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Olivine-type lithium manganese iron phosphate (LMFP) has been a promising cathode for Li-ion batteries (LIB) owing to its superior safety performance and low cost, yet the intrinsic low ionic/electronic conductivities result in large electrochemical polarization and inferior rate performance. Herein, we report a LMFP with high-power Li-storage capability through a Na/Co co-doped strategy. The Na+ with a larger ionic radius (1.02 Å) locates at Li-sites, effectively widening the Li+ diffusion channel to improve the Li-ion transfer dynamic. The Co2+ located at transition metal sites (TM-sites) can lower the band gap to improve the electronic conductivity, while it can also alleviate the increase in the b-axis parameter to shorten the Li+ transfer path. Accordingly, the concurrently improved ionic/electronic transfer rate endows the superior rate performance of LMFP, with a high reversible capacity of 113.5 mAh g−1 at 5 C, much higher than the pristine sample (only 79.5 mAh g−1). The modified LMFP also displays excellent cycling stability, maintaining 97.1% of its initial capacity after 1000 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Olivine-type LiMnxFe1−xPO4 (LMFP, 0 < x < 1) is poised to supplant LiFePO4 cathode materials with a ∼20% energy-density increase for Li-ion batteries (LIBs). However, its intrinsic low conductivities and MnO6 octahedral unit-cell Jahn–Teller distortion limit its power capability and cycling life. Herein, we report a Mg/Ni dual-doped and carbon-coated LMFP micro-sized secondary sphere with greatly enhanced reaction kinetics and superior structure stability. Ni2+ reduces the average valence state of Mn ions to alleviate Jahn–Teller distortion by participating in charge compensation during charging while improving electronic conductivity together with carbon coating. Mg2+ with a smaller ion radius (65 pm) significantly widens the Li-ion transfer channel by extending Li–O bonds. The as-obtained LMFP cathodes increase reversible specific capacity by about 2.4 times at 5C compared with a pristine sample, reaching 115 mA h g−1. In a pouch-type full cell, 92% of its initial capacity is still maintained after 2000 cycles at 1C, demonstrating its attractive potential for practical application in high-power and long-life LIBs. [ABSTRACT FROM AUTHOR]

Single-crystalline Ni-rich Co-poor cathodes with high safety and competitive cost have recently attracted widespread attention, yet they still suffer from poor rate capability owing to the long Li-ion transfer path. Herein, a small-size (∼2.01 μm) single-crystalline LiNi0.85Co0.05Mn0.10O2 cathode with high power and superior stability is designed and synthesized by in situ introducing W-doping and perovskite La4NiLiO8 coating. The W-doping in high-temperature lithiation can obviously decrease the size of single-crystalline Ni-rich cathodes with high dispersion compared with the conventional strategy by directly doping W into NCM cathodes (∼3.09 μm). The perovskite coating layer has a high ion-conductivity and stable crystal structure, greatly enhancing the Li-ion diffusion rate and interfacial chemical stability. As a consequence, the as-obtained single-crystalline cathodes deliver a high reversible specific capacity of 213.6 mA h g−1 at 0.1C and 111.8 mA h g−1 even at 10C in coin-type half-cells. After assembled into pouch-type full-cells with commercial graphite anodes, a durable cycling retention of 89.6% is obtained after 1000 cycles at 1C within 2.7–4.3 V. This work proves a way for developing high-power and stable single-crystalline Ni-rich cathodes. [ABSTRACT FROM AUTHOR]

