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1.
Proc Natl Acad Sci U S A ; 117(6): 2815-2823, 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-31996477

RESUMO

Existing lithium-ion battery technology is struggling to meet our increasing requirements for high energy density, long lifetime, and low-cost energy storage. Here, a hybrid electrode design is developed by a straightforward reengineering of commercial electrode materials, which has revolutionized the "rocking chair" mechanism by unlocking the role of anions in the electrolyte. Our proof-of-concept hybrid LiFePO4 (LFP)/graphite electrode works with a staged deintercalation/intercalation mechanism of Li+ cations and PF6 - anions in a broadened voltage range, which was thoroughly studied by ex situ X-ray diffraction, ex situ Raman spectroscopy, and operando neutron powder diffraction. Introducing graphite into the hybrid electrode accelerates its conductivity, facilitating the rapid extraction/insertion of Li+ from/into the LFP phase in 2.5 to 4.0 V. This charge/discharge process, in turn, triggers the in situ formation of the cathode/electrolyte interphase (CEI) layer, reinforcing the structural integrity of the whole electrode at high voltage. Consequently, this hybrid LFP/graphite-20% electrode displays a high capacity and long-term cycling stability over 3,500 cycles at 10 C, superior to LFP and graphite cathodes. Importantly, the broadened voltage range and high capacity of the hybrid electrode enhance its energy density, which is leveraged further in a full-cell configuration.

2.
Adv Mater ; 31(24): e1901372, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31026108

RESUMO

Aluminum is regarded as a promising alternative for graphite anode in next-generation lithium-ion batteries, but its application is hindered by the simultaneous presence of aluminum oxide and the huge volume changes. Herein, hydrogenation-induced self-assembly of robust Al nanocrystals with high purity that are uniformly anchored on graphene is demonstrated. The strong molecular interaction between Al and graphene can not only thermodynamically facilitate the homogenous distribution of Al on graphene but also effectively alleviate the volume changes and preserve the structural integrity of the electrode. More importantly, density functional theory calculations reveal that the absence of oxidation can lower the energy barrier for Li diffusion inside the Al matrix to less than 1/6 of that in an Al matrix with only one monolayer coverage of oxygen. These unique structural features enable the aluminum/graphene nanosheets (Al@GNs) electrode to realize a high reversible capacity of 1219 mAh g-1 and an excellent cycling stability with capacity of 766 mAh g-1 after 1000 cycles at the 3 A g-1 rate. Furthermore, a full cell, comprising an Al@GNs anode and LiFePO4 cathode, exhibits remarkable capacity retention of 96.4% after 100 cycles at the 0.5 A g-1 rate.

3.
ACS Nano ; 12(12): 12741-12750, 2018 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-30485062

RESUMO

Magnesium sulfide (MgS), representative of alkaline-earth metal chalcogenides (AEMCs), is a potential conversion/alloy-type electrode material for lithium ion batteries (LIBs), by virtue of its low potential, high theoretical capacity, and abundant magnesium resource. However, the limited capacity utilization and inferior rate performance still hinder its practical application, and the progress is rather slow due to the challenging fabrication technique for MgS. Herein, we report a series of controlled-size hollow MgS nanocrystals (NCs) homogeneously distributed on graphene (MgS@G), fabricated through a metal hydride framework (MHF) strategy, and its application as advanced electrode material for LIBs. The hollow structure of MgS NCs is mainly attributed to the Kirkendall effect and the escape of hydrogen atoms from metal hydride during sulfuration. The as-synthesized MgS@G demonstrates robust nanoarchitecture and admirable interactions, which ensure a spatially confined lithiation/delithiation process, optimize the dynamics of two-steps conversion/alloying reactions, and induce a synergetic pseudocapacitive storage contribution. As a result, a representative MgS@G composite delivers a largely enhanced capacity of >1208 mAh g-1 at a current density of 100 mA g-1 and a long-term cycle stability at a high current density of 5 A g-1 with a capacity of 838 mAh g-1 over 3000 cycles, indicating well-sustained structural integrity. This work presents an effective route toward the development of high-performance magnesium-based material for energy storage.

