Binder-free Anodes For Li-ion Batteries Research Articles

Efficient synthesis and lithium storage performance of SiO2/TiO2 composite film anode by plasma electrolytic oxidation

SiO2/TiO2 composite films with different phase ratios have been successfully fabricated via the one-step plasma electrolytic oxidation (PEO) method in an alkaline electrolyte on Ti foil to obtain a binder-free anode for Li-ion batteries. The formed composite films present porous morphology of TiO2 with a uniform distribution of SiO2. The specific capacity can stabilize above 400 mAh/g at the current density of 100 μA cm−2 for 500 cycles, together with the apparent improved initial coulombic efficiency of 88.7 % and excellent rate capability, which arises from the peculiar structure and the synergic enhancement effect of SiO2 active materials and TiO2 matrix. This work provides an efficient and low-cost route for the preparation of Li-ion battery binder-free anodes and enriches the application of plasma electrolysis technology in energy field.

CoS Nanosheets Coated with Dopamine-Derived Carbon Standing on Carbon Fiber Cloth as Binder-Free Anode for Li-ion Batteries

CoS Nanosheets Coated with Dopamine-Derived Carbon Standing on Carbon Fiber Cloth as Binder-Free Anode for Li-ion Batteries

Germanium decorated on three dimensional graphene networks as binder-free anode for Li-ion batteries

Three-dimensional (3D) graphene networks are successfully fabricated on nickel (Ni) foam by the chemical vapor deposition (CVD) technique. Amorphous Ge layer is then deposited on the 3D graphene supporting skeleton via the facile radio frequency magnetron sputtering (RFMS) method. The Ge decorated on the 3D graphene (3D Ge@Gr) networks deliver improved electrochemical performance when employed as anode for lithium ion batteries (LIBs), which is obvious superior than the two dimensional Ge nanoelectrode directly coated on the bare Ni foam (2D Ge). Significantly enhanced electrochemical cyclability upon 1500 long-term cycles under the higher current density of 1.2 mA cm−2 is accomplished in the optimized 3D Ge@Gr hybrid electrode. The interconnected 3D graphene with enlarge surface area can not only effectively provide enough space to buffer the volume change of the Ge anode during cycling, but also bring improved electrical/ionic conductivity to promote the electrochemical kinetics, thus eventually bring superb stable cyclability.

Binder-free silicon anodes wrapped in multiple graphene shells for high-performance lithium-ion batteries

Si-based composites wrapped in multiple graphene shells were successfully fabricated as binder-free anodes for Li-ion batteries (LIBs). Reduced graphene oxide (rGO) and Si nanoparticles were prepared as spherical composite structures using a facile spray-drying process. The microspheres were homogeneously incorporated into a 3D porous graphene aerogel (GA) structure using an aerogel synthesis process. The inner rGO shell surrounding the Si nanoparticles promoted an effective electron transfer from the surface of the Si nanoparticles to electrolytes and suppressed the continuous formation of an unstable solid–electrolyte interface layer. Moreover, the 3D, porous GA framework, which demonstrated high electrical conductivity and mechanical stability, promoted the homogeneous dispersion of the Si nanoparticles, an effective and fast Li+ ion diffusion, and the suppression of volume expansion during lithiation. The rGO/Si/GA composite anode constructed by multiple graphene shells had an extremely high initial discharge capacity (1217 mAh g−1), excellent cyclic stability (462 mAh g−1 at 1.0 C after 200 cycles), and superior rate capability (819 mAh g−1 at 10 C) owing to its multilayered structure. We expect that our simple and scalable approach for fabricating Si-based anodes wrapped in multiple graphene shells can contribute to the development of high-performance LIBs for use in electric vehicles.

3D Interconnected MoO2 Nanocrystals on Nickel Foam as Binder-free Anode for Li-ion Batteries

MoO2 nanocrystals (NCs) on Ni foam were simply synthesized via a facile hydrothermal method and a dip-coating method. It was worth noting that ultrafine interconnected MoO2 nanocrystals (about 10 nm) were uniformly anchored on Ni foam to fabricate a particular three-dimensional architecture, which may provide more active sites and shorter transmission pathways for lithium ions. As binder-free anode, MoO2 NCs on Ni foam deliver a high initial discharge capacity of 990 mAh·g-1 and retain a reversible capacity of 924 mAh· g-1 after 100 cycles at a current density of 0.1 C. More importantly, when the current density returns from 2 C to 0.1 C, the capacity recovers to 910 mAh·g-1 (about 92% of the original high capacity), suggesting excellent cycling stability and rate capability. The particular 3D electrode as binder-free anode makes it a promising anode candidate for high-performance lithium-ion batteries.

