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A Review of Rechargeable Battery Technologies Naveen SINGAMSETTI, Sabri TOSUNOGLU Department of Mechanical and Materials Engineering, Florida International University Miami, Florida 33174, USA ABSTRACT Modern day dependence on the electricity has grown enormously, especially the portable form of energy storage systems; that is, batteries. The exponential growth in the modern day-to-day usage of electronic devices, such as cellphones, mp3 players, tablets, laptops, and so on, demands a more efficient way of storing excess amount of energy. Hence, rechargeable batteries represent a very important area of technology where improvements would greatly help engineers to create longer-lasting, lighter devices and reduce waste at the same time. In order to develop new batteries, a basic understanding of available battery technologies is important and this paper focuses on reviewing most important rechargeable battery types and assesses advantages and disadvantages. Keywords: Rechargeable batteries, classification, primary battery, secondary battery. 2. CLASSIFICATION OF CELLS & BATTERIES Electrochemical cells and batteries are identifies as primary or secondary (rechargeable), depending on their capability of being electrically recharged. Within this classification, other classifications are used to identify particular structures or designs. The classification is as follow: 1. CELLS AND BATTERIES A battery is a device that converts the chemical energy contained in its active materials directly into electric energy by means of an electrochemical oxidation-reduction (redox) reaction. This type of reaction involves the transfer of electrons from one material to another through an electric circuit. Batteries currently contain one or more of the following eight metals: cadmium, lead, zinc, manganese, nickel, silver, mercury and lithium. While the term ‘‘battery’’ is often used, the basic electrochemical unit being referred to is the ‘‘cell.’’ Cell: A cell is the basic electrochemical unit providing a source of electrical energy by direct conversion of chemical energy. Battery: A battery consists of one or more electrochemical cells, electrically connected in an appropriate series/parallel arrangement to provide the required operating voltage and current levels, including, if any, monitors, controls and other ancillary components, case, terminals and markings . The primary battery is a convenient, usually inexpensive, lightweight source of packaged power for portable electronic and electric devices, lighting, photographic equipment, toys, memory backup, and a host of other applications, giving freedom from utility power. The general advantages of primary batteries are good shelf life, high energy density at low to moderate discharge rates, little, if any, maintenance, and ease of use. Although large high- capacity primary batteries are used in military applications, signaling, standby power, and so on, the vast majority of primary batteries are the familiar single cell cylindrical and flat button batteries or multicell batteries using these component cells. Major Components of Cells: 1. The anode or negative electrode: the reducing or fuel electrode—which gives up electrons to the external circuit and is oxidized during the electrochemical reaction. 2. The cathode or positive electrode: the oxidizing electrode—which accepts electrons from the external circuit and is reduced during the electrochemical reaction. 3. The electrolyte: the ionic conductor—which provides the medium for transfer of charge, as ions, inside the cell between the anode and cathode. The electrolyte is typically a liquid, such as water or other solvents, with dissolved salts, acids, or alkalis to impart ionic conductivity. Some batteries use solid electrolytes, which are ionic conductors at the operating temperature of the cell. Primary Cells or Batteries The term “primary” was first used to describe this type based on the fact that the materials inside the battery were the prime source of the electric power it delivered. These batteries are not capable of being easily or effectively recharged electrically and, hence, are discharged once and discarded. Many primary cells in which the electrolyte is contained by an absorbent or separator material (there is no free or liquid electrolyte) are termed ‘‘dry cells.’’ Secondary or Rechargeable Cells or Batteries Passing current through them in the opposite direction to that of the discharge current can recharge these batteries electrically. They are storage devices for electric energy and are known also as ‘‘storage batteries’’ or ‘‘accumulators.’’ The applications of secondary batteries fall into two main categories: (i) Those applications in which the secondary battery is used as an energy-storage device, generally being electrically connected to and charged by a prime energy source and delivering its energy to the load on demand. Examples are automotive and aircraft systems, emergency no-fail and standby (UPS) power sources, hybrid electric vehicles and stationary energy storage (SES) systems for electric utility load leveling. (ii). Those applications in which the secondary battery is used or discharged essentially as a primary battery, but recharged after use rather than being discarded. Secondary batteries are used in this manner as, for example, in portable consumer electronics, power tools, electric vehicles, etc., for cost savings (as they can be recharged rather than replaced), and in applications requiring power drains beyond the capability of primary batteries. The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012. 3. COMPONENTS OF A CELL A cell is a basic building block of all batteries. It consists of two electrodes (an anode and a cathode), electrolyte, a separator between the anode and cathode, and some type of cell container. Anode Anode is the negative electrode. It is the reducing electrode, also known as the fuel electrode. The anode gives up its electrons to the external circuit and is oxidized in the process. Anodes are made from materials with very few electrons in their valence shell. Almost all anodes are made from either metals or compounds that include metals. Cathode The positive electrode, also known as the oxidizing electrode. This is designed to accept electrons from the external circuit and is reduced in the process. Cathodes are made from materials that have nearly full valence shells. Cathodes are typically made from compounds that include oxygen, chlorine, or both. Electrolyte The ionic conductor. While the electrons pass through the external circuit, the electrode materials inside the cell change into ions. In order to sustain the flow of electrons, the newly formed ions have to pass between the electrodes through the electrolyte. Electrolytes are typically either acids or bases (alkaline), although newer technologies tend to use organic solvent and salt solutions. Acids, bases, and salt solutions all make good ionic conductors. Separator The separator provides insulation between the anode and cathode while allowing ionic transport between the electrodes. 4. ELECTROCHEMICAL ACTION When the anode is connected to the cathode through an external circuit, the cell undergoes discharge. REDOX occurs: the anode material loses electrons (oxidation) and the cathode material gains electrons (reduction). For rechargeable batteries, applying a voltage in the reverse direction (from discharge) institutes REDOX in the opposite direction. In a battery, REDOX occurs only at the surface of the electrodes. A reaction involving the entire mass of both a reducing agent and an oxidizer would be either a fire or an explosion. Discharge The flow of electrons from the anode to the cathode through an electric circuit. Ions form on both electrodes and flow through the electrolyte to react with one another to form new stable compounds. In most practical batteries, the discharge product is formed on the surface of the cathode. Charge The flow of electrons from the cathode to the anode induced by an external power source. The discharge product separates out into ions that travel through the electrolyte. The original electrode materials return to their starting points Cell Voltage Cell voltage is dependent in part on the electrode potential of the materials chosen, typically referred to as the “standard reduction potential”. A table of common electrode potentials is given in table 1 and the theoretical voltage of a given cell is the difference in potential between the two materials. This can be determined using a number line in figure 1. Figure 1 Number line showing theoretical cell voltage Table 1 Electrode potential for some common battery chemistries ANODE MATERIALS CATHODE MATERIALS Material Potential Material Potential Zinc Zinc Lithium Lead Cadmium Hydroxide -0.76 (in acid electrolyte) -1.25 (in base electrolyte) -3.01 -0.13 -0.81 Chlorine Oxygen Sulfur Dioxide Lead Dioxide Nickel (as NiOOH) 1.36 1.23 0.0 1.69 0.49 El e c t r o n f l o w (-) El e c t r o n f l o w (+ ) D IS C H A R G E (-) (+ ) CHARGE Figure 2 Discharge and charge process in a basic cell The potential is an “absolute” value, determined by the total value between the two points. The lithium sulfur dioxide potential is obvious, since sulfur dioxide has a zero-volt potential. The absolute value of the difference between them is 3.01 volts. The nickel-cadmium potential isn’t so obvious. The absolute difference between –0.81 volts and +0.49 volts is 1.30 volts, the total difference between them, or rather, the total distance between the two points on the number line. 5. IMPORTANT RECHARGEABLE BATTERY TYPES i. Lead acid batteries Brief History Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large powerto-weight ratio. These features, along with their low cost, make them attractive for use in motor vehicles to provide the high current required by automobile starter motors. Table 2 Lead acid battery characteristics Specific energy Energy density Specific power Charge discharge efficiency Self discharge rate Cycle durability Nominal cell voltage 30-40 Wh/kg 60-75 Wh/l 180 W/kg 50%-92% 3-20% / month 500-800 cycles 2.105 volts The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012. 