Li-ion batteries dominate the secondary battery market due to their features like high energy conversion efficiency, low self-discharge rate, wide working temperature range and no memory effect. Currently, Li-ion battery is a hot global research field. Since high capacity, cycling stable, weight-light and small batteries are highly desired by high-tech products such as electric vehicles and unmanned planes, it becomes much more significant for exploring high capacity (including gravimetric and volumetric capacities) than ever before.

A series of research progresses on nanostructured electrodes have been accomplished by Dr. LIU Jinyun and co-workers at Prof. LIU Jinhuai and Prof. HUANG Xingjiu’s group at the Institute of Intelligent Machines, Chinese Academy of Sciences. A three-dimensional nanoelectrode which possesses a high volumetric capacity was fabricated successfully; while a new mechanism for the capacity decay of nanostructured Li-ion batteries was proposed and demonstrated by modeling. Research findings have been published at top journals such as Advanced Materials, (http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-4095), ACS Nano (http://pubs.acs.org/journal/ancac3), and Small (http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1613-6829).

Nanostructured electrodes possess many fascinating features, such as highly-active electrodes, short pathway for ion diffusion and electron transfer. Researchers focus on the instinct capacity decay mechanism firstly, then construct high-capacity and stable nanoelectrodes, as well as establish a general fabrication approach. For example, a Si/C nanotube array electrode in which silicon is coated with carbon layers on both sides was proposed (Figure 1). This design can be able to reduce the influence of solid electrolyte interphase to battery stability during cycling. Through an in-situ SEM technology, the dynamic volume and structure changes of nanotubes during lithiation/delithiation was demonstrated (Figure 2). Moreover, a fatigue-induced capacity decay mechanism was put forward and demonstrated on the basis of theoretical modeling.

In addition, on the basis of the general preparation method on three-dimensional nanoelectrode, a template-free nanoelectrode was fabricated (Figure 3). Over 200 cycles, the presented electrode gave a full electrode basis capacity of about 1000 mAh cm^-3), far exceeding the current commercial graphite-based anode (550 mAh cm^-3). Such a high performance nanoelectrode enables an opportunity for the development of microscale batteries which can be applied in wearable electronics. These progresses were achieved on the basis of the collaboration between the Institute of Intelligent Machines and the University of Illinois at Urbana-Champaign. As the research is proceeding, more research progresses on the high performance nanostructured electrodes and their electrochemical properties are expected.