Binder-free Anode For Lithium-ion Batteries Research Articles

Vertically standing ultrathin MoS2 nanosheet arrays on molybdenum foil as binder-free anode for lithium-ion batteries

Layered MoS2 nanostructures are outstanding anode materials for lithium-ion batteries due to their potentially high capacity. Here, we report a flexible binder-free anode for LIBs, which was fabricated from vertically standing ultrathin MoS2 nanosheet arrays grown directly on a molybdenum foil as the current collector. The self-supported MoS2 nanosheet arrays exhibit high specific capacity (1041 mAh g−1 at a current density of 0.1 A g−1), good cycling stability (maintained 84% of the initial capacity after 40 cycles) and outstanding rate performance. The excellent performance should be ascribed to the short ionic diffusion length, good contact between the electrode materials and current collector, and easy transportation of lithium ions. And it also arises from the nano-/microscale pores and extensively exposed edges that effectively accommodate for the volume change of MoS2 nanosheets during the charge–discharge processes.

Folded-hand silicon/carbon three-dimensional networks as a binder-free advanced anode for high-performance lithium-ion batteries

Folded-hand silicon/carbon (Si/C) three-dimensional (3D) networks were fabricated by chemical vapor deposition coupled with ultrasonic atomization and successfully applied for a binder-free anode in lithium-ion batteries. The microstructure, morphology and electrochemical performance for Si/C 3D networks were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and galvanostatic charge-discharge tests. The repeated folded-hand units for Si/C composites are assembled into interconnected 3D networks. The folded-hand Si/C 3D networks show an outstanding charge capacity of 2277 mAh g−1 at 0.1 C, and still remain 2167 mAh g−1 after 100 cycles. They reveal an excellent rate capacity of 1848 mAh g−1 and capacity retention of 99% after 100 cycles at 2 C, the charge capacities of 862 mAh g−1 and capacity retention of 93% after 500 cycles at 5 C. The LiFePO4//Si-C full cell can maintain high capacity of 137 mAh g−1 and capacity retention of 92% after 500 cycles at 1 C rate. The superior electrochemical performance is attributed to the formation of three-dimensional folded-hand interconnected networks.

Solvent-controlled synthesis of mesoporous CoO with different morphologies as binder-free anodes for lithium-ion batteries

The solvent-controlled synthesis of mesoporous CoO with different morphologies was investigated through a facile route including hydrothermal reaction and subsequent calcination. By altering the solvent of reaction, CoO nanowires (CoO-NWs) and CoO polyhedron (CoO-PHn) were favorably loaded on nickel foam with robust adhesion. Compared with CoO-PHn, CoO-NWs for lithium storage has enhanced electrochemical performance in term of high reversible capacity and extraordinary rate capability. After 80 cycles, an outstanding reversible specific capacity for CoO-NWs was 1398 mA h/g at a current density of 200 mA/g. Furthermore, a reversible specific capacity was up to 1175 mA h/g even at a current density of 1000 mA/g. The extraordinary electrochemical property was owing to the presence of free voids, which significantly buffered the mechanical stress during the insertion/de-insertion process. In addition, one-dimensional (1D) morphology ensured a relatively short transmission route to accelerate electron transport.

One-step solid-phase synthesis of binder-free molybdenum disulfide/carbon fibers paper anode for high-performance lithium-ion batteries

A facile one-step solid-phase synthesis strategy is developed for synthesizing a binder-free molybdenum disulfide/carbon fibers paper (MoS2/CFP) anode. The microstructure, composition, morphology and electrochemical performances were investigated. It is found that the thin MoS2 layers are well anchored on the interlaced carbon fibers to form MoS2/CFP, which has mesoporous structure and large specific surface area of ∼18.8 m2g-1. As a result, the obtained MoS2/CFP anode exhibits a reversible capacity of 261 mAh·g−1 with 31.2% loading ratio of MoS2. After subtracting the capacity of CFP, the MoS2 in the composite anode delivers a reversible capacity of 539 mAh·g−1 and shows better cycle stability than commercial MoS2 after 100 cycles at 100 mA g−1. The remarkable electrochemical performances could be attributed to the buffer space among carbon fibers for the volume changes of MoS2 as well as the highly conductive carbon fibers network, suggesting that the MoS2/CFP is a promising binder-free anode for lithium-ion batteries.

