Silicon nano-trees as high areal capacity anodes for lithium-ion batteries

• Silicon “nano-tree” structure for high surface capacities up to 7.1 mAh cm−2.
• Remarkable rate capabilities compared to high loading Si electrodes in literature.
• Excellent rate capability performance during delithiation.
• Architecture ensuring combination of high energy and high power.

Nanostructured silicon electrodes have attracted attention as a potential candidate for high capacity anode in lithium-ion batteries, thanks to their high specific capacity and their ability to accommodate silicon volume changes upon cycling. However, the silicon amount deposited on these nanostructured electrodes is generally low and leads to low surface capacities. Here, a new structure is proposed to increase the areal density of silicon on the electrode. A second growth of secondary nanowires on a silicon nanowires electrode leads to a “nano-tree” structure with surface capacities between 1.8 and 7.1 mAh cm−2. These high loaded electrodes maintain very good rate capabilities and a rather stable cycling is observed for the intermediate loadings, with a capacity maintained above 2 mAh cm−2 after 100 cycles at C/5. This paper provides evidence of a successful synthesis of high loaded silicon electrodes for practical applications, of which the electrochemical performances outperform those of graphite commercial anodes.