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Title: Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage

Abstract

A key technical challenge for capacitive energy storage devices to rival the performance of lithium-ion batteries is to improve their energy density (E), which is proportional to the capacity (C) and square of potential window (V) as following equation shows: E = ½ C V 2. Therefore, the primary objective of this project is to develop the electrode materials with high capacity and/or wide potential window. Through this research support, the PI has been working on two major groups of metal oxides materials to tackle this challenge. (i) The first group of materials are the manganese oxide-based nanoparticles (e.g., Mn 5O 8) having a kinetically stable potential window. Through hydroxylated interphase formed on the surface evidenced by synchrotron-based soft X-ray absorption analysis, such materials show high overpotential towards gas evolution reaction and enable a kinetically stable potential window (2.5 V in half cell and 3.0 V in full cell) for aqueous electrochemical energy storage, beyond the thermodynamically stable potential window (1.23 V). Besides the technological breakthrough, we have provided the fundamental understanding of this superior system by employing synchrotron-based soft X-ray spectroscopy, neutron scattering, electron microscope and density functional theory (DFT) calculations, as well as other hard X-ray and electrochemicalmore » tests. Our spectroscopic data reveals a well ordered ice-like surface hydroxyl layer that were only proposed in theory before (Science 304, 995, 2004). The unprecedented high voltage (3.0 V) and high-rate performance have been attributed to (i) high overpotential (> 0.6 V) of Mn 5O 8 towards HER and OER through interplay between Mn 2+ terminated surface and this special hydroxylated interphase; (ii) the unique bivalence (Mn 2+ 2Mn 4+ 3O 8) structure that enables two-electron charge transfer via Mn 2+/Mn 4+ redox couple; and (iii) facile pathway for Na-ion transport via intra-/inter-layer defects of Mn 5O 8. (ii) The second group of the materials are the vanadium oxide-based (e.g., V 2O 5) disordered layered nanostructures having larger storage capacity. Through the engagement of structural water evidenced by neutron total scattering, such materials have exhibited a high capacity of towards K-ion storage in an aqueous electrolyte. we have implemented a complementary characterization package entailing performance measurement in device level, in situ synchrotron X-ray diffraction, and X-ray/neutron total scattering (pair distribution analyses), from which the roles of the structural water on the stability and performance of disordered V 2O 5 layered materials have been studied. We discovered that the hydration (intercalation of structural water) primarily causes structural rearrangements of the [VO 6] octahedra that make up the V-O bilayers of the highly disordered V 2O 5 nanosheets. The disordered V 2O 5 nanosheets engaged with structural water exhibit superior high capacity and excellent stability for K-ion storage in an aqueous electrolyte. To our knowledge, this is one of the most stable and high capacity electrode materials ever reported for an aqueous K-ion storage. We believe our results will trigger more fundamental studies of the effects of structural water on stability and electrochemical performance of the disordered electrode materials.« less

Authors:
 [1]
  1. University of New Hampshire
Publication Date:
Research Org.:
Xiaowei Teng/University of New Hampshire
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1546597
Report Number(s):
DOE-UNH-SC0010286
DOE Contract Number:  
SC0010286
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE

Citation Formats

Teng, Xiaowei. Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage. United States: N. p., 2019. Web. doi:10.2172/1546597.
Teng, Xiaowei. Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage. United States. doi:10.2172/1546597.
Teng, Xiaowei. Thu . "Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage". United States. doi:10.2172/1546597. https://www.osti.gov/servlets/purl/1546597.
@article{osti_1546597,
title = {Transition Metal Oxides Nanomaterials for Aqueous Electrochemical Energy Storage},
author = {Teng, Xiaowei},
abstractNote = {A key technical challenge for capacitive energy storage devices to rival the performance of lithium-ion batteries is to improve their energy density (E), which is proportional to the capacity (C) and square of potential window (V) as following equation shows: E = ½ C V2. Therefore, the primary objective of this project is to develop the electrode materials with high capacity and/or wide potential window. Through this research support, the PI has been working on two major groups of metal oxides materials to tackle this challenge. (i) The first group of materials are the manganese oxide-based nanoparticles (e.g., Mn5O8) having a kinetically stable potential window. Through hydroxylated interphase formed on the surface evidenced by synchrotron-based soft X-ray absorption analysis, such materials show high overpotential towards gas evolution reaction and enable a kinetically stable potential window (2.5 V in half cell and 3.0 V in full cell) for aqueous electrochemical energy storage, beyond the thermodynamically stable potential window (1.23 V). Besides the technological breakthrough, we have provided the fundamental understanding of this superior system by employing synchrotron-based soft X-ray spectroscopy, neutron scattering, electron microscope and density functional theory (DFT) calculations, as well as other hard X-ray and electrochemical tests. Our spectroscopic data reveals a well ordered ice-like surface hydroxyl layer that were only proposed in theory before (Science 304, 995, 2004). The unprecedented high voltage (3.0 V) and high-rate performance have been attributed to (i) high overpotential (> 0.6 V) of Mn5O8 towards HER and OER through interplay between Mn2+ terminated surface and this special hydroxylated interphase; (ii) the unique bivalence (Mn2+2Mn4+3O8) structure that enables two-electron charge transfer via Mn2+/Mn4+ redox couple; and (iii) facile pathway for Na-ion transport via intra-/inter-layer defects of Mn5O8. (ii) The second group of the materials are the vanadium oxide-based (e.g., V2O5) disordered layered nanostructures having larger storage capacity. Through the engagement of structural water evidenced by neutron total scattering, such materials have exhibited a high capacity of towards K-ion storage in an aqueous electrolyte. we have implemented a complementary characterization package entailing performance measurement in device level, in situ synchrotron X-ray diffraction, and X-ray/neutron total scattering (pair distribution analyses), from which the roles of the structural water on the stability and performance of disordered V2O5 layered materials have been studied. We discovered that the hydration (intercalation of structural water) primarily causes structural rearrangements of the [VO6] octahedra that make up the V-O bilayers of the highly disordered V2O5 nanosheets. The disordered V2O5 nanosheets engaged with structural water exhibit superior high capacity and excellent stability for K-ion storage in an aqueous electrolyte. To our knowledge, this is one of the most stable and high capacity electrode materials ever reported for an aqueous K-ion storage. We believe our results will trigger more fundamental studies of the effects of structural water on stability and electrochemical performance of the disordered electrode materials.},
doi = {10.2172/1546597},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2019},
month = {8}
}