TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - The nonaqueous electrolyte contains the compound (G1) having at least two nitrile groups in the molecule (0.005-1 wt.%). The positive electrode comprises at least two lithium-containing transition metal oxides having different average particle sizes as active materials. The lithium-containing transition metal oxide having the smallest average particle size among at least two lithium-containing transition metal oxides is a lithium-containing transition metal oxide of formula (Li)x(M1)y(M2)z(M)3)vO2. The lithium-containing transition metal oxide other than a lithium-containing transition metal oxide having the smallest average particle size is a lithium-containing transition metal oxide of formula (Li)a(M1)b(M2)c(M3)dO2.M1=at least one transition metal element selected from cobalt, nickel and manganese;M2=at least one metal element selected from magnesium, titanium, zirconium, germanium, niobium, aluminum and tin;M3=element other than lithium;x=0.97-1.02;y=0.8-1.02;z=0.002-0.05;v=0-0.05;a=0.97-1.02;b=0.8-1.02;c=0-0.02;d=0-0.02.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The compound (G1) has at least two nitrile groups in the molecule is a dinitrile compound. The dinitrile compound is a compound of the formula NC-R-CN.R=linear or branched 1-10C hydrocarbon. EXAMPLE - LiCu0.998Mg0.0008Ti0.0004Al0.0008O2 as a positive electrode active material, and LiCu0.994Mg0.0024Ti0.0012Al0.0024O2 as a positive electrode active material at a weight ratio of 65:35 were mixed to obtain a mixture (G1). Then, the mixture (G1) (97.3 wt.%) and a carbonaceous material (1.5 wt.%) as an electric conductive aid were charged in a volumetric feeder as a device for supplying powder. A solution of polyvinylidene fluoride (10 wt.%) in N-methyl-2-pyrrolidone was supplied to the feeder. While the amount of the mixed materials supplied in a unit time was controlled to a predetermined amount, the materials were supplied in a biaxial kneading extruder and then kneaded to obtain a positive electrode (T1). A graphite type carbonaceous material (with average particle size of 18 mu m) (70 wt.%) and graphite type carbonaceous material (with average particle size of 21 mu m) (30 wt.%) were mixed to obtain a graphite mixture (G2). Then, the graphite mixture (98 wt.%), carboxymethylcellulose (1 wt.%) and a styrene-butadiene rubber (1 wt.%) were mixed in the presence of water to prepare a paste containing negative electrode mixture (G3). The paste (G3) was uniformly applied to both surfaces of a negative electrode current collector made of a strip-form copper foil, and then dried to form negative electrode mixture layers. The resultant sheet was pressed with a roller until the density of the negative electrode mixture layers became 1.75 g/cm3. The resultant sheet was then cut out in a predetermined size. Then, a lead member made of nickel was welded to the cut piece to form a negative electrode (T2). The positive electrode (T1) and the negative electrode (T2) were spirally wound with interposing, a separator made of a microporous polyethylene film to form an electrode body having a spiral structure. Then, the electrode body was pressed to form a flat-shaped electrode body and inserted into a box-shaped battery case made of an aluminum alloy. The positive and negative lead members were welded and a cover plate was laser welded to the edge portion of an opening of the battery case to obtain a nonaqueous electrolytic solution (G3). Then, the nonaqueous electrolytic solution (G3) was poured into the battery case through an inlet made in the cover plate. The nonaqueous electrolytic solution (G3) was sufficiently infiltrated into the separator. Thereafter, the battery was partially charged, and gas generated during the partial charging was discharged. Then, the inlet was sealed up to make the battery airtight. Then, the battery was charged and aged to obtain a nonaqueous secondary battery (test). A control nonaqueous secondary battery was fabricated in the same manner as in test nonaqueous secondary battery except that only LiCu0.998Mg0.0008Ti0.0004Al0.0008O2 was used as a positive electrode active material and no succinonitrile was added to the nonaqueous electrolyte. The test/control batteries were then evaluated for discharge capacity after charge-discharge cycles. The results for test/control batteries were: discharge capacity after charge-discharge cycles = 102/100, respectively. The results showed that the test battery had excellent discharge capacity after charge-discharge cycles as compared to the control battery.