5. 6. performance Good float service Low cost compared with other secondary batteries Disadvantages 1. Relatively low cycle life (50–500 cycles) 2. Limited energy density—typically 30–40 Wh/kg 3. Difficult to manufacture in very small sizes 4. Hydrogen evolution in some designs can be an explosion hazard 5. Stibene and arsine evolution in designs with antimony and arsenic in grid alloys can be a health hazard Figure 2 Schematic of Lead acid battery Electrochemistry In the charged state, each cell contains negative electrodes of elemental lead (Pb) and positive electrodes of lead(IV) oxide (PbO2) in an electrolyte of approximately 33.5% v/v (4.2 Molar) sulfuric acid (H2SO4). In the discharged state both the positive and negative become lead (II) sulfate (PbSO4) and the electrolyte loses much of its dissolved sulfuric acid and becomes primarily water. Due to the freezing-point depression of water, as the battery discharges and the concentration of sulfuric acid decreases, the electrolyte is more likely to freeze during winter weather. During discharge, both plates return to lead sulfate. The process is driven by the conduction of electrons from the positive plate back into the cell at the negative plate. Applications Automotive, marine, aircraft, diesel engines in vehicles and for stationary power, Industrial trucks, Electric vehicles, golf carts, hybrid vehicles, mine cars, personnel carriers ii. Alkaline battery Brief History The first generation rechargeable alkaline technology was developed by Battery Technologies Inc. in Canada and licensed to Pure Energy, EnviroCell, Rayovac, and Grandcell. Subsequent patent and advancements in technology have been introduced. The shapes include AAA, AA, C, D, and Snap-on 9-volt batteries. Rechargeable alkaline batteries have the ability to carry their charge for years, unlike most NiCd and NiMH batteries which self-discharge in 90 days (see below **). However, new low self-discharge NiMH cells, such as Sanyo "Eneloop", claim to retain 90% charge after 1 year. If produced properly, rechargeable alkaline batteries can have a charge/recharge efficiency of as much as 99.9% and be an environmentally friendly form of energy storage. Negative Plate Reaction: Pb(s) + HSO−4(aq) → PbSO4(s) + 2e− Positive Plate Reaction: PbO2(s) + HSO-4(aq) + 3H+(aq) + 2e− → PbSO4(s) + 2H2O(l) Subsequent charging places the battery back in its charged state, changing the lead sulfates into lead and lead oxides. The process is driven by the forcible removal of electrons from the negative plate and the forcible introduction of them to the positive plate. Negative Plate Reaction: PbSO4(s) + H+(aq) + 2e− → Pb(s) + HSO−4(aq) Figure 3 Schematic of alkaline manganese dioxide battery Positive Plate Reaction: PbSO4(s) + 2H2O(l) → PbO2(s) + HSO−4(aq) + 3H+(aq) + 2e− Table 3 Alkaline battery characteristics Overcharging with high charging voltages generates oxygen and hydrogen gas by electrolysis of water, which is lost to the cell. Periodic maintenance of lead acid batteries requires inspection of the electrolyte level and replacement of any water that has been lost. Advantages 1. Popular low-cost secondary battery—capable of manufacture on a local basis, worldwide, from low to high rates of production 2. Available in large quantities and in a variety of sizes and designs—manufactured in sizes from smaller than 1 Ah to several thousand Ampere-hours 3. Good high-rate performance—suitable for engine starting 4. Moderately good low- and high-temperature Specific energy Energy density Specific power Charge discharge efficiency Self discharge rate Cycle durability Nominal cell voltage 85 Wh/kg 250 Wh/l 50 W/kg 85% 12% / month 100-1000 cycles 1.5 volts Electrochemistry In an alkaline battery, the anode (negative terminal) is made of zinc powder, which gives more surface area for increased current, and the cathode (positive terminal) is composed of manganese dioxide. Unlike zinc-carbon (Leclanché) batteries, the electrolyte is potassium hydroxide rather than ammonium chloride or zinc chloride. The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012. The half-reactions are Zn(s) + 2OH−(aq) → ZnO(s) + H2O(l) + 2e− 2MnO2(s) + H2O (l) + 2e− →Mn2O3(s) + 2OH−(a A single charge/discharge process makes a cycle. Advantages 1. Low initial cost (and possible lower operating cost than other rechargeable batteries) 2. Manufactured in a fully charged state 3. Good retention of capacity 4. Completely sealed and