A 3.5 V Lithium-Iodine Hybrid Redox Battery with Vertically Aligned Carbon Nanotube Current Collector

A lithium-iodine (Li-I-2) cell using the triiodide/iodide (I-3(-)/I-) rcdox couple in an aqueous cathode has superior gravimetric and volumetric energy densities (similar to 330 W h kg(-1) and similar to 650 W h L-1, respectively, from saturated I-2 in an aqueous cathode) to the reported aqueous Li-ion batteries and aqueous cathode-type batteries, which provides an opportunity to construct cost-effective and high-performance energy storage. To apply this I-3(-)/I- aqueous cathode for a portable and compact 3.5 V battery, unlike for grid-scale storage as general target of redox flow batteries, we use a three-dimensional and millimeter thick carbon nanotube current collector for the I-3(-)/I- redox reaction, which can shorten the diffusion length of the redox couple and provide rapid electron transport. These endeavors allow the Li-I-2 battery to enlarge its specific capacity, cycling retention, and maintain a stable potential, thereby demonstrating a promising candidate for an environmentally benign and reusable portable battery.