To address the issues of large volume change and low conductivity of silicon (Si) materials, carbon coatings have been widely employed as surface protection agent and conductive medium to encapsulate the Si materials, which can improve the electrochemical performance of Si-based electrodes. There has been a strong demand to gain a deeper understanding of the impact of efficient carbon coating over the lithiation and delithiation process of Si materials. Here, we report the first observation of the extended two-phase transformation of carbon-coated Si nanoparticles (Si/C) during electrochemical processes. The Si/C nanoparticles were prepared by sintering Si nanoparticles with polyvinylidene chloride precursor. The Si/C electrode underwent a two-phase transition during the first 20 cycles at 0.2 C, but started to engage in solid solution reaction when the ordered compact carbon coating began to crack. Under higher current density conditions, the electrode was also found to be involved in solid solution reaction, which, however, was due to the overwhelming demand of kinetic property rather than the breaking of the carbon coating. In comparison, the Si/C composites prepared with sucrose possessed more disordered and porous carbon structures, and presented solid solution reaction throughout the entire cycling process.

Baseline Si electrodes were developed and characterized based on Si nanomaterials. Silicon (Si) with a designed nanostructure has attracted much attention as potential anode materials for lithium-ion batteries due to its high gravimetric specific capacity. Because of a resulted poor tap density of Si from the electrode while using nano-sized Si and also from including other additives like conductive carbon and binder, it is difficult to maintain a high loading of active materials at the anode side in lithium-ion batteries. In this report, we aim to investigate how the thickness of Si-based electrode influences the cycling performance, rate performance and impedance. We also discuss the variation of gravimetric, area and volumetric capacity along with increasing of electrode thickness. It is found that with a thinner electrode of 7 μm the volumetric capacity could reach up to 920 mAh cm-3 but a poor area capacity of 0.7 mAh cm-2, while a thicker one of 33 μm enables to provide a high area capacity up to 1.5 mAh cm-2 and gives a volumetric capacity less than 500 mAh cm-3. A cell operated under 0 °C shows a gravimetric capacity of 2000 mAh g-1 after 60 cycles.

Mg2Si films, prepared by pulsed laser deposition (PLD), were amorphous, as prepared, and nanocrystalline following annealing. Their micro-structure and electrochemical characteristics were studied by high resolution transmission electron microscopy (HRTEM) and electrochemical cycling against lithium. HRTEM analysis revealed that some excess Si was present in the films. The more amorphous thinner film exhibited excellent cyclability. However, when the film becomes crystalline, the irreversible capacity loss was more significant during the initial cycling and after *50 cycles. Interpretations of the superior stability of the amorphous films are examined.

Pure tin (Sn) nanoparticles can be cycled in stable and high gravimetric capacity (>500 mAh/g) with a polyfluorene-type conductive polymer binder in composite electrodes. Crystalline Sn nanoparticles (<150 nanometers, nm) were used as anode materials in this study. The average diameter of Sn secondary particles is 270 nm, calculated based on BET surface area. The composite electrodes contain a conductive polymer binder that constitutes 2% to 10% of the material, without any conductive additives (e.g., acetylene black). The electrode containing the 5% conductive binder showed the best cycling performance, with a reversible capacity of 510 mAh/g. Crystallinity of Sn particles gradually degrades during cycling, and pulverization of particles was observed after long-term cycling, leading to the capacity fade. The conductive polymer binder shows advantages over other conventional binders, such as Poly(vinylidene difluoride) (PVDF) and carboxymethylcellulose (CMC) binders, because it can provide electrical conductivity and strong adhesion during Sn volume change. © 2013 The Electrochemical Society. All rights reserved.

Li[Ni1/3Mn1/3Co1/3]02 cathodes of approximately the same loading of active material with different amounts of inactive materials were fabricated and calendared to different porosity. EV and HPPC tests revealed that Li[Ni1/3Mn1/3Co1/3]O2 cathode performance is a strong function of inactive material amount and porosity with respect to energy density, pulse power, and cycling capability. Li[Ni1/3Mn1/3Co1/3]02 laminates containing 2% PVdF and 1.6% acetylene black at 30% porosity exhibits the best overall electrochemical properties including energy density, pulse power, and cycleability. Combined with an MCMB anode, the full cell delivers an energy density of 520 Wh/L which well exceeds the 40-mile energy-density goal announced by FreedomCar of 207 Wh/L. The result illustrates that proper engineering of the cell, module, and pack design may meet the PHEV 40-mile goal. ©The Electrochemical Society.

An electric-current-assisted method was used to mineralize dense hydrogels and create hydroxyapatite/hydrogel composites with unique hierarchical structures. The microstructure of the final material can be controlled by the mineralization technique and the chemistry of the organic matrix. A hydroxyapatite/hydrogel composite was obtained with a large inorganic content (approximately 60% of the weight of the organics). After being heated to 1050 degrees C, the sintered inorganic phase has a very uniformly distributed porosity and its Brunauer-Emmett-Teller (BET) surface area is 0.68 m(2)/g.

Copper sulfide nanowires/reduced graphene oxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-pot and template-free solution method in a dimethyl sulfoxide (DMSO)-ethyl glycol (EG) mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of the nanocomposites structure. SEM, TEM, XRD, IR and Raman spectroscopy are used to investigate the morphological and structural evolution of CuSNWs/rGO nanocomposites. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improved Li-storage performance, excellent cycling stability as well as high-rate capability compared with pristine CuS nanowires. It obtains a reversible capacity of 620 mAh g(-1) at 0.5C (1C = 560 mA g(-1)) after 100 cycles and 320 mAh g(-1) at a high current rate of 4C even after 430 cycles. The excellent lithium storage performance is ascribed to the synergistic effect between CuS nanowires and rGO nanosheets. The as-formed CuSNWs/rGO nanocomposites can effectively accommodate large volume changes, supply a 2D conducting network and trap the polysulfides generated during the conversion reaction of CuS.

Pure Sn nanoparticles electrode with Poly(9,9-dioctylfluorene-co- fluorenone-co-methylbenzoic ester) (PFM) conductive binder was prepared and tested in sodium ion battery. It showed higher specific capacity and higher cycling stability without any carbon black compared with Sn/CMC (carboxy methylated cellulose) and Sn/PVDF (polyvinylidene fluoride) electrode. The Sn in Sn/PFM electrodes delivered 806 mAh g-1 at C/50 and 610 mAh g-1 at C/10. After 10 cycles at C/10, the capacity of Sn had no decay. SEM and TEM images showed that the Sn particles in Sn/PFM electrode were still in good conductive network despite big volume change, but parts of Sn particles in Sn/CMC or Sn/PVDF electrode are electrically isolated.