All Publications

  • Alumina - Stabilized SEI and CEI in Potassium Metal Batteries. Angewandte Chemie (International ed. in English) Liu, P., Hao, H., Singla, A., Vishnugopi, B. S., Watt, J., Mukherjee, P. P., Mitlin, D. 2024: e202402214


    Aluminum oxide (Al2O3) nanopowder is spin-coated onto both sides of commercial polypropene separator to create artificial solid-electrolyte interphase (SEI) and artificial cathode electrolyte interface (CEI) in potassium metal batteries (KMBs). This significantly enhances the stability, including of KMBs with Prussian Blue (PB) cathodes. For example, symmetric cells are stable after 1,000 cycles at 0.5 mA/cm2 - 0.5 mAh/cm2 and 3.0 mA/cm2 - 0.5 mAh/cm2. Alumina modified separators promote electrolyte wetting and increase ionic conductivity (0.59 vs. 0.2 mS/cm) and transference number (0.81 vs. 0.23). Cryo-stage focused ion beam (cryo-FIB) analysis of cycled modified anode demonstrates dense and planar electrodeposits, versus unmodified baseline consisting of metal filaments (dendrites) interspersed with pores and SEI. Alumina-modified CEI also suppresses elemental Fe crossover and reduces cathode cracking. Mesoscale modeling of metal - SEI interactions captures crucial role of intrinsic heterogeneities, illustrating how artificial SEI affects reaction current distribution, conductivity and morphological stability.

    View details for DOI 10.1002/anie.202402214

    View details for PubMedID 38745375

  • Tuned Reactivity at the Lithium Metal-Argyrodite Solid State Electrolyte Interphase ADVANCED ENERGY MATERIALS Hao, H., Liu, Y., Greene, S. M., Yang, G., Naik, K. G., Vishnugopi, B. S., Wang, Y., Celio, H., Dolocan, A., Tsai, W., Fang, R., Watt, J., Mukherjee, P. P., Siegel, D. J., Mitlin, D. 2023; 13 (46)
  • Intermetallics Based on Sodium Chalcogenides Promote Stable Electrodeposition-Electrodissolution of Sodium Metal Anodes ADVANCED ENERGY MATERIALS Wang, Y., Dong, H., Katyal, N., Vishnugopi, B. S., Singh, M. K., Hao, H., Liu, Y., Liu, P., Mukherjee, P. P., Henkelman, G., Watt, J., Mitlin, D. 2023; 13 (27)
  • Stable Anode-Free All-Solid-State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector ADVANCED MATERIALS Wang, Y., Liu, Y., Nguyen, M., Cho, J., Katyal, N., Vishnugopi, B. S., Hao, H., Fang, R., Wu, N., Liu, P., Mukherjee, P. P., Nanda, J., Henkelman, G., Watt, J., Mitlin, D. 2023; 35 (8): e2206762


    A stable anode-free all-solid-state battery (AF-ASSB) with sulfide-based solid-electrolyte (SE) (argyrodite Li6 PS5 Cl) is achieved by tuning wetting of lithium metal on "empty" copper current-collector. Lithiophilic 1 µm Li2 Te is synthesized by exposing the collector to tellurium vapor, followed by in situ Li activation during the first charge. The Li2 Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous electrodeposition experiments using half-cells (1 mA cm-2 ), the accumulated thickness of electrodeposited Li on Li2 Te-Cu is more than 70 µm, which is the thickness of the Li foil counter-electrode. Full AF-ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryogenic focused ion beam (Cryo-FIB) sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector-SE interface. Electrodissolution is uniform and complete, with Li2 Te remaining structurally stable and adherent. By contrast, an unmodified Cu current-collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive "dead metal," dendrites that extend into SE, and thick non-uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory (DFT) and mesoscale calculations provide complementary insight regarding nucleation-growth behavior. Unlike conventional liquid-electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF-ASSBs.

