Non-aqueous liquid electrolyte and non-aqueous liquid electrolyte secondary battery

摘要

A non-aqueous liquid electrolyte secondary battery using negative-electrode active material having Si, Sn and/or Pb, with high charge-capacity, superior characteristics including discharge-capacity retention rate over long is provided. The non-aqueous liquid electrolyte of the battery contains carbonate having unsaturated bond and/or halogen and compounds such as LiPF6 and/or LiBF4 (first lithium salt) and lithium salt different from the first lithium salt.

主权项

1. A non-aqueous liquid electrolyte secondary battery, comprising:
a negative electrode comprising graphite and a negative-electrode active material containing Si atoms, a positive electrode capable of intercalating and deintercalating lithium ions, and a non-aqueous liquid electrolyte comprising
a carbonate having a halogen atom selected from the group consisting of fluoroethylene carbonate, difluoroethylene carbonate and mixtures thereof, and(A) at least one first lithium salt selected from the group consisting of LiPF6 and LiBF4 and at least one second lithium salt, which is different from the first lithium salt, and is represented by the formula (A-1):
Lil(αmXan)  (A-1)wherein
l represents an integer of 1 or larger and 10 or smaller, m represents an integer of 1 or larger and 100 or smaller, and n represents an integer of 1 or larger and 200 or smaller, α represents any atom selected from the group consisting of boron atom, carbon atom, nitrogen atom, oxygen atom and phosphorus atom; when m is 2 or larger, the two or more of α may be the same as or different from each other, Xa represents a functional group having at least one kind of atom selected from 14 group to 17 group of the periodic table at its binding position to the α, when n is 2 or larger, the two or more of Xa may be the same or different from each other, in addition, two or more Xa may be connected to each other to form a ring structure, except such a compound in which α is boron atom and Xa is represented by
(CiH2(i-2)O4)(CjH2(j-2)O4) wherein, i and j each represent, independently of each other, an integer of 2 or larger, andwherein
the concentration of the first lithium salt in the non-aqueous liquid electrolyte is 0.5 mol/liter to 2.5 mol/liter, the concentration of the second lithium salt in the non-aqueous liquid electrolyte is 0.001 mol/liter to 1 mol/liter, and the molar ratio of the second lithium salt relative to the first lithium salt is 1 or smaller.