4.
ACS Nano ; 12(10): 10430-10438, 2018 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-30253087

RESUMO

Recently, heterostructures have attracted much attention in widespread research fields. By tailoring the physicochemical properties of the two components, creating heterostructures endows composites with diverse functions due to the synergistic effects and interfacial interaction. Here, a simple in situ localized phase transformation method is proposed to transform the transition-metal oxide electrode materials into heterostructures. Taking molybdenum oxide as an example, quasi-core-shell MoO3@MoO2 heterostructures were successfully fabricated, which were uniformly anchored on reduced graphene oxide (rGO) for high-rate and highly durable lithium ion storage. The in situ introduction of the MoO2 shell not only effectively enhances the electronic conductivity but also creates MoO3@MoO2 heterojunctions with abundant oxygen vacancies, which induces an inbuilt driving force at the interface, enhancing ion/electron transfer. In operando synchrotron X-ray powder diffraction has confirmed the excellent phase reversibility of the MoO2 shell during charge/discharge cycling, which contributes to the excellent cycling stability of the MoO3@MoO2/rGO electrode (1208.9 mAh g-1 remaining at 5 A g-1 after 2000 cycles). This simple in situ heterostructure fabrication method provides a facile way to optimize electrode materials for high-performance lithium ion batteries and possibly other energy storage devices.

5.
ACS Nano ; 12(8): 8177-8186, 2018 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-30063322

RESUMO

Metal hydrides have attracted great intentions as anodes for lithium-ion batteries (LIBs) due to their extraordinary theoretical capacity. It is an unsolved challenge, however, to achieve high capacity with stable cyclability, owing to their insulating property and large volume expansion upon lithium storage. Here, we introduce self-initiated polymerization to realize molecular-scale functionality of metal hydrides with conductive polymer, that is, polythiophene (PTh), on graphene, leading to the formation of MgH2@PTh core-shell nanoparticles on graphene. The nanoscale characteristics of MgH2 not only relieve the induced stress upon volume changes but also allow fast diffusivity and high reactivity for Li-ion transport. More importantly, the conformal coating of ultrathin PTh membrane can effectively suppress the detrimental reactions between MgH2 and electrolyte, provide enhanced performance with facile electron and Li+ transport, and preserve its structural integrity, attributed to the strong molecular interaction between PTh and MgH2 as well as its various products during electrochemical reactions. With this structure, a high reversible specific capacity of 1311 mAh g-1 at 100 mA g-1, excellent rate performance of 1025 mAh g-1 at 2000 mA g-1, and a capacity retention of 84.5% at 2000 mA g-1 after 500 cycles are observed for MgH2@PTh nanoparticles as anode for LIBs.

6.
ACS Nano ; 12(4): 3816-3824, 2018 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-29608285

RESUMO

MgH2 nanoparticles (NPs) uniformly anchored on graphene (GR) are fabricated based on a bottom-up self-assembly strategy as anode materials for lithium-ion batteries (LIBs). Monodisperse MgH2 NPs with an average particle size of ∼13.8 nm are self-assembled on the flexible GR, forming interleaved MgH2/GR (GMH) composite architectures. Such nanoarchitecture could effectively constrain the aggregation of active materials, buffer the strain of volume changes, and facilitate the electron/lithium ion transfer of the whole electrode, leading to a significant enhancement of the lithium storage capacity of the GMH composite. Furthermore, the performances of GMH composite as anode materials for LIBs are enabled largely through robust interfacial interactions with poly(methyl methacrylate) (PMMA) binder, which plays multifunctional roles in forming a favorable solid-electrolyte interphase (SEI) film, alleviating the volume expansion and detachment of active materials, and maintaining the structural integrity of the whole electrode. As a result, these synergistic effects endow the obtained GMH composite with a significantly enhanced reversible capacity and cyclability as well as a good rate capability. The GMH composite with 50 wt % MgH2 delivers a high reversible capacity of 946 mA h g-1 at 100 mA g -1 after 100 cycles and a capacity of 395 mAh g-1 at a high current density of 2000 mA g-1 after 1000 cycles.

