Neutron Scattering Studies of Glassy Solid-State Lithium Ion Based Electrolytes

摘要

We present neutron diffraction results on superionic materials that are good candidates for use as solid-state electrolytes in next generation Li~+ ion batteries. Lithium ion conducting glasses of the compositions xLi_2SO_4-(1-x) [0.5Li_2O-0.5(2NH_4H_2PO_2)]; x=0 and 0.1 were synthesized by conventional melt-quenching. The transparent homogeneous glassy flakes were thus obtained and used for the characterization. The materials are glassy in nature and composed of a complex network of the following sub-units: Li_2O, Li_2SO_4, and 2NH_4H_2PO_2. This disordered structure is integral to its function in that it promotes Li~+ ion conduction while suppressing electronic conduction, the necessary qualities of a good Li~+ electrolyte. We used neutron diffraction to study the formation of crystallites upon heating of the material above 400°C. The crystallite formation is understood to be detrimental to the Li~+ ion mobility and, hence, is identified with a diminished performance in devices that require heating in their fabrication process. Here, we report the changes in the material, as observed by neutron diffraction, as a function of annealing temperature and temperature history.