Evolving MXene species

A Li-ion battery (LIB) with superior interior thermal management behavior to avoid thermal runaway is crucial for safe and long-lasting operation, especially at high temperatures or during fast discharging and charging. However, due to the lack of low-resistance electrode materials with comparatively low mid-infrared emission, such interior thermal management properties are usually achieved by focusing on the separator and electrolyte when overheating occurs. Herein, we developed a Se-terminated MXene free-standing electrode with superior electrical conductivity and low infrared emissivity to synergistically couple high-rate capacity with reduced heat radiation ability for safe, large and fast Li+ storage, which was achieved through one-step organic Lewis acid-assisted solid-state reaction and vacuum filtration. Compared to conventional disordered O/OH/F-terminated materials, Se-terminated Nb2Se2C was found to enhance the Li+-storage capacity by approximately 1.5-folds in the fifth cycle (221 mAh·g−1 at 1 A·g−1) and promote the mid-infrared adsorption with low thermal radiation. These effects are mainly induced by its superior electrical conductivity, excellent structural stability, and high permittivity in the infrared region. Further calculation by infrared spectra selectivity revealed that the increase in permittivity and the oriented enhancement of conductivity along the z-direction could reduce the heat radiation of electrodes. This work sheds light on a promising surface groups-terminated layered material-based free-standing flexible electrodes with novel self-thermal management ability and high-rate performance for safe and fast energy storage.