Insights Into Improving the Li-Ion Transference Number and Li Deposition Uniformity Toward a High-Current-Density Lithium Metal Anode

Abstract

The practical application of lithium (Li) metal batteries (LMBs) faces challenges due to the irreversible Li deposition/dissolution process, which promotes Li dendrite growth with severe parasitic reactions during cycling. To address these issues, achieving uniform Li-ion flux and improving Li-ion conductivity of the separator are the top priorities. Herein, a separator (PCELS) with enhanced Li-ion conductivity, composed of polymer, ceramic, and electrically conductive carbon, is proposed to facilitate fast Li-ion transport kinetics and increase Li deposition uniformity of the LMBs. The PCELS immobilizes PF₆^– anions with high adsorption energies, leading to a high Li-ion transference number. Simultaneously, the PCELS shows excellent electrolyte wettability on both its sides, promoting rapid ion transport. Moreover, the electrically conductive carbon within the PCELS provides additional electron transport channels, enabling efficient charge transfer and uniform Li-ion flux. With these advantages, the PCELS achieves rapid Li-ion transport kinetics and uniform Li deposition, demonstrating excellent cycling stability over 100 cycles at a high current density of 12.0 mA cm^–2. Furthermore, the PCELS shows stable cycling performances in Li–S cell tests and delivers an excellent capacity retention of 95.45% in the Li|LiFePO₄ full-cell test with a high areal capacity of over 5.5 mAh cm^–2.

Keywords

Li metal batteries / Li-ion conductivity / separator modification / uniform Li deposition

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