Heterostructural composite of few-layered MoS2/hexagonal MoO2 particles/graphene as anode material for highly reversible lithium/sodium storage

The heterostructural construction of metal disulfide/oxide is essential in the electrochemical performance as anode material for lithium- and sodium-ion batteries (LIBs and SIBs). In this work, an integrated composite of molybdenum disulfide (MoS₂) and hexagonal molybdenum dioxide (MoO₂) together enwrapped in reduced graphene oxide (rGO) is synthesized under hydrothermal condition. In the pelletizing MoS₂-MoO₂/rGO composite, rGO as substrate effectively prevents the restacking and pulverization of MoS₂-MoO₂ during a long cycling process. Meanwhile, the synergistic effect among the MoS₂, MoO₂, and rGO components are responsible for abundant active sites and shorten ionic transport channels. When evaluating as anode material for LIB, MoS₂-MoO₂/rGO sample presents excellent cyclic performance and still delivers a high capacity of 1062.3 mA h g⁻¹ after 120 cycles at 0.2 A g⁻¹; evaluating in a SIB at 0.04 A g⁻¹, it presents excellent cyclic performance and delivers 430 mA h g⁻¹ at the 80th cycle. The heterostructural composite MoS₂-MoO₂/rGO is one of the candidate anode materials for high-performance LIB and SIB.     

Improved potassium ion storage performance of graphite by atomic layer deposition of aluminum oxide coatings

In the context of large scale and low-cost energy storage, the emerging potassium-ion batteries (PIBs) are one potential energy storage system. Graphite, a commercial anode material widely used in lithium-ion batteries (LIBs), can be directly applied to PIBs through forming the stage I graphite intercalation compound (KC₈). However, the dramatic volume expansion during the formation of KC₈ can result in poor cycling performance. In this work, one Al₂O₃ atomic layer coated on the surface of graphite via atomic layer deposition (ALD) process, aiming to construct a stable solid electrode interface and enhance the performance of graphite anode in PIBs. The electrochemical performance analysis shows that the 20 cycles Al₂O₃ deposited graphite have improved cycle stability of 223 mAh g⁻¹ at 50 mA g⁻¹ after 50 cycles compared with the raw graphite anode of 92 mAh g⁻¹.     

Improving the performance of graphite anodes in rechargeable lithium batteries

A low cost graphite was examined as a negative electrode for rechargeable lithium batteries. The use of an electrolyte solution consisting of LiPF₆ (1 mol dm⁻³) in ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 2:1 resulted in a capacity loss of 35% on the first cycle. When small quantities of dimethyl pyrocarbonate (DMPC) were added to the binary electrolyte system, the capacity loss on the first cycle was only 18% and thereafter a practical capacity value of 357 mA h g⁻¹ was sustained for more than 50 cycles, representing more than 2000 h of cycling.     

Improved electrochemical performance of modified natural graphite anode for lithium secondary batteries

Modified natural graphite is synthesized by surface coating and graphitizing process on the base of spherical natural graphite. The modified natural graphite is examined discharge capacity and coulombic efficiency for the initial charge–discharge cycle. Modification process results in marked improvement in electrochemical performance for a larger discharge capacity and better coulombic efficiency. The mechanism of the enhancement are investigated by means of X-ray powder diffraction, scan electron microscopy, and physical parameters examination. The proportion of rhombohedral crystal structure was reduced by the heat treatment process. The modified natural graphite exhibits 40 mAh g⁻¹ reduction in the first irreversible capacity while the reversible capacity increased by 16 mAh g⁻¹ in comparison with pristine graphite electrode. Also, it has an excellent capacity retention of ∼94% after 100 cycles and ∼87% after 300 cycles.     

Facile sonochemical synthesis of strontium phosphate based materials for potential application in supercapattery devices

Among hybrid energy storage devices, supercapattery gained profound research interest due to its ability to give high energy density while maintaining the power density and cyclic stability. Herein, novel low-cost strontium based materials are synthesized by controlled sonochemical method and subsequently calcined at various temperatures. The multiple phases of the material synergistically contributed in the electrochemical charge storage process and give high specific capacity of 220 C g⁻¹ (as-prepared material) and 213 C g⁻¹ (calcined at 200 °C) at 0.5 A g⁻¹. A thorough electrochemical performance of optimized material is investigated as an electrode in asymmetric device. The supercapattery (SP2//AC) exhibits a specific capacity of 103.4 C g⁻¹ at 0.5 A g⁻¹ in the voltage range of 0–1.7 V. Furthermore, supercapattery offers a considerably high specific energy of 24.4 Wh kg⁻¹ at a specific power of 425 W kg⁻¹ and an excellent specific power of 1870 W kg⁻¹ by maintaining specific energy at 14.5 Wh kg⁻¹. In addition, the device retained its specific capacity to 90% after 3000 charging/discharging cycles at 1 A g⁻¹. Strontium based materials could be proposed as an appropriate electrode material for energy storage systems.     

