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The microflower-like composites, constructed by two-dimensional core/shell FeSe/carbon nanosheet, are synthesized based on carbon-confined oriented-attachment mechanism. This unique structure can effectively enhance sodium-ion diffusion kinetics, accelerate the electron transfer and inhibit the volume expansion of FeSe kernel. When used as anode materials of sodium ion batteries (SIBs), the composites can deliver a high capacity of 460.2 mA h g−1 with ultrahigh initial Coulombic efficiency (ICE) of 99.8%. Moreover, the composites exhibit excellent rate-performance and super-long cycling stability. The capacity can be as high as 343.8 and 341.3 mA h g−1 at 5 and 10 A g−1. At ultrahigh current density of 30 A g−1, the composites can still deliver a capacity of 183.8 mA h g−1 and maintain a value of ca. 100 mA h g−1 after 10000 cycles. Interestingly, the composites can be directly assembled with Na3V2(PO4)3 into full battery without presodiation. The full battery delivers a capacity of 214.6 mA h g−1 after 140 cycles with a retention of 99.9% at 1 A g−1, showing superior rate and cyclic performances. Accordingly, this work is of great significant for design of non-presodiate anode materials to promote the practical applications of SIBs.

Silicon (Si) is the most promising next-generation anode of lithium-ion batteries (LIBs), which has attracted considerable interest due to its high theoretical capacity, low lithium storage potential and rich resource reserves. However, the development of Si anode is still hindered by many obstacles, such as large volume change during lithium insertion/extraction and low electrical conductivity. Recently, abundant Si/C composites have been designed to overcome the problems of Si anode. However, most preparation methods are complicated and difficult for industrialized applications and the Si nanoparticles in composites are usually coated with disorder carbon. In this work, we designed an onion-like Si/C composite through a simple one-step injection pyrolysis using pyridine as the carbon source. In this way, Si nanoparticles were successfully encapsulated into onion-like carbon shells. When used as the anode material for LIBs, this composite exhibits outstanding Li-storage performance with the capacity as high as 1391 mAh g−1 after 400 cycles at a current density of 0.2 A g−1 and rate capacity retention of 63.9% at 2 A g−1 to 200 mA g−1. The excellent electrochemical performance mainly benefits from higher structure stability and better buffer effect of the unique onion-like structure for expanded Si nanoparticles. In addition, in this process we can easily control the lithium storage capacity and particle size in gradient through changing the raw material ratio of pyridine to Si nanoparticles. Hence, we have developed a facile method to prepare onion-like Si/C anodes, which can effectively improve the capacity and cycle life of commercial LIBs.

Electrospun hard carbon nanofibers (CNFs) have been considered as promising anode materials for sodium-ion batteries (SIBs). The beads-on-string nanofibers have been frequently appeared as a universal phenomenon during electrospinning, but the influence of beads-on-string on Na-ion storage have never been investigated. Here, in order to clarify this issue, the electrospun polyimide-based CNFs with/without beads-on-string are designed by controlling the concentration of electrospinning solution, and their Na-ion storage properties are investigated as free-standing electrode and slurry-coating electrode, respectively. Generally, the discharge/charge curves of hard carbons consist of slope- and plateau-regions. When used as free-standing electrode, the beads-on-string can depress Na-ion storage behavior of plateau-region, but do not influence storage behavior of slope-region, and, interestingly, the plateau capacity increases with the decreasing of the beads-on-string, while the slope capacity is unaffected by the beads-on-string. When used as slurry-coating electrodes, the beads-on-string can hardly influence Na-ion storage behaviors of slope- and plateau-regions, and CNFs with/without beads-on-string display nearly similar slope and plateau capacities and rate-performance. Moreover, benefiting from the special micro-nanostructure, beads-on-string CNFs exhibit better high rate cycling stability than ones without beads as slurry-coating electrode. Therefore, these interesting phenomena will provide valuable inspiration for designing advanced electrospun CNFs electrode for SIBs.

