Interface chemistry engineering of protein-directed SnO₂ nanocrystal-based anode for lithium-ion batteries with improved performance.

A novel uniform amorphous carbon-coated SnO2 nanocrystal (NCs) for use in lithium-ion batteries is formed by utilizing bovine serum albumin (BSA) as both the ligand and carbon source. The SnO2 -carbon composite is then coated by a controlled thickness of polydopamine (PD) layer through in situ polymerization of dopamine. The PD-coated SnO2 -carbon composite is finally mixed with polyacrylic acid (PAA) which is used as binder to accomplish a whole anode system. A crosslink reaction is built between PAA and PD through formation of amide bonds to produce a robust network in the anode system. As a result, the designed electrode exhibits improved reversible capacity of 648 mAh/g at a current density of 100 mA/g after 100 cycles, and an enhanced rate performance of 875, 745, 639, and 523 mAh/g at current densities of 50, 100, 250, and 500 mA/g, respectively. FTIR spectra confirm the formation of crosslink reaction and the stability of the robust network during long-term cycling. The great improvement of capacity and rate performance achieved in this anode system is attributed to two stable interfaces built between the active material (SnO2 -carbon composite) and the buffer layer (PD) and between the buffer layer and the binder (PAA), which effectively diminish the volume change of SnO2 during charge/discharge process and provide a stable matrix for active materials.