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Rechargeable aqueous Zn/MnO2 batteries are very attractive large‐scale energy storage technologies, but still suffer from limited cycle life and low capacity. Here the novel adoption of a near‐neutral acetate‐based electrolyte (pH ≈ 6) is presented to promote the two‐electron Mn4+/Mn2+ redox reaction and simultaneously enable a stable Zn anode. The acetate anion triggers a highly reversible MnO2/Mn2+ reaction, which ensures high capacity and avoids the issue of structural collapse of MnO2. Meanwhile, the anode‐friendly electrolyte enables a dendrite‐free Zn anode with outstanding stability and high plating/stripping Coulombic efficiency (99.8%). Hence, a high capacity of 556 mA h g−1, a lifetime of 4000 cycles without decay, and excellent rate capability up to 70 mA cm−2 are demonstated in this new near‐neutral aqueous Zn/MnO2 battery by simply manipulating the salt anion in the electrolyte. The acetate anion not only modifies the surface properties of MnO2 cathode but also creates a highly compatible environment for the Zn anode. This work provides a new opportunity for developing high‐performance Zn/MnO2 and other aqueous batteries based on the salt anion chemistry. [ABSTRACT FROM AUTHOR]

In situ neutron powder diffraction experiments are applied to physical, kinetic, and microstructural characterization of uranium mononitride as a promising light water reactor fuel material. The temperature-variable coefficient of thermal expansion and isotropic Debye Waller factors are obtained by sequential Rietveld refinement over 499–1873 K. Oxidation of a UN pellet (95.2% density) under flow of 11 mg/min D 2 O is observed to initiate above 623 K and the rate increases by a factor of approximately 10 from 673 to 773 K, with activation energy 50.6 ± 1.3 kJ/mol; uranium oxide is the only solid corrosion product. [ABSTRACT FROM AUTHOR]

Li 2 MSiO 4 (M = Mn, Fe, Co, Ni, et al.) has received great attention because of the theoretical possibility to reversibly deintercalate two Li + ions from the structure. However, the silicates still suffer from low electronic conductivity, sluggish lithium ion diffusion and structural instability upon deep cycling. In order to solve these problems, a “hard-soft” templating method has been developed to synthesize three-dimensionally ordered macroporous (3DOM) Li 2 FeSiO 4 /C composites. The 3DOM Li 2 FeSiO 4 /C composites show a high reversible capacity (239 mAh g −1 ) with ∼1.50 lithium ion insertion/extraction, a capacity retention of nearly 100% after 420 cycles and excellent rate capability. The enhanced electrochemical performance is ascribed to the interconnected carbon framework that improves the electronic conductivity and the 3DOM structure that offers short Li ion diffusion pathways and restrains volumetric changes. [ABSTRACT FROM AUTHOR]

U 3 Si 2 nuclear fuel is corroded in deuterated steam with in situ neutron diffraction. Density functional theory is coupled with rigorous thermodynamic description of the hydride including gas/solid entropy contributions. H absorbs in the 2 b interstitial site of U 3 Si 2 H x and moves to 8 j for x ≥ 0.5. Hydriding forces lattice expansion and change in a/c ratio linked to site preference. Rietveld refinement tracks the corrosion reactions at 350–500 °C and preference for the 8 j site. Above 375 °C, formation of UO 2 , U 3 Si 5 and USi 3 take place in the grain boundaries and bulk. Hydriding occurs in bulk and precedes other reactions. [Display omitted] • In situ neutron diffraction measures U 3 Si 2 corrosion in deuterated steam. • Rigorous thermodynamic description of hydride using key entropy contributions. • H absorption at 2 b interstitial site of U 3 Si 2 H x , moves to 8 j site for x ≥ 0.5. • From 350 °C, U 3 Si 2 H x fragmented by 1–2% anisotropic lattice expansion. • From 375 °C, UO 2 , U 3 Si 5 and USi 3 form in bulk and in grain boundaries. [ABSTRACT FROM AUTHOR]

