A researcher holds the gel electrolyte over a large-area lignin electrode coated on a metal collector. Photo: Thor Balkhed.
A researcher holds the gel electrolyte over a large-area lignin electrode coated on a metal collector. Photo: Thor Balkhed.

Safe, cheap and sustainable technology for energy storage has been developed in the Laboratory of Organic Electronics at Linköping University, Sweden. It is based on two major breakthroughs: the manufacture of wood-based electrodes in rolled form, and a new type of water-based electrolyte. Reported in a paper in Advanced Energy & Sustainability Research. the technology has already been patented and is set to be commercialized by Norrköping-based spin-off company Ligna Energy.

An increasing share of renewable energy in the energy mix and increasing consumption of electricity in society are causing major challenges for balancing power supply networks. In principle, electricity is consumed at the instant of its production, and there are currently limited options for storing large amounts of electricity. The problem is particularly acute during cold periods, when the demand for electricity is highest. Imbalance in the grid can cause serious power outages.

Xavier Crispin and his colleagues at the Laboratory of Organic Electronics have now developed a concept for large-scale energy storage that is safe, cheap and sustainable, based on organic batteries. The potential power output of these batteries is sufficiently high for them to maintain power balance in the electricity supply.

“Our results allow for safe, environmentally sustainable organic energy storage with high power density, 5kW/kg, where the electrodes are manufactured from wood-based material in a printing press,” says Crispin. “We must, however, increase the energy density: our organic batteries are better than normal supercapacitors, and have about the same performance as lead-acid batteries. But lithium-ion batteries are better.”

Previous attempts to develop a sustainable system for energy storage based on cheap organic and water-based electrolytes with carbon-based electrodes have all had problems with rapid self-discharge: it has been difficult to store energy for more than one day.

The excellent results reported in the paper are based on two breakthroughs: a new type of water-based electrolyte, and electrodes made from lignin, which is a readily available, cheap by-product from the manufacture of paper. The organic battery thus comprises a polyelectrolyte that consists of a highly concentrated water-based polymer, potassium polyacrylate, together with biopolymer lignin (as the positive electrode) and polyimide mixed with conductive carbon (as the negative electrode).

“The voltage drop, which measures the self-discharge, is less than 0.5V in 100 hours, which is a world record for energy storage with organic electrodes in water-based electrolytes,” says Crispin.

The new technology also uses cheap raw materials: neither lignin, carbon nor the polyelectrolyte cost more than US$1/kg. These are readily available and non-flammable materials, and the technology can be scaled up to large batteries. It is a sustainable solution for large-scale and safe energy storage.

This story is adapted from material from Linköping University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.