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WS2 with layered graphite-like structure as anode for sodium ion batteries has high specific capacity. However, the poor cycling performance and rate capability of WS2 caused by the low electronic conductivity and structure changes during cycles inhibit its practical application. Herein, metallic phase (1T) WxMo1−xS2 (x = 1, 0.9, 0.8 and 0.6) with high electronic conductivity and expanded interlayer spacing of 0.95 nm was directly prepared via a simple hydrothermal method. Specially, 1T W0.9Mo0.1S2 as anode for sodium ion batteries displays high capacities of 411 mAh g−1 at 0.1 A g−1 after 180 cycles and 262 mAh g−1 at 1 A g−1 after 280 cycles and excellent rate capability (245 mAh g−1 at 5 A g−1). The full cell based on Na3V2(PO4)2O2F/C cathode and 1T W0.9Mo0.1S2 anode also exhibits high capacity and good cycling performance. The irreversible electrochemical reaction of 1T W0.9Mo0.1S2 with Na ions during first few cycles results in the main products of W-Mo alloy and S. The strong adsorption of W-Mo alloy with polysulfides can effectively suppress the dissolution and shuttle effect of polysulfides, which ensures the excellent cycling performance of 1T W0.9Mo0.1S2.

Tin has been considered an ideal anode material for lithium ion batteries because of its high theoretical capacity. However, its practical application is limited due to the poor cycling stability, which is induced by the huge volume variation upon lithiation/delithiation. Moreover, amorphous and crystalline structures can significantly influence the electrochemical performance of Sn-based electrode for lithium ion batteries. Herein, the specific capacity, cycling performance, rate capability, and kinetic process of amorphous-Sn@C (am-Sn@C) and crystalline-Sn@C (cr-Sn@C) as anodes for lithium ion batteries have been compared. The am-Sn@C electrode exhibits higher capacity, better cycling stability (711 mAh g−1 after 200 cycles at 0.1 A g−1; 510 mAh g−1 after 500 cycles at 1 A g−1) and rate capability than cr-Sn@C electrode (574 mAh g−1 after 200 cycles at 0.1 A g−1; 156 mAh g−1 after 500 cycles at 1 A g−1) as anode for lithium ion batteries. The enhanced electrochemical performance of the am-Sn@C electrode can be attributed to the enhanced strain regulation to accommodate volume change and defect sites to improve lithium storage capacity. The preparation method can be viewed as a reference for the further development of alloy-based anodes with high capacity and long cycle life for lithium ion batteries.

Fe-based Prussian blue (Fe-PB) has attracted wide attention as cathode materials for sodium-ion batteries due to its open frame structure, abundant iron ore resources, and simple preparation. Nevertheless, the poor cycle performance caused by the [Fe(CN)6] defects and crystal water hinders its practical application. Herein, the Fe-PB structure is regulated by Zn-substitution, and the effect of Zn-substitution induced structural regulation on sodium storage performance of Fe-PB is systematically investigated. The density functional theory calculation results confirm that Zn-substitution can reduce the bandgap and decrease the energy barrier of Na+ ions migration. Our experiment results further confirm the Zn-substituted Fe-PB composite (FeZn-PB) has a typical monoclinic structure with higher Na content, fewer [Fe(CN)6] vacancies and lower crystal water. Moreover, Zn-substitution accelerates electrons and sodium ions migration and enhances the activity of both low-spin Fe and high-spin Fe. As a cathode material for sodium-ion batteries, the FeZn-PB electrode has a higher capacity and better cycle stability than Fe-PB. Especially, FeZn-PB delivers an initial capacity as high as 145.0 mAh g-1 with a capacity contribution of 60.5 mAh g-1 from low-spin Fe at 20 mA g-1. Even at a high current density of 1 A g-1, FeZn-PB still delivers a high initial capacity of 98.5 mAh g-1 with a very low capacity decay rate per cycle of only 0.05% over 500 cycles.

