Atomically Dispersed Dual-Site Cathode with a Record High Sulfur Mass Loading for High-Performance Room-Temperature Sodium–Sulfur Batteries

Room-temperature sodium–sulfur (RT-Na/S) batteries possess high potential for grid-scale stationary energy storage due to their low cost and high energy density. However, the issues arising from the low S mass loading and poor cycling stability caused by the shuttle effect of polysulfides seriously limit their operating capacity and cycling capability. Herein, sulfur-doped graphene frameworks supporting atomically dispersed 2H-MoS₂ and Mo₁ (S@MoS₂-Mo₁/SGF) with a record high sulfur mass loading of 80.9 wt.% are synthesized as an integrated dual active sites cathode for RT-Na/S batteries. Impressively, the as-prepared S@MoS₂-Mo₁/SGF display unprecedented cyclic stability with a high initial capacity of 1017 mAh g⁻¹ at 0.1 A g⁻¹ and a low-capacity fading rate of 0.05% per cycle over 1000 cycles. Experimental and computational results including X-ray absorption spectroscopy, in situ synchrotron X-ray diffraction and density-functional theory calculations reveal that atomic-level Mo in this integrated dual-active-site forms a delocalized electron system, which could improve the reactivity of sulfur and reaction reversibility of S and Na, greatly alleviating the shuttle effect. The findings not only provide an effective strategy to fabricate high-performance dual-site cathodes, but also deepen the understanding of their enhancement mechanisms at an atomic level.     

Details of an imaging atom probe

An imaging atom probe has been incorporated in a conventional field ion microscope in our laboratory. The principle and instrumentation of the probe has been discussed.     

Ni对RPV模拟钢中富Cu原子团簇析出的影响

用原子探针层析技术和时效模拟方法,研究了不同N i含量并且提高了Cu含量的反应堆压力容器(RPV)用模拟钢中富Cu、富N i和富Mn原子团簇的形成。结果表明,提高钢中的N i含量会促使富Cu原子团簇的析出,富Cu原子团簇中含有N i和Mn。实验检测到富N i的原子团簇,团簇中含有Cu和Mn,富N i原子团簇可以作为富Cu原子团簇析出时的形核区。实验还检测到富Mn原子团簇,当Mn原子团簇中含有较高的N i时,它也可以成为富Cu原子团簇析出时成核的地方。由于钢中的合金元素N i在形成富N i原子团簇后会成为富Cu原子团簇析出时成核区,因而提高N i的含量将促进富Cu原子团簇的析出,这是合金元素N i会增加压力容器钢中子辐照脆化敏感性的本质原因。     

Cu clusters evolvement in Fe-1.18% Cu binary alloy

Microstructure evolution of Fe-1.18%Cu binary alloy during solution and aging at 550°C was investigated under a high-resolution electron microscopy (HREM). In addition, the aging strengthening mechanism was investigated based on the precipitation strengthening theory. Results show that there were lots of Cu atom clusters in the ferrite matrix during solid solution and initial aging stage, and Cu-rich metastable Fe-Cu particles precipitate subsequently at the aging hardness peak. It is found that there were high-density dislocations and stacking fault substructure in the Cu clusters that forms the obstacle of the dislocation motion, which should be the dominant reason of strengthening in the Fe-Cu alloy.     

纳米团簇碰撞合并过程的分子动力学模拟

一直以来,金属纳米材料有着非常重要的应用价值且受到广泛关注,金属团簇碰撞合并过程的研究成果对认清团簇的沉积和纳米金属膜及块体材料的形成有重要的意义。采用Johnson的嵌入原子势(Embeded atom method,EAM)模型并结合分子动力学模拟方法,模拟金原子团簇在不同的碰撞平动速度作用下的碰撞合并过程,仅给弹团簇一定大小的碰撞动能,迫使两个团簇产生相对速度并发生相互碰撞合并,研究在不同的碰撞平动速度下和不同的团簇大小下对团簇碰撞合并过程产生的影响及对碰撞合并之后新团簇的性质产生的影响。在进行模拟碰撞之前,先对团簇进行了\"退火\"处理,只模拟了同等尺度大小的两个金原子团簇之间的碰撞合并过程。