Ni based lithium-ion secondary battery comprising a fluorinated electrolyte
A liquid electrolyte lithium secondary battery cell comprising: —a positive electrode material comprising a lithium transition metal-based oxide powder having a general formula Li 1+a ((Ni z (Ni 0.5 Mn 0.5 ) y Co x ) 1−k A k ) 1−a O 2 , wherein A is a dopant, −0.025≤a≤0.025, 0.18≤x≤0.22, 0.42≤z≤0.52, 1.075<z/y<1.625, x+y+z=1 and k≤0.01; and—an electrolyte composition comprising: a) at least one cyclic carbonate, b) at least one fluorinated acyclic carboxylic acid ester, c) at least one electrolyte salt, d) at least one lithium compound selected from lithium phosphate compounds, lithium boron compounds, lithium sulfonate compounds and mixtures thereof, e) at least one cyclic sulfur compound, and f) optionally at least one cyclic carboxylic acid anhydride.
1 . A liquid electrolyte lithium secondary battery cell comprising:
a positive electrode material comprising a lithium transition metal-based oxide powder having a general formula
Li 1+a ((Ni z (Ni 0.5 Mn 0.5 ) y CO x ) 1−k A k ) 1−a O 2 , wherein A is a dopant, −0.025≤a≤0.025, 0.18≤x≤0.22, 0.42≤z≤0.52, 1.075<z/y<1.625, x+y+z=1 and k<0.01; and
an electrolyte composition comprising:
a) at least one cyclic carbonate, wherein the at least one cyclic carbonate is propylene carbonate,
b) monofluoroethylene carbonate,
c) at least one fluorinated acyclic carboxylic acid ester, wherein the at least one fluorinated acyclic carboxylic acid ester is 2,2-difluoroethyl acetate,
d) at least one electrolyte salt, wherein the at least one electrolyte salt is lithium hexafluorophosphate (LiPFO),
e) at least one lithium compound, wherein the at least one lithium compound is lithium bis(oxalato)borate,
f) at least one cyclic sulfur compound, wherein the at least one cyclic sulfur compound is 1,3,2-dioxathiolane 2,2-dioxide, and
g) at least one cyclic carboxylic acid anhydride, wherein the at least one cyclic carboxylic acid anhydride is maleic anhydride.
2 . The liquid electrolyte lithium secondary battery cell according to claim 1 , wherein the lithium transition metal-based oxide powder has a carbon content ≤1000 ppm.
3 . The liquid electrolyte lithium secondary battery cell according to claim 1 , wherein the lithium transition metal-based oxide powder has a carbon content ≤400 ppm.
4 . The liquid electrolyte lithium secondary battery cell of claim 1 , wherein the lithium transition metal-based oxide powder has a sulfur content between 0.05 and 1.0 wt %.
5 . The liquid electrolyte lithium secondary battery cell of claim 1 , wherein the lithium transition metal-based oxide powder further comprises between 0.15 and 5 wt % of a LiNaSO 4 secondary phase.
6 . The liquid electrolyte lithium secondary battery cell of claim 5 , wherein the lithium transition metal-based oxide powder comprises a core comprising a lithium transition metal-based oxide and a coating comprising the LiNaSO 4 secondary phase.
7 . The liquid electrolyte lithium secondary battery cell of claim 5 , wherein the LiNaSO 4 secondary phase further comprises up to 1 wt % of one or more of Al 2 O 3 , LiAlO 2 , LiF, Li 3 PO 4 , MgO or Li 2 TiO 3 .
8 . The liquid electrolyte lithium secondary battery cell of claim 1 , wherein the lithium transition metal-based oxide powder comprises a core comprising a lithium transition metal-based oxide and a surface layer comprising lithium and transition metals, the surface layer being delimited by an outer and an inner interface, the inner interface being in contact with the core, wherein the dopant A comprises Al, wherein the core has an Al content of 0.3-3 mol %, and wherein the surface layer has an Al content that increases from the Al content of the core at the inner interface to at least 10 mol % at the outer interface, the Al content being determined by XPS.
9 . The liquid electrolyte lithium secondary battery cell of claim 1 , wherein the electrolyte composition comprises:
from 15% to 35% propylene carbonate,
from 30% to 70% 2,2-difluoroethyl acetate,
from 9% to 16% lithium hexafluorophosphate (LiPF 6 ),
from 0.4% to 2% lithium bis(oxalato)borate,
from 0.4% to 5% 1,3,2-dioxathiolane 2,2-dioxide, and
from 0.25% to 1% maleic anhydride.