Disclosed herein is a lithium ion battery comprising an electrode core, an electrolyte solution, a metal shell and an end cover assembly, said metal shell comprising an outer wall, an inner wall and a chamber, said electrode core and electrolyte solution being located in the chamber of the metal shell, and said electrode core being connected to the end cover assembly with a electrode terminal of the electrode core, wherein the number of said electrode core is more than one, and the multiple electrode cores are located in the chamber of the metal shell. The lithium ion battery according to the present invention possesses excellent disperse heat dispersion, high mechanical safety, and good high rate discharge performance. In addition, the battery according to the present invention solves the problems of the “wound battery” of the prior art that the electrode plate is long and difficult to wind, and the “stacked battery” of the prior art that the electrode plate is difficult to prepare and pile up by dividing the electrode core of high capacity into multiple electrode core of low capacity placed abreast in the metal shell, whereby simplifying the preparation thereof.