Search

Alkali (Li, Na, K)-ion batteries have attracted tremendous attention in current power supply systems. However, it remains a great challenge to explore universal anodes for the desired de-/intercalation of these three alkali-metal ions (Li+, Na+, K+). Herein, hollow hierarchical porous olive-like carbon (HHPOC) structure is prepared through a self-templated strategy and post acid-etching treatment. The unique hollow hierarchical porous structure can facilitate the electrolyte penetration, shorten the transport pathway of ions, and endure well the volume change during the insertion/extraction of alkali ions. Meanwhile, the abundant self-doped N/O heteroatoms provide sufficient active sites for Li+/Na+/K+ storage, thereby resulting in a capacitive-dominating storage mechanism for the HHPOC electrode especially in sodium/potassium ion batteries. The HHPOC electrode delivers high reversible discharge capacity of 1121.8 mA h g−1 at 0.1 A g−1 for lithium-ion battery, 386.8 mA h g−1 at 0.1 A g−1 for sodium-ion battery, and 305.6 mA h g−1 at 0.1 A g−1 for potassium-ion battery. Moreover, the HHPOC electrode exhibits promising cycling stability with negligible capacity decay over 800 cycles at 1 A g−1 for the three alkali-ion batteries. Therefore, this work provides a new perspective for the development of universal carbon anodes with efficient Li+/Na+/K+ storage and the delicate structural design of biomass carbon materials. A novel hollow hierarchical porous olive-like carbon (HHPOC) structure was successfully prepared via a self-templated strategy with agaric as the raw material for efficient Li+, Na+, K+ storage. Image 1 [ABSTRACT FROM AUTHOR]

A major challenge for the practical application of lithium-sulfur batteries is the polysulfide shuttling and sluggish redox kinetics due to the notorious adsorption-catalysis underperformance. However, conventional carbonaceous materials generally suffer from poor adsorption of polysulfides due to their intrinsic nonpolar surface. Herein, porous carbon nanosheets modified with metallic cobalt and nonmetallic nitrogen/boron heteroatoms, denoted as Co-NBC, is reported as sulfur immobilizer. The presence of conductive metallic cobalt as well as the doped N/B heteroatoms can enhance the electronic conductivity of carbon matrix, and significantly improve the chemical entrapment of soluble polysulfides. Kinetics measurements show that metallic Co catalysts can greatly promote the polysulfide redox kinetics of both liquid-liquid and liquid-solid conversion. As a result, the S/Co-NBC composite realizes remarkable rate performance with high specific capacity of 509 mAh g−1 at a high C-rate of 5 C, and excellent cycle stability with a low capacity fading rate of ∼0.09% per cycle within 500 cycles. Moreover, the S/Co-NBC cathodes realize promising cycle performance even at harsh working condition of high sulfur loading (∼4.6 mg cm−2) or low electrolyte addition (∼3 μL mg−1). This work proposes a meaningful strategy to obtain efficient carbon nanomaterials for high-performance Li–S batteries. Image 1 [ABSTRACT FROM AUTHOR]

