Jeffrey W. Long

Zinc-based batteries are attracting renewed interest for next-generation energy-storage needs as a safer and more sustainable alternative to lithium-based batteries. To overcome historic roadblocks to rechargeable zinc batteries, the Naval Research Laboratory has developed and demonstrated 3D zinc “sponge” electrodes whose porous, aperiodic architectures hinder dendrite formation and shape change while also enabling near-theoretical zinc utilization and high rate capability when operated in alkaline cells.^1,2 Fabrication protocols for zinc sponges have progressed through multiple generations with a focus on enhancing scalability and manufacturability, the latest generation being based on a simple salt-templating and chemical-sintering approach. We describe the fabrication of these latest zinc sponges in multiple form factors and assess their electrochemical properties in two-terminal alkaline cells, testing for cycle life, power capability, and utilization. The 3D structure of the zinc sponge is visualized with ex situ and in situ X-ray computed microtomography (XCMT) to assess the degree of networked interconnectivity³ and monitor for changes in morphology with cycling. F. Parker, C.N. Chervin, E.S. Nelson, D.R. Rolison, J.W. Long, Energy Environ. Sci. 7, 1117–1124 (2014). F. Parker, C.N. Chervin, I.R. Pala, M. Machler, M.F. Burz, J.W. Long, D.R. Rolison, Science 356, 415–418 (2017). S. Ko, A.B. Geltmacher, B.J. Hopkins, D.R. Rolison, J.W. Long, J.F. Parker, ACS Appl. Energy Mater. 2, 212–216 (2019).

Alkali-rich transition-metal chalcogenides offer the opportunity to tap both cation- and anion-centered redox reactions for high-capacity, reversible charge-storage when used in the cathodes of advanced rechargeable batteries. A prime example is Li₂FeS₂, in which sulfide/persulfide redox augments Fe^2+/3+ reactions to support Li⁺-storage capacity >350 mAh g^–1 [1]. We recently introduced a new synthetic pathway to Li₂FeS₂ that is based on redox-mediated lithiation of FeS₂, as facilitated by select organic reducing agents [2]. With this approach, we are able to generate Li₂FeS₂ in nanometric and architecture-supported forms that are not achievable with conventional high-temperature, solid-state synthesis. We now extend such concepts to controlled chemical sodiation of FeS₂, with the goal of generating new Na₂FeS₂ structures that serve as high-capacity cathode materials for Na-ion batteries. The electrochemical characteristics of Na₂FeS₂ are evaluated in Na half-cells to determine fundamental and battery-relevant characteristics, including current–potential profile, capacity, reversibility, and rate capability. We assess the electronic and structural properties of these Na₂FeS₂ materials with X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). In situ XAS and XRD measurements with prototype pouch cells and coin cells provide further insight to deconvolve multi-site redox mechanisms and track structural changes during Na-ion insertion/deinsertion reactions.

