Decorating ZnO nanoflakes on carbon cloth: Free-standing,highly stable lithium-ion battery anodes

A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion -battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g⁻¹ at a current density of 0.1 A g⁻¹, a capacity retention of almost 52.9% at a current density of 2 A g⁻¹, as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g⁻¹ and only 6% capacity fading at a current density of 0.1 A g⁻¹, even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs.     

Novel binder-free electrode of NiCo2O4@NiMn2O4 core-shell arrays modified carbon fabric for enhanced electrochemical properties

There is still a great challenge to develop new-style battery-type electrode materials with low resistance, large surface area, and stable microstructures on carbon fabric, which limited the development of flexible devices. In this work, NiCo₂O₄ nanoneedle@NiMn₂O₄ nanosheet core-shell arrays are constructed on the carbon fabric as a high-capacitance and long-life supercapacitor electrode for the first time. Benefiting from this kind of binder-free core-shell microstructure, the CF@NiCo₂O₄@NiMn₂O₄ electrode displays extraordinary specific-capacitance of 539.2 F g⁻¹ at a current density of 2 A g⁻¹, and nearly 93.0% retention of total capacitance even after discharging 5000 cycles. The outstanding properties of the hybrid electrode demonstrate that it is of great potential for flexible supercapacitors and batteries the application.     

Graphene-supported cubic hollow carbon shell-coated germanium particles as high-performance anode for lithium-ion batteries

Germanium-based materials are considered to be an alternative material for high energy density lithium-ion battery anodes due to their superior theoretical capacity. However, the severe volume expansion during the lithium insertion and the easily agglomerated tendency of Ge nanoparticles become the key obstacles to the stable cycle and capacity retention of Ge anodes. Herein, we designed a double-layered protective structure in which the cubic hollow Ge@C hybrids are uniformly dispersed on reduced graphene oxide sheets (Ge@C-rGO) through conventional dopamine-coated precursor and subsequent carbothermal reduction processes. In the synthesized Ge@C-rGO hybrids, the large-area rGO sheets cooperate with the amorphous carbon layer to accommodate and buffer the volume expansion of Ge particles, and to ensure that the Ge nanoparticles are in a separated state to the utmost extent. The Ge@C-rGO electrode which is employed in lithium-ion battery owns the reversible capacities of 1183 mAh·g⁻¹ at the specific current of 100 mA g⁻¹ and 710 mAh·g⁻¹ at 1 A g⁻¹ for 200 cycles. In addition, it exhibited good cycle stability, rate reversibility and electronic conductivity, and is a potential anode material with high performance and long-cycle capability.     

Single source precursor-derived SiOC/TiOxCy as an anode component for Li-ion batteries

Amorphous silicon oxycarbides are known to be an effective anode material for lithium-ion batteries. Despite their exceptional properties and high charge capacities, however, their practical uses are limited by their significant first-cycle loss, considerable hysteresis, and low cyclic ability. Comparatively, SiOC/metal oxide materials have demonstrated increased rate capability and cyclic stability. This study utilized a liquid precursor-derived ceramic method to modify SiOC with titanium (IV) butoxide precursor to synthesize SiOC/TiO_xC_y. X-ray diffractograms confirmed the amorphous nature of SiOC/TiO_xC_y. The elemental composition and bonding properties were investigated using X-ray photoelectron spectroscopy, and electron microscopy was used to explore morphological features. In the first cycle, the reversible capacity of pyrolyzed SiOC/TiO_xC_y was 520 mAh g⁻¹, which then increased to 736 mAh g⁻¹ for the 1200°C annealed SiOC/TiO_xC_y due to the increased free carbon network and TiC conductive phases. The irreversible capacity of the first cycle was 568 mAh g⁻¹, which was lower than the annealed SiOC irreversible capacity of 695 mAh g⁻¹. Interestingly, the rate stability of the pyrolyzed SiOC/TiO_xC_y performed more stability than the annealed sample. Localized carbothermal reactions between amorphous SiOC/TiO_xC_y and free carbon at annealing temperatures resulted in loss of structure stability.     

