Chalcogenide thin film battery electrodes by chemical vapour deposition

Abstract

In this project, chemical vapour deposition was used to synthesise thin film electrode materials as high-capacity anodes for experimental investigation in secondary batteries. The underlying mechanism was explored using ex situ experimental characterisation, including X-ray diffraction, extended X-ray absorption fine structure and X-ray absorption near edge structure. All alloying materials in this study were layered structures and the crystalline structure is orthorhombic. SnSe, stoichiometric SnS and sulfur-deficient SnS thin films were obtained by aerosol assisted CVD on metal foil with good substrate coverage. The best deposition condition for SnS-SIBs cell was 440 ℃, at a nitrogen flow of 0.1 L min-1 . The SnS0.89 sample consists of rods with a diameter of about 100 nm with some Sn contamination due to vapour-liquid-solid growth. The rod-like structure provides higher capacity and better cycling stability than other SnS-only materials in sodium half-cells, due to increasing reaction surface area and better electronic conductivity. This improved performance can be directly attributed to the SnS film itself, while other high-capacity SnS materials reported previously are composites with carbon supports. Sb2Se3 thin films were coated by aerosol-assisted chemical vapour deposition (AACVD) directly on stainless steel foil. The sample for Sb2Se3-SIB cells was deposited at 470 ℃, and a short deposition time of 0.5 h. The Sb2Se3 samples consisted of needles with a length of about 10 μm, and the thin film electrodes in sodium half-cells showed good battery capacity compared with other larger crystallite size (50 μm) Sb2Se3 materials, all of which are known to be composites with carbon supports. In situ X-ray absorption near edge structure (XANES) and ex situ X-ray diffraction (XRD) were used to study both Sb and Se changes in redox reactions. GeSe materials, like Sb materials, have better electrochemical performance with smaller particles. The XANES results of GeSe and Sb2Se3 both show first-cycle intercalation reactions and the structure and bond length around both Ge and Se also have significant changes.

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Identifiers

ORCID for Andrew Hector: orcid.org/0000-0002-9964-2163

ORCID for Geoffrey Hyett: orcid.org/0000-0001-9302-9723

ORCID for Gill Reid: orcid.org/0000-0001-5349-3468

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