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| Fig. 1: The figure shows one of the earlier developments of the Na ion battery with sulfur (Source: Wikimedia Commons) |
Ever-growing energy needs and depleting fossil-fuel resources demand the pursuit of sustainable energy alternatives, including both renewable energy sources and sustainable storage technologies. It is therefore essential to incorporate material abundance, eco- efficient synthetic processes and life-cycle analysis into the design of new electrochemical storage systems.An economic and ecological way of storing large-scale current will be the key to the energy revolution. [1]
At present, lithium-ion batteries are the best technology, but they still require expensive materials, which are only found in a few places around the world. In addition, they often use polluting cobalt. In each case, fundamental and technological hurdles remain to be overcome; and there needs to be a balance. [2]
Worldwide, scientists are therefore actively seeking new technologies that can take over from lithium-ion. Sodium-ion batteries are possible successors. Sodium-ion batteries are not only far more powerful than nickel-metal hydride or lead acid accumulators, but also represent an alternative to lithium-ion technology, as the initial materials needed are highly abundant, easily accessible, and available at low cost. Sodium makes up some 2.6 percent of the earths crust and can be generated much more easily and economically than lithium. In addition, these batteries can discharge completely without any damage. [2,3]
Hence, sodium-ion batteries are a very promising technology for stationary energy storage systems that play a central role in the transformation of the energy system and will be a highly attractive market in the future. Interest in sodium-ion batteries dates back to the 1980s, but discoveries havent taken off until recently and is not yet produced on a commercial scale. Fig. 1 shows a schematic of one of the earlier developments of the sodium ion battery with sulfur. [3,4]
Now, researchers of the team of Professor Stefano Passerini and Dr. Daniel Buchholz of the Helmholtz Institute Ulm of Karlsruhe Institute of Technology have made an important step towards the development of active materials for sodium-based energy storage systems thanks to rotten apples. [3]
Who knew the saying: an apple a day keeps the doctor away; would go a long way and redevelop to be the potential answer to the next generation of energy storage technology. [2,3]
The research team have analysed and proven that it is possible to develop a carbonaceous material from dried apple waste from a which appears to have excellent electrochemical properties as a negative electrode in a sodium battery material of layered oxides; and it just might help reduce the costs of future energy storage systems. [3,4]
This porous hard carbon was proven to exhibit good cycling stability and rate capability, delivering a capacity of 181 mA h g-1 at 200 mA g-1 after 220 cycles and retaining a capacity of 71 mA h g-1 at 5 A g-1 from experimentation - exploiting the usefulness of Na ion battery storage. [4]
The material developed for the positive electrode consisted of several layers of sodium oxides. This active material goes without the expensive and environmentally hazardous element cobalt that is frequently used in active materials of commercial lithium-ion batteries. At the laboratory, the new active material, in which electrochemical energy storage proper takes place, reaches the same efficiency, cyclic stability, capacity, and voltage without any cobalt. [2]
Both materials also mark an important step towards the development of inexpensive and environmentally friendly sodium-ion batteries. [2]
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| Fig. 2: Rotten apples could be the future in energy - reducing the waste also resulting from it (Source: Wikimedia Commons) |
Initial tests, carried out on prototypes feeding no electronic devices, were carried out. They have covered more than 1000 cycles of charge and discharge and have proved the stability of the system as well as a large storage capacity. An important milestone is reached, but the research and development phases still have a few years to go. [3]
This discovery represents an important step towards the sustainable use and exploitation of resources, such as organic waste. [3]
According to the researchers, the new technology could not only benefit the energy transition but also be a good solution to end the current waste of apples. Indeed, apples of a not perfect form or crushed are often discarded because they rot too quickly to be used in the feed for livestock; just like the rotten apples seen in Fig. 2. [2,3]
Ultimately, sodium-ion batteries (based on apples or not) could replace lithium-ion batteries for equipment where size and weight matter less like the power packs of electric cars. Lithium being three times lighter than sodium, it remains well suited for mobile electronics and be the potential future of battery technologies. [5]
© Valmik Lakhlani. 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] D. Larcher and J.-M. Tarascon, "Towards Greener and More Sustainable Batteries for Electrical Energy Storage," Nat. Chem. 7, 19 (2015).
[2] M. Keller, D. Duchholz, and S. Passerini, "Layered Na-Ion Cathodes with Outstanding Performance Resulting from the Synergetic Effect of Mixed P- and O-Type Phases," Adv. Energy Mater. 6, 1501555 (2016).
[3] L. Wu, et al., "Apple-Biowaste-Derived Hard Carbon as a Powerful Anode Material for Na-Ion Batteries," ChemElectroChem. 3, 292 (2016).
[4] K.-L. Hong et al., "Biomass Derived Hard Carbon Used as a High Performance Anode Material for Sodium Ion Batteries," J. Mater. Chem. A 2, 12733 (2014).
[5] L. Chen et al., "Readiness Level of Sodium-Ion Battery Technology: A Materials Review," Adv. Sustainable Syst. 2, 1700153 (2018).
