Reversible Discharge Specific Capacity Research Articles

Microwave-etched V2C MXene-activated carbon hybrid as a high-performance anode material for lithium-ion batteries

Activated carbon (AC) has been widely utilized as an active material in lithium-ion batteries (LIB) due to its stability and abundance. Nevertheless, the performance of AC anode materials alone falls short of competing with hybrid anode materials, which can attain maximum discharge capacity. Recently, a new two-dimensional (2D) transition metal carbide, MXene, has shown promising performance as an anode in LIB applications. The combination between AC and MXene has proved to improve battery performance previously. Thus, in this study, the electrode was prepared using a hybrid of activated carbon with vanadium carbide MXene (V2C), which was synthesized by etching V2AlC with in situ of hydrochloric acid (HCl) and lithium fluoride (LiF) at 90 °C for 30 min via microwave-assisted hydrothermal technique. The characterization by XRD pattern shows the appearance of V2C MXene peak at 7.23°, indicating the successful etching from V2AlC MAX. The as-prepared AC/V2C_D at ratio 9:1 revealed excellent electrochemical properties as anode LIB, owned capacity up to 562 mAh g−1 (at 50 mA g−1) with cycling stability and columbic efficiency of 95.87 % and 98.2 %, respectively after 50 cycles. Moreover, AC/V2C_D exhibited the smallest Rct (18.50 Ω), and the discharge capacity of 370.25 mAh g−1 was restored after 60 cycles when the current density returned to 50 mAg−1, implying a good reversibility performance and high endurance for LIB. Furthermore, the fabricated full cell of AC/V2C_D//LiFePO4 exhibits initial discharge and charge capacity at 159.6 and 199.8 mAh g−1, respectively, with 79.9 % of CE and delivers a stable cycling performance with reversible discharge specific capacity of 82.72 mAh g−1 after 100 cycles. These promising results prove that the hybrid of AC/V2C_D MXene can be good potential as an anode material in future LIBs applications.

Construction of high-rate performance sulfurized Poly(acrylonitrile) nanofibers cathodes for practical lithium–sulfur batteries via tellurium catalytic regulation

The rapid charge-discharge and wide operating temperature range are of great significance to the research of lithium-sulfur batteries. However, the poor electronic and ionic conductivity of sulfurized polyacrylonitrile limits the high-rate and low-temperature performance of lithium-sulfur batteries. In this work, a tellurium-doped sulfurized polyacrylonitrile nanofibers-based cathode material (Te0.02S0.98FPAN) is successfully fabricated by air-blow spinning for lithium-sulfur batteries. It is found that Te0.02S0.98FPAN maintained a high reversible specific capacity of 742 mAh·g−1composites after 200 cycles at a current density of 0.2 C (0.014% decay per cycle), whereas it provides a reversible specific capacity of 641 mAh·g−1composites after 500 cycles even at a large current density of 1.0 C (0.021% decay per cycle), manifesting its excellent high-rate performance. Moreover, Te0.02S0.98FPAN still maintained a high reversible specific discharge capacity of 586 mAh·g−1composites after 100 cycles at 0.2 C at a low temperature of 5.0 °C, confirming its wide operating temperature range. Both the eutectic accelerator (tellurium) and the one-dimensional nanofibrous structure greatly improve the migration rate and electron transport ability of Li+ ions, enhancing reaction kinetics and providing fast and stable migration channels for ions and electrons. Therefore, Te0.02S0.98FPAN has a higher oxidation-reduction reaction rate and less polarization. This study not only provides new ideas for the cathode design of lithium-sulfur batteries with high rate and wide temperature range, but also paves the way for the development of practical lithium-sulfur batteries. In particular, when tested in practical conditions of high areal loading (Te0.02S0.98: 5.0 mg cm−2) and lean electrolyte (E/Te0.02S0.98: 10 μL mg−1), this cathode delivers high reversible capacities of 725 mAh g−1 composite (0.1 C) and 663 mAh g−1 composite (0.2 C), demonstrating its great potential for future application.

