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SUMMARYGraphite has been used as the negative electrode in lithium-ion batteries for more than a decade. To attain higher energy density batteries, silicon and tin, which can alloy reversibly with lithium, have been considered as a replacement for graphite. However, the volume expansion of these metal elements upon lithiation can result in poor capacity retention. Alloying the active metal element with an inactive material can limit the overall volume expansion and improve cycle life. This paper presents a summary of tin-based materials as negative electrodes. After reviewing attempts to improve and understand the electrochemical behaviour of metallic tin and its oxides, the focus turns to alloys of tin with a transition metal (TM) and, optionally, carbon. To do so, a combinatorial sputtering technique was used to simultaneously prepare many different compositions of Sn-TM-based materials. The structural and electrochemical results of these samples are presented and they show that cobalt is the preferred TM to give optimal performance. Finally, a comparison of a Sn-Co-C negative electrode material prepared by a rapid quenching method (sputtering) with a material prepared by an economical milling method (mechanical attrition) is presented and discussed.

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Sodium insertion into nanostructured (Sn0.5Co0.5)1-xCx, (0.2 ≤ x ≤ 1), was investigated. This is the first report to our knowledge of an active/inactive alloy with tin being used for sodium-ion batteries. Although the cycle life of the alloy is superior to pure tin, the capacity obtained was low, compared to lithium insertion into the same material. It was found that only 8% of the tin in (Sn0.5Co0.5)1-xCx is active at 30°C, while 38% of the Sn is active at 60°C. The carbon phase in (Sn0.5Co0.5)1-xCx was found to have a capacity of about 130 mAh/g below 1.2 V and was 100% active at all temperatures measured.

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