Self-supporting Cathode Research Articles

Nickel-decorated TiO2 nanotube arrays as a self-supporting cathode for lithium-sulfur batteries

Lithium-sulfur batteries are considered to be one of the strong competitors to replace lithium-ion batteries due to their large energy density. However, the dissolution of discharge intermediate products to the electrolyte, the volume change and poor electric conductivity of sulfur greatly limit their further commercialization. Herein, we proposed a self-supporting cathode of nickel-decorated TiO2 nanotube arrays (TiO2 NTs@Ni) prepared by an anodization and electrodeposition method. The TiO2 NTs with large specific surface area provide abundant reaction space and fast transmission channels for ions and electrons. Moreover, the introduction of nickel can enhance the electric conductivity and the polysulfide adsorption ability of the cathode. As a result, the TiO2 NTs@Ni-S electrode exhibits significant improvement in cycling and rate performance over TiO2 NTs, and the discharge capacity of the cathode maintains 719 mA·h·g−1 after 100 cycles at 0.1 C.

Three-dimensional CoNi alloy nanoparticle and carbon nanotube decorated N-doped carbon nanosheet arrays for use as bifunctional electrocatalysts in wearable and flexible Zn-air batteries

A novel three-dimensional (3D) bifunctional electrocatalyst, CoNi alloy nanoparticle and carbon nanotube decorated N-doped carbon nanosheet arrays on carbon cloth (CoNi alloy/NCNSAs/CC) derived from polymetallic organic frameworks, is firstly prepared. The CoNi alloy/NCNSAs/CC-800 fabricated by pyrolyzing at 800 °C exhibits an oxygen reduction reaction (ORR, limiting current density) of 6.5 mA cm−2 and a superior oxygen evolution reaction (OER, at 10 mA cm−2) of 1.51 V, as well as a smaller potential difference of 0.676 V between OER and ORR half-wave potential, outperforming previous self-supporting cathodes. Flexible Zn-air batteries (FZABs) assembled with the CoNi alloy/NCNSAs/CC-800 exhibit higher energy density (98.8 mW cm−2) and higher capacity (879 mAh g−1), as well as excellent mechanical cycle ability (lower voltage gap of 0.66 V during the charge/discharge cycles at flat and folded state), significantly outstripping all other FZABs with self-supporting electrodes currently reported. Such a remarkable performance is ascribed to the 3D hierarchical nanostructure which promotes mass transport, the higher graphitization facilitating electronic mobility and the evenly dispersed active sites which accelerate kinetic reactions. So CoNi alloy/NCNSAs/CC-800 is a promising cathode candidate for ideal wearable energy devices and has great potential application in the field of electrochemical energy storage and conversion.

A Facile Synthesis of Monodispersed Na3V2(PO4)3 Nanospheres Anchored on Cellular Graphene Oxide as a Self-supporting Cathode for High-Rate Sodium Storage

Na3V2(PO4)3 (NVP) has been considered as a promising cathode for its high operating voltage and large capacity, though it suffers from an inherent low electronic conductivity and Na+ ion mobility. ...

P-doped ternary transition metal oxide as electrode material of asymmetric supercapacitor

Transition-metal oxides have been widely investigated in the fields of asymmetric supercapacitor electrode materials on account of the high specific capacitance, low cost, and environmentally benign nature. To overcome inherently slow reaction kinetics and limited electroactive sites of pure transition-metal oxides, we herein put forward a facile strategy for preparing P-doped Co0.21Ni0.79MoO4 on Ni foam, which is used as the self-supporting cathode for asymmetric supercapacitor. Compared with pure Co0.21Ni0.79MoO4, the optimized P-Co0.21Ni0.79MoO4 displays a high specific capacitance of 1127.5 F g−1 at 0.5 A g−1 and even at a ultrahigh current density of 20 A g−1, it also exhibits a specific capacitance of 547.1 F g−1. The optimized P-Co0.21Ni0.79MoO4 exhibits outstanding electrochemical performance because they couple the merits of the high electrical conductivity of Co0.21Ni0.79MoO4, the high specific capacitance of P-Co0.21Ni0.79MoO4, the good mechanical stability of interconnected nanosheets arrays and the 3D hierarchical structure. Moreover, an asymmetric device assembled by the optimized P-Co0.21Ni0.79MoO4 and activated carbon delivers a high energy density of 49.2 Wh kg−1 at 747.7 W kg−1 as well as good cyclic stability.

