Nowadays, millimeter scale power sources are key devices for providing autonomy to smart, connected and miniaturized sensors. However, until now, planar solid state microbatteries do not yet exhibit a sufficient surface energy density. In that context, architectured 3D (3 dimensional) microbatteries appear therefore to be a good solution to improve the material mass loading while keeping small the footprint area. Beside the design itself of the 3D microbaterry, one important technological barrier to address is the conformal deposition of thin films (lithiated or not) on 3D structures. For that purpose, Atomic Layer Deposition (ALD) technology is a powerful technique that enable conformal coatings of thin film on complex substrate. In this paper, an original, robust and highly efficient 3D scaffold is proposed to significantly improve the geometrical surface of miniaturized 3D microbattery.Four functional layers composing the 3D lithium ion microbattery stacking has been Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))

The development of high voltage spinel LiMn 1.5 Ni 0.5 O 4 (LMNO) sputtered thin films on functional current collector was reported within the framework of this study. We have first solved the technological issue due to the PtSi phase which originates from the interdiffusion between silicon wafer and chromium/platinum current collector to form PtSi phase under annealing treatment. By substituting the Cr layer with a very dense and pinhole free Al 2 O 3 thin film deposited by ALD acting as a barrier diffusion between the silicon substrate and the LMNO layer, the synthesis process (sputtered thin films annealed under air at 700°C) has been validated. In the second part of this study, the behavior of the sputtered LMNO thin films as a function of the deposition pressure and the film thickness has been investigated. The deposition pressure has been found to play a key role on the Mn−Ni cations ordering in spinel-like structures (P4 3 32 ordered vs Fd3̅ m disordered spinel) and consequently on the electrochemical performance. We have thus shown that LMNO thin films deposited at 10 −2 mbar and annealed at 700°C deliver a normalized capacity of 65 μAh•cm −2 •μm −1 with good capacity retention upon cycling thanks to its disordered spinel structure. Moreover, the Coulombic efficiency has been shown to be highly dependent on the film thickness for high voltage LMNO thin film electrodes. To the best of the authors' knowledge, this work is one of the most complete study combining structural and electrochemical characterizations of the LMNO thin film obtained by sputtering deposition on Si/Al 2 O 3 /Pt functional current collectors.

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in: http://oatao.univ-toulouse.fr/ Eprints ID: 18012To link to this article:

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Taking advantage of strain engineering, Nd2WO6 (NdWO) thin films have been successfully grown on (001)-oriented SrTiO3 single-crystal substrates by pulsed-laser deposition. High-resolution X-ray diffraction characterizations highlight the stabilization of a new orthorhombic (Pm21 n) NdWO polymorphic form, isostructural to α-La2WO6. Reciprocal space mappings have been used in the determination of the NdWO thin-film structure. Coupled with the 2θ-ω X-ray patterns, the cell parameters were calculated: a = 16.34(5) Å, b = 5.46(5) Å, and c = 8.68(1) Å. X-ray-diffraction pole-figure measurements show the crystallographic relationships between the film and substrate: [100]NdWO∥[110]STO, [010]NdWO∥[11̅0]STO, and [001]NdWO∥[001]STO. Both X-ray diffraction and transmission electron microscopy studies reveal the existence of (510)-oriented crystallites with respect to the plane of the substrate mainly at the interface film/substrate and dispersed in the (001)-NdWO matrix. In addition, robust piezoelectricity and ferroelectricity are revealed at room temperature through both local hysteresis loops and domain manipulation experiments using the piezoresponse force microscopy technique. Typical polarization retention behaviors associated with specific nanoscale conduction are in good agreement with the classical ferroelectric phenomenon in oxide materials. The successful observation of piezo-/ferroelectricity at room temperature in innovative strain-stabilized α-NdWO thin films paves the way for new lead-free functional materials devoted to numerous applications, including actuators, sensors, or nonvolatile memory devices.

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This work reports the conformal coating of poly(poly(ethylene glycol) methyl ether methacrylate) (P(MePEGMA)) polymer electrolyte on highly organized titania nanotubes (TiO2nts) fabricated by electrochemical anodization of Ti foil. The conformal coating was achieved by electropolymerization using cyclic voltammetry technique. The characterization of the polymer electrolyte by proton nuclear magnetic resonance (1H NMR) and size-exclusion chromatography (SEC) shows the formation of short polymer chains, mainly trimers. X-ray photoelectron spectroscopy (XPS) results confirm the presence of the polymer and LiTFSI salt. The galvanostatic tests at 1C show that the performance of the half cell against metallic Li foil is improved by 33% when TiO2nts are conformally coated with the polymer electrolyte.