Chueh Liu

Scalable Synthesis of Nano-Silicon from Beach Sand for Long Cycle Life Li-ion Batteries

Herein, porous nano-silicon has been synthesized via a highly scalable heat scavenger-assisted magnesiothermic reduction of beach sand. This environmentally benign, highly abundant, and low cost SiO2 source allows for production of nano-silicon at the industry level with excellent electrochemical performance as an anode material for Li-ion batteries. The addition of NaCl, as an effective heat scavenger for the highly exothermic magnesium reduction process, promotes the formation of an interconnected 3D network of nano-silicon with a thickness of 8-10 nm. Carbon coated nano-silicon electrodes achieve remarkable electrochemical performance with a capacity of 1024 mAhg−1 at 2 Ag−1 after 1000 cycles.

Template Free and Binderless NiO Nanowire Foam for Li-ion Battery Anodes with Long Cycle Life and Ultrahigh Rate Capability

Herein, NiO-decorated Ni nanowires with diameters ca. 30–150 nm derived from Ni wire backbone (ca. 2 μm in diameter) is directly synthesized on commercially available Ni foam as a renovated anode for Li-ion batteries. Excellent stability with capacity 680 mAh g−1 at 0.5C (1C = 718 mA g−1) is achieved after 1000 cycles. Superior rate capability is exhibited by cycling at extremely high current rates, such as 20C and 50C with capacities ca. 164 and 75 mAh g−1, respectively. The capacity can be recovered back to ca. 430 mAh g−1 in 2 cycles when lowered to 0.2C and stably cycled for 430 times with capacity 460 mAh g−1. The NiO nanowire foam anode possesses low equivalent series resistance ca. 3.5 Ω, resulting in superior power performance and low resistive losses. The NiO nanowire foam can be manufactured with bio-friendly chemicals and low temperature processes without any templates, binders and conductive additives, which possesses the potential transferring from lab scale to industrial production.

Towards flexible binderless anodes: silicon/carbon fabrics via double-nozzle electrospinning

Flexible electrodes (C-Si/C) composed of Si/C fibers trapped in carbon fiber frames via double-nozzle electrospinning improve the cycling stability and rate capability of Si/C fabrics. Polyacrylonitrile (PAN) has been demonstrated as a superior carbon matrix for Si compared with polyvinylpyrrolidone (PVP) annealed using the same heat-treatment process.

Silicon Derived from Glass Bottles as Anode Materials for Lithium Ion Full Cell Batteries

Every year many tons of waste glass end up in landfills without proper recycling, which aggravates the burden of waste disposal in landfill. The conversion from un-recycled glass to favorable materials is of great significance for sustainable strategies. Recently, silicon has been an exceptional anode material towards large-scale energy storage applications, due to its extraordinary lithiation capacity of 3579 mAh g−1 at ambient temperature. Compared with other quartz sources obtained from pre-leaching processes which apply toxic acids and high energy-consuming annealing, an interconnected silicon network is directly derived from glass bottles via magnesiothermic reduction. Carbon-coated glass derived-silicon (gSi@C) electrodes demonstrate excellent electrochemical performance with a capacity of ~1420 mAh g−1 at C/2 after 400 cycles. Full cells consisting of gSi@C anodes and LiCoO2 cathodes are assembled and achieve good initial cycling stability with high energy density.

Silicon and Carbon Nanocomposite Spheres with Enhanced Electrochemical Performance for Full Cell Lithium Ion Batteries

Herein, facile synthesis of monodisperse silicon and carbon nanocomposite spheres (MSNSs) is achieved via a simple and scalable surface-protected magnesiothermic reduction with subsequent chemical vapor deposition (CVD) process. Li-ion batteries (LIBs) were fabricated to test the utility of MSNSs as an anode material. LIB anodes based on MSNSs demonstrate a high reversible capacity of 3207 mAh g−1, superior rate performance, and excellent cycling stability. Furthermore, the performance of full cell LIBs was evaluated by using MSNS anode and a LiCoO2 cathode with practical electrode loadings. The MSNS/LiCoO2 full cell demonstrates high gravimetric energy density in the order of 850 Wh L−1 with excellent cycling stability. This work shows a proof of concept of the use of monodisperse Si and C nanocomposite spheres toward practical lithium-ion battery applications.

