BEYOND LI ION: INTERFACE ENGINEERING ENABLES HIGH ENERGY DENSITY LI AND NA METAL BATTERIES

Abstract

The ever-increasing demand from electric vehicles and consumer electronics, as well as the expanding market of intermittent renewable energy storage, has sparked extensive research on energy-storage devices with low cost, high energy density, and safety. Although the state-of-the-art Li-ion battery (LIB) based on highly reversible intercalation chemistry has approached its theoretical limit after several decades’ incremental improvement, there is still no great progress in the exploration of alkaline metal chemistry (Li & Na) for next-generation batteries. Compared with Li-ion chemistry, alkaline metal anode is more attractive due to the extremely high capacity (3860/1166 mA g-1 for Li/Na) and low negative electrochemical potential (-3.04/-2.71 V for Li/Na vs. the standard hydrogen electrode), thus enables next-generation batteries with high energy density. To achieve this, significant advances have been made in liquid or solid-state electrolytes that cater to the high capacity Li/Na anodes and high-voltage cathodes, but performance of the battery is still not comparable to that of commercial LIB due to dendrite formation and unstable interphase formation. Such situation requires a deep exploration on the rational design of electrolytes and interfacial stability between the electrolytes and electrodes for realizing next-generation batteries. In this dissertation, I detailed our efforts in exploring new electrolyte systems and proposed some interface engineering strategies or methods to stabilize the electrolyte-electrode interfaces, thus supporting the next-generation battery chemistries beyond LIB technology. They include nonflammable fluorinated electrolytes, polymer composites electrolytes, as well as solid-state garnet-type (Li6.75La3Zr1.75Ta0.25O12) and Na-beta-alumina (β''-Al2O3) electrolytes for Li/Na metal batteries. We studied the dendrite formation and electrode-electrolyte interface stability in the corresponding chemistry, thermodynamics, as well as kinetics. Based on the learned mechanisms, we also proposed our strategies to suppress dendrite formation and realize good performance Li/Na metal batteries by forming stable electrolyte-electrode interphases. Being enabled by the fundamental and scientific breakthroughs in terms of electrochemical mechanisms, interface chemistry, as well as interface modification techniques, this work has provided insights into the development of high-energy Li/Na metal batteries for both academic and industrial communities.