Yingjian Yu

The Effects of Different Core-Shell Structures on the Electrochemical Performances of Si-Ge Nanorod Arrays as Anodes for Micro-Lithium Ion Batteries

Connected and airbag isolated Si-Ge nanorod (NR) arrays in different configurations have been fabricated on wafer scale Si substrates as anodes in micro-lithium ion batteries (LIBs), and the impacts of configurations on electrochemical properties of the electrodes were investigated experimentally and theoretically. It is demonstrated that the Si inner cores can be effectively protected by the connected Ge shells and contribute to the enhanced capacity by ∼68%, derived from an activation process along with the amorphization of the crystalline lattice. The first-principles calculations further verify the smaller forces on the Si layers at the atomic level during the restricted volume expansion with the covering of Ge layers. This work provides general guidelines for designing other composites and core-shell configurations in electrodes of micro-LIBs to accomplish higher capacities and longer cycle lives.

Si/Ge core-shell nanoarrays as the anode material for 3D lithium ion batteries

The rapid development of small scale electronic devices, such as M/NEMS devices, smart dust, micro or nano bio-sensors and so on, is leading to the urgent need for micro or nano power sources with the possibility for integration. In this work, 3D Si/Ge composite nanorod (NR) arrays were fabricated on wafer-scale Si substrates as anode materials in micro or nano Li ion batteries (LIBs) by a low cost, simple and Si-compatible process. Significantly improved capacities and cycling performances were accomplished in the optimized 3D Si/Ge composite NR array electrode by successfully addressing the volume expansion and conductivity issues. Further theoretical calculations gain more insights into the origins of the improved electrochemical properties by considering the adsorption and diffusion energies of Li ion in Si and Si/Ge unit cells. This study technically and fundamentally provides a perspective idea for practical applications of wafer-scale Si substrates in LIBs with the aim of supplying integrated power for micro or nano scale electronic devices.

Fabrication of 3D hexagonal bottle-like Si–SnO2 core–shell nanorod arrays as anode material in on chip micro-lithium-ion-batteries

Three-dimensional (3D) Si–SnO2 composite core–shell nanorod arrays were fabricated as the anode material in lithium ion micro-batteries by nanosphere lithography (NSL) combined with inductive coupled plasma (ICP) dry etching technology. The hexagonal bottle-like Si NR arrays in wafer scale with homogeneous morphology and good mechanical structure provide enough space to accommodate the volume expansion during Li ion insertion/de-insertion processes, while the additionally deposited SnO2 thin film was prepared to successfully improve the capacities and cycle performance by configuring the 3D Si–SnO2 NR composite electrode arrays. This fabrication method has the advantages of simplicity, large scale production, easy size and shape manipulations, low cost and Si-process compatibility. This work will facilitate the configuration of solid state micro-batteries for power supply in micro-electronic devices, such as MEMS devices or smart IC chips.

ZIF-8 Cooperating in TiN/Ti/Si Nanorods as Efficient Anodes in Micro-Lithium-Ion-Batteries

Zeolite imidazolate framework-8 (ZIF-8) nanoparticles embedded in TiN/Ti/Si nanorod (NR) arrays without pyrolysis have shown increased energy storage capacity as anodes for lithium ion batteries (LIBs). A high capacity of 1650 μAh cm(-2) has been achieved in this ZIF-8 composited multilayered electrode, which is ∼100 times higher than the plain electrodes made of only silicon NR. According to the electrochemical impedance spectroscopy (EIS) and (1)H nuclear magnetic resonance (NMR) characterizations, the improved diffusion of lithium ions in ZIF-8 and boosted electron/Li(+) transfer by the ZIF-8/TiN/Ti multilayer coating are proposed to be responsible for the enhanced energy storage ability. The first-principles calculations further indicate the favorable accessibility of lithium with appropriate size to diffuse in the open pores of ZIF-8. This work broadens the application of ZIF-8 to silicon-based LIBs electrodes without the pyrolysis and provides design guidelines for other metal-organic frameworks/Si composite electrodes.

High Stability Induced by the TiN/Ti Interlayer in Three-Dimensional Si/Ge Nanorod Arrays as Anode in Micro Lithium Ion Battery

Three-dimensional (3D) Si/Ge-based micro/nano batteries are promising lab-on-chip power supply sources because of the good process compatibility with integrated circuits and Micro/Nano-Electro-Mechanical System technologies. In this work, the effective interlayer of TiN/Ti thin films were introduced to coat around the 3D Si nanorod (NR) arrays before the amorphous Ge layer deposition as anode in micro/nano lithium ion batteries, thus the superior cycling stability was realized by reason for the restriction of Si activation in this unique 3D matchlike Si/TiN/Ti/Ge NR array electrode. Moreover, the volume expansion properties after the repeated lithium-ion insertion/extraction were experimentally investigated to evidence the superior stability of this unique multilayered Si composite electrode. The demonstration of this wafer-scale, cost-effective, and Si-compatible fabrication for anodes in Li-ion micro/nano batteries provides new routes to configurate more efficient 3D energy storage systems for micro/nano smart semiconductor devices.

Si nanorod arrays modified with metal–organic segments as anodes in lithium ion batteries

Metal–organic segments (MOSs) have been controllably synthesized to composite with Si nanorod (NR) arrays as electrodes in lithium ion batteries (LIBs). These kinds of MOSs are suggested to be derived from solution species such as [Zn(C4H6N2)Ac]+, [Zn(C4H6N2)2Ac]+ and [Zn(C3H4N2)(C4H6N2)Ac]+ as detected by electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). It is found that solution concentration and growth time have significant effects on the MOS coating around Si NRs. The uniform coating of MOSs around Si NRs has been successfully produced at relatively low solution concentrations or for shorter growth time, which was proved to be helpful to enhance the capacity of the composite electrode up to ∼1.1 mA h cm−2 at a current density of 10 μA cm−2 and ∼0.5 mA h cm−2 on increasing the current density to 50 μA cm−2. Furthermore, at an even higher current density of 200 μA cm−2 (vs. initial 10 μA cm−2) the composite electrodes still can maintain more than 50% of the initial capacities. While, given a higher solution concentration or longer reaction time, large ZIF-61 crystals, a kind of metal–organic framework (MOF), would form on the top of Si NRs. Unlike MOSs, large ZIF-61 crystals fail to cover the Si NR homogeneously, and consequently the capacities of ZIF-61/Si NR composite electrodes are much lower than those of MOS/Si NR electrodes. This work not only demonstrates a simple method for Si surface modification to enhance its corresponding electrochemical performance, but also provides a potential general strategy for the coating of different surfaces by the cross-linking of metal nodes and organic ligands.