Nanoscale Surface Modification of Li6PS5Cl Particles To Stabilize Lithium Solid-State Battery Interfaces

Thiophosphate solid electrolytes (SEs) may enable the energy storage transformation to solid-state batteries, but interface instability and lithium dendrite formation significantly limit their practical application. To address these challenges, we present a scalable N-methyl-2-pyrrolidone (NMP) surface modification to boost the performance of Li6PS5Cl (LPSCl) SE. This NMP surface modification on LPSCl improves electrochemical stability of the SE in the positive electrode and stabilizes the lithium-metal interface when used as a separator. When used as SE in positive electrode and separator, the modified LPSCl (m-LPSCl) increases the first cycle discharge capacity by ∼11 mAh g-1 at a current density of 0.21 mA cm-2 and improves capacity retention by 10% over pristine LPSCl (p-LPSCl) after 100 cycles. As a separator, higher critical current density is reached with m-LPSCl (1.6 mA cm-2) than with p-LPSCl (1 mA cm-2) before shorting of the cell. For the pair of single-crystal LiNiO2 (LNO)-positive electrode and lithium metal-negative electrode, m-LPSCl enables over 100 stable cycles, significantly outperforming the cell with p-LPSCl, which shorts after 25 cycles. Overall, this study introduces a scalable method for modifying LPSCl by solvent treatment that improves positive electrode performance and increases stability of the lithium metal-negative electrode interface.