    View details for DOI 10.1002/adma.202206762

    View details for Web of Science ID 000904031600001

    View details for PubMedID 36445936

  • Phase Engineering of Defective Copper Selenide toward Robust Lithium-Sulfur Batteries ACS NANO Yang, D., Li, M., Zheng, X., Han, X., Zhang, C., Jacas Biendicho, J., Llorca, J., Wang, J., Hao, H., Li, J., Henkelman, G., Arbiol, J., Ramon Morante, J., Mitlin, D., Chou, S., Cabot, A. 2022; 16 (7): 11102-11114


    The shuttling of soluble lithium polysulfides (LiPS) and the sluggish Li-S conversion kinetics are two main barriers toward the practical application of lithium-sulfur batteries (LSBs). Herein, we propose the addition of copper selenide nanoparticles at the cathode to trap LiPS and accelerate the Li-S reaction kinetics. Using both computational and experimental results, we demonstrate the crystal phase and concentration of copper vacancies to control the electronic structure of the copper selenide, its affinity toward LiPS chemisorption, and its electrical conductivity. The adjustment of the defect density also allows for tuning the electrochemically active sites for the catalytic conversion of polysulfide. The optimized S/Cu1.8Se cathode efficiently promotes and stabilizes the sulfur electrochemistry, thus improving significantly the LSB performance, including an outstanding cyclability over 1000 cycles at 3 C with a capacity fading rate of just 0.029% per cycle, a superb rate capability up to 5 C, and a high areal capacity of 6.07 mAh cm-2 under high sulfur loading. Overall, the present work proposes a crystal phase and defect engineering strategy toward fast and durable sulfur electrochemistry, demonstrating great potential in developing practical LSBs.

    View details for DOI 10.1021/acsnano.2c03788

    View details for Web of Science ID 000821904000001

    View details for PubMedID 35758405

  • Molybdenum Carbide Electrocatalyst In Situ Embedded in Porous Nitrogen-Rich Carbon Nanotubes Promotes Rapid Kinetics in Sodium-Metal-Sulfur Batteries ADVANCED MATERIALS Hao, H., Wang, Y., Katyal, N., Yang, G., Dong, H., Liu, P., Hwang, S., Mantha, J., Henkelman, G., Xu, Y., Boscoboinik, J., Nanda, J., Mitlin, D. 2022; 34 (26): e2106572


    This is the first report of molybdenum carbide-based electrocatalyst for sulfur-based sodium-metal batteries. MoC/Mo2 C is in situ grown on nitrogen-doped carbon nanotubes in parallel with formation of extensive nanoporosity. Sulfur impregnation (50 wt% S) results in unique triphasic architecture termed molybdenum carbide-porous carbon nanotubes host (MoC/Mo2 C@PCNT-S). Quasi-solid-state phase transformation to Na2 S is promoted in carbonate electrolyte, with in situ time-resolved Raman, X-ray photoelectron spectroscopy, and optical analyses demonstrating minimal soluble polysulfides. MoC/Mo2 C@PCNT-S cathodes deliver among the most promising rate performance characteristics in the literature, achieving 987 mAh g-1 at 1 A g-1 , 818 mAh g-1 at 3 A g-1 , and 621 mAh g-1 at 5 A g-1 . The cells deliver superior cycling stability, retaining 650 mAh g-1 after 1000 cycles at 1.5 A g-1 , corresponding to 0.028% capacity decay per cycle. High mass loading cathodes (64 wt% S, 12.7 mg cm-2 ) also show cycling stability. Density functional theory demonstrates that formation energy of Na2 Sx (1 ≤ x ≤ 4) on surface of MoC/Mo2 C is significantly lowered compared to analogous redox in liquid. Strong binding of Na2 Sx (1 ≤ x ≤ 4) on MoC/Mo2 C surfaces results from charge transfer between the sulfur and Mo sites on carbides' surface.

    View details for DOI 10.1002/adma.202106572

    View details for Web of Science ID 000798762600001

    View details for PubMedID 35451133

  • Review of Multifunctional Separators: Stabilizing the Cathode and the Anode for Alkali (Li, Na, and K) Metal-Sulfur and Selenium Batteries CHEMICAL REVIEWS Hao, H., Hutter, T., Boyce, B. L., Watt, J., Liu, P., Mitlin, D. 2022; 122 (9): 8053-8125


