Synthesis and characterization of GaNb11O29@C for high-performance lithium-ion battery

The GaNb₁₁O₂₉ shows an open Wadsley-Roth shear structure, which is of great benefit to store ions in rechargeable batteries. In this work, we successfully synthesize GaNb₁₁O₂₉@C via a simple solid-state reaction method combined with carbon-coating modification. As anode for LIBs, the as-synthesized GaNb₁₁O₂₉@C sample exhibits wonderful electrochemical behaviors. It exhibits high reversible capacity (227.3 mA h g⁻¹), outstanding rate capability (58.91% retention at 700 mA g⁻¹) and excellent long cycle performance (0.036% capacity decay per cycle). The enhancement of diffusion kinetics and rate performance assigns to the increased surface reaction activity and electrical conductivity. The open and stable crystal framework structure guarantees rapid lithium-ion migration, excellent rate performance and long cycle performance. These results tell that GaNb₁₁O₂₉@C is promising anode material for the application in advanced LIBs.     

Binder-free carbon-coated TiO2@graphene electrode by using copper foam as current collector as a high-performance anode for lithium ion batteries

Anatase TiO₂ is widely used in lithium ion batteries (LIBs) due to its excellent safety and excellent structural stability. However, due to the poor ion and electron transport and low specific capacity (335 mAh g⁻¹) of TiO₂, its application in LIBs is severely limited. For the first time, we report a binder-free, carbon-coated TiO₂@graphene hybrid by using copper foam as current collector (TG-CM) to enhance the ionic and electronic conductivity and increase the discharge specific capacity of the electrode material without adding conductive carbon (such as super P, etc.) and a binder (such as polyvinylidene fluoride (PVDF), etc.). When serving as an anode material for LIBs, TG-CM displays excellent electrochemical performance in the voltage range of 0.01–3.0 V. Moreover, the TG-CM hybrid delivers a high reversible discharge capacity of 687.8 mAh g⁻¹ at 0.15 A g⁻¹. The excellent electrochemical performance of the TG-CM hybrid is attributed to the increased lithium ion diffusion rate due to the introduction of graphene and amorphous carbon layer, and the increased contact area between the active material and electrolyte, and small resistance with copper foam as the current collector without an additional binder (PVDF) and conductivity carbon (super P).     

Ti2Nb10O29@C hollow submicron ribbons for superior lithium storage

Titanium niobate prepared by traditional techniques has the shortcomings of low ion diffusion coefficient as well as poor electrical conductivity, which drastically reduce its applicability. In this work, we prepare carbon coated Ti₂Nb₁₀O₂₉ hollow submicron ribbons (Ti₂Nb₁₀O₂₉@C HSR) using a simple electrospinning procedure. As anode material for lithium-ion batteries (LIBs), it delivers a high charge capacity of 259.7 mAh g^?1 at 1 C with low capacity loss of 0.013% in long-term cycles. Increased the current density to 5 C, Ti₂Nb₁₀O₂₉@C HSR can maintain a reversible capacity of 189.9 mAh g^?1, indicating its good rate performance. Additionally, this work uses in-situ X-ray diffraction (XRD) to provide an explanation for the lithium storage process in Ti₂Nb₁₀O₂₉@C HSR, demonstrating the high reversibility during charge/discharge cycles. Therefore, Ti₂Nb₁₀O₂₉@C HSR has outstanding cycle adaptability and structural reversibility to be a promising anode for LIBs.     

Hollow CuFe2O4 spheres encapsulated in carbon shells as an anode material for rechargeable lithium-ion batteries

We report here a polymer-templated hydrothermal growth method and subsequent calcination to achieve carbon coated hollow CuFe₂O₄ spheres (H–CuFe₂O₄@C). This material, when used as anode for Li-ion battery, retains a high specific capacity of 550 mAh g⁻¹ even after the 70th cycle, which is much higher than those of both CuFe₂O₄@C (∼300 mAh g⁻¹) and H–CuFe₂O₄ (∼120 mAh g⁻¹). And galvanostatic cycling at different current densities reveals that a capacity of 480 mAh g⁻¹, 91% recovery of the specific capacity cycling at 100 mA g⁻¹, can be obtained even after 50 cycles running from 100 to 1600 mA g⁻¹. The significantly enhanced electrochemical performances of H–CuFe₂O₄@C with regard to Li-ion storage are ascribed to the following factors: (1) the hollow void, which could mitigate the pulverization of electrode and facilitate the lithium-ion, electron and electrolyte transport; (2) the conductive carbon coating, which could enhance the conductivity, alleviate the agglomeration problem, prevent the formation of an overly thick SEI film and buffer the electrode. Such a structural motif of H–CuFe₂O₄@C is promising, for electrode materials of LIBs, and points out a general strategy for creating other hollow-shell electrode materials with improved electrochemical performances.     

