Explore the vast range of titles available.

Through engineering of oxygen stacking and cation–cation interactions, a methodology to design high-energy and long-cycle-life lithium-rich battery materials is proposed.

Large-scale high-energy batteries with electrode materials made from the Earth-abundant elements are needed to achieve sustainable energy development. On the basis of material abundance, rechargeable sodium batteries with iron- and manganese-based positive electrode materials are the ideal candidates for large-scale batteries. In this review, iron- and manganese-based electrode materials, oxides, phosphates, fluorides, etc, as positive electrodes for rechargeable sodium batteries are reviewed. Iron and manganese compounds with sodium ions provide high structural flexibility. Two layered polymorphs, O3- and P2-type layered structures, show different electrode performance in Na cells related to the different phase transition and sodium migration processes on sodium extraction/insertion. Similar to layered oxides, iron/manganese phosphates and pyrophosphates also provide the different framework structures, which are used as sodium insertion host materials. Electrode performance and reaction mechanisms of the iron- and manganese-based electrode materials in Na cells are described and the similarities and differences with lithium counterparts are also discussed. Together with these results, the possibility of the high-energy battery system with electrode materials made from only Earth-abundant elements is reviewed.

Considering the need for designing better batteries to meet the rapidly growing demand for large-scale energy storage applications, an aspect of primary importance for battery materials is elemental abundance. To achieve sustainable energy development, we must reconsider the feasibility of a sustainable lithium supply, which is essential for lithium(-ion) batteries. Lithium is widely distributed in the Earth, but is not regarded as an abundant element. Therefore, widespread use of large-scale lithium batteries would be inevitably restricted. Sodium(-ion) batteries are thus promising candidates for large-scale applications because sodium is the most advantageous next to lithium considering its atomic weight, standard potential, and natural abundance. Rechargeable sodium-ion batteries consist of two different sodium insertion materials similar to Li-ion batteries. Sodium insertion materials, especially layered oxides, have been studied since the early 1980s, but not extensively for energy storage devices due to the expanded interest in lithium insertion materials in the 1990s. In recent years, materials researchers have again been extensively exploring new sodium insertion materials to enhance battery performance. This article reviews recent advancements and trends in layered sodium transition metal oxides as positive electrode materials for Na-ion batteries.

Further increase in energy density of lithium batteries is needed for zero emission vehicles. However, energy density is restricted by unavoidable theoretical limits for positive electrodes used in commercial applications. One possibility towards energy densities exceeding these limits is to utilize anion (oxide ion) redox, instead of classical transition metal redox. Nevertheless, origin of activation of the oxide ion and its stabilization mechanism are not fully understood. Here we demonstrate that the suppression of formation of superoxide-like species on lithium extraction results in reversible redox for oxide ions, which is stabilized by the presence of relatively less covalent character of Mn 4+ with oxide ions without the sacrifice of electronic conductivity. On the basis of these findings, we report an electrode material, whose metallic constituents consist only of 3 d transition metal elements. The material delivers a reversible capacity of 300 mAh g −1 based on solid-state redox reaction of oxide ions. Energy storage by metal redox reactions sets strict limits on capacity in metal oxide cathode materials used in lithium-ion batteries. Here authors study stabilization of redox reactions at oxygen sites and demonstrate a cathode with a high reversible capacity enabled by the process.

Rechargeable lithium batteries have rapidly risen to prominence as fundamental devices for green and sustainable energy development. Lithium batteries are now used as power sources for electric vehicles. However, materials innovations are still needed to satisfy the growing demand for increasing energy density of lithium batteries. In the past decade, lithium-excess compounds, Li₂MeO₃ (Me = Mn⁴⁺, Ru⁴⁺, etc.), have been extensively studied as high-capacity positive electrode materials. Although the origin as the high reversible capacity has been a debatable subject for a long time, recently it has been confirmed that charge compensation is partly achieved by solid-state redox of nonmetal anions (i.e., oxide ions), coupled with solid-state redox of transition metals, which is the basic theory used for classic lithium insertion materials, such as LiMeO₂ (Me = Co³⁺, Ni³⁺, etc.). Herein, as a compound with further excess lithium contents, a cation-ordered rocksalt phase with lithium and pentavalent niobium ions, Li₃NbO₄, is first examined as the host structure of a new series of high-capacity positive electrode materials for rechargeable lithium batteries. Approximately 300 mAh·g⁻¹ of high-reversible capacity at 50 °C is experimentally observed, which partly originates from charge compensation by solid-state redox of oxide ions. It is proposed that such a charge compensation process by oxide ions is effectively stabilized by the presence of electrochemically inactive niobium ions. These results will contribute to the development of a new class of high-capacity electrode materials, potentially with further lithium enrichment (and fewer transition metals) in the close-packed framework structure with oxide ions.

