Organic compounds offer new possibilities for high energy/power density, cost-effective, environmentally friendly, and functional rechargeable lithium batteries. For a long time, they have not constituted an important class of electrode materials, partly because of the large success and rapid development of inorganic intercalation compounds. In recent years, however, exciting progress has been made, bringing organic electrodes to the attention of the energy storage community. Herein thirty years' research efforts in the fi eld of organic compounds for rechargeable lithium batteries are summarized. The working principles, development history, and design strategies of these materials, including organosulfur compounds, organic free radical compounds, organic carbonyl compounds, conducting polymers, non-conjugated redox polymers, and layered organic compounds are presented. The cell performances of these materials are compared, providing a comprehensive overview of the area, and straightforwardly revealing the advantages/disadvantages of each class of materials.

Spinels can serve as alternative low-cost bifunctional electrocatalysts for oxygen reduction/evolution reactions (ORR/OER), which are the key barriers in various electrochemical devices such as metal-air batteries, fuel cells and electrolysers. However, conventional ceramic synthesis of crystalline spinels requires an elevated temperature, complicated procedures and prolonged heating time, and the resulting product exhibits limited electrocatalytic performance. It has been challenging to develop energy-saving, facile and rapid synthetic methodologies for highly active spinels. In this Article, we report the synthesis of nanocrystalline M(x)Mn(3-x)O(4) (M = divalent metals) spinels under ambient conditions and their electrocatalytic application. We show rapid and selective formation of tetragonal or cubic M(x)Mn(3-x)O(4) from the reduction of amorphous MnO(2) in aqueous M(2+) solution. The prepared Co(x)Mn(3-x)O(4) nanoparticles manifest considerable catalytic activity towards the ORR/OER as a result of their high surface areas and abundant defects. The newly discovered phase-dependent electrocatalytic ORR/OER characteristics of Co-Mn-O spinels are also interpreted by experiment and first-principle theoretical studies.

There is an ever-growing demand for rechargeable batteries with reversible and efficient electrochemical energy storage and conversion. Rechargeable batteries cover applications in many fields, which include portable electronic consumer devices, electric vehicles, and large-scale electricity storage in smart or intelligent grids. The performance of rechargeable batteries depends essentially on the thermodynamics and kinetics of the electrochemical reactions involved in the components (i.e., the anode, cathode, electrolyte, and separator) of the cells. During the past decade, extensive efforts have been dedicated to developing advanced batteries with large capacity, high energy and power density, high safety, long cycle life, fast response, and low cost. Here, recent progress in functional materials applied in the currently prevailing rechargeable lithium-ion, nickel-metal hydride, lead acid, vanadium redox flow, and sodium-sulfur batteries is reviewed. The focus is on research activities toward the ionic, atomic, or molecular diffusion and transport; electron transfer; surface/interface structure optimization; the regulation of the electrochemical reactions; and the key materials and devices for rechargeable batteries.

This paper reports a systematical study on the electrochemical properties of MnO2-based nanostructures as low-cost catalysts for oxygen reduction reaction (ORR) in alkaline media. The results show that the catalytic activities of MnO2 depend strongly on the crystallographic structures, following an order of α- > β- > γ-MnO2. Meanwhile, morphology is another important influential factor to the electrochemical properties. Among various micro and nanostructures, α-MnO2 nanospheres and nanowires outperform the counterpart microparticles. Furthermore, a new nanocomposite catalyst by depositing Ni nanoparticles on α-MnO2 nanowires (denoted as MnO2-NWs@Ni-NPs) was prepared and characterized. The as-prepared MnO2-NWs@Ni-NPs nanocomposite exhibits an onset potential of 0.08 V, a specific current of 33.5 mA/mg, and an overall quasi 4-electron transfer involved in oxygen reduction reaction, indicating its potential application as the electrocatalyst of oxygen reduction reaction.

