Improved\nCyclability of Lithium-Ion Batteries Using\nPyroprotein-Assisted Silicon Anodes

Abstract

With a 10-fold higher theoretical\ncapacity than that of graphite,\nsilicon has excellent potential for use as an active anode material\nin lithium-ion (Li-ion) batteries, especially when high capacity and\nhigh energy density are required. In this study, we improved the lifetime\ncharacteristics of silicon nanoparticles (SINPs) by synthesizing a\nSi/C composite anode composed of carbonized fibroin (pyroprotein)\nand SINPs. The pyroprotein matrix effectively accommodates the volume\nexpansion of the SINPs during charging and discharging, thereby suppressing\nthe formation of surface defects on the electrode. This pyroprotein\nmatrix also provides additional storage sites for Li-ion chemisorption\nand uniformly delivers Li ions to the SINP surfaces through a solid–solution\nreaction. The Si/C anode exhibits improved rate capability compared\nto that of the SINPs, with a 30% higher capacity retention over 50\ncycles. Furthermore, even in a graphite-silicon (G-Si) composite anode,\nthe G-Si/C anode showed a capacity retention rate of 99.5% over 100\ncycles, which is superior to the performance of silicon-based anode\nmaterials; hence, it is a potential candidate for use in long-life\nG-Si composite anodes.