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1.
Angew Chem Int Ed Engl ; 58(50): 18108-18115, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31593347

RESUMO

A highly oriented mesoporous graphitic carbon nanospring (OGCS) with graphitic layers that are perpendicular to the axis is prepared by hydrothermal treatment of epoxy resin at 500 °C and annealing at 1400 °C. Water plays an important role in not only forming the graphitic carbon nanospring with a high [002] orientation and a large amount of active edge-plane sites, but also in the generation of the mesoporous structure, which facilitate fast K-ion adsorption and diffusion. In situ and ex situ measurements confirm that OGCS undergoes K-adsorption in mesopores and then K-intercalation in the graphite layer to form KC8 with a low discharge voltage. The spring-like nanostructure can expand one-dimensionally along the axial direction to accommodate the volume variation. The OGCS electrode thus shows a much better K-storage performance than that of unoriented graphitic carbon.

2.
ACS Nano ; 13(10): 11676-11685, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31585034

RESUMO

Dendrite growth of metal anodes is one of the key hindrances for both secondary aqueous metal batteries and nonaqueous metal batteries. In this work, a freestanding Ti3C2Tx MXene@Zn paper is designed as both zinc metal anode and lithium metal anode host to address the issue. The binder-free Ti3C2Tx MXene@Zn paper exhibits merits of good mechanical flexibility, high electronic conductivity, hydrophilicity, and lithiophilicity. The crystal growth mechanism of Zn metal on common Zn foil and Ti3C2Tx MXene@Zn composite is also studied. It is found that the Ti3C2Tx MXene@Zn paper can effectively suppress the dendrite growth of Zn, enabling reversible and fast Zn plating/stripping kinetics in an aqueous electrolyte. Moreover, the Ti3C2Tx MXene@Zn paper can be used as a 3D host for a lithium metal anode. In this host, Zn is utilized as a nucleation agent to suppress the Li dendrite growth. The freestanding Ti3C2Tx MXene@Zn@Li anode exhibits superior reversibility with high Coulombic efficiency (97.69% over 600 cycles at 1.0 mA cm-2) and low polarization compared with the Cu@Li anode. These findings may be useful for the design of dendrite-free metal-based energy storage systems.

3.
Small ; 15(46): e1903214, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31583828

RESUMO

Exploring flexible lithium-ion batteries is required with the ever-increasing demand for wearable and portable electronic devices. Selecting a flexible conductive substrate accompanying with closely coupled active materials is the key point. Here, a lightweight, flexible, and freestanding MXene/liquid metal paper is fabricated by confining 3 °C GaInSnZn liquid metal in the matrix of MXene paper without any binder or conductive additive. When used as anode for lithium-ion cells, it can deliver a high discharge capacity of 638.79 mAh g-1 at 20 mA g-1 . It also exhibits satisfactory rate capacities, with discharge capacities of 507.42, 483.33, 480.22, 452.30, and 404.47 mAh g-1 at 50, 100, 200, 500, and 1000 mA g-1 , respectively. The cycling performance is obviously improved by slightly reducing the charge-discharge voltage range. The composite paper also has better electrochemical performance than liquid metal coated Cu foil. This study proposes a novel flexible anode by a clever combination of MXene paper and low-melting point liquid metal, paving the way for next-generation lithium-ion batteries.

4.
ACS Nano ; 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31639296

RESUMO

Owing to its distinctive structure and properties, 2D silicon (2DSi) has been widely applied in hydrogen storage, sensors, electronic device, catalysis, electrochemical energy storage, etc. However, scalable and low-cost fabrication of high-quality 2DSi remains a great challenge. In this work, a physical vacuum distillation method is designed to obtain high-quality 2DSi from a bulk layered calcium-silicon alloy. With this method, the lower boiling point calcium metal is evaporated to construct 2DSi and can be further recycled. The effect of vacuum conditions on morphology, components, and electrochemical properties is further explored. As an anode for lithium-ion batteries, the 2DSi delivers a stable cyclability of 835 mAh g-1 after 3000 cycles at 5000 mA g-1 (0.003025% capacity decay per cycle). The electrochemical performance enhancing mechanism is also probed. In addition, a 2D/2D flexible and binder-free paper by combining 2DSi with 2D MXene is constructed. As a lithiophilic nuclear agent for lithium metal anodes, the 2DSi can efficiently suppress the Li dendrite growth and reduce nucleation barriers, achieving a high Coulombic efficiency (98% at 1 mA cm-2, 97% at 2 mA cm-2) around 600 cycles and a long lifespan of 1000 h. The crystal growth difference of lithium metal on Cu foil and 2DSi is studied. This work may provide a pathway for green, low-cost, and scalable synthesis of 2D materials.

