Lithium-Ion and Other Cell Chemistries 67 Table 1: Non Lithium-based chemistries power applications where weight and size are not issues and cost sensitivity is important. It is still the most readily available battery and continues to set the cost targets for other chemistries. A lead acid battery consists of a grouping of lead plates or lead grids that are coated with a paste made of red lead and sulfuric acid. Those plates are then connected in series and immersed in an acid solution that acts as the electrolyte. The positive plates are typically made from lead dioxide while the negative plates are made from “spongy” lead.
Many current plate or grid designs alloy a material such as antimony, tin, calcium, or selenium into the lead plate in order to improve the manufacturing process and quality and to add strength to the historically weak lead plate structures. The plates are most often separated by a plastic divider to separate the positive from the negative plates in order to prevent short circuiting. There are usually an odd number of plates and every other plate is connected together in series, one half form up the positive pole (cathode) and the remainder of the plates form the negative pole (anode) ( Figure 1 ).
The active material in the plates (lead) absorbs sulfur from the acid electrolyte during dis- charge and then the sulfur flows back into the electrolyte when the battery is charged.
Over time this process tends to cause the active material on the plates to flake off and collect at the Lead Acid Nickel Cadmium Nickel Metal Hydride Sodium Sulfur Sodium Nickel Chloride Chemistry PbA/LAB NiCd NiMh NaS NaNiCl descriptor Specific energy 30–40 40–60 30–80 90–110 100–120 (Wh/kg) Energy density 60–70 50–150 140–300 345 160–190 (Wh/L) Specific power 60–180 150 250–1000 150–160 150 (W/kg) Power density 100 210 400 – – (W/L) Nominal 2.0 1.2 1.2 2.0 2.6 voltage (per cell) (V) Cycle life 300–800 1000–2000 500–1500 1000–2500 1000 Self-discharge 3–5% 20% 30% 0% 0% (% per month) Operating −20 to +60 −40 to +60 −20 to +60 300 to 400 300 to 400 temperature range (°C) Cost (per kWh) $150–$200 $400–$800 $200–$300 $350 $100–$300 Maintenance 3–6 months 30–60 days 60–90 days None None