Electrodes For Flexible Lithium-ion Batteries Research Articles

Room temperature growth of NiS hierarchical nanoflowers on the flexible electrode surface as a cathode for lithium-ion batteries

A facile additive-free approach of cathode fabrication using a chemical bath deposition route is proposed to grow nickel sulfide nano-architectures on Ni foam at ambient conditions as a flexible electrode for lithium-ion batteries. The hierarchical nanostructure on the electrode surface provided high specific capacities of 437 and 360 mAh/g at current rates of 0.1 and 1.0C after 50cycles respectively, accompanied by Coulombic efficiency of about 100% after only 5 cycles. The designed electrodes offered a faster ion and electron transfer, a larger surface area, and a high degree of structural integrity.

Nano GeSe2/C anchored in carbon sponge skeleton for free-standing flexible lithium-ion battery electrodes

As a typical conversion alloyed anode material, Germanium selenide (GeSe2) exhibits isotropic lithiation behavior and high theoretical charge-discharge specific capacity. However, pure GeSe2 anode faces significant volume expansion (∼250 %−360 %) and further exploration is needed in the preparation of flexible electrode materials and structural design. Herein, a simple strategy is designed to load GeSe2/C-2 nanoparticles with porous carbon-coated structure on a flexible cross-networking substrate. The 3D network substrate is composed of highly conductive carbon nanotubes and adhesive cotton cellulose fibers. A two-step method involving coating and cross-linking is designed to achieve the fabrication of self-supporting flexible electrodes. As an anode for LIBs, the one layer GeSe2 discs with ∼0.65 mm thickness manifest capacities of 827.1, 744.4, 676.3, and 472.9 mAh g−1 at 0.1, 0.2, 0.5, and 1 A g−1, respectively. This superior Li+ storage performance can be attributed to the positive collective impact from the integration of nano-scale material, low crystalline properties, and carbon sponge skeleton. Furthermore, the GITT tests indicate that the diffusion coefficient of Li+ in the GeSe2-based electrodes ranged from 10−15 to 10−12 cm2/s, and the thickness of the flexible electrode (including two layers) has a negligible impact on its electrochemical performance.

Achieving high initial coulombic efficiencies and cycle stability of free-standing anodes by chemical prelithiation of carbon matrix

The influence of carbon matrix in freestanding electrodes for flexible lithium-ion batteries (LIBs) cannot be neglected because of the strong intercalation ability of Li+ which could result in low initial columbic efficiencies (ICEs). Based on electrostatic potential, inorganic lithium salts and graphene oxide (GO) with opposite zeta potential in ethanol is utilized as chemical prelithiation reagent, which enables a successful prelithiation of GO-based SnTiS3 anodes. By molecular dynamic calculation and experimental evaluation, the prelithiated GO matrix with enlarged layer distance enables an improved ion conductivity and suppresses Li consumption. Consequently, prelithiated free-standing membranes as anodes for LIBs can demonstrate significantly improved ICEs and capacity utilization compared with their counterparts without prelithiation. This strategy can shed new light on prelithiated free-standing electrodes with high performance for flexible wearable energy storage devices.

Textile Based Electrodes for Flexible Lithium-ion Batteries: New Updates

: The electrodes are the basis for building flexible lithium-ion batteries (FLIBs), and many attempts have been made to develop flexible electrodes with high efficiency in terms of electrical conductivity, chemical and mechanical properties. Most studies showed relatively satisfactory results when testing the electrochemical properties of laboratory-produced electrodes, but most of these electrodes could not meet the expected requirements of flexible electrodes in practical applications. Quantitative production faces many problems that must be overcome, such as the gradual decline in electrochemical performance, deformation of the electrode structure, high production costs, and difficulties in the production process itself. In this research, developments in the production of flexible electrodes, especially those that depend on carbon materials and metal nanoparticles, will be discussed and summarized in this research. The electrochemical performance and stability of the produced flexible electrodes will be compared. The factors contributing to the progress in the production of flexible lithium-ion batteries will also be discussed.