Abstract A novel 3D porous CoP@C-CNTs composite with CNTs threaded CoP@C nanocubes is rationally designed and demonstrated as a promising anode for lithium-ion battery. The CoP@C-CNTs composite displays high surface area and abundant pores resulted from the pyrolysis of metal-organic frameworks (MOFs). CoP nanoparticles are well encapsulated in MOFs-derived carbon nanocubes, which can effectively accommodate the volume change of active CoP during charge/discharge processes. Besides, the N/P co-doped feature induced in-situ in the synthesis process helps to improve the electrical conductivity. Moreover, the presence of intertwined CNTs network threaded CoP@C nanocubes is the vital part for rapid electron transportation within the whole electrode. As a result, the CoP@C-CNTs electrode exhibits a high initial discharge capacity of 1254 mAh g−1 at a current density of 0.1 A g−1, and an outstanding rate performance (532 mAh g−1 at current densities of 5 A g−1), as well as excellent cycling stability with a capacity fade rate of ∼0.02% per cycle over 500 cycles at the current density of 2 A g−1. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract Deficiencies of sulfur cathode including polysulfide shuttling and poor redox kinetics severely limit cycling performance of lithium-sulfur (Li-S) batteries. Herein, we have designed a binary host featuring highly sulfiphilic Ni-Fe bimetallic oxide (NiFe 2 O 4) nanoparticles anchored on carbon nanotubes for Li-S batteries. NiFe 2 O 4 nanoparticles provide highly sulfiphilic sites to confine lithium polysulfides by the formation of Li-O and S-O bonds, and act as an electrocatalyst to promote the conversion of polysulfides. The carbon nanotubes play an important synergistic role by providing efficient electron conduction pathways and preventing agglomeration of the catalyst. As a result, the sulfur cathode enables stable cycling with a very low capacity fade rate (∼0.029% per cycle upon 1000 cycles) at 1.0 C and a reversible capacity of ∼550 mAh g−1 at 5.0 C. Further, the superior cycling stability could be retained even for high sulfur loading of ∼5.0 mg cm−2. The development of such hybrid electrodes comprised of bimetallic oxides supported on carbon nanotubes could help realize long-lasting and stable Li–S batteries. Graphical abstract Ni-Fe bimetallic oxide nanoparticles anchored on carbon nanotube supports are reported to show highly sulfiphilic sites for polysulfide immobilization and the conversion of polysulfides/sulfides for long-lasting and stable lithium-sulfur batteries. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Iron phosphide (FeP) is a promising anode material for Li-ion batteries (LIBs) due to its low cost and high theoretical capacity. To design FeP anode materials with multi-channels for both ions and electrons will greatly help to realize fast ion and electron diffusion and high-rate capability of LIBs, and effectively overcome its intrinsic shortcomings of low conductivity and large volume expansion. Herein, a novel octahedral multi-channel FeP@C/rGO composite has been fabricated by a simple solvothermal process followed by carbonization and phosphorization. The as-prepared FeP@C/rGO composite displays an excellent rate capacity (497 mAh g−1 at 5 A g−1), as well as a high reversible capacity (1080 mAh g−1 at 0.1 A g−1) and superior cyclability with a capacity decay rate of 0.04% per cycle upon 500 cycles. The outstanding electrochemical performance of FeP@C/rGO composite can be attributed to the unique stable carbon octahedral multi-channel frameworks and N/P co-doping interconnect graphene conductive network, which significantly facilitate the Li-ion and electron transfer and accommodate the large volume change during cycling. This work shows a feasible strategy to fabricate FeP-based composites with multi-channels structure as a high-performance anode for lithium-ion batteries. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Carbon materials are appealing as electrodes for electrochemical energy storage due to their high surface area and tunable pore structures. In this work, hierarchical porous carbon microcubes (PCM) are synthesized through in-built template method from renewable agaric. Cubic MnO@C composite is obtained by hydrothermal treatment of agaric and subsequent calcination with the presence of manganese source. The in-built MnO-template is sacrificed by acid etching to prepare PCM sample with high specific surface area of 1052 m2 g−1, rational pore size distribution, and self N-doped property. The refined architecture endows PCM sample with significantly improved performance including high specific capacitance, superior rate capability and long-term cyclic stability when employed as electrodes for both lithium-ion batteries and supercapacitors. We believe that this work proposes a new concept to construct carbon architecture with well-refined, hierarchical porous structure for electrochemical energy storage. Image 1 [ABSTRACT FROM AUTHOR]