Facile synthesis of mesoporous NiCo2O4 nanoneedle arrays on three dimensional graphene thin film grown on Ni foam for a high-performance binder-free lithium-ion battery anode

Mesoporous NiCo2O4 nanoneedle arrays on graphene film grown directly on a three-dimensional Ni foam have been fabricated by a facile hydrothermal method, accompanied by annealing under air atmosphere. The BET specific surface area of NiCo2O4@graphene film@Ni foam is as high as 47.65 m2 g−1. The porous composites served as a binder-free anode material for lithium-ion batteries display an excellent and stable electrochemical performance with high specific capacities of 1232 mAh g−1 at the current density of 500 mA g−1 over 100 cycles and 1493 mAh g−1 at the current density of 1500 mA g−1 after 230 cycles with Coulombic efficiency higher than 97%. Moreover, a fairly high rate capacity of 586 mAh g−1 retained even at a high current density of 8000 mA g−1. The outstanding electrochemical performance should be attributed to synergetic effect of NiCo2O4 nanoneedle arrays with mesoporous nature and high specific area as well as graphene substrate supporting, which can accommodate the volume variation during the electrochemical reactions and facilitate the ion and electron transmission.

Zn2SnO4-carbon cloth freestanding flexible anodes for high-performance lithium-ion batteries

Zn2SnO4-carbon cloth, prepared via the coherent growth of Zn2SnO4 on pre-functionalized carbon cloth, was employed as a freestanding and binder-free anode for lithium-ion batteries. The 2D Zn2SnO4 nano-plates were uniformly anchored on the surface of 1D carbon cloth to form a hierarchical structure, providing the fast Li-ion and electron exchange path and reducing the volume change during the Li-ion planting/stripping. The binder-free electrode delivered significantly enhanced electrochemical performance by maintaining a reversible capacity of 1510 mA h/g after 60 discharge-charge cycles at a current density of 100 mA/g compared with that of the Zn2SnO4. Systematic structural and electrochemical characterizations suggested that the synergistic effect between Zn2SnO4 nanoplates and carbon cloth was responsible for the high electrochemical performance. Therefore, this study would be of significance for promoting the application of binary transition metal oxides in lithium-ion batteries.

A novel flexible electrode of Fe3O4-embedded in carbon felt as binder-free anode for lithium-ion batteries

The paper reports a novel flexible electrode based on Fe3O4-embedded in carbon felt via a facile hydrothermal method. As a binder-free anode for Lithium ion batteries, it exhibits a stable reversible capacity of 590 mA h g−1 after 100 cycles at a current density of 200 mA g−1, together with modified rate capability. The improved lithium storage properties can be attributed to the synergistic effect between nano-sized embedded Fe3O4 and carbon felt substrate. The elastic carbon fibers are beneficial for alleviating the volume expansion of Fe3O4 during continuous discharge/charge cycling. Besides, the designed structure leads to shorter ion transport path and better diffusion of electrolyte, resulting in the enhanced rate capacity and reversible capacity. The structure, morphology and the electrochemical performances of Fe3O4/carbon felt electrode for flexible Lithium ion batteries are analyzed in details.

