Multifunctional Dual Carbon Framework for Self-Healing Silicon Anodes

Developing next-generation anodes with high silicon (Si) contents requires thoughtful embedment of Si particles in protective media, mainly carbonaceous materials. However, it has been challenging to simultaneously realize optimal electrical conduction, structural integrity, and low-cost synthesis for advancing Si-carbon materials. In this work, we addressed these challenges by synthesizing a composite, where commercial Si nanoparticles are embedded in a dual carbon framework via a facile solution mixing and annealing process. Dopamine hydrochloride and graphene oxide were utilized as low-cost carbon precursors to obtain nitrogen doping (for improved electrical conductivity) and mechanical resilience (for accommodating volume fluctuations). Our synthesis process resulted in Si@C-rGO particles in which Si nanoparticles are conformally coated with a nitrogen-doped carbon layer and anchored to a reduced GO (rGO) sheet. Compared to electrodes with pristine Si, the Si@C-rGO electrodes (>60 wt % Si) exhibit reduced charge-transfer resistance, enhanced rate performance, and improved capacity retention. Notably, for the first time (to the best of our knowledge), we analyze the oscillations in long cycling data by converting it to capacity versus cumulative time and show that (i) the oscillations in both Si and Si@C-rGO exhibit largely similar shapes, and (ii) minute differences in oscillation shapes and amplitude may be used as signatures of self-healing behavior. Furthermore, microstructural studies of cycled electrodes confirm that rGO provides a self-healing behavior (via crack bridging), playing a critical role in maintaining the structural integrity of the Si@C-rGO electrode. Single-layer Si@C-rGO||NMC532 pouch cell with a specific energy density of 142 Wh kg^-1 delivered a capacity of 141.5 mAh g^-1 and exhibited a capacity retention of ∼62.2% over 75 cycles.