Lithium nickel manganese-containing composite oxide, method for preparation thereof, positive electrode plate, secondary battery and electrical device

1 . A lithium nickel manganese-containing composite oxide, wherein the lithium nickel manganese-containing composite oxide is a particle with a monocrystal morphology or a quasi-monocrystal morphology, the lithium nickel manganese-containing composite oxide has a spherical or spherical-like grain shape, and the lithium nickel manganese-containing composite oxide has a general formula of Li 1+x Ni 0.5+y M z Mn 1.5−x−y−z−a A a O 4−k , −0.2≤x≤0.5, −0.2≤y≤0.2, 0≤z≤0.2, 0≤a≤0.2, 0≤k≤0.2, A comprises one or more selected from Si, P and S, M comprises one or more selected from a metal-doping element.

2 . The lithium nickel manganese-containing composite oxide according to claim 1 , wherein a ratio of long diameter L to short diameter S of the lithium nickel manganese-containing composite oxide grain satisfies 1.0≤L/S≤1.25, and/or wherein M comprises one or more selected from Mo, Nb, Ru, Te, Ta, Ce, and Yb.

3 . The lithium nickel manganese-containing composite oxide according to claim 1 , wherein,

0.01

≤

a

≤

0.2

;

and

/

or

,

0

<

z

≤

0.2

.

4 . The lithium nickel manganese-containing composite oxide according to claim 1 , wherein,

0.01

≤

z

+

a

≤

0.2

;

and

/

or

,

0

<

z

≤

0.2

and

⁢

1

≤

a

/

z

≤

5

,

and/or wherein the lithium nickel manganese-containing composite oxide has a 4V plateau charging capacity ratio R satisfying 0<R≤0.125,

the 4V plateau charging capacity ratio R of the lithium nickel manganese-containing composite oxide is measured as follows: assembling a button battery with an electrode plate comprising the lithium nickel manganese-containing composite oxide as a positive electrode and a lithium plate as a negative electrode, charging the battery to 4.95V at a current of 0.1C, and then charging to a current of 0.05C at the constant voltage, using a ratio of the charging capacity in the range of 3.5V to 4.4V to the total charging capacity of the button battery as the 4V plateau charging capacity ratio R of the lithium nickel manganese-containing composite oxide.

5 . The lithium nickel manganese-containing composite oxide according to claim 1 , wherein the lithium nickel manganese-containing composite oxide satisfies at least one of the following conditions (1) to (3):

(1) the lithium nickel manganese-containing composite oxide has a volume particle size Dv50 satisfying 3 μm≤Dv50≤16 μm;

(2) the lithium nickel manganese-containing composite oxide has a BET specific surface area S0 of ≤0.8 m 2 /g;

(3) the lithium nickel manganese-containing composite oxide has a tap density TD satisfying 1.5 g/cm 3 ≤TD≤3.0 g/cm 3 .

6 . The lithium nickel manganese-containing composite oxide according to claim 1 , wherein the lithium nickel manganese-containing composite oxide further has a cladding layer on the surface, the cladding layer comprises one or more selected from a conductive carbon material, a metal oxide, a metal fluoride and a polyanionic material,

optionally, the conductive carbon material comprises one or more selected from soft carbon, hard carbon, graphene and graphene oxide,

optionally, the metal oxide comprises one or more selected from Al 2 O 3 , B 2 O 3 , TiO 2 , ZrO 2 , WO 3 , MoO 3 , Y 2 O 3 , Ta 2 O 5 , TeO 2 , and Nb 2 O 5 ,

optionally, the metal fluoride comprises one or more selected from LiF, AlF 3 , and GaF 3 ,

optionally, the polyanionic material comprises one or more selected from orthophosphates and fluoro-orthophosphates of at least one element of Li, Ni, Co, Mn, Fe, Nb, Mo, W, Ta and Te.

7 . A preparation method of a lithium nickel manganese-containing composite oxide comprising the following steps:

S1: providing a raw material obtained by mixing a source of element Li, a source of element Ni, a source of element Mn, a source of element A, and an optional source of element M in a predetermined proportion;

S2: heating the raw material obtained in S1 to a first temperature T1 under an oxygen-containing atmosphere, maintaining at the first temperature T1 for a first time t1, cooling to room temperature, after which a intermediate product is obtained, 850° C.≤T1≤1100° C.; and

S3: heating the intermediate product obtained in S2 to a second temperature T2 under an oxygen-containing atmosphere, maintaining at the second temperature T2 for a second time t2, after which a lithium nickel manganese-containing composite oxide is obtained, 0° C. ≤T1−T2≤200° C., and T2≥800° C., wherein the lithium nickel manganese-containing composite oxide is a particle with a monocrystal morphology or quasi-monocrystal morphology, the lithium nickel manganese-containing composite oxide has a spherical or spherical-like grain shape, and the lithium nickel manganese-containing composite oxide has a general formula of Li 1+x Ni 0.5+y M z Mn 1.5−x−y−z−a A a O 4−k , −0.2≤x≤0.5, −0.2≤y≤0.2, 0≤z≤0.2, 0<a≤0.2, 0≤k≤0.2, A comprises one or more selected from Si, P and S, M comprises one or more selected from a metal-doping element.

8 . The preparation method according to claim 7 , wherein,

900

⁢

°

⁢

C

.

≤

T

⁢

1

≤

1100

⁢

°

⁢

C

.

;

and

/

or

,

0

⁢

°

⁢

C

.

≤

T

⁢

1

-

T

⁢

2

≤

100

⁢

°

⁢

C

.

,

and

⁢

850

⁢

°

⁢

C

.

≤

T

⁢

2

≤

1000

⁢

°

⁢

C

.

9 . The preparation method according to claim 7 , wherein, t2≤t1.

10 . The preparation method according to claim 7 , wherein,

2

⁢

h

≤

t

⁢

1

≤

50

⁢

h

;

and

/

or

,

0.5

h

≤

t

⁢

2

≤

20

⁢

h

;

and

/

or

,

10

⁢

h

≤

t

⁢

1

+

t

⁢

2

≤

40

⁢

h

.

11 . The preparation method according to claim 7 , further comprising a step S4: annealing the product obtained in S3 to obtain a lithium nickel manganese-containing composite oxide,

optionally, the annealing temperature is 500° C. to 800° C.,

optionally, the annealing time is 5 h-50 h and optionally further comprising steps: after mixing the lithium nickel manganese-containing composite oxide obtained in S4 with a cladding agent, sintering under a protective gas atmosphere to obtain a lithium nickel manganese-containing composite oxide with cladding layer, optionally, the cladding agent is a precursor compound for forming one or more of a conductive carbon material, a metal oxide, a metal fluoride, and a polyanionic material.

12 . The preparation method according to claim 7 , further comprising steps:

after mixing the lithium nickel manganese-containing composite oxide obtained in S3 with a cladding agent, sintering under a protective gas atmosphere to obtain a lithium nickel manganese-containing composite oxide with cladding layer, optionally, the cladding agent is a precursor compound for forming one or more of a conductive carbon material, a metal oxide, a metal fluoride, and a polyanionic material.

13 . A positive electrode plate comprising a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the lithium nickel manganese-containing composite oxide according to claim 1 , and the lithium nickel manganese-containing composite oxide is present in the positive electrode film layer in a content of 1 wt % to 99 wt % based on total weight of the positive electrode film layer.

14 . A secondary battery comprising the positive electrode plate according to claim 13 .

15 . An electrical device comprising the secondary battery according to claim 5 .