Enhancing Silicon Performance via LiPON Coating: A Prospective Anode for Lithium Ion Batteries

Thin film bilayers of silicon and LiPON are synthesized via rf magnetron sputtering, whereas the thickness of both layers is in the nanometer range, i.e. between 50 and 400 nm. Electron microscopy on the samples confirms a well-defined layer structure and a high interface quality of the layer stacks. Cyclic lithiation/delithiation of the bilayers via chronopotentiometry, moreover, reveals an astonishing capacity retention and high coulombic efficiency when compared to pure silicon films. This strong improvement in electrochemical performance is attributed to a stabilization of the silicon electrode by the nano-sized LiPON coating. Moreover, it is found that the rate of improvement depends on the thickness ratio between LiPON and silicon. Hence, samples with different thickness of LiPON and silicon, respectively, are investigated to get detailed insight into the electrochemical long term stability of the bilayer samples. Based on these investigations, an electro-mechanical model is suggested that describes in detail the microscopic degradation mechanism of LiPON coated silicon electrodes.