Developing a high-performance anode with high reversible capacity, rate performance, and great cycling stability is highly important for sodium-ion batteries (SIBs). MoS2 has attracted extensive interest as the anode for SIBs. Herein, the vertically oxygen-incorporated MoS2 nanosheets/carbon fibers are constructed via a facile hydrothermal method and then by simple calcination in air. Oxygen incorporation into MoS2 can increase the defect degree and expand the interlayer spacing. Vertical MoS2 nanosheet array coated on carbon fibers not only can expose rich active sites and reduce the diffusion distance of Na+, but also improve the electronic conductivity and enhance structural stability. Meanwhile, interlayer-expanded MoS2 can decrease Na+ diffusion resistance and increase accessible active sites for Na+. In this work, the electrode combining the oxygen-incorporated strategy with vertical MoS2 nanosheet-integrated carbon fibers displays high specific capacities of 330 mAh g–1 over 100 cycles at a current...

Carbon materials with high initial Coulombic efficiency (ICE) and specific capacity in lithium-ion batteries are highly attractive. Herein, P-doped carbon has been prepared, and as an anode for lithium-ion batteries, it exhibits remarkably improved ICE and reversible capacity. P atoms are apt for the formation of the P–O bond in carbon with oxygen-containing groups. The doped P content strongly depends on the O content in carbon. The high-doped P content of 5.79 at. % can be obtained through changing the O content in carbon. Carbon with high contents of P and O displays high ICE and capacity as an anode for lithium-ion batteries. The P–O bond in carbon changes the morphology and composition of the solid electrolyte interface (SEI) layer and is beneficial to the formation of a thin and dense SEI layer. The P–O bond in carbon prevents the permeation and decomposition of solvated PF6– in the interior of the electrode during cycling, resulting in the improved ICE, reversible capacity, and rate capability. As ...

MoO2 with low electrical resistivity and high specific capacity as anode for lithium ion batteries is hindered because of its large volume variation during Li+ insertion/extraction process, which leads to fast capacity fading. Herein, three-dimensional (3D) core-shell MoO2@few-layered MoS2 covered by S-doped graphene (MO/MS/SG) aerogel has been fabricated through hydrothermal reaction and freeze-drying process together with sulfidation. MoO2 nanoparticles coated by few-layer MoS2 can promote good dispersion of MoO2 nanoparticles and avoid the restacking of MoS2. S doping in graphene can increase the defects and active sites. S-doped graphene aerogel as flexible framework and conductive network not only provides the transmission path for ions and electrons, but also maintains the structural integrity of electrode during cycles. Core-shell MoO2@few-layer MoS2 hybrid well-dispersed in S-doped graphene matrix buffers the volume changes during cycles and contributes to high reversible capacity. Free-standing electrode without binder and current collector prevents the separation of electrode materials from current collector during cycles. Benefitting from the unique structures, the MO/MS/SG aerogel as anode for lithium ion battery exhibits high reversible capacities of 683 mAh g−1 at 0.1 A g−1 after 100 cycles and 533 mAh g−1 at 0.5 A g−1 after 350 cycles together with excellent rate capability. This work demonstrates the potential application of the Mo-based materials in lithium ion batteries.

Three-dimensional foam with integrated core-shell carbon nanotubes-MoS2 with reduced graphene oxide (MoS2/CNT/rGO) has been fabricated by a hydrothermal reaction together with freeze drying. Thin MoS2 nanosheets are coated on the carbon nanotubes (CNT) and distributed on the surface of reduced graphene oxide (rGO) nanosheets. One-dimensional CNT and two-dimensional rGO conductive network not only effectively improves the electron transport and mechanical property, but also prevents the aggregation of MoS2 nanosheets. MoS2 with large interlayer spacing provides more active sites and channels for insertion of lithium ions, while CNT and rGO network acts as a conductive skeleton. The 3D porous and interconnected foam can directly as electrode without any binders and conductive agents. After optimizing the ratio of CNT to rGO, the MoS2/CNT/rGO foam as a freestanding electrode for lithium ion batteries exhibits a high specific capacity of 745 mAh g−1 at a current density of 0.1 A g−1 after 170 cycles and 420 mAh g−1 at 0.5 A g−1 after 200 cycles. This method is easily extended to prepare the other electrode materials, especially the freestanding and flexible electrode.

