Spatial Molecular Layer Deposition of Ultrathin Polyamide To Stabilize Silicon Anodes in Lithium-Ion Batteries

Abstract

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.

CO2-based atomic/molecular layer deposition of lithium ethylene carbonate thin films

“…2,4 It is clear from numerous studies that an articially pre-fabricated SEI could improve battery performance by preventing cracks and stopping the consumption of the electrolyte and Li-ions. [5][6][7][8][9][10][11][12][13][14][15][16] An articial SEI could also help prevent damage caused by mechanical stress and by volume expansion during (de)insertion of Li-ions, but this feature is dependent on the cell chemistry.…”

Atomic and molecular layer deposition in pursuing better batteries

“…Thus, the AlGL coating has proved to be robust and resilient enough to accommodate the extreme volumetric changes of the Si nanocomposite electrodes. In a recent work, Wallas et al [128] deposited a layer of polyamide coating [Fig. 5(a)] over Si anodes using a spatial MLD system at 150°C.…”

“…On the contrary, the 3-and 15-nm-thick polyamide coatings did not perform well. Wallas et al [128] pointed out that the 0.5-nm coating was deposited with a 6-s exposure time, while the 3and 6-nm coatings were deposited with a 0.6-s exposure. The shorter exposure might have led to less conformal coatings, compared to the ones deposited using the longer exposure.…”

“…The shorter exposure might have led to less conformal coatings, compared to the ones deposited using the longer exposure. Wallas et al [128] emphasized that this polyamide coating was an all-organic polymer, five times thinner than that of the MLD AlGL, and deposited using a spatial reactor. In addition to these studies using MLD organic coatings, readers may refer to our recent review article [16] for the effects of ALD coatings on Si anodes.…”

Silicon Anodes for High‐Performance Storage Devices: Structural Design, Material Compounding, Advances in Electrolytes and Binders

“…However, PAA binders have the property of thermal degradation, and electrode structure pyrolysis leads to incomplete electrode structure during electrode drying and electrochemical cycling. Therefore, this structural degradation is counteracted by modifying the PAA binder . The PAA/PVA mixed binder shows higher stiffness, adhesion strength, and electrochemical performance (100 cycles with 240 mA g −1 and 40 cycles with 400 mA g −1 ) compared with those of unmodified PAA (38 cycles with 240 mA g −1 and 25 cycles with 400 mA g −1 ) .…”