Self-standing Electrode Research Articles

Binder-free nitrogen-doped carbon paper electrodes derived from polypyrrole/cellulose composite for Li–O2 batteries

This work presents a novel binder-free nitrogen-doped carbon paper electrode (NCPE), which was derived from a N-rich polypyrrole (PPy)/cellulose-chopped carbon filaments (CCFs) composite, for Li–O2 batteries. The fabrication of NCPE involved cheap raw materials (e.g., Cladophora sp. green algae) and easy operation (e.g., doping N by a carbonization of N-rich polymer), which is especially suitable for large-scale production. The NCPE exhibited a bird's nest microstructure, which could provide the self-standing electrode with considerable mechanic durability, fast Li+ and O2 diffusion, and enough space for the discharge product deposition. In addition, the NCPE contained N-containing function groups, which may promote the electrochemical reactions. Furthermore, binder-free architecture designs can prevent binder-involved parasitic reactions. A Li–O2 cell with the NCPE displayed a cyclability of more than 30 cycles at a constant current density of 0.1 mA/cm2. The 1st discharge capacity for a cell with the NCPE reached 8040 mAh/g at a current density of 0.1 mA/cm2, with a cell voltage around 2.81 V. A cell with the NCPE displayed a coulombic efficiency of 81% on the 1st cycle at a current density of 0.2 mA/cm2. These results represent a promising progress in the development of a low-cost and versatile paper-based O2 electrode for Li–O2 batteries.

Microwave synthesized self-standing electrode of MoS2 nanosheets assembled on graphene foam for high-performance Li-Ion and Na-Ion batteries

Three-dimensional (3D) graphene foams (GF) were grown on nickel foam by chemical vapor deposition method, and then flowerlike MoS2 nanosheets assembled on GF were achieved by single mode microwave-assisted hydrothermal technique. The flexible MoS2@GF electrode with high conductive network and interconnected channel shows excellent electrochemical performance for lithium ion batteries (LIBs) and sodium ion batteries (SIBs). For LIBs, the specific capacity of MoS2@GF can reach up to 1400 mAh g−1 at a current rate of 100 mA g−1, moreover, the high specific capacity (1127 mAh g−1) can be achieved at a rate of 250 mA g−1 after 100 cycles. In addition, the obtained specific capacity for SIBs after 50 cycles is 290 mAh g−1 at a rate of 100 mA g−1. The excellent performance of the flexible MoS2@GF electrode is attributed to fast electron transport, more efficient penetration of electrolyte and shortened ion diffusion time for high conductive, stable 3D architectures.

Self-standing carbon nanotube forest electrodes for flexible supercapacitors

A self-standing, vertically aligned carbon nanotube forest grown on unidirectional carbon fibers has been fabricated by using chemical vapour deposition.

Ligno-Cellulosic Materials for the Next-Generation of Eco-Friendly Polymeric Energy Power Sources

