High mass loading, binder-free MXene anodes for high areal capacity Li-ion batteries

Though anodes with high Li gravimetric capacities, beyond commercial graphite, have been intensively studied, gravimetric capacity does not precisely reflect the performance of a packed cell. Li anodes with high mass loadings, which can achieve high areal capacities, are required for many commercial applications. Herein, anodes with high mass loadings were fabricated using two-dimensional transition metal carbides (MXenes). Powders of the latter were cold pressed, without binders, at a pressure of 1 GPa, to create ∼300 μm thick, free-standing discs. When Ti₃C₂ was used as the anode for lithium, the initial reversible areal capacity was ∼15 mAh/cm², which decreased to 5.9 mAh/cm² after 50 cycles, but the decrease after the first ∼20 cycles was very gradual. The latter is one of the highest values ever reported to date. When Nb₂C was used as the anode instead, the initial reversible capacity was ∼16 mAh/cm²; this value decreased to 6.7 mAh/cm² after 50 cycles, which is about a 14% increase compared to Ti₃C₂. As the research on MXenes for lithium ion batteries has just begun, there is certainly room for further improving their electrochemical performance.