Jesús Santos-Peña

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

Abstract 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 Sn 0.044 C 6 . 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 Sn 0.044 C 6 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.

A LiFePO4-Based Cell with Li x ( Mg ) as Lithium Storage Negative Electrode

Lithium was electroplated on a fresh magnesium surface. The deposit was tested as a negative electrode in a cell containing LiFePO 4 as a positive electrode. The reactions that took place on charging the cell were total conversion of phospholivine into a heterosite structure and lithium deposition onto Li(Mg). On discharging, the heterosite phase was partially converted to LiFePO 4 and lithium extracted from the Li 1+x (Mg) electrode. The performance of this cell surpassed that of lithium foil as an electrode, providing higher capacities under C/10 and C/5 regimes. Several factors associated with the Li 1+x (Mg) surface and the Li/Mg interface account for this good behavior.

Negative electrodes for lithium ion batteries : Tin/silica nanocomposites obtained from chemical reduction of SnI4 grafted Si-MCM-41

In this letter, the authors are reporting a time saving and cost-effective procedure to obtain tin-MCM-41 nanocomposites. This particular method simultaneously extracted the surfactant from MCM-41 and grafted the tin precursor creating Si–O–Sn–I bonds in the pore surface. The obtained solid reacted with KBH4, yielding tin containing nanospheres (average diameter of 75nm) embedded in a silica matrix. This nanocomposite electrochemically reacted with lithium forming Li–Sn alloys at 0.6V versus Li. The silica matrix hindered the formation of large Li–Sn aggregates during the reaction. Capacities up to 340mAhg−1 could be provided by the tin/silica nanocomposite at least for 10cycles.