Synthesis of MXene/Ag Composites for Extraordinary Long Cycle Lifetime Lithium Storage at High Rates

A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge–discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g–1 at 1 C (theoretical value being ∼320 mAh·g–1), 260 mAh·g–1 at 10 C, and 150 mAh·g–1 at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1–50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process.