Search

Here, we report a new enhanced extrinsic pseudocapacitve Li-ion storage mechanism via lithiation-induced structural optimization strategy. The flower-like C@SnS and bulk SnS exhibit initial capacity decay and subsequent increase of capacity on cycling. After a long-term lithiation/delithiation process, flower-like C@SnS and bulk SnS exhibit improved rate performance and reversible capacity in comparison with those of initial state. Moreover, a high capacity of 530 mAh g −1 is still remained even after 1550 cycles at a high current density of 5.0 A g −1 for flower-like C@SnS after pre-lithiation of 350 cycles. According to the comprehensive analysis of structural evolution and electrochemical performance, it demonstrates that SnS electrodes experience crystal size reduction and further amorphization on cycling, which enhances the reversibility of conversion reaction for SnS, leading to increasing capacity. On the other hand, surface-dominated extrinsic pseudocapacitive contribution results in enhanced rate performance because electrodes expose a large fraction of Li + sites on surface or near-surface region with structural optimization on cycling. This study reveals that extrinsic pseudocapacitance of SnS can be stimulated via lithiation-induced structural optimization, which gives rise to high-rate and long-lived performances.

Enhancing the conductivity of electrode materials is critically important for improving the high-rate performance of Na-ion batteries (NIBs). Herein, we report a multifaceted strategy for optimizing the conductivity and electrochemical properties of nickel cobalt selenides via the combination of fine component regulation and C coating. The electrical conductivity of C@Ni0.33Co0.67Se2/C nanofiber (CNF) (Co0.67) hybrids achieved in this study was 0.3733 S mm−1, a conductivity five-fold higher than that of selenides with a Ni/Co ratio of 2 : 1. Coupled with desirable three-dimensional (3D) nanobrush morphology and the 1D conducting path of CNFs, the Co0.67 electrode achieved a superior rate performance of 413.1 mA h g−1, even at 2 A g−1. Furthermore, the Co0.67 electrode exhibited an impressive cycling performance of 499 mA h g−1 after 100 cycles (exhibiting an 89.5% capacity retention of the second cycle). Finally, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry analysis at different sweep rates were conducted to demonstrate the Co0.67 electrode's fast charge/ion transport ability and increased electrode kinetics.

In this article, tufted NiCo 2 O 4 nanoneedles directly grown on carbon nanofibers (CNFs) were successfully fabricated by a facile hydrothermal procedure and subsequent annealing. The morphology of tufted NiCo 2 O 4 nanoneedles/carbon nanofibers (TNN/CNFs) composite appears like clustered acicular leaves on branches, forming a unique three dimensional (3D) hybrid structure. Compared to NiCo 2 O 4 nanoneedles spheres (NNS) without CNFs, the TNN/CNFs material presents a reversible discharge specific capacity up to 1033.6 mAh g −1 at a current density of 200 mA g −1 even after 250 cycles, with the coulombic efficiency of above 98%. The unique 3D hybrid structure formed with CNFs should be responsible for the superior lithium storage capacity and enhanced cycling performance, which provides short distance for ions transport, high specific surface area for large contact areas between electrode and electrolyte, together with the interspace to accommodate volume change and smaller agglomeration tendency. Moreover, the design route proposed offers more possibility to preparation of high-performance anode materials for LIBs.

Carbon coated SnS/SnO2 heterostructures wrapping on carbon nanofibers (C@SnS/SnO2@CNFs) was demonstrated to have excellent performance as an anode material for Li-ion batteries. C@SnS/SnO2@CNFs electrode delivers high reversible capacity of 826.8 mA h g–1 (500th cycle) at the current density of 1.0 A g–1. However, an interesting phenomenon of increasing capacity on cycling can be observed. According to the analysis of the evolution of structure and electrochemical property, C@SnS/SnO2@CNFs is demonstrated to experience the progress of conversion from nanowalls containing polycrystals into amorphous nanosheets with high porosity and larger surface upon cycling. The above lithiation-induced structural optimization provides larger effective surface areas and encourages the conversion reactions, which can promote charge transfer and also enhance the reversibility of the conversion reactions of SnS and SnO2 inducing the increasing reversible capacity. The study explains the progress of increasing capacity of C...

A novel heterostructured cathode material, comprised of a core of Li-rich layered (Rm) oxides integrated with Li+-conductive Li2SiO3 and an in situ formed spinel (Fdm) nano-coating layer, has been successfully synthesized. The ionic conductor Li2SiO3 in the bulk facilitates the Li+ intercalation/deintercalation process and stabilizes the layered structure. This is coupled with the fast 3D Li+ diffusion channels of an electrochemically active spinel coating layer, leading to superior rate capability (94 mA h g−1 at 10C) and excellent cycling stability in the heterostructured cathode material. This synergistic strategy may provide some new directions for synthesizing high-performance Li-ion battery cathode materials.