Haisheng Han,Hongyu Wang,Yongguang Zhang,Guihua Liu
Rational design of a porous sulfur host material is important to mitigate the lithium polysulfide (LiPS) shuttle effect in lithium–sulfur (Li–S) batteries. In this study, a three-dimensionally ordered macropore N-doped TiO2 embedded with dense carbon nanotubes and CoNiO nanoparticles (CNT/CoNiO@N–TiO2) is prepared as a sulfur host material. This porous structured metal oxide N–TiO2 framework offers good structural stability and polarity toward LiPS accommodation and adsorption. The in situ-grown CNT within the porous N–TiO2 provides a physical barrier for the LiPS migration and benefits the conductivity of the host material. Furthermore, the embedded CoNiO nanoparticles have high synergistic catalytic activity for the LiPS conversion. Accordingly, the sulfur-loaded CNT/CoNiO@N–TiO2 host achieves a high initial capacity of 1004 mA h g–1 at 0.2 C and excellent cycling performance with a capacity decay of 0.047% per cycle in 500 cycling test at 1.0 C. This work provides an effective strategy for the design of metal oxide-based sulfur host materials in Li–S batteries.
Bolin Zhao,Rana Muhammad Irfan,Chuhao Liu,Shamraiz Hussain Talib,Azhar Mahmood,Li Niu
Rare-earth based transition metal oxides have proved to be the most promising candidates in the exploration of non-precious oxygen evolution reaction (OER) catalysts. However, the knowledge regarding their active sites and electrocatalytic mechanism is very limited due to their different crystallization behaviors and there are still big challenges in the efficient coupling of transition and rare-earth metals with full utilization of active sites. To improve and stabilize OER catalysis, we developed the core-shell CeO 2 @CoNiO 2 nanoplates (NPLs) for enhanced and stable OER catalysis. Surprisingly, CeO 2 shell regulates the electronic structure of CoNiO 2 core and increases the number of active sites and oxygen vacancies to achieve high electrochemical performance in a three-electrode system. Compared with CoNiO 2 nanoparticles, the developed core-shell NPLs exhibit favorable performance with an overpotential of only 206 mV at 10 mA/cm 2 and robust electrochemical stability of 500 h at 10 mA/cm 2 and 300 h at 50 mA/cm 2 . In situ Raman spectroscopy unveils that CeO 2 @CoNiO 2 is structurally more stable than CoNiO 2 , which is consistent with its performance persistence. Besides, theoretical calculations confirm that the Ce shell serves as the active centers for OER, and the formed core-shell metal oxides NPLs promote the adsorption and dissociation of water, thus causing the fast generation of O 2 . This work provides a new perspective for designing highly active core-shell structure of mixed metal oxides of transition and rare-earth metals for OER.
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