discussions. All this needs big efforts in research and development.
Figure 1.23 Energy and power density for different storage systems. Source: R. Kötz, M. Hahn, R. Gallay, 9th UECT‐Ulm, Electrochemical Talks, 2004, Neu‐Ulm, Germany.
Lightweight construction is one precondition for the breakthrough of e‐mobility. Another challenge is the storage of electrical energy. Different storage systems are available or under development. Due to their differences in power density and loading and unloading characteristics, the intelligent combination of all of them is necessary. This could provide the desired acceleration and cruising range (Figure 1.23). Capacitive systems with fast unloading enable the powerful acceleration: Li‐ion batteries will cover the midsize cruising range, and fuel cell system will provide the energy for longer distances. In all these systems that are available or under development, carbon materials play an essential role.
The anode in Li‐ion batteries is made from graphite. The electrical characteristics are determined by a bunch of parameters, from the raw material source toward processing temperatures, grain shaping, coating, and many others. Natural graphite‐based anode material provides good charging and discharging characteristics. An advantage of natural graphite versus synthetic graphite is the unneeded graphitization treatment. A forecast for the expected demand for Li‐ion batteries storage capacity is shown in Figure 1.24.
As in many other cases the know‐how and production capacity are located in Japan (Figure 1.25). Europe with its high end car industry did hard to invest into this development. Currently, Europe is struggling to catch up.
Figure 1.24 Expected Li‐ion battery demand. Sources: H. Takeshita, IIT, 25th Int. Batt. Sem and Exhibit. Fort Lauderdale, FL, USA, 2008; Next‐mobility news 09/2017; Roland Berger Study on LiB /2018.
Figure 1.25 Li‐ion anode material producer and their capacity.
Electrical discharge layer capacitors (EDLCs) are fast loading and unloading systems. In contrary to the Li‐ion batteries, in which the intercalation in between the graphite layers is the storage process, EDLCs require an easy accessible high surface area with a preferred porosity in the nano‐range for the adsorption/desorption of charge carriers. Suitable carbon materials can be produced from a wide variety of sources. One source is from renewables like nutshells and others that are known from the production of activated carbons. Also synthetic sources can be used. Essential is the activation of the carbon surface. One advantage of these EDLCs is their high cycle life with more than one million cycles.
In a fuel cell the reactive components hydrogen and oxygen are separated from each other by a gas diffusion layer (GDL). The components diffuse through a gas penetrable layer formed by carbon materials until they reach the catalyst (Figure 1.26). The application of fuel cells is expected to concentrate on automotives and less on portable and stationary systems (Figure 1.27). Main industrial players in the field of GDL are located in Germany and Japan (Figure 1.28).
Figure 1.26 Fuel cell schematics.
Figure 1.27 Fuel cell demand distribution by application.
Redox flow battery systems are suitable for stationary energy storage systems. As carbon components they contain graphite felt and a bipolar plate out of graphite. Although this storage system is not yet widely installed, the forecast is promising (Figure 1.29). Yet the production capacities are small (Figure 1.30).
Graphite is an interesting candidate for systems for the storage of thermal energy. The thermal conductivity of fine‐dispersed graphite can be used in cooling and heating systems, for example, for the room conditioning of buildings or the storage of thermal energy. These systems are developed and tested currently. Latent heat storage systems have been commercially installed in air‐conditioning system for trucks.
Figure 1.28 Gas diffusion layer production capacity.
Figure 1.29 Redox flow battery production. Source: EscoVale Study – FlowBatteries, Dec. 2006.
1.4 Future Application of Carbon Materials
Tremendous future perspectives for carbon were forecasted with the discovery of nanoscaled new allotropes of carbon. Fullerenes were discovered in 1985 and became immediately a main research area in the field of carbon. The first Nobel Price was conferred in 1996 to H.W. Kroton, R.F. Curl, and R.E. Smalley for the discovery of fullerenes. The number of discussed potential applications reached from anti‐abrasive application to drug carrier in living organisms. None of the discussed applications were realized. The discovery of single‐wall nanotubes (SWCNT) and multiwall nanotubes (MWCNT) created new ideas in regard to their outstanding mechanical and electrical properties (Figure 1.31). SWCNT are still of academic interest only. MWCNT are industrialized in a few hundred ton scale and seem to find applications in functional polymers. The second Nobel Prize on carbon was granted to Konstantin Novoselov and André Geim for their work on graphene and its electrical properties. A very promising application of revolutionary impact in microelectronics may come from graphene sheets. Template‐grown graphenes are considered as very promising in this regard. The work of W. de Heer in this field was granted in 2011 by the SGL Carbon Group with the new established Utz‐Hellmuth Felcht
