positive electrode, the negative electrode, and the separator are spirally wound, wherein a negative electrode expansion ratio is 1.7 or greater, where the negative electrode expansion ratio is a ratio of the thickness of the negative electrode active material layer after charge to the thickness of the negative electrode active material layer before charge.