High Areal Capacity Li-Ion Storage of Binder-Free Metal Vanadate/Carbon Hybrid Anode by Ion-Exchange Reaction.

Storing more energy in a limited device area is very challenging but crucial for the applications of flexible and wearable electronics. Metal vanadates have been regarded as a fascinating group of materials in many areas, especially in lithium-ion storage. However, there has not been a versatile strategy to synthesize flexible metal vanadate hybrid nanostructures as binder-free anodes for Li-ion batteries so far. A convenient and versatile synthesis of Mx Vy Ox+2.5y @carbon cloth (M = Mn, Co, Ni, Cu) composites is proposed here based on a two-step hydrothermal route. As-synthesized products demonstrate hierarchical proliferous structure, ranging from nanoparticles (0D), and nanobelts (1D) to a 3D interconnected network. The metal vanadate/carbon hybrid nanostructures exhibit excellent lithium storage capability, with a high areal specific capacity up to 5.9 mAh cm-2 (which equals to 1676.8 mAh g-1 ) at a current density of 200 mA g-1 . Moreover, the nature of good flexibility, mixed valence states, and ultrahigh mass loading density (over 3.5 mg cm-2 ) all guarantee their great potential in compact energy storage for future wearable devices and other related applications.

SnO2 Nanowires on Carbon Nanotube Film as a High Performance Anode Material for Flexible Li-ion Batteries

Today, Li-ion batteries (LIBs) are the most common rechargeable batteries used in electronic devices. SnO2 with theoretical specific capacity of 782 mAh/g is among the best anode materials for LIBs. In this report, Three-dimensional SnO2 nanowires (NWs) on carbon nanotube (CNT) thin film (SnO2 / CNT) is fabricated using a combination of vacuum filtration and thermal evaporation techniques. The resulting 3D heterostructure SnO2/CNT was characterized by X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This fabricated SnO2/CNT electrode has been tested as a flexible and binder-free anode for LIB, which exhibits high initial discharge/charge capacity of 4.8/2.25 mAh/cm2 at a current density of 0.25 A/g, much larger than discharge/charge capacity of bare CNT film (2.2/0.3 mAh/cm2). Relatively high areal capacity of 1.23 mAh/cm2 has been achieved for the fabricated LIB with SnO2/CNT electrode after 20 cycles, proposing this material as a high performance flexible LIB anode material.

3D MnCo₂O4.5 Nanorod Arrays on Ni Foam as Binder-Free Anodes for Li-Ion Batteries.

It is a key to develop novel electrode materials with high energy and power density for advanced batteries to meet the demand of electric vehicles (EVs). Manganese cobalt oxides which can react with a large number of ions from the electrolyte for electrochemical energy storage are developing into the promising electrode materials. In this work, well-ordered MnCo2O4.5 nanorod arrays (MCO NRAs) are prepared on Ni foam by a general route of hydrothermal growth and low-temperature annealing treatment. The samples deliver a high initial capacity of 1402.6 mAh g-1 at the current density of 100 mA g-1 and rate capacity of 528 mAh g-1 when the current density is improved 10 times as binder-free anodes for Li-ion batteries (LIBs). After 60 cycles at the current density of 200 mA g-1, the MnCo2O4.5 nanorods still achieve 603 mAh g-1 with capacity retention of 66% (compared with the second discharge capacity). The superior electrochemical properties are due to the fascinating architecture which increases the reaction area and structural stability, reduces ion and electron transport distance and provides good strain release. Hence, MnCo2O4.5 nanorod arrays are promised as advanced anodes for future LIBs with completely meeting the demand of EVs.

Synthesis and Characterization of CuFe2O4 Nano/Submicron Wire-Carbon Nanotube Composites as Binder-free Anodes for Li-Ion Batteries.

A series of one-dimensional CuFe2O4 (CFO) nano/submicron wires possessing different diameters, crystal phases, and crystal sizes have been successfully generated using a facile template-assisted coprecipitation reaction at room temperature, followed by a short postannealing process. The diameter and crystal structure of the resulting CuFe2O4 (CFO) wires were judiciously tuned by varying the pore size of the template and the postannealing temperature, respectively. Carbon nanotubes (CNTs) were incorporated to generate CFO-CNT binder-free anodes, and multiple characterization techniques were employed with the goal of delineating the relationships between electrochemical behavior and the properties of both the CFO wires (crystal phase, wire diameter, crystal size) and the electrode architecture (binder-free vs conventionally prepared approaches). The study reveals several notable findings. First, the crystal phase (cubic or tetragonal) did not influence the electrochemical behavior in this CFO system. Second, regarding crystallite size and wire diameter, CFO wires with larger crystallite sizes exhibit improved cycling stability, whereas wires possessing smaller diameters exhibit higher capacities. Finally, the electrochemical behavior is strongly influenced by the electrode architecture, with CFO-CNT binder-free electrodes demonstrating significantly higher capacities and cycling stability compared to conventionally prepared coatings. The mechanism(s) associated with the high capacities under low current density but limited electrochemical reversibility of CFO electrodes under high current density were probed via X-ray absorption spectroscopy mapping with submicron spatial resolution for the first time. Results suggest that the capacity of the binder-free electrodes under high rate is limited by the irreversible formation of Cu0, as well as limited reduction of Fe3+ to Fe2+, not Fe0. The results (1) shed fundamental insight into the reversibility of CuFe2O4 materials cycled at high current density and (2) demonstrate that a synergistic effort to control both active material morphology and electrode architecture is an effective strategy for optimizing electrochemical behavior.