Currently, the development of carbonaceous materials for potassium ion batteries (PIBs) with ultrafast rate performance is limited by the huge volume expansion and sluggish electrochemical kinetics derived from the insertion/de-insertion of large radius of K+. Herein, the high edge-nitrogen-doped porous carbon nanosheets (EN-PCNs) were obtained via a simple and scalable pyrolysis strategy. The synergistic effect of two-dimensional (2D) porous nanosheet structure and ultrahigh content of edge-nitrogen (79.6 at%) provide the EN-PCNs with multiple advantages including rich defect sites, enlarge interlayer spacing (0.378 nm) and high specific surface area (417.0 m2 g−1), which can enhance the K+ storage. As excepted, the as-prepared EN-PCNs electrode delivers a high reversible capacity of 345.2 mA h g−1 at 0.7 C, ultrafast rate capacity of 108.4 mA h g−1 at 7 C and good cycling stability of 121.4 mA h g−1 with a retention of 72% after 1000 cycles at 3.5 C. Moreover, in-depth electrochemical kinetic analysis further verifies that the boosted potassium ion storage of EN-PCNs electrode is attributed to the rapid pseudocapacitance mechanism. This work not only demonstrates a simple and scalable strategy for the construction of advanced high edge N-doped porous nanosheet carbon materials, but also provides a new reference for adjusting the pseudocapacitance mechanism to achieve enhanced potassium storage capacity. The high edge-nitrogen-doped porous carbon nanosheets (EN-PCNs) were prepared via a simple and scalable pyrolysis strategy and exhibited boosted potassium ion storage including the high reversible capacity, ultrafast rate performance along with excellent cycling stability. [Display omitted] • The EN-PCNs were synthesized via a simple and scalable pyrolysis strategy. • High nitrogen doping level (5.7 at%) and unique 2D porous nanosheet structure. • High reversible capacity, ultrafast rate performance and good cycling stability of EN-PCNs electrode. • In-depth electrochemical kinetic analysis verifies the rapid pseudocapacitance mechanism of EN-PCNs electrode. [ABSTRACT FROM AUTHOR]

MnO based composites are regarded as advanced conversion-type anode materials for lithium-ion batteries (LIBs) due to the low cost and high theoretical specific capacities (∼756 mA h g−1). Nevertheless, the undesirable structural stability and sluggish electrochemical reaction kinetics of the electrode materials lead to poor lithium storage performance. Herein, inspired by the structure of areca, the areca-like core-shell MnO@C composites containing of the MnO core and N-doped porous carbon shell are prepared via a biomass-assisted strategy. The formation mechanism of the MnO@C composites with well-defined core-shell structure are successfully clarified through heterogeneous contraction and carbon pyrolysis processes. As anodes for LIBs, the MnO@C composite delivers superior specific capacities of 915.9 and 218.1 mA h g−1 at 0.1 and 5.0 A g−1, respectively, and maintains outstanding cycling performance over 900 cycles at 1.0 A g−1. More importantly, electrochemical kinetics tests further confirm that the improved LIBs capacity mainly originated from the unique areca-like core-shell structure and self-N doped porous carbon shell. Inspired by the structure of areca, unique areca-like core-shell structured MnO@C composites containing of the MnO core and N-doped porous carbon shell are prepared via a biomass-assisted strategy. As a result, the as-prepared MnO@C-800 composite presents remarkable electrochemical performance as LIBs anodes. [Display omitted] • Unique areca-like core-shell MnO@C composites are synthesized via a biomass-assisted strategy. • An enhanced cycling performance of 314.3 mA h g−1 can be obtained over 900 cycles at high current density of 1.0 A g−1. • The remarkable Li + storage originates from the core-shell structural stability and fast electrochemical kinetics. [ABSTRACT FROM AUTHOR]

