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Separator media for electrochemical cells

a technology of electrochemical cells and separator media, which is applied in the direction of cell components, cell component details, batteries, etc., can solve the problems of high self-discharge rate and constant loss of charge during storag

Inactive Publication Date: 2014-05-15
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a new type of separator medium for batteries and capacitors that can be used in alkaline batteries. This medium is made of a nonwoven sheet made of polymeric fibers that has a specific pore size. The nonwoven sheet has a surface area of 0.5 to 1.5 m2 / g and its maximum pore size is at least 2.5 times its mean flow pore size and more than 11 times its minimum pore size. The polymeric fibers can also be sulfonated and contain at least 0.67% of sulfur. This new separator medium can help improve the performance of batteries and capacitors.

Problems solved by technology

One of the major deficiencies in nickel metal hydride (NiMH) battery systems is their high rate of self-discharge, that is, continuously losing their charge during storage.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples

[0040]Test Methods

[0041]Ionic Resistance in KOH electrolyte is a measure of a separator's resistance to the flow of ions, and was determined as follows. Samples were cut into small pieces (1″×1″) and soaked in 35% potassium hydroxide overnight to ensure thorough wetting. Samples were sandwiched between two Teflon® shims with a 1 cm2 window exposing the sample. The sandwich of Teflon® shims and sample was placed in a resistance cell having two platinum electrodes such that the window was facing the two electrodes. The resistance was measured at 1 KHz using an HP milliohmeter. The measurement was repeated without any separator between the Teflon® shims. The difference between the two readings is the resistance (milliohms) of the sample. The separator resistance is then multiplied by the area of the electrodes (1 cm2 in this case) and the results are reported in milliohms-cm2.

[0042]Basis Weight was determined by ASTM D-3776, which is hereby incorporated by reference and reported in g / m...

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Abstract

A separator medium for electrochemical cells that contains at least one nonwoven sheet of polymeric fibers. The nonwoven sheet has a surface area of about 0.5 to about 1.5 m2 / g and has a maximum pore size that is equal to or more than 2.5 times the mean flow pore size and more than 11 times the minimum pore size. The sheet may be sulfonated to a level of 0.67% and demonstrates superior tensile properties after sulfonation and relative to previously known separators.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to the field of separators for electrochemical cells, and in particular alkaline batteries.[0003]2. Description of the Related Art[0004]Alkaline batteries have become increasingly more popular because of their high energy density. As such, these batteries are increasingly used in applications normally reserved for the traditional lead-acid battery systems.[0005]In order to achieve extended battery life and efficiency in alkaline systems, the use of battery separators is required. The battery separators are located between the positive and negative plates so as to provide, (1) a separation between the electrodes of opposite charge, (2) an electrolyte reservoir, (3) a uniform electrolyte distribution across the electrode surface so as to permit uniform current density and (4) a space for electrode expansion.[0006]Battery separators used in alkaline batteries at present are commonly formed of a polyo...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M2/16H01M2/14H01M50/403H01M50/417H01M50/489H01M50/491H01M50/494
CPCH01M2/145H01M2/162D04H3/007D04H3/009D04H3/011D01D5/11D01F6/04D01F6/06H01G9/02H01M10/24H01M10/345H01G11/52D06M11/54D04H1/724Y02E60/10H01M50/44H01M50/403H01M50/417H01M50/491H01M50/494H01M50/489D04H3/166Y02E60/13D04H3/16D01D10/02H01M6/045H01M10/26H01M2220/10H01M2220/20
Inventor LIM, HYUN SUNGARORA, PANKAJ
Owner EI DU PONT DE NEMOURS & CO
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