The utilization of thin carbon layers in Si/C architectures promises improved ion/charge kinetics, although structural stability is still a concern due to the aggregation of Si nanoparticles (SiNPs).
Study: Self-deformed Si/[email protected] anode for stress relief in lithium ion batteries. Image Credit: Illus_man/Shutterstock.com
In an article published in the journal Materials Today Sustainability, SiNPs were distributed on large-sized graphene (Si/[email protected]) having strong linking, which successfully controlled graphene’s self-limiting effect caused by dispersed SiNPs.
Silicon Anodes for Lithium-Ion Batteries
Silicon is considered the most desirable anode material for next-generation lithium-ion batteries (LIB). During cycling, the surface electrode based on Si interacts with the electrolyte to generate a solid electrolyte interphase (SEI) film on the interface, which is characterized by active lithium consumption that reduces coulombic efficiency (CE), notably for the initial coulombic efficiency (ICE).
Challenges Associated with Using Silicon in LIBs
The significant volume growth causes pulverization of anode substances based on Si, which causes electrode exfoliation and removes the SEI film, resulting in the reaction between the newly re-exposed region and the electrolyte to form an expanding region SEI layer.
The aggregation of silicon nanoparticles causes their exfoliation from the encapsulated mass and further from the present collector during cycling, resulting in a large volume increase of SiNPs in a small space (self-limiting effect). Considering the specific rate potential and capacity, all these conditions cause silicon-based electrodes to degrade.
As a result, nanostructure technology and engineering, including Si nanoparticles, porous Si, Si nanosheets and Si nanotubes/nanowires, have received much attention to preserving their structural integrity. These silicon materials, which have a variety of morphological shapes, have ample space to store volumetric changes.
Furthermore, the minimal electronic conductivity of silicon anodes and its unstable interface problem remain significant roadblocks. Carbon coatings on materials consisting of Si anode are one potential approach.
Silicon/Carbon Composites – The Way Forward
Si/C structures will produce functional heterostructures with better electric field performance, allowing for rapid charge movement. On the other hand, carbon coatings provide a strong protective layer on Si anode components, generating a robust SEI layer and reducing stress accumulation.
The carbon layer on SiNPs causes the aggregation of Silicon nanoparticles into microclusters. Dense carbon film in Si/C anode, on the other hand, diminishes specific capacitance and ion kinetics. As a result, Si/C architectures with sustainable design are critical for good ion/charge kinetics.
Recent Advancements in the Field of Silicon/Carbon Composites
Numerical models of stress evolutions produced by lithium diffusion were used in one research to investigate the impact of different carbon layer thicknesses on the tensile hoop stress of Si/SiO2/C for a robust architecture.
To minimize severe pulverization and breaking of Si/C anode materials, a recent study revealed the formation of a three-dimensional network of Si/C by chemical vapor deposition. The Si/C that resulted had an exceptional rate capacity.
Lithium chloride has also been utilized as a template to make permeable [email protected] materials recently, which have proven to buffer generated stress and speed up ion/charge movement while offering reduced electrode swelling.
Salient Features of the Study
This paper suggests a reasonable construction of silicon nanoparticles distributed on large-scale graphene with strong linkages to alleviate self-limiting impact of SiNPs, having thin layers of carbon that lower ion diffusion obstacles.
Finite element simulations show that graphene effectively releases accumulated stress by immobilizing SiNPs and deforming graphene, which helps to better understand the stress evolution of Si/[email protected]
Graphene having a self-deformed structure, which is caused by the volume growth of silicon nanoparticles during cycling, can efficiently release deposited stress and keep Si/[email protected] structurally intact. According to density functional theory research, Si/C heterostructures in Si/[email protected] permit the rearrangement of an electrostatic field, enabling quick charge transfer, primarily at the interface of carbon and Si.
The large-scale graphene also aids in constructing an electrical network with a large area, significantly decreasing the impedance of Si/[email protected] In conclusion, Si/[email protected] will surpass other materials in ion/charge kinetics, capacity retention and rate capability upon cycling.
After 303 cycles, Si/[email protected] displayed outstanding structural stability, with only approximately 3.60 percent electrode swelling.
As a result, the structures of scattered SiNPs stabilized on graphene through strong linking pave the way for an enhanced Si-based anode in LIB to optimize ion/charge kinetics and reduce stress accumulation.
Ge, J., Shen, H. et al. (2022). Self-deformed Si/[email protected] anode for stress relief in lithium ion batteries. Materials Today Sustainability. Available at: https://www.sciencedirect.com/science/article/pii/S2589234722000574?via%3Dihub
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