Negatively Charged Laponite Sheets Enhanced Solid Polymer Electrolytes for Long-Cycling Lithium-Metal Batteries

Solid polymer electrolytes suffer from the low ionic conductivity and poor capability of suppressing lithium dendrites, which have greatly hindered the practical application of solid-state lithium-metal batteries. Here, we report a novel laponite sheet (LS) with a large negatively charged surface as an additive in a solid composite electrolyte (poly(ethylene oxide)-LS) to rearrange the lithium-ion environment and enhance the mechanical strength of the electrolytes (PEO-LS). The strong electrostatic regulation of laponite sheets assists the dissociation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and constructs multiple transport channels for free lithium ions, achieving a high ionic conductivity of 1.1 x 10-3 S cm-1 at 60 degrees C. Furthermore, LS facilitates the in situ formation of a LiF-rich interface because of the boosting TFSI- anion concentration, which significantly suppresses lithium dendrites and prevents short circuit. As a result, the assembled LiFePO4|PEO-LS|Li battery demonstrates a long cycle life of over 800 cycles and a high Coulombic efficiency of 99.9% at 1C and 60 degrees C. When paired with a high-voltage NCM811 cathode, the battery also demonstrates excellent cycling stability and rate capability.

Automated summary

A novel laponite sheet has been used as an additive in a solid composite electrolyte to rearrange the lithium-ion environment and enhance the mechanical strength of the electrolyte. The laponite sheets assist the dissociation of LiTFSI and create multiple transport channels for free lithium ions, resulting in high ionic conductivity. Additionally, the laponite sheet facilitates the in situ formation of a LiF-rich interface, which significantly suppresses lithium dendrites and prevents short circuit.