Composite positive-electrode material and preparation method thereof, positive-electrode plate, secondary battery, and battery module, battery pack, and apparatus containing such secondary battery

1. A composite positive-electrode material, comprising a core and a coating layer covering at least part of a surface of the core, wherein:

the core comprises a positive-electrode pre-lithiation material, the positive-electrode pre-lithiation material comprises a lithium-rich metal oxide, and the coating layer comprises a positive-electrode active material;

a charging cut-off voltage of the positive-electrode active material is 3.5V-4.2V (vs. Li/Li + ), and the lithium-rich metal oxide is selected from one or more of Li 5 FeO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , and Li 2 MnO 2 , wherein 0<x1 <1, 0≤y1<0.1, M is selected from one or more of Zn, Sn, Mg, Fe, and Mn; and

the positive-electrode active material is selected from one or more of LiFePO 4 , Li 3 V 2 (PO 4 ) 3 and LiFe y Mn 1-y PO 4 , wherein 0<y<1.

2. The composite positive-electrode material according to claim 1 , wherein, in the composite positive-electrode material, the positive-electrode active material is distributed on the surface of the core in a form of independent particles; and

a mass ratio of the positive-electrode pre-lithiation material to the positive-electrode active material is 1:2-1:35.

3. The composite positive-electrode material according to claim 1 , wherein a median particle size D v 50 of the positive-electrode pre-lithiation material is 2 μm-35 μm.

4. The composite positive-electrode material according to claim 1 , wherein a median particle size D v 50 of the positive-electrode active material is 0.1 μm-15 μm.

5. The composite positive-electrode material according to claim 1 , wherein

a valence state of each metal element other than Li in the lithium-rich metal oxide is lower than its own highest oxidation valence state.

6. The composite positive-electrode material according to claim 1 , wherein the median particle size D v 50 of the positive-electrode active material is 1 μm-15 μm. .

7. The composite positive-electrode material according to claim 1 , wherein the median particle size D v 50 of the positive-electrode active material is 0.1 μm-3.5 μm.

8. A positive-electrode plate, comprising a positive-electrode current collector and a positive-electrode film layer disposed on the positive-electrode current collector, wherein the positive-electrode film layer comprises the composite positive-electrode material according to claim 1 .

9. The positive-electrode plate according to claim 8 , wherein the positive-electrode film layer further comprises a conductive agent and a binder; and based on a total weight of the positive-electrode film layer, the positive-electrode film layer comprises 70 wt %-97 wt % of the composite positive-electrode material, 2 wt %-20 wt % of a conductive agent, and 1 wt %-25 wt % of a binder.

10. A secondary battery, comprising the positive-electrode plate according to claim 8 .

11. A preparation method of a composite positive-electrode material, comprising the following steps:

providing a core, wherein the core comprises a positive-electrode pre-lithiation material, the positive-electrode pre-lithiation material comprises a lithium-rich metal oxide, and the lithium-rich metal oxide is selected from one or more of Li 5 FeO 4 , Li 2 CuO 2 , Li 2 Cu x1 Ni 1-x1-y1 M y1 O 2 , and Li 2 MnO 2 , wherein 0<x1 <1, 0≤y1<0.1, M is selected from one or more of Zn, Sn, Mg, Fe, and Mn;

providing a coating material, wherein the coating material comprises a positive-electrode active material, a charging cut-off voltage of the positive-electrode active material is 3.5 V-4.2 V (vs. Li/Li + ), and the positive-electrode active material is selected from one or more of LiFePO 4 , Li 3 V 2 (PO 4 ) 3 and LiFe y Mn 1-y PO 4 , wherein 0<y<1; and

coating at least part of a surface of the core by using the coating material to obtain a composite positive-electrode material.