1. BATTERIES

2. Battery :- Definition :  A battery is a storage device used for the storage of chemical energy and for the transformation of chemical energy into electrical energy  Battery consists of group of two or more electric cells connected together electrically in series. Battery acts as a portable source of electrical energy. Primary Batteries (or) Primary Cells Secondary Batteries (or) Secondary Cells Fuel Cells (or) Flow Batteries Photo voltaic Cell –Solar cell

7. 1) Primary Cell: In primary cells, a chemical reaction proceeds spontaneously and the free energy of the reaction is converted into electrical energy. The production of electrical energy at the expense of the free energy of the cell reaction is called DISCHARGING of the cell. In a primary cell the chemical reactions can’t be reversed by passing electricity through the cell and hence a discharged cell can’t be used again and the battery become dead. In a primary cell the cathode at which reduction occurs is designated positive by conversion. Eg: voltaic cell, Daniel cell, leclanche cell (or) dry cell, lithium cell….

8. Requirements of Primary cell: It should satisfy these requirements 1)It must be convenient to use. 2)Cost of discharge should be low. 3)Stand-by power is desirable. Dry cell (Leclanche Cell) It consists of a cylindrical Zinc container that acts as an anode. A graphite rod placed in the centre (but not touching the base) acts as a cathode. The space between anode and cathode is packed with the paste of NH4Cl and ZnCl2 and the graphite rod is surrounded by powdered MnO2 and carbon. The cell is called dry cell because of the absence of any liquid phase, even the electrolyte consists of NH4Cl,ZnCl2 and MnO2 to with starch is added to make a thick paste which prevents leakage. The graphite rod is fitted with a metal cap and the cylinder is sealed at the top with a pitch.

9. B. Leclanche Cell (or) Dry Cell :

10. The Zn-MnO2 cell (dry cell) is represented as Zn/Zn +2,NH4 + /MnO 2 /C (EMF = 1.5V) At anode : (Oxidation ) Zn(s)  Zn +2 (aq)+2e - At Cathode : (Reduction ) 2MnO 2 (s)+H 2 o+2e -  Mn 2 O 3 (s)+2OH – The net cell reaction is Zn(s)+2MnO 2 (s)+H2O  Zn 2+ + Mn 2 O 3 + 2OH - The resulting OH - ions react with NH4Cl to produce NH 3 which is not liberated as gas but immediately combines with the Zn 2+ and the Cl - ions to form a complex salt [Zn(NH3)2Cl2] (diammine dichloro zinc). 2 NH4Cl + 2 OH -  2NH 3 + Cl - +2 H2O Zn 2+ + 2NH 3 + 2 Cl -  [Zn(NH 3 ) 2 Cl 2 ]

11. Advantages: 1) These cells have voltage ranging from 1.25v to 1.50v. 2) Primary cells are used in the torches,radios,transistors,hearing aids,pacemakers,watches etc. 3) Price is low. Disadvantages: These cells does not have a long life, because the acidic NH4Cl corrodes the container even when the cell is not in use.

12. PH 0101 Unit-5 Lecture-712 3.Lithium battery Lithium is the lightest of metals and it can float on water. The electrochemical properties of lithium are excellent and it is also a highly reactive material. These properties gives Lithium the potential to achieve very high energy and power densities in high-density battery applications such as automotive and standby power. Lithium batteries are primary batteries in which lithiun metal (or) lithium compound acts as a Anode. A lithuim cell can produce voltage from 1.5 V to about 3 V based on the types of materials used.

13. PH 0101 Unit-5 Lecture-713 There are two types of lithium-based batteries available. 1.Lithium batteries 2.Lithium-ion batteries In lithium batteries, a pure lithium metallic element is used as anode. These types of batteries are not rechargeable. In lithium-ion batteries, lithium compounds are used as anode. These batteries are known as re-chargeable batteries. Therefore, Lithium ion batteries are considered as best than pure Lithium based batteries.

14. LITHIUM CELL: Li battery chemistry comprises a number of cell designs, in that Li is used as anode due to its light weight and highest standard potential greater than 3V.

