Regulating Lithium Metal Deposition for Safe Cell Operation and to Extend Cyclic Performance of an Anode-Free Lithium Metal Battery

Abstract

Using the ideal Lithium metal (Li) as an anode material for Lithium metal batteries (LMBs) displays considerable potential in enlightening energy density and power density than conventional lithium-ion batteries (LIBs). Nevertheless, the low Coulombic efficiency, significant volume changes during operation, which reduces electrode mechanical stability, and Lithium (Li) dendrites formed and growth from nonuniform Li deposition during cell operation causes safety issues and limits potential uses of Li as an anode material for LMBs. Recently, anode free (Lithium free) lithium metal batteries (AFLMBs) protocol have got great attention due to their higher energy density, reduces cell weight, costs effectiveness, easy fabrication, and safety during the process of cell manufacture. Nevertheless, in AFLMBs, the uncontrolled plating of lithium on bare copper foil imposes a more severe lithium dendrite growth. Hence, planning proper design on an anode current collector which is appropriate for AFLMBs is essential. Herein, we handle the growth of lithium dendrite by guiding lithium metal deposition site to the backside of the gold-sputtered perforated polyimide film (PI@Au), which used as an anode current collector. Hence, metallic lithium (Li) starts to plate on the modified PI@Au surface, and sequentially, growth of Li takes place in the direction away from the separator face (ASF). This backside deposition and growth approach allow the battery to operate safely, even when lithium dendrite exists. . Surprisingly, the dendrite-free surface on the separator-facing side (SF) of PI@Au anode reveals significantly improved cycling stability. As a result PI@Au//Li cell (2 mAh/cm2 and 0.5 mA/cm2) offers stable cycling performance for 1400 h without significant voltage polarization. Conversely, Cu//Li cell cycling with results higher voltage hysteresis and face short-circuit below 600 h at same working conditions. Besides, PI@Au//LFP anode-free full cell configuration maintained 20 % capacity retention (CR) with average Coulombic efficiency of 98.7 % after 340 cycles (0.5 mA/cm2). On the contrary, the Cu//LFP full cell runs only for 165 cycles under the same value of CR. Guiding the plating of Li to the backside of perforated polyimide film insights into an innovative technique for developing ultra-safe AFLMBs and also proves the viability of the electrical insulator substrates as anode current collectors by improving their conductivity and lithiophilicity.