锂金属负极界面修饰及其在硫化物全固态电池中的应用

Interficial Engineering of Lithium Metal Anode for Sulfide Solid State Batteries

随着我国新能源产业的快速发展,全固态电池由于其理论上的高能量密度和高安全性受到广泛关注,而硫化物全固态电池具有离子电导率高的优势成为目前的研发热点,但是金属锂负极的锂枝晶生长和与硫化物电解质之间的不稳定性严重阻碍了硫化物全固态电池的研发.本工作在高温150℃下制备了均匀的LiF界面层来抑制金属锂负极/硫化物电解质之间的界面反应和锂枝晶.LiF/Li之间具有较高的界面能,所以可以有效抑制锂枝晶的生长.LiNbO_(2)@LiCoO_(2)//Li_(6)PS_(5)Cl//LiF@Li(LNO@LCO//LPSCl//LiF@Li)全电池0.05 C,0.1 C,0.2 C和0.5 C倍率的正极放电克容量分别为138.4 mAh/g,105.0 mAh/g,80.3 mAh/g和60.4 mAh/g,0.05 C循环50周后,正极容量保持率为80.2%.该方法为后续金属锂负极在全固态电池中的应用提供了新的方案.

Lithium metal anode is recognized as the“Holy Grail”electrode because of its high specific capacity(3860 mAh/g)and low reduction potential(-3.04 V vs.standard hydrogen electrode),which is meaningful for batteries systems.Remarkable improvement of ionic conductivity of sulfide electrolyte exceeding 10 mS/cm at room temperature has opened up the opportunity to realized the commercialization of lithium metal anode.However,the practical implement of Li anode in solid-state batteries is hundered by the poor cycle stability and the low energy efficiency stemming from the unstable inter-faces due to the ultrahigh reactivity of lithium metal.At the anode interface,the lithium dendrite growth and solid electrolytes(SE)reduction by lithium metal are serious challenges for lithium metal anode.To suppress the interfacial reactions and lithium dendrite formation at the sulfide electrolyte/Li metal anode interface,various strategies have been implemented by re-searchers,such as in situ formed robust SEI(solid electrolyte interface),surface modification and SE modification,etc.In this article,we focus on the artificial solid electrolyte interface(ASEI)to strengthening the Li metal and solid electrolyte interface.We fabricate the uniform LiF-rich ASEI using CF_(3)(CF_(2))_(3)OCH_(3) by heating at a temperature of 150℃ for 6 h.LiF layer at the interface between Li and sulfide electroyte could prevent Li dendrite growth.Compared to the Li/sulfide electrolyte interface,the Li/LiF/sulfide electrolyte interface is more stable.The symmetrical cell LiF@Li//Li_(6)PS_(5)Cl//LiF@Li(LiF@Li//LPSCl//LiF@Li)does not short-circuit after 40 cycles at the current density of 0.1 mAh/cm^(2) with a lower polarization potential.A solid-state battery LiNbO_(2)@LiCoO_(2)//LPSCl//LiF@Li(LNO@LCO//LPSCl//LiF@Li)employing LiF coated Li metal as anode shows a high reversible discharge capacity of 138.4 mAh/g at 0.05 C and retains 110.9 mAh/g after 50 cycles.This interficial engineering for lithium metal and sulfide solid electrolyte provides new opportunity to commercialize the Li metal batteries.