The design of carbon anode materials with both high gravimetric and volumetric performances is one of the main limitations in the real applications of sodium-ion batteries (SIBs). Herein, we develop novel micro/nanostructure carbon microspheres (CMSs) assembled of onion-like carbons via an in situ pyrolysis approach. When used as anode materials for SIBs, the CMSs electrode possesses a high pressing density of 1.36 g cm−3. The CMSs exhibit a high reversible gravimetric capacity of 275 mAh g−1 and a reversible volumetric capacity of 374 mAh cm−3 at 100 mA g−1, which can be comparable to the volumetric capacity of graphite for lithium-ion batteries. At high current densities of 1, 2 and 5 A g−1, the reversible gravimetric capacities can still be maintained at 195, 165 and 115 mAh g−1 and the volumetric capacities can reach up to 265, 224 and 156 mAh cm−3. Such excellent electrochemical performances should be attributed to the special spherical micro/nanostructure of CMSs, which can not only guarantee a high density, but also provide void spaces to alleviate the volume variation and enhance Na ions diffusion kinetics. Accordingly, this study proposes a new strategy for the design of carbon materials with both high gravimetric and volumetric performances.

A flake-like carbon coated Mn2SnO4 nanomaterial was synthesized via a two-step carbonization method using Mn-based metal-organic frameworks (Mn-MOFs) as precursor. The composite demonstrates a two-dimensional (2D) micro/nano-scale combined configuration with Mn2SnO4 nanoparticles dispersed uniformly in flake-like porous carbon matrix. The unique 2D and porous morphology is favorable for lithium ions (Li-ions) storage due to higher surface for electrode/electrolyte interaction and reducing diffusion length of Li-ions. This material gives a high specific capacity of 986 mA h g−1 with 90.1% capacity retention after 100 cycles at 100 mA g−1 and a capacity of 428 mA h g−1 even at a high current density of 2 A g−1. Moreover, the performance of the carbon coated Mn2SnO4 was compared with carbon coated MnO/SnO2 which has the same element composition with Mn2SnO4. It is believed that the “synergistic effect” in Mn2SnO4 helps to improve the reversibility of the lithium storage reactions, resulting in both higher capacity and better stability of carbon coated Mn2SnO4.

Metal-organic-frameworks (MOFs) have recently been an emerging self-templated precursor to derive various nanomaterials for Na-ion storage. However, synthesis of MOF-derived two-dimensional nanomaterials has been rarely explored. Here, Ni(NO3)2/hexamine coordination-frameworks are employed as a precursor to prepare NiTe2/nitrogen-doped graphitic carbon nanosheets (NiTe2@NCNs) via pyrolysis and subsequent tellurization. Layered NiTe2 nanoparticles are uniformly anchored on the carbon nanosheets. As anode materials, NiTe2@NCNs exhibit ultrafast and long-life Na-ion storage performance. NiTe2@NCNs can deliver a reversible capacity of 289.5 mA h g−1 at 0.1 A g−1 and exhibit a negligible capacity fading with the increasing of current density from 0.1 to 10 A g−1. Even at 10 and 20 (ca. 70 C) A g−1, reversible capacities remain at 267.7 and 189.0 mA h g−1, respectively, and cyclic life can be up to 5000 cycles. Besides, NiTe2@NCNs exhibit minimal increasing of polarization from 0.1 to 5 A g−1. The superior electrochemical performance of NiTe2@NCNs should be attributed to the two-dimensional structure, N-doped graphitic carbon matrix and lager interlayer spacing of NiTe2, which contribute to enhance kinetics of electron and Na-ion transfer so as to result in a capacitive-controlled Na-ion storage process. Therefore, NiTe2@NCNs have a promising potential as anode materials for practical Na-ion storage applications.

Metal-organic frameworks can provide excellent templates for the preparation of nanomaterials for green energy storage. However, it is still a formidable challenge for the synthesis of MOF-templated Sn-based nanomaterials with controllable morphologies and structures. Here, Sn-based MOFs with different morphologies are synthesized by a facial and controllable method, then SnO/C polyhedrons with shapes of cube and stellated octahedron are obtained using the Sn-based MOFs as template by further heat treatment, respectively. Benefited from the composite structures, the SnO/C polyhedrons exhibit excellent electrochemical performances in lithium storage. A high reversible capacity of 950 mA h g−1 is obtained at a current density of 50 mA g−1 after 100 cycles, together with superior cyclic stability and remarkable rate capacity. This paper provides an effective route to prepare high-performance Sn-based anode materials from the morphology-controlled MOFs for lithium-ion batteries.

