Key Takeaways & Executive Findings
- •• Summarizes three main modification methods for lithium battery separators: surface coating, in situ modification, and grafting modification. • Compares adhesion and electrolyte wettability of modified separators prepared by these methods. • Highlights the role of separators in regulating ion transport and lithium deposition to enhance battery safety and cycle life. • Proposes future research directions including new materials, manufacturing processes, and quantitative adhesion analysis.
Abstract
The growing demands for energy storage systems, electric vehicles, and portable electronics have significantly pushed forward the need for safe and reliable lithium batteries. It is essential to design functional separators with improved mechanical and electrochemical characteristics. This review covers the improved mechanical and electrochemical performances as well as the advancements made in the design of separators utilizing a variety of techniques. In terms of electrolyte wettability and adhesion of the coating materials, we provide an overview of the current status of research on coated separators, in situ modified separators, and grafting modified separators, and elaborate additional performance parameters of interest. The characteristics of inorganics coated separators, organic framework coated separators and inorganic–organic coated separators from different fabrication methods are compared. Future directions regarding new modified materials, manufacturing process, quantitative analysis of adhesion and so on are proposed toward next-generation advanced lithium batteries.
1. Introduction
For a more sustainable society, it is now critical to develop renewable, clean energy as well as effective energy conversion and storage systems. Because of their high energy density and low redox potential, lithium batteries as one type of secondary batteries are widely utilized in energy storage systems [1]. Lithium-ion batteries were first developed and commercialized by Sony in 1991 [2]. However, the energy density of the state-of-the-art lithium-ion batteries, which use graphite anodes and insertion compound cathodes, has achieved its maximum (~150 Wh kg−1) [3]. Theoretically, lithium metal batteries offer a more appealing and higher energy density. The unstable solid electrolyte interphase (SEI) of the lithium anodes and severe lithium dendrite growth readily lead to short circuits and rapid, uncontrolled discharge of the battery, causing a series of safety issues [4]. Lithium-sulfide batteries and lithium-oxygen batteries also form multiple lithium sulfides and lithium oxide intermediate products during the cycling process, which seriously passivates the lithium anodes, resulting in a decline in cycle efficiency and battery performance [5]. In addition, the overheating of lithium batteries causes fire and explosion accidents. For instance, fast charging and rapid heating might cause the liquid electrolyte to burn, which is extremely dangerous for human life and health. Although extending the energy density and cycle life of lithium batteries is a popular objective, cost and safety are also receiving a lot of attention. Improving the physical and chemical characteristics of battery components proves to be a successful and efficient route.
Until now, tremendous advances have been made in optimization of electrodes for improved performance of lithium metal batteries, including the creation of artificial SEI, modulation of the anode’s three-dimensional structure, and control of the cathode’s surface structure. Recently, there has been a greater focus on the role separators play in regulating ion transport and, consequently, the behavior of lithium deposition. Uniform and fast transport of Li+ through separators is essential to reduce the risk of local overcharge and growth of lithium dendrite [6]. Ion flux distribution is greatly influenced by the chemical composition and pore structure of the separators [7], and micro-channels within the separators facilitate the migration of Li+. It has been demonstrated that separators can significantly increase the cycle life of lithium batteries. Lithium battery separators have advanced quickly since the turn of the twenty-first century due to the widespread use of lithium batteries. Figure 1 illustrates the increase in pertinent research publications as well as papers on different separators used in battery systems.
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Zixin Fan, Xiaoyu Chen, Jingjing Shi, Hui Nie, Xiaoming Zhang, Xingping Zhou, Xiaolin Xie, Zhigang Xue (2025). Functionalized Separators Boosting Electrochemical Performances for Lithium Batteries. Nano-Micro Letters. https://doi.org/10.1007/s40820-024-01596-x
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Frequently Asked Questions
What are the main modification methods for lithium battery separators?
The main modification methods are surface coating, in situ modification, and grafting modification.
How do modified separators improve lithium battery performance?
Modified separators enhance electrolyte wettability, adhesion, and ion transport, which help regulate lithium deposition and reduce dendrite growth, thereby improving safety and cycle life.
What is the significance of separator adhesion and wettability?
Good adhesion ensures coating stability, while high wettability promotes uniform electrolyte distribution and efficient Li+ transport, both critical for battery performance.
What are the future research directions for separator modification?
Future directions include developing new modified materials, optimizing manufacturing processes, and performing quantitative analysis of adhesion.
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