Every year in the United States, Americans buy, use and throw out billions of batteries. The demand for batteries can be traced largely to the rapid increase in cordless, portable products such as cellular phones, video cameras, laptop computers, and battery-powered tools and toys. Because some types of batteries still contain toxic constituents, such as mercury and cadmium, they can pose a potential threat to human health and the environment if improperly disposed. Batteries, especially those with toxic constituents, should be recycled.
All batteries can be described as either primary or secondary. Primary batteries are those batteries that are used only once and then discarded; they cannot be recharged. Secondary batteries are the rechargeable batteries.
Primary battery construction ranges from the basic construction used in carbon zinc and zinc chloride batteries to the more complex construction of more powerful batteries such as alkaline and lithium manganese. Changes in the components and the construction allow for the improved battery life of alkaline and lithium batteries.
Carbon zinc, zinc chloride and alkaline batteries are similar in that they each have a zinc anode, a manganese dioxide cathode, and a paste electrolyte. In carbon zinc and zinc chloride batteries, the zinc anode is the battery cylinder (or can). The electrolyte is a zinc chloride paste, and the manganese dioxide cathode mix is in the center of the can, surrounding a carbon rod electrode.
In alkaline batteries, the zinc anode is a zinc powder in the center of the can, surrounding a brass current collector. The electrolyte is potassium hydroxide, and the zinc and potassium hydroxide are combined in a gel. The manganese-dioxide cathode is contained between the can wall and the separator, which keeps the cathode and anode from direct contact. The can wall in alkalines is steel, rather than zinc.
Lithium batteries have a lithium foil anode, a manganese dioxide cathode, and a lithium-based electrolyte. Lithium manganese batteries use a variety of shapes and constructions, with the most common being button cells, solid-core cylindrical batteries and wound-core cylindrical batteries.
How It Works
Regardless of the battery type, all batteries operate in a similar manner. In broad terms, a three-way chemical reaction takes place between the electrolyte, cathode and anode. This reaction produces negative ions at the negative terminal (the base), and positive ions gathered at the positive post (the small post on top). The generation and gathering of the positive and negative elements creates the battery energy.
As energy is used, the effectiveness of the basic battery ingredients diminish. The cathode and anode materials become depleted, and the reaction between the anode and the electrolyte produces byproducts. As these byproducts build up, the battery’s voltage diminishes and performance drops. For this reason, the life of the battery increases as the amounts of the anodic, cathodic and electrolytic chemicals increase.
All battery types should be recycled whenever possible. Many states have specifically passed legislation prohibiting incineration and landfilling of mercury-containing and lead-acid batteries.
In 1996, U.S. legislation was signed that required alkaline manufacturers to phase out the use of mercury in their batteries. However, this regulation only addresses added mercury; small quantities of mercury are still present in most alkaline batteries as an unavoidable part of the manufacturing and mining processes. When the other metals in alkaline batteries, like zinc and manganese, are mined, small amounts of mercury are included in the raw ore.
Even for those batteries that are truly mercury-free, recycling should be attempted. Because of the heavy metals they contain, environmental health risks are still present.
As one example, cadmium can accumulate in the environment by leaching into ground water and surface water from landfills, and it can enter the atmosphere through incinerator smokestack emissions. Effective air pollution control equipment at incinerators traps cadmium, which ends up in the ash, causing problems of cadmium in ashfill leachate. Cadmium is toxic to fish and wildlife and can pass to humans through the food chain. It has been associated with numerous human illnesses particularly lung and kidney damage. Once absorbed in the body, cadmium can remain for decades.
Battery manufacturers are producing more rechargeable batteries each year, relative to the number of non-rechargeable batteries produced. The National Electrical Manufacturers Association has estimated that U.S. demand for rechargeables is growing twice as fast as demand for non-rechargeables. Manufacturers and retailers are partnering to help increase the collection and recycling of used rechargeable batteries.
The U.S. DOT requires reporting of incidents involving batteries and battery-powered devices that result in a fire, violent rupture, explosion, or dangerous evolution of heat. Significant quantities of batteries should be labeled in accordance with DOT regulations.