Graphene and batteries
Graphene, a sheet of carbon atoms bound together in a honeycomb lattice pattern, is hugely recognized as a âwonder materialâ due to the myriad of astonishing attributes it holds. It is a potent conductor of electrical and thermal energy, extremely lightweight chemically inert, and flexible with a large surface area. It is also considered eco-friendly and sustainable, with unlimited possibilities for numerous applications.
In the field of batteries, conventional battery electrode materials (and prospective ones) are significantly improved when enhanced with graphene. A graphene battery can be light, durable and suitable for high capacity energy storage, as well as shorten charging times. It will extend the batteryâs life, which is negatively linked to the amount of carbon that is coated on the material or added to electrodes to achieve conductivity, and graphene adds conductivity without requiring the amounts of carbon that are used in conventional batteries.
Graphene can improve such battery attributes as energy density and form in various ways. Li-ion batteries (and other types of rechargeable batteries) can be enhanced by introducing graphene to the batteryâs anode and capitalizing on the materialâs conductivity and large surface area traits to achieve morphological optimization and performance.
It has also been discovered that creating hybrid materials can also be useful for achieving battery enhancement. A hybrid of Vanadium Oxide (VO2) and graphene, for example, can be used on Li-ion cathodes and grant quick charge and discharge as well as large charge cycle durability. In this case, VO2 offers high energy capacity but poor electrical conductivity, which can be solved by using graphene as a sort of a structural âbackboneâ on which to attach VO2 - creating a hybrid material that has both heightened capacity and excellent conductivity.
Another example is LFP (Lithium Iron Phosphate) batteries, that is a kind of rechargeable Li-ion battery. It has a lower energy density than other Li-ion batteries but a higher power density (an indicator of of the rate at which energy can be supplied by the battery). Enhancing LFP cathodes with graphene allowed the batteries to be lightweight, charge much faster than Li-ion batteries and have a greater capacity than conventional LFP batteries.
In addition to revolutionizing the battery market, combined use of graphene batteries and graphene supercapacitors could yield amazing results, like the noted concept of improving the electric carâs driving range and efficiency. While graphene batteries have not yet reached widespread commercialization, battery breakthroughs are being reported around the world.
Batteries serve as a mobile source of power, allowing electricity-operated devices to work without being directly plugged into an outlet. While many types of batteries exist, the basic concept by which they function remains similar: one or more electrochemical cells convert stored chemical energy into electrical energy. A battery is usually made of a metal or plastic casing, containing a positive terminal (an anode), a negative terminal (a cathode) and electrolytes that allow ions to move between them. A separator (a permeable polymeric membrane) creates a barrier between the anode and cathode to prevent electrical short circuits while also allowing the transport of ionic charge carriers that are needed to close the circuit during the passage of current. Finally, a collector is used to conduct the charge outside the battery, through the connected device.
When the circuit between the two terminals is completed, the battery produces electricity through a series of reactions. The anode experiences an oxidation reaction in which two or more ions from the electrolyte combine with the anode to produce a compound, releasing electrons. At the same time, the cathode goes through a reduction reaction in which the cathode substance, ions and free electrons combine into compounds. Simply put, the anode reaction produces electrons while the reaction in the cathode absorbs them and from that process electricity is produced. The battery will continue to produce electricity until electrodes run out of necessary substance for creation of reactions.
Battery types and characteristics
Batteries are divided into two main types: primary and secondary. Primary batteries (disposable), are used once and rendered useless as the electrode materials in them irreversibly change during charging. Common examples are the zinc-carbon battery as well as the alkaline battery used in toys, flashlights and a multitude of portable devices. Secondary batteries (rechargeable), can be discharged and recharged multiple times as the original composition of the electrodes is able to regain functionality. Examples include lead-acid batteries used in vehicles and lithium-ion batteries used for portable electronics.
Batteries come in various shapes and sizes for countless different purposes. Different kinds of batteries display varied advantages and disadvantages. Nickel-Cadmium (NiCd) batteries are relatively low in energy density and are used where long life, high discharge rate and economical price are key. They can be found in video cameras and power tools, among other uses. NiCd batteries contain toxic metals and are environmentally unfriendly. Nickel-Metal hydride batteries have a higher energy density than NiCd ones, but also a shorter cycle-life. Applications include mobile phones and laptops. Lead-Acid batteries are heavy and play an important role in large power applications, where weight is not of the essence but economic price is. They are prevalent in uses like hospital equipment and emergency lighting.
Lithium-Ion (Li-ion) batteries are used where high-energy and minimal weight are important, but the technology is fragile and a protection circuit is required to assure safety. Applications include cell phones and various kinds of computers. Lithium Ion Polymer (Li-ion polymer) batteries are mostly found in mobile phones. They are lightweight and enjoy a slimmer form than that of Li-ion batteries. They are also usually safer and have longer lives. However, they seem to be less prevalent since Li-ion batteries are cheaper to manufacture and have higher energy density.
Batteries and supercapacitors
While there are certain types of batteries that are able to store a large amount of energy, they are very large, heavy and release energy slowly. Capacitors, on the other hand, are able to charge and discharge quickly but hold much less energy than a battery. The use of graphene in this area, though, presents exciting new possibilities for energy storage, with high charge and discharge rates and even economical affordability. Graphene-improved performance thereby blurs the conventional line of distinction between supercapacitors and batteries.
