Olivine composite cathode material, preparation method and application thereof, and lithium-ion battery

1 . An olivine composite cathode material, comprising:

a matrix; and

a composite phase;

wherein the matrix has a composition represented by formula I:

Li x M 1 y Mn z Fe 1-z-u M 2 u (PO 4 ) w (RO a ) b Cv formula I, where:

0.5≤x<1.3, 0≤y≤0.5, 0<z≤1, 0≤u≤0.01, 0<w≤1, 0<v≤0.05, 0≤a≤8, 0<b≤1, and 0.3≤1-z-u<0.4;

M 1 is selected from at least one element of Mg, Na, and K;

M 2 is selected from at least one element of Ga, Sn, V, Y, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si,

W, and In; and

R is selected from at least one element of Si, Cl, Br, S, Sb, and Sn; and

wherein the composite phase has a composition represented by formula II:

T m G n formula II, where:

0.1≤m≤5, and 0.1≤n≤5;

T is selected from at least one element of Ti, Mo, Co, W, Zn, Cu, B, V, Nb, Ta, Pd, Cr, Ag, Al, Mn, Sn, Mg, Sc, Zr, and Hf, and

G is selected from N, or N and C.

2 . The olivine composite cathode material according to claim 1 , wherein:

in formula I, 0.9≤x<1.1, 0<y≤0.01, 0.5≤z≤1, 0<u≤0.005, 0.5≤w<1, 0.001<v≤0.03, 0≤a≤4, and 0<b≤0.1; and

in formula II, 0.5≤m≤3, 1≤n≤5, and T is selected from at least one element of Ti, Mo, Co, W, Zn, Cu, B, V, Nb, Ta, Cr, Ag, Al, Mn, Sn, Mg, Sc, and Zr.

3 . The olivine composite cathode material according to claim 1 , wherein based on a total weight of the composite cathode material, a content of the composite phase ranges from 0.01 wt % to 10 wt %.

4 . The olivine composite cathode material according to claim 1 , wherein:

the composite cathode material has a pellet density ranging from 1.5 g/cm 3 to 3 g/cm 3 .

5 . A preparation method of the olivine composite cathode material according to claim 1 , the preparation method comprising:

(1) performing a first mixing on a compound containing element T with a compound containing element G to obtain a first mixture, and performing a first heat treatment on the first mixture in the presence of a protective atmosphere to obtain a compound containing elements T and G;

(2) performing a second mixing on a lithium source, a carbon source, a phosphorus source, an optional iron source, a manganese source, an optional R source, an optional M 1 source, an optional M 2 source with a solvent to obtain a second mixture, and grinding the second mixture to obtain a slurry;

(3) performing a third mixing on the compound containing elements T and G with the slurry and drying to obtain powder; and

(4) performing a second heat treatment on the powder in the presence of a non-oxidizing atmosphere and performing crushing to obtain the olivine composite cathode material, wherein:

in step (1), the compound containing element T is selected from at least one of an elementary substance of element T, an oxide of element T, a nitrate of element T, and a hydroxide of element T; and

the compound containing element G is selected from at least one of nitrogen, ammonia, melamine, polydopamine, and urea; or the compound containing element G is selected from at least one of nitrogen, ammonia, melamine, polydopamine and urea and at least one of glucose, starch, sucrose, and graphite.

6 . The preparation method according to claim 5 , wherein:

conditions of the first heat treatment comprise: a heat treatment temperature ranging from 400° C. to 1,000° C., and a heat treatment duration ranging from 2 hours to 8 hours; and

a molar ratio of the compound containing element T in terms of element T to the compound containing element G in terms of element G is (0.5 to 7): 1.

7 . The preparation method according to claim 5 , wherein:

in step (2), the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium nitrate;

the phosphorus source is selected from at least one of phosphoric acid, metaphosphoric acid, pyrophosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphorus oxide;

the carbon source is selected from at least one of glucose, sucrose, starch, graphene, and carbon nanotube;

the iron source is selected from at least one of ferric phosphate, ferrous oxalate, ferric acetate, ferric oxide, and hydroxyl iron oxide;

the manganese source is selected from at least one of manganese oxide, manganese carbonate, and manganese nitrate;

the R source is selected from a compound containing at least one element of Si, Cl, Br, S, Sb, and Sn;

the M 1 source is selected from a compound containing at least one element of Mg, Na, and K;

the M 2 source is selected from a compound containing at least one element of Ga, Sn, V, Y, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si, W, and In,

the solvent is selected from at least one of water, ethanol, methanol, N-methylpyrrolidone (NMP), and isopropanol; and

a molar ratio of the lithium source in terms of Li, the phosphorus source in terms of P, the carbon source in terms of C, the iron source in terms of Fe, the manganese resource in terms of Mn, the R source in terms of R, the M 1 source in terms of M 1 , and the M 2 source in terms of M 2 is (0.5 to 1.3): (0 to 1): (0 to 0.05): (0 to 1): (0 to 1): (0 to 1): (0 to 0.5): (0 to 0.01).

