Song Huawei, Cui Hao, Wang Chengxin
State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics Science and Engineering, Sun Yat-sen (Zhongshan) University , Guangzhou 510275, People's Republic of China.
ACS Appl Mater Interfaces. 2014 Aug 27;6(16):13765-9. doi: 10.1021/am503016s. Epub 2014 Jul 23.
Electrochemical pulverization, a commonly undesirable process for durable electrodes, is reinterpreted in popular yolk-shell nanostructures. In comparison with core-shell counterparts, the yolk-shell ones exhibit enhancing ion storage and rate capability for lithium ion battery anodes. The enhancement benefits from lowered activation barriers for lithiation and delithiation, improved surfaces and interfaces for ion availability contributed by endless pulverization of active materials. By controlled etching, stable cycling with significantly improved capacity (∼800 mAh g(-1) at 0.1 A g(-1), 600 mAh g(-1) at 0.5 A g(-1), and 490 mAh g(-1) at 1 A g(-1) vs 140 mAh g(-1) at 0.1 A g(-1)) is achieved at various rates for Ni@Graphene yolk-shell structures. Meanwhile, large rate of 20 A g(-1) with capacity of 145 mAh g(-1) is retained. Given initial pulverization for the activation, the tailored electrodes could stably last for more than 1700 cycles with an impressive capacity of ca. 490 mAh g(-1) at 5 A g(-1). Insights into electrochemical processes by TEM and STEM reveal dispersive pulverized active nanocrystals and the intact protective graphene shells play the leading role.
电化学粉碎，这一通常对耐用电极不利的过程，在常见的蛋黄壳纳米结构中得到了重新诠释。与核壳结构相比，蛋黄壳结构在锂离子电池负极方面展现出增强的离子存储能力和倍率性能。这种增强得益于锂化和脱锂的活化能降低，以及活性材料不断粉碎所带来的离子可及性更好的表面和界面。通过可控蚀刻，对于镍@石墨烯蛋黄壳结构，在不同倍率下实现了稳定循环，且容量显著提高（0.1 A g⁻¹ 时约为800 mAh g⁻¹，0.5 A g⁻¹ 时为600 mAh g⁻¹，1 A g⁻¹ 时为490 mAh g⁻¹，而在0.1 A g⁻¹ 时为140 mAh g⁻¹）。同时，在20 A g⁻¹ 的大倍率下仍保留了145 mAh g⁻¹ 的容量。鉴于初始粉碎用于活化，定制的电极在5 A g⁻¹ 时能够稳定循环超过1700次，容量高达约490 mAh g⁻¹，令人印象深刻。通过透射电子显微镜（TEM）和扫描透射电子显微镜（STEM）对电化学过程的深入研究表明，分散的粉碎活性纳米晶体和完整的保护性石墨烯壳起到了主导作用。
