Fabricating Solid-State Electrolyte Li-Ion Cells through Composite Ionogel Electrodes

Abstract

Fabricating high loading electrodes is essential to realizing Li-ion cells with solid-state electrolytes (SSE) that have relevant energy densities. However, making sure lithium can reach the active materials is complicated if the ions are isolated in the electrolyte phase. Low loading electrodes can prevent this issue by having all active material in contact with the SSE, but this tactic makes scalability and relevance to commercialization an issue. To this end we devised a strategy to create electrodes with sufficient Li+ conductance and 10 mg/cm2 loading to ensure cells without liquid electrolyte are capable of achieving high capacity utilization at room temperature. This was done through creating an ionogel-derived SSE and using the same ionogel based precursors to fabricate composite electrodes. By tuning the ratio of ion conducting polymer, carbon, and active material composite lithium titanate electrodes were cycled with an ionogel SSE in a half cell configuration that achieve theoretical capacity at C/5 and stable cycling at ~6 mA/cm2. Full solid state coin cells were also constructed with a composite lithium iron phosphate cathode, SSE, and composite lithium titanate anode. These cells were able to cycle at 1C rate at room temperature. We believe this version of cells is a scalable approach to solid state batteries. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525