Patent ID: 8334076

Claim:
A lithium ion secondary battery comprising: a positive electrode including a lithium composite oxide; a negative electrode including a material capable of electrochemically absorbing and desorbing lithium; a separator for separating said positive electrode and said negative electrode; a non-aqueous electrolyte; and a porous film formed on at least one electrode surface of said positive electrode and said negative electrode; said positive electrode, said negative electrode, and said separator being wound to form an electrode assembly: (a) said porous film including inorganic compound particles and a resin binder; (b) said resin binder in said porous film being polyvinylidene fluoride; (c) a viscosity of an 8 wt % solution of said polyvinylidene fluoride dissolved in Nmethyl-2-pyrrolidone is 600 to 2400 mPa·s at 25° C.; and (d) an amount of said polyvinylidene fluoride in said porous film being 1 to 10 parts by weight per 100 parts by weight of said inorganic compound particles.