Gassing behavior and safety issues for Li-Rich cathodes

Abstract

Over the past decades, lithium-rich layered oxides (LLOs) have garnered significant research attention on account of their prominent advantage of high-energy-density. However, gas evolution is one of crucial issues, exerting a detrimental impact on battery's cycle performance and intrinsic safety. This perspective systematically presents that the gas evolution is largely attributable to the release of high-reactivity oxygen species under both high-voltage or high-temperature conditions. We suggest that future research of gas-related thermal runaway (TR) safety issue should focus on twe aspect scientific questions.(i) Thermal stability of de-lithiated LLOs cathode: What is the intrinsic correlation between the microstructural characteristics and thermal stability of de-lithiated LLOs, and what are the key governing factors that dictate their thermal stability? (ii) Thermal stability of the cathode-electrolyte interface: what is the detailed transformation pathways of reactive oxygen species and the specific interfacial reaction mechanisms occurring at the cathode-electrolyte interface (for delithiated LLOs) under heating process? On this basis, the development of multimodal combined characterization platform is proposed innovatively, including in-situ XRD, in-situ gas analyzer, DSC, TGA, and other complementary technologies. Based on collected comprehensive information (e.g., phase transitions, gassing behavior, heat generation, and weight loss ), the intrinsic structure-activity relationships between microstructural characteristics, gassing behavior and TR risks are expected to be unveiled. Assisted with artificial intelligence (AI), R&D cycle for low-gas-emission, high-safety LLOs materials and matched electrolyte could be substantially shortened.