Wet-chemistry synthesis of Li4Ti5O12 as anode materials rendering high-rate Li-ion storage

Compared with traditional anode materials, spinel-structured Li₄Ti₅O₁₂ (LTO) with “zero-strain” characteristic offers better cycling stability. In this work, by a wet-chemistry synthesis method, LTO anode materials have been successfully synthesized by using CH₃COOLi·2H₂O and C₁₆H₃₆O₄Ti as raw materials. The results show that sintering conditions significantly affect purity, uniformity of particle sizes, and electrochemical properties of as-prepared LTO materials. The optimized LTO product calcined at 650°C for 20 hours demonstrates small particle sizes and excellent electrochemical performances. It delivers an initial discharge capacity of 242.3 mAh g⁻¹ and remains at 117.4 mAh g⁻¹ over 500 cycles at the current density of 60 mA g⁻¹ in the voltage range of 1.0 to 3.0 V. When current density is increased to 1200 mA g⁻¹, its discharge capacity reaches 115.6 mAh g⁻¹ at the first cycle and remains at 64.6 mAh g⁻¹ after 2500 cycles. The excellent electrochemical performances of LTO can be attributed to the introduction of rutile TiO₂ phase and small particle sizes, which increases electrical conductivity and electrode kinetics of LTO. Therefore, as-synthesized LTO in this study can be regarded as a promising anode candidate material for lithium-ion batteries.     

In situ self‐template synthesis of cobalt/nitrogen‐doped nanocarbons with controllable shapes for oxygen reduction reaction and supercapacitors

Shape‐controlled Co/N‐doped nanocarbons derived from polyacrylonitrile (PAN) were synthesized by a one‐step in situ self‐template method followed by a pyrolysis procedure. This is the first study to tune the nanostructure of Co/N‐doped carbon materials by providing a metal salt as the template and additive. The moderate surface area (699.47 m² g^?1), highly developed pore structure, homogenous Co and N doping and designed “egg‐box” structure impart Co/N‐doped cross‐linked porous carbon (Co/N‐CLPC) with excellent electrocatalytic activity and capacitive performance. This material displayed an onset potential of 0.805 V (vs RHE), a current density of ?5.102 mA cm^?2, excellent long‐term durability, and good resistance to methanol crossover, which are comparable with the characteristics of a commercial 20‐wt% Pt/C catalyst. In addition, Co/N‐CLPC demonstrated a high specific capacitance of 313 F g^?1 at 0.5 A g^?1, notable rate performance of 63% at 50 A g^?1, and good cycling stability of 104.8% retention after 5000 cycles when used as a supercapacitor electrode. This method enables new routes to obtaining Co/N‐doped nanocarbons with shape‐controlled structures for energy conversion and storage applications.     

Facile synthesis of nitrogen-doped Sn@NC composites as high-performance anodes for lithium-ion batteries

Owing to its high capacity of 994 mAh g^?1, low cost, and environmental friendliness, tin (Sn) is considered as an advanced anode material for high-capacity lithium-ion batteries (LIBs). Here, a facile strategy to fabricate core-shell structured Sn@NC composites with one-step and large-scale production is introduced in a liquid-phase reaction under room temperature. When used as anode materials for LIBs, the optimal Sn@NC composite delivers a high reversible discharge capacity of 761.2 and 476 mAh g^?1 at a current density of 200 and 1000 mA g^?1 after 200 cycles, respectively. A high capacity of 328.3 mAh g^?1 can also be obtained even at a current density of 2000 mA g^?1. The excellent cycling stability and rate performance of the composite can be ascribed to the synergistic effect of the nanometer size of Sn powder and porous structure of the carbon shell, both of which can effectively reduce the absolute volume change of electrode during the repeated charge-discharge cycles, and thus lead to excellent electrochemical performances at both rate capability and cycling life.     

