Controllable synthesis of hierarchical porous nickel oxide sheets arrays as anode for high-performance lithium ion batteries

Rational synthesis of silicon into polyimide-derived hollow electrospun carbon nanofibers for enhanced lithium storage

Flexible energy devices with high energy density and long cycle life are considered to be promising applications in portable electronics. In this study, silicon/carbon nanofiber (Si@CNF) core–shell electrode has been prepared by the coaxial electrospinning method. The precursors of polyimide (PI) were for the first time used to form the core–shell structure of Si@CNF, which depicts outstanding flexibility and mechanical strength. The effect of doping concentrations of silicon (Si) nanoparticles embedded in the fiber is investigated as a binder-free anode for lithium-ion batteries. A 15 wt% doped composite electrode demonstrates superior performance, with an initial reversible capacity of 621 mA h g−1 at the current density of 100 mA g−1 and a high capacity retention up to 200 cycles. The excellent cycling performance is mainly due to the carbonized PI core–shell structure, which not only can compensate for the insulation property of Si but also has the ability to buffer the volume expansion during the repeated charge–discharge process.

Bifunctional Electrocatalytic Activity of Nitrogen-Doped NiO Nanosheets for Rechargeable Zinc-Air Batteries

In order to improve the efficiencies and service lifetimes of rechargeable Zn-air batteries, it is necessary to develop highly efficient air electrocatalysts. In the present study, we prove that the bifunctional electrocatalytic activity in NiO nanosheets is effectively improved by the synergistic effects of N dopants and considerably porous structure. As an electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), the as-prepared porous N-doped NiO nanosheets exhibit good activities with the small overpotential and ideal half-wave potential, which is superior to Ir/C electrocatalyst. Besides, it is proved that the process of HO* being oxidized to O* is the OER potential rate-determining step; also the OER electrocatalytic performance of NiO can be markedly promote by the doping of N atoms using the density functional theory calculations. Furthermore, the fabricated Zn-air battery based on the porous N-doped NiO nanosheets also exhibits superior activities, outperforming many reported NiO-based electrocatalyst materials. Two series Zn-air cells with a voltage of 2.80 V can power a red light-emitting diode, which shows their large potential for various applications.

Hierarchically Nanostructured Transition Metal Oxides for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have been widely used in the field of portable electric devices because of their high energy density and long cycling life. To further improve the performance of LIBs, it is of great importance to develop new electrode materials. Various transition metal oxides (TMOs) have been extensively investigated as electrode materials for LIBs. According to the reaction mechanism, there are mainly two kinds of TMOs, one is based on conversion reaction and the other is based on intercalation/deintercalation reaction. Recently, hierarchically nanostructured TMOs have become a hot research area in the field of LIBs. Hierarchical architecture can provide numerous accessible electroactive sites for redox reactions, shorten the diffusion distance of Li-ion during the reaction, and accommodate volume expansion during cycling. With rapid research progress in this field, a timely account of this advanced technology is highly necessary. Here, the research progress on the synthesis methods, morphological characteristics, and electrochemical performances of hierarchically nanostructured TMOs for LIBs is summarized and discussed. Some relevant prospects are also proposed.

Graphitic carbon-wrapped NiO embedded three dimensional nitrogen doped aligned carbon nanotube arrays with long cycle life for lithium ion batteries

In this work, a three-dimensional nitrogen doped aligned carbon nanotube array (NACNTs)@NiO@graphitic carbon composite was fabricated by an effective strategy involving nebulized ethanol assisted infiltration, In this structure, the NiO nanoparticles were wrapped by graphitic carbon layers and NiO@graphitic carbon core–shell nanoparticles adhered strictly to the surface of NACNTs to form a highly ordered 3D structure. When this composite was used as an anode for lithium ion batteries, the well-ordered pore of its NACNTs can facilitate the electrolyte to penetrate and improve electronic conductivity. At the same time, the graphitic layers can promote the stability of a solid electrolyte interface film. Therefore, the NACNTs@NiO@graphitic carbon composite containing 68.1 wt% NiO delivers excellent capacity retention of 91.6% after 200 cycles at 0.2C.

NACNTs@NiO@graphitic carbon composites were synthesized with the help of nebulizing. The outstanding performances are attributed to the original structure of NACNTs@NiO@graphitic carbon.

ZnO Nanomembrane/Expanded Graphite Composite Synthesized by Atomic Layer Deposition as Binder-Free Anode for Lithium Ion Batteries

A zinc oxide (ZnO)/expanded graphite (EG) composite was successfully synthesized by using atomic layer deposition with dimethyl zinc as the zinc source and deionized water as the oxidant source. In the composite structure, EG provides a conductive channel and mechanical support to ZnO nanomembranes, which effectively avoids the electrode pulverization caused by the volume change of ZnO. The anodes made from the flexible composite films without using binder, conductive agent, and current collector show high stable capacities especially for that with a moderate ZnO concentration. The highest capacity stayed at 438 mAh g^-1 at a current rate of 200 mA g^-1 after 500 cycles. The good performance is considered to be due to the co-effects of the high capacity of ZnO and the support of the EG framework. Such composite structures may have great potential in low-cost and flexible batteries.