Atomic layered coating enabling ultrafast surface kinetics at silicon electrodes in lithium ion batteries

The interfacial charge-transfer kinetics plays an important role in the rate capabilities of lithium ion batteries (LIBs). The control of the charge-transfer kinetics, by engineering the surface coating so as to provide an artificial solid electrolyte interphase (SEI), can facilitate the lithiation/delithiation processes; however, unwanted interfacial resistance can be generated if the surface coating is too thick. Here, we provide an experimental study of the interfacial kinetics of a model LIB electrode system, silicon electrodes with alumina coatings by atomic layer deposition (ALD). A modified potentiostatic intermittent titration technique (PITT) is used to characterize the electrode operation and extract physicochemical parameters, including the lithium diffusion coefficient within silicon, the interfacial exchange current density, and the reaction rate constant. For the alumina-Si system, an optimum coating thickness exists in terms of delivering maximum charge-transfer rate. This work provides new tools to modify and improve key properties of engineered electrode/electrolyte interfaces.