Free-standing porous carbon nanofibers–sulfur composite for flexible Li–S battery cathode

Zeng, Linchao; Pan, Fei; Li, Weihan; Jiang, Yu; Zhong, Xing; Yu, Yan

doi:10.1039/c4nr02498b

Cited by 152 publications

(122 citation statements)

References 77 publications

(177 reference statements)

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“…Currently, the sizes of most reported fl exible free-standing carbon-based electrodes synthesized by electrospinning methods are less than 1 cm × 1 cm, which is much smaller than our N-CNF. [ 18,27,28 ] The crystal structure and phase compositions of the N-CNF are revealed by X-ray diffraction (XRD) ( Figure S3a, Supporting Information). The diffraction peak located at ≈24° is indexed to the (0 0 2) plane of graphite, which is a typical characteristic peak of graphitic carbon with a low degree of graphitization.…”

Section: Doi: 101002/aenm201502217mentioning

confidence: 99%

Free‐Standing Nitrogen‐Doped Carbon Nanofiber Films: Integrated Electrodes for Sodium‐Ion Batteries with Ultralong Cycle Life and Superior Rate Capability

Wang

et al. 2015

Advanced Energy Materials

455

257

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for high energy density because it typically uses copper or aluminum as the current collectors and insulating polymers as the binder. These inactive materials (metal substrate, binder, and carbon black) signifi cantly reduce the overall energy density of the electrodes. To construct SIBs with high energy density, one elegant strategy is to design a free-standing and binder-free electrode in which all of the materials participate in the sodium storage. With excellent fl exibility, carbon-based materials, such as carbon nanofi ber networks, [ 20 ] carbon nanotube, [ 22 ] and graphene paper, [23][24][25] have been fabricated as free-standing fl exible electrodes with improved performance for LIBs. As for SIBs, Singh and co-workers have fabricated MoS 2 /graphene composite paper for SIBs by vacuum fi ltration. [ 26 ] Compared with vacuum fi ltration, the electrospinning technique might be more practical for large-scale fabrication and thickness modifi cation of fl exible fi lm. However, only a few free-standing carbon-based anode materials fabricated by electrospinning for SIBs have been investigated and most of them have a limited cycle life. [ 21 ] Therefore, the fabrication of free-standing fl exible electrodes for SIBs with excellent electrochemical performance is still a great challenge. Herein, we report a new electrospinning strategy to fabricate a free-standing fl exible nitrogen-doped carbon nanofi ber fi lm (N-CNF) using polyamic acid (PAA) as a polymer precursor (as shown in Figure 1 ). After imidation, the PAA nanofi bers are transformed into polyimide (PI) nanofi bers with high thermal stability and carbon residue. A free-standing N-CNF with excellent fl exibility and structural stability can be successfully obtained by carbonization. The as-prepared freestanding N-CNF features a three-dimensional (3D) carbon fi ber network structure with multiscale nanopores, high nitrogen doping level, high structural durability, and excellent mechanical fl exibility. This unique nanostructure can effectively facilitate the insertion/extraction of sodium ions. Remarkably, this new N-CNF exhibits a reversible capacity of 210 mAh g −1 at the 7000th cycle at a current density of 5 A g −1 (corresponding to a capacity retention of 99%) and retained a capacity of 154 mAh g −1 even at a very high current density of 15 A g −1 . To the best of our knowledge, such high rate capability and ultralong cycle life has not been achieved in previous works on carbon-based anode materials for SIBs.As shown in Figure 2 a, compared with the precursor, the N-CNF shrinks by ≈20% after thermal treatment, still featuring stable smoothness surface without any pulverization. The residual carbon of the PI fi lm is ≈50% ( Figure S1, Supporting Information). The relatively high carbon residue content sustains the high structural stability of the fi lm, which is beneficial to the mechanical properties of the fi lm. The small size change before and after thermal treatment with a large reduced Sodium ion batteries (SIBs) have received great interest a...

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Section: Doi: 101002/aenm201502217mentioning

confidence: 99%

Free‐Standing Nitrogen‐Doped Carbon Nanofiber Films: Integrated Electrodes for Sodium‐Ion Batteries with Ultralong Cycle Life and Superior Rate Capability

Wang

et al. 2015

Advanced Energy Materials

455

257

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“…[83] In energy storage devices, the concept of flexible substrates has been extended to other components, thereby propelling the development of flexible LIBs and SCs by utilizing flexible electrodes. For example, a large range of flexible carbonbased materials, such as CNT films, [16,[84][85][86][87][88][89] carbon non-woven fabric, [90] carbon nanofiber paper, [91,92] graphene or graphene oxide paper, [93][94][95][96] and graphene foam (GF), [97,98] have been widely used as current collectors in flexible power source devices. Compared with traditional metal foil current collectors, flexible carbon-based materials present excellent flexibility, high contact area, and strong adhesion to electrode materials.…”

Section: Flexible Substrates and Membranesmentioning

confidence: 99%

Mechanical Analyses and Structural Design Requirements for Flexible Energy Storage Devices