16. Types of lithium cells: Three types : 1)Lithium primary cell with Liquid cathode 2) Lithium primary cell with solid cathode 3) Lithium primary cell with solid electrolyte

17. Liquid cathode cells: Anode : Li Cathode : SOCl 2 Electrolyte : LiAlCl 2 Anode : Li  Li + + e - Cathode : 4Li + + 4e - +2 SOCl 2  4 LiCl + SO 2 + S -------------------------------------------------------------------- Overall reaction : 4Li + + 2SOCl 2  4 LiCl + SO 2 + S

18. The discharging voltage is 3.3- 3.5 V. Uses: 1) They are used for military and space application. 2) In Medicinal devices like neuro- stimulators drug delivery system lithium batteries are widely used. 3) They are also used in electric circuit boards for supplying fixed voltage for memory protection and standby functions.

19. They perform best in low current applications and have a very long service life. For this reason they are used in pacemaker. {a medical device that uses electrical impulses, delivered by electrodes contacting the heart muscles, to regulate the beating of the heart. The primary purpose of a pacemaker is to maintain an adequate heart rate}electrodesheartheart rate

20. solid cathode (LiMnO 2 ) cell: Anode : Li Cathode : MnO 2 Electrolyte : propylene carbonate & 1,2-dimethoxy ethane Anode : xLi  Li + + e - Cathode : xLi + + e - + Mn +4 O 2  LiMn 1-x +4 Mn x +3 O 2 ----------------------------------------------------------------- xLi + Mn +4 O 2  LiMn 1-x +4 Mn x +3 O 2 ---------------------------------------------------------------------------------------------------

21. Uses: 1.Low rate cells are used commercially for small electronics and memory back up. 2.These cells can be used in temp conditions (-20 to 55 o c). 3.They are used generally for memory back up,watches and portable electronic devices

22. solid electrolyte cells: Anode : Li Cathode : poly -2- vinyl pyridine(P2VP) Electrolyte : solid LiI Anode : 2Li  2Li + + 2e - Cathode : 2Li + + 2e - + P2VP.n I 2  P2VP.(n-1) I 2 + 2LiI ----------------------------------------------------------------------------------- Overall reaction: 2Li + P2VP.n I 2  P2VP.(n-1) I 2 + 2LiI

23. These cells offer higher discharge rates due to the reactions occur at the cathode surface. The direct contact between the liquid cathode and the Li forms a film over the Li, called Solid Electrolyte Interface.(SEI) This prevents further chemical reaction when not in use, thus preserving the self life. The thick film causes an initial voltage delay.

25. 2)SECONDARY CELLS (ACCUMULATORS) : In secondary cells chemical reactions proceeds both in the forward and reverse directions depending on weather electrical energy is supplied from an external source Electrical energy is passed into the cell to induce a chemical reaction and the products remained at the electrodes, this process is called charging the cell. Secondary cells can accumulate electrical energy in the form of chemical reaction and later on the reaction is reversed to liberate electrical energy. Hence these cells are called accumulators or storage batteries. The cathode at which reduction occurs during the discharge of the cell is designated +ve. while it becomes anode during charging. Eg: lead-acid battery, alkaline storage battery, nickel –cadmium battery.

26. LEAD ACID BATTERY: This battery consists of a number of spongy lead anodes and a grid of lead dioxide coated lead-antimony alloy cathode. The electrode pairs separated by inert porus partitions are kept immersed in the electrolyte sulphuric acid.

