An eco-friendly, inexpensive system for storing high-power energy from pine biomass

The Solid State and Materials Research Group has come up with a lithium-ion capacitor using electrodes produced from wood particles that are discarded as waste in sawmills. This biomass is very easily available across the Basque Country, and sustainable, inexpensive processes have been used to produce electrodes. The results reveal that the materials derived from biomass have excellent properties for obtaining eco-friendly, cost-effective systems designed to store high-power energy.

The paper is published in the Journal of Power Sources.

In the quest for sustainable energy solutions capable of meeting the energy needs of modern society, energy storage systems play a hugely important role. Indeed, “in the field of renewable energies we cannot control the wind, heat, light, etc. that nature offers us. And the energy demand sometimes does not coincide with the energy supply; so resources need to be developed to store that energy produced by renewable systems,” explained Eider Goikolea, a researcher in the Solid State and Materials Research Group.

Materials for the next generation of electrochemical energy storage technologies are being developed by the members of the research group Goikolea and Idoia Ruiz de Larramendi (UPV/EHU lecturers).

“We develop new materials that can be used to store energy. In this case, to create electrodes we prepared carbon from the wood particles of the insignis pines that are all around us and are used in carpentry workshops. At the end of the day, this sawdust is not used for anything and has a very high carbon content,” said Ruiz de Larramendi.

Hybrid system

Batteries and supercapacitors are used, among other things, to store energy. Supercapacitors are able to store less energy than batteries, but they are able to provide a greater amount of energy at a given moment. “Supercapacitors are not suitable for providing a system with energy over a long period; unlike batteries, they are used if we want a large amount of energy during a short period of time,” explained Goikolea.

A hybrid lithium-ion device was developed in this research. “This offers the advantages of both systems: high-power energy can be stored (as in batteries), it can operate at high-power levels and is able to withstand many charge-discharge cycles (like supercapacitors),” she said. So a battery type electrode and a supercapacitor type electrode have been combined within the same device.

Different types of carbon were used to produce these electrodes. “Carbon is a very general term, but there are many different types. Not all biomass provides the right carbon for this application, but we have shown that very satisfactory results can be obtained from the biomass of the insignis pine,” added Ruiz de Larramendi.

One of the electrodes was made of hard carbon and the other was made of activated carbon.

What is more, great importance was attached in the research to the use of cost-efficient, sustainable processes for producing the electrodes: “The process to produce the electrodes was energy-efficient. The synthesis temperatures did not exceed 700 °C,” and economical additives were used.

This work shows that very good results were obtained even with the use of local biomass. “It constitutes a cost-effective, sustainable alternative for improving conventional lithium-ion capacitors. Materials originating from biomass offer great opportunities for developing eco-friendly, cost-effective high-power energy storage systems. It is important to further this line of research,” explained the UPV/EHU researchers.