Rechargeable aqueous zinc-ion batteries (ZIB) are emerging as one promising alternative for Li-ion batteries on account of the high energy density, environmental friendliness, rich earth abundance and good safety characteristics. Nevertheless, almost all the ZIBs suffer from sluggish kinetics of Zn 2+ diffusion in electrodes, leading to poor rate capability and inadequate cycle life in practical applications. To tackle this issue, herein we develop an in situ polyaniline (PANI) intercalation strategy to facilitate the Zn 2+ (de)intercalation kinetics in V2O5. In this way, a remarkably enlarged interlayer distance (13.90 Å) can be constructed alternatively between the V-O layers, offering expedite This article is protected by copyright. All rights reserved.3 channels for facile Zn 2+ diffusion. More importantly, the electrostatic interactions between Zn 2+ and host O 2-, which is another key factor in hindering the Zn 2+ diffusion kinetics, can be effectively blocked by the unique π-conjugated structure of PANI. As a result, the PANI-intercalated V2O5 exhibits a stable and highly reversible electrochemical reaction during repetitive Zn 2+ insertion and extraction, as demonstrated by in situ synchrotron X-ray diffraction and Raman studies. Further first-principles calculations clearly reveal a remarkably lowered binding energy between Zn 2+ and host O 2+ , which explains the favorable kinetics in PANI-intercalated V2O5. Moreover, the intercalation of PANI leads to an intermediated energy band lying across the Fermi level, thereby offering a step for electron transport during charging/discharging process. Benefitting from the above, the overall electrochemical performance of PANI-intercalated V2O5 electrode has been remarkable improved, exhibiting excellent high rate capability of 197.1 mAh g −1 at current density of 20 A g −1 with capacity retention of 97.6% over 2000 cycles. Our approach presents a prospective guideline for the electrode design of high performance aqueous ZIBs, which could be also expanded to widespread battery researches.

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.

No abstract

Developing advanced high‐rate electrode materials has been a crucial aspect for next‐generation lithium ion batteries (LIBs). A conventional nanoarchitecturing strategy is suggested to improve the rate performance of materials but inevitably brings about compromise in volumetric energy density, cost, safety, and so on. Here, micro‐size Nb14W3O44 is synthesized as a durable high‐rate anode material based on a facile and scalable solution combustion method. Aberration‐corrected scanning transmission electron microscopy reveals the existence of open and interconnected tunnels in the highly crystalline Nb14W3O44, which ensures facile Li+ diffusion even within micro‐size particles. In situ high‐energy synchrotron XRD and XANES combined with Raman spectroscopy and computational simulations clearly reveal a single‐phase solid‐solution reaction with reversible cationic redox process occurring in the NWO framework due to the low‐barrier Li+ intercalation. Therefore, the micro‐size Nb14W3O44 exhibits durable and ultrahigh rate capability, i.e., ≈130 mAh g−1 at 10 C, after 4000 cycles. Most importantly, the micro‐size Nb14W3O44 anode proves its highest practical applicability by the fabrication of a full cell incorporating with a high‐safety LiFePO4 cathode. Such a battery shows a long calendar life of over 1000 cycles and an enhanced thermal stability, which is superior than the current commercial anodes such as Li4Ti5O12.

Metal‐organic frameworks (MOFs) are of quite a significance in the field of inorganic‐organic hybrid crystals. Especially, MOFs have attracted increasing attention in recent years due to their large specific surface area, desirable electrical conductivity, controllable porosity, tunable geometric structure, and excellent thermal/chemical stability. Some recent studies have shown that carbon materials prepared by MOFs as precursors can retain the privileged structure of MOFs, such as large specific surface area and porous structure and, in contrast, realize in situ doping with heteroatoms (eg, N, S, P, and B). Moreover, by selecting appropriate MOF precursors, the composition and morphology of the carbon products can be easily adjusted. These remarkable structural advantages enable the great potential of MOF‐derived carbon as high‐performance energy materials, which to date have been applied in the fields of energy storage and conversion systems. In this review, we summarize the latest advances in MOF‐derived carbon materials for energy storage applications. We first introduce the compositions, structures, and synthesis methods of MOF‐derived carbon materials, and then discuss their applications and potentials in energy storage systems, including rechargeable lithium/sodium‐ion batteries, lithium‐sulfur batteries, supercapacitors, and so forth, in detail. Finally, we put forward our own perspectives on the future development of MOF‐derived carbon materials.