We live in an electric world and electricity should be stored unless it is currently consumed. We are surrounded by electronic devices carrying batteries, and vehicles are leaving fossil fuels behind to become electricity. In this context, development new sustainable batteriesgood benefits and being economical is a real necessity.
Various CSIC research groups work to improve energy storage and supply systems. Either to seek more sustainable and abundant materials, or to seek or obtain complementary systems to meet future energy needs. thermoelectric This can power devices without the need to store energy.
“Batteries are chemical devices that store energy,” explains M. Rosa Palacín, a researcher at the Barcelona Institute for Materials Science (ICMAB). “A battery consists of one or more electrochemical cells consisting of two electrodes separated by an electrolyte, a liquid that conducts ions and does not conduct electricity. Electrons are transferred from one electrode to another via an external circuit that creates the electric current we use. In parallel, balancing this electric current, the ions flow from one electrode inside the battery to the other via the electrolyte,” he adds.
During discharge, the negative electrode material is oxidized (donates electrons) and the positive electrode material is reduced (gains electrons). When these reactions are reversible, it is possible to recharge the battery by connecting it to an electric current for the reverse process to occur. The most widely used rechargeable battery technology in electronic devices and electric vehicles is lithium-ion.
“If metallic lithium could be used, the batteries could provide much more energy,” explains Palacín. “One of the alternatives being worked on is solid electrolytesbut in this case although it is necessary for the batteries to work at high temperature so that ions conduction is efficient, which is not the most ideal,” he adds.
In every situation, lithium is scarce and expensive. Alternatives to using a metal as a negative electrode might include calcium and magnesium, which are more abundant and less expensive, considering increasing energy density and keeping in mind sustainability criteria.
Calcium and magnesium batteries
The main advantage of calcium and magnesium batteries is their very high energy density., twice that of lithium. And they would be cheaper. Since it will not be possible to reach potentials similar to those of lithium, the researchers concluded. hybridization It consists of high energy density calcium and magnesium batteries with high power super capacitors.
M. Rosa Palacín and Alexandre Ponrouch at ICMAB, They are working on the development of the components of these batteries: the two electrodes and the electrolyte. A complete battery has not yet been obtained, but electrolytes have been obtained that improve the performance of calcium and magnesium electrodes.
“Research in this area is at an early stage where each battery component needs to be individually optimized,” explains Ponrouch. “As lithium technology has already been developed, it is a great advantage to study the key challenges with new materials: the mobility of ions in the electrodes and electrolyte, the susceptibility of materials to contamination or moisture, and the complex processes that occur at the interfaces between the electrodes and the electrolyte,” adds Ponrouch.
Redox flow batteries to store renewable energy
Alternative and new electrical energy storage systems include the vanadium redox flow battery.. To investigate the development of redox flow batteries, CSIC has dedicated the Interdisciplinary Thematic Platform (PTI), a research structure that brings together scientists, companies, and administrations to solve high-impact social problems. The Flowbat platform, created in 2019 and coordinated by researcher Ricardo Santamaría from the Institute of Carbon Science and Technology (INCAR), has already achieved a promising prototype.
“Can Having redox flow batteries with higher performance would mean a significant improvement in the energy storage framework. Large-scale electricity, traditionally driven by hydroelectric pumping and compressed air technologies, poses serious problems both in terms of the environment and the geographic location of its facilities,” explains the researcher. Zoraida Gonzalezfrom the same centre.
these batteries They are electrochemical energy storage systems with lower cost and environmental impact. more than other systems such as lithium-ion batteries. The initial goal of the platform was to create a small-scale demonstrator, 1 kilowatt vanadium redox flow cell. The demonstrator is available from June 2021 with excellent results.
The next goal of the platform is the design, manufacture, commissioning and testing of a 50 kilowatt battery in the real environment by the end of 2022. Like other batteries it has two electrodes (where there are redox reactions related to charging and discharging). processes) and separators (ionic exchange membranes between two half-cells). Its differentiators are the two external tanks for storing electrolytes.
The modularity of these batteries also increases the possibility of using them on a smaller scale.
Commissioning the 50 kW battery in a real environment will demonstrate the potential of the platform to the scientific community and end users of the technology, both CSIC like Spain In the redox flow battery market in line with the European Green Deal and the UN Sustainable Development Goals.
Thermoelectric generators for the internet of things
Luis Fonseca of the Barcelona Microelectronics Institute (IMB), Working with his team on the development of silicon microstructures taking advantage of the ambient temperature to generate electricity that can power low-consumption sensors.
With silicon technologies, thermoelectric microgenerators that can be applied to the internet of things and power sensors that can operate autonomously wherever there is a hot surface are produced. When used with a secondary (rechargeable) battery, they keep the battery constantly charged.
Fonseca explains: “Silicon technology, the Information Society and A mature champion of technology, miniaturization and large-scale production based on abundant materials”.
In order to create thermoelectric devices from this material, it is important that they both have an architecture that allows the difference in ambient temperature to be physically transferred into them and integrate thermoelectric materials compatible with silicon into them. for now, succeeded in integrating silicon nanowires into silicon structuresallows an approach made entirely with this material.
“Combining silicon technologies with the integration of foreign functional materials has been a dialogue between two different technological worlds: micronanofabrication and materials. Fonseca is the right way to be able to manufacture the number of devices demanded by Internet of Things applications on a large scale, at a reasonable cost and with an acceptable environmental impact,” he said. explains.
Beyond thermoelectric applications, but within microenergy, the technological compatibility effort of functional oxides has increased its involvement in the Epistore project, which produces micro fuel cells that use hydrogen as an energy source to replace fossil fuels.
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