Trivalent Ti self-doped Li 4 Ti 5 O 12 : A high performance anode material for lithium-ion capacitors

Abstract

Abstract To enhance kinetics of lithium insertion/extraction of anode materials for hybrid lithium-ion capacitors (hybrid LICs), we develop a new applicable strategy toward the synthesis of trivalent Ti self-doped Li 4 Ti 5 O 12 nanoparticles. Starting with Ti 2 O 3 , we show that subsequent solid state reaction with Li 2 CO 3 leads to the formation of trivalent Ti self-doped Li 4 Ti 5 O 12 . The presence of trivalent Ti gives rise to high electric conductivity and the nanostructure reduces the transport path lengths of lithium-ions and electrons, permitting fast kinetics for both transported lithium-ions and electrons, thus enabling high-power performance. A high performance hybrid LIC is fabricated by using Ti 3 + self-doped Li 4 Ti 5 O 12 as an insertion-type anode and activated carbon derived from outer peanut shell as cathode, which delivers high energy density (67 Wh kg − 1 ), high power density (8000 W kg − 1 ). Additionally, the device still retains about 79% of its original capacity even after 5000 cycles at 0.5 A g − 1 .