Free-standing SiOC/nitrogen-doped carbon fibers with highly capacitive Li storage

Silicon oxycarbide (SiOC) as a prospective electrode material for next-generation lithium ion batteries (LIBs) was restricted by the unsatisfactory discharge capacity and inflexibility used in flexible and wearable electronics. Herein, freestanding flexible SiOC/nitrogen-doped carbon fiber films are constructed through electrospinning process followed by carbonizing in NH₃ atmosphere. In this way, SiOC particles are tightly embedded in N-doped carbon fibers, forming a 3D conductive network to promote electron transport and faster reaction kinetics. The nitrogen dopants create more defects in carbon fibers matrix, which improve the electronic conductivity and electrochemical active sites of the electrodes. Owing to the above synergistic effect, SiOC/nitrogen-doped carbon fiber electrodes exhibit a high initial Coulombic efficiency of 73 % and a reversible remaining capacity of 595 mA h g⁻¹ at 200 mA g⁻¹ even after 200 cycles. The electrodes with good flexibility can successfully drive a light-emitting diode even when the package battery is bended to 180°.     

Lightweight,robust, porous heterocyclic para-aramid aerogel hollow fibers for multifunctional applications

In nature, many fibers with warmth-retention properties, such as the hair of polar bears and rabbits, both have a hollow cross-section structure. The static air in fiber cavities can effectively inhibit heat conduction and serve as an effective thermal insulator. In this work, the high-performance heterocyclic para-aramid polymer was selected as the spinning solution, and aerogel hollow fiber was prepared by coaxial wet spinning and freeze-drying techniques. The effects of spinning solution concentration and lyophilized solvent on the micromorphology, mechanical properties, and specific surface area of heterocyclic para-aramid aerogel hollow fiber (HPAAHF) were systematically studied. The produced HPAAHF possessed excellent mechanical properties (tensible strength ~3.85 MPa), high specific surface area (~ 260.90 m² g⁻¹), and lightweight advantages. The thermal conductivity of HPAAHF was only 0.0278 W m⁻¹ K⁻¹, indicating its excellent thermal insulation properties. The aerogel fabric exhibited outstanding flame retardancy properties, with a total heat release of only 0.7 MJ m⁻² in the cone calorimetric experiment, making it a self-extinguishing fabric. In addition, phase change material was injected into the hollow structure to obtain aerogel-phase change material composite fibers, which exhibited great energy storage prospects. As a result, the high-performance heterocyclic para-aramid polymer-based aerogel hollow fiber was successfully prepared and had multifunctional applications in thermal insulation, flame retardancy, and heat energy storage fields.     

MnO anchored reduced graphene oxide nanocomposite for high energy applications of Li-ion batteries: The insight of charge-discharge process

In the present work, a new class of anode material for high energy applications of Li-ion battery is prepared by easy and large-scale producible process. Herein, the nanocomposite of MnO and reduced graphene oxide (rGO) is prepared by anchoring MnO nanoparticles into 3D matrix of rGO hydrogel followed by annealing process. The composite which has homogeneous distribution of MnO particles on conducting rGO layers demonstrated superior electrochemical performance such as high reversible capacity, stable cycle life and better rate capability. It has shown initial discharge capacity of 2358 mAh g⁻¹ and retained 570 mAh g⁻¹ after 100 cycles as compared to pristine MnO which shown initial discharge capacity of 820 mAh g⁻¹ and retained only 45 mAh g⁻¹ after 100 cycles. The retained capacity of new MnO/rGO anode is much higher than the theoretical capacity of conventional graphite anode. Moreover, the MnO/rGO nanocomposite shows six times higher Li⁺ ion diffusion of 4.18 × 10⁻¹² cm² s⁻¹ as compared to 6.84 × 10⁻¹³ cm² s⁻¹ of MnO. In addition, the study provides insight of charge-discharge process, which conducted in initial, discharge and charge states of pristine MnO and MnO/rGO composite using ex-situ X-ray diffraction and X-ray photon spectroscopy techniques.     

