Electrochemical device with high capacity and method for preparing the same

Abstract

Disclosed is a method for preparing an electrochemical device, comprising the steps of: charging an electrochemical device using an electrode active material having a gas generation plateau potential in a charging period to an extent exceeding the plateau potential; and degassing the electrochemical device. An electrochemical device, which comprises an electrode active material having a gas generation plateau potential in a charging period, and is charged to an extent exceeding the plateau potential and then degassed, is also disclosed. Some electrode active materials provide high capacity but cannot be applied to a high-capacity battery due to the gas generation. This is because a battery using such electrode active materials should be charged to an extent exceeding the gas generation plateau potential in order to realize a high capacity. To solve the problems caused by the gas generation, the battery is charged to an extent exceeding the plateau potential, and then degassed. In other words, the problems including variations in outer shape of a battery and degradation in cycle life characteristics and C-rate characteristics of a battery can be solved. After the first cycle, the battery can be charged to an extent exceeding the plateau potential with no further gas generation, thereby providing a significant increase in capacity.