A New Developed Fluorinated Electrolyte for Anode-Free Lithium Metal Battery

Abstract The glob is in need of efficient energy storage materials with an affordable cost, better energy density, safe and extended cycle life. To this end, scholars are investigating an alternative idea to boost the energy density, safety and minimize cost to satisfy the need of the society. One of the new ideas is the use of alternative design such as anode-free rechargeable lithium metal battery. In anode-free, the absence of Li+ host anode material reduces the cell weight and space required for the anode as a result; energy density of the cell will therefore be, significantly larger compared to the conventional Li-ion batteries. Nevertheless, realizing this anode-free battery in practical applications is still handicapped. The major reason for the failure of this system is depletion of the active Li and consumption of electrolyte solvents during repair of the solid electrolyte interphase. To mitigate this issue developing a functional electrolyte is therefore the key solution to bring it into practical application. Therefore, here we developed cost effective, highly fluorinated interphases forming new electrolyte solution of carbonate-ether mixed fluorinated electrolyte design with the standardized commercial salt LiPF6 which is stable at wider potential (2.5-4.5 V). The designed electrolyte suppresses dendrite growth, form conductive and stable LiF dominated solid electrolyte interface (SEI) for anode-free lithium metal battery using Cu‖LiNi0.3Mn0.3Co0.3O2. It shows stable cyclic performance with high average Coulombic efficiency > 98.7 % and high retention capacity for long cycles with 0.5 mA/cm2 current density both in the anode free system and NMC/MCMB full cell. The enhanced cycle life and well retained in capacity using the as-prepared electrolyte is mainly because of the synergistic effect of the partially fluorinated carbonated and ether based functional groups in which on contributes to the higher voltage and the other contributes to the higher efficiency. This is electrolyte combination is new and the best electrolyte ever reported for anode-free lithium metal battery to our knowledge. Keywords: SEI ; anode-free Lithium metal battery ; carbonate-ether mixed solvent ; copper foil, Fluorinated Interphase