Flexible and thin energy storage devices have attracted enormous attentions. An easy and large-scale method has been employed to fabricate flexible and interwoven N, P dual-doped carbon fibers/graphitic carbon nitride ( hu CP/g-C 3 N 4 ) using filter paper as a precursor. The hu CP/g-C 3 N 4 composite as self-supporting anode for lithium ion batteries exhibits high reversible capacities of 1030 mAh g −1 after 1000 cycles at 1 A g −1 and 360 mAh g −1 after 4000 cycles at 10 A g −1 along with excellent rate performance (133 mAh g −1 at 30 A g −1 ). For sodium ion batteries, hu CP/g-C 3 N 4 as anode delivers high reversible capacities of 345 mAh g −1 after 380 cycles at 0.1 A g −1 and 110 mAh g −1 after 4000 cycles at 1 A g −1 . This excellent electrochemical performance can be attributed to the high contents of doped N and P in hu CP/g-C 3 N 4 and graphitic carbon nitride network, which not only create more defects and active sites but also expand the layer planes and provide interconnected conductive network.

Porous Si/C/reduced graphene oxide (Si/C/rGO) microspheres have been prepared by the spray drying and subsequent carbonization process using the polyvinyl alcohol (PVA) as cross-linking agent. PVA plays an important role in the spray drying process. The designed micrometer-size reduced graphene oxide wrapped Si/C ball structure offers a buffer space for the volume change of Si during the charge-discharge process. Double carbon layers can effectively protect the Si core and improve the cycling stability of the electrode. The fabricated Si/C/rGO microspheres as anode for lithium ion batteries exhibit a high reversible capacity of 928 mAh g− 1 after 70 cycles at a current density of 100 mA g− 1, good rate capability and cycling stability.

An in-situ prepared binder-free Li 3 V 2 (PO 4 ) 3 /C membrane electrode supported on 3D N-doped carbon fibers (LVP/C@NCF) has been developed. The residual carbon in LVP/C@NCF consists of the pyrolytic carbon from glucose and the N-doped carbon fibers decomposed from filter paper. The former uniformly covers on the surface of LVP particles, while the latter is functioned as both a 3D conductive network and a current collector for LVP. Compared with the traditional LVP/C electrode supported on Al foil (LVP/C@Al), the LVP/C@NCF membrane electrode displays higher rate capability and better cycle stability. Especially, when cycled at a high rate of 10 C, it still delivers a specific capacity as high as 107.6 mA h g −1 with a very low capacity fading ratio of ~0.0048% per cycle after 1000 cycles. The excellent electrochemical performance is ascribed to the synergetic effect from the 3D effectively conductive network and the in-situ produced current collector of carbon fibers. The method of using filter paper as the source of carbon and current collector to prepare integrated membrane electrode may provide feasible and effective strategy to fabricate binder-free flexible and lightweight lithium ion batteries as well as sodium ion batteries.

