Abstract: A positive electrode composite material includes a first type of material and at least one of a second type of material or a third type of material. The first type of material is a lithium iron phosphate material. The second type of material is ABb, where A is at least one selected from Fe, Mn, Co, Ni, Ti, V, Nb, Ta, Zr, Hf, Cr, Mo, W, Re, Pt, Sn, Pb, and Sb, B is any one selected from S and Se, and a value of b is in a range of 1-4. The third type of material is a two-dimensional metal carbide, nitride, or carbonitride MXene material of formula Mn+1Xn or Mn+1XnTx, where M is a transition metal element, X is C element and/or N element, Tx represents a surface functional group including -O, —OH, -Cl, or -F. The third type of material has a layered structure, and n represents a number of layers and n = 1, 2, or 3.