Graphene-enhanced batteries are almost here
Graphene-based batteries have exciting potential and while they are not yet fully commercially available yet, R&D is intensive and will hopefully yield results in the future. Companies all over the world (including Samsung, Huawei, and others) are developing different types of graphene-enhanced batteries, some of which are now entering the market. The main applications are in electric vehicles and mobile devices.
Some batteries use graphene in peripheral ways - not in the battery chemistry. For example in 2016, Huawei unveiled a new graphene-enhanced Li-Ion battery that uses graphene to remain functional at higher temperature (60Â° degrees as opposed to the existing 50Â° limit) and offer a double the operation time. Graphene is used in this battery for better heat dissipation - it reduces battery's operating temperature by 5 degrees.
The latest graphene batteries news:
An international research group, including teams from CHOSE at the University of Rome Tor Vergata, Hellenic Mediterranean University in Greece and others, has developed a large-area perovskite solar panel with graphene-doped electron transporting layers (ETLs) and functionalized molybdenum disulfide (fMoS2) buffer layers inserted between the perovskite layer and the hole transporting layer (HTL).
The team reported that with increasing temperatures, the module exhibited a smaller drop in open-circuit voltage than commercially available crystalline silicon panels.
Zero Emissions Developments (ZED) is an Australia-based company that has announced the development of a technology to build longer lasting, greener, more efficient and more affordable graphene-based solar and EV batteries. It is now seeking AUD$30 million (around USD$22,300,000) in private investment to build a manufacturing plant that will produce these batteries.
The planned manufacturing plant will produce the PowerCap batteries in southeast Queensland through the entity, PowerCap Un Ltd.
Recent research has shown that the incorporation of graphene-related materials improves the performance and stability of perovskite solar cells. Graphene is hydrophobic, which can enhance several properties of perovskite solar cells. Firstly, it can enhance stability and the passivation of electron traps at the perovskite’s crystalline domain interfaces. Graphene can also provide better energy level alignment, leading to more efficient devices.
In a recent study, Spain-based scientists used pristine graphene to improve the properties of MAPbI3, a popular perovskite material. Pristine graphene was combined with the metal halide perovskite to form the active layer of the solar cells. By analyzing the resulting graphene/perovskite material, it was observed that an average efficiency value of 15% under high-stress conditions was achieved when the optimal amount of graphene was used.
University of Cambridge researchers have designed a lithium-ion battery that can be directly charged in sunlight. This was done in an effort to improve the general process of connecting solar panels to batteries to store energy when the sun is shining.
The idea is to simplify how solar energy is harvested and stored, says Michael De Volder, a mechanical engineer at the University of Cambridge who led the work. If the team can improve the efficiency and lifetime of the hybrid device, its cost will likely be lower than combining solar cells and batteries. For the price of a battery, you get both functionalities, he says.
A research team, led by Dr. Luigi Angelo Castriotta at the at University of Rome Tor Vergata's CHOSE Center for Hybrid and Organic Solar Energy, has reported impressive results on methylammonium free perovskites processed in air, using a scalable technique based on infrared annealing and potassium doped graphene oxide as an interlayer.
The team reached excellent efficiencies of 18.3% and 16.10% on 0.1cm2 cell and on 16cm2 module respectively, with enhanced stability compared to the standard multi cation reference.
Researchers at Northwestern University and Clemson University in the U.S, along with researchers from Sejong University in Korea, have examined the origins of degradation in high energy density LIB cathode materials and developed graphene-based strategies for mitigating those degradation mechanisms and improving LIB performance.
Their research could be valuable for many emerging applications, particularly electric vehicles and grid-level energy storage for renewable energy sources, such as wind and solar.
Researchers from the University of Nottingham’s Centre for Additive Manufacturing (CfAM) have reported a breakthrough in the study of 3D printing electronic devices with graphene.
The scientists utilized an inkjet-based 3D printing technique to deposit inks that contained flakes of graphene, in a promising step towards replacing single-layer graphene as a contact material for 2D metal semiconductors.
Researchers led by Professor Tony McNally, from WMG, at the University of Warwick, in partnership with Senergy Innovations, have launched the first nanomaterial enabled all polymer solar thermal cell. This achievement was supported by funding from BEIS (Department for Business, Energy & Industrial Strategy).
The thermal properties of the polymers that were used were modified to enable heat from sunlight to be transferred with high efficiency to heat water in a low cost and sustainable way. The modular design of the cells reportedly allows for the rapid construction of a solar thermal cell array on both domestic and industry roofing.
An experimental graphene-based perovskite solar farm has been operating in Greece for several months, and early results are said to be very promising when it comes to power output and efficiency.
Located at the Hellenic Mediterranean University in Crete and spearheaded by the EU’s Graphene Flagship, the new solar farm consists of nine grapheneperovskite panels with a total area of 4.5m2 and a total output of approximately 261 watt-peak (Wp).
Researchers at MIT have developed a new roll-to-roll production process for large sheets of high-quality graphene, which the team says could lead to ultra-lightweight, flexible solar cells, and to new classes of light-emitting devices and other thin-film electronics.
The new manufacturing process, which the team says should be relatively easy to scale up for industrial production, involves an intermediate buffer layer of material that is key to the technique’s success. The buffer allows the ultrathin graphene sheet, less than a nanometer (billionth of a meter) thick, to be easily lifted off from its substrate, allowing for rapid roll-to-roll manufacturing.