Lithium-rich layered oxides (LLOs) exhibit great potential as high-capacity cathode materials for lithium-ion batteries, but usually suffer from capacity/voltage fade during electrochemical cycling. Herein, a gradient polyanion-doping strategy is developed to initiate surface structural transition to form a spinel-like surface nanolayer and a polyanion-doped layered core material in LLOs simultaneously. This strategy integrates the advantages of both bulk doping and surface modification as the oxygen close-packed structure of LLOs is stabilized by polyanion doping, and the LLO cathodes are protected from steady corrosion induced by electrolytes. A LLO material modified with 5 at% phosphate (5%P@LLO) shows a high reversible discharge capacity of ≈300 mAh g−1 at 0.1 C, excellent cycling stability with a capacity retention of 95% after 100 cycles, and enhanced electrode kinetics. This gradient doping strategy can be further extended to other polyanion-doped LLO materials, such as borate and silicate polyanions. [ABSTRACT FROM AUTHOR]

The phase evolution and anion redox behaviours under electrochemical cycling of sodium transition metal layered oxides have both been intensively studied. In this review, we focus on the relationship between them at high voltage states-of-charge, in the context of growing evidence that anion redox begins at an earlier state of charge than previously thought, and that the final structural change can behave in either a biphasic or a pseudo-solid solution manner, depending on the transition metal element. By systematically reviewing major breakthroughs in experimental materials discovery, characterization techniques and theoretical understanding, we tentatively propose a new way to think about the phase transition dynamics and a path to improving the theory of anion redox. • The most updated theories on structural evolution and anion redox are reviewed. • High voltage layered oxides for sodium ion battery cathode materials are examined. • Characterization techniques that can help to build our understanding are suggested. • Shortcomings of the current theories and future perspectives are discussed. [ABSTRACT FROM AUTHOR]

Two polymorphs of lithium magnesium tellurate Li 4–2 x Mg 1+ x TeO 6 have been prepared by solid-state reactions and their crystal structures characterised by powder X-ray and neutron diffraction. For x ​≈ ​0, a monoclinic C 2/ m phase is obtained, structurally similar to other O3 type honeycomb layered tellurate and antimonate compounds. The basic structure consists of [Mg 2 TeO 6 3− honeycomb layers alternating with Li layers, with some anti-site disorder of Li and Mg between layers, analogous to the structure of Li 4 ZnTeO 6. For 0 ​< ​ x ​< ​~0.5 (specifically, x ​= ​0.33) an orthorhombic Fddd phase is obtained, with a rock-salt superstructure containing disordered Li/Mg cation sites surrounding ordered TeO 6 octahedra, analogous to the structure of Li 3 Co 2 TaO 6. Figure caption : XRD pattern and illustration of the crystal structure of the O3-type monoclinic phase obtained for x ​≈ ​0 of the Li 4–2 x Mg 1+ x TeO 6 phase space. Image 1 • Layered oxides; Honeycomb; Neutron diffraction; polymorphs. [ABSTRACT FROM AUTHOR]

Here, we report a new enhanced extrinsic pseudocapacitve Li-ion storage mechanism via lithiation-induced structural optimization strategy. The flower-like C@SnS and bulk SnS exhibit initial capacity decay and subsequent increase of capacity on cycling. After a long-term lithiation/delithiation process, flower-like C@SnS and bulk SnS exhibit improved rate performance and reversible capacity in comparison with those of initial state. Moreover, a high capacity of 530 mAh g −1 is still remained even after 1550 cycles at a high current density of 5.0 A g −1 for flower-like C@SnS after pre-lithiation of 350 cycles. According to the comprehensive analysis of structural evolution and electrochemical performance, it demonstrates that SnS electrodes experience crystal size reduction and further amorphization on cycling, which enhances the reversibility of conversion reaction for SnS, leading to increasing capacity. On the other hand, surface-dominated extrinsic pseudocapacitive contribution results in enhanced rate performance because electrodes expose a large fraction of Li + sites on surface or near-surface region with structural optimization on cycling. This study reveals that extrinsic pseudocapacitance of SnS can be stimulated via lithiation-induced structural optimization, which gives rise to high-rate and long-lived performances. [ABSTRACT FROM AUTHOR]

