NOVELTY - A nonaqueous electrolyte secondary battery comprises positive electrode (1), negative electrode (2), nonaqueous electrolyte, and separator (3). The positive electrode comprises electrical power collector and positive mix layer formed on electrical power collector. The positive mix layer contains positive electrode active material and binder. The positive electrode active material contains lithium/nickel-containing composite oxide containing nickel and cobalt and/or manganese.    USE - Nonaqueous electrolyte secondary battery is used for portable electronic device e.g. mobile telephone and notebook-type personal computer, and for electric vehicles.    ADVANTAGE - The nonaqueous electrolyte secondary battery has high upper limit voltage, excellent charging/discharging cycling characteristics and favorable high-temperature-storage characteristics.    DETAILED DESCRIPTION - A nonaqueous electrolyte secondary battery comprises positive electrode, negative electrode, nonaqueous electrolyte, and separator. The positive electrode comprises electrical power collector and positive mix layer formed on electrical power collector. The positive mix layer contains positive electrode active material and binder. The positive electrode active material contains lithium/nickel-containing composite oxide containing nickel and cobalt and/or manganese. The lithium/nickel-containing composite oxide contains 30 mol% or more nickel when amount of elements other than lithium and oxygen is 100 mol%. The binder comprises vinylidene fluoride-chlorotrifluoroethylene copolymer. A heat-resistant fine particle layer containing heat-resistant fine inorganic particles and binder, is arranged between positive electrode and negative electrode. The upper limit voltage for charging of nonaqueous electrolyte secondary battery is 4.3 V or more.    DESCRIPTION OF DRAWING(S) - The drawing shows top view and sectional view of nonaqueous electrolyte secondary battery.    Positive electrode (1)    Negative electrode (2)    Separator (3)    Battery case (4)    Insulator (5)