Engineering topics

Zhuang, Minghao

Publications and source records attributed to Zhuang, Minghao.

6 records

DOE OSTI2020

Highly Reversible Sodiation/Desodiation from a Carbon-Sandwiched SnS2 Nanosheet Anode for Sodium Ion Batteries

The further improvement of sodium ion batteries requires the elucidation of the mechanisms pertaining to reversibility, which allows the novel design of the electrode structure. Her; through a hydrogel-embedding method, we are able to confine the growth of few-layer SnS 2 nanosheets between a nitrogen- and sulfur-doped carbon nanotube (NS-CNT) and amorphous carbon. The obtained carbon-sandwiched SnS 2 nanosheets demonstrate excellent sodium storage properties. In operando small-angle X-ray scattering combined with the ex situ X-ray absorption near edge spectra reveal that the redox reactions between SnS 2 /NS-CNT and the sodium ion are highly reversible. Furthermore, on the contrary, the nanostructure evolution is found to be irreversible, in which the SnS 2 nanosheets collapse, followed by the regeneration of SnS 2 nanoparticles. This work provides operando insights into the chemical environment evolution and structure change of SnS 2 -based anodes, elucidating its reversible reaction mechanism, and illustrates the significance of engineered carbon support in ensuring the electrode structure stability.

25 ENERGY STORAGE↗

DOE OSTI2019

Building ultraconformal protective layers on both secondary and primary particles of layered lithium transition metal oxide cathodes

Despite their relatively high capacity, layered lithium transition metal oxides suffer from crystal and interfacial structural instability under aggressive electrochemical and thermal driving forces, leading to rapid performance degradation and severe safety concerns. In this paper, we report a transformative approach using an oxidative chemical vapour deposition technique to build a protective conductive polymer (poly(3,4-ethylenedioxythiophene)) skin on layered oxide cathode materials. The ultraconformal poly(3,4-ethylenedioxythiophene) skin facilitates the transport of lithium ions and electrons, significantly suppresses the undesired layered to spinel/rock-salt phase transformation and the associated oxygen loss, mitigates intergranular and intragranular mechanical cracking, and effectively stabilizes the cathode-electrolyte interface. This approach remarkably enhances the capacity and thermal stability under high-voltage operation. Building a protective skin at both secondary and primary particle levels of layered oxides offers a promising design strategy for Ni-rich cathodes towards high-energy, long-life and safe lithium-ion batteries.

25 ENERGY STORAGE↗

DOE OSTI2019

Methacrylated gelatin-embedded fabrication of 3D graphene-supported Co 3 O 4 nanoparticles for water splitting

In this work, we developed a general platform for the fabrication of transition metal oxide nanoparticles supported by a graphene foam (GF) by first coating it with a methacrylated gelatin (GelMA) hydrogel, which served as a 3D matrix for nanoparticle dispersion. The engineered GelMA/GF matrix was hydrophilic with good mechanical strength and high conductivity, therefore providing a good platform for the dispersion of a variety of metal/oxide precursors. Due to this platform, well-dispersed Co 3 O 4 nanoparticles with the smallest size of 3 nm assembled on the nitrogen-doped graphene foam (Co 3 O 4 /NGF). The crystalline transformation from a CoCl 2 [H 2 O] 2 precursor to Co 3 O 4 was revealed by in operando X-ray diffraction and absorption techniques. After applying Co 3 O 4 /NGF as a free-standing electrocatalyst for water splitting, the nanoparticles of size 3 nm exhibited optimal catalytic activity in alkaline media; the corresponding cell could promote water splitting at a current density of 10 mA cm -2 with only 1.63 V and exhibited excellent stability in a 25 h long-term operation. Our results demonstrate that the GelMA hydrogel-coated 3D graphene foam can be a promising platform for the design and fabrication of graphene-based multifunctional materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Sub-5 nm edge-rich 1T'-ReSe 2 as bifunctional materials for hydrogen evolution and sodium-ion storage