Carbon-coated Bi5Nb3O15 as anode material in rechargeable batteries for enhanced lithium storage

Bismuth can alloy with lithium to generate Li₃Bi with the volumetric capacity of about 3765 mAh cm^?3 (386 mAh g^?1), rendering bismuth-based materials as attractive alloying-type electrode materials for rechargeable batteries. In this work, bismuth-based material Bi₅Nb₃O₁₅ @C is fabricated as anode material through a traditional solid-state reaction with glucose as carbon source. Bi₅Nb₃O₁₅ @C composite is well dispersed, with small particle size of 0.5–2.0?µm. The electrochemical performance of Bi₅Nb₃O₁₅ @C is reinforced by carbon-coated layer as desired. The Bi₅Nb₃O₁₅ @C exhibits a high specific capacity of 338.56 mAh g^?1 at a current density of 100?mA?g^?1. And it also presents an excellent cycling stability with a capacity of 212.06 mAh g^?1 over 100 cycles at 100?mA?g^?1. As a comparison, bulk Bi₅Nb₃O₁₅ without carbon-coating only remains 319.62 mAh g^?1 at 100?mA?g^?1, revealing poor cycle and rate performances. Furthermore, in-situ X-ray diffraction experiments investigate the alloying/dealloying behavior of Bi₅Nb₃O₁₅ @C. These insights will benefit the discovery of novel anode materials for lithium-ion batteries.     

Ultrathin N‐doped carbon‐coated TiO2 coaxial nanofibers as anodes for lithium ion batteries

The structural optimization of TiO₂ materials has a significance for improving the electrochemical performance since TiO₂ suffers from poor electronic conductivity. For this purpose, ultrathin N‐doped carbon‐coated TiO₂ coaxial nanofibers have been designed and synthesized by a facile electrospinning approach. Microstructure analysis indicates that the TiO₂ nanofibers can be coated by the ultrathin carbon layers. Electrochemical tests reveal that the rate performance and cycling ability of TiO₂@C nanofibers have been enhanced obviously. The TiO₂@C6 nanofibers carbonized at 600°C exhibit superior features with a specific discharge capacity of 284 mAh g^?1 at a current density of 100 mA g^?1 after 100 cycles. Besides improved rate performance of 117 mAh g^?1 at a high current density of 2000 mA g^?1 and excellent cycling stability with only about 0.008% capacity loss per cycle were also obtained in the sample TiO₂@C6 after 500 cycles at the current density of 1000 mA g^?1. Such remarkable performance may be ascribed to the unique one‐dimensional nanofibers as flexible carbon matrix.     

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.     

High-rate capability of three-dimensional CNTs-decorated NaTi2(PO4)3@C microspheres for sodium energy storage

One of the newest materials for sodium energy storage is NaTi₂(PO₄)₃, which is widely researched due to its considerable Na⁺ conductivity and excellent safety characteristics. However, NaTi₂(PO₄)₃ exhibits unfavorable electronic conductivity, restricting its application in sodium-ion batteries. Herein, three-dimensional CNTs-modified NaTi₂(PO₄)₃@C microspheres were synthesized by spray-drying method and solid-state high-temperature annealing. Within the designed composite, the NaTi₂(PO₄)₃@C nanoparticles were uniformly fixed on the CNTs surfaces, forming a three-dimensional CNTs-NaTi₂(PO₄)₃@C architecture. As an anode in a sodium-ion battery, the resulting CNTs-NaTi₂(PO₄)₃@C exhibited exceptional sodium storage potential, with a high reversible capacity, stable cycling properties, and a good rate capability. An excellent discharge capacity of about 128.5 mAh g^-1 was achieved with a low rate of 0.1C, and the anode displayed a reversible capability of 75.8 mAh g^-1 at 20C over 1000 cycles, with a low capacity fading rate of about 0.011% per cycle. Therefore, this novel strategy is highly effective and can be adopted to enhance the battery properties of other electrode materials.     