Nanowires embedded porous TiO2@C nanocomposite anodes for enhanced stable lithium and sodium ion battery performance

A porous carbon nanocomposite with embedded TiO₂ nanowires (NWs) was synthesized using a two-step synthetic method in which carbon matrix was obtained by carbonizing a vacuum dried gel. This unique structure in which TiO₂ nanowires uniformly distributed in and tightly bonded to the carbon matrix shortened the electron transport path and reduced the transmission resistance. Nanoporous structure ensured continuous transfer of Li⁺/Na⁺ and supplied a large specific surface area of 280.82 m² g⁻¹ to provide more active sites. Different from other existing works on TiO₂@C anode materials with TiO₂ loading higher than 60 wt%, the obtained very small amount of TiO₂ (~12 wt%) improved the electrochemical and long-cycle performance of carbon substrate with TiO₂ NWs embedded significantly, due to uniformly distributed TiO₂ NWs throughout the carbon matrix. These TiO₂@C composite anodes could deliver a specific capacity of 286 mA h g⁻¹ at 0.3 C, 197 mA h g⁻¹ at 0.15 C for lithium and sodium ion batteries, respectively. It maintained remarkably stable reversible capacities of 128 and 125 mA h g⁻¹ for lithium and sodium ion batteries at 3 C during 2500 cycles, respectively. Smaller fluctuations and smoother curves demonstrated that sodium ion storage was more stable than lithium ion storage for the TiO₂@C composite anode. In addition, the capacitive contributions of TiO₂@C in both systems are quantified by kinetics analysis.     

Multilayered silicon embedded porous carbon/graphene hybrid film as a high performance anode

Silicon (Si) has been regarded as one of the most attractive anode materials for the next generation lithium-ion batteries because of its large theoretical capacity, high safety, low cost and environmental benignity. However, the architecture of Si-based anode material still needs to be well designed to overcome the structure degradation and instability of the solid-electrolyte interphase caused by a large volume change during cycling. Here we report the electrochemical performances of a novel binder-free Si/carbon composite film consisting of alternatively stacked Si-porous carbon layers and graphene layers, which is synthesized by electrostatic spray deposition followed by heat treatment. For this composite film, Si nanoparticles are embedded in the porous carbon layer composed of nitrogen-doped carbon framework, carbon black and carbon nanotubes. And the combined Si-porous carbon layer is further sandwiched by flexible and conductive graphene sheets. The multilayered Si-porous carbon/graphene electrode shows a maximum reversible capacity of 1020 mAh g⁻¹ with 75% capacity retention after 100 cycles and a good rate capability on the basis of the total electrode weight. The excellent electrochemical performances are attributed to the fact that the layer-by-layer porous carbon matrix can accommodate the volume change of Si particles and maintain the structural and electrical integrities.     

Strategy for improving the capacity and rate performance of LiNixCoyMn1−x−y electrode using Ti3C2Tx MXene additives

With the expanding range of applications for lithium-ion batteries, a great deal of research is being conducted to improve their capacity, stability, and charge/discharge rates. This study was performed to investigate the effects of MXene, which has a large surface area and metallic conductivity, as a conductive additive to the cathode, on electrochemical performance. The two-dimensional material MXene constructs a conductive network with zero-dimensional carbon black in plane-to-point mode to improve conductivity and contact area with active materials, thereby facilitating fast charge transfer. The conductive network reduces the internal resistance and polarization of the cathode and aids the diffusion of electrons. The electrode containing an appropriate amount of MXene showed improved rate performance, high discharge capacity (123.9 mAh g⁻¹ at 4 C), and excellent cycle stability at a high scan rate (125.8 mAh g⁻¹ at 2 C after 150 cycles) compared to pristine electrodes. Based on these results, Ti₃C₂T_x MXene is a promising conductive additive in the battery field.     