The rhenium-based transition metal dichalcogenides (TMDs), as new members in the TMDs family, have raised great interests recently. Due to the anisotropic structure and unique photoelectric properties, they have potential applications for electrochemical energy conversion and storage. In this work, we performed density functional theory (DFT) calculations on pristine 1T'-ReSe 2 toward hydrogen evolution reaction (HER). The results indicated that the Gibbs free energy of the 1T'-ReSe 2 edge site for HER could be as small as 0.01 eV, superior to other reported TMDs. Experimentally, we developed a strategy to fabricate sub-5 nm sized 1T'-ReSe 2 nanoflakes on carbon nanotubes. Such a small size for the nanoflakes brought abundant edge exposure, which boosted the catalytic activity in the HER. Specifically, the 1T'-ReSe 2 nanoflakes needed only 23 and 60 mV overpotentials to achieve –1 and –10 mA cm –2 current densities, along with a low Tafel slope of 37 mV dec –1 and a high exchange current density of 0.3 mA cm –2 . The edge-rich and layered 1T'-ReSe 2 was also explored as an anode for sodium ion battery. The in operando X-ray absorption near edge structure (XANES) technique was applied to investigate the TMD behavior in real-time during the sodiation/desodiation process. Furthermore, the in situ results revealed that the nanosized 1T'-ReSe 2 is electrchemically reversible during discharge/charge cycles. The electrochemical test results demonstrated that 1T'-ReSe 2 could be a promising anode material for alkaline batteries.

25 ENERGY STORAGE↗

DOE OSTI2019

Rational Design of Graphene-Supported Single Atom Catalysts for Hydrogen Evolution Reaction

The proper choice of nonprecious transition metals as single atom catalysts (SACs) remains unclear for designing highly efficient electrocatalysts for hydrogen evolution reaction (HER). In this article, reported is an activity correlation with catalysts, electronic structure, in order to clarify the origin of reactivity for a series of transition metals supported on nitrogen-doped graphene as SACs for HER by a combination of density functional theory calculations and electrochemical measurements. Only few of the transition metals (e.g., Co, Cr, Fe, Rh, and V) as SACs show good catalytic activity toward HER as their Gibbs free energies are varied between the range of -0.20 to 0.30 eV but among which Co-SAC exhibits the highest electrochemical activity at 0.13 eV. Electronic structure studies show that the energy states of active valence d z 2 orbitals and their resulting antibonding state determine the catalytic activity for HER. The fact that the antibonding state orbital is neither completely empty nor fully filled in the case of Co-SAC is the main reason for its ideal hydrogen adsorption energy. Moreover, the electrochemical measurement shows that Co-SAC exhibits a superior hydrogen evolution activity over Ni-SAC and W-SAC, confirming the theoretical calculation. Lastly, this systematic study gives a fundamental understanding about the design of highly efficient SACs for HER.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Solid-State Lithium/Selenium–Sulfur Chemistry Enabled via a Robust Solid-Electrolyte Interphase

Lithium/selenium-sulfur batteries have recently received considerable attention due to their relatively high specific capacities and high electronic conductivity. Different from the traditional encapsulation strategy for suppressing the shuttle effect, an alternative approach to directly bypass polysulfide/polyselenide formation via rational solid-electrolyte interphase (SEI) design is demonstrated here. It is found that the robust SEI layer that in situ forms during charge/discharge via interplay between rational cathode design and optimal electrolytes could enable solid-state (de)lithiation chemistry for selenium-sulfur cathodes. Hence, Se-doped S 22.2 Se/Ketjenblack cathodes can attain a high reversible capacity with minimal shuttle effects during long-term and high rate cycling. Moreover, the underlying solid-state (de)lithiation mechanism, as evidenced by in situ 7 Li NMR and in operando synchrotron X-ray probes, further extends the optimal sulfur confinement pore size to large mesopores and even macropores that have been long considered as inferior sulfur or selenium host materials, which play a crucial role in developing high volumetric energy density batteries. It is expected that the findings in this study will ignite more efforts to tailor the compositional/structure characteristics of the SEI layers and the related ionic transport across the interface by electrode structure, electrolyte solvent, and electrolyte additive screening.

(de)lithiation chemistry↗