Nanosized Alloy Anodes

At room temperature, SiNPs and SiNWs show reversible capacities of 1700 mA-h-g and 900 mA-h-g , respectively 

Due to the difficulty of synthesizing nanosized silicon at that time, SnSb alloy attracted our attention. 

Besenhard etal. prepared Sno ygSbo 22 alloy (0.56 Sn+ 0.22 SnSb] with particle size about 200 nm by electroplate and reductive precipitation. Dendrite-like nanosized pure rhombohedral phase P-SnSb alloys were obtained by reductive coprecipitation method (Fig. 5.113. The morphology and particle size can be controlled by choosing solvent, temperature, and stirring conditions.  

The cyclability of nano-SnSb is obviously better than individual Sn and Sb anode. Besenhard proposed that reacted SnSb may be embedded in unreacted soft and ductile Sn matrix (in their case, mole ratio of Sn SnSb in precursor is 0.78 0.22]. Therefore, SnSb alloy can be regarded as an active/active composite at atomic level. 

It was interesting to find that several peaks appeared in the cyclic voltammogram of nanosized SnSb alloy anode (Fig. 5.12]. It seems that Li-Sb alloy reactions occur first, followed by the Li-Sn alloy reactions. This was confirmed by ex situ XRD results as shown in Fig. 5.13. 

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Due to the continuous demand on higher energy density battery, the research on nanosized materials for Li-ion batteries was stimulated since 1996 for searching high capacity materials. In this chapter, research on the nanosized anode materials are summarized following the line of tin oxide, tin and silicon alloys, and transitional metal oxides. 

Similar to the Si anode, serious electrochemical agglomeration occurs for nano-SnSb alloy. It is not good to achieve high reversible capacity and good cyclic performance since the SEl film is covered on the particles.In order to solve this problem, nano-SnSb ahoy was deposited on surface of mesocarbon microbead (MCMB] and hard carbon spherules (HCS], respectively as shown in Fig. 5.14. It was expected and confirmed that nanosized... 

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