Batteries are ubiquitous in modern day technology. Batteries are available in a wide range of types, each specialised for particular applications, from small button cell batteries used in watches, larger Li-ion batteries used in mobile devices, to large industrial scale batteries. There is often a trade-off between the physical size of the battery versus the capacity required for the battery's application, the two of which are directly related.
An important subclass of batteries is rechargeable batteries, which provide the functionality of being able to be used repeatedly. Rechargeable batteries are the power source of choice for most portable applications, from cellphones and tablets, to electric motors for hybrid or electric vehicles. However, their limited capacity means that once their charge is expended they need to be connected to an external power source in order to be recharged. For applications such as hybrid or electric vehicles this puts a limit on the range these vehicles can travel before having to be recharged, which may be less than desirable.
For cellphones, balancing the desire for batteries to be light and portable against the power drain of large LED displays and power hungry processors, leads to batteries that have to be charged almost daily. The charging process for these batteries is time consuming, typically requiring a few hours for a full charge. It is not always desirable to have to recharge these devices this frequently.
In addition, rechargeable battery performance can deteriorate as repeated charge and discharge cycles lead to damage to the battery's electrodes. Causes of such deterioration include sulfation and grid corrosion for lead acid batteries, cell oxidation for Li-ion batteries, and crystalline formations for nickel-based batteries. These result in it becoming harder for the battery to regain its initial charge with the capacity of the battery depleting over time.
There is therefore a need to improve the functionality of batteries in order to increase their capacity whilst being able to keep them portable enough for specific applications. In addition, more efficient charge and discharge cycles are desirable in order to keep up with development in electronics.