Electrochemical capacitance of titanium nitride modified lithium titanate nanotube array

Abstract

Titanium nitride modified lithium titanate nanotube array (TiN-Li4Ti5O12 NTA) was designed as the electrode material of lithium-ion supercapacitor for electrochemical energy storage. Li4Ti5O12 NTA was prepared through lithiation treatment of anodic TiO2 NTA and then annealing treatment in argon. TiN-Li4Ti5O12 NTA was formed through coating TiO2 sol on the surface of Li4Ti5O12 NTA and then full nitridation treatment in ammonia. Partially nitridized Li4Ti5O12 (N-Li4Ti5O12) NTA was also prepared through a controlled nitridation treatment of Li4Ti5O12 NTA in ammonia. TiN-Li4Ti5O12 NTA with full TiN coating layer exhibited higher conductivity than N-Li4Ti5O12 NTA with partially incorporated TiN. The capacitance accordingly increased from 79.58 F g−1 for N-Li4Ti5O12 to 143.83 F g−1 for TiN-Li4Ti5O12 at 0.5 A g−1 in 0.5 M Li2SO4. The capacitance retention ratio also increased from 72.95% to 82.41% after 1000 cycles at 3.0 A g−1. The all-solid-state supercapacitor was constructed using TiN-Li4Ti5O12 NTA electrode and polyvinyl alcohol gel electrolyte containing Li2SO4, showing high capacitance of 40.45 F g−1, energy density of 32.36 Wh kg−1 and power density of 0.6 kW kg−1 at the high output voltage of 2.4 V and current density of 0.5 A g−1. Therefore, TiN-Li4Ti5O12 NTA could act as a feasible electrode material of lithium-ion supercapacitor.