Demonstration of Li-Ion Capacity of MAX Phases

Herein we report on the reversible electrochemical intercalation of Li ions into Ti2SC and Ti3SiC2, layered ternary transition-metal carbides, known as MAX phases. It is demonstrated that the particle size plays an important role in the electrochemical performance of MAX phases. Ti2SC particles with a size of hundreds of nanometers showed an initial reversible capacity of ∼80 mAh g–1 at 4 C, which increased to ∼180 mAh g–1 after 1000 cycles. This capacity was two times higher than that of Ti2SC with micrometer-sized particles. The increasing capacity with cycling was considered evidence for the reversible intercalation of Li ions into Ti2SC, as confirmed by transmission electron microscopy and Raman spectroscopy. In addition to Ti2SC, other MAX phases, such as Ti3SiC2, also exhibit promising Li-ion storage capability. This work suggests that the MAX phases, a large family of more than 70 stoichiometric phases and numerous solid solutions, are promising anode materials for Li-ion batteries and capacitors.