Metal Bulletin Research STRATEGIC OUTLOOK FOR THE PRIMARY BATTERY 2 | Seite 5

Battery Metals

3 Battery Chemistry
required for some electronic devices, Li-poly-Li-ion hybrid batteries are made which include a certain
amount of gelled electrolyte, reducing internal resistance and increasing the maximum current.
Typically Li-poly batteries have a higher average power density range than Li-ion batteries, at 130-200Wh/
kg, with some up to 250Wh/kg. They can be built into more varying shapes than Li-ion batteries and are
considered to be more rugged. However, they have a reduced lifespan in comparison with Li-ion batteries.
Like Li-ion batteries, they may overheat and potentially explode. They also require specific chargers, as the
cells in each Li-poly battery should be charged evenly.

3.7 Alkaline (Zinc-Manganese)

Alkaline batteries are the most common disposable/primary/non-rechargeable batteries used in personal
electronics. They consist of a zinc anode and a manganese dioxide cathode with a potassium hydroxide
electrolyte. Approximately 80% of batteries produced worldwide are alkaline batteries. Smaller alkaline
batteries will have a 1.5V rating, with less widely used forms having a 6- or 9-volt rating. Alkaline energy
density extends to between 80 and 145Wh/kg depending on size, which is typically higher than similarly
shaped rechargeable batteries using different chemistries. Alkaline batteries using manganese have an
energy density of between 66 and 99 W/kg.
The primary benefit of the alkaline battery is the low cost of its construction materials in relation to other
batteries. Zinc and manganese are and have been much cheaper than cadmium or cobalt for battery
manufacturers to purchase. They also have a much longer shelf life than other battery types, with a selfdischarge rate of around 2% a year, in comparison with 20-30% for batteries using nickel. Historically there
has been a problem with disposing of alkaline batteries, owing to the mercury used in their construction;
however, declining use of mercury has reduced their toxicity. The primary drawbacks of alkaline batteries
are their non-reusability and their tendency to leak their potassium hydroxide electrolyte if built poorly or
stored improperly.
Although the bulk of alkaline batteries produced are non-rechargeable, rechargeable ones have been
developed. Once the chemicals inside an alkaline battery cell have reached equilibrium, the cells cease to
produce electricity. The rechargeable alkaline battery works by reversing the electrical current to the battery,
which shifts the chemicals out of equilibrium. In order to reduce the crystallization of the zinc within the cell,
which prevents recharging, additives are introduced into either the cathode, anode or electrolyte solution.
A rechargeable alkaline battery will typically have an energy density of 80Wh/kg and a life cycle of 50-500
recharges. The primary benefit of rechargeable alkaline over Ni-MH or Ni-Cd is the absence of highly toxic
chemicals and the lower cost of the materials. However, they do not hold their recharge as long as these
battery types and they are not fully rechargeable; they lose capacity with each subsequent recharge at a
faster rate than Ni-MH or Ni-Cd.

3.8 Zinc-Air

Zinc-air batteries work by oxidizing zinc with oxygen [