NOVELTY - A lithium secondary battery consisting of a positive electrode, a negative electrode, a separator, and an electrolyte is charged/discharged as follows. The reversible capacity of the negative electrode is larger than the utilization capacity of the positive electrode. Charging/discharging where the charged positive electrode is discharged to electric potential (I) lower than 2.7 V based on lithium metal and at which discharge is terminated, is carried out.    USE - Charging/discharging of lithium secondary battery used in battery packs of electronic devices (all claimed). Uses include but are not limited to mobile telephones, personal digital assistants, notebook personal computers, video cameras, handheld game machines, vacuum cleaners, electric tools, fuel cell electric vehicles, hybrid electric vehicles, and plug-in hybrid electric vehicles.    ADVANTAGE - The method is capable of gradually reducing the negative-electrode utilization factor with charging/discharging cycle process. Deterioration (precipitation of lithium) of negative electrode by repetitive charging/discharging cycle is prevented, without reduction in initial battery capacity.    DETAILED DESCRIPTION - A lithium secondary battery consisting of a positive electrode containing an active material which can occlude/release lithium ion, a negative electrode containing an active material which can occlude/release lithium ion, a separator arranged between the positive and negative electrodes, and an electrolyte with lithium ion conductivity, is charged/discharged as follows. The positive-electrode active material contains a lithium-containing transition metal oxide. The reversible capacity of the negative electrode is larger than the utilization capacity of the positive electrode. Charging/discharging where the charged positive electrode is discharged to electric potential (I) lower than 2.7 V based on lithium metal and at which discharge is terminated, is carried out. INDEPENDENT CLAIMS are included for the following:    (1) charging/discharging system;    (2) electronic device provided with the charging/discharging system; and    (3) battery pack provided with the charging/discharging system.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the lithium secondary battery.    Positive electrode (11)    Positive-electrode collector (11a)    Positive-electrode active-material layer (11b)    Negative material (12)    Separator (13)