SnO2 nanoparticles uniformly encapsulated in polyaniline-derived nitrogen-doped carbon as anode materials for lithium-ion batteries

SnO2 nanoparticles encapsulated in polyaniline (PANI)-derived nitrogen-doped carbon composite powders (SnO2/NC) are successfully synthesized by in-situ polymerization and carbonization processes under an inert atmosphere. The results indicate that SnO2 nanoparticles of the targeted powders (SnO2/NC-3) are uniformly dispersed in the N-doped carbon matrix when the added amount of SnCl4·5H2O is precisely controlled at 3 mmol, in which PANI suppresses the aggregation of SnO2 nanoparticles and is converted into N-doped carbon during the calcination process. The cell assembled with the SnO2/NC-3 electrode displays high initial discharge specific capacity of 1116.3 mAh g−1 and reversible discharge specific capacity of 567.2 mAh g−1 after 100 cycles at 100 mA g−1. Moreover, the SnO2/NC-3 electrode also exhibits relatively high Li+ ions diffusion coefficient of about 1.22 × 10−12 cm2 s−1. The improved electrochemical performance can be partly ascribed to the fact that the proper amount of SnO2 nanoparticles contributes to the enhancement of lithium storage capacity, and partly to that the N-doped carbon effectively relieves the volume expansion of SnO2 nanoparticles. Therefore, the proposed method of using PANI as N-doped carbon source may provide a feasible strategy to fabricate anode materials for high-performance lithium-ion batteries.

Semi-Ionic C-F bond enabling fluorinated carbons rechargeable as Li-ion batteries cathodes

Fluorinated carbon (CFx) cathodes possess the highest theoretical energy density among lithium primary batteries. However, achieving reversibility in CFx remains a significant challenge. This work employs a high-voltage sulfolane electrolyte and achieves a highly reversible CFx cathodes in lithium-ion batteries (LIBs) via fine modification of the C-F bond character. The improved reversibility of CFx originates from the semi-ionic CFx phase, with a superior bond length and weaker bond energy than a covalent bond. This characteristic significantly mitigates the challenges encountered during the charging process. We screen and identify the fluorinated graphene CF1.12 as a suitable cathode, providing an appropriate fluorine content and sufficient semi-ionic C-F bonds for rechargeable LIBs. This fluorinated graphene CF1.12 exhibits an initial discharge specific capacity of 814 mAh g−1 and a reversible discharge specific capacity of 350 mAh g−1. This work provides a new clue for chemical bond regulation studies and provides insights into stimulating reversibility of primary-cell cathodes.

Expanded MoS2@C nanosheets by three-roll milling for high-performance potassium ion batteries

Molybdenum disulfide (MoS2) as a candidate material for potassium ion storage has attracted extensive attention. However, the slow reaction kinetics and nanosheet stacking during K+ intercalation result in poor rate performance and cycling performance. It is claimed that increasing the layer spacing and carbon coating are effective methods to improve these problems. So, MoS2@C nanosheets with large layer spacing (0.711 nm) are prepared by hydrothermal combined with three-roll milling. As the anode electrode for K+ storage, the MoS2@C nanosheet electrode remains a reversible discharge specific capacity of 164.5 mAh/g at 0.5 A/g after 300 cycles. Even at 2 A/g, it can still maintain 125.5 mAh/g at the 150th cycle. This study provides a new strategy for the preparation of large-spaced layered sulfide nanosheets and their application in rechargeable batteries.

Interplanar Spacing Engineering on Copper‐Benzenedicarboxylate Toward Stabilized Lithium Storage

