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Interconnecting Carbon Fibers with the In-situ Electrochemically Exfoliated Graphene as Advanced Binder-free Electrode Materials for Flexible Supercapacitor.

Zou Y, Wang S - Sci Rep (2015)

Bottom Line: The low surface area of CC and the presence of big gaps (ca. micro-size) between individual CFs lead to poor performance.The in-situ electrochemical intercalation technique ensures the low contact resistance between electrode (graphene) and current collector (carbon cloth) with enhanced conductivity.The as-prepared electrode materials show significantly improved performance for flexible supercapacitors.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China [2] School of Chemistry, The University of Manchester, Oxford Road, Greater Manchester, M13 9PL, United Kingdom.

ABSTRACT
Flexible energy storage devices are highly demanded for various applications. Carbon cloth (CC) woven by carbon fibers (CFs) is typically used as electrode or current collector for flexible devices. The low surface area of CC and the presence of big gaps (ca. micro-size) between individual CFs lead to poor performance. Herein, we interconnect individual CFs through the in-situ exfoliated graphene with high surface area by the electrochemical intercalation method. The interconnected CFs are used as both current collector and electrode materials for flexible supercapacitors, in which the in-situ exfoliated graphene act as active materials and conductive "binders". The in-situ electrochemical intercalation technique ensures the low contact resistance between electrode (graphene) and current collector (carbon cloth) with enhanced conductivity. The as-prepared electrode materials show significantly improved performance for flexible supercapacitors.

No MeSH data available.


Related in: MedlinePlus

(A) The cyclic voltammetry curves of carbon cloth in 0. 1 M TMAClO4 in NMP recorded at a scan rate of 20 mV/s; (B) the chronoamperometric curve of carbon cloth for the mild exfoliation at the constant potential of −2.5 V; SEM images of interconnected carbon fibers by the in-situ electrochemically exfoliated graphene (Ex-CC) at low magnification (C) and high magnification (D).
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f1: (A) The cyclic voltammetry curves of carbon cloth in 0. 1 M TMAClO4 in NMP recorded at a scan rate of 20 mV/s; (B) the chronoamperometric curve of carbon cloth for the mild exfoliation at the constant potential of −2.5 V; SEM images of interconnected carbon fibers by the in-situ electrochemically exfoliated graphene (Ex-CC) at low magnification (C) and high magnification (D).

Mentions: The electrochemical cation intercalation of carbon cloth was conducted by using a three-electrode system with carbon cloth as working electrode, Pt mesh as counter electrode, Ag/AgClO4 as reference electrode, and tetramethylammonium perchlorate (TMAClO4) as electrolyte. We performed the cyclic voltammetry (CV) scanning to define a proper potential for the chronoamperometric (CA) mode to start the electrochemical cation intercalation process. As shown by the CV curves in Fig. 1A, scanning from 0 to −4 V resulted in a clear cathodic current (starting from around −2 V) associated with the intercalation of cations into the graphite of carbon fibers1718. At more negative potential, the current is much higher, indicating obviously better intercalation efficiency17. Initially, we conducted the CA running at a constant most negative potential of −4 V for 10000 s. At this potential, graphene was successfully exfoliated from graphite of carbon fibers, but most of them were de-attached from carbon fibers into the electrolyte and participated, as shown by the digital photograph in Figure S2. For the final use in flexible supercapacitor, it is required to keep the exfoliated graphene in the matrix of carbon fibers. Therefore, the potential of −4 V is too negative and too strong for this purpose. Subsequently, a milder potential of −2.5 V was chosen for the CA running (Fig. 1B) to exfoliate graphene from carbon fibers. After the intercalation process of 10000 s, no apparent participates were observed, indicating that the as-exfoliated graphene was well reserved in the matrix of carbon fibers. The SEM images were collected for the exfoliated carbon cloth (denoted as Ex-CC) obtained at the potential of −2.5 V. Different from the pristine carbon cloth (SEM images shown in Figure S1) in which carbon fibers were individually distributed and showed big gaps of around 1–4 μm, the carbon fibers in Ex-CC were interconnected by the in-situ exfoliated graphene, as shown in Figs 1C,D. As observed in Figs 1C,D, it seems that the exfoliated graphene acted as conductive “binder” to interconnect the individual carbon fibers. The conductive “binder” (graphene) linked with carbon fibers could effectively enhance the conductivity of the composites due to the high conductivity of graphene. The transmission electron microscopy (TEM) and atomic force microscopy (AFM) images were used to identify the structural information of the as-obtained materials. The TEM and AFM images, as shown in Figure S3, show the typical graphene structure. The graphene–interconnected carbon fibers would contribute more available charging sites per a unit area due to the high surface area of graphene, thus leading to higher area-normalized capacitance when used in supercapacitors.