In the last 20 years, the Li-ion battery (LIB) market has rapidly grown thanks to the extensive diffusion of mobile electronics devices. The optimisation of existing chemistries by the introduction of environmentally friendly materials and the simplification of the production process are intriguing challenges to promote the future widespread diffusion of LIBs. In order to lower the cost and reduce the environmental impact of LIBs, which is crucial in the perspective of their large-scale diffusion, an effort must be made to reduce the amount of inactive components in the cell, to substitute high cost materials, such as synthetic polymer binders / separators and organic solvents, with low-cost and bio-based/bio-inspired materials and to develop new eco-friendly processes for the manufacture of cell components [1].Nanoscale-microfibrillated cellulose particles (NMFC), first studied by Herrick and Tubark, are easily available and biodegradable; they show stiffness, impressive mechanical properties and reinforcing capability, low weight and, furthermore, their preparation process is easy, low cost and does not involve chemical reactions. They can significantly reinforce polymer electrolytes already at low filler loadings and also replace the commonly used PVdF as binder for self-standing and flexible electrodes, thus serving as a promising candidate for bio-composite production [2-4].In the present work paper-making technique was used for manufacturing low cost bio-inspired all-paper Li-ion cells, constituted by two paper-electrodes, prepared using micrometric size graphite (anode) and LiFePO4 (cathode) as active materials, and paper hand-sheets reinforced polymers as electrolyte. Considering the interesting properties of NMFC and the potentials of free radical photo-polymerisation, a UV cured NMFC-polymer composite membrane could surely result highly promising. Thus, NMFC particles as reinforcement for composite methacrylic/ethylene-oxide based solid or quasi solid polymer electrolyte membranes were also prepared by UV curing. The use of such a filler/binder results extremely interesting, giving the possibility to produce high performing, safe and extremely flexible electrolytes for Li-ion batteries. No organic solvents or synthetic polymer binders are used during the entire electrode/electrolyte/cell preparation process. The all-paper-cell can be easily re-dispersed in water by simple mechanical stirring, as well as common paper hand sheets and paper-battery materials can be recovered using well-known water-based recycling process. Finally, the results of an all-solid paper-cell, comprising methacrylic and/or PEO-based membranes as polymer electrolytes are presented, which demonstrate the possibility of obtaining in the next future “truly green” Li-based energy storage devices.[1] L. Jabbour, R. Bongiovanni, D. Chaussy, C. Gerbaldi, D. Beneventi Cellulose 20 (2013) 1523.[2] L. Jabbour, C. Gerbaldi, D. Chaussy, E. Zeno, S. Bodoardo, D. Beneventi, J. Mater. Chem. 20 (2010) 7344.[3] L. Jabbour, M. Destro, D. Chaussy, C. Gerbaldi, N. Penazzi, S. Bodoardo, D. Beneventi, Cellulose 20 (2013) 571.[4] A. Chiappone, Jijeesh R. Nair, C. Gerbaldi, L. Jabbour, R. Bongiovanni, E. Zeno, D. Beneventi, N. Penazzi, J. Power Sources 196 (2011) 10280.

MoS2/Graphene Composite Paper for Sodium-Ion Battery Electrodes

We study the synthesis and electrochemical and mechanical performance of layered free-standing papers composed of acid-exfoliated few-layer molybdenum disulfide (MoS2) and reduced graphene oxide (rGO) flakes for use as a self-standing flexible electrode in sodium-ion batteries. Synthesis was achieved through vacuum filtration of homogeneous dispersions consisting of varying weight percent of acid-treated MoS2 flakes in GO in DI water, followed by thermal reduction at elevated temperatures. The electrochemical performance of the crumpled composite paper (at 4 mg cm(-2)) was evaluated as counter electrode against pure Na foil in a half-cell configuration. The electrode showed good Na cycling ability with a stable charge capacity of approximately 230 mAh g(-1) with respect to total weight of the electrode with Coulombic efficiency reaching approximately 99%. In addition, static uniaxial tensile tests performed on crumpled composite papers showed high average strain to failure reaching approximately 2%.

Pilot-scale elaboration of graphite/microfibrillated cellulose anodes for Li-ion batteries by spray deposition on a forming paper sheet

A new spray coating water-based process is here proposed for the rapid and reliable large-scale production of self-standing Li-ion battery electrodes using truly natural microfibrillated cellulose as binder. The graphite/carbon black microfibrillated cellulose slurry was spray coated on a wet paper substrate which, subsequently pressed and dried on a conventional pilot paper machine, led to the formation of a bilayered electrode with excellent mechanical properties, cycling performances vs Li metal comparable to those of anodes with standard composition, (i.e. Young Modulus of 2.5GPa and specific capacity of 350mAhg−1 at 0.1C) but a Coulombic efficiency (ca. 98% in the first 50 cycles) which needs to be improved to maintain good cycling performances in Li-ion systems.This work demonstrated that well-established industrial papermaking techniques and materials can be adapted to the elaboration of well-functioning electrodes thus paving the way for the transfer the Li-ion battery industrial area of high-throughput paper production technologies.

