Patent ID: 7910240

Claim:
A lithium ion secondary battery comprising a cathode, an anode, a separator interposed between the cathode and the anode, and a liquid electrolyte, wherein the cathode comprises a coating layer of crosslinked polymer formed on a surface of electrode active material particles, while maintaining a pore structure formed among the electrode active material particles interconnected to each other in the cathode, and the coating layer of the crosslinked polymer has a thickness of 1 nm ˜1 μm, wherein the crosslinked polymer is formed by crosslinking at least one monomer selected from the group consisting of the compounds represented by the following formula 1 and formula 2: wherein each of R 1 , R 2 and R 3 independently represents a hydrogen atom or a C1˜C6 lower alkyl group; R 4 represents a single bond or X represents each of n and m represents an integer of 0˜1000, each of p and q is an integer of 0˜20 with the proviso that p and q cannot represent 0 at the same time, and r is an integer of 1˜6; and each of i and j represents an integer of 1˜1000, and s is an integer of 1˜20, and the liquid electrolyte includes a salt represented by the formula of A + B 31 , wherein A 30 represents an alkali metal cation selected from the group consisting of Li + , Na + , K + and combinations thereof, and B − represents an anion selected from the group consisting of PF 6 − , BF 4 − , Cl − ,Br − ,I − , ClO 4 − , ASF 6 − , CH 3 CO 2 − , CF 3 SO 3 − , N(CF 3 SO 2 ) 2 − , and C(CF 2 SO 2 ) 3 − , the salt being dissolved or dissociated in an organic solvent selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) and gamma-butyrolactone (γ-butyrolactone).