The increasing demand for electrochemical energy-storage technologies necessitates exploration beyond today's Li-ion batteries, which may be difficult to implement at a global scale due to concerns of safety and supply-chain risks. This presentation will focus on nanostructured iron oxides that store electrochemical charge in aqueous electrolytes from mild-pH to alkaline conditions. We use epoxide-driven sol–gel synthesis to initially form amorphous, high-surface-area iron oxides whose structure can be further tuned by post-synthesis thermal processing to generate nanocrystalline variants. Using this series of iron oxides we explore their redox behavior using such techniques as cyclic voltammetry, pulse voltammetry, and electrochemical quartz microbalance methods. Preliminary electrochemical characterization in moderately basic-pH electrolytes indicates that proton insertion is the primary redox mechanism, particularly for disordered iron oxides. We correlate electrochemical behavior with key materials properties, as characterized by X-ray spectroscopy and diffraction. The composition, structure, and electrochemical properties of iron oxides can be further varied by substitution with high-valency metals such as V⁵⁺ and Mo⁶⁺, which generate additional disorder and vacancies that are beneficial for charge storage [1–4]. This work establishes fundamental design rules for an under-explored class of high-performance, safe, and cost-effective aqueous redox materials, paving the way for next-generation energy storage. P. Hahn, J.W. Long, A.N. Mansour, K.A. Pettigrew, M.S. Osofsky, and D.R. Rolison. Energy Environ. Sci. 4, 1495–1502 (2011). C. Chervin, J.S. Ko, B.W. Miller, L. Dudek, A.N. Mansour, M.D. Donakowski, T.H. Brintlinger, P. Gogotski, S. Chattopadhyay, T. Shibata, J.F. Parker, B.P. Hahn, D.R. Rolison, and J.W. Long. J. Mater. Chem. A, 3, 12059–12068 (2015). C. Chervin, R.H. DeBlock, J.F. Parker, B.M. Hudak, N.L. Skeele, J.S. Ko, D.R. Rolison, and J.W. Long. RSC Adv. 11, 14495–14503 (2021). R. DeBlock, M.D. Johannes, H.O. Ford, M.W. Swift, D.R. Rolison, J.W. Long. PhysChemChemPhys. 27, 6146–6153 (2025).

Straightforward low-temperature chemical synthesis of Na-ion storing compound Na ₂ FeS ₂ (>250 mAh g ⁻¹ ) that exhibits anion- and cation-sited redox.

Next-generation rechargeable zinc-based batteries require efficient deposition and stripping (D/S) of Zn in mild-pH aqueous electrolyte. With the move away from conversion of bulk Zn electrodes, the properties of D/S substrates, such as surface functionality and electrode architecture, can impact Zn redox processes. To investigate these effects, we adapt planar and 3D pyrolytic carbon (pyC) substrates previously reported for fundamental electroanalytical studies. Thin films of pyC are fabricated by benzene pyrolysis, yielding a low oxygen-content, oleophobic surface that can be further functionalized by plasma oxidation and nitridation or with heteroatom doping by adding precursors such as thiophene to the benzene feed. We evaluate Zn/Zn²⁺ redox at a series of pyC electrodes with varied surface characteristics, cycling in either zinc sulfate (ZnSO₄) or zinc acetate (Zn(OAc)₂) mild-pH aqueous electrolytes of relevance to “zinc-ion” batteries. Characteristics such as wettability, deposition morphology, Zn D/S reversibility, and coulombic efficiency are correlated with pyC surface functionality. Aromatic sulfur doping followed by plasma nitridation (pyC∼S:N) yields the best balance of uniform Zn electrodeposition and effective electrostripping from the substrate: a two-terminal cell charges/discharges at >98% coulombic efficiency for >350 cycles. We then conformally coat macroscale thick fiber-paper electrodes with pyC and plate Zn at 1, 5, and 10 mAh cm⁻². Even at 10 mAh cm⁻², 3D pyC electrodes deposit Zn without a charge-transfer resistance penalty, confirming the viability of such pyC architected electrodes for practical areal capacity.

Meeting the growing demand for fresh water requires innovative desalination technologies, particularly for decentralized and resource-constrained settings. Redox-mediated desalination, leveraging redox couples to drive salt removal, offers a promising alternative to energy-intensive methods like reverse osmosis and inherently intermittent techniques like capacitive deionization. This work investigates the impact of electrode surface modifications on the performance of redox-flow desalination systems, specifically focusing on carbon-based modifications to enhance key performance metrics such as salt removal rate and energy efficiency. We utilize pyrolytic carbon (pyC) as a versatile platform for electrode surface engineering, employing a simple chemical vapor deposition route based on the pyrolysis of benzene and related aromatic precursors.[1] This process allows us to precisely tune the electronic structure (e.g., work function) and surface functionality of the pyC through modifications such as heteroatom doping during pyrolysis and plasma oxidation post-pyrolysis. Utilizing the ferricyanide/ferrocyanide redox couple, we explore how these tailored pyC coatings, applied to both 2D and 3D electrode architectures, influence desalination performance. This presentation will highlight the structure-property-performance relationships of these modified electrodes, emphasizing the potential of pyC engineering for enhancing the efficiency and scalability of next-generation redox-mediated desalination. [1] Parker, J.F.; So, C.R.; Sassin, M.B.; Ko, J.S.; Jeon, S.; Chervin, C.N.; Lytle, J.C.; Helms, M.E.; Rolison, D.R.; Long, J.W. Pyrolytic Carbon Films with Tunable Electronic Structure and Surface Functionality: A Planar Stand‐in for Electroanalysis of Energy‐Relevant Reactions. ChemElectroChem 2020 , 7 , 627–683.