Flexible supercapacitor based on three‐dimensional cellulose/graphite/polyaniline composite

Fast charge‐discharge rate and high areal capacitance, along with high mechanically stability, are the pre‐requisites for flexible supercapacitors to power flexible electronic devices. In this paper, we have used three‐dimensional polyacrylonitrile graphite foam as flexible current collector for electro‐deposition of polyaniline (PANI) nanowires. The graphite foam with PANI was then used to fabricate symmetric supercapacitor. The fabricated supercapacitor in the three‐electrode system shows a high specific capacitance (C_sp) of 357 F.g^?1 and areal capacitance (C_areal) of 7142 mF.cm^?2 in 1 M H₂SO₄ at current density of 80 mA.cm^?2, while using two‐electrode system, it shows C_sp of 256 F.g^?1 and C_areal of 5120 mF.cm^?2 in 1 M H₂SO₄ at current density of 100 mA.cm^?2. The current density of 100 mA.cm^?2 is up to 10 folds higher than reported current densities of many PANI‐based supercapacitors. The high capacitance can be attributed to the spongy network of PANI‐NWs on three‐dimensional graphite surface which provides an easy path for electrolyte ions in active electrode materials. The developed supercapacitor shows specific energy of 64.8 Whkg^?1 and a specific power of 6.1 kWkg^?1 with a marginally decrease of 1.6% in C_sp after 1000^th cycles, along with coulombic efficiency retention of 87% in polyvinyl alcohol/H₂SO₄ gel electrolyte. This flexible supercapacitor exhibits great potential for energy storage application.     

High‐performance porous lead/graphite composite electrode for bipolar lead‐acid batteries

In general, thicker active material bipolar electrode's specific capacity and cycle life are very poor owing to its low bonding strength between the active material and the substrate and the diffusion rate of the sulfuric acid electrolyte inside the active material. In this paper, we synthesize a novel attached and porous lead/graphite composite electrode for bipolar lead‐acid battery and can effectively solve these problems. The graphite/polytetrafluoroethylene emulsion is employed to improve the bonding strength and conductivity and the porous can provide electrolyte diffusion channels. The specific capacities of 2‐mm thick positive active material at 0.25, 0.5, 1 and 2 C can attain 75.99, 58.98, 47.97, and 33.36 mAh·g^?1. The discharge voltage platform is also relatively high and no rapid decline with increasing discharge rate. Furthermore, after 80 cycles, the specific capacity does not drop evidently. Copyright © 2017 John Wiley & Sons, Ltd.     

Magnetic tubular carbon nanofibers as anode electrodes for high‐performance lithium‐ion batteries

Novel magnetic tubular carbon nanofibers (MTCFs) are prepared through the combination technique of hypercrosslinking, control extraction, and carbonization. The diameter of MTCFs is mainly concentrated between 90 and 120 nm, and the average tube diameter is about 30 nm. A trace amount of Fe₃O₄ exists inside the MTCFs with a particle size of 3 nm, which is formed by in situ conversion of the catalyst (FeCl₃) for the hypercrosslinking reaction. The MTCFs with high surface area (448.74 m² g^?1) and porous wall are used as anode material for lithium‐ion batteries. The electrochemical properties of MTCFs are compared, and tubular carbon nanofibers (TCFs) prepared by the complete extraction. Electrochemical analysis shows that the introduction of Fe₃O₄ nanoparticles makes MTCFs have higher reversible capacity and better rate performance. MTCFs exhibit high reversible specific capacity of 1011.7 mAh g^?1 after 150 cycles at current density of 100 mA g^?1. Even at high current density of 3000 mA g^?1, a remarkable reversible capacity of 270.0 mAh g^?1 is still delivered. Thus, the novel MTCFs show potential application value in anode material for high‐performance lithium‐ion battery.     

Polymer-derived-SiCN ceramic/graphite composite as anode material with enhanced rate capability for lithium ion batteries

We report on a new composite material in view of its application as a negative electrode in lithium-ion batteries. A commercial preceramic polysilazane mixed with graphite in 1:1 weight ratio was transformed into a SiCN/graphite composite material through a pyrolytic polymer-to-ceramic conversion at three different temperatures, namely 950 °C, 1100 °C and 1300 °C. By means of Raman spectroscopy we found successive ordering of carbon clusters into nano-crystalline graphitic regions with increasing pyrolysis temperature. The reversible capacity of about 350 mAh g⁻¹ was measured with constant current charging/discharging for the composite prepared at 1300 °C. For comparison pure graphite and pure polysilazane-derived SiCN ceramic were examined as reference materials. During fast charging and discharging the composite material demonstrates enhanced capacity and stability. Charging and discharging in half an hour lead to about 200 and 10 mAh g⁻¹, for the composite annealed at 1300 °C and pure graphite, respectively. A clear dependence between the final material capacity and pyrolysis temperature is found and discussed with respect to possible application in batteries, i.e. practical discharging potential limit. The best results in terms of capacity recovered under 1 V and high rate capability were also obtained for samples synthesized at 1300 °C.     

