Electrolyte, electrolyte solution, gel electrolyte, electrolyte membrane, method for manufacturing gel electrolyte battery, and lithium ion secondary battery

A lithium ion secondary battery comprising an electrolytic solution which is a mixture of an organic acid lithium salt (A), a boron compound (B) and an organic solvent (C),

• said organic acid lithium salt (A) being lithium oxalate,
• said boron compound (B) being at least one member selected from the group consisting of boron trifluoride and boron trifluoride complex,
• wherein the number of moles of lithium atoms in the organic acid lithium salt (A):the number of moles of the boron compound (B) is 100:80 to 100:106 (molar ratio), and
• wherein a concentration of lithium atoms (Li) in the electrolytic solution is 0.2 to 3.0 mol/kg, in terms of [number of moles (mol) of lithium atoms in the organic acid lithium salt (A)/total mixed amount (kg) of (the organic acid lithium salt (A)+the boron compound (B)+the solvent (C))].