Search NASA⌕ Search

Engineering topics

Xin, Sen

Publications and source records attributed to Xin, Sen.

18 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Short O–O separation in layered oxide Na 0.67 CoO 2 enables an ultrafast oxygen evolution reaction

The layered oxide Na 0.67 CoO 2 with Na + occupying trigonal prismatic sites between CoO 2 layers exhibits a remarkably high room temperature oxygen evolution reaction (OER) activity in alkaline solution. The high activity is attributed to an unusually short O–O separation that favors formation of peroxide ions by O - –O – interactions followed by O 2 evolution in preference to the conventional route through surface O–OH – species. The dependence of the onset potential on the pH of the alkaline solution was found to be consistent with the loss of H + ions from the surface oxygen to provide surface O - that may either be attacked by solution OH - or react with another O - ; a short O–O separation favors the latter route. The role of a strong hybridization of the O-2 p and low-spin Co III /Co IV π-bonding d states is also important; the OER on other Co III /Co IV oxides is compared with that on Na 0.67 CoO 2 as well as that on IrO 2 .

Wang, Hao↗
DOE OSTI2019

Exceptional oxygen evolution reactivities on CaCoO 3 and SrCoO 3

We investigated the roles of covalent bonding, separation of surface oxygen, and electrolyte pH on the oxygen evolution reaction (OER) on transition metal oxides by comparing catalytic onset potentials and activities of CaCoO 3 and SrCoO 3 . Both cubic, metallic perovskites have similar Co IV intermediate spin states and onset potentials, but a substantially smaller lattice parameter and shorter surface oxygen separation make CaCoO 3 a more stable catalyst with increased OER activity. The onset potentials are similar, occurring where H + is removed from surface -OH - , but two competing surface reactions determine the catalytic activity. In one, the surface -O - is attacked by electrolyte OH - to form the surface -OOH - ; in the other, two -O - form a surface peroxide ion and an oxygen vacancy with electrolyte OH - attacking the oxygen vacancy. The second pathway can be faster if the surface oxygen separation is smaller.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Na 3 MnZr(PO 4 ) 3 : A High-Voltage Cathode for Sodium Batteries

Sodium batteries have been regarded as promising candidates for large-scale energy storage application, provided cathode hosts with high energy density and long cycle life can be found. Herein, we report NASICON-structured Na 3 MnZr(PO 4 ) 3 as a cathode for sodium batteries that exhibits an electrochemical performance superior to those of other manganese phosphate cathodes reported in the literature. Both the Mn 4+ /Mn 3+ and Mn 3+ /Mn 2+ redox couples are reversibly accessed in Na 3 MnZr(PO 4 ) 3 , providing high discharge voltage plateaus at 4.0 and 3.5 V, respectively. A high discharge capacity of 105 mAh g –1 was obtained from Na 3 MnZr(PO 4 ) 3 with a small variation of lattice parameters and a small volume change on extraction of two Na + ions per formula unit. Moreover, Na 3 MnZr(PO 4 ) 3 exhibits an excellent cycling stability, retaining 91% of the initial capacity after 500 charge/discharge cycles at 0.5 C rate. On the basis of structural analysis and density functional theory calculations, we have proposed a detailed desodiation pathway from Na 3 MnZr(PO 4 ) 3 where Mn and Zr are disordered within the structure. We further show that the cooperative Jahn–Teller distortion of Mn 3+ is suppressed in the cathode and that Na 2 MnZr(PO 4 ) 3 is a stable phase

Chemistry↗
DOE OSTI2018

Room‐Temperature Liquid Na–K Anode Membranes

Abstract The Na–K alloy is a liquid at 25 °C over a large compositional range. The liquid alloy is also immiscible in the organic‐liquid electrolytes of an alkali‐ion rechargeable battery, providing dendrite‐free liquid alkali‐metal batteries with a liquid–liquid anode‐electrolyte interface at room temperature. The two liquids are each immobilized in a porous matrix. In previous work, the porous matrix used to immobilize the alloy was a carbon paper that is wet by the alloy at 420 °C; the alloy remains in the paper at room temperature. Here we report a room‐temperature vacuum infiltration of the alloy into a porous Cu or Al membrane and a reversible stripping/plating of the liquid alloy with the immobilized organic‐liquid electrolyte; no self‐diacharge is observed since the liquid Na–K does not dissolve into the liquid carbonate electrolytes. The preparation and stripping/plating of the liquid alkali‐metal anode can both now be done safely at room temperature.

Xue, Leigang↗
DOE OSTI2018

A Perovskite Electrolyte That Is Stable in Moist Air for Lithium‐Ion Batteries

Abstract Solid‐oxide Li + electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H + exchanges for the mobile Li + of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid–electrolyte separator. We report a new perovskite Li + solid electrolyte, Li 0.38 Sr 0.44 Ta 0.7 Hf 0.3 O 2.95 F 0.05 , with a lithium‐ion conductivity of σ Li =4.8×10 −4 S cm −1 at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li + ‐conducting polymer on its surface to prevent reduction of Ta 5+ is wet by metallic lithium and provides low‐impedance dendrite‐free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all‐solid‐state Li/LiFePO 4 cell, a Li‐S cell with a polymer‐gel cathode, and a supercapacitor.

Li, Yutao↗
DOE OSTI2018

A High‐Energy‐Density Potassium Battery with a Polymer‐Gel Electrolyte and a Polyaniline Cathode

Abstract A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K + ion of the KPF 6 salt is plated/stripped on the potassium‐metal anode. The use of a p‐type polymer cathode increases the cell voltage. By replacing the organic‐liquid electrolyte in a glass‐fiber separator with a polymer‐gel electrolyte of cross‐linked poly(methyl methacrylate), a dendrite‐free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross‐linked architecture provides small pores of adjustable sizes to stabilize a solid‐electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low‐cost potassium batteries for the stationary storage of electric power.

Gao, Hongcai↗
DOE OSTI2017

A Plastic–Crystal Electrolyte Interphase for All‐Solid‐State Sodium Batteries

Abstract The development of all‐solid‐state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid‐state sodium cells with 1) solid electrolyte Na 3 Zr 2 (Si 2 PO 4 ) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all‐solid‐state battery cells.

Gao, Hongcai↗
DOE OSTI2017

A Plastic-Crystal Electrolyte Interphase for All-Solid-State Sodium Batteries

The development of all-solid-state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. In this work, comparison of solid-state sodium cells with 1) solid electrolyte Na 3 Zr 2 (Si 2 PO 4 ) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all-solid-state battery cells.

25 ENERGY STORAGE↗
DOE OSTI2016

Hybrid Polymer/Garnet Electrolyte with a Small Interfacial Resistance for Lithium-Ion Batteries

Li 7 La 3 Zr 2 O 12 -based Li-rich garnets react with water and carbon dioxide in air to form a Li-ion insulating Li 2 CO 3 layer on the surface of the garnet particles, which results in a large interfacial resistance for Li-ion transfer. In this work, we introduce LiF to garnet Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT-2 wt % LiF (LLZT-2LiF) has less Li 2 CO 3 on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic-liquid electrolytes. Lastly, an all-solid-state Li/polymer/LLZT-2LiF/LiFePO 4 battery has a high Coulombic efficiency and long cycle life; a Li-S cell with the LLZT-2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li-metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.

25 ENERGY STORAGE↗