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1.
Small ; : e1906374, 2020 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-32077623

RESUMO

Critical to the development of all-solid-state lithium-ion batteries technology are novel solid-state electrolytes with high ionic conductivity and robust stability under inorganic solid-electrolyte operating conditions. Herein, by using density functional theory and molecular dynamics, a mixed oxygen-sulfur-based Li-superionic conductor is screened out from the local chemical structure of ß-Li3 PS4 to discover novel Li14 P2 Ge2 S8 O8 (LPGSO) with high ionic conductivity and high stability under thermal, moist, and electrochemical conditions, which causes oxygenation at specific sites to improve the stability and selective sulfuration to provide an O-S mixed path by Li-S/O structure units with coordination number between 3 and 4 for fast Li-cooperative conduction. Furthermore, LPGSO exhibits a quasi-isotropic 3D Li-ion cooperative diffusion with a lesser migration barrier (≈0.19 eV) compared to its sulfide-analog Li14 P2 Ge2 S16 . The theoretical ionic conductivity of this conductor at room temperature is as high as ≈30.0 mS cm-1 , which is among the best in current solid-state electrolytes. Such an oxy-sulfide synergistic effect and Li-ion cooperative migration mechanism would enable the engineering of next-generation electrolyte materials with desirable safety and high ionic conductivity, for possible application in the near future.

2.
ACS Appl Mater Interfaces ; 12(5): 6007-6014, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-31941270

RESUMO

A crystalline solid electrolyte interphase Li2CO3 material with a large band gap shows promise toward next-generation all-solid-state lithium batteries (ASSLBs). However, the inferior ionic diffusivity restricts such structures to a real battery setup. Herein, based on density functional theory calculation and Python materials genomics, we theoretically develop the chemistry and local structural motifs to build a mixed boron-carbon framework Li2+xC1-xBxO3 (LCBO). We examine the electrochemical and chemical stabilities of LCBO-electrode interfaces by analyzing the thermodynamics of formation of interfacial phases. Interestingly, the LCBO material is automatically protected from further decomposition through the self-generated resistive interphase (Li2CO3 and Li3BO3), which gives a wide range of operating potential. LCBO shows high interfacial stability with LiCoO2, LiMnO2, and LiMn2O4. More importantly, the theoretical Li-ion migration barrier of LCBO (x = 0.375) is approximately 0.23 ± 0.02 eV through a cooperative migration mechanism. Therefore, the LCBO material combines high Li-ion diffusivity with good interfacial stability, which makes it a promising solid-state electrolyte material for ASSLBs.

3.
Adv Mater ; 32(7): e1906357, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31880000

RESUMO

Lithium-sulfur (Li-S) batteries are considered to be one of the most promising candidate systems for next-generation electrochemical energy storage. The major challenge of this system is the polysulfide shuttle, which results in poor cycling efficiency. In this work, a highly N-doped carbon/graphene (NC/G) sheet is designed as a sulfur host, which combines the merits of abundant N active sites and high electrical conductivity to achieve in situ anchoring-conversion of lithium polysulfides (LiPSs). Such a host not only has strong binding with LiPSs but also promotes redox kinetics, which are revealed by both experimental investigations and theoretical studies. The sulfur cathode based on the NC/G host exhibits a high initial capacity of 1380 mA h g-1 and a superior cycle stability with a low capacity decay of 0.037% per cycle within 500 cycles at 2 C. Steady areal capacity with a high sulfur loading (5.6 mg cm-2 ) is also attained even without the addition of LiNO3 in the electrolyte. This work proposes and illustrates the importance of in situ anchoring-conversion of LiPSs, offering a new strategy to design multifunctional sulfur hosts for high-performance Li-S batteries.

4.
Chem Commun (Camb) ; 56(5): 786-789, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31845676

RESUMO

Lithium-sulfur batteries are one of the most promising candidates for next-generation energy storage systems. The major challenge hindering their commercialization is the polysulfide shuttle effect, which causes a series of problems including the loss of active materials, corrosion of the lithium anode, low coulombic efficiency, and poor cycling performance. In this work, we develop a mesoporous silica-based cathode for efficient trapping of lithium polysulfides (LiPSs). This cathode material consists of mesoporous silica (HMS), highly dispersed NiO nanoparticles embedded in the silica structure, and a conductive polymer (polypyrrole-ppy) prepared by in situ polymerization. We employ the concept of both the physical and chemical entrapment of LiPSs, i.e., physically trapping LiPSs by spatial confinement of LiPSs in the silica porous structure and physical adsorption of LiPSs by the silica surface, and chemically binding LiPSs by highly dispersed NiO nanoparticles in the silica structure. The NiO/silica/ppy/S cathode exhibits good cycling stability and maintains over 700 mA h g-1 after 300 cycles. As far as we know, this is the first time that mesoporous silica has been directly employed as a sulfur host material, rather than an additive. The present study opens up a window for nanoporous silica to be employed as the sulfur host.