Improvement of cyclic behavior of a ball-milled SiO and carbon nanofiber composite anode for lithium-ion batteries

The cyclic performance of a composite SiO and carbon nanofiber (CNF) anode was examined for lithium-ion batteries. SiO powder of several micrometers was pulverized using high energy mechanical milling. The SiO was ball-milled for 12 h with CNF to produce a composite electrode material that exhibited excellent cycling performance. A reversible capacity of approximately 700 mAh g⁻¹ was observed after 200 cycles. The excellent cyclic performance was discussed with respect to the change of the valence state of Si by ball-milling. A large irreversible capacity at the first cycle for the SiO/CNF composite electrode was reduced to 2% by chemically pre-charging with a lithium film attached to the rim of the electrode.     

Self-assembled Mo doped Ni-MOF nanosheets based electrode material for high performance battery-supercapacitor hybrid device

The application of MOF materials in supercapacitors has been greatly restricted due to the poor conductivity and structural stability. Given that, this work improves the conductivity and stability of Ni-MOF by self-assembled strategy. We report here the Mo-doped Ni-MOF nanosheets (M-NMN), in which the Mo-based clusters are encapsulated in the holes of the Ni-MOF frame structure by self-assembly. The results show that the M-NMN-1 material with a Mi/Mo molar ratio of 1: 1 exhibits an excellent electrochemical performance. Furthermore, the nanosheet structure of the M-NMN-1 materials acts as a “superhigh way” for charge transport to accelerate charge transfer rate and enhance the conductivity of the electrode materials. As-prepared M-NMN-1 electrode material exhibits high specific capacity of 802 C g⁻¹ at 1 A g⁻¹. Furthermore, assembled battery-supercapacitor hybrid device exhibits an excellent energy density of 59 Wh kg⁻¹ at a power density of 802 W kg⁻¹, and superior cycle retention of 93% after 20,000 cycles.     

Multiporous core-shell structured MnO@N-Doped carbon towards high-performance lithium-ion batteries

It is imminently to seek for high energy density in addition to a sensational lifetime of lithium-ion batteries (LIBs) to meet growing requisition in the energy storage application. Anode containing metal oxide composite is being thoroughly investigated for their higher capacity than that of the commercial graphite. A multiporous core-shell structured metal oxide composite anode possessing the excellent capacity and superb lifespan for LIBs is designed. In detail, metal oxide (i.e., MnO) is encapsulated in N-doped carbon shell (MnO@N–C) via coprecipitation-annealing technique. During annealing, abundant void space among MnO cores/between MnO cores and N–C shells is obtained. This space can efficaciously buffer volume changes of MnO upon cycles. Benefiting from the unique structure and heteroatom doping, the capacity of MnO@N–C microcube anode exhibits 576 mAh g⁻¹ at 5 A g⁻¹ with an ultra-long lifespan more than 3500 cycles. The connection between the electrode characteristics and structure is concurrently examined by adopting kinetic analysis. Finally, a full lithium-ion battery is presented, applying the MnO@N–C (anode) and Nick-rich layered oxide (cathode). It is believed that structural designing with heteroatom doping can be utilized in vaster fields for superior capabilities.     

Simple synthesis of honeysuckle-like CuCo2O4/CuO composites as a battery type electrode material for high-performance hybrid supercapacitors

In this paper, porous CuCo₂O₄/CuO composites with novel honeysuckle-like shape (CuCo₂O₄/CuO HCs) have been prepared for the first time by a simple hydrothermal method and followed with an additional annealing process in air. The unique CuCo₂O₄/CuO HCs consisted of dense and slender petals with length of 1.3–1.5 μm and width of about 50 nm, and possessed a specific surface area of 36.09 m² g^?1 with main pore size distribution at 10.63 nm. When used as the electrode materials for supercapacitors, the CuCo₂O₄/CuO HCs exhibited excellent electrochemical performances with a high specific capacity of 350.69 C g^?1 at 1 A g^?1, a rate capability of 78.6% at 10 A g^?1, and 96.2% capacity retention after 5000 cycles at a current density of 5 A g^?1. In addition, a hybrid supercapacitor (CuCo₂O₄/CuO HCs//AC HSC) was assembled using the CuCo₂O₄/CuO HCs as positive electrode and activated carbon (AC) as negative electrode. The HSC device delivered a specific capacity of 187.85 C g^?1 at 1 A g^?1 and a superior cycling stability with 104.7% capacity retention after 5000 cycles at 5 A g^?1, and possessed a high energy density of 41.76 W h kg^?1 at a power density of 800.27 W kg^?1. These outstanding electrochemical performances manifested the great potential of CuCo₂O₄/CuO HCs as a promising battery-type electrode material for the next-generation advanced supercapacitors with high-performance.     

