In this paper, the use of nanostructured anode materials for rechargeable lithium-ion batteries (LIBs) is reviewed. Nanostructured materials such as nano-carbons, alloys, metal oxides, and metal sulfides/nitrides have been used as anodes for next-generation LIBs with high reversible capacity, fast power capability, good safety, and long cycle life. This is due to their relatively short mass and charge pathways, high transport rates of both lithium ions and electrons, and other extremely charming surface activities. In this review paper, the effect of the nanostructure on the electrochemical performance of these anodes is presented. Their synthesis processes, electrochemical properties, and electrode reaction mechanisms are also discussed. The major goals of this review are to give a broad overview of recent scientific researches and developments of anode materials using novel nanoscience and nanotechnology and to highlight new progresses in using these nanostructured materials to develop high-performance LIBs. Suggestions and outlooks on future research directions in this field are also given.

Recent developments in nanostructured anode materials for rechargeable lithium-ion batteries

Progress in material selection for solid oxide fuel cell technology: A review

Transport properties of solid oxide electrolyte ceramics: a brief review

Electrolytes for solid oxide fuel cells

Lithium-ion rechargeable batteries are used as portable power sources for a wide variety of electronic devices, such as cellular phones, notebook computers, and camcorders. Intensive research efforts have been made over the past decade to increase the gravimetric and volumetric energy density of lithium ion batteries. At present, graphite (372 mAhg) is used as an anode material for lithium ion batteries, but higher capacity alternatives are being actively pursued. Among the many possible alternatives, a lot of work has been devoted to Sn-based oxide, Si-based composite, transition metal oxide, metal nitride and metal phosphide systems, due to their ability to react reversibly with large amounts of Li per formula unit. Although alloy-based systems have a higher energy density, they suffer from poor capacity retention, since a large volume change occurs during charge/discharge. Among these alternatives, a concept based on the quasi-topotactic intercalation mechanism was proposed, in which lithium is inserted into monoclinic binary MnP4 to form the cubic ternary Li7MnP4 phase. [10] Since then, Li insertion/extraction in transition metal phosphides has been investigated as a possible candidate for the anode material in lithium ion batteries. In these systems, commercial red P and transition metals were used to synthesize metal phosphides, but the energy density is reduced due to the heavy transition metals employed. If phosphorus were used for electrode materials, it would have a good energy density, but little is known about its electrochemical behavior, since commercial red P has an amorphous structure with a poor bulk conductivity and poor cyclability. Phosphorus, an element of the fifth group in the periodic table, has three main allotropes: white, red, and black. Among these modifications of allotropes, black phosphorus is thermodynamically the most stable, insoluble in most solvents, practically non-flammable, and chemically the least reactive form, and exists in three known crystalline modifications (orthorhombic, rhombohedral, and simple cubic), as well as in an amorphous form. Since orthorhombic black phosphorus was obtained from white phosphorus at 200 C and 1.2 GPa, many studies designed to synthesize black phosphorus have been reported. However, the basic concept of a high temperature and high pressure being required has not been changed, and black phosphorus still remains difficult to synthesize, and has the lowest commercial value of the three forms. Considering that orthorhombic black phosphorus exhibits a layer structure similar to that of graphite, which is currently used as an anode material for Li ion batteries, we developed a simple method of transforming commercially available amorphous red phosphorus into orthorhombic black phosphorus using a high energy mechanical milling (HEMM) technique at ambient temperature and pressure. It is known that the temperature during HEMM can rise above 200 C and the pressure generated can be of the order of 6 GPa. These conditions should be sufficient to transform red P into its high-pressure allotrope, the black phosphorus phase, at ambient temperature and pressure. Figure 1a shows the color photo image, XRD pattern, and TEM electron diffraction pattern showing a diffuse ring of red P, which confirms the amorphous nature of the red P. The sample prepared by HEMM corresponds to orthorhombic black P according to the XRD data and color photo image (Fig. 1b), and was also identified by high resolution TEM electron diffraction, and by its lattice spacing. Figure 2a and 2b show the voltage profiles of red P and black P, respectively. Their electrochemical behaviors are very different from each other. The discharge and charge capacities of red P are 1692 and 67 mAhg, respectively, and it cannot be used as an anode material since its charge capacity is negligible. Although black P shows an increased charge capacity of 1279 mAhg, the first cycle efficiency is only 57%. The electrochemical performance of Si as an anode material for Li ion batteries can be much improved using Si–carbon composites. Black P also has a low electronic conductivity inherited from its characteristic as a semiconductor. The electrochemical behaviors of the black P-carbon composite during the discharge/charge reaction with Li were excellent compared with the above two cases, as shown in Figure 2c. The first discharge and charge capacities are 2010 and 1814 mAhg, respectively, and the first cycle efficiency is about 90%, which is one of the highest reported. The good coulombic efficiency of the black P–carbon composite for the C O M M U N IC A IO N