Flexible and robust silicon/carbon nanotube anodes exhibiting high areal capacities

The fast development of flexible devices has greatly boosted the demands for flexible lithium-ion batteries (LIBs). Accordingly, a broad exploration of flexible electrodes in LIBs is crucial. At present, the major challenge in the flexible electrode for lithium-ion batteries (LIBs) is how to achieve an excellent electrochemical performance (particularly high-energy density) while maintaining superior mechanical flexibility. Herein, flexible silicon/carbon nanotube (Si/CNT) electrode is prepared via a common blade-coating, which is adoptable to large-scale production. The CNT network from monodispersed CNT solution endows the electrode with superior tensile strength and mechanical toughness. The tensile strength of the flexible electrodes is up to 3.75 MPa, and the corresponding strain at break is 43.9%. The flexible electrode delivers an areal capacity of 10.6 mAh cm−2 at 0.06 mA cm−2, which is completely meet the practical requirement (1–3 mAh cm−2). And a high reversible capacity of 5.64 mAh cm−2 can be retained at 0.3 mA cm−2 after 200 cycles. In addition, the pouch cell exhibits a promising cycling stability under the repeated deformation state. Moreover, this work also provides a feasible and scalable method to fabricate flexible electrodes for other wearable energy storage systems.

Simple way of making free-standing cathode electrodes for flexible lithium-ion batteries.

The flexible electrodes used in the lithium-ion battery (LIB) offer an excellent opportunity to be bent and folded without deforming their electrochemical characteristics. However, a flexible electrode does not include metal foil as a current collector, limiting the LIB's flexibility and weakening the mechanical strength. This study fabricates flexible LiFePO4 (LFP) free-standing electrodes by a scalable and straightforward solution-based etching process. The obtained free-standing electrodes show capacities and bending performances that are similar to the conventional electrodes with aluminum current collectors. This study opens a new avenue for developing a free-standing electrode for low-cost and flexible lithium-ion batteries.

Preparation and Characterization of Carbonized Nano-Cellulose-Based Flexible Lithium-Ion Battery Electrodes

Preparation and Characterization of Carbonized Nano-Cellulose-Based Flexible Lithium-Ion Battery Electrodes

Multilayered interlaced SnO2 nanosheets @ porous copper tube textile as thin and flexible electrode for lithium-ion batteries

The flexible integrated electrode structural design is a promising strategy for improved electrochemical conductivity and mitigated volume expansion of metal oxides electrodes in lithium-ion batteries. Here, a series of SnO2 nanostructures is synthesized directly on porous copper tube textile substrate (TS) via a simple hydrothermal method and the shape-depended electrochemical properties are further investigated. As flexible electrodes with the thickness of ca. 7 μm, the interlaced SnO2 nanosheets grown on textile substrate (SnO2 NS@TS) can deliver a high reversible capacity of 0.35 mAh cm−2 at 400 μA cm−2 after 200 cycles. The multiplied capacity of 0.49, 1.13, 1.42 and 1.92 mAh cm−2 (at 200 μA cm−2) and superior rate performance are easily achieved in multilayered electrodes only with a slightly increase in impedance. It is revealed that the porous tubular framework of copper textile plays significant roles in constructing conductive network and promoting electrolyte penetration. Furthermore, benefiting from the high specific surface area, abundant pores and crystal boundaries of interlaced SnO2 nanosheets, the optimized SnO2 NS@TS electrodes are demonstrated with high lithium diffusion coefficient and capacitive effect, which boost excellent electrochemical performance. Thus, this novel electrode structural design is expected to provide useful instructions, especially for thin and flexible energy storage devices.

Review on carbonaceous materials and metal composites in deformable electrodes for flexible lithium-ion batteries.

