Toward efficient and stable lithium storage: molten salt electrolysis-constructed amorphous Si-dominant anodes with synergistic interfaces
Silicon anodes offer an ultrahigh theoretical capacity (4200 mAh g−1) but suffer from >300% volumetric expansion during cycling and unstable solid electrolyte interphase (SEI) formation, leading to rapid capacity fading. Here, we design a hierarchical composite p-cSi@aSi@MgSiN2@C featuring a porous crystalline-amorphous silicon core (p-cSi@aSi), an in-situ MgSiN2 transition layer, and an outer nitrogen-doped carbon shell. The 3D interconnected pores accommodate volume expansion, while amorphous silicon enables isotropic lithiation-induced strain, eliminating crystalline phase transition barriers. The MgSiN2 layer transforms into a tough Li3N-rich SEI with ultra-fast ion channels, and the carbon shell provides mechanical confinement and electronic conductivity. This synergistic interface engineering achieves an initial coulombic efficiency (ICE) of 81.4%, a charge transfer resistance of 16.4 Ω after 200 cycles (64% reduction), and a Li+ diffusion coefficient of 1.72×10−11 cm2 s−1. The anode delivers 1719.3 mAh g−1 at 0.2 C after 200 cycles and 823.8 mAh g−1 at 0.5 C after 500 cycles. The molten salt electrolysis synthesis achieves a current efficiency of 68.12% and specific energy consumption of 12.76 kWh kg−1, with an estimated electricity cost of 1154.69 USD ton−1, only 20% of commercial Si/C anodes. This work resolves the ICE-cycle life trade-off and provides a scalable, cost-effective approach for next-generation high-energy batteries.