Direct growth of MnO2 on carbon fiber cloth for electrochemical capacitor

Self-standing MnO2 electrodes have been fabricated through the redox reaction between carbon fiber and potassium permanganate. The porous film of birnessite-type MnO2 deposited tightly onto surfaces of the carbon fibers to form manganese dioxide/carbon fiber cloth electrode. The electrodes have not only excellent capacitive performances, but also superior electrochemical stability. Owing to the formation of thin-film morphology, porous structure and the intimate contact between the electroactive material and the current collector, the MnO2 film provides an enhancement of the kinetics by short transport/diffusion path lengths, timely accompanying of electrolyte and large specific surface areas, thus both high energy density and high power density are achieved. In addition to the effective release of stress resulting from charge/discharge, the porous structure also facilitates accompanying electrolyte at high rate operation and avoiding dramatic capacitance fade in cycling. The specific capacitance still retains at least about 84% after continuous 5000 charge/discharge cycles.

Thick vertically aligned carbon nanotube/carbon composite electrodes for electrical double-layer capacitors

We present a new method for synthesis of thick, self-standing porous carbon electrodes with improved physicochemical properties and unique porous structure. The synthesis is based on the use of vertically aligned carbon nanotubes (VACNT) as templates for polymer-based activated carbon materials. The VACNT template enables the production of 1mm thick, binder-free electrodes with high capacity values even at high rates (>160Fg−1 at more than 1Ag−1 for 1mm thick electrode), and very good stability upon cycling. The electrochemical performance after more than 50,000 cycles, the pore characterization by adsorption isotherms, and the structural analysis of the composite electrode are also reported.

Highly reversible Li/dissolved polysulfide batteries with binder-free carbon nanofiber electrodes

Conventional lithium–sulfur batteries suffer from rapid capacity fade which limits their commercialization applications. Li/dissolved polysulfide cells with binder-free, interwoven, self-standing carbon electrodes show outstanding performance in terms of capacity utilization and reversibility. To further understand this system, we present here a binder-free carbon nanofiber (CNF) paper electrode with large interspaces between fibers, low manufacturing cost, and high polysulfide loadings. The 3D interwoven structure of the CNF paper electrode allows transitions between high-order polysulfides (charged products) and lithium sulfide (discharged product) to occur within a confined environment. Crystalline Li2S is found within the large interspaces of the 3D electrode framework after the 1st discharge, avoiding the formation of dense passivation layers on the cathode. The robust porous CNF paper electrode leads to superior electrochemical performance with a reversible capacity of 1094 mA h g−1 after 80 cycles at a C/5 rate and Coulombic efficiencies above 98% with a sulfur loading of 1.7 mg cm−2. A stable reversible capacity of ∼900 mA h g−1 is obtained with a much higher sulfur loading of 5.1 mg cm−2, making this battery configuration promising for practical applications.

Highly flexible self-standing film electrode composed of mesoporous rutile TiO2/C nanofibers for lithium-ion batteries

There is increasing interest in flexible, safe, high-power thin-film lithium-ion batteries which can be applied to various modern devices. Although TiO2 in rutile phase is highly attractive as an anode material of lithium-ion batteries for its high thermal stability and theoretical capacity of 336mAhg−1 and low price, its inflexibility and sluggish lithium intercalation kinetics of bulk phase strongly limit its practical application for particular in thin-film electrode. Here we show a simple way to prepare highly flexible self-standing thin-film electrodes composed of mesoporous rutile TiO2/C nanofibers with low carbon content (<15wt.%) by electrospinning technique with outstanding electrochemical performance, which can be applied directly as electrodes of lithium-ion batteries without the further use of any additive and binder. The atmosphere during calcination plays a critical role in determining the flexible nature of thin film and particle size of TiO2 in as-fabricated nanofibers. Big size (10cm×4cm), flexible thin film is obtained after heat treatment under 10%H2–Ar at 900°C for 3h. After optimization, the diameter of fibers can reach as small as ∼110nm, and the as-prepared rutile TiO2 films show high initial electrochemical activity with the first discharge capacity as high as 388mAhg−1. What is more, very stable reversible capacities of ∼122, 92, and 70mAhg−1 are achieved respectively at 1, 5 and 10C rates with negligible decay rate within 100 cycling times.

