The lithium ion capacitor with a negative electrode of lithium titanium zirconium phosphate

Nanoparticles of LiTi1.5Zr0.5(PO4)(3) (LT(1.5)Z(0.5)P) with a nasicon-type structure have been prepared through a sol-gel modified pechini method, which allows a low synthesis temperature and yields a small crystallite size of 36 nm. When implemented as the negative electrode in a hybrid capacitor, LT(1.5)Z(0.5)P exhibits a sizable lithium capacity of 6-4 mol below 2.0 V vs. Li/Li+. But the actual capacity being exploited depends on the position of open circuit potential (OCP) at 0% state of charge (SOC). For the capacitor with a 1:1 mass ratio of LT(1.5)Z(0.5)P over activated carbon (AC), OCP at 0% SOC generally decreases with increasing mass-specific current and voltage window size, varying between 2.0 and 1.5 V vs. Li/Li+. Hence the LT(1.5)Z(0.5)P electrode surpasses the AC electrode in capacitance at high currents, leading to the LT(1.5)Z(0.5)P/AC capacitor behaves similar to a double layer capacitor. Conversely, the LT-LT(1.5)Z(0.5)P/AC capacitor exhibits more battery-like traits at low specific currents. The maximum energy density of this hybrid cell measures 46.7 Wh kg(-1) at voltage window 3.4 V and specific current 70 mA g(-1) (C) 2014 Elsevier B.V. All rights reserved.