Today’s lithium batteries generally use a liquid electrolyte to carry ions between two electrodes. But scientists are looking at an interesting alternative using wood-derived cellulose as the basis for one of the solid electrolytes. It is as thin as paper and can be bent and flexed to absorb voltage just like a battery cycle.
Batteries as we know them today contain volatile liquids, which carry a risk of fire if the device is short-circuited. In addition, another drawback is that the battery can encourage the formation of dendritic growth, namely tentacles that interfere with performance.
Meanwhile, solid electrolytes can be made from non-combustible materials thus making the device less susceptible to dendrite formation. And it might open up entirely new possibilities around battery architecture.
Many solid electrolytes developed so far are made of ceramic materials which are very effective at conducting ions. Unfortunately, it does not withstand pressure during charging and discharging due to its brittle nature.
Scientists from Brown University and the University of Maryland looked for alternatives to this and used cellulose nanofibrils found in wood as their starting point.
These wood-derived polymer tubes are combined with copper to form solid ion conductors. It has a similar conductivity to ceramics and is between 10 and 100 times better than other polymeric ion conductors.
According to the team, this is because the addition of copper creates spaces between the cellulose polymer chains for “ion superhighways” to form, allowing lithium ions to travel at record efficiency.
“By combining copper with one-dimensional cellulose nanofibrils, we show that ionically insulated cellulose offers faster lithium-ion transport in polymer chains,” said study author Liangbing Hu. “We found that this ionic conductor achieves a record high ionic conductivity among all solid polymer electrolytes.”
Furthermore, study author Yue Qi says, “Lithium ions move in these organic solid electrolytes via a mechanism we normally find in inorganic ceramics, enabling a record high ionic conductivity,” said study author Yue Qi. “Using materials provided by nature will reduce the overall impact of manufacturing batteries on our environment.”