SiNW Composite Electrodes

1 Supercritical fluid-liquid-solid SiNW/carbon composite electrodes 

Similar to the example with the SiNP/SiNW electrode, the contact between adjacent NWs may be impeded by the native oxide. Carbon coating ° of battery materials has been frequently used to improve the electron flux to the surface of the Li insertion 

The galvanostatic cycling data of the SFLS SiNW electrodes with different slurry compositions are shown in Fig. 1.38. The first charge capacity has been omitted for clarity, but the charge and discharge capacities for the first three cycles are shown in the inset. The uncoated SiNWs mixed with carbon black and binder at a weight 

The large irreversible capacity loss may also be due to NWs losing electronic contact after the initial volume change. An SEM image of the electrode is shown in Fig. 1.37a, with the inset image showing the CB particles alone. Because the size of the carbon particles was on the same order as the size of the SiNWs, the CB did not form a percolating network with the SiNWs. Rather, the particles only made contact to some of the NWs. 

SEM images of SFLS SiNWs mixed with (a) carbon black and [b] MWNTs. Reprinted with permission from Ref. 70. Copyright 2010, American Chemical Society. 

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Nonetheless, the SFLS SiNW/MWNT composite electrode still displays better performance than other reports in the literature that used ball-milling or ultrasonication of Si and CNTs or direct CVD growth " " of CNTs onto Si. These techniques are energy-intensive and require many steps. Our procedure shows that better performance can be achieved using simple mixing. We attribute this improvement to the good conductivity and connectivity of the... 

Structural integrity and electronic conductivity throughout the SiNW electrode. Several example strategies using core-shell structures and composites are described in the following sections. 

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