Although there exist several types of batteries, all of them function with a common concept—batteries are devices that store electrical energy as chemical energy and convert this chemical energy into electricity when necessary. Although it is not possible to capture and store electricity, it is possible to store electrical energy in the form of chemicals within a battery.
All batteries have three main components—two electrodes or terminals made of different metals, known as anode and cathode, and the electrolyte separating these terminals. The electrolyte is the chemical medium allowing the flow of electrical charges between the terminals inside the battery, When a load connects to a battery, such as an electrical circuit or a light bulb, a chemical reaction near the electrodes creates a flow of electrical energy through the load.
The most commonly used battery today, the lithium battery, typically uses a liquid electrolyte for carrying electrical charges or ions between its electrodes. Scientists are also looking at alternatives like solid electrolytes for future opportunities. A new study offers cellulose derived from wood as one type of solid electrolyte. The advantage of this solid electrolyte from wood is its paper-thin width, allowing the battery to bend and flex for absorbing stress while cycling.
The electrolyte presently in use today in lithium cells has the disadvantage of containing volatile liquids. There is thus a risk of fire in case the device short-circuits. Moreover, there is the possibility of the formation of dendrites—tentacle-like growths—and this can severely compromise the battery’s performance. On the other hand, solid electrolytes, made from non-flammable materials, allow the battery to be less prone to dendrite formation, thereby opening up totally modern possibilities with different battery architecture.
For instance, one of these possibilities involves the anode, one of the two electrodes in the battery. Today’s batteries usually have an anode made from a mix of copper and graphite. With solid electrolytes, scientists claim they can make the battery work with an anode made from pure lithium. They claim the use of pure lithium anode can help to break the bottleneck of energy density. Increased energy density will allow planes and electric cars to travel greater distances before recharging.
Most solid electrolytes that scientists have developed so far are from ceramic materials. Although these solid electrolytes are very good at conducting ions, they cannot withstand the stress of repeated charging and discharging, as they are brittle. Scientists from the University of Maryland and Brown University were seeking an alternative to these solid electrolytes, and they started with cellulose nanofibrils found in wood.
They combined the polymer tubes they derived from wood with copper. This formed a solid ion conductor with conductivity very similar to that in ceramics, and much better than that from any other polymer ion conductor. The scientists claim this happens as the presence of copper creates space within the cellulose polymer chains allows the formation of ion superhighways, enabling lithium ions to travel with substantially high efficiency.
With the material being paper-thin and thereby highly flexible, scientists claim it will be able to tolerate the stresses of battery cycling without damage.