Powering Your Life: The Lithium-ion Battery Anthony Allegretti 7 May, 2013 Allegretti 2 Abstract Although you may not know it, you modern lifestyle depends on a modern piece of electrical engineering known as the lithium-ion battery. Lithium-ion batteries are seen in our everyday lives from within our smartphones and laptops, to our hybrid cars. They have a wide range of advantages over other batteries, like lower weight and higher charge density, making them widely used in many aspects of life. While recent incidents have set these batteries back a ways, continued engineering and technology design shows the future of these batteries is bright. What Is It? If you are reading this then it is too late. I’m already dead… well, maybe not quite yet. Though chances are if you are reading this article, you are reading it on an electronic device powered by a lithium-ion battery. Whether it’s your tablet, smartphone, or laptop, you are most likely utilizing a lithium-ion battery. These are so common in our daily lives, but why? What makes these batteries so useful and efficient? Mostly used in portable electronics, there are other useful applications of today’s of the lithium-ion battery. Below we will discuss the advantages and disadvantages of using lithium-ion batteries, as well as very interesting integration of lithium-ion batteries in today’s world. First what is a lithium-ion battery? A lithium-ion battery, like most batteries, uses two metals in a catalyst or electrolyte, to exchange electrons between the metals resulting in an electric flow. Lithium-ion cells are composed of a negative electrode, otherwise known as an anode that is made of graphite, and a positive electrode or cathode that is lithium metal compound . There are multiple compound types used for the positive electrode, such as Lithium cobalt oxide, lithium nickel oxide, lithium aluminum oxide, Allegretti 3 lithium manganese oxide, all of which are lithium metal compounds. Lithium becomes an obvious choice due to its high energy density compared to other metal batteries, which means it can store large amounts of power or energy within the battery. A non-aqueous electrolyte is used, mainly comprising a mixture of organic carbonates, due to the battery’s large voltage output, . But what is exactly going on in our battery? When our battery is stable, or not charging or discharging, both the anode and cathode of the battery hold a number of lithium ions. When a flow of current is introduced, these lithium ions move through the electrolyte from the positive electrode to the negative electrode and attach to the carbon within the graphite anode. This becomes your stored power. Once a load is required from the battery (essentially turning on and using your phone or laptop) the lithium ions move back to the lithium compound from the carbon discharging energy along the way. Figure 1 below shows the charging and discharging process. Source: Chemical and Engineering News, cen.acs.org Figure 1: The above figure displays the components of a lithium ion cell. The cathode of this battery is Lithium Nickel Cobalt Aluminum Oxide. Allegretti 4 Why are these Batteries Better? Many characteristics of the lithium-ion battery give it an array of advantages, like total weight and charge density, over other types of batteries, like nickel-cadmium, another common rechargeable battery type. The first advantage would lithium-ion batteries characteristic lightweight. “Lithium is the lightest of all metals ,” which means lithium-ion batteries are relatively light, making your smartphone or laptop weigh significantly less creating increased portability. Lithium has an atomic mass of 6.541 while nickel has an atomic mass of 58.6934 making nickel about 9 times heavier than lithium. Imagine if your laptop utilized a nickel-cadmium battery instead of a lithium-ion battery, your laptop would be around 8 to 9 times heavier. Low weight allows lithium-ion batteries to be key players in mobile electronics. Lithium-ion’s high use can be also attributed to its electric potential, or its electric potential to store energy. “Lithium is… a highly reactive element, meaning that a lot of energy can be stored in its atomic bonds. This translates into a very high energy density for lithium-ion batteries .” But exactly how much energy is this? Well, a lithium-ion battery typically store 150 watt-hours of electricity in 1 kg of battery, while a nickel-metal hydride battery can store around 60 to 70 watt-hours, and a lead-acid battery can only store 25 watt-hours per kilogram . A Nickel-Cadmium battery can only store about 40 to 60 watt-hours per kilogram. A watt-hour is the rate at which an appliance uses power or watts, so a 1000-watt rated heater operating for an hour uses 1000 watthours. The more watt-hours a battery can store, the longer it lasts powering an appliance. It would take a 6-kilogram lead-acid battery to store the same power as a 1-kilogram Allegretti 5 lithium-ion battery. This allows a smaller, lighter battery to be used while still supplying the same amount of charge. Most of today's mobile phones run on a single cell battery, consisting of only one set of a cathode and anode. Multiple cells comprise of multiple sets of cathodes and anodes. A nickel-based battery pack, consisting of multiple cells, would require three 1.2volt cells connected in series in order to provide the same amount of voltage as one lithium-ion battery pack, . Can you imagine have a battery three times the size of your current battery in your smartphone? The relative lightweight and high potential qualities of lithium allow us to use mobile electronic devices every day without lugging