Evaluation of components of Li-O2 battery positive electrode capacitance by a voltammetric method

Abstract

• Capacitance components of a lithium-oxygen battery positive electrode are measured. • Correlation between the double-layer capacitance and current density is established. • Pseudocapacitance increases during the discharge and cycling due to side processes. In the present work, the capacitance of a positive electrode based on CNT OH is addressed. The variations in its double-layer ( C DL ) and pseudocapacitance ( C PC ) components were evaluated using cyclic voltammetry during testing lithium-oxygen battery (LOB). A decrease in C DL during the discharge process is established, equal to 64 %, 26 %, and 12 % of the initial value at current densities of 100, 200, and 500 mA g C -1 , respectively. The behavior of the C DL values and maximum discharge capacity under various current densities indicates that the oxygen concentration polarization affects the discharge characteristics of LOB. This influence exceeds the effect of blocking the positive electrode surface by the products formed in the cathode process. During LOB cycling, a decrease in the maximum discharge capacity correlates with a reduction in C DL , possibly, due to corrosion of the carbon material. An increase in C PC with prolonged cycling is explained by the accumulation of side products formed during discharging and charging.