High-density lithium-ion cells with silicon anodes and various commercial cathodes for automotive applications

P. Selinis, Filippos Farmakis, C. Elmasides, DimitriosTsiplakidis, Stella Mpalomenou.
2016. 8th German Symposium Advanced Battery Development for Automotive and Utility Applications and their Electric Power Grid, Muenster, April 2016

Abstract: As more and more applications require high energy density electrochemical storage systems, Lithium-ion batteries with silicon-based anodes provide promising electrochemical properties. Silicon's high theoretical specific capacity to lithium (more than 3800 mAh/g at room temperature), environmental friendliness, low potential compared to lithium and material abundance turns silicon to a strong candidate for the replacement of carbon-based anodes. However, the electrochemical behavior of silicon anodes highly depends on the chemical composition of the used electrolyte solution, since it affects the formation of the solid electrolyte interphase, and, thus, the irreversible capacity and the cycling stability. Moreover, silicon anodes have to be matched properly with existing commercial cathodes, in order to provide Lithium-ion cells with high energy density.

In this work, we present the experimental results of full-cells with 3.5-um-thick silicon anodes deposited by DC sputtering technique on special treated copper foils and a variety of cathodes, such as Lithium Cobalt Oxide (LiCoO2), Lithium Iron Phosphate (LiFePO4), Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO2 or NMC) and Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2 or NCA). The electrolyte solutions used in the experiments are 1Μ LiPF6 in 1:1 (v/v) mixture solvents of ethylene carbonate (EC) and dimethyl carbonate (DMC) with various wt.% content of Vinylene Carbonate (VC) or Fluoroethylene Carbonate additive.

In order to investigate the electrochemical behavior and correct matching of the silicon anodes with each commercial cathode and electrolyte, Cyclic Voltammetry and Electrochemical Impedance measurements were conducted. Moreover, post-mortem analysis was conducted using SEM images and XPS measurements of the silicon anode in lithiated or delithiated state after a number of cycles. It is demonstrated that full-cells with specific capacity of more than 2.0 mAh cm-2 are obtained for more than 100 cycles.