Cs4PbBr6 QDs silicate glass-ceramic: A potential anode material for LIBs

Lithium-ion batteries (LIBs) have attracted special attention in the new energy field, while halide perovskites are potential materials in the field of energy. In this work, Cs₄PbBr₆ quantum dots silicate glass-ceramic is synthesized by melt-quenching methods and examined as LIBs anode materials. The half-battery provides a high initial discharge specific capacity of about 1986.9 mAh g^?1 and a remarkably high reversible capacity of 426.7 mAh g^?1. Also, the present glass material shows good rate performance. Between the perovskite quantum dots and the silicate glass exists an interesting synergistic effect, and the observed prominent electrochemical performance proves that the quantum dots glass-ceramic materials are viable for lithium-ion batteries application.     

Hollow Co2SiO4 microcube with amorphous structure as anode material for construction of high performance lithium ion battery

To solve the problem of large volume expansion of cobalt silicate electrode during cyclic process and low electric conductivity, Co₂SiO₄ with amorphous, porous and hollow structure is firstly designed to act as high performance lithium ion battery (LIB) anode. Compared with crystalline materials, the amorphous Co₂SiO₄ microcube could facilitate Li⁺ diffusion to enhance their performance of LIBs because of isotropic characteristics. Here, the amorphous Co₂SiO₄ hollow microcube (named as a-Co₂SiO₄ HC) was prepared by mild hydrothermal method with use of MnCO₃ microcube as hard-template. Benefitting from the advantages of such structure, Li⁺ diffusion rate was greatly accelerated and the volume expansion can be alleviated. The as-prepared amorphous Co₂SiO₄ hollow microcube as anode material of LIBs exhibited significantly improved electrochemical performance of 610 mAh g⁻¹ even after 380 cycles at 500 mAh g⁻¹ than their crystalline counterpart (only 280 mAh g⁻¹ retained after 380 cycles). This work is a good try to employ amorphous metal silicate in LIBs and simultaneously motivate the exploration of other amorphous materials for high performance LIBs, SIBs, catalysts, etc.     

In-situ fabrication of heterostructured SnOx@C/rGO composite with durable cycling life for improved lithium storage

Due to their ultra-high theoretical capacity and low discharge potential, rich Sn-based materials are considered promising candidates for lithium ion battery (LIB) anodes; however, the development of SnO_x electrodes is restricted by their low conductivity and severe volume change during repeated cycling. In this study, carbon matrix encapsulating heterostructured SnO_x ultrafine nanoparticles (SnO_x@C/rGO) were synthesized in situ through a facile solvent mixing, followed by thermal calcination. During the decomposition of the Sn-organic precursor, the sizes of the as-prepared SnO_x nanoparticles were strictly controlled to 5–10 nm; they were intimately wrapped by the in-situ formation of ultrathin carbon layers, which prevented the agglomeration of nanograins. Furthermore, the SnO_x@C nanoparticles were evenly anchored on the surface of reduced graphene oxide (rGO) to construct a highly conductive carbon framework. It is notable that the carbon matrix prepared in situ can accommodate the volumetric change of SnO_x and facilitate the transport of Li⁺ ions during continuous cycling. Benefiting from the synergistic effect between the SnO_x nanoparticles and carbon matrix prepared in situ, the heterostructured SnO_x@C/rGO will confer improved structural stability and reaction kinetics for lithium storage. It delivers a stable reversible discharge capacity of 1092.2 mAh g⁻¹ at a current rate of 0.1 A g⁻¹, and enhanced cycling retention with a capacity of 447.8 mAh g⁻¹ after 1200 cycles at a current rate of 5.0 A g⁻¹. This strategy provides a rational avenue to design oxide anodes with efficient hierarchical structure for LIB development.     

In-situ grown hierarchical ZnCo2O4 nanosheets on nickel foam as binder-free anode for lithium ion batteries

Nickle foam-supported hierarchical ZnCo₂O₄ nanosheets was prepared via a facile solution-based method. Porous ZnCo₂O₄ nanosheets were in-situ grown on current collector, forming a binder-free electrode. When evaluated as anode for Lithium ion batteries (LIB_S), the binder-free electrode showed an attractive electrochemical performance. A reversible capacity of 773?mAh?g^?1 could be stably delivered after a 500-cycle test at a current density of 0.25?A?g^?1, with a high capacity retention of 87%. The electrode could maintain a high reversible capacity of 245?mA?h?g^?1 even at an elevated current density of 8.0?A?g^?1. Integrated structure and rich porosity of the binder-free electrode were believed to contribute to the superior performance. Thus, the Nickle foam-supported ZnCo₂O₄ electrode is a promising anode for high performance LIBs in the coming future.     