Ionic liquid assisted fabrication of cellulose-based conductive films for Li-ion battery

An imidazolium-based ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) was used to dispense graphene nanoplates (GN) and multiwalled carbon nanotubes (MWCNTs) as well as dissolve cellulose for fabricating composite conductive films. The effects of GN, MWCNTs, and cellulose mass ratios on the electrical conductivity and morphology of the films were investigated. The interaction between GN, MWCNTs, and cellulose was analyzed by SEM, X-ray diffraction (XRD), TGA, and Raman spectroscopy. The results indicate that [Emim]DEP plays a vital and irreplaceable role in GN and MWCNTs dispersion, cellulose dissolution, and porous formation during the regeneration and drying processes. MWCNTs linked flaky GN and a hybrid structure was constructed elaborately to form a better conductive path and improve the conductivity as well as increase the film stability. For the XRD result, the carbonized GN-MWCNTs-cellulose films exhibited the graphitic peaks, showing that the films still retained the structure of carbon atoms or molecules. Besides, the maximum conductivity of carbonized GN-MWCNTs-cellulose (7:3:2) composite film was up to 9,009 S m⁻¹, due to the small carbon clusters formation and the high degree of graphitization. Further, the carbonized films were applied as anodes in Li-ion battery and showed good electrochemical performance. The best cyclic stability (i.e., discharge/charge capacity) of 438/429 mA h g⁻¹ and coulomb efficiency of 50.2% were obtained. This novel and sustainable design is a promising approach to obtain cellulose-based conductive films and anodes for Li-ion battery applications.     

Microwave autoclave synthesized multi-layer graphene/single-walled carbon nanotube composites for free-standing lithium-ion battery anodes

Multi-layer graphene sheets have been synthesized by a time-efficient microwave autoclave method and used to form composites in situ with single-walled carbon nanotubes. The application of these composites as flexible free-standing film electrodes was then investigated. According to the transmission electron microscopy and X-ray diffraction characterizations, the average d-spacing of the graphene–single-walled carbon nanotube composites was 0.41 nm, which was obviously larger than that of the as-prepared pure graphene (0.36 nm). The reversible Li-cycling properties of the free-standing films have been evaluated by galvanostatic discharge–charge cycling and electrochemical impedance spectroscopy. Results showed that the free-standing composite film with 70 wt% graphene exhibited the lowest charge transfer resistance and the highest charge capacity of about 303 mAh g⁻¹ after 50 cycles, without any noticeable fading.     

Si nanoparticles encapsulated in CNTs arrays with tubular sandwich structure for high performance Li ion battery

Silicon has been widely researched as next-generation lithium-ion batteries (LIBs) anodes on account of its high energy density. To solve the large volume expansion and low electroconductivity, carbon coating Si strategies have been developed and shown some progress. In this study, Si nanoparticles were injected into the inner of the double-deck carbon nanotubes for the formation of a sandwich-like structure to enhance the electrochemical properties of Si electrodes. Thereinto, carbon nanotube arrays (CNTs) were fabricated by liquid paraffin as the carbon resource instead of unsaturated hydrocarbon for the first time by chemical vapor deposition (CVD) method. Due to the advantage of the specific structure designed, the as-prepared material shows superior rate performance and excellent cycling stability with high capacity retention (1310 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles and 1050 mAh g⁻¹ at 1 A g⁻¹ after 500 cycles with 98% of Coulombic efficiency). Furthermore, the full cell was also assembled with LiFePO₄ as the cathode and manifested a high energy density of 374 Whkg⁻¹ with stable cycling performances (92% capacity retention ratio after 200 cycles).     

