Extraordinary Cycling Stability Research Articles

Fabrication of a flexible film electrode based on cellulose nanofibers aerogel dispersed with functionalized graphene decorated with SnO2 for supercapacitors

Flexible electrode film was fabricated using cellulose nanofibers aerogel as a framework dispersed with reduced graphene decorated with SnO2 for supercapacitors. The electrode film was synthesized through a simple hydrothermal reduction method followed by a free-drying process. Scanning electron microscope showed that cellulose nanofibers were uniformly wrapped around by reduced graphene, and a high specific area capacitance of 4.314 F cm−2 at 1 mA/cm2 in 1 M H2SO4 was obtained due to the 3D porous network of the aerogel. Furthermore, the aerogel electrodes showed extraordinary cycling stability for 2000 cycles with retention up to 60.47% at 10 mA cm−2. In view of its great electrical performance, easy synthesis, low cost, and environmentally friendly nature, the CNF/RGO/SnO2 aerogel may find promising application for flexible supercapacitors.

Few-Layer Silicene Nanosheets with Superior Lithium-Storage Properties.

Silicene, a 2D silicon allotrope with unique low-buckled structure, has attracted increasing attention in recent years due to its many superior properties. So far, epitaxial growth is one of the very limited ways to obtain high-quality silicene, which severely impedes the research and application of silicene. Therefore, large-scale synthesis of silicene is a great challenge, yet urgently desired. Herein, the first scalable preparation of free-standing high-quality silicene nanosheets via liquid oxidation and exfoliation of CaSi2 is reported. This new synthesis strategy successfully induces mild oxidation of the (Si2n )2n- layers in CaSi2 into neutral Si2n layers without damage of pristine silicene structure and promotes the exfoliation of stacked silicene layers. The obtained silicene sheets are dispersible and ultrathin ones with monolayer or few-layer thickness and exhibit excellent crystallinity. As a unique 2D layered silicon allotrope, the silicene nanosheets are further explored as new anodes for lithium-ion batteries and exhibit a nearly theoretical capacity of 721 mAh g-1 at 0.1 A g-1 and an extraordinary cycling stability with no capacity decay after 1800 cycles in contrast to previous most silicon anodes showing rapid capacity decay, thus holding great promise for energy storage and beyond.

Construction of NiCo2O4@graphene nanorods by tuning the compositional chemistry of metal–organic frameworks with enhanced lithium storage properties

NiCo2O4@graphene nanorods synthesized by tuning the compositional chemistry of metal–organic frameworks exhibit high Li-storage capacity, excellent rate capability and extraordinary cycling stability.

Supercapacitor with extraordinary cycling stability and high rate from nano-architectured polyaniline/graphene on Janus nanofibrous film with shape memory

Layer-by-layer polyaniline–graphene on multifunctional polyvinyl alcohol nanofibers leads to extremely stable flexible electrodes with high power and rate capability.

Hierarchical 3D Zn–Ni–P nanosheet arrays as an advanced electrode for high-performance all-solid-state asymmetric supercapacitors

A hierarchical 3D Zn–Ni–P nanosheet arrays based all-solid-state ASC exhibits an excellent energy density of ∼90.12 W h kg−1 at 0.61 kW kg−1, power density of ∼8.77 kW kg−1 at 65.83 W h kg−1, and extraordinary cycling stability of ∼93.05% capacitance retention after 20 000 cycles.

A Binder-Free and Free-Standing Cobalt Sulfide@Carbon Nanotube Cathode Material for Aluminum-Ion Batteries.

Rechargeable aluminum-ion batteries (AIBs) are considered as a new generation of large-scale energy-storage devices due to their attractive features of abundant aluminum source, high specific capacity, and high energy density. However, AIBs suffer from a lack of suitable cathode materials with desirable capacity and long-term stability, which severely restricts the practical application of AIBs. Herein, a binder-free and self-standing cobalt sulfide encapsulated in carbon nanotubes is reported as a novel cathode material for AIBs. The resultant new electrode material exhibits not only high discharge capacity (315 mA h g-1 at 100 mA g-1 ) and enhanced rate performance (154 mA h g-1 at 1 A g-1 ), but also extraordinary cycling stability (maintains 87 mA h g-1 after 6000 cycles at 1 A g-1 ). The free-standing feature of the electrode also effectively suppresses the side reactions and material disintegrations in AIBs. The new findings reported here highlight the possibility for designing high-performance cathode materials for scalable and flexible AIBs.

