Optimizing interface concentration and electric fields for enhanced lithium deposition behavior in lithium metal anodes

Abstract

Understanding dynamic fluctuations in complex multi-physics fields at the electrolyte/electrode interface is crucial for explaining the lithium deposition mechanism and developing efficient interface structures, but there are significant challenges. Here, we introduce an internal standard substance (1,1,2, 2-tetrafluoroethyl-2,2,3, 3-tetrafluoropropyl ether (TTE)) to propose a quantitative in-situ Raman spectroscopy method to disclose the variation of interfacial concentration filed. It is proved that the formation of anion depletion layer at the electrolyte/electrode interface during lithium deposition leads to the formation of space charge layer (SCL) with local electric field, which can accelerate dendrite growth and is closely related to the withdrawth of anion from interface. Further, a high anion-concentration interface (HACI) with immobilized anions is proposed. This HACI can effectively prevents the anion depletion at interface and enhance the interfacial Li+ transference number from 0.30 to 0.57, thus alleviating formation of SCL and facilitating uniform lithium deposition. Hence, the full cell with high-load NCM523 cathode (~14 mg cm-2) and limited HACI@Li anode (~50 μm) delivers excellent cycling over 200 cycles with a high discharge capacity retention of 77.6 % (~125.7 mAh g-1). This offers critical insights for designing lithium battery systems from the perspective of multi-physics field.