Synthesis and characterization of porous maghemite as an anode for Li-ion batteries

The synthesis of porous maghemite via a simple glycerol-mediated solution method was successfully accomplished. Thermal analysis, X-ray diffraction and Mössbauer spectroscopy results disclosed the formation of maghemite. The morphological and structural features of maghemite were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, and nitrogen adsorption–desorption. The powder showed Brunauer–Emmett–Teller surface area of 285 m² g⁻¹ with micro-, meso- and macropores.The anode body was doctor bladed using primary powder with a binder and a conductive agent. Galvanostatic charge–discharge cycling of the porous maghemite exhibited a specific reversible capacity of approximately 1180 mAh g⁻¹ at 100 mA g⁻¹ current density, which was two times higher than that of common nanomaghemite with average particle size of 19 nm. The cell showed stability even at the high current charge–discharge rates of 3000 mA g⁻¹ and more than 94% retention. After multiple high current cycling regimes, the cell recovered to nearly full reversible capacity of ~1120 mAh g⁻¹ at 100 mA g⁻¹. The reason for this remarkable performance of the present anode was thought to be dependent upon the role of pores in increasing the surface area and resistance against volume changes during lithium insertion/extraction.     

Synthesis of MnOx/reduced graphene oxide nanocomposite as an anode electrode for lithium-ion batteries

We report the high performance of the manganese oxide/reduced graphene oxide (MnOx/rGO) nanocomposite as an anode electrode of a lithium-ion battery. The composite is synthesized by a low temperature (83 °C) chemical solution reaction, and shows relatively high specific capacities (660 mAh g⁻¹) after 50 cycles. For MnOx/rGO composites, the cycling stability is increased remarkably as compared to that seen with individual MnOx, and this is due to the synergistic effects of both the components in the composite. The rGO acts as a conductive buffer layer that suppresses the volume change of MnOx, and simultaneously promotes the conductivity of MnOx. The functional groups of graphene oxide facilitate MnOx formation at low temperature, and this retains the MnOx-graphene oxide connection, thus improving the capacity and cycling stability.     

Facile fabrication of porous NiMoO4@C nanowire as high performance anode material for lithium ion batteries

Herein, porous NiMoO₄@C nanowire is purposefully synthesized using oleic acid as carbon source, and further evaluated as high performance anode material for Li-ion batteries (LIBs). Compared with the pure NiMoO₄, porous NiMoO₄@C nanowire exhibits high reversible charge/discharge specific capacity, excellent cycle stability and preeminent rate capability. A stable reversible lithium storage capacity of 975 mAh g⁻¹ can still be maintained after 100 cycles at 200 mA g⁻¹. When the current density decreases back from 3000 mA g⁻¹ to 100 mA g⁻¹, a high discharge specific capacity of 884 mAh g⁻¹ is recovered. The porous structure and carbon layers can enhance the electronic transmission and structural stability, shorten the path lengths for ion and electron transport, and provide a mechanical buffer space to accommodate the volume expansion/contraction during the repeated Li⁺ insertion/extraction processes. All the results highlight that the porous NiMoO₄@C nanowire composite would be a promising candidate for high performance anode material of LIBs owing to its excellent electrochemical properties.     

Preparation of graphene supported porous Si@C ternary composites and their electrochemical performance as high capacity anode materials for Li-ion batteries

Graphene supported porous Si@C ternary composites had been synthesized by various routes and their structural, morphological and electrochemical properties were investigated. Porous Si spheres coated with carbon layer and supported by graphene have been designed to form a 3D carbon conductive network. Used as anode materials for lithium ion batteries, graphene supported porous Si@C ternary composites demonstrate excellent electrochemical performance and cycling stability. The first discharge capacity is 2184.7 mA h/g at a high current density of 300 mA/g. After 50 cycles, the reversible capacity is 652.4 mA h/g at a current density of 300 mA/g and the coulomb efficiency reaches at 98.7%. Due to their excellent electrochemical properties, graphene supported porous Si@C ternary composites can be a kind of promising anode materials for lithium ion batteries.     

