Scalable Synthesis of Defect Abundant Si Nanorods for High-Performance Li-Ion Battery Anodes

Abstract

Microsized nanostructured silicon-carbon composite is a promising anode material for high energy Li-ion batteries. However, large-scale synthesis of high-performance nano-Si materials at a low cost still remains a significant challenge. We report a scalable low cost method to synthesize Al/Na-doped and defect-abundant Si nanorods that have excellent electrochemical performance with high first-cycle Coulombic efficiency (90%). The unique Si nanorods are synthesized by acid etching the refined and rapidly solidified eutectic Al-Si ingot. To maintain the high electronic conductivity, a thin layer of carbon is then coated on the Si nanorods by carbonization of self-polymerized polydopamine (PDA) at 800 °C. The carbon coated Si nanorods (Si@C) electrode at 0.9 mg cm(-2) loading (corresponding to area-specific-capacity of ∼2.0 mAh cm(-2)) exhibits a reversible capacity of ∼2200 mAh g(-1) at 100 mA g(-1) current, and maintains ∼700 mAh g(-1) over 1000 cycles at 1000 mA g(-1) with a capacity decay rate of 0.02% per cycle. High Coulombic efficiencies of 87% in the first cycle and ∼99.7% after 5 cycles are achieved due to the formation of an artificial Al2O3 solid electrolyte interphase (SEI) on the Si surface, and the low surface area (31 m(2) g(-1)), which has never been reported before for nano-Si anodes. The excellent electrochemical performance results from the massive defects (twins, stacking faults, dislocations) and Al/Na doping in Si nanorods induced by rapid solidification and Na salt modifications; this greatly enhances the robustness of Si from the volume changes and alleviates the mechanical stress/strain of the Si nanorods during the lithium insertion/extraction process. Introducing massive defects and Al/Na doping in eutectic Si nanorods for Li-ion battery anodes is unexplored territory. We venture this uncharted territory to commercialize this nanostructured Si anode for the next generation of Li-ion batteries.

Effect of Silicon Crystallite Size on Its Electrochemical Performance for Lithium‐Ion Batteries

“…Therefore, Si electrode shows poor cycle stability. To mitigate Si electrode degradation, nanostructured Si materials, such as nanoparticles, nanowires, and nanorods, have been utilized as the active material. It has also been reported that Si anodes with smaller crystallite size show better electrochemical performance for LIBs, and Si with different particle diameters has been used in the previous reports .…”

Leveraging Titanium to Enable Silicon Anodes in Lithium‐Ion Batteries

“…When 20 at% of Ti is added, a capacity of 1532 mAh g −1 is achieved at 100 mA g −1 , corresponding to a volumetric capacity of 1554 Ah L −1 (Equation ). To the best of our knowledge, this value is one of the highest volumetric capacity values reported in the literature . The 80 at% Si electrode also shows a capacity retention of 94.8% after 50 cycles.…”

“…Even with 20 at% Ti, FCE of the Si-Ti electrode is as high as 94.8%, similar to that of commercial graphite anode material and is one of the highest values for Si electrode reported in the literature. [7,8,[35][36][37][38][39][40] The most notable effect of Ti addition is the superior cycle performance of the electrode. Figure 3a illustrates the cycling performance of Si-Ti electrodes at a current rate of 100 mA g −1 .…”

A Facile Path to Graphene‐Wrapped Polydopamine‐Entwined Silicon Nanoparticles with High Electrochemical Performance

“…[3] The second one is to use a thin layer of porous carbon on Si to provide a protective coating with good electronic conductivity, such as the carbonization of resorcinolformaldehyde resin (RF) [4] or polydopamine (PDA). [5][6][7][8] As a synthetic mimic of mussel adhesive proteins, PDA are easily coated onto various nanostructures with controllable thickness. [9,10] However, the specific capacity was still significantly degraded to around 48 % after 100 cycles.…”