Shan Fang

Rational design of void-involved Si@TiO2 nanospheres as high-performance anode material for lithium-ion batteries.

A unique core-shell structure of silicon@titania (Si@TiO2) composite with silicon nanoparticles encapsulated in TiO2 hollow spheres is synthesized by a simple hydrolysis method combined with magnesiothermic reduction method. It is found that the TiO2 shell is effective for improving the electrical conductivity and structural stability. More importantly, the well-designed nanostructure with enough empty space would accommodate the volume change of silicon during the cycling. Reversible capacities of 1911.1 and 795 mAh g(-1) can be obtained at 0.05 C and a high current rate of 1 C, respectively. After 100 cycles at 0.1 C, the composite electrode still maintains a high capacity of 804 mAh g(-1). This excellent cycling stability and high-rate capability can be ascribed to the unique core-shell nanostructure and the synergistic effect between Si and TiO2.

Ge–graphene–carbon nanotube composite anode for high performance lithium-ion batteries

A Ge–graphene–carbon nanotube composite electrode was constructed by germanium (Ge) nanoparticles anchored on reduced graphene oxide (Ge–RGO) intertwined with carbon nanotubes (CNT). In this unique structure, the graphene sheets improve the electrical conductivity and buffer severe volume changes. Additionally, the CNT mechanically binds together with Ge–RGO to maintain the integrity of the electrodes and stabilize the electric conductive network for the active Ge nanoparticles, leading to better cycling performance. As a result, the designed anode exhibits an outstanding energy capacity up to 863.8 mA h g−1 at a current density of 100 mA g−1 after 100 cycles and good rate performances of 1181.7, 1073.8, 1005.2, 872.0, 767.6, and 644.8 mA h g−1 at current densities of 100, 200, 400, 800, 1600, and 3200 mA g−1, respectively. Our results indicate that the hybrids exhibit considerably improved lithium storage performance.

Three-dimensionally ordered porous TiNb2O7 nanotubes: a superior anode material for next generation hybrid supercapacitors

Hybrid supercapacitors are a very appealing power source with high energy density and power density because they employ both the merits of lithium ion batteries and supercapacitors. To balance such hybrid systems, the rate of the redox component must be substantially comparative to the levels of the double layer process. As far as the insertion-host material TiNb2O7 is concerned, we have used facile step electrode design consisting of the physically assisted template infusion of Ti–Nb sol into the pores of AAO followed by in situ conversion into porous TiNb2O7 nanotubes within the AAO walls under calcination, and finally making those templates dissolve away. Using such an electrode as the battery type anode and a graphene grass electrode as the capacitor type cathode, we successfully constructed a novel hybrid supercapacitor. Within a voltage range of 0–3 V, a high energy density of ∼74 W h kg−1 is achieved and it could remain as much as ∼34.5 W h kg−1 at a power of 7500 W kg−1. The present research sheds new light on the development of energy storage devices with both high energy density and high power density.

Synthesis of hydrogenated TiO2–reduced-graphene oxide nanocomposites and their application in high rate lithium ion batteries

A hydrogenated TiO2–reduced-graphene oxide (H-TiO2–RGO) nanocomposite is synthesised via a facile one-pot hydrogenation treatment process. The morphologies and structures are characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nitrogen adsorption–desorption isotherms revealed that the H-TiO2–RGO exhibited large specific surface area of 114.4 m2 g−1. Compared with the TiO2–RGO nanocomposite, the H-TiO2–RGO nanocomposite exhibits a much higher rate capability and better capacity retention. At a current rate of 5 C, the reversible capacity of the H-TiO2–RGO electrode is up to 166.3 mA h g−1 and with only 2.4% capacity loss after 100 cycles. The excellent electrochemical performance is strongly related to the high electronic conductivity derived from hydrogenated TiO2 frameworks and the good contact between the zero-dimensional (0D) H-TiO2 nanoparticles with two-dimensional (2D) reduced-graphene oxide nanosheets, which efficiently shortened the Li+ diffusion path lengths, enhanced the electrolyte–active material contact area and facilitated rapid e− transfer.