Metal–organic frameworks (MOFs) have drawn intensive attention for their prospect as electrode materials of lithium‐ion batteries. However, MOFs with high capacity usually suffer from poor cycling stability, due to the volume fluctuation during cycles. Herein, based on the structure tenability of MOFs, copper phthalate (Cu‐oBDC), copper isophthalate (Cu‐mBDC), and copper terephthalate (Cu‐pBDC) with the same active sites for lithium storage are chosen as target materials and investigated as anodes for LIBs. The three MOF materials display different cycle stability in the galvanostatic charge–discharge test. Cu‐mBDC and Cu‐pBDC show obvious performance attenuation in cycles, while Cu‐oBDC with the largest interplanar spacing (13.02 Å) is eventually stabilized, and the solid electrolyte interface membrane is formed in the later cycling. At a current density of 100 mA g−1, the Cu‐oBDC delivers a reversible specific discharge capacity of 683.6 mAh g−1after 250 cycles, outperforming the other two counterparts. This work adjusts the crystal structure of MOFs toward the improvement of cycle stability and provides a strategy to optimize the electrochemical performances of MOFs.

Critical roles of synthesis temperature and an effective solid electrolyte interphase in improving the electrochemical performance of carbon coated Fe3BO5 anode at high C-rates

Samples of core/yolk-shell structured, carbon-coated vonsenite (Fe3BO5) are synthesized by the solid-state method and utilized as conversion-type anode materials. The core consists of vonsenite nanoparticles, while the shell is composed of a defective (partially graphitized) carbon layer. A higher synthetic temperature leads to the formation of larger amounts of metallic impurities as a result of the carbothermal reduction. The electrochemical characteristics of the sample synthesized at a lower temperature (600 °C) are better than those of the samples synthesized at higher temperatures and without the carbon coating. This can be attributed to the smaller-sized crystallites having the least amount of metallic impurities and a better-formed solid electrolyte interphase (SEI). This optimized sample demonstrates an outstanding reversible specific discharge capacity of 976 mAh g-1 at a current density of 0.05 A g-1. Long cyclability test at an ultra-high C-rate of 5 A g-1 outlines the critical role of an effective SEI and carbon coating. Remarkably, this sample is able to sustain even further electrochemical abuse, and shows electrochemical activity up to a C-rate of 20 A g-1, thus validating the usefulness of this material as a safe and stable anode for fast charging-discharging Li-ion battery applications.

A nonflammable diethyl ethylphosphonate-based electrolyte improved by synergistic effect of lithium difluoro(oxalato)borate and fluoroethylene carbonate

The vital physical and chemical properties of the lithium conducting salt, solvent/co-solvent and functional additive determine the overall properties and performance of the resulting electrolyte formulation. Explorations on right combinations of the carefully selected electrolyte components are expected to further balance the electrochemical and safety performances of chosen electrolyte formulations in given cell chemistries. In this study, a new nonaqueous aprotic electrolyte is designed by using lithium difluoro(oxalato)borate (LiODFB) as conducting salt, diethyl ethylphosphonate (DEEP) as solvent, and fluoroethylene carbonate (FEC) as co-solvent to achieve a nonflammable electrolyte formulation with competent electrochemical performance. The LiODFB and FEC are believed to take part in complex interfacial interactions with a synergistic effect. LiNi0.8Co0.1Mn0.1O2 (NCM811)‖Li cells using the optimized electrolyte formulation of 1.3 M LiODFB/DEEP 30% FEC exhibits a stable long-term cycling performance at 1.0 C with a reversible average specific discharge capacity of 169.5 mAh g−1 during 100 cycles, which is comparable to cells using commercial electrolytes. Furthermore, the 1.3 M LiODFB/DEEP 30% FEC electrolyte shows good thermal stability and effectively reduces the heat generation during thermal decomposition of NCM811 cathode. The results provide a good reference for the design of next generation of safe, nonflammable electrolytes for lithium-based battery application.