MoS2 nanoflowers with expanded interlayer spacing of the (002) plane were synthesized and used as high-performance anode in Na-ion batteries. By controlling the cut-off voltage to the range of 0.4-3 V, an intercalation mechanism rather than a conversion reaction is taking place. The MoS2 nanoflower electrode shows high discharge capacities of 350 mAh g(-1) at 0.05 A g(-1) , 300 mAh g(-1) at 1 A g(-1) , and 195 mAh g(-1) at 10 A g(-1) . An initial capacity increase with cycling is caused by peeling off MoS2 layers, which produces more active sites for Na(+) storage. The stripping of MoS2 layers occurring in charge/discharge cycling contributes to the enhanced kinetics and low energy barrier for the intercalation of Na(+) ions. The electrochemical reaction is mainly controlled by the capacitive process, which facilitates the high-rate capability. Therefore, MoS2 nanoflowers with expanded interlayers hold promise for rechargeable Na-ion batteries.

Batteries and supercapacitors as electrochemical energy storage and conversion devices are continuously serving for human life. The electrochemical performance of batteries and supercapacitors depends in large part on the active materials in electrodes. As an important family, Mn-based oxides have shown versatile applications in primary batteries, secondary batteries, metal-air batteries, and pseudocapacitors due to their high activity, high abundance, low price, and environmental friendliness. In order to meet future market demand, it is essential and urgent to make further improvements in energy and power densities of Mn-based electrode materials with the consideration of multiple electron reaction and low molecular weight of the active materials. Meanwhile, nanomaterials are favourable to achieve high performance by means of shortening the ionic diffusion length and providing large surface areas for electrode reactions. This article reviews the recent efforts made to apply nanostructured Mn-based oxides for batteries and pseudocapacitors. The influence of structure, morphology, and composition on electrochemical performance has been systematically summarized. Compared to bulk materials and notable metal catalysts, nanostructured Mn-based oxides can promote the thermodynamics and kinetics of the electrochemical reactions occurring at the solid-liquid or the solid-liquid-gas interface. In particular, nanostructured Mn-based oxides such as one-dimensional MnO2 nanostructures, MnO2-conductive matrix nanocomposites, concentration-gradient structured layered Li-rich Mn-based oxides, porous LiNi0.5Mn1.5O4 nanorods, core-shell structured LiMnSiO4@C nanocomposites, spinel-type Co-Mn-O nanoparticles, and perovskite-type CaMnO3 with micro-nano structures all display superior electrochemical performance. This review should shed light on the sustainable development of advanced batteries and pseudocapacitors with nanostructured Mn-based oxides.

FeSe2 microspheres assembled by nano-octahedra are used as an anode material for Na-ion batteries for the first time, showing a high discharge capacity (447 mA h g(-1) at 0.1 A g(-1)), excellent rate performance (388 mA h g(-1) at 5 A g(-1) and 226 mA h g(-1) at 25 A g(-1)), and long cycling stability (372 mA h g(-1) after 2000 cycles at 1 A g(-1)).

Extensive research activities have been directed to develop flexible rechargeable lithium-ion batteries with large capacity, high power, and long cycling life. Template technology offers the benefits in terms of either designing new-type electrode materials or modifying traditional battery configurations. With the aid of "hard" or "soft" templates, a variety of functional materials with diverse structures and morphologies such as one-dimensional (1D) nanostructures, 2D films, and 3D porous frameworks have been synthesized. This review highlights the recent progress in the template-prepared electrode materials for lithium storage, mainly focusing on the Li + intercalation reactions and the Li conversion properties with the nanostructures of LiCoO 2 , C, SnO 2 , Fe 2 O 3 , Co 3 O 4 , VO x , and MnO 2 . In some specifically demonstrated examples, the templated cathode materials (e.g., lithium metal oxides) show significantly improved reversibility and high rate capability over a voltage of 3 V after 100 cycles, whereas the templated anode materials (e.g., metal oxides) can deliver high capacity exceeding 1000 mA h g -1 . The structural and morphological merits of the template-directed materials have been especially addressed in comparison with their traditional bulk forms.