NOVELTY - An electric double layer capacitor has liquid amphiphilic polyether compound and/or lipophilic compound included under normal temperature and pressure in electrolyte. Electrolyte is swollen with the amphiphilic polyether compound and/or lipophilic compound. Freezing point or softening point of amphiphilic polyether compound is 0 degrees Celsius or less. Amphiphilic polyether compounds are polyethyleneglycol mono-alkylate, polypropylene glycol mono-alkylate, polyethyleneglycol monoalkylether, polypropylene glycol monoalkylether and/or related compounds.    USE - Electric double layer capacitor used for power supply of electronic or electric device. Uses include but not limited to high capacity machine, next-generation eco-friendly car, motor vehicle electrical component, natural power source electric power generator, implanted medical apparatus, timepiece, mobile telephone of portable electronic device, quick charge condenser, digital camera, electrically-driven toy, home appliances, uninterruptible power system, home-use electrical storage system, flyback transformer used for cathode ray tube for TV receiver, audio amplifier, surge protector, electric apparatus such as resistance spot-welding device, disposable camera, control module or inverter apparatus used for electric vehicle drive device    ADVANTAGE - Prevents falling of the capacitance electric double-layer capacitor even if charging and discharging are performed repeatedly since lithium alloy is easily formed in the interface of negative electrode and polyelectrolyte during charging of electric double-layer capacitor. Prevents short pass or corrosion since protective layer that becomes the lead root portion is formed from insulation substance. Prevents short-circuit since corner portion of metal electrode is fully covered with electroconductive polymeric layer. Suppresses defect generation of oxide film and suppresses leakage current defect since lead base is reinforced so that stress is not received. Ensures space saving and/or reduces size and weight of the electric double-layer capacitor.