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Cao, Longsheng

Publications and source records attributed to Cao, Longsheng.

14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Pd-Ru pair on Pt surface for promoting hydrogen oxidation and evolution in alkaline media

Hydrogen oxidation reaction in alkaline media is critical for alkaline fuel cells and electrochemical ammonia compressors. The slow hydrogen oxidation reaction in alkaline electrolytes requires large amounts of scarce and expensive platinum catalysts. While transition metal decoration can enhance Pt catalysts’ activity, it often reduces the electrochemical active surface area, limiting the improvement in Pt mass activity. Here, we enhance Pt catalysts’ activity without losing surface-active sites by using a Pd-Ru pair. Utilizing a mildly catalytic thermal pyrolysis approach, Pd-Ru pairs are decorated on Pt, confirmed by extended X-ray absorption fine structure and high-angle annular dark-field scanning transmission electron microscopy. Density functional theory and ab-initio molecular dynamics simulations indicate preferred Pd and Ru dopant adsorption. The Pd-Ru decorated Pt catalyst exhibits a mass-based exchange current density of 1557 ± 85 A g –1 metal for hydrogen oxidation reaction, demonstrating superior performance in an ammonia compressor.

25 ENERGY STORAGE↗
DOE OSTI2022

Electrohydrodynamic Enabled Electrochemical Membrane Dehumidifier for Separate Sensible and Latent Cooling

In hot and humid parts of the world, air conditioning is a necessity for an adequate standard of living. Cooling and heating represent one-third of building energy consumption. When cooling humid air, a substantial amount of the cooling energy is absorbed by water vapor condensation. The dehumidification cooling load is referred to as the latent cooling load and the dry bulb cooling load is referred to as the sensible cooling load. In most residential applications, the total cooling load is processed by a vapor compression cycle. Processing the latent load separately would not only reduce energy consumption. It would also reduce the required refrigeration capacity. Refrigerants often have adverse ecological impacts, contributing to the greenhouse effect and depletion of the ozone layer. Reduction of the cooling capacity in a system could reduce the amount of refrigerant charge required.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Electrochemical Ammonia Compression

An electrochemical (EC) compressor is a solid-state compression device. For decades, researchers have been studying EC compressors for applications for a variety of energy systems. As the world transitions away from fossil fuel energy sources, EC compression emerges as a promising technique for energy storage, specifically energy stored in the form of pressurized ammonia. Ammonia is also a commonly used refrigerant. The present studies examine the viability of EC compression for ammonia storage and refrigeration. EC ammonia compression increases the concentration of an ammonia-hydrogen mixture via the input of electrical energy and a series of chemical reactions. A polymer electrolyte membrane separates the low-concentration side from the high-concentration side of the device. On the low-pressure (anode) side hydrogen atoms oxidize and react with ammonia molecules, forming positively charge ammonium ions. The ions traverse the membrane electrolytically. The ammonium ions are reduced and revert back to hydrogen and ammonia upon reaching the high-pressure (cathode). An external circuit provides the current needed to sustain the reactions. In this project, we studied the performance of the ammonia EC compressor under a variety of different conditions. We replicated preliminary data and using a small cell with 5 cm2 of active area. We demonstrated the operation of larger cells with 100 cm2 of active area. Further, we used a commercially available hydrogen EC compressor stack to analyze the scaled-up compressor performance. While previous experiments examined only the transient EC compressor performance, we developed test facilities that allowed the compressor to reach steady state. We analyzed the effects of pressure and current on the EC compressor performance. We measured the flow rates of gas leaving the compressors and analyzed the composition using gas chromatography. We tested methods of separating ammonia from the effluent vapor, which contained hydrogen and water vapor. We found that back diffusion adversely affected the performance, especially when we maintained high pressure lifts.