Self-assembled hierarchical CuO nanostructures with fractal structures were prepared by a mild method and exhibited excellent lithium storage properties, certain of which even demonstrated a high reversible capacity of 827 mAh g−1 at a rate of 0.1 C. An interesting phenomenon was observed that the electrochemical performance varies along with the structure complexity, and the products with higher surface factal dimensions exhibited larger capability and better cyclability. Structural and electrochemical analysis methods were used to explore the lithiation kinetics of the samples and the reasons for the outstanding electrochemical performances related to the complexities of hierarchical nanostructures and the irregularities of surface and mass distribution.

A free-standing Co0.85Se nanosheets/graphene (Co0.85Se NSs/G) composite film was developed as a high performance anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) by a simple vacuum filtration and thermal reduction process. The Co0.85Se NSs/G film demonstrates good flexibility, and the Co0.85Se NSs are uniformly anchored on the graphene to form “sheet-on-sheet” nanostructures with strong interfacial interactions. The hybrid lamellar film demonstrated excellent electrochemical performances when used as a binder-free anode for LIBs and SIBs. As an anode material for LIBs, the Co0.85Se NSs/G film exhibited a high initial reversible capacity of 680 mA h g−1 at 50 mA g−1 and an excellent cycling stability and rate performance. The specific capacity of the Co0.85Se NSs/G film shows almost no fading from 0.05 to 0.5 A g−1, and the capacities were maintained at 613.3 and 522.7 mA h g −1 at 1 and 2 A g−1, respectively. When used as an anode for SIBs, the reversible capacity of the Co0.85Se NSs/G film reached up to 388 mA h g−1 with an initial coulombic efficiency as high as 82.5% at 50 mA g−1. Even at the higher current densities of 1 and 2 A g−1, the reversible capacities remained at 137.5 and 112.4 mA h g−1 after 500 cycles, respectively. The excellent electrochemical performances should be attributed to the special structure of the Co0.85Se NSs/G film. On one hand, graphene not only provides an efficient electrically conductive network, but also acts as an elastic layer to buffer the volumetric expansion of the Co0.85Se NSs during the discharge/charge process in LIBs/SIBs, which is helpful for enhancing the cycling stability of the Co0.85Se NSs/G film. On the other hand, strong interfacial interactions can further enhance electron transfer between Co0.85Se NSs and graphene, which is beneficial for improving the cycling stability and rate-performance of the Co0.85Se NSs/G film.

With the objective of improving the capacity and cycling stability of SnO 2 -based anode materials, a new material of SnO 2 /TiO 2 nanocomposites dispersed at porous carbon was synthesized via a route of absorption and carbonization by using Ti-MOF (MIL-125) as both titanium and carbon sources and SnCl 2 as tin source. The composite shows micro-/nano-scale combined configuration: a monodisperse sub-micro cylinder structure formed by well-dispersed SnO 2 and TiO 2 nanoparticles in amorphous carbon matrix. Benefiting from the synergistic effect of TiO 2 nanoparticle and amorphous carbon on maintaining the robust architecture as well as the uniform and stable nano-sized particles, the composite exhibits excellent performance as anode material for lithium-ion batteries: a high specific capacity of 1177 mA h g −1 and 88.7% capacity retention after 100 cycles at 100 mA h g −1 , and a stable capacity of 487 at high current density of 2 A g −1 .

Chrysanthemum-like carbon/FeS microspheres (CL-C/FeS) are prepared from a one-step solvothermal method. The morphology and structure of the CL-C/FeS are characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscope. We note that the prepared CL-C/FeS microspheres exhibit the average diameter of 15 μm and possess a sheet-on-sheet structure. FeS nanosheets are stacked on the carbon sheets to form a 2D sheet-on-sheet structure, these 2D C/FeS nanosheets are self-assembled to form a 3D chrysanthemum-like morphology. Due to the unique structure, CL-C/FeS microspheres show the excellent sodium-storage performance of 500 mAh g−1 at 0.2 A g−1 and 260 mAh g−1 at 1 A g−1, which are higher than those of most reported values. Therefore, the CL-C/FeS with appropriate structure is expected to be a competitive choice for anode materials for sodium ion batteries.

