It's important to know that batteries must not get into our garbage bins.
"Batteries contain heavy metals such as mercury, lead, cadmium, and nickel, which can contaminate the environment when batteries are improperly disposed of. When incinerated, certain metals might be released into the air or can concentrate in the ash produced by the combustion process. The Environmental Protection Agency categorizes rechargeable batteries as household hazardous waste."
Know more about battery recycling at US EPA website.