29. Lead storage battery

31. Discharge In the discharged state both the positive and negative plates become lead(II) sulfate (PbSO 4 ) and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. The discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate in the external circuit. lead(II) sulfateelectrolytesulfuric acid Negative plate reaction: Pb(s) + HSO − 4 (aq) → PbSO 4 (s) + H + (aq) + 2e - Positive plate reaction: PbO 2 (s) + HSO − 4 (aq) + 3H + (aq) + 2e - → PbSO 4 (s) + 2H 2 O(l) The total reaction can be written: Pb(s) + PbO 2 (s) + 2H 2 SO 4 (aq) → 2PbSO 4 (s) + 2H 2 O(l) Fully Discharged: Two identical lead sulfate plates

32. Charging In the charged state, each cell contains negative plates of elemental lead (Pb) and positive plates of lead(IV) oxide (PbO 2 ) in an electrolyte of approximately 33.5% v/v (4.2 Molar) sulfuric acid (H 2 SO 4 ). The charging process is driven by the forcible removal of electrons from the positive plate and the forcible introduction of them to the negative plate by the charging source.lead(IV) oxideelectrolytesulfuric acid Negative plate reaction: PbSO 4 (s) + H + (aq) + 2e - → Pb(s) + HSO−4(aq) Positive plate reaction: PbSO 4 (s) + 2H 2 O(l) → PbO 2 (s) + HSO−4(aq) + 3H + (aq) + 2e - Fully Charged Lead and Lead oxide plates

33. There are few problems with this design if the cell voltages exceed 2.39v, the water breaks down into H2 and O2 and may lead to explosion. Another problem arising from this system is that fumes from the acid solution may have a corrosive effect on the area surrounding the battery. These cells have a low cycle life, a quick self discharge and low energy densities.

34. Uses: Electrical vehicles, gas engine ignition in telephone exchanges…. They are used in back-up power supplies for alarm and smaller computer systems (particularly in uninterruptible power supplies ("UPS")) and for electric scooters, electric wheelchairs, electrified bicycles, marine applications, battery electric vehicles or micro hybrid vehicles, and motorcycles. Large lead–acid batteries are also used to power the electric motors in diesel- electric (conventional) submarines and are used on nuclear submarines as well.back-up power electric scooterswheelchairselectrified bicycleshybrid vehicleselectric motorsdieselsubmarines

35. NICKEL-CADMIUM CELL: It consists of a steel grid containing cadmium powder as the anode and cathode made of NiO(OH)(s) An aqueous solution of KOH placed in an inert steel container is used as the electrolyte. The cell generates the voltage of 1.35v and the reaction may be represented as Cd +2OH -  Cd(OH) 2 +2 e- (at anode) 2NIO(OH) + 2H 2 O +2e-  2 Ni(OH) 2 +2OH- (at cathode) The net reaction is Cd +2NiO(OH) + 2H2O  Cd(OH) 2 + 2NI(OH) 2 The disadvantage of this battery is the reaction can be reversed, b’cos the reaction products Cd(OH) 2 & Ni(OH) 2 remain adhered to the electrodes called MEMORY EFFECT or FALSE BOTTOM.

36. applications: Ni-Cd battery, fairly recently developed is a portable,rechargeable cell and it is cell voltage 1.4v Like a dry cell, it can be packed in a sealed container. It can be left for long periods of time without any appreciable deterioration, since no gases are produced during discharging or charging It is used in calculators,flash units cordless electronic shavers and transistors.

37. The cell contains a paste of NaOH – this provides the OH - ions needed for the reaction, while also providing a medium to pass charge (electrolyte) The anode consists of solid metal which is transformed into cadmium hydroxide The cathode consists of Ni 3+ ions in a NiO(OH) paste which are transformed into nickel hydroxide

38. It is because the products of the reaction are solids that the Ni-Cd battery can be recharged The solid hydroxides are sticky, cling to the innards of the battery, and remain in place. If current is applied, the reaction can be driven backwards!

39. Nickel-Cadmium battery

40. PH 0101 Unit-5 Lecture-740 4.Lithium-ion battery (Li-ion Battery) Li-ion batteries are secondary batteries. The battery consists of a anode of Lithium, dissolved as ions, into a carbon. The cathode material is made up from Lithium liberating compounds, typically the three electro-active oxide materials, Lithium Cobalt-oxide (LiCoO 2 ) Lithium Manganese-oxide (LiMn 2 O 4 ) Lithium Nickel-oxide (LiNiO 2 )

41. PH 0101 Unit-5 Lecture-741 Principle During the charge and discharge processes, lithium ions are inserted or extracted from interstitial space between atomic layers within the active material of the battery. Simply, the Li-ion is transfers between anode and cathode through lithium Electrolyte. Since neither the anode nor the cathode materials essentially change, the operation is safer than that of a Lithium metal battery.

