The invention relates to preparation methods of a
lithium ion battery composite positive
electrode, a flexible
lithium battery and a
solid-state
lithium battery. A composite positive
electrode material of which a surface is coated with an inorganic rapid lithium
ion conductor is obtained by uniformly mixing a precursor liquid of the rapid lithium
ion conductor and a
lithium ion battery positive
electrode material under a certain temperature, and an inorganic rapid lithium ion conductor coated composite positive
electrode material is obtained after thermal
processing is performed on the composite positive electrode, wherein the inorganic rapid lithium ion conductor is a high-electrical
conductivity garnet-shaped
solid-state
electrolyte Li<5+x>N<x>La<3-x>M<2>O<12> (X is more than or equal to 0 but less than or equal to 2, M is Nb, Ta, Sb or Bi, and N is Ca, Ba, Sr or Ge) and a modified compound thereof Li<7+x>(La<2-x>M<x>)B<2>O<12> (X is more than or equal to 0 but less than or equal to 2, M is Ca, Ba, Sr or Ge, and B is Zr, Hf or Sn), or Li<7-x>La<3>Zr<2-x>Ta<x>O<12> (X is more than or equal to 0 but less than or equal to 2); and / or the inorganic rapid lithium ion conductor is LiM<2>O<4> with a
spinel structure, and M is Ni and / or Mn; and / or the inorganic rapid lithium ion conductor is LiMO<2> with a
layered structure, and M is at least one of Ni, Co, Mn and Al; and / or the inorganic rapid lithium ion conductor is a lithium-rich
manganese-based positive
electrode material (x)Li<2>MnO<3>.(1-x)LiMO<2>, x is more than 0.1 but less than 0.9, and M is one of Ni, Co and Mn. By the composite positive
electrode material, the cycle performance, the high-temperature performance and the rate performance of the
lithium ion battery positive electrode material can be improved.