Illinois Tech physics researchers have recently published three new papers that study the structural basis for improved battery electrode performance and suggest that higher capacities are possible with engineered materials. The researchers are Carlo Segre, interim chair of the Department of Chemistry and Duchossois Leadership Professor of Physics, Elena Timofeeva, research associate professor of chemistry, and chemistry and physics Ph.D. candidates Elahe Moazzen, Shankar Aryal, and Yujia Ding,
The first paper, “Role of Crystal Lattice Templating and Galvanic Coupling in Enhanced Reversible Capacity of Ni(OH)2/Co(OH)2 Core/Shell Battery Cathode,” was published in Electrochimica Acta. The study explored novel core/shell nanoscale architectures for nickel hydroxide electrodes for aqueous rechargeable batteries. The findings of this study showed that a cobalt hydroxide additive, typically considered as inactive material, can also be part of a reversible charge and discharge reaction, adding to the material’s capacity. The reversibility of the cobalt hydroxide redox reaction is dependent on the Co(OH)2 shell thickness around the Ni(OH)2 core nanoparticles, with the optimal thickness leading to a more complete utilization of the nickel hydroxide and enhanced performance.
The next paper, “Structural Studies of Capacity Activation and Reduced Voltage Fading in Li-Rich, Mn-Ni-Fe Composite Oxide Cathode,” was published in Journal of The Electrochemical Society. Lithium-ion batteries have the advantage of high cell voltage and high energy density, which make them first-choice solutions for portable electronic devices, electric vehicles, and stationary energy storage. Only a few types of Lithium-ion battery cathode materials are currently used in commercial cells, including cobalt-based layered oxides, iron-based olivine phosphates, and manganese-based spinel oxides. As cobalt is expensive and toxic, attempts have been made to replace it with cheaper and more environmentally friendly iron. This study investigates the mechanisms behind the reversible capacity and reduced voltage fading mechanisms of nanoscale cobalt-free, lithium and manganese rich cathodes, specifically the complementary role played by the intimate mixing of two distinct structures that are present in these compounds.
The third paper, published in Advanced Energy Materials, is “In Situ EXAFS-Derived Mechanism of Highly Reversible Tin Phosphide/Graphite Composite Anode for Li-Ion Batteries.” This study examines the reversibility of an anode material for lithium-ion batteries. Tin phosphide is a conversion-type material with high theoretical capacity but poor cycling performance . However, this study demonstrated that higher reversibility can be achieved through formation of a nanocomposite with graphite. Using the advanced x-ray characterization techniques available through Illinois Tech’s Center for Synchrotron Radiation Research and Instrumentation, this paper reveals the detailed structural mechanisms contributing to the high reversibility of nanocomposite and explains the fading mechanisms in regular tin phosphide. This research indicates that composites may offer a path to improved performance for other battery materials.