maintenance-free 5. No ‘‘memory effect’’ problem Disadvantages 1. Useful capacity about two-thirds of primary battery but higher than most rechargeable batteries 2. Limited cycle life 3. Available energy decreases rapidly with cycling and depth of discharge 4. Higher internal resistance than NiCd and NiMH iii. Nickel iron battery Brief History The nickel–iron battery (NiFe battery) is a storage battery having a nickel (III) oxide-hydroxide cathode and an iron anode, with an electrolyte of potassium hydroxide. The active materials are held in nickel-plated steel tubes or perforated pockets. It is a very robust battery, which is tolerant of abuse, (overcharge, over discharge, and short-circuiting) and can have very long life even if so treated. It is often used in backup situations where it can be continuously charged and can last for more than 20 years. Due to its low specific energy, poor charge retention, and its high cost of manufacture, other types of rechargeable batteries have displaced the nickel–iron battery in most applications. They are currently gaining popularity for off-the-grid applications where daily charging makes them an appropriate technology Electrochemistry The cell electrodes are able to store energy obtained from an exterior charging source to return this energy. To do this they need to be immersed in an electrolyte. Initial active material of the positive electrodes is nickel dihydroxide and active material of the negative electrode is ferrous dihydroxide. The basic processes taking place in accumulators during charging and discharging can be represented with the following equation. Charge: 2Ni(OH)2 + Fe(OH)2 2NiOOH + 2H2O Discharge: 2NiOOH + 2H2O 2Ni(OH)2 + Fe(OH)2 During charging, the basic current generating process of ferrous reduction will consume water and release oxygen from negative (iron) plate, and oxidation of nickel dihydroxide will release hydrogen from the positive (nickel) plate. During discharge, ferrous oxidation will consume water and release hydrogen from the negative plate and reduction at the positive plate will consume water and release oxygen. Also during charging a certain amount of electrolysis of water from the electrolyte takes place, with the formation of hydrogen at the negative electrode and oxygen on the positive electrode. Figure 4 Changes that occur during charge and discharge of a nickel iron cell Table 4 Nickel iron battery characteristics Specific energy Energy density Specific power Charge discharge efficiency Self discharge rate Cycle durability Nominal cell voltage 85 Wh/kg 250 Wh/l 50 W/kg 85% 12% / month 100-1000 cycles 1.5 volts Advantages 1. Physically almost indestructible 2. Long life 3. Withstands electrical abuse: discharged, short-circuiting overcharge, over Disadvantages 1. High self-discharge 2. Hydrogen evolution on charge and discharge 3. Low power density 4. Damaged by high temperatures Applications 1. Railways 2. Mining industry 3. Industrial enterprises 4. Various equipment 5. Electric cars and bikes 6. Solar, renewable power storage iv. Nickel cadmium battery Brief History The nickel–cadmium battery (Ni–Cd battery) (commonly abbreviated NiCd or NiCad) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all Ni–Cd batteries. The abbreviation NiCd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd). Electrochemistry Ni–Cd batteries usually have a metal case with a sealing plate equipped with a self-sealing safety valve. The positive and negative electrode plates, isolated from each other by the separator, are rolled in a spiral shape inside the case. This is known as the jellyroll design and allows a Ni–Cd cell to deliver a much higher maximum current than an equivalent size The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012. alkaline cell. Alkaline cells have a bobbin construction where the cell casing is filled with electrolyte and contains a graphite rod, which acts as the positive electrode. As a relatively small area of the electrode is in contact with the electrolyte (as opposed to the jelly-roll design), the internal resistance for an equivalent sized alkaline cell is higher which limits the maximum current that can be delivered. The chemical reactions during discharge are: Cd + 2OH- Cd(OH)2 + 2eat the cadmium electrode, and 2NiO(OH) + 2H2O + 2e- 2Ni(OH)2 + 2OHat the nickel electrode. The net reaction during discharge is 2NiO(OH) + Cd + 2H2O 2Ni(OH)2 + Cd(OH)2 During recharge, the reactions go from right to left. The alkaline electrolyte (commonly KOH) is not consumed in this reaction and therefore its Specific Gravity, unlike in lead–acid batteries, is not a guide to its state of charge. small electronics Used in cord less phones, wireless telephones, emergency lighting v. Lithium ion batteries Brief History A lithium-ion battery (sometimes Li-ion battery or LIB) is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types. Unlike lithium primary batteries (which are disposable), lithium-ion electrochemical cells use an intercalated lithium compound as the electrode material instead of metallic lithium. 3. Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, no memory effect, and a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for military, electric vehicle, and aerospace applications. Research is yielding a stream of improvements to traditional LIB technology, focusing on energy density, durability, cost, and intrinsic safety. Figure 6 Schematic diagram of a wound prismatic cell Figure 5 Schematic of Nickel cadmium battery Advantages 1. Rugged; can withstand electrical and physical abuse 2. Long cycle life 3. Reliable; no sudden death 4. Good charge retention 5. Excellent long-term storage 6. Low maintenance Disadvantages 1. Low energy density 2. Higher cost than lead-acid batteries 3. Contains cadmium Applications 1. Used in portable electronics and toys. 2. Comes in the forms of button cells and can be used in Specific energy Energy density Specific power Charge discharge efficiency Self discharge rate Cycle durability Nominal cell voltage 40-60 Wh/kg 50-150 Wh/l 150 W/kg 70-90% 10% / month 2000 cycles 1.2 volts Table 5 Lithium ion battery characteristics Specific energy Energy density Specific power Charge discharge efficiency Self discharge rate Cycle durability Nominal cell voltage 100-250 Wh/kg 250-620 Wh/l ~250-~350W/kg 80-90% 8% / month 400-1200 cycles 3.6/3.7 volts Electrochemistry The three participants in the electrochemical reactions in a lithium-ion battery are the anode, cathode, and electrolyte. Both the anode and cathode are materials into which, and from which, lithium can migrate. During insertion (or intercalation) lithium moves into the electrode. During the reverse process, extraction (or deintercalation), lithium moves back out. When a lithium-based cell is discharging, the lithium is extracted from the anode and inserted into the cathode. When the cell is charging, the reverse occurs. Useful work can only be extracted if electrons flow through a The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012. closed external circuit. The following equations are in units of moles, making it possible to use the coefficient x. The positive electrode half-reaction (with charging being forwards) is  Little, A. D. (1993). Survey of rechargeable battery technologies. Cambridge.  Reddy, J. O. (1970). Modern Electrochemistry. Plenum.  Sequeira, C. Solid State Batteries. North Atlantic Treaty Organization. LiCoO2Li1-xCoO2 + xLi+ + xeThe negative electrode half-reaction is: xLi+ + xe- + 6C LixC6 The overall reaction has its limits. Over discharge supersaturates lithium cobalt oxide, leading to the production of lithium oxide, possibly by the following irreversible reaction: Li+ + e- + LiCoO2 Li2O + CoO Advantages 1. Sealed cells; no maintenance required 2. Broad temperature range of operation 3. Rapid charge capability 4. High rate and high power discharge capability 5. High coulombic and energy efficiency 6. No memory effect Disadvantages 1. Moderate initial cost 2. Degrades at high temperature 3. Need for protective circuitry 4. Capacity loss or thermal runaway when over-charged. 5. Venting and possible thermal runaway when crushed Applications Portable electronics, medicine, military equipment, LithiumIon-Polymer Battery Chemical Hazards of Using Rechargeable Batteries Batteries are usually filled with solutions (electrolytes) containing either sulphuric acid or potassium hydroxide. These very corrosive chemicals can permanently damage the eyes and produce serious chemical burns to the skin. Sulphuric acid and potassium hydroxide are also poisonous if swallowed. The lead, nickel, lithium or cadmium compounds often found in batteries are harmful to humans and animals. These chemicals can also seriously damage the environment. 6. CONCLUSION This paper reviewed previously-developed batteries and provided a classification of technologies indicating advantages and disadvantages of each. Emphasis is made on rechargeable batteries since they require urgent improvements required by the ever increasing demand on electronic devices – cell phones, tablets and so on. The summary of past developments is intended to provide a roadmap for future developments. 7. REFERENCES  Broad, R. J. Recent Developments in Batteries for Portable Consumer Electronics Applications. pennington, NJ, 1999: electrochemical society.  Connolly, D. (2009). A Review of Energy Strorage Technologies. University of Limerick.  Espinar, B. (2011). The role of energy storage for minigrid stabilization. Armines: Mines Paris Tech.  Linden, D. (2002). Handbook of batteries. new york: McGraw Hill. The 8th International Symposium on Management, Engineering and Informatics, MEI 2012, and The 16th World Multi-Conference on Systemics, Cybernetics and Informatics, WMSCI 2012, Orlando, Florida, July 17-20, 2012.