A New Solid Electrolyte with A High Lithium Ionic Conductivity for Solid-State Lithium-Ion Batteries

Solid-state lithium-ion batteries that use a solid electrolyte may potentially operate at wide temperatures and provide satisfactory safety. Moreover, the use of a solid electrolyte, which blocks the formation of lithium dendrites, allows batteries to use metallic lithium for the anode, enabling the batteries gain an energy density significantly higher than that of traditional lithium-ion batteries. Solid electrolytes play a role of conducting lithium ions and are the core of solid-state lithium-ion batteries. However, the development of solid lithium electrolytes towards a high lithium ionic conductivity, good chemical and electrochemical stability and scalable manufacturing method has been challenging. We report a new material composed of nitrogen-doped lithium metaphosphate, denoted as NLiPO₃. The material delivers a lithium ionic conductivity on the order of 10^-4 S/cm at room temperature, which is about two orders of magnitude higher than that of conventional LiPON – the electrolyte currently used in solid-state thin-film lithium-ion batteries, and is comparable or generally higher than that of most of the existing solid electrolytes. The high lithium ionic conductivity was attributed to the formation of $\mathrm{P}-\mathrm{N}<\begin{array}{c}\mathrm{P}\\ \mathrm{P}\end{array}$ bonds in amorphous LiPO₃. The material is stable in ambient environment over a wide range of temperature and can be handled and processed easily. These merits make the material a promising electrolyte for solid-state lithium-ion battery applications.