NOVELTY - A lithium secondary battery comprises a positive electrode (1) and a negative electrode (2) which reversibly intercalate and deintercalate lithium; and an electrolyte containing an ion conductive material and an electrolyte salt, where the ion conductive material contains a polymerizable boron-containing compound.    USE - The invention is used as electronic source of, e.g. integrated circuit cards, personal computers, large-sized electronic computers notebook type personal computers, pen input personal computers, notebook type word processors, portable telephones, portable cards, wristwatches, cameras, electric shavers, cordless telephones, facsimiles, video, video cameras, electronic pocketbooks, desk electric calculators, electronic pocketbooks with communication functions, portable copying machines, liquid crystal televisions, electric tools, cleaners, game devices having functions such as virtual reality, toys, electric bicycles, walk assisting machines for medical care, escalators, elevators, forklifts, golf carts, electric sources for emergency, load conditioners, power storage systems, and war materials and space materials.    ADVANTAGE - The invention has excellent output characteristics.    DETAILED DESCRIPTION - A lithium secondary battery comprises a positive electrode and a negative electrode which reversibly intercalate and deintercalate lithium; and an electrolyte containing an ion conductive material and an electrolyte salt, where the ion conductive material contains a polymerizable boron-containing compound of formula (I).    B = boron;    Z1, Z2, Z3 = organic group having an acryloyl group, methacryloyl group, or 1-10C hydrocarbon;    AO = 1-6C oxyalkylene;    l, m, n = an average degree of polymerization of oxyalkylene group, more than 0 but less than 4.    One or two of Z1, Z2, or Z3 are the organic groups having an acryloyl group or methacryloyl group.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic oblique view of the battery.    Positive electrode (1)    Negative electrode (2)    Stainless steel terminals (5, 6)    Laminate film (7)