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1. Enhancing magnetic pinning by BaZrO 3 nanorods forming coherent interface by strain-directed Ca-doping in YBa 2 Cu 3 O 7−x nanocomposite films

   https://doi.org/10.1088/1361-6668/ac1fd3  

   Ogunjimi, Victor ; Sebastian, Mary Ann ; Zhang, Di ; Gautam, Bibek ; Jian, Jie ; Huang, Jijie ; Zhang, Yifan ; Haugan, Timothy ; Wang, Haiyan ; Wu, Judy ( September 2021 , Superconductor Science and Technology)

   BaZrO₃(BZO) one-dimensional artificial pinning centers (1D-APCs) aligned along thec-axis of the YBa₂Cu₃O₇(YBCO) have been adopted to enhance the magnetic vortex pinning in BZO/YBCO nanocomposite films. However, the pinning force densityF_pof the BZO 1D-APCs remains moderate at temperatures near 77 K. A hypothesis of the major limiting factor is the defective BZO 1D-APCs/YBCO interface as a direct consequence of the large interfacial strain originated from the BZO/YBCO lattice mismatch of ∼7.7%. Herein, we explore enlarging thec-axis of the YBCO dynamically to reduce the lattice mismatch and hence to prevent formation of the defective BZO 1D-APCs/YBCO interface. Specifically, thec-axis enlargement was achieved by partial replacement of Cu with Ca on the YBCO lattice using strain-directed Ca diffusion into YBCO from two Ca_0.3Y_0.7Ba₂Cu₃O_7−x(CaY-123) spacers of only 10 nm in thickness inserted into the 2 vol% BZO 1D-APC/YBCO nanocomposite thin films of ∼150 nm in total thickness. The achieved elongatedc-axis is attributed to the formation of stacking faults induced by Ca-replacement of Cu on YBCO lattice. The reduced BZO/YBCO lattice mismatch allows formation of a coherent BZO 1D-APC/YBCO interface with negligible defects. This leads to an enhancedF_pvalue up to 98 GN m⁻³at 65 K, which is 70% higher than that of the reference 2 vol% BZO 1D-APC/YBCO sample. Furthermore, the benefit of the enhanced pinning of the BZO 1D-APCs with a coherent interface with YBCO can be extended to a large angular range of the magnetic field orientation. This study reveals the significant effect of the BZO/YBCO interface on the pinning efficiency of BZO 1D-APCs and provides a promising approach to achieve a coherent interface in BZO/YBCO nanocomposite films.

    

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2. Enabling coherent BaZrO 3 nanorods/YBa 2 Cu 3 O 7−x interface through dynamic lattice enlargement in vertical epitaxy of BaZrO 3 /YBa 2 Cu 3 O 7−x nanocomposites

   https://doi.org/10.1088/1361-6668/ac4aff  

   Wu, Judy Z ; Ogunjimi, Victor ; Sebastian, Mary Ann ; Zhang, Di ; Jian, Jie ; Huang, Jijie ; Zhang, Yifan ; Gautam, Bibek ; Haugan, Timothy ; Wang, Haiyan ( February 2022 , Superconductor Science and Technology)

   Abstract One-dimensional c -axis-aligned BaZrO 3 (BZO) nanorods are regarded as strong one-dimensional artificial pinning centers (1D-APCs) in BZO-doped YaBa 2 Cu 3 O 7− x (BZO/YBCO) nanocomposite films. However, a microstructure analysis has revealed a defective, oxygen-deficient YBCO column around the BZO 1D-APCs due to the large lattice mismatch of ∼7.7% between the BZO (3a = 1.26 nm) and YBCO (c = 1.17 nm), which has been blamed for the reduced pinning efficiency of BZO 1D-APCs. Herein, we report a dynamic lattice enlargement approach on the tensile strained YBCO lattice during the BZO 1D-APCs growth to induce c -axis elongation of the YBCO lattice up to 1.26 nm near the BZO 1D-APC/YBCO interface via Ca/Cu substitution on single Cu-O planes of YBCO, which prevents the interfacial defect formation by reducing the BZO/YBCO lattice mismatch to ∼1.4%. Specifically, this is achieved by inserting thin Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7− x (CaY-123) spacers as the Ca reservoir in 2–6 vol.% BZO/YBCO nanocomposite multilayer (ML) films. A defect-free, coherent BZO 1D-APC/YBCO interface is confirmed in transmission electron microscopy and elemental distribution analyses. Excitingly, up to five-fold enhancement of J c ( B ) at magnetic field B = 9.0 T// c -axis and 65 K–77 K was obtained in the ML samples as compared to their BZO/YBCO single-layer (SL) counterpart’s. This has led to a record high pinning force density F p together with significantly enhanced B max at which F p reaches its maximum value F p,max for BZO 1D-APCs at B // c -axis. At 65 K, the F p,max ∼158 GN m −3 and B max ∼ 8.0 T for the 6% BZO/YBCO ML samples represent a significant enhancement over F p,max ∼ 36.1 GN m −3 and B max ∼ 5.0 T for the 6% BZO/YBCO SL counterparts. This result not only illustrates the critical importance of a coherent BZO 1D-APC/YBCO interface in the pinning efficiency, but also provides a facile scheme to achieve such an interface to restore the pristine pinning efficiency of the BZO 1D-APCs. 

