Spontaneous Encapsulation of Silicon Nanoparticles By Hydroxyl-Rich Graphene Oxide for High Performance Core-Shell Anode Materials
Authors: Kim Byeong Guk , Hong DongGyun , Jeong Sooyeon , Lee Hye Jung , Nam Ki-Hun , Kim Ick-Jun , Yang Sunhye , Jeong Seung Yol 
Published: December 2024

Silicon is one of possible candidate as anode materials for high performance lithium-ion battery (LIB). However, it has several significant drawbacks such as huge volume expansion and formation of unstable surface electrolyte interfaces (SEI) layers. Therefore, carbon-based encapsulation of silicon as an active material is necessary for high performance LIBs. In particular, it plays a role in passivation without side-reaction and conducting path simultaneously as well as formation of core-shell structure. Graphene is one of ideal materials for the application of core-shell structuring with silicon as a carbon material. To date, various surface modification has been introduced such as polymer coating, silane treatment, and oxide coating etc. However, these methods can reduce the electrochemical active area in an electrode due to large amount of residue. Graphene oxide (GO) could be applicable for the reasonable coating on silicon without additives. The GO encapsulated silicon active materials has been introduced because of its homogeneous aqueous dispersion. It is easy and straightforward method. In spite of several advantages of GO encapsulation, the adhesion and stable core-shell structuring of anode composite are still challenging due to post reduction process. It can be affected the adhesion between silicon and graphene. Therefore, strong chemical interaction is necessary for the structuring of anode composites. The spontaneous encapsulation of GO reveals self-assembling silicon nanoparticles with GO via siloxane reactions. This method utilizes the reactive silanol (Si-OH) and siloxane (Si-O-Si) groups on the silicon nanoparticles surface, along with the hydroxyl groups of graphene oxide. In the GO, nucleophilic opening of epoxy rings by pH control leads to the conversion from epoxy to hydroxyl groups. The reactive hydroxyl groups generate new siloxane bonds (G-O-Si) between the silanol and siloxane groups on the silicon surface. The strong adhesion occurs with stable bonding with silicon. The epoxy and hydroxyl rich-GO enhance the chemical interaction. The GO comes from highly crystallized hexagonal surfaces. Therefore, it can be described the representative two advantages with respect to the strong adhesion for composite anode materials and high electrical conductivity as a conducting path. In this work, we introduced preparation of high-quality GO and its application as encapsulation of silicon anode materials. The silicon nanoparticles and high-quality GO anode composite reveals enhanced electrochemical characteristics compared to that of the previous works. It reveals high charge capacity, coulombic efficiency, and cyclic stability. This is a potential approach for high performance anode materials with advanced lithium-ion batteries. This result overcomes the limitations of silicon through effective interfacial bonding, providing higher energy density and cyclic stability in battery applications.