Electrospinning fabrication of Sb-SnSb/TiO2@CNFs composite nanofibers as high-performance anodes for lithium-ion batteries

The SnSb and TiO2 nanoparticles uniformly embedded into continuous and conductive carbon nanofibers (CNFs) are successfully fabricated through facile electrospinning combined with calcination treatments. The characterization results of the targeted composite nanofibers (Sb-SnSb/TiO2@CNFs-2) confirm that the presence of TiO2 is of significant importance to construct the elaborately designed and intact fiber structure, in which the optimal dosage of the TiO2 precursor is precisely controlled at 2 mmol. Moreover, high theoretical specific capacity of SnSb, available inhibitory effect of TiO2, and great electronic conductivity of CNFs are cooperatively integrated into the Sb-SnSb/TiO2@CNFs-2 composite nanofibers, guaranteeing the enhanced lithium storage capacity and cycling performance when being employed as the anode electrodes. Specifically, the Sb-SnSb/TiO2@CNFs-2 electrode can not only deliver initial discharge specific capacity of 1146.6 mAh/g at 100 mA/g and reversible discharge specific capacity of 580.4 mAh/g after 100 cycles, but also retain discharge specific capacity of 561.3 mAh/g after rate cycles along with recovering the current density to 100 mA/g. Importantly, the Sb-SnSb/TiO2@CNFs-2 electrode is also endowed with prominent advantages in the pseudocapacitive contribution of 66.89 % at 0.8 mV/s. Those investigations and findings of the Sb-SnSb/TiO2@CNFs-2 composite electrodes with facile fabrication process and excellent electrochemical performance can contribute to the practical application of the alloy anodes in the field of the energy storage.

Lychee seed-derived microporous carbon for high-performance sodium-sulfur batteries

Sodium-sulfur (Na–S) batteries are regarded as one of the promising next-generation energy storage systems; while being more cost-effective than lithium-sulfur batteries, Na–S batteries also suffer from the shuttle effect. Different strategies to tackle the long-chain polysulfide product shuttling issue have been proposed, mainly focusing on sulfur product confinement with costly materials and complex methods. Seeking high-performance and low-cost electrode material precursors is of great importance to promoting Na–S battery applications. We present a high specific surface area microporous carbon framework synthesized from degradable biowaste, namely lychee seeds, with a facile room-temperature etching process. Unlike the traditional dissolution-precipitation mechanism, a quasi-solid-state route takes place with the help of micropore (0.48 nm) confinement, preventing the formation of long-chain polysulfides for excellent electrochemical performance. The obtained Na–S battery exhibits an outstanding initial reversible discharge specific capacity of 1395 mAh g−1 at 0.2C and still maintains a high capacity of 518 mAh g−1 after 500 cycles at 1.0C. The lychee seed-derived microporous carbon provides insights into sustainable and scalable host fabrication for high-performance sulfur-based batteries.

Enabling deep conversion reactions by weakening molybdenum-oxygen bonds through K+ pre-intercalation

Conversion-type transition metal oxides (TMOs) anodes with fascinating high theoretical capacities are considered potential candidates for high-energy-density alkali-ion batteries. However, the tremendous advantages of conversion reaction are yet to be fully exploited due to sluggish reaction kinetics and unfavorable thermodynamics. This is especially in the case of non-layered TMOs, where high ion intercalation energy and ion diffusion barriers compared to layered TMOs impede subsequent conversion reaction, while thermodynamically stable metal-oxide bonds with high bond energies prevent efficient cleavage. This work selects MoO2 as a typical non-layered anode of lithium-ion batteries and demonstrates that pre-intercalating K+ ions in MoO2 crystal can decrease the intercalation energy, enhance the diffusion kinetics, and weaken Mo-O bonds to efficiently facilitate conversion reactions by the the density functional theory calculations and experiments. K+ pre-intercalated MoO2 can deliver a higher reversible discharge specific capacity (989 mAh g−1) than the pristine MoO2 sample (720 mAh g−1) at 0.2 A g−1 after 100 cycles. This work provides a novel and crucial method to realize the functionality of non-layered TMOs based anodes and offers a potentially universal optimization strategy toward high-capacity alkali-ion batteries.

