Patent ID: 7601463

Claim:
A nonaqueous electrolyte secondary battery, comprising: an outer housing; a nonaqueous electrolyte which fills the outer housing, the nonaqueous electrolyte comprising a nonaqueous solvent of diethyl carbonate and at least one of ethylene carbonate or propylene carbonate, the nonaqueous electrolyte having a diethyl carbonate content of 80 to 95% by volume; a positive electrode housed in the outer housing, the positive electrode comprising a positive electrode active substance having a positive electrode potential in the fully charged state of 4.4 V or higher with respect to a potential of metallic lithium; a negative electrode housed in the outer housing, the negative electrode comprising a negative electrode active substance, which is at least one of a lithium titanium complex oxide or a lithium iron complex sulfide, having a negative electrode potential in the fully charged state of 1.0 V or higher with respect to the potential of metallic lithium; and a separator disposed between the negative electrode and the positive electrode, the separator being impregnated with the nonaqueous electrolyte, wherein the positive electrode active substance comprises at least one material selected from the group consisting of LiCoO 2 , LiMnO 2 , LiMn 2 O 4 , LiNiO 2 , LiAlO 2 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.75 Co 0.20 Al 0.05 O 2 , LiNi 0.5 Mn 0.5 O 2 , LiN 1−y Co y O 2 , LiMn y Co 1−y O 2 , and Li 1−x Mn 1.5−y Ni 0.5−z M y+z O 4 , where y for LiNi 1−y Co y O 2 and LiMn y Co 1−y O 2 satisfies 0<y<1, and M for Li 1−x Mn 1.5−y Ni 0.5−z M y+z O 4 is at least one element selected from the group consisting of Mg, Al, Ti, Fe, Go, Ni, Cu, Zn, Ga, Nb, Sn, Zr and Ta; 0≦x≦1 and 0≦y+z≦0.15.