Influence of inactive electrode components on degradation phenomena in nano-Si electrodes for Li-ion batteries
2016 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 325, 513-524 p.Article in journal (Refereed) Published
The electrode morphology and electrochemistry of silicon nanocomposite electrodes containing either carboxymethyl cellulose (CMC-Na) or poly(acrylic acid) (PAA) binders are examined in context of their working surface area. Using porous carbon (Ketjenblack) additives, coatings with poor adhesion properties and deep cracks were obtained. The morphology is also reflected in the electrochemical behavior under capacity-limited conditions. Mapping the differential capacity versus potential over all cycles yields detailed insights into the degradation processes and shows the onset of cell failure with the emergence of lithium-rich silicon alloys at low potentials, well before capacity fading is observed. Fading occurs faster with electrodes containing PAA binder. The surface area of the electrode components is a major cause of increased irreversible reaction and capacity fade. Synchrotron-based X-ray photoelectron spectroscopy on aged, uncycled electrodes revealed accelerated conversion of the native SiOx-layer to detrimental SiOxFy in presence of Ketjenblack. In contrast, a conventional carbon black better preserved the SiOx-layer. This effect is attributed to preferred adsorption of binder on high surface area electrode components and highlights the role of binders as 'artificial SEI-layers'. This work demonstrates that optimization of nanocomposites requires careful balancing of the surface areas and amounts of all the electrode components applied.
Place, publisher, year, edition, pages
2016. Vol. 325, 513-524 p.
Silicon anode, Carbon black, Binder, Artificial solid-electrolyte interface, X-ray photoelectron spectroscopy
IdentifiersURN: urn:nbn:se:uu:diva-307859DOI: 10.1016/j.jpowsour.2016.06.059ISI: 000381165600059OAI: oai:DiVA.org:uu-307859DiVA: diva2:1048921
FunderSwedish Research Council, 2012-3837Swedish Energy Agency