金属锂表面Sn-Al双金属包覆层的构筑及其空气稳定性研究

Fabrication and air stability investigation of metallic Sn-Al bilayer protected lithium metal anode

金属锂是下一代高能量密度锂电池的首选负极材料,然而其空气稳定性差导致金属锂二次电池工业化制备成本大大提高,开发具有高空气稳定性、优异电化学性能、低制备成本的表面包覆改性锂负极是其商业化的必由之路。在金属锂箔衬底上通过磁控溅射技术沉积一层74 nm厚的Al薄膜,再以相同参数沉积一层3μm厚的Sn薄膜,得到双层金属包覆膜样品Sn@Al@Li。采用扫描电子显微镜观察空气腐蚀前后样品表面形貌变化,结合X射线衍射测试,发现Sn@Al@Li表面金属包覆层形成的表面钝化膜起到了保护作用,使得样品在空气中放置3 h后其表面仍然存在单质金属Sn层,呈现明显的金属光泽。组装半电池进行放电容量测试,容量释放率达到80%,而纯锂样品仅剩14%。Sn@Al@Li不仅大大提高了空气稳定性,同时也一定程度提高了电化学性能,对称电池在1 mA/cm^(2),1 mAh/cm^(2)条件下能稳定循环300 h。双层金属薄膜包覆方法提高空气稳定性的同时也改善了电化学性能,对锂二次电池的商业化应用具有重要意义。

Lithium is the preferred anode material for next generation high-energy-density battery.Unfortunately,its poor air stability leads to high cost of the secondary lithium battery.So the development of surface-protected lithium anode with high air stability,excellent electrochemical performance and low fabrication cost is one of the ways toward the commercialization.A 74 nm thick Al layer followed by a 3μm thick Sn film on the lithium metal foil substrate via magnetron sputtering with the same process resulted in the preparation of metallic bilayer protected sample Sn@Al@Li.The surface morphology change before and after air corrosion was recorded with scanning electron microscopy.X-ray diffraction results indicate that a tin oxide film is formed as a protective layer and the metallic Sn phase still exists on the surface of the exposed Sn@Al@Li,displaying metallic luster after exposure in air for 3 h.Furthermore,the capacity release rate reaches 80%,while the exposed lithium electrode delivers only 14%of the initial capacity.The symmetric battery can stably cycle for 300 h under the conditions of 1 mA/cm^(2) and 1 mAh/cm^(2).The air stability and electrochemical performance can be effectively improved by the coating of metallic bilayer film on lithium anode,which is of great significance for the commercial application of the secondary lithium battery.