Printable Lithium Technology for Pre-Lithiation and Solid-State Battery Applications
Authors: Fitch Brian , Xia Jian , Watson Andrew , Cabaniss Emory , Black Rebecca , Yakovleva Marina 
Published: December 2020

The need for pre-lithiation has become more important due to the commercialization of anodes containing silicon for high energy density batteries. When Si / Graphite mixtures are used, there can be 10-20% or higher active lithium loss on the first charge depending on the amount of Si used. Pre-lithiation can introduce sacrificial lithium into a lithium ion cell which will off-set the irreversible lithium loss. There are many proposed pre-lithiation techniques such as roll-to-roll electrochemical baths, sacrificial salts, vacuum deposition and lithium sputtering. (1) None of these pre-lithiation methods have been scaled beyond the laboratory or pilot scale due to safety, cost, manufacturing inefficiencies or cell performance issues. Currently, the pre-lithiation method that has shown the most promise is the addition of lithium metal to the prefabricated anode (2), (3), (4). Because of its high capacity, lithium metal causes a negligible increase in cell mass and volume. In comparison, when sacrificial salts are used, the energy density can decrease due inactive phases remaining after lithium extraction.
One solution has been to use stabilized lithium metal powder (SLMP®) to pre-lithiate silicon-based anodes (5), (6). The use of Livent’s advanced material, Lectro® Max Powder (SLMP) has been demonstrated worldwide as an effective and efficient pre-lithiation material (7). SLMP can deliver capacity close to the theoretical lithium capacity of 3860 mAh/g and, after addition of the electrolyte, it intercalates or alloys with the anode material in-situ, and; therefore, exists in the lithium ion form in the cell. By incorporating this sacrificial source of lithium in the anode to compensate for first cycle irreversible losses, the lithium provided by the cathode can be fully utilized.
The use of dry SLMP in large scale deployments presents challenges that have delayed wide-spread adoption of the technology. To this end, Livent has developed a proprietary technology that incorporates SLMP into a stable printable formulation. Printable Lithium Technology (PLT) is uniquely positioned to address challenges associated with handling of a high surface area reactive powder; thus, allowing to mitigate both industrial hygiene and process safety issues. Printable Lithium Formulation (PLF) is comprised of SLMP dispersed in a compatible solvent along with other rheology and performance modifiers to create a formulation that is chemically stable and not prone to separation for extended periods of time. The solvent used is compatible with commercial electrode slurry solvent removal and recovery practices and is less toxic than NMP. The technology is easily scalable using industry standard coating and printing equipment to apply the formulation to the surface of a prefabricated anode. PLT is adaptable to any anode or cathode chemistry where an independent source of lithium is required. PLT can be used in anodes with a range of silicon content, because lithium loading can be accurately controlled based on the applications’ requirements. Lithium loading control is achieved through modification of the print head to print stripes of various width and spacing on the electrode surface. The patterns can range from narrow stripes spaced evenly across the electrode to a monolithic lithium layer.

F
igure 1. Cycle performance for commercially available electrode materials with anode loading > 4mAh/cm2. A) NMC811/Graphite-10% SiO; B) NCA/Graphite-10% SiO, C) LCO/80% SiO Composite; D) LFP/Hard carbon. Cycling condition: A and B: CCCV (0.5C rate with charge current cut off 0.1C), 2.8-4.2V at RT. Every 50th cycle is at C/10 rate. C: 2.8-4.45V, 0.1C-0.1C at RT. D: 2.5-3.5V, 0.1C-0.1C at RT.

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Figure 1