锂硫电池硫还原反应金属催化剂的研究进展

Research Progr ess of Metal Catalysts for Sulfur Reduction of Lithium Sulfur Batteries

一直以来,储能技术着重在能量密度、功率密度、寿命、安全性和成本方面不断改进。近年来不断扩大的电子设备市场,包括电动汽车和便携式电子产品,促使电池逐渐向高能量密度方向发展。尽管锂离子电池已被广泛应用于电动工具、电子通讯设备甚至电动汽车等应用领域,但是锂离子电池的能量密度已接近其理论极限,仅能驱动一辆电动汽车行驶约300公里,或为全功能智能手机供电不到一天。锂硫电池因其较高的理论容量(1675 mAh g−1)和丰富的硫储量而受到了广泛的关注。但是,S8和Li2S的导电性差、循环时巨大的体积膨胀(80%)、多硫化物溶解引起的“穿梭效应”等,会导致活性物质利用率低,电池容量衰减迅速,进而限制了其高功率输出。此外,充放电过程中的非均相氧化还原反应通常伴随着缓慢的反应动力学,这导致了电池的倍率性能不理想。考虑到这些阻碍因素,除了可以通过引入中间层或设计合适的隔膜来捕获和限制锂离子外,寻找合适的正极主体材料也是提高锂硫电池电化学性能的有效途径。具体来说,利用极性材料作为高效的多硫化物介质来加速多硫化锂的反应已经成为近年来的研究热点。一些研究人员发现在硫正极材料中引入电催化剂可以加快硫的氧化还原过程,抑制多硫化锂的穿梭。本综述详细总结了加速硫还原反应的金属催化剂材料的最新进展,包括金属单原子材料、金属纳米材料、金属化合物材料,并为进一步优化锂硫电池的电化学性能指明了方向。

Energy storage technology has always focused on improvements in energy density, power density, longevity, safety and cost. The expanding market for electronic devices in recent years, including electric cars and portable electronics, has led to the gradual development of batteries in the direction of higher energy density. Although lithium-ion batteries are already widely used in applications such as power tools, electronic communications devices and even electric cars, their energy density is approaching its theoretical limit, allowing them to drive only about 300 km in an electric car or power a fully functional smartphone for less than a day. Lithium-sulfur batteries due to its high theoretical capacity (1675 mAh g−1) and abundant sulfur reserves and has received the widespread attention. However, the high power output of S8 and Li2S is limited by the low utilization of active materials and the rapid decline of battery capacity due to the poor conductivity of S8 and Li2S, the huge volume expansion (80%) during the cycle, and the shuttle effect caused by the dissolution of polysulfides. Worse still, the heterogeneous redox reaction during charge and discharge is usually accompanied by sluggish reaction kinetics, which leads to the unsatisfactory rate performance of the battery. Considering these hindering factors, in addition to the introduction of an intermediate layer or the design of a proper separator to trap and confine lithium ions, finding a suitable anode main material is also an effective way to improve the electrochemical performance of lithium-sulfur batteries. Specifically, the use of polar materials as efficient polysulfide medium to accelerate the reaction of polysulfide lithium has become a research hotspot in recent years. Some researchers have found that the introduction of electrocatalysts in sulfur cathode materials can accelerate the sulfur redox process and inhibit the shuttle of polylithium sulfide. This review summarizes in detail the latest progress of metal catalysts materials for accelerating sulfur reduction reactions, including metal monatomic materials, metal nanomaterials, metal compound materials, and points out the direction for further optimization of the electrochemical performance of Li-sulfur batteries.