Silicon Nanoparticles - Polymer - Carbon Composite As Anode for Lithium Ion Battery

Silicon is a very promising anode material for next generation lithium ion battery due to its high lithiation capacity. Despite the intense research that has focused on silicon, this material has yet to demonstrate a performance that is compatible with commercial applications. The main shortcomings obstructing its commercializing are (a) the large volume change during lithiation/delithiation which leads to failure of the material, (b) its poor charge transport properties and (c) the formation of an unstable and/or insulating solid-electrolyte interphase on the active material surface. We propose a novel processing technique that allows addressing these problems using a simple and scalable manufacturing protocol. Silicon nanoparticles with an average particle size of ≤10 nm were produced by plasma enhanced chemical vapor deposition (PECVD)  and then functionalized with 12-carbon long aliphatic chains. The resulting silicon ink was composed with polyvinylpyrrolidone (PVP) and carbon nanotubes (CNTs) to give a printable dispersion which was then coated onto copper foil and annealed to produce a binder-free anode for lithium ion battery. This unique electrode structure has an average charge/discharge capacity of ~1000 mAh/g (normalized over the total weight of the coated material) for >200  deep cycles (from 1.5 to 0V) and coulombic efficiency exceeding 99.6% after few cycles. Control experiments for the same anode without PVP suggests that the presence of the polymer during thermal annealing inhibits the particle size growth and covers the silicon particles with a layer of carbon contained material, thus enhancing the stability of the anode structure. Preliminary results regarding the extension of this approach to other materials (conductive polymers and graphene flakes) will also be discussed.