Facile synthesis of three-dimensional Cu/Fe3O4 nanowires as binder-free anode for lithium-ion batteries

A three-dimensional (3D) Cu/Fe3O4 anodematerial was synthesized successfully via a simple and flexible route. Cu nanowires grew on Cu sheet directly by oxidation and reduction as 3D current collector, Fe3O4 nanosheets were coated on the collector surface by electrodeposition to form 3D Cu/Fe3O4 nanocomposite. The characterization results showed that oxidation time affects the morphology of Cu nanowires greatly, the collector has optimum 3D nanostructure at 200 s oxidation with high performance. The 3D Cu/Fe3O4 anode possessed high cycling capability, the capacity reached 700 mAh/g after 300 cycles at 0.5 A/g. And it exhibited high rate performance, the capacity reached 482 mAh/g at 2 A/g and it recovered to 853.5 mAh/g at 0.2 A/g after 100 cycles of different rate tests. The high performance is ascribed to the unique 3D nanostructure of current collector, which provides sufficient space for large volume change and stress release, and reduces the distance for transporting lithium ions and electrons.

Multishelled Si@Cu Microparticles Supported on 3D Cu Current Collectors for Stable and Binder-free Anodes of Lithium-Ion Batteries.

Silicon has proved to be a promising anode material of high-specific capacity for the next-generation lithium ion batteries (LIBs). However, during repeated discharge/charge cycles, Si-based electrodes, especially those in microscale size, pulverize and lose electrical contact with the current collectors due to large volume expansion. Here, we introduce a general method to synthesize Cu@M (M = Si, Al, C, SiO2, Si3N4, Ag, Ti, Ta, SnIn2O5, Au, V, Nb, W, Mg, Fe, Ni, Sn, ZnO, TiN, Al2O3, HfO2, and TiO2) core-shell nanowire arrays on Cu substrates. The resulting Cu@Si nanowire arrays were employed as LIB anodes that can be reused via HCl etching and H2-reduction. Multishelled Cu@Si@Cu microparticles supported on 3D Cu current collectors were further prepared as stable and binder-free LIB anodes. This 3D Cu@Si@Cu structure allows the interior conductive Cu network to effectively accommodate the volume expansion of the electrode and facilitates the contact between the Cu@Si@Cu particles and the current collectors during the repeated insertion/extraction of lithium ions. As a result, the 3D Cu@Si@Cu microparticles at a high Si-loading of 1.08 mg/cm2 showed a capacity retention of 81% after 200 cycles. In addition, charging tests of 3D Cu@Si@Cu-LiFePO4 full cells by a triboelectric nanogenerator with a pulsed current demonstrated that LIBs with silicon anodes can effectively store energy delivered by mechanical energy harvesters.

Synthesis of heterostructure Sn|SnO2 submicron particles supported by carbon fibers as binder-free anodes for highly reversible lithium storage

Tin-based materials are considered to be next-generation anode materials for lithium-ion batteries (LIBs) due to their high theoretical capacity and safety, but their large volume expansion results in rapid capacity fading. In this work, the heterostructure of Sn|SnO2 submicron particles supported by carbon fibers and amorphous carbon layers (CF/Sn|SnO2@C) is successfully synthesized by hydrothermal and thermal treatments. Sn|SnO2 submicron particles are uniformly grown on CF and encased in the CF network. Herein, CF together with a layer of amorphous carbon not only buffers the volume change of Sn|SnO2 to prevent its pulverization and dissolution but also improves the electric and lithium ionic transportation capabilities during the lithiation/delithiation cycle. The CF/Sn|SnO2@C film can directly act as a binder-free anode for LIBs, exhibits a stable capacity of 657.6 mAh g−1 at a current density of 0.1 A g−1 after 50 cycles and presents better rate capacities than the Sn|SnO2@C comparison sample. Taking advantage of the stabilization and conductive channels of CF, this work demonstrates potential applications in the preparation of CF-based, binder-free anodes for LIBs in which metal oxide submicron particles can be effectively supported by a CF network.

