Most of beyond lithium ion chemistries and next generation lithium ion chemistries will require thin lithium metal anode use to achieve targeted volumetric energy density. Today, production of thin lithium foil involves extrusion of lithium metal followed by rolling to achieve desired thinness, which is complicated and expensive; thus, no commercially viable source of thin foil exists. SLMP-derived thin Li foil offers the possibility of achieving thin foil with width being limited only by the substrate used.
In this work, we show the effectiveness of SLMP in improving the performance of commercially available silicon-based anode material. The anode composition is 85% SiO/C composite material and 15% Polyimide binder. The cathode composition is LiCoO2 (90%) + carbon black (5%) + PVdF (5%). Surface application technique was used to apply SLMP slurry onto the surface of prefabricated SiO electrodes. Single layer pouch SiO/LiCoO2 cells were assembled and 1M LiPF6 /EC+DEC (1:1) was used as the electrolyte. The pouch cells were conditioned at room temperature for 24 hours before the battery test. The pouch cell test protocol was: constant current charge at C/10 to 4.3 V, constant voltage charge at 4.3 V to C/100; constant current discharge at C/10 to 3.0 V. SLMP utilization has been evaluated based on its ability to compensate first cycle irreversible capacity.
Figure 1 below shows the effect of SLMP on first cycle efficiency of SiO/LiCoO2 pouch cells.
One of the important properties of SLMP is its specific capacity. SLMP contains at least 97% metallic lithium which can be fully utilized. To demonstrate this, an electrochemical system has been designed to test SLMP’s capacity, Li/Electrolyte/SLMP+Cu. About 1 mg of SLMP was deposited onto a half-inch Cu disc using a slurry of SLMP. After the solvent was fully evaporated, the electrode was calendered using 12,000 lbs pressure creating SLMP-derived thin Li foil. The electrodes were used to assemble coin cells with lithium foil counter electrode. 1M LiPF6/EC+DEC was used as the electrolyte. The cells were charged at 0.1 mA to 3.0 V.
Figure 2 shows the voltage profiles for the cells comprised of SLMP-derived thin foil. The voltage profiles and the SLMP capacity are reproducible. Close to theoretical lithium capacity can be extracted from the SLMP derived thin foil.
We will also discuss a novel SLMP delivery system which can be used at commercial scale to safely and economically incorporate SLMP into existing LIB systems as well as being used to produce ultra-thin lithium foil for solid state lithium applications.
References
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