NiCo2O4 nanosheets and nanocones as additive-free anodes for high-performance Li-ion batteries

Development of novel electrode materials with high energy and power densities for lithium-ion batteries (LIBs) is the key to meet the demands of electric vehicles. Transition metal oxides that can react with large amounts of Li⁺ for electrochemical energy storage are considered promising anode materials for LIBs. In this work, NiCo₂O₄ nanosheets and nanocones on Ni foam have been synthesized via general hydrothermal growth and low-temperature annealing treatment. They exhibit high rate capacities and good cyclic performance as LIB anodes owing to their architecture design, which reduces ion and electron transport distance, expands the electrode–electrolyte contact, increases the structural stability, and buffers volume change during cycles. Notably, NiCo₂O₄ nanosheets deliver an initial capacity of 2239 mAh g⁻¹ and a rate capacity of 964 mAh g⁻¹ at current densities of 100 and 5000 mA g⁻¹, respectively. The corresponding values of nanocones are 1912 and 714 mAh g⁻¹. Hence, the as-synthesized NiCo₂O₄ nanosheets and nanocones, which are carbon-free and binder-free with higher energy densities and stronger connections between active materials and current collectors for better stability, are promising for use in advanced anodes for high-performance LIBs.     

Cyclability study of silicon–carbon composite anodes for lithium-ion batteries using electrochemical impedance spectroscopy

The effects of carbonization process and carbon nanofiber/nanotube additives on the cycling stability of silicon–carbon composite anodes were investigated by monitoring the impedance evolution during charge/discharge cycles with electrochemical impedance spectroscopy (EIS). Three types of Si–C anodes were investigated: the first type consisted of Si nanoparticles incorporated into a network of carbon nanofibers (CNFs) and multi-walled carbon nanotubes (MWNTs), with annealed polymer binder. The second type of Si–C anodes was prepared by further heat treatment of the first Si–C anodes to carbonize the polymer binder. The third Si–C anode was as same as the second one except no CNFs and MWNTs being added. Impedance analysis revealed that the carbonization process stabilized the Si–C anode structure and decreased the charge transfer resistance, thus improving the cycling stability. On the other hand, although the MWNTs/CNFs additives could enhance the electronic conductivity of the Si–C anodes, the induced inhomogeneous structure decreased the integrity of the electrode, resulting in a poor long term cycling stability.     

Hollow C/Co9S8 hybrid polyhedra-modified carbon nanofibers as sulfur hosts for promising Li–S batteries

Lithium-sulfur (Li–S) batteries hold great expectations as next-generation advanced capacity storage devices due to their higher theoretical energy density and low cost. Even so, polysulfide shuttles, insulation, and volume expansion of sulfur impede its commercial progress. To suppress these problems, we used electrospinning and self-templating to construct C/Co₉S₈ hybrid polyhedra-modified carbon nanofibers (denoted as C/Co₉S₈–C@S fibers) as sulfur hosts. The quasi-metallic polar Co₉S₈ strongly bonds and locks polysulfides, and the hollow polyhedra provide sulfur storage space. Moreover, the overall nanofiber forms an interconnected conductive network to assist the transmission of Li⁺/e⁻ and restrain the escape of the sulfur phase to a certain extent. Compared with C/Co₉S₈ polyhedra and carbon nanofibers, the C/Co₉S₈–C@S fiber delivers excellent adsorption characteristics for polysulfides. As a Li–S battery cathode, the C/Co₉S₈–C@S fiber (sulfur content: 87.20 wt%) exhibits an initial specific capacity of 1013.7 mAh g⁻¹ at 0.1 C, displaying a stable capacity of 694.9 mAh g⁻¹ after 150 cycles. Additionally, it shows a high specific capacity of 894.7 mAh g⁻¹ at 1C with a capacity decay of ~0.116% per cycle over 500 cycles.     

Facile fabrication of porous NiMoO4@C nanowire as high performance anode material for lithium ion batteries

Herein, porous NiMoO₄@C nanowire is purposefully synthesized using oleic acid as carbon source, and further evaluated as high performance anode material for Li-ion batteries (LIBs). Compared with the pure NiMoO₄, porous NiMoO₄@C nanowire exhibits high reversible charge/discharge specific capacity, excellent cycle stability and preeminent rate capability. A stable reversible lithium storage capacity of 975 mAh g⁻¹ can still be maintained after 100 cycles at 200 mA g⁻¹. When the current density decreases back from 3000 mA g⁻¹ to 100 mA g⁻¹, a high discharge specific capacity of 884 mAh g⁻¹ is recovered. The porous structure and carbon layers can enhance the electronic transmission and structural stability, shorten the path lengths for ion and electron transport, and provide a mechanical buffer space to accommodate the volume expansion/contraction during the repeated Li⁺ insertion/extraction processes. All the results highlight that the porous NiMoO₄@C nanowire composite would be a promising candidate for high performance anode material of LIBs owing to its excellent electrochemical properties.     