Nanorod Mn3O4 anchored on graphene nanosheet as anode of lithium ion batteries with enhanced reversible capacity and cyclic performance

Nanorod Mn3O4 anchored on graphene nanosheet (Mn3O4@GNS) using GNSs and MnSO4·H2O as precursor materials have been prepared by a simple, effective and scalable method. The nanorod Mn3O4@GNS as anode materials in lithium-ion batteries exhibits the better electrochemical properties in the composite than the bare nanorod Mn3O4 owing to its special structure, including a maximum reversible specific capacity of 1155.2 mA h g−1 at 100 mA g−1, and the extraordinary cycling stability, with no decay in capacity for up to 100 cycles. The nanorod Mn3O4@GNS could be a promising candidate material for high reversible specific capacity, stable columbic efficiency, long cycle life and outstanding rate capacity. This study would offer a new method to improve the properties of insulating materials, holding a promising potential for high-performance lithium-ion batteries in energy storage fields.

Controlled synthesis of hierarchically-structured MnCo2O4 and its potential as a high performance anode material

To satisfy the upsurging demand for energy storage in modern society, anode materials which can deliver high capacity have been intensively researched for the next generation lithium ion batteries. Typically, the binary MnCo2O4 with a characteristic coupled metal cations showed promising potential due to its high theoretical capacity and low cost. Here, by means of a well-designed synthesis control, we demonstrated a scalable process to achieve a hierarchical structure of MnCo2O4, which existed as uniform microspheres with embedded mesopores, showing favorable structural characters for high performance during a fast charge/discharge process. Our synthesis highlighted the importance of sodium salicylate as an essential additive to control the precipitation of the two involved metal cations. It was proved that a dual role was played sodium salicylate which cannot only facilitate the formation of microspheric shape, but also act as an effective precursor for the creation of inner mesopores. We confirmed that the hierarchically-structured MnCo2O4 showed outstanding performance when it was tested as an anode material in lithium ion batteries as revealed by its extraordinary cycling stability and high rate capability.

Preparation and supercapacitor performance of functionalized graphene aerogel loaded with polyaniline as a freestanding electrode

Graphene aerogel (GA) has wide applications in energy storage, catalysis, and adsorption. However, as a candidate for supercapacitor electrode, it suffers from low specific capacitance. In this paper, we conceived and conducted a two-step strategy to improve the electrochemical properties of GA: First, GA was selective functionalized with p-phenylenediamine. Then PANI was grafted onto GA by in situ polymerization. The results suggest that surface functionalization enhances the interface bonding between GA and PANI and charge transfer during electrode redox. As a result, the obtained GAp/PANI composites, applied as the freestanding electrodes for supercapacitor, exhibit high specific capacitance (810 F/g at 1 A/g, 2.4 times of GA), good rate capability, and extraordinary cycling stability (83.2% of retention at 10 A/g after 10,000 cycles, 1.25 times of PANI/GA), indicating its great potential in the construction of high-performance energy-storage systems.

3D Interconnected Carbon Fiber Network-Enabled Ultralong Life Na3 V2 (PO4 )3 @Carbon Paper Cathode for Sodium-Ion Batteries.

Sodium-ion batteries (NIBs) are an emerging technology, which can meet increasing demands for large-scale energy storage. One of the most promising cathode material candidates for sodium-ion batteries is Na3 V2 (PO4 )3 due to its high capacity, thermal stability, and sodium (Na) Superionic Conductor 3D (NASICON)-type framework. In this work, the authors have significantly improved electrochemical performance and cycling stability of Na3 V2 (PO4 )3 by introducing a 3D interconnected conductive network in the form of carbon fiber derived from ordinary paper towel. The free-standing Na3 V2 (PO4 )3 -carbon paper (Na3 V2 (PO4 )3 @CP) hybrid electrodes do not require a metallic current collector, polymeric binder, or conducting additives to function as a cathode material in an NIB system. The Na3 V2 (PO4 )3 @CP cathode demonstrates extraordinary long term cycling stability for 30 000 deep charge-discharge cycles at a current density of 2.5 mA cm-2 . Such outstanding cycling stability can meet the stringent requirements for renewable energy storage.

Facile Synthesis of Nitrogen-Containing Mesoporous Carbon for High-Performance Energy Storage Applications.

