The materials from which the electrodes are made have a major affect on the battery chemistry, and hence affect the battery voltage and its charging and discharging characteristics. The geomtry of the eelctrode determines the internal series resitance and the charging and discharging rate.
The basic anode and cathode materials in a lead acid battery are lead and lead dixodie (PbO2). The lead electrode is in the form of sponge lead. Sponge lead is desirable as it is very porous, and therefore the surface area between the lead and the sulfic acid electrolyte is very large. The addition of small amoints of other elements to the lead electrode to form lead alloys can reduce several of the disadvantages associated with the lead. The main types of electrodes used are lead/antimony (using several percent antimony), lead/calcium alloys, and lead/antimony/calcium alloys.
Antimony lead alloy batteries have several advantages over pure lead electrodes. These advantages include: the lower cost of lead/antimony; the increased strength of the lead/anitmony electrode; and the ability to be deeply discharged for short period of time. However, lead/antimony alloys are prone to sulfation and should not be left at low states of charge for extended periods of time. I addition, lead/antimony alloys increase the gassing of the battery during charging leading to high levels of water loss. Since the water must be addedto these batteries, they have higher maintenance. Furthermore, lead/antimony batteries have a high discharge rate and a short lifetime. These problems (xx- check if both problems are caused by plating)) are caused by the dissolution ofantimony from one electrode and its deposition or plating on the other electrode. (xx the increased adhesion of PbO2 xx)
Lead calcium batteries are an intermediate cost technology. Like antimony, calcium also adds strength to the lead of the negative electrode, but unlike antimony, the addition of calcium reduces the gassing of the battery and also produces a lower self-discharge rate. However, lead calcium batteries should not be deeply discharged. Consequently, these types of batteries may be considered "maintenance-free", but are only shallow cycle batteries.
Adding antimony as well as calcium to the electrodes provides some of the advantages of both antimony and lead, but at an increased cost. Deep discharge batteries such as these can also have a high lifetime. Furthermore, trace amounts of other materials can be added to the electrodes to increase battery performance.
In addition to the material used to make the electrode plates, the physical configuration of the electrodes also has an impact on the charging and discharging rates and on the lifetime. Thin plates will allow faster charging and discharging, but are less robust and more prone to shedding of material from the plates. As high charging or discharging currents are not typically a required feature of batteries for renewable energy systems, thicker plates can be used, which have lower charge and discharge times, but also have longer lifetimes.