around a heavy device or recharging every hour. A few other factors make lithium-ion batteries more useful than other types of batteries when dealing with mobile electronics. First, a prolonged priming of the cell is not needed upon initial use, contrary to popular belief (the old myth that when you first use your laptop, you should fully charge and then discharge the battery). Priming would require charging and discharging the battery pack a certain way, like trickle charging, or having the battery perform a few full discharge and recharge cycles before use. After being manufactured, a regular charge is all that is required , allowing you to open your new laptop, plug it in, and instantly begin use. Lithium batteries also hold their charge very efficiently. A lithium ion battery loses about 5 percent of its charge a month as compared to nickel-metal hydride, which loses 20 percent of its charge a month . While 20 percent doesn’t seem like a lot, if you rarely use your digital camera and pull it out to photograph an event after letting it sit for 3 months, the battery will likely be half dead. Very small charge losses during Allegretti 6 inactivity allow you to use a lithium-powered device even after storing the device for upwards of a year. Probably one of the most important features of lithium-ion batteries is their lack of memory . A battery with a memory effect would require a complete discharging before recharging it. You would not be able to partially discharge the battery and begin recharging it.. Basically if you wanted to recharge your laptop using a battery with memory effect, you would have to discharge it completely, and let your computer die. Only then could you begin to recharge the battery. Lastly, lithium-ion batteries can handle hundreds of charge and discharge cycles giving them longevity in your electronics . It would be a hassle and expensive if you needed to change your laptop’s battery every single year. It is no wonder that most portable electronic devices utilize lithium-ion batteries. Their light weight, high charge density, lack of priming needed, ability to hold charge efficiently and to accept a charge without fully discharging, and their long lifespan allow our mobile electronic devices to run efficiently, remain portable, and keep working for a long time. In fact, all the big brand name electronic providers use lithium-ion batteries. Your laptop, smart phone, camera, and even your MP3 player all use these types of batteries. There are Some Drawbacks The lithium-ion battery isn’t perfect, however, and there are a few drawbacks. First would be cost. Lithium-ion batteries are about 40 percent more expensive than Nickel-Cadmium batteries, and require an attached computer to manage their charge and discharge cycles increasing cost, which might be why your new smartphone costs Allegretti 7 upwards of $400. These computers can often be small, and only provide simple commands, but are required none-the-less. These batteries also degrade as soon as they leave the factory as their components are not fully mature in order to cycle charges causing continuous change , . While they may have longer life than some other batteries, eventually they will break down, and will need to be replaced. The lithium-ion battery is also sensitive to high temperatures, which limits its applications. If the temperatures reach critical levels, it is possible the batteries will combust. This will be explained more, further down. These problems will require future engineering, but due to the abilities of this battery, constant upgrades and changes are being mode all the time. Hybrid Technology While useful in mobile electronics, the lithium-ion battery has more important, noteworthy applications. Most people have probably seen a lithium-ion battery in action within hybrid vehicles. In fact, both the Toyota Prius and the Ford Fusion utilize lithiumion batteries in order to power their motors using electricity instead of gasoline. Most hybrids will utilize battery power in speeds under 20 miles per hour. After accelerating past 20 miles per hour, the engine starts combusting gasoline to power the vehicle. When the vehicle begins braking, energy from the wheels is transferred back into the lithiumion battery. The lithium-ion battery’s ability to actively charge and discharge without requiring a full discharge/charge cycle is an important factor for hybrid cars. The fact that lithium-ion batteries have a generally high charge to weight ratio also make them very useful in hybrids, where more weight reduces your available mileage. There is another car that depends on lithium-ion batteries, but unlike hybrid vehicles, it solely uses electricity to power its engine. The Tesla Model S is Tesla Allegretti 8 Motors’ new sedan that is completely powered by lithium-ion batteries, can travel a distance of up to 300 miles (with the largest 85kWh battery) and can go 0 to 60 mph in 4.4 seconds, . For a car that relies completely on an electric battery for use, the lithium-ion battery is a perfect fit. Remember that lithium-ion batteries have low weight and high charge density, useful for a car to gain significantly high mpg or travel long distances on a single charge. This lets you forget about charging during the day and charge only at night. The Lithium-ion battery also allows your car to sit, say, at an airport for a week or so without losing any charge, and because of the lack of memory effect, the Model S can charge whenever it needs to, without fully discharging first . Without the lithium-ion battery, the Model S might not even be possible in today’s world. The “Dream” Liner Most recently, you