Invention has it that the oak leaf could be used to create a rechargeable sodium battery. Just like a potato or lemon that is used to demo battery made out of organic matter, a baked oak leaf can also be utilized.
For a long time, a rechargeable battery made from sodium has been of interest to many scientists. Theory has it that sodium holds more charge than the commonly used lithium material in batteries. Scientists drawn from the National Center for Nanoscience and Technology in Beijing and University of Maryland made a stunning discovery last month regarding rechargeable sodium battery. They realized that a baked oak leaf pumped with sodium created a negative terminal in a battery setup demo.
Oak leaf characteristics match key battery components
As aforementioned, sodium has been theorized to hold more charge than lithium; however, pragmatically the element cannot support numerous charge and discharge cycles. In trying to create a battery setup containing sodium, scientists have had issues with a stable anode material that can work well with sodium. The commonly used graphite in Li-ion cells does not go well with sodium as the latter has larger-sized ions than lithium. The suitable identified and compatible material with sodium is graphene though it takes a lot of time and expenses to produce it.
Fei Shen, who was part of the project, says that the natural shape of the oak leaf makes it suitable for a battery component. The oak leaf has tiny closely packed structures that maximize space; has a low surface area that reduces defects and has just the right shaped and sized internal structures that are compatible with sodium electrolyte.
The process involved
A dried oak leaf is first baked for an hour at 18320 F (1000 Celsius degrees) in an oxygen-deficient medium. This is to eliminate all carbon except the underlying ones. The leaf is then immersed in hydrogen chloride for six hours so as to remove probable inorganic impurities that would otherwise interfere with the electrochemical process.
The above process yields a carbonized oak leaf with pores on the underside. In this state, the pores are suitable for absorbing a sodium electrolyte. The upper side of the leaf has tiny carbon structures that absorb sodium containing the charge. The carbonized state of the leaf acts as a current-collecting surface as the electrochemical reactions are ongoing since it is dense and flat.
Oak leaf acts as the anode of the rechargeable sodium battery with a capacity of 360mAh per each gram of its net gross weight. Coin batteries fused with sodium plates are used as reference electrodes. Oak leaf designed anode has a capacity of around 90% after about 200 cycles.
The researchers are planning to test a number of other leaves in relation to energy storage but have so far not hinted any commercialization plans for the idea.