Lithium ion battery and preparation method thereof

The invention discloses a lithium ion battery and a preparation method thereof. The lithium ion battery comprises an upper metal shell and a lower metal shell, the lower metal shell comprises a bottom wall and a side wall, an accommodating space is defined by the bottom wall and the side wall, and the bottom wall and the upper metal shell are oppositely arranged; the lithium ion battery further comprises a battery core body and a pole, the battery core body is accommodated in the accommodating space, and the battery core body comprises a first pole lug leading-out end and a second pole lug leading-out end; the pole is arranged on the side wall in an insulating manner, and the first pole lug leading-out end is connected with the pole; and the lead-out end of the second pole lug is connected with the side wall or the bottom wall. According to the lithium ion battery provided by the invention, the battery capacity of the lithium ion battery can be improved, so that the overall energy density and the endurance ti