Designing High Performance Lithium Metal Batteries via Interfacial Engineering of Electrodes with Functional Coatings

Abstract

Over the past decades, the global energy paradigm has rapidly shifted from fossil fuels to renewable energy sources, leading to an increasing demand for high-energy-density energy storage systems. Since their first commercialization in 1991, lithium-ion batteries (LIBs) have continued to evolve and are now widely used in various applications such as portable electronics and electric vehicles. However, despite extensive research and technological advances, LIBs have reached their theoretical capacity limits due to the intrinsic limitations of electrode materials. In this regard, lithium metal anodes (LMAs) have emerged as the most promising anode candidates due to their high theoretical gravimetric specific capacity (3860 mAh g-1) and low redox potential (-3.04 V vs. S.H.E.), which enable approximately twice the energy density and specific energy (>450 Wh kg-1) compared to conventional LiBs. Nevertheless, the practical implementation of LMAs has been severely hindered by uncontrollable dendritic growth, significant volume fluctuations, and unstable solid electrolyte interphase (SEI) formation during cycling. The growth of Li dendrites can penetrate the separator and reach the cathode, causing short circuits and raising serious safety concerns. Moreover, the uneven stripping of Li dendrites leads to the formation of inactive Li, referred to as "dead Li," which decreases the Coulombic efficiency (CE) and causes substantial volume expansion. Therefore, suppressing the growth of Li dendrites remains a top priority in the development of long-lasting and stable lithium metal batteries (LMBs). To address these challenges, this thesis proposes the design of functional interfacial coatings aimed at reversible Li plating/stripping under practical conditions. In particular, comprehensive investigations were conducted to elucidate how interfacial phenomena influence Li deposition behavior. The proposed coatings offer multiple advantages, including simple fabrication, strong adhesion, scalability, and uniformity. The overall contents of this thesis are organized as follows:

1. The first chapter provides a brief review of Li metal battery systems, highlighting their critical limitations and summarizing previous strategies developed to address these issues.

2. The second chapter introduces a polar and electrically insulating scaffold. A rationally designed nonconductive framework is presented, capable of accommodating Li within its internal structure to suppress volume expansion, while abundant surface polar functional groups facilitate uniform Li deposition.

3. The third chapter presents a semiconductive interfacial coating engineered to form a conductivity-gradient architecture. This design enhances interfacial compatibility with Li metal and promotes the formation of an inorganic-rich SEI, thereby achieving uniform and stable lithium plating/stripping even under fast-charging conditions.

4. The last chapter presents a dual-layer interfacial coating for achieving high-energy-density LMBs. The flexible outer organic layer alleviates volume expansion, whereas the inner inorganic SEI layer establishes a robust and ionically conductive interface on the lithium surface. The synergistic effect of these two layers enables excellent cycling stability under high energy conditions.