Search

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]

To increase cycle life and reduce costs for natural graphite anode, graphite tailings grafted with polyether amine (PEA) is prepared for artificial solid electrolyte interphase (SEI). The complex of PEA and Li+ has a well-tuned lowest unoccupied molecular orbital (LUMO) energy (0.216 eV∼-0.239 eV) to improve the chemical stability of SEI components, effectively hinders electron transfer from anode to electrolyte, and inhibits electrolyte decomposition. Meanwhile, the strong adsorption between Li+ and PEA enhances the de-solvation ability of SEI, thus improving the rate performance of the anode. After 1000 cycles, the capacity retention of the anode material with grafted PEA molecular weight of 2000 is increased from 22% to 98%. The method can also improve rate performance for graphite anode, with the capacity retention rate at a current density of 1 A g−1 (vs. 0.1 A g−1) increasing from 42% to 72%. As expected, the full cell life with LiFePO 4 as the cathode material is significantly extended, the capacity retention improved from 44% to 77% after 200 cycles. [ABSTRACT FROM AUTHOR]