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.     

Synthesis and characterization of MnCo2O4 microspheres based air electrode for rechargeable sodium-air batteries

In this work, the nanosized porous MnCo₂O₄ microspheres were synthesized by a hydrothermal method and their electrochemical behaviors were investigated based on a carbon supported composite air electrode for rechargeable sodium-air batteries. Under dry air test condition, the MnCo₂O₄/C air electrode demonstrated a stable working voltage of around 2.1 V vs. Na⁺/Na and a high initial discharge capacity of 7709.4 mA h g⁻¹, based on the active material mass, at a current density of 0.1 mA cm⁻². By a limit on the depth of discharge, the cell exhibited a specific capacity of 1000 mA h g⁻¹ with a high cycling stability up to 130 cycles. The considerable electrocatalytic activity suggests that the as-proposed MnCo₂O₄ is a highly efficient catalyst as air electrode for rechargeable sodium-air batteries.     

Bitter gourd-shaped Ni3V2O8 anode developed by a one-pot metal-organic framework-combustion technique for advanced Li-ion batteries

The present study reports on the one-pot synthesis of Ni₃V₂O₈ (NVO) electrodes by a simple metal organic framework-combustion (MOF-C) technique for anode applications in Li-ion batteries (LIBs). The particle morphology of the prepared NVO is observed to vary as irregular rods, porous bitter gourd and hybrid micro/nano particles depending on the concentration of the framework linker used during synthesis. In specific, the orthorhombic phase and the unique bitter gourd-type secondary structure comprised of agglomerated nanoparticles and porous morphologies is confirmed using powder X-ray diffraction, electron microscopies, X-ray photoelectron spectroscopy and N₂ adsorption–desorption measurements. When tested for lithium batteries as anode, the bitter gourd-type NVO electrode shows an initial discharge capacity of 1362 mA h g⁻¹ and a reversible capacity of 822 mA h g⁻¹ are sustained at a rate of 200 mA g⁻¹ after 100 cycles. Moreover, at 2000 mA g⁻¹, a reversible capacity of 724 mA h g⁻¹ is retained after 500 cycles. Interestingly, the porous bitter gourd-shaped NVO electrode registered significantly high rate performance and reversible specific capacities of 764, 531 and 313 mA h g⁻¹ at high rates of 1, 5 and 10 A g⁻¹, respectively.     

Carbon-coated SiO/ZrO2 composites as anode materials for lithium-ion batteries

A combination of high-energy ball milling and constant pressure chemical vapor deposition was used to prepare carbon-coated SiO/ZrO₂ composites. It was found that the as-prepared composites were composed of amorphous carbon, amorphous SiO, and paracryslalline ZrO₂. The electrochemical analysis results revealed excellent electrochemical performances for the composites, including a high initial discharge capacity (1737 mA h g⁻¹), a remarkable cyclic stability (reversible capacity of 721 mA h g⁻¹ at 800 mA g⁻¹, after 100 cycles), and a good rate capability (870 mA h g⁻¹ at 800 mA g⁻¹). These features demonstrate that these composites are promising alternative candidates for high-efficiency electrode materials of Li-ion batteries.     

3D NiCo2S4 nanorod arrays as electrode materials for electrochemical energy storage application

It is essential to develop new electrode materials for electrochemical energy storage to meet the increasing energy demands, reduce environmental pollution and develop low-carbon economy. In this work, binder-free NiCo₂S₄ nanorod arrays (NCS NRAs) on nickel foam electrodes are prepared by an easy and low energy-consuming route. The electrodes exhibit superior electrochemical properties both for alkaline and Li-ion batteries. In 3 M KOH electrolyte, the NCS NRAs achieve a specific capacity of 240.5 mA h g⁻¹ at a current density of 0.2 A g⁻¹, and 105.7 mA h g⁻¹ after 1500 cycles at the current density of 5 A g⁻¹ with capacity retention of 87.3%. As the anode for LIBs, it shows a high initial capacity of 1760.7 mA h g⁻¹ at the current density of 100 mA g⁻¹, corresponding coulombic efficiency of 87.6%, and a rate capacity of 945 mA h g⁻¹ when the current density is improved 10 times. Hence, the NiCo₂S₄ nanorod arrays are promised as electrode materials with competitive performance.     

