Increased Cycling Efficiency and Rate Capability of Copper-coated Silicon Anodes in Lithium-ion Batteries

TL;DR

This study demonstrates that copper coating on silicon anodes improves cycling efficiency and rate capability in lithium-ion batteries by preventing silicon particle isolation and reducing capacity fade, with optimal coating thickness being crucial.

Contribution

It introduces a copper coating method that enhances silicon anode performance by improving structural integrity and electronic connectivity, which was not previously well understood.

Findings

Copper-coated silicon electrodes show 8-18% less energy loss at various discharge rates.

Higher cycling efficiency and lower capacity fade with copper coating.

Optimal copper coating thickness is essential for maximizing capacity and rate performance.

Abstract

Cycling efficiency and rate capability of porous copper-coated, amorphous silicon thin-film negative electrodes are compared to equivalent silicon thin-film electrodes in lithium-ion batteries. The presence of a copper layer coated on the active material plays a beneficial role in increasing the cycling efficiency and the rate capability of silicon thin-film electrodes. Between 3C and C/8 discharge rates, the available cell energy decreased by 8% and 18% for 40 nm copper-coated silicon and equivalent silicon thin-film electrodes, respectively. Copper-coated silicon thin-film electrodes also show higher cycling efficiency, resulting in lower capacity fade, than equivalent silicon thin-film electrodes. We believe that copper appears to act as a glue that binds the electrode together and prevents the electronic isolation of silicon particles, thereby decreasing capacity loss. Rate capability decreases significantly at higher copper-coating thicknesses as the silicon active-material is not accessed, suggesting that the thickness and porosity of the copper coating need to be optimized for enhanced capacity retention and rate capability in this system.