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CN-121983543-A - Composite positive electrode material with core-shell structure, preparation method thereof and lithium battery

CN121983543ACN 121983543 ACN121983543 ACN 121983543ACN-121983543-A

Abstract

The invention discloses a composite anode material with a core-shell structure, a preparation method thereof and a lithium battery, and relates to the technical field of lithium batteries. The composite anode material of the core-shell structure comprises a core layer, a functional layer wrapping the core layer and an outer shell layer wrapping the functional layer, wherein the core layer comprises a high-nickel ternary material with nickel content exceeding 50%, the functional layer comprises a conductive network structure formed by carbon nanotubes and salts containing lithium ions and ferrous ions embedded in the conductive network structure, the outer shell layer comprises a carbon material, and potential difference between the core layer and the functional layer drives lithium ions to migrate to the core layer. The composite positive electrode material with the core-shell structure is beneficial to lithium ion transmission, can drive lithium ions to migrate to the inner core layer better, supplements lithium ions for the high-nickel ternary material in time, and improves the thermal stability and the first coulombic efficiency of the positive electrode of the lithium battery.

Inventors

  • RAN LINGBING

Assignees

  • 梅赛德斯-奔驰集团股份公司

Dates

Publication Date
20260505
Application Date
20260128

Claims (10)

  1. 1. A composite anode material with a core-shell structure is characterized by comprising an inner core layer (10), a functional layer (20) wrapping the inner core layer (10) and an outer shell layer (30) wrapping the functional layer (20), wherein, The inner core layer (10) comprises a high nickel ternary material with nickel content exceeding 50%; The functional layer (20) comprises a conductive network structure (21) formed by carbon nanotubes and salts (22) containing lithium ions and ferrous ions, wherein the salts are embedded in the conductive network structure (21); -the outer shell layer (30) comprises a carbon material; The potential difference between the inner core layer (10) and the functional layer (20) drives lithium ions to migrate towards the inner core layer (10).
  2. 2. The composite positive electrode material of core-shell structure according to claim 1, wherein, The diameter of the inner core layer (10) is 700 nm-2000 nm; And/or the number of the groups of groups, The thickness of the functional layer (20) is 50 nm-120 nm; And/or the number of the groups of groups, The thickness of the shell layer (30) is 10 nm-50 nm; And/or the number of the groups of groups, The density of the carbon nanotubes is not less than 15 tubes/mu m2.
  3. 3. The composite positive electrode material of core-shell structure according to claim 1, wherein, The lithium ion and ferrous ion containing salt (22) is LiFeP ; And/or the number of the groups of groups, A potential difference between the core layer (10) and the functional layer (20) is not less than 250mV; Preferably, the potential of the inner core layer (10) is 3.20V, and the potential of the functional layer (20) is 3.45V.
  4. 4. The composite positive electrode material with the core-shell structure according to claim 1, which is applied to a lithium battery, Under the condition that the SOC of the lithium battery is less than 30%, the potential difference between the inner core layer (10) and the functional layer (20) drives lithium ions to migrate to the inner core layer (10).
  5. 5. The preparation method of the positive electrode composite material with the core-shell structure is characterized by comprising the following steps of: step 1, blending a primary sintered inner core layer material, a ferrite precursor, lithium salt, a carbon source, a lithium supplementing agent and a carbon nano tube, and spraying and granulating, wherein the primary sintered inner core layer material comprises a high-nickel ternary material with nickel content exceeding 50%; And 2, sintering the spray granulation product twice in different temperature ranges to obtain the core-shell structured anode composite material.
  6. 6. The method of manufacturing according to claim 5, further comprising: Will N C M (OH With LiOH ] O is mixed, and the mixture is sintered for 10 to 15 hours in the oxygen atmosphere with the temperature of 600 to 750 ℃ to obtain the primary sintered inner core layer material.
  7. 7. The method of claim 5, wherein step 1 comprises: step 11, according to the mass ratio of (55-65): (20-30): (3:9): (3:10): (1:6): 1, acidizing the carbon nano tube, ferrous salt and L C Mixing sucrose and a lithium supplementing agent, and ball milling for 2-6 hours to form mixed slurry, wherein the content of-COOH in the acidified carbon nano tube is preferably 9-15%; Step 12, adding a certain amount of primary sintered inner core layer material into the mixed slurry, and stirring at a low speed for 20-50 min to obtain the mixed slurry with the inner core layer material; step 13, atomizing and granulating the mixed slurry with the inner core layer material at the air inlet temperature of 180-230 ℃ and the atomization pressure of 0.1-0.5 MPa; And/or the number of the groups of groups, The average particle diameter of the atomized and granulated product is 15-20 mu m.
  8. 8. The method according to any one of claims 5 to 7, wherein step 2 comprises: Step 21, sintering the spray granulation product for 4.5 to 5.5 hours at 600 to 650 ℃ under Ar/H 2 mixed atmosphere with the volume ratio of (15 to 20): 1, and synthesizing salts containing lithium ions and ferrous ions in situ; and 22, carrying out secondary sintering on the product after primary sintering for 2.5-3.5 hours in Ar atmosphere at the temperature of 700-750 ℃ to construct the carbon material of the conductive network structure and the outer layer.
  9. 9. The method according to claim 6, wherein, The residual lithium content of the primary sintered inner core layer material is less than 0.5%; And/or the number of the groups of groups, The lattice parameter c/a of the primary sintered core layer material is >4.93.
  10. 10. A lithium battery is characterized by comprising a positive electrode, an electrolyte and a negative electrode, wherein, The positive electrode comprises the composite positive electrode material of the core-shell structure according to any one of claims 1 to 4.

