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Microstructural control of new intercalation layered titanoniobates with large and reversible d-spacing for easy Na⁺ ion uptake.

ABSTRACT: Key issues for Na-ion batteries are the development of promising electrode materials with favorable sites for Na⁺ ion intercalation/deintercalation and an understanding of the reaction mechanisms due to its high activation energy and poor electrochemical reversibility. We first report a layered H_0.43Ti_0.93Nb_1.07O₅ as a new anode material. This anode material is engineered to have dominant (200) and (020) planes with both a sufficiently large d-spacing of ~8.3 Å and two-dimensional ionic channels for easy Na⁺ ion uptake, which leads to a small volume expansion of ~0.6 Å along the c direction upon Na insertion (discharging) and the lowest energy barrier of 0.19 eV in the [020] plane among titanium oxide-based materials ever reported. The material intercalates and deintercalates reversibly 1.7 Na ions (~200 mAh g^-1) without a capacity fading in a potential window of 0.01 to 3.0 V versus Na/Na⁺. Na insertion/deinsertion takes place through a solid-solution reaction without a phase separation, which prevents coherent strain or stress in the microstructure during cycling and ensures promising sodium storage properties. These findings demonstrate a great potential of H_0.43Ti_0.93Nb_1.07O₅ as the anode, and our strategy can be applied to other layered metal oxides for promising sodium storage properties.

SUBMITTER: Park H

PROVIDER: S-EPMC5630241 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Microstructural control of new intercalation layered titanoniobates with large and reversible d-spacing for easy Na+ ion uptake.

Park Hyunjung H Kwon Jiseok J Choi Heechae H Song Taeseup T Paik Ungyu U

Science advances 20171006 10

Key issues for Na-ion batteries are the development of promising electrode materials with favorable sites for Na+ ion intercalation/deintercalation and an understanding of the reaction mechanisms due to its high activation energy and poor electrochemical reversibility. We first report a layered H0.43Ti0.93Nb1.07O5 as a new anode material. This anode material is engineered to have dominant (200) and (020) planes with both a sufficiently large ...[more]

PMID: 28989960

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Project description:Na/K pumps build essential ion gradients across the plasmalemma of animal cells by coupling the extrusion of three Na+, with the import of two K+ and the hydrolysis of one ATP molecule. The mechanisms of selectivity and competition between Na+, K+, and inhibitory amines remain unclear. We measured the effects of external tetrapropylammonium (TPA+) and ethylenediamine (EDA2+) on three different Na/K pump transport modes in voltage-clamped Xenopus oocytes: 1) outward pump current (IP), 2) passive inward H+ current at negative voltages without Na+ or K+ (IH), and 3) transient charge movement reporting the voltage-dependent extracellular binding/release of Na+ (QNa). Both amines competed with K+ to inhibit IP. TPA+ inhibited IH without competing with H+, whereas EDA2+ did not alter IH at pH 7.6. TPA+ competed with Na+ in QNa measurements, reducing Na+-apparent affinity, evidenced by a ?-75 mV shift in the charge-voltage curve (at 20 mM TPA+) without reduction of the total charge moved (Qtot). In contrast, EDA2+ and K+ did not compete with Na+ to inhibit QNa; both reduced Qtot without decreasing Na+-apparent affinity. EDA2+ (15 mM) right-shifted the charge-voltage curve by ?+50 mV. Simultaneous occlusion of EDA2+ and Na+ by an E2P conformation unable to reach E1P was demonstrated by voltage-clamp fluorometry. Trypsinolysis experiments showed that EDA2+-bound pumps are much more proteolysis-resistant than Na+-, K+-, or TPA+-bound pumps, therefore uncovering unique EDA2+-bound conformations. K+ effects on QNa and IH were also evaluated in pumps inhibited with beryllium fluoride, a phosphate mimic. K+ reduced Qtot without shifting the charge-voltage curve, indicating noncompetitive effects, and partially inhibited IH to the same extent as TPA+ in non-beryllium-fluorinated pumps. These results demonstrate that K+ interacts with beryllium-fluorinated pumps inducing conformational changes that alter QNa and IH, suggesting that there are two external access pathways for proton transport by IH.

Dataset Information

Microstructural control of new intercalation layered titanoniobates with large and reversible d-spacing for easy Na⁺ ion uptake.

Publications

Microstructural control of new intercalation layered titanoniobates with large and reversible d-spacing for easy Na<sup>+</sup> ion uptake.

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