Advanced Fluorinated Electrolytes Supporting High-Energy Lithium Batteries with Ni-Rich Cathodes

Abstract

Developing new electrolytes that cater to the needs of lithium anode and Ni-rich cathodes is critical for next-generation battery technologies with high energy density and enhanced safety. Although significant advances have been made in non-aqueous electrolytes with wide electrochemical stability window (ESW), the performance of lithium battery is still not comparable to that of commercial Li-ion batteries (LIBs) due to the notorious reactivity of metallic lithium as well as the catalytic nature of high-voltage cathode. Such situations require rational design of advanced electrolytes and mechanistic understanding on interphase formation for stabilizing the electrolyte-electrode interfaces and supporting the next-generation battery chemistries beyond LIB technology.In the presentation, I will introduce the design and development of nonflammable fluorinated electrolytes (NFEs) in Prof. Chunsheng Wang group. We demonstrated that the NFEs with wide ESW are able to form thin fluorinated interphase on both Li anode and high-voltage Ni-rich cathodes, thus leading to high efficiencies of Li-metal plating/stripping (> 99.2%) for a 5 V cathode LiCoPO4 (~99.81%) and a Ni-rich LiNi0.8Mn0.1Co0.1O2 cathode (~99.93%).[1] Meanwhile, the NFEs with LiDFOB additive enables high-energy cobalt-free LiNiO2 (LNO) cathode to achieve a good cycle life.[2] The in-situ-formed F, B-rich interphase is proved to protect the LNO from continuous reactions with electrolyte and suppress the structural transformation from layered to disordered rock-salt (NiO) phase. Further study found that the non-polar fluorinated solvent could help maintain the high Li-ion conductivity of NFEs even under -125 oC, thus enable good cycling of all-temperature Li metal batteries operating from -80 to +70 oC.[3] The key findings on NFEs system provide a new avenue towards high-energy and safe Li metal batteries with wide operational temperature range.