5.
Nanoscale ; 11(36): 16781-16787, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31468041

RESUMO

The application of Si-based anode materials is hindered by their extreme volume change, poor cycling stability, and low coulombic efficiency. Solving these problems generally requires a combination of strategies, such as nanostructure designing or surface coating. However, these strategies increase the difficulty of the fabrication process. Herein, a simple and one-pot replacement reaction route was designed to produce an Al2O3 layer anchored on mesoporous Si nanospheres (Si@Al2O3) by employing Al nanospheres with a naturally formed Al2O3 layer as a reducing agent and self-sacrificial template. The obtained Si@Al2O3 was mesoporous, with enough porous space to buffer the volume change and provide a fast lithium ion transfer channel. Furthermore, the coated Al2O3 layer could stabilize the structure and SEI layer of the mesoporous Si nanospheres, endowing the Si@Al2O3 nanospheres with improved initial coulombic efficiency, cycling performance and rate capability. As a result, a high capacity of 1750.2 mA h g-1 at 0.5 A g-1 after 120 cycles and 1001.7 mA h g-1 at 2 A g-1 after 500 cycles were delivered for lithium ion batteries. The good performance could be attributed to the mesoporous structure and the outer-coated Al2O3 layer.

6.
J Colloid Interface Sci ; 554: 674-681, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31351338

RESUMO

Silicon is regarded as the most promising electrode material to meet the high-capacity demand for lithium-ion batteries (LIBs). Nevertheless, the large volume expansion during charging/discharging process restricts its practical application. In this report, a facile chemical dealloying method is conducted to prepare porous silicon materials from Al-Si alloys with different proportions at ambient temperature. The porosity of anode materials could buffer the huge volume change of Si anode and enhance the ion transport. Finally, the optimized Si20 sample delivers a capacity of 1662 mAh g-1 after 145 cycles at 500 mA g-1 and a high rate capability up to 908 mAh g-1 at 5000 mA g-1.

7.
ACS Appl Mater Interfaces ; 11(25): 22371-22379, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31149799

RESUMO

The exploration of high-performance anode materials is imperative for the development of sodium-ion batteries (SIBs). Herein, a molten-salt-assisted approach is developed to prepare crystallized Zn2GeO4 clusters constructed by interconnected nanorods, and the Na-ion storage mechanism is studied systemically through in situ X-ray diffraction, ex situ X-ray photoelectron spectroscopy, and high-resolution transmission microscopy associated with galvanostatic intermittent titration technique. The Zn2GeO4 anode undergoes conversion reactions followed by the alloying reaction. The large channel in the Zn2GeO4 crystal structure ensures insertion of sodium ions. The amorphous transformation during the initial discharge process increases the active site for the fast electrochemical reaction. As the anode for SIBs, the Zn2GeO4 cluster exhibits good rate capability with a capacity retention of 111.1 mA h g-1 at 20 A g-1 in half cells and 118.9 mA h g-1 at 2 A g-1 in full cells, associated with a capacity of 184.2 mA h g-1 at 0.5 A g-1 after 500 cycles. The ex situ scanning electron microscopy images of the electrode material disclose that the hierarchical structure can accommodate the volume variation of Zn2GeO4 during discharge/charge cycling, facilitating long cycling stability. The investigation of Zn2GeO4 provides new insight for the development of high-rate anode materials for SIBs.

8.
ACS Appl Mater Interfaces ; 11(20): 18305-18312, 2019 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-31046217

RESUMO

SiO x coating is an effective strategy to prolong the cycling stability of Si-based anodes due to the robust interaction between Si and the SiO x layer. However, the SiO x layer-protected Si anode is limited by the relatively low initial Coulombic efficiency and sluggish Li+ diffusion ability induced by the SiO x layer. Herein, we present the preparation of selectively prelithiated Si@SiO x (Si@Li2SiO3) anode by using a facile strategy to resolve the above issues. As the anode for lithium ion batteries, Si@Li2SiO3 exhibits a high initial Coulombic efficiency (ICE) of 89.1%, an excellent rate performance (959 mA h g-1 at 30 A g-1), and a superior capacity retention (3215 mA h g-1). The full cell with LiFePO4 cathode and Si@Li2SiO3 anodes is successfully assembled, disclosing a high ICE of 91.1% and excellent long cycling stability. The superior electrochemical performance of Si@Li2SiO3 can be attributed to the coating layer, which can strengthen the integrity of the electrode, decrease irreversible reactions, and provide efficient Li+ diffusion channels.

