A battery is an electronic cell that generates electricity by chemical reactions. A battery is a combination of multiple cells that are connected in series or parallel. However, the term is often used to refer to a single cell. A cell is composed of a negative and an electrolyte that conducts ions, as well as a separator and an ion conductor. The electrolyte can be either aqueous (made of water) or nonaqueous, and may come in liquid, paste, or solid forms. The negative electrode provides electrons to the cell when it is connected to an external device or load. These electrons flow through the load to the positive electrode and are then accepted by the cell. The reaction stops when the load is removed.
Primary batteries are those that can only convert their chemicals into electricity once, and must then be discarded. Secondary batteries have electrodes that can be reconstituted by passing electricity through them. Also known as a storage battery or rechargeable battery it can be used many times.
Nickel Cadmium Battery:-
Two plates make up a nickel-cadmium cell. When fully charged, the active material of the anode (positive plate) is Ni(OH),4. The cathode (negative plate) is of cadmium. The electrolyte consists of potassium hydroxide, KOH, and a small amount of lithium hydrate. This increases the battery’s capacity and longevity. The electrolyte has a specific gravity of 1.2.
Because the voltage produced from a single cell can be very low, it is necessary to connect multiple cells in series. This arrangement is called the nickel/cadmium battery.
These batteries have one more positive plate than negative plates. This battery’s container is connected to the positive plates by an electrical connection.
Nickel Hydrogen Battery:-
Nickel-hydrogen batteries combine the nickel-cadmium nickel battery’s positive nickel electrode with the negative nickel electrode (including the catalyst and gas diffusion elements) of fuel cells. The nickel oxyhydroxide and nickel oxyoxide electrodes are reduced to nickel hydroxide during discharge. The nickel electrode consumes water and the hydrogen electrode produces water. Therefore, the concentration of potassium hydroxide electrolyte doesn’t change.
The hydrogen pressure decreases as the battery is discharged, which provides a reliable indicator of the state of charge. One communication satellite battery had a pressure of over 500 pounds/square inches (3.4 MPa). It dropped to about 15 PSI (0.1MPa) when it was fully charged.
The oxygen from the nickel electrode reacts to the hydrogen in the cell, forming water.
These cells are subject to a high rate of self-discharge, which is a disadvantage. Chemical reduction of Ni(III), into Ni(II in the cathode.
A nickel-hydrogen battery offers specific energy that is 55-60 watts/kg. It also has a very long life expectancy (40,000 cycles at 40% DOD) and a longer operating life (>15 years) for satellite applications. The cells are capable of surviving overcharging and accidental reverse polarity.
The hydrogen pressure within the cell is a good indicator of the charge state. The gaseous nature of hydrogen makes it difficult to achieve high volume efficiency (60-100 Wh/L in an IPV cell). Also, high pressure is required which results in high-cost pressure vessels.
The positive electrode is composed of a dry porous Nickel plaque that has nickel Hydroxide. The negative hydrogen electrode uses a Teflon-bonded platinum Black catalyst at a loading rate of 7 mg/cm2. The separator is knit zirconia fabric (ZYK-15 Zircar).
Hubble replacement batteries can be made using a wet-slurry process. A binder agent and ground metallic materials are molded and then heated to boil off.
Primary lithium batteries have metallic lithium as an anode. These batteries are also known as lithium-metal or primary batteries.
Because of their high charging density, and high price per unit, they stand out from other batteries. The voltage range of lithium cells is dependent on their design and chemical composition. They can produce 1.5V (comparable with a Zinc-carbon, or Alkaline Battery) up to about 3.7V.
Secondary lithium-ion and a lithium-polymer are rechargeable batteries. Disposable primary lithium batteries must be distinguished from disposable secondary lithium-ion batteries. Because lithium can be used to move between the anode & the cathode using an intercalated li-ion compound for the cathode, but not using lithium metal for the anode, it is particularly useful.
Pure lithium reacts immediately with water or moisture in the atmosphere. Lithium-ion batteries are made from a less reactive substance.
Portable consumer electronics devices are often powered by lithium batteries. The term “lithium batteries” refers to a variety of lithium-metal chemistries. These include many types of cathodes, and electrolytes, and all of them with metallic lithium as their anode.
The battery needs 0.15 to 0.3kg of lithium per kWh. These primary systems are designed with a charged cathode. This is an electro-active material that has crystallographic vacancies and is gradually filled during discharge.
Most lithium cells used for consumer applications use metallic lithium as an anode and Manganese dioxide to serve as the cathode. A salt of lithium is added to an organic solvent to dissolve it.