An Extended Mixed Conduction Governs Cation Transport in Magnesium Cathode Hosts

Magnesium batteries have been proposed to complement the existing Lithium-ion technology for the ever-growing battery market¹. While several candidate cathode materials have been identified based on theoretical Mg-ion intercalation capacity, open circuit potential, and cation self-diffusion barriers², the electrochemical response of corresponding electrodes falls short of expectations and is not fully understood³. Of various mechanisms governing the electrochemical response, transport inside active particles is a plausible limitation. In this talk, based on careful electroanalytical measurements, we show that such bulk cation transport is indeed nontrivial, and does not agree with the conventional Li-ion understanding^4,5. We propose an extended mixed conduction theory to explain these observations and characterize properties governing the transport behavior. We further discuss the implications of such an unusual behavior to engineering porous electrodes as well as screening new battery intercalation host materials.<br/><br/><b>References</b>:<br/>1. Ingram (2019) "High Energy Density Insertion Cathode Materials" in <i>Magnesium Batteries, </i>pp. 187-207<br/>2. Canepa et al. (2017) Chem. Rev. 117(5) 4287, doi: 10.1021/acs.chemrev.6b00614<br/>3. Johnson, Ingram & Cabana (2021) ACS Energy Lett. 6(5) 1892, doi: 10.1021/acsenergylett.1c00416<br/>4. Amin, Ravnsbæk & Chiang (2015) J. Electrochem. Soc. 162(7) A1163, doi: 10.1149/2.0171507jes<br/>5. Amin & Chiang (2016) J. Electrochem. Soc. 163(8) A1512, doi: 10.1149/2.0131608jes