Carbon-coated Li 4 Ti 5 O 12 composites (LTO/C) with tablet-like morphology are firstly in-situ synthesized from lithium-doped Ti-based metal-organic framework precursor by thermal annealing in N 2 atmosphere at 800 and 900 °C, denoted as LTO/C-800 and LTO/C-900, respectively. The TEM and TG results demonstrate that LTO is embedded in carbon uniformly and LTO/C-800 presents more carbon content than LTO/C-900. The electrochemical results show that the LTO/C electrodes deliver a high reversible capacity, high-rate performance and excellent cycling stability as lithium-ion battery anodes. At the current density of 500 mA g −1 , the reversible capacities of LTO/C-900 and LTO/C-800 are 277 and 223 mA h g −1 after 700 cycles, respectively. At 1000 and 2000 mA g −1 , the reversible capacities of LTO/C-900 and LTO/C-800 can reach 181, 150 mA h g −1 and 174, 88 mA h g −1 after 1000 cycles with no attenuation, respectively. The facile and economical synthesis strategy will extend the scope of lithium-doped MOFs synthesis for other materials in energy storage application.

Heteroatom-doped multilocular carbon nanospheres (HMCSs) are synthesized by carbonizing multilocular polyaniline nanospheres (MPSs) which are prepared via metal-catalyzed polymerization in the presence of cupric nitrate as catalyst and ammonium persulfate as oxidant. The impacts of carbonization temperature on the morphology, structure and property of HMCSs are investigated. The results show that the carbonized sample at 800 °C (HMCSs-800) has a specific surface area of 283 m 2 g −1 , nitrogen content of 7.15% and oxygen content of 8.78%, and exhibits the specific capacitance of 186 F g −1 at the current density of 0.5 A g −1 . Most importantly, HMCSs-800 possesses high surface utilization (0.66 F m −2 ) and excellent rate capability (73.8% retention at 20 A g −1 relative to the capacitance of 0.5 A g −1 ). These results are superior to that of other carbon materials in most reports. The specific capacitance still preserves 91.3% after 5000 charge/discharge cycles at the current density of 5 A g −1 , demonstrating good cyclic stability. The outstanding electrochemical performance of HMCSs-800 can be ascribed to the providential integrate of particular multilocular structure, high micropore content and proper heteroatom content.

Novel hierarchical porous carbons (NHPCs) containing 3D carbon nanosheets and slit-mesopores are prepared in this work, using MgAl-layered double hydroxides as template and sucrose as carbon source, and their electrochemical performances as anodes of lithium-ion batteries are also investigated. Owing to the existence of abundant carbon nanosheets and slit-mesopores, the NHPCs electrode exhibits the specific reversible capacity of 1151.9 mA h/g at the current density of 50 mA/g, which is significantly higher than other hierarchical porous carbons reported in previous literatures. The contributions of carbon nanosheets and mesopores to the electrochemical performance are further clarified by nitrogen adsorption-desorption test, electrochemical impedance spectroscopy, cyclic voltammograms and galvanostatic charge/discharge test. This work not only provides an easy and effective method to prepare hierarchical porous carbon materials, but also is beneficial for the design of high-performance anode materials for lithium ion batteries.

