Cycling Performance of NMC811 Anode-Free Pouch Cells with 65 Different Electrolyte Formulations

Abstract

Liquid electrolytes for anode-free Li metal batteries (LMBs) provide a cost-effective path to high energy density. However, liquid electrolytes are challenging due to the reactivity of Li0 with the electrolyte and the resulting Li loss, as well as mossy Li deposits leading to inactive Li and dendrite formation. Thus, more research is needed to develop electrolytes capable of 80 % capacity retention after 800 cycles to meet electric vehicle (EV) demands. Here, we report cycle life results from 65 electrolyte mixtures consisting of various additives or co-solvents added to a dual-salt base electrolyte previously reported by our group. We tested these electrolyte systems using a practical anode-free pouch cell design with a high-loading (16 mg cm−2, or 3.47 mAh cm-2) LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, with a bare Cu foil as the counter electrode. All cells in this work were cycled at 40 °C with 0.2C/0.5C charge/discharge rates between 3.55–4.40 V. Based on the total energy delivered over 140 cycles, only four electrolytes showed marginal improvement over the baseline, while the other electrolytes were uncompetitive. This data set can serve as a guide for LMB researchers investigating electrolyte systems and highlights the challenges associated with liquid electrolytes.