Each cell of a battery stores electrical energy as chemical energy in two electrodes, a reductant (anode) and an oxidant (cathode), separated by an electrolyte that transfers the ionic component of the chemical reaction inside the cell and forces the electronic component outside the battery. The output on discharge is an external electronic current I at a voltage V for a time Deltat. The chemical reaction of a rechargeable battery must be reversible on the application of a charging I and V. Critical parameters of a rechargeable battery are safety, density of energy that can be stored at a specific power input and retrieved at a specific power output, cycle and shelf life, storage efficiency, and cost of fabrication. Conventional ambient-temperature rechargeable batteries have solid electrodes and a liquid electrolyte. The positive electrode (cathode) consists of a host framework into which the mobile (working) cation is inserted reversibly over a finite solid-solution range. The solid-solution range, which is reduced at higher current by the rate of transfer of the working ion across electrode/electrolyte interfaces and within a host, limits the amount of charge per electrode formula unit that can be transferred over the time Deltat = Deltat(I). Moreover, the difference between energies of the LUMO and the HOMO of the electrolyte, i.e., electrolyte window, determines the maximum voltage for a long shelf and cycle life. The maximum stable voltage with an aqueous electrolyte is 1.5 V; the Li-ion rechargeable battery uses an organic electrolyte with a larger window, which increase the density of stored energy for a given Deltat. Anode or cathode electrochemical potentials outside the electrolyte window can increase V, but they require formation of a passivating surface layer that must be permeable to Li(+) and capable of adapting rapidly to the changing electrode surface area as the electrode changes volume during cycling. A passivating surface layer adds to the impedance of the Li(+) transfer across the electrode/electrolyte interface and lowers the cycle life of a battery cell. Moreover, formation of a passivation layer on the anode robs Li from the cathode irreversibly on an initial charge, further lowering the reversible Deltat. These problems plus the cost of quality control of manufacturing plague development of Li-ion rechargeable batteries that can compete with the internal combustion engine for powering electric cars and that can provide the needed low-cost storage of electrical energy generated by renewable wind and/or solar energy. Chemists are contributing to incremental improvements of the conventional strategy by investigating and controlling electrode passivation layers, improving the rate of Li(+) transfer across electrode/electrolyte interfaces, identifying electrolytes with larger windows while retaining a Li(+) conductivity sigma(Li) > 10(-3) S cm(-1), synthesizing electrode morphologies that reduce the size of the active particles while pinning them on current collectors of large surface area accessible by the electrolyte, lowering the cost of cell fabrication, designing displacement-reaction anodes of higher capacity that allow a safe, fast charge, and designing alternative cathode hosts. However, new strategies are needed for batteries that go beyond powering hand-held devices, such as using electrode hosts with two-electron redox centers; replacing the cathode hosts by materials that undergo displacement reactions (e.g. sulfur) by liquid cathodes that may contain flow-through redox molecules, or by catalysts for air cathodes; and developing a Li(+) solid electrolyte separator membrane that allows an organic and aqueous liquid electrolyte on the anode and cathode sides, respectively. Opportunities exist for the chemist to bring together oxide and polymer or graphene chemistry in imaginative morphologies.

The development of new electrode materials for lithium-ion batteries (LIBs) is of great interest because available electrode materials may not meet the high-energy demands for electronic devices, especially the demands for good cyclic and rate performance. Mn-based oxides have received substantial attention as promising anode materials for LIBs due to their high theoretical specific capacities, low charge potential vs. Li/Li+, environmental benignity and natural abundance. Herein, the preparation of Mn-based oxide nanomaterials with various nanostructures and chemical compositions along with their applications as negative electrodes for LIBs are reviewed. The review covers MnO, Mn3O4, Mn2O3, MnO2, CoMn2O4, ZnMn2O4 and their carbonaceous composite/oxide supports with different morphologies and compositions. The aim of this review is to provide an in-depth and rational understanding of the relationships among the chemical compositions, morphologies and electrochemical properties of Mn-based anode materials and, to understand how electrochemical performance can be improved using materials engineering strategies. Special attention has been paid to the discussion of challenges in the practical applications of Mn-based oxides in LIB full cells.

Sheet-like agglomerates β-Bi₂O₃ were synthesized via an extraction-precipitation stripping-decomposition method using a leaching solution of bismuthinite as raw materials in acidic chloride media. Phase form of as-prepared Bi₂O₃ was confirmed by X-ray diffraction (XRD) and its morphology was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Moreover, photocatalytic activity of the β-Bi₂O₃ was evaluated by measuring the degradation of Rhodamine B (RhB) under visible light irradiation. The results showed that the powders consisted of nanoflakes. The β-Bi₂O₃ exhibited a smaller band gap energy and larger absorbance edge than α-Bi₂O₃ and reported β-Bi₂O₃. In addition, 99.23% of the RhB was degraded under 4 h visible light irradiation and β-Bi₂O₃ was a fairly stable photocatalyst under the experimental conditions.

