Stability Investigation of Inorganic Li Conductors As Protective Layers for Li-Air Batteries

Wednesday, 8 October 2014
Expo Center, 1st Floor, Center and Right Foyers (Moon Palace Resort)
K. Z. Fung (Research Center for Energy Technology and Strategy, Dept. of Materials Science and Engineering, National Cheng Kung University, Taiwan), C. T. Ni (Dept. of Materials Science and Engineering, National Cheng Kung University), S. Y. Tsai, and M. H. Chen (Dept. of Materials Science and Engineering, National Cheng Kung University, Taiwan)
The development of Li-air battery has received great attention recently. However, using metallic lithium directly as an anode has been challenging due to the high reactivity of Li. Protective coatings with ionic conduction on metallic Li has be proposed to overcome this problem. Inorganic Li ion conductors may be suitable for being used as the protection layer.

NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 are known to be inorganic solid electrolytes with adequate conductivity in a range of 10-3 S/cm after required modification. However, Li tends to react with La0.56Li0.33TiO3 due to the incorporation of the released electrons with Ti+4 ions. Simultaneously, Li+ ions will migrate into the vacant sites in the cation sublattice. As a result, La0.50Li0.50TiO3 perovsikte becomes a mixed ionic/electronic conductor after reacting with Li. On the other hand, limited reaction was observed on the Li1+xAlxTi2-x(PO4)3 electrolyte when the metallic Li was used as the anode.

In order to improve the stability of Li1+xAlxTi2-x (PO4)3, a concept of composite electrolyte based on NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 is proposed. With proper mixing and distribution of these two electrolytes, a better stability from the composite electrolyte is expected.

Thus, the objective of this work is (1) to develop a composite electrolyte based on the mixture of Li1+xAlxTi2-x (PO4)3, and La0.50Li0.50TiO3, (2) to analyze the interface reaction between two components of composite cathode, (3) to investigate the electrical conduction/stability of composite as a function of volume fraction, grain size, and thickness, (4) to evaluate the feasibility of using composite electrolyte for Li-Air battery. The stability of composite electrolyte will be determined based on the measurement of the induced electronic conductivity and the open circuit voltage after a Li-air cell is assembled.