Abstract: A porous element containing a fluoropolymer comprising vinylidene fluoride as a main unit and having a density of 0.55–1.30 g/cm3 and a Gurley value of not more than 150 sec/100 cc is used as a polymer substrate of a solid electrolyte to be placed between a positive electrode and a negative electrode. As a result, the solid electrolyte layer shows fine ion conductivity and an ion polymer secondary battery having strikingly improved low temperature characteristics, cycle characteristics and high-rate discharge characteristics as compared to conventional batteries can be obtained.

Abstract: A porous element containing a fluoropolymer comprising vinylidene fluoride as a main unit and having a density of 0.55-1.30 g/cm3 and a Gurley value of not more than 150 sec/100 cc is used as a polymer substrate of a solid electrolyte to be placed between a positive electrode and a negative electrode. As a result, the solid electrolyte layer shows fine ion conductivity and an ion polymer secondary battery having strikingly improved low temperature characteristics, cycle characteristics and high-rate discharge characteristics as compared to conventional batteries can be obtained.

Abstract: An alloy for a negative electrode of a lithium secondary battery, comprising an Li-Ag-Te type alloy having an atomic ratio of Li:Ag:Te=15-120:1-20:0.001-2, an alloy for a negative electrode of a lithium secondary battery, comprising an Li-Ag-Te-(M1-M2) type alloy having an atomic ratio of Li:Ag:Te:M1:M2=15-120:1-20:0.001-2:1-50:1-30 wherein M1 is a 3A-5A group metal and M2 is a transition metal other than Ag, and a lithium secondary battery comprising a negative electrode composed of the above-mentioned alloy. According to the present invention, a negative electrode, wherein the growth of dendrite is suppressed, charge-discharge capacity is high, energy density is high and degradation due to repetitive charge-discharge is less, can be obtained.