Porous carbon with high specific surface area (SSA), a reasonable pore size distribution, and modified surface chemistry is highly desirable for application in energy storage devices. Herein, we report the synthesis of nitrogen-containing mesoporous carbon with high SSA (1390 m(2) g(-1)), a suitable pore size distribution (1.5-8.1 nm), and a nitrogen content of 4.7 wt % through a facile one-step self-assembly process. Owing to its unique physical characteristics and nitrogen doping, this material demonstrates great promise for application in both supercapacitors and encapsulating sulfur as a superior cathode material for lithium-sulfur batteries. When deployed as a supercapacitor electrode, it exhibited a high specific capacitance of 238.4 F g(-1) at 1 A g(-1) and an excellent rate capability (180 F g(-1), 10 A g(-1)). Furthermore, when an NMC/S electrode was evaluated as the cathode material for lithium-sulfur batteries, it showed a high initial discharge capacity of 1143.6 mA h g(-1) at 837.5 mA g(-1) and an extraordinary cycling stability with 70.3% capacity retention after 100 cycles.

Large-scale synthesis of hybrid metal oxides through metal redox mechanism for high-performance pseudocapacitors.

Electrochemical performance and production cost are the main concerns for the practical application of supercapacitors. Here we report a simple and universally applicable method to prepare hybrid metal oxides by metal redox reaction utilizing the inherent reducibility of metals and oxidbility of for the first time. As an example, Ni(OH)2/MnO2 hybrid nanosheets (NMNSs) are grown for supercapacitor application by self-reaction of Ni foam substrates in KMnO4 solution at room temperature. The obtained hybrid nanosheets exhibit high specific capacitance (2,937 F g−1). The assembled solid-state asymmetric pseudocapacitors possess ultrahigh energy density of 91.13 Wh kg−1 (at the power density of 750 W kg−1) and extraordinary cycling stability with 92.28% capacitance retention after 25,000 cycles. Co(OH)2/MnO2 and Fe2O3/MnO2 hybrid oxides are also synthesized through this metal redox mechanism. This green and low-cost method is capable of large-scale production and one-step preparation of the electrodes, holding promise for practical application of high-performance pseudocapacitors.

High Rate and Stable Cycling of Lithium Metal Anode

Lithium (Li) metal is an ideal anode material for Li batteries due to its extremely high theoretical specific capacity (3860 mAh g-1), low density (0.59 g cm-3) and the lowest negative electrochemical potential (−3.040 V vs. standard hydrogen electrode).1 However, dendritic Li growth and limited Coulombic efficiency (CE) during Li deposition/stripping have prevented their applications in rechargeable Li batteries, especially at high current densities.2,3 Electrolyte is one of the most critical elements that affect the cycling stability of Li metal anode, since Li is thermodynamically unstable with any kinds of organic solvents and salts.4 The interactions between organic electrolytes and Li metal results in significant side reactions that not only lead to low CE but also consume Li metal and/or electrolyte materials. This phenomena becomes especially serious at high current densities.5Therefore, extensive studies have been conducted to understand how electrolyte formulations affect the cycling of Li metal electrodes. Here, we demonstrate that the use of a highly concentrated electrolyte composed of 1,2-dimethoxyethane (DME) solvent and the salt lithium bis(fluorosulfonyl)imide (LiFSI) results in the nondendritic plating of Li metal at high rates and with high efficiency. The electrochemical performance of Li metal plating/stripping with a concentrated LiFSI-DME electrolyte is shown in Figure 1. Figure 1a gives the typical voltage profile of Li plating/stripping on Cu substrate using different current densities varying from 0.2 to 10 mA/cm2. A pair of well-defined charge/discharge plateaus can be distinguished for all the voltage curves with applied current densities up to 10 mA/cm2, and almost all the Li deposition capacity can be recovered during the stripping process as seen from the charge capacity. The voltage polarization at 0.2 mA/cm2 is as low as 13 mV, and just slightly increases to 122 mV at 4 mA/cm2. Even when the current density increases to 10 mA/cm2, the voltage polarization is still only 270 mV. The average Coulombic efficiency of the cycling is > 99% (0.2, 0.5, and 1 mA/cm2), 98% (4 mA/cm2), 97% (8 mA/cm2), 96.7% (10 mA/cm2), respectively. Long term cycle tests as shown in Figure 1b indicate the Coulombic efficiency keeps stable without any decrease up to 400 cycles, manifesting an extraordinary cycling stability of Li metal in this electrolyte. These results provide a route for future efforts to optimize electrolytes for the safe and highly efficient utilization of Li metal electrodes for advanced energy storage applications. Detailed electrochemical characterization and study of the fundamental mechanisms behind the high rate Li cycling and stability of the electrolytes will be discussed in the presentation. Figure 1. Electrochemical performance of Li metal plating/stripping with a concentrated LiFSI-DME electrolyte: (a) Voltage profile of Li plating/stripping on Cu substrate using different current densities. (b) Coulombic efficiency of Cu|Li cells at different current densities. Acknowledgements This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the Basic Energy Sciences, Office of Science of the U.S. DOE. References W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang and J.-G. Zhang, Energy Environ. Sci., 7, 513-537 (2014).D. Aurbach, E. zinigrad, Y. Cohen, and H. Teller, Solid state ionics, 148, 405-416 (2002).F. Ding, W. Xu, X. Chen, J. Zhang, M. H. Engelhard, Y. Zhang, B. R. Johnson, J. V. Crum, T. A. Blake, X. Liu, J.-G. Zhang, J. Electrochem. Soc. 160, A1894-A1901 (2013).F. Ding, W. Xu, G. L. Graff, J. Zhang, M. L. Sushko, X. Chen, Y. Shao, M. H. Engelhard, Z. Nie, J. Xiao, X. Liu, P. V. Sushko, J. Liu, J.-G. Zhang, J. Am. Chem. Soc., 135, 4450-4456 (2013).D. Lv, Y. Shao, T. Lozano, W. D. Bennett, G. L. Graff, B. Polzin, J. Zhang, M. H. Engelhard, N. T. Saenz, W. A. Henderson, P. Bhattacharya, J. Liu and J. Xiao, Adv. Energy Mater., DOI: 10.1002/aenm.201400993 (2014). Figure 1