Facile synthesis of Co3V2O8 nanoparticle arrays on Ni foam as binder-free electrode with improved lithium storage properties

The Co3V2O8 nanoparticle arrays on Ni foam were synthesized by a simple one-step procedure using a low-temperature hydrothermal method. This architecture consisted of ultrafine Co3V2O8 nanoparticles with a mean size of 30–60nm, which covered homogeneously onto the porous Ni foam, forming a uniform film-like morphology. The Co3V2O8 nanoparticles not only provided sufficient electro-active interactions for Li-storages reaction, but also had good mechanical contact with the Ni foam, hence improving reaction kinetics and enhancing electrode integrity. When used as a new sort of binder-free anode for Li-ion batteries (LIBs), this unique electrode delivered high initial discharge capacity of 1586.9mAhg−1 at 200mAg−1 and retained at 1289mAhg−1 after 100 cycles, and the discharge capacity maintained at 1004.4mAhg−1 after 800 cycles at 500mAg−1. Even when the current was 10Ag−1, discharge capacity of 471.4mAhg−1 could be achieved. In addition, the charge/discharge mechanism of Co3V2O8 based on conversion and intercalation reaction routes were verified by ex-situ XRD diffraction. Therefore, the Co3V2O8 nanoparticle arrays on Ni foam might open a new insight for transition metal oxides as electrode materials for LIBs.

Nanoporous Anodic TiO2-TiO-TiN Composite Films with Enhanced Capacity As Anode Materials for Lithium Ion Batteries

Introduction. Recently, nanoporous or nano-tubular TiO2 films on Ti foils formed by anodization have attracted great attention as promising candidate anode materials for Li-ion batteries (LIBs) to substitute the commercially used graphite. TiO2 materials have a theoretical specific capacity of 330 mAh g-1, which is slightly lower than graphite of 372 mAh g-1. Importantly, TiO2 the operating potential of Li insertion is at ~1.8 V vs Li+/Li, which is much higher than graphite (0.2 V vs. Li+/Li), thus assuring an enhanced battery safety. Especially, nanostructured anodic TiO2 films can provide a high surface area that facilitates the intercalation of Li ions, with limited volume change less than 4% upon lithium insertion/deinsertion, thus improving the safety and lifetime of LIBs. Usually, anodic TiO2 films were formed by anodizing Ti foils in ethylene glycol containing corrosive F- ions and a small amount of water, which may cause environmental concerns. It is highly desirable to explore an aqueous electrolyte with less corrosion and low cost, considering on the practical applications. Therefore, the present study proposed a facile anodizing process to fabricate nanoporous TiO2-TiN composite films on Ti foils by using a nitric-based aqueous electrolyte system without containing corrosive F-ions. The microstructures, chemical composition, and the electrochemical charge-discharge performance as binder-free electrode materials for LIBs were investigated. Experimental. Titanium foils (99.5%, 20 × 40 × 0.1 mm) were used as staring specimens without mechanical or electro-polishing. The specimens, after ultrasonically cleaned for 10 min in acetone and then dried under flowing Ar gas were anodized in various acidic electrolytes containing NH+ and/or NO3 - ions in a constant current density or a voltage mode for 1 – 3 h. Moreover, in order to investigate the effects of crystalline structure of the nanoporous anodic TiO2-TiN films on the electrochemical properties, the anodic specimens were annealed at 423 – 573 K for 1 – 4 h. The morphology, chemical composition, chemical state, and crystalline structure of the anodized specimens before and after annealed were investigated FE-SEM, EDS, TEM (FIB), XRD, and XPS. Moreover, various TiO2-TiN composite films on Ti foils after heating at different temperatures were used as binder-free anodes for LIBs. The charge-discharge performances were investigated using a home-made pouch cell assembled in an Ar-filled glove box. The cathode was utilized with a lithium foil, and the electrolyte solution was made of 1M LiPF6 in a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) with a volumetric ratio of 1:1:1. The charge-discharge performances were investigated by using a multi-channel battery test unit in a galvanostatic mode over 1.0 – 3.0 V (vs. Li/Li+) at 303 K at 5 – 50 mA cm−2for 1 – 50 cycles. Results and Discussion. Figure 1a demonstrated a cross-sectional TEM image of as-anodized titania film on Ti foil. The anodic film possessed a nanoporous structure with cylindrical pores of ~Φ50 nm and nano-laminated layers with layer thickness of 250 – 600 nm, indicating a 3D nanostructure. Figure 1b shows the XRD patterns of the anodic titania film before and after annealed at 773 K for 4 h. The as-anodized specimen exhibited a crystalline structure with sharp peaks at 37.1º and 43.3º, close to the (111) and (200) facets of cubic TiO, as well as to TiN. Whereas the specimen after annealed delivered several new peaks that indexed to anatase TiO2. Figure 1c gives the XPS spectra of N1s for the as-anodized specimen. The spectrum for the film surface showed two peaks corresponding to NO3 - and NH+, whereas the spectra after Ar+ sputtering revealed a strong peak close to the binding energy of TiN, thus confirming the formation of TiO2-TiO-TiN composite film. Moreover, it was found that the performance or the specific area capacity of the nanoporous TiO2-TiO-TiN composite films was greatly dependent on the anodizing conditions and the crystalline structure. Especially, the anodized specimen after annealed at 523 K for 1 h exhibited the highest initial discharge capacity of 440 μAh cm-2 upon ~1 μm film, in a charge-discharge test as anode material for LIBs at a constant current density of 5 μA cm-2. Figure 1

