Vanadium Phosphate Nanosheets with Organic Intercalation for Zinc Ion Batteries

Cory Lam1, Liu Chaofeng2, Wenchao Bi2, Guozhong Cao1,2 1Clean Energy Institute, 2Department of Materials Science & Engineering University of Washington, Seattle, WA

Abstract Battery efficiency is determined by various parameters of electrochemical performance tests. The goal is to explore the changes in electrochemical performance through the injection of pentanol and butanol via organic intercalation in zinc ion batteries. To determine the structural and electrochemical impacts of the added organics, a series of morphological and voltaic tests are conducted, concluding that the increased interlayer distance correlates to enhanced electrochemical performance while maintaining the nanostructure. This leads to better resistance to energy capacity degradation over large quantities of charge-discharges, as well as long-term cycling stability. Thus, organic intercalation provides opportunities to advance large scale commercial and industrial energy storage. Goals Methodology Electrochemical Performance

a b Charge 1. Investigation of organic intercalation expanding the 1) Synthesis of VOPO4 Discharge ) ) interlayer distance in vanadium phosphate nanosheets. -1 2+ H PO V O VOPO4·2H2O 2. Comparison of morphology and electrochemical 3 4 2 5 X-Ray performance with pentanol and butanol intercalation. Centrifuge Sonicate Diffraction 3. Determination of zinc as a replacement anode material in and Scanning place of lithium. H2O Heat 24h Wash + Dry Electron Microscopy

Introduction (V vs Zn/Zn Potential Specific capacity (mAh g

Energy Storage 2) Synthesis of Intercalated VOPO4 -1 Cycle number c Specific capacity (mAh g ) VOPO4·2H2O C3H8O C4H10O or C5H12O P-VOPO4 or B-VOPO4 )

• Transfers ions from -1 one electrode to the Sonicate Stir 16h X-Ray other Diffraction • Depends on active and Scanning Centrifuge Centrifuge + Electron electrode material Wash + Dry Microscopy and ion size/charge

3) Construction of Battery Specific capacity (mAh g Previous Research Anode Cap Ti + Sample + Super-P + PVDF Cycle number Wave Spring Figure 3. (a) Galvanostatic charge/discharge curves at 0.1 A g-1. (b) Rate Steel Plate performance at various current densities (A g-1). (c) Cycling-stability of as-prepared Zn Anode samples at 0.1 A g-1. Both B-VOPO and P-VOPO show better electrochemical Dry Seal Cyclic 4 4 Cellulose + Voltammetry performance than pure VOPO4·2H2O, indicating organic intercalation can improve electrochemical performance of pure VOPO ·2H O. Zn(CF3SO4)2 and Charge- 4 2 Cathode Discharge Cathode Cap Cycles Conclusion  Lower than expected electrochemical values Morphology  Samples with organic intercalation perform better than pure

VOPO4·2H2O nanosheets a VOPO4·2H2O b VOPO4 c P-VOPO4  Increased interlayer distance confirmed by XRD  Equivalent for butanol and pentanol  Capacity increases with cycle number  Inconclusive if complete displacement occurred Future Research

Figure 1. (a) Crystal structure of the intrinsic VOPO4·2H2O nanosheets. (b) Chemical structure of the TEG and THF intercalants. (c,d) Schematic of  Examine electrodes after cycling intercalation process and the intercalated structure. (e) The bonding  XRD to determine possible Zn2+ intercalation 1 structure of the TEG and THF in VOPO4 nanosheets.  SEM to identify possible deformation of nanostructure

 Use thermogravimetric analysis (TGA) to determine if the H2O was Electrode Materials d OH Figure 2. (a, b, c) SEM images of synthesized completely displaced during organic intercalation samples. Snapshot of nanosheets with varying levels of structural integrity. (d) X-ray Acknowledgements Vanadium Phosphate Zinc Diffraction (XRD) of the synthesized samples. OH The interlayer distance is calculated via ratios 1. Dr. Guozhong Cao, Dr. Liu Chaofeng, Wenchao Bi, and other members of the Cao Lab. • Maintains Structural • High Theoretical Capacity using Bragg’s Law: 2. Lisa Peterson, Gregory Diggs-Yang, and the University of Washington ALVA program 3. University of Washington Clean Energy Institute for funding this research experience -1 𝒏𝝀 Integrity (820 mAh g ) 𝒅 4. University of Washington Office of Research • High Redox Potential • Low Oxidation Potential 𝟐𝐬𝐢𝐧𝜽 • Lower Energy Diffusion • Radius of Zn2+ is Close to The calculated distance (d) shows that the References + Barrier Li organic intercalations are responsible for the • Easier Intercalation of • Abundant, Safe and Low 1. Peng, L., et al. (2017). Nano Letters, 17(10), 6273-6279. increase in interlayer spacing. 2. Liu, C., et al. (2016). Materials Today, 19(2), 109-123. Organic Molecules Cost 3. He, P., et al. (2018). Adv. Energy Mater., 8(10), 1702463.

University of Washington Clean Energy Institute: ALVA 2018