Multilayer-Coating on Silicon Nanoparticles Assisted by Supercritical CO2 for Better Li-ion Batteries

Silicon (Si) anode architectural design is an important factor to develop better Li-ion batteries (LIBs)[1]. In this work, a systematic study to make optimal multilayer-coating on silicon nanoparticles (C/SiOx/Si) nanoparticles to withstand volume expansion and stabilize solid electrolyte interphase[2] has been conducted. A green and facile method for multilayer-coating has been developed by a supercritical carbon-dioxide (SCCO2) process[3]. It beneficially uses liquid-like CO2 as a primary solvent and is supported by ethanol as a co-solvent. C/SiOx/Si produced from SCCO2 uses several kinds of saccharide precursors, such as glucose (SC-G) and sucrose (SC-S), also citric acid (SC-CA). Furthermore, glucose is also applied with a traditional wet-chemical mixing process (T-G) for comparison. The experimental results show that SC-G has a better coating layer than T-G, SC-S, and SC-CA. For example, the SC-G has a high tap density due to a more compact and homogeneous coating layer. In addition, the SC-G electrode exhibits high reversible capacities of >2150 and ~920 mAh g–1 at 0.2 and 5 A g–1, respectively. The same electrode can retain ≈65 % of its initial capacity after 300 charge-discharge cycles at 1 A g–1. The obtained energy density of a SC-G||LiNi0.8Co0.1Mn0.1O2 full cell (based on the total mass of anode and cathode active materials) is ≈555 Wh kg−1, which indicates the excellence of the proposed anode. This study demonstrates the great potential of using SCCO2 for Si surface multilayer-coating. The process is facile and easily scaled-up for producing better Si-based anode materials for LIBs application. References: [1] P. G. Bruce, B. Scrosati, J. M. Tarascon, Angew. Chem., 47, 2930-2946 (2008).[2] B. Koo, H. Kim, Y. Cho, K. T. Lee, N. S. Choi, J. Cho, Angew. Chem., 51, 1-7 (2012).[3] R. F. H. Hernandha, P. C. Rath, B. Umesh, J. Patra, C. Y. Huang, W. W. Wu, Q. F. Dong, J. Li, J. K. Chang, Adv. Funct. Mater., 2104135 (2021).