From: B.Hamilton@irl.cri.nz (Bruce Hamilton)
Newsgroups: sci.energy
Subject: Re: Performance of Electric Vehicles
Date: Sat, 28 Oct 1995 19:19:45 GMT
Organization: Industrial Research Limited
Lines: 86
ssmith@paltech.com (Bob Ssmith) wrote:
>In article <hatunenDGvG72.51K@netcom.com> hatunen@netcom.com
>(DaveHatunen) writes:
>>In article <...>,Robin van Spaandonk <rvanspaa@netspace.net.au> wrote:
>>>In article <...>, DaveHatunen wrote :
>>>>In article <...>,Will Stewart <will1000@ix.netcom.com> wrote:
.....
>>>>>On the subject of range, it is important to note that "a Solectria EV
>>>>>with the roominess of a Ford Taurus powered by environmentally safe
>>>>>NiMH batteries produced by Ovonic Battery Company,
>>>>
>>>>Nickel is not an environmentlly safe substance. How is it used in this
>>>>battery that makes it safe?
It isn't. That is why spent Ovonics NiMH batteries will be hazardous
waste in California ( Science v.269 p744 ). By their nature, the batteries
have some of the metals in a mobile form. The negative electrode is
a multiple-alloy metal matrix using Vanadium, Nickel, Titanium, Zirconium,
Chromium as major components , but also contains Cobalt, Manganese,
Aluminium and Iron. The positive electrode is nickel hydroxide and the
current-carrying electrolyte is potassium hydroxide. Water in the aqueous
electrolyte splits into hydrogen and hydroxyl ions when the battery is
charged. Hydrogen is absorbed into the negative electrode, which then
changes from metal to metal hydride. At the same time, hydroxyl ions
react at the positive electrode and are converted from nickel hydroxide to
nickel oxyhydroxide. During discharge, hydrogen leaves the negative
electrode and hydroxyl ions leave the positive electrode. They combine
in the electrolyte to form water and release an electron to the battery's
external circuit, thus generating electricity. The discharge reaction for the
cell generates an open-circuit voltage of about 1.3V
2 NiOOH + MH(x) <=> Ni(OH)2 + MH(x-1)
>>>In that case all those people with Nickel plated taps in their kitchen
>>>and bathroom, are in big trouble.
>>I'm not sure if that's supposed to be a joke (a lame one) or it was an
>>earnest, but ignorant, comment.
>Assuming the latter, Dave -- i.e., earnest ignorance -- how DOES one
>reconcile the wide use of nickel plating with the official toxic status of
>nickel?
The toxicity of nickel has been known for a very long time, thus
it has been limited in its applications where it could be inhaled
or ingested in a soluble form. Until the late 1980s exposures were
rated differently, depending on whether it was metal, insoluble
compoumds or soluble compounds, with some volatile nickel
compounds ( eg nickel carbonyl ) having stringent limits. From
1990 nickel was rated by the ACGIH as a confirmed human
carcinogen - which requires exposure to be as low as possible,
and a limit of 0.05mg/m3 was set for all forms.
Now, the issue then becomes, how much exposure do you
receive from bathroom taps that usually are nickel metal,
often covered with a much thinner layer of chromium ( another
metal that is toxic ). These pure metals are virtually insoluble in
water, they have to be dissolved by reacting with species in
the water. Consider the better known cases of cadmium and
lead that more readily formed soluble species. Consider also that
many cooking utensils are stainless steel, containing significant
% of both nickel and chromium with the iron. Fortunately the
metals do not readily form compounds that increase our intake
to hazardous levels. It is another story if we deal with batteries
with soluble or volatile nickel compounds in large quantities.
They have to be disposed of and recycled in such a way that the
nickel does not pollute, and the track record is not good. That is
why many people believe that NiMH batteries aren't
environmentally-friendly, and that more efforts should be made
at producing solid electrolyte batteries like the lithium solid-state
(using conducting polymers), or batteries that don't require
large quantities of toxic metals ( sodium/sulfur ). The Ovonics
prototype NiMH battery was called "The Green Battery" and
"Environmentally Safe" by Ovonics, but just saying that doesn't
mean that it will be. They are attempting to counter current
concerns by making the battery "recyclable".
Bruce Hamilton