Investigation of Lithium-Ion Diffusion and Irreversible Processes in Dual-Ion Cell

In 2012 Placke et al. proposed so called „dual-ion cells“ as a new type of energy storage system. They reported an extraordinary cycling stability with a capacity retention of more than 99% after 500 cycles. Even though the achievable cell voltage in this kind of cells is about 4.6 V, the specific energy is still quite low compared to common lithium-ion batteries. The reason for this is a fundamental difference from conventional lithium-ion batteries, since not only the electrodes, but also the electrolyte acts as active material. During charging, lithium cations are reduced and deposited at a metallic lithium anode, while the anions are intercalated into graphite. During discharging, anions and cations are released back into the electrolyte (see figure 1).[1] Therefore the electrolyte acts as ion source, and the concentration hereby limits the energy density. As the cell voltage of “dual-ion cells” is very high the electrolyte needs to have a wide electrochemical window. For this reason, typically ionic liquid based electrolytes are used for this application. However, the concentration of lithium salts in ionic liquids is strongly limited due to solubility, increasing viscosity and decreasing conductivity.[2] During cycling the concentration underlies changes due to the extraction of lithium salt. This fact gives the possibility to investigate fundamental processes during charging and discharging by measuring the electrolyte resistance. In this work we therefore use electrochemical impedance spectroscopy in 2- and 3-electrode setup to gather information about diffusion processes in the electrolyte and about the reversibility of the processes during charging and discharging. Figure 1: Functionality of a dual-ion cell (derived from [1]). [1] T. Placke, P. Bieker, S. F. Lux, O. Fromm, H.-W. Meyer, S. Passerini, M. Winter, Zeitschrift für Physikalische Chemie, 226, 391 (2012). [2] T. Frömling, M. Kunze, M. Schönhoff, J. Sundermeyer, B. Roling, Journal of Physical Chemistry B, 112, 12985 (2008). Figure 1

Mesoporous Mn3 O4 Nanobeads/Graphene Hybrids: Facile Gel-Like Film Synthesis, Rational Structure Design, and Excellent Performance for Lithium Storage

Mesoporous Mn3O4 nanobeads are uniformly dispersed on the surface of graphene via a facile gel-like film method proposed for the first time with the help of H2O2. Graphene can effectively improve the intrinsically poor conductivity of Mn3O4, whereas the mesopores can accommodate the huge volume swings during the repeated lithiation/delithiation processes. The Mn3O4/graphene displays extraordinary cycling stability and excellent rate performance.

