Lithium Ion Battery Essay

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Lithium-ion batteries were commercially introduced for the first time in 1991[1]. Since their introduction, they have revolutionized consumer electronics by becoming the dominant power-source for devices such as laptops and cell phones. This is mainly due to their superior energy-density compared to other energy sources. Lithium-ion batteries are becoming the subject of even greater interest these days, since they are the power-source of choice for electric vehicles (hybrid and otherwise). This is especially relevant considering the focus on finding carbon-neutral sources of energy to replace the reliance on fossil-fuels for automobiles.
Lithium-ion batteries do not contain lithium metal. Instead, they contain a negative electrode (composed of graphite), a liquid electrolyte (non-aqueous), and a positive electrode which is composed of a layered lithium and transition-metal oxide like LiCoO2 (Figure 1). When charged, the lithium ions de-intercalate from the cathode, make their way through the electrolyte, and then intercalate themselves between layers of graphite in the anode. During discharge, the process is reversed.

After their initial introduction in 1991 numerous improvements have been made to Lithium-ion technology, which has greatly improved their rate of charge and discharge, safety, and cycle life. However, with Lithium-ion batteries being the energy-source of choice for electric vehicle, such as Tesla’s Model S, new challenges are being placed on this form of technology. Specifically, newer forms of lithium-ion batteries need to optimize for fast charge/discharge rates while also being immune to overheating. In the succeeding sections, we will look at different approaches that have been used to optimize performance in...

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...l cations have the ability to order on the octahedral sublattice. Interestingly, a disordered spinel structure seems to have a higher capacity [24]. Partially substituting cobalt for nickel (i.e Li[Mn1.42N0.43Co0.16]O4) seems to reduce the formation of LixNi1-xO, which tends to degrade cell performance during cycling [25]. Another way to improve capacity retention is to add nickel to the surface of LiMn2O4 through coatings rather than as a bulk dopant.
LiFePO4 and other phosphates
Phosphates (LiMPO4) with the olivine structure (Pnma) are another promising class of candidates. Here, phosphorus occupies tetrahedral sites, whereas the transition metal M occupies octahedral sites, and lithium forms one-dimensional chains along the [0 1 0] direction [26]. The phosphate that is most-commonly used is LiFePO4, and delithiates to FePO4 when Fe2+ is oxidized to Fe3+ [27].

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