In the positive electrode material in this application, the lithium-nickel transition metal oxide A has a single-particle pressure-resistant strength of ≥100 MPa and the lithium-nickel transition metal oxide B has a single-particle pressure-resistant strength of ≥50 MPa. In this application, the lithium-nickel transition metal oxides with such two single-particle pressure-resistant strengths are mixed to obtain the positive electrode material, so as to improve the pressure-resistant performance of the entire positive electrode material. The monocrystalline/monocrystalline-like particles with a small particle size are mainly used to fill the gap between the secondary-particle powder with a large particle size, and withstand relatively small force; however, may be still crushed under the action of swelling of electrode plates or external force when the pressure-resistant strength is excessively low. The secondary particles with a larger particle size withstand most of the external force during the swelling or pressing of the electrode plates. Because there are a large quantity of crystalline boundaries inside the secondary particles, microcracks easily occur under the external force or during cycling. In this application, the mixed positive electrode material of the lithium-nickel transition metal oxide B with the single-particle pressure-resistant strength of ≥50 MPa and the lithium-nickel transition metal oxide A with the single-particle pressure-resistant strength of ≥100 MPa is selected to ensure that the pressure-resistant performance of the positive electrode material obtained through mixing can adapt to the external force during electrode plate preparation and cycling. In some embodiments, the single-particle pressure-resistant strength of the lithium-nickel transition metal oxide A is higher than the single-particle pressure-resistant strength of the lithium-nickel transition metal oxide B.