Interconnecting Carbon Fibers with the In-situ Electrochemically Exfoliated Graphene as Advanced Binder-free Electrode Materials for Flexible Supercapacitor.

Zou Y, Wang S - Sci Rep (2015)

(A) The cyclic voltammetry curves of carbon cloth in 0. 1 M TMAClO4 in NMP recorded at a scan rate of 20 mV/s; (B) the chronoamperometric curve of carbon cloth for the mild exfoliation at the constant potential of −2.5 V; SEM images of interconnected carbon fibers by the in-situ electrochemically exfoliated graphene (Ex-CC) at low magnification (C) and high magnification (D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493559&req=5

f1: (A) The cyclic voltammetry curves of carbon cloth in 0. 1 M TMAClO4 in NMP recorded at a scan rate of 20 mV/s; (B) the chronoamperometric curve of carbon cloth for the mild exfoliation at the constant potential of −2.5 V; SEM images of interconnected carbon fibers by the in-situ electrochemically exfoliated graphene (Ex-CC) at low magnification (C) and high magnification (D).
Mentions: The electrochemical cation intercalation of carbon cloth was conducted by using a three-electrode system with carbon cloth as working electrode, Pt mesh as counter electrode, Ag/AgClO4 as reference electrode, and tetramethylammonium perchlorate (TMAClO4) as electrolyte. We performed the cyclic voltammetry (CV) scanning to define a proper potential for the chronoamperometric (CA) mode to start the electrochemical cation intercalation process. As shown by the CV curves in Fig. 1A, scanning from 0 to −4 V resulted in a clear cathodic current (starting from around −2 V) associated with the intercalation of cations into the graphite of carbon fibers1718. At more negative potential, the current is much higher, indicating obviously better intercalation efficiency17. Initially, we conducted the CA running at a constant most negative potential of −4 V for 10000 s. At this potential, graphene was successfully exfoliated from graphite of carbon fibers, but most of them were de-attached from carbon fibers into the electrolyte and participated, as shown by the digital photograph in Figure S2. For the final use in flexible supercapacitor, it is required to keep the exfoliated graphene in the matrix of carbon fibers. Therefore, the potential of −4 V is too negative and too strong for this purpose. Subsequently, a milder potential of −2.5 V was chosen for the CA running (Fig. 1B) to exfoliate graphene from carbon fibers. After the intercalation process of 10000 s, no apparent participates were observed, indicating that the as-exfoliated graphene was well reserved in the matrix of carbon fibers. The SEM images were collected for the exfoliated carbon cloth (denoted as Ex-CC) obtained at the potential of −2.5 V. Different from the pristine carbon cloth (SEM images shown in Figure S1) in which carbon fibers were individually distributed and showed big gaps of around 1–4 μm, the carbon fibers in Ex-CC were interconnected by the in-situ exfoliated graphene, as shown in Figs 1C,D. As observed in Figs 1C,D, it seems that the exfoliated graphene acted as conductive “binder” to interconnect the individual carbon fibers. The conductive “binder” (graphene) linked with carbon fibers could effectively enhance the conductivity of the composites due to the high conductivity of graphene. The transmission electron microscopy (TEM) and atomic force microscopy (AFM) images were used to identify the structural information of the as-obtained materials. The TEM and AFM images, as shown in Figure S3, show the typical graphene structure. The graphene–interconnected carbon fibers would contribute more available charging sites per a unit area due to the high surface area of graphene, thus leading to higher area-normalized capacitance when used in supercapacitors.

Bottom Line: The low surface area of CC and the presence of big gaps (ca. micro-size) between individual CFs lead to poor performance.The in-situ electrochemical intercalation technique ensures the low contact resistance between electrode (graphene) and current collector (carbon cloth) with enhanced conductivity.The as-prepared electrode materials show significantly improved performance for flexible supercapacitors.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Chem/Bio-Sensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, P. R. China [2] School of Chemistry, The University of Manchester, Oxford Road, Greater Manchester, M13 9PL, United Kingdom.

ABSTRACT
Flexible energy storage devices are highly demanded for various applications. Carbon cloth (CC) woven by carbon fibers (CFs) is typically used as electrode or current collector for flexible devices. The low surface area of CC and the presence of big gaps (ca. micro-size) between individual CFs lead to poor performance. Herein, we interconnect individual CFs through the in-situ exfoliated graphene with high surface area by the electrochemical intercalation method. The interconnected CFs are used as both current collector and electrode materials for flexible supercapacitors, in which the in-situ exfoliated graphene act as active materials and conductive "binders". The in-situ electrochemical intercalation technique ensures the low contact resistance between electrode (graphene) and current collector (carbon cloth) with enhanced conductivity. The as-prepared electrode materials show significantly improved performance for flexible supercapacitors.

No MeSH data available.


Related in: MedlinePlus