Cycling stability is central to implementing silicon (Si) anodes in next-generation high-energy lithium-ion batteries. However, challenges remain due to the lack of effective strategies to enhance the structural integrity of the anode during electrochemical cycling. Here, we develop a nanoscale polyamide coating, using spatial molecular layer deposition (MLD) of m-phenylenediamine and trimesoyl chloride precursors, to preserve the structural integrity of Si anodes. Poly(acrylic acid) (PAA) has been widely used in Si-based anodes as a binding agent due to its effective binding interactions with Si particles. However, the structural integrity of the anode is compromised by thermochemical decomposition of the poly(acrylic acid) binder, which can occur during electrode drying or during electrochemical cycling. Decomposition causes a 62% decrease in the elastic modulus of the Si anode, as measured by nanoindentation in electrolyte-soaked conditions. This study shows that an ultrathin polyamide coating counteracts this structural degradation, increases the elastic modulus of the degraded anode by 345%, and improves cohesion. Electrochemical analysis of polyamide-coated anodes reveals a film thickness dependence in cycling behavior. High overpotentials and fast capacity fading are observed for Si anodes with a 15 nm coating, whereas Si anodes with a 0.5 nm coating demonstrate stable cycling over 150 cycles with a capacity >1400 mAh g-1. Our findings identify polyamide as an effective electrode coating material to enhance structural integrity, leading to excellent cyclability with higher capacity retention. Furthermore, the use of the spatial MLD approach to deposit the coating enables short deposition time and a facile route to scale-up.
|Number of pages||9|
|Journal||ACS Applied Energy Materials|
|State||Published - Jun 24 2019|
Bibliographical noteFunding Information:
This work was authored in part by Alliance for Sustainable Energy, LLC, the manager and operator of the National Renewable Energy Laboratory for the U.S. Department of Energy (DOE) under Contract DE-AC36-08GO28308. The research is supported by the Vehicle Technologies Office of the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, under the supervision of David Howell, Brian Cunningham, and Peter Faguy. The authors also want to thank the startup grant from the Department of Mechanical Engineering at Virginia Tech.
© Copyright 2019 American Chemical Society.
- lithium-ion batteries
- molecular layer deposition
- silicon anodes
- surface modification
ASJC Scopus subject areas
- Chemical Engineering (miscellaneous)
- Energy Engineering and Power Technology
- Materials Chemistry
- Electrical and Electronic Engineering