NOVELTY - The battery has a negative electrode (103) comprising of negative electrode active material layer (102) and a negative electrode current collector (101), and a positive electrode (106) comprising of positive electrode active material layer (105) and a positive electrode current collector (104). The positive electrode active material layer and negative electrode active material layer satisfy predetermined conditions involving their capacities per unit weight and densities. The negative electrode active material layer has alloy particles as active material with silicon as major component.    USE - Lithium secondary battery.    ADVANTAGE - Provides a lithium secondary battery having a high capacity and a long life and so designed as to exhibit these characteristics at the same time. Provides a lithium secondary battery with a negative electrode of high capacity working in combination with a positive electrode to exhibit high capacity and long life. Provides a lithium secondary which can freely be designed so as to meet either or both of the objects of high capacity use and long life use.    DETAILED DESCRIPTION - The predetermined conditions to be satisfied are expressed as the quantity of CN times DN over the quantity of CP times DP is equal to or less than 8, where CN times DN is equal to 1,200 to 2,500 mAh per cubic centimeter, CN is equal to 1,000 to 2,200 mAh per gram, and DN is equal to 0.9 to 1.5 grams per cubic centimeter. The parameter CN represents the capacitor per unit weight of the negative electrode active material layer, DN represents the density of the negative electrode active material layer, CN represents the capacity per unit weight of the positive electrode active material layer, and DP represents the density of the positive electrode active material layer.    DESCRIPTION OF DRAWING(S) - The figure is a sectional view schematically showing the lithium secondary battery.    Negative electrode current collector (101)    Negative electrode active material layer (102)    Negative electrode (103)    Positive electrode current collector (104)    Positive electrode active material layer (105)    Positive electrode (106)