7.
Nanoscale ; 9(38): 14612-14619, 2017 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-28936500

RESUMO

NaAlH4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH4 inside CeO2 HNTs, synthesized via the infiltration of molten NaAlH4 into the CeO2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO2 HNTs-catalyzed NaAlH4. The onset dehydrogenation temperature of the NaAlH4@CeO2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO2 HNTs-catalyzed NaAlH4, respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH4.

8.
Adv Sci (Weinh) ; 4(9): 1600257, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28932654

RESUMO

A facile hydrogenation-induced self-assembly strategy to synthesize lithium hydride (LiH) nanosheets with a thickness of 2 nm that are uniformly distributed on graphene is reported and designed. Taking advantage of LiH nanosheets with high reactivity and a homogeneous distribution on graphene support as a nanoreactor, the confined chemical synthesis of oxygen-free lithiated composites is effectively and efficiently realized.

9.
Small ; 13(44)2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28722318

RESUMO

Fe2 O3 is regarded as a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe2 O3 anodes, leading to rapid fading of the capacity. Herein, a novel peapod-like nanostructured material, consisting of Fe2 O3 nanoparticles homogeneously encapsulated in the hollow interior of N-doped porous carbon nanofibers, as a high-performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea-like Fe2 O3 nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na-ions. As a consequence, this peapod-like structure exhibits a stable discharge capacity of 1434 mAh g-1 (at 100 mA g-1 ) and 806 mAh g-1 (at 200 mA g-1 ) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g-1 after 1000 cycles and 396 mAh g-1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g-1 . This study provides a promising strategy for developing long-cycle-life LIBs and SIBs.

10.
ACS Appl Mater Interfaces ; 9(18): 15502-15509, 2017 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-28436647

RESUMO

An effective route based on space-confined chemical reaction to synthesize uniform Li2Mg(NH)2 nanoparticles is reported. The hierarchical pores inside the one-dimensional carbon nanofibers (CNFs), induced by the creation of well-dispersed Li3N, serve as intelligent nanoreactors for the reaction of Li3N with Mg-containing precursors, resulting in the formation of uniformly discrete Li2Mg(NH)2 nanoparticles. The nanostructured Li2Mg(NH)2 particles inside the CNFs are capable of complete hydrogenation and dehydrogenation at a temperature as low as 105 °C with the suppression of ammonia release. Furthermore, by virtue of the nanosize effects and space-confinement by the porous carbon scaffold, no degradation was observed after 50 de/rehydrogenation cycles at a temperature as low as 130 °C for the as-prepared Li2Mg(NH)2 nanoparticles, indicating excellent reversibility. Moreover, the theoretical calculations demonstrate that the reduction in particle size could significantly enhance the H2 sorption of Li2Mg(NH)2 by decreasing the relative activation energy barrier, which agrees well with our experimental results. This method could represent an effective, general strategy for synthesizing nanoparticles of complex hydrides with stable reversibility and excellent hydrogen storage performance.

11.
Adv Mater ; 27(39): 5981-8, 2015 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-26315783

RESUMO

Monodisperse MgH2 nanoparticles with homogeneous distribution and a high loading percent are developed through hydrogenation-induced self-assembly under the structure-directing role of graphene. Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.

12.
Sci Rep ; 4: 6599, 2014 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-25307874

RESUMO

The hierarchical porous Li2Mg(NH)2@C nanowires full of micropores, mesopores, and macropores are successfully fabricated via a single-nozzle electrospinning technique combined with in-situ reaction between the precursors, i.e., MgCl2 and LiN3, under physical restriction upon thermal annealing. The explosive decomposition of LiN3 well dispersed in the electrospun nanowires during carbothermal treatment induces a highly porous structure, which provides a favourable way for H2 delivering in and out of Li2Mg(NH) nanoparticles simultaneously realized by the space-confinement of the porous carbon coating. As a result, the thus-fabricatedLi2Mg(NH)@C nanowires present significantly enhanced thermodynamics and kinetics towards hydrogen storage performance, e.g., a complete cycle of H2 uptake and release with a capacity close to the theoretical value at a temperature as low as 105°C. This is, to the best of our knowledge, the lowest cycling temperature reported to date. More interestingly, induced by the nanosize effects and space-confinement function of porous carbon coating, a excellently stable regeneration without apparent degradation after 20 de-/re-hydrogenation cycles at a temperature as low as 130°C was achieved for the as-prepared Li2Mg(NH)2@C nanowires.

