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gram and per liter), power density (watts per kilogram and per liter), service life (cycles to failure), and cost (per kilowatthour). Table I summarizes the performance characteristics of some secondary battery types. Such comparisons are made difficult by the fact that many performance characteristics are functions of battery size and service conditions. For example, service life is greatly affected by discharge current and depth of discharge, DOD (a fully charged battery is considered to be at 0% DOD, while a “dead” battery is considered to be at 100% DOD). However, both of these operating parameters can be very different for cells based upon the same chemistry but designed for different applications. With this caveat, Table I is presented. With its low density (0.53 g cm
3), low electronegativity, and high electron/atom mass ratio, lithium has become the preferred choice for the active element of the anode, which on discharge functions as an electron donor according to

Portable Power:

Advanced Rechargeable Lithium Batteries

Donald R. Sadoway and Anne M. Mayes, Guest Editors Abstract The full potential of wireless devices remains unattainable due to limitations in battery performance. It is the thesis of the guest editors and contributing authors of this issue of MRS Bulletin that there is much room for improvement, that we are still far from the practical limits of the technology, and that materials research has the capability to pave the way for a new generation of rechargeable batteries that will offer a dramatic improvement in power delivery over anything available today. The basics of battery operation, including the relevant electrochemistry, are reviewed, unsolved problems are enumerated, and prospective solutions are indicated.

anode:

Keywords: electrical properties, energy-storage materials, polymers, rechargeable lithium batteries.

Introduction Major advances in materials have paved the way for an array of wireless devices with ever-increasing functionality. Oddly, their full potential remains unattainable, and this is almost exclusively due to the limitations of the batteries that power them. Ironically, it was more than 200 years ago that Alessandro Volta at the University of Pavia demonstrated for the world the first battery, comprising a stack of coin-sized disks of zinc and silver arranged in pairs separated by cardboard soaked in salt water.1 Yet, battery technology has seemingly been untouched by radical innovation in the decades since then. It is the thesis of the guest editors and contributing authors of this issue of MRS Bulletin that there is much room for improvement, that we are still far from the practical limits of the technology, and that materials research has the capability to pave the way for a new generation of rechargeable batteries that will offer a dramatic improvement in power delivery over anything available today.

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Rechargeable Batteries: The Basics There are many chemistries that will serve as the basis for rechargeable, or secondary, batteries.2 Distinctions can be