SnO2–graphene–carbon nanotube mixture for anode material with improved rate capacities

SnO₂–graphene–carbon nanotube (SnO₂–G–CNT) mixture is synthesized using graphene oxide as precursor for application as anode material in rechargeable Li ion batteries. It is shown that the SnO₂ nanoparticles of 3–6 nm in diameter are not only attached onto the surface of graphene sheets by anchoring with surface functional groups, but they also are encapsulated in pore channels formed by entangled graphene sheets. The incorporation of carbon nanotubes reduces the charge transfer resistance of the anode made from the mixture through the formation of 3D electronic conductive networks. The SnO₂–G–CNT anodes deliver remarkable capacities of 345 and 635 mAh g⁻¹ at 1.5 and 0.25 A g⁻¹, respectively. Flexible electrodes consisting of highly-aligned SnO₂–G–CNT papers are also prepared using a simple vacuum filtration technique. They present a stable capacity of 387 mAh g⁻¹ at 0.1 A g⁻¹ after 50 cycles through the synergy of the high specific capacity of SnO₂ nanoparticles and the excellent cycleability of G–CNT paper.     

A novel carbon microspheres@SnO2/reduced graphene composite as anode for lithium-ion batteries with superior cycle stability

Many advantages made SnO₂ a potential anode for lithium-ion batteries, but huge volume expansion during cycling seriously impeded its practical application. Here, a novel double-carbon structure with low graphene weight proportion was successfully prepared using a facile hydrothermal method to enhance the long-cycle stability of SnO₂ as anodes for lithium-ion batteries. In this structure, SnO₂ nanoparticles were formed around the surface of the carbon microspheres (CMS), and the reduced graphene (GR) shuttled through the outer layer. As anodes for lithium-ion batteries, the SnO₂ protected by dual carbon (CMS@SnO₂/GR) exhibited outstanding cycle performance with an initial reversible capacity of 789.5 mAh g^-1 and the reversible capacity retention rate of 68.6% after 350 cycles at 200 mA g^-1. The abundance free space among CMS, nano-scale, and the excellent flexibility of graphene were all contributed to alleviating the volume variation of CMS@SnO₂/GR during the lithiation and delithiation.     

High reversible capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion batteries

A gas–liquid interfacial synthesis approach has been developed to prepare SnO₂/graphene nanocomposite. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO₂ nanoparticles (2–6 nm in size) on graphene matrix. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The SnO₂/graphene nanocomposite prepared by the gas–liquid interface reaction exhibits a high reversible specific capacity of 1304 mAh g⁻¹ at a current density of 100 mA g⁻¹ and excellent rate capability, even at a high current density of 1000 mA g⁻¹, the reversible capacity was still as high as 748 mAh g⁻¹. The electrochemical test results show that the SnO₂/graphene nanocomposite prepared by the gas–liquid interfacial synthesis approach is a promising anode material for lithium-ion batteries.     

Multilayer Si@SiOx@void@C anode materials synthesized via simultaneously carbonization and redox for Li-ion batteries

In the development of high-performance lithium-ion batteries (LIBs), the composition and structure of electrode materials are of critical importance. Silicon has a theoretical specific capacity 10 times that of graphite, nonetheless, its application as an anode material confronts challenge as it undergoes huge volume change and pulverization amidst the alloying and dealloying processes. Herein, a novel method to prepare a multilayer Si-based anode was proposed. Three layers, SiO₂, nickel and triethylene glycol (TEG), were coated successively on Si nanoparticles, which served respectively as the sources of SiO_x, sacrificial templates and carbon. Nickel can not only serve as a hollow template, but also play a catalytic role, which makes carbonization and redox reactions occur synchronously under a mild condition. Amid the carbonization process of TEG at 450 °C, several-nm-thick SiO₂ layer can react with the as-derived carbon to form a silicon suboxides (SiO_x (0 < x < 2)) intermedium layer. After removing the nickel template, a micro-nano scaled Si@SiO_x@void@C with conformal multilayer-structure can be obtained. The BET specific surface area and pore volume of powders were increased dramatically because of the derivation of abundant voids, which can not only buffer the swelling effect of silicon, but also provide richer ionic conductivity. The as-assembled half-cell with Si@SiOx@void@C as the anode material possesses high capacity (～1000 mAh g^?1 at 3 A g^?1), long cycle life (300 cycles with 77% capacity retention) and good rate performance (558 mAh g^?1 at 5 A g^?1).     

