Positive electrode sheet and secondary battery including the same, battery module, battery pack, and electrical apparatus

A secondary battery, comprising:

• a positive electrode comprising a positive electrode sheet, the positive electrode sheet comprising:
• a current collector comprising a coating region and a non-coating region other than the coating region;
• a resistance layer disposed on the current collector and comprising a conductive agent, a first binder, and a first positive electrode active material;
• and
• a positive electrode active material layer comprising a second positive electrode active material, a conductive agent, and a second binder;
• wherein:
• a resistance of the resistance layer is greater than a resistance of the positive electrode active material layer;
• in a cross section of the positive electrode sheet, a projection of at least a part of the positive electrode active material layer on the current collector and a projection of the resistance layer on the current collector do not overlap, and
• a polarization parameter P of the positive electrode sheet is in a range of 0.4-65.0, and the polarization parameter P=((1−S)/S)·(R1/R2), wherein S is an area ratio of the resistance layer relative to the coating region of the current collector, R1 is a film resistance value of the positive electrode sheet in a part where the resistance layer is provided, and R2 is a film resistance value of the positive electrode sheet in a part of the coating region where the resistance layer is not provided.

A battery module, comprising:

• a secondary battery comprising a positive electrode, the positive electrode comprising a positive electrode sheet, and the positive electrode sheet comprising:
• a current collector comprising a coating region and a non-coating region other than the coating region;
• a resistance layer disposed on the current collector and comprising a conductive agent, a first binder, and a first positive electrode active material;
• and
• a positive electrode active material layer comprising a second positive electrode active material, a conductive agent, and a second binder;
• wherein:
• a resistance of the resistance layer is greater than a resistance of the positive electrode active material layer;
• in a cross section of the positive electrode sheet, a projection of at least a part of the positive electrode active material layer on the current collector and a projection of the resistance layer on the current collector do not overlap, and
• a polarization parameter P of the positive electrode sheet is in a range of 0.4-65.0, and the polarization parameter P=((1−S)/S)·(R1/R2), wherein S is an area ratio of the resistance layer relative to the coating region of the current collector, R1 is a film resistance value of the positive electrode sheet in a part where the resistance layer is provided, and R2 is a film resistance value of the positive electrode sheet in a part of the coating region where the resistance layer is not provided.