## 1 Introduction  
Arpotic lithium-oxygen batteries (LOBs) have emerged as a promising alternative candidate for large-scale energy storage and practical electric vehicle applications by virtue of their low cost, non-pollution, and high theoretical energy density (3500 Wh kg\({}^{-1}\)) [1, 2]. In 1996, the concept of secondary LOBs was first proposed, which set off a wave of research in the field [3]. However, to achieve large-scale commercial applications of LOBs, there are still many key scientific issues that need to be resolved, including the low activity of the positive electrode catalyst, serious polarization, and poor cycle stability [4, 5]. These problems can be attributed to the slow kinetics of oxygen reduction (ORR) and oxygen evolution (OER) reactions in LOBs during cycling [6, 7]. The introduction of high-efficiency and stable electrocatalysts can significantly increase the rate of oxygen reduction and oxygen evolution reactions, thereby reducing the overpotential during cycling and improving the overall performance of LOBs [8, 9]. The general working mechanism of typical LOBs could be summarized as follows: O\({}_{2}\) (diffusion from the cathode) can react with Li\({}^{+}\) (coming from the anode) to form a discharge product (Li\({}_{2}\)O\({}_{2}\)) on the surface of the cathode in the discharge process, which could be, subsequently, decomposed after the following charging [10]. Therefore, the preparation of cathode materials with high catalytic activities and structural stabilities is the key to the development of LOBs [11]. Thus far, many catalytic materials have been widely fabricated and applied in LOBs, such as carbonaceous materials, noble-metal-based electrocatalysts, transitional metal oxide, etc. [12]. In order to achieve an efficient balance between the cost and electrochemical activity of cathode materials, the utilization of coal-based solid waste has become quite a good choice. Coal gangue is the main associated waste in the process of coal mine construction, mining, and washing [13]. It is a hard mixture with a low carbon content and complex composition (mainly containing SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\)) [14]. Coal gangue has a loose and porous needle-like flake structure with apparent densities ranging from 1960 kg/m\({}^{3}\) to 2760 kg/m\({}^{3}\)[15]. On the one hand, the clay minerals kaolinite and bentonite, which are rich in coal gangue, have unique lamellar structures and surface chemical properties. The unique lamellar structures could provide sufficient storage space for discharge products and surface chemical properties with excellent adsorption performance, which could improve the formation/decomposition efficiency of discharge products, giving rise to a well-knit Li\({}_{2}\)O\({}_{2}\) formation [16]. On the other hand, there are abundant adsorption sites and abundant hydroxyl groups on the surfaces of coal gangue, which are prone to interfacial reactions [17]. The enhanced adsorption sites and hydroxyl groups could act as the active sites for oxygen reduction and oxygen evolution reactions to further improve the electrochemical performances of LOBs [18]. Thus, coal gangue is an ideal precursor for constructing highly active electrochemical materials in energy storage devices (especially LOBs). However, the complex composition of coal gangue has been proven to be the main reason hindering its efficient comprehensive utilization. Coal gangue contains a variety of trace heavy metal elements, such as lead, zinc, cadmium, arsenic, chromium, etc., which are non-degradable, carcinogenic, teratogenic, and bring potential environmental risks [19; 20]. In addition, the organics and minerals in coal gangue are easily oxidized in lithium-air batteries to form various harmful substances, such as nitrogen oxides and sulfides [21]. The functional modification and high-value utilization of coal gangue has become an important research topic to solve the overall planning of mineral development and environmental protection.