There is no one answer to the question of which battery is best for the environment, because different battery chemistries have different effects on the environment depending on how they are made, used, and thrown away. But in general, lithium-ion batteries are thought to be better for the environment than lead-acid and nickel-cadmium batteries because they have a higher energy density, last longer, and are less toxic. Lithium-ion batteries can also be recycled more often and are easier to recycle than other kinds of batteries. But it's important to remember that making and getting rid of lithium-ion batteries still has effects on the environment, and work is still being done to develop even more environmentally friendly battery technologies for industrial and other uses.