Investigation and Design of Electrode-Electrolyte Interfaces to Enable Li-Ion Batteries for Extreme Temperature Operation

There is a growing demand for increasing the operating temperature of Li-ion batteries to improve thermal safety and extreme temperature performance to use in medical electronics, downhole drilling, and space applications (e.g. NASA’s Venus missions). Currently, Li-SOCl₂ primary batteries can work up to 150^oC, but primary cells have a huge negative impact on the environment, particularly spent batteries that are accumulated as e-waste. Surprisingly, global e-waste scrap generation is expected to double by 2030. Conversely, state-of-the-art rechargeable Li-ion batteries can operate optimally up to 50^oC, beyond this temperature range will lead to irreversible degradation, and sometimes catastrophic failures (fires and explosions). Unlike organic electrolytes, thermally stable ionic liquid-based electrolytes have immense potential to work with elevated temperature operation (~ 200 ^oC). However, understanding of the electrochemical interaction between ionic liquids and state-of-the-art electrode materials for elevated temperature operation is limited. Here, we investigate the electrode and electrolyte interface, particularly cathode electrode interphase (CEI), obtained at 100^oC and identify the nature of surface degradation using multimodal characterization methods.
This presentation will focus on discussing the depth-dependent nature of the CEI and transition metal heterogeneity on the reactive cathode (NMC-type) surface operated in an extreme environment. In addition, we will focus on the bulk and surface electronic structure evolution at extreme temperatures probed using soft and hard X-ray synchrotron spectroscopy investigations, followed by understanding of phase transformation through high-resolution microscopy imaging. In this talk, we will correlate the importance of stabilizing electrode-electrolyte interface with high temperature operation of Li-ion batteries. Understanding the high-temperature interfacial stability of the NMC-type cathode materials through multimodal spectroscopy and microscopy enables us to demonstrate the ambient temperature Li-ion battery technology to extreme temperature applications.