A hierarchically porous TiN/N-C electrocatalyst with high interface utilization for lithium-sulfur batteries

Lithium-Sulfur Batteries (LiSBs) are prevented to apply in practice by the irreversible loss from the cathode and difficult conversation kinetics of lithium polysulfides (LiPSs). An ideal S host material should possess high conductivity and sufficiently dispersed catalytic active sites to precisely restore the dissolved LiPSs to the surface of the S host material. In traditional catalyst design, porous carbonaceous materials are often selected as carriers for the nano-catalytic activity sites. However, non-polar pure carbon interfaces, where without nano-catalytic activity sites covered, have a very weak affinity to LiPSs. Here, we use ammonia as a nitrogen source to anneal the reduced aerogel (graphene oxide (rGO) supported nano-TiO2) at high temperatures. The N element is atomically doped into the lattice ofthe carbon matrix, and the nano-TiO2 is converted to nano-TiN. A hierarchically porous and high conductivity TiN/N-C is prepared, in which the nano-TiN is well dispersed on the surface of N-doped rGO as an active center for catalyzing LiPSs conversion. The doped-N elements significantly increase the proportion of the polar surface. The S@TiN/N-C composite cathode delivered an excellent long-life cycling performance, and the reversible discharge specific capacity faded from 1224 ± 16 to 675 ± 31 mAh g−1 after 930 cycles. More importantly, after 150 cycles with a high S loading, a reversible areal capacity of 4.1 mAh cm−2 can be achieved.

The effect of different poly fibers separator-modified materials on blocking polysulfides for high performance Li-S batteries.

Herein, we reported that KOH impregnation can generate a large number of porous structures with fruitful nitrogen self-doped groups during the carbonized process for poly (p-phenylene terephthalamide) fiber and poly (p-phenylene benzobisoxazole) fiber (denoted as PPTA and PBO, respectively). The intrinsical insulation, volume change, and shuttle effect of polysulfides then can be more significantly improved for the PBO-coated separator than the PPTA case. The discharge capacity primary achieves 1,322 mA h/g, which retains 827 mA h/g even after 200 cycles at 0.2 C for the cell with PBO-coated separator. The reversible specific discharge capacity maintains 841 mA h/g with a Coulomb efficiency of 99.7% at 5 C. The nitrogen self-doped nanocarbon particles are etched by KOH with the simple one-step preparation, which has promising application as Li-S battery cathode.

Green Synthesis of a Reduced‐Graphene‐Oxide Wrapped Nickel Oxide Nano‐Composite as an Anode For High‐Performance Lithium‐Ion Batteries

AbstractAeschynomene aspera (AA) plant, a sustainable, waste natural carbon source, is used towards green and scalable synthesis of carbon two‐dimensional materials by simply altering the heating temperature and its composites with nickel oxide (NiO) are fabricated as an anode for high‐performance lithium‐ion batteries (LIBs). Interestingly, a wide range of carbon materials (amorphous carbon, graphene‐oxide (GO), and reduced‐graphene‐oxide(RGO)) can be synthesized from this carbon source that can be used in different applications. Among them, GO synthesized at 500 °C shows best lithium storage properties. While incase of composite the RGO‐NiO fabricated using heated AA plant, at 1000 °C shows excellent lithium storage properties. The RGO‐NiO composite exhibits reversible specific discharge capacity of 847 mAh g−1 at 100 mA g−1 and an excellent rate capability up to 1000 mA g−1. In addition, ex‐situ XRD and XPS measurements reveal reversible nature of the conversion reaction occurring in the composite electrodes.

Self‐Supported CuO In‐Situ‐Grown on Copper Foil as Binder‐Free Anode for Lithium‐Ion Batteries

AbstractTransition metal oxides as anode materials for lithium‐ion batteries (LIBs) possess the advantages of high specific capacity and abundance. However, most reported transition metal oxides based active anode materials were coated on the copper current collector with the addition of inactive polymer binder and conductive agents, resulting in low utilization of active substances. To solve this problem, nanostructured CuO with different morphologies (CuO bunches, CuO nanosheets, CuO nanotubes) were in‐situ grown on the copper current collectors via a simple wet chemical oxidation method. The as‐obtained CuO@Cu foils were used directly as anode for LIBs. CuO nanotubes exhibited excellent electrochemical performance and sustained a reversible discharge specific capacity of 798 mA h g−1 after 60 cycles at 100 mA g−1. At current density of 1000 mA g−1, a high specific capacity of 758 mA h g−1 can be obtained after 200 cycles. The satisfying electrochemical performances of the CuO nanotubes anode indicated that a stable composite structure of CuO@Cu foils was achieved in the binder free electrode. This work demonstrated the feasibility of this binder free strategy in the development of electrode materials for high performance lithium‐ion batteries design.