ZnIn2S4: A promising anode material with high electrochemical performance for sodium-ion batteries

In this study, ZnIn₂S₄ (B-ZIS) and ZnIn₂S₄/C (S-ZIS) composites anode are synthesized using hydrothermal method and followed by ball-milling process. The initial discharge/charge capacities for bare ZnIn₂S₄ (B-ZIS) are 524 and 378 mAh g⁻¹ under a current density of 1 A g⁻¹, which suffers from gradually capacity fading. To improve its cycle stability, high-energy ball-milling process (HEBM) with carbon black is applied to fabricate S-ZIS spherical particles. The as-obtained composite anode exhibits enhanced electrochemical performances not only on cycle stability, but also reversible capacity. The discharge and charge capacity of S-ZIS approach to 823 and 679 mAh g⁻¹ at the first cycle and retain 468 and 459 mAh g⁻¹ after 500 cycles at the high current density of 1 A g⁻¹. Furthermore, ex situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopy (XPS) techniques are used to monitor the evaluation of crystal structure of B-ZIS during charge and discharge processes. The results indicate that the metallic Zn and In were observed at low potential voltage during sodiation process and successfully converted back to spinel phase at above 0.5 V. The presence of high reversibility nature of B-ZIS may leads to the superior cycling and excellent rate capability of S-ZIS which makes ZnIn₂S₄ a potential anode material of sodium ion batteries.     

Electrochemical performance of SiOC anodes prepared by a different silicone

SiOC is one of the most promising anodes for lithium-ion batteries, which shows the good structural stability and high capacity comparing to commercial graphite anode. In this paper, different SiOC anodes (SiOC-217, SiOC-H44, and SiOC-MK) were prepared from polymer precursors with different side groups (phenyl, methyl-phenyl, methyl) to investigate the effects of free carbon on the electrochemical performance of SiOC anodes. The results of X-ray photoelectron spectroscopy presented that SiOC was composed by different SiO_xC_4−x units and free carbon phase. The initial discharge capacity of SiOC-217 was 742.67 mA h g⁻¹. After 100 cycles, the reversible capacity of SiOC-217 reached 450.65 mA h g⁻¹ at 0.2 C, indicating a capacity retention rate of 60.68%. After cycling at high current densities, SiOC-217 exhibited a high discharge capacity of 592.88 mA h g⁻¹ at 0.1 C. SiOC-217 exhibited excellent electrochemical performance due to the high content of free carbon phase. Furthermore, the high contents of SiO₂C₂ and SiO₃C units further enhanced the improvement of electrochemical performance.     

A hierarchical carbon fiber/sulfur composite as cathode material for Li–S batteries

A novel hierarchical structure carbon/sulfur composite is presented based on carbon fiber matrices, which are synthesized by electrospinning. The fibers are constituted with hollow graphitized carbon spheres formed using catalytic Ni nano-particles as hard templates. Sulfur is loaded to the carbon substrates via thermal vaporization. The structure and composition of the hierarchical carbon fiber/S composite are characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption isotherms. The electrochemical performance is evaluated by cyclic voltammetry and galvanostatic charge–discharge. The results exhibit an initial discharge capacity of 845 mA h g⁻¹ at 0.25 C (420 mA g⁻¹), with a retention of 77% after 100 cycles. A discharge capacity of 533 mA h g⁻¹ is still attainable when the rate is up to 1.0 C. The good cycling performance and rate capability are contributed to the uniform dispersion of sulfur, the conductive network of carbon fibers and hollow graphitized carbon spheres.