Abstract: A lithium ion secondary battery includes a negative electrode including a mixture layer which contains a niobium titanium oxide as a negative electrode active material, and non-aqueous electrolyte containing lithium alkoxysulfonate represented by RSOOO?Li+ (where R is at least one selected from the group consisting of OCH3 and OC2H5).

Abstract: A lithium secondary battery having a positive electrode, a negative electrode, a separator and an electrolyte solution, in which the positive electrode contains a first active material and a second active material each capable of intercalating and deintercalating lithium. The first active material is in the state under which only deintercalation of lithium can be carried out in a battery reaction with the negative electrode immediately after assembly of the lithium secondary battery, and the second active material is in the state under which lithium can be intercalated in the battery reaction with the negative electrode immediately after assembly of the lithium secondary battery. The negative electrode contains metal lithium as an active material. The separator has a structure in which pores are three-dimensionally regularly arranged.

Abstract: The object of the present invention is to provide a lithium transition metal silicate-type cathode active material that shows superior cycle characteristics, and shows little deterioration of discharge capacity even after repeated charge-and-discharge. In the present invention, a cathode active material that is expressed by the general formula Li2-yFe1-xMxSi1-yXyO4 (M=at least one transition metal selected from the group consisting of Mn, Ti, Cr, V, Ni, Co, Cu, Zn, Al, Ge, Zr, Mo, W; X=at least one element selected from the group consisting of Ti, Cr, V, Zr, Mo, W, P, B; 0?x<1, 0?y<0.25), and contains a lithium transition metal silicate, which comprises a mixed phase of an orthorhombic-type structure with a space group Pmn21 symmetry, and a monoclinic-type structure with a space group P21/n symmetry, is provided.