From Paper to Paper-like Hierarchical Anatase TiO2 Film Electrode for High-Performance Lithium-Ion Batteries

A paper-like self-standing film electrode composed of hierarchical mesoporous anatase TiO2 was designed and prepared through a facile route of filter paper templating in combination with an additional deep hydrolysis treatment process. The specific surface area of hierarchical mesoporous TiO2 increased to 155.6 m2 g–1 compared to the sample without the additional deep hydrolysis, which is only 16.0 m2 g–1. The results are consistent with a simple model of sphere stacking which suggests that the rich mesopores were from the void space created by the TiO2 stacking. By applying such film as binder-free electrode in lithium-ion batteries (LIBs), good rate performance was demonstrated, and the capacity was still 100 mA h g–1 even at the high rate of 20 C. The contributions of Li+ insertion/extraction reaction and capacitive effect on the capacities were investigated by cyclic voltammetry and calculation. With the sweep rate increased from 0.1 to 10 mV s–1, the contributions of capacitive effects increased from 46% to 88% of the total capacities. The uniquely architectural TiO2 film electrode showed excellent cycling performance at high rate of 10 C through 400 cycles. It highly promises as a new anode for thin-film batteries with versatile application fields.

Self-standing positive electrodes of oxidized few-walled carbon nanotubes for light-weight and high-power lithium batteries

Binder-free and self-standing carbon nanotube (CNT) electrodes of tens of microns in thickness have been assembled via a vacuum-filtration process of oxidized few-walled CNTs (FWNTs), with different amounts of oxygen functional groups on FWNTs. Sub-millimetre long FWNTs can provide high electrical conductivity and mechanical strength in self-standing porous networks by reducing the number of junctions among FWNTs. We show that the gravimetric capacity of FWNT electrodes in lithium cells can be enhanced by increasing oxygen functional groups on FWNTs, which results from Faradaic reactions between lithium ions and surface oxygen functional groups. These self-standing FWNT electrodes (free of binder/additive and current collector) can provide a high gravimetric energy of ∼200 W h kg−1 at a high power of ∼10 kW kg−1, showing promise as the positive electrode for light-weight, high-power lithium batteries.

State of hydrogen electrochemically stored using nanoporous carbons as negative electrode materials in an aqueous medium

Nanoporous carbons were used as negative electrode material in aqueous KOH medium to store hydrogen by electrodecomposition of water at atmospheric pressure. The storage capacity by this process is approximately one order of magnitude higher than in the gas phase at ambient conditions. By considering the particularities of the electrochemical characteristics, this paper gives information on the mechanism and on the kind of bond between hydrogen and the carbon host. For most experiments, a self-standing porous carbon cloth electrode has been used in order to avoid any side effect which could be due to additives. After galvanostatic hydrogen charging, the carbon material was analyzed by galvanostatic discharge and temperature-programmed desorption in order to determine the nature of the carbon–hydrogen bond and the amount of hydrogen sorbed. The activation energy for hydrogen desorption was estimated to be 110 kJ/mol, that confirms a weak chemical character of the hydrogen–carbon bond. Although the bond is stronger than in the case of physisorption, the fraction of hydrogen irreversibly trapped is low compared to the reversible fraction. Finally, we show that the reversible capacity can be significantly enhanced by increasing the temperature to 60 °C during the electrochemical reduction of water. The well-defined plateau during the oxidation step demonstrates high potentialities of this technique for electrochemical energy storage in nanoporous carbons using an aqueous medium.

US 4,891,391 Stabilizer/antimicrobial agents in polymers

Conjugated microporous polymers with active functional groups have attracted more and more attentions in energy conversion systems. However, their low electrical conductivity results in low capacitance, thus limiting their practical application. Herein, conjugated microporous polymer with triphenylamine aldehyde linked to metal phthalocyanines (MNC) is synthesized and then compounded with high-conductivity carbon nanotubes (CNTs) (denoted as CoNCCs) by vacuum filtration. Moreover, CoNCCs exhibit flexibility, which could be served as a self-standing and binder-free flexible electrode of supercapacitors. As a result, the optimized CoNCCs as the flexible electrode show high specific capacitance of 213.4 F g−1 at 0.5 A g−1. In addition, the higher capacity retention rate 85.3% can be retained after 1750 cycles at 20 A g−1. The good electrochemical properties can be attributed to the synergistic effect and strong dual-phase interaction between MNC and CNTs. This work opens the way to develop high-performance and low environmental footprint organic electrode materials for SCs.