Mechanical and Electrochemical Stability Improvement of SiC-Reinforced Silicon-Based Composite Anode for Li-Ion Batteries

Extreme volume changes and concomitant mechanical instabilities (viz., origin and proliferation of cracking) in Si-based anodes are responsible for premature failure in lithium-ion batteries. Thus, it is a crucial hurdle toward the development of high-performance Si-based batteries, especially in the current scenario of electric vehicles. Accordingly, this research demonstrates a significant improvement in the mechanical stainability of Si-based anode material via in situ incorporation of carbide with a specific design, thereby bestowing outstanding stability in the electrochemical performance. At this juncture, we have established a bridge between nanomechanical and electrochemical properties, investigated via nanoindentation and in-operando stress measurements during electrochemical cycling for Si and in situ reinforced Si-SiC composite. Enhancing the hardness (H) of Si-SiC composite to almost twice as well as enhancing the hardness to effective Young's modulus (E*) ratio (H3/E*2) of the same to almost thrice than that of Si, helped resist the occurrence of plastic deformation and cracking in significant terms. In-operando study shows the typical stress flattening (cum, anisotropic behavior) in the case of the unreinforced Si electrode, which is a manifestation of plastic flow/cracking. By contrast, monotonous stress profiles and absence of the signature of plastic flow/cracking are observed for the Si-SiC electrode, which is an advantage for long cycle life, as observed here. Overall, this kind of experimental study could establish the nanomechanical to electrochemical tie-up, leading to 82% capacity retention over 650 cycles in a Li-ion full-cell along with the Si-SiC composite anode. The "power cycle"of the Si-SiC composite anode, with a variation of current density from 0.5 to 6.0 A g-1, also reveals excellent stability up to 2500 cycles.