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| 20 | Table 1 Summary of Most Common Li-ion Chemistries for Battery Application Figure 1 Forcasted Growth in Lithium-Ion Sales Overview of Lithium-Ion Battery Chemistries Consulting and market research firm Avicennes has predicted that the usage of lithium-ion (Li-ion) battery cells for energy storage and automotive applications will continue to grow significantly through 2025 with compound annual growth rates up to 30 percent forecasted in China's transport sector. As Li-ion usage grows and expands into new applications, it is important to understand the nature and use of various battery chemistries. Table 1 summarizes the most popular chemistries by energy density, cell voltage, and charge rate for 48V and higher-voltage battery packs. These next-generation packs match the power density required to drive new electronics and motor designs. The latest battery cell developments in different chemistries deliver the increased power energy over longer periods necessary for full-electric battery power. There are several factors to consider when choosing the chemistry for a battery-powered application. As can be seen in Table 1, Lithium Nickel Manganese Cobalt (NMC) with Graphite has the highest energy density among the commonly used chemistries. This is advantageous for heavy loads such as consumer energy storage or plug- in electric vehicles. However, the disadvantage of this chemistry is that it creates a higher risk of lithium plating on the anodes, which can reduce battery life and lead to thermal runaway (fire or explosion). The potential for these harmful conditions can be exacerbated by today's faster- charging connectors. Lithium Titanate (LTO) has a lower energy density than NMC and does not suffer from the problem of cracking graphite, which together improves the estimated battery life. The lower internal resistance of LTO facilitates faster- charging rates making this battery chemistry beneficial for plug-in electric vehicles (EVs). The downside is the higher cost for heavier battery packs as more cells are needed to provide the necessary energy in kilowatt hours (kWh). Lithium chemistries have very narrow operating temperature ranges, typically from 20°C to 40°C. Operating outside these temperatures leads to a loss of capacity and a shorter lifespan. Elevated temperatures can also cause further degradation and a thermal runaway condition. A paper by NASA, which studied the protection within 18,650 cells, found that the interrupt devices in all the cells connected in series and parallel were not as effective as single cells in preventing thermal runaway during fault conditions. This study illustrates the strong need for a Battery Management System when multiple cells are interconnected.