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ELECTROCHEMICAL CAPACITOR ELECTROLYTE FABRICATION BY SELF-ASSEMBLED MOLECULAR FILM TECHNOLOGY

IP.com Disclosure Number: IPCOM000008820D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2002-Jul-16
Document File: 2 page(s) / 146K

Publishing Venue

Motorola

Related People

Robert H. Reuss: AUTHOR

Abstract

Electrochemical capacitors (ECCs) are a promising technology for applications where high power at low voltage is needed for short periods (I) of time. Examples where ECCs are of interest include pulsed communication handsets, distributed power supplies such as in PCs, and electrical and hybrid vehicle power trains. ECCs are energy storage devices, blrt unlike batteries they can be charged and discharged at very high rates for thousands of cycles. In many situations a battery and ECC are being envisioned as a hybrid power supply. The battery provides the traditional energy storage function while the ECC provides the high rate (or pulsed power) function which is becom- ing common for many advanced electrical systems. Commercially available capacitors (film, ceramic, electrolytic) are capable of high rate charge/discharge cycles, but they store relatively little energy at a low voltage and hence have only limited capability to meet the demands of pulsed power systems which are designed to operate at low voltage.

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MOZOROLA Technical Developments

ELECTROCHEMICAL CAPACITOR ELECTROLYTE FABRICATION BY SELF-ASSEMBLED MOLECULAR FILM TECHNOLOGY

by Robert H. Reuss

INTRODUCTION

  Electrochemical capacitors (ECCs) are a promising technology for applications where high power at low voltage is needed for short periods (I) of time. Examples where ECCs are of interest include pulsed communication handsets, distributed power supplies such as in PCs, and electrical and hybrid vehicle power trains. ECCs are energy storage devices, blrt unlike batteries they can be charged and discharged at very high rates for thousands of cycles. In many situations a battery and ECC are being envisioned as a hybrid power supply. The battery provides the traditional energy storage function while the ECC provides the high rate (or pulsed power) function which is becom- ing common for many advanced electrical systems. Commercially available capacitors (film, ceramic, electrolytic) are capable of high rate charge/discharge cycles, but they store relatively little energy at a low voltage and hence have only limited capability to meet the demands of pulsed power systems which are designed to operate at low voltage.

resistivity, L = electrolyte thickness, and A = electrode cross-sectional area), electrolyte resistance can be seen to be directly proportional to thickness. As a practical consideration, R can only be significantly reduced by thinning the electrolyte. Electrode area (A) is dictated by the allowed size of the device. Rho is a material property that is limited to no less than between IO-100 ohmcm for practical electrolyte systems. Thus, if the electrolyte thickness was reduced from about O.lmm (typical) to less than O.Olmm, a IOX improvement in ESR should result (for a device dominated by elec- trolyte resistance). What is needed is a means to effec- tively accomplish this. Merely thinning the electrolyte has not been successful because the layer is no longer uniform and pinholes are created that allow the elec- trodes to short.

PROBLEM TO BE SOLVED

   To help meet the demanding requirements of the pulse power applications mentioned above, higher per- formance ECCs are required. Of particular importance is low electrical series resistance (ESR) which must be minimized so that the ECC can respond rapidly to the demand for power over a wide range of loads, tempera- tures, and duty cycles. While considerable effort has been directed to development of high conductivity materials for current collectors, electroactive formula- tions, and electrolytes, a major source of high ESR stems from the thick electrolyte (or separator) typical in existing cell fabrication technology.

  Lower ESR via thinner electrolyte is the most promising means to improve ECC performance. Since R = (rho) L/A (where R = resistance, rho = electrolyte

TECHNICAL APPROACH

  Molecular self-assembly and mesoporous material techniques (2,3) are receiving increased attention as a ,, means to create thin, uniform fi...