Interrupted anion-network enhanced Li+-ion conduction in Li3+yPO4Iy

For solid-state batteries to outperform the current lithium-ion battery technology in energy density and cost, high-performance solid electrolytes produced using low-cost precursors and scalable processes are the key. In this study, we demonstrate using inexpensive Li3PO4 of low conductivity 10(-6) mS/cm and turning it into a fast Li+ -ion conductor, with an ionic conductivity of >= 0.15 mS/cm, by engineering the anion sublattice. I- anions are used to interrupt the ordered PO43- network in Li3PO4, which destabilizes Li+-PO43- interaction and liberates Li+ -ions with enhanced Li+ mobility as evidenced by NMR relaxometry measurements. The optimal conductivity and activation energy are achieved when PO43-/I- =1, in which Li+-ions spend equal time with PO43- and I- on their diffusion paths without being trapped. Tracer-exchange NMR shows that Li4PO4I is more conductive than Li3+yPO4Iy when y &NOTEQUexpressionL; 1. Further conductivity enhancement is possible by stabilizing pure-phase glassy Li4PO4I. Overall, this study shows an effective and general strategy to significantly enhance ion conduction for creating inexpensive solid electrolytes with high performance.