Triggered reversible phase transformation between layered and spinel structure in manganese-based layered compounds.

Irreversible phase transformation of layered structure into spinel structure is considered detrimental for most of the layered structure cathode materials. Here we report that this presumably irreversible phase transformation can be rendered to be reversible in sodium birnessite (NaMnO·yHO) as a basic structural unit. This layered structure contains crystal water, which facilitates the formation of a metastable spinel-like phase and the unusual reversal back to layered structure.

In situ analyses for ion storage materials.

Development of high performance electrode materials for energy storage is one of the most important issues for our future society. However, a lack of clear analytical views limits critical understanding of electrode materials. This review covers useful analytical work using X-ray diffraction, X-ray absorption spectroscopy, microscopy and neutron diffraction for ion storage systems.

Controlling Solid-Electrolyte-Interphase Layer by Coating P-Type Semiconductor NiOx on Li4Ti5O12 for High-Energy-Density Lithium-Ion Batteries.

Li4Ti5O12 is a promising anode material for rechargeable lithium batteries due to its well-known zero strain and superb kinetic properties. However, Li4Ti5O12 shows low energy density above 1 V vs Li(+)/Li. In order to improve the energy density of Li4Ti5O12, its low-voltage intercalation behavior beyond Li7Ti5O12 has been demonstrated.

Lithium-ion transport through a tailored disordered phase on the LiNi0.5 Mn1.5 O4 surface for high-power cathode materials.

The phase control of spinel LiNi0.5 Mn1.5 O4 was achieved through surface treatment that led to an enhancement of its electrochemical properties.

Tailored surface structure of LiFePO4/C nanofibers by phosphidation and their electrochemical superiority for lithium rechargeable batteries.

We offer a brand new strategy for enhancing Li ion transport at the surface of LiFePO4/C nanofibers through noble Li ion conducting pathways built along reduced carbon webs by phosphorus. Pristine LiFePO4/C nanofibers composed of 1-dimensional (1D) LiFePO4 nanofibers with thick carbon coating layers on the surfaces of the nanofibers were prepared by the electrospinning technique. These dense and thick carbon layers prevented not only electrolyte penetration into the inner LiFePO4 nanofibers but also facile Li ion transport at the electrode/electrolyte interface.

Tailored Oxygen Framework of Li4Ti5O12 Nanorods for High-Power Li Ion Battery.

Here we designed the kinetically favored Li4Ti5O12 by modifying its crystal structure to improve intrinsic Li diffusivity for high power density. Our first-principles calculations revealed that the substituted Na expanded the oxygen framework of Li4Ti5O12 and facilitated Li ion diffusion in Li4Ti5O12 through 3-D high-rate diffusion pathway secured by Na ions. Accordingly, we synthesized sodium-substituted Li4Ti5O12 nanorods having not only a morphological merit from 1-D nanostructure engineering but also sodium substitution-induced open framework to attain ultrafast Li diffusion.

A nano-Si/FeSi2Ti hetero-structure with structural stability for highly reversible lithium storage.

A nano-Si/FeSi2Ti hetero-structure has been synthesized for highly reversible Li-ion batteries by using a simple melt-spinning method. We demonstrate that this composite has a very peculiar core/shell structure in which the FeSi2Ti alloy plays various pivotal roles as a mechanically supporting backbone and as an electronic pathway for the active Si attached to its surface, and is responsible for the altered electrochemical reactions with relatively small volume expansion routes. The FeSi2Ti matrix significantly contributes to not only the stabilization of cyclic retention, but also the enhancement of conductivity, as well as a high rate capability unprecedented in research on Si-based anodes.

A novel co-precipitation method for one-pot fabrication of a Co-Ni multiphase composite electrode and its application in high energy-density pseudocapacitors.

A multiphase composite film composed of nickel(II) hydroxide and cobalt(II) hydroxide was synthesized by a novel co-precipitation method. The film exhibited high capacitance and stable cyclic retention because of its 3D network nanostructure and high conductivity due to CoOOH evolved during cycling.

Structurally and electronically designed TiO₂Nx nanofibers for lithium rechargeable batteries.

The morphology and electronic structure of metal oxides, including TiO(2) on the nanoscale, definitely determine their electronic or electrochemical properties, especially those relevant to application in energy devices. For this purpose, a concept for controlling the morphology and electrical conductivity in TiO(2), based on tuning by electrospinning, is proposed. We found that the 1D TiO(2) nanofibers surprisingly gave higher cyclic retention than 0D nanopowder, and nitrogen doping in the form of TiO(2)N(x) also caused further improvement.

Comprehensive design of carbon-encapsulated Fe3O4 nanocrystals and their lithium storage properties.

Controlling the bulk and surface structure of metal oxide nanostructures is crucial to obtain superior electronic and electrochemical properties. However, the synthetic or post-treatment techniques for preparing such structures, especially those with complex configurations, still remains a challenge. Herein, we report a completely novel approach-an amorphous carbon coating on the surface coupled with a controlled metal oxidation state in the bulk-via a simple glucose treatment.

Tailored Li4Ti5O12 nanofibers with outstanding kinetics for lithium rechargeable batteries.

We report on the synthesis of one-dimensional (1D) Li(4)Ti(5)O(12) nanofibers through electrospinning and their outstanding electrochemical performances. Li(4)Ti(5)O(12) with a spinel structure is a promising candidate anode material for lithium rechargeable batteries due to its well-known zero-strain merits. In order to improve the electronic properties of spinel Li(4)Ti(5)O(12), which are intrinsically poor, we processed the material into a nanofiber type of architecture to shorten the Li(+) and electron transport distance using a versatile electrospinning approach.

Hollow Sn-SnO(2) nanocrystal/graphite composites and their lithium storage properties.

Hollow spheres have been constructed by applying the Kirkendall effect to Sn nanocrystals. This not only accommodates the detrimental volume expansion but also reduces the Li(+) transport distance enabling homogeneous Li-Sn alloying. Hollow Sn-SnO2 nanocrystals show a significantly enhanced cyclic performance compared to Sn nanocrystal alone due to its typical structure with hollow core.

[100] Directed Cu-doped h-CoO nanorods: elucidation of the growth mechanism and application to lithium-ion batteries.

Thermal decomposition of Co(acac)(3) and Cu(acac)(2) in benzylamine leads to the formation of [100] directed Cu-doped h-CoO nanorods, which are very stable in an aqueous solution. The formation mechanism of the [100] directed Cu-doped h-CoO nanorods is fully elucidated by using first-principles calculations, demonstrating that Cu-doping not only changes the growth direction but also enhances the stability of the nanorods significantly. Evaluation of the electrochemical performance of Cu-doped h-CoO nanorods shows high initial Coulombic efficiency and ultrahigh capacity with excellent cycling performance, indicating their suitability as an anode material for next generation lithium-ion batteries.

Phosphidation of Li4Ti5O12 nanoparticles and their electrochemical and biocompatible superiority for lithium rechargeable batteries.

Phosphidated-Li(4)Ti(5)O(12) shows high capacity with a significantly enhanced kinetics opening new possibilities for ultra-fast charge/discharge of lithium rechargeable batteries. The in vitro cytotoxicity test proves its fabulous cell viability, indicating that the toxicity problem of nanoparticles can be also solved by phosphidation.