Electrochemically controllable coating of a functional silicon film on carbon materials

A silicon deposit of various forms was successfully coated on graphite by electrodeposition in molten CaCl2 containing nano-SiO2 as a silicon precursor. The morphologies of the deposited silicon can be tuned from Si nanowires to a dense film by controlling constant electrolysis cell voltage. In addition to controlling electrochemical polarizations, the substrate plays a key role in forming a dense silicon film. By analyzing the interface between the Si film and graphite substrate, a thin transition layer comprising of Si, SiC and C enables the good adhesion of the Si film with the carbon substrate and thereby helps the growth of a dense Si film. Besides the application for photovoltaics, the electrolytic p-type Si film was employed as a binder-free anode for lithium-ion batteries delivering a capacity of over 2500 mAh g−1 in the first 10 cycles and retaining 800 mAh g−1 after 40 cycles. Moreover, this method was applied for coating Si on carbon fibers, which could be a general way to prepare Si with controllable forms and silicon/carbon core-shell structures for functional materials.

High-yield fabrication of graphene-wrapped silicon nanoparticles for self-support and binder-free anodes of lithium-ion batteries

Composites of graphene-wrapped Si nanoparticles (NPs) have been assembled via a one-pot liquid nitrogen fast freezing followed by a thermal reduction. It is found that, as a self-support and binder-free anode of lithium-ion battery, the composited graphene is helpful to form a uniform morphology, reduce the resistance of the electrode and isolate the Si NPs from the electrolyte to suppress the formation of unstable solid electrolyte interphase. Moreover, it can buffer the strain from the volume change of the Si NPs. The composite with an optimized mass ratio of reduced graphene oxide (rGO) to Si NPs exhibits significantly improved lithium storage performance with an excellent rate capability and a large reversible capacity of 1482 mAh g−1 at a current density of 210 mA g−1 after 300 cycles. Furthermore, the electrochemical reaction kinetics and interfacial behavior of the rGO/Si composites are investigated in-depthly. The work reported here can be extended to the fabrication of the other graphene-based materials.

CTAB-assisted growth of self-supported Zn2GeO4 nanosheet network on a conductive foam as a binder-free electrode for long-life lithium-ion batteries.

The Ge-based compounds show great potential as replacements for traditional graphite anode in lithium-ion batteries (LIBs). However, large volume changes and low conductivity of such materials result in a poor electrochemical cycling and rate performance. Herein, we fabricate a self-supported and three-dimensional (3D) sponge-like structure of interlinked Zn2GeO4 ultrathin nanosheets anchored vertically on a nickel foam (ZGO NSs@NF) via a simple hydrothermal process assisted by cetyltrimethyl ammonium bromide (CTAB). Such robust self-supported hybrid structures greatly improve the structural tolerance of the active materials and accommodate the volume variation that occurs during repeated electrochemical cycling. As expected, the self-supported ZGO NSs@NF composites demonstrate an excellent lithium storage with a high discharge capacity, a long cycling life, and a good rate capability when used as binder-free anodes for LIBs. A high reversible discharge capacity of 794 mA h g-1 is maintained after 500 cycles at 200 mA g-1, corresponding to 81% capacity retention of the second cycle. Further evaluation at a higher current density (2 A g-1) also delivers a reversible discharge capacity (537 mA h g-1) for this binder-free anode. This novel 3D structure of the self-supported ultrathin nanosheets on a conductive substrate, with its volume buffer effect and good interfacial contacts, can stimulate the progress of other energy-efficient technologies.

A 3D MoOx/carbon composite array as a binder-free anode in lithium-ion batteries.

Molybdenum(vi) oxide (MoO3) nanorod arrays were synthesized employing a template-assisted method. A polycarbonate membrane as a template was vacuum infiltrated with an aqueous solution of ammonium heptamolybdate. Template removal by oxygen plasma etching and calcination leads to the formation of highly crystalline 3D MoO3 nanorod arrays as a negative replica of the template. By applying sucrose as the carbon precursor, the mantling of the MoO3 nanorods with a thin carbon coating is obtained. Simultaneously, the direct and binder-free contact between the 3D MoOx nanorod arrays and the current collector resulting from the carbon coating could be achieved and leads to high capacities of up to 1376, 783, 856, 804 and 324 mA h g-1 for cycles 1, 2, 20, 50 and 200 as well as a coulombic efficiency of 99% for such 3D MoOx/C composite electrodes. The cycling performance of this 3D MoOx/C composite material is even more impressive, when comparing the determined experimental capacities with the theoretical capacities of graphite (372 mA h g-1) and MoO2 (838 mA h g-1). Additionally, MoO3 nanorod array electrodes without such an encapsulating carbon coating show an average capacity of only 175 mA h g-1 between cycles 20 and 200. Thus, the carbon coating of the MoO3 nanorod array can increase the electrochemical performance of a lithium-ion cell compared to conventional carbon additives when using MoO3 as the active anode material. This emphasizes the positive effects of the intimate and efficient electron transport and large surface area of the electrode material based on a minimal footprint architecture in Li-ion cells.