42. PH 0101 Unit-5 Lecture-742 Li-Ion battery Principle Li- ion Electrolyte

43. PH 0101 Unit-5 Lecture-743 Construction Li-ion cell has a four-layer structure. A positive electrode made with Lithium Cobalt Oxide has a current collector made of thin aluminum foil - cathode A negative electrode made with specialty carbon has a current collector of thin copper foil – anode A separator is a fine porous polymer film. An electrolyte made with lithium salt in an organic solvent.

44. PH 0101 Unit-5 Lecture-744 Construction cont.. The electrolytes are selected in such a way that there should be an effective transport of Li-ion to the cathode during discharge. The type of conductivity of electrolyte is ionic in nature rather than electronic

45. PH 0101 Unit-5 Lecture-745 Working The traditional batteries are based on galvanic action but Lithium ion secondary battery depends on an "intercalation" mechanism. This involves the insertion of lithium ions into the crystalline lattice of the host electrode without changing its crystal structure. These electrodes have two key properties. One is the open crystal structure, which allow the insertion or extraction of lithium ions and the second is the ability to accept compensating electrons at the same time. Such electrodes are called intercalation hosts.

46. PH 0101 Unit-5 Lecture-746 Working Cont… The chemical reaction that takes place inside the battery is as follows, during charge and discharge operation:

47. PH 0101 Unit-5 Lecture-747 The lithium ion is inserted and exerted into the lattice structure of anode and cathode during charging and discharging During discharge current flows through external circuit and light glows During charging, no the electrons flows in the opposite direction

48. PH 0101 Unit-5 Lecture-748

49. PH 0101 Unit-5 Lecture-749 During charging, lithium in positive electrode material is ionized and moves from layer to layer and inserted into the negative electrode. During discharge Li ions are dissociated from the anode and migrate across the electrolyte and are inserted into the crystal structure of the host compound of cathode. At the same time the compensating electrons travel in the external circuit and are accepted by the host to balance the reaction. The process is completely reversible. Thus the lithium ions pass back and forth between the electrodes during charging and discharging.

50. PH 0101 Unit-5 Lecture-750 Because of this reason, the lithium ion batteries are called ‘ Rocking chair, ‘Swing’ cells. A typical Li-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery as compared to lead acid batteries can sore only 25 watt-hours of electricity in one kilogram All rechargeable batteries suffer from self-discharge when stored or not in use. Normally, there will be a three to five percent of self- discharge in lithium ion batteries for 30 days of storage.

51. PH 0101 Unit-5 Lecture-751 Advantages They have high energy density than other rechargeable batteries They are less weight They produce high voltage out about 4 V as compared with other batteries. They have improved safety, i.e. more resistance to overcharge No liquid electrolyte means they are immune from leaking. Fast charge and discharge rate Disadvantage They are expensive They are not available in standard cell types. 5.Advantage, disadvantage and applications

52. PH 0101 Unit-5 Lecture-752 Applications The Li-ion batteries are used in cameras, calculators They are used in cardiac pacemakers and other implantable device They are used in telecommunication equipment, instruments, portable radios and TVs, pagers They are used to operate laptop computers and mobile phones and aerospace application

53. FUEL CELLS A fuel cell is an electrochemical cell which converts chemical energy contained in a easily available fuel oxidant system into electrical energy. The basic principle of a fuel cell is the chemical energy is provided by a fuel and an oxidant stored outside the cell. The fuel and the oxidizing agent are continuously and separately supplied to the electrodes of the cell at which they undergo reactions. These are also primary cells & they are capable of current as long as the reactants are supplied.