    Alkali metal batteries based on lithium, sodium, and potassium anodes and sulfur-based cathodes are regarded as key for next-generation energy storage due to their high theoretical energy and potential cost effectiveness. However, metal-sulfur batteries remain challenged by several factors, including polysulfides' (PSs) dissolution, sluggish sulfur redox kinetics at the cathode, and metallic dendrite growth at the anode. Functional separators and interlayers are an innovative approach to remedying these drawbacks. Here we critically review the state-of-the-art in separators/interlayers for cathode and anode protection, covering the Li-S and the emerging Na-S and K-S systems. The approaches for improving electrochemical performance may be categorized as one or a combination of the following: Immobilization of polysulfides (cathode); catalyzing sulfur redox kinetics (cathode); introduction of protective layers to serve as an artificial solid electrolyte interphase (SEI) (anode); and combined improvement in electrolyte wetting and homogenization of ion flux (anode and cathode). It is demonstrated that while the advances in Li-S are relatively mature, less progress has been made with Na-S and K-S due to the more challenging redox chemistry at the cathode and increased electrochemical instability at the anode. Throughout these sections there is a complementary discussion of functional separators for emerging alkali metal systems based on metal-selenium and the metal-selenium sulfide. The focus then shifts to interlayers and artificial SEI/cathode electrolyte interphase (CEI) layers employed to stabilize solid-state electrolytes (SSEs) in metal-sulfur solid-state batteries (SSBs). The discussion of SSEs focuses on inorganic electrolytes based on Li- and Na-based oxides and sulfides but also touches on some hybrid systems with an inorganic matrix and a minority polymer phase. The review then moves to practical considerations for functional separators, including scaleup issues and Li-S technoeconomics. The review concludes with an outlook section, where we discuss emerging mechanics, spectroscopy, and advanced electron microscopy (e.g. cryo-transmission electron microscopy (cryo-TEM) and cryo-focused ion beam (cryo-FIB))-based approaches for analysis of functional separator structure-battery electrochemical performance interrelations. Throughout the review we identify the outstanding open scientific and technological questions while providing recommendations for future research topics.

    View details for DOI 10.1021/acs.chemrev.1c00838

    View details for Web of Science ID 000801915600003

    View details for PubMedID 35349271

  • Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries ADVANCED MATERIALS Liu, P., Hao, H., Celio, H., Cui, J., Ren, M., Wang, Y., Dong, H., Chowdhury, A., Hutter, T., Perras, F. A., Nanda, J., Watt, J., Mitlin, D. 2022; 34 (7): e2105855


    This is the first report of a multifunctional separator for potassium-metal batteries (KMBs). Double-coated tape-cast microscale AlF3 on polypropylene (AlF3 @PP) yields state-of-the-art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5 mA cm-2 and 0.5 mAh cm-2 , with 0.042 V overpotential. Stability is maintained at 5.0 mA cm-2 for 600 cycles (240 h), with 0.138 V overpotential. Postcycled plated surface is dendrite-free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and "dead metal" and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF3 @PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF3 partially reacts with K to form an artificial SEI containing KF, AlF3 , and Al2 O3 phases. The AlF3 @PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K+ transference number is ascribed to the strong interaction between AlF3 and FSI- anions, as revealed through 19 F NMR. The enhancement in wetting and performance is general, being demonstrated with ester- and ether-based solvents, with K-, Na-, or Li- salts, and with different commercial separators. In full batteries, AlF3 prevents Fe crossover and cycling-induced cathode pulverization.

    View details for DOI 10.1002/adma.202105855

    View details for Web of Science ID 000729435700001

    View details for PubMedID 34738260

  • A Sodium-Antimony-Telluride Intermetallic Allows Sodium-Metal Cycling at 100% Depth of Discharge and as an Anode-Free Metal Battery ADVANCED MATERIALS Wang, Y., Dong, H., Katyal, N., Hao, H., Liu, P., Celio, H., Henkelman, G., Watt, J., Mitlin, D. 2022; 34 (1): e2106005