Enhanced electrochemical performance of an electrospun carbon/MoO2 composite nanofiber membrane as self-standing anodes for lithium-ion batteries

A flexible carbon nanofiber membrane (NFM) containing uniformly dispersed MoO2 nanoparticles is facilely fabricated via electrospinning and subsequent controlled reduction-carbonization. This NFM is used directly as a binder-free anode in lithium-ion batteries (LIBs). The self-standing carbon/MoO2 (C/MoO2) NFM electrode has a good capacity retention, a satisfactory rate capability and a high reversible capacity of 811 mAh g–1 after 100 cycles at a current density of 100 mA g–1, which is superior to most other MoO2-based anodes. The superior electrochemical properties of the resultant C/MoO2 NFM are attributed to the cooperative effects from the excellent conductivity of the carbon nanofiber matrix, the high electrochemical performance of MoO2, the unique one-dimensional nanofiber structure and the three-dimensional porous network structure. The present C/MoO2 NFM may be an attractive candidate as an anode material for LIBs.

Mechanically robust and size-controlled MoS2/graphene hybrid aerogels as high-performance anodes for lithium-ion batteries

Controllable layered MoS2 on 3D graphene aerogel (MoS2/GA) was synthesized via a facial hydrothermal process. As-prepared MoS2/graphene hybrid aerogels with desirable sizes serve directly as free-standing and binder-free anodes for lithium-ion batteries (LIB) without the need for mechanical cutting or mixing. The mechanical properties of MoS2/GA samples were quantitatively investigated to demonstrate their high mechanical robustness with Young’s modulus values up to 59.2 kPa and recoverable deformability of 90% elastic strain, indicating their ability to resist large-scale deformation or fatigue stress during LIB applications. Moreover, the effects of the MoS2 mass loading on both microstructure and electrochemical performance of MoS2/GA were systematically investigated. Hierarchical nanostructures of MoS2/GA with a mass ratio of MoS2 to graphene oxide as 1:2.5 exhibit a high specific capacity of 1360.5 mAh g−1 at a current density of 100 mAh g−1. These materials also have desirable rate capability and good cyclic stability, demonstrating their utility in energy storage devices.

Flexible Co0.85Se nanosheets/graphene composite film as binder-free anode with high Li- and Na-Ion storage performance

A free-standing Co0.85Se nanosheets/graphene (Co0.85Se NSs/G) composite film was developed as a high performance anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) by a simple vacuum filtration and thermal reduction process. The Co0.85Se NSs/G film demonstrates good flexibility, and the Co0.85Se NSs are uniformly anchored on the graphene to form “sheet-on-sheet” nanostructures with strong interfacial interactions. The hybrid lamellar film demonstrated excellent electrochemical performances when used as a binder-free anode for LIBs and SIBs. As an anode material for LIBs, the Co0.85Se NSs/G film exhibited a high initial reversible capacity of 680 mA h g−1 at 50 mA g−1 and an excellent cycling stability and rate performance. The specific capacity of the Co0.85Se NSs/G film shows almost no fading from 0.05 to 0.5 A g−1, and the capacities were maintained at 613.3 and 522.7 mA h g −1 at 1 and 2 A g−1, respectively. When used as an anode for SIBs, the reversible capacity of the Co0.85Se NSs/G film reached up to 388 mA h g−1 with an initial coulombic efficiency as high as 82.5% at 50 mA g−1. Even at the higher current densities of 1 and 2 A g−1, the reversible capacities remained at 137.5 and 112.4 mA h g−1 after 500 cycles, respectively. The excellent electrochemical performances should be attributed to the special structure of the Co0.85Se NSs/G film. On one hand, graphene not only provides an efficient electrically conductive network, but also acts as an elastic layer to buffer the volumetric expansion of the Co0.85Se NSs during the discharge/charge process in LIBs/SIBs, which is helpful for enhancing the cycling stability of the Co0.85Se NSs/G film. On the other hand, strong interfacial interactions can further enhance electron transfer between Co0.85Se NSs and graphene, which is beneficial for improving the cycling stability and rate-performance of the Co0.85Se NSs/G film.