Three-dimensional (3D) and flexible N-doped carbon (NC) foam was prepared by the carbonization of low-cost and commercial melamine foam. Flexible reduced graphene oxide wrapped Si/C assembled on N-doped carbon (Si/C/RGO/NC) foam was further prepared by the pyrolysis of the Si/polyvinyl alcohol/graphene oxide coated on the melamine foam. The polyvinyl alcohol enhances the bonding strength of Si and melamine, which ensures the uniform distribution of Si in the 3D NC foam after the pyrolysis process. The NC foam and composited reduced graphene oxide (RGO) in the electrode as continuous conductive frameworks and elastic matrix can maintain the structural integrity, improve electron and ion transport and accommodate the severe volume change of Si-based electrode. Double carbon layers (amorphous carbon and RGO) coated Si core can effectively protect the Si core and avoid the direct contact between Si and electrolyte. The flexible 3D Si/C/RGO/NC foam with ∼40 wt% Si as freestanding anode for lithium ion batteries exhibits a high reversible capacity of 740 mAh g−1 after 100 cycles at 100 mA g−1 and 314 mAh g−1 after 500 cycles at 1 A g−1 (based on the weight of the composite), along with excellent rate capability and cycling stability.

Flexible and lightweight reduced graphene oxide wrapped Si/carbon fibers paper (Si@RGO/CFP) anodes have been prepared by pyrolysis of the common filter paper, which was soaked into the suspension containing graphene oxide and Si. The reduced graphene oxide wrapped Si nanoparticles (Si@RGO) homogeneously distributed on the interlaced carbon fibers and void among the carbon fibers. The Si@RGO/CFP as a flexible binder-free electrode exhibits an initial reversible capacity of 2055 mAh g −1 and 1092 mAh g −1 after 100 cycles for Si@RGO at 100 mA g −1 along with good rate performance. The superior electrochemical performance of the Si@RGO/CFP is attributed to the interconnected carbon fibers substrate, which provides electronic conduction pathways and works as mechanical support, and the void among carbon fibers accommodates the volume changes of Si and maintains the integrity of the electrode materials.

A three-dimensional carbon-coated SnO2/reduced graphene oxide (SnO2/RGO/C) foam has been prepared by using glucose as the carbon source and cross-linking agent through a one-step hydrothermal process followed by freeze drying. The foam, as a free-standing anode for lithium-ion batteries, exhibits a large capacity and excellent cycling stability (717 mAh g−1 after 130 cycles at 100 mA g−1). The outstanding electrochemical performance could be related to the synergistic effect between the nano-sized high-capacity SnO2, the excellent electronic conductivity and large specific surface area of RGO, and the carbon coating layer, which could enhance the bonding strength of SnO2 nanoparticles and RGO nanosheets, keep the structural integrity, and increase the electronic conductivity. The strong interaction between SnO2 and RGO, the high electronic conductivity, and the porous structure of the composite result in high electrochemical activity and stable cycling performance as a binder-free anode for lithium-ion batteries.

Red P is one of the most prospective anode material for sodium ion battery because of its highest theoretical capacity of 2596 mAh g−1 and satisfactory potentials for sodium ions insertion and extraction. However, the large volume expansion during cycles and poor intrinsic electronic conductivity limit the electrical performance practical application of red P. Herein, Mo-modified P/C (P Mo C) composite has been prepared through a simple mechanical milling using low-cost anthracite as carbon sources to increase the electrical conductivity and adapt to the volume variation. The addition of Mo plays a crucial role in enhancing electronic conductivity and structural stability of P Mo C composite during cycles. The formation of MoP2 facilitates the intimate contact of red P and Mo, providing the superior ionic diffusion and electron conducting pathways between the particles. The electrode of P Mo C exhibits high reversible capacity, excellent cycling and rate performance as anode for sodium ion battery. At 0.1 and 0.5 A g−1, the P Mo C electrode displays high reversible capacities of 763 and 705 mAh g−1 after 60 and 100 cycles, respectively. Due to the superior electrochemical performance, low cost and simple preparation, the P Mo C composite is a prospective negative electrode material for high-performance sodium ion battery.

