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| Fig. 1: Lithium Ion Battery. This diagram shows the structure of a lithium-ion battery with the positive electrode / cathode on the left and negative electrode / anode on the right, with flow of electrons to the cathode. (Source: Wikimedia Commons) |
Due to improvements in technology, government support for reduced greenhouse gas emissions, and reduced costs, electric vehicles are becoming increasingly prominent. [1] However, there are disadvantages to electric vehicles. These include long battery recharging time, high cost, and the lack of available charging stations. [1] Much research has been conducted to identify battery technologies that offer a high lifespan and capacity while remaining as affordable as possible.
Lithium-ion batteries have become the battery technology of choice for electric and hybrid vehicles. [2] On the other hand, lead-acid batteries are widely used for auxiliary power for motor vehicles that are not electric vehicles. [1] To understand why lithium-ion batteries are superior to lead-acid for electric vehicles, it is useful to compare their properties. Lithium-ion batteries have a specific energy of 125 Wh / kilogram. This energy density is greater than for lead-acid batteries, which have a specific energy around 40 Wh / kilogram. As can be seen visually in Fig. 1, lithium-ion batteries have positively and negatively charged electrodes, with flow of electrons to the positive electrode. Lithium ions can move between the cathode and anode during discharge and charging. Lithium-ion batteries have an energy / volume coefficient of 270 Wh / L, which is greater than the value of 70 Wh / L for lead- acid batteries. Furthermore, lithium-ion batteries on average can operate over 1,000 recharging cycles, while lead-acid batteries last 500 recharging cycles. [1] Lithium-ion batteries also have 10 times the power / weight coefficient of lead-acid batteries. While lead-acid batteries are cheap to manufacture, lithium-ion batteries benefit from high energy density, a larger range, less maintenance, and increased lifespan compared to lead-acid batteries. These advantages are of particular importance to electric vehicles given the difficulties of recharging electric vehicles.
Lithium-ion batteries have decreased in price from $1,100 / kilowatt hour to $156 / kilowatt hour in 2020, improving affordability significantly. [3] Concerns with lithium-ion batteries are that costs remain high, recharging infrastructure requires additional development, and more adoption can be done in recycling lithium-ion batteries. [4] New areas of research include solid-state batteries, which may promise higher energy densities and faster recharging times.
Lithium-ion batteries have emerged as the main source of energy for electric vehicles due to its advantages of a high energy density, lifespan, capacity, and less maintenance in comparison to lead-acid batteries and other battery types. Lead-acid batteries remain popular for auxiliary power in internal combustion engines for non-electric vehicles due to lower production costs. New research and development are targeting other battery technologies as well as reducing the costs of lithium-ion batteries, but only time will tell how the market will evolve.
© Alexander Donovan. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] S. Manzetti and F. Mariasiu, "Electric Vehicle Battery Technologies: From Present State to Future Systems," Renew. Sust. Energ. Rev. 51, 1004 (2015).
[2] N. Nitta et al., "Li-Ion Battery Materials: Present and Future," Mater. Today 18, 252 (2015).
[3] L. Trahey et al., "Energy Storage Emerging: A Perspective From the Joint Center for Energy Storage Research," P. Natl. Acad. Sci. USA 117, 12550 (2020).
[4] C. Iclodean et al., "Comparison of Different Battery Types for Electric Vehicles," IOP Conf. Ser.: Mater. Sci. Eng. 252, 012058 (2017).
