Ti 3 C 2 T x MXene Interface Layer Driving Ultra-Stable Lithium-Iodine Batteries with Both High Iodine-Content and Mass Loading.

Lithium-iodine (Li-I2) batteries are promising candidates for next-generation electrochemical energy storage systems due to their high energy density and the excellent kinetic rates of I2 cathodes. However, dissolution of iodine and iodide has hindered their widespread adoption for practical applications. Herein, a Ti3C2Tx MXene foam with a three-dimensional hierarchical porous architecture is proposed as a cathode-electrolyte interface layer in Li-I2 batteries, enabling high-rate and ultra-stable cycling performance at a high iodine content and loading mass. Theoretical calculations and empirical characterizations indicate that Ti3C2Tx MXene sheets with high metallic conductivity not only provide strong chemical binding with iodine species to suppress the shuttle effect, but also facilitate fast redox reactions during cell cycling. As a result, the Li-I2 battery using a cathode with 70 wt% I2 cycled stably for over 1000 cycles at a rate of 2 C, even at an ultra-high loading mass of 5.2 mg cm-2. To the best of the authors' knowledge, this is the highest reported loading at such a high iodine content. This work suggests that using a Ti3C2Tx MXene interface layer can enable the design and application of high-energy Li-I2 batteries.