The main development goals for double-layer capacitor are

• long lifetime
• increase of the rated voltage
• improvement of the range of operating temperature
• increase of the energy and power densities.

According to Montena, the rated voltage will be increased up to 3 V within the next years. To easily access automotive applications a temperatures range from –35 up to 105 °C seems realistic. Montena fixes energy and power density goals for double-layer technology at 10 Wh/kg and 10 kW/kg.

From on-going research and development, Montena expects an increase of the electrolyte decomposition voltage and ionic conductance, an increase of the electrode accessible surface, chemical and mechanical stability as well as electronic conductance and the separator electronic insulation level and ionic conductance. A main activity lies in the development of new electrolytes based on the combination of novel organic solvents and improved conduction salts, permitting not only a higher rated voltage and a higher conductivity but also a larger operating temperature range.

State of development

Double-layer capacitors are only starting to become a mature and reliable technology.

As can be seen from Figure 4 the performance of double-layer capacitors is fitted for the range from light rail vehicles to regional trains.

Figure 4: Ragone diagram and charging times (corresponding to braking times of different trains)

Source: IZT, data mainly from: Hentschel et al. 2000