    Repeated cold rolling and folding is employed to fabricate a metallurgical composite of sodium-antimony-telluride Na2 (Sb2/6 Te3/6 Vac1/6 ) dispersed in electrochemically active sodium metal, termed "NST-Na." This new intermetallic has a vacancy-rich thermodynamically stable face-centered-cubic structure and enables state-of-the-art electrochemical performance in widely employed carbonate and ether electrolytes. NST-Na achieves 100% depth-of-discharge (DOD) in 1 m NaPF6 in G2, with 15 mAh cm-2 at 1 mA cm-2 and Coulombic efficiency (CE) of 99.4%, for 1000 h of plating/stripping. Sodium-metal batteries (SMBs) with NST-Na and Na3 V2 (PO4 )3  (NVP) or sulfur cathodes give significantly improved energy, cycling, and CE (>99%). An anode-free battery with NST collector and NVP obtains 0.23% capacity decay per cycle. Imaging and tomography using conventional and cryogenic microscopy (Cryo-EM) indicate that the sodium metal fills the open space inside the self-supporting sodiophilic NST skeleton, resulting in dense (pore-free and solid electrolyte interphase (SEI)-free) metal deposits with flat surfaces. The baseline Na deposit consists of filament-like dendrites and "dead metal", intermixed with pores and SEI. Density functional theory calculations show that the uniqueness of NST lies in the thermodynamic stability of the Na atoms (rather than clusters) on its surface that leads to planar wetting, and in its own stability that prevents decomposition during cycling.

    View details for DOI 10.1002/adma.202106005

    View details for Web of Science ID 000718270900001

    View details for PubMedID 34679207

  • Selenium infiltrated hierarchical hollow carbon spheres display rapid kinetics and extended cycling as lithium metal battery (LMB) cathodes JOURNAL OF MATERIALS CHEMISTRY A Wang, Y., Hao, H., Hwang, S., Liu, P., Xu, Y., Boscoboinik, J., Datta, D., Mitlin, D. 2021; 9 (34): 18582-18593

    View details for DOI 10.1039/d1ta04705a

    View details for Web of Science ID 000687272500001

  • Stable Potassium Metal Anodes with an All-Aluminum Current Collector through Improved Electrolyte Wetting ADVANCED MATERIALS Liu, P., Wang, Y., Hao, H., Basu, S., Feng, X., Xu, Y., Boscoboinik, J., Nanda, J., Watt, J., Mitlin, D. 2020; 32 (49): e2002908


    This is the first report of successful potassium metal battery anode cycling with an aluminum-based rather than copper-based current collector. Dendrite-free plating/stripping is achieved through improved electrolyte wetting, employing an aluminum-powder-coated aluminum foil "Al@Al," without any modification of the support surface chemistry or electrolyte additives. The reservoir-free Al@Al half-cell is stable at 1000 cycles (1950 h) at 0.5 mA cm-2 , with 98.9% cycling Coulombic efficiency and 0.085 V overpotential. The pre-potassiated cell is stable through a wide current range, including 130 cycles (2600 min) at 3.0 mA cm-2 , with 0.178 V overpotential. Al@Al is fully wetted by a 4 m potassium bis(fluorosulfonyl)imide-dimethoxyethane electrolyte (θCA  = 0°), producing a uniform solid electrolyte interphase (SEI) during the initial galvanostatic formation cycles. On planar aluminum foil with a nearly identical surface oxide, the electrolyte wets poorly (θCA  = 52°). This correlates with coarse irregular SEI clumps at formation, 3D potassium islands with further SEI coarsening during plating/stripping, possibly dead potassium metal on stripped surfaces, and rapid failure. The electrochemical stability of Al@Al versus planar Al is not related to differences in potassiophilicity (nearly identical) as obtained from thermal wetting experiments. Planar Cu foils are also poorly electrolyte-wetted and become dendritic. The key fundamental takeaway is that the incomplete electrolyte wetting of collectors results in early onset of SEI instability and dendrites.

