Positive Electrode Active Material, Positive Electrode Plate, Electrode Assembly, Battery Cell, Battery and Electrical Apparatus

A positive electrode active material, comprising:

• a low-to-medium nickel ternary material;
• and
• a high-lattice-volume-change positive electrode material;
• wherein:
• the low-to-medium nickel ternary material has a mass ratio W1≥45% in the positive electrode active material, and the low-to-medium nickel ternary material is LiNixCoyM11−x−yO2, wherein 0.5≤x≤0.69, y>0, 1−x−y>0, and M1 is selected from one or more of Al, Mn, Mg, Nb, Ti, and Ba;
• and
• the high-lattice-volume-change positive electrode material satisfies a thickness change rate of a positive electrode active substance layer being ≥2.6%, wherein the thickness change rate is (H1−H2)/H1, wherein H1 is a fully discharged thickness of the positive electrode active substance layer, and H2 is a fully charged thickness of the positive electrode active substance layer.