American Chemical Society
nn0c05925_si_001.pdf (2.01 MB)

Enhancing Na-Ion Storage at Subzero Temperature via Interlayer Confinement of Sn2+

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journal contribution
posted on 2020-10-07, 12:35 authored by Lan-Fang Que, Fu-Da Yu, Yang Xia, Liang Deng, Kokswee Goh, Chang Liu, Yun-Shan Jiang, Xu-Lei Sui, Zhen-Bo Wang
Sluggish kinetics and limited reversible capacity present two major challenges for layered titanates to achieve satisfactory sodium-ion storage performance at subzero-temperatures (subzero-T). To facilitate sodiation dynamics and improve reversible capacity, we proposed an additive-free anode with Sn­(II) located between layers. Sn-5s in interlayer-confining Sn­(II), which has a larger negative charge, will hybridize with O-2p to trigger charge redistribution, thereby enhancing electronic conductivity. H-titanates with an open framework are designed to stabilize Sn­(II) and restrain subsequent volume expansion, which could potentially surpass the capacity limitation of titanate-based materials via a joint alloying–intercalation reaction with high reversibility. Moreover, the generation of conductive Na14Sn4 and the expansion of interlayer spacing resulting from the interlayered alloying reaction are beneficial for charge transfer. These effects synergistically endow the modified sample with a considerably lower activation energy and a 3-fold increase in diffusion. Consequently, the designed anode delivers excellent subzero-T adaptability when compared to the unmodified sample, maintaining capacity retention of 91% after 1200 cycles at −20 °C and 90% after 850 cycles at −30 °C.