PPy modified 1T-MoS2 hollow spheres with cohesive architecture as high-performance anode material for Li-ion batteries

A cohesive architecture of 1T-MoS₂ covered by PPy composite (1T-MoS₂@PPy) is successfully fabricated by a simple hydrothermal reaction followed by an in-situ polymerization route. The composite material consists of 1T-MoS₂ hollow microsphere and conductive PPy coating layer. The cohesive architecture enables the composite to show rapid shuttle of electrons/lithium ions and good ductility to buffer the volume changes during charging and discharging process when it is used as anode material. As expected, 1T-MoS₂@PPy composite exhibits a favorable discharge capacity up to 970.3 and 407.1 mAh g^?1 at 0.2 and 3 A g^?1, respectively. In addition, the composite also achieves impressive cycling performance of 717.1 mAh g^?1 at 1 A g^-1 after 500 cycles. This study provides a meaningful guidance in rational design of anode materials with cohesive architecture as well as high electrochemical performance.     

A ternary MnO/MnTiO3@C composite anode with greatly enhanced cycle stability for Li-ion batteries

Manganese monoxide (MnO) has been widely studied as a potential anode material of Li-ion batteries because of its high specific capacity and abundant raw materials. However, the poor cycling stability of MnO associating to its large volume change during the repeated conversion reaction with Li⁺ has restricted its practical applications. Herein, ternary MnO/MnTiO₃@C composite anode materials are prepared by in situ capturing TiO₂ nanoparticles into sea urchin-like MnO₂ in a mild hydrothermal reaction, followed by resorcinol-formaldehyde (RF) resin coating and thermal treatment. With the strong stabilization effect of the MnTiO₃ component, the optimized ternary MnO/MnTiO₃@C composite anode exhibits greatly enhanced cycling performance as compared to MnO@C. A reversible capacity of 383 mAh g^?1 is preserved after 500 cycles at 1000 mA g^?1. This improved cycle performance can be originated from the stable TiO crystals and the highly reversible amorphous Li_xMnTiO₃ phase generated in the first lithiation process. The reasonably high specific capacity and robust cycle stability enable the ternary MnO/MnTiO₃@C composites to be promising alternative anode materials to graphite for Li-ion batteries.     

锂离子电池锡钴和锡钴碳负极材料的研究进展

综述了锂离子电池锡钴二元合金和锡钴碳三元复合材料的结构、电化学性能,反应机理及制备方法.改善锡基材料的循环性能主要有3个途径:元素多元化,减小颗粒粒度,无定形化.仅靠上述单一途径很难达到产业化对循环性能的要求,因此多种途径联合运用成为解决循环性能的研究趋势.     

A high capacity NiFe2O4/RGO nanocomposites as superior anode materials for sodium-ion batteries

NiFe₂O₄/reduced graphene oxide (NFO/RGO) nanocomposites were prepared by a facile one-step hydrothermal method and used as anode for sodium ion batteries (SIBs). The crystal structures, morphologies and electrochemical properties of as-prepared samples were evaluated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge tests. The results show that NFO/RGO-20 (20 wt%) delivers the highest reversible capacity of ~450 mA h g⁻¹ at 50 mA g⁻¹ after 50 cycles with good cycling stability. The excellent sodium storage performance of NFO/RGO should be attributed to the synergistic effect between NFO and RGO to form conductive network structure, which offers the increased specific surface area, the facilitated electron transfer ability and the buffering of volume expansion.     

