A Review of Cathode and Anode Materials for Lithium-Ion Batteries Yemeserach Mekonnen Aditya Sundararajan Arif I. Sarwat IEEE Student Member IEEE Student Member IEEE Member Department of Electrical & Department of Electrical & Department of Electrical & Computer Engineering Computer Engineering Computer Engineering Florida International University Florida International University Florida International University Email: [email protected] Email: [email protected] Email: [email protected] Abstract—Lithium ion batteries are one of the most technologies such as plug-in HEVs. For greater application use, commercially sought after energy storages today. Their batteries are usually expensive and heavy. Li-ion and Li- based application widely spans from Electric Vehicle (EV) to portable batteries show promising advantages in creating smaller, devices. Their lightness and high energy density makes them lighter and cheaper battery storage for such high-end commercially viable. More research is being conducted to better applications [18]. As a result, these batteries are widely used in select the materials for the anode and cathode parts of Lithium (Li) ion cell. This paper presents a comprehensive review of the common consumer electronics and account for higher sale existing and potential developments in the materials used for the worldwide [2]. Lithium, as the most electropositive element making of the best cathodes, anodes and electrolytes for the Li- and the lightest metal, is a unique element for the design of ion batteries such that maximum efficiency can be tapped. higher density energy storage systems. The discovery of Observed challenges in selecting the right set of materials is also different inorganic compounds that react with alkali metals in a described in detail. This paper also provides a brief history of reversible way has opened doors to the design of rechargeable battery technology and their wide applicability in the energy Li-ion batteries [15]. This phenomenon, as defined later, is market today, the chemistry and principle of operation behind called intercalation, which is the reversible inclusion of the batteries, and their potential applications even beyond the molecules between two other molecules [2]. energy sector. Safety concerns related to Li-ion batteries have also been taken into account considering recent events. Index Terms—Cathode, Anode, Graphite, Lithium ion, Battery, Safety I. INTRODUCTION Lithium-ion batteries are used in different technologies such as the Hybrid Electric Vehicles (HEV), which use both battery as well as electric motor engines to increase the fuel efficiency [1]. A battery is essentially many electrochemical cells connected in series or parallel to provide voltage and capacity. Each cell contains a positive (cathode) and negative (anode) electrode divided by an electrolytic solution, simply called as an electrolyte, with dissociated salt that allows ion transfer between electrodes [2]. When these electrodes are connected to an external source, electrons are released as a result of chemical reaction and therefore for current to be tapped [25]. The electrical energy that a battery is able to give Figure 1 Energy density of different batteries [1] is a function of both the cell and its capacity which are dependent on the chemistry of the battery. For the purpose of application, Nickel Metal Hydride (Ni-MH) is the common II. CHEMISTRY battery technology currently being used [1]. However, different The materials involved in Li-ion batteries consist of carbon research efforts have proven that Lithium ion (Li-ion) which is porous in nature, usually graphite, as the anode, and chemistry has twice the power efficiency and density of Ni- metal oxide for the cathode [15][24]. Like most battery MH. Out of the common batteries used in various applications, technologies, the working principle of Li-ion batteries involves lead acid, Nickel Cadmium (Ni-Cd), Nickel Metal Hydroxide Lithium stored in the anode terminal that is transported to the (Ni-MH), and Li-ion batteries have higher energy density, as cathode terminal by an electrolyte [2]. Some of the most shown in Fig.1. These advances are reshaping the current common cathode components are Lithium Nickel, Manganese This material is based on work supported by the National Science Foundation under Grant No. 1541108. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. 