PI: Jennifer L.M. Rupp, Electrochemical Materials Laboratory, MIT
Abstract
Batteries are among the primary products to supply and manage energy from renewable sources for electric vehicles, ensure grid stability and power portable electronics. However, despite decades of effort, the majority of commercial batteries (>90%) operate on conflict elements such as cobalt and have an inherent risk for inflammation operating on liquid electrolytes. Cobalt is a geopolitically sensitive element as 60% of the world`s share is mined in a single country, often under violation of the environment and human rights. Here, we propose the design and fabrication of conflict-free and safe solid state batteries based on Li-garnet ceramics. For this, we explore novel cobalt-free materials for high-voltage cathodes and investigate their interfaces through thin film model experiments to tune lithium diffusion for fast charging and high storage capacities. For rapid implementation, inexpensive ceramic processing techniques are in focus and consumer safety is increased by the solid nature of the battery materials.
Report
- Project Title: Safe All Solid State Batteries
- Principal Investigator: Jennifer L.M. Rupp, Electrochemical Materials, Department of Materials Science and Engineering, MIT
- GrantPeriod: September 2017 – August 2018
Results summary
One of the big issues of successful operation of all-solid state battery is interfacial resistance between solid electrolyte and solid active materials. State-of-the-art Li-ion battery use liquid type electrolyte which can be easily dispersed through the cathode and wet with active material, thus this provides high enough number of contact points (active sites for Li intercalation/deintercalation) and reasonable energy capacity. However, the extremely poor contact quality and limited Li charge transfer will take place when the liquid electrolyte is replaced with solid electrolyte. To enhance Li charge transfer at the solid-solid interface, strong connection as a result from neck formation, thereby sintering at elevated temperature is necessary. In this project, we selected one of the co-free cathodes, namely Li Iron Phosphate, as a model active cathode material to develop design principle of solid-state battery.
During the project period, we have investigated: i)Synthesis, fabrication and characterization of cubic Li-garnet electrolyte (Li6.5La3Zr1.5Ta0.5O12, LLZO) (pellet and powder), ii)Chemical compatibility study of between Li Iron Phosphate and Li-garnet solid electrolyte,iii)Optimize sintering temperature by means of impedance spectroscopy, iv)Fabrication and characterization of full cell: optimizing ceramic processing route and applying interface engineering until to obtain theoretical capacity of a Co-free cathode.