NiO nanosheets grown on graphene nanosheets as superior anode materials for Li-ion batteries

This paper reports a hydrothermal preparation of NiO-graphene sheet-on-sheet and nanoparticle-on-sheet nanostructures. The sheet-on-sheet nanocomposite showed highly reversible large capacities at a common current of 0.1 C and good rate capabilities. A large initial charge capacity of 1056 mAh/g was observed for the sheet-on-sheet composite at 0.1 C, which decreased by only 2.4% to 1031 mAh/g after 40 cycles of discharge and charge. This cycling performance is better than that of NiO nanosheets, graphene nanosheets, NiO-graphene nanoparticle-on-sheet, and previous carbon/carbon nanotube supported NiO composites. It is believed that the mechanical stability and electrical conductivity of NiO nanosheets are increased by graphene nanosheets (GNS), the aggregation or restacking of which to graphite platelets are, on the other hand, effectively prevented by NiO nanosheets.     

Hard carbon/lithium composite anode materials for Li-ion batteries

Hard carbon/lithium composite anode electrode is prepared to reduce the initial irreversible capacity of hard carbon, which hinders practical application of hard carbon in lithium ion batteries, by introducing lithium into hard carbon. Lithium foil effectively compensates the irreversible capacity of hard carbon in the first cycle. A full cell using LiCoO₂ cathode and the composite anode shows much higher initial coulombic efficiency than that of a cell using LiCoO₂ cathode and hard carbon anode. This paves the way to reduce the large initial irreversible capacity of hard carbon. Besides that, this composite anode enables conductive polymer/sulfur composite cathode to be used in Li-ion batteries with non-lithiated anode materials.     

A review study on titanium niobium oxide-based composite anodes for Li-ion batteries: Synthesis,structure, and performance

The growing demands for Li-ion batteries (LIBs) in the electrification revolution, require the development of advanced electrode materials. Recently, intercalating titanium niobium oxide (TNO) anode materials with the general formula of TiNb_xO_2+2.5x have received lots of attention as an alternative to graphite and Li₄Ti₅O₁₂ commercial anodes. The desirability of this family of compounds stems from their high theoretical capacities (377–402 mAh/g), high safety, high working voltage, excellent cycling stability, and significant pseudocapacitive behavior. However, the rate performance of TNO-based anodes is poor owing to their low electronic and ionic conductivities. TNO-based composites generally are prepared with two aims of enhancing the conductivity of TNO and achieving a synergic effect between the TNO and the other component of the composite. Compositing with carbon matrices, such as graphene and carbon nanotubes (CNTs) are the most studied strategy for improving the conductivity of TNO and optimizing its high-rate performance. Also, for obtaining anode materials with high capacity and high long-term stability, the composites of TNO with transition metal dichalcogenides (TMDs) materials were proposed in previous literature. In this work, a comprehensive review of the TNO-based composites as the anodes for LIBs is presented which summarizes in detail the main recent literature from their synthesis procedure, optimum synthesis parameters, and the obtained morphology/structure to their electrochemical performance as the LIBs anode. Finally, the research gaps and the future perspective are proposed.     

A novel micro-spherical CoSn2/Sn alloy composite as high capacity anode materials for Li-ion rechargeable batteries

Micro-scaled spherical CoSn₂/Sn alloy powders synthesized from oxides of Sn and Co via carbothermal reduction at 800 °C were examined for use as anode materials in Li-ion battery. The phase composition and particle morphology of the CoSn₂/Sn alloy composite powders were investigated by XRD, SEM and TEM. The prepared CoSn₂/Sn alloy composite electrode exhibits a low initial irreversible capacity of ca. 140 mAh g⁻¹, a high specific capacity of ca. 600 mAh g⁻¹ at constant current density of 50 mA g⁻¹, and a good rate capability. The stable discharge capacities of 500-515 mAh g⁻¹ and the columbic efficiencies of 95.8-98.1% were obtained at current density of 500 mA g⁻¹. The relatively large particle size of CoSn₂/Sn alloy composite powder is apparently favorable for the lowering of initial capacity loss of electrode, while the loose particle structural characteristic and the Co addition in Sn matrix should be responsible for the improvement of cycling stability of CoSn₂/Sn electrode.     

