Although often thought of as an area of low technology that is stagnant and
uninteresting in the past, the use of electrochemical cells for energy sto
rage and conversion purposes has received greatly increased attention recen
tly. There are two general directions of interest. One is the long term goa
l of the development of electrical propulsion for vehicles, and the other i
s the rapid growth of portable electronic devices that require power source
s with maximum energy content and the lowest possible size and weight. Most
of the activities have been aimed at the development of electrochemical ce
lls that are optimized toward either maximum specific energy or energy dens
ity. On the other hand, some of the current applications require electrical
energy at high power levels for short times. These include very short puls
es for digital electronic devices, the somewhat longer power pulse demands
of some implantable medical devices, and the much larger transient power ne
eds in connection with vehicle traction. Several mechanisms can be used to
provide short term energy, and they have fundamentally different characteri
stics, and thus are potentially applicable to different types of transient
output requirements. Some of these provide behavior that is analogous to an
electrical capacitor, whereas others have more the character of batteries.
The several electrochemical methods that can be used to evaluate the criti
cal materials parameters in materials that might be applicable to such appl
ications are discussed, as well as the use of LaPlace transform methods to
convert information about the physical mechanisms and parameters of individ
ual components into the dynamic response of an electrochemical system. (C)
2000 Elsevier Science B.V. All rights reserved.