With the rapid propagation of flexible electronic devices, flexible lithium-ion batteries (FLIBs) are emerging as the most promising energy supplier among all of the energy storage devices owing to their high energy and power densities with good cycling stability. As a key component of FLIBs, to date, researchers have tried to develop newly designed high-performance electrochemically and mechanically stable pliable electrodes. To synthesize better quality flexible electrodes, based on high conductivity and mechanical strength of carbonaceous materials and metals, several research studies have been conducted. Despite both materials-based electrodes demonstrating excellent electrochemical and mechanical performances in the laboratory experimental process, they cannot meet the expected demands of stable flexible electrodes with high energy density. After all, various significant issues associated with them need to be overcome, for instance, poor electrochemical performance, the rapid decay of the electrode architecture during deformation, and complicated as well as costly production processes thus limiting their expansive applications. Herein, the recent progression in the exploration of carbonaceous materials and metals based flexible electrode materials are summarized and discussed, with special focus on determining their relative electrochemical performance and structural stability based on recent advancement. Major factors for the future advancement of FLIBs in this field are also discussed.

Design of quadruple-layered metal oxides/nitrogen, oxygen-doped carbon nanotube arrays as binder-free electrodes for flexible lithium-ion batteries

Designing flexibly binder-free metal oxide electrodes, which could effectively alleviate the mechanical stress and maintain the structural integrity during the lithiation/delithiation process, is still a major challenge. Here we report a facile strategy for successfully synthesizing free-standing quadruple-layered metal oxides/nitrogen, oxygen-doped carbon nanotube array electrodes. In the quadruple-layered structure, metal oxides are protected by carbon layer to minimize the direct exposure to the electrolyte and accommodate the huge volume change during cycling, and thus form the solid-electrolyte interface layer. Besides that, the abundant oxygen and nitrogen-containing functional groups of carbon layer shows a strong interaction with metal oxides to prevent the electrode pulverization during charging and discharging. Meanwhile, carbon layer is introduced to facilitate the stable and fast electrons mobility. As a result, the as-prepared quadruple-layered electrodes show excellent electrochemical performance in terms of high reversible capacity, good rate capability, and stable cyclability. This work may pave the way for the construction of flexible binder-free lithium ion batteries with superior lithium storage properties.

Retraction Note to: Fabrication of flexible lithium-ion battery electrodes for wearable full battery with high electrochemical performance

Retraction Note to: Fabrication of flexible lithium-ion battery electrodes for wearable full battery with high electrochemical performance

SnO2 nanoflower arrays on an amorphous buffer layer as binder-free electrodes for flexible lithium-ion batteries

The SnO2 nanoflower arrays were firmly glued on copper collectors by an amorphous SnO2 layer deposited on Cu foils in advance, combining pulsed laser deposition and facile hydrothermal method. As a self-supported anode for Li-ion batteries, the rationally designed heterostructure exhibits excellent electrochemical performance in terms of high specific capacity, good rate capability and improved cycle stability and is successfully assembled into flexible cells made of quasi-solid electrolytes. The improved performance of as-prepared anodes can be attributed to the introducing of the SnO2 buffer layer that provides more growth sites for nanoflowers, assures the solid contact between the active materials and substrate, facilitates electron transport, and furthermore accommodates the internal strain from SnO2 nanoflowers induced by volume change during cycling. The results demonstrate that the electrode shows great promising in high performance Li-ion batteries, especially in the emerging flexible batteries.

RETRACTED ARTICLE: Fabrication of flexible lithium-ion battery electrodes for wearable full battery with high electrochemical performance

A new method is provided for preparing self-supporting flexible lithium-ion battery electrodes of a textile structure by using extrusion 3D printing technology, using a high concentration of polyvinylidene fluoride as a viscosity modifier, carbon nanotube as a conductive agent, lithium iron phosphate or lithium titanate as an electrode active material. A printable ink prepared in the paper, with an apparent viscosity of approximately 105 Pa s, exhibits significant shear thinning behavior, and the storage modulus platform value reaches a high value of 105 Pa; its excellent rheological properties are beneficial for the printing and solidification process. Electrochemical test results show that the two printing electrodes have a stable and well-matched charge–discharge specific capacity, so the assembled soft-packed lithium-ion battery displays a discharge specific capacity of up to 108 mAh·g−1, and after bending the battery, the discharge specific capacity under the same current density (50 mA·g−1) is about 111 mAh·g−1. The outstanding electrochemical properties open up possibilities for flexible and wearable electronics applications.

