Lithium-ion batteries have witnessed meteoric advancement the last two decades. The anode area has seen unprecedented research activity on Si and Sn, the two anode alternatives to currently used carbon following the initial seminal work by Fuji on tin oxide nanocomposites. Recent reports on silicon nanowires, porous Si, and amorphous Si coatings on graphite nanofibers (GNF) have been very encouraging. High capacity and long cycle life anodes are still, however, elusive and much needed to meet the ever increasing energy storage demands of modern society. Herein, we report for the first time the synthesis of novel 1D heterostructures comprising vertically aligned multiwall CNTs (VACNTs) containing nanoscale amorphous/nanocrystalline Si droplets deposited directly on VACNTs with clearly defined spacing using a simple two-step liquid injection CVD process. A hallmark of these single reactor derived heterostructures is an interfacial amorphous carbon layer anchoring the nanoscale Si clusters directly to the VACNTs. The defined spacing of nanoscale Si combined with their tethered CNT architecture allow for the silicon to undergo reversible electrochemical alloying and dealloying with Li with minimal loss of contact with the underlying CNTs. The novel heterostructures thus exhibit impressive reversible stable capacities approximately 2050 mAh/g with very good rate capability and an acceptable first cycle irreversible loss approximately 20% comparable to graphitic anodes indicating their promise as high capacity Li-ion anodes. Although warranting further research, particularly with regard to long-term cycling, it can be envisaged that optimization of this simple approach could lead to reversible high capacity next generation Li-ion anodes.

http://ma.ecsdl.org/content/MA2010-01/5/352.full.pdf

Nanostructured Hybrid Silicon/Carbon Nanotube Heterostructures: Novel Reversible High-Capacity Lithium-Ion Anodes

Silicon has attracted ever-increasing attention as a high-capacity anode material in Li-ion batteries owing to its extremely high theoretical capacity. However, practical application of silicon anodes is seriously hindered by its fast capacity fading as a result of huge volume changes during the charge/discharge process. Here, an interpenetrated gel polymer binder for high-performance silicon anodes is created through in-situ crosslinking of water-soluble poly(acrylic acid) (PAA) and polyvinyl alcohol (PVA) precursors. This gel polymer binder with deformable polymer network and strong adhesion on silicon particles can effectively accommodate the large volume change of silicon anodes upon lithiation/delithiation, leading to an excellent cycling stability and high Coulombic efficiency even at high current densities. Moreover, high areal capacity of ∼4.3 mAh/cm2 is achieved based on the silicon anode using the gel PAA–PVA polymer binder with a high mass loading. In view of simplicity in using the water soluble gel polymer binder, it is believed that this novel binder has a great potential to be used for high capacity silicon anodes in next generation Li-ion batteries, as well as for other electrode materials with large volume change during cycling.

Interpenetrated Gel Polymer Binder for High Performance Silicon Anodes in Lithium-Ion Batteries

Urchin-like Co3O4 microspheres have been obtained through a two-step hydrothermal method followed by a post-calcination process and show a unique hollow structure with mesoporous nanosheets on their surface. Oxygen vacancies on the ultrathin nanosheets were introduced by annealing treatment, inducing a local built-in electric field to promote the migration of Li ions by Coulomb force during cycling and leading to a superior electrochemical performance for lithium-ion batteries. The electrodes containing urchin-like mesoporous hollow Co3O4 microspheres delivered a high discharge capacity of 2164.1 mA h g−1 at 0.05 A g−1 after 100 cycles. Even at a higher current density of 1.0 A g−1, a remarkable discharge capacity of 1307.9 mA h g−1 after 1000 cycles could still be achieved.

Oxygen vacancy derived local build-in electric field in mesoporous hollow Co3O4 microspheres promotes high-performance Li-ion batteries

Ionically Conductive Self-Healing Binder for Low Cost Si Microparticles Anodes in Li-Ion Batteries

Metal oxide-based nanomaterials are widely studied because of their high-energy densities as anode materials in lithium-ion batteries. However, the fast capacity degradation resulting from the large volume expansion upon lithiation hinders their practical application. In this work, the preparation of walnut-like multicore–shell MnO encapsulated nitrogen-rich carbon nanocapsules (MnO@NC) is reported via a facile and eco-friendly process for long-cycling Li-ion batteries. In this hybrid structure, MnO nanoparticles are uniformly dispersed inside carbon nanoshells, which can simultaneously act as a conductive framework and also a protective buffer layer to restrain the volume variation. The MnO@NC nanocapsules show remarkable electrochemical performances for lithium-ion batteries, exhibiting high reversible capability (762 mAh g−1 at 100 mA g−1) and stable cycling life (624 mAh g−1 after 1000 cycles at 1000 mA g−1). In addition, the soft-packed full batteries based on MnO@NC nanocapsules anodes and commercial LiFePO4 cathodes present good flexibility and cycling stability.

