Researchers from the Functional Nanomaterials department at IREC explored the role of the electronic spin configuration in the design of catalytic additives in a study published in two prestigious journals: ACS Nano and Advanced Materials. This research, conducted by Jing Yu and Chen Huang as first authors and co-led by ICREA Prof. Andreu Cabot, head of the Functional Nanomaterials department, offers profound insights into the need for considering electronic spin configuration in catalysts for enhancing chemical reactions besides the charge distribution, especially for the development of robust Lithium-sulfur batteries (LSBs).
Lithium-sulfur batteries (LSBs) are gaining attention as a promising alternative to traditional lithium-ion batteries due to their higher energy density, lower cost, and environmental friendliness. However, several challenges including the low conductivity of the cathode active material, the migration of sulfur species, and the slow lithium-sulfur redox reactions, hinder their commercialization.
During the discharge and charge cycles of an LSB, sulfur (S₈) undergoes a series of electrochemical reactions resulting in various intermediate components called polysulfides such as Li₂S₂. These polysulfides are soluble in the electrolyte and can move between anode and cathode impacting the battery’s capacity, efficiency, and lifespan. To enhance the performance of LSBs, the use of catalytic additives is essential to accelerate the lithium-sulfur redox reaction which prevents the loss of sulfur.
In the recently published study “Electronic Spin Alignment within Homologous NiS2/NiSe2 Heterostructures to Promote Sulfur Redox Kinetics in Lithium-Sulfur Batteries” from Advanced Materials, researchers could activate the Li-S reaction using catalysts to maximize the capacity and stability of Li-S batteries. Here, hollow NiS2/NiSe2 heterostructures encapsulated in a nitrogen-doped carbon matrix (NiS2/NiSe2@NC) were synthesized and used as a catalytic additive in sulfur cathodes. The high spin configuration of the resulting heterostructure raises the electronic energy level, activating the electronic state. This accelerated the charge transfer and optimized the adsorption energy, lowering the reaction energy barrier of the polysulfides conversion.
In the parallel study “Promoting Polysulfide Redox Reactions through Electronic Spin Manipulation” from ACS Nano, researchers manipulated the electronic spin configuration, through defect engineering, of a catalyst to improve LSB performance. Specifically, they introduced Co vacancies to CoSe nanosheets, the chosen catalytic material for the study. This manipulation changed how the electron spins were arranged increasing the number of unpaired electrons aligned in the same direction. Consequently, less energy was needed for the lithium-sulfur redox reaction to occur and the formation of Li2S was more consistent and even. In other words, the manipulation of the electronic spin configuration resulted in a more efficient and stable battery. These studies are relevant since they show that the manipulation of the spin state distribution resulted in highly improved LSB performance, with higher capacity, and longer-lasting stability. This demonstrates the need for considering electron spin distribution in the design of electrocatalysts, particularly for designing more efficient and cost-effective LSBs.
This research was a collaborative effort, with invaluable contributions from researchers at the Catalonia Institute for Energy Research (IREC), Catalan Institute of Nanoscience and Nanotechnology (ICN2), Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), ALBA Synchrotron, University of Catania, Lanzhou University, South China Normal University, University of Wollongong, Chengdu University, Chongqing University of Technology. Their collective expertise and dedication have been instrumental in this pioneering study.
For a more in-depth exploration of this research, please refer to the original article in the ACS Nano Journal on American Chemical Society Publications and Advanced Materials from Wiley and their Supporting Information available.