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3. Temperature dependent pinning efficiency in multilayer and single layer BZO/YBCO nanocomposite films

   https://doi.org/10.1088/1757-899X/1241/1/012021  

   Panth, M ; Ogunjimi, V ; Sebastian, M A ; Zhang, D ; Gautam, B ; Jian, J ; Huang, J ; Zhang, Y ; Haugan, T ; Wang, H ; et al ( May 2022 , IOP Conference Series: Materials Science and Engineering)

   Abstract The BaZrO 3 /YBa 2 Cu 3 O 7 (BZO/YBCO) interface has been found to affect the vortex pinning efficiency of one-dimensional artificial pinning centers (1D-APC) of BZO. A defective BZO/YBCO interface due to a lattice mismatch of ∼7.7% has been blamed for the reduced pinning efficiency. Recently, we have shown incorporating Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7-x spacer layers in BZO/YBCO nanocomposite film in multilayer (ML) format can lead to a reduced lattice mismatch ∼1.4% through the enlargement of lattice constant of YBCO via Ca diffusion and partial Ca/Cu replacement on Cu-O planes. In this work, the effect of this interface engineering on the BZO 1D-APC pinning efficiency is investigated at temperatures of 65-81 K through a comparison between 2 and 6 vol.% BZO/YBCO ML samples with their single-layer (SL) counterparts. An overall higher pinning force ( F p ) density has been observed on the ML samples as compared to their SL counterparts. Specifically, the peak value of F p ( F p,max ) for the 6% BZO/YBCO ML film is about ∼ 4 times of that of its SL counterpart at 65 K. In addition, the location of the F p,max ( B max ) in the ML samples shifts to higher values as a consequence of enhanced pinning. For the 6% BZO/YBCO ML sample, a much smaller “plateau-like” decrease of the B max with increasing temperature was observed, which is in contrast to approximately linear decrease of B max with increasing temperature in the 6% SL film. This result indicates the importance of restoring the BZO/YBCO interface quality for better pinning efficiency of BZO 1D-APCs especially at higher BZO doping concentration. 

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4. The benefit of Ca in improving pinning of BaZrO 3 -Y 2 O 3 doubly-doped YBa 2 Cu 3 O 7-x /Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7-x multilayer nanocomposite films

   https://doi.org/10.1088/2053-1591/acc7e3  

   Panth, Mohan ; Ogunjimi, Victor ; Sebastian, Mary Ann ; Gautam, Bibek ; Haugan, Timothy ; Wu, Judy ( April 2023 , Materials Research Express)

   Abstract This work examines the pinning enhancement in BaZrO 3 (BZO) +Y 2 O 3 doubly-doped (DD) YBa 2 Cu 3 O 7 (YBCO) nanocomposite multilayer (DD-ML) films. The film consists of two 10 nm thin Ca 0.3 Y 0.7 Ba 2 Cu 3 O 7-x (CaY-123) spacers stacking alternatively with three BZO + Y 2 O 3 /YBCO layers of 50 nm each in thickness that contain 3 vol% of Y 2 O 3 and BZO doping in the range of 2–6 vol%. Enhanced magnetic vortex pinning and improved pinning isotropy with respect to the orientation of magnetic field (B) have been achieved in the DD-ML samples at lower BZO doping as compared to that in the single-layer counterparts (DD-SL) without the CaY-123 spacers. For example, the pinning force density ( F p ) of ∼58 GNm −3 in 2 vol.% of DD-ML film is ∼110% higher than in 2 vol% of DD-SL at 65 K and B // c -axis, which is attributed to the improved pinning efficiency by c -axis aligned BZO nanorods through diffusion of Calcium (Ca) along the tensile-strained channels at BZO nanorods/YBCO interface for improvement of the interface microstructure and hence pinning efficiency of BZO nanorods. An additional benefit is in the considerably improved J c ( θ ) and reduced J c anisotropy in the former over the entire range of the B orientations. However, at higher BZO doping, the BZO nanorods become segmented and misoriented, which may change the Ca diffusion pathways and reduce the benefit of Ca in improving the pinning efficiency of BZO nanorods. 