Ultrahigh volumetric capacity enabled by dynamic evolutions of host-guest pairs in self-supporting lithium-sulfur batteries

Conductive porous carbons are promising sulfur host materials for improving mass and areal capacities in lithium-sulfur (Li–S) batteries, but they face a few congenital deficiencies, such as low tap density and weak entrapment ability toward lithium polysulfides (LiPS), resulting in poor volumetric performance. Herein, we report a self-supporting cathode based on electrochemical active graphene-like RuO2 (GRO) without the incorporation of any carbon hosts and additives to synchronously acquire high mass, areal and volumetric capacities. It has been certified that dynamic evolutions of both conductive GRO host and sulfur guest during cell operation expedite chemisorption/conversion of LiPS and regulate nucleation/growth of solid Li2S, which enables GRO-S with medium sulfur loading to achieve an almost theoretical capacity at 0.2 C. Remarkably, the electrode with higher sulfur loading of 8.4 mg cm−2 delivers mass, areal and volumetric capacities of 1225 mAh g−1, 10.3 mAh cm−2 and 1981 mAh cm−3 at 0.2 C, respectively. The volumetric capacity records the highest value in reported Li–S batteries. The cathode material reported in this work opens new avenues for the development of high-energy-density and long-life Li–S batteries.

A flexible LiFePO4/carbon nanotube/reduced graphene oxide film as self-supporting cathode electrode for lithium-ion battery

By a rational design and facile vacuum filtration, a flexible and free-standing LiFePO4/carbon nanotube/reduced graphene oxide film electrode is fabricated for lithium-ion batteries. The carbon nanotube and reduced graphene oxide substrates are favor of improving the conductivity of the electrode; meanwhile, the LiFePO4 particles can efficiently reduce aggregation between carbon nanotube and reduced graphene oxide. The resultant self-supporting LiFePO4/carbon nanotube/reduced graphene oxide electrode delivers excellent electrochemical performance beyond the metal-base electrode. After 100 cycles at 0.2 C, the capacity maintains 151 mAh g−1, nearly staying the same with initial value. Especially, at 10 C, the specific capacity still keeps 98 mAh g−1. Moreover, these findings in this work supply a means of manufacturing LiFePO4 electrode and urge the practical application of LiFePO4 in flexible facilities.

Stabilization of Li-Se Batteries by Wearing PAN Protective Clothing.

Lithium-selenium (Li-Se) batteries have recently attracted more and more attentions as new secondary battery systems due to the similarity but better performances than lithium-sulfur (Li-S) batteries. However, the dissolution of selenium in electrolytes results in low selenium utilization, concentration polarization, inferior capacities, and unstable cycling performances. Herein, 46.58 wt% of selenium is loaded on carbon cloths through the calcination process, which were directly used as self-supporting cathodes. Carbonized polyacrylonitrile (PAN) nanofiber membranes produced by electrospinning are worn as the protective clothing between the cathode and separator to avoid the loss and dissolution of selenium. The stabilization of Li-Se batteries was enhanced by introducing two interlayers, as expected, they exhibit a stable reversible average capacity of 590 mA h g-1 during 1000 cycles at a current density of 0.5 C (1 C = 675 mA g-1). No polyselenide formation is found during charging/discharging, and the effects of the introduced PAN interlayers on improving the stability and reducing the polarization of the assembled Li-Se batteries are confirmed by mechanistic characterizations. These regulated Li-Se batteries present great application potential in the future, and the design idea can also be promoted to explore other energy storage systems.

Poly(ionic liquid)-Based Quasi-Solid-State Copolymer Electrolytes for Dynamic-Reversible Adsorption of Lithium Polysulfides in Lithium-Sulfur Batteries.

The shuttle of the long-chain lithium polysulfides (LiPSs) is the main obstacle to the practical application of lithium-sulfur batteries. Herein, a poly(butyl acrylate/1-ethyl-3-vinylimidazole bis[(trifluoromethyl)sulfonyl]imide)-based quasi-solid-state copolymer electrolyte poly(ethylene glycol) diacrylate (PEGDA-P(BA-co-[EVIm]TFSI) QPE-IL) was prepared for lithium-sulfur batteries. The butyl acrylate component with abundant ester groups ensures the strong chemical capture for LiPSs. What is more, the introduction of ionic liquid ([EVIm]TFSI) can greatly improve the ionic conductivity and lithium-ion migration rate. More importantly, the dynamic-reversible adsorption of LiPSs was realized by chemical adsorption of ester-rich groups and electrostatic repulsion of free-moving negatively charged ions. As a result, the lithium-sulfur battery assembled by a reduced graphene oxide/carbon nanotube film@sulfur (rGOCTF@S) self-supporting cathode and QPE-IL displayed a high initial discharge capacity of 1179 mA h g-1, good cycling stability (72% capacity retention after 200 cycles at 0.5 C), and superior rate performance.

