Lithium nickel manganese cobalt composite oxide as a positive electrode active material for rechargeable lithium ion batteries
A positive electrode active material powder suitable for lithium-ion batteries, comprising lithium transition metal-based oxide particles, said particles comprising a core and a surface layer, said surface layer being on top of said core, said particles comprising the elements: Li, M′ and oxygen, wherein M′ has a formula: M′=Ni z Mn y Co x A k , wherein A is a dopant, 0.60≤z≤0.90, 0.05≤y≤0.20, 0.05≤x≤0.20, x+y+z+k=1, and k≥0.01, said positive electrode active material powder having a median particle size D50 ranging from 5 μm to 15 μm, a span ranging from 0.25 to 0.90, and a surface layer thickness ranging from 10 nm to 200 nm, said surface layer comprising: sulfur in a content superior or equal to 0.150 wt % and inferior or equal to 0.375 wt % with respect to the total weight of the positive electrode active material powder, and sulfate ion (SO 4 2− ) in a content superior or equal to 4500 ppm and inferior or equal to 11250 ppm.
1. A positive electrode active material powder suitable for lithium-ion batteries, comprising lithium transition metal-based oxide particles, said particles comprising a core and a surface layer, said surface layer being on top of said core, said particles comprising the elements:
Li, M′ and oxygen, wherein M′ has a formula: M′=Ni z Mn y Co x A k , wherein A is a dopant, 0.80≤z≤0.87, 0.05≤y≤0.20, 0.05≤x≤0.20, x+y+z+k=1, and k≤0.01,
said positive electrode active material powder having a median particle size D50 ranging from 5 μm to 15 μm, a span ranging from 0.25 to 0.90, and a surface layer thickness ranging from 10 nm to 200 nm,
said surface layer comprising:
sulfur in a content superior or equal to 0.150 wt % and inferior or equal to 0.375 wt % with respect to the total weight of the positive electrode active material powder,
sulfate ion (SO 4 2− ) in a content superior or equal to 4500 ppm and inferior or equal to 11250 ppm, and
aluminum and having an Al surface coverage value A1/A2 that is superior or equal to 100, wherein A1 is an atomic ratio Al/(Ni+Mn+Co+Al+S) of the elements Al, Ni, Mn, Co, and S contained in the surface layer, said atomic ratio A1 being obtained by XPS spectrum analysis and wherein A2 is an atomic ratio Al/(Ni+Mn+Co+Al+S) obtained by ICP.
2. The positive electrode active material powder according to claim 1 , having a carbon content of less than 200 ppm.
3. The positive electrode active material powder according to claim 1 , having a Li/(Ni+Mn+Co+A) atomic ratio or a Li/(Ni+Mn+Co+A+Al) atomic ratio superior or equal to 0.96 and inferior or equal to 1.05.
4. The positive electrode active material powder according to claim 1 , wherein said surface layer exhibits an Al2p peak with a maximum peak intensity in the binding energies range from 73.0±0.2 eV to 74.5±0.2 eV, said intensity being obtained by XPS spectrum analysis.
5. The positive electrode active material powder according to claim 1 , wherein said surface layer of lithium transition metal-based oxide particles comprises a LiAlO 2 phase and a LiM″ 1-a Al a O 2 phase wherein M″ comprising Ni, Mn, and Co, said LiAlO 2 phase being present in the surface layer in a content superior or equal to 0.10 at % and inferior or equal to 0.30 at % with respect to the total atomic content of M′ in the positive electrode active material powder, said LiM″ 1-a Al a O 2 phase being present in the surface layer in a content inferior to 0.14 at % with respect to the total atomic content of M′ in the positive electrode active material powder.
6. The positive electrode active material powder according to claim 1 , wherein said lithium transition metal-based oxide particles have a sulfate ion surface coverage S1/S2 that is superior to 0.85 and inferior or equal to 1.00, wherein S1 is an amount of sulfate ion contained in the surface layer, and wherein S2 is a total amount of sulfate ion contained in the particles.
