Facile fabrication of highly porous TiO2 microrods anode with enhanced Al-ion storage for hybrid capacitors

Hybrid capacitor has attracted great interest owing to the higher energy density compared with traditional double-layer capacitor. However, the fabrication of high-performance hybrid aqueous capacitor based on low-cost and multivalent ion storage remains challenging. In this work, highly porous TiO2 microrods (P-TiO2 MRs) with uniform and large pore size are prepared extensively with a simple hydrothermal synthesis. Such micro/nano-structured anode exhibit remarkably enhanced Al ion intercalation/deintercalation performance in optimized AlCl3 aqueous electrolyte. The electrode has large discharge capacity with 111.1 mAh g(-1) @ 1 A g(-1) and superior rate capability with 49.8 mAh g(-1) @ 5 A g(-1). For the first time, a novel hybrid device is fabricated through assembling insertion-type P-TiO2-MRs anode and absorption-type active carbon (AC) cathode (P-TiO2 MRs//AC) in AlCl3 aqueous electrolyte. The fabricated hybrid capacitor delivers a high energy density of 26.3 Wh kg(-1) @ 627.3 W kg(-1) as well as an outstanding high power of 5454.5 W kg(-1) @ 10.9 Wh kg(-1). In addition, it also displays excellent rate capability and superior retention of 63% even after 1000 cycles.