Confining Ultrathin 2D Superlattices in Mesoporous Hollow Spheres Renders Ultrafast and High‐Capacity Na‐Ion Storage

• Published in: Advanced energy materials 2020-09, Vol.10 (36), p.n/a
• Main Authors: Xia, Qingbing, Liang, Yaru, Lin, Zeheng, Wang, Shiwen, Lai, Weihong, Yuan, Ding, Dou, Yuhai, Gu, Qinfen, Wang, Jia‐Zhao, Liu, Hua Kun, Dou, Shi Xue, Fang, Shaoming, Chou, Shu‐Lei
• Format: Article
• Language: English
• Subjects: 2D superlattices; Carbon; Crystallography; Flux density; intercalation pseudocapacitance; Ion storage; Kinetics; Nanospheres; Rechargeable batteries; sheet‐in‐sphere; Sodium-ion batteries; Storage batteries; Structural stability; Superlattices; Synchrotrons; titania; Titanium dioxide; Two dimensional analysis
• ISSN: 1614-6832; 1614-6840
• DOI: 10.1002/aenm.202001033

Sodium‐ion batteries have attracted ever‐increasing attention in view of the natural abundance of sodium resources. Sluggish sodiation kinetics, nevertheless, remain a tough challenge, in terms of achieving high rate capability and high energy density. Herein, a sheet‐in‐sphere nanoconfiguration of 2D titania–carbon superlattices vertically aligned inside of mesoporous TiO2@C hollow nanospheres is constructed. In such a design, the ultrathin 2D superlattices consist of ordered alternating monolayers of titania and carbon, enabling interpenetrating pathways for rapid transport of electrons and Na+ ions as well as a 2D heterointerface for Na+ storage. Kinetics analysis discloses that the combination of 2D heterointerface and mesoporosity results an intercalation pseudocapacitive charge storage mechanism, which triggers ultrafast sodiation kinetics. In situ transmission electron microscope imaging and in situ synchrotron X‐ray diffraction techniques elucidate that the sheet‐in‐sphere architecture can maintain robust mechanical and crystallographic structural stability, resulting an extraordinary high rate capability, remarkable stable cycling with a low capacity fading ratio of 0.04% per cycle over 500 cycles at 0.2 C, and exceptionally long‐term cyclability up to 20 000 cycles at 50 C. This study offers a method for the realization of a high power density and long‐term cyclability battery by designing of a hierarchical nanoarchitecture. A sheet‐in‐sphere nanoconfiguration of 2D nanosheets vertically aligned in mesoporous hollow nanosphere structured titania, which enables robust mechanical and crystallographic structural stability as well as enriched Na‐ion storage reactivity, renders unprecedented high rate capability and exceptional long‐term cycling capability up to 20 000 cycles at 50 C.