9.
Chem Commun (Camb) ; 55(47): 6751-6754, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31119232

RESUMO

An amine-induced phase transition strategy is developed for converting white phosphorus into red or black phosphorus. Amorphous red phosphorus is prepared through the chemical dissolution of white phosphorus in amines and post-treatment at room temperature. It is demonstrated that the phase transformation mechanism involves an amine-induced nucleophile attack on white phosphorus and the generation of polyphosphorus ions. The amorphous phosphorus exhibits a specific capacity of 955.5 mA h g-1 at 1.5 A g-1 after 1000 cycles, and a capacity retention of 1210.2 mA h g-1 even at 20 A g-1 for Li-ion batteries. This methodology is also applicable to produce red phosphorus micro-spheres and black phosphorus particles by varying the types of organic amines and the reaction temperature.

10.
Nat Commun ; 10(1): 1217, 2019 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-30872576

RESUMO

Molybdenum disulfide is naturally inert for alkaline hydrogen evolution catalysis, due to its unfavorable water adsorption and dissociation feature originated from the unsuitable orbital orientation. Herein, we successfully endow molybdenum disulfide with exceptional alkaline hydrogen evolution capability by carbon-induced orbital modulation. The prepared carbon doped molybdenum disulfide displays an unprecedented overpotential of 45 mV at 10 mA cm-2, which is substantially lower than 228 mV of the molybdenum disulfide and also represents the best alkaline hydrogen evolution catalytic activity among the ever-reported molybdenum disulfide catalysts. Fine structural analysis indicates the electronic and coordination structures of molybdenum disulfide have been significantly changed with carbon incorporation. Moreover, theoretical calculation further reveals carbon doping could create empty 2p orbitals perpendicular to the basal plane, enabling energetically favorable water adsorption and dissociation. The concept of orbital modulation could offer a unique approach for the rational design of hydrogen evolution catalysts and beyond.

11.
Adv Mater ; 31(16): e1807780, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30811711

RESUMO

Although it is commonly believed that the water-dissociation-related Volmer process is the rate-limiting step for alkaline hydrogen evolution reaction (HER) on Pt-based catalysts, the underlying essence, particularly on the atomic scale, still remains unclear. Herein, it is revealed that the sluggish water-dissociation behavior probably stems from unfavorable orbital orientation and the kinetic issue is successfully resolved via N-induced orbital tuning. Impressively, N modified Pt-Ni nanowires deliver an ultralow overpotential of 13 mV at 10 mA cm-2 , which represents a new benchmark for alkaline HER catalysis. Fine-structural characterization and density functional theory analysis illustrate that the introduced nitrogen can uniquely modulate the electron densities around the Ni sites, and further create empty dz 2 orbitals with superior orientation for water adsorption and activation. More importantly, it is demonstrated that N-induced orbital modulation can generally boost the alkaline HER activities of Pt-Co, Pt-Ni, and Pt-Cu, offering a new perspective for the design of HER catalysts and beyond.

12.
Small ; 15(12): e1804916, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30740881

RESUMO

The significant issues with alkali metal batteries arise from their poor electrochemical properties and safety problems, limiting their applications. Herein, TiO2 nanoparticles embedded into N-doped porous carbon truncated ocatahedra (TiO2 ⊂NPCTO) are engineered as a cathode material with different metal anodes, including solid Na or K and liquid Na-K alloy. Electrochemical performance and kinetics are systematically analyzed, with the aim to determine detailed electrochemistry. By using a galvanostatic intermittent titration technique, TiO2 ⊂NPCTO/NaK shows faster diffusion of metal ions in insertion and extraction processes than that of Na-ions and K-ions in solid Na and K. The lower reaction resistance of liquid Na-K alloy electrode is also examined. The higher b-value of TiO2 ⊂NPCTO/NaK confirms that the reaction kinetics are promoted by the surface-induced capacitive behavior, favorable for high rate performance. This superiority highly pertains to the distinct liquid-liquid junction between the electrolyte and electrode, and the prohibition of metal dendrite growth, substantiated by symmetric cell testing, which provides a robust and homogeneous interface more stable than the traditional solid-liquid one. Hence, the liquid Na-K alloy-based battery exhibits to better cyclablity with higher capacity, rate capability, and initial coulombic efficiency than solid Na and K batteries.

