New ceramic materials derived from pyrolyzed poly(1,2-dimethylsilazane) and starch as a potential anode for Li-ion batteries

New materials were obtained by pyrolysis of starch (S) and poly(1,2-dimethylsilazane) (PSN) (weight ratio: PSN/S 30/70) at temperature a) 500 °C, b) 700 °C and c) 900 °C. Ceramic materials were characterized by infrared spectroscopy, TGA, Raman spectroscopy and SEM. New SiO and shifted SiC stretching vibration modes emerged confirming direct interaction between silicon originating from silazane and oxygen coming from starch. The specific capacity of PSN/S 30/70 pyrolyzed at 900 °C was 301 mAh/g with capacity fading about 6% after 100th cycles. These values are higher (~ 50%) in comparison with the capacity of pure starch pyrolyzed at the same conditions. Electrochemical impedance spectroscopy allowed to establish temperature dependence of the particular components of an electrical equivalent circuit. The Arrhenius type behavior was confirmed for ionic transport within SEI. The charge transfer resistance, being a part of modified Randles circuit, was found to increase with temperature. Ionic transport within the electrode bulk material is represented by semi-infinitive Warburg impedance. The reciprocal of Warburg coefficient (1/σW) diminishes with temperature.