The influence of LiNO3 on the electrochemical performance of anode-free LMBs with carbonate-based electrolytes

Stuckenberg, Silvan; Bela, Marlena Maria; Lechtenfeld, Christian-Timo; Mense, Maximilian; Küpers, Verena; Ingber, Tjark Thorben Klaus; Winter, Martin; Stan, Marian Cristian

Zusammenfassung

The increased energy density and safety properties promised by zero-excess lithium metal batteries (ZELMBs) are shadowed by continuous lithium (Li) depletion. Guiding the Li deposits towards more homogeneous and denser lithium morphology, results in an improvement of electrochemical performance. Herein, a lithium nitrate (LiNO3) enriched separator that improves the morphology of the Li deposits and facilitates the formation of an inorganic-rich solid electrolyte interphase (SEI), resulting in an extended cycle life in Li ‖ Li symmetric cells as well as an increase of the Coulombic efficiency in Cu ‖ Li cells is reported. Furthermore, using a LiNi0.6Co0.2Mn0.2O2 positive electrode in NCM622 ‖ Cu ZELMBs cells and a carbonate-based electrolyte, a LiNO3 enriched separator shows an extension of the cycle life by more than 50 cycles with a moderate capacity fading compared to the unmodified separator. The reason for the improved performance can be explained by the relatively constant level of LiNO3 in the electrolyte, maintained by the LiNO3 enriched separator throughout the cycling process. Ion chromatography measurements carried out at different cycles support the proposed mechanism of a slow and constant release of LiNO3 from the separator. The results presented here indicate that the strategy of using a LiNO3 enriched separator instead of LiNO3 as sacrificial electrolyte additive can improve the performance of ZELMBs further by maintaining a compact and thus stable SEI layer on the Li deposits.