TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The sulfur-containing organic compound is a chain sulfonic acid ester. The sulfur-containing organic compound has cyclic structure of formulae (I) or (II). The sulfur-containing organic compound is selected from at least one of 1,3-propane sultone or 1,4-butane sultone. The sulfur-containing organic compound is selected from at least one of cyclic disulfonic acid ester selected from methylenemethane disulfonate, ethylenemethane disulfonate and propylene-methane disulfonate. The sulfur-containing organic compound is contained in an amount of 0.005-10 parts by mass per 100 parts by weight of a total of the aprotic organic solvent plus carrier salt. The aprotic organic solvent contains at least one cyclic polycarbonates, chain carbonates, aliphatic carboxylic acid esters, gamma -lactone, cyclic ethers, chain ethers and their fluorine derivatives. The carrier salt contains at least one substance selected from LiPF6, LiBF4, LiAsF6, LiSbF6, LiClO4, LiAlCl4, and LiN(Cn'F2n'+1SO2) (CmF2m+1SO2).X=alkylene group that can optionally have a side chain, or O;Y1=alkylene group that can optionally have a side chain or unsubstituted alkylene group;Z1=methylene group or a single bond;n=0-2;R1-R6=H, 1-12C alkyl, 3-6C cycloalkyl or 6-12C;andn' and m=natural number.    TECHNOLOGY FOCUS - POLYMERS - Preferred Electrolyte: The polymer gel electrolyte further comprises vinylene carbonate or its derivative. Preferred Components: A polymer that forms a polymer gel is at least one selected from polyacrylate, polyethylene oxide, and polypropylene oxide. SPECIFIC COMPOUNDS - Use of 1,3-propane sultone, 1,4-butane sultone, methylenemethane disulfonate, ethylenemethane disulfonate and propylene-methane disulfonate are specifically claimed as the sulfur-containing organic compound.    EXAMPLE - To prepare the polymer gel electrolyte-formation composition, 1,3-propane sultone (1 part by mass (pbm)), triethylene glycol diacrylate acting as a gelation agent (3.8 pbm) and trimethylolpropane triacrylate (1 pbm) were fully mixed with electrolysis solution (100 pbm) containing 30% by mass of ethylene carbonate (EC), 58% by mass of diethyl carbonate (DEC) and 12% by mass of LiPF6 behaving as a lithium salt. Then, tert-butyl peroxypivalate (0.5 pbm) working as a polymerization initiator was mixed with the resultant mixture. Then, the cell was placed in a vacuum system, internal gases were evacuated off from within the system, the polymer gel electrolyte-formation composition was poured in the cell through the inlet portion, and vacuum impregnation was carried out to obtain test lithium polymer secondary battery. A comparative battery was prepared as test battery with the exception that 1,3-propane sultone added was not added. The obtained test and comparative lithium polymer secondary batteries were charged at 20 degrees C up to a battery voltage of 4.2 V on a constant charge current of 0.2 C, it was charged at a constant voltage until an overall charging time amounted to 6.5 hours. Then, the battery was discharged down to a battery voltage of 3 V on a discharge current of 0.2 C. It was the then discharge capacity that was defined as an initial capacity. The rate performance of the obtained test and comparative batteries was measured in terms of percentage rate performance. Percentage capacity sustenance was measured by the ratio between the discharge capacity at the first cycle and the discharge capacity at the hundredth cycle. The volume of the cell after initial charge was also measured in terms of the ratio with respect to the volume of the cell after the cycle testing. The test/comparative batteries showed rate performance (%), capacity sustenance (%) and volume change (%) of 95/40, 91/5 and 1/20 respectively.