Addition of various tetraalkyl quarternary ammonium salts, to alkaline zincate electrolyte of cell, prevents formation of zinc dendrites during charging of zinc electrode. Electrode capacity is not impaired and elimination of dendrites prolongs cell life

Damjanovic, A.

Diggle, J. W.

English

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December 1970	 Brief 70-10434 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Suppression of Zinc Dendrites in Zinc Electrode Power Cells 
0	 -50	 -60	 -70	 -80	 -100	
-120	 -140 
Zinc Overpotential. mV 
Effects of Addition of Lead Salts 
Addition of one of various tetraalkyl quaternary 
ammonium salts, to the alkaline zincate electrolyte 
of a cell, prevents formation of zinc dendrites during 
charging of the zinc electrode (see table); the elçc-
trode's capacity is not impaired. Elimination of 
dendrites prolongs the cell's life.
The fact that 0.2M Br (as KBr) is completely 
ineffective in preventing initiation of dendrites implies 
that the influence of the tetraalkyls is due to the 
adsorbed cation. The effect of the tetrapentyl cation on 
both initiation and propagation is exactly analogous. 
to that of the same concentration of lead (see 
Tech Brief 70-10153). It is concluded that at the same 
continued Ove rkal) 
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Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
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concentration the tetrapentyl is as effective as lead 
at -100-mV overpotential. 
Addition of soluble lead salts (acetate or nitrate) 
confirmed the results reported in Tech Brief 70-10153 
(see fig.). At a lead concentration of 10 4.M, dendrites 
are eliminated provided that the zinc overpotential 
does not exceed -140 mV. 
It is proposed that adsorption of either lead ions 
or tetraalkyl cations interferes with the initiation of 
zinc dendrites because of the adsorption at certain 
preferential sites and of the slowing of the normally 
fast surface-diffusion step. The net result of these 
effects is formation of many very small grains rather' 
than of fewer large grains that normally precedes 
initiation of dendrites. 
Minimum concentrations of quaternary ammonium 
salts for complete suppression of zinc dendrites 
from an electrolyte of IOM zincate-10% KOH at 
30°C and -100 mV. At higher concentrations the dcc-
trodeposit's morphology is always compact. 
	
Quaternary	 Minimum 
salt	 concentration, M 
	
(C 2 H 5 ) 4 NBr	 2 x 10 
	
(C 3 H 7 )4 NBR	 2 x 10-2 
	
(C4H9)4 NBr	 2 x 10 
	
(C 5 H 11 )Nl	 -	 2 x 1.0-4
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Headquarters 
National Aeronautics 
and Space Administration 
Washington, D.C. 20546 
Reference: TSP70- 10434 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: J. W. Diggle and A. Damjanovic of

University of Pennsylvania

under contract to

NASA Headquarters
(HQN- 10550) 
Brief 70-10434	 Category 02


Suppression of zinc dendrites in zinc electrode power cells

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