Black Phosphorus and its Composite for Lithium Rechargeable Batteries

Electrical conductivity of stabilized zirconia with ytterbia and scandia

Cubic-stabilized zirconia and alumina composites as electrolytes in planar type solid oxide fuel cells

Li[sub 7]MnN[sub 4] which has cubic symmetry, P[bar 4]3n, a = 9.5453 is prepared by heating a mixture of Li[sub 3]N and Mn[sub 4]N in a 1%H[sub 2]-99%N[sub 2] gas stream. The li ion is easily deintercalated in a Li/Li[sub 7]MnN[sub 4] cell forming Li[sub 7[minus]x]MnN[sub 4] over a wide range of 0 [le] x [le] 1.25. The specific capacity of the cell is about 210 mAh/g. With an increase in x, a new phase which also has cubic symmetry but has a smaller lattice parameter appears. The original phase decreases with an increase in x, and disappears at x = 0.625. A two-phase reaction then occurs. In the range of 0.625 [le] x [le] 1.25, the lattice parameter of the second phase decreases with an increase in x. The Li/Li[sub 7]MnN[sub 4] cell shows a good reversibility under high current density (1,200 [mu]A/cm[sup 2]). Li[sub 7]MnN[sub 4] is thus suggested to be a good candidate for an electrode for a lithium secondary battery.

Li Deintercalation‐Intercalation Reaction and Structural Change in Lithium Transition Metal Nitride, Li7MnN4

Solid-solution Sr2 –xLaxFeO4 crystallizing in the K2NiF4 structure has been obtained for 0 ⩽x⩽ 1. In the Sr-rich region, the K2NiF4 structure was stable only at low temperature. Heat treatment under an oxygen pressure of 100-500 atm was carried out to form oxygen stoichiometric samples. The structure was refined by the Rietveld method assuming space group I4/mmm. The FeO6 octahedron in Sr2FeO4 showed almost cubic symmetry, the La substitution causing an increase in the Fe–O (apical) length without modifying the a-axis length. All the samples showed semiconducting behaviour and positive Seebeck coefficients. An antiferromagnetic transition at 60 K was observed for Sr2FeO4, becoming obscure with increasing La content. The room-temperature Mossbauer spectra showed a symmetric singlet due to Fe4+ and a doublet due to Fe3+, except for Sr2FeO4 which showed a quadrupole doublet.

Osamu Yamamoto

Papers

Electrical conductivity of stabilized zirconia with ytterbia and scandia

Cubic-stabilized zirconia and alumina composites as electrolytes in planar type solid oxide fuel cells

Li Deintercalation‐Intercalation Reaction and Structural Change in Lithium Transition Metal Nitride, Li7MnN4

Preparation and characterization of Sr2 –xLaxFeO4(0 ⩽x⩽ 1)

Chemical stability between NiO/8YSZ cermet and alkaline-earth metal substituted lanthanum chromite