Interfacial nitrogen stabilizes carbon-coated mesoporous silicon particle anodes

Abstract

We report for the first time that the dehydrogenation process of PAN was suppressed and the silicon oxide of the MSP surface was reduced during annealing in Ar + H₂. Consequently, the remaining –NH bonds of the carbon chain can interact with the fresh amorphous Si on the surface of the MSPs to form a Si–N–C layer, which improves the adhesion between Si and C and serves as a stable electrolyte blocking layer. In addition, based on micron-sized MSPs, the structural stability of the electrode is dramatically enhanced through in situ formation of Si nanocrystals of less than 5 nm. The low Li⁺ diffusion kinetics of the Si–N–C layer and self limiting inhomogeneous lithiation in MSPs jointly create unlithiated Si nanocrystals, acting as supporting frames to prevent pulverization of the anode material. Our nitriding MSP anode has exhibited for the first time a 100% capacity retention (394 mA h g⁻¹) after 2000 cycles (10 cycles each at 0.1, 0.5, 1, 2, and 1 and then 1950 cycles at 0.5 A g⁻¹) and a 100% capacity retention at 0.1 A g⁻¹ (540 mA h g⁻¹) after 400 cycles. Thus, our work proposes a novel avenue to engineer battery materials with large volume changes.