13.
Chem Commun (Camb) ; 55(10): 1406-1409, 2019 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-30640332

RESUMO

In this work, carbon nanotube-coated dual-shell Co9S8 hollow spheres are studied as anode materials for K-ion batteries. The unique hollow structure and carbon nanotubes synergistically enhance the conductivity and resolve the critical drawbacks of Co9S8 electrodes, including large volume variation, structural instability and interfacial changes. Thus, the electrode delivers a stable reversible capacity of 320.5 mA h g-1 at 0.1 A g-1 after 200 cycles with a capacity retention of 91%. At 1.0 A g-1, the capacity is 163.9 mA h g-1 after 1000 cycles with a capacity retention of 73.6%. An investigation of the electrode reaction mechanism indicates that the surface capacity also contributes to the outstanding electrochemical performance.

14.
Artigo em Inglês | MEDLINE | ID: mdl-30421912

RESUMO

A molten salt metallothermic reduction strategy is developed for preparing phosphorus (P) or phosphides controllably at low temperature, which is simple, energy-saving, and easy to scale up. Typically, synthesis of spongelike porous amorphous P (a-P) is realized through reduction of PCl5 with Zn (or Al) at 50 °C assisted by AlCl3. It is demonstrated that an adduct salt PCl5·AlCl3 composed of PCl4+ and AlCl4- ions with a low melting point below 50 °C is formed from covalent salts PCl5 and AlCl3. This system is also suitable for producing nanostructured phosphides by adding corresponding transition-metal (Co, Fe, and Cu) chlorides even at 50 °C. As a Li storage anode, the as-prepared a-P exhibits a capacity of 1605 mA h g-1 at 0.2 C, a good rate capability of 1283 mA h g-1 at 10 C, and a long-term cycling stability of 1082 mA h g-1 after 200 cycles. Additionally, the Na-/K-ion storage performance is investigated systematically.

15.
ACS Nano ; 2018 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-30481455

RESUMO

Potassium-ion batteries (KIBs) are considered favorable candidates for post-lithium-ion batteries, a quality attributed to their low cost, abundance as a resource, and high working potential (-2.93 V for K+/K). Owning to its relatively low potassiation potential and high theoretical capacity, antimony (Sb) is one of the most favorable anodes for KIBs. However, the large volume changes during K-Sb alloying and dealloying causes fast capacity degradation. In this report, nanoporous Sb (NP-Sb) is fabricated by an environmentally friendly vacuum-distillation method. The NP-Sb is formed via evaporating low-boiling-point zinc (Zn). The byproduct Zn can be recycled. It is further found that the morphology and porosity can be controlled by adjusting Zn-Sb composition and distillation temperature. The nanoporous structure can accommodate volume expansion and accelerate ion transport. The NP-Sb anode delivers an improved electrochemical performance. These results suggest that the vacuum-distillation method may provide a direction for the green, large-scale, and tunable fabrication of nanoporous materials.

16.
ACS Nano ; 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30452226

RESUMO

Sodium ion batteries are one of most promising alternatives to lithium ion batteries for large-scale energy storage, due to the high abundance and low cost of sodium in the earth. However, the lack of advanced electrode materials greatly affects their applications. Here, layered-structure SbPO4 is explored as an anode material for sodium ion batteries in terms of SbPO4 nanorods on reduced graphene oxide (SbPO4/rGO). In situ transmission electron microscopy images reveal the preferential expansion along the transverse direction of the nanorods upon the first discharging, which arises from the reduction of SbPO4 to Sb and the subsequent alloying of Sb as supported by in situ X-ray diffraction and selected area electron diffraction patterns. SbPO4/rGO exhibits a capacity retention of 99% after 100 cycles at 0.5 A g-1 both in half cells and in full cells. Its specific capacity at 5 A g-1 is 214 mA h g-1 in half cells or 134 mA h g-1 in full cells. Moreover, the energy density of the full cells at 1.2 kW kg-1total is still 99.8 W h kg-1total, very promising as an advanced electrode material.