Heteroatom-doping is an effective way to regulate the electronic structure of carbon so as to improve their Na-ion storage capability. In all kinds of heteroatoms, selenium (Se)-doping has rarely been investigated even though Se has unique physicochemical properties. Herein, we report a facile fabrication of Se/N-codoped carbon nanosheets (N/Se-CNs) with 10 at% N and 2 at% Se by an oxidation-selenization process. The synchrotron X-ray photoelectron spectroscopy (XPS) measurements indicate that Se doping can significantly change the electronic structures of carbon nanosheets, because Se can act as stronger electron-withdrawing units for Na storage compared with C and N. Therefore, Se can better play the role of improving the conductivity and wettability of the carbon materials. And Se atoms effectively enlarge the interlayer distance of carbon nanosheets to enhance the Na-ion diffusion kinetics and also generate extra active sites for Na-ion storage. Served as anode materials for SIBs, the N/Se-CNs delivers higher specific capacity and better rate capability compared with only N-doped carbon nanosheets. Therefore, Se-doping is an effective way for improvement of Na-storage capability of carbon materials. Moreover, this work should provide a new pathway for design of carbons doped by heteroatoms with large atomic size towards excellent Na-ion storage.

Porous carbon (PC) materials with a large specific surface area and high volume of mesopores were produced using iron-doped calcium tartrate (CaTr) as a template precursor and ethanol as a carbon source. The iron doping concentration was varied from 0.2 to 1.6 at%. Template precursor was decomposed in argon at 800 °C, the formed template nanoparticles were immediately used for chemical vapor deposition (CVD) of ethanol, and after the synthesis, they were removed by HCl treatment. It was shown that the template consisted of CaO nanoparticles 5–20 nm in size with oxidized carbon layers on the surface. The incorporation of iron into CaTr promoted graphitization of the carbon layers and led to formation of iron oxide nanoparticles 3–4 nm in size. These nanoparticles served as a replica for small mesopores in the graphitic layers obtained in the ethanol CVD process. PC materials grown on the templates with an iron doping 0.2–0.4 at% were enriched with small mesopores, and due to this, they had a surface area of 907–931 m2 g−1 and pore volume of 3.3 cm3 g−1. These materials showed the highest specific capacitances of 280–230 F g−1 at 2 mV s−1 in 1 M H2SO4 electrolyte and a good rate capability.

Leaky graphene oxide (LGO) was gram-scale prepared by oxidation of graphite oxide using mixed acid. The LGO showed a dual-wavelength photoluminescence (PL) with the absolute quantum yield of 11.6%. Three routes including hydrothermal method, hydrazine-assisted hydrothermal method, and hydrazine reflux were used to reduce the LGO. The contents of oxygen- and nitrogen-bearing functional groups varied depending on the reduction methods. The reduced LGOs showed a blue-shifted dual-wavelength PL and strong decrease of the quantum yields. To understand the contribution of different kind of functional groups to the PL, we used density functional theory calculation of the ground states of graphene fragments modified by various functional groups according to our experimental results. The energy gaps broadened with the removal of functional groups, indicating the blue-shift of the PL after reduction. We proposed that the blue-green PL of the LGO arose from small aromatic domains by quantum size effect. Functional groups surrounded the aromatic domains induced the red shift of the PL. The high quantum yield may ascribe to the defective and holey structure of the LGO. Our work provided a simple method to prepare high performance graphene based PL materials, and could help for understanding the nature of dual-wavelength PL.

Functional groups (FGs) in graphene oxide (GO) play an important role in the properties and applications of GO and its related materials. However, there are limited studies about the reversible transformation of FGs in response to external stimuli. In this paper, we report an experimental investigation on the response of FGs to the stimuli of transitional metal compounds. Reversible transformation of FGs on GO with loading and unloading of metal compounds was found. This interesting phenomenon could be helpful to not only enrich the reactivity of FGs in GO, but also provide new insights for designing advanced graphene-based nanomaterials.

Heteroatom-doped carbon with 4.06% of nitrogen and 10.42% of oxygen was synthesized by pyrolysis of ortho-aminophenol/formaldehyde resin. After high temperature hydrogen reduction, 2.22% of the surface oxygen was removed while the nitrogen content remained almost no change. The specific surface area enlarged from 90 m2 g−1 to 226 m2 g−1 and abundant micropores appeared. But we found that the specific capacitance of the reduced carbon as electrode for supercapacitors was decreased nearly 25 %. By measuring the conductivity, surface wettability, and electrochemical impedance, we proposed that (a) surface oxygen played an important role in the capacitive performance, especially the pseudocapacitance; (b) though the doped-oxygen reduced the electronic conductivity, on the other hand, enhanced the surface wettability and ion diffusion rate of the carbon electrodes.

