![Electrolyte:
• The electrolyte is the medium that permits ionic conduction between
positive and negative electrodes of a cell. The electrolyte must have high
and selective conductivity for the ions that take part in electrode
reactions, but it must be a nonconductor for electrons in order to avoid
self-discharge of batteries. The electrolyte may be liquid, gel, or solid
material.
• Also, the electrolyte can be acidic or alkaline, depending on the type of
battery. Traditional batteries such as lead-acid and nickel-cadmium use
liquid electrolytes. In lead-acid batteries, the electrolyte is the aqueous
solution of sulfuric acid [H2SO4(aq)].
• Advanced batteries currently under development for EVs, such as sealed
lead-acid, nickel-metal-hydride (NiMH), and lithium-ion batteries use an
electrolyte that is gel, paste, or resin. Lithium-polymer batteries use a solid
electrolyte.](https://image.slidesharecdn.com/battery-240307142444-a0a2d375/85/BATTERY-pptx-presentation-Introduction-to-Electric-vehicles-4-320.jpg)
BATTERY.pptx presentation Introduction to Electric vehicles
- 1. BATTERY
- 2. BASICS • The batteries are made of unit cells containing the chemical energy that is convertible to electrical energy. One or more of these electrolytic cells are connected in series to form one battery. • The grouped cells are enclosed in a casing to form a battery module. A battery pack is a collection of these individual battery modules connected in a series and parallel combination to deliver the desired voltage and energy to the power electronic drive system.
- 3. Positive electrode: • The positive electrode is an oxide or sulfide or some other compound that is capable of being reduced during cell discharge. This electrode consumes electrons from the external circuit during cell discharge. Examples of positive electrodes are lead oxide (PbO2) and nickel oxyhydroxide (NiOOH). The electrode materials are in the solid state. Negative electrode: • The negative electrode is a metal or an alloy that is capable of being oxidized during cell discharge. This electrode generates electrons in the external circuit during cell discharge. Examples of negative electodes are lead (Pb) and cadmium (Cd). Negative electrode materials are also in the solid state within the battery cell.
- 4. Electrolyte: • The electrolyte is the medium that permits ionic conduction between positive and negative electrodes of a cell. The electrolyte must have high and selective conductivity for the ions that take part in electrode reactions, but it must be a nonconductor for electrons in order to avoid self-discharge of batteries. The electrolyte may be liquid, gel, or solid material. • Also, the electrolyte can be acidic or alkaline, depending on the type of battery. Traditional batteries such as lead-acid and nickel-cadmium use liquid electrolytes. In lead-acid batteries, the electrolyte is the aqueous solution of sulfuric acid [H2SO4(aq)]. • Advanced batteries currently under development for EVs, such as sealed lead-acid, nickel-metal-hydride (NiMH), and lithium-ion batteries use an electrolyte that is gel, paste, or resin. Lithium-polymer batteries use a solid electrolyte.
- 5. Separator: • The separator is the electrically insulating layer of material that physically separates electrodes of opposite polarity. • Separators must be permeable to the ions of the electrolyte and may also have the function of storing or immobilizing the electrolyte. • Present day separators are made from synthetic polymers.
- 6. There are two basic types of batteries: primary batteries and secondary batteries. The major types of rechargeable batteries considered for EV and HEV applications are: • Lead-acid (Pb-acid) • Nickel-cadmium (NiCd) • Nickel-metal-hydride (NiMH) • Lithium-ion (Li-ion) • Lithium-polymer (Li-poly) • Sodium-sulfur (NaS) • Zinc-air (Zn-Air)
- 7. LEAD-ACID BATTERY • Lead-acid batteries have been the most popular choice of batteries for EVs. Lead-acid batteries can be designed to be high powered and are inexpensive, safe, and reliable. A recycling infrastructure is in place for them. • However, low specific energy, poor cold temperature performance, and short calendar and cycle life are among the obstacles to their use in EVs and HEVs. • Relatively low cost • Easy availability of raw materials (lead, sulfur) • Ease of manufacture • Favorable electromechanical characteristics
- 10. ALTERNATIVE BATTERIES NICKEL-CADMIUM BATTERY • Nickel-cadmium (NiCd) and nickel-metal-hydride (NiMH) batteries are examples of alkaline batteries with which electrical energy is derived from the chemical reaction of a metal with oxygen in an alkaline electrolyte medium. • The specific energy of alkaline batteries is lowered due to the addition of weight of the carrier metal. • The NiCd battery employs a nickel oxide positive electrode and a metallic cadmium negative electrode.
