Mechanisms and applications of layer/spinel phase transition in Li-and Mn-rich cathodes for lithium-ion batteries

Li-and Mn-rich(LMR)cathode materials have received tremendous attention due to the highly reversible specific capacity(>250 m Ah·g^(-1)).In the analysis of its crystal structure,the two-phase composite model gains increasing acceptance,and the phase transition behaviors in LMR cathode materials have been extensively studied.Herein,the structure controversy of LMR cathode materials,and the mechanisms of phase transition are summarized.Particularly,the causes of initiating or accelerating the phase transition of LMR cathode materials have been summarized into three main driving forces,i.e.,the electrochemical driving force,the component driving force and the thermodynamic driving force.Additionally,the applications of phase transition behavior in improving the electrochemical performance of LMR cathode materials,including the construction of spinel surface coating and spinel/layered hetero-structure are discussed.

Facile synthesis of PdCu nanocluster-assembled granular films as highly efficient electrocatalysts for formic acid oxidation

Developing efficient and stable bimetallic Pdbased anode electrocatalysts toward formic acid oxidation(FAO)is of great significance for commercial applications of direct formic acid fuel cells(DFAFCs).Herein,we report a facile synthesis approach to fabricate PdCu nanoclusters(NCs)catalysts with granular-film structure.The introduction of Cu can adjust the electronic structure and d-band center of Pd,which can improve the catalytic performance of the catalysts.Compared with Pd NCs catalyst,the catalytic durability and activity of PdCu NCs catalysts for FAO are greatly improved.The order for catalytic activity of NC metals is Pd_(85)Cu_(15)NCs>Pd_(70)Cu_(30)NCs>Pd NCs.The maximum mass activity can be acquired with the Pd_(85)Cu_(15)NCs catalyst,which is about1.7 times that of the Pd NCs catalyst.And Pd_(85)Cu_(15)NCs catalyst still maintains the highest catalytic current density after 50 cycles,indicating that Pd_(85)Cu_(15)NCs catalyst has the best durability and electrocatalytic activity for FAO.Our work provides a new prospect for the design of highly efficient anode catalysts materials for DFAFCs.

Preparation and high-frequency soft magnetic property of FeCo-based thin films

A series of FeCo-based thin films were pre- pared by magnetron sputtering without applying an induced magnetic field. The microstructure, electrical properties, magnetic properties and thermal stability of FeCo, FeCoSiN monolayer thin film and [FeCoSiN/SiNx]n multilayer thin film were investigated systematically. When FeCo thin film was doped with Si and N, the resis- tivity and soft magnetic properties of the obtained FeCo- SiN thin film can be improved effectively. The coercivity （He）, resistivity （p） and ferromagnetic resonance frequency （fr） can be further optimized for the [FeCoSiN/SiNx]n multilayer thin film. When the thickness of FeCoSiN layer and SiNx layer is maintained at 7 and 2 nm, the He, p andfr for [FeCoSiN/SiNx]n multilayer thin film are 225 A·m^-1 392 μΩ·cm^-1 and 4.29 GHz, respectively. In addition, the low coercivity of easy axis （Hoe ≈ 506 A·m^-1） of [FeCoSiN/SiNx]n multilayer thin film can be maintained after annealing at 300℃ in air for 2 h.

Facile fabrication of ZnO-CuO porous hybrid microspheres as lithium ion battery anodes with enhanced cyclability

ZnO–CuO porous hybrid microspheres were successfully produced through a facile aging process of zinc citrate solid microspheres in copper sulfate solution combined with the subsequent annealing treatment in air atmosphere. The electrochemical performance investigation suggests that the harvested ZnO–CuO porous hybrid microspheres illustrate much higher specific capacity and better cycling stability than single ZnO counterparts. A reversible capacity of 585 mAh·g^-1 can be acquired for ZnO–CuO porous hybrid microspheres after cycling 500 times at a current density of 200 mA·g^-1. The porous configuration and the incorporation of CuO are responsible for the enhanced lithium storage properties of ZnO–CuO hybrids.