Siloxene: A potential layered silicon intercalation anode for Na, Li and K ion batteries

The alloying reaction between 14th group elements and alkali can be detrimental for Li, Na or K-ion batteries due to the large associated volume expansion that leads to a rapid capacity fading. In order to overcome this issue, their associated 2D phases are promising anodes that enable alkali intercalation without alloying reaction and volume expansion. In this study, the lamellar siloxene obtained from topotactic deintercalation of Ca from CaSi2 delivered reversible capacities of 2300, 311 and 203 mAh/g for Li, Na and K, respectively, with good capacity retention and coulombic efficiency for Li and Na. The intercalation mechanism taking place upon cycling is highlighted on the basis of ex situ Raman characterization combined with IR spectroscopy, SEM and TEM. To the best of our knowledge, it is the first time that a lamellar Silicon based material shows such high stable capacity without volume expansion, representing a real breakthrough for the batteries field and particularly for NIB.