Cobalt is not a heavy metal and is in fact essential for life and is a constituent of vitamin B12 and not all that toxic. While nickel can be toxic in some cases it is also plays an important role in plant and microorganism biology. Nickel also is not a heavy metal. Lithium also is also likely an essential trace element for mammals although they have not yet identified any physiological role. Aluminum also is not really toxic. If nickel were all that toxic then nobody would be using stainless steel cookware and silverware since it leaches into the food.
While nobody is suggesting that anyone eat the contents of lithium batteries, they are not considered toxic waste and can be disposed of in municipal wastes in most places, though it is more profitable to recycle them.