8 . The preparation method according to claim 5 , wherein:

in step (3), a solid-liquid ratio of the compound containing elements T and G to the slurry ranges from 0.000001 g/mL to 10 g/mL; and

in step (4), conditions of the second heat treatment comprise: a heat treatment temperature ranging from 400° C. to 1,000° C., and a heat treatment duration ranging from 4 hours to 12 hours.

9 . A lithium-ion battery, comprising an olivine composite cathode material, the olivine composite cathode material comprising:

a matrix; and

a composite phase;

wherein the matrix has a composition represented by formula I:

Li x M 1 y Mn z Fe 1-z-u M 2 u (PO 4 ) w (RO a ) b Cv formula I, where:

0.5≤x<1.3, 0≤y≤0.5, 0<z≤1, 0≤u≤0.01, 0<w≤1, 0<v≤0.05, 0≤a≤8, 0≤b≤1, and 0.3≤1-z-u≤0.4;

M 1 is selected from at least one element of Mg, Na, and K;

M 2 is selected from at least one element of Ga, Sn, V, Y, Mo, Al, Mg, Ce, Ti, Zr, Nb, Si, W, and In; and

R is selected from at least one element of Si, Cl, Br, S, Sb, and Sn; and

wherein the composite phase has a composition represented by formula II:

T m G n formula II, where:

0.1≤m≤5, and 0.1≤n≤5;

T is selected from at least one element of Ti, Mo, Co, W, Zn, Cu, B, V, Nb, Ta, Pd, Cr, Ag, Al, Mn, Sn, Mg, Sc, Zr, and Hf; and

G is selected from N, or N and C.

10 . The lithium-ion battery according to claim 9 , wherein:

the lithium-ion battery is a liquid lithium-ion battery; and

subsequent to 1,000 cycles at 45° C., an amount of manganese dissolved from a negative electrode of the liquid lithium-ion battery is ≤3000 ppm.

11 . The lithium-ion battery according to claim 9 , wherein:

in formula I, 0.9≤x<1.1, 0<y≤0.01, 0.5≤z≤1, 0<u≤0.005, 0.5≤w<1, 0.001<v≤0.03, 0≤a≤4, and 0<b≤0.1; and

in formula II, 0.5≤m≤3, 1≤n≤5, and T is selected from at least one element of Ti, Mo, Co, W, Zn, Cu, B, V, Nb, Ta, Cr, Ag, Al, Mn, Sn, Mg, Sc, and Zr.

12 . The lithium-ion battery according to claim 9 , wherein based on a total weight of the composite cathode material, a content of the composite phase ranges from 0.01 wt % to 10 wt %.

13 . The lithium-ion battery according to claim 9 , wherein:

the composite cathode material has a pellet density ranging from 1.5 g/cm 3 to 3 g/cm 3 ;

the composite cathode material has an electrical resistivity of ≤2,500 Ω/cm;

in the composite cathode material, 0.5≤m/n≤7;

the composite cathode material has an average particle size D 50 ranging from 0.5 μm to 20 μm; and

in an EDS elemental analysis of the composite cathode material, m/n has a standard deviation of ≤1% at any position.

14 . The olivine composite cathode material according to claim 1 , wherein the composite cathode material has an electrical resistivity of ≤2,500 Ω/cm.

15 . The olivine composite cathode material according to claim 1 , wherein in the composite cathode material, 0.5≤m/n≤7.

16 . The olivine composite cathode material according to claim 1 , wherein the composite cathode material has an average particle size D 50 ranging from 0.5 μm to 20 μm.

17 . The olivine composite cathode material according to claim 1 , wherein in an EDS elemental analysis of the composite cathode material, m/n has a standard deviation of ≤1% at any position.

18 . The preparation method according to claim 5 , wherein in step (2):

the slurry has a solid content ranging from 10 wt % to 60 wt %; and

the slurry has an average particle size D 50 ranging from 0.1 μm to 1 μm.