Synthesis of novel pseudo-capacitive perovskite nanostructured flowerlike KTaO3 for lithium ion storage

Research and technology development of lithium ion battery is very important nowadays because of its high energy and power density, low self discharge, no/less memory effect, comparatively high current output. It has been largely used in various fields like hybrid electric vehicles (EV's), portable devices, digital cameras and many more. As per our knowledge this is the first report on the synthesis of KTaO₃ and examination of electrochemical performance on lithium ion batteries (LIB). The flower like nanostructured KTaO₃ exhibits high interfacial area and less path length for charge transfer, which was the main reason to exhibit good electrochemical properties. The average crystallite size of material was confirmed by XRD analysis and found to be ~26 nm. The high irreversible capacity was recorded at 1307 mAh g⁻¹ with high Columbic efficiency (~99%) at potential window of 0.01–3.00 V. Moreover, reversible first discharge capacity was measured at 432 mAh g⁻¹ at 0.1 C current rates with exemplary cyclic stability. The capacity fade was negligible for consecutive cycles. Even at very high current rate (3C) also it presents good capacity of 74 m Ahg⁻¹ with excellent reversibility. In addition, electrochemical impedance spectra prove the less conductive resistance at higher frequency region. Finally the present work explains the excellent electrochemical performance of nanostructured flower like KTaO₃ for Li-ion battery as anode material.     

Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

Cobalt-doped layered lithium nickel oxide as a three-in-one electrode for lithium-ion and sodium-ion batteries and supercapacitor applications

Layered LiNi_0.94Co_0.06O₂ (LNCO) was prepared and explored as an energy-storage material for Li-ion (LIBs), Na-ion (SIBs) batteries as well as supercapacitor application for the first time. All the physical and morphological characterizations were studied for the sample LNCO. The result displays good thermal stability, phase purity in the crystal structure, appreciable Brunauer-Emmett-Teller (BET) surface area (5.53 m² g⁻¹) and possesses cubic morphology. The cobalt was identified in lithium nickel oxide with binding energies at 794.02, 779.04 and 784.30 eV, respectively. In the case of LIBs, LNCO exists with a minimal difference of 5 mAh g⁻¹, even when cycled from 2C to 0.1C. After 200 cycles, the specific capacity, 247 mAh g⁻¹, is obtained for the cell with retention of 97.8% (efficiency 99.8%) at 0.1C. In SIBs, at 0.1C, the discharge capacity of 182 mAh g⁻¹ was restored even when cycled after 2C. After 200 cycles, a discharge capacity of 204 mAh g⁻¹ is ensured with retention of 96.6% (efficiency of 99.4% at 0.1C). In supercapacitor, the electrode, LNCO, delivered a specific capacity of 300 F g⁻¹ at 0.5 A g⁻¹. Therefore, LNCO is highly recommended as a suitable electrode material for fulfilling the requirement of energy-storage applications.     

Niobium carbide/reduced graphene oxide hybrid porous aerogel as high capacity and long‐life anode material for Li‐ion batteries

Two‐dimensional material MXenes owing to their hydrophilic nature, surface termination, and high conductivity can be used in the energy storage device as an anode material. However, poor ion transfer and less available intercalating sites due to self‐stacking of MXene sheets prevent comprehensive utilization of their electrochemical properties. To resolve this problem, a facile method is introduced in this paper to disperse MXene sheets onto reduced graphene oxide sheets to form a porous structure by enhancing electrostatic interactions between two components, which can facilitate ion movement and provide access of ions to more intercalating sites. This hybrid material delivered a capacity of 357 mAh g^?1 at 0.05 A g^?1 as anode in case of lithium‐ion batteries. Furthermore, the hybrid material showed exceptional stability even after 1000 cycles at 1 A g^?1. Current work offers an easy approach for the synthesis of high‐performance niobium carbide‐based hybrid energy storage materials.