    View details for DOI 10.1002/adma.202002908

    View details for Web of Science ID 000583242700001

    View details for PubMedID 33135265

  • Sulfur-nitrogen rich carbon as stable high capacity potassium ion battery anode: Performance and storage mechanisms ENERGY STORAGE MATERIALS Tao, L., Yang, Y., Wang, H., Zheng, Y., Hao, H., Song, W., Shi, J., Huang, M., Mitlin, D. 2020; 27: 212-225
  • Photocatalytic Hydrogen Evolution Coupled with Efficient Selective Benzaldehyde Production from Benzyl Alcohol Aqueous Solution over ZnS-Ni<i><sub>x</sub></i>S<i><sub>y</sub></i> Composites ACS SUSTAINABLE CHEMISTRY & ENGINEERING Hao, H., Zhang, L., Wang, W., Qiao, S., Liu, X. 2019; 7 (12): 10501-10508
  • High Selective Oxidation of Benzyl Alcohol to Benzylaldehyde and Benzoic Acid with Surface Oxygen Vacancies on W<sub>18</sub>O<sub>9</sub>/Holey Ultrathin g-C<sub>3</sub>N<sub>4</sub> Nanosheets ACS SUSTAINABLE CHEMISTRY & ENGINEERING Xiao, C., Zhang, L., Hao, H., Wang, W. 2019; 7 (7): 7268-7276
  • Facile Modification of Titania with Nickel Sulfide and Sulfate Species for the Photoreformation of Cellulose into Hydrogen CHEMSUSCHEM Hao, H., Zhang, L., Wang, W., Zeng, S. 2018; 11 (16): 2810-2817


    Photocatalytic cellulose reformation is regarded as a potential and affordable route for sustainable H2 evolution. However, direct photoreformation still suffers from challenges such as the limited solubility of cellulose and the dependence on the catalytic activity of noble metals. Herein, we report a new photoreformation of cellulose into H2 over TiO2 that is modified with nickel sulfide (Nix Sy ) and chemisorbed sulfate species (SO42- ) by a one-pot approach. A significant elevation in the photocatalytic hydrogen evolution rate is achieved with a maximal value of 3.02 mmol g-1  h-1 during the first 3 h, which is almost 76-fold higher than that of P25 and comparable to that of Pt-P25. Aided by systematic investigation, it is proposed that nickel sulfide and sulfate modification contribute synergistically to the remarkably increased efficiency of biomass transformation. Specifically, Nix Sy acts as a cocatalyst for photocatalytic H2 production, and we infer that SO42- ions promote cellulose hydrolysis and the consequent accessibility of the biomass to catalysts. Further, the accumulated formate intermediates have a poisoning effect on the catalysts, the desorption of which can be controlled by tuning the aqueous alkalinity. Overall, our strategy for the modification of TiO2 with SO42- and Nix Sy provides a new perspective for the concurrent acceleration of cellulose hydrolysis and increase of the number of hydrogen evolution sites for the efficient photocatalytic reformation of cellulose into H2 .

    View details for DOI 10.1002/cssc.201800743

    View details for Web of Science ID 000442491300020

    View details for PubMedID 29920974

  • Enhanced H<sub>2</sub> evolution from photocatalytic cellulose conversion based on graphitic carbon layers on TiO<sub>2</sub>/NiO<sub>x</sub> GREEN CHEMISTRY Zhang, L., Wang, W., Zeng, S., Su, Y., Hao, H. 2018; 20 (13): 3008-3013

    View details for DOI 10.1039/c8gc01398e

    View details for Web of Science ID 000437187500011

  • Modification of heterogeneous photocatalysts for selective organic synthesis CATALYSIS SCIENCE & TECHNOLOGY Hao, H., Zhang, L., Wang, W., Zeng, S. 2018; 8 (5): 1229-1250

    View details for DOI 10.1039/c7cy01853c

    View details for Web of Science ID 000427157000002

  • Hydrogen evolution based on the electrons/protons stored on amorphous TiO<sub>2</sub> PHYSICAL CHEMISTRY CHEMICAL PHYSICS Zeng, S., Zhang, L., Wang, W., Shao, D., Hao, H. 2017; 19 (43): 29053-29056


    The hydrogen evolution reaction (HER) using recyclable mediator is being actively pursued as a route for solar energy conversion. Herein, we introduce a catalyst mediator (MoS2) that enables proton-coupled electron transfer (PCET) process on the recyclable TiO2 (H+-TiO2/e-) to a separate, catalytic hydrogen production step without requiring post-light energy input. This approach supplies a new insight to hydrogen evolution with the recyclable proton-electron pairs, stored at the semiconductor after the light irradiation. It was found that 80% of the electrons stored on TiO2 could be devoted to the reduction of H+ into H2 on MoS2 nanosheets in the dark. The electron transfer to MoS2 occurs at a rate of 455 μmol h-1 g-1 and 947 μmol h-1 g-1 in the dark and excited state, respectively.

    View details for DOI 10.1039/c7cp06067j

    View details for Web of Science ID 000414773100003

    View details for PubMedID 29083014