Utilizing van der Waals Slippery Interfaces to Enhance the Electrochemical Stability of Silicon Film Anodes in Lithium-Ion Batteries

Abstract

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals "slippery" interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress "cycling" on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

Recent Advances in Silicon‐Based Electrodes: From Fundamental Research toward Practical Applications

“…There are two main methods to fabricate Si films: physical vapor deposition (PVD) and CVD. [ 200,201 ] Additionally, micrometer‐scale Si thin films have been fabricated via electron‐beam deposition, and the influence of thickness (ranging from 0.2 to 6 µm) on performance was studied. [ 202 ] It was discovered that an upper‐limit thickness exists, beyond which cycling stability decreases, and that lifetime can be greatly improved by adjusting the Li‐ion insertion depth.…”

Facile and Efficient Fabrication of Branched Si@C Anode with Superior Electrochemical Performance in LIBs

“…[ 41 ] Cracks were generated in the anode to release the stress concentration due to the continuously growing SEI on the surface of Si. [ 42 ] There was no obvious exfoliation observed. The swelling rate of the branched Si anode was 13.9% (Figure S13a,b, Supporting Information), similar to previously reported Si‐based anodes, [ 43–45 ] indicating the good stability of the branched structure.…”

A Review on the Thermal Hazards of the Lithium-Ion Battery and the Corresponding Countermeasures

“…Such large stress cycling over extended lithiation/delithiation cycles will invariably lead to fatigue damage, leaving battery materials susceptible to fracture and pulverization. Moreover, traditional electrode materials, such as silicon and transition metal oxides, may result in extreme volume changes during operation and further result in fracturing, electrical conductivity loss and mechanical integrity [65].…”