Phase Engineering of 2D Tin Sulfides.

Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

High energy and power density Li–O2 battery cathodes based on amorphous RuO2 loaded carbon free and binderless nickel nanofoam architectures

Herein, amorphous RuO2 nanoflakes deposited on Ni nanofoam (NF) with diameters of ca. 30–100 nm are utilized as an innovative cathode in Li–O2 batteries for the first time. The stability of the RuO2/Ni NF cathode is shown to possess ca. 87.7% capacity retention after 75 cycles with minute alteration of the charge–discharge profiles. A capacity as high as 6537.8 mA h g−1 based on RuO2 weight can be reached at 0.02 mA cm−2 with a low charge potential of 3.78 V leading to a high voltaic efficiency of 70.11%. Energy densities range from 2702.97 W h kg−1 at a power density of 29.22 W kg−1 to 1746.32 W h kg−1 at 822.20 W kg−1. The superior performance of the RuO2/Ni NF results from the intimate contact between catalysts and current collector, and the porous nanostructure providing sufficient space for deposition of lithium oxides, and short lithium ion and oxygen diffusion pathways, as evidenced by the impedance analysis. The binder-less and carbon-free nature of the electrode prevent binder, electrode and excessive electrolyte decomposition, rendering it a prospective candidate for rechargeable Li–O2 batteries.

Kinetics and electrochemical evolution of binary silicon–polymer systems for lithium ion batteries

Silicon is a promising anode material for lithium-ion batteries owing to its high specific capacity and low discharge potential. To diminish Si structural degradation and its anode-capacity fading due to the vast volume change during alloying and dealloying, effective binders assisted in the encapsulation of Si anode materials and enhanced their integral stability. Herein, two conducting-hydrogel coatings, polyaniline (PANI) and polypyrrole (PPy), are formed to trap the Si surface via a facile and environmentally benign sol–gel polymerization process. Functional groups from polymer hydrogels chemically promote the confinement of conducting shells on the Si surface, rendering the Si-hydrogel frameworks without resistive binders and carbon black. The effects of coating thickness and conductivity of PPy and PANI coatings on the electrochemical properties of Si anodes have been investigated, and compared to insulating polyacrylic acid (PAA)–Si blended electrodes. The kinetics and the physical evolution of the binary Si–polymer systems during electrochemical reactions have been systematically studied via electrochemical impedance spectroscopy (EIS). It has been observed that the degree of improvement of the cycling stability and the rate capability of the three Si–polymer systems decrease in the order of PPy > PANI > PAA.

High-Potential Metalless Nanocarbon Foam Supercapacitors Operating in Aqueous Electrolyte

Light-weight graphite foam decorated with carbon nanotubes (dia. 20-50 nm) is utilized as an effective electrode without binders, conductive additives, or metallic current collectors for supercapacitors in aqueous electrolyte. Facile nitric acid treatment renders wide operating potentials, high specific capacitances and energy densities, and long lifespan over 10 000 cycles manifested as 164.5 and 111.8 F g-1 , 22.85 and 12.58 Wh kg-1 , 74.6% and 95.6% capacitance retention for 2 and 1.8 V, respectively. Overcharge protection is demonstrated by repetitive cycling between 2 and 2.5 V for 2000 cycles without catastrophic structural demolition or severe capacity fading. Graphite foam without metallic strut possessing low density (≈0.4-0.45 g cm-3 ) further reduces the total weight of the electrode. The thorough investigation of the specific capacitances and coulombic efficiencies versus potential windows and current densities provides insights into the selection of operation conditions for future practical devices.