Unexpected intercalation-dominated process is observed during K+ insertion in WS2 in a voltage range of 0.01–3.0 V. This is different from the previously reported two-dimensional (2D) transition metal dichalcogenides that undergo a conversion reaction in a low voltage range when used as anodes in potassium-ion batteries. Charge/discharge processes in the K and Na cells are studied in parallel to demonstrate the different ion storage mechanisms. The Na+ storage proceeds through intercalation and conversion reactions while the K+ storage is governed by an intercalation reaction. Owing to the reversible K+ intercalation in the van der Waals gaps, the WS2 anode exhibits a low decay rate of 0.07% per cycle, delivering a capacity of 103 mAh·g-1 after 100 cycles at 100 mA·g-1. It maintains 57% capacity at 800 mA·g-1 and shows stable cyclability up to 400 cycles at 500 mA·g-1. Kinetics study proves the facilitation of K+ transport is derived from the intercalation-dominated mechanism. Furthermore, the mechanism is verified by the density functional theory (DFT) calculations, showing that the progressive expansion of the interlayer space can account for the observed results. [ABSTRACT FROM AUTHOR]

Abstract: Electroactive materials (especially pseudocapacitive materials) are generally in the form of ultrathin conformal coating in supercapacitor electrodes based on nanostructured current collectors; thus, the resultant low mass loading of electroactive materials largely limits the applications of nanostructured current collectors. Here, supercapacitor electrodes with nickel nanorod arrays as nanostructured current collectors and MnO2 as electroactive materials are fabricated to study the role of nanostructured current collectors in determining the energy storage capability when electroactive materials are in thick layer rather than ultrathin conformal coating. Electrochemical analysis reveals that Ni nanorods could create numerous electrical conductive tunnels in the thick‐layer electrodes to dramatically alleviate the contact resistance at the electroactive‐material/current‐collector interface. With 1 µm thick MnO2 layer, the Ni nanorods based electrodes have much higher areal capacitance than those with Ni foils as current collectors, which is more than six times of that with the same MnO2 mass loading or more than 18 times of that with the same 1 µm thick MnO2 layer. Moreover, better rate capability and higher structural stability is maintained in Ni nanorods based electrodes even with 3 µm thick MnO2 layer. These results open up new opportunities for nanostructured current collectors to construct supercapacitors with superior energy storage capability. [ABSTRACT FROM AUTHOR]

Constructing core/shell nanostructures with optimal structure and composition could maximize the solar light utilization. Here, using an Al nanocone array as a substrate, a well-defined regular array of AZO/TiO2 core/shell nanocones with uniformly dispersed Au nanoparticles (AZO/TiO2/Au NCA) is successfully realized through three sequential steps of atomic layer deposition, physical vapor deposition, and annealing processes. By tuning the structural and compositional parameters, the advantages of light trapping and short carrier diffusion from the core/shell nanocone array, as well as the surface plasmon resonance and catalytic effects from the Au nanoparticles can be maximally utilized. Accordingly, a remarkable photoelectrochemical (PEC) performance can be acquired and the photocurrent density of the AZO/TiO2/Au NCA electrode reaches up to 1.1 mA cm−2 at 1.23 V, versus reversible hydrogen electrode (RHE) under simulated sunlight illumination, which is five times that of a flat AZO/TiO2 electrode (0.22 mA cm−2). Moreover, the photoconversion of the AZO/TiO2/Au NCA electrode approaches 0.73% at 0.21 V versus RHE, which is one of the highest values with the lowest applied bias ever reported in Au/TiO2 PEC composites. These results demonstrate a feasible route toward the scalable fabrication of well-modulated core/shell nanostructures and can be easily applied to other metal/semiconductor composites for high-performance PEC. [ABSTRACT FROM AUTHOR]

Solution processibility is one of the most intriguing properties of organic semiconductors. However, it is difficult to find a suitable solvent and solution process for most semiconductors. For example, metal phthalocyanines (MPcs) are only soluble in non-volatile solvents, which prevent their applications from solution process. For the first time, vectorial diffusion is utilized for solution processing of MPcs. The obtained large F16CuPc and α-phase CuPc crystals and the efficient phase separation of them suggest the vectorial diffusion process is as slow as a self-assembly process, which is helpful to yield large crystals and purify the semiconductors. This method, which only uses common commercial solvents without any complex and expensive instruments and high-temperature operation, provides a facile approach for purification of organic semiconductors and growth of their crystals in large quantities., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)