Rational design of mesoporous LiFePO4@C nanofibers as cathode materials for energy storage

In this work, the mesoporous LiFePO₄@C nanofibers have been successfully fabricated through a facile electrospinning method. The structure, morphology, chemical composition and lithium storage performance have been systematically investigated. The results reveal that the LiFePO₄ grains with particle size of ～15 nm are uniformly dispersed in the mesoporous carbon nanofibers. The LiFePO₄@C electrode presents a high reversible capacity and excellent rate performance. It delivers a discharge capacity of 107 mAh g⁻¹ and retains 105 mAh g⁻¹ over 200 cycles at 10C. The excellent electrochemical performances are attributed to the novel nanostructure where LiFePO₄ nanoparticles are embedded in the carbon fibers. This designed structure can significantly enhance the conductivity of LiFePO₄@C, accelerate the diffusion of electrolyte, and thus facilitate the transport of electrons and Li-ions.     

SnO2 prepared by ion-exchange method of sodium alginate hydrogel as robust anode material for lithium-ion batteries

Tin-based anode materials are important components of lithium-ion batteries (LIBs) owing to their larger theoretical capacitance and lower working potential. However, the synthesis of tin-based anode materials is very complex, impeding their industrialization. In this work, tin dioxide nanoparticles were synthesized using sodium alginate hydrogel as a chelating agent for the ion-exchange reaction with tin tetrachloride. The resulting nano-tin dioxide was uniformly distributed with a porous structure morphology. The addition of sodium alginate at 0.1 g yielded a sample (SA-0.1) with a high reversible specific capacity, excellent multiplicative properties, and good cycling stability. After 702 cycles, the capacity of reversible discharge of the SA-0.1 maintained 621.1 mAh g^?1 at the current density of 0.5A g^?1, which cooperates with the facile synthesis method making the composite promising for commercialization.     

Synthesis and electrochemical performance of LiVOPO4–Li3V2(PO4)3 cathode materials for lithium ion batteries

Lithium-ion batteries (LIBs) present the advantages of long cycle life, high voltage, and energy density and are widely made in the field of energy storage. LiVOPO₄ (LVOP), a cathode material used in LIBs, has a high conceptual capacity of 159 mAh g⁻¹ and high operating voltage of 3.9 V. However, its low electrical conductivity and cycle performance limit its commercial applications. According to the X-ray diffraction results, orthogonal crystal LVOP and monoclinic crystal Li₃V₂(PO₄)₃ (LVP) coexisted in the synthesised composite material. The transmission electron microscopy results also indicated that the LVOP and LVP phases coexist, which were coated by carbon layer of about 2.5 nm. The discharge of LVOP–LVP composite material initially was 143.2 mAh g⁻¹, and that after 120 cycles was 132.2 mAh g⁻¹ (at 0.1 C and 3–4.5 V). Thus, the electronic conductivity and first discharge specific capacity of the material enhanced due to the introduction of fast ion conductor LVP into LVOP. Electrochemical performance improved because the introduction of LVP led to an increase in Li⁺ pervasion channels in the original material and the acceleration of the Li⁺ transmission speed.     

Nanoparticles constructed mesoporous coral-like Mn2O3 as high performance anode for lithium-ion batteries

As well established, the morphology and architecture of electrode materials greatly contribute to the electrochemical properties. Herein, a novel structure of mesoporous coral-like manganese (III) oxide (Mn₂O₃) is synthesized via a facile solvothermal method coupled with the carbonization under air. When fabricated as anode electrode for lithium-ion batteries (LIBs), the as-prepared Mn₂O₃ exhibits good electrochemical properties, showing a high discharge capacity of 1090.4 mAh g^?1 at 0.1 A g^?1, and excellent rate performance of 410.4 mAh g^?1 at 2 A g^?1. Furthermore, it maintains the reversible discharge capacity of 1045 mAh g^?1 at 0.1 A g^?1 after 380 cycles, and 755 mAh g^?1 at 1 A g^?1 after 450 cycles. The durable cycling stability and outstanding rate performance can be attributed to its unique 3D mesoporous structure, which is favorable for increasing active area and shortening Li⁺ diffusion distance.     

