3.8 V (vs Li + /Li), making them a class of promising cathode material and attracting considerable attention. Nevertheless, the inferior cycling stability and poor rate capability of Ni-rich oxide cathode materials have to be overcome before they can compete in practical implementation. [2,4] These drawbacks are largely attributed to their spherical micrometer-sized secondary particles aggregated densely by many randomly oriented primary nanoparticles, [4][5][6] as shown in Figure 1a. On the one hand, concomitant with this structure, the surface of secondary particles is terminated with random crystal planes. As Li + can only diffuse along the 2D {010} plane in the hexagonal-layer structure of NCM materials, [4,7] the randomly exposed crystal planes (not solely the active {010} plane) may substantially hinder the Li + exchange at the electrode/electrolyte interface. Meanwhile, the randomly oriented primary nanoparticles induce a prolonged and mazy Li + diffusion pathway inside the secondary particles, because Li + ions have to migrate across the grain boundaries, especially between the grains with inconsistent crystal planes. On the other hand, the successive phase transition accompanied by repeated Li + insertion/extraction would result in anisotropic variation of the lattice parameters, and such variation is severely aggravated with the increase of Ni content. [8] Accordingly, in the Ni-rich oxide cathode materials, the substantial anisotropic lattice expansion/contraction would result in drastic microstrains at the boundaries of randomly oriented primary particles due to the asynchronous volume Ni-rich Li[Ni x Co y Mn 1−x−y ]O 2 (x ≥ 0.8) layered oxides are the most promising cathode materials for lithium-ion batteries due to their high reversible capacity of over 200 mAh g −1 . Unfortunately, the anisotropic properties associated with the α-NaFeO 2 structured crystal grains result in poor rate capability and insufficient cycle life. To address these issues, a micrometersized Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 secondary cathode material consisting of radially aligned single-crystal primary particles is proposed and synthesized. Concomitant with this unique crystallographic texture, all the exposed surfaces are active {010} facets, and 3D Li + ion diffusion channels penetrate straightforwardly from surface to center, remarkably improving the Li + diffusion coefficient. Moreover, coordinated charge-discharge volume change upon cycling is achieved by the consistent crystal orientation, significantly alleviating the volume-change-induced intergrain stress. Accordingly, this material delivers superior reversible capacity (203.4 mAh g −1 at 3.0-4.3 V) and rate capability (152.7 mAh g −1 at a current density of 1000 mA g −1 ). Further, this structure demonstrates excellent cycling stability without any degradation after 300 cycles. The anisotropic morphology modulation provides a simple, efficient, and scalable way to boost the performance and applicability of Ni-rich layered oxide cathode materials.

of the most attractive inventions because they have dramatically improved our daily lives by enabling portable electronics, the onset of electronic mobility and electrical vehicles. [1] With the development of materials science, anionic redox chemistry, typically O redox, has enabled more energy storage than the traditional electrochemical reactions, in which the energy and power density are solely determined by the cation redox reaction of transition metals. [2] On the other hand, the rapid growth of lithium consumption leads to continuously increasing demand for lithium. Considering the uneven distribution of lithium resources, the inherent drawbacks of lithium supply and demand are difficult to overcome. [3] Therefore, an alternative to lithium must be considered, especially for large-scale energy storage applications in the foreseeable future.The Na-ion battery, which has a reaction pattern comparable with that of the Li-ion battery, is one of the promising alternatives because of its low cost and the abundance of sodium resources. [4] Currently, the study of Na-ion batteries is focused on improving their energy density. Considering the successful study of Lirich materials, one of the possible solutions to improve the capacity of Na-ion batteries is to develop Na-rich materials. It is very important to involve reversible O redox and expand the material series from the material design point of view.Recent research disclosed, the increasing of the Li(Na) content within layered structure materials can effectively influence the local atom coordination around oxygen atoms which could improve O redox upon cycling and lead to a higher capacity. [5] As demonstrated by Tarascon and Ceder et al., increasing the Li(Na) ratio can shift the O 2p nonbonding band gradually up near the Fermi level. This labile nonbonding O offers an extra way for electrons to move away, hence increasing the capacity by triggering an extra redox process. [2e,5c,6] This explanation has been successfully applied to Li 2 MnO 3 Li-rich materials [7] and is widely agreed upon. Benefitting from the established Li 2 MnO 3 Li-rich prototype, Li-rich material development has highly improved during the past decades, achieving additional capacity. [8] For the counterpart Na-ion battery design, although anionic redox was recently realized in the Mn-based To improve the energy and power density of Na-ion batteries, an increasing number of researchers have focused their attention on activation of the anionic redox process. Although several materials have been proposed, few studies have focused on the Na-rich materials compared with Li-rich materials. A key aspect is sufficient utilization of anionic species. Herein, a comprehensive study of Mn-based Na 1.2 Mn 0.4 Ir 0.4 O 2 (NMI) O3-type Na-rich materials is presented, which involves both cationic and anionic contributions during the redox process. The single-cation redox step relies on the Mn 3+ /Mn 4+ , whereas Ir atoms build a strong covalent bond with O and effectively suppress the O 2 release....

Nickel-rich layered oxides (NLOs) exhibit great potential to meet the ever-growing demand for further increases in the energy density of Li-ion batteries because of their high specific capacities. However, NLOs usually suffer from severe structural degradation and undesired side reactions when cycled above 4.3 V. These effects are strongly correlated with the surface structure and chemistry of the active NLO materials. Herein, we demonstrate a preformed cation-mixed (Fm3̅m) surface nanolayer (∼5 nm) that shares a consistent oxygen framework with the layered lattice through Zr modification, in which Ni cations reside in Li slabs and play the role of a “pillar”. This preformed nanolayer alleviates the detrimental phase transformations upon electrochemical cycling, effectively enhancing the structural stability. As a result, the Zr-modified Li­(Ni0.8Co0.1Mn0.1)0.985Zr0.015O2 material exhibits a high reversible discharge capacity of ∼210 mA h/g at 0.1 C (1 C = 200 mA/g) and outstanding cycling stability with a capacity retention of 93.2% after 100 cycles between 2.8 and 4.5 V. This strategy may be further extended to design and prepare other high-performance layered oxide cathode materials.

Sodium‐ion batteries are in high demand for large‐scale energy storage applications. Although it is the most prevalent cathode, layered oxide is associated with significant undesirable characteristics, such as multiple plateaus in the charge−discharge profiles, and cation migration during repeated cycling of Na‐ions insertion and extraction, which results in sluggish kinetics, capacity loss, and structural deterioration. Here, a new strategy, i.e., the manipulation of transition‐metal ordering in layered oxides, is proposed to show a prolonged charge−discharge plateau and cation‐migration‐free structural evolution. The results demonstrate that the transition‐metal ordering with a honeycomb‐type superlattice can adjust the crystal lattice and suppress cation migration by modifying the crystal strain to realize a large reversible capacity and excellent cycling performance, which are not characteristics of the widely used common layered oxides. These findings can provide new insight that can be used to improve the design of high‐performance electrode materials for secondary‐ion batteries.

Graphene-based electrocatalytic materials are potential low-cost electrocatalysts for the oxygen evolution reaction (OER).

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A general chemical method has been developed to prepare semiconductor hollow microspheres with various electronic bandgaps (see SEM image), as well as a number of core/shell structures. These hollow structures have potential applications in the fields of optoelectronic technology, photovoltaic devices, photonic bandgap crystals, and photochemical solar cells.