Abstract: The present invention discloses a positive pole piece, an electrochemical device including the positive pole piece, and an electronic device, and falls within the technical field of batteries. The positive pole piece includes a positive current collector and a positive active material layer provided on at least one surface of the positive current collector. The positive active material layer includes a ternary positive active material. The positive pole piece satisfies the following relationship: 1.2?D/(R/5+P/2)?3.5. D is a particle size change rate of Dv50 before and after the positive active material is held for 30 seconds at a pressure of 35 KN, and Dv50 is a particle size corresponding to 50% of a volume cumulative distribution percentage of the positive active material. R is a roughness of the positive pole piece, and P is a porosity of the positive pole piece.