If you buy NiMH (nickel-metal hydride) batteries you will get a high performance battery with low environmental impact and excellent recycling potential. Lithium-ion (Li-on) betteries are apparently harder to recycle. Older rechargeable batteries are made with cadmium (they are known as NiCd or Nickel Cadmium) and their impact may be less because cadmium is toxic and they are less valuable for recycling. However the means of extraction and manufacture used affect the benefit.

From the Wikipedia article:

NiMH batteries are commonly considered to have lower environmental impact than NiCd batteries, due to absence of toxic cadmium. The overall environmental impact of mining the various alternate metals that form the negative electrode may be more or less than cadmium, depending on the metal, mining method, and environmental practices of the mine.

Most industrial nickel is recycled, due to the relatively easy retrieval of the metal from scrap, and due to its high value.

As far as a comparison with a traditional battery is concerned. In a high drain device like a camera a NiMH battery is still a better bet even if you only use it once as it remains usable for far longer than a traditional alkaline battery.

Again from the Wikipedia article:

NiMH cells are often used in digital cameras and other high drain devices, where they often vastly outperform primary batteries even on a single charge.

[...] NiMH cells are particularly advantageous for high current drain applications, due in large part to their low internal resistance. Alkaline batteries, which might have approximately 3000mAh capacity at low current demand (200mA), will have about 700mAh capacity with a 1000mA load. Digital cameras with LCDs and flashlights can draw over 1000mA, quickly depleting alkaline batteries. NiMH cells can handle these current levels and maintain their full capacity.

In a very low drain device such as a remote control it is difficult to establish which is better from an environmental perspective because you won't have information on the manufacturing and mining processes used. From a finance perspective a rechargeable battery will not cover the increased cost of purchase in a very low drain device for as much as a decade.

Also, its worth noting that many rechargeable batteries lose their charge fairly quickly. I disovered the problem when fitting an external flash unti to my camera setup. The flash needed 4 x AA batteries so I bought some new NiMh rechargeable batteries and charger. On full charge they worked brilliantly and lasted longer than disposable batteries. However, having charged them fully and putting them into the flash unit I discovered that when I came to use it the following week they did not have enough charge to fire the unit, so had to be charged again, using more energy.

I realise this is a high drain piece of equipment but my point is that there are newer batteries on the market of which the sanyo eneloop battery is one example. These are a rechargeable battery which discharge very slowly, so you can charge them and then keep them with infrequently used kit in a ready to go condition. They even get sold with a full charge.

Not entirely environmental advice I realise, but I was pleased to hear about such a product so no doubt some others will be as well.