Hollow ZnSnO3 cubes@carbon/reduced graphene oxide ternary composite as anode of lithium ion batteries with enhanced electrochemical performance

The ternary composite, carbon coated hollow ZnSnO₃ (ZS@C) cubes encapsulated in reduced graphene oxide sheets (ZS@C/rGO), was synthesized via low-temperature coprecipitation and colloid electrostatic self-assembly. The uniform carbon-coating layer not only plays a role in buffering the volume change of ZnSnO₃ cubes in the charging/discharging processes, but also forms three-dimensional network with the cooperation of graphene to maintain the structural integrity and improve the electrical conductivity. The results show that the reduced graphene oxide sheets encapsulated ZS@C microcubes with a typical core-shell structure of ~700 nm in size exhibit an improved electrochemical performance compared with bare ZS@C microcubes. The ZS@C/rGO electrode delivered an initial discharge capacity of 1984 mA h g⁻¹ at a current density of 0.1 A g⁻¹ and maintained a capacity of 1040 mA h g⁻¹ after 45 cycles. High specific capacity and superior cycle stability indicate that the ZS@C/rGO composite has a great potential for the application of lithium-ion anode material.     

Synthesis and electrochemical properties of artificial graphite as an anode for high-performance lithium-ion batteries

Artificial graphite containing abundant in situ grown onion-like carbon hollow nanostructures (OCHNs) was prepared from nickel nanoparticles doped pitch and natural graphite flakes by hot-pressing sintering method. Galvanostatic discharge–charge tests indicate that the synthetic graphite with abundant OCHNs exhibits a high specific capacity of 460 mA h g⁻¹ at 20 mA g⁻¹ as well as an excellent rate capability, with a reversible capacity of 220 mA h g⁻¹ at 1 A g⁻¹. Besides the advantages of common graphite anode materials, these superiorities make synthetic graphite a very promising anode for high-performance lithium-ion batteries.     

Facile synthesis of lithium-vanadium-molybdenum oxide nanocomposite as high-performance anode material for lithium ion batteries

A lithium-vanadium-molybdenum-oxide composite has been prepared by a soft chemical route with mechanical activation assistance followed by low-temperature heat treatment in argon atmosphere. The X-ray diffraction reveals that the synthesized sample is made up of Li₃V(MoO₄)₃ and LiVOMoO₄ crystal phases. The SEM images show the fine particles ~300 nm in size. HRTEM image shows a clear crystal boundary between the two phases. The composite possesses good electrochemical performance as anode material. Particularly, it delivers an initial charge capacity of 927 mAh g⁻¹ at 50 mA g⁻¹ with a high initial coulombic efficiency of 81.2% and maintains 87.8% of its initial capacity after 50 cycles. Even if tested at 1000 mA g⁻¹, it can deliver a reversible capacity of 542 mA h g⁻¹.     

Pseudocapacitive Li+ intercalation in ZnO/ZnO@C composites enables high-rate lithium-ion storage and stable cyclability

Metallic oxide ZnO is considered to be a promising alternative anode material for lithium ion battery because of its high theoretical capacities (978 mA h g⁻¹). However, its inherent low electronic conductivity and undesirable large volume change result in inferior electrochemical performances and hinder its practical application. Herein, ZnO/ZnO@C composites are prepared by a simple carbonization process of ZnO/ZnO@ZIFs-8, which are constructed by using ZnO particles as both template and zinc sources for zeolitic imidazolate frameworks-8 (ZIF-8) preparation via a facile solution reaction. When evaluated as anode for lithium ion batteries, the as-prepared composites show an initial capacity of 878 mA h g⁻¹ at current density of 0.1 A g⁻¹ with high capacity retention of 95.6% after 50 cycles, and an initial capacity of 359 mA h g⁻¹ tested at 5.0 A g⁻¹ with a capacity retention of 85.3% after 500 cycles, exhibiting outstanding cycling stability and excellent rate capability. The ameliorated electrochemical performances are mainly attributed to the elevated conductivity and cushioning effects provided by carbon framework derived from ZIF-8, and the enhanced pseudocapacitance behavior originated from the decreased size of ZnO particles and high surface area of ZIFs-derived carbon.     