Triple-Layered Carbon-SiO2 Composite Membrane for High Energy Density and Long Cycling Li–S Batteries

Here we report a highly scalable yet flexible triple-layer structured porous C/SiO2 membrane via a facile phase inversion method for advancing Li-sulfur battery technology. As a multifunctional current-collector-free cathode, the conductive dense layer of the C/SiO2 membrane offers hierarchical macropores as an ideal sulfur host to alleviate the volume expansion of sulfur species and facilitate ion/electrolyte transport for fast kinetics, as well as spongelike pores to enable high sulfur loading. The triple-layer structured membrane cathode enables the filling of most sulfur species in the macropores and additional loading of a thin sulfur slurry on the membrane surface, which facilitates ion/electrolyte transport with faster kinetics than the conventional S/C slurry-based cathode. Furthermore, density functional theory simulations and visual adsorption measurements confirm the critical role of the doped SiO2 nanoparticles (∼10 nm) in the asymmetric C membrane in suppressing the shuttle effect of polysulfides via chemisorption and electrocatalysis. The rationally designed C/SiO2 membrane cathodes demonstrate long-term cycling stability of 300 cycles at a high sulfur loading of 2.8 mg cm-2 with a sulfur content of ∼75%. This scalable yet flexible self-supporting cathode design presents a useful strategy for realizing practical applications of high-performance Li-S batteries.

In suit synthesis of Fe3O4 on carbon fiber paper@polyaniline substrate as novel self-supported electrode for heterogeneous electro-Fenton oxidation

In this study, a self-supported CFP@PANI@Fe3O4 cathode with three-layer structure was fabricated using a two-step synthetic route and characterized to reveal the morphology, composition and electrochemical performance of the novel electrode. The as-prepared CFP@PANI@Fe3O4 electrode showed enhanced electrocatalytic performance for p-nitrophenol degradation in electro-Fenton (EF) process with boron-doped diamond (BDD) electrode as anode. The results showed that for CFP@PANI@Fe3O4 cathode, 20 mg L−1 of p-nitrophenol was almost degraded in 60 min and the removal efficiency of total organic carbon (TOC) was 51.2% under the condition of applied current density 5 mA cm−2 and initial pH 3.0, which accompanied with more effective mineralization current efficiency (MCE) and less energy consumption (EC) compared with CFP and CFP@PANI electrodes. This enhancement was due to the increased electrocatalytic ability of in suit grown Fe3O4 on the surface of conductive substrates. Further investigation indicated that the fabricated electrode retained a high level of stability after consecutive runs. The reasonable reaction mechanism of p-nitrophenol was finally proposed according to the analysis of radical trapping experiments and fluorescence spectra, in which the hydroxyl radical (·OH) was deemed to the primary active oxidants. This work demonstrates the enormous potential of establishing an EF system with an efficient self-supported cathode based on in suit Fe3O4 immobilization for environmental remediation.

Fiber network composed of interconnected yolk-shell carbon nanospheres for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are a promising candidate for next-generation energy storage devices. However, rapid performance decay at high-sulfur-loading condition is emerged as one of the main obstacles restricting the practical application of Li-S batteries. Here we develop a facile electrospinning method for synthesizing the interconnected yolk-shell carbon nanospheres assembled fiber network to construct self-supporting sulfur cathodes. Benefiting from high surface area, nitrogen atom doping, and synergetic effect between yolk and shell, the yolk-shell carbon fiber network is a promising sulfur hosting material for high-sulfur-loading Li-S batteries. With 70 wt% and 4 mg cm−2 of sulfur, the yolk-shell carbon fiber network derived self-supporting cathode exhibits a high capacity retention of 82.8% after 500 cycles at 1 C. In addition, the self-supporting cathode with 16 mg cm−2 of sulfur delivers a stable areal capacity of 15.5 mAh cm−2. This work provides a new strategy for the development of high-performance Li-S batteries.

