Pulsed Current Electrodeposition of Silicon Thin Films Anodes for Lithium Ion Battery Applications

Abstract

Electrodeposition of amorphous silicon thin films on Cu substrate from organic ionic electrolyte using pulsed electrodeposition conditions has been studied. Scanning electron microscopy analysis shows a drastic change in the morphology of these electrodeposited silicon thin films at different frequencies of 0, 500, 1000, and 5000 Hz studied due to the change in nucleation and the growth mechanisms. These electrodeposited films, when tested in a lithium ion battery configuration, showed improvement in stability and performance with an increase in pulse current frequency during deposition. XPS analysis showed variation in the content of Si and oxygen with the change in frequency of deposition and with the change in depth of these thin films. The presence of oxygen largely due to electrolyte decomposition during Si electrodeposition and the structural instability of these films during the first discharge-charge cycle are the primary reasons contributing to the first cycle irreversible (FIR) loss observed in the pulse electrodeposited Si-O-C thin films. Nevertheless, the silicon thin films electrodeposited at a pulse current frequency of 5000 Hz show a stable capacity of~805 mAh·g −1 with a fade in capacity of~0.056% capacity loss per cycle (a total loss of capacitỹ 246 mAh·g −1 ) at the end of 500 cycles.

N‐Type Doped Silicon Thin Film on a Porous Cu Current Collector as the Negative Electrode for Li‐Ion Batteries

“…However, commercialization of this amazing material is delayed by an unsolved issue of its significant volume expansion (up to 280 %) during the electrochemical reaction with lithium and the formation of lithiated Li 3.75 Si alloy. The mechanical stress occurring during alloying leads to degradation, cracking, and electrical contact loss in the electrode . Another resulting issue of Si expansion is the formation of a non‐uniform thick solid electrolyte interphase (SEI), which obstructs the movement of Li + ions, leading to capacity fading .…”

“…It has been observed that the decrease of Si particle size to the nanoscale prevents the cracking of particles . Amorphous phase Si (a‐Si) has been found to be preferable over crystalline Si, because it experiences uniform expansion during the repetitive lithiation/delilthiation reaction and mitigates the cracking of Si particles . Incorporation of dopants, especially n‐type dopants, into Si materials leads to enhanced electron mobility .…”

Electrodeposition of Silicon from Molten KCl-K2SiF6 for Lithium-Ion Batteries

“…40 However, silicon films deposited from organic electrolytes are often considered as anode material. 42,43 Information on the electrochemical properties of silicon materials synthesized from fluoridecontaining melts is poorly presented in the literature, 22,44 nevertheless there are many papers focused on synthesis alone. 45 The advantages of chloride melts with low fluorine content include the low cost and high purity of reagents, low solubility of oxides, and also the non-hygroscopic nature of the system.…”