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.