A. Physical dimension
NanoEnergy® can be customized to fit specific size requirements. The following are two typical battery sizes.
Electrical connections are typically metal foils with 10 mm long, 2 mm wide and 0.1 mm thick. The following figure shows an example of the terminal configuration.
D. Battery chemistry
The battery is composed of solid-state thin films. There is no liquid in the package. The electrolyte is Lithium Phosphorus Oxynitride (LiPON) developed by Oak Ridge National Laboratories (ORNL). Front Edge Technology has a licensing agreement established with ORNL. Cathode material is LiCoO2, and the anode is Lithium.
E. Electrical characteristics
Battery is charged at 4.2 V constant voltage. No other charging protection is needed. Temperature rise during charging is less then 1 oC. Continuous charging at 4.2 V does not degrade the battery’s performance. There is no overcharging effect.
NanoEnergy® can be charged at very high rate without affecting its performance. A 0.25 mAh NanoEnergy® can be charged to 70% of the rated capacity in two minutes and to full capacity in four minutes. For a 0.9 mAh NanoEnergy® charged at 4.2 V, the battery reaches 70% of the rated capacity in six minutes and 100% rated capacity in 20 minutes. Figure 2 shows a typical charging curve of a 0.9 mAh battery. A charging curve of a 0.25 mAh battery is shown in figure 6.
NanoEnergy® can be continuously discharged at rates more than 10 C, and more than 20 C in pulsed discharge. Figure 3 shows the discharge characteristics of a 0.9 mAh NanoEnergy®.
When charged at 4.2 V and discharged at 1 mA to 3.0 V, the battery has less than 10% capacity loss over 1,000 charge/discharge cycles, see figure 4. Figure 5 shows the discharge curves at the 1st, 500th, and 1000th cycle. Charging rate is lower at the 1000th cycle than that of the first cycle. The charging time required to obtain 95% of the rated capacity is 4 minutes at the first cycle and increases to 6 minutes at the 1000th cycle.
The self-discharge rate is less than 5% per year.
F. Storage temperature
Battery can be stored at -40 to 80 oC without damage.
G. High temperature performance
NanoEnergy® performs better at elevated temperature due to lower internal resistance. When operated at 100 oC, NanoEnergy® can be charged and discharged at higher rate and with higher capacity. Figure 7 shows typical discharge curves of a 0.1 mAh NanoEnergy® discharged at room temperature, 60 oC, and 100 oC. NanoEnergy® can even be operated at temperatures as high as 170 oC, however, the capacity drops much faster during cycling.
H. Low temperature performance
NanoEnergy® can be operated at temperature as low as -40 oC, however, with lower charge and discharge rates. Figure 8 shows discharge curves of a 0.9 mAh NanoEnergy® discharged at 30, 0 and -40 oC. The discharge current was 0.5 mA at 30 and 0 oC, and 0.01 mA at -40 oC. Figure 9 is a charging curve of a 0.9 mAh NanoEnergy® charged at 0 oC. It takes about 80 minutes to reach 95% of the rated capacity. When charged at -40 oC, the battery can be charged to 0.6 mAh in 25 hours.
I. Safety and toxicity
The battery contains no toxic liquid electrolyte. There is no source for out-gassing or explosion. The small amount of Lithium metal in the battery does not cause fire even if the hermetic seal is broken.