Optimizing the Composition of the Cu/Si Thin Film Anodes Produced via Magnetron Sputtering

Abstract

The reversible cyclability of Si based composite anodes is greatly improved by optimizing the atomic ratio of Cu/Si in the films fabricated via magnetron sputtering. The galvanostatic test results show that the thin film anode made of 20%at. Cu delivers 1950 mAhg-1 as the initial discharge capacity with 80% Coulombic efficiency. Then, after the 50th cycles 80% of the initial discharge capacity is retained, with 99.5 % Coulombic efficiency. This remarkable performance can be explained by small crystalline sizes, amorphous structures of the thin film and its enhanced physical and mechanical properties due to the 20 %at. Cu content. High specific capacities achieved in this study prove that magnetron sputtering deposition might be a good alternative production technique to fabricate high performance anode materials. Furthermore, this one step, environmentally friendly process enables one to control the film composition, structure as well as adhesion which minimizes delamination and pulverization.

Improving Electrochemical Performance of CuSi Thin Film by Depositing Cu Thin Film via Magnetron Sputtering

“…The cracks are formed during the first lithiation reactions, then such cracks propagate and widen when cycling continues, resulting in lower coulombic efficiency and a continuous decay in the capacity. The trends seen in the capacity-cycle data of the bare SiCu thin film is close to that of the one we mentioned in our previous study [15]. However, since this film is thicker (around 2 microns) than what was tested (1.3 micron) previously, its performance is noted weaker than the thinner film, as expected.…”

Copper-Nanoparticle-Induced Porous Si/Cu Composite Films as an Anode for Lithium Ion Batteries

“…Third, the amorphous feature of the Si active layer can release mechanical strain more effectively than ordered crystalline Si because of the more homogeneous volume change associated with the inherent isotropic feature of amorphous materials, which plays a positive role in the improvement of structure stability and cycling performance. 40,41 Finally, the absence of any binders that are always electrical insulators due to the binder-free film-based anodes benefits the electronic conductivity and thus the performance of batteries. 42,43 Increasing the mass loading of active materials is of great importance to achieve high-energy lithium ion batteries.…”

“…Second, the predeposited Cu nanoparticle-assembled film not only acts as the growth direction template but also can strengthen the overall electronic conductivity and prohibit the volume variation of Si active materials to some extent, benefiting the improvement of rate capability and cycling stability. , In addition, the rough substrate (the predeposited Cu-nanoparticle-assembled film) also benefits the effective anchoring of the subsequently deposited Si active layer. Third, the amorphous feature of the Si active layer can release mechanical strain more effectively than ordered crystalline Si because of the more homogeneous volume change associated with the inherent isotropic feature of amorphous materials, which plays a positive role in the improvement of structure stability and cycling performance. , Finally, the absence of any binders that are always electrical insulators due to the binder-free film-based anodes benefits the electronic conductivity and thus the performance of batteries. , …”

Nanocolumnar-Architectured, Layered Cu/Si Film as Anodes for Rechargeable LIB

“…Moreover, an unstable solid electrolyte interface (SEI) formation on the Si anode is another problem causing a rapid decay in capacity [3]. Recently, different assumptions have been made to design Si electrodes [4][5][6]. One of them is using low dimensional structured Si (such as nanotubes, nanowires, nanocolumns, thin films) to decrease the tendency for crack initiation and propagation.…”

“…However, deciding the amount of Cu added into the Si film is a challenging task since Cu being electrically inactive versus Li decreases the initial discharge capacity of the anode. Thereby, some researchers have co-deposited limited amount of Cu with Si [6] or have changed the composition (the ratio of Cu/Si) along the film thickness to form graded nanostructures with low Cu content [23][24]. In this work to benefit from the advantageous of Cu while using it in a very limited amount, we deposit very thin (around 20nm) Cu layer on Si nanocolumn arrays by OAD method.…”