The nominal voltage of the LiFePO4 battery is 3.2V, the termination charging voltage is 3.6V, and the termination discharge voltage is 2.0V. Due to the quality and process of the positive and negative materials and electrolyte materials used by various manufacturers, there will be some differences in their performance. For example, the same model (standard battery of the same package) has a large difference in battery capacity (10% to 20%).
It should be noted here that lithium iron phosphate power batteries produced by different factories have some differences in various performance parameters; in addition, some battery performances are not included, such as battery internal resistance, self-discharge rate, charge and discharge temperature, and the like.
Lithium iron phosphate power batteries have large differences in capacity and can be divided into three categories: small fractions to a few milliamperes, medium tens of milliampere-hours, and large hundreds of milliampere-hours. There are some differences in the same parameters for different types of batteries.
Overdischarge to zero voltage test:
The STL18650 (1100mAh) lithium iron phosphate power battery was used for over-discharge to zero voltage test. Test conditions: A 1100 mAh STL 18650 battery was charged at a charging rate of 0.5 C, and then discharged at a discharge rate of 1.0 C until the battery voltage was 0 C. The batteries placed in 0V are divided into two groups: one group is stored for 7 days, and the other group is stored for 30 days; after the storage expires, it is filled with a charging rate of 0.5 C, and then discharged with 1.0 C. Finally, compare the differences between the two zero voltage storage periods.
The result of the test is that the battery has no leakage after 7 days of zero voltage storage, and the performance is good, the capacity is 100%; after 30 days of storage, there is no leakage, the performance is good, the capacity is 98%; after 30 days of storage, the battery is further charged and discharged for 3 times. The capacity is restored to 100%.
This test shows that even if the lithium iron phosphate battery is over-discharged (even to 0V) and stored for a certain period of time, the battery will not leak or be damaged. This is a characteristic that other types of lithium-ion batteries do not have.
Advantages of lithium iron phosphate battery
1. Improvement of safety performance
The P-O bond in the lithium iron phosphate crystal is stable and difficult to decompose, and does not collapse or heat like a lithium cobaltate or form a strong oxidizing substance even at a high temperature or overcharge, and thus has good safety. It has been reported that in the actual operation, a small part of the sample was found to have a burning phenomenon in the acupuncture or short-circuit test, but there was no explosion event. In the overcharge experiment, a high-voltage charge that was several times higher than the self-discharge voltage was used, and it was found that there was still Explosion phenomenon. Nevertheless, its overcharge safety has been greatly improved compared to the ordinary liquid electrolyte lithium cobalt oxide battery.
2, the improvement of life
The lithium iron phosphate battery refers to a lithium ion battery using lithium iron phosphate as a positive electrode material.
The long-life lead-acid battery has a cycle life of about 300 times, and the highest is 500 times. The lithium iron phosphate power battery has a cycle life of more than 2000 times, and the standard charge (5 hour rate) can be used up to 2000 times. The same quality lead-acid battery is "new half year, old half year, maintenance and maintenance for half a year", up to 1~1.5 years, while lithium iron phosphate battery is used under the same conditions, the theoretical life will reach 7~8 years. Considering comprehensively, the performance price ratio is theoretically more than four times that of lead-acid batteries. High-current discharge can be quickly charged and discharged with high current 2C. Under the special charger, the battery can be fully charged within 1.5 minutes of 1.5C charging, and the starting current can reach 2C, but the lead-acid battery has no such performance.
3, high temperature performance
The peak temperature of lithium iron phosphate can reach 350 ° C -500 ° C while lithium manganate and lithium cobaltate are only around 200 ° C. Wide operating temperature range (-20C--75C), high temperature resistance, lithium iron phosphate electric heating peak up to 350 ° C -500 ° C and lithium manganate and lithium cobalt oxide only around 200 ° C.
4, large capacity
The battery is often operated under full load and the capacity will quickly fall below the rated capacity. This phenomenon is called the memory effect. There are memories like nickel-metal hydride and nickel-cadmium batteries, but lithium iron phosphate batteries do not have this phenomenon. No matter what state the battery is in, it can be used with charging, no need to discharge and recharge.
6, light weight
The volume of the lithium iron phosphate battery of the same specification capacity is 2/3 of the volume of the lead-acid battery, and the weight is 1/3 of the lead-acid battery.
7, environmental protection
Lithium iron phosphate battery is generally considered to be free of any heavy metals and rare metals (Ni-MH batteries require rare metals), non-toxic (SGS certification passed), no pollution, in line with European RoHS regulations, is an absolute green battery certificate. Therefore, the reason why lithium batteries are favored by the industry is mainly environmental considerations. Therefore, the battery has been included in the “863” national high-tech development plan during the “Tenth Five-Year Plan” period, and has become a national key support and encouragement development project. With China's accession to the WTO, the export volume of electric bicycles in China will increase rapidly, and electric bicycles entering Europe and the United States have been required to be equipped with non-polluting batteries.
However, some experts said that the environmental pollution caused by lead-acid batteries mainly occurs in the production process and recycling process of enterprises. In the same way, lithium batteries are good in the new energy industry, but it can not avoid the problem of heavy metal pollution. Lead, arsenic, cadmium, mercury, chromium, etc. in the processing of metal materials may be released into dust and water. The battery itself is a chemical substance, so there may be two kinds of pollution: one is the process waste pollution in the production process; the other is the battery pollution after the scrap.
Lithium iron phosphate batteries also have their disadvantages: for example, poor low temperature performance, low tap density of the positive electrode material, and a lithium iron phosphate battery having a capacity of more than lithium cobalt oxide, and thus have no advantage in terms of a micro battery. When used in a power battery, a lithium iron phosphate battery, like other batteries, needs to face battery consistency problems.
Contact Person: Ms. Alice