A self-adhesive graphene nanoscroll/nanosheet paper with confined Fe1−xS/Fe3O4 hetero-nanoparticles for high-performance anode material of flexible Li-ion batteries

Graphene based free-standing membrane/paper materials have been proved to be promising electrodes for flexible Lithium-ion batteries, whereas the rate capability is still unsatisfied unfortunately due to the typical layer-by-layer configuration of the graphene building blocks. Herein, a novel 3D porous architecture with a graphene nanoscroll (GNS)/nanosheet hybrid as the framework and ultrasmall Fe1−xS/Fe3O4 hetero-nanoparticles (NPs) as the primary active matter is developed by a facile and scalable route of cold quenching, freeze drying and the subsequent roll-in treatment. The crumpled graphene nanosheets and GNSs with high length/diameter ratio are found to intertwine together and construct a 3D network with multiscale pores. Meanwhile, the Fe1−xS/Fe3O4 NPs with a uniform dimension of <10 nm and homogeneous dispersion are firmly anchored on the graphene nanosheets or confined in the gallaries of the GNSs through their strong interface interaction. Benefiting from the unique and robust 3D hybridized design, the self-adhesive flexible electrode exhibits high reversible capacity (946 mAh g−1 at 0.1 A g−1) and excellent long-term stability up to 400 cycles with a low capacity loss rate of 0.047% per cycle. In addition, the prominently enhanced rate performance (capacity retention of 40.1% at 6 A g−1) compared with the traditional 2D structured graphene materials is also stressed.

Flexible TiO2 /SiO2 /C Film Anodes for Lithium-Ion Batteries.

Flexible TiO2 /SiO2 /C films are prepared by using an electrospinning approach and used as self-supporting electrodes for lithium-ion batteries (LIBs), which exhibit excellent high-rate capability with a capacity of 115.5 mAh g-1 at 8 A g-1 (9.8 C rate) and good storage performance. The LIBs also show high long-term cycling stability of 700 cycles at 200 mA g-1 with a capacity of 380.1 mAh g-1 and a high capacity retention of 88.3 %. Thus, the TiO2 /SiO2 /C films have the potential to serve as electrodes for flexible LIBs, owing to their flexibility and excellent electrochemical performance.

Directly-prelithiated carbon nanotube film for high-performance flexible lithium-ion battery electrodes

Carbon nanotube (CNT) films are very flexible and serve as active materials for lithium-ion batteries (LIBs). Hence, they have high potential as flexible free-standing electrodes for wearable batteries. However, nanocarbon materials such as CNTs and graphene are of limited use as electrodes because they have a large initial irreversible capacity due to the formation of a solid electrolyte interphase (SEI). Herein, we prelithiated the CNT films to make them available as electrodes for flexible batteries by reducing their irreversible capacity. The SEI is pre-formed through a direct prelithiation (DP) method that brings lithium metal into direct contact with CNT films in an electrolyte. As a result, the capacity of directly-prelithiated CNT film electrodes continues to increase to 1520 mAh/g until 350th cycle of charge/discharge and their initial irreversible capacity vanishes. The changes in the electrochemical properties of CNT film electrodes by DP treatment and their flexibility are investigated.

