High-cycle high-specific energy lithium ion power battery and preparation method thereof

The invention discloses a high-cycle high-specific energy lithium ion power battery and a preparation method thereof. The preparation method comprises the following steps: (1) coating the front surface and the back surface of a positive pole current collector with positive pole slurry, then drying, rolling, dividing strips, and producing a piece to obtain a positive pole piece; (2) coating the front surface and the back surface of a negative pole current collector with negative pole slurry, then drying, rolling, dividing strips, and producing a piece to obtain a negative pole piece; (3) preparing the positive pole piece, a diaphragm and the negative pole piece into a pole group, then filling a steel shell with the pole group, and point welding a bottom and rolling a groove; (4) injecting an electrolyte into the steel shell, point welding a cover, pressing the cover, and sealing to obtain a battery cell; (5) pre-forming the battery cell by adopting gradient current to obtain the high-cycle high-specific energy lithium ion power battery. The high-cycle high-specific energy lithium ion power battery prepared by the method has excellent specific energy, cycle life and high low-temperature initial capacity; moreover, the preparation method is simple in process and easy to operate so as to facilitate industrialization.