Optimization Strategies for Cathode Materials in Lithium–Oxygen Batteries

Abstract

Developing high energy density, low-cost, and safe batteries remains a constant challenge that not only drives technological innovation but also holds the potential to transform human lifestyles. Although lithium-ion batteries have been widely adopted, their theoretical energy density is nearing its limit. Consequently, there is an urgent need to explore and investigate other battery systems with higher power capacities to propel technological advancements in this field. In this context, metal–oxygen batteries have attracted considerable interest because of their exceptionally high theoretical energy densities. Among the various metal–oxygen batteries, lithium–oxygen (Li–O₂) batteries stand out for their highest thermodynamic equilibrium potential (∼2.96 V) and greatest theoretical specific energy (∼3500 Wh kg^–1), positioning them as a promising avenue for future energy storage advancements. Over the past few decades, global scientists have conducted extensive research into the electrochemical reaction mechanisms, material sciences, and system designs of Li–O₂ batteries (LOBs), achieving numerous significant breakthroughs. Despite these remarkable advancements, research on LOBs is still in its infancy, confronting numerous unresolved critical issues. First, the deposition of Li₂O₂ on the electrode surface severely hinders further electrochemical reactions, resulting in actual discharge capacities that are far below theoretical values. Second, the kinetics of the oxygen electrode reactions are relatively slow, failing to meet high power demands and inducing severe polarization phenomena, which significantly reduces energy efficiency. Last, byproducts generated during the charge/discharge process lead to the degradation of electrode materials and electrolytes, markedly shortening the cycle life of the battery. The rational design of efficient and durable catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is considered one of the most effective strategies for overcoming the aforementioned obstacles. In this Account, we summarize the major electronic modulation strategies for developing efficient cathode catalysts, including structural design, composite material construction, surface and interface engineering, and heteroatom doping. First, specific methods to enhance catalyst performance through optimizing material morphology and structural design are discussed. Then, the construction of composite materials is presented to highlight the synergistic effects of various components in improving battery performance. Next, surface and interface engineering, which could regulate charge transfer and reaction activity, is outlined. Finally, the function of heteroatom doping in enhancing catalytic activity and stability by modifying the electronic structure of catalysts is summarized. Building on the optimization of the performance and reliability of each component in LOBs, the outlook for enhancing the overall electrochemical performance of these batteries is presented. We believe that this Account will inspire the development of effective and stable cathode catalysts for Li–air batteries and foster the practical application of this promising energy storage technology in the future.