Porous carbon spheres as anode materials for sodium-ion batteries with high capacity and long cycling life

Porous carbon spheres (PCSs) with high surface area were fabricated by the reaction of D-Glucose monohydrate precursor with sodium molybdate dihydrate (Na₂MoO₄·2H₂O) via a facile hydrothermal method followed by carbonization and aqueous ammonia solution (NH₃·H₂O) treatment. The as-prepared PCSs exhibit a highly developed porous structure with a large specific surface area and show an excellent electrochemical performance as anode material of sodium-ion batteries (SIBs). A reversible capacity of 249.9 mA h g⁻¹ after 50 cycles at a current density of 50 mA g⁻¹ and a long cycling life at a high current density of 500 mA g⁻¹ are achieved. The excellent cycling performance and high capacity make the PCSs a promising candidate for long cycling SIBs.     

Lead-based systems as suitable anode materials for Li-ion batteries

Three lead-based materials formed by PbO₂, PbO and Pb as main phases were prepared by following different synthetic procedures and tested as anodic materials in Li-ion batteries by using potentiostatic and galvanostatic methods. While the reduction of Pb(IV) to Pb(II) takes place in a single step, that of Pb(II) to Pb is a complex process involving several steps. Both reduction reactions are irreversible. Lead, whether electrochemically or chemically formed, undergoes an electrochemical reaction with lithium that over the 1.0-0.0 V potential range yields Li_xPb alloys (0≤x≤4.4). The anodic and cathodic potentiostatic curves exhibit various signals that account for: (i) the formation of different intermediates with variable lithium contents; (ii) the reversibility of the alloying/de-alloying processes; (iii) the increase in complexity of such processes as the oxidation state of lead in them decreases. This results in capacity fading with cycling, particularly in the samples having Pb as the main component. One way of avoiding the capacity loss on cycling involves depositing the active material on lead sheets from spraying suspensions. These coatings exhibit a good capacity retention, which can be ascribed to the formation of a Li_xPb layer at the active material/substrate interface that facilitates electron and ion transfer across the electrode.     

Effect of synthesis temperature on the phase structure,morphology and electrochemical performance of Ti3C2 as an anode material for Li-ion batteries

Ti₃C₂, the most widely studied MXene, was successfully synthesised by etching Al layers from Ti₃AlC₂ in HF solution. Given its distinct 2D layered structure, Ti₃C₂ is a promising anode material in Li-ion batteries because of its efficient ion transport, available large surface areas for improved ion adsorption and fast surface redox reactions. Herein, the effects of synthesis temperature on the phase structure, morphology and electrochemical performance were investigated. The materials synthesised at different temperatures were characterised by using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Optimal etching occurred at 100?°C, and the synthesised Ti₃C₂ exhibited smooth surface and large layer space. The synthesised Ti₃C₂, as anode material for Li-ion batteries, can accommodate more Li⁺ than those of others, and it exhibits the most ideal electrochemical performance.     

Facile synthesis of porous hollow Co3O4 microfibers derived-from metal-organic frameworks as an advanced anode for lithium ion batteries

Co₃O₄, as a promising anode material for the next generation lithium ion batteries to replace graphite, displays high theoretical capacity (890 mAh g⁻¹) and excellent electrochemical properties. However, the drawbacks of its poor cycle performance caused by large volume changes during charge-discharge process and low initial coulombic efficiency due to large irreversible reaction impede its practical application. Herein, we have developed a porous hollow Co₃O₄ microfiber with 500 nm diameter and 60 nm wall thickness synthesized via a facile chemical precipitation method with subsequent thermal decomposition. As an advanced anode for lithium ion batteries, the porous hollow Co₃O₄ microfibers deliver an obviously enhanced electrochemical property in terms of lithium storage capacity (1177.4 mA h g⁻¹ at 100 mA g⁻¹), initial coulombic efficiency (82.9%) and cycle performance (76.6% capacity retention at 200th cycle). This enhancement could be attributed to the well-designed microstructure of porous hollow Co₃O₄ microfibers, which could increase the contact surface area between electrolyte and active materials and accommodate the volume variations via additional void space during cycling.     

