Thin film batteries for a greener future

Three years ago, the GREENBAT Project set out to create thin-film batteries that were environmentally friendly, economically viable to mass produce and that integrated materials already optimised in conventional batteries. Now over, VARTA Microbattery explains how successful the work was in doing this and how the future looks for green batteries.

Three years ago, the GREENBAT Project set out to produce green and safe thin-film batteries, which can be used for flexible cost-efficient energy storage. With funding for this work recently coming to an end, assessment of the research concludes that it could have provided long-term benefits for us all in terms of the efficiency and flexibility of the batteries we use in many applications as well as the impact these essential sources of energy have on the environment.

The project set out with three clear aims. Firstly, the work, which was coordinated by VARTA Microbattery GmbH at Ellwangen in Germany, concentrated on the use of environmentally-friendly base products for battery construction. This meant moving away from organic formulations used in conventional batteries, towards aqueous ones as well as improving their operating lifetime, in order to decrease the rate of replacement.

Secondly, the project set out to create cost-efficient, thin-film battery production technology to make any development of the eventual product economically viable. This work applied to both the base products and the application process, which need to be developed in line with each other in the perspective of devices’ mass production.

Finally, GREENBAT wanted to integrate materials specifically (and already) optimised for lithium-ion battery application into its solutions. This meant using high-energy density or high-power density depending on the application, as well as high cyclability.

So from printing and cycling tests, the best one was selected and improved. In parallel, the organic solution was developed to be printable in order to be used as a back-up solution, in the case when cycling tests with no aqueous binder appeared possible. Currently some candidate aqueous binders are testing and preliminary results seem promising. Lengthy cycling tests are necessary, however, to evaluate the electrochemical stability of the inks.

In 2007 VARTA Microbattery decided to apply for funding for the GREENBAT project.

Partners for a consortium were found and VARTA Microbattery applied for funding at the EC’s DG INFSO. We called the project GREENBAT and our aim was to develop a green, thin and flexible Li-Ion-Battery for organic electronics applications.

We began work in 2008 together with our project partners.

These partners were: CEA Liten, (electrochemistry, SbS printing); VTT, (R2R printing); Imperial College London (electrolyte development); Norbert Schläfli Maschinen (lab-scale printing tools) and Plastic Electronics, (application).

It is a project with far-reaching applications, cutting across a variety of commercial outlets and, as the project’s name suggests, there are environmental benefits in adopting this technology.

The new batteries will avoid the use hazardous substances for printing a battery, there will also be high energy density for a long lifetime along with flexible design for easy shape change.

VARTA Microbattery has been involved in the scheme of printed electronics since the foundation of the Organic Electronics Association (OE-A) in 2005. VARTA Microbattery´s role in the GREENBAT project is leader of the Demonstrator Group, where interesting items using printed electronics have been prepared as demonstrators and shown in a brochure and at many events worldwide. The most important one is the LOPE-C with nearly 1.000 visitors.

One of the main contributory factors in analysing the successful impact of any commercial research project is assessing the time to market. In the case of GREENBAT, this success largely depends on external factors as convergence and harmonisation are crucial.

The time to market strongly depends on the development of the other printed electronics components. This is because a direct harmonisation with end users is important.

A big advantage for a thin-film battery is the flexible design. A change of size and electrical properties can easily be achieved compared to common known battery technologies.

We expect that printed batteries will be used first of all in energy autarkic sensors, advertisement items, smart card applications and active RFID tags. And due to the fact that this is a new battery technology there could be even new market segments or applications in the areas healthcare, logistics or packaging.

VARTA Microbattery is a very innovative company. They are involved in many all- important research and development projects, for example loading of Piezo generators, all-solid-state batteries, loading of organic photovoltaics, smart textiles, carbo-nano- tubes in batteries, metal/air systems, lithium/air-cells and stationary energy storage.

We believe there are a number of advantages in moving from organic formulations towards aqueous ones? These include:

• There are environmental benefits (solvents are hazardous and maybe prohibited).

• There is no hazard in the production, so fewer precautions are needed.

• There may well be cost savings in production.

In general, products have to be developed in tight contact with marketing. Our aim is to reach a marketable product in the areas of smart packaging, logistics, healthcare, sensors and gaming as a result of the GREENBAT workshop, which took place in May 2011. And with VARTA coordinating this work we can be ambitious.

VARTA Microbattery is a leading international manufacturer of OEM and retail batteries with more than 100 years’ experience.

They develop and produce batteries of all electrochemical system types and sizes in Ellwangen.

With professional teams in the fields of engineering, production, logistics and distribution they meet the requirements of customers around the world. VARTA Microbattery invests continuously in research and development to ensure their position as market leader.

Click here to access the project website.

Published: Friday, 21st October 2011