High-capacity graphene oxide/graphite/carbon nanotube composites for use in Li-ion battery anodes

A composite of graphene oxide sheets, carbon nanotubes (CNTs), and commercial graphite particles was prepared. The composite’s use as a high-capacity and binder-free anode material for Li-ion batteries was examined. Results showed that this novel composite had a very high reversible Li-storage capacity of 1172.5 mA h g⁻¹ at 0.5C (1C = 372 mA g⁻¹), which is thrice that of commercial graphite anode. The composite also exceeded the theoretical sum of capacities of the three ingredients. More importantly, its reversible capacity below 0.25 V can reach up to 600 mA h g⁻¹. In summary, the graphene oxide/graphite/CNT composite had higher reversible capacity, better cycling performance, and similar rate capability compared with the graphene oxide/graphite composite.     

A hierarchical carbon fiber/sulfur composite as cathode material for Li–S batteries

A novel hierarchical structure carbon/sulfur composite is presented based on carbon fiber matrices, which are synthesized by electrospinning. The fibers are constituted with hollow graphitized carbon spheres formed using catalytic Ni nano-particles as hard templates. Sulfur is loaded to the carbon substrates via thermal vaporization. The structure and composition of the hierarchical carbon fiber/S composite are characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption isotherms. The electrochemical performance is evaluated by cyclic voltammetry and galvanostatic charge–discharge. The results exhibit an initial discharge capacity of 845 mA h g⁻¹ at 0.25 C (420 mA g⁻¹), with a retention of 77% after 100 cycles. A discharge capacity of 533 mA h g⁻¹ is still attainable when the rate is up to 1.0 C. The good cycling performance and rate capability are contributed to the uniform dispersion of sulfur, the conductive network of carbon fibers and hollow graphitized carbon spheres.     

Electrochemical presodiation promoting lithium storage performance of Mo-based anode materials

Stabilizing the layer structures of Mo-based anode materials is still a challenge for Li ion batteries. Herein, we proposed an electrochemical presodiation strategy for MoS₂ and MoO₃ to improve their cycling stability. It is interesting to note that the cycling stability of as-treated MoS₂ and MoO₃ was significantly improved. Although the reversible discharge capacity was slightly decreased, the capacity of the pretreated MoS₂ at 300 mA g⁻¹ was retained at 345 mA h g⁻¹ after 100 cycles while that of the pristine one decreased to 151 mA h g⁻¹. The capacity of the pretreated MoO₃ after 60 cycles was also improved from 275 mA h g⁻¹ (the pristine one) to 460 mA h g⁻¹. The stabilizing effect was further verified by scanning electron microscope (SEM) analysis. Electrochemical presodiation here could be a promising modification strategy for Mo-based anode materials.     

Sulfur-doped mesoporous carbon from surfactant-intercalated layered double hydroxide precursor as high-performance anode nanomaterials for both Li-ion and Na-ion batteries

We describe a preparation of sulfur-doped mesoporous amorphous carbon (SMAC) from a commercially available alkyl surfactant sulfonate anion-intercalated NiAl-layered double hydroxide precursor via thermal decomposition and subsequent acid leaching. The resultant amorphous carbon is endowed with the integrated advantage of featuring high reversible capacity and long cycling stability: intrinsic doping of sulfur, large specific area, and broad mesopore size distribution. Electrochemical evaluation shows that the SMAC electrode exhibits highly enhanced electrochemical performances, compared with the electrode of non-doped mesoporous and amorphous carbon prepared by using a different surfactant (sodium laurate). A high reversible capacity of 958 mA h g⁻¹ is achieved for the SMAC electrode after 110 cycles at 200 mA g⁻¹, and especially a superlong cycle life with a reversible capacity of 579 mA h g⁻¹ after 970 cycles at 500 mA g⁻¹. Moreover, the SMAC electrode can facilitate the reversible insertion/extraction of Na ion, owing to the proper specific area and mesopore size distribution, as well as the improved electronic conductivity resulted from doping of sulfur.     

