Scaly MoS2/rGO Composite as an Anode Material for High-Performance Potassium-Ion Battery.

Potassium-ion batteries (PIBs) have been widely studied owing to the abundant reserves, widespread distribution, and easy extraction of potassium (K) resources. Molybdenum disulfide (MoS2) has received a great deal of attention as a key anode material for PIBs owing to its two-dimensional diffusion channels for K+ ions. However, due to its poor electronic conductivity and the huge influence of embedded K+ ions (with a large ionic radius of 3.6 Å) on MoS2 layer, MoS2 anodes exhibit a poor rate performance and easily collapsed structure. To address these issues, the common strategies are enlarging the interlayer spacing to reduce the mechanical strain and increasing the electronic conductivity by adding conductive agents. However, simultaneous implementation of the above strategies by simple methods is currently still a challenge. Herein, MoS2 anodes on reduced graphene oxide (MoS2/rGO) composite were prepared using one-step hydrothermal methods. Owing to the presence of rGO in the synthesis process, MoS2 possesses a unique scaled structure with large layer spacing, and the intrinsic conductivity of MoS2 is proved. As a result, MoS2/rGO composite anodes exhibit a larger rate performance and better cycle stability than that of anodes based on pure MoS2, and the direct mixtures of MoS2 and graphene oxide (MoS2-GO). This work suggests that the composite material of MoS2/rGO has infinite possibilities as a high-quality anode material for PIBs.

Recent progress in aqueous aluminum-ion batteries.

Aqueous aluminum-ion batteries have many advantages such as their safety, environmental friendliness, low cost, high reserves and the high theoretical specific capacity of aluminum. So aqueous aluminum-ion batteries are potential substitute for lithium-ion batteries. In this paper, the current research status and development trends of cathode and anode materials and electrolytes for aqueous aluminum-ion batteries are described. Aiming at the problem of passivation, corrosion and hydrogen evolution reaction of aluminum anode and dissolution and irreversible change of cathode after cycling in aqueous aluminum-ion batteries. Solutions of different research routes such as ASEI (artificial solid electrolyte interphase), alloying, amorphization, elemental doping, electrolyte regulation, etc and different transformation mechanisms of anode and cathode materials during cycling have been summarized. Moreover, it looks forward to the possible research directions of aqueous aluminum-ion batteries in the future. We hope that this review can provide some insights and support for the design of more suitable electrode materials and electrolytes for aqueous aluminum-ion batteries.

Robust α-Fe2O3@TiO2 Core-Shell Structures With Tunable Buffer Chambers for High-Performance Lithium Storage.

α-Fe2O3 has high potential energy storage capacity and can serve as a green and low-cost anode material for lithium-ion batteries. However, α-Fe2O3 suffers large volume expansion and pulverization. Based on DFT calculations, TiO2 can effectively maintain the integrity of the crystal structure during the discharge/charge process. Well-defined cubic α-Fe2O3 is coated with a TiO2 layer using the hydrothermal method with the assistance of oxalic acid surface treatment, and then α-Fe2O3@TiO2 with tunable buffer chambers is obtained by altering the hydrochloric acid etching time. With the joint efforts of the buffer chamber and the robust structure of the TiO2 layer, α-Fe2O3@TiO2 alleviates the expansion of α-Fe2O3 during the discharge/charge process. The optimized sample (FT-1h) achieves good cycling performance. The reversible specific capacity remains at 893.7 mA h g-1, and the Coulombic efficiency still reaches up to 98.47% after 150 cycles at a current density of 100 mA g-1. Furthermore, the reversible specific capacity can return to 555.5 mA h g-1 at 100 mA g-1 after cycling at a high current density. Hence, the buffer chamber and the robust TiO2 layer can effectively improve the cycling stability and rate performance of α-Fe2O3.

Peculiar magnetism of BiFeO3 nanoparticles with size approaching the period of the spiral spin structure.

Size effect of multiferroics is important for its potential applications in new type miniaturized multifunctional devices and thus has been widely studied. However, is there special size effect in the materials with spiral modulated spin structure (such as BiFeO3)? It is still an issue to be investigated. In this report, structural, magnetic and magnetoelectric coupling properties are investigated for sol-gel prepared BiFeO3 nanoparticles with various sizes. It is found that a structural anomaly arises for the particles with size close to the 62 nm period of the spiral modulated spin structure, which induces an obviously increased ferromagnetism. In addition, large magnetoelectric coupling effect is observed in 62 nm BiFeO3 nanoparticles. Our result provides another insight into the size effect of BiFeO3, and also a clue to the magnetic structure at nanoscale.