A Highly Stable Li₄Ti₅O₁₂ Suspension Anolyte for Lithium Ion Flow Batteries

Abstract

A flow battery is one of the most promising candidates for large scale energy storage devices due to its ease of design, construction, and control, while its energy density is yet to be enhanced. The lithium ion suspension electrode, which is usually comprised of electrolyte, active material and other additives, is an effective way to enhance the energy density of flow batteries due to their relatively high active material loading per unit of volume. However, a stable suspension electrode is difficult to be obtained mainly for two reasons, the high density of common electrode materials and the poor conductive network in the suspension. In this work, a stable Li₄Ti₅O₁₂ (LTO) suspension anolyte is successfully prepared with the aid of polyethylene oxide (PEO) and carbon nanotubes (CNTs), in which PEO stabilizes the anolyte by intramolecular repulsion force, and CNT builds an integrated conductive network. The anolyte delivers a high reversible capacity of more than 140 mA h/g under 0.5C rate, and it keeps more than 80% of its initial capacity in 200 cycles was never been achieved in any previous research work. This strategy is also hopefully suitable for the design of other suspension electrodes, such as graphite and LiFePO₄, which shine a light on high energy density flow battery development.