The switch away from NiCad is happening or being considered in many applications because other batteries have superior characteristics such as power cycle, recharge time, and weight. Li ion batteries have been around for a while, but are not considered the final stop in battery evolution, mostly they use a liquid or paste electrolyte. One variant that is gaining acceptance, and is even available in some power tools, are the Li polymer ion (LiPON) batteries. Here is where you could have some real influence on environmental outcomes. Many of the first LiPON batteries were based on lithum cobalt carbonate, and involved a messy and wasteful vapor deposition process. But many other types are available and under investigation, some of which replace the cobalt with molybdenum or manganese, and others with far simpler and less wasteful fabrication techniques.
None are exactly engineered with end-of-life in mind, and the final package looks very tricky to take apart. But the mass of materials is greatly minimized compared to Li ion and NiCad, and the life is much better. Some are being considered for use by contractors in circular saws, a very demanding application.