Graphene Ball : A New Material Which Fully Charged in 12 Minutes

Battery plays a vital role as a power source ranging from smartphone to electric vehicles. The lithium ion battery is the most widely used battery and is also the best battery type to date in terms of energy storage and charging speed. The components of lithium ion battery consist of electrolytes, anodes and cathodes. The anode of lithium ion battery use nano carbon materials such as Carbon Nano Tube (CNT) or graphene which can be made from graphite minerals. China is the world’s largest producer and exporter of graphite equivalent to US$ 246,377,000 in 2015 [1]. Graphite is a carbon alotropy-shaped mineral like a diamond, but the atomic structure affects its physical and chemical properties. Graphite is an electrical conductor and heat insulator while diamond is an electrical insulator and heat conductor. The difference in the structure of graphite and diamond atoms is described in Figure 1. 


Figure 1. (a) graphite atomic structure (b) diamond atom structure [2] 


Since Richard Feynman orated his famous speech “ There’s plenty of room at the bottom ” in 1959, researchers are working hard to synthesize materials of the smaller size than micrometers for technological development and advanced materials. The physical and chemical properties of a material are affected by the size so that the materials on the nanometer scale (1-100 nm) with a micrometer scale (1 μm or 10-3 mm) each have chemical and physical properties. Carbon-based nano materials steal the attention of many scientists because they have unique properties and availability in nature is very abundant. 

In 2004,  Andre K Geim and Konstantine Novoselov from Manchester University, UK conducted a study to take a thin layer of carbon with a thickness of only one atom found in pencil using tape. From that simple experiment, there was a thin layer in which each carbon was packed tightly in the form of a honeycomb-like crystal which was then called graphene. The research made them rewarded a nobel in the field of physics in 2010. Graphene is a nanomaterial composed of carbon atoms that make up a hexagonal structure like a two-dimensional honeycomb. Today, research on graphene has grown rapidly because graphene is the basic structure in the formation of other carbon-based nano materials such as Carbon Nano Tube CNT (multiple layers graphene which is rolled in the axial direction and Fullerene (a spherical carbon layer). 



Figure 2.  CNT and Fullerene structures formed from layers of graphene[3] 

Graphene is referred to as “super material” or “smart material” because it has unique properties such as high electric mobility (~ 10,000 cm2/V s), good optical transparency (97.7%), modulus young (~ 1 TPa) better than graphite (27.6 GPa), heat conductivity (~ 3000 W / m K) better than graphite (114 W / m K) and electrical conductivity (~ 106 S/cm) better than graphite (20 S/cm)[4]. Graphene material is utilized in areas such as health (for cancer therapy, biosensors), energy (solar cells, fuel cells, supercapacitors and batteries), electronics, catalysts and composites. 

Figure 3. Application of material graphene in various fields [3] 

On Wednesday, 28th November 2017, The Samsung Advanced Institute of Technology (SAIT) in collaboration with Seoul National University has developed a new battery material made of graphene ball and is able to recharge the battery 5x faster than the current lithium ion battery. The graphene ball material will be used as the anode on the lithium ion battery because it can increase energy density (energy storage capability) up to 27.6% (5000 – 6000 mAh) and can fully recharge the battery within 12 min [5] . The method used in manufacturing graphene ball is Chemical Vapor Depositionition (CVD) using methane gas (CH4)  as its raw material and SiO2 as growth medium. To produce graphene on the surface of SiO2 nanoparticles with a diameter of 20-30 nm, SAIT fed methane and SiO2 gases into the furnace at a temperature of 1000oC. The reaction is as follows: 

Graphene ball grew on the surface of SiO2 as when creating popcorn. Dr. Son In-Hyuk, who led the research, said that the cost of producing commercial scale graphene ball is less expensive when using the CVD method. From the results of the research, the process of growing graphene for 240 minutes was able to produce 84.5% mass of graphene with an electrical conductivity value of 65.5 S/cm. The results are better than 60-minute graphene filing process with a electrical conductivity value of 48.4 S/cm. 


Figure 4. (a) Graphene ball growing process on the surface of SiO 2 (b) The morphology of the graphene material ball  using SEM [6] 


The main problem in lithium ion batteries is the side reactions that occur in batteries that can produce hydrogen gas (H2) which when reacted with oxygen gas (O2) in the air can produce explosions especially when the battery is recharged too quickly. This happens in the case of Samsung Galaxy Note 7 which burned at the airport when recharged in 2016. Researchers at SAIT believe that the graphene ball material is able to reduce the potential danger and is safer to use. They also hope that lithium ion batteries using graphene ball material can be applied to electric vehicles because of their speed in recharging and greater energy storage capacity. 

References

[1] Sousa, G. 2017. Top 10 Graphite Exporting Countries. http://www.worldatlas.com/articles/top-10-graphite-exporting-countries.html (accessed on 7 Desember 2017)

[2] The Chemical Properties of Diamond. 2017. http://www.yarss.com/diamonds/Chemical-Properties-of-a-Diamond30pzuxantq/ (accessed on 7 Desember 2017)

[3] Samantara, Aneeya K. 2015. Graphene : Synthesis, Properties and Application. India : KIIT University

[4] Junaidi, M dan Diah S. 2014. Pengaruh Variasi Waktu Ultrasonikasi dan Waktu Tahan Hydrothermal Terhadap Struktur dan Konduktivitas Listrik Material Graphene. Surabaya : Institut Teknologi Sepuluh Nopember

[5] Shilov, A. 2017. Samsung’s Reveals Li-ion Battery with Graphene balls : Higher Capacity, Faster Charging. https://www.anandtech.com/show/12093/samsungs-liion-battery-with-graphene-balls-enables-higher-capacity-faster-charging (accessed on 7 Desember 2017)

[6] Son, In Hyuk, Jong H P, Seongyong P, Kwangjin P, Sangil H, Jaeho S, Seok-Gwang D, Yunil H, Hyuk C, dan Jang W C. 2017. Graphene balls for Lithium Rechargeable Batteries with Fast Charging and High Volumetric Energy Densities. Republic of Korea : Samsung Advanced Institute of Technology & Seoul National University

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