- 11. • The practical cell voltage is 1.2 to 1.3 V, and the atomic mass of cadmium is 112. The specific energy of NiCd batteries is 30 to 50 Wh/kg, which is similar to that of lead-acid batteries. • The advantages of NiCd batteries are superior low-temperature performance compared to lead-acid batteries, flat discharge voltage, long life, and excellent reliability. The maintenance requirements of the batteries are also low. • The biggest drawbacks of NiCd batteries are the high cost and the toxicity contained in cadmium. • Environmental concerns may be overcome in the long run through efficient recycling, but the insufficient power delivered by the NiCd batteries is another important reason for not considering these batteries for EV and HEV applications.
- 13. Charging
- 14. NICKEL-METAL-HYDRIDE BATTERY • The nickel-metal-hydride battery is a successor to the nickel-hydrogen battery and is already in use in production HEVs. In NiMH batteries, the positive electrode is a nickel oxide similar to that used in a NiCd battery, while the negative electrode is a metal hydride where hydrogen is stored. • The concept of NiMH batteries is based on the fact that fine particles of certain metallic alloys, when exposed to hydrogen at certain pressures and temperatures, absorb large quantities of the gas to form the metalhydride compounds. • Furthermore, the metal hydrides are able to absorb and release hydrogen many times without deterioration
- 15. • The NiMH batteries have penetrated the market in recent years at an exceptional rate. The Chrysler electric minivan “Epic” uses a NiMH battery pack, which gives a range of 150 km. In Japan, NiMH battery packs produced by Panasonic EV Energy are being used in Toyota EV RAV-EV and Toyota HEV Prius. • The components of NiMH are recyclable, but a recycling structure is not yet in place. • NiMH batteries have a much longer life cycle than lead-acid batteries and are safe and abuse tolerant. • The disadvantages of NiMH batteries are the relatively high cost, higher self-discharge rate compared to NiCd, poor charge acceptance capability at elevated temperatures, and low cell efficiency. • NiMH is likely to survive as the leading rechargeable battery in the future for traction applications, with strong challenge coming only from lithium- ion batteries.
- 16. LI-ION BATTERY • The use of metallic-lithium is bypassed in Li-ion batteries by using lithium intercalated (absorbed) carbons (LixC) in the form of graphite or coke as the negative electrode, along with the lithium metallic oxides as the positive electrode. • The graphite is capable of hosting lithium up to a composition of LiC6. • The majority of the Li-ion batteries uses positive electrodes of cobalt oxide, which is expensive but proven to be the most satisfactory. • The alternative positive electrode is based on nickel oxide LiNiO2, which is structurally more complex but costs less. Performance is similar to that of cobalt oxide electrodes. • Manganese oxide-based positive electrodes (LiMn2O4 or LiMnO2) are also under research, because manganese is cheaper, widely available, and less toxic.
- 17. • Lithium-ion batteries have high specific energy, high specific power, high energy efficiency, good high-temperature performance, and low self- discharge. The components of Li-ion batteries are also recyclable. • These characteristics make Li-ion batteries highly suitable for EV and HEV and other applications of rechargeable batteries.
- 18. DISCHARGING
- 19. CHARGING
- 20. LI-POLYMER BATTERY • Lithium-polymer evolved out of the development of solid state electrolytes, i.e., solids capable of conducting ions but that are electron insulators. • The solid state electrolytes resulted from research in the 1970s on ionic conduction in polymers. These batteries are considered solid state batteries, because their electrolytes are solids. • The most common polymer electrolyte is polyethylene oxide compounded with an appropriate electrolyte salt. • The most promising positive electrode material for Li-poly batteries is vanadium oxide V6O13.