Molybdenum carbide embedded in carbon nanofiber as a 3D flexible anode with superior stability and high-rate performance for Li-ion batteries

The fabrication process and material design of flexible lithium-ion batteries (LIBs) are essential in flexible portable devices. In particular, the carbon nanofiber (CNF)-based active anodes with flexibility synthesized using an electrospinning technique showed fairly stable cycling performance in the LIBs. In this study, we synthesized the molybdenum carbide (MoC) embedded in CNFs as an anode for LIBs (MoC/CNF) using an electrospinning technique with amorphous Mo precursor and polyacrylonitrile as the molybdenum and carbon sources, respectively, and using a heating process under an N₂ atmosphere. The as-prepared flexible MoC/CNF showed a 3D porous structure consisting of crystalline MoC and amorphous CNF. MoC/CNF, directly utilized as an active electrode without binder, conductor, or current collector, exhibited superior LIB performance, i.e. high capacity, cyclability, and high-rate properties. In particular, at a considerably high charge/discharge rate of 10?A?g^?1, the specific capacity of MoC/CNF (109?mAh?g^?1) was significantly higher than that of pure CNF electrode (3?mAh?g^?1).     

Characterization of vacuum-annealed TiNb2O7 as high potential anode material for lithium-ion battery

Electrochemical properties of mixed titanium-niobium oxide TiNb₂O₇ (TNO) synthesized via vacuum annealing as high potential anode material for lithium-ion batteries were investigated. Crystal structure, size, and morphology are nearly independent of the annealing atmosphere for starting materials but the color of vacuum-annealed TNO (TNO-V) is dark blue while white for the air-annealed one (TNO-A). X-ray photoelectron spectroscopy analysis also indicated that Ti⁴⁺ and Nb⁵⁺ in TNO are partially reduced into Ti³⁺ and Nb⁴⁺ due to the introduction of oxygen vacancy. Electronic conductivity for TNO-V was around 10⁻³ S cm⁻¹ at room temperature and much higher than that for TNO-A (=10⁻¹¹ S cm⁻¹). In electrochemical testing, both TNO-A and TNO-V electrodes showed reversible capacity of 260-270 mAh g⁻¹ at low current density of 0.5 mA cm⁻², while at higher current density of 5.0 mA cm⁻², TNO-V electrode retained higher reversible capacity of 140 mAh g⁻¹ than that for TNO-A electrode (=80 mAh g⁻¹). The enhancement of intrinsic electronic conductivity greatly contributes to improve the rate performance of TNO.     

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).     

Microwave-assisted one-pot synthesis of SnC2O4/graphene composite anode material for lithium-ion batteries

Currently, SnC₂O₄ is considered as one of the most promising anode materials for high-energy lithium-ion batteries (LIBs) because its charge capacity is higher than that of metal oxides. Herein, a facile microwave-assisted solvothermal method was employed to obtain SnC₂O₄/GO composites within only 30?min, which is time-efficient. The amount of SnC₂O₄ was increased to 95.3?wt% to improve the capacity of the composite. Pure SnC₂O₄ with a high specific surface area of 19.6?m² g^?1 without any other tin compound was used for fabrication. The SnC₂O₄/GO composite exhibited excellent electrochemical performance, with reversible discharge/charge capacity of 657/659?mA?h?g^?1 after 100 cycles at 0.2?A?g^?1. Furthermore, at high current densities of 1.0 and 2.0?A?g^?1, the SnC₂O₄/GO composite anode exhibited high reversible discharge/charge capacities of 553/552 and 418/414?mA?h?g^?1, respectively, after 200 cycles at room temperature. These improvements were likely obtained because SnC₂O₄ was well composited with graphene, which not only offered rapid electron transfer but also released the tension produced by the volumetric effect during repeated lithiation/delithiation. Cyclic voltammetry (CV) was also performed to further study the electrochemical reactions of SnC₂O₄/GO. The facile microwave-assisted solvothermal method used herein is considered as a highly efficient method to fabricate metal oxalate/graphene composites for use as anode materials in LIBs.