Walnut-Like Multicore–Shell MnO Encapsulated Nitrogen-Rich Carbon Nanocapsules as Anode Material for Long-Cycling and Soft-Packed Lithium-Ion Batteries

A novel design of hollow structured SnO2@Si nanospheres was presented, which not only demonstrates high volumetric capacity as anode of LIBs, but also prevents aggregation of Sn and confines solid electrolyte interphase thickening. An impressive volumetric specific capacity of 1030 mAh cm–3 was maintained after 500 cycles. The electrochemical impedance spectroscopy and differential scanning calorimetry indicated that solid electrolyte interphase can be confined in pores of as-prepared hollow structured SnO2@Si.

High Volumetric Capacity of Hollow Structured SnO2@Si Nanospheres for Lithium-Ion Batteries.

A design of coaxial hollow nanocables of carbon nanotubes and silicon composite (CNTs@Silicon) was presented, and the lithiation/delithiation behavior was investigated. The FIB-SEM studies demonstrated hollow structured silicon tends to expand inward and shrink outward during lithiation/delithiation, which reveal the mechanism of inhibitive effect of the excessive growth of solid–electrolyte interface by hollow structured silicon. The as-prepared coaxial hollow nanocables demonstrate an impressive reversible specific capacity of 1150 mAh g–1 over 500 cycles, giving an average Coulombic efficiency of >99.9%. The electrochemical impedance spectroscopy and differential scanning calorimetry confirmed the SEI film excessive growth is prevented.

Lithiation Behavior of Coaxial Hollow Nanocables of Carbon-Silicon Composite.

Silicon anodes for lithium-ion batteries are of much interest owing to their extremely high specific capacity but still face some challenges, especially the tremendous volume change which occurs in cycling and further leads to the disintegration of electrode structure and excessive growth of solid electrolyte interphase (SEI). Here, we designed a novel approach to confine the inward growth of SEI by filling solid polymer electrolyte (SPE) into pores of hollow silicon spheres. The as-prepared composite delivers a high specific capacity of more than 2100 mAh g–1 and a long-term cycle stability with a reversible capacity of 1350 mAh g–1 over 500 cycles. The growing behavior of SEI was investigated by electrochemical impedance spectroscopy and differential scanning calorimetry, and the results revealed that SPE occupies the major space of SEI growth and thus confines its excessive growth, which significantly improves cycle performance and Coulombic efficiency of cells embracing hollow silicon spheres.

Confined Solid Electrolyte Interphase Growth Space with Solid Polymer Electrolyte in Hollow Structured Silicon Anode for Li-Ion Batteries

The invention discloses a lithium ion battery silicon-based tin-based composite granule, a preparation method thereof and a cathode and a lithium ion battery with the same. The lithium ion battery silicon-based tin-based composite granule is characterized by comprising hollow tin granules or hollow tin oxide granules and a silicon layer wrapping the outer surfaces of the hollow tin granules or hollow tin oxide granules. The invention further provides a cathode which comprises the composite granules and is used in a secondary lithium ion battery and the secondary lithium ion battery with the cathode. The preparation method of the composite granules disclosed by the invention is simple, due to a hollow structure, the granule is capable of effectively contain volume expansion of silicon-based and tin-based materials in the lithium embedding process, and thus stability of an electrode structure is maintained. In addition, By virtue of an external silicon-based material, nano tin granules can be effectively prevented from agglomeration, and the stability of a tin-based material is maintained, so that a lithium ion battery cathode composite material which is large in specific capacity and good in circulation property can be prepared.

Lithium ion battery silicon-based tin-based composite granule, preparation method thereof and cathode and lithium ion battery with same

In the present work, the compatibility relationship on the failure criteria between aluminium and polymer was established, and a mechanics-based model for a three-layered sandwich panel was developed based on the M-K model to predict its Forming Limit Diagram (FLD). A case study for a sandwich panel consisting of face layers from AA5754 aluminium alloy and a core layer from polyvinylidene difluoride (PVDF) was subsequently conducted, suggesting that the loading path of aluminium was linear and independent of the punch radius, while the risk for failure of PVDF increased with a decreasing radius and an increasing strain ratio. Therefore, the developed formability model would be conducive to the safety evaluation on the plastic forming and critical failure of composite sandwich panels.

/pdf/development-of-a-formability-prediction-model-for-aluminium-19oi9drt.pdf

Xiangnan Yu

Papers

High Volumetric Capacity of Hollow Structured SnO2@Si Nanospheres for Lithium-Ion Batteries.

Lithiation Behavior of Coaxial Hollow Nanocables of Carbon-Silicon Composite.

Confined Solid Electrolyte Interphase Growth Space with Solid Polymer Electrolyte in Hollow Structured Silicon Anode for Li-Ion Batteries

Lithium ion battery silicon-based tin-based composite granule, preparation method thereof and cathode and lithium ion battery with same

Development of a Formability Prediction Model for Aluminium Sandwich Panels with Polymer Core