In 1996, the University of Texas discovered that phosphate can be used as a cathode material for rechargeable lithium batteries. Lithium phosphate has good electrochemical properties and low resistance. This is achieved through nano-scale phosphate cathode materials. The main advantages are high rated current and long cycle life; good thermal stability, enhanced safety and tolerance to abuse.

 

If kept at a high voltage for a long time, lithium phosphate is more resistant to all charging conditions and has less stress than other lithium-ion systems. The disadvantage is that the lower nominal voltage of the 3.2V battery makes the specific energy lower than the cobalt-doped lithium-ion battery. For most batteries, low temperatures will reduce performance, and elevated storage temperatures will shorten their service life, and lithium phosphate is no exception. Lithium phosphate has a higher self-discharge than other lithium-ion batteries, which may cause aging and thus balance problems, but these can be compensated by selecting high-quality batteries or using advanced battery management systems. The figure below summarizes the properties of lithium phosphate.

 11-11 LiFePO4 Battery 性能

Lithium phosphate is commonly used instead of lead-acid starter batteries. Four batteries in series produce 12.80V, which is similar to the voltage of six 2V lead-acid batteries in series. By reducing the number of batteries to reduce the overall weight of the car, the car can start more quickly and powerfully, which is for those who pursue car start performance.

 

By connecting four lithium phosphate batteries in series, the voltage of each battery is 3.60V, which is the correct full charge voltage. At this time, the charging should be disconnected, but continue charging while driving. Lithium phosphate tolerates some overcharging; however, since most vehicles keep the voltage at 14.40V for long periods of time during long-distance travel, it may increase the mechanical stress of the lithium phosphate battery. Time will tell us how long lithium phosphate can withstand overcharge as an alternative to lead-acid batteries. Low temperature will also reduce the performance of Li-ion, which may affect the starting ability under extreme conditions. However, compared with the low temperature of lead-acid batteries that cannot be started, the LiFePO4 Battery's instantaneous discharge current reaches 6C and it can still start normally.

 

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