Li-ion batteries have gained intensive attention as a key technology for realizing a sustainable society without dependence on fossil fuels. To further increase the versatility of Li-ion batteries, considerable research efforts have been devoted to developing a new class of Li insertion materials, which can reversibly store Li-ions in host structures and are used for positive/negative electrode materials of Li-ion batteries. Appropriate evaluations of electrochemical properties of Li insertion materials are essential for the research of electrode materials in laboratory. In this article, we describe fundamental methods of electrochemical characterization of Li insertion materials including electrode preparation, cell assembly, and electrochemical measurement in the laboratory-scale research. The importance of selection for battery components such as electrolyte solutions, polymer binders, separators, and current collectors on the electrochemical properties of Li insertion materials, is also discussed. This article offers basic knowledge and techniques for electrochemical characterizations of Li insertion materials to students and beginners for battery research.

The electrification of heavy-duty transport and aviation will require new strategies to increase the energy density of electrode materials 1 , 2 . The use of anionic redox represents one possible approach to meeting this ambitious target. However, questions remain regarding the validity of the O 2− /O − oxygen redox paradigm, and alternative explanations for the origin of the anionic capacity have been proposed 3 , because the electronic orbitals associated with redox reactions cannot be measured by standard experiments. Here, using high-energy X-ray Compton measurements together with first-principles modelling, we show how the electronic orbital that lies at the heart of the reversible and stable anionic redox activity can be imaged and visualized, and its character and symmetry determined. We find that differential changes in the Compton profile with lithium-ion concentration are sensitive to the phase of the electronic wave function, and carry signatures of electrostatic and covalent bonding effects 4 . Our study not only provides a picture of the workings of a lithium-rich battery at the atomic scale, but also suggests pathways to improving existing battery materials and designing new ones. High-energy X-ray Compton measurements and first-principles modelling reveal how the electronic orbital responsible for the reversible anionic redox activity can be imaged and visualized, and its character and symmetry determined.

Energy storage devices that can deliver high powers have many applications, including hybrid vehicles and renewable energy. Much research has focused on increasing the power output of lithium batteries by reducing lithium-ion diffusion distances, but outputs remain far below those of electrochemical capacitors and below the levels required for many applications. Here, we report an alternative approach based on the redox reactions of functional groups on the surfaces of carbon nanotubes. Layer-by-layer techniques are used to assemble an electrode that consists of additive-free, densely packed and functionalized multiwalled carbon nanotubes. The electrode, which is several micrometres thick, can store lithium up to a reversible gravimetric capacity of ∼200 mA h g −1 electrode while also delivering 100 kW kg electrode −1 of power and providing lifetimes in excess of thousands of cycles, both of which are comparable to electrochemical capacitor electrodes. A device using the nanotube electrode as the positive electrode and lithium titanium oxide as a negative electrode had a gravimetric energy ∼5 times higher than conventional electrochemical capacitors and power delivery ∼10 times higher than conventional lithium-ion batteries. A lithium battery whose positive electrode consists of functionalized carbon nanotubes can achieve higher energy densities than electrochemical capacitors while delivering higher power than conventional lithium-ion batteries.

The development of inherently safe energy devices is a key challenge, and aqueous Li-ion batteries draw large attention for this purpose. Due to the narrow electrochemical stable potential window of aqueous electrolytes, the energy density and the selection of negative electrode materials are significantly limited. For achieving durable and high-energy aqueous Li-ion batteries, the development of negative electrode materials exhibiting a large capacity and low potential without triggering decomposition of water is crucial. Herein, a type of a negative electrode material (i.e., LiₓNb2/7Mo3/7O₂) is proposed for high-energy aqueous Li-ion batteries. LiₓNb2/7Mo3/7O₂ delivers a large capacity of ∼170 mA · h · g−1 with a low operating potential range of 1.9 to 2.8 versus Li/Li⁺ in 21 m lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) aqueous electrolyte. A full cell consisting of Li1.05Mn1.95O₄/Li9/7Nb2/7Mo3/7O₂ presents high energy density of 107 W · h · kg−1 as the maximum value in 21 m LiTFSA aqueous electrolyte, and 73% in capacity retention is achieved after 2,000 cycles. Furthermore, hard X-ray photoelectron spectroscopy study reveals that a protective surface layer is formed at the surface of the negative electrode, by which the high-energy and durable aqueous batteries are realized with LiₓNb2/7Mo3/7O₂. This work combines a high capacity with a safe negative electrode material through delivering the Mo-based oxide with unique nanosized and metastable characters.

A novel vinyl polymer bearing an extended conjugated disodium dicarboxylate structure, specifically, the terphenyl side chain structure, which has a favorable electrochemical performance, has been synthesized and evaluated as an anode for sodium-ion batteries. The electrochemical performance was significantly improved over that of the vinyl polymer with disodium terephthalate. In particular, the discharge potential shifted by ~0.1 V to a lower potential at 0.28 V (vs. Na/Na+). Additionally, a specific capacity of 121 mAh g–1 at 10 mA g–1, which corresponds to an 88% theoretical capacity, was observed. Moreover, better rate performance was also achieved through the extended π-conjugated system.Organic compounds with conjugated carbonyl groups used as electrode material for secondary battery is attractive attention. We have been focused on disodium terephthalate and its polymer derivative as active anode material for secondary battery. Herein, we synthesized a novel vinyl polymer bearing an extended conjugated disodium dicarboxylate and it was evaluated as an anode active material for sodium-ion battery to discuss the correlation between structure and electrochemical properties. We suggest that the longer π-extended systems on the side chains provide a better anode performance of sodium-ion batteries.