Structural Transformations at the Atomic Scale in Vanadium Oxides upon Mg²⁺ Intercalation

The advancement of mobile energy storage systems depends on the development of rechargeable batteries with higher energy densities.[1] Despite the widespread use of lithium-ion batteries in portable devices, there is growing research into alternative battery chemistries, including those using more abundant elements or electrodes that may also offer higher energy densities.[2] Mg-ion batteries are one such candidate, showing advantages such as greater material abundance, enhanced safety, and reduced cost compared to Li-ion batteries.[3]<br/>In this contribution, we will study two possible Mg²⁺ intercalation cathodes, MgV₂O₄ and α-V₂O₅, using scanning transmission electron microscopy (STEM), electron energy-loss spectroscopy (EELS), and energy dispersive spectroscopy (EDS). We analyze structural changes with atomic resolution, quantify changes in the local bonding structures and valence states, and quantify variations in chemical distribution of these multi-valent cathode materials during charge/discharge cycles at elevated temperatures. A previous study demonstrated morphological changes in α-V₂O₅ during chemical cycling at elevated temperatures. [4] It was found that the charge-discharge cycle induces structural transformation and the formation of an amorphous layer with a distinct bond structure compared to the crystalline region. [5] Here, we will focus on identifying the reduction of the local crystalline order and morphological changes caused by electrochemical cycling to elucidate the Mg (de)intercalation pathways. [6]<br/> <br/>References:<br/>[1] N. Sa <i>et al.</i>, “Is alpha-V2O5 a cathode material for Mg insertion batteries?,” <i>Journal of Power Sources</i>, vol. 323, pp. 44–50, Aug. 2016, doi: 10.1016/j.jpowsour.2016.05.028.<br/>[2] R. Trócoli <i>et al.</i>, “β-V2O5 as Magnesium Intercalation Cathode,” <i>ACS Appl. Energy Mater.</i>, vol. 5, no. 10, pp. 11964–11969, Oct. 2022, doi: 10.1021/acsaem.2c02371.<br/>[3] K. W. Leong <i>et al.</i>, “Next-generation magnesium-ion batteries: The quasi-solid-state approach to multivalent metal ion storage,” <i>Sci. Adv.</i>, vol. 9, no. 32, p. eadh1181, Aug. 2023, doi: 10.1126/sciadv.adh1181.<br/>[4] H. D. Yoo <i>et al.</i>, “Intercalation of Magnesium into a Layered Vanadium Oxide with High Capacity,” <i>ACS Energy Lett.</i>, vol. 4, no. 7, pp. 1528–1534, Jul. 2019, doi: 10.1021/acsenergylett.9b00788.<br/>[5] F. Lagunas <i>et al.</i>, “Structural Transformations at the Atomic Scale in Spinel Vanadium Oxides upon Mg ²⁺ Extraction,” <i>ACS Appl. Energy Mater.</i>, vol. 6, no. 11, pp. 5681–5689, Jun. 2023, doi: 10.1021/acsaem.3c00035.<br/>[6] The authors acknowledge support from the National Science Foundation (NSF-CBET 2312359) and by the Army Research Office under Grant Number W911NF-23-1-0225. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.