Solid polymer electrolyte membranes (SPEMs) with star-shaped structure, consisting of octavinyl octasilsesquioxane (OV-POSS) with nanoscale organic/inorganic hybrid structure and poly(ethylene glycol) methyl ether methacrylate (PEGMEM), have been prepared by one-step free radical polymerization. OV-POSS with eight functional corner groups was used to produce star-shaped nanocomposites and PEGMEM was used as the polymer matrix to dissolve lithium ion. For comparison, SPEMs based on the corresponding linear copolymers, containing POSS moieties and PEGMEM segments, were also prepared. The SPEM with star-shaped structure containing 5.1 mol% POSS exhibits the highest ionic conductivity of 1.13×10 −4 S cm −1 and Li + transference number of 0.35 at 25 °C, which are about two times of that of SPEM with linear structure containing the same POSS content. Moreover, the Li/LiFePO 4 cell assembled with such star-shaped SPEM delivers the highest discharge capacity of 137.1 mAh g −1 under a current density of 0.5 C at 25 °C. At an evaluated temperature of 80 °C, this cell exhibits an initial discharge capacity of 163.8 mAh g −1 at 0.5 C, and even at high discharging C-rates of 5 and 10 C, the discharge capacity of 75.6 and 45.7 mAh g −1 can still be obtained, respectively. [ABSTRACT FROM AUTHOR]

Nanohybrid polymer electrolytes (NHPE) with ceramic particles have attracted significant attention owing to their improvement in electrochemical performance. However, particle aggregation and weak nanoparticle/polymer matrix interaction restrict their further application in lithium-ion batteries (LIBs). We demonstrate a facile in-situ polymerization/crystallization method to synthesize a homogeneous TiO 2 -grafted NHPE with a cross-linked branching structure, comprised of ion-conducting poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and non-polar stearyl methacrylate (SMA). This technique is different from existing methods of blending functionalized ceramic particles into the polymer matrix. Highly monodispersed TiO 2 nanocrystals enhance the effective interfacial interactions between particles and polymer matrix, which suppress the crystallization of ethylene oxide (EO) groups and facilitate forming continuously interconnected ion-conducting channels. Moreover, an increased dissociation degree of Li salt can also be achieved. The TiO 2 -grafted NHPE exhibits superior electrochemical properties with an ionic conductivity of 1.1 × 10 −4 S cm −1 at 30 °C, a high lithium ion transference number and excellent interfacial compatibility with the lithium electrode. In particular, a lithium-ion battery based on TiO 2 -grafted NHPE demonstrates good C-rate performance, as well as excellent cycling stability with an initial discharge capacity of 153.5 mAh g −1 and a capacity retention of 96% after 300 cycles at 1 C (80 °C). [ABSTRACT FROM AUTHOR]

A novel composite electrolyte membrane (CEM), consisting of a viscous PEGMEM-co-SMA copolymer, lithium salt and cellulose matrix, has been prepared as a new class of electrolyte for high performance lithium-ion batteries (LIBs). This CEM exhibits a wide electrochemical stability window (>5 V vs. Li/Li + ), reasonably high ionic conductivity and thermal stability up to 315 °C. At temperature above the melting temperature (31.98–35.71 °C), the viscous flow nature of the copolymer is beneficial to fully infiltrate the electrode materials like liquid electrolyte to maintain uniform contact with electrode surfaces during charge/discharge process. The interfacial resistance ( R intf ) of the fresh cell based on this CEM is extremely low (3.8 Ω cm −2 ) and the Li/LiFePO 4 cell deliveries a discharge capacity as high as 156.9 mA h g −1 with a current density of 1 C at 80 °C. It is anticipated that this work provides a new insight for designing advanced electrolyte materials for LIBs with enhanced interfacial contact and excellent cycling performance. [ABSTRACT FROM AUTHOR]