A kind of nitrogen- and oxygen-containing activated carbon nanotubes (ACNTs) has been prepared by carbonization and activation of polyaniline nanotubes obtained by rapidly mixed reaction. The ACNTs show oxygen content of 15.7% and nitrogen content of 2.97% (atomic ratio). The ACNTs perform high capacitance and good rate capability (327 F g−1 at the current density of 10 A g−1) when used as the electrode materials for supercapacitors. Hydrogen reduction has been further used to investigate the effects of surface functional groups on the electrochemical performance. The changes for both structural component and electrochemical performance reveal that the quinone oxygen, pyridinic nitrogen, and pyrrolic nitrogen of carbon have the most obvious influence on the capacitive property because of their pseudocapacitive contributions.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been retracted at the request of the Authors. The authors deeply apologize that due to their misunderstanding of the nature of the conference proceedings of WCPT7, this article became a duplicate of a paper that has already been published in RSC Adv., (2014), 4, 29435-29438. DOI: 10.1039/C4RA02236J.One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper is not under consideration for publication elsewhere. As such this article represents a severe abuse of the scientific publishing system.The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the processing of this submission.

Novel hierarchical porous carbon microspheres (HPCM) with quantities of micropores and mesopores have been prepared by an alcohol-in-oil emulsion technique using thermoplastic phenolic formaldehyde resin (PF) as the carbon source and copper nitrate (CN) as the template precursor. The effects of CN loading content on the morphology and structure of HPCM were investigated. The results showed that, when the mass ratio of PF and CN is 1:4, the HPCM not only can maintain hierarchical porous microsphere structure, but also display high electrochemical performance with a reversible capacity of 585 mA h g−1 at a current density of 50 mA g−1 and favorable high-rate performance when used as the anode materials for lithium-ion batteries.

Generally, the capacity of lithium-ion batteries (LIBs) will fade gradually during cycling especially under large current densities because of the structural collapse of electrode materials. Herein, dramatic and favorable electrochemical performance enhancement was observed in a simply achieved MnO nanowire/graphene composite during long-term cycling when utilized as the anode material for LIBs. Characterized by high-resolution transmission electron microscopy, X-ray diffraction and Fourier-transfer infrared spectroscopy, the MnO nanowires were gradually collapsed to nano-spindles and further nanoparticles but these newly formed nanoparticles are still stably anchored on the graphene lamellas. Correspondingly, the specific capacity of the MnO nanowire/graphene electrode exhibited a significant enhancement with a durable life after a slight decrease in the first several cycles. The reason for the self-enhancement could be ascribed to the strong interphase interaction between MnO and graphene flakes. Our work provides a new understanding and insight for the electrochemical behavior of composite electrodes in LIBs and is helpful for the fabrication of high-performance anode materials.

A novel tremella-like graphene/polyaniline composite was achieved from self-assembly of graphene nanosheets during polymerization of aniline in H 2 O/N, N -dimethylformamide solution, and was further employed as an electrode for supercapacitors. This graphene/polyaniline composite demonstrates a spherical tremella-like structure and a large specific capacity of 497 F g −1 at a current density of 0.5 A g −1 . Particularly, an outstanding rate capability of 456 F g −1 under 5 A g −1 after 1000 cycles was obtained. Scanning electron microscopy showed that polyaniline nanoparticles were uniformly deposited on free-standing graphene nanosheets, and self-assembled to a spherical tremella-like structure. Therefore, this unique nanostructure is promising for high-performance electrochemical applications.

Copper oxide nanowires with an average length of 7.4 μm are prepared by in-situ thermal oxidation at 500 °C for 6 h in air, and their lithium storage performances are promoted by a further ammonia treatment. The morphologies, structures and lithium storage properties of copper oxide nanowire arrays are investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and a series of electrochemical measurements. The results show that after the reprocessing, the CuO nanowire arrays exhibit a higher reversible capacity of 645 mAhg −1 after 100 cycles at a current density of 50 mAg −1 , excellent cyclability and high-rate capability. The good electrochemical performance and simple preparation process make it a promising anode material for lithium-ion batteries.