Biomass materials show great potential in replacing mineral carbon source to fabricate novel high-energy electrode materials. However, it is greatly challenging to prepare core-shell carbon hybrid materials with homogeneous dispersion and high tap density features from biomass since biomass-carbons often exhibit blocky structure. Herein, we facilely fabricate the core-shell microcubes of MnO@C (CCM, average size of ∼5 μm) composite with high tap density of 2.17 g cm−3 using natural agaric as raw materials through simple hydrothermal treatments and calcination process. And the formation mechanism of core-shell microcube structures is analysized by the phase separator theory. It is found that the high-tap-density CCM composite with the stable porous carbon shell (∼1 μm) greatly contributes to accommodate the volume change of MnO active material during lithiation/delithiation process and enable rapid electron/ion transport. As expected, the CCM electrode offers a superhigh volumetric capacity of 1628.7 mAh cm−3, the high reversible capacity (1147 mAh g−1 at 0.1 A g−1), outstanding rate performance (552 mAh g−1 at 2 A g−1) and cycling stability (802 mAh g−1 after 950 cycles at 1 A g−1). We believe that the facile and low-cost biomass-intervened strategy is feasible to fabricate practical core-shell structured metal oxide@carbon composites for efficient electrochemical energy storage. Core-shell MnO@C microcubes obtained from a biomass-intervened strategy are investigated as LIB anode, and shows high specific volumetric capacity, good cycle stability and rate capability. Image 1 • A simple agaric-intervened strategy for core-shell MnO@C microcubes. • The uniform size of ∼5 μm and stable porous carbon shell (∼1 μm). • The composite shows high-tap-density (2.17 g cm−3). • To accommodate the volume change of MnO during lithiation/delithiation. • Superhigh specific volumetric capacity of 1628.7 mAh cm−3 at 0.1 A g−1 • Excellent cycling stability (802 mAh g−1 after 950 cycles at 1 g−1). [ABSTRACT FROM AUTHOR]

Understanding the degradation of carbon nanotubes (CNTs) is critically important for their potential biological and environmental applications. In this work, the chemical degradation of CNTs in aqueous solution in the presence of strong oxidizing hydroxyl radicals was directly investigated through liquid cell transmission electron microscopy. The real-time observation on degradation of CNTs revealed three types of degradation behaviors: (Ι) the radial shrinkage of CNTs; (ΙΙ) the rupture of CNTs caused by perforation degradation; (ΙΙΙ) the axial disappearance of CNTs initiated from both end caps of CNTs and newly formed defects. Among them, the axial degradation was found to be predominant based on statistic results. Moreover, the degradation mechanism and its dependence on the structure of CNTs were explicated. This work provides insights to further understand the microscopic mechanisms governing the degradation of CNTs in solution, and will shed the light on the practical applications of CNTs. Image 1 [ABSTRACT FROM AUTHOR]

Morphology-controllable carbon nanocoils (CNCs) are synthesized by thermal chemical vapor deposition using Ni nanoparticle as catalyst prepared by spray-coating method. It is found that, with the increase of number of spray-coating times, the helicity of CNCs increases whereas the average line diameter and coil pitch decrease. Additionally, infrequent Y-junction CNCs and plait-like CNCs are found in the deposits. What is noteworthy is that, compared with dip-coating, spray-coating method can prepare more uniform catalyst on substrate, resulting in more CNCs with high purity. [ABSTRACT FROM AUTHOR]

Abstract: Single-walled carbon nanotubes (SWCNTs) were dispersed in water with the help of surfactants to achieve high concentration SWCNT ink. SWCNT transparent conducting films (TCFs) were fabricated by rod coating using the SWCNT ink. A combination of two surfactants provided optimal rheological behaviour, which produced uniform films by preventing dewetting and rupture of SWCNTs during drying. The combination led to a dramatic increase of shear viscosities but no change of their wettability. The viscosity of SWCNT ink was controlled by the ratio of two surfactants. The thickness of SWCNT films could be easily varied by controlling both the concentration of SWCNT ink and the size of the wire-wound rod. The produced uniform SWCNT-TCFs treated by nitric acid have a relatively low sheet resistance of ∼80Ωsq−1 at 80% transmittance. The performance has a wide range of applied interest for touch screen and flexible electronics. [Copyright &y& Elsevier]