Homeostatic Solid Solution Reaction in Phosphate Cathode: Breaking High-Voltage Barrier to Achieve High Energy Density and Long Life of Sodium-Ion Batteries.

The stable phase transformation during electrochemical progress drives extensive research on vanadium-based polyanions in sodium-ion batteries (SIBs), especially Na3V2(PO4)3 (NVP). And the electron transfer between V3+/4+ redox couple in NVP could be generally achieved, owing to the confined crystal variation during battery service. However, the more favorable V4+/5+ redox couple is still in hard-to-access situation due to the high barrier and further brings about the corresponding inefficiency in energy densities. In this work, the multilevel redox in NVP frame (MLNP) alters reaction pathway to undergo homeostatic solid solution process and breaks the high barrier of V4+/5+ at high voltage, taking by progressive transition metal (V, Fe, Ti, and Cr) redox couple. The diversified reaction paths across diffusion barriers could be realized by distinctive release/uptake of inactive Na1 site, confirmed by the calculations of density functional theory. Thereby its volume change is merely 1.73% during the multielectron-transfer process (≈2.77 electrons). MLNP cathode could achieve an impressive energy density of 440 Wh kg-1, driving the leading development of MLNP among other NASICON structure SIBs. The integration of multiple redox couples with low strain modulates the reaction pathway effectively and will open a new avenue for fabricating high-performance cathodes in SIBs.

Syntheses and structures of a series of uranyl phosphonates and sulfonates: an insight into their correlations and discrepancies.

Six uranyl phosphonates and sulfonates have been hydrothermally synthesized, namely, (H2tib)[(UO2)3(PO3C6H5)4]·2H2O (UPhP-1), Zn(pi)2(UO2)(PO3C6H5)2 (UPhP-2), Zn(dib)(UO2)(PO3C6H5)2·2H2O (UPhP-3), (HTEA)[(UO2)(5-SP)] (USP-1), (Hdib)2[(UO2)2(OH)(O)(5-SP)] (USP-2), and Zn(phen)3(UO2)2(3-SP)2 (USP-3) (tib = 1,3,5-tri(1H-imidazol-1-yl)benzene, pi = 1-phenyl-1H-imidazole, dib = 1,4-di(1H-imidazol-1-yl)benzene, TEA = triethylamine, phen = 1,10-phenanthroline, 5-SP = 5-sulfoisophthalic acid, and 3-SP = 3-sulfoisophthalic acid). UPhP-1 has been determined to be a layered structure constructed by UO7 pentagonal bipyramids, UO6 octahedra, and phenylphosphonates. Protonated tib plays a role in balancing the negative charge and holding its structure together. UPhP-2 is made up of UO6 octahedra, ZnO2N2 tetrahedra and PO3C tetrahedra in phenylphosphonates, forming a 1D assembly, which is stabilized by chelate phen ligand. Further connection of such chainlike structure via dib yields a 2D layered architecture of UPhP-3. Although sulfonate group possesses similar tetrahedral structure as the phosphonate group, a unidentated coordination mode is only found in this work. UO7 pentagonal bipyramids are linked by 5-SP to form the layered assembly of USP-1. USP-2 also consists of the same sulfonate ligand, but features tetranulear uranyl clusters. Similarly, protonated TEA and dib molecules enable stabilization of their structures, respectively. Formed by dinuclear uranyl cluster and 3-SP ligand, USP-3 appears as a 1D arrangement, in which Zn(phen)3 acts as the counterion to compensate the negative charge. All of these compounds have been characterized by IR and photoluminescent spectroscopy. Their characteristic emissions have been attributed as transition properties of uranyl cations.

From 1D chain to 3D framework uranyl diphosphonates: syntheses, crystal structures, and selective ion exchange.

In this work, we demonstrate a family of new inorganic-organic hybrid uranyl diphosphonates based on 1-hydroxyethylidenediphosphonic acid (H(4)L) linker by using hydrothermal method. These compounds, (Hbpi)[(UO(2))(H(2)O)(HL)]·H(2)O (UP-1), represents 1D structure, (Hbpi)[(UO(2))(H(2)O)(HL)] (UP-2), (H(2)dib)(0.5)[(UO(2))(H(2)O)(HL)] (UP-3), and [(UO(2))(H(2)O)(H(2)L)]·2H(2)O (UP-4) feature 2D architectures, (H(2)bipy){[(UO(2))(H(2)O)](2)[(UO(2))(H(2)O)(2)](L)(2)}·2H(2)O (UP-5), and (H(3)O)(2){[(UO(2))(H(2)O)](3)(L)(2)}·2H(2)O (UP-6) adopt 3D networks (bpi: 1-(biphenyl-4-yl)-1H-imidazole, dib: 1,4-di(1H-imidazol-1-yl)benzene, bipy: 2,2'-bipyridine). Among them, UP-1, UP-2, UP-3, and UP-4 possess the same structural building unit but with different structures. UP-5 and UP-6 feature the same UO(2)/L ratio of 3:2 but a different structural building unit. Photoluminescence studies reveal that UP-5 displays characteristic emissions of uranyl cations. Ion-exchange experiments demonstrate that the H(3)O(+) in UP-6 can be easily and selectively exchanged by monovalent cations including Na(+), K(+), Cs(+), and Ag(+) cations, whereas the framework retains identical as confirmed by single-crystal X-ray diffractions.

3-Fold-interpenetrated uranium-organic frameworks: new strategy for rationally constructing three-dimensional uranyl organic materials.

The first series of 3-fold-interpenetrated uranium-organic frameworks, UOF-1 and UOF-2, have been synthesized by hydrothermal reactions of flexible semirigid carboxylic acids and uranyl nitrate. Structure analyses indicate that UOF-1 and UOF-2 possess flu and pts topologies, respectively.

Anion Conductive Triblock Copolymer Membranes with Flexible Multication Side Chain.

To achieve highly conductive and stable anion exchange membranes (AEMs) for fuel cells, novel triblock copolymer AEMs bearing flexible side chain were synthesized. The triblock structure and flexible side chain are responsible for the developed hydrophilic/hydrophobic phase separated morphology and well-connected ion conducting channels, as confirmed by transmission electron microscopy. As a result, the triblock copolymer AEMs with flexible side chain (ABA-TQA- x) demonstrated considerably higher conductivities, up to 130.5 mS cm-1 at 80 °C, than the AEMs with monocation side chain (ABA-MQA). Furthermore, the long alkyl spacer between the backbone and quaternary ammonium groups, as well as long intercation spacer limits the water swelling of the membranes to some degree, resulting in good alkaline stability. The ABA-TQA-44 membrane retained 84.7% and 83.1% of its original conductivity and ionic exchange capacity, respectively, after immersed in a 1 M aqueous KOH solution at 80 °C for 480 h. Furthermore, the peak power density of a H2/O2 single cell using ABA-TQA-44 is 204.6 mW cm-2 at a current density of 500 mA cm-2 at 80 °C.