Despite the imminent commercial introduction of Li-ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li-ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two-to-five times larger than those attained with currently used materials, such as graphite and LiCoO(2), can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.

Novel ZnMn(2)O(4) ball-in-ball hollow microspheres are fabricated by a facile two-step method involving the solution synthesis of ZnMn-glycolate hollow microspheres and subsequent thermal annealing in air. When evaluated as an anode material for lithium-ion batteries, these ZnMn(2)O(4) ball-in-ball hollow microspheres show significantly enhanced electrochemical performance with high capacity, excellent cycling stability and good rate capability.

Binary metal oxides have been regarded as ideal and potential anode materials, which can ameliorate and offset the electrochemical performance of the single metal oxides, such as reversible capacity, structural stability and electronic conductivity. In this work, monodisperse NiCo(2)O(4) mesoporous microspheres are fabricated by a facile solvothermal method followed by pyrolysis of the Ni(0.33)Co(0.67)CO(3) precursor. The Brunauer-Emmett-Teller (BET) surface area of NiCo(2)O(4) mesoporous microspheres is determined to be about 40.58 m(2) g(-1) with dominant pore diameter of 14.5 nm and narrow size distribution of 10-20 nm. Our as-prepared NiCo(2)O(4) products were evaluated as the anode material for the lithium-ion-battery (LIB) application. It is demonstrated that the special structural features of the NiCo(2)O(4) microspheres including uniformity of the surface texture, the integrity and porosity exert significant effect on the electrochemical performances. The discharge capacity of NiCo(2)O(4) microspheres could reach 1198 mA h g(-1) after 30 discharge-charge cycles at a current density of 200 mA g(-1). More importantly, when the current density increased to 800 mA.g(-1), it can render reversible capacity of 705 mA h g(-1) even after 500 cycles, indicating its potential applications for next-generation high power lithium ion batteries (LIBs). The superior battery performance is mainly attributed to the unique micro/nanostructure composed of interconnected NiCo(2)O(4) nanocrystals, which provides good electrolyte diffusion and large electrode-electrolyte contact area, and meanwhile reduces volume change during charge/discharge process. The strategy is simple but very effective, and because of its versatility, it could be extended to other high-capacity metal oxide anode materials for LIBs.

The low specific capacity of graphite limits the further increase of the energy density of lithium-ion batteries and their widespread applications. Exploring new anode materials is the key issue. Herein, a new mullite-type compound Bi2Mn4O10 is designed and synthesized. The Bi2Mn4O10/C composite delivers a high reversible specific capacity of 846 mA h g-1 (more than twice that of graphite), and exhibits a high capacity retention of 100% after 300 cycles at 600 mA g-1, which is reported for the first time. The high specific capacity originates from the combination of the conversion reaction and alloying-dealloying reaction, which has been confirmed by the ex situ XRD, IR, SEM and TEM studies. In addition, the unique nanocomposite generated during the charge-discharge process provides excellent cycling stability. This work proves that Bi2Mn4O10/C is a potential anode material for advanced lithium-ion batteries.

A new polyacrylamide gel route was used to prepare BiFeO₃ nanoparticles. In this route, the solution containing the required cations was gelled by using acrylamide; during the gelation process, acrylamide was polymerized to form a polymer network, which provided a structural framework for the growth of particles. It is demonstrated that highpurity BiFeO3 powders can be prepared using ethylenediaminetetraacetic acid (EDTA) as the chelating agent. On the other hand, it is found that adding an appropriate amount of glucose to the precursor solution can effectively suppress the gel shrinkage during drying, and consequently lead to a significant improvement of powder quality. Scanning electron microscope (SEM) observation reveals that the asprepared BiFeO₃ powder has a uniform particle size, and the particles are almost spherical without any agglomeration or adhesion. Differential scanning calorimetry (DSC) analysis reveals that the product has an antiferromagnetic phase transition at about 370℃ and a ferroelectric phase transition at about 830℃. Ferroelectric and magnetic hysteresis loop measurements show that the product exhibits clear ferroelectric property and weak ferromagnetism.

Multilayered Si/RGO anode nanostructures, featuring alternating Si nanoparticle (NP) and RGO layers, good mechanical stability, and high electrical conductivity, allow Si NPs to easily expand between RGO layers, thereby leading to high reversible capacity up to 2300 mAh g(-1) at 0.05 C (120 mA g(-1)) and 87% capacity retention (up to 630 mAh g(-1)) at 10 C after 152 cycles.

