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1.
ACS Appl Mater Interfaces ; 11(50): 46776-46782, 2019 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-31755259

RESUMO

Design and fabrication of flexible Li-ion batteries (FLIBs) with excellent electrochemical and structural stability via scalable fabrication techniques are important for their practical applications. A wide range of FLIBs with excellent flexibility have been reported. However, sophisticated designs and complex fabrication techniques are often used in fabricating FLIBS, making them difficult to be realized in industrial production. Here, we fabricate FLIBs with an integrated structure by assembling the LiFePO4 cathode, Li4Ti5O12 anode, graphene current collectors, and poly(vinylidene fluoride) (PVDF) electrolyte all together on commercial printing paper via conventional and scalable Meyer rod coating. In the design, the commercial paper serves as a flexible substrate to enable good flexibility of the device, and the paper is coated twice with PVDF to avoid the short-circuit problem and create a strong binding to integrate the device. The resultant integrated FLIBs exhibit excellent internal structural stability and good electrochemical performance under cycling bending for 100 times.

2.
Small ; 14(9)2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29280299

RESUMO

Selenium cathode has attracted more and more attention because of its comparable volumetric capacity but much higher electrical conductivity than sulfur cathode. Compared to Li-Se batteries, Na-Se batteries show many advantages, including the low cost of sodium resources and high volumetric capacity. However, Na-Se batteries still suffer from the shuttle effect of polyselenides and high volumetric expansion, resulting in the poor electrochemical performance. Herein, Se is impregnated into microporous multichannel carbon nanofibers (Se@MCNFs) thin film with high flexibility as a binder-free cathode material for Na-Se batteries. The fibrous unique structure of the Se@MCNFs is beneficial to alleviate the volume change of Se during cycling, improve the utilization of active material, and suppress the dissolution of polyselenides into electrolyte. The freestanding Se@MCNF thin-film electrode exhibits high discharge capacity (596 mA h g-1 at the 100th cycle at 0.1 A g-1 ) and excellent rate capability (379 mA h g-1 at 2 A g-1 ) for Na-Se batteries. In addition, it also shows long cycle life with a negligible capacity decay of 0.067% per cycle over 300 cycles at 0.5 A g-1 . This work demonstrates the possibility to develop high performance Na-Se batteries and flexible energy storage devices.

3.
Small ; 13(19)2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28371449

RESUMO

A one-step synthesis procedure is developed to prepare flexible S0.6 Se0.4 @carbon nanofibers (CNFs) electrode by coheating S0.6 Se0.4 powder with electrospun polyacrylonitrile nanofiber papers at 600 °C. The obtained S0.6 Se0.4 @CNFs film can be used as cathode material for high-performance Li-S batteries and room temperature (RT) Na-S batteries directly. The superior lithium/sodium storage performance derives from its rational structure design, such as the chemical bonding between Se and S, the chemical bonding between S0.6 Se0.4 and CNFs matrix, and the 3D CNFs network. This easy one-step synthesis procedure provides a feasible route to prepare electrode materials for high-performance Li-S and RT Na-S batteries.

4.
ACS Appl Mater Interfaces ; 8(1): 689-95, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26653567

RESUMO

Sodium ion batteries (NIBs) have been considered as an alternative for Li ion batteries (LIBs). NaTi2(PO4)3 (denoted as NTP) is a superior anode material for NIBs. However, the poor electrochemical performance of NTP resulting from the low electronic conductivity prevents its application. Here, NTP nanoparticles embedded in carbon network (denoted as NTP/C) were fabricated using a simple soft-template method. This anode material exhibits superior electrochemical performance when used as anode electrodes for NIBs, including highly reversible capacity (108 mAh g(-1) at 100 C) for excellent rate performance and long cycle life (83 mAh g(-1) at 50 C after 6000 cycles). The excellent sodium storage property can be resulted from the synergistic effects of nanosized NTP, thinner carbon shell and the interconnected carbon network, leading to the low charge transfer resistance, the large surface area for electrolyte to soak in and enough void to buffer the volume variation during the repeated cycle.

