High-safety high-energy long-cycle lithium iron phosphate type 18650 lithium battery and preparation method thereof

The invention provides a high-safety high-energy long-cycle lithium iron phosphate type 18650 lithium battery and a preparation method thereof. The cathode active material of the battery is carbon doped coated lithium iron phosphate with a small particle size and uniform particle size distribution, with the specific capacity being not less than 155 mAh/g and the compaction density being 2.0 - 2.8g/cm ; the anode active material is graphite with the specific capacity being 350 - 375 mAh/g and the compaction density being not less than 1. 7 g/cm ; a membrane is a PE base membrane coated with a nanometer Al2O3 ceramic membrane. The method comprises the steps of homogenizing, coating, rolling, cutting, winding, shelling, liquid injection, cleaning, oiling, forming and mixing. The batteryenergy density of the invention is as high as 390Wh/L, the discharge capacity of the monomer cell 0.2 C is not less than 2000 mAh, the cycle performance is excellent, the capacity retention rate of the cell 0.5 C/0. 5C100% DOD aft