Hiroki Nara

A Lithium-Ion Sulfur Battery Based on a Carbon-Coated Lithium- Sulfide Cathode and an Electrodeposited Silicon-Based Anode

In this paper, we report a lithium-ion battery employing a lithium sulfide cathode and a silicon-based anode. The high capacity of the silicon anode and the high efficiency and cycling rate of the lithium sulfide cathode allowed optimal full cell balance. We show in fact that the battery operates with a very stable capacity of about 280 mAh g(-1) at an average voltage of 1.4 V. To the best of our knowledge, this battery is one of the rare examples of lithium-metal-free sulfur battery. Considering the high theoretical capacity of the employed electrodes, we believe that the battery here reported may be of potential interest as high-energy, safe, and low-cost power source for electric vehicles.

Zinc–Air Battery: Understanding the Structure and Morphology Changes of Graphene-Supported CoMn2O4 Bifunctional Catalysts Under Practical Rechargeable Conditions

Nitrogen-doped/undoped thermally reduced graphene oxide (N-rGO) decorated with CoMn2O4 (CMO) nanoparticles were synthesized using a simple one-step hydrothermal method. The activity and stability of this hybrid catalyst were evaluated by preparing air electrodes with both primary and rechargeable zinc-air batteries that consume ambient air. Further, we investigated the relationship between the physical properties and the electrochemical results for hybrid electrodes at various cycles using X-ray diffraction, scanning electron microscopy, galvanodynamic charge-discharging and electrochemical impedance spectroscopy. The structural, morphological and electrocatalytic performances confirm that CMO/N-rGO is a promising material for safe, reliable, and long-lasting air cathodes for both primary and rechargeable zinc-air batteries that consume air under ambient condition.

Highly durable SiOC composite anode prepared by electrodeposition for lithium secondary batteries

A highly durable SiOC composite anode was prepared for use in lithium secondary batteries. The SiOC composite was synthesized by electrodeposition of SiCl4. The composite anode delivered a discharge capacity of 1045 mA h per gram of Si at the 2000th cycle and 842 mA h per gram of Si even at the 7200th cycle. The reason for the excellent cyclability was investigated by methods including field emission scanning electron microscopy (FESEM), scanning transmission electron microscopy with an energy dispersive X-ray analyser (STEM-EDX), and X-ray photoelectron spectroscopy (XPS). The results revealed that the excellent cyclability was achieved by the homogeneous dispersion of SiOx and organic/inorganic compounds at the nanometre scale. The structural uniformity of the SiOC composite is believed to have suppressed the crack formation attributable to the stress resulting from the reaction of silicon with lithium during charge–discharge cycles.

Mechanical analysis and in situ structural and morphological evaluation of Ni-Sn alloy anodes for Li ion batteries

In lithium ion batteries, it has previously been shown that Ni–Sn thin film anodes containing 62 at.% Sn show outstanding electrochemical characteristics, e.g. good capacity and endurance, during charge–discharge cycling. However, their mechanical response, which is likely related to their lifetime in service, has so far received relatively little attention. To address this, nanoindentation and nanowear techniques have been used to characterize the mechanical properties of thin Ni–Sn films electrodeposited on a copper substrate. In situ morphology analysis together with in situ stress measurement has been performed to assess the properties of Ni–Sn thin film anodes during electrochemical cycling. The change in mechanical properties, residual stress and fracture behaviour of the anodes is related to the phase changes which occur during charge–discharge cycling. The correlation between the mechanical properties of the films and their charge–discharge characteristics serves as a useful indicator for optimized design of a Sn-based intermetallic anode film for lithium ion secondary batteries.

Li-Rich Li-Si Alloy As A Lithium-Containing Negative Electrode Material Towards High Energy Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are generally constructed by lithium-including positive electrode materials, such as LiCoO2, and lithium-free negative electrode materials, such as graphite. Recently, lithium-free positive electrode materials, such as sulfur, are gathering great attention from their very high capacities, thereby significantly increasing the energy density of LIBs. Though the lithium-free materials need to be combined with lithium-containing negative electrode materials, the latter has not been well developed yet. In this work, the feasibility of Li-rich Li-Si alloy is examined as a lithium-containing negative electrode material. Li-rich Li-Si alloy is prepared by the melt-solidification of Li and Si metals with the composition of Li21Si5. By repeating delithiation/lithiation cycles, Li-Si particles turn into porous structure, whereas the original particle size remains unchanged. Since Li-Si is free from severe constriction/expansion upon delithiation/lithiation, it shows much better cyclability than Si. The feasibility of the Li-Si alloy is further examined by constructing a full-cell together with a lithium-free positive electrode. Though Li-Si alloy is too active to be mixed with binder polymers, the coating with carbon-black powder by physical mixing is found to prevent the undesirable reactions of Li-Si alloy with binder polymers, and thus enables the construction of a more practical electrochemical cell.

