Biology Reference
In-Depth Information
There has been increased demand in developing novel electrode materials
to boost the transport of lithium ions and electrons. Enhanced transport
means enhanced storage capacity. Further interest in developing novel
electrode materials is driven by lower cost, lower toxicity, and improved
thermal and chemical stability.
Initial studies in the Belcher laboratory (MIT; Cambridge, MA, USA)
focused on the development of cobalt-oxide-based battery electrodes.
Hybrid cobalt oxide nanowires were employed, which were synthesized
using the M13 bioscaffold and the above-described peptide-mediated
mineralization protocols. Electrochemical evaluation of such wires indicated
good discharge and charge capacities; thus, it was proposed that the hybrid
would provide a promising system for integration in lithium ion batteries.
Two-dimensional film battery electrode assemblies were organized on
polyelectrolyte multilayer arrays. Microbatteries were fabricated using a
combination of polyelectrolyte-driven assembly and microcontact printing
(the assembly techniques are explained in Chapter 7) (Lee
et al
., 2009; Nam
et al
., 2006, 2008).
More recently, research has turned toward using iron-phosphate-
based materials as components for battery cathodes. A combinatorial
genetic approach was used to (i) grow iron phosphate wires using the
M13 platform, and (ii) interlink the nanowires with single-walled carbon
nanotubes (SWCNTs). To achieve this, two genetic modifications were made:
(i) a tetraglutamate peptide (EEEE) was inserted into pVIII (major coat
protein) to facilitate synthesis of anhydrous FePO
4
α
) wires on silver
nanoparticle-coated M13 particles; (ii) peptides that specifically bind to
SWCNT were inserted in pIII (minor coat protein at one virus end) to allow
interlinking and network formation with SWCNTs. Environmentally benign
synthesis of anhydrous FePO
(
-FePO
4
α
) nanowires and network formation
by mixing with SWCNTs were demonstrated. Carbon nanotubes with their
high aspect ratio (length by width ratio) and highly conducting properties
were expected to lead to efficient percolating networks (percolation
describes the movement or diffusion of fluids, here the lithium ions, through
a porous matrix).
Battery electrodes were assembled and tested. The electrodes showed
high and stable capacity. The functionality of such M13-based electrodes was
demonstrated by powering a light-emitting diode (LED) (Fig. 6.14) (Lee
(
-FePO
4
4
et
al
., 2006, 2008). In summary, the nucleation of inorganic
materials on the M13 scaffold in combination with its alignment into
higher-order heterostructures is an exciting and promising route to novel
nanoelectronic devices. Additional data storage and electrode devices are
discussed in Chapter 7.
., 2009; Nam
et al
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