Li ion battery technology continues to be the leader in energy storage applications, however growing demand for higher capacity, longer lifetime and more cost effective options has motivated researchers to both improve existing Li ion technology and also explore multivalent battery technology. From consumer electronics to electric cars, designing better models for future calls for a vast improvement in the existing battery technology. ^[1] Of course, traditional intercalation compounds are drawing up interest as potential cathode candidates. V₂O₅ has been a promising cathode for Li ion batteries. Several first principle studies have also concluded that V₂O₅ could be a potential cathode for Mg ion intercalation.^[2] The unique structure of V₂O₅ consisting of layers of VO₅ square pyramids held by weak bonds along the interlayer direction facilitates ion intercalation between the layers. ^[3] According to a recent paper, a new tunnel structured polymorph of V₂O₅ [zeta-V₂O₅] has been stabilized which can accommodate both Li and Mg ions. ^[4]

In this talk, I will present results using in-situ TEM “open cell battery” approach to study in situ lithiation of these tunnel structured zeta-V₂O₅ nanowires to better understand the reaction kinetics and progression of lithiation as well as study lithiation induced changes in the structure at an atomic scale. I will compare these results with previous results we obtained studying in situ lithiation of orthorhombic alpha-V₂O₅ nanowires using electron diffraction and electron energy loss spectroscopy.^[5]   I will also use aberration corrected scanning transmission electron microscopy (STEM) imaging to study the magnesium intercalated beta structure and present the results as well, again comparing with previous results we have obtained studying electrochemically cycled thin film orthorhombic V₂O₅  with Mg metal anode.^[6][7] Figure 1(a) shows typical TEM image of the zeta-V₂O₅ nanowire, electron diffraction pattern in Figure 1(b) can be indexed using XRD data for zeta-V₂O5. The tunnel framework of zeta- V₂O₅ can be identified in the filtered High angle annular dark field (HAADF) image presented in Fig 1(c), and the electron energy loss spectra presented in Fig 1(d) establishes the valence state of Vanadium as V⁵⁺ (as expected in V₂O₅) by confirming the energy difference between V L₃and O K edges as 9.8 eV.

References

1) Noorden, R V, The rechargeable revolution: A better battery, Nature, 2014, 507, 26-28

2) B. Zhou, H. Shi, R. Cao, X. Zhang, Z. Jiang, Theoretical study on the initial stage of a

magnesium battery based on a V₂O₅ cathode, Phys Chem Chem Phys, 2014,16,18578

3) G S Gautam, P. Canepa, A.Abdellahi, A.Urban, R.Malik, G. Ceder, The Intercalation Phase Diagram of Mg in V2O5 from First-Principles, Chem Mat, 2015

4) P.M Marley, T. A Abtew, K. E Farley, G.A Horrocks, R.V Dennis,  P. Zhang,  S Banerjee, Emptying and Filling a Tunnel Bronze, Chem. Sci, 2015, 6, 1712

5) A Mukherjee, H A Ardakani, T Yi, J Cabana, R S Yassar, R F Klie, Investigation of Li intercalation mechanism into V₂O₅nanowire cathode using in situ Transmission Electron Microscopy methods[Manuscript in preparation]

6) A. Mukherjee, N.Sa, P J Phillips, A Burrell, R F Klie.Investigation of Mg intercalation into thin film orthorhombic V₂O₅cathode using Aberration corrected STEM and EELS[Manuscript in preparation]

7) This work is supported by the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy (DOE),Office of Science, Basic Energy Sciences.