Class 12- Electrochemistry || Primary & secondary battery || fuel cell || lead storage battery
A rechargeable battery, storage battery, or secondary cell, (or archaically accumulator) is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery, which is supplied fully charged and discarded after use. It is composed of one or more electrochemical cells. The term "accumulator" is used as it accumulates and stores energy through a reversible electrochemicalreaction. Rechargeable batteries are produced in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network. Several different combinations of electrode materials and electrolytesare used, including lead–acid, zinc-air, nickel–cadmium (NiCd), nickel–metal hydride (NiMH), lithium-ion (Li-ion), and lithium-ion polymer (Li-ion polymer).
Secondary Battery: The Lead Storage Battery
The electrodes of the cells in a lead storage battery consist of lead grids. The openings of the anodic grid is filled with spongy (porous) lead. The openings of the cathodic grid is filled with lead dioxide {PbO2}. Dilute sulfuric acid {H2SO4} serves as the electrolyte. When the battery is delivering a current, i.e.discharging, the lead at theanode is oxidized:
Pb Pb2+ + 2 e–
Because the lead ions are in the presence of aqueous sulfate ions (from the sulfuric acid), insoluble lead sulfate precipitates onto the electrode. The overall reaction at the anode is therefore:
Pb + SO42– PbSO4 (electrode) + 2 e–
Electrons that flow from the anode simultaneously reduce the lead dioxide at the cathode:
2 e– + PbO2 + 4 H+ Pb2+ + 2 H2O
Again, the lead ions that are formed react with aqueous sulfate ions to form insoluble lead sulfate on the electrode, and the overall reaction at the cathode is:
2 e– + PbO2 + 4 H+ + SO42– PbSO4 (electrode) + 2 H2O
Fuel Cells
A fuel cell is a tiny device, capable of generating electricity by force of a chemical reaction. In the presence of two electrodes, a fuel cell generates electricity.
Within every fuel cell are two electrodes, known as anode and cathode. These electrodes are the base around which the respective chemical reactions take place, making it possible for electricity to be generated. Every fuel cell consists of electrolytes, which essentially carry the electrically charged particles from the anode to the cathode and vice versa. Thus, electrolytes act as the catalyst which makes it possible for the chemical reaction to take place in a speedy manner.
What are the Advantages of Fuel Cells?More efficient: Fuel cells prove to be much more efficient than a normal combustion engine since it converts chemical energy directly into electrical energy. In comparison to the other powering mechanism devices, the fuel cells are largely effective. They have a direct channel for energy to get converted, without undergoing a double conversion process. Thus, these are widely recommended.Saves wasteful emission: Unlike other cells which generate greenhouse gases in the process of energy conversion, fuel cells prove to be a major improvement as the only emission that they create are heat and water. Hence, great for the environment.More stable: The fuel cells assure minimal movement of various parts within and around the cell. They are, therefore, more reliable and convenient than a traditional cell.Takes care of natural resources: The process of atom separation and energy generation is very clean and an ergonomic method in fuel cells. Thus, beneficial for natural resources.