CoO/CoFe2O4 nanocomposites, derived from scalably prepared CoFe-layered double hydroxide (CoFe-LDH) single-resource precursors, exhibit tunable cycle performances and rate capabilities, which are supported by the homogenous dispersion of bi-component active CoO and CoFe2O4 phases.

The cathode material Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ was synthesized by sol-gel method modified by glucose as carbon source. The structure, morphology and electrochemical performances of the as-prepared sample was studied by methods of XRD, SEM, EDS, BET, Laser Particle Size Analysis, cyclic voltammetry, galvanostatic charge-discharge and AC impedance. Test results showed that the distribution of particles became uniform and the sizes became smaller for the modification by glucose. The D₅₀ decreased from 11.56 to 9.94 μm. The specific surface area nearly doubled. The initial discharge specific capacity at 0.2C reached 183.4 mAh·g^-1 and 211.6 mAh·g^-1 after been activated by 0.05C for blank and compared groups, respectively. The capacity at 2C retained 62.2% and 77.6% of that at 0.2C for the two samples, respectively. After 50 cycles at 1C, the discharge specific capacities retained 133.3 mAh·g^-1 and 173.6 mAh·g^-1, and the capacity retention rates were 95.1% and 100% for the two samples, respectively. The initial irreversible capacity loss was reduced for the modification by glucose. The rate performance and cycle stability were obviously improved. The impedance of charge transfer and Warburg, and dispersion effect of the electric double layer were decreased. The crystal structure of the sample stayed unchanged.

Thermally reduced graphene oxide (rGO)-wrapped ZnMn2O4 nanorods have been successfully fabricated via a facile bottom-up approach. Characterization results show that porous ZnMn2O4 nanorods are uniformly wrapped by ultrathin rGO sheets. The unique structure of this rGO-ZnMn2O4 composite could facilitate both ion and electron diffusion, thus providing suitable characteristics of an anode material for high performance lithium-ion batteries. Specifically, the conductive rGO sheets could act as an efficient buffer to relax the volume changes from Li+ insertion/extraction, and enable the structural and interfacial stabilization of ZnMn2O4 crystals. As a consequence, a high and stable reversible capacity (707 mA h g(-1) at 100 mA g(-1) over 50 cycles) and an excellent rate capability (440 mA h g(-1) at 2000 mA g(-1)) are achieved with this composite material.

Bismuth oxide directly grown on nickel foam (p-Bi2O3/Ni) was prepared by a facile polymer-assisted solution approach and was used directly as a lithium-ion battery anode for the first time. The Bi2O3 particles were covered with thin carbon layers, forming network-like sheets on the surface of the Ni foam. The binder-free p-Bi2O3/Ni shows superior electrochemical properties with a capacity of 668 mA h g(-1) at a current density of 800 mA g(-1), which is much higher than that of commercial Bi2O3 powder (c-Bi2O3) and Bi2O3 powder prepared by the polymer-assisted solution method (p-Bi2O3). The good performance of p-Bi2O3/Ni can be attributed to higher volumetric utilization efficiency, better connection of active materials to the current collector, and shorter lithium ion diffusion path.

Bismuth oxide/reduced graphene oxide (termed Bi2O3@rGO) nanocomposite has been facilely prepared by a solvothermal method via introducing chemical bonding that has been demonstrated by Raman and X-ray photoelectron spectroscopy spectra. Tremendous single-crystal Bi2O3 nanoparticles with an average size of approximately 5 nm are anchored and uniformly dispersed on rGO sheets. Such a nanostructure results in enhanced electrochemical reversibility and cycling stability of Bi2O3@rGO composite materials as anodes for lithium ion batteries in comparison with agglomerated bare Bi2O3 nanoparticles. The Bi2O3@rGO anode material can deliver a high initial capacity of approximately 900 mAh/g at 0.1C and shows excellent rate capability of approximately 270 mAh/g at 10C rates (1C = 600 mA/g). After 100 electrochemical cycles at 1C, the Bi2O3@rGO anode material retains a capacity of 347.3 mAh/g with corresponding capacity retention of 79%, which is significantly better than that of bare Bi2O3 material. The lithium ion diffusion coefficient during lithiation-delithiation of Bi2O3@rGO nanocomposite has been evaluated to be around approximately 10(-15)-10(-16) cm(2)/S. This work demonstrates the effects of chemical bonding between Bi2O3 nanoparticles and rGO substrate on enhanced electrochemical performances of Bi2O3@rGO nanocomposite, which can be used as a promising anode alterative for superior lithium ion batteries.

A facile and cost-effective approach for the fabrication of a hierarchical nanocomposite material of graphene-wrapped MnO2 -graphene nanoribbons (GMG) is developed. The resulting composite has a high specific capacity and an excellent cycling stability owing to the synergistic combination of the electrically conductive graphene, graphene nanoribbons, and MnO2 .