978-1-5090-2246-5/16/$31.00 ©2016 IEEE Cobalt Oxide, Nickel Oxide, Cobalt Oxide, Manganese spinel, flexibility and shape versatility when compared to the Iron Phosphate, and Titanate. Among them, Lithium Nickel cylindrical, prismatic or coin cell geometries. and Manganese Cobalt Oxide have a higher energy density and cell voltage. The electrolytic solution is lithium salt in organic carbonate solvent containing “lithiated” ions [25]. The operating principle behind Li-ion batteries is a recurring transmission of lithium ions between the anode and the cathode [11][12]. During the discharge process, solid state Li disperses to the surface of the anode material to undergo an electrochemical reaction which enables it to transfer Li+ ion into the electrolytic solution [1]. The equilibrium equation for such a reaction with graphite as the cathode material is as follows: + The Li ion in turn passes through the electrolytic state through dispersion and ionic conduction to react with the anode Fig. 3 Different types of cell geometry a) cylindrical b) coin c) prismatic d) and change back to its solid state. The equilibrium reaction at pouch [4] cathode in this case with lithium metal oxide is presented as III. APPLICATIONS AND MARKET follows: Having a higher energy density when compared to other battery technologies, rechargeable Li-ion batteries are and will Lithium will be stored inside the cell until the battery is continue to control the market. By 2011, the rechargeable Li- later recharged. At times of high current discharge, there is a ion battery market reached an approximate $11 billion and has possibility that the cell can suddenly lose power depending on continued to grow [5]. These rechargeable batteries are utilized the Li concentration, if saturated or depleted at the electrolyte in market segments where high energy and power density surface. applications are favored. The future of smart grid will heavily consist of the Plug-in Electric Vehicles (PIEVs) as part of the smart home power systems [20] [28] [29]. The EV and the Plug-in Hybrid EVs (PHEVs) are perfect examples of such applications [20] [21]. After many significant research efforts, it is now plausible for consumers to use EVs such as Tesla model S, or PHEVs like Chevrolet Volt, all powered by Li-ion batteries [22]. The challenges for these market segments are the manufacturing cost, higher price of Li-ion batteries and safety concerns. A few of the other Li-ion applications are commercial portable technologies such as cellphones, laptops and tablets, aeronautics, and industrial energy power stations [23]. There are numerous advantages to Li-ion batteries. They are light weight which makes them the perfect candidates for the recently sought-after portable technologies. They have a high open circuit voltage and high energy density. They are characterized by lack of memory, small self-discharge rate, and less environmental impact when disposed. They, however, Fig.2 Schematics showing the working principles of a) Rechargeable Li-metal have their own challenges where recent cases of unprovoked battery, b) rechargeable Li-ion battery [1] inflammation have raised a constant safety concern [26]. The use of Li-ion batteries for the aforementioned There are different types Li-ion cell geometries according applications faces challenges. For one, the battery performance to the current manufacturing practices, namely the prismatic, has to be in tune with the applications it is used for. Safety, as cylindrical, coin, and the pouch cell geometry which is the mentioned, remains a concern. The battery performance, most recent method. Both the cylindrical and prismatic cells usually measured in capacity, energy density, and cell are commonly made of “laser-welded” aluminum can and potential, is directly related to the properties of the materials consist of liquid electrolyte. The pouch cell with aluminized which form the positive and negative electrodes [13]. Safety plastic bag contains Li-ion polymer electrolyte or gel. Bellcore concerns can be addressed through extensive studies of battery researchers were the first to advance their research on the chemistry, and cell engineering [17]. Present research is being polymeric electrolyte called “plastic Li-ion (PLiON)” [2]. This conducted in finding new materials which can act as anode and thin film battery technology gives the advantage of lightness, cathode, to offer better performance arrangements of electrode- electrolyte-electrode [2]. In addition, finding the right electrolyte combination to avoid damaging reactions associated acceptance of Li, flexibility to temperature control as result of with “electrode-electrolyte interface” is another challenge that its organic structure, and optimal cycling ability [4]. Through is currently being researched about [19]. structural and surface modifications, carbonaceous anodes have shown consistent improvements in their charge-discharge IV. ANODE MATERIALS efficiency and discharge capacity. There have been new