Fabrication of electrospun trace NiO-doped hierarchical porous carbon nanofiber electrode for capacitive deionization

Trace nickel oxide-embedded hierarchical porous carbon nanofibers (CNF-NiO) were fabricated by electrospinning polyacrylonitrile-Ni(NO3)2 (PAN-Ni) followed by stabilization, carbonization and acid treatment. The resultant CNF-NiO was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, thermo gravimetric analysis and nitrogen adsorption-desorption isotherm. The NiO amount and porous structure can be tuned by varying the PAN/Ni ratio and acid treatment time. The electrochemical properties of the electrospun CNF-NiO nanofibers were analyzed by cyclic voltammetry and impedance method. The specific capacity of 157.9 F/g was obtained at the PAN/Ni mass ratio of 90:3 with 3 h HCl wash. This porous CNF-NiO composite has been applied as a self-supporting cathode for capacitive deionization. The desalination amount arrived at 6.2 mg/g, which is 3 times as high as that of the electrospun pure carbon fibers. Longer wash time leads to decreased capacitance and desalination performance.

Sulfur nanoparticles encapsulated in reduced graphene oxide nanotubes for flexible lithium-sulfur batteries

Rapid development of flexible electronic devices is promoting the design of flexible energy-storage devices. Lithium-sulfur (Li-S) batteries are considered as promising candidates for high energy density energy-storage devices. Therefore, flexible Li-S batteries are desired. In this study, we fabricated composite films of freestanding reduced graphene oxide nanotubes wrapped sulfur nanoparticles (RGONTs@S) by pressing RGONTs@S composite foams, which were synthesized by combining cold quenching with freeze-drying and a subsequent reduction process. These RGONTs@S composite films can serve as self-supporting cathodes for Li-S batteries without additional binders and conductive agents. Their interconnected tubular structure allows easy electron transport throughout the network and helps to confine the polysulfides produced during the charge/discharge process. As a result, the RGONTs@S composite films exhibited a high initial specific capacity, remarkable cycling stability, and excellent rate capability. More importantly, the RGONTs@S composite films can serve as electrodes in flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled using these electrodes and they displayed stable electrochemical performance at different bending states.

A carbon foam-supported high sulfur loading composite as a self-supported cathode for flexible lithium-sulfur batteries.

A binder-free, self-supported, flexible cathode is explored for application in flexible lithium-sulfur (Li-S) batteries. The cathode is constructed using nitrogen (N)-doped carbon foam/carbon nanotubes (CNTs) as the scaffold and filled with poly(3,4-ethylenedioxythiophene) (PEDOT)-encapsulated sulfur nanoparticles as the active material. The dense CNTs coated on the skeleton of the 3D N-doped foam enhance flexibility, and the highly conductive CNTs are crossed and twined together to create an interconnected skeleton for rapid electron transport. The conductive PEDOT shell of sulfur nanoparticles and the N-doping of the carbon foams restrain the dissolution of polysulfides through the enhanced chemisorption of lithium polysulfides. The best cathode with a sulfur loading of 2.6 mg cm-2 has an eminent capacity of 1395 mA h g-1 during the initial cycle at 0.1 C. Furthermore, freestanding cathodes are assembled into flexible Li-S batteries, which demonstrate significant achievement at various bending angles. The capacity fading rate is 0.16% per cycle at 30° after 120 cycles. Its high sulfur loading, high capacitance, and good flexibility make this cathode material a promising candidate for potential application in flexible electronics.

Hydrogen evolution activity enhancement by tuning the oxygen vacancies in self-supported mesoporous spinel oxide nanowire arrays

The development of facile strategies to tune the oxygen vacancy (OV) content in transition metal oxides (TMOs) is paramount to obtain low-cost and stable electrocatalysts, but still highly challenging. Taking NiCo2O4 as a model system, we have experimentally established a facile calcination and electrochemical activation (EA) methodology to dramatically increase the concentration of OVs and provide theoretical insight into how the concentration of OVs affects the performance of spinel TMOs towards the electrochemical hydrogen evolution reaction (HER). A self-supported cathode of OV-rich NiCo2O4 nanowire arrays was found to exhibit higher HER activity and better stability in alkaline media than its counterparts with fewer OVs. The electrocatalytic HER activity was in good agreement with the increasing concentration of OVs in the studied samples. A large current density of 360 mA·cm–2 was reached with an overpotential of only 317 mV. Additionally, such a facile strategy was able to efficiently generate OVs in other TMOs (e.g., CoFe2O4 and NiFe2O4) for enhanced HER performance. In addition, our theoretical results suggest that the increasing OV concentration reduces the adsorption energy of water molecules and their dissociation energy barrier on the surface of the catalyst, thus leading to performance improvement of spinel TMOs toward the electrochemical HER. This work may open a new avenue to increase the concentration of OVs in TMOs in a controlled manner for promising applications in a variety of fields.

