High specific energy (Wh/kg) and energy density (Wh/L) anode and cathode materials play a crucial role in enhancing the energy content of lithium-ion batteries (LIBs), and most experts in the field have been concentrating in these areas. In this case, these materials' specific gravimetric and volumetric capacities have been highlighted from a researchers' viewpoints. On the other hand, some specific parameters are often neglected. Therefore, for practical applications of large size battery cells, the coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) must be considered, which means that these parts need special attention.
The main reason for energy inefficiency is voltage inefficiency. This is because of the voltage hysteresis between the charge and discharge curves. It has also been shown that materials with larger voltage hysteresis, such as the ZnFe2O4 (ZFO) anode or the Li-rich cathode material, demonstrate a lower VE and EE than, for example, graphite and LiNi0.5Mn1.5O4. Moreover, the additional energy costs are estimated according to industry and domestic electricity costs in Germany, Japan, and the United States from the accumulated EE losses. In general, in the countries in which electricity has a high cost, the accumulated extra energy that is required to compensate for the energy inefficiency has a significant effect on the additional energy costs and, consequently, on the total cost of ownership of the battery cell system.
A specific cost difference occurs to compensate the respective materials' energy inefficiency, based on the country and its electricity prices. In countries with high electricity prices, high additional energy costs show a low EE. The most important fact is that the impact of energy inefficiency on absolute electricity costs relies on the size of the battery. Thus, for example, when a smartphone is charging, additional electricity costs might be very little. On the other hand, when an electric car is charging, this number probably will rise significantly.
Additionally, the total cost of ownership of a battery does not just depend on the battery's cost, and it relates to many more factors. Therefore, additional studies have to be done for alternative battery systems, including metal/air, metal/sulfur, magnesium, or sodium chemistries. Most of these alternative cell chemistries indicate poorer EE than the graphite-based LIB. Focusing on enhancing EE should be considered in future studies on these alternative systems, and creating alternative battery chemistry with lower cost, based on TCO considerations, should be defined as these studies' main goal .
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In general, efficient energy storage and battery technology are significant needs in the current daily lives of individuals. The battery materials are rare and expensive, and they are not appropriate for new practical applications. Therefore, lithium-ion battery technology has to be replaced with an alternative. Alloys are able to provide noticeable capacity for anodes; however, altering the volume requires complicated and expensive solutions. It should be mentioned that pure metal anodes still show the highest performance. Problems like dendrite and solid electrolyte have to be solved in order to use the anodes. The simplest and most cost-effective method to solve these problems is to search for different electrolytes. This can be either with entirely different types of electrolytes, or with the addition of additives to overcome unwanted chemical behavior.
Although lithium-ion batteries dominate the current market, this cannot go on, because lithium is such a rare material. In this regard, research about lithium-free battery alternatives has been highlighted. Future studies in this area have to pay more attention to the recent facts, and concentrate more efficiently on finding renewable alternatives for lithium batteries. For instance, high-performing lithium-ion batteries may be used in high energy density areas, while sustainable alternatives, such as sodium or aluminum-ion batteries, could be used in cost-effective areas .
Many advanced studies have been done for decades on lithium-ion batteries to develop them into high energy density, high cycle life, and high efficiency batteries. However, the research is still looking for new electrode materials to enhance the performance of energy density, power density, cycle life, safety, and cost. Anode and cathode materials are suffering from several problems, including slow Li transport, high volume expansion, limited electrical conductivity, low thermal stability, dissolution, or other unfavorable interactions with the electrolyte, and mechanical brittleness.
Different methods have been developed to solve these problems. Many intercalation cathodes have been made available on the market, and conversion material technology is expected to become more common. Research about lithium-ion battery electrode materials has reached an exciting point. Developments from lithium-ion batteries could greatly impact our lives, given the fact that new materials are being found .
The sufficiency of lithium is the key problem of lithium-ion batteries. Although it seems that currently, this material is abundant on Earth's crust, there are doubts that it will be enough for the future. South American salt mines currently contain several billion cubic meters of lithium carbonate. Also, a new deposit has been discovered recently in Afghanistan. This deposit is estimated to contain a thousand billion dollars of lithium, which could make Afghanistan the main supplier of the world's lithium. In addition, lithium is also available in seawater. Therefore, it seems that based on all these reservoirs, the amount of lithium will be sufficient, even if all gasoline vehicles in the world were to be replaced with electric cars .
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