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An in-Depth Investigation of the Alucone Coating Impact on the Performance of the Silicon Anode

Monday, 29 May 2017: 11:00
Grand Salon C - Section 15 (Hilton New Orleans Riverside)
S. B. Son (National Renewable Energy Laboratory), Y. Wang (University of Kentucky), X. Li, A. Stokes (Colorado School of Mines), Y. T. Cheng (University of Kentucky), and C. Ban (National Renewable Energy Laboratory)
Si is one of the promising candidates that can replace the graphite, owing to its high theoretical capacity of 3,579 mAh g-1, which is greater than any other Lithium-ion battery anode materials including graphite (372 mAh g-1). However commercialization of Si has not been successful yet because of following issues: First, the Si experiences huge volume expansion up to ~ 300 % with lithiation (formation of Li15Si4) that can cause mechanical failure of Si with repeated lithiation and delithiation. And second, unstable and insulate solid electrolyte interface (SEI) layer forms on the surface of Si as a result of exposure to organic solvent in the electrolyte. Mechanical failure of Si during repeated lithiation/delithiation creates new Si surfaces and those surfaces are susceptible to formation of SEI layer that makes Si anode more insulated and leads to rapid degradation of cycling performance. Our previous work demonstrated, for the first time, the success in utilizing molecular layer deposition (MLD) to grow mechanically robust and flexible surface coatings to address the challenges associated with Si’s dramatic volume changes. In this work, we further investigate the advantages of MLD coating on thick electrodes in a mechanical point of view. The presence of MLD coating on the electrodes increases the mechanical properties such as elastic modulus and hardness, which makes thick electrode robust and resistant to volume changes. Scratch test also reveals the stronger bonding strengths of Si anode materials to the Cu current collector with MLD coating. Remarkably improved electrochemical performance of the Si electrode with MLD coating was observed and specific capacity of 1,490 mAh g-1 at 500 cycles is achieved while uncoated Si anode delivered negligible amount of specific capacity. And this study exactly states the advantages and limits of MLD coated Si-CB-PVDF system and motivate us further to investigate the novel system that is still unexplored.