Biomedical Engineering Reference
In-Depth Information
15.8
Schematic illustration of Li-O
2
/air cell and its component
materials. Lithium is protected by copper foil, which is also used as a
current collector. The current collector on the cathode side is a metal
casing not shown in the diagram.
ceramic (PC) membranes. A PC membrane of PEO:LiBETI (8.5:1)-(1 wt%
Li
2
O) electrochemically couples the lithium anode and GC membrane. The
PC membrane that couples the cathode with the GC membrane is also a
PEO-based lithium ion conductor containing Li
2
O. Details on the
development of the PC membranes can be found elsewhere (Kumar and
Scanlon, 1994; Kumar et al., 2001; Kumar and Kumar, 2009; Kumar et al.,
2010). The PC membranes are nanocomposites of the type discussed in
Section 15.3. These nanocomposites reduce impedance of the cell, enhance
charge transfer reaction (Li
Li
+
+e
), passivate lithium, and electro-
chemically couple the cathode to the GC membrane. The central part of the
membrane laminate (GC) is also a nanocomposite. The cathode of the cell is
a porous nanocomposite made from predominantly LAGP and carbon. The
cells of Fig. 15.8 reversibly carry the reaction:
↔
2Li
þ
O
2
$
Li
2
O
2
½
15
:
20
The open circuit voltage of this reaction is 2.90 V. Li-O
2
cells that exhibit a
lifetime greater than 500 cycles have been developed.
15.4.2 Power generation
SOFCs are believed to be a critical element of future power generation
technologies due to their high fuel-to-power conversion efficiency with
minimal adverse influence on the environment. However, significant hurdles
remain before they can become widely acceptable. The hurdles include
operating temperatures, mechanical integrity, thermal instability, and cost.
Nanocomposites based on the YSZ-Al
2
O
3
system were successfully used to