- 21. • Li-poly batteries have the potential for the highest specific energy and power. The solid polymers, replacing the more flammable liquid electrolytes in other type of batteries, can conduct ions at temperatures above 60°C. • The use of solid polymers also has a great safety advantage in case of EV and HEV accidents. Because the lithium is intercalated into carbon electrodes, the lithium is in ionic form and is less reactive than pure lithium metal. • The thin Li-poly cell gives the added advantage of forming a battery of any size or shape to suit the available space within the EV or HEV chassis. The main disadvantage of the Li-poly battery is the need to operate the battery cell in the temperature range of 80 to 120°C. • Li-poly batteries with high specific energy, initially developed for EV applications, also have the potential to provide high specific power for HEV applications. • The other key characteristics of the Li-poly are good cycle and calendar life.
- 22. ZINC-AIR BATTERY • Zinc-air batteries have a gaseous positive electrode of oxygen and a sacrificial negative electrode of metallic zinc. • The practical zinc-air battery is only mechanically rechargeable by replacing the discharged product, zinc hydroxide, with fresh zinc electrodes. • The discharged electrode and the potassium hydroxide electrolyte are sent to a recycling facility. In a way, the zinc-air battery is analogous to a fuel cell, with the fuel being the zinc metal.
- 23. SODIUM-SULFUR BATTERY • Sodium, similar to lithium, has a high electrochemical reduction potential (2.71 V) and low atomic mass (23.0), making it an attractive negative electrode element for batteries. • Moreover, sodium is abundant in nature and available at a low cost. Sulfur, which is a possible choice for the positive electrode, is also a readily available and low-cost material. The use of aqueous electrolytes is not possible due to the highly reactive nature of sodium, and because the natures of solid polymers like those used for lithium batteries are not known. • The solution of electrolyte came from the discovery of beta-alumina by scientists at Ford Motor Company in 1966. Beta-alumina is a sodium aluminum oxide with a complex crystal structure. • Despite several attractive features of NaS batteries, there are several practical limitations. The cell operating temperature in NaS batteries is around 300°C, which requires adequate insulation as well as a thermal control unit.
- 24. • Another disadvantage of NaS batteries is the absence of an overcharge mechanism. At the top-of-charge, one or more cells can develop a high resistance, which pulls down the entire voltage of the series-connected battery cells. • Yet another major concern is safety, because the chemical reaction between molten sodium and sulfur can cause excessive heat or explosion in the case of an accident. Safety issues were addressed through efficient design, and manufactured NaS batteries have been shown to be safe.
- 25. SODIUM-METAL-CHLORIDE BATTERY • The sodium-metal-chloride battery is a derivative of the sodium-sulfur battery with intrinsic provisions of overcharge and overdischarge. • The construction is similar to that of the NaS battery, but the positive sulfur electrode is replaced by nickel chloride (NiCl2) or a mixture of nickel chloride and ferrous chloride (FeCl2). The negative electrode and the electrolyte are the same as in a NaS battery. • In order to provide good ionic contact between the positive electrode and the electrolyte, both of which are solids, a second electrolyte of sodium chloraluminate (NaAlCl4) is introduced in a layer between NiCl2 and beta- alumina. • The NaAlCl4 electrolyte is a vital component of the battery, although it reduces the specific energy of the battery by about 10%.3 The operating temperature is again high, similar to that of the NaS battery.
- 26. • This procedure has two significant advantages: pure sodium is manufactured in situ through diffusion in beta-alumina, and the raw materials for the battery (common salt and metal powder) are inexpensive. • Although iron is cheaper than nickel, the latter is more attractive as the metallic component because of fewer complications and a wider operating temperature range. • Sodium chloride batteries are commonly known as ZEBRA batteries, which originally resulted from a research collaboration between scientists from the United Kingdom and South Africa in the early 1980s. • ZEBRA batteries have been shown to be safe under all conditions of use. They have high potential for being used as batteries for EVs and HEVs.