1. College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian Province, China;2. College of Materials, Xiamen University, Xiamen 361005, Fujian Province, China
Abstract:
Owing to the rapid development of scientific technology, the demand for energy storage equipment is increasing in modern society. Among the current energy storage devices, lithium-ion batteries (LIBs) have been widely used in portable electronics, handy electric tools, medical electronics, and other fields owing to their high energy density, high power density, long lifespan, low self-discharge rate, wide operating temperature range, and environmental friendliness. However, in recent years, with rapid development in various technological fields, such as mobile electronics and electric vehicles, the demand for batteries with much higher energy densities than the current ones has been increasing. Hence, the development of LIBs with a high energy density, prolonged cycle life, and high safety has become a focal interest in this field. To achieve the above objectives, it is important to strategically use novel anode materials with relatively high specific capacities. At present, artificial graphite is commonly used as an anode material for commercialized traditional LIBs, which can only deliver a practical capacity of 360–365 mAh·g-1. Therefore, LIBs using graphite anodes have limited room for improvement in energy density. In the past two decades, considerable efforts have been devoted to silicon-based anode materials, which belong to the same family as carbon. To date, common silicon anode materials primarily include nano-silicon (nano-Si), silicon monoxide (SiO), suboxidized SiO (SiOx), and amorphous silicon metal alloy (amorphous SiM). Among them, SiO has attracted the most attention for use as a negative electrode material for LIBs. As an anode for lithium-ion batteries (LIBs), silicon monoxide (SiO) has a high specific capacity (~2043 mAh·g-1) and suitable charge (delithiation) potential (< 0.5 V). In addition, with the abundance of its raw material resource, low manufacturing cost, and environmental friendliness, SiO is considered a promising candidate for next-generation high-energy-density LIBs. Based on the testing of existing commercialized SiO materials, the reversible specific capacity of pure SiO can reach 1300–1700 mAh·g-1. However, when acting as the anode for LIBs, SiO undergoes a severe volume change (~200%) during the lithiation/delithiation process, which can result in severe pulverization and detachment of the anode material. Meanwhile, lithium silicate and lithium oxide are irreversibly formed during the initial discharge–charge cycle. Moreover, the electrical conductivity of SiO is relatively low (6.7 × 10-4 S·cm-1). These shortcomings seriously impact the interfacial stability and electrochemical performance of SiO-based LIBs, leading to a low initial Coulombic efficiency and poor long-term cycling stability, which has significantly restricted its commercial application. In recent years, substantial efforts have been made on structural optimization and interfacial modification of SiO anodes. However, there is still a lack of a more comprehensive summary of these important developments. Therefore, this review aims to introduce the research work in this area for readers interested in this emerging field and to summarize in detail the research work on the performance optimization of SiO in recent years. Based on the structural characteristics of the SiO anode material, this review expounds the main challenges facing the material, and then summarizes the structural and interfacial modification strategies from the perspectives of SiO structure optimization, SiO/carbon composites, and SiO/metal composites. The methods and their features in all the studies are concisely introduced, the electrochemical performances are demonstrated, and their correlations are compared and discussed. Finally, we propose the development of the structural and interfacial optimization of the SiO anode in the future.
