Abstract
We have found that the addition of tin nanoparticles to a silicon-based anode provides dramatic improvements in performance in terms of both charge capacity and cycling stability. Using a simple procedure and off-the-shelf additives and precursors, we developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface. Even a minor addition of tin, as small as ∼2% by weight, results in a significant decrease in the anode resistance, as confirmed by electrochemical impedance spectroscopy. This leads to a decrease in charge transfer resistance, which prevents the formation of electrically inactive “dead spots” in the anode structure and enables the effective participation of silicon in the lithiation reaction.
Highlights
Silicon has been intensively investigated as generation anode material for lithium ion batteries because of its high lithiation capacity and because it is generally considered an earth-abundant, non-toxic material[1,2,3,4,5,6]
We have used commercial silicon particles and off-the-shelf additive such as tin dichloride and PVP to realize anodes that show good performance in both capacity and stability. These structures show a dramatic improvement compared to those prepared without tin
Electrochemical impedance spectroscopy (EIS) measurements suggest that these composites have overall lower active layer resistance compared to the silicon-only case
Summary
Silicon has been intensively investigated as generation anode material for lithium ion batteries because of its high lithiation capacity and because it is generally considered an earth-abundant, non-toxic material[1,2,3,4,5,6]. Promising results have been attained by over-coating silicon nanostructures with carbon layers either via chemical vapor deposition[20,21] or by thermally decomposing a polymer additive[10] It is well-known that the conductivity of silicon-based active layers can be improved by increasing the weight fraction of conductive carbon-based additives such as nanotubes or carbon black, but this approach inevitably “dilutes” the active layer, i.e. decreases its average gravimetric and volumetric capacity[22,23]. This last consideration motivates this study: tin has significantly higher electrical conductivity compared to silicon (10−7 Ω·m versus 2 × 103 Ω·m). The same mesoporous, silicon-based structure would rapidly fail upon cycling without the addition of tin
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