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Tin diselenide, a promising anode material for sodium ion batteries (SIBs), still faces sluggish Na+ diffusion kinetics and severe volume change, resulting in undesirable cycling stability and rate capability. Heterostructure construction is an effective strategy for boosting Na+ storage of SnSe2. Herein, an appealing yolk‐shell nanostructure of SnSe2/NiSe2 heterointerface with rich Se vacancies embedded into N‐doped carbon (SnSe2/NiSe2@NC) is precisely designed through a facile hydrothermal process followed by a selenization strategy. The experimental studies coupled with theoretical calculations results verify that the heterostructure interfaces and Se vacancies accelerate the charge and Na+ transfer efficiency, improve Na+ adsorption energy and supply ample active sites. The yolk‐shell nanostructure and N‐doped carbon buffer the volume variation and improve the structural stability of the electrode material during sodium storage processes. The SnSe2/NiSe2@NC delivers ultra‐long term cycling stability (322.7 mAh g−1 after 7500 cycles at 3 A g−1) and exceptional rate capability (314.6 mAh g−1 at 10 A g−1). The Na‐ion storage mechanism of SnSe2/NiSe2@NC is explored through in situ X‐ray diffraction and ex situ high‐resolution transmission electron microscopy analysis. The present work provides an effective avenue to the rational design of heterostructure anode materials for high efficiency SIBs. [ABSTRACT FROM AUTHOR]

This work reports the preparation of unique hierarchical yolk/double‐shelled SiOx@TiO2@C nanospheres with different voids by a facile sol‐gel method combined with carbon coating. In the preparation process, SiOx nanosphere is used as a hard template. Etch time of SiOx yolk affects the morphology and electrochemical performance of SiOx@TiO2@C. With the increase in etch time, the yolk/double‐shelled SiOx@TiO2@C with 15 and 30 nm voids and the TiO2@C hollow nanospheres are obtained. The yolk/double‐shelled SiOx@TiO2@C nanospheres exhibit remarkable lithium‐ion battery performance as anodes, including high lithium storage capacity, outstanding rate capability, good reversibility, and stable long‐term cycle life. The unique structure can accommodate the large volume change of the SiOx yolk, provide a unique buffering space for the discharge/charge processes, improve the structural stability of the electrode material during repeated Li+ intercalation/deintercalation processes, and enhance the cycling stability. The SiOx@TiO2@C with 30 nm void space exhibits a high discharge specific capacity of ≈1195.4 mA h g−1 at the current density of 0.1 A g−1 after 300 cycles and ≈701.1 mA h g−1 at 1 A g−1 for over 800 cycles. These results suggest that the proposed particle architecture is promising and may have potential applications in improving various high performance anode materials. [ABSTRACT FROM AUTHOR]

At present, lithium-ion batteries (LIBs) have received widespread attention as substantial energy storage devices; thus, their electrochemical performances must be continuously researched and improved. In this paper, we demonstrate a simple self-template solvothermal method combined with annealing for the synthesis of NiFe2O4 yolk-shell (NFO-YS) and NiFe2O4 solid (NFO-S) nanospheres by controlling the heating rate and coating them with a carbon layer on the surface via high-temperature carbonization of resorcinol and formaldehyde resin. Among them, NFO-YS@C has an obvious yolk-shell structure, with a core-shell spacing of about 60 nm, and the thicknesses of the NiFe2O4 shell and carbon shell are approximately 15 and 30 nm, respectively. The yolk-shell structure can alleviate volume changes and shorten the ion/electron diffusion path, while the carbon shell can improve conductivity. Therefore, NFO-YS@C nanospheres as the anode materials of LIBs show a high initial capacity of 1087.1 mA h g−1 at 100 mA g−1, and the capacity of NFO-YS@C nanospheres impressively remains at 1023.5 mA h g−1 after 200 cycles at 200 mA g−1. The electrochemical performance of NFO-YS@C is significantly beyond NFO-S@C, which proves that the carbon coating and yolk-shell structure have good stability and excellent electron transport ability. [ABSTRACT FROM AUTHOR]

Transition metal selenides (TMSes) are considered promising candidates for the anodes of sodium‐ion batteries (SIBs) due to their substantial theoretical capacity. However, TMSes still face with inferior cycling lifespan caused by sluggish Na+ diffusion kinetics and vigorous volume variations during dis/charge processes. Engineering heterostructure is an attractive solution for rapid Na+ transfer, and introducing carbonaceous materials also facilitates enhanced conductivity and structural stability. Herein, CoSe/MoSe2 heterostructure combined with homogeneous carbon composites are rational designed. The kinetic analysis and theoretical calculations verified that heterointerface engineering induced build‐in electric field effect can amplifies the Na+ diffusion kinetics, while carbon contributes to enhanced electrical conductivity and structural stability. Expectedly, the CoSe/MoSe2‐C exhibits high capacity and extremely ultra‐long lifespan (320.9 mAh g−1 at 2.0 A g−1 over 10,000 cycles with an average decay of only 0.01781 mAh g−1 per cycle). Furthermore, in situ X‐ray diffraction (XRD), ex situ X‐ray photoelectorn (XPS), and high‐resolution electron microscopy (HRTEM) are exploited to explore the Na+ storage mechanism. In addition, the Na3V2(PO4)3@rGO//CoSe/MoSe2‐C (NVP@rGO//CoSe/MoSe2‐C) pouch‐type full‐cells are successfully assembled and delivered satisfactory performance. This research presents a viable strategy for the targeted engineering of TMSes aimed at enhancing the efficiency of SIBs. [ABSTRACT FROM AUTHOR]