New Si–O–C composite film anode materials for LIB by electrodeposition

Silicon is one of the most promising materials for lithium secondary battery anodes. However, silicon anodes have a critical drawback to their practical application, which is capacity degradation due to pulverization of the active material by the large volume change of silicon during charge–discharge cycles. This paper reviews recent studies on silicon-based anodes that have attempted to overcome this poor cycle durability through structural control such as through thin films, porous structures, core–shell structures, and by alloying with other metals, and by application of proper binders. Among them, binder-free Si–O–C composite films prepared by electrodeposition exhibit outstanding cycle durability. The origin of this excellent durability is discussed in depth from the standpoint of chemical and morphological changes. Consequently, the combination of active materials such as Si and Li2Si2O5 and inactive materials such as Li2O, Li2CO3, and organic compounds is suggested to result in outstanding properties as a lithium secondary battery anode.

New Analysis of Electrochemical Impedance Spectroscopy for Lithium-ion Batteries

ABSTRACT: First of all, we express our deepest sympathies for the passing of Professor Su-Moon Park. In thepresent paper, an electrochemical impedance spectroscopy (EIS), which Professor Su-Moon Parkalso used frequently for the investigation of electroconducting polymer, is introduced as a recentevaluation tool for a commercially available lithium-ion battery (LIB). The paper surveys how todesign equivalent circuits while explaining physical and chemical phenomena in the LIB and howto get more accurate impedance spectra with varying the measuring temperatures. Additionally, asquare current EIS (SC-EIS) technique, which we have suggested, is introduced for the larger LIBsystem as a promising technique for the future.Keywords: Electrochenmical impedance spectroscopy, Lithium-ion battery, Equivalent circuit Received December 16, 2013 : Accepted December 23, 2013 1. Introduction Today, the economic growth in China and Indialeads motorization in the countries. The motorizationaccelerates the crises of fossil fuel shortage and envi-ronmental destruction. Therefore, the widespread useof green vehicles in the future is a necessity. In addi-tion, renewable energies such as solar power and windpower, whose energy generation depends on weatherof the area, have been introduced to reduce CO

Influence of the diffusion-layer thickness during electrodeposition on the synthesis of nano core/shell Sn-O-C composite as an anode of lithium secondary batteries

Electrodeposition was conducted from an organic carbonate solvent via the potentiostatic technique through three consecutive steps in order to synthesise Sn–O–C composite, which delivered a discharge capacity of 596 mA h g of Sn−1 after 50 cycles. However, the composite anode suffered from a significantly low initial discharge capacity, delivering a discharge capacity of 79 mA h g of Sn−1 until the 5th cycle. It was deduced that the improbably low initial capacity was induced by the deposition of Li-rich compounds, which were formed by electrolyte decomposition accompanied by the reduction product of supporting electrolyte salts during the electrodeposition process, on the surface layer. In order to improve the poor initial capacity, we modified the chemical composition of the surface layer by means of implementing the agitation of the electrolyte during the deposition process. This gave rise to varying the diffusion-layer thickness during the deposition process due to the enhancement of convection by movement of the electrolyte itself. As a result, we achieved improvement of the initial discharge capacity, delivering 572 mA h g of Sn−1 at the 1st cycle and 586 mA h g of Sn−1 at the 50th cycle. It was revealed that the surface layer was composed of a decomposition product of the organic carbonate solvent. Furthermore, a smaller particle size of the Sn–O–C composite was obtained via electrolyte agitation, giving rise to homogeneous shell formation on the Sn compound core. Herein, we thoroughly examined the influence of varying diffusion-layer thickness during the deposition process on the properties of the Sn–O–C composites from an electrochemical standpoint.

Possibility and Prospect for Future Energy Storages

This chapter shows that batteries in the future will be supported by the development of each component material. For example, research on silicon-based anode is discussed and the impact of capacity increase of active materials is estimated. Various types of lithium batteries are briefly summarized with respect to their safety.