5.
Phys Chem Chem Phys ; 21(25): 13758-13765, 2019 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-31210190

RESUMO

Coating materials in lithium-ion batteries (LIBs) have attracted extensive attention due to their ability to retard the decay of electrochemical performance in long-term cycling. Most of these coating materials, however, exhibit inferior ionic diffusivity. Herein, we report a novel coating material, LiAl5O8, which possesses a spinel-type structure. Our first principles calculation results show that the diffusion coefficient of Li ions in LiAl5O8 is over thirty orders of magnitude higher than that of Al2O3, and its electrochemical stability window is sufficiently wide, from 0.80 to 4.08 V versus Li/Li+. The facile Li ion diffusion pathways and high electrochemical stability make LiAl5O8 an effective coating material for next-generation LIBs.

6.
Phys Chem Chem Phys ; 21(19): 9883-9888, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-31038528

RESUMO

Solid state electrolytes (SSEs) based on two dimensional covalent organic frameworks (2D-COFs) with Li salts and solvents impregnated in their large pores have emerged as novel candidate materials for solid state lithium batteries. Here, using ab initio molecular dynamics simulation, we track the atomic-scale structural evolution during Li+ ion diffusion in a 2D-COF SSE composed of COF-5, LiClO4 and tetrahydrofuran (THF). Our simulation results show the transient dynamics of the Li+ diffusion events, the free rotation of ClO4- ions and the essential role of THFs in partitioning between the ions and the solid framework. We find clear evidence that Li+ ion diffusion adopts a one-dimensional (1D) liquid-like behavior with the coordination evolution driven by facile rotation and short-range diffusion of ClO4- ions and THFs. The fast Li+ diffusion pathway in the 1D tunnels of COFs may shed light on future design of high-performance COF based SSEs.

7.
Nano Lett ; 17(10): 6018-6026, 2017 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-28771015

RESUMO

Because of their enhanced kinetic properties, nanocrystallites have received much attention as potential electrode materials for energy storage. However, because of the large specific surface areas of nanocrystallites, they usually suffer from decreased energy density, cycling stability, and effective electrode capacity. In this work, we report a size-dependent excess capacity beyond theoretical value (170 mA h g-1) by introducing extra lithium storage at the reconstructed surface in nanosized LiFePO4 (LFP) cathode materials (186 and 207 mA h g-1 in samples with mean particle sizes of 83 and 42 nm, respectively). Moreover, this LFP composite also shows excellent cycling stability and high rate performance. Our multimodal experimental characterizations and ab initio calculations reveal that the surface extra lithium storage is mainly attributed to the charge passivation of Fe by the surface C-O-Fe bonds, which can enhance binding energy for surface lithium by compensating surface Fe truncated symmetry to create two types of extra positions for Li-ion storage at the reconstructed surfaces. Such surface reconstruction nanotechnology for excess Li-ion storage makes full use of the large specific surface area of the nanocrystallites, which can maintain the fast Li-ion transport and greatly enhance the capacity. This discovery and nanotechnology can be used for the design of high-capacity and efficient lithium ion batteries.

8.
J Hazard Mater ; 321: 154-161, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-27619961

RESUMO

MnFe2O4 has been regarded as a very promising sorbent for mercury emission control in coal-fired power plants because of its high adsorption capacity, magnetic, recyclable and regenerable properties. First-principle calculations based on density functional theory (DFT) were used to elucidate the mercury adsorption and oxidation mechanisms on MnFe2O4 surface. DFT calculations show that Mn-terminated MnFe2O4 (1 0 0) surface is much more stable than Fe-terminated surface. Hg0 is physically adsorbed on Fe-terminated MnFe2O4 (1 0 0) surface. Hg0 adsorption on Mn-terminated MnFe2O4 (1 0 0) surface is a chemisorption process. The partial density of states (PDOS) analysis indicates that Hg atom interacts strongly with surface Mn atoms through the orbital hybridization. HgO is adsorbed on the MnFe2O4 surface in a chemical adsorption manner. The small HOMO-LUMO energy gap implies that HgO molecular shows high chemical reactivity for HgO adsorption on MnFe2O4 surface. The energy barriers of Hg0 oxidation by oxygen on Fe- and Mn-terminated MnFe2O4 surfaces are 206.37 and 76.07kJ/mol, respectively. Mn-terminated surface is much more favorable for Hg0 oxidation than Fe-terminated surface. In the whole Hg0 oxidation process, the reaction between adsorbed mercury and surface oxygen is the rate-determining step.

