Abstract: Disclosed is an electrochemical device, which comprises: (A) a binder comprising polymer particles obtained from the polymerization of: (a) 20-70 parts by weight of a (meth)acrylic acid ester monomer; (b) 20-60 parts by weight of a vinyl monomer; and (c) 0.01-30 parts by weight of an unsaturated carboxylic acid monomer, based on 100 parts by weight of a binder polymer; and (B) electrochemical cells stacked multiply by using the binder, wherein the binder allows electrode active material particles in an electrode to be fixed and interconnected among themselves and between the electrode active material and a collector, and the electrode and a separator that is in contact with the electrode are bonded to each other by way of hot fusion. The binder is also disclosed. The binder has excellent adhesion and thermal bonding characteristics, and thus is useful for an electrochemical device comprising multiply stacked electrochemical cells, and can improve the overall quality of a battery.

Abstract: Disclosed is a cathode active material comprising a lithium-free metal oxide and a material with high irreversible capacity. A novel lithium ion battery system using the cathode active material is also disclosed. The battery, comprising a cathode using a mixture of a Li-free metal oxide and a material with high irreversible capacity, and an anode comprising carbon instead of Li metal, shows excellent safety compared to a conventional battery using lithium metal as an anode. Additionally, the novel battery system has a higher charge/discharge capacity compared to a battery using a conventional cathode active material such as lithium cobalt oxide, lithium nickel oxide or lithium manganese oxide.

Abstract: Disclosed are an electrode including Li2CuO2 as an additive, and a lithium secondary battery having the same. The additive is added to a cathode as to adjust unbalance of the irreversible reaction between the cathode and an anode of the lithium secondary battery, thereby increasing the capacity of the lithium secondary battery without degrading performance of the lithium secondary battery after over-discharge of the lithium secondary battery.

Abstract: Disclosed is a method for regulating terminal voltage of a cathode during overdischarge. Also disclosed is a lithium secondary battery, which is low in capacity loss after overdischarge, having excellent capacity restorability after overdischarge and shows an effect of preventing a battery from swelling at a high temperature.