A team of researchers in China has devised a simple and mass-produceable method to modify a Li metal anode to avoid the formation of an unstable solid electrolyte interphase (SEI) and the subsequent growth of Li dendrites in high-energy-density Li-S batteries. A paper on their work is published in the journal Energy Storage Materials.

The team placed a LiPON (lithium phosphorus oxynitride) coating on the Li metal anode via nitrogen plasma-assisted deposition of electron-beam reaction evaporation.

With exceptional chemical and electrochemical stability, lithium phosphorus oxynitride (LiPON) is very promising to form a stable interface between Li metal and organic electrolytes. Furthermore, as the high elastic modulus (77 GPa) and hardness (3.9 GPa), LiPON is mechanically strong enough to suppress and withstand the incursion of Li dendrites at the Li/LiPON interface.

… Here, we develop a facile method to directly deposit a dense, interfacially stable, mechanically robust, and highly ionic conductive LiPON coating layer (~250 nm) on the Li metal surface, via nitrogen plasma-assisted deposition of electron-beam reaction evaporation. Combined with the high deposition rates (> 66 nm min^-1) and nonuse of large-scaled targets, the method is inexpensive and suitable for continual and large-scale roll-to-roll production.

—Wang et al.

The LiPON coating serves as a highly ionic conductive, chemically stable and mechanically robust protective layer, which suppresses the corrosion reaction with organic electrolytes and promotes uniform Li plating/stripping, thus enabling a stable and dendrite-free cycling of the symmetric Li metal cells for more than 900 cycles under a current density up to 3 mA cm^-2.

Using the LiPON-coated Li as anode, the Li-S pouch cell (sulfur loading: 7 mg cm^-2) was obtained with a specific energy density of ~300 Wh kg^-1, a relatively stable Coulombic efficiency of ~91% and an extended lifespan of more than 120 cycles with respect to 1.0 Ah capacity retention.

This facile and effective approach opens a new route for stabilizing the Li metal anode and could lead to the practical application in the field of rechargeable Li metal batteries.

—Wang et al.

Resources

• Weiwen Wang, Xinyang Yue, Jingke Meng, Jianying Wang, Xinxin Wang, Hao Chen, Dingren Shi, Jing Fu, Yongning Zhou, Jian Chen, Zhengwen Fu (2018) “Lithium phosphorus oxynitride as an efficient protective layer on lithium metal anodes for advanced lithium-sulfur batteries,” Energy Storage Materials doi: 10.1016/j.ensm.2018.08.010