Highly flexible energy-storage devices strongly depend on both mechanical integrity of the constitutive materials and electrical properties. The preparations and electrochemical properties of reduced graphene oxide (RGO) foams used as electrodes in supercapacitors have been systematically investigated. The rational design of preparation led to excellent electrochemical performance in supercapacitors such as high specific capacitance (224 F g−1 at 0.1 A g−1) and rate performance. Highly flexible solid-state supercapacitors based on RGO foams exhibit high gravimetric specific capacitances (193 F g−1 at 0.1 A g−1) with excellent cycling stability (∼100% retention after 5000 cycles). This work provides the proper preparation of RGO foams by hydrothermal process with excellent electrochemical performance and high mechanical flexibility in solid-state supercapacitors, suggesting that the RGO foams have great potential in the development of lightweight high-performance flexible energy storage device.

Reduced graphene oxide (RGO) decorated ternary Cu2SnS3 composite has been synthesized by one-step facile hydrothermal route. The formation of Cu2SnS3 nanoparticles and reduction of graphene oxide occur at the same time during the hydrothermal process. The Cu2SnS3 nanoparticles with a size of 5–10 nm are uniformly distributed on the RGO, which prevents effectively the agglomeration of Cu2SnS3 nanoparticles. The Cu2SnS3/RGO composite electrode exhibits an initial reversible capacity of 704 mAh g− 1 and 560 mAh g− 1 after 100 cycles. Such excellent electrochemical performance can be attributed to the presence of RGO, which improves the electronic conductivity and prevents the agglomeration of Cu2SnS3 nanoparticles. In addition, the Cu induced by the Cu2SnS3 reaction with lithium ions during the discharge process can increase the electronic conductivity.

Natural graphite treated by mechanical activation can be directly applied to the preparation of Li3V2(PO4)3. The carbon-coated Li3V2(PO4)3 with monoclinic structure was successfully synthesized by using natural graphite as carbon source and reducing agent. The amount of activated graphite is optimized by X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectrum, galvanostatic charge/discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy tests. Our results show that Li3V2(PO4)3 (LVP)-10G exhibits the highest initial discharge capacity of 189 mAh g−1 at 0.1 C and 162.9 mAh g−1 at 1 C in the voltage range of 3.0–4.8 V. Therefore, natural graphite is a promising carbon source for LVP cathode material in lithium ion batteries.

N-doped graphene/SnS composite as high-performance anode materials has been synthesized by a simultaneous solvothermal method using ethylene glycol as solvent. The morphology, structure, and electrochemical performance of N-doped graphene/SnS composite were investigated by transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectra, Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The SnS nanoparticles with sizes of 3–5 nm uniformly distribute on the N-doped graphene matrix. The N-doped graphene/SnS composite exhibits a relatively high reversible capacity and good cycling stability as anode materials for lithium ion batteries. The good electrochemical performance can be due to that the N-doped graphene as electron conductor improves the electronic conductivity of composite and elastic matrix accommodates the large volume changes of SnS during the cycles.

Nickel sulfide/N-doped graphene composite as high performance anode materials has been synthesized through a simultaneous hydrothermal method. The morphology, structure and electrochemical performance of nickel sulfide/N-doped graphene composite were investigated by field emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, Raman spectra, Fourier transform infrared spectra, X-ray photoelectron spectroscopy and electrochemical measurements. The nickel sulfide with a length of about 500 nm and diameter of 100 nm clung to the N-doped graphene matrix. The nickel sulfide/N-doped graphene composite exhibits a relatively high reversible capacity and good cycling stability as anode materials for lithium ion batteries. The good electrochemical performance can be attributed to N-doped graphene, which improves the electronic conductivity of composite and suppresses the volume effect as elastic matrix. The one-dimensional structure of nickel sulfide facilitates the diffusion of lithium ions and electrons.