Superior cycling stability of saturated graphitic carbon nitride in hydrogel reduced graphene oxide anode for Sodium-ion battery

A layered composite g-C3N4@RGO of graphitic carbon nitride (g-C3N4) and reduced graphene oxide (RGO) is reported as an anode material for rechargeable sodium ion batteries (SIBs). Initially, conducting interconnected hydrogel RGO was prepared by hydrothermal method and was further soaked in saturated urea solution, followed by calcination to synthesize g-C3N4@RGO composites. The coin type half cells were prepared by using composite g-C3N4@RGO and pristine RGO as anode and their electrochemical performances were compared. The prepared half-cell of the composite anode delivers maximum reversible specific discharge capacity of ∼ 170 mAh.g−1 and ∼ 160 mAh.g−1 at 0.1C and at 0.2C, respectively. Whereas, prepared half-cell using RGO anode shows maximum reversible discharge capacity of ∼ 146 mAh.g−1 and ∼ 133 mAh.g-1at 0.1C and 0.2C, respectively. This composite material g-C3N4@RGO shows excellent cyclability (2000 cycles) and columbic efficiency ∼ 100% with no capacity fading compared to the RGO. The binding of g-C3N4 with RGO prevents stacking of RGO sheets and provides macro and sub-micron porous structure for smooth intercalation and trapping of Na+-ions in composite g-C3N4@RGO anode during electrochemical cycling. The design of g-C3N4@RGO composite as a negative electrode improves the cell performance and offers effective strategy to develop low-cost and long cycle life SIBs.

Strengthened the structural stability of in-situ F− doping Ni-rich LiNi0.8Co0.15Al0.05O2 cathode materials for lithium-ion batteries

Layered Ni-rich oxides have always been considered as highly promising cathode materials for high-energy–density lithium-ion batteries, whereas they have been confronted with technical bottlenecks sprung from short cycle life and thermal instability. In this work, F− doping as one feasible approach has been introduced into LiNi0.8Co0.15Al0.05O2 for alleviating the limitations by stabilizing the layered structure. The stoichiometric LiNi0.8Co0.15Al0.05O2-xFx (0 ≤ x ≤ 0.1) composite powders doped with different amounts of NH4F powders are precisely synthesized by in-situ modified method, which are strictly identified by physicochemical methods. The characterization results demonstrate that F ions successfully enter into the lattice of LiNi0.8Co0.15Al0.05O2-xFx (0 ≤ x ≤ 0.1) and that the targeted LiNi0.8Co0.15Al0.05O1.96F0.04 composite powders possess the most ordered layered structure with compact surface morphology when the doping amount of F− is up to 4 % based on the weight of the precursor Ni0.8Co0.15Al0.05(OH)2 composite powders. Moreover, the half-cell assembled with the LiNi0.8Co0.15Al0.05O1.96F0.04 composite electrode presents a reversible discharge specific capacity of 157.8 mAh g−1 with remarkable capacity retention of 98.3 % after 100cycles at 2.0C at 25 °C. Even at an elevated temperature of 60 °C and a high current density of 5.0C, it still delivers an improved discharge specific capacity of 142.6 mAh g−1 with excellent capacity retention of 89.1 %. The outstanding improvements in the terms of the lithium storage performance are principally attributed to the stronger metal-F bonds substituting the metal-O bonds with introducing F ions into the lattice, which can not only effectively stabilize the host structure to preserve the structural integrity, but also prevent the erosion of HF and suppress the increment of the polarization degree during continuous cycling processes. Therefore, the F− doping strategy may provide a novel horizon to construct layered Ni-rich cathode materials with improved structural stability and durable electrochemical performance for lithium-ion batteries.

