Solid-state Li-ion batteries utilize a solid-state electrolyte, which has significantly improved safety as compared to current commercial Li-ion batteries, as the ceramic electrolyte is inflammable, as well as the ability to operate at greater voltage and thus obtain higher energy density. Through this project, UMERC researchers are developing new material structures to improve cyclability, coulumbic efficiency, and provide higher energy and power density. Advancements in solid-state Lithium-ion battery technology will improve fuel efficiency of plug-in electric vehicles and reduce their costs.
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Our lab has made crucial strides in all areas of SOFC performance and operating temperature. A recent breakthrough in electrolyte material called SNDC shows a five-fold increase in ionic conductivity over the popular yttria-stabilized zirconia (YSZ) electrolyte. Dr. Wachsman's continuum-level electrochemical model showed an end to the trend of thinner electrolyte layers helped optimize fuel cell design. We have successfully constructed a 3D model of an LSCF cathode which provides the ability to quantify porous cathode microstructure at the submicrometer level.
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Ion transport membranes are useful in gas separation such as production of O2 and H2 gasses and the manufacturing of syn gas. Our lab’s advances in fundamentals of ionic transport have led to increased ion selectivity and permeability of membranes. We have developed materials that not only provide higher ionic conductivity, but do so at a dramatically lower temperatures than previously required.
Our development of a bismuth oxide bi-layer electrolyte is particularly exciting. The study of ionic transport in cubic bismuth oxides is important technically because these materials exhibit the highest oxygen-ion conductivity of any material known to date. From a scientific point of view, the study of ionic transport in cubic bismuth oxides also provides an understanding of how anion transport in oxides with the fluorite structure is influenced by high vacancy concentration and how this is influenced by local structure.
We have developed solid state sensor technology that can provide an inexpensive, rugged, solid-state device capable of measuring the concentration of multiple species (such as NO and CO) in coal combustion exhaust. Our goal is to extend this technology to create a single potentiometric (voltage output) sensor that is sensitive to multiple gasses (NOx, CO2, O2). Such a sensor can be used to improve combustion control, resulting in both improved fuel utilization and reduced emissions.
Our research has shown that the Mixed Potential Theory is insufficient for the NOx sensing mechanism of sensors that employ metal oxide semi-conducting electrodes. We developed a more comprehensive mechanism called the Differential Electrode Equilibria that produces a more accurate model.
Electrocatalysis is a catalytic chemical reaction in which electrons are produced as a product. Work in all of our projects is directed by and contributes to advances in electrocatalysis. SOFC's and solid-state sensors require fuels to be modified for their systems. This can happen using a separate reformer or internally. Ideally, an external reformer would not be necessary but due to the carbon and sulfur in many fuels causes coking (build up of carbon in fuel lines) and fouling. Advances in electrocatalysis help minimize these problems without pre-processing of fuels.
Our lab has advanced the understanding electrocatalytic CH4 conversion and the post- combustion reduction of NOx. We recently showed that the Mixed Potential Theory is insufficient for metal oxide semi conducting electrodes such as LaFeO3 and LaMnO3. We developed a more comprehensive mechanism called the Differential Electrode Equilibria that considers adsorption behavior in addition to the response from electrochemical reactions.
Advances in the understanding of ionic transport phenomena drive the development of many of our lab's technologies. Solid oxide fuel cells (SOFC's), solid state sensors, and ion transport membranes are all, in essence, ionic transport harnessed for a specific technological purpose. Whether the objective is to separate gasses, produce electricity, or purify water, ionic transport rests at the heart.
Our lab focuses on high temperature ionic transport through ceramic materials. We published insights that show the importance of the topological connectivity of the triple phase boundary (TPB) in ion conductivity which led directly to increased SOFC performance. Similarly, our development of SNDC electrolyte with a 30% higher grain ionic conductivity than gadolinium doped cerium (GDC) led directly to a low ohmic resistance SOFC at 500ºC, an unprecedented performance at that temperature.
Many energy-related materials rely on the uptake and release of large quantities of ions, for example, Li+ in batteries, H+ in hydrogen storage materials, and O2− in solid-oxide fuel cell and related materials. These compositional changes often result in large volumetric dilation of the material, commonly referred to as chemical expansion. Chemical expansion is a new means to probe other materials properties, and it contributes to investigations of electromechanical coupling.