Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca , via Cozzi 55, 20125 Milano, Italy.
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari Venezia and Centro di Microscopia Elettronica "G. Stevanato" , Via Torino 155/b, 30172 Venezia-Mestre, Italy.
Nano Lett. 2017 Feb 8;17(2):992-1000. doi: 10.1021/acs.nanolett.6b04347. Epub 2017 Jan 6.
Rechargeable sodium-ion batteries are becoming a viable alternative to lithium-based technology in energy storage strategies, due to the wide abundance of sodium raw material. In the past decade, this has generated a boom of research interest in such systems. Notwithstanding the large number of research papers concerning sodium-ion battery electrodes, the development of a low-cost, well-performing anode material remains the largest obstacle to overcome. Although the well-known anatase, one of the allotropic forms of natural TiO, was recently proposed for such applications, the material generally suffers from reduced cyclability and limited power, due to kinetic drawbacks and to its poor charge transport properties. A systematic approach in the morphological tuning of the anatase nanocrystals is needed, to optimize its structural features toward the electrochemical properties and to promote the material interaction with the conductive network and the electrolyte. Aiming to face with these issues, we were able to obtain a fine tuning of the nanoparticle morphology and to expose the most favorable nanocrystal facets to the electrolyte and to the conductive wrapping agent (graphene), thus overcoming the intrinsic limits of anatase transport properties. The result is a TiO-based composite electrode able to deliver an outstandingly stability over cycles (150 mA h g for more than 600 cycles in the 1.5-0.1 V potential range) never achieved with such a low content of carbonaceous substrate (5%). Moreover, it has been demonstrated for the first time than these outstanding performances are not simply related to the overall surface area of the different morphologies but have to be directly related to the peculiar surface characteristics of the crystals.
可充电钠离子电池由于其丰富的钠原料，在储能策略中正在成为锂离子技术的可行替代品。在过去的十年中，这种电池引起了研究兴趣的激增。尽管有大量关于钠离子电池电极的研究论文，但开发低成本、性能良好的阳极材料仍然是最大的障碍。尽管最近有人提出将锐钛矿（TiO 的一种同素异形体）用于此类应用，但由于动力学上的限制和较差的电荷传输性能，该材料通常循环性能较差，功率有限。需要对锐钛矿纳米晶体的形态进行系统的调整，以优化其结构特征，使其电化学性能得到优化，并促进材料与导电网络和电解质的相互作用。为了解决这些问题，我们能够对纳米颗粒的形态进行微调，并使最有利的纳米晶面暴露在电解质和导电包裹剂（石墨烯）中，从而克服了锐钛矿传输特性的固有限制。结果是得到了一种基于 TiO 的复合电极，它能够在循环中提供出色的稳定性（在 1.5-0.1 V 的电位范围内，超过 600 个循环的 150 mA h g-1），这是以前从未用如此低含量的碳质基底（5%）实现的。此外，首次证明这些出色的性能不仅仅与不同形态的总表面积有关，而是与晶体的特殊表面特性直接相关。
