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/TiO2 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 similar to 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 similar to 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.