MoO3/reduced graphene oxide composites as anode material for sodium ion batteries

MoO₃/reduced graphene oxide (MoO₃/RGO) composites were successfully prepared via a facile one-step hydrothermal method, and evaluated as anode materials for sodium ion batteries (SIBs). The crystal structures, morphologies and electrochemical properties of the as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge tests, respectively. The results show that the introduction of RGO can enhance the electrochemical performances of MoO₃/RGO composites. MoO₃/RGO composite with 6 wt% RGO delivers the highest reversible capacity of ~208 mA h g⁻¹ at 50 mA g⁻¹ after 50 cycles with good cycling stability and excellent rate performance for SIBs. The excellent sodium storage performance of MoO₃/RGO should be attributed to the synergistic effect between MoO₃ and RGO, which offers the increased electrical conductivity, the facilitated electron transfer ability and the buffering of volume expansion.     

Unique porous yolk-shell structured Co3O4 anode for high performance lithium ion batteries

This paper introduces a unique porous yolk-shell structured Co₃O₄ microball, which is synthesized by spray pyrolysis from precursor solution with polyvinylpyrrolidone (PVP) additive. PVP acts as an organic template in the pyrolytic reaction facilitating the formation of yolk-shell structure. The electrochemical properties of porous yolk-shell Co₃O₄ microballs evaluated as anode materials for lithium ion batteries exhibit high initial columbic efficiency of 77.9% and high reversible capacity of 1025 mAh g⁻¹ with capacity retention of 98.8% after 150 cycles at 1 A g⁻¹. In contrast, the hollow microballs obtained without PVP addition show obvious capacity decay from 1033 to 748 mAh g⁻¹ after 150 cycles with the capacity retention of 72.3%. In addition, the microballs with porous yolk-shell structure exhibit better rate performance. The superior electrochemical performance is mainly attributed to the unique porous yolk-shell structure which provides large voids to buffer volume expansion and enlarge the contact area with the electrolyte, shortening the diffusion path of the lithium ions.     

One-step microwave-assisted synthesis of Sb2O3/reduced graphene oxide composites as advanced anode materials for sodium-ion batteries

Sb₂O₃/reduced graphene oxide (RGO) composites were prepared through a facile microwave-assisted reduction of graphite oxide in SbCl₃ precursor solution, and investigated as anode material for sodium-ion batteries (SIBs). The experimental results show that a maximum specific capacity of 503 mA h g⁻¹ is achieved after 50 galvanostatic charge/discharge cycles at a current density of 100 mA g⁻¹ by optimizing the RGO content in the composites and an excellent rate performance is also obtained due to the synergistic effect between Sb₂O₃ and RGO. The high capacity, superior rate capability and excellent cycling performance of Sb₂O₃/RGO composites demonstrate their excellent sodium-ion storage ability and show their great potential as electrode materials for SIBs.     

Three-dimensional porous amorphous SnO2 thin films as anodes for Li-ion batteries

Three-dimensional (3D) porous amorphous SnO₂ thin films were deposited on Ni foam substrates by Electrostatic Spray Deposition (ESD) technique as anodes for Li-ion batteries. These films display good capacity retention of 94.8% after 100 cycles at 0.5 C and rate capability of 362 mAh/g at 10 C. The improved performance originates from the fact that the 3D porous structure offers a “buffer zone” to accommodate the large volume change during cycling, and the foam-like substrate maximizes the contact area between electrode and electrolyte. The facile ESD method can be potentially extended to prepare other 3D porous functional materials.