A novel high-performance cylindrical hybrid supercapacitor with Li4−xNaxTi5O12/activated carbon electrodes

A cylindrical hybrid supercapacitor was fabricated using Li4−xNaxTi5O12 as an anode and activated carbon as a cathode. Li4−xNaxTi5O12 (0 ≤ x ≤ 0.6) powder was successfully crystallized, and the grain size of Li4−xNaxTi5O12 decreased with increasing Na content. This indicated that Na can enhance the electrochemical performance due to smaller grain size and ionic conductivity. However, excessive Na content causes a distortion of the original Li4Ti5O12 structure during cycling. The hybrid supercapacitor with the Li3.7Na0.3Ti5O12 anode shows similar electrochemical performance to Li3.4Na0.6Ti5O12, and approximately 92% of the maximum cycle performance is retained, even after 5000 cycles at 2.5 Ag−1.