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Valiyaveettil, SM, Nguyen D-L, Wong DP, Hsing C-R, Paradis-Fortin L, Qorbani M, Sabbah A, Chou T-L, Wu K-K, Rathinam V, Wei C-M, Chen L-C, Chen K-H.  2022.  Enhanced Thermoelectric Performance in Ternary Skutterudite Co(Ge0.5Te0.5)3 via Band Engineering, 2022. Inorganic Chemistry. : American Chemical Society AbstractWebsite


Valiyaveettil, SM, Qorbani M, Hsing C-R, Chou T-L, Paradis-Fortin L, Sabbah A, Srivastava D, Nguyen D-L, Ho T-T, Billo T, Ganesan P, Wei C-M, Chen L-C, Chen K-H.  2022.  Enhanced thermoelectric performance of skutterudite Co1−yNiySn1.5Te1.5−x with switchable conduction behavior, 2022. Materials Today Physics. 28:100889. AbstractWebsite

A fine control of carriers in solids is the most essential thing while exploring any functionality. For a ternary skutterudite like CoSn1·5Te1.5−x, which has been recently recognized as a potential material for thermoelectric conversion, the dominant carrier could be either electrons or holes via chemically tuning the quaternary Sn2Te2 rings in the structure. Both theoretical calculation and different spectroscopic probes, such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) were employed to unveil the conduction type switching details. On the other hand, a Ni-for-Co substitution was applied to enhance electronic transport, and thereby the thermoelectric power factor. Thanks to the substantial cut-off of lattice thermal conductivity by the characteristic Sn2Te2 rings in the skutterudite structure, ultimately a 70-fold increase in the dimensionless figure-of-merit (zT) is achieved at 723 K with the nominal composition Co0·95Ni0·05Sn1·5Te1.5.

Venugopal, B, Shown I, Samireddi S, Syum Z, Krishnamoorthy V, Wu H-L, Chu C-W, Lee C-H, Chen L-C, Chen K-H.  2021.  Microstructural intra-granular cracking in Cu2ZnSnS4@C thin-film anode enhanced the electrochemical performance in lithium-ion battery applications, 2021. Materials Advances. 2(17):5672-5685.: RSC AbstractWebsite

Cu2ZnSnS4 (CZTS) has demonstrated excellent performance as an anode material for lithium-ion batteries. However, the repeated lithiation and delithiation create a cracking pattern and lead to island formation in the thin-film electrode, resulting in a capacity fading over cycling in lithium-ion batteries (LIB's). In order to control this crack behaviour, we introduce carbon into CZTS thin-films by a hydrothermal method to form CZTS@C composite. CZTS@C significantly reduced the crack pattern formation on the electrode surface as well as improved the conductivity of the CZTS@C electrode. At the early stages of lithiation and delithiation, the volume expansion and contraction of Li–CZTS@C create intra-granular cracking only at the surface level, and it offers a high capacity of about 785 mA h g−1 after 150 cycles at 1000 mA g−1 charging rate, excellent rate capability (942 mA h g−1, 678 mA h g−1 and 435 mA h g−1 at 500 mA g−1, 2000 mA g−1 and 5000 mA g−1), and superior cyclability (925 mA h g−1 even after 200 cycles at 500 mA g−1). The excellent electrochemical performance at high-current rates can be attributed to intra-granular cracking together with carbon coating that provides a short transportation length for both lithium ions and electrons. Moreover, the controlled cracking pattern formation in CZTS@C facilitates faster reaction kinetics, which open up a new solution for the development of high-power thin-film anodes for next-generation LIBs applications.

Venugopal, B, Syum Z, Yu S-Y, Sabbah A, Shown I, Chu C-W, Chen L-C, Lee C-H, Wu H-L, Chen K-H.  2022.  Enhancing the Areal Capacity and Stability of Cu2ZnSnS4 Anode Materials by Carbon Coating: Mechanistic and Structural Studies During Lithiation and Delithiation, 2022. ACS Omega. 7(11):9152-9163.: American Chemical Society AbstractWebsite