Enhanced electrochemical properties of LiFePO4–silicon composites as positive electrode materials fabricated using a solid-state method

LiFePO₄–silicon composites were fabricated by using a solid-state method for applying positive electrodes in lithium ion batteries. The LiFePO₄–silicon composites were characterized with X-ray diffraction and field emission scanning electron microscopy. Their electrochemical properties were investigated with cyclic voltammetry, electrochemical impedance spectroscopy, and charge–discharge tests. The added silicon not only suppressed the surface corrosion caused by the decreasing H⁺ concentration in the electrolyte, but it also acted as a barrier between the LiFePO₄ particles and LiPF₆ electrolyte, thereby preventing the dissolution of Fe²⁺ in the electrode and enhancing the electrolyte/active material interactions. This resulted in improved lithium-ion transfer kinetics and excellent positive electrode performance, especially at high current densities and different operating temperatures (0, 25, and 50 °C). At 25 °C, the LiFePO₄ composite containing 2 wt% of silicon delivered the best electrochemical performance with a lithium-ion diffusion coefficient of 1.81×10⁻⁹ cm² s⁻¹, a specific discharge capacity of 143 mA h g⁻¹ for the initial cycle, and a capacity retention of 98% after 100 cycles. In contrast, the corresponding values for the pure LiFePO₄ were 1.19×10⁻¹¹ cm² s⁻¹, 115 mA h g⁻¹, and a capacity retention of 76% after 100 cycles, respectively.     

Effect of Fe-doping followed by C+SiO2 hybrid layer coating on Li3V2(PO4)3 cathode material for lithium-ion batteries

A novel Li₃V₂(PO₄)₃ composite modified with Fe-doping followed by C+SiO₂ hybrid layer coating (LVFP/C-Si) is successfully synthesized via an ultrasonic-assisted solid-state method, and characterized by XRD, XPS, TEM, galvanostatic charge/discharge measurements, CV and EIS. This LVFP/C-Si electrode shows a significantly improved electrochemical performance. It presents an initial discharge capacity as high as 170.8 mA h g⁻¹ at 1 C, and even delivers an excellent initial capacity of 153.6 mA h g⁻¹ with capacity retention of 82.3% after 100 cycles at 5 C. The results demonstrate that this novel modification with doping followed by hybrid layer coating is an ideal design to obtain both high capacity and long cycle performance for Li₃V₂(PO₄)₃ and other polyanion cathode materials in lithium ion batteries.     

Polymer microsphere-assisted synthesis of lithium-rich cathode with improved electrochemical performance

The Li-rich layered cathode material Li_1.165Mn_0.501Ni_0.167Co_0.167O₂ with porous structure has been successfully synthesized through a facile co-precipitation approach followed with a high-temperature calcination treatment, adopting polymer microsphere (PSA) as a template and conductive agent. The PSA-assisted Li_1.165Mn_0.501Ni_0.167Co_0.167O₂ composite exhibits remarkably improved cycling stability and rate capability compared with the bare composite. It delivers a high initial discharge capacity of 267.0 mA h g⁻¹ at 0.1 C (1 C=250 mA g⁻¹) between 2.0 V and 4.65 V. A discharge capacity of 214.9 mA h g ⁻¹ is still obtained after 100 cycles. Furthermore, the diffusion coefficients of Li⁺ investigated by the cyclic voltammetry technique are approximately 10⁻¹⁵–10⁻¹⁴ cm² s⁻¹. Such outstanding performance is mainly ascribed to: on one hand, the carbon residue of PSA after being calcined at high temperature contributes to enhance the electronic conductivity of the electrode and alleviates the volume changes during the Li⁺-insertion/extraction, leading to an improved rate capability; on the other hand, the unique porous structure and small particle size are conductive to increase the exposed electrochemical active surface, shorten Li⁺ diffusion distance and thus enhance the lithium storage capacity.     

Evaluation of reduced graphene oxide-supported NiSb2O6 nanocomposites for reversible lithium storage

NiSb₂O₆ and reduced graphene oxide (NiSb₂O₆/rGO) nanocomposites are successfully fabricated by a solid-state method combined with a subsequent solvothermal treatment and further used as anode material of lithium-ion battery. The NiSb₂O₆/rGO nanocomposites exhibit a higher reversible capacity (of ca. 1240.5 mA h g⁻¹ at a current density of 50 mA g⁻¹), along with a good rate capability (395.2 mA h g⁻¹ at a current density of 1200 mA g⁻¹) and excellent capacity retention (684.5 mA h g⁻¹ after 150 cycles). These good performances could be attributed to the incorporated reduced grapheme oxide, which significantly improves the electronic conductivity of the NiSb₂O₆.     