Potassium‐Based α‐Manganese Dioxide Nanofiber Binder‐Free Self‐Supporting Electrodes: A Design Strategy for High Energy Density Batteries

AbstractThis work minimizes the passive components of electrodes and moves toward bridging the gap between actual and theoretical battery gravimetric energy density. Binder‐free self‐supporting (BFSS) cathodes were prepared from redox‐active, high aspect ratio, potassium α‐MnO2 nanofibers (K‐OMS‐2) by eliminating the binder and current collector. The electroactive and structural element, K‐OMS‐2, was prepared by using a scalable, moderate temperature, aqueous synthesis. The BFFS electrode approach allows fabrication of thick, high energy density electrodes with low impedance, with up to 10‐fold improvement in delivered specific energy relative to conventional cathodes. This could enable the design of high‐capacity large form factor cells, as required for applications demanding high energy content. In principle, this approach suggests a widely applicable paradigm for the construction of other BFFS electrodes through the targeted synthesis of other transition‐metal oxides with high aspect, fibrous morphologies.

Self-standing porous LiMn2O4 nanowall arrays as promising cathodes for advanced 3D microbatteries and flexible lithium-ion batteries

Three-dimensional self-supported cathode nanoarchitectures are the key to develop high-performance thin film lithium-ion microbatteries and flexible lithium-ion batteries. In this work, we have developed a facile “hydrothermal lithiation” strategy to prepare vertically aligned porous LiMn2O4 nanowall arrays, comprising highly crystallized spinel nanoparticles, on various conductive substrates without high temperature treatment. The “hydrothermal lithiation” can effectively convert Mn3O4 spinel nanowall arrays into LiMn2O4 spinel nanowall arrays without severe morphology change. The binder-free three-dimensional porous LiMn2O4 nanowall arrays exhibit high specific reversible capacity up to 131mAhg−1 (or 0.29mAhcm−2) as well as outstanding cycling stability and rate capability, making them promising as cathodes for both three-dimensional thin film lithium-ion microbatteries and flexible lithium-ion batteries. A flexible lithium-ion full cell is demonstrated by using LiMn2O4 nanowall arrays on carbon cloth as the cathode and Li4Ti5O12 nanowall arrays on carbon cloth as the anode. The flexible Li4Ti5O12//LiMn2O4 full cell device, employing three-dimensional nanoarchitectures for both cathode and anode, can deliver specific reversible capacities of 124.8mAhg−1 (based on the weight of cathode material) at 1C and 92.1mAhg−1 at 20C with excellent cycle performance. Our work demonstrates the great potential for flexible energy storage technology using low cost fabrication method of nanoarchitectures.

A nickel cobaltate nanoparticle-decorated hierarchical porous N-doped carbon nanofiber film as a binder-free self-supported cathode for nonaqueous Li–O2batteries

Rechargeable nonaqueous lithium–oxygen (Li–O2) batteries have been considered a promising power source candidate due to their high theoretical energy densities.

Effective recycling of manganese oxide cathodes for lithium based batteries

A facile cathode recycling process is demonstrated where the previously used binder-free self-supporting cathodes (BFSSC) are removed from a cell, heat treated, and then inserted into a new cell restoring the delivered capacity and cycle life.

Nitrogen-doped carbon cloth as a stable self-supported cathode catalyst for air/H2-breathing alkaline fuel cells

The power output of a fuel cell is limited by among others, the intrinsic activity of the active matrix and the mass transport of the products and reactants. Of equally crucial importance is the long-term durability of the cell components including the electrocatalysts. Herein, carbon cloth (CC) was functionalized with nitrogen-containing groups by treatment with NH3 at 400°C or by pyrolysis of a composite of polypyrrole on CC at 800°C. The resulting N-doped CC (NCC) was employed as an air-breathing cathode in a custom-made air/H2 alkaline fuel cell, serving as the current collector as well as catalytic matrix with enhanced oxygen transport. The cell exhibited high operational durability with only 2% loss in activity after 25 days and delivered a maximum power density of 120mWm−2 at a voltage of 0.35V. The concept of a self-supported highly stable metal-free catalyst and the breathing H2/air cell design provide platforms for the design and investigation of catalysts. Moreover, a higher cell voltage can be realized if the cell is operated under pressurized conditions or by replacing air with O2.