7. The positive electrode active material powder according to claim 2 , having a general formula: Li 1+a′ ((Ni z′ Mn y′ Co x′ Al v S w ) 1-k A k ) 1-a′ O 2 , wherein only A is a dopant, wherein 0.80≤z′≤0.87, 0.05≤y′≤0.20, 0.05≤x′≤0.20, x′+y′+z′+v+w+k=1, 0.0018≤v≤0.0053, 0.006≤w≤0.012, −0.05≤a′≤0.05, and k≤0.01.
8. The positive electrode active material powder according to claim 1 , wherein A comprises one or more of Al, B, S, Mg, Zr, Nb, W, Si, Ba, Sr, Ca, Zn, Cr, V, Y, or Ti, wherein the amount of each of the elements of A is superior to 100 ppm with respect to the total weight of the positive electrode active material powder.
9. The positive electrode active material powder according to claim 1 , wherein the thickness of the surface layer corresponds to a minimal distance D defined either as:
D (in nm)= L S1 −L S2 ,
wherein L S1 is a first point location at the center of a particle, L S2 is a second point location in a line defined between said first point location and a geometric center of said particle,
wherein a content of S is measured by TEM-EDS at the second point location L S2 is superior or equal to 0 at % and inferior or equal to 5.0 at % of a content of S measured at the first point location, said second content of S (S 2 ) being defined as:
S 2 (in at %)= S 3 ±0.1 at %,
S 3 being a content of S (in at %) at a third point location (LS 3 ) in said line, said third point being located at any location between the geometric center of said particle and the second point location L S2 .
10. The positive electrode active material powder according to claim 9 , wherein:
S 1 −S 2 ≥10.0 at %
S 1 being the first content of S (in at %) at the first point location (LS 1 ).
11. The positive electrode active material powder according to claim 9 , wherein Al is present in the surface layer in a content/defined as:
l
(
mol
%
)
=
(
Al
M
*
)
ICP
×
(
Al
surface
/
Al
total
)
with:
(
Al
M
*
)
ICP
is the atomic ratio of Al content on M* content in the powder measured by ICP, and
Al
s
u
r
f
a
c
e
/
Al
total
=
4
3
π
(
Area
2
)
3
-
4
3
π
(
Area
2
-
Area
1
)
3
4
3
π
(
Area
2
)
3
×
100
,
wherein:
Al surface is the content of Al in at % in the surface layer measured by EDS;
Al total the total content of Al in at % in the particles of said powder measured by EDS;
Area1 is the integral of the Al/M* content measured by cross-section-TEM-EDS over D:
Area
1
(
at
%
/
at
%
)
=
∫
x
=
0
x
=
D
Al
M
*
(
x
)
,
where:
Al(x) is the atomic content of Al at a point x of a cross sectional particle measured by cross-section-TEM EDS,
M*(x) is the atomic content of Ni, Mn, Co, Al, and S, at a point x of a cross sectional particle measured by cross-section-TEM EDS, and
x is the distance expressed in nm measured by TEM between said first and second point locations,
Area2 is the integral of the Al/M* content measured by cross-SEM EDS over a distance C:
Area
2
(
at
%
/
at
%
)
=
∫
x
=
0
x
=
C
Al
M
*
(
x
)
,
where:
Al(x) is the atomic content of Al at a point x of a cross sectional particle measured by cross-section-TEM EDS,
M* (x) is the atomic content of Ni, Mn, Co, Al, and S, at a point x of a cross sectional particle measured by cross-section-TEM EDS, and
x is the distance expressed in nm and measured by TEM between said first point location (at x=0 nm) and the geometric center of said particle (at x=C), wherein C ranges from 2.5 μm to 7.5 μm.
12. Process for the manufacturing of a positive electrode active material according to claim 1 , comprising the consecutive steps of:
a) preparing a lithium transition metal-based oxide compound,
b) mixing said lithium transition metal-based oxide compound with a source of sulfate ion, and with water, thereby obtaining a mixture, and
c) heating the mixture in an oxidizing atmosphere in a furnace at a temperature between 350° C. and less than 500° C., for a time between 1 hour and 10 hours so as to obtain the positive electrode active material powder according to the present invention.
13. A battery comprising the positive electrode active material powder according to claim 1 .
14. An electric vehicle or a hybrid electric vehicle comprising the battery according to claim 13 .