Mao

Meng

Ahmad

et al. 2017

Advanced Energy Materials

180

146

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degree of the entire electronic systems. In the integrated flexible electronic system, energy storage devices [14,[16][17][18][19][20] play important roles in connecting the preceding energy harvesting devices and the following energy utilization devices (Figure 1). Rechargeable secondary batteries and supercapacitors (SCs) are two typical energy storage devices. [21] Several excellent review papers [21][22][23][24][25][26] reported significant progresses achieved in flexible lithium-ion batteries (LIBs) and SCs by taking advantage of novel electrode materials, current collectors, and solid-state electrolytes. The application areas and lifetime of flexible power sources strongly depend on their mechanical deformation tolerance and the electrical property retention under deformation. Qualified flexible power sources should be able to endure high strain induced by external mechanical deformation, such as bending, compressing, stretching, folding, and twisting, while maintaining their electrochemical performance stability and structural integrity. Therefore, the mechanical reliability assessment and electrical property analysis of flexible devices need to be given much attention for future application.Tolerance in bending into a certain curvature is the major mechanical deformation characteristic of flexible energy storage devices. Thus far, several bending characterization parameters and various mechanical methods have been proposed to evaluate the quality and failure modes of the said devices by investigating their bending deformation status and received strain. Some of these mechanical metrologies were derived from the early research on flexible semiconductor devices of micro-electromechanical system (MEMS) [27,28] and TFTs. [29] However, comparing those numerous measurement data with one another is difficult because of the various theories and methods adopted by different research groups and the lack of unified assessment criteria. [26] The flexibility of flexible devices is generally realized not only by use of intuitive soft electrode materials but also by optimizing their mechanical structural design. [25] Detailed analysis on bending mechanics combining experimental and theoretical results provide not only reliable test methods to describe the bending state but also guidance for configuration design of devices against mechanical failure.The current review emphasizes on three main points: (1) key parameters that characterize the bending level of flexible energy storage devices, such as bending radius, bending Flexible energy storage devices with excellent mechanical deformation performance are highly required to improve the integration degree of flexible electronics. Unlike those of traditional power sources, the mechanical reliability of flexible energy storage devices, including electrical performance retention and deformation endurance, has received much attention. To provide the guideline for the construction design of devices, the strain distribution and failure modes in the entire architecture should b...

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“…24 In addition, by taking advantage of their porous structure, the use of freestanding electrodes cannot only improve electrolyte accessibility and better absorbability of sulfur species, but also provide better electron and Li + pathways, significantly improving the electrochemical activity. [24][25][26][27] Although excellent electrochemical performance has been achieved by using various types of freestanding electrodes in Li-S cells, [26][27][28][29][30][31] several challenges still persist for practical implementation. First, the three-dimensional interconnected porous structure of freestanding electrodes lead to low volumetric energy density.…”

mentioning

confidence: 99%

Controlling the Wettability between Freestanding Electrode and Electrolyte for High Energy Density Lithium-Sulfur Batteries

Hwang

Kim

Sun

2017

J. Electrochem. Soc.

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The present study demonstrates how to improve the electrochemical performance and energy density of lithium-sulfur batteries based on controlling the wettability between the freestanding electrode and the electrolyte. First, to improve the volumetric energy density, we reduced the thickness of freestanding electrode by the applying pressure. Second, in order to improve electrolyte conductivity and wettability for pressed freestanding electrode, we reduced the viscosity of electrolyte solution by reducing the LiTFSI salt concentration. Through these controls, the Li-S cell is constructed from a pressed freestanding carbon nanotube-sulfur cathode, 0.5 M LiTFSI in DME/DOL with 0.4 M LiNO 3 as a low-viscosity electrolyte (0.72 cP), and Li-metal foil as an anode. As a result, we can obtain a high discharge capacity of 1,400 mAh g −1 at 0.1 C and excellent cycle retention of 95% after 80 cycles at 0.5 C in coin-type cell. In addition, scale-up (3 by 5 cm) pouch-type Li-S cell delivers a high discharge capacity of 500 mAh at 0.1 C with high gravimetric (954. In order to mitigate the global environmental issues associated with the use of fossil fuels and the resulting greenhouse gas emissions, clean and sustainable energy production and storage technologies are urgently needed.1,2 In this context, lithium-ion battery (LIB) technology has progressed considerably, with continuing applications in potential energy storage devices. However, current LIBs have limited applications in electric vehicles, hybrid electric vehicles, and power grids, owing to their low theoretical energy densities.3-6 Therefore, for mid-to-large-scale applications, it is imperative that we explore alternatives that offer the possibility of going beyond the limits of the intercalation chemistry of current Li-ion technology. 7The lithium-sulfur (Li-S) battery has emerged as a next-generation rechargeable battery, owing to the involvement of multiple electrons during the redox reactions between Li and S, which provides high theoretical energy density (2,600 Wh kg −1 ) and specific capacity (1,675 mAh g −1 ). 8,9 In addition, due to abundance of elemental sulfur and its environmental compatibility, Li-S battery has been considered the much more attractive power sources. Despite these advantages, current Li-S battery have various disadvantages such as poor electrical conductivities of sulfur and Li 2 S, 10,11 undesirable shuttle reactions, 12,13 and huge volume changes of sulfur (∼80%) upon cycling, 14 which have severely delayed the commercialization of Li-S batteries.In order to overcome these problems, various strategies have been implemented to improve the design of both the electrode and the electrolytes materials.15-23 A freestanding electrode is one of attractive choice as the cathode for a Li-S battery, because it is fabricated without a binder or any powdery conductive materials, thereby allowing higher percentages of active material (S 8 ) in the cathode. 24 In addition, by taking advantage of their porous structure, the use of freestanding ele...

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Free-standing porous carbon nanofibers–sulfur composite for flexible Li–S battery cathode

Cited by 152 publications

References 77 publications

Free‐Standing Nitrogen‐Doped Carbon Nanofiber Films: Integrated Electrodes for Sodium‐Ion Batteries with Ultralong Cycle Life and Superior Rate Capability

Free‐Standing Nitrogen‐Doped Carbon Nanofiber Films: Integrated Electrodes for Sodium‐Ion Batteries with Ultralong Cycle Life and Superior Rate Capability

Mechanical Analyses and Structural Design Requirements for Flexible Energy Storage Devices

Controlling the Wettability between Freestanding Electrode and Electrolyte for High Energy Density Lithium-Sulfur Batteries

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