13.
Nanoscale ; 6(21): 12333-9, 2014 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-25184240

RESUMO

Well-distributed lithium amidoborane (LiAB) nanoparticles were successfully fabricated via adopting carbon nanofibers (CNFs) with homogenous pores uniformly containing Li3N as the nanoreactor and reactant, simply prepared by a single-nozzle electrospinning technique, for the subsequent interaction with AB. The hierarchical porous structure consists of various macropores, mesopores and micropores in situ produced during the formation of Li3N simultaneously serving as the reaction initiator, which not only controllably realizes the well-distribution of LiAB nanoparticles but also provides favorable channels for hydrogen release. Because of the hierarchical porous architecture and nanoscale size effects, the LiAB nanoparticles start to release hydrogen at only 40 °C, which is 30 °C lower than that of pure LiAB, and dehydrogenate completely within only 15 min at 100 °C (10.6 wt%). This work provides a new perspective to the controllable fabrication of nanosized hydrogen storage materials.

14.
Adv Mater ; 25(43): 6238-44, 2013 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-23966063

RESUMO

3D porous carbon-coated Li3 N nanofibers are successfully fabricated via the electrospinning technique. The as-prepared nanofibers exhibit a highly improved hydrogen-sorption performance in terms of both thermodynamics and kinetics. More interestingly, a stable regeneration can be achieved due to the unique structure of the nanofibers, over 10 cycles of H2 sorption at a temperature as low as 250 °C.


Assuntos
Carbono/química , Hidrogênio/química , Compostos de Lítio/química , Nanofibras/química , Compostos de Nitrogênio/química , Adsorção , Cinética , Álcool de Polivinil/química , Porosidade , Termodinâmica
15.
Chem Commun (Camb) ; 48(37): 4408-10, 2012 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-22454033

RESUMO

Ammine aluminium borohydride system is found to release >12 wt% pure H(2) below 120 °C via a combined strategy of changing the coordination number and adopting mixed cations.

16.
Chem Commun (Camb) ; 46(15): 2599-601, 2010 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-20449320

RESUMO

Amminelithium borohydride, LiBH(4) x NH(3) which has two temperature sensitive chemical bonds N:-->Li(+) and N-H...H-B, is shown to release hydrogen at low temperatures by stabilizing the ammonia and promoting the recombination of the NH...HB bond.

17.
Chemistry ; 16(12): 3763-9, 2010 Mar 22.
Artigo em Inglês | MEDLINE | ID: mdl-20157906

RESUMO

The monoammoniate of lithium amidoborane, Li(NH(3))NH(2)BH(3), was synthesized by treatment of LiNH(2)BH(3) with ammonia at room temperature. This compound exists in the amorphous state at room temperature, but at -20 degrees C crystallizes in the orthorhombic space group Pbca with lattice parameters of a = 9.711(4), b = 8.7027(5), c = 7.1999(1) A, and V = 608.51 A(3). The thermal decomposition behavior of this compound under argon and under ammonia was investigated. Through a series of experiments we have demonstrated that Li(NH(3))NH(2)BH(3) is able to absorb/desorb ammonia reversibly at room temperature. In the temperature range of 40-70 degrees C, this compound showed favorable dehydrogenation characteristics. Specifically, under ammonia this material was able to release 3.0 equiv hydrogen (11.18 wt %) rapidly at 60 degrees C, which represents a significant advantage over LiNH(2)BH(3). It has been found that the formation of the coordination bond between ammonia and Li(+) in LiNH(2)BH(3) plays a crucial role in promoting the combination of hydridic B-H bonds and protic N-H bonds, leading to dehydrogenation at low temperature.

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