Dual-functional iodine photoelectrode enabling high performance photo-assisted rechargeable lithium iodine batteries

An integrated battery system, which integrates solar power and a rechargeable battery in the same unit, is an effective solution for the shortage and inefficiency of power energy. We initially present an integrated photo-assisted rechargeable lithium-iodine (Li-I 2 ) battery system using a hybrid I 2 /N719-dye/TiO 2 composite as a dual-functional photoelectrode. In this integrated battery system, the photovoltage generated on the hybrid photoelectrode compensates for the charging voltage of the cell, which decreases the charging potential by ∼100 mV under a chronoamperometry test. To be exact, under illuminated conditions, the integrated Li-I 2 battery extends the charge/discharge capacity from 171/166 mA h g −1 to 204/193 mA h g −1 , with a higher energy efficiency of 93% (output electric energy/input electric energy) compared to that of an Li-I 2 battery (that is ∼87%). Furthermore, the accelerated redox kinetics of lithium polyiodine conversion are also revealed by the enhanced electrochemical behavior and density functional theory calculation. We believe that such a design with an integrated photo-assisted rechargeable Li-I 2 battery can hew out a new way to realize the application of efficient solar energy conversion and storage. We demonstrate an integrated photo-assisted rechargeable lithium-iodine battery by using a hybrid I 2 /N719-dye/TiO 2 composite as a dual-functional photoelectrode, which could convert solar energy into electrical power and store it simultaneously.