Integrating robust SEI on recycled micro-sized silicon scrap for stable lithium ion battery

Abstract

Targeting recycling of silicon (Si) scrap, a byproduct from photovoltaic industry, LiF inducer strategy through synthesis of an elastic polymer layer endowed with fluorinated terminations enabled by the cross-linking of silane coupling agent (KH570) and trifluoromethyl ethyl methacrylate (TFEMA) are investigated. This approach yields a durable LiF rich solid electrolyte interface (SEI), which significantly enhances the resilience of recycled silicon during cycles, thus ensuring exceptional cycling stability and high-rate performance in lithium ion batteries . • A scalable smart organic molecular coating strategy for micro-sized Si are developed. • This approach provides a strategy for recycling use of micro-sized Si scrap generated from photovoltaic industry . • The modified Si electrode tends to form a LiF-rich SEI layer during cycling, which significantly reduces the electrode’s charge transfer impedance. Silicon (Si) based anode materials for lithium ion (Li + ) batteries have garnered significant attention due to their high specific capacity, low lithium insertion potential, but higher cost than usual graphite anode. The slicing of photovoltaic silicon generate a significant amount of silicon scrap, resulting in substantial waste and pollution. Here, we present a novel technique that an organic molecular encapsulation with elastic polymer silane coupling agent (KH570) crosslinking with trifluoromethyl ethyl methacrylate (TFEMA) on the surface of micrometer-scale photovoltaic Si scrap particles via hydrolysis followed by polymerization. The fluorination-terminated functional groups would induce a more stable LiF-rich solid electrolyte interface (SEI). resulting in reduced SEI and charge transfer resistance. More importantly, the crosslinking network of the elastic polymer, enables a high capacity of 985 mAh g −1 (5 times than pure Si scrap) over 500 cycles at 5 A g −1 and achieves a 90 % retention rate after 100 cycles (131 mAh g −1 ) in a full cell system. Furthermore, the modified Si could be matching with a polymer-based solid-state electrolyte, delivering a specific capacity of 1000 mAh g −1 . This organic molecular encapsulation technique is straightforward, highly reproducible and demonstrate considerable practical value for the recycling of resources.