High-performance nickel manganese ferrite/oxidized graphene composites as flexible and binder-free anodes for Li-ion batteries

The obtained binder-free and flexible free-standing Ni0.5Mn0.5Fe2O4/oxidized graphene (NMFO/OGP) and NMFO/OGP coated on polypropylene microporous film exhibited good electrochemical performance.

Homogeneously assembling like-charged WS2 and GO nanosheets lamellar composite films by filtration for highly efficient lithium ion batteries

It is well known that the nanocomponents with opposite charges can be easily assembled into hybrid composites via electrostatic interaction, but it is difficult for like-charged nanomaterials. Here, we developed a general method to directly assemble lamellar composite paper composed of both negative-charged WS2 and graphene oxide (GO) nanosheets from their aqueous dispersion through filtration process. After hydrothermal reduction, the flexible lamellar WS2/reduced-graphene oxide (rGO) paper was evaluated as binder-free anodes for Li-ion batteries, which presented a reversible capacity of 697.7mAhg−1 after 100 cycles, 8 times higher than 88.5mAhg−1 of pure WS2 nanosheets and 60.2mAhg−1 of rGO, excellent cyclic stability and good rate capacity. In the uniformly alternated lamellar structures, rGO nanosheets efficiently prevent the restacking of WS2 sheets, increase the conductivity of the electrode, and sustain the volume expansion during Li+ insertion/extraction, which significantly improved the electrochemical performances. This simple filtration assembling method provides a general and efficient way to synthesize functional composite films from like-charged colloid solutions.

PH-driven dissolution–precipitation: a novel route toward ultrathin Ni(OH)2 nanosheets array on nickel foam as binder-free anode for Li-ion batteries with ultrahigh capacity

In this paper, for the first time, we report on the growth of ultrathin Ni(OH)2 nanosheet arrays on a nickel foam (NF) via a novel pH-driven dissolution–precipitation route, carried out by a hydrothermal treatment of the NF in an acidic medium without the introduction of other nickel sources. Acid etching of the NF surface leads to nano-pits and produces Ni(H2O)n2+ ions at the early stage of the reaction. With the elapsed time, an increase in the pH level occurs and the Ni(H2O)n2+ ions gradually hydrolyze and preferentially precipitate on the nano-pits, serving as nucleation sites and leading to ultrathin Ni(OH)2 nanosheet arrays on an NF. The effects of the experimental parameters, such as reaction time, acid type and starting pH value, on the Ni(OH)2 growth are also investigated. Because the nano-pits are integrated parts of the NF and the deposition of Ni(OH)2 nanosheets on such nano-pits ensures intimate contact between them, the Ni(OH)2/NF is robust enough to withstand a violent sonication process and efficient and rapid electron transfer is achieved. As a binder-free anode for Li-ion batteries, the Ni(OH)2/NF exhibits an unexpected ultrahigh capacity of 1689 mA h g−1 and excellent cycling stability.