Research
PROJECT CHALLENGES

THE RESEARCH IN THIS PROJECT REACHES FROM UNDERSTANDING THE MECHANISMS GOVERNING THE FUNCTIONALITY OF THE STORAGE DEVICE TO DEVELOPING UP-SCALABLE COMPONENTS AND INTEGRATED DEVICES.

The research focus on four general areas. The following describes shortly these areas and the greatest challenges of the project. You can read more about our research in our publications.


1. HIGH ENERGY DENSITY MATERIALS

The energy content of a battery is given by its capacity to store charge and the battery cell voltage. By attaching high capacity substituent on the conducting polymer backbone it is possible to increase the energy storage capacity of the material by an order of magnitude. In this project, quinone functionalities are targeted as they provide high charge storage capacities and large variability. The possibility to systematically vary the quinone properties will be crucial as one of the main challenges is to enable electronic communication between the substituent and the conducting polymer backbone which in turn requires precise energy matching of the two components.


2. NANOSTRUCTURED SUBSTRATE MATERIALS AND ADDITIVES
The current trends in the battery design aim for developing large surface area 3D electrodes which can both facilitate the ion diffusion into the bulk of the electroactive component as well as enhance the overall capacity per weight or volume of the device. 
In this project we are working with electroactive polymers which are coated on a high surface area lightweight non-electroactive templates for manufacturing 3D porous electrodes. The nanostructured carrier also serves the purpose of armoring the otherwise mechanically brittle conductive polymers.
The challenges are to obtain mechanically strong, flexible, lightweight, porous, 3D electrodes of low internal resistance and high charge storage capacity both per weight and per volume.


3. DEVELOPMENT OF ENERGY STORAGE SYSTEMSSUBSTRATE MATERIALS AND ADDITIVES
We aim at the development of paper-based energy storage devices with unprecedented energy and power densities based on the use of thin electroactive organic films on large surface area cellulose substrates.
The main associated challenges in this project involve the development of inexpensive and well-functioning non-metallic current collectors and packaging materials.
4. CURRENT PERFORMANCE AND PERFORMANCE OPTIMISATION

We are continuously optimising the performance of our devices. The present performance data for a (two-electrode) symmetrical device are summarised below.  


Cell voltage: 0.6 to 1.0 V 
Cell resistance: >0.4 Ohm
Active material: up to 65% in the composite
Electrode area: up to 246 m2/g 
Cell capacitance: up to 60 F/g (active material)*
up to 2.1 F/cm2
Charge time: 22 s for a 12 F device (0.8 V)
Current density: up to 31 A/g (active material)
Energy density: up to 1.75 Wh/kg (active material)*
up to 0.18 Wh/L ((active material)* 
Power density: up to 2.7 kW/kg (active material) *
up to 0.27 kW/L (active material)*
Cycling stability: 0.7% capacitance loss during 4000 cycles 
Self discharge time: a few days
*using twice the amount of the active material of the smaller electrode.

Further details regarding these data can be found in our publications.


5. Challenges


To further improve the performance of our devices, we are at present mainly addressing the following issues:

  • How can the stability of the electroactive components be increased?
  • What is causing the self-discharge?
  • How can the cell resistance be decreased?
  • What processes should be used when up-scaling the devices?