The Significance of Carbon Nanotubes and Graphene in Batteries and Supercapacitors Elena Ream and Solomon Astley

Introduction Many technologies to store electric charge Vary in shape, size, capacity, etc. Two specific technologies: Lithium-ion batteries Can improve power output through an electrode material that allows electrochemical reactions to occur at a faster rate Supercapacitors Can improve energy density by using a plate material that is capable of storing more charges

Modern Electrical Storage Devices Lithium Ion Batteries Three main components: Two electrodes (anode and cathode) Electrolyte Electrochemical reactions create an electric potential difference between the electrodes These reactions are oxidation and reduction reactions

Modern Electrical Storage Devices Lithium Ion Batteries Oxidation Ions in solution combine with anode, causing the release of free electrons through a wire Reduction Electrons combine with cathode and ions in the electrolyte solution to create another compound Lithium-ion batteries have a lithium cobalt-oxide cathode and carbon anode Nanotubes can help create a better anode.

Modern Electrical Storage Devices Capacitors Consist of two charged electrode plates and a dielectric Dielectric material is something that can be polarized Plates are connected to a power source, creating a build up of charge Initial electric field polarizes dielectric material Material polarizes to oppose the electric field

Modern Electrical Storage Devices Supercapacitors Electrolyte in place of dielectric Plates are coated in carbon dust to increase surface area Carbon nanotubes and graphene can be used within plates and as the carbon powder coating

Allotropic Carbon Materials GrapheneCarbon Nanotubes (CNT)

Use of Carbon Nanotubes and Graphene in Batteries Graphene has been proposed as an anode High conductivity and electron mobility Low energy density due to two-dimensional structure Combination of graphene and CNT could fix this Graphene nanosheet-carbon nanotube (GNS-CNT) Made through growing carbon nanotubes on top of graphene sheets After the CNTs have been grown, another graphene sheet is placed on top

Use of Carbon Nanotubes and Graphene in Batteries Performance GNS-CNT material has been determined to function as a superior anode compared to traditional amorphous carbon anodes CNTs store charge, graphene gives high conductivity Generally, shorter CNTs lead to higher electrochemical performance Improved lifespan of lithium-ion batteries, the amount of charge they can hold, and recharge time

Functional Groups Functional groups on CNTs can increase lithium-ion density per unit mass Electron withdrawing groups achieve this More electronegative atoms than carbon Greater pull on electrons than carbon Gives greater stability when excess charge is introduced Allow oxidation reactions to occur at a faster rate Withdrawing groups improve charge and discharge times Use of Carbon Nanotubes and Graphene in Batteries

Results Lithium-ion batteries are used in portable devices and vehicles because they can be recharged GNS-CNT materials are superior to traditional electrodes, could improve lifespan, charge capacity, and recharge times of batteries in these devices Battery Powered Vehicles Need to be recharged frequently, impractical for long distances Take a long time to charge GNS-CNT based lithium-ion batteries reduce these issues because they last longer and recharge faster. Medical Devices GNS-CNT based batteries can last longer and will be more light- weight, more convenient for patients

Use of Carbon Nanotubes and Graphene in Supercapacitors Benefits of supercapacitors over traditional batteries Quicker charge and discharge time Higher power density Last longer Not a a high energy density Current commercial supercapacitors use activated carbon as a current collector, CNT and graphene could make supercapcitors more efficient Lighter-weight and more conductive

Use of Carbon Nanotubes and Graphene in Supercapacitors Study on supercapacitors 3 different types of supercapacitors used Vary in what acts as electrode and current collector Prepared on flexible polyethylene napthalate (PEN) paper

Use of Carbon Nanotubes and Graphene in Supercapacitors Results Graphene film as electrode and CNT as current collector was most efficient Increasing thickness of graphene increased energy density Comparable to that of traditional lithium-ion batteries Lighter-weight that traditional supercapacitors Made paper thin and flexible

Energy and Power Densities of CNT based Supercapacitors with Graphene of Different Lengths

Sustainability Promotes humans and nature existing with one another in productive harmony Addresses environmental concerns Batteries and supercapacitors alone are self-sustaining and nonpolluting Impact of improved batteries and supercapacitors on other technologies can promote sustainability Two major types of impact: Improve clean energy Reduce waste

Clean Energy Fossil fuels are commonly used Limited resource Contribute to climate change Wind turbines and Solar panels Unlimited Nonpolluting Rely on a varying source Advancements in energy storage can help store energy Once harvested, can be saved for a time when there is no wind or sunlight Solar powered cars may be feasible

Decrease Waste Longer lasting devices will not be as frequently disposed of Heavy metals in batteries are harmful to surrounding environment Materials made of more organic materials can decrease this effect Creating carbon materials for batteries from recycled waste A group of researchers recently discovered a way to create carbon anodes from packing peanuts If CNTs and graphene could likely be synthesized from similar sources Decrease carbon based waste and create better batteries

Conclusion Lithium-ion batteries and supercapacitors are both devices for storing energy Graphene and CNTs are carbon allotropes When implemented in lithium-ion batteries and supercapacitors, graphene and CNTs improve the function of these devices Better energy storage is necessary to harness and store clean energy like wind and solar power Improved energy devices can help reduce waste