A series of Li2Fe1-xVxSiO4/C (x = 0.00, 0.03, 0.05 and 0.07) composites have been synthesized via a refluxing-assisted solid-state reaction. XRD results confirm the monoclinic structure with space group P21 for Li2Fe1-xVxSiO4/C compounds. TEM and Raman spectroscopy demonstrate V-doping can increase the graphitization degree of residual carbon. XPS confirms that V-incorporation does not change the divalent state of Fe, and the oxidation state of V in V-doped Li2FeSiO4/C is +3. Combined Ar-ion sputtering with XPS, it is found that V has been successfully doped into the crystal lattice of Li2FeSiO4. Electrochemical tests show that LFS/C-5 V delivers the highest initial discharge capacity of 220.4 mAh g−1 and the biggest Li-ion diffusion coefficient of 1.60 × 10−11 cm2 s−1. In addition, the density functional theory (DFT) calculations predict that V-doping decreases the electronic band gap of Li2FeSiO4, thus leads to significant improvement in the electrical conductivity of Li2FeSiO4. The enhanced electrochemical performance can be attributed to the increased electronic conductivity, the decreased charge transfer impedance, and the improved Li-ion diffusion coefficient. Our results clarified the nature of V doping into Li2FeSiO4 and demonstrated that V-doping is a promising approach to improve the electrochemical performance of Li2FeSiO4.

A series of Li2−xNaxFe0.5Mn0.5SiO4/C (x = 0.00, 0.01, 0.03 and 0.05) composites have been synthesized via a refluxing-assisted solid-state reaction, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), galvanostatic charge–discharge measurements, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests. XRD results show that Li2−xNaxFe0.5Mn0.5SiO4/C can be well indexed as the structure of two mixed polymorphs with space group P21 and Pmn21. XPS results confirms that Na not only exists on the surface of Li2Fe0.5Mn0.5SiO4 particles, but also has been successfully doped into the crystal lattice of Li2Fe0.5Mn0.5SiO4. Na-doping can significantly improve the discharge capacity and the rate capability of Li2Fe0.5Mn0.5SiO4/C. The enhanced electrochemical performance can be attributed to the increased electronic conductivity, the decreased charge transfer impedance, and the improved Li-ion diffusion coefficient.

CuS/graphene composite has been synthesized by the one-pot hydrothermal method using thiourea as the sulfur source and reducing agent. The formation of CuS nanoparticles and the reduction of graphene oxide occur simultaneously during the hydrothermal process, which enables a uniform dispersion of CuS nanoparticles on the graphene nanosheets. The electrochemical performance of CuS/graphene composite was studied as anode materials for lithium ion batteries. The obtained CuS/graphene composite exhibits a relative high reversible capacity and good cycling stability. The good electrochemical performance of CuS/graphene composite can be attributed to graphene, which improves the electronic conductivity of composite and enhances the interfacial stability of electrode and electrolyte.

Chemically activated graphene/porous Si@SiOx (CAG/Si@SiOx) composite has been synthesized via magnesiothemic reduction of mesoporous SiO2 (MCM-48) to porous Si@SiOx and dispersing in the suspension of chemically activated graphene oxide (CAGO) followed by thermal reduction. The porous Si@SiOx particles are well encapsulated in chemically activated graphene (CAG) matrix. The resulting CAG/Si@SiOx composite exhibits a high reversible capacity and excellent cycling stability up to 763 mAh g−1 at a current density of 100 mA g−1 after 50 cycles. The porous structure of CAG layer and Si@SiOx is beneficial to accommodate volume expansion of Si during discharge and charge process and the interconnected CAG improves the electronic conductivity of composite.

Carbon-coated Li2FeSiO4 composite (LFS/C-AA) was synthesized via a refluxing-assisted solid-state reaction by using ascorbic acid as additive and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, galvanostatic charge/discharge measurements, and electrochemical impedance spectra (EIS) tests. The results show that ascorbic acid can to some extent prohibit the oxidation of Fe2+ during the synthesis process, and the pyrolytic carbon from ascorbic acid shows higher electronic conductivity and improves the degree of graphitization of residual carbon in the LFS/C-AA composite. Compared with LFS/C prepared without ascorbic acid, LFS/C-AA displays better electrochemical performance. The desirable property is attributed to the reduced particle size, the enhanced electronic conductivity, and the improved diffusion coefficient of lithium ions.