Stabilized titanium nitride nanowire supported silicon core–shell nanorods as high capacity lithium-ion anodes

In this work, TiN NW supported silicon nanorods (TiN@Si NRs) are produced via direct radio frequency (RF) magnetron sputtering of Si deposition onto the surface of TiN NWs. Due to its superior mechanical stability and electrical conductivity, TiN provides more stable support and better conductive pathways for Si when compared with TiO2. The unique core–shell TiN@Si NR structure has enough void space to accommodate the large volume changes of Si during charge/discharge cycling. The novel 3D architecture electrode demonstrates exceptional electrochemical performances with ultrahigh specific capacity. Comparing with TiO2@Si NRs, TiN@Si NR electrodes exhibit improved cycling performances, which can still retain a capacity of 3258.8 mA h g−1 after 200 cycles at 1 A g−1. It should be noted that the TiN@Si NRs show an excellent rate performance even at a high current density (2256.6 mA h g−1 is realized at 10 A g−1). These results endow the electrodes with high power and long cycling stability.

Raspberry-like Nanostructured Silicon Composite Anode for High-Performance Lithium-Ion Batteries

Adjusting the particle size and nanostructure or applying carbon materials as the coating layers is a promising method to hold the volume expansion of Si for its practical application in lithium-ion batteries (LIBs). Herein, the mild carbon coating combined with a molten salt reduction is precisely designed to synthesize raspberry-like hollow silicon spheres coated with carbon shells (HSi@C) as the anode materials for LIBs. The HSi@C exhibits a remarkable electrochemical performance; a high reversible specific capacity of 886.2 mAh g-1 at a current density of 0.5 A g-1 after 200 cycles is achieved. Moreover, even after 500 cycles at a current density of 2.0 A g-1, a stable capacity of 516.7 mAh g-1 still can be obtained.

Confined germanium nanoparticles in an N-doped carbon matrix for high-rate and ultralong-life lithium ion batteries

In this study, a relatively simple and direct method is used to prepare germanium nanoparticles (Ge NPs) embedded in the pore tunnels of an N-doped mesoporous carbon matrix. In the Ge/CMK-3 nanocomposite, the highly ordered porous structure and large pore volume guarantee a sufficient Ge loading and buffer the large volume changes of Ge during the discharge/charge cycles. More specifically, the mesoporous carbon matrix can supply sufficient pathways for Li+ and electron transport to the encapsulated nanometer-sized Ge, as well as restrain the agglomeration and growth of Ge during the crystallization process. Accordingly, the electrode of Ge/CMK-3 attained a capacity as high as 755.7 mA h g−1 at 500 mA g−1 after 420 cycles with a capacity retention of 93.3% based on the 11th cycle. The study shows that the electrochemical properties of Ge/CMK-3 are significantly improved compared to that of the bulk Ge anode, and it demonstrates that Ge/CMK-3 could potentially show promise as an anode material for energy storage.

Application of Carbon Nanotubes in Lithium-Ion Batteries

Abstract With their unique one-dimensional tubular structure, high electrical and thermal conductivities, and extremely large surface area, carbon nanotubes (CNTs) have been considered as a promising candidate as anode materials for lithium-ion batteries (LIBs). In this chapter, we discuss the mechanism of lithium-ion intercalation and diffusion in CNTs, and the influence of different structures and morphologies on their performance as anode materials for LIBs. At the end of this chapter, we summarize and discuss the CNTs as a role for the framework and conductive additives in LIBs.

Highly Graphitized Carbon Coating on SiO with a π–π Stacking Precursor Polymer for High Performance Lithium-Ion Batteries

A highly graphitized carbon on a silicon monoxide (SiO) surface coating at low temperature, based on polymer precursor π–π stacking, was developed. A novel conductive and electrochemically stable carbon coating was rationally designed to modify the SiO anode materials by controlling the sintering of a conductive polymer, a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate; PPy), which achieved high graphitization of the carbon layers at a low temperature and avoided silicon carbide formation and possible SiO material transformation. When evaluated as the anode of a lithium-ion battery (LIB), the carbon-coated SiO composite delivered a high discharge capacity of 2058.6 mAh/g at 0.05 C of the first formation cycle with an initial Coulombic efficiency (ICE) of 62.2%. After 50 cycles at 0.1 C, this electrode capacity was 1090.2 mAh/g (~82% capacity retention, relative to the capacity of the second cycle at 0.1 °C rate), and a specific capacity of 514.7 mAh/g was attained at 0.3 C after 500 cycles. Furthermore, the coin-type full cell composed of the carbon coated SiO composite anode and the Li[Ni0.5Co0.2Mn0.3O2] cathode attained excellent cycling performance. The results show the potential applications for using a π–π stacking polymer precursor to generate a highly graphitize coating for next-generation high-energy-density LIBs.