A positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector. The positive electrode active material layer includes an inner active material layer and an outer active material layer successively stacked. The inner active material layer has a three-level pore size distribution: an inner primary pore size distribution from 3 nm to 10 nm, an inner secondary pore size distribution from 10 nm to 100 nm, and an inner tertiary pore size distribution from 0.1 μm to 2 μm. The outer active material layer has a three-level pore size distribution: an outer primary pore size distribution from 0.5 nm to 3 nm, an outer secondary pore size distribution from 10 nm to 100 nm, and an outer tertiary pore size distribution from 0.1 μm to 2 μm.