Red Phosphorus-Embedded Cross-Link-Structural Carbon Films as Flexible Anodes for Highly Reversible Li-Ion Storage.

Red phosphorus (P) is considered to be one of the most attractive anodic materials for lithium-ion batteries (LIBs) due to its high theoretical capacity of 2596 mAh g-1. However, intrinsic characteristics such as the poor electronic conductivity and large volume expansion at lithiation impede the development of red P. Here, we design a new strategy to embed red P particles into a cross-link-structural carbon film (P-C film), in order to improve the electronic conductivity and accommodate the volume expansion. The red P/carbon film is synthesized via vapor phase polymerization (VPP) followed by the pyrolysis process, working as a flexible binder-free anode for LIBs. High cycle stability and good rate capability are achieved by the P-C film anode. With 21% P content in the film, it displays a capacity of 903 mAh g-1 after 640 cycles at a current density of 100 mA g-1 and a capacity of 460 mAh g-1 after 1000 cycles at 2.0 A g-1. Additionally, the Coulombic efficiency reaches almost 100% for each cycle. The superior properties of the P-C films together with their facile fabrication make this material attractive for further flexible and high energy density LIB applications.

Electrostatically Assembled Magnetite Nanoparticles/Graphene Foam as a Binder-Free Anode for Lithium Ion Battery.

Lithium ion batteries (LIBs) are promising candidates for energy storage, with the development of novel anode materials. We report the fabrication of Fe3O4 nanoparticles/graphene foam via electrostatic assembly and directly utilize it as a binder-free anode for LIBs. Owing to the integrated effect of the well-dispersed Fe3O4 nanoparticles and the conductive graphene foam network, such composite exhibited remarkable electrochemical performances. It delivered a large reversible specific capacity reaching to ∼1198 mAh g-1 at a current density of 100 mA g-1, a good rate capacity, and an excellent cyclic stability over 400 cycles. This work demonstrated a facile methodology to design and construct high-performance anode materials for LIBs.

Forcespinning: An Alternative Method to Produce Metal-Oxides/Carbon Composite Fibers as Anode Materials for Lithium-Ion Batteries

We present results on the Forcespinning (FS) of Metal-oxides (MOx)/PAN fiber precursors for the mass production of MOx/C composite fibers as anode materials for Lithium-ionbatteries. Metal oxides such as NiO, CuO, ZnO and SnO2, were chosen with carbon fiber matrix as the active materials for the composite fiber anodes. The microfiber preparation process involved the FS of MOx/PAN precursors into microfibers and subsequent stabilization in air at 280ºC and calcination at 700ºC under Argon atmosphere. The MOx/C composite fiber anodes exhibited a specific discharge capacity between 300 and 800 mAhg-1 at the first cycle and a high irreversible capacity. The initial high irreversible capacity observed for most MOx/C composite fibers, was attributed to the formation of the SEI layer and the high surface area of the Forcespun composite microfibers. In the subsequent cycles, the MOx/C composite fiber anodes exhibited a much stable cycling performance, .i.e. 200-300 mAhg-1 was maintained after 100 cycles at 100 mAg-1. The observed electrochemical performance and the simple processing method of these MOx/C composite fibers makes them promising candidates for next generation and cost effective flexible binder-free anodes for Lithium-ion batteries.