17.
Adv Mater ; 30(45): e1804684, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30276879

RESUMO

A thin and adjustable Li3 PS4 (LPS) solid-state electrolyte protection layer on the surface of Li is proposed to address the dynamic plating/stripping process of Li metal. The LPS interlayer is formed by an in situ and self-limiting reaction between P4 S16 and Li in N-methyl-2-pyrrolidone. By increasing the concentration of P4 S16 , the thickness of the LPS layer can be adjusted up to 60 nm. Due to the high ionic conductivity and low electrochemical activity of Li3 PS4 , the intimate protection layer of LPS can not only prevent the formation of Li dendrites, but also reduces parasitic side reactions and improves the electrochemical performance. As a result, symmetric cells with the LPS protection layer can deliver stable Li plating/stripping for 2000 h. Full cells assembled with the LPS-protected Li exhibit two times higher capacity retention in Li-S batteries (≈800 mAh g-1 ) at 5 A g-1 for over 400 cycles compared to their bare Li counterparts. Furthermore, high rate performances can be achieved with Li-LPS/LiCoO2 cells, which are capable of cycling at rates as high as 20 C. This innovative and scalable approach to stabilizing the Li anode can serve as a basis for the development of next-generation high-performance lithium-metal batteries.

18.
Small ; 14(47): e1802457, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30328267

RESUMO

To better couple with commercial cathodes, such as LiCoO2 and LiFePO4 , graphite-based composites containing a small proportion of silicon are recognized as promising anodes for practical application in lithium-ion batteries (LIBs). However, the prepared Si/C composite still suffers from either rapid capacity fading or the high cost up to now. Here, the facile preparation of hierarchical graphene-scaffolded silicon/graphite composite is reported. In this designed 3D structure, Si nanoparticles are homogeneously dispersed on commercial graphites and then uniformly encapsulated in the hierarchical graphene scaffold. This hierarchical structure is also well characterized by the synchrotron X-ray computed nanotomography technique. When evaluated as anodes for LIBs, the hierarchical composite, with the Si weight ratio of 5 wt%, exhibits a reversible capacity of 559 mA h g-1 at 75 mA g-1 , suggesting an unprecedented utilization of Si up to 95%. Even at 372 mA g-1 , the composite can still maintain a high capacity retention of 90% after 100 cycles. Coupled with the LiFePO4 cathode, the full cell shows the high capacity of 114 mA h g-1 at 170 mA g-1 . The excellent Li-storage properties can be ascribed to the unique designed hierarchical structure.

19.
Data Brief ; 20: 1999-2002, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30306104

RESUMO

The data presented in this article are related to the research article entitled "Sandwich-like Ni2P Nanoarray/Nitrogen-Doped Graphene Nanoarchitecture as a High-Performance Anode for Sodium and Lithium Ion Batteries (Dong et al., 2018)". This work shows the morphology and structural of Ni2P/NG/Ni2P and the electrochemial performance of Ni2P/NG/Ni2P.

20.
Nanoscale ; 10(37): 17435-17455, 2018 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-30207360

RESUMO

Developing high-performance lithium ion batteries (LIBs) requires optimization of every battery component. Currently, the main problems lie in the mismatch of electrode capacities, especially the excessively low capacity of cathodes compared with that of anodes. Due to the anisotropy of the crystal structure, different crystal planes play different roles in the transmission of lithium ions. Among these, the {010} facets of layered-structure materials, the (110) planes of spinel cathodes and the (010) planes of olivine cathodes can provide open surface structures, which furnish express channels for the rapid and efficient transmission of lithium ions, leading to enhanced rate performance. However, due to the high-energy surfaces of these crystal planes, they tend to disappear in the synthetic process, forming thermodynamic equilibrium products dominated by low-energy and electrochemically-inactive planes. From the structure design of the material itself, preparing functional materials with specific morphologies and crystal structures is considered to be the most effective way to improve the cyclability and rate performance of LIB cathodes. In this review, we highlight the latest developments in selectively exposing the crystal planes of LIB cathode materials. The synthetic method, the corresponding electrochemical performance, especially the rate capability, and the growth mechanism have been systematically summarized for layered-structure cathodes of LiCoO2, LiNixCoyMn1-x-yO2 and Li2MnO3·LiMO2, spinel cathodes of LiMn2O4 and LiNi0.5Mn1.5O4, and olivine cathodes of LiFePO4. This in-depth discussion and understanding is beneficial for the rational design of well-performing LIB cathodes and can provide direction and perspectives for future work.

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