Practical anodes for Li-ion batteries comprising metallurgical silicon particles and multiwall carbon nanotubes

Silicon is considered to be a very attractive anode material for next-generation lithium-ion batteries due to its high theoretical capacity (4200 mAh g of silicon for a stoichiometry of Li_4.4Si) and the abundance of silicon in the Earth’s crust. To overcome some of the fundamental challenges of silicon anodes (such as conductivity and volume expansion effects in the anodes), multiwall carbon nanotubes (MWCNT) were added to the metallurgical silicon anode material. The superior properties of CNT, as well as their low density and enormous aspect ratio, make them ideal candidates for reinforcement and conductive additives for composite electrodes. The selection of appropriate binder and electrolyte solution is also very important for achieving good performance Li-Si anodes. Here, we report the use of micrometer-sized metallurgical Si particles as the anode material in Li-ion batteries, with MWCNT in the composite electrodes. With 5% MWCNT, the first cycle efficiency was 90%. These Si anodes demonstrated average cycling efficiency of 99.5% and reasonable capacity retention during prolonged cycling. Full cells with LiNi_0.8Co_0.15Al_0.05O₂ cathodes were also demonstrated. We believe that upon optimization, such composite silicon electrodes based on relatively cheap and available materials, in terms of both additives (CNT) and binders, may be used as promising practical anodes for Li-ion batteries.