Kunyoung Kang

A simple method for solving the voltage overshoots of LiFePO4-based lithium-ion batteries with different capacity classes

To simulate the energy storage process of an energy harvesting device, a step-charging current protocol for LiFePO4-based lithium-ion batteries is considered, in which lower current rates are applied in both the earlier and latter steps of the voltage profile, while the maximum current (0.2 C-rate) is applied in the middle voltage region. The protocol is applied to three stages of voltage profile, i.e., initial step (stage 1), middle plateau (stage 2), and final step (stage 3) regions. In spite of their capacity-classes, lithium-ion batteries containing sub-μm-sized LiFePO4 have shown voltage overshoots in the step regions of the voltage profile, thus involving anomalous degradation of active materials and diminishing the stability and safety of the batteries. In order to overcome this overshoot problem, a simple method of blending a small amount of μm-sized LiCoO2 with the LiFePO4 is proposed. The results show that adding the LiCoO2 eliminates voltage overshoots. The small quantity of μm-sized LiCoO2 extends the operating voltage region as the short appearance of the LiCoO2 plateau serves to block the emergence of an overvoltage. In addition, battery performance is further improved by an increase in the electrode density brought about by the close packing of different-sized particles.

Preparation and Electrochemical Performance of 1.5 V and 3.0 V-Class Primary Film Batteries for Radio Frequency Identification (RFID)

1.5 V and 3.0 V-class film-type primary batteries were designed for radio frequency identification (RFID) tag. Efficient fabrication processes such as screen-printings of conducting layer (), active material layer ( for anode and for cathode), and electrolyte/separator/electrolyte layer (), were adopted to give better performances of the 1.5 V-class film-type Leclanch primary battery for battery-assisted passive (BAP) RFID tag. Lithium (Li) metal is used as an anode material in a 3.0 V-class film-type Li primary battery to increase the operating voltage and discharge capacity for application to active sensor tags of a radio frequency identification system. The fabricated 3.0 V-class film-type Li primary battery passes several safety tests and achieves a discharge capacity of more than 9 mAh .