Researchers build metal-free micro-supercapacitor arrays

Researchers working on the Horizon Europe-funded REFORM project have constructed high-rate metal-free micro-supercapacitor arrays using highly conductive organic inks.

Specifically designed to store high-voltage pulse electricity efficiently, the metal-free array developed by the research team can be printed onto paper substrates using the conducting polymer PEDOT:PSS.

It is anticipated that REFORM’s micro-supercapacitor array could form the basis for the development of future technology that could harvest clean and renewable energy from ambient mechanical sources, such as wind, ocean waves, water droplets, and human motion.

Writing in Advanced Science, researchers from KTH Royal Institute of Technology and Spanish R&D company, CIDETEC Surface Engineering, detailed how their metal-free micro-supercapacitor arrays employ highly conductive organic inks to capture ambient mechanical energy sources.

Speaking to coincide with the publication of the journal article, Dr Jiantong Li from KTH Royal Institute of Technology described how the project’s full-printed micro-supercapacitor arrays can directly store high-voltage (>150 V) pulse electricity produced by droplet-based electricity generators at a high energy storage efficiency of 62%.

Enable scalable direct ink writing of micro-supercapacitors on paper

“The key to our innovation is the formulation of highly conductive organic inks based on properly doped poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) that enable scalable direct ink writing of micro-supercapacitors on paper substrates with excellent electrochemical performance”.

“Our printed symmetric micro-supercapacitors simultaneously exhibit a wide voltage window of 1.6 V and a high areal capacitance over 60 mF cm⁻² at a high scan rate of 1 V s⁻¹”.

“We printed highly dense micro-supercapacitor arrays that consist of 100 cells connected in series on paper substrates, delivering a large overall capacitance of 3 µF at an ultrahigh scan rate of 30 V s⁻¹ and an ultrawide voltage window of 160 V”.

REFORM project coordinator, Dr Yolanda Alesanco, believes that the research team have developed a simple and scalable process to print ultrahigh-rate large-scale metal-free micro-supercapacitor arrays on paper substrates to store high-voltage pulse electricity directly.

“Our compact and metal-free micro-supercapacitor arrays are excellent candidates for sustainable high-performance energy storage in self-charging power systems”.

Additional electronic components are also required in power management modules

“Current energy storage devices only work at low voltage and possess low charging rates. Additional electronic components, like buck converters, inductors, capacitors and transformers are also required in power management modules to step down the high voltage or buffer the electricity Not only do these added components increase the complexity, but they also induce considerable extra losses during energy conversion”.

“Our on-paper, metal-free, and large-scale micro-supercapacitor arrays provide an efficient, compact, and sustainable solution to address the challenge of directly storing the high-voltage instantaneous electricity produced by mechanical energy harvesters”.

“As such, we believe they will contribute to the development of entirely sustainable self-charging power systems for emerging electronics”.

REFORM’s large-scale micro-supercapacitor arrays consisting of up to 100 cells can be fully printed on paper substrates within a small footprint area of 2.4 × 3.4 cm².

Micro-supercapacitor arrays can directly store instantaneous high-voltage

Thanks to their striking performance of large capacitance >3 µF, ultrawide working voltage window up to 160 V, and ultrahigh rate capability over 30 V s⁻¹, the micro-supercapacitor arrays can directly store instantaneous high-voltage (>150 V) electricity with a high energy storage efficiency of 62%, over one order of magnitude higher than that of the present batteries and capacitors.

REFORM is a 42-month project and was awarded funding under the European Union’s Horizon Europe programme. The project brings together world-leading academics, non-profit research organisations, industry experts and innovative businesses from across eight different European countries.

According to the organization’s credo, REFORM is a female-led project aiming to develop printed green electronics that will accelerate and guide the creation of a new European functional electronics supply chain. The project employs eco-design principles to produce green printable electronics that meet the demands of multiple industries and sectors so that e-waste will cease to be a problem in the future.