Reduced graphene oxide/porous Si composite was fabricated through magnesiothermic reduction of mesoporous silica and subsequent dispersing porous Si in the suspension of graphene oxide followed by reduced process. The electrochemical performance of the obtained reduced graphene oxide/porous Si composite was investigated as anode for lithium ion batteries, and it delivers a reversible capacity of about 815 mAh g−1 at a rate of 100 mA g−1 in the voltage range of 0.01–1.5 V after 50 cycles. The excellent electrochemical performance of the composite can be attributed to that of the porous structure of conductive reduced graphene oxide network, and dispersed Si particles can improve electronic conductivity and accommodate the large volume changes.

SnS/graphene nanocomposite has been prepared through a simple one-step and in situ method using thiourea as the sulfur source and reducing agent. The formation of SnS nanoparticles and the reduction of graphene oxide occur simultaneously during the hydrothermal process. The SnS nanoparticles are dispersed uniformly on graphene nanosheets and the SnS/graphene nanocomposite exhibits a relatively high reversible capacity and good cycling stability. The excellent electrochemical performance can be attributed to graphene, which prevents the agglomeration of SnS nanoparticles and improves the electronic conductivity of overall nanocomposite. The SnS/graphene nanocomposite combines the advantages of the good cycling stability of graphene and the high capacity of SnS nanoparticles.

Double-walled core-shell structured Si@SiO2@C nanocomposite has been prepared by calcination of silicon nanoparticles in air and subsequent carbon coating. The obtained Si@SiO2@C nanocomposite demonstrates a reversible specific capacity of about 786 mAh g−1 after 100 cycles at a current density of 100 mA g−1 with a capacity fading of 0.13 % per cycle. The enhanced electrochemical performance can be due to that the double walls of carbon and SiO2 improve the electronic conductivity and enhance the compatibility of electrode materials and electrolyte as a result of accommodating the significant volumetric change during cycles. The interlayer SiO2 may release the mechanical strain and enhance the interfacial adhesion between carbon shell and silicon core.

Polyaniline encapsulated silicon (Si/PANI) nanocomposite as anode materials for high-capacity lithium ion batteries has been prepared by an in situ chemical polymerization of aniline monomer in the suspension of Si nanoparticles. The obtained Si/PANI nanocomposite demonstrates a reversible specific capacity of 840 mAh g−1 after 100 cycles at a rate of 100 mA g−1 and excellent cycling stability. The enhanced electrochemical performance can be due to that the polyaniline (PANI) matrix offers a continuous electrically conductive network as well as enhances the compatibility of electrode materials and electrolyte as a result of suppressing volume stress of Si during cycles and preventing the agglomeration of Si nanoparticles.

Hollow core-shell structured Si/C nanocomposites were prepared to adapt for the large volume change during a charge-discharge process. The Si nanoparticles were coated with a SiO2 layer and then a carbon layer, followed by etching the interface SiO2 layer with HF to obtain hollow core-shell structured Si/C nanocomposites. The Si nanoparticles are well encapsulated in a carbon matrix with an internal void space between the Si core and the carbon shell. The hollow core-shell structured Si/C nanocomposites demonstrate a high specific capacity and excellent cycling stability, with capacity decay as small as 0.02% per cycle. The enhanced electrochemical performance can be attributed to the fact that the internal void space can accommodate the volume expansion of Si during lithiation, thus preserving the structural integrity of electrode materials, and the carbon shell can increase the electronic conductivity of the electrode.

