Graphene

What is Graphene?

A form of carbon arranged in an infinite 2-D honeycomb structure. It is a single thin layer of graphite. It is very strong and equivalent to 100 times that of steel and density far lower, making it strong and light material. The conduction of heat and electricity is also very good in this material.

Since the rediscovery of graphene in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, it's been a very hot topic both in research and industries. The rediscovery took place when the duo were researching for its application in transistors, eventually they have got Nobel prize for their work in 2010

“There is a huge demand for improvement in lithium batteries and graphene has shown great potential in the improvement of structural, electrical, thermal and mechanical properties. Unfortunately, these improvements are not yet realized in present batteries due to the cost factor and the lack of feasible techniques for large-scale production.”

Graphene, Its advantages

Having uniquely great properties at the nanoscale, 2D materials have attracted too many for their applications in quite many areas. Graphene, a crystalline allotrope of carbon forming a 2D hexagonal structure. In spite of the abundantly available source, graphene is not economic because of the costly preparation the method at present.

As said, it is a form of carbon and has been used as an anode in research but it does not have a long life due to side reactions, maybe a suitable electrolyte would make it stable for having a graphene-based battery in future. At present, it promisingly fills at many roles enhancing the performance. Graphene transfers electrons and ions faster, making this material suitable as a supercapacitor or micro-capacitor. In batteries, most of the time it’s been used along with anode or cathode material acting as a conductive additive, since it is not stable it is used in less quantity or around 1%.

Conductive additives are necessary to improve the electronic conductivity of the electrode, which is especially necessary for electroactive materials with low electronic conductivities, such as LiMn₂O₄ (10⁻⁴ S cm⁻¹),  LiFePO₄(10⁻⁹ S cm⁻¹),

What could be the side reactions?

When used as an anode, it exhibits high specific capacity in the first lithiation step, while in subsequent delithation and lithiation shows reduced capacity, which means that a large fraction of lithium is irreversibly consumed instead of reversibly stored.

Few Points

•  Doping of the electron-rich donor N atoms leads to better Electron- and Ion-Transport.
•  Silicon and various alternatives of carbon have the problem of volume expansion while cycling and graphene can be used as buffer.
•  Graphene has low gravimetric density and good electrical conductor and it’s a great alternative to replace current collectors like aluminium and copper by acting itself as independent current collector.
•  Current collectors have poor interfacial properties due to weak adhesion between active materials and the smooth metal surface which may lead to peeling away of active material from the current collector. After long cycles current collectors react with electrolyte and enhancing the problem even more. Coating of graphene is one of a solution for this.
• Coating of graphene over separator towards cathode or towards lithium metal when it is used in LIB’s can control of lithium nucleation.