Surface confined titania redox couple for ultrafast energy storage

Abstract

Practical large-scale energy storage should deliver high capacitance/capacity with an ultrahigh rate and do so economically over multiple cycles. Existing electrode materials, however, have fallen short of these requirements in one measure or another. Here, we have discovered a surface confined titania redox couple on black TiO₂ nanotube arrays (B-TNAs). Such rapid Ti³⁺/Ti⁴⁺ conversion provides an outstanding rate for B-TNAs of 400 mA cm⁻² in supercapacitors (SCs) and 200 C in lithium ion batteries (LiBs), with negligible capacitance/capacity fading for up to 15 000 cycles. The ultrafast pseudocapacitive behaviour from black titania suggests a new family of electrode materials, which may offer a way to overcome the present difficulties of SCs and LiBs in grid-scale energy storage systems.