Effect of graphene nanosheets on electrochemical performance of Li4Ti5O12 in lithium-ion capacitors

In order to improve the electrochemical performance of lithium titanium oxide, Li₄Ti₅O₁₂ (LTO), for the use in the lithium-ion capacitors (LICs) application, LTO/graphene composites were synthesized through a solid state reaction. The composite exhibited an interwoven structure with LTO particles dispersed into graphene nanosheets network rather than an agglomerated state pristine LTO particles. It was found that there is an optimum percentage of graphene additives for the formation of pure LTO phase during the solid state synthesis of LTO/graphene composite. The effect of graphene nanosheets addition on electrochemical performance of LTO was investigated by a systemic characterization of galvanostatic cycling in lithium and lithium-ion cell configuration. The optimized composite exhibited a decreased polarization upon cycling and delivered a specific capacity of 173 mA h g⁻¹ at 0.1 C and a well maintained capacity of 65 mA h g⁻¹ even at 20 C. The energy density of 14 Wh kg⁻¹ at a power density of 2700 W kg⁻¹ was exhibited by a LIC full cell with a balanced mass ratio of anode to cathode along with a superior capacitance retention of 97% after 3000 cycles at a current density of 0.4 A g⁻¹. This boost in reversible capacity, rate capability and cycling performance was attributed to a synergistic effect of graphene nanosheets, which provided a short lithium ion diffusion path as well as facile electron conduction channels.     

Electrochemical properties of amorphous GeOx-C composite microspheres prepared by a one-pot spray pyrolysis process

Amorphous GeO₂-GeO-C (GeO_x-C) composite powders, containing a small amount of the GeC phase, are prepared by a one-pot spray pyrolysis process. The GeO_x-C composite powders have a completely spherical shape and are non-aggregated. The Ge 3d components in the XPS spectrum of the composite occupy 53.3%, 40.1%, and 6.6% of the total for GeO₂, GeO, and GeC, respectively. The amount of amorphous carbon in the GeO_x-C composite powder is estimated at 18.3%, based on the TG and XPS analysis. The initial discharge and charge capacities of the GeO_x-C composite powders at a current density of 1 A g⁻¹ are 1873 and 908 mA h g⁻¹, respectively. The discharge capacities of the GeO_x-C composite and commercial GeO₂ powders for the 1200th cycle are 723 and 169 mA h g⁻¹, respectively, and their corresponding capacity retentions from the 2nd cycle are 70.1% and 19.0%, respectively. The high structural stability of the composite during repeated lithium insertion and desertion processes results in excellent long-term cycling performance.     

One-pot synthesis of core–shell-structured tin oxide–carbon composite powders by spray pyrolysis for use as anode materials in Li-ion batteries

Core–shell-structured tin oxide–carbon composite powders with mixed SnO₂ and SnO tetragonal crystals are prepared by one-pot spray pyrolysis from a spray solution with tin oxalate and polyvinylpyrrolidone (PVP). The aggregate, made up of SnO_x nanocrystals (several tens of nanometers), is uniformly coated with an amorphous carbon layer. The initial discharge capacities of the bare SnO₂ and SnO_x–carbon composite powders at a current density of 1 A g⁻¹ are 1473 and 1667 mA h g⁻¹, respectively; their discharge capacities after 500 cycles are 78 and 1033 mA h g⁻¹, respectively. The SnO_x–carbon composite powders maintain their spherical morphology even after 500 cycles. On the other hand, the bare SnO₂ powder breaks into several pieces after cycling. The structural stability of the SnO_x–carbon composite powders results in a low charge transfer resistance and high lithium ion diffusion rate even after 500 cycles at a high current density of 2 A g⁻¹. Therefore, the SnO_x–carbon composite powders have superior electrochemical properties compared with those of the bare SnO₂ powders with a fine size.