Abstract: Li-ion power battery with 20 Ah nominal capacity is designed and fabricated with high levels ofLithium and Manganese cathode and graphite anode. This paper focuses on the design, performance test of thebattery. Cycled with 0.3 C in 2.5-4.2 V, the first discharge capacity of the prepared single cell is 19 568.8 mAh; cycled with 1 C, specific energy is 137 Wh/kg, and discharge capacity retains about 101.8 % after 500 cycles.The results of over charge, extrusion, needle-punching and external short circuit test show that the battery hasfine safety performance.