Search for suitable matrix for the use of tin-based anodes in lithium ion batteries

Graphite is proposed as matrix for tin which is able to react inside the graphite sheets with lithium. If this matrix should be able to support the cell changes associated to the formation of lithium–tin alloys, an improvement of the performance of the lithium ion battery anode would be expected. Two techniques, (vapor phase and molten salt techniques, respectively) have been considered to obtain graphite intercalation compounds (GIC) with tin chlorides. The subsequent reduction of these systems with hydrogene at 400°C must lead to tin GICs. Due to the little extent of the intercalation reaction, the obtained compounds possess a maximal composition of Sn0.044C6. Despite the small amount of intercalated tin, potentiostatic tests reveal that both tin and graphite are electrochemically active versus lithium. Galvanostatic tests indicate that the contribution of tin to the system total capacity increases for the molten salt samples and remains almost constant for the vapor phase samples. This behavior seems to indicate that the activity of tin intercalated atoms is very stable compared to pure graphite. The upper capacity found, 400 mAh/g, corresponds to the Sn0.044C6 system, obtained by the molten salt technique. Its good electrochemical properties agree with our idea that graphite is an adequate matrix for the tin atoms or clusters presents therein.