Artificial solid-electrolyte-interphase layer on silicon/graphite anode formed by atomic layer deposited ZnO films

Operation of Li-ion batteries is based on an insertion of Li ions in layered materials. Intercalation of Li into the graphite anode takes part during charging, while Li-ions are stored in the layered cathode materials during discharging.

Graphite anode: intercalation of Li, excellent cycling performance, but low specific energy capacity (372 mAh/g).

Silicon/graphite anode: Alloying Li with Si – high specific energy capacity (3579 mAh/g for the Li₁₅Si₄ phase). Huge expansion/shrinkage of silicon (_V~300%) during lithiation/delithiathion, resp., _ capacity fade and degradation.

Solid-electrolyte interphase (SEI) formation on silicon/graphite anode SEI (product of continuous electrolyte reduction on the surface of the anode). SEI formation is essential for the operation of lithium-battery systems. Uncontrolled SEI growth can cause capacity degradation upon cycling .

Our contribution: Control of the SEI growth using ZnO ultrathin layer grown by atomic layer deposition (ALD). Improved performance of the ZnO coated silicon/graphite anodes was observed notably at 1 and 2 c-rates. Enhanced capacity retention is linked with a suppressed and more stable SEI, as observed by impedance spectroscopy.