TECHNOLOGY FOCUS - ELECTRONICS - Preferred battery: The lithium secondary battery comprising a positive electrode having a positive electrode active material that can intercalate and deintercalate lithium and a negative electrode having a negative electrode active material that can intercalate and deintercalate lithium, are separated by the precursor of the polymer electrolyte (II). Preferred Definitions:    Y=-C(=O)-O-, -O-C(=O)-, -NH-, -NH-C(=O)-, -C(=O)-NH- or -R1-OC(=O)OMe/Et;and    m=8.    EXAMPLE - Allyl methyl carbonate (50 g) was dissolved in tetrahydrofuran (0.5 dm3) and azobisisobutyronitrile (0.25 g) was added to it. The mixture was stirred at 70?C to give a polymer. The polymer (1 g) and lithium bis(1,1,2,2,2-pentafluoroethanesulnyl) amide (LiN(CF3CF2 resulting solution was cast on a poly(tetrafluoroethylene) sheet. The sheet was subjected to vacuum drying at 80?C, and a cast film (test) having a thickness of 100 microns was prepared. A copolymer (37 g) of ethylene oxide (80% by mole) and 2-(2-methoxyethoxy)ethyl glycidyl ether (20% by mole) was mixed with lithium hexafluorophosphate (6.6 g) as an electrolytic salt. The mixture was dissolved in acetonitrile. The g solution was cast on a poly(tetrafluoroethylene) sheet, the sheet was subjected to vacuum drying at 80?C. and a cast film (control) having a thickness of 100 microns was prepared. The cast films (test and control) were inserted between stainless electrodes with diameters of 15 mm to prepare a test cell (test and control). An amplitude voltage of 10 mV was applied to the cell at room temperature to measure a.c. impedance. The frequency range was 1 Hz - 1 MHz. Based on the reciprocal of the bulk ohmic value obtained by the measurement of a.c. impedance, ionic conductivity was determined. Ionic conductivity was deduced to be approximately 5x10-5 Scm-1 at room temperature. A.c. impedance was measured to examine the temperature dependence of the ionic conductivity using the test cell. The test cells were allowed to stand in a thermostat at a given temperature level for 30 minutes, and the measurement was carried out in a manner such that the cell was set in the thermostat. Ionic conductivity was determined. The activation energy of the ionic conduction calculated based on the correlation between ionic conductivity and temperature, was deduced. The activation energy for test/control was found to be 5 kJ/mol and 40 kJ/mol.