25 ENERGY STORAGE↗
DOE OSTI2021

In situ formation of polymer-inorganic solid-electrolyte interphase for stable polymeric solid-state lithium-metal batteries

Composite polymer electrolytes (CPEs) for solid-state Li-metal batteries (SSLBs) still suffer from gradually increased interface resistance and unconstrained Li-dendrite growth. Herein, we addressed the challenges by designing a LiF-rich inorganic solid-electrolyte interphase (SEI) through introducing a fluoride-salt-concentrated interlayer on CPE film. The rigid but flexible CPE helps accommodate the volume change of electrodes, while the polymeric highly concentrated electrolyte (PHCE) surface-layer regulates Li-ion flux due to the formation of a stable LiF-rich SEI via anion reduction. The designed CPE-PHCE presents enhanced ionic conductivity and high oxidation stability of >5.0 V (versus Li/Li + ). Furthermore, it dramatically reduces the interfacial resistance and achieves a high critical current density of 4.5 mA cm –2 . The SSLBs, fabricated with thin CPE-PHCE membranes (<100 μm) and Co-free LiNiO 2 cathodes, exhibit exceptional electrochemical performance and long cycling stability. Lastly, this approach of SEI design can also be applied to other types of batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Water-Pillared Sodium Vanadium Bronze Nanowires for Enhanced Rechargeable Magnesium Ion Storage

Owing to the advantages of high safety, low cost, high theoretical volumetric capacities, and environmental friendliness, magnesium-ion batteries (MIBs) have more feasibility for large-scale energy storage compared to lithium-ion batteries. However, lack of suitable cathode materials due to sluggish kinetics of magnesium ion is one of the biggest challenges. Herein, water-pillared sodium vanadium bronze nanowires (Na 2 V 6 O 16 ·1.63H 2 O) are reported as cathode material for MIBs, which display high performance in magnesium storage. The hydrated sodium ions provide excellent structural stability. The charge shielding effect of lattice water enables fast Mg 2+ diffusion. It exhibits high specific capacity of 175 mAh g -1 , long cycle life (450 cycles), and high coulombic efficiency (≈100%). At high current density of 200 mA g -1 , the capacity retention is up to 71% even after 450 cycles (compared to the highest capacity), demonstrating excellent long-term cycling performance. The nature of charge storage kinetics is explored. Furthermore, a highly reversible structure change during the electrochemical process is proved by comprehensive electrochemical analysis. The remarkable electrochemical performance makes Na 2 V 6 O 16 ·1.63H 2 O a promising cathode material for low-cost and safe MIBs.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Enabling safe aqueous lithium ion open batteries by suppressing oxygen reduction reaction

Abstract Due to the non-flammable nature of water-based electrolytes, aqueous lithium-ion batteries are resistant to catching fire. However, they are not immune to the risk of explosion, since the sealing structure adopted by current batteries limits the dissipation of heat and pressure within the cells. Here, we report a safe aqueous lithium-ion battery with an open configuration using water-in-salt electrolytes and aluminum oxide coated anodes. The design can inhibit the self-discharge by substantially suppressing the oxygen reduction reaction on lithiated anodes and enable good cycle performance over 1000 times. Our study may open a pathway towards safer lithium-ion battery designs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Tuning the Anode–Electrolyte Interface Chemistry for Garnet-Based Solid-State Li Metal Batteries

Lithium (Li) metal anode is a promising candidate for high energy density solid-state batteries. However, the interface issues, including large interfacial resistance and Li dendrite generation, have always frustrated the attempt to commercialize solid-state Li metal batteries (SSLBs). Here, we report that infusing the garnet-type solid electrolytes (GSEs) with air-stable electrolyte Li 3 PO 4 (LPO) dramatically reduces the interfacial resistance to ~1 Ω cm 2 and achieves a high critical current density of 2.2 mA cm -2 under ambient condition due to enhanced interfacial stability to Li metal anode. The coated and infused LPO electrolytes not only improve the mechanical strength and Li-ion conductivity of grain boundaries, but also form a stable Li-ion conductive but electron-insulating LPO-derived solid-electrolyte interphase between Li metal and GSEs, and consequently eliminates the Li dendrites growth and prevents the direct reduction of GSEs by Li metal over a long cycle life. This interface engineering approach together with grain-boundary modification on GSEs represents a promising strategy to revolutionize the anode-electrolyte interface chemistry for SSLBs and provides new design strategy for other-types of solid-state batteries.

25 ENERGY STORAGE↗