Synthesis of 1D-MoS2/graphene nanotubes aided with sodium chloride for reversible lithium storage

A novel negative material consisting of graphene nanotubes and ultrathin MoS₂ is synthesized by a simple one-step hydrothermal method assisted with Sodium chloride. The MoS₂/Graphene electrodes deliver a specific capacity of 1350 mAh g^?1 under 0.1 A g^?1 and high rate capability (retaining 85.5% capacity from 0.1 A g^?1 to 0.8 A g^?1). A high remarkable capacity of 820 mAh g^?1 can still be recovered at 0.5 A g^?1 after 500 cycles, and the average coulombic efficiency was as high as 99.98% during the additional 500 cycles. The excellent Li-ion storage performance of MoS₂/Graphene nanotubes may be attributed to the ultra-thin MoS₂ flakes and curled graphene nanotubes. This structural feature has a strong adsorption capacity for lithium ions, which can provide a broad space for ion storage. A large number of active sites dispersed in the layered molybdenum disulfide promote the kinetics of the electrochemical reaction, empowering the ultra-thin layered molybdenum disulfide to get a higher theoretical capacity. In addition, the existence of the tubular structure alleviates volume expansion and provides a way for the rapid movement of electrons and diffusion of Li⁺ during repeated cycles.     

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.     

An environmentally friendly and low-cost catalyst for Li–CO2 batteries based on Co recovered from waste lithium-ion batteries

With the use of lithium batteries increasing year by year, resulting in a large number of waste lithium-ion batteries generated, bringing pressure to the ecological system while also causing a waste of Co resources. Although Co-based catalysts are also of interest in the Li–CO₂ system, no research has been reported on the preparation of catalysts for value-added utilization of recovered Co. In this paper, Li–CO₂ batteries with Co₃O₄/CNT cathodes were prepared by environmentally friendly hydrothermal method employing cobalt oxalate recycled from waste lithium-ion batteries as a Co source in combination with commercial CNT. Unlike traditional noble metal and transition metal-based catalysts, which are expensive and complicated, this work can further reduce the cost of batteries by recycling valuable Co sources from waste lithium-ion batteries. As a result, the battery has the discharge capacity of 2728 mAh g^?1 at a current density of 100 mA g^?1. Not only that, but it can reach more than 85 cycles at a limited capacity of 400 mAh g^?1.     

Graphene aerogel encapsulated Co3O4 microcubes derived from prussian blue analog as integrated anode with enhanced Li-ion storage properties

In lithium-ion batteries (LIB), cobalt oxide is considered an ideal anode material because of its theoretical specific capacity of up to 890 mAh g⁻¹, abundant resources, and low price. However, the volume expansion during the charging and discharging process and its lower conductivity have hindered its development. In this work, a metal-organic framework (MOF) was used as an initial template, encapsulated in graphene aerogels (GA) by hydrothermal and programmed temperature-controlled annealing and eventually formed into Co₃O₄ microcubes@GA composite. GA acts as a three-dimensional conductive network and mechanical skeleton, providing high electrical conductivity and structural stability to the composites. Moreover, the precursor's high porosity and stable structure are retained after annealing treatment. As an anode, the best long cycle life of Co₃O₄ microcubes@GA was achieved when the graphene oxide (GO) concentration was 3.0 mg ml⁻¹, reaching 1234.9 mAh g⁻¹ after 200 cycles at 1 A g⁻¹ with a coulomb efficiency (CE) of 98.97%.     

