Lithium secondary battery

1 . A lithium secondary battery comprising: a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte, wherein

the non-aqueous electrolyte includes an oxalate complex lithium salt, CF 2 ═CH—O—CF2-CF2H as a fluorinated vinylene ether compound A having a —CF═CH—O— bond, and a non-aqueous solvent an amount of the fluorinated vinylene ether compound A included in the non-aqueous electrolyte is 10 ppm or more and 100 ppm or less relative to a total amount of the non-aqueous electrolyte,

the non-aqueous solvent includes an ether compound different from the fluorinated vinylene ether compound A

the ether compound includes an alkyl ether compound Y represented by R 1 (OCH 2 CH 2 )n-OR 2 , where, R 1 and R 2 are each an alkyl group with a number of carbon atoms of 1 to 5, n is an integer of 1 or more, or a saturated hydrofluoro ether compound Z represented by (C x1 H y1 F z1 )—O—(C x2 H y2 F z2 ), where, x1, x2, z1 is an integer of 1 or more, y1, y2, z2 is an integer of 0 or more, and x1+x2≤10, 1≤y1+y2, and the positive electrode includes a lithium transition metal oxide A having a Ni ratio relative to a total number of moles of metal elements excluding Li of 80 mol % or more.

2 . The lithium secondary battery of claim 1 , wherein in the non-aqueous electrolyte, a ratio of the ether compound X is 50 vol % or more.

3 . The lithium secondary battery of claim 1 , wherein in the negative electrode, lithium metal deposits during charging and the lithium metal dissolves into the non-aqueous electrolyte during discharging.

4 . The lithium secondary battery of claim 1 , wherein the oxalate complex lithium salt includes lithium difluorooxalateborate.