55. HYDROGEN – OXYGEN FUEL CELL It consists of two inert porous electrodes made of either graphite impregnated with finely divided Pt or a 75/25 alloy of Pd with Ag(Ni) and an electrolyte solution which is 25% KOH solution. Through the anode, H2 gas is bubbled and through the cathode O2 gas bubbled. At anode: 2H 2 (g) + 4OH-(g)  4H 2 O(l) + 4e- At cathode : O 2 (g) + 2H 2 O(l) + 4e-  4OH-(aq) Net rxn : 2H 2 (g) + O 2 (g)  2H 2 O(l) The emf of the cell is 0.8 to 1.0v A no of such cells are stacked together in series to make a battery, called fuel cell battery.

56. How does a Fuel Cell work?

57. Hydrogen-oxygen fuel cell

59. Uses of H2- O2 fuel cell They are used as auxiliary energy source in space vehicles (ex: Apollo space craft), submarines & other military vehicles. For space craft, they are preferred due to their lightness & product water is available as source of fresh water for astronauts. Fuel cells are categorized on the basis of electrolyte used: 1)Proton exchange membrane fuel cell 2)Alkaline Fuel cell 3) Molten carbonate Fuel cell 4) Phosphoric acid fuel cell 5) Solid oxide fuel cell

60. Methanol – Oxygen fuel cell

62. Photovoltaic Cells

63. Photovoltaic cells A solar cell (also called a photovoltaic cell) is an electrical device that converts the energy of light directly into electricity by the photovoltaic effect. It is a form of photoelectric cell (in that its electrical characteristics-- e.g. current, voltage, or resistance-- vary when light is incident upon it) which, when exposed to light, can generate and support an electric current without being attached to any external voltage source. They are the most cost-efficient choice for energy production in remote areas with little or no infrastructure,including rural households in developing countries. Centralizedpower generation by PV systems is ten times more expensive than conventional sources of electricity.lightelectricityphotovoltaic effect

64. A solar cell made from a monocrystalline silicon wafer monocrystalline siliconwafer Solar cells can be used to build small solar collection devices such as this portable monocrystalline solar charger.monocrystalline A monocrystalline solar cell

65. The term "photovoltaic" comes from the Greek φ ῶ ς (phōs) meaning "light", and from "Volt", the unit of electro-motive force, the volt, which in turn comes from the last name of the Italian physicist Alessandro Volta, inventor of the battery (electrochemical cell). The term "photo- voltaic" has been in use in English since 1849. GreekvoltItalian Alessandro Voltaelectrochemical cell

66. Photovoltaics is the field of technology and research related to the practical application of photovoltaic cells in producing electricity from light, though it is often used specifically to refer to the generation of electricity from sunlight. Cells can be described as photovoltaic even when the light source is not necessarily sunlight (lamplight, artificial light, etc.). In such cases the cell is sometimes used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.Photovoltaicsphotodetector infrared detectors electromagnetic radiation

67. The operation of a photovoltaic (PV) cell requires 3 basic attributes: The absorption of light, generating either electron-hole pairs or excitons.electronholeexcitons The separation of charge carriers of opposite types. The separate extraction of those carriers to an external circuit. In contrast, a solar thermal collector collects heat by absorbing sunlight, for the purpose of either direct heating or indirect electrical power generation. "Photoelectrolytic cell" (photoelectrochemical cell), on the other hand, refers either a type of photovoltaic cell (like that developed by A.E. Becquerel and modern dye- sensitized solar cells) or a device that splits water directly into hydrogen and oxygen using only solar illumination.solar thermal collectorphotoelectrochemical cellA.E. Becquereldye- sensitized solar cells

68. Applications Solar powered house Water pumping systems Garden lights Automobiles Source utility grid Satellites, shuttles In the most popular application of a solar powered house, PV cells absorb photons, send DC current through an inverter which transforms the signal to 120 or 240-volt so AC appliances can be used. The AC power enters the utility panel in the house and is then distributed to appliances throughout the house. Electricity that is not used will be recycled and reused in other facilities[2,6].

69. Conclusions Environmentally benign Inefficient  uncommon  Still fuel Future  Efficiency increasing  Cheaper Because current PV systems are still highly inefficient and uncommon, they are not yet cost competitive with fossil fuel- based generators and are only regularly used where there is no nearby power source