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5. (Digital Presentation) Ultrathin Stabilized Zn Metal Anode for Highly Reversible Aqueous Zn-Ion Batteries

   https://doi.org/10.1149/MA2022-024439mtgabs  

   Zhang, Yuxuan ; Song, Han Wook ; Lee, Sunghwan ( October 2022 , ECS Meeting Abstracts)

   Ever-increasing demands for energy, particularly being environmentally friendly have promoted the transition from fossil fuels to renewable energy.¹Lithium-ion batteries (LIBs), arguably the most well-studied energy storage system, have dominated the energy market since their advent in the 1990s.²However, challenging issues regarding safety, supply of lithium, and high price of lithium resources limit the further advancement of LIBs for large-scale energy storage applications.³Therefore, attention is being concentrated on an alternative electrochemical energy storage device that features high safety, low cost, and long cycle life. Rechargeable aqueous zinc-ion batteries (ZIBs) is considered one of the most promising alternative energy storage systems due to the high theoretical energy and power densities where the multiple electrons (Zn²⁺) . In addition, aqueous ZIBs are safer due to non-flammable electrolyte (e.g., typically aqueous solution) and can be manufactured since they can be assembled in ambient air conditions.⁴As an essential component in aqueous Zn-based batteries, the Zn metal anode generally suffers from the growth of dendrites, which would affect battery performance in several ways. Second, the led by the loose structure of Zn dendrite may reduce the coulombic efficiency and shorten the battery lifespan.⁵

   Several approaches were suggested to improve the electrochemical stability of ZIBs, such as implementing an interfacial buffer layer that separates the active Zn from the bulk electrolyte.⁶However, the and thick thickness of the conventional Zn metal foils remain a critical challenge in this field, which may diminish the energy density of the battery drastically. According to a theretical calculation, the thickness of a Zn metal anode with an areal capacity of 1 mAh cm^-2is about 1.7 μm. However, existing extrusion-based fabrication technologies are not capable of downscaling the thickness Zn metal foils below 20 μm.

   Herein, we demonstrate a thickness controllable coating approach to fabricate an ultrathin Zn metal anode as well as a thin dielectric oxide separator. First, a 1.7 μm Zn layer was uniformly thermally evaporated onto a Cu foil. Then, Al₂O₃, the separator was deposited through sputtering on the Zn layer to a thickness of 10 nm. The inert and high hardness Al₂O₃layer is expected to lower the polarization and restrain the growth of Zn dendrites. Atomic force microscopy was employed to evaluate the roughness of the surface of the deposited Zn and Al₂O₃/Zn anode structures. Long-term cycling stability was gauged under the symmetrical cells at 0.5 mA cm^-2for 1 mAh cm^-2. Then the fabricated Zn anode was paired with MnO₂as a full cell for further electrochemical performance testing. To investigate the evolution of the interface between the Zn anode and the electrolyte, a home-developed in-situ optical observation battery cage was employed to record and compare the process of Zn deposition on the anodes of the Al₂O₃/Zn (demonstrated in this study) and the procured thick Zn anode. The surface morphology of the two Zn anodes after circulation was characterized and compared through scanning electron microscopy. The tunable ultrathin Zn metal anode with enhanced anode stability provides a pathway for future high-energy-density Zn-ion batteries.

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   Goodenough, J. B.; Park, K. S., The Li-ion rechargeable battery: a perspective.J Am Chem Soc2013,135(4), 1167-76.

   Li, C.; Xie, X.; Liang, S.; Zhou, J., Issues and Future Perspective on Zinc Metal Anode for Rechargeable Aqueous Zinc‐ion Batteries.Energy & Environmental Materials2020,3(2), 146-159.

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   Yang, J.; Yin, B.; Sun, Y.; Pan, H.; Sun, W.; Jia, B.; Zhang, S.; Ma, T., Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives.Nanomicro Lett2022,14(1), 42.

   Yang, Q.; Li, Q.; Liu, Z.; Wang, D.; Guo, Y.; Li, X.; Tang, Y.; Li, H.; Dong, B.; Zhi, C., Dendrites in Zn-Based Batteries.Adv Mater2020,32(48), e2001854.

   Acknowledgment

   This work was partially supported by the U.S. National Science Foundation (NSF) Award No. ECCS-1931088. S.L. and H.W.S. acknowledge the support from the Improvement of Measurement Standards and Technology for Mechanical Metrology (Grant No. 22011044) by KRISS.

   Figure 1

    

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