SixLinks Wiki

Research: Should distinguish between Energy and Power here as well as a basic battery intro. Also, this needs to be constantly updated, this more or less is our metric. Also might be cool to apply some of these metrics to large scale storage.

Metric	Importance	Lead Acid (23)	NiCd (24)	NiMH (25)	Litium Ion (26)
Charge/Discharge Efficiency	% of energy entered vs. energy returned	70-92%	70-90%	66%	99.9%
Energy to Weight	Amount of energy stored per weight	30-40 Wh/kg	40-60 Wh/kg	30-80 Wh/kg	160 Wh/gk
Energy to Volume	Amount of energy stored per volume	60-75 Wh/L	50-150 Wh/L	140-300 Wh/L	270 Wh/L
Power to Weight	Amount of work stored per weight	180 W/kg	150 W/kg	250-1000 W/kg	1800 W/kg
Self-Discharge Rate	% energy lost over time	3-20%/month	10%/month	30%/month temp. dependent	None in \"dumb\" batteries, 5-10%/month in \"smart\"
Nominal Cell Voltage	Voltage of each cell	2.105V	1.2V	1.2 V	3.6/3.7 V
Lifespan	Number of hours or cycles the battery will last	500-800 cycles	2000 cycles	500-1000 cycles	1200 cycles or 24-36 months
Energy to Cost	Amount of energy stored per dollar	7-18 Wh/$	Unknown	2.75 Wh/$	2.8-5 Wh/$

Different technologies and where they are (efficiency, power density, cost, toxicity, lifespan) (Table in (28))

Lead Acid:

Oldest type of rechargable battery (1859) (23). It consists of electrodes of lead metal (Pb) and lead (IV) dioxide (PbO2) in an electrolyte of about 33.5% w/w (6 Molar) sulfuric acid (H2SO4).

Pros

• Low Cost
• Established technology

Cons

• Don't mix well, can discharge or charge only the interface (surface)
• Heavy for the amount of energy they can store
• Toxicity: Acid in disposal, lead smelting is very energy consuming but lead recycling campaigns have been very successful

NiCd:

Low voltage batteries with a high discharge current, a NiCd battery contains a nickel hydroxide positive electrode, a cadmium negative electrode, and an alkaline electrolyte (potassium hydroxide).

Pros

• Much higher power density than lead acid batteries
• Can be very deeply discharged, are often stored at 0% charge
• Very long lifespan
• Minimal loses at high discharge rates
• Can charge and discharge much quicker than lead acid

Cons

• A short circuit can cause the battery to explode
• Can short cycle
• As the cell temperature rises, internal resistance falls. In a typical charging system lead acid batteries are used for, the current to continue to rise until the over current triggers or the battery destroys itself. These batteries would need a more complicated charging system
• Cadmium is very toxic
• Very labor intensive to make and includes some very expensive materials

NiMH:

NiMH batteries are very similar to NiCd except that the cadmium is replaced with an intermetallic compound. Many different compounds have been developed for this application, but those in current use fall into two classes. The most common is AB5, where A is a rare earth mixture of lanthanum, cerium, neodymium, praseodymium and B is nickel, cobalt, manganese, and/or aluminium. Very few batteries use higher-capacity negative material electrodes based on AB2 compounds, where A is titanium and/or vanadium and B is zirconium or nickel, modified with chromium, cobalt, iron, and/or manganese, due to the reduced life performances

Pros

• Nickel is recycled and there is no use of cadmium, so the total environmental impact depends on the other metal used, but is usually less than NiCd
• 2-3 times the capacity of NiCd

Cons

• Very high self discharge rate, 5-10% on the first day, and 0.5-1% per day after that at room temperature
• Short lifespan, although one manufacturer claims they can maintain 70-85% of their capacity after one year by using a new separator if the battery is stored at room temperature

Lithium Ion:

Litium Ion batteries are the battery technology most people in the auto industry are resting their hopes on. It is currently used for home electronics, such as laptops. Both the anode and cathode are materials into which and from which lithium can migrate. The process of lithium moving into the anode or cathode is referred to as insertion (or intercalation), and the reverse process, in which lithium moves out of the anode or cathode is referred to as extraction (or deintercalation). When a cell is discharging, the lithium is extracted from the anode and inserted into the cathode. When the cell is charging, the reverse process occurs: lithium is extracted from the cathode and inserted into the anode. The anode of a conventional Li-ion cell is made from carbon, the cathode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent.

Pros

• Very high efficiency
• Very low discharge rate
• No \"memory\" or \"short cycling\"
• Very light

Cons

• Most dangerous of the batteries to handle
• Least durable of the batteries, with a limit not just on the number of possible cycles, these batteries also degrade over time regardless of use
• Performance is temperature dependent
• Have safety issues with possible overheating
• If they are discharged too deeply, they may never return to health
• Expensive