Ajay Ravi

All Publications

• NiSO4-Driven In Situ Alloy Formation To Unlock Highly Reversible Iron Electrochemistry in Aqueous Batteries. Journal of the American Chemical Society Feng, G., Liu, Z., Li, J., Li, Y., Guan, X., Ravi, A., Liu, C., Chi, X., Ai, H., Zheng, X., Cui, Y. 2026

  Abstract

  Grid-scale stationary energy storage requires technologies that are both safe and economically viable. Iron (Fe) metal-based aqueous batteries offer an attractive option owing to the abundance, low cost, and environmental benignity of iron, but their development has been hampered by uncontrolled hydrogen evolution and poor reversibility of iron plating and stripping. Here, we report using nickel sulfate (NiSO4) as an electrolyte additive to induce the in situ formation of a FeNi3 alloy interphase during early cycling. This alloy lowers the Fe nucleation barrier and promotes uniform iron deposition. Moreover, dynamic codeposition and stripping of Ni with Fe sustains fast reaction kinetics and stabilizes the alloy interphase during long-term cycling. As a result, Fe||Fe symmetric cells achieve over 3000 h of stable cycling, nearly an order of magnitude improvement over the baseline electrolyte. Fe||Cu cells with NiSO4 additives enable stable long-term cycling with a high average Coulombic efficiency (CE) of ∼99.4%, while the control electrolyte rapidly fails with an average CE of 82.9%. These findings demonstrate that functional electrolyte additives and the controlled alloying interphase provide a viable pathway to high-performance, cost-effective iron metal-based aqueous batteries for large-scale energy storage.

  View details for DOI 10.1021/jacs.5c15954

  View details for PubMedID 41593008

• Revealing and Quantifying Carbon Corrosion in Aqueous Manganese-Based Batteries. Nano letters Ravi, A., Zhang, G., Holoubek, J., Li, Y., Hao, H., Cai, A., Shuchi, S. B., Feng, G., Han, J., Li, J., Bent, S. F., Zheng, X., Cui, Y. 2025

  Abstract

  The MnO2/Mn2+ cathode chemistry represents a promising avenue for high-energy-density and low-cost aqueous batteries. However, its practical application for grid-scale storage is limited by insufficient cycling stability. Extensive reports have highlighted the poor reversibility of MnO2 deposition and stripping. Here, we reveal an overlooked source of capacity loss under typical operating conditions: corrosion of the carbon current collector. Using gas chromatography, we show that carbon corrosion can account for up to ∼25% of initial capacity losses and can cause thickness losses approaching 200 nm in the first cycle. Corrosion-induced thickness losses are largest under acidic and near-neutral conditions. Corroborating our corrosion measurements, X-ray photoelectron spectroscopy and scanning electron microscopy results indicate the formation of surface oxygen species and carbon fiber degradation after cycling. Our work provides a quantitative understanding of carbon corrosion in aqueous batteries that can inform strategies for extending their cycle life.

  View details for DOI 10.1021/acs.nanolett.5c02166

  View details for PubMedID 40576618

• Comparison of Al- and Hf-based hybrid photoresists grown by molecular layer deposition for extreme ultraviolet lithography JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A Ravi, A., Than, L., Lewis, J., Shi, J., Werbrouck, A., Han, J., Mattinen, M., Bent, S. F. 2024; 42 (6)

  View details for DOI 10.1116/6.0003975

  View details for Web of Science ID 001351079400001

• Molecular layer deposition of an Al-based hybrid resist for electron-beam and EUV lithography Ravi, A., Shi, J., Lewis, J., Bent, S. F. edited by Guerrero, D., Amblard, G. R. SPIE-INT SOC OPTICAL ENGINEERING. 2023

  View details for DOI 10.1117/12.2657636

  View details for Web of Science ID 001022961000031

• Molecular Layer Deposition of a Hafnium-Based Hybrid Thin Film as an Electron Beam Resist. ACS applied materials & interfaces Shi, J., Ravi, A., Richey, N. E., Gong, H., Bent, S. F. 2022

  Abstract

  The development of new resist materials is vital to fabrication techniques for next-generation microelectronics. Inorganic resists are promising candidates because they have higher etch resistance, are more impervious to pattern collapse, and are more absorbing of extreme ultraviolet (EUV) radiation than organic resists. However, there is limited understanding about how they behave under irradiation. In this work, a Hf-based hybrid thin film resist, known as "hafnicone", is deposited from the vapor-phase via molecular layer deposition (MLD), and its electron-beam and deep-ultraviolet (DUV)-induced patterning mechanism is explored. The hafnicone thin films are deposited at 100 °C by using the Hf precursor tetrakis(dimethylamido)hafnium(IV) and the organic precursor ethylene glycol. E-beam lithography, scanning electron microscopy, and profilometry are used to investigate the resist performance of hafnicone. With 3 M HCl as the developer, hafnicone behaves as a negative tone resist which exhibits a sensitivity of 400 muC/cm2 and the ability to resolve 50 nm line widths. The resist is characterized via X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) to investigate the patterning mechanism, which is described in the context of classical nucleation theory. This study of hafnicone hybrid MLD demonstrates the ability for the bottom-up vapor deposition of inorganic resists to be utilized in advanced e-beam and DUV lithographic techniques.

  View details for DOI 10.1021/acsami.2c04092

  View details for PubMedID 35653232