Towards a Higher Energy Density for Lithium-Ion Battery Anodes Via Hierarchically Structured Silicon/Carbon Supraparticles Using Spray Drying
Authors: Amin Adil , Loewenich Moritz , Wiggers Hartmut , Özcan Fatih , Segets Doris 
Published: February 2024

Silicon has a high potential to replace commercial graphite anodes in lithium-ion batteries (LiBs). It can facilitate achieving excellent energy densities because of its high theoretical specific lithiation capacity (Chan et al. 2008). However, major challenges such as rapid capacity fading and low Coulombic efficiency due to the huge volume change (∼300 %) during cycling have seriously hindered its commercialization (Wu et al. 2013). Although nanostructuring has been successful in minimizing volume expansion issues, the electrochemical performance of nano-sized silicon is still limited due to unstable solid-electrolyte interphase, low coating density and overall poor electrical properties due to the higher interparticle resistance (Liu et al. 2014). To tackle those challenges, here we introduce a new concept of post-synthesis spray drying to produce hierarchically structured micro-agglomerates from silicon/carbon (Si/C) composite nanoaggregates synthesized in the gas phase (Amin et al. 2023; Adil Amin et al.).
The resulting agglomerates were characterized i) on the powder level by scanning electron microscopy (Fig. 1a) and N2 sorption, ii) on the dispersion level by rheometry and analytical centrifugation, iii) on the electrode level by atomic force microscopy for structure and iv) via electrochemical testing on half-cells for electrochemical performance (Fig. 1b). These results show that electrodes from Si/C supraparticles with the highest concentration of stabilizer exhibit better redispersion stability and excellent first cycle specific discharge capacity as well as better cycling stability as compared to the Si/C composite nanoaggregates (4 wt.% carbon content). Furthermore, compared to the reference electrodes made of nanoaggregates, the more stable supraparticles (3 wt.% stabilizer) showed the highest first Coulombic efficiency. This is due to the reduction of their surface to volume ratio which helps in forming less volume of solid electrolyte interface.
To conclude, our investigation suggests how an established industrial process (gas phase synthesis of nanoparticle in a hot-wall reactor) can be combined with scalable one-step spray drying to get dense active materials for LiBs. This enables to fully utilize the new materials’ potential by the right packaging into optimum electrode structures with high performance and longevity. Furthermore, we are of the opinion that this pioneering method can be utilized as a broadly relevant design principle to enhance other (anode) materials that encounter analogous problems of volume expansion.

Publication bibliography

Amin, Adil; Özcan, Fatih; Loewenich, Moritz; Kilian, Stefan O.; Wiggers, Hartmut; Segets, Doris; Wassmer, Theresa; Bade, Stefan; Lyubina, Julia: Hierarchically Structured Si/C Agglomerates by Spray-Drying. Patent no. PCT / EP 2022/ 052453.
Amin, Adil; Loewenich, Moritz; Kilian, Stefan O.; Wassmer, Theresa; Bade, Stefan; Lyubina, Julia et al. (2023): One-Step Non-Reactive Spray Drying Approach to Produce Silicon/Carbon Composite-Based Hierarchically Structured Supraparticles for Lithium-Ion Battery Anodes. In J. Electrochem. Soc. 170 (2), p. 20523. DOI: 10.1149/1945-7111/acb66b.
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Wu, Hui; Yu, Guihua; Pan, Lijia; Liu, Nian; McDowell, Matthew T.; Bao, Zhenan; Cui, Yi (2013): Stable Li-ion battery anodes by in-situ polymerization of conducting hydrogel to conformally coat silicon nanoparticles. In Nature communications 4, p. 1943. DOI: 10.1038/ncomms2941.

Figure 1