Composite positive electrode active material, battery cell, battery and electric device

The embodiment of the invention provides a composite positive electrode active material, a battery monomer, a battery and a power utilization device, the composite positive electrode active material comprises a first manganese-iron-lithium phosphate material and a second manganese-iron-lithium phosphate material, the first manganese-iron-lithium phosphate material has a nanometer sheet structure, and the second manganese-iron-lithium phosphate material has a nanometer sheet structure. The ratio of the (010) crystal face area of the first lithium manganese iron phosphate material to the total crystal face area of the first lithium manganese iron phosphate material is A1%; the second lithium manganese iron phosphate type material has a spherical and/or sphere-like structure, and the (010) crystal face area of the second lithium manganese iron phosphate type material accounts for A2% of the total crystal face area of the second lithium manganese iron phosphate type material; the composite positive electrode active material meets the condition that A1 is greater than A2.