Two Birds with One Stone: A NaCl-Assisted Strategy toward MoTe2 Nanosheets Nanoconfined in 3D Porous Carbon Network for Sodium-Ion Battery Anode

The larger van der Waals interlayer distance of MoTe2 is favorable for Na+ insertion/extraction when MoTe2 is used as sodium-ion battery (SIB) anode. However, engineering of stoichiometric 2D MoTe2 and high-conductivity carbon networks with robust interfacial bonding for SIB anodes is still a great challenge and rarely reported. In this work, high-crystallized 2D MoTe2 nanosheets nanoconfined by interconnected 3D porous carbon networks (indicated with 2D-MoTe2@3DPCN) for SIB anode is successfully constructed via a facile NaCl-assisted strategy. During the synthesis process, the NaCl demonstrates the two birds with one stone effect: the template effect for the formation of interconnected 3D hierarchical porous carbon networks, and the promoting effect of chalcogen atom exchange for in situ conversion from 2D-MoS2 to 2D-MoTe2, which was validated by both experimental results and first-principles simulations. The as-constructed unique architecture not only facilitates both ions and electrons transportation and diffusion throughout the overall electrode, but also can effectively prevent the aggregation of MoTe2 nanosheets and buffer their volume change during the insertion and extraction of Na+. As a result, 2D-MoTe2@3DPCN as SIB anode displays high reversible discharge specific capacity (∼412 mA h g−1 at 100 mA g−1), excellent rate capability (213.8 mA h g−1 at 20 A g−1) and outstanding long cycle life even at high charge/discharge current density (the capacity retention after 3000 cycles is 77.4% at 20 A g−1). This work provides a new path to construct MoTe2-based composites for application in energy-storage fields and beyond.

Tin antimony oxide @graphene as a novel anode material for lithium ion batteries

Bimetal oxides have attracted much attention due to their unique characteristics caused by the synergistic effect of bimetallic elements, such as adjustable operating voltage and improved electronic conductivity. Here, a novel bimetal oxide Sn 0.918 Sb 0.109 O 2 @graphene (TAO@G) was synthesized via hydrothermal method, and applied as anode material for lithium ion batteries. Compared with SnO 2 , the addition of Sb to form a bimetallic oxide Sn 0.918 Sb 0.109 O 2 can shorten the band gap width, which is proved by DFT calculation. The narrower band gap width can speed up the lithium ions transport and improve the electrochemical performances of TAO@G. TAO@G is a structure in which graphene supports nano-sized TAO particles, and it is conducive to the electrons transport and can improve its electrochemical performances. TAO@G achieved a high initial reversible discharge specific capacity of 1176.3 mA h g −1 at 0.1 A g −1 and a good capacity of 648.1 mA h g −1 at 0.5 A g −1 after 365 cycles. Results confirm that TAO@G is a novel prospective anode material for LIBs.

Dual-layer carbon protected coaxial cable-like Si-based composites as high-performance anodes for lithium-ion batteries

The Si-based composites (NC@Si@CNTs) are synthesized successfully by a facile route. Using tetraethylorthosilicate as Si-source, carbon nanotubes (CNTs) and polydopamine as C-source, a dual-layer carbon protected coaxial cable-like structure is achieved. As an anode for Li-ion battery, the dual-layer carbon protection to Si layer gives a initial specific discharge and reversible specific discharge capacity of 2804 and 1752 mAh g−1 at 200 mA g−1 after 150 cycles. Even at 2 A g−1, the NC@Si@CNTs electrode can still display an initial and reversible specific capacities of 2297 mAh g−1 and 910 mAh g−1. The dual-layer carbon protected coaxial cable-like structure also improves the rate performance and cycling stability greatly compared to Si. This might be ascribed mainly to high conductivity and buffer effect of two carbon layers during cycling, which provide more effective transmission paths for electrons and promote fast diffusion for Li ions. In addition, the N-doping of carbon layer for extra Li ions and more stable structure of the as-prepared coaxial cable also contribute to the enhanced specific capacity and cycle stability during the charging/discharging process.