Description

Composite positive electrode material with core-shell structure, preparation method thereof and lithium battery Technical Field The invention relates to the technical field of lithium batteries, in particular to a composite anode material with a core-shell structure, a preparation method thereof and a lithium battery. Background For lithium batteries, it is common to use a high nickel ternary material such as NCM811 (LiNi 0.8Co0.1Mn0.1) directly as the positive electrode material. However, due to the problems of low thermal stability and low initial coulombic efficiency of the high-nickel ternary material, a physical mixed material of lithium iron phosphate (LFP) and the high-nickel ternary material is generally used as a positive electrode material of the lithium battery, so as to overcome the problems of the high-nickel ternary material. However, on one hand, the interface contact between the lithium iron phosphate (LFP) and the high-nickel ternary material is poor, which is unfavorable for ion/electron transmission and lithium ion migration, and on the other hand, the high-nickel ternary material still directly contacts the electrolyte, which causes lithium ion consumption. Therefore, the positive electrode material of the existing lithium battery still has a great room for improvement. Disclosure of Invention In view of the above, the embodiment of the invention provides a composite positive electrode material with a core-shell structure, a preparation method thereof and a lithium battery, wherein the composite positive electrode material with the core-shell structure is beneficial to lithium ion transmission, and can better drive lithium ions to migrate to an inner core layer, so that lithium ions can be timely supplemented for a high-nickel ternary material, and the thermal stability and the first coulombic efficiency of the positive electrode of the lithium battery can be improved. In order to achieve the above object, according to a first aspect, there is provided a composite cathode material of a core-shell structure, including an inner core layer, a functional layer wrapping the inner core layer, and an outer shell layer wrapping the functional layer, wherein, The inner core layer comprises a high-nickel ternary material with nickel content exceeding 50%; The functional layer comprises a conductive network structure formed by carbon nanotubes and salts containing lithium ions and ferrous ions, wherein the salts are embedded in the conductive network structure; The outer shell layer comprises a carbon material; And the potential difference between the inner core layer and the functional layer drives lithium ions to migrate to the inner core layer. Optionally, the diameter of the inner core layer is 700-2000 nm. Optionally, the thickness of the functional layer is 50 nm-120 nm. Optionally, the thickness of the outer shell layer is 10 nm-50 nm. Alternatively, the density of the carbon nanotubes is not less than 15 tubes/μm2. Alternatively, the salt containing lithium ions and ferrous ions is LiFeP。 Optionally, the potential difference between the core layer and the functional layer is not less than 250mV. Alternatively, the potential of the core layer is 3.20V and the potential of the functional layer is 3.45V. Optionally, the composite cathode material with the core-shell structure is applied to a lithium battery, and under the condition that the SOC of the lithium battery is less than 30%, the potential difference between the inner core layer and the functional layer drives lithium ions to migrate to the inner core layer. In a second aspect, an embodiment of the present invention provides a method for preparing a cathode composite material with a core-shell structure, including: step 1, blending a primary sintered inner core layer material, a ferrite precursor, lithium salt, a carbon source, a lithium supplementing agent and a carbon nano tube, and spraying and granulating, wherein the primary sintered inner core layer material comprises a high-nickel ternary material with nickel content exceeding 50%; And 2, sintering the spray granulation product twice in different temperature ranges to obtain the core-shell structured anode composite material. Alternatively, NCM(OHWith LiOH ]O is mixed, and the mixture is sintered for 10 to 15 hours in the oxygen atmosphere with the temperature of 600 to 750 ℃ to obtain the primary sintered inner core layer material. Optionally, step1 includes: step 11, according to the mass ratio of (55-65): (20-30): (3:9): (3:10): (1:6): 1, acidizing the carbon nano tube, ferrous salt and L CMixing sucrose and a lithium supplementing agent, and ball milling for 2-6 hours to form mixed slurry, wherein the content of-COOH in the acidified carbon nano tube is preferably 9-15%; Step 12, adding a certain amount of primary sintered inner core layer material into the mixed slurry, and stirring at a low speed for 20-50 min to obtain the mixed slurry with the inner core layer material;