There is an ever-growing need for electrochemical energy storage devices that circumvent the safety and critical materials pitfalls of current Li-ion technologies. This work details analysis of a class of earth abundant vanadium ferrite materials, developed at NRL, that can operate in both standard non-aqueous- and in aqueous-based electrolyte environments [1]. We conduct a density functional theory investigation of the intercalation mechanisms, comparing Li+ to Na+ and evaluating the effect of V concentration. We find that strong V-Fe bonding is behind an unexpected upward shift in the Fe ^2+/3+ redox potential (compared to standard Fe oxide materials. Concurrent experimental XAS evaluation of the K-edge of V and Fe as a function of state-of-charge find the same redox sequence and shift in voltage [2]. We then proceed to investigate the effect of various redox inactive dopants (Al, Zn) on both voltage profile and capacity to find optimal chemical composition for safer, aqueous-based operation. We conclude that defect states, still of the same V-Fe character, form just below the conduction band, and have a strong effect on the voltage. The number and energy position of these states depends strongly on the site preference of the dopant which may be controlled by temperature/oxygen partial pressure, resulting in an experimental knob by which these materials may be synthesized according to need. [1] C. N. Chervin, J. S. Ko, B. W. Miller, L. Dudek, A. N. Mansour, M. D. Donakowski, T. H. Brintlinger, P. Gogotski, S. Chattopadhyay, T. Shibata, J. F. Parker, B. P. Hahn, D. R. Rolison, J. W. Long, "Defective by design: vanadium-substituted iron oxide nanoarchitectures as cation insertion hosts for electrochemical charge storage." J. Mater. Chem. A, 3.22 (2015): 12059–12068. [2] R. H. DeBlock, M. D. Johannes, H. O. Ford, M. W. Swift, D. R. Rolison, J. W. Long, “Deconvolving lithium-ion redox in vanadium-iron oxide aerogels using X-ray absorption spectroscopy and density functional theory.” PhysChemChemPhys., 2025 DOI: 10.1039/D4CP04351K.

Understanding the nucleation and growth mechanisms of manganese dioxide (MnO₂) during electrodeposition is essential for optimizing the performance of Manganese-based aqueous battery [1], [2]. This study employs potentiostatic chronoamperometry to examine MnO₂ deposition in mild aqueous electrolyte with and without complexing agents across a range of substrates including bare carbon, pyrolytic carbon (pyC), Ni/Ni-alloy-coated KAPTON and carbon substrates. Current-time transient analysis reveals that in aqueous MnSO₄ electrolytes, NiMoP-coated Kapton, NiP-coated Kapton, and NiP-coated carbon exhibit a distinct double-layer charging phase prior to nucleation, while NiMoP-coated carbon and bare carbon show no such capacitive response. These observations indicate electrode surface-dependent nucleation mechanisms, with deviations from classical Scharifker–Hills behavior attributed to surface heterogeneity, double-layer effects, and concurrent side reactions. Further investigations demonstrate that the modification of electrolyte with complexing agents changes the nucleation mechanism, reinforcing the significance of electrolyte chemistry. A modified kinetic model incorporating double-layer capacitance and electrolyte decomposition accurately fits the experimental data and is used to extract nucleation rates. These findings highlight the critical influence of both electrode surface and electrolyte engineering on the electrodeposition and stripping of MnO ₂ . Comparative results will be presented on the import of the different substrates studied. By establishing a mechanistic understanding of MnO₂ nucleation dynamics, this work contributes to the rational design of anode materials for efficient, stable, and scalable aqueous energy storage systems. REFERENCES [1] M. Wang et al. , “Aqueous all-manganese batteries,” Energy Environ. Sci. , vol. 16, no. 11, pp. 5284–5293, Nov. 2023, doi: 10.1039/D3EE01679J. [2] E. R. Cooper, M. Li, I. Gentle, Q. Xia, and R. Knibbe, “A Deeper Understanding of Metal Nucleation and Growth in Rechargeable Metal Batteries Through Theory and Experiment,” Angew. Chem. Int. Ed. , vol. 62, no. 51, p. e202309247, 2023, doi: 10.1002/anie.202309247. Figure 1