Subeutectic Growth of Carbon-Coated Silicon Nanowires on Carbon Fabric As Self-Supported Electrodes for Flexible Lithium-Ion Batteries

Developing rechargeable lithium-ion batteries (LIBs) with high energy density, which is of critical importance in energy storage applications such as portable electronics, hybrid electric vehicles (HEVs), and electric vehicles (EVs), requires the development of electrode materials with high capacity. Among the many candidates, silicon (Si) holds great promise and has been extensively studied as anode material owing to its natural abundance and theoretical specific capacity higher than that of graphite (4200 vs 372 mA h g–1) with similar working potential, giving a significantly higher energy density of LIBs. However, Si suffers from a dramatic volume and structure variation during the Li alloying/dealloying process, resulting in the severe pulverization and delamination from current collectors. Moreover, the dynamic formation and decomposition of the solid electrolyte interphase (SEI) layer caused by the side reaction between electrolyte and newly exposed Si surface leads to large irreversible capacities and further causes the rapid performance degradation of the Si-based electrodes. To conquer these critical obstacles, nanostructured Si materials have been widely investigated because they are capable of tolerating extreme changes in volume. Particularly, Si nanowire (NWs) has been considered as the most compelling candidate, since the one-dimensional structure provides not only the shorter lithium-ion diffusion distance due to the narrow diameter combined with long continuous paths for electron transport down their length but also a highly porous architecture, allowing volume variation. The most common approach for the growth of Si NWs involves the medium- or high-pressure chemical vapor deposition (CVD) through the vapor–liquid–solid mechanism, where expensive catalysts (e.g., Au, Ag, and Ga) and hazardous materials (e.g., silane) are often applied. Therefore, advanced technology is highly demanded in the synthesis of high-quality Si NWs for scalable production at low cost. On the other hand, conventional electrode fabrication technology requires significant fractions of binder and conductive agent, which inevitably sacrifice overall energy. Direct deposition of active materials on highly conductive current collectors avoids the use of inert components, resulting in a higher total capacity and a better active material utilization. Moreover, the intimate contact facilitates the electron transport and efficiently improves the electrode integrity as well. Furthermore, the utilization of flexible current collectors enables flexible electrodes, which have been attracting tremendous interest in applications such as wearable electronics and health care devices. So far, there are only a few reports on the fabrication of Si NW-based binder-free and flexible electrodes; however, these flexible electrodes either involve complex synthesis, which is hard for scale-up, or are composed of Si NWs with unsatisfactory quality or nonuniform size. In this context, it is of great importance and challenge as well for effective design and scalable fabrication of high-performance flexible Si NW-based electrodes for practical LIB applications. Herein, we demonstrate self-supported, binder-free, flexible electrodes with long cycling life and controllable high mass loading based on carbon-coated Si NWs grown in situ on highly conductive carbon fabric substrates (c-Si NWs/CF). The carbon-coated Si NWs are synthesized through a nickel catalyzed, bottom-up growth process via a one-pot atmospheric pressure CVD. Ni nanoparticles are first electrodeposited onto a piece of precleaned CF before the Si NWs are grown on the Ni catalyst using SiCl4 as the precursor through a vapor–solid–solid mechanism at a subeutectic temperature of 900 °C (below the eutectic temperature of 993 °C for Ni–Si system in the VLS growth mechanism). A thin carbon layer is coated on the Si NWs using toluene as the carbon source, forming a core–shell structure. Such novel electrodes with a unique three-dimensional architecture possess several characteristics needed for high-performance Si-based electrodes. First, the 1D Si NWs and the porous electrode architecture accommodate the volume change well, while the thin-layer carbon coating effectively confines the Si NWs during cycling. Second, the in-situ growth not only ensures intimate contact of the Si NWs with highly conductive CF, enabling a fast electron transport, but also improves the electrode integrity. Third, high mass loading of carbon-coated Si NWs can be achieved, which holds great potential for next-generation LIBs with high areal capacity and energy density. The high-quality carbon-coated Si nanowires resulted in high reversible specific capacity (∼3500 mA h g–1 at 100 mA g–1), while an exceptionally long cyclability with a capacity retention of ∼66% over 500 cycles at 1.0 A g–1 was achieved. The controllable high mass loading enables an electrode with extremely high areal capacity of ~5.0 mA h cm–2. Such a scalable electrode fabrication technology and the high-performance electrodes hold great promise in future practical applications in high energy density LIBs. Figure 1