MnO2 nanoflakes/hierarchical porous carbon nanocomposites for high-performance supercapacitor electrodes

A facile strategy is developed for the synthesis of MnO2 nanoflakes/hierarchical porous carbon spheres (HPCs) nanocomposites via a two-step redox process. The external MnO2 nanoflakes with thickness of ∼10nm deposited on the surface of the HPCs result in the formation of hierarchical architecture of the composites, while the internal MnO2 layer stabilizes the interaction between MnO2 nanoflakes and HPCs. The resultant composites still retain porous structure after removal of mesoporous SiO2 template and exhibit relatively high specific surface area. The morphology control of the composites can be easily achieved by varying the initial content of Mn(NO3)2 and KMnO4. Electrochemical performance of the composites as supercapacitor electrode materials was evaluated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy techniques. The MnO2 nanoflakes/HPCs composite with 75wt% MnO2 possesses the highest specific capacitance at a high scan rate or current density (417.2Fg−1 at 20mVs−1 and 326.9Fg−1 at 1Ag−1, respectively) and extraordinary cycling stability (slightly over 100% capacitance retention after 10000 cycles at a scan rate of 100mVs−1), which are superior to other reported MnO2/carbon composites. The results suggest that rational design and synthesis of MnO2/porous carbon composite electrode materials with maximum electrochemical active sites is important to further improve their electrochemical performance.

Graphene and maghemite composites based supercapacitors delivering high volumetric capacitance and extraordinary cycling stability

Metal oxides (like MnO2, Fe2O3, and Co3O4, etc) based supercapacitors have disadvantages, such as low volumetric capacitance for thick-film electrodes, or short cycling life because a Faradaic process involves chemical changes of state of the reactant species. In the present work, we report that supercapacitors based on reduced graphene oxide and maghemite (γ-Fe2O3) composites (GγM) exhibit superior performance. GγM electrodes with average electrode thickness up to ∼60μm have a high volumetric capacitance of 230Fcm−3, together with an outstanding electrode package density of 1.44gcm−3. Particularly, the GγM electrodes have excellent cycling performance of ∼90% capacitance retention over 100,000 galvanostatic charge–discharge cycles or voltage floating at 0.9V for 300h. No detectable change in phase and an effective inhibition of γ-Fe2O3 refinement after cycle-life test are confirmed by X-ray diffraction and transmission electron microscopy.

Synergistically engineered self-standing silicon/carbon composite arrays as high performance lithium battery anodes

Self-standing, ordered arrays of uniform Si/C wire-in-tube nanocomposites are developed, showing high specific capacity and extraordinary cycling stability whilst delivering competitive areal capacity.

Electrochemical hydrogen storage properties of TixV65−xNi35 (x=45, 55) alloys produced by rapid-quenching

Electrochemical discharge performances of TixV65−xNi35 (x=45, 55) alloy are measured by electrochemical measurements at galvanostatic conditions, and alloy ribbon is prepared by rapid-quenching under argon atmosphere. XRD analysis of TixV65−xNi35 (x=45) alloy shows that the Ti45V20Ni35 (x=45) is mostly the amorphous phase, V-based solid solution phase with BCC structure phase and a negligible amount of (Ni, V) phase. While x=55, namely the Ti55V10Ni35 alloy, mainly consists of the icosahedral quasicrystal (I-phase), face centered cubic (FCC) phase with Ti2Ni-type structure and V-based solid solution phase with BCC structure phase. In the electrochemical tests, the maximum discharge capacity of Ti45V20Ni35 is about 150.4mAh/g at a current density of 30mA/g. However, Ti55V10Ni35 alloy shows that the best discharge capacity is 221.8mAh/g under the same condition. In addition, it exhibits extraordinary cycling stability of 87.2% at 30 charge–discharge cycles. It can be found that the discharge capacity of the amorphous electrode is lower than those of the I-phase ones under the similar composition levels.

Solid-state synthesis of submicron-sized Li4Ti5O12/Li2TiO3 composites with rich grain boundaries for lithium ion batteries

Submicron-sized Li4Ti5O12/Li2TiO3 composites with Li-rich grain boundaries are successfully synthesized by a simple, environmentally benign, mass production preferred solid state process. The crystal phase and morphology are characterized by XRD and SEM. The electrochemical performance is collected by galvanostatic discharge–charge tests, cyclic voltammograms (CV) and electrochemical impedance spectra (EIS) tests. The initial discharge capacity of Li4Ti5O12/Li2TiO3 composite is 155 mAh g−1 at 0.5 C. While the current rate is as high as 10 C, the specific capacity is 113 mAh g−1, and the capacity retention is 98.2% even after 500 cycles. As a reference, the ionic conductivity and the electrochemical performance of Li2TiO3 and Li4Ti5O12/TiO2 composite are also characterized. The extraordinary high rate performance and cycling stability are explained by high ionic conductivity and rich grain boundaries of Li4Ti5O12/Li2TiO3 composite.