9.
Environ Sci Technol ; 50(10): 5398-404, 2016 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-27135958

RESUMO

Catalytic oxidation of elemental mercury (Hg(0)) through a selective catalytic reduction (SCR) system is a promising method to reduce mercury emissions from coal-burning power plants. The density functional theory (DFT) and periodic slab models were used to study the reaction mechanism of Hg(0) oxidation by HBr on V2O5/TiO2 SCR catalyst surface. The interaction mechanisms of Hg(0), HBr, HgBr, and HgBr2 on V2O5/TiO2(001) were investigated. The oxidation reaction energy profiles and the corresponding geometries of the intermediates, final states, and transition states were researched. The results indicate that Hg(0) and HgBr2 are weakly adsorbed on the oxygen sites of the V2O5/TiO2(001) surface with physisorption. HgBr is chemically adsorbed on the surface. HBr is dissociatively adsorbed on the surface with an energy barrier of 85.59 kJ/mol. The reaction of Hg(0) oxidation by HBr follows the Eley-Rideal mechanism: Hg(0) interacts with a surface Br from HBr dissociation to form HgBr, and surface HgBr further interacts with HBr to form HgBr2, last HgBr2 desorbs from the surface. Comparing the energy pathway of Hg(0) oxidation over V2O5/TiO2(001) surface by HBr to that of HCl, it is found that the dissociation energy barrier of HBr is lower than that of HCl, the formation and desorption energy barriers of HgBr2 are also lower than that of HgCl2, which explains why HBr is much more effective than HCl in promoting Hg(0) oxidation.


Assuntos
Mercúrio , Oxirredução , Catálise , Carvão Mineral , Centrais Elétricas
10.
Chem Commun (Camb) ; 52(33): 5706-9, 2016 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-27040601

RESUMO

We report tuning band alignment by optimized CdS layers using a SILAR method to achieve the recorded best performance with about 6% PCE in TiO2/CdS/CdSe QDSSCs. Combining experimental and theoretical studies, we find that a better lattices match between CdS and TiO2 assists the growth of CdSe, and the combined effect of charge transfer and surface dipole moment at the TiO2/CdS/CdSe interface shifts the energy levels of TiO2 upward and increases Voc of the solar cells. More importantly, the band gap of CdS buffer layers is sensitive to the distortion induced by lattice mismatch and numbers of CdS layers. For example, the barrier for charge transfer disappears when there are more than 4 layers of CdS, facilitating the charge injection from CdSe to TiO2.

11.
Anal Chem ; 82(19): 8217-25, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20804162

RESUMO

Field effect regulation of DNA nanoparticle translocation through a nanopore using a gate electrode is investigated using a continuum model, composed of the coupled Poisson-Nernst-Planck equations for the ionic mass transport and the Navier-Stokes equations for the hydrodynamic field. The field effect regulation of the DNA translocation relies on the induced electroosmotic flow (EOF) and the particle-nanopore electrostatic interaction. When the electrical double layers (EDLs) formed adjacent to the DNA nanoparticle and the nanopore wall are overlapped, the particle-nanopore electrostatic interaction could dominate over the EOF effect, which enables the DNA trapping inside the nanopore when the applied electric field is relatively low. However, the particle-nanopore electrostatic interaction becomes negligible if the EDLs are not overlapped. When the applied electric field is relatively high, a negative gate potential can slow down the DNA translocation by an order of magnitude, compared to a floating gate electrode. The field effect control offers a more flexible and electrically compatible approach to regulate the DNA translocation through a nanopore for DNA sequencing.


Assuntos
DNA/química , Nanoporos , Análise de Sequência de DNA/métodos , Eletrodos , Eletro-Osmose , Hidrodinâmica , Transporte de Íons , Nanopartículas/química , Eletricidade Estática
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