might have heard about other lithium-ion batteries in the news, concerning the Boeing 787 Dreamliner commercial jet that has been experiencing problems with its lithium-ion batteries. The 787 uses lithium-ion batteries in order to save weight allowing the aircraft to fly more efficiently. To compare, the 777 uses Nickel Cadmium batteries, which require 20 cells that provide 24 V, weigh 107 lbs., and have a power of 16A. The 787 lithium-ion batteries are made up of 8 cells, which have a voltage of 32 V, weigh 63 lbs. (almost half of the nickel-cadmium batteries), and provide a power of 150 Amps . So what does this all mean? The lithium ion batteries can provide more power and voltage in a few, lighter cells, meaning while the 777 requires 20 cells for its flight systems, the 787 only requires 8. These 8 cells are more powerful and lighter than the other combined 20. Allegretti 9 But the 787’s batteries have had numerous incidents, several resulting in the batteries combusting in flight. According to Cnet, “As a result of an in-flight, Boeing 787 battery incident earlier today in Japan, the FAA will issue an emergency airworthiness directive (AD) to address a potential battery fire risk in the 787 and require operators to temporarily cease operations,” . Figure 2 below shows a comparison a battery that combusted, and a normal battery for the 787. Whether or not the batteries are experiencing temperature regulation problems, or are experiencing problems with pressurization is unknown. Boeing is still currently working to fix the problem costing them vast amounts of time and money. Because of this problem, Airbus has moved away form using lithium-ion batteries in its new A350-XWB, saying, “Airbus considers this to be the most appropriate way forward in the interest of program execution and reliability,” . It will continue to use Nickel-Cadmium batteries instead. Source: NPR Figure 2: The 787 lithium-ion battery cell on the left combusted on the ground, while the battery on the right is in normal condition. Allegretti 10 According to the Journal of Power Sources, lithium-ion failure is caused by thermal runaway. Lithium-ion batteries are always undergoing chemical reactions within the their cells. These reactions are exothermic giving off large amounts of heat that can usually dissipate, but they can sometimes run out of control. The reaction rate increases due to an increase in temperature causing a further increase in temperature. This cycle speeds up until the battery becomes to hot. This is thermal runaway and it can often cause an explosion. The proposed temperature where this occurs is 80 degrees Celsius, . This case is far from isolated however, as back in 2006 in September, computer manufacturer Lenovo recalled a large portion of their lithium-ion batteries due to failure. These batteries were swelling, and in certain cases, exploding in their laptops causing a recall of the product. This occurred again in 2007 in March as another recall was issued for another set of batteries, . As you can see, these batteries are far from perfect, however, there has not been another recall like this in past years. And while these batteries have a few drawbacks, their benefits greatly outweigh them. The Future The future of these batteries looks bright, even with recent setbacks in Boeing’s 787. In fact recently, Researchers at the University of Illinois at Urbana-Champaign have developed a new lithium-ion battery technology that is 2,000 times more powerful than comparable batteries. . These batteries act both like a super capacitor which can release large amounts of power and a fuel cell which can store vast amounts of energy. When creating batteries for electronic devices, engineers are often forced to make trade offs in both departments (energy and power) creating a battery that has poor performance in both respects (but they do perform in both fields). The new lithium–ion battery acts Allegretti 11 proficiently in both respects, due to its 3-D porous anode and cathode design shown below in Figure 3. Traditional anodes and cathodes are 2 dimensional, but the 3-D structures allow for more chemical reactions to take place in a given space, ultimately providing a massive boost to discharge speed (power output) and charging, . This type of battery would be a game changer for both the electronics industry and the automotive industry, creating large energy sources that provide large amounts of power for a longer time. Imagine your smartphone with a battery as thin as a credit card, . Source: Extreme Tech Figure 3: A new porous, 3-D design allows greater and faster charging and discharging. Lithium-ion batteries have been and continue to shape the world around you. They allow you world to remain portable and powered even when you are far from the nearest outlet. Its properties allow for a lightweight, high-energy battery that can power your busy life. While these batteries have experienced minor setbacks, they Allegretti 12 continue to advance allowing us to use more technologically complex, power hungry machines. And these batteries are always changing to the point that in a few years, what seemed completely impossible will come reality. It truly is the battery of the future, today. Allegretti 13 Work Cited  "Lithium-ion (Li-ion)." Saft Batteries. N.p., n.d. Web. 19 Feb. 2013. <http://www.saftbatteries.com/Technologies_Lithium_Liion_301/Default.aspx>.  "Advantages & Limitations of the Lithium-ion Battery." Battery University. N.p., n.d. Web. 19 Feb. 2013. <http://batteryuniversity.com/learn/article/is_lithium_ion_the_ideal_battery>.  Brain, Marshall. 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