Lg Chem, Ltd

Eui Yong Bang

Sung Kyun Chang

Min Chul Jang

Sang Hoon Choy

Jae Hyun Lee

Ki Young Lee

Jeong Ju Cho

Soo Hyun Ha

Joon Hwan Lee

Sun Sik Shin

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.

Electrochemical device with high capacity and method for preparing the same

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.

Disclosed is a secondary battery having a constant-voltage device for preventing the secondary battery from being excessively overcharged. The breakdown voltage of the constant-voltage device is lower than the explosion or ignition voltage of the secondary battery, so the discharge operation may occur before the secondary battery is exploded or ignited even if the voltage of the secondary battery rises above the overcharge voltage, thereby protecting the secondary battery from explosion or ignition. The leakage current value of the constant-voltage device is less than 0.05% of the capacity value of the secondary battery under the maximum charge voltage of the secondary battery, or the breakdown voltage of the constant-voltage device is higher than the maximum charge voltage of the secondary battery. Thus, the constant-voltage device rarely generates the leakage current even if the secondary battery has been charged with the maximum charge voltage.

Secondary battery having constant-voltage device

Disclosed are a safety element for a battery, which is provided with material having a Metal-Insulator Transition (MIT) characteristic where resistance abruptly drops at or above a certain temperature, and a battery with such a safety element. This battery with an MIT safety element is turned into a stable discharged state when it is exposed to an elevated temperature or a battery temperature rises due to external impact, so that it can ensure its safety.

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Daejeon, South Korea

Eui Yong Bang