Al2O3 protective coating on silicon thin film electrodes and its effect on the aging mechanisms of lithium metal and lithium ion cells. (15th December 2021)

• Record Type: Journal Article
• Authors: Casino, Simone; Heidrich, Bastian; Makvandi, Ardavan; Beuse, Thomas; Gallasch, Tobias; Peterlechner, Martin; Wilde, Gerhard; Winter, Martin; Niehoff, Philip
• Is Part Of: Journal of energy storage. Volume 44(2021)Part B
• Publication Date: 2021-12-15
• Subjects: Silicon -- Thin film -- Al2O3-coating -- Aging mechanism -- Lithium ion battery -- Loss lithium inventory; Energy storage -- Periodicals; Energy storage -- Research -- Periodicals; 621.3126
• DOI: 10.1016/j.est.2021.103479
• Languages: English
• ISSNs: 2352-152X

Abstract

Highlights: Silicon thin film lithium metal and lithium ion cells aging mechanism quantified. Effect of the Al2O3-coating on silicon thin film aging mechanisms investigated. Al2O3-coating is effective in reducing loss of lithium inventory. Loss of lithium due to SEI formation is the main contribution to lithium loss. Abstract: In this work, an investigation of the effect of Al2 O3 -coating on the aging mechanisms of silicon anode thin films in lithium metal and lithium ion cells is presented. Aging mechanisms, namely: loss of lithium inventory, loss of silicon active material and loss of utilizable capacity due to an increase of cell resistance were determined for both, Li||Si and Si||LiFePO4 cells. Al2 O3 -coating was shown to be an effective strategy to reduce the loss of lithium inventory, while having a marginal effect on decreasing the loss of silicon active material. Indeed, in case of Si||LiFePO4 cells, where fading is governed by loss of lithium inventory, a 5 nm Al2 O3 -coating leads to a significant reduction (-64%) of the capacity fade per cycle. On the contrary, in case of Li||Si, where the aging mechanism is governed by the loss of active material, Al2 O3 -coated and uncoated silicon showed comparable tendencies regarding the capacity fade per cycle. It emerges, also, that loss of silicon active material and loss of lithium inventory are independent of each other. This indicates that the main contribution of loss of lithium inventory is not the lithium trapped in electrically insulated silicon, but rather lithium consumed in the ongoing SEI formation. Al2 O3 -coating could reduce the latter due the insulating nature of the coating. Ex situ investigations of the SEI by means of X-ray photoelectron spectroscopy confirmed a decrease in solvent decomposition in presence of the Al2 O3 -coating. Graphical abstract: Image, graphical abstract