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

Abstract

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 generation of Si scrap from the slicing of photovoltaic Si leads to substantial material scrap. 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 termination functional groups would induce a more stable LiF-rich solid electrolyte interface (SEI) during the cycling, which lead to the reduction in Li⁺ and charge transfer resistance. More importantly, the crosslinking network of the elastic polymer, enables micrometer-sized Si scrap maintain the capacity retention of at 5 A/g for 500 cycles (985mAh/g, 5 times than pure Si scrap) and achieves a 90 % retention rate after 100 cycles (131mAh/g) in a full cell system. Furthermore, the Si scraps with such a functional organic coating could be matching with a polymer-based electrolyte as an all-solid battery, which present a specific capacity of 1000mAh/g. This technique of organic molecular encapsulation is straightforward, replicable and holds considerable practical value for the recycling of resources.