Mesoporous Silicon Nanostructures by Pulsed Laser Deposition as Li-ion Battery Anodes

Silicon is very attractive as active material for Li-ion battery anodes due to its high theoretical capacity, but proper nanostructuring is needed to accommodate the large volume expansion/shrinkage upon reversible cycling. This would overcome the destructuration induced by the lithiation/delithiation processes, often resulting in poor long-term performance. Hereby, novel mesoporous silicon nanostructures are grown at room temperature by Pulsed Laser Deposition (PLD) directly on top of the Cu current collector surface, and their promising electrochemical behaviour demonstrated in lab-scale lithium cells. Depending on the porosity, easily tunable by PLD, initial specific capacities approaching 300 Ah/cm2 are obtained with a quasi-stable reversible cycling. Engineering voids at the nanoscale, by direct introduction of specific porosity during growth, opens up the route for the effective use of silicon as lithium battery anode without the need for any binder or conductive additive which would lower the overall energy density

Room Temperature Fabrication of Silicon Nanocrystals by Pulsed Laser Deposition

In this work a room temperature single-step physical vapour deposition process is presented for the fabrication of nanosized Si crystals (diameter below 10 nm) embedded in an amorphous matrix, together with unique novel nanostructures consisting of silicon amorphous-crystalline core-shell nanostructures. Pulsed laser deposition in a background atmosphere (Ar or a mixture of < 3 vol. % of H2 in Ar) is used to induce cluster nucleation in the gas phase and to vary the deposition kinetic energy, in order to grow Si films of different morphology and porosity, at the nanoscale, as a function of gas pressure. Relatively high-pressure processing (100 Pa) leads to a hierarchically nanostructured film composed of Si nanocrystals embedded in a columnar porous amorphous matrix, as assessed by high resolution transmission electron microscopy. Raman spectroscopy analysis shows quantum-confinementinduced shift of the Si peak at 520 cm-1, thus confirming the occurrence of nanocrystals. Finally, in-situ silicon oxidation has been effectively shown to be decreased after adaptation of a mixture of few-percent-hydrogen in argon as background gas

Silicon Algae with Carbon Topping as Thin-film Anodes for Lithium-ion Microbatteries by a Two-step facile Method

Silicon-based electrodes for Li-ion batteries (LIB) attract much attention because of their high theoretical capacity. However, their large volume change during lithiation results in poor cycling due to mechanical cracking. Moreover, silicon can hardly form a stable solid electrolyte interphase (SEI) layer with common electrolytes. We present a safe, innovative strategy to prepare nanostructured silicon-carbon anodes in a two-step process. The nanoporosity of Si films accommodates the volume expansion while a disordered graphitic C layer on top promotes the formation of a stable SEI. This approach shows its promises: carbon-coated porous silicon anodes perform in a very stable way, reaching the areal capacity of ~175µAh cm-2, and showing no decay for at least 1000 cycles. With requiring only a two-step deposition process at moderate temperatures, this novel very simple cell concept introduces a promising way to possibly viable up-scaled production of next-generation nanostructured Si anodes for lithium-ion microbatteries