Intergrowth Domains of Various Coloration Types in Metastable Li _2.76 Sn—A Phase Occurring in Tin Anodes of Lithium‐Ion Batteries

A metastable intermetallic phase with composition Li 2.76 Sn, according to chemical analysis, was obtained from lithium depletion of Li 17 Sn 4 with liquid ammonia. Differential scanning calorimetry reveals a monotropic exothermic transition above 395 K mostly transforming the material to Li 13 Sn 5 with a similar atomic ratio of the constituents. Temperature‐dependent X‐ray diffraction experiments support these results. The powder X‐ray diffraction pattern of Li 2.76 Sn has a striking similarity to those reported for transient phases observed in operando and in situ studies of tin anodes for lithium‐ion batteries exhibiting sharp and very broad reflections, while crystallites show diffuse reflections. A multiphase model including dominating fractions of both a disordered bcc‐type and a NaTl‐type Li 1− x Sn x structure next to an ABBA‐type stacking variant as coloration variations of the W‐type structure leads to a satisfying fit of the X‐ray diffraction pattern, if short coherence lengths of only a few nanometers are taken into account. The interfaces of the different domains in this respect can be regarded as resembling antiphase domain disorder. With these structural insights, we shed light on such transient metastable phases occurring during lithium (de)intercalation cycles in tin anodes, as important information for designing and modeling lithium‐ion batteries.