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All-solid-state sodium batteries (ASSSBs) are attractive alternatives to lithium-ion batteries for grid-scale energy storage due to their high safety and ubiquitous distribution of Na sources. A critical component for ASSSB is sodium-ion conducting solid-state electrolyte (SSE). Here, we report a high-performance sodium-ion SSE with the recently developed bulk interfacial superionic conductor (BISC) concept. The ionic conductivity and areal conductance of the Na+ BISC at 25 °C reaches 6.5 × 10-4 S cm-1 and 260 mS cm-2, respectively. Using NaxCo0.7Mn0.3O2 (x ≈ 1.0, NaCMO) as the cathode active material, all-solid-state Na||NaCMO batteries exhibiting small overpotential and ∼180 cycle life are demonstrated under room temperature. This approach may also be used to prepare other metal ion, such as Mg2+, Al3+, and K+, based all-solid-state batteries.

Ferroelectric barium titanate nanoparticles (BTO NPs) may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors. While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade, the majority of the investigation was carried out in thin-film materials; therefore, the doping effect on nanoparticles remains unclear. Especially, doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled. In this work, we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), integrated differential phase contrast (iDPC)-STEM, and energy dispersive X-ray spectroscopy (EDX) mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles. Powder X-ray diffraction (PXRD) results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase, but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles. Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.

P2-Na0.67Ni0.33Mn0.67O2 presents high working voltage with a theoretical capacity of 173 mAh g-1. However, the lattice oxygen on the particle surface participates in the redox reactions when the material is charged over 4.22 V. The resulting oxidized oxygen aggravates the electrolyte decomposition and transition metal dissolution, which cause severe capacity decay. The commonly reported cation substitution methods enhance the cycle stability by suppressing the high voltage plateau but lead to lower average working voltage and reduced capacity. Herein, we stabilized the lattice oxygen by a small amount of Sn substitution based on the strong Sn-O bond without sacrificing the high voltage performance and further protected the particle surface by polypyrrole (PPy) coating. The obtained Na0.67Ni0.33Mn0.63Sn0.04O2@PPy (3.3 wt %) composite showed excellent cycling stability with a reversible capacity of 137.6 (10) and 120.0 mAh g-1 (100 mA g-1) with a capacity retention of 95% (10 mA g-1, 50 cycles) and 82.5% (100 mA g-1, 100 cycles), respectively. The present work indicates that slight Sn substitution combined with PPy coating could be an effective approach to achieving superior cycling stability for high-voltage layered transition metal oxides.

NaTaO3/reduced graphene oxide (RGO) composite were prepared via a two-step hydrothermal method. The as-prepared NaTaO3/RGO composite were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-Vis diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and X-ray photoelectron spectroscopy (XPS). The results indicated the reduction of graphene oxide and the chemical bonding between RGO and NaTaO3 are achieved simultaneously. As a result, NaTaO3/RGO composite possessed efficient charge separation properties. Hence, in the photocatalytic measurement toward the H2 production from an aqueous Na2S/Na2SO3 solution under UV illumination, a significant improvement in the H2 production rate was observed over NaTaO3/RGO composite, compared to the pure NaTaO3 and mechanically mixed NaTaO3-RGO composite with the same RGO content. In particular, the photocatalytic H2 production rate over NaTaO3/2%RGO with RGO content of 2 wt% was 3.82 times higher than that of pure NaTaO3. Moreover, the photocatalytic hydrogen production performance of NaTaO3/2%RGO was rather stable. A plausible electron transfer mechanism was proposed to discuss the improved photocatalytic H2 production performance.