Space-limited and low-temperature environments demand battery materials with both high volumetric capacity and fast charge-storage kinetics. To address this need, we investigate the electrochemical Li⁺-insertion behavior of high-density niobium–tungsten oxide (NWO) Wadsley–Roth compounds at room temperature and 0 °C. These compounds contain orthogonal crystallographic shear planes that form an m × n block structure around a corner-sharing network. We compare three NWO materials: Nb12WO33 (3 × 4), Nb14W3O44 (4 × 4), and Nb16W5O55 (4 × 5). Operando electrochemical X-ray diffraction shows that structural evolution during Li⁺ insertion becomes more complex as block size increases. At a C/10 rate and 25 °C, all three compounds store more than 1 Li⁺/e⁻ per transition metal (T.M.), with Nb14W3O44 (4 × 4) and Nb16W5O55 (4 × 5) reaching volumetric capacities of 1,315 mAh/cm³ and 1,247 mAh/cm³, respectively. Rate-capability measurements at 25 °C and 0 °C show that larger block sizes maintain higher capacity at slow (dis)charge rates, whereas asymmetric block sizes (m ≠ n) deliver greater rate capability. All three materials outperform a commercial graphite anode in volumetric capacity, rate capability, and long-term cycling with each material retaining over 90% of capacity at 25 °C and 95% at 0 °C after 500 cycles. These results highlight NWO phases as promising candidates for lithium-ion batteries that require high volumetric energy density, high power, and reliable low-temperature operation.

Li-S battery systems are promising alternatives to traditional lithium-ion batteries by enabling an increase in deliverable capacities by an order of magnitude without needing expensive or exotic materials. Unfortunately, sulfur cathodes are challenged by poor electronic conductivity and the redox shuttling of soluble polysulfide intermediates, resulting in capacity fade, inhibiting commercial development of these systems. These challenges are especially exacerbated when trying to scale up the electrodes to practical areal and volumetric capacities. To overcome these known weaknesses, our work utilizes highly scalable porous carbon nanofoam papers (CNFPs) developed at the U.S. Naval Research Laboratory (NRL) with tunable porosity and pore size. Sulfur is deposited onto the CNFP framework via a simple vapor deposition technique to ensure a uniform distribution of sulfur within the free-standing electrodes, aiding both ionic and electronic transport.¹ With tunable properties like pore size and sulfur loading, the CNFP electrodes can be optimized to maximize desirable electrochemical results like utilization and areal capacity. Moreover, we demonstrate that the CNFPs can access thicknesses beyond conventional slurry casting (>100 µm) using multi-ply configurations. Herein we highlight these configurations, as well as pouch cell level prototype demonstrations. Neale, Z.G.; Lefler, M.J.; Long, J.W.; Rolison, D.R.; Sassin, M.B.; Carter, R.; Freestanding Carbon Nanofoam Papers with Tunable Porosity as Lithium-Sulfur Battery Cathodes. Nanoscale, 2023, 15, 16924-16932. DISTRIBUTION STATEMENT A. Approved for public release: distribution is unlimited.