Understanding the Influence of Temperature on Phase Evolution during Lithium-Graphite (De-)Intercalation Processes: An Operando X-ray Diffraction Study

Kurzfassung

Knowing the phase evolution behavior of battery materials isimportant for optimizing the operating conditions and under-standing the aging behavior of the material. Phase changes ofstate-of-the-art battery materials at room temperature are wellunderstood, but the influence of temperature on the phaseevolution is barely investigated. In this study, operando X-raydiffraction (XRD) is applied for the observation of phasechanges of graphite during cycling at different temperatures.The phase evolution is altered at lower temperatures (0°C)compared to room temperature due to slower kinetics anddiffusion rates even at low current rates of C/20. Differences inphase evolution between charge and discharge are morepronounced at 0°C compared to higher temperatures. Duringdelithiation at 43°C, the formation of stage 2L is more distinctthan at 25°C whereas at 0°C, no stage 2L formation is observed.However, at 0°C, several phases co-exist, supporting the theoryof the shrinking annuli mechanism for phase evolution during(de-)lithiation of graphite.