Synergistic engineering of prelithiation and carbon coating for silicon microsphere anodes in advanced Li-ion batteries

Abstract

Despite notable progress in understanding interfacial mechanisms and the alloying–dealloying behavior of nanostructured silicon anodes, significant challenges remain in meeting the performance standards necessary for commercialization. Specifically, these include charge-induced large volume changes, redundant side reactions with the electrolyte, and poor initial coulombic efficiency. Herein, we report a method of pre-lithiation of silicon microspheres followed by conformal carbon coating (PL-Si/C). The resulting products exhibited an enhanced ICE of 84.2% and a stable reversible capacity of ∼1600 mA h/g at a 0.5C rate, with 83% retention, compared to spray-dried silicon microspheres (Si-MS), which showed 77.6% ICE and 81% retention. When integrated with graphite, PL-Si/C shows 90% ICE and 79.5% retention after 200 cycles at 1C rate, while Si-MS shows 62.5% capacity retention. The cycling stability of materials can be credited to the unique microsphere morphology in which Si nanodomains are embedded in carbon nanotube interwoven amorphous lithium silicate (Li_xSiO_y) matrix, followed by conformal carbon coating using the chemical vapor deposition technique. The primary layer acts as a buffering medium during volume expansion, suppresses initial lithium loss, and enhances ICE. Further carbon coating supports the mechanical integrity. Further to realize the practical applicability of the material, full cells were tested with lithium and LiNCA cathodes.