Core–shell structured Si/C nanocomposites with different nitrogen contents are prepared by in situ polymerization of aniline in the suspension of silicon nanoparticles followed by carbonization of Si/polyaniline (PANI) nanocomposites at different temperatures. The nitrogen contents of Si/C nanocomposites decrease gradually with increasing carbonization temperatures. The effect of nitrogen contents on the electrochemical performance of Si/C nanocomposites as anode materials for lithium ion batteries is investigated. It is found that the Si/C nanocomposites with 4.75 wt.% nitrogen exhibit the high specific capacity of 795 mAh g−1 after 50 cycles at a current density of 100 mA g−1 and excellent cycling stability. The appropriate nitrogen in Si/C nanocomposites plays a beneficial role in the improvement of electrochemical performance. The nitrogen in Si/C nanocomposites increases the reversible capacity, which may be due to the formation of vacancies and dangling bonds around the nitrogen sites.

Si@SiO x /C nanoporous spheres as anode materials for high-performance lithium ion batteries were fabricated through a facile magnesiothermic reduction of well-ordered mesoporous silica and subsequent impregnating of carbon precursor into the Si@SiO x nanoporous spheres followed by carbonization at 800 °C. The obtained nanoporous spheres present an interweaved porous structure composed of high-capacity Si, inactive SiO x and conductive carbon, which can effectively enhance the electrochemical performance of the composite materials. The resulting Si@SiO x /C nanoporous spheres display a reversible specific capacity of 913 mA h g − 1 at the first cycle and the capacity retention ratio is 97% after 60 cycles at a current density of 100 mA g − 1 . The nanoporous structure of Si, SiO x and C can effectively accommodate the volume change for Si-based materials' expansion, release the mechanical stress and improve the electronic conductivity. The Si@SiO x /C nanoporous spheres exhibit a great potential as anode materials for lithium ion batteries.

TiO2–graphene nanosheets (GNS) composites are prepared via an in situ chemical synthesis method, which enables a homogenous dispersion of TiO2 nanoparticles on the graphene nanosheets. The obtained TiO2–GNS composites are anatase-GNS, while TiO2 is nanosized rutile without the incorporation of GNS. The resulting TiO2–GNS composites are employed as anode materials for lithium-ion batteries, showing a high initial reversible capacity of 306 mAh g−1 as well as a good cycling stability. The TiO2–GNS composites can deliver 60 mAh g−1 at a current rate as high as 5 A g−1 and demonstrate negligible fade even after 400 cycles. The superior electrochemical performances of the TiO2–GNS composites can be attributed to their unique structures, which intimately combine the conductive graphene nanosheets network with uniformly dispersed TiO2 nanoparticles. The TiO2–GNS composites could be promising candidate materials for high-power, low-cost, and environmentally friendly anodes for lithium ion batteries.

Self-supporting Si/Reduced Graphene Oxide (RGO) nanocomposite films have been prepared by thermal reduction of Si/graphene oxide nanocomposite, which is fabricated by dispersing silicon nanoparticles into an aqueous suspension of graphene oxide nanosheets. The Si nanoparticles are well encapsulated in a RGO matrix and the Si/RGO composite has much higher reversible discharge capacity and a better cycle stability than pure nanosized Si particles as well as the RGO. Such enhancement can be attributed to the RGO matrix, which offers an efficient electrically conductive channel and a flexible mechanical support for strain release. Keywords: Silicon, Reduced Graphene Oxide, Lithium ion batteries, Anode

CuInS 2 nanoflakes were synthesized successfully by a convenient solvothermal route in ethylene glycol under the open-air condition using copper chloride, indium chloride and thiourea as starting materials. The factors which might affect the purity of the product during the synthesis were discussed. It's found that the products were significantly affected by the reaction time, temperature and the diffusion of the reactors. CuInS 2 nanoflakes ink was prepared and coated onto Mo substrate using blade technology, and after sintering, a dense and compact CuInS 2 film was produced. The morphological of the precursor films and CuInS 2 films were done by scanning electron microscope (SEM), and the photoelectrochemical properties and morphology of the CuInS 2 thin film were characterized.