Advancing Technology to Change the World
lithium iron phosphate as cathode (LiFePO4 technology)
Due to the shortage of fossil fuels and environmental concerns, we�re convinced that the green energy industry and related industries will become the main stream in the coming 30-50 years. This causes a strong demand of rechargeable batteries. However, the existing lithium ion cell systems including lithium cobalt oxide and lithium manganese oxide still suffer from low discharge rate, safety concern and short cycle life.
To solve those issues, Dr. John Goodenough and his team at University of Texas patented as potential cathode material LiFePO4 as a potential cathode in 1996. It is a very stable material due to the covalent P-O bonding which stabilize the fully charged cathode versus O2 release. Scientists have developed the LiFePO4 battery using lithium iron phosphate as cathode to answer concerns in the battery for electric vehicles and other battery useages.
Under its pure form, the olivine-structured material showed specific capacities up to 170 mAh/g.
Heterosite structure..........................Olivine structure
Currently, many electric vehicles use the lead acid battery for the 36V/10Ah mold with 360 W total energy, 26.4 lbs. (12 kg) weight, and can be used to drive 30 miles (50km) under 100% optimal circumstances. Its cycle life is only about 100 - 300 times. Each 12v battery price is about 35 - 40 USD, and the service life is about 12 months. A big problem is the pollution produced by lead acid batteries. If LiFePO4 material is adopted as anode to make 10Ah batteries, it requires 12 battery pieces as series in a whole pack. The whole mold is only about 7 lbs. (3-4 kg) weight. If it can be made 11 lbs. (5 kg) weight, the ebike can travel over 48 miles (80 km) in laboratory experiments.
Comparing LiFePO4 Batteries with Other EV Batteries
There are three types of lithium ion cells based on different cathode materials. They are lithium cobalt oxide, lithium manganese oxide and lithium iron phosphate types. Although lithium cobalt oxide cell has the advantage of high energy density, it suffers from safety concerns. Lithium manganese oxide cell has been evaluated for the application on high rate due to the better safety characteristics. However, its high temperature performance is the major drawback.
Lithium iron phosphate cells have the best safety characteristics—long cycle life (up to 2000 cycles) and good availability. They are very suitable for high discharge rate occasions such as EV (including e-bike, electric scooter, and electric car), power tools, UPS and solar energy system. According to different applications, Liberty can modify the design of battery packs to provide the best solution to satisfy our customer�s needs.
COMPARISON DATA AMONG VARIOUS LITHIUM BASE BATTERIES:
|Safety||Safest||Not Stable||Acceptable||Not Stable|
|Environmental Concern||Most Enviro-friendly||Very Dangerous||Very Dangerous|
|Cycle Life||Best/ Excellent||Acceptable||Acceptable||Acceptable|
|Long Term Cost||Most Economic/ Excellent||High||Acceptable||High|
(-20C to 70C)
(-20C to 55C)
|Decay Extremely Fast over 50 C||-20C to 55C|
1. Although, lead acid batteries are lower in cost and safety acceptable; however, they are extremely toxic, worse for the environmental concern, short cycle life, heavy in weight, therefore, we don�t put it as a group for comparison.
2. Nickel Hydride battery has a characteristic of low power weight density, decayed faster under the high temperature, worse in memory effect, not suitable for high output usage.
3. The C-coated Lithium Iron Phosphate Battery has been proven as the most environmental friendly battery. It is the safest and most suitable for high output usage. It is also the best for storage battery usage. It is not necessary to use the equalizer and the protecting PC Board module.
The LiFePO4 battery does not have the security hidden danger.
When phosphate batteries are overcharged under 3A 5V, the temperature of the battery could not surpass 55°C. The battery is extremely safe; Heats up after 7-8 hour to 300°C in hot box process, battery temperature nearly the same with temperature of hot box, the battery cannot appear hotly out of control; after extrusion or acupuncture, the battery temperature cannot surpass 110°C.
The safety of lithium battery is guaranteed by using LiFePO4 as anode pole. LiFePO4 is one kind of phosphate gathering the anion, the P-O chemical bond is extremely strong, material is thermodynamically stable, do not worry about it can release the oxygen, simultaneously LiFePO4�s olivine crystal structure decides its crystal lattice deformation smaller in the sufficient electric discharge process, its material structure is stable and safe, and also its cycle life are extremely long. These characteristics also can make LiFePO4 withstand oxidation and acidic environment, the battery has more electrolyte choice, the battery performance can be optimized.
The safety characteristics inherent to LiFePo4 technology result from the incorporation of phosphates as the cathode material. Phosphates are extremely stable in overcharge or short circuit conditions and have the ability to withstand high temperatures without decomposing. When abuse does occur, phosphates are not prone to thermal runaway and will not burn. As a result, LiFePo4 technology possesses safety characteristics that are fundamentally superior to those of lithium-ion batteries made with other cathode materials.
LiFePo4 technology does not contain any heavy metals and does not exhibit the "memory effect" of Nickel-Cadmium and Nickel-metal Hydride solutions. LiFePo4 technology demonstrates excellent shelf life, long cycle life and is maintenance free.
Another key benefit of LiFePo4 technology is its flexibility, both in terms of battery application and cell design. It can be used in wound cylindrical, wound prismatic and polymer battery construction types and manufactured to fit smaller applications.
The advantages of traditional lithium-ion coupled with the safety features of phosphates, make LiFePo4 technology the lithium-ion technology for the future. Our LiFePo4 technology utilizes natural, phosphate-based material and offers the greatest combination of performance, safety, cost, reliability and environmental characteristics.
We all use and take for granted the benefits of lithium-ion energy storage systems in our cell phones, notebooks, PDA�s, consumer appliances and other devices. However, recent recalls by the US Consumer Protection Commission have brought to light the potential hazards of lithium-ion batteries. Just imagine what could happen to a large lithium-ion battery if an electric/hybrid electric vehicle were rear-ended or if a manufacturing defect or other abuse caused a thermal event in a mission critical telecom backup system. The results could be devastating.
Liberty is intent on working on developing and making available to all EV applications the LiFePo4 technology—the only safe large format lithium-ion rechargeable battery technology. We sincerely hope to have a chance to cooperate with our customers all over the world and contribute the latest world-wide technology to our customers� prosperous business future.