Lithium ion battery preparation method and lithium ion battery

The invention discloses a lithium ion battery and a preparation method of the lithium ion battery. A positive electrode active material is made of lithium cobaltate or lithium cobaltate doped with a part of nickel manganese lithium manganate ternary materials, a negative electrode active material is made of natural modified graphite wrapped by carbon, electrolyte adopts mixed solvent of diethyl carbonate (DEC), ethyl cellulose (EC) and poly carbonate (PC), vinylene carbonate and propylene sulfite annexing agents are added, solid electrolyte interphase (SEI) film is formed preferentially, joint insertion of the organic solvent is restrained, and high temperature performance is excellent. A battery system obviously improves high temperature storage property of the battery on the premise of meeting safety performance, high and low temperature discharge performance and circulation performance of a conventional lithium ion battery. The preparation method is simple, manufacture procedures are easy to control, and t