Portable Electronics, Wearable Electronics, Flexible Electronics are few of the terms we are quite familiar with. Today we are successfully making ultra portable & sleek electronic gadgets, flexible electronics products, medical invasive devices that can be worn by the patients for live monitoring etc. These products cannot run on conventional electrochemical batteries like alkaline batteries or Li-ion batteries which are quite bulky, heavy for such sleek & ultra portable electronic gadgets of future. In this article we are going to talk about a new battery technology which is still in its nascent state as far as commercial availability is concerned due to several reasons but offers numerous advantages over conventional electrochemical batteries.

It is called Paper Battery. Paper Battery is made of 90% cellulose (paper) with a thickness less than a printer paper (.025mm) and carbon nanotubes. Paper battery is flexible, durable, & being a thin flat sheet it can easily fit into tight places thus reducing the size & weight of the device it powers. Apart from just being flexible & light weight there are other several important advantages of Paper Battery over conventional electrochemical batteries. Since it is made of Paper, this battery is biodegradable hence disposing it is inexpensive. Because of its structural composition & features it is not harmful & is fully recyclable. It doesn’t suffer from leakage problems and corrosion.

Construction & Working of Paper Battery

Paper battery is made up of cellulose or paper coated with ink made up of carbon nanotubes thus producing a highly conductive storage device that can be used in variety of applications. Cellulose & Carbon nanotubes have properties like high-tensile strength, biodegradability, low-shear Strength, biocompatibility, non-toxicity, reusability & recyclability. Also Carbon nanotubes are good conductors of electricity. Paper Battery has high energy storage capacity.

Structure of Paper Battery

Like any electrochemical battery, paper battery consists of electrodes, electrolyte & separator. A sheet of paper or cellulose is coated with ionic solution that works as electrolyte. Specially prepared carbon nanotube ink is spread on this ionic coated paper; it serves as one of the electrode (cathode). The other side is laminated with a thin film of lithium oxide which serves as anode. Aluminium rods are used to transfer current between the 2 electrodes. Now when the load is connected the chemical energy (flow of electrons) is converted into electrical energy. The use of paper increases the electron flow which is well suited for high performance applications. Paper allows for capillary action thus electrolyte can move without the use of an external pump. This cellulose based separator is compatible with many possible electrolytes (mainly ionic liquids). Many natural occurring electrolytes like human sweat, blood and urine could also be used. Moreover ionic electrolyte with no water could be used in paper battery meaning batteries would not freeze, evaporate thus allowing operation in extreme temperatures.

Applications of Paper Batteries

• Paper batteries can be used as super capacitors. Super capacitors are made in same way as electrochemical batteries but they feature extremely fast charging & discharging which is achieved with paper batteries. Super Capacitors are used in high power applications.
• In health care it can be used in making pace maker for the heart, artificial tissues, drug delivery systems & in biosensors.
• In portable electronics devices, fashionable technology, wearable technology because it can be can be folded, twisted, moulded, crumpled, shaped and cut for various applications without any loss of efficiency.
• In automotive applications in powering light weight electric vehicles.
• In defence applications for making systems for guided missiles etc.

Though Paper Battery has the potential to power next generation electronics technology, today it suffers from drawback. The biggest drawback is that today the technology is not very cost effective as carbon nano tubes are quite expensive. Also manufacturing process of paper battery today is quite complicated.

By Sagar Juneja, Research Associate & Mitika Sandha, Student ECE Final Year Chitkara university, Himachal Pradesh

References
www.edgefx.in/paper-battery-working-and-construction
www.gizmag.com/paper-battery-nanotechnology/13537/
http://www.sciencedirect.com/science/article/pii/S1369702107702250
http://www.nature.com/nnano/journal/v2/n10/full/nnano.2007.318.html