Robust Free-standing Electrodes for Flexible Lithium-ion Batteries Prepared by a Conventional Electrode Fabrication Process

Highly flexible free-standing electrodes for flexible lithium-ion batteries (LIBs) are prepared by casting slurry on a glass substrate and detaching the film after drying. The slurry is composed of lithium cobalt oxide (LiCoO2) as a cathode material and Super-P as a conductive agent. These are currently used in conventional electrode fabricating. The flexible electrode contains the similar constituents and composition to the electrodes in commercial LIBs, but does not include metal foil as a current collector as that limits the flexibility of the LIB. Polyvinylidene fluoride (PVDF) with hexafluoropropylene (HFP) is used as a binder instead of PVDF alone due to its better mechanical properties (tensile stress, strain, and peel-off strength). In order to compensate for the low electronic conductivity of flexible electrodes without metal foil, a carbon nanotube (CNT) is incorporated into the electrode. The flexible electrodes offer great flexibility with the ability to be bent and folded without deforming. The flexible electrode exhibits high overpotential during charging/discharging process and inferior electrochemical performance (rate capability, energy density and cycling stability) to conventional electrodes with metal foil due to the low electronic conductivity but it delivers reasonable performance in a punch cell with an aluminum-deposited PET substrate as a current collector. Using CNT enhances the electrochemical properties of flexible electrodes, but weakens its mechanical strength at the same time. Therefore, the optimum amount of CNT needs to be determined.

2D Film of Carbon Nanofibers Elastically Astricted MnO Microparticles: A Flexible Binder-Free Anode for Highly Reversible Lithium Ion Storage.

MnO as anode materials has received particular interest owing to its high specific capacity, abundant resources, and low cost. However, serious problems related to the large volume change (>170%) during the lithiation/delithiation processes still results in poor rate capability and fast capacity decay. With homogenous crystals of MnO grown in the network of carbon nanofibers (CNF), binding effect of CNF can effectively weaken the volume change of MnO during cycles. In this work, a CNF/MnO flexible electrode for lithium-ion batteries is designed and synthesized. The CNF play the roles of conductive channel and elastically astricting MnO particles during lithiation/delithiation. CNF/MnO as binder-free anode delivers specific capacity of 983.8 mAh g-1 after 100th cycle at a current density of 0.2 A g-1 , and 600 mAh g-1 at 1 A g-1 which are much better than those of pure MnO and pure CNF. The ex-situ morphologies clearly show the relative volume change of MnO/CNF as anode under various discharging and charging times. CNF can elastically buffer the volume change of MnO during charging/discharging cycles. A facile and scalable approach for synthesizing a novel flexible binder-free anode of CNF/MnO for potential application in highly reversible lithium storage devices is presented.

Flexible anodes with carbonized cotton covered by graphene/SnO2 for advanced lithium-ion batteries

Recent attention has been focused on the synthesis and application of flexible lithium-ion battery electrodes for the development of high-performance and durable electronic devices. Herein, we synthesize a novel composites with carbonized cotton covered by graphene/SnO2 (CGN/SnO2), in which SnO2 nano-particles grow in-situ on the cotton fibers covered with graphene oxide (CGO) under the following thermal annealing process. The conductivity of the composites and the sizes of the SnO2 particles in the composites could be expediently adjusted by changing the thermal annealing temperatures. The as-prepared flexible CGN/SnO2 composites can be directly used as an anode for lithium-ion batteries without the addition of conductive additive, binder and current collector. The CGN/SnO2 composites prepared at 500°C have exhibited a good reversible specific capacity (calculated by the weight of whole electrode) of 406mAh·g−1 (1.70mAh·cm−2) after 80cycles. This work provides an effective way for the metal oxide composed with flexible carbon framework, promising to develop a new portable electrochemical energy-storage electrode.