Most disposable batteries are based on zinc chemistry. Years ago they contained mercury as well, but happily this was outlawed.
Zinc ores can contain trace levels of cadmium, but generally this is not entirely serious as is the case with nickel cadmium batteries of the rechargeable type.
This said, nickel cadmium batteries may be superior in a purely environmental sense since in many areas they are recyclable and are not part of the throwaway culture. (Inevitably they do end up in landfills however, where they represent a long term hazard to future generations, and the mining of cadmium in China for batteries and so called "renewable energy" has presented serious and observed health risks, including health risks to the food supply there.
The chemistry of batteries, including the other (and rapidly growing major) alternative to nickel cadmium, lithium batteries of various types, is actually appalling on many levels, but I would agree that in many places they are essential. In batteries for electric cars there is an extreme ethical question connected with cobalt, cobalt mining representing a case of a "conflict metal," involving the use of human slavery.
There is the issue of the organic chemistry of some batteries which is also not pretty, but is seldom discussed.
A great deal of research has gone into sodium batteries, which would potentially be cleaner than existing battery types.
Personally, if pressed, a caring person will decide between rechargables - where recycling exists they can be cleaner - and disposable zinc batteries. If there is a recycling program and you are committed to using it, go with rechargables. If no such program exists, go with zinc.
My environmental philosophy is that there should be no such thing as waste, and that all matter should be recycled. This would require high density energy; any form of matter can be recycled if and only if there is sufficient energy to overcome the entropy of mixing, and moreover, the energy must be clean and sustainable, which limits the case to nuclear energy.
In general every battery of every type is a device which wastes energy.
Thanks for asking. The more we think about these things, the less onerous we will be to future generations.
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