An ordered mesoporous network consisting of carbon-coated ultrasmall SnO2 nanoparticles with enhanced Lithium storage

An unique ordered mesoporous network consisting of carbon-coated SnO₂ nanoparticles (NPs) is developed by a facile self-assemble strategy via a solvethermal route in which employs N,N-dimethylformamide/H₂O as mixture solvent and polyvinyl pyrrolidone as barrier agent and carbon source. The SnO₂-NPs with an uniform dimension of ~5 nm are observed to interconnect with each other, and assemble into high-compact blocks where abundant mesopores with an average diameter of ~4 nm are found throughout the body. The carbon coating with a thickness of <1 nm are confirmed to exist on these SnO₂-NPs, which is of great importance to avoid the severe sintering that occurs in the case of bare SnO₂-NPs. Furthermore, the carbon coating plays roles in enhancing conductivity and keeping the active particles from being directly contacted with electrolyte, and thus contributes to enhanced reversible capacity of 949 mAh g⁻¹ and improved initial Coulombic efficiency. The composite electrode with a high tap density of 2.0 g cm⁻³ exhibits substantially elevated electrochemical performances, such as a charge capacity of 565 mAh g⁻¹ vs 223 mAh g⁻¹ of common SnO₂-NPs after 60 cycles and greatly improved rate capability, indicating the promising applications of this advanced micro-nano architecture for next-generation lithium-ion batteries.     

Graphene-supported SnO2 nanoparticles prepared by a solvothermal approach for an enhanced electrochemical performance in lithium-ion batteries

SnO₂ nanoparticles were dispersed on graphene nanosheets through a solvothermal approach using ethylene glycol as the solvent. The uniform distribution of SnO₂ nanoparticles on graphene nanosheets has been confirmed by scanning electron microscopy and transmission electron microscopy. The particle size of SnO₂ was determined to be around 5 nm. The as-synthesized SnO₂/graphene nanocomposite exhibited an enhanced electrochemical performance in lithium-ion batteries, compared with bare graphene nanosheets and bare SnO₂ nanoparticles. The SnO₂/graphene nanocomposite electrode delivered a reversible lithium storage capacity of 830 mAh g⁻¹ and a stable cyclability up to 100 cycles. The excellent electrochemical properties of this graphene-supported nanocomposite could be attributed to the insertion of nanoparticles between graphene nanolayers and the optimized nanoparticles distribution on graphene nanosheets.     

Preparation and electrochemical performance of SnO2@carbon nanotube core–shell structure composites as anode material for lithium-ion batteries

Carbon nanotube-encapsulated SnO₂ (SnO₂@CNT) core–shell composite anode materials are prepared by chemical activation of carbon nanotubes (CNTs) and wet chemical filling. The results of X-ray diffraction and transmission electron microscopy measurements indicate that SnO₂ is filled into the interior hollow core of CNTs and exists as small nanoparticles with diameter of about 6 nm. The SnO₂@CNT composites exhibit enhanced electrochemical performance at various current densities when used as the anode material for lithium-ion batteries. At 0.2 mA cm^?2 (0.1C), the sample containing wt. 65% of SnO₂ displays a reversible specific capacity of 829.5 mAh g^?1 and maintains 627.8 mAh g^?1 after 50 cycles. When the current density is 1.0, 2.0, and 4.0 mA cm^?2 (about 0.5, 1.0, and 2.0C), the composite electrode still exhibits capacity retention of 563, 507 and 380 mAh g^?1, respectively. The capacity retention of our SnO₂@CNT composites is much higher than previously reported values for a SnO₂/CNT composite with the same filling yield. The excellent lithium storage and rate capacity performance of SnO₂@CNT core–shell composites make it a promising anode material for lithium-ion batteries.     

Hollow tremella-like graphene sphere/SnO2 composite for high performance Li-ion battery anodes

A hollow tremella-like graphene sphere/tin dioxide (HTGS/SnO₂) composite was successfully prepared by simple emulsification and impregnation followed by calcination. In this material, tin dioxide adheres to the folds on the surface of the hollow tremella-like graphene spheres. Hollow tremella-like graphene spheres as the matrix of SnO₂ not only provide a space of volumetric expansion for the tin oxide particles, relieve the internal stress of the tin dioxide, but also effectively avoid aggregation of the tin dioxide and increase the electrical conductivity. As an anode electrode material for batteries, the initial discharge/charge capacities of HTGS/SnO₂ are 1762.4 mAh g^-1 and 1169.4 mAh g^-1, and the Coulomb efficiency is 96.9%. After 50 cycles, capacity remains 80.4% of reversible capacity. The excellent electrochemical stability is attributed to the extraordinary structure of HTGS/SnO₂. The hollow structure of graphene sphere allows simultaneous insertion of lithium ions from the inner and outer surfaces. Meanwhile, the tin dioxide particles are uniformly dispersed by the wrinkles on the surface of the graphene, thereby enlarging the space for the volume expansion of tin dioxide in order to avoid contact with the electrolyte.     

Enhancing the electrochemical performance of d-Mo2CTx MXene in lithium-ion batteries and supercapacitors by sulfur decoration

With the development of the energy industry, electrochemical energy storage technology is increasingly involved in developing innovations in the field. The materials of the electrode have a significant influence on the performance of energy storage devices. For this purpose, two-dimensional MXene with excellent electrical conductivity, mechanical strength, and a variety of possible surface-active terminations are attracting much attention. In the present work, S-decorated d-Mo₂CT_x (d-Mo₂CT_x--S) is designed. The first-principles calculations reveal that it may possess good energy storage characteristics. Due to the decoration with S, unique morphology and structure are obtained, conferring stability, optimized Li⁺ storage, improved charge transport, and lithium-ion adsorption capabilities. Compared with d-Mo₂CT_x, d-Mo₂CT_x--S exhibits higher discharge capacity (623 mAh g⁻¹ at 1 A g⁻¹) as lithium-ion electrode material and higher specific capacitance (561 F g⁻¹ at 1 A g⁻¹). As a supercapacitor, the material also shows excellent cyclic stability (20,000 charge-discharge cycles). This work may inspire the exploration of other MXene and new surface functionalization methods to improve the performance of MXene as electrode materials for new energy devices.     

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_0.918Sb_0.109O₂@graphene (TAO@G) was synthesized via hydrothermal method, and applied as anode material for lithium ion batteries. Compared with SnO₂, the addition of Sb to form a bimetallic oxide Sn_0.918Sb_0.109O₂ 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.     

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.     

Binder-free multilayered SnO2/graphene on Ni foam as a high-performance lithium ion batteries anode

The reasonable structure construction of electrode materials with superior performance is desired for the new generation lithium ion batteries (LIBs). Herein, binder-free multilayered SnO₂/graphene (GN) on Ni foam was fabricated via a dip coating method. SnO₂ nanoparticles and GN were alternatively coated on Ni foam to form a sandwich-like structure. The wrapping of GN can raise the conductivity and keep the structural integrality of the binder-free material, preventing structure collapse arised from the volume expansion of SnO₂. Benefiting from the porous Ni foam framework and sandwich-like structure, the SnO₂/GN composite exhibited good rate performance and excellent cycle stability. High capacities of 708 and 609?mAh?g^?1 were achieved at rates of 1 and 2?A?g^?1. Besides, the SnO₂/GN electrode delivered a high capacity of 757?mAh?g^?1 after 500 cycles at 1?A?g^?1.     

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.     

Lithium storage behaviors of PbNb2O6 in rechargeable batteries

Herein, we propose a new anode material, PbNb₂O₆, for use in lithium-ion batteries. PbNb₂O₆ can be synthesized via a simple and traditional solid-state method. The as-prepared powder exhibits an average size distribution of about 0.5 μm. When tested in a lithium-ion cell, the PbNb₂O₆ electrode can exhibit a charge capacity of 245.2 mAh g⁻¹ at 200 mA g⁻¹, and after 80 cycles, the capacity can retain a charge capacity of 181.4 mAh g⁻¹, showing 0.32% capacity fading per cycle. Furthermore, the capacity of the PbNb₂O₆ electrode is 223.1 mAh g⁻¹, even when cycled at 1000 mA g⁻¹, and a capacity of 150.7 mAh g⁻¹ is maintained up to 500 cycles. In addition, the lithiation mechanism of PbNb₂O₆ is investigated via various techniques. Interestingly, PbNb₂O₆ exhibits high capacity without the contribution of two redox couples of niobium after the initial cycles. Finally, all Results suggest that PbNb₂O₆ has potential for use as an electrode in lithium-ion batteries.     

Interface bonding engineering for constructing a battery-type supercapacitor cathode with ultralong cycle life and high rate capability

The low rate and poor cycle greatly limit the large-scale applications of supercapacitors electrodes in energy storage field. In this work, the SnS₂/Ni₃S₂ nanosheets arrays are bonded on N/S co-doped graphene nanotubes though N–Sn/Ni and S–Sn/Ni interface bonds employing a simple hydrothermal method to form a self-supported battery-type supercapacitors cathode. A series of characterization and DFT calculations indicate that the interface bonding not only automatically generates the internal electric field and allows more redox reactions to carry out easily, but also effectively reduces the OH^? ions adsorption energy and maintains the integration of the electrode structure. This unique design greatly promotes the electronics/ions transfer and reaction kinetics of the cathode, and substantially enhances its rate capability and durability. Detailedly, a high specific capacity of 296.9 mAh g^?1 at 2 A g^?1 is obtained. More impressively, the cathode still holds 155.6 mAh g^?1 when the current density is enlarged to 100 A g^?1, as well as it can retain 84% initial capacity over 50,000 cycles. Besides, an assembled asymmetric supercapacitor utilizing the prepared N/S-GNTs@B–SnS₂/Ni₃S₂ nanosheets arrays cathode and activated carbon anode presents a large energy density of 51 W h kg^?1 at 850 W kg^?1 and outstanding cycling stability. This work provides an effective strategy for improving rate capability and cycle lifespan of battery-type supercapacitors electrodes, and pushes the metal compounds forward a significant step in the practical applications of energy storage devices.     

Carbon coated porous tin peroxide/carbon composite electrode for lithium-ion batteries with excellent electrochemical properties

A porous tin peroxide/carbon (SnO₂/C) composite electrode coated with an amorphous carbon layer is prepared using a facile method. In this electrode, spherical graphite particles act as supporter of electrode framework, and the interspace among particles is filled with porous amorphous carbon derived from decomposition of polyvinylidene fluoride and polyacrylonitrile. SnO₂ nanoparticles are uniformly embedded in the porous amorphous carbon matrix. The pores in amorphous carbon matrix are able to buffer the huge volume expansion of SnO₂ during charge/discharge cycling, and the carbon framework can prevent the SnO₂ particles from pulverization and re-aggregation. The carbon coating layer on the outermost surface of electrode can further prevent porous SnO₂/C electrode from contacting with electrolyte directly. As a result, the repeated formation of solid electrolyte interface is avoided and the cycling stability of electrode is improved. The obtained SnO₂/C electrode presents an initial coulombic efficiency of 77.3% and a reversible capacity of 742 mA h g⁻¹ after 130 cycles at a current density of 100 mA g⁻¹. Furthermore, a reversible capacity of 679 mA h g⁻¹ is obtained at 1 A g⁻¹.