As used in the present disclosure, the term “intrinsic specific surface area” refers to the BET specific surface area measured after the tested material undergoes an extreme water washing. In particular, the particles of the tested material are added to deionized water at a solid-liquid weight ratio of 1:40 at room temperature, and washed for 30 minutes at a stirring rate of 500 rpm/min. The particles of the tested material after water washing are subjected to BET specific surface area testing, to obtain their BET specific surface area, regarded as the “specific surface area after water washing”. The above water washing and BET specific surface area testing are repeated until adjacent two “specific surface areas after water washing” basically do not change (for example, the difference between the two is not more than 5%, preferably not more than 2%, more preferably not more than 1%, more preferably not more than 0.5%, most preferably not more than 0.1%). Then, the last measured “specific surface area after water washing” is the “intrinsic specific surface area” of the positive electrode material.

Correspondingly, as used in the present disclosure, the term “intrinsic pore size” refers to the values of the pore size of each pore in the particles measured after the positive electrode material undergoes an extreme water washing. R10, R50 and R90 corresponding to the values of the pore size are used to characterize the “intrinsic pore size” of the positive electrode material. The values of the pore size are listed from small to large. Then, the pore sizes located at the 10%, 50% and 90% positions corresponding to all values are R10, R50 and R90, respectively.