Thanks to a number of highly publicized incidents over the past few years, we've learned that, though common, lithium-ion batteries can indeed be dangerous. Significant flexion or pressure on a Li-ion cell can cause a short, leading to a runaway reaction — also known as an explosion. A team of Chinese researchers have successfully tested batteries made with alternative sodium-based electrolytes, termed Sodium-ion batteries (SIBs).
The team tested three types of electrolytes: Sodium sulfate, saline, and cell-culture medium. The compounds were chosen for their lack of corrosive or toxic properties meaning leakage would not be as much of a problem as it is for Li-ion batteries (it is because of the issues Li-ion leakage causes that current batteries have thick casing and, as such, are generally inflexible). According to the results, the research team's SIBs showed "excellent electrochemical performance" and maintained a high degree of flexibility.
Two designs were tested, including a circular "belt" shape and a nanotube for biological implantation. The circular belt-like design showed the most promise, exhibiting a high level of competitiveness with similarly sized Li-ion batteries. The nanotube SIB, on the other hand, did not do so well for power generation — yet it suggested interesting implementations for medical usage: the nanotubes were found to increase the conversion of oxygen into hydroxide ions, deoxygenating the area. Co-author Yonggang Wang suggested that the deoxygenating property of the nanotube SIB could hypothetically prove useful in fighting cancer by changing cellular pH levels.