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Using Si as anode materials for Li-ion batteries remain challenging due to its morphological evolution and SEI modification upon cycling. The present work aims at developing a composite consisting of carbon-coated Si nanoparticles (Si@C NPs) intimately embedded in a three-dimensional (3D) graphene hydrogel (GHG) architecture to stabilize Si inside LiB electrodes. Instead of simply mixing both components, the novelty of the synthesis procedure lies in the in situ hydrothermal process, which was shown to successfully yield graphene oxide reduction, 3D graphene assembly production, and homogeneous distribution of Si@C NPs in the GHG matrix. Electrochemical characterizations in half-cells, on electrodes not containing additional conductive additive, revealed the importance of the protective C shell to achieve high specific capacity (up to 2200 mAh.g−1), along with good stability (200 cycles with an average Ceff > 99%). These performances are far superior to that of electrodes made with non-C-coated Si NPs or prepared by mixing both components. These observations highlight the synergetic effects of C shell on Si NPs, and of the single-step in situ preparation that enables the yield of a Si@C-GHG hybrid composite with physicochemical, structural, and morphological properties promoting sample conductivity and Li-ion diffusion pathways. [ABSTRACT FROM AUTHOR]

Carbon coatings can help to stabilize the electrochemical performance of high-energy anodes using silicon nanoparticles as the active material. In this work, the comparison of the behavior and chemical composition of the Solid Electrolyte Interphase (SEI) was carried out between Si nanoparticles and carbon-coated Si nanoparticles (Si@C). A combination of two complementary analytical techniques, Electrochemical Impedance Spectroscopy and X-ray Photoelectron Spectroscopy (XPS), was used to determine the intrinsic characteristics of the SEI. It was demonstrated that the SEI on Si particles is more resistive than the SEI on the Si@C particles. XPS demonstrated that the interface on the Si particles contains more oxygen when not covered with carbon, which shows that a protective layer of carbon helps to reduce the number of inorganic components, leading to more resistive SEI. The combination of those two analytical techniques is implemented to highlight the features and evolution of interfaces in different battery technologies. [ABSTRACT FROM AUTHOR]

Silicon nanowires are appealing structures to enhance the capacity of anodes in lithium-ion batteries. However, to attain industrial relevance, their synthesis requires a reduced cost. An important part of the cost is devoted to the silicon growth catalyst, usually gold. Here, we replace gold with tin, introduced as low-cost tin oxide nanoparticles, to produce a graphite–silicon nanowire composite as a long-standing anode active material. It is equally important to control the silicon size, as this determines the rate of decay of the anode performance. In this work, we demonstrate how to control the silicon nanowire diameter from 10 to 40 nm by optimizing growth parameters such as the tin loading and the atmosphere in the growth reactor. The best composites, with a rich content of Si close to 30% wt., show a remarkably high initial Coulombic efficiency of 82% for SiNWs 37 nm in diameter. [ABSTRACT FROM AUTHOR]

Bringing solid-state lithium batteries to market is a challenge; in part because their fabrication requires a technically difficult step of solid-electrolyte separator assembly, and because thus far, solid-state cells have only cycled under high pressure. Here, we address both these bottlenecks by assembling lithium-ion batteries based on the argyrodite Li 6 PS 5 Cl as the electrolyte using standard coating processes. Moreover, we upscaled to 10 cm2 pouch cells in a dry room by a double casting technique, thanks to the use of fluorine-free polyisobutene as the binder and nanosilicon and LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) respectively as the anode and cathode active materials. Electrode casting is shown to significantly improve the cycling stability when compared to the conventional pelletizing process. The all-coated pouch cells, cycled at a pressure as low as 1 MPa over 160 cycles, show a better capacity retention than the pelletized cells cycling under >100 MPa. The higher performance of the sheet-type cell is thought to originate in the better densification and homogeneity of the cell, attested by its low resistance. [Display omitted] • Si-NMC pouch cells with Li 6 PS 5 Cl solid electrolyte. • Both electrodes and separator casted via conventional ink coating process. • Cell scaled up from 0.4 cm2 (pelletized cell) to 10 cm2 (all-coated pouch cell). • The coating process improved long-term stability. • Pouch cells cycled under 1 MPa perform better than pelletized cells at 127 MPa. [ABSTRACT FROM AUTHOR]

Thanks to their high ionic conductivity and appropriate mechanical properties, sulfide-based solid electrolytes (SSE) are increasingly studied for a use in all-solid-state batteries (ASSBs). Silicon is abundant, non toxic and has a high theoretical capacity, and therefore is a promising active material in ASSBs. We first study the compatibility between two different solid electrolytes with similar ionic conductivity, Li 10 SnP 2 S 12 (LSnPS) and Li 6 PS 5 Cl (LPSCl), and micron-sized silicon based anode. LPSCl appears to be less reactive than LSnPS and it is then used to determine the most appropriate silicon size and shape for efficient cycling. Two silicon materials are compared, micron-sized silicon particles (μSi) and silicon nanowires (SiNWs). Energy Dispersive X-ray spectroscopy (EDX) mapping of the composite powders shows a better dispersion of the SiNWs in the LPSCl matrix. Galvanostatic cycling and Electrochemical Impedance Spectroscopy (EIS) measurements highlight the greater compatibility of SiNWs compared to μSi in ASSBs with a high specific delithiation capacity of 2600 mAh/g Si at the first cycle, while limiting the polarization and maintaining a relatively stable lithiation mechanism during cycling. [Display omitted] • Comparing solid electrolytes Li 10 SnP 2 S 12 and Li 6 PS 5 Cl for reactivity to Si. • Thinner SEI formed on Si nanowires. • Si nanowires more suitable for ASSB cycling than micron-sized Si. [ABSTRACT FROM AUTHOR]