BYD磷酸铁锂电池性能测试

1、1Outline1. What is LiFePO4?2. Discharge curve3. GSM discharge4. High temperature Storage5. Low temperature discharge6. Cycle life7. Overcharge8. Fire exposure2What is LiFePO4? LiFePO4 is a new kind of positive material. LiFePO4 also has the function that release or receive Li-ion like LiCoO2.LiFePO4

2、Olivine structureFePO4Olivine structureLiFePO4ChargeDischarge3Discharge curve 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.4GSM discharge Following shows GSM discharge curve (cut off vol

3、tage is 2.8V).GSM1/0.2CGSM2/0.2C1#90.3%86.0%2#88.9%84.7%5High temperature Storage Following 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 befor

4、e 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%LiCoO2LiFePO46Low temperature discharge Fol

5、lowing shows discharge of different temperature.Temp.60/2545/250/25-10/25-20/25ratio(%)93.498.272.664.245.47Cycle life LiFePO4 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 struct

6、ureFePO4Olivine structureLiFePO4ChargeDischarge8Overcharge 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#120.64Pass9Overcharge Following sh

7、ow 1C/12V overcharge curve and cell photos.Before testAfter test10Overcharge 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.Pass11Overcharge Following show 3C/32V

8、 overcharge curve and cell photos.After test12Fire exposure 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

9、, fire, no explosion.Pass251#3.5856.0 PassBefore testAfter test1314Discharge curve 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.15High temperature Storage Following show storage results

10、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%LiCoO2LiFePO416Overcharge LiFePO4 has good safet