Chemistry Reference
In-Depth Information
10
5
10
4
EDLC
Radical
Battery
Li-ion
10
3
Ni-MH
10
2
10
0
10
1
Energy Density (Wh/kg)
10
2
10
3
Figure14.7
Projectionofthe''organicradicalbattery''intheenergyandpowerdensitydiagram(Ragoneplot).
by both remarkably high power density and relatively high energy density (i.e., high capacity). By using
its high power performance and relatively high capacity, the radical battery has been tested, for example,
as an uninterruptible power supply system for the data backup of personal computers and computer servers
during power failure. Optimization of the composition of polymer/carbon electrode and electrolyte, as well
as fabrication method of the battery, has led to a 100-mAh class of aluminum laminated film packaged
organic battery.
8,22,23
Applications for which high power capabilities, rather than high energy density, are
important, such as the subbattery in electronic devices and motor drive assistance in electric vehicles,
would be appropriate for organic radical batteries in the future.
14.4 Molecular design and synthesis of redox active radical polymers
As described in Section 14.3, redox active radical groups are immobilized in the form of electrode materials
to impede self-discharge accompanied by the dissolution into the electrolyte solution. One of the simplest
ways for immobilization is to incorporate the radical group into the (aliphatic) polymer structure, in
which the radical groups are electrochemically isolated and non-interacting. For several years, various
combinations of the durable radicals and polymer structures have been extensively investigated. In this
section, we focus on the p-type redox active radical polymers, and summarize the molecular design and
synthetic methodology of these polymers in view of the polymer backbone as a radical carrier (Table 14.1).
Conventional radical polymerization of radical-containing monomers does not yield radical polymers due
to the high reactivity of radical pendant groups, which terminates the polymerization. Therefore, polymer-
ization procedures are categorized by (i) radical polymerization of the precursor monomers, followed by
chemical oxidation, and (ii) anionic, cationic, and transition metal-catalyzed polymerization of the radical
monomers.
14.4.1 Poly(methacrylate)s and poly(acrylate)s
Poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate)
1
was obtained by the polymerization of 2,2,6,6-
tetramethylpiperidine methacrylate, a material known as a light stabilizer, followed by the oxidation reaction
of the precursor polymer with
m
-chloroperbenzoic acid.
8
The radical density of the obtained polymer
often remained lower (80 - 90 %) than the theoretical density due to incomplete polymer reaction. The
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