Three dimensional Ti₃C₂ MXene nanoribbon frameworks with uniform potassiophilic sites for the dendrite-free potassium...

Potassium (K) metal batteries hold great promise as an advanced electrochemical energy storage system because of their high theoretical capacity and cost efficiency. However, the practical application of K metal anodes has been limited by their poor cycling life caused by dendrite growth and large volume changes during the plating/stripping process. Herein, three-dimensional (3D) alkalized Ti₃C₂ (a-Ti₃C₂) MXene nanoribbon frameworks were demonstrated as advanced scaffolds for dendrite-free K metal anodes. Benefiting from the 3D interconnected porous structure for sufficient K accommodation, improved surface area for low local current density, preintercalated K in expanded interlayer spacing, and abundant functional groups as potassiophilic nuleation sites for uniform K plating/stripping, the as-formed a-Ti₃C₂ frameworks successfully suppressed the K dendrites and volume changes at both high capacity and current density. As a result, the a-Ti₃C₂ based electrodes exhibited an ultrahigh coulombic efficiency of 99.4% at a current density of 3 mA cm^-2 with long lifespan up to 300 cycles, and excellent stability for 700 h even at an ultrahigh plating capacity of 10 mA h cm^-2. When matched with K₂Ti₄O₉ cathodes, the resulting a-Ti₃C₂-K//K₂Ti₄O₉ full batteries offered a greatly enhanced rate capacity of 82.9 mA h g^-1 at 500 mA g^-1 and an excellent cycling stability with high capacity retention (77.7% after 600 cycles) at 200 mA g^-1, demonstrative of the great potential of a-Ti₃C₂ for advanced K-metal batteries.