BYD磷酸铁锂电池性能测试

1LiFePO4 performance2006-06-212What is LiFePO4?Discharge curveGSM dischargeHigh temperature StorageLow temperature dischargeCycle lifeOverchargeFire exposure3 LiFePO4 is a new kind of positive material.LiFePO4 also has the function that release or receive Li-ion like LiCoO2.LiFePO4Olivine structureFePO4Olivine structureLiFePO4ChargeDischarge4 LiFePO4 has the same discharge curve as LiCoO2.LiFePO4 has the lower MPV(Mid-point voltage)than LiCoO2.MPV of LiFePO4 is 3.13.2V,MPV of LiCoO2 is 3.63.7V.5 Following shows GSM discharge curve(cut off voltage is 2.8V).GSM1/0.2CGSM2/0.2C1#90.3%86.0%2#88.9%84.7%6Following show storage results of LiFePO4 and LiCoO2 system.Storage conditionCapacity keeping ratio(capacity after storage/capacity before storage)Capacity recovering ratio(capacity after recharge/capacity before storage)60,7days85.2%92.8%85,48hours75.1%80.2%Storage conditionCapacity keeping ratio(capacity after storage/capacity before storage)Capacity recovering ratio(capacity after recharge/capacity before storage)60,7days83.1%89.2%85,48hours72.5%79.3%LiCoO2LiFePO47 Following shows discharge of different temperature.Temp.60/2545/250/25-10/25-20/25ratio(%)93.498.272.664.245.48LiFePO4 structure keeps stable before and after discharge,so it has good cycle life.Basing on experience of other projects,LiFePO4 cycle life can be more than 1000.Olivine structureFePO4Olivine structureLiFePO4ChargeDischarge9 LiFePO4 has good safety performance.Following show 1C/12V overcharge result.ConditionCell No.Max temp.PhenomenaResult1C/12V260#117.10Swelling,vent open lightly,no fire,no explosion.Pass253#120.05Pass271#120.64Pass10 Following show 1C/12V overcharge curve and cell photos.Before testAfter test11 LiFePO4 has good safety performance.Following show 3C/32V overcharge result.ConditionCell No.Max temp.PhenomenaResult3C/12V273#145.44Swelling,vent open lightly,no fire,no explosion.Pass12 Following show 3C/32V overcharge curve and cell photos.After test13 LiFePO4 has good safety performance.Following show the fire exposure result.Cell No.Voltage before test(V)Impedance before test(m)PhenomenaResult258#3.4758.7 Swelling,vent open,no fire,no explosion.Pass268#3.4352.8 Swelling,vent open,fire,no explosion.Pass251#3.5856.0 PassBefore testAfter test14