5.
Nanoscale ; 7(35): 14723-9, 2015 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-26284915

RESUMO

Sodium super ion conductor (NASICON) type structure materials (e.g. Na3V2(PO4)3, NaTi2(PO4)3) have been considered as promising electrode materials for sodium-ion batteries (NIBs). However, the inherent poor electronic conductivity of the NASICON type structure materials owing to their poor electronic conductivity of phosphates leads to poor cyclability and rate capability. Here, we develop a general strategy to achieve high rate capability and long cycle life by preparing "double carbon coating" NASICON NaTi2(PO4)3 using a soft-chemical method. The obtained carbon-coated NaTi2(PO4)3 within the porous carbon matrix (denoted as NTP@C@PC) imparts a reversible capability of 103 mA h g(-1) at 5 C after 5000 cycles and a rate capability of 64 mA h g(-1) at 50 C for sodium storage. The high capacity, stable cyclability and excellent rate capability of the NTP@C@PC are attributed to the advantages of the special structure: the fast Na(+)/e(-) transfer in the nanocomposites, large surface area and mesoporous nature of the 3D porous carbon matrix that facilitate the electrolyte to soak in, an intimate interaction between the particles and the carbon matrix. In addition, the 3D porous carbon matrix could effectively accommodate the volume variation during a repeated sodiation/desodiation process.

6.
Nanoscale ; 7(25): 10940-9, 2015 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-26059471

RESUMO

By rational design, we fabricated a flexible and free-standing copper-immobilized sulfur-porous carbon nanofiber (denoted as S@PCNFs-Cu) electrode by simply impregnating sulfur into electrospun derived Cu embedded porous carbon nanofibers (PCNFs-Cu). The PCNF film with a 3D interconnected structure is used as a conducting matrix to encapsulate sulfur. In addition, the introduction of Cu leads to the formation of a chemical bond between Cu and S, preventing the dissolution of polysulfide during cycling. The micropores and mesopores of PCNF hosts provide free space to accommodate the volume change of S and polysulfide. When used as a cathode material for Li-S batteries, the S@PCNFs-Cu (S content: 52 wt%) exhibits much better electrochemical performance compared to the Cu-free S@PCNF electrode. The S@PCNFs-Cu displays high reversible capacity (680 mA h g(-1) after 100 cycles at 50 mA g(-1)), excellent rate capability (415 mA h g(-1) at 1 A g(-1)) and super Coulombic efficiency of 100%. This strategy of stabilizing S with a small amount of copper nanoparticles can be a very promising method to prepare free-standing cathode material for high-performance Li-S batteries.

7.
Small ; 11(23): 2762-7, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25644610

RESUMO

A hybrid structure with carbon-coated germanium nanowires grown on the surface of carbon nanofibers is fabricated using an in situ vapor-liquid-solid process. It is used as a self-supported and flexible anode for Li-ion batteries.

8.
Nanoscale ; 6(16): 9579-87, 2014 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-25008943

RESUMO

Flexible and free-standing sulphur/(PCNFs-CNT) composite (S@PCNFs-CNT) electrode was successfully prepared by infiltrating sulfur into microporous carbon nanofibers-carbon nanotube (PCNFs-CNT) composite. When used as a cathode material for Li-S batteries, the S@PCNFs-CNT exhibits much better cycle performance and rate performance compared to CNT-free S@PCNFs. It delivers a reversible capacity of 637 mA h g(-1) after 100 cycles at 50 mA g(-1) and a rate capability of 437 mA h g(-1) at 1 A g(-1). The improved electrochemical performance is attributed to synergistic effect of the 3D interconnected structure, the additive of CNT, and the uniform distribution of micropores (<2 nm) in the PCNFs-CNT matrix. Our results indicate the potential suitability of PCNFs-CNT for efficient, free-standing, and high-performance batteries.

9.
Nanoscale ; 6(2): 693-8, 2014 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-24356437

RESUMO

Free-standing and binder-free porous carbon nanofibers (P-CNFs) electrodes were prepared by pyrolysis of PAN-F127/DMF nanofibers via an electrospinning process as potential anodes for Na-ion batteries (NIB). The P-CNFs delivers a reversible capacity of 266 mA h g(-1) after 100 cycles at 0.2 C, corresponding to ~80% of the initial charge capacity. When cycled at a current density as high as 500 mA g(-1) (2 C), it still delivers a reversible capacity of ~140 mA h g(-1) after 1000 cycles. The improvement of electrochemical performance is attributed to the special design and microstructure of P-CNFs, which conferred a variety of advantages: hierarchical porous channels enabling short transport length for ions and electrons, 3D interconnected structure resulting in low contact resistances, good mechanical properties leading to the excellent morphology stability.


Assuntos
Carbono/química , Fontes de Energia Elétrica , Nanofibras/química , Sódio/química , Técnicas Eletroquímicas , Eletrodos , Íons/química , Lítio/química , Porosidade
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