In a method of measuring a closed-pore change rate, the method includes: measuring, by small-angle X-ray scattering (SAXS) and Brunauer, Emmett, and Teller (BET), a specific surface area in a first powder state and a specific surface area in a second powder state with respect to pores created in a powder state; measuring, by SAXS and BET, a specific surface area in a first electrode plate state and a specific surface area in a second electrode plate state with respect to pores created in an electrode plate state; and calculating a closed-pore change rate of an electrode plate based on the specific surface areas in the first and second powder states and the specific surface areas in the first and second electrode plate states.

In a method of measuring a closed-pore change rate, the method includes: measuring, by small-angle X-ray scattering (SAXS) and Brunauer, Emmett, and Teller (BET), a specific surface area in a first powder state and a specific surface area in a second powder state with respect to pores created in a powder state; measuring, by SAXS and BET, a specific surface area in a first electrode plate state and a specific surface area in a second electrode plate state with respect to pores created in an electrode plate state; and calculating a closed-pore change rate of an electrode plate based on the specific surface areas in the first and second powder states and the specific surface areas in the first and second electrode plate states.