Hierarchical porous carbon nanosheets (HPCS) were prepared by using thermoplastic phenolic formaldehyde resin as the carbon source and copper nitrate as the template precursor. The effects of Cu(NO 3 ) 2 loading content on the pore property and electrochemical performance of HPCS as anode material for lithium ion batteries were investigated. It was found that, with the addition of Cu(NO 3 ) 2 , both the specific surface area and mesopore percentage increase. Correspondingly, the electrochemical performances of HPCS electrodes in terms of the specific capacity and rate performance improve for lithium ion batteries. The reasons were deduced and discussed from the view point of different pore size, especially the function of mesopores.

Iron titanium oxide (Fe 1.5 Ti 0.5 O 3 ) nanoparticles with the diameter of about 150 nm were prepared by hydrothermal process and further heat treatment at 300 °C for 2 h. The morphology, structure and electrochemical performance of Fe 1.5 Ti 0.5 O 3 nanoparticles as anode material for lithium-ion batteries were investigated by scanning electron microscopy, X-ray diffraction and a variety of electrochemical testing techniques. It was found that, compared with TiO 2 and Fe 2 O 3 , the iron titanium oxide electrode exhibited higher specific capacity of 734.9 mAh g −1 after 50 cycles at the current density of 50 mA g −1 , good cycle stability and high-rate performance, suggesting that the Fe 1.5 Ti 0.5 O 3 nanoparticle synthesized by this method is a promising anode material for lithium-ion batteries.

Carbon-encapsulated iron carbide nanoparticles have been produced by co-carbonization of a mixture of an aromatic heavy oil and ferrocene at 450 °C under autogenous pressure. Transformations of the morphology and electronic structure of nanoparticles induced by air oxidation and subsequent heat treatment in a nitrogen atmosphere were examined using transmission electron microscopy, X-ray diffraction, near edge X-ray absorption fine structure spectroscopy, and X-ray emission spectroscopy. It was found that hollow nanoparticles, composed of iron oxides and oxidized carbon, were developed with thermal air oxidation of the initial product at 280 °C for 5 h. The mild oxidation of the product (250 °C for 3 h) followed by the carbonization at 500–550 °C yielded the hollow nanoparticles containing iron carbide/oxides and defective graphite-like carbon. The further annealing of nanoparticles at 1000 °C produced carbon nanocapsules with highly graphitized carbon walls and partially filled by spherical iron carbide nanoparticles.

Carbon nanotube-encapsulated SnO 2 (SnO 2 @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 SnO 2 is filled into the interior hollow core of CNTs and exists as small nanoparticles with diameter of about 6 nm. The SnO 2 @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 (0.1 C ), the sample containing wt. 65% of SnO 2 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 2.0 C ), the composite electrode still exhibits capacity retention of 563, 507 and 380 mAh g −1 , respectively. The capacity retention of our SnO 2 @CNT composites is much higher than previously reported values for a SnO 2 /CNT composite with the same filling yield. The excellent lithium storage and rate capacity performance of SnO 2 @CNT core–shell composites make it a promising anode material for lithium-ion batteries.

Graphite oxide was prepared by the Hummers method. Then after further oxidation, a new kind of carbon nanoparticle, with diameter 10–30 nm, was formed in the aqueous solution. On the basis of structural characterization by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy it is deduced that the nanoparticles are generated by the self-assembly of few-layer graphene oxides. A possible formation mechanism is proposed.

Rod-type ordered mesoporous carbons were synthesized by the direct carbonization of sulfuric-acid-treated silica/triblock copolymer composites, followed by etching the silica with a HF solution. The morphologies, microstructures and pore structures of the mesoporous carbons were investigated by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction and nitrogen sorption. Their electrochemical performance as electrodes for supercapacitors was investigated by impedance spectroscopy and charge/discharge tests. It was found that the rod length of the mesoporous carbons can be